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we study ultra-diffuse galaxies (udgs) in zoom in cosmological simulations, seeking the origin of udgs in the field versus galaxy groups. we find that while field udgs arise from dwarfs in a characteristic mass range by multiple episodes of supernova feedback (di cintio et al.), group udgs may also form by tidal puffing up and they become quiescent by ram-pressure stripping. the field and group udgs share similar properties, independent of distance from the group centre. their dark-matter haloes have ordinary spin parameters and centrally dominant dark-matter cores. their stellar components tend to have a prolate shape with a sérsic index n ∼ 1 but no significant rotation. ram pressure removes the gas from the group udgs when they are at pericentre, quenching star formation in them and making them redder. this generates a colour/star-formation-rate gradient with distance from the centre of the dense environment, as observed in clusters. we find that ∼20 per cent of the field udgs that fall into a massive halo survive as satellite udgs. in addition, normal field dwarfs on highly eccentric orbits can become udgs near pericentre due to tidal puffing up, contributing about half of the group-udg population. we interpret our findings using simple toy models, showing that gas stripping is mostly due to ram pressure rather than tides. we estimate that the energy deposited by tides in the bound component of a satellite over one orbit can cause significant puffing up provided that the orbit is sufficiently eccentric. we caution that while the simulations produce udgs that match the observations, they under-produce the more compact dwarfs in the same mass range, possibly because of the high threshold for star formation or the strong feedback. | formation of ultra-diffuse galaxies in the field and in galaxy groups |
black holes formed in dense star clusters, where dynamical interactions are frequent, may have fundamentally different properties than those formed through isolated stellar evolution. theoretical models for single-star evolution predict a gap in the black hole mass spectrum from roughly 40-120 m⊙ caused by (pulsational) pair-instability supernovae. motivated by the recent ligo/virgo event gw190521, we investigate whether black holes with masses within or in excess of this "upper-mass gap" can be formed dynamically in young star clusters through strong interactions of massive stars in binaries. we perform a set of n-body simulations using the cmc cluster-dynamics code to study the effects of the high-mass binary fraction on the formation and collision histories of the most massive stars and their remnants. we find that typical young star clusters with low metallicities and high binary fractions in massive stars can form several black holes in the upper-mass gap and often form at least one intermediate-mass black hole. these results provide strong evidence that dynamical interactions in young star clusters naturally lead to the formation of more massive black hole remnants. | intermediate-mass black holes from high massive-star binary fractions in young star clusters |
a spectral-energy distribution (sed) model for type ia supernovae (sne ia) is a critical tool for measuring precise and accurate distances across a large redshift range and constraining cosmological parameters. we present an improved model framework, salt3, which has several advantages over current models-including the leading salt2 model (salt2.4). while salt3 has a similar philosophy, it differs from salt2 by having improved estimation of uncertainties, better separation of color and light-curve stretch, and a publicly available training code. we present the application of our training method on a cross-calibrated compilation of 1083 sne with 1207 spectra. our compilation is 2.5× larger than the salt2 training sample and has greatly reduced calibration uncertainties. the resulting trained salt3.k21 model has an extended wavelength range 2000-11,000 å (1800 å redder) and reduced uncertainties compared to salt2, enabling accurate use of low-z i and iz photometric bands. including these previously discarded bands, salt3.k21 reduces the hubble scatter of the low-z foundation and cfa3 samples by 15% and 10%, respectively. to check for potential systematic uncertainties, we compare distances of low (0.01 < z < 0.2) and high (0.4 < z < 0.6) redshift sne in the training compilation, finding an insignificant 3 ± 14 mmag shift between salt2.4 and salt3.k21. while the salt3.k21 model was trained on optical data, our method can be used to build a model for rest-frame nir samples from the roman space telescope. our open-source training code, public training data, model, and documentation are available at https://saltshaker.readthedocs.io/en/latest/, and the model is integrated into the sncosmo and snana software packages. | salt3: an improved type ia supernova model for measuring cosmic distances |
inspired by the recent conjecture originated from graduated dark energy that the universe has recently transitioned from anti-de sitter vacua to de sitter vacua, we extend the standard λ cdm model by a cosmological constant (λs ) that switches sign at a certain redshift z†, and we call this model λscdm . we discuss the construction and theoretical features of this model in detail and find out that, when the consistency of the λscdm model with the cosmic microwave background (cmb) data is ensured, (i) z†≳1.1 is implied by the condition that the universe monotonically expands, (ii) h0 and mb (type ia supernovae absolute magnitude) values are inversely correlated with z† and reach h0≈74.5 km s−1 mpc−1 and mb≈-19.2 mag for z†=1.5 , in agreement with the sh0es measurements, and (iii) h (z ) presents an excellent fit to the ly-α measurements provided that z†≲2.34 . we further investigate the model constraints by using the full planck cmb data set, with and without baryon acoustic oscillation (bao) data. we find that the cmb data alone does not constrain z†, but the cmb +bao data set favors the sign switch of λs , providing the constraint z†=2.44 ±0.29 (68% c.l.). our analysis reveals that the lower and upper limits of z† are controlled by the galaxy and ly-α bao measurements, respectively, and the larger z† values imposed by the galaxy bao data prevent the model from achieving the highest local h0 measurements. in general, the λscdm model (i) relaxes the h0 tension while being fully consistent with the tip of the red giant branch measurements, (ii) relaxes the mb tension, (iii) removes the discrepancy with the ly-α measurements, (iv) relaxes the s8 tension, and (v) finds a better agreement with the big bang nucleosynthesis constraints on the physical baryon density. we find no strong statistical evidence to discriminate between the λscdm and λ cdm models. however, interesting and promising features of the λscdm model, which we describe in our study, provide an advantage over λ cdm . | relaxing cosmological tensions with a sign switching cosmological constant |
stripped-envelope (se) supernovae (sne) include h-poor (type iib), h-free (type ib), and he-free (type ic) events thought to be associated with the deaths of massive stars. the exact nature of their progenitors is a matter of debate with several lines of evidence pointing towards intermediate mass (minit< 20 m⊙) stars in binary systems, while in other cases they may be linked to single massive wolf-rayet stars. here we present the analysis of the light curves of 34 se sne published by the carnegie supernova project (csp-i) that are unparalleled in terms of photometric accuracy and wavelength range. light-curve parameters are estimated through the fits of an analytical function and trends are searched for among the resulting fit parameters. detailed inspection of the dataset suggests a tentative correlation between the peak absolute b-band magnitude and δm15(b), while the post maximum light curves reveals a correlation between the late-time linear slope and δm15. making use of the full set of optical and near-ir photometry, combined with robust host-galaxy extinction corrections, comprehensive bolometric light curves are constructed and compared to both analytic and hydrodynamical models. this analysis finds consistent results among the two different modeling techniques and from the hydrodynamical models we obtained ejecta masses of 1.1-6.2m⊙, 56ni masses of 0.03-0.35m⊙, and explosion energies (excluding two sne ic-bl) of 0.25-3.0 × 1051 erg. our analysis indicates that adopting κ = 0.07 cm2 g-1 as the mean opacity serves to be a suitable assumption when comparing arnett-model results to those obtained from hydrodynamical calculations. we also find that adopting he i and o i line velocities to infer the expansion velocity in he-rich and he-poor sne, respectively, provides ejecta masses relatively similar to those obtained by using the fe ii line velocities, although the use of fe ii as a diagnostic does imply higher explosion energies. the inferred range of ejecta masses are compatible with intermediate mass (mzams ≤ 20m⊙) progenitor stars in binary systems for the majority of se sne. furthermore, our hydrodynamical modeling of the bolometric light curves suggests a significant fraction of the sample may have experienced significant mixing of 56ni, particularly in the case of sne ic. based on observations collected at las campanas observatory.bolometric light curve tables are only available at the cds via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?j/a+a/609/a136 | the carnegie supernova project i. analysis of stripped-envelope supernova light curves |
estimates of the hubble constant, h0, from the local distance ladder and from the cosmic microwave background (cmb) are discrepant at the ∼3σ level, indicating a potential issue with the standard λ cold dark matter (λcdm) cosmology. a probabilistic (i.e. bayesian) interpretation of this tension requires a model comparison calculation, which in turn depends strongly on the tails of the h0 likelihoods. evaluating the tails of the local h0 likelihood requires the use of non-gaussian distributions to faithfully represent anchor likelihoods and outliers, and simultaneous fitting of the complete distance-ladder data set to ensure correct uncertainty propagation. we have hence developed a bayesian hierarchical model of the full distance ladder that does not rely on gaussian distributions and allows outliers to be modelled without arbitrary data cuts. marginalizing over the full ∼3000-parameter joint posterior distribution, we find h0 = (72.72 ± 1.67) km s-1 mpc-1 when applied to the outlier-cleaned riess et al. data, and (73.15 ± 1.78) km s-1 mpc-1 with supernova outliers reintroduced (the pre-cut cepheid data set is not available). using our precise evaluation of the tails of the h0 likelihood, we apply bayesian model comparison to assess the evidence for deviation from λcdm given the distance-ladder and cmb data. the odds against λcdm are at worst ∼10:1 when considering the planck 2015 xiii data, regardless of outlier treatment, considerably less dramatic than naïvely implied by the 2.8σ discrepancy. these odds become ∼60:1 when an approximation to the more-discrepant planck intermediate xlvi likelihood is included. | clarifying the hubble constant tension with a bayesian hierarchical model of the local distance ladder |
a lingering mystery in core-collapse supernova theory is how collective neutrino oscillations affect the dynamics. all previously identified flavor instabilities, some of which might make the effects considerable, are essentially collisionless phenomena. here it is shown that collisional instabilities exist as well. they are associated with asymmetries between the neutrino and antineutrino interaction rates, are possibly prevalent deep inside supernovae, and pose an unusual instance of decoherent interactions with a thermal environment causing the sustained growth of quantum coherence. | collisional flavor instabilities of supernova neutrinos |
the measurements of cosmic microwave background (cmb) anisotropies made by the planck satellite provide extremely tight upper bounds on the total neutrino mass scale (σmν< 0.26 ev at 95% c.l.). however, as recently discussed in the literature, the planck data show anomalies that could affect this result. here we provide new constraints on neutrino masses using the recent and complementary cmb measurements from the atacama cosmology telescope dr4 and the south pole telescope spt-3g experiments. we found that both the act-dr4 and spt-3g data, when combined with wmap, mildly suggest a neutrino mass with σmν= 0.68 ± 0.31 and ${0.46}_{-0.36}^{+0.14}$ ev at 68% c.l., respectively. moreover, when cmb lensing from the planck experiment is included, the act-dr4 data now indicate a neutrino mass above the two standard deviations, with ${\rm{\sigma }}{m}_{\nu }={0.60}_{-0.50}^{+0.44}$ ev at 95% c.l., while wmap+spt-3g provides a weak upper limit of σmν< 0.37 ev at 68% c.l. interestingly, these results are consistent with the planck cmb+lensing constraint of ${\rm{\sigma }}{m}_{\nu }={0.41}_{-0.25}^{+0.17}$ ev at 68% c.l. when variations in the a lens parameter are considered. we also show that these indications are still present after the inclusion of bao or type ia supernova data in extended cosmologies that are usually considered to solve the so-called hubble tension. in this respect, we note that in these models, cmb+bao constraints prefer a higher neutrino mass for higher values of the hubble constant. a combination of act-dr4, wmap, bao, and constraints on the hubble constant from the sh0es collaboration gives ${\rm{\sigma }}{m}_{\nu }={0.39}_{-0.25}^{+0.13}$ ev at 68% c.l. in extended cosmologies. | neutrino mass bounds in the era of tension cosmology |
we explore the use of the mass spectrum of neutron stars and black holes in gravitational-wave compact binary sources as a cosmological probe. these standard siren sources provide direct measurements of luminosity distance. in addition, features in the mass distribution, such as mass gaps or peaks, will redshift and thus provide independent constraints on their redshift distribution. we argue that the entire mass spectrum should be utilized to provide cosmological constraints. for example, we find that the mass spectrum of ligo-virgo-kagra events introduces at least five independent mass "features": the upper and lower edges of the pair instability supernova (pisn) gap, the upper and lower edges of the neutron star-black hole gap, and the minimum neutron star mass. we find that although the pisn gap dominates the cosmological inference with current detectors (second generation, 2g), as shown in previous work, it is the lower mass gap that will provide the most powerful constraints in the era of cosmic explorer and einstein telescope (third generation, 3g). by using the full mass distribution, we demonstrate that degeneracies between mass evolution and cosmological evolution can be broken, unless an astrophysical conspiracy shifts all features of the full mass distribution simultaneously following the (nontrivial) hubble diagram evolution. we find that this self-calibrating "spectral siren" method has the potential to provide precision constraints of both cosmology and the evolution of the mass distribution, with 2g achieving better than 10% precision on h (z ) at z ≲1 within a year and 3g reaching ≲1 % at z ≳2 within one month. | spectral sirens: cosmology from the full mass distribution of compact binaries |
gamma-ray bursts (grbs) are classified into long and short events. long grbs (lgrbs) are associated with the end states of very massive stars, while short grbs (sgrbs) are linked to the merger of compact objects. grb 200826a was a peculiar event, because by definition it was an sgrb, with a rest-frame duration of ~0.5 s. however, this event was energetic and soft, which is consistent with lgrbs. the relatively low redshift (z = 0.7486) motivated a comprehensive, multiwavelength follow-up campaign to characterize its host, search for a possible associated supernova (sn), and thus understand the origin of this burst. to this aim we obtained a combination of deep near-infrared (nir) and optical imaging together with spectroscopy. our analysis reveals an optical and nir bump in the light curve whose luminosity and evolution are in agreement with several sne associated to lgrbs. analysis of the prompt grb shows that this event follows the e p,i-e iso relation found for lgrbs. the host galaxy is a low-mass star-forming galaxy, typical of lgrbs, but with one of the highest star formation rates, especially with respect to its mass ( $\mathrm{log}{m}_{* }/{m}_{\odot }=8.6$ , sfr ~ 4.0 m ⊙ yr-1). we conclude that grb 200826a is a typical collapsar event in the low tail of the duration distribution of lgrbs. these findings support theoretical predictions that events produced by collapsars can be as short as 0.5 s in the host frame and further confirm that duration alone is not an efficient discriminator for the progenitor class of a grb. * based on data obtained with the lbt programs: lbt-2019b-18 (pi a. rossi), ddt-2019b-9 (pi p. d'avanzo), and ld-2020b-0100 (pi. b. rothberg); and the tng programme a41 tac15 (pi v. d'elia). | the peculiar short-duration grb 200826a and its supernova |
white dwarfs represent the last stage of evolution of stars with mass less than about eight times that of the sun and, like other stars, are often found in binaries1,2. if the orbital period of the binary is short enough, energy losses from gravitational-wave radiation can shrink the orbit until the two white dwarfs come into contact and merge3. depending on the component masses, the merger can lead to a supernova of type ia or result in a massive white dwarf4. in the latter case, the white dwarf remnant is expected to be highly magnetized5,6 because of the strong magnetic dynamo that should arise during the merger, and be rapidly spinning from the conservation of the orbital angular momentum7. here we report observations of a white dwarf, ztf j190132.9+145808.7, that exhibits these properties, but to an extreme: a rotation period of 6.94 minutes, a magnetic field ranging between 600 megagauss and 900 megagauss over its surface, and a stellar radius of 2140−230+160? kilometres, only slightly larger than the radius of the moon. such a small radius implies that the star's mass is close to the maximum white dwarf mass, or chandrasekhar mass. ztf j190132.9+145808.7 is likely to be cooling through the urca processes (neutrino emission from electron capture on sodium) because of the high densities reached in its core. | a highly magnetized and rapidly rotating white dwarf as small as the moon |
we perform a comprehensive search for optical precursor emission at the position of sn 2023ixf using data from the dlt40, ztf, and atlas surveys. by comparing the current data set with precursor outburst hydrodynamical model light curves, we find that the probability of a significant outburst within 5 yr of explosion is low, and the circumstellar material (csm) ejected during any possible precursor outburst is likely smaller than ~0.015m ⊙. by comparing to a set of toy models, we find that, if there was a precursor outburst, the duration must have been shorter than ~100 days for a typical brightness of mr≃ -9 mag or shorter than 200 days for mr≃ -8 mag; brighter, longer outbursts would have been discovered. precursor activity like that observed in the normal type ii sn 2020tlf (mr≃ -11.5) can be excluded in sn 2023ixf. if the dense csm inferred by early flash spectroscopy and other studies is related to one or more precursor outbursts, then our observations indicate that any such outburst would have to be faint and only last for days to months, or it occurred more than 5 yr prior to the explosion. alternatively, any dense, confined csm may not be due to eruptive mass loss from a single red supergiant progenitor. taken together, the results of sn 2023ixf and sn 2020tlf indicate that there may be more than one physical mechanism behind the dense csm inferred around some normal type ii supernovae. | a comprehensive optical search for pre-explosion outbursts from the quiescent progenitor of sn 2023ixf |
the fast flavor conversions (ffcs) of neutrinos generally exist in core-collapse supernovae and binary neutron-star merger remnants and can significantly change the flavor composition and affect the dynamics and nucleosynthesis processes. several analytical prescriptions were proposed recently to approximately explain or predict the asymptotic outcome of ffcs for systems with different initial or boundary conditions, with the aim for providing better understandings of ffcs and for practical implementation of ffcs in hydrodynamic modeling. in this work, we obtain the asymptotic survival probability distributions of ffcs in a survey over thousands of randomly sampled initial angular distributions by means of numerical simulations in one-dimensional boxes with the periodic boundary condition. we also propose improved prescriptions that guarantee the continuity of the angular distributions after ffcs. detailed comparisons and evaluation of all these prescriptions with our numerical survey results are performed. the survey dataset is made publicly available to inspire the exploration and design for more effective methods applicable to realistic hydrodynamic simulations. | evaluating approximate asymptotic distributions for fast neutrino flavor conversions in a periodic 1d box |
massive binaries that merge as compact objects are the progenitors of gravitational-wave sources. most of these binaries experience one or more phases of mass transfer, during which one of the stars loses all or part of its outer envelope and becomes a stripped-envelope star. the evolution of the size of these stripped stars is crucial in determining whether they experience further interactions and understanding their ultimate fate. we present new calculations of stripped-envelope stars based on binary evolution models computed with mesa. we use these to investigate their radius evolution as a function of mass and metallicity. we further discuss their pre-supernova observable characteristics and potential consequences of their evolution on the properties of supernovae from stripped stars. at high metallicity, we find that practically all of the hydrogen-rich envelope is removed, which is in agreement with earlier findings. only progenitors with initial masses below 10 m⊙ expand to large radii (up to 100 r⊙), while more massive progenitors remain compact. at low metallicity, a substantial amount of hydrogen remains and the progenitors can, in principle, expand to giant sizes (> 400 r⊙) for all masses we consider. this implies that they can fill their roche lobe anew. we show that the prescriptions commonly used in population synthesis models underestimate the stellar radii by up to two orders of magnitude. we expect that this has consequences for the predictions for gravitational-wave sources from double neutron star mergers, particularly with regard to their metallicity dependence. the models are only available at the cds via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/cat/j/a+a/637/a6 | the expansion of stripped-envelope stars: consequences for supernovae and gravitational-wave progenitors |
in our quest to identify the progenitors of type ia supernovae (sne ia), we first update the nucleosynthesis yields for both near-chandrasekhar- (ch) and sub-ch-mass white dwarfs (wds) for a wide range of metallicities with our 2d hydrodynamical code and the latest nuclear reaction rates. we then include the yields in our galactic chemical evolution code to predict the evolution of elemental abundances in the solar neighborhood and dwarf spheroidal (dsph) galaxies fornax, sculptor, sextans, and carina. in the observations of the solar neighborhood stars, mn shows an opposite trend to α elements, showing an increase toward higher metallicities, which is very well reproduced by the deflagration-detonation transition of ch-mass wds but never by double detonations of sub-ch-mass wds alone. the problem of ch-mass sne ia was the ni overproduction at high metallicities. however, we found that ni yields of ch-mass sne ia are much lower with the solar-scaled initial composition than in previous works, which keeps the predicted ni abundance within the observational scatter. from the evolutionary trends of elemental abundances in the solar neighborhood, we conclude that the contribution of sub-ch-mass sne ia to chemical enrichment is up to 25%. in dsph galaxies, however, larger enrichment from sub-ch-mass sne ia than in the solar neighborhood may be required, which causes a decrease in [(mg, cr, mn, ni)/fe] at lower metallicities. the observed high [mn/fe] ratios in sculptor and carina may also require additional enrichment from pure deflagrations, possibly as sne iax. future observations of dsph stars will provide more stringent constraints on the progenitor systems and explosion mechanism of sne ia. | new type ia supernova yields and the manganese and nickel problems in the milky way and dwarf spheroidal galaxies |
the most common way to discover extragalactic fast transients, which fade within a few nights in the optical, is via follow-up of gamma-ray burst and gravitational-wave triggers. however, wide-field surveys have the potential to identify rapidly fading transients independently of such external triggers. the volumetric survey speed of the zwicky transient facility (ztf) makes it sensitive to objects as faint and fast fading as kilonovae, the optical counterparts to binary neutron star mergers, out to almost 200 mpc. we introduce an open-source software infrastructure, the ztf realtime search and triggering, ztfrest, designed to identify kilonovae and fast transients in ztf data. using the ztf alert stream combined with forced point-spread-function photometry, we have implemented automated candidate ranking based on their photometric evolution and fitting to kilonova models. automated triggering, with a human in the loop for monitoring, of follow-up systems has also been implemented. in 13 months of science validation, we found several extragalactic fast transients independently of any external trigger, including two supernovae with post-shock cooling emission, two known afterglows with an associated gamma-ray burst (ztf20abbiixp, ztf20abwysqy), two known afterglows without any known gamma-ray counterpart (ztf20aajnksq, ztf21aaeyldq), and three new fast-declining sources (ztf20abtxwfx, ztf20acozryr, ztf21aagwbjr) that are likely associated with grb200817a, grb201103b, and grb210204a. however, we have not found any objects that appear to be kilonovae. we constrain the rate of gw170817-like kilonovae to r < 900 gpc-3 yr-1 (95% confidence). a framework such as ztfrest could become a prime tool for kilonova and fast-transient discovery with the vera rubin observatory. | fast-transient searches in real time with ztfrest: identification of three optically discovered gamma-ray burst afterglows and new constraints on the kilonova rate |
with the recent increase in precision of our cosmological datasets, measurements of λcdm model parameter provided by high- and low-redshift observations started to be in tension, i.e., the obtained values of such parameters were shown to be significantly different in a statistical sense. in this work we tackle the tension on the value of the hubble parameter, h0, and the weighted amplitude of matter fluctuations, s8, obtained from local or low-redshift measurements and from cosmic microwave background (cmb) observations. we combine the main approaches previously used in the literature by extending the cosmological model and accounting for extra systematic uncertainties. with such analysis we aim at exploring non standard cosmological models, implying deviation from a cosmological constant driven acceleration of the universe expansion, in the presence of additional uncertainties in measurements. in more detail, we reconstruct the dark energy equation of state as a function of redshift, while we study the impact of type-ia supernovae (snia) redshift-dependent astrophysical systematic effects on these tensions. we consider a snia intrinsic luminosity dependence on redshift due to the star formation rate in its environment, or the metallicity of the progenitor. we find that the h0 and s8 tensions can be significantly alleviated, or even removed, if we account for varying dark energy for snia and cmb data. however, the tensions remain when we add baryon acoustic oscillations (bao) data into the analysis, even after the addition of extra snia systematic uncertainties. this points towards the need of either new physics beyond late-time dark energy, or other unaccounted systematic effects (particulary in bao measurements), to fully solve the present tensions. | cmb tensions with low-redshift h0 and s8 measurements: impact of a redshift-dependent type-ia supernovae intrinsic luminosity |
we present a hydrodynamical simulation of the turbulent, magnetized, supernova (sn)-driven interstellar medium (ism) in a stratified box that dynamically couples the injection and evolution of cosmic rays (crs) and a self-consistent evolution of the chemical composition. crs are treated as a relativistic fluid in the advection-diffusion approximation. the thermodynamic evolution of the gas is computed using a chemical network that follows the abundances of h+, h, h2, co, c+, and free electrons and includes (self-)shielding of the gas and dust. we find that crs perceptibly thicken the disk with the heights of 90% (70%) enclosed mass reaching ≳ 1.5 {kpc} (≳ 0.2 {kpc}). the simulations indicate that crs alone can launch and sustain strong outflows of atomic and ionized gas with mass loading factors of order unity, even in solar neighborhood conditions and with a cr energy injection per sn of {10}50 {erg}, 10% of the fiducial thermal energy of an sn. the cr-driven outflows have moderate launching velocities close to the midplane (≲ 100 {km} {{{s}}}-1) and are denser (ρ ∼ 10-24-10-26 g cm-3), smoother, and colder than the (thermal) sn-driven winds. the simulations support the importance of crs for setting the vertical structure of the disk as well as the driving of winds. | launching cosmic-ray-driven outflows from the magnetized interstellar medium |
galactic outflows play an important role in galactic evolution. despite their importance, a detailed understanding of the physical mechanisms responsible for the driving of these winds is lacking. in an effort to gain more insight into the nature of these flows, we perform global three-dimensional magnetohydrodynamical simulations of an isolated milky way-size starburst galaxy. we focus on the dynamical role of cosmic rays (crs) injected by supernovae, and specifically on the impact of the streaming and anisotropic diffusion of crs along the magnetic fields. we find that these microphysical effects can have a significant effect on the wind launching and mass loading factors, depending on the details of the plasma physics. due to the cr streaming instability, crs propagating in the interstellar medium scatter on self-excited alfvén waves and couple to the gas. when the wave growth due to the streaming instability is inhibited by some damping process, such as turbulent damping, the coupling of crs to the gas is weaker and their effective propagation speed faster than the alfvén speed. alternatively, crs could scatter from “extrinsic turbulence” that is driven by another mechanism. we demonstrate that the presence of moderately super-alfvénic cr streaming enhances the efficiency of galactic wind driving. cosmic rays stream away from denser regions near the galactic disk along partially ordered magnetic fields and in the process accelerate more tenuous gas away from the galaxy. for cr acceleration efficiencies broadly consistent with the observational constraints, crs reduce the galactic star formation rates and significantly aid in launching galactic winds. | global simulations of galactic winds including cosmic-ray streaming |
the next core-collapse supernova in the milky way or its satellites will represent a once-in-a-generation opportunity to obtain detailed information about the explosion of a star and provide significant scientific insight for a variety of fields because of the extreme conditions found within. supernovae in our galaxy are not only rare on a human timescale but also happen at unscheduled times, so it is crucial to be ready and use all available instruments to capture all possible information from the event. the first indication of a potential stellar explosion will be the arrival of a bright burst of neutrinos. its observation by multiple detectors worldwide can provide an early warning for the subsequent electromagnetic fireworks, as well as signal to other detectors with significant backgrounds so they can store their recent data. the supernova early warning system (snews) has been operating as a simple coincidence between neutrino experiments in automated mode since 2005. in the current era of multi-messenger astronomy there are new opportunities for snews to optimize sensitivity to science from the next galactic supernova beyond the simple early alert. this document is the product of a workshop in june 2019 towards design of snews 2.0, an upgraded snews with enhanced capabilities exploiting the unique advantages of prompt neutrino detection to maximize the science gained from such a valuable event. | snews 2.0: a next-generation supernova early warning system for multi-messenger astronomy |
reionization in the early universe is likely driven by dwarf galaxies. using cosmological radiation-hydrodynamic simulations, we study star formation and the escape of lyman continuum (lyc) photons from mini-haloes with {m_halo}≲ 10^8 {m_{⊙}}. our simulations include a new thermo-turbulent star formation model, non-equilibrium chemistry and relevant stellar feedback processes (photoionization by young massive stars, radiation pressure and mechanical supernova explosions). we find that feedback reduces star formation very efficiently in mini-haloes, resulting in the stellar mass consistent with the slope and normalization reported in kimm & cen and the empirical stellar mass-to-halo mass relation derived in the local universe. because star formation is stochastic and dominated by a few gas clumps, the escape fraction in mini-haloes is generally determined by radiation feedback (heating due to photoionization), rather than supernova explosions. we also find that the photon number-weighted mean escape fraction in mini-haloes is higher (∼20-40 per cent) than that in atomic-cooling haloes, although the instantaneous fraction in individual haloes varies significantly. the escape fraction from pop iii stars is found to be significant ( ≳ 10 per cent) only when the mass is greater than ∼100 m⊙. based on simple analytic calculations, we show that lyc photons from mini-haloes are, despite their high escape fractions, of minor importance for reionization due to inefficient star formation. we confirm previous claims that stars in atomic-cooling haloes with masses 10^8 {m_{⊙}}≲ {m_halo}≲ 10^{11} {m_{⊙}} are likely to be the most important source of reionization. | feedback-regulated star formation and escape of lyc photons from mini-haloes during reionization |
the silcc project (simulating the life-cycle of molecular clouds) aims at a more self-consistent understanding of the interstellar medium (ism) on small scales and its link to galaxy evolution. we present three-dimensional (magneto)hydrodynamic simulations of the ism in a vertically stratified box including self-gravity, an external potential due to the stellar component of the galactic disc, and stellar feedback in the form of an interstellar radiation field and supernovae (sne). the cooling of the gas is based on a chemical network that follows the abundances of h+, h, h2, c+, and co and takes shielding into account consistently. we vary the sn feedback by comparing different sn rates, clustering and different positioning, in particular sne in density peaks and at random positions, which has a major impact on the dynamics. only for random sn positions the energy is injected in sufficiently low-density environments to reduce energy losses and enhance the effective kinetic coupling of the sne with the gas. this leads to more realistic velocity dispersions (σ _h i≈ 0.8σ _{300{-}8000 k}∼ 10-20 km s^{-1}, σ _h α ≈ 0.6σ _{8000-3× 10^5 k}∼ 20-30 km s^{-1}), and strong outflows with mass loading factors (ratio of outflow to star formation rate) of up to 10 even for solar neighbourhood conditions. clustered sne abet the onset of outflows compared to individual sne but do not influence the net outflow rate. the outflows do not contain any molecular gas and are mainly composed of atomic hydrogen. the bulk of the outflowing mass is dense (ρ ∼ 10-25-10-24 g cm-3) and slow (v ∼ 20-40 km s-1) but there is a high-velocity tail of up to v ∼ 500 km s-1 with ρ ∼ 10-28-10-27 g cm-3. | the silcc (simulating the lifecycle of molecular clouds) project - ii. dynamical evolution of the supernova-driven ism and the launching of outflows |
we consider generic neutrino dipole portals between left-handed neutrinos, photons, and right-handed heavy neutral leptons (hnl) with dirac masses. the dominance of this portal significantly alters the conventional phenomenology of hnls. we derive a comprehensive set of constraints on the dipole portal to hnls by utilizing data from lep, lhc, miniboone, lsnd as well as observations of supernova 1987a and consistency of the standard big bang nucleosynthesis. we calculate projected sensitivities from the proposed high-intensity ship beam dump experiment, and the ongoing experiments at the short-baseline neutrino facility at fermilab. dipole mediated primakoff neutrino upscattering and dalitz-like meson decays are found to be the main production mechanisms in most of the parametric regime under consideration. proposed explanations of lsnd and miniboone anomalies based on hnls with dipole-induced decays are found to be severely constrained, or to be tested in the future experiments. | dipole portal to heavy neutral leptons |
even if the fundamental action of gravity is local, the corresponding quantum effective action, that includes the effect of quantum fluctuations, is a nonlocal object. these nonlocalities are well understood in the ultraviolet regime but much less in the infrared, where they could in principle give rise to important cosmological effects. here we systematize and extend previous work of our group, in which it is assumed that a mass scale λ is dynamically generated in the infrared, giving rise to nonlocal terms in the quantum effective action of gravity. we give a detailed discussion of conceptual aspects related to nonlocal gravity (including causality, degrees of freedom, ambiguities related to the boundary conditions of the nonlocal operator, scenarios for the emergence of a dynamical scale in the infrared) and of the cosmological consequences of these models. the requirement of providing a viable cosmological evolution severely restricts the form of the nonlocal terms, and selects a model (the so-called rr model) that corresponds to a dynamical mass generation for the conformal mode. for such a model: (1) there is a frw background evolution, where the nonlocal term acts as an effective dark energy with a phantom equation of state, providing accelerated expansion without a cosmological constant. (2) cosmological perturbations are well behaved. (3) implementing the model in a boltzmann code and comparing with observations we find that the rr model fits the cmb, bao, sne, structure formation data and local h0 measurements at a level statistically equivalent to λcdm. (4) bayesian parameter estimation shows that the value of h0 obtained in the rr model is higher than in λcdm, reducing to 2.0σ the tension with the value from local measurements. (5) the rr model provides a prediction for the sum of neutrino masses that falls within the limits set by oscillation and terrestrial experiments (in contrast to λcdm, where letting the sum of neutrino masses vary as a free parameter within these limits, one hits the lower bound). (6) gravitational waves propagate at the speed of light, complying with the limit from gw170817/grb 170817a. | nonlocal gravity. conceptual aspects and cosmological predictions |
as one of the closest supernovae (sne) in the last decade, sn 2023ixf is an unprecedented target to investigate the progenitor star that exploded. however, there is still significant uncertainty in the reported progenitor properties. in this work, we present a detailed study of sn 2023ixf's progenitor with two independent analyses. we first modeled its spectral energy distribution (sed) based on hubble space telescope optical, spitzer mid-infrared (ir), and ground-based near-ir data. we find that stellar pulsation and circumstellar extinction have great impacts on sed fitting, and the result suggests a relatively massive red supergiant surrounded by c-rich dust with an initial mass of 16.2-17.4 m ⊙. the corresponding rate of mass loss occurring at least 3 yr before the sn explosion is about 2 × 10-4 m ⊙ yr-1. we also derived the star formation history of the sn environment based on resolved stellar populations, and the most recent star-forming epoch corresponds to a progenitor initial mass of 17-19 m ⊙, in agreement with that from our sed fitting. therefore, we conclude that the progenitor of sn 2023ixf is close to the high-mass end for type ii sn progenitors. | the dusty red supergiant progenitor and the local environment of the type ii sn 2023ixf in m101 |
up-to-date cosmological data analyses have shown that (a) a closed universe is preferred by the planck data at more than 99% cl, and (b) interacting scenarios offer a very compelling solution to the hubble constant tension. in light of these two recent appealing scenarios, we consider here an interacting dark matter-dark energy model with a non-zero spatial curvature component and a freely varying dark energy equation of state in both the quintessential and phantom regimes. when considering cosmic microwave background data only, a phantom and closed universe can perfectly alleviate the hubble tension, without the necessity of a coupling among the dark sectors. accounting for other possible cosmological observations compromises the viability of this very attractive scenario as a global solution to current cosmological tensions, either by spoiling its effectiveness concerning the h0 problem, as in the case of supernovae ia data, or by introducing a strong disagreement in the preferred value of the spatial curvature, as in the case of baryon acoustic oscillations. | 2021-h0 odyssey: closed, phantom and interacting dark energy cosmologies |
energy-transport effects can alter the structure that develops as a supernova evolves into a supernova remnant. the rayleigh-taylor instability is thought to produce structure at the interface between the stellar ejecta and the circumstellar matter, based on simple models and hydrodynamic simulations. here we report experimental results from the national ignition facility to explore how large energy fluxes, which are present in supernovae, affect this structure. we observed a reduction in rayleigh-taylor growth. in analyzing the comparison with supernova sn1993j, a type ii supernova, we found that the energy fluxes produced by heat conduction appear to be larger than the radiative energy fluxes, and large enough to have dramatic consequences. no reported astrophysical simulations have included radiation and heat conduction self-consistently in modeling supernova remnants and these dynamics should be noted in the understanding of young supernova remnants. | how high energy fluxes may affect rayleigh-taylor instability growth in young supernova remnants |
group-iv monochalcogenides are a family of two-dimensional puckered materials with an orthorhombic structure that is comprised of polar layers. in this article, we use first principles calculations to show the multistability of monolayer sns and gese, two prototype materials where the direction of the puckering can be switched by application of tensile stress or electric field. furthermore, the two inequivalent valleys in momentum space, which are dictated by the puckering orientation, can be excited selectively using linearly polarized light, and this provides an additional tool to identify the polarization direction. our findings suggest that sns and gese monolayers may have observable ferroelectricity and multistability, with potential applications in information storage. | polarization and valley switching in monolayer group-iv monochalcogenides |
large dust reservoirs (up to approximately 108 m⊙) have been detected1-3 in galaxies out to redshift z ≃ 8, when the age of the universe was only about 600 myr. generating substantial amounts of dust within such a short timescale has proven challenging for theories of dust formation4,5 and has prompted the revision of the modelling of potential sites of dust production6-8, such as the atmospheres of asymptotic giant branch stars in low-metallicity environments, supernova ejecta and the accelerated growth of grains in the interstellar medium. however, degeneracies between different evolutionary pathways remain when the total dust mass of galaxies is the only available observable. here we report observations of the 2,175 å dust attenuation feature, which is well known in the milky way and galaxies at z ≲ 3 (refs. 9-11), in the near-infrared spectra of galaxies up to z ≃ 7, corresponding to the first billion years of cosmic time. the relatively short timescale implied for the formation of carbonaceous grains giving rise to this feature12 suggests a rapid production process, possibly in wolf-rayet stars or supernova ejecta. | carbonaceous dust grains seen in the first billion years of cosmic time |
object grb 221009a is the brightest gamma-ray burst (grb) detected in more than 50 yr of study. in this paper, we present observations in the x-ray and optical domains obtained by the grandma collaboration and the insight collaboration. we study the optical afterglow with empirical fitting using the grandma+hxmt-le data sets augmented with data from the literature up to 60 days. we then model numerically using a bayesian approach, and we find that the grb afterglow, extinguished by a large dust column, is most likely behind a combination of a large milky way dust column and moderate low-metallicity dust in the host galaxy. using the grandma+hxmt-le+xrt data set, we find that the simplest model, where the observed afterglow is produced by synchrotron radiation at the forward external shock during the deceleration of a top-hat relativistic jet by a uniform medium, fits the multiwavelength observations only moderately well, with a tension between the observed temporal and spectral evolution. this tension is confirmed when using the augmented data set. we find that the consideration of a jet structure (gaussian or power law), the inclusion of synchrotron self-compton emission, or the presence of an underlying supernova do not improve the predictions. placed in the global context of grb optical afterglows, we find that the afterglow of grb 221009a is luminous but not extraordinarily so, highlighting that some aspects of this grb do not deviate from the global known sample despite its extreme energetics and the peculiar afterglow evolution. | grandma and hxmt observations of grb 221009a: the standard luminosity afterglow of a hyperluminous gamma-ray burst-in gedenken an david alexander kann |
blue supergiant stars develop into core-collapse supernovae—one of the most energetic outbursts in the universe—when all nuclear burning fuel is exhausted in the stellar core. previous attempts have failed to explain observed explosions of such stars, which have a zero-age main-sequence mass of 50 m⊙ or more. here, we exploit the largely uncertain state of matter at high density, and connect the modelling of such stellar explosions with a first-order phase transition from nuclear matter to the quark-gluon plasma. the resulting energetic supernova explosions can account for a large variety of light curves, from peculiar type ii supernovae to superluminous events. the remnants are neutron stars with a quark matter core, known as hybrid stars, of about 2 m⊙ at birth. a galactic event of this kind could be observable owing to the release of a second neutrino burst. its observation would confirm such a first-order phase transition at densities relevant for astrophysics. | quark deconfinement as a supernova explosion engine for massive blue supergiant stars |
motivated by an updated compilation of observational hubble data (ohd) that consist of 51 points in the redshift range of 0.07 < z < 2.36, we study an interesting model known as cardassian that drives the late cosmic acceleration without a dark energy component. our compilation contains 31 data points measured with the differential age method by jimenez & loeb (2002), and 20 data points obtained from clustering of galaxies. we focus on two modified friedmann equations: the original cardassian (oc) expansion and the modified polytropic cardassian (mpc). the dimensionless hubble, e(z), and the deceleration parameter, q(z), are revisited in order to constrain the oc and mpc free parameters, first with the ohd and then contrasted with recent observations of type ia supernova (sn ia) using the compressed and full joint-light-analysis (jla) samples (betoule et al.). we also perform a joint analysis using the combination ohd plus compressed jla. our results show that the oc and mpc models are in agreement with the standard cosmology and naturally introduce a cosmological-constant-like extra term in the canonical friedmann equation with the capability of accelerating the universe without dark energy. | the cardassian expansion revisited: constraints from updated hubble parameter measurements and type ia supernova data |
the third observing run by lvc has brought the discovery of many compact binary coalescences. following the detection of the first binary neutron star merger in this run (ligo/virgo s190425z), we performed a dedicated follow-up campaign with the zwicky transient facility (ztf) and palomar gattini-ir telescopes. the initial skymap of this single-detector gravitational wave (gw) trigger spanned most of the sky observable from palomar observatory. covering 8000 deg2 of the initial skymap over the next two nights, corresponding to 46% integrated probability, ztf system achieved a depth of ≈21 m ab in g- and r-bands. palomar gattini-ir covered 2200 square degrees in j-band to a depth of 15.5 mag, including 32% integrated probability based on the initial skymap. the revised skymap issued the following day reduced these numbers to 21% for the ztf and 19% for palomar gattini-ir. we narrowed 338,646 ztf transient “alerts” over the first two nights of observations to 15 candidate counterparts. two candidates, ztf19aarykkb and ztf19aarzaod, were particularly compelling given that their location, distance, and age were consistent with the gw event, and their early optical light curves were photometrically consistent with that of kilonovae. these two candidates were spectroscopically classified as young core-collapse supernovae. the remaining candidates were ruled out as supernovae. palomar gattini-ir did not identify any viable candidates with multiple detections only after merger time. we demonstrate that even with single-detector gw events localized to thousands of square degrees, systematic kilonova discovery is feasible. | growth on s190425z: searching thousands of square degrees to identify an optical or infrared counterpart to a binary neutron star merger with the zwicky transient facility and palomar gattini-ir |
the phenomenological parametrizations of dark-energy (de) equations of state can be very helpful, since they allow for the investigation of its cosmological behavior despite the fact that its underlying theory is unknown. however, although there has been a large amount of research on de parametrizations which involve two or more free parameters, the one-parameter parametrizations seem to be underestimated. we perform a detailed observational confrontation of five one-parameter de models, with observational data from cosmic microwave background (cmb), joint light-curve analysis sample from supernovae type ia observations (jla), baryon acoustic oscillations (bao) distance measurements, and cosmic chronometers (cc). we find that all models favor a phantom de equation of state at present time, while they lead to h0 values in perfect agreement with its direct measurements and therefore they offer an alleviation to the h0-tension. finally, performing a bayesian analysis we show that although λ cdm cosmology is still favored, one-parameter de models have similar or better efficiency in fitting the data comparing to two-parameter de parametrizations, and thus they deserve a thorough investigation. | observational constraints on one-parameter dynamical dark-energy parametrizations and the h0 tension |
in a recent paper, we investigated possible systematic uncertainties related to the cepheid color-luminosity calibration method and their influence on the tension between the hubble constant as inferred from distances to type ia supernovae and the cosmic microwave background as measured with the planck satellite. here, we study the impact of other sources of uncertainty in the supernova distance ladder, including cepheid temperature and metallicity variations, supernova magnitudes, and gaia parallax distances. using cepheid data in 19 type ia supernova host galaxies from riess et al., anchor data from riess et al., and a set of recalibrated milky way cepheid distances, we obtain h 0 = 71.9 ± 2.2 km s-1 mpc-1, 2.0σ from the planck value. excluding cepheids with estimated color excesses \hat{e}(v-i)=0.15$ mag to mitigate the impact of the cepheid color-luminosity calibration, the inferred hubble constant is h 0 = 68.1 ± 2.6 km s-1 mpc-1, removing the tension with the planck value. | the hubble tension revisited: additional local distance ladder uncertainties |
we investigate the light-curve properties of a sample of 26 spectroscopically confirmed hydrogen-poor superluminous supernovae (slsne-i) in the palomar transient factory survey. these events are brighter than sne ib/c and sne ic-bl, on average, by about 4 and 2 mag, respectively. the peak absolute magnitudes of slsne-i in rest-frame g band span -22 ≲ mg≲ -20 mag, and these peaks are not powered by radioactive 56ni, unless strong asymmetries are at play. the rise timescales are longer for slsne than for normal sne ib/c, by roughly 10 days, for events with similar decay times. thus, slsne-i can be considered as a separate population based on photometric properties. after peak, slsne-i decay with a wide range of slopes, with no obvious gap between rapidly declining and slowly declining events. the latter events show more irregularities (bumps) in the light curves at all times. at late times, the slsn-i light curves slow down and cluster around the 56co radioactive decay rate. powering the late-time light curves with radioactive decay would require between 1 and 10 m ⊙ of ni masses. alternatively, a simple magnetar model can reasonably fit the majority of slsne-i light curves, with four exceptions, and can mimic the radioactive decay of 56co, up to ∼400 days from explosion. the resulting spin values do not correlate with the host-galaxy metallicities. finally, the analysis of our sample cannot strengthen the case for using slsne-i for cosmology. | light curves of hydrogen-poor superluminous supernovae from the palomar transient factory |
if the neutrino luminosity from the proto-neutron star formed during a massive star core collapse exceeds a critical threshold, a supernova (sn) results. using spherical quasi-static evolutionary sequences for hundreds of progenitors over a range of metallicities, we study how the explosion threshold maps onto observables, including the fraction of successful explosions, the neutron star (ns) and black hole (bh) mass functions, the explosion energies (e sn) and nickel yields (m ni), and their mutual correlations. successful explosions are intertwined with failures in a complex pattern that is not simply related to initial progenitor mass or compactness. we predict that progenitors with initial masses of 15 ± 1, 19 ± 1, and ~21-26 m ⊙ are most likely to form bhs, that the bh formation probability is non-zero at solar-metallicity and increases significantly at low metallicity, and that low luminosity, low ni-yield sne come from progenitors close to success/failure interfaces. we qualitatively reproduce the observed e sn-m ni correlation, we predict a correlation between the mean and width of the ns mass and e sn distributions, and that the means of the ns and bh mass distributions are correlated. we show that the observed mean ns mass of ~= 1.33 m ⊙ implies that the successful explosion fraction is higher than 0.35. overall, we show that the neutrino mechanism can in principle explain the observed properties of sne and their compact objects. we argue that the rugged landscape of progenitors and outcomes mandates that sn theory should focus on reproducing the wide ranging distributions of observed sn properties. | the landscape of the neutrino mechanism of core-collapse supernovae: neutron star and black hole mass functions, explosion energies, and nickel yields |
we explore the cosmological implications of anisotropic clustering measurements in configuration space of the final galaxy samples from data release 12 of the sloan digital sky survey iii baryon oscillation spectroscopic survey. we implement a new detailed modelling of the effects of non-linearities, bias and redshift-space distortions that can be used to extract unbiased cosmological information from our measurements for scales s ≳ 20 h-1 mpc. we combined the information from baryon oscillation spectroscopic survey (boss) with the latest cosmic microwave background (cmb) observations and type ia supernovae samples and found no significant evidence for a deviation from the λ cold dark matter (λcdm) cosmological model. in particular, these data sets can constrain the dark energy equation-of-state parameter to wde = -0.996 ± 0.042 when to be assumed time independent, the curvature of the universe to ωk = -0.0007 ± 0.0030 and the sum of the neutrino masses to ∑mν < 0.25 ev at 95 per cent confidence levels. we explore the constraints on the growth rate of cosmic structures assuming f(z) = ωm(z)γ and obtain γ = 0.609 ± 0.079, in good agreement with the predictions of general relativity of γ = 0.55. we compress the information of our clustering measurements into constraints on the parameter combinations dv(z)/rd, fap(z) and fσ8(z) at zeff = 0.38, 0.51 and 0.61 with their respective covariance matrices and find good agreement with the predictions for these parameters obtained from the best-fitting λcdm model to the cmb data from the planck satellite. this paper is part of a set that analyses the final galaxy clustering data set from boss. the measurements and likelihoods presented here are combined with others by alam et al. to produce the final cosmological constraints from boss. | the clustering of galaxies in the completed sdss-iii baryon oscillation spectroscopic survey: cosmological implications of the configuration-space clustering wedges |
in core-collapse supernovae or compact binary merger remnants, neutrino-neutrino refraction can spawn fast pair conversion of the type νeν¯ e↔νxν¯ x (with x =μ , τ ), governed by the angle-dependent density matrices of flavor lepton number. in a homogeneous and axially symmetric two-flavor system, all angle modes evolve coherently, and we show that the nonlinear equations of motion are formally equivalent to those of a gyroscopic pendulum. within this analogy, our main innovation is to identify the elusive characteristic of the lepton-number angle distribution that determines the depth of conversion with the "pendulum spin." the latter is given by the real part of the eigenfrequency resulting from the linear normal-mode analysis of the neutrino system. this simple analogy allows one to predict the depth of flavor conversion without solving the nonlinear evolution equations. our approach provides a novel diagnostic tool to explore the physics of nonlinear systems. | neutrino flavor pendulum reloaded: the case of fast pairwise conversion |
we present a new constraint on the hubble constant h 0 using a sample of well-localized gravitational-wave (gw) events detected during the first three ligo/virgo observing runs as dark standard sirens. in the case of dark standard sirens, a unique host galaxy is not identified, and the redshift information comes from the distribution of potential host galaxies. from the third ligo/virgo observing run detections, we add the asymmetric-mass binary black hole gw190412 and the high-confidence gw candidates s191204r, s200129m, and s200311bg to the sample of dark standard sirens analyzed in palmese et al. our sample contains the top 20% (based on localization) gw events and candidates to date with significant coverage by the dark energy spectroscopic instrument legacy survey. we combine the h 0 posterior for eight dark siren events, finding ${h}_{0}={79.8}_{-12.8}^{+19.1}\,\mathrm{km}\,{{\rm{s}}}^{-1}\,{\mathrm{mpc}}^{-1}$ (68% highest density interval) for a prior in h 0 uniform between [20, 140] km s-1 mpc-1. this result shows that a combination of eight well-localized dark sirens combined with an appropriate galaxy catalog is able to provide an h 0 constraint that is competitive (~20% versus 18% precision) with a single bright standard siren analysis (i.e., assuming the electromagnetic counterpart) using gw170817. when combining the posterior with that from gw170817, we obtain ${h}_{0}={72.77}_{-7.55}^{+11.0}\,\mathrm{km}\,{{\rm{s}}}^{-1}\,{\mathrm{mpc}}^{-1}$ . this result is broadly consistent with recent h 0 estimates from both the cosmic microwave background and supernovae. | a standard siren measurement of the hubble constant using gravitational-wave events from the first three ligo/virgo observing runs and the desi legacy survey |
galaxy-cluster gravitational lenses can magnify background galaxies by a total factor of up to 50. here we report an image of an individual star at redshift z = 1.49 (dubbed macs j1149 lensed star 1) magnified by more than ×2,000. a separate image, detected briefly 0.26″ from lensed star 1, is probably a counterimage of the first star demagnified for multiple years by an object of ≳3 solar masses in the cluster. for reasonable assumptions about the lensing system, microlensing fluctuations in the stars' light curves can yield evidence about the mass function of intracluster stars and compact objects, including binary fractions and specific stellar evolution and supernova models. dark-matter subhaloes or massive compact objects may help to account for the two images' long-term brightness ratio. | extreme magnification of an individual star at redshift 1.5 by a galaxy-cluster lens |
we present three-dimensional hydrodynamic simulations of the evolution of core-collapse supernovae (sn) from blast-wave initiation by the neutrino-driven mechanism to shock breakout from the stellar surface, using an axis-free yin-yang grid and considering two 15 m⊙ red supergiants (rsg) and two blue supergiants (bsg) of 15 m⊙ and 20 m⊙. we demonstrate that the metal-rich ejecta in homologous expansion still carry fingerprints of asymmetries at the beginning of the explosion, but the final metal distribution is massively affected by the detailed progenitor structure. the most extended and fastest metal fingers and clumps are correlated with the biggest and fastest-rising plumes of neutrino-heated matter, because these plumes most effectively seed the growth of rayleigh-taylor (rt) instabilities at the c+o/he and he/h composition-shell interfaces after the passage of the sn shock. the extent of radial mixing, global asymmetry of the metal-rich ejecta, rt-induced fragmentation of initial plumes to smaller-scale fingers, and maximum ni and minimum h velocities depend not only on the initial asphericity and explosion energy (which determine the shock and initial ni velocities), but also on the density profiles and widths of c+o core and he shell and on the density gradient at the he/h transition, which leads to unsteady shock propagation and the formation of reverse shocks. both rsg explosions retain a large global metal asymmetry with pronounced clumpiness and substructure, deep penetration of ni fingers into the h-envelope (with maximum velocities of 4000-5000 km s-1 for an explosion energy around 1.5 bethe) and efficient inward h-mixing. while the 15 m⊙ bsg shares these properties (maximum ni speeds up to ~3500 km s-1), the 20 m⊙ bsg develops a much more roundish geometry without pronounced metal fingers (maximum ni velocities only ~2200 km s-1) because of reverse-shock deceleration and insufficient time for strong rt growth and fragmentation at the he/h interface. | three-dimensional simulations of core-collapse supernovae: from shock revival to shock breakout |
we present the first successful simulation of a neutrino-driven supernova explosion in three dimensions (3d), using the prometheus-vertex code with an axis-free yin-yang grid and a sophisticated treatment of three-flavor, energy-dependent neutrino transport. the progenitor is a nonrotating, zero-metallicity 9.6 {{m}⊙ } star with an iron core. while in spherical symmetry outward shock acceleration sets in later than 300 ms after bounce, a successful explosion starts at ∼130 ms postbounce in two dimensions (2d). the 3d model explodes at about the same time but with faster shock expansion than in 2d and a more quickly increasing and roughly 10% higher explosion energy of >1050 erg. the more favorable explosion conditions in 3d are explained by lower temperatures and thus reduced neutrino emission in the cooling layer below the gain radius. this moves the gain radius inward and leads to a bigger mass in the gain layer, whose larger recombination energy boosts the explosion energy in 3d. these differences are caused by less coherent, less massive, and less rapid convective downdrafts associated with postshock convection in 3d. the less violent impact of these accretion downflows in the cooling layer produces less shock heating and therefore diminishes energy losses by neutrino emission. we thus have, for the first time, identified a reduced mass accretion rate, lower infall velocities, and a smaller surface filling factor of convective downdrafts as consequences of 3d postshock turbulence that facilitate neutrino-driven explosions and strengthen them compared to the 2d case. | neutrino-driven supernova of a low-mass iron-core progenitor boosted by three-dimensional turbulent convection |
one of the most exciting and pressing issues in cosmology today is the discrepancy between some measurements of the local hubble constant and other values of the expansion rate inferred from the observed temperature and polarization fluctuations in the cosmic microwave background (cmb) radiation. resolving these differences holds the potential for the discovery of new physics beyond the standard model of cosmology: lambda cold dark matter (λcdm), a successful model that has been in place for more than 20 years. given both the fundamental significance of this outstanding discrepancy, and the many-decades-long effort to increase the accuracy of the extragalactic distance scale, it is critical to demonstrate that the local measurements are convincingly free from residual systematic errors. we review the progress over the past quarter century in measurements of the local value of the hubble constant, and discuss remaining challenges. particularly exciting are new data from the james webb space telescope (jwst), for which we present an overview of our program and first results. we focus in particular on cepheids and the tip of the red giant branch (trgb) stars, as well as a relatively new method, the jagb (j-region asymptotic giant branch) method, all methods that currently exhibit the demonstrably smallest statistical and systematic uncertainties. jwst is delivering high-resolution near-infrared imaging data to both test for and to address directly several of the systematic uncertainties that have historically limited the accuracy of extragalactic distance scale measurements (e.g., the dimming effects of interstellar dust, chemical composition differences in the atmospheres of stars, and the crowding and blending of cepheids contaminated by nearby previously unresolved stars). for the first galaxy in our program, ngc 7250, the high-resolution jwst images demonstrate that many of the cepheids observed with the hubble space telescope (hst) are significantly crowded by nearby neighbors. avoiding the more significantly crowded variables, the scatter in the jwst near-infrared (nir) cepheid pl relation is decreased by a factor of two compared to those from hst, illustrating the power of jwst for improvements to local measurements of h 0. ultimately, these data will either confirm the standard model, or provide robust evidence for the inclusion of additional new physics. | progress in direct measurements of the hubble constant |
a dark photon is a well-motivated new particle which, as a component of an associated dark sector, could explain dark matter. one strong limit on dark photons arises from excessive cooling of supernovae. we point out that even at couplings where too few dark photons are produced in supernovae to violate the cooling bound, they can be observed directly through their decays. supernovae produce dark photons which decay to positrons, giving a signal in the 511 kev annihilation line observed by spi/integral. further, prompt gamma-ray emission by these decaying dark photons gives a signal for gamma-ray telescopes. existing grs observations of sn1987a already constrain this, and a future nearby sn could provide a detection. finally, dark photon decays from extragalactic sn would produce a diffuse flux of gamma rays observable by detectors such as smm and heao-1. together these observations can probe dark photon couplings several orders of magnitude beyond current constraints for masses of roughly 1-100 mev. | observable signatures of dark photons from supernovae |
the combination of baryonic acoustic oscillation (bao) data together with light element abundance measurements from big bang nucleosynthesis (bbn) has been shown to constrain the cosmological expansion history to an unprecedented degree. using the newest luna data and dr16 data from sdss, the bao+bbn probe puts tight constraints on the hubble constant (h 0 = 67.6 ± 1.0 km/s/mpc), resulting in a 3.7σ tension with the local distance ladder determination from sh0es in a λcdm model. in the updated bao data the high- and low-redshift subsets are mutually in excellent agreement, and there is no longer a mild internal tension to artificially enhance the constraints. adding the recently-developed shapefit analysis yields h 0 = 68.3 ± 0.7 km/s/mpc (3.8σ tension). for combinations with additional data sets, there is a strong synergy with the sound horizon information of the cosmic microwave background, which leads to one of the tightest constraints to date, h 0 = 68.30 ± 0.45 km/s/mpc, in 4.2σ tension with sh0es. the region preferred by this combination is perfectly in agreement with that preferred by shapefit. the addition of supernova data also yields a 4.2σ tension with sh0es for pantheon, and a 3.5σ tension for pantheonplus. finally, we show that there is a degree of model-dependence of the bao+bbn constraints with respect to early-time solutions of the hubble tension, and the loss of constraining power in extended models depends on whether the model can be additionally constrained from bbn observations. | bao+bbn revisited - growing the hubble tension with a 0.7 km/s/mpc constraint |
in this white paper, we outline some of the scientific opportunities and challenges related to detection and reconstruction of low-energy (less than 100 mev) signatures in liquid argon time-projection chamber (lartpc) detectors. key takeaways are summarized as follows. 1) lartpcs have unique sensitivity to a range of physics and astrophysics signatures via detection of event features at and below the few tens of mev range. 2) low-energy signatures are an integral part of gev-scale accelerator neutrino interaction final states, and their reconstruction can enhance the oscillation physics sensitivities of lartpc experiments. 3) bsm signals from accelerator and natural sources also generate diverse signatures in the low-energy range, and reconstruction of these signatures can increase the breadth of bsm scenarios accessible in lartpc-based searches. 4) neutrino interaction cross sections and other nuclear physics processes in argon relevant to sub-hundred-mev lartpc signatures are poorly understood. improved theory and experimental measurements are needed. pion decay-at-rest sources and charged particle and neutron test beams are ideal facilities for experimentally improving this understanding. 5) there are specific calibration needs in the low-energy range, as well as specific needs for control and understanding of radiological and cosmogenic backgrounds. 6) novel ideas for future lartpc technology that enhance low-energy capabilities should be explored. these include novel charge enhancement and readout systems, enhanced photon detection, low radioactivity argon, and xenon doping. 7) low-energy signatures, whether steady-state or part of a supernova burst or larger gev-scale event topology, have specific triggering, daq and reconstruction requirements that must be addressed outside the scope of conventional gev-scale data collection and analysis pathways. | low-energy physics in neutrino lartpcs |
we present four ab initio axisymmetric core-collapse supernova simulations initiated from 12, 15, 20, and 25 {m}⊙zero-age main sequence progenitors. all of the simulations yield explosions and have been evolved for at least 1.2 s after core bounce and 1 s after material first becomes unbound. these simulations were computed with our chimera code employing rbr spectral neutrino transport, special and general relativistic transport effects, and state-of-the-art neutrino interactions. continuing the evolution beyond 1 s after core bounce allows the explosions to develop more fully and the processes involved in powering the explosions to become more clearly evident. we compute explosion energy estimates, including the negative gravitational binding energy of the stellar envelope outside the expanding shock, of 0.34, 0.88, 0.38, and 0.70 bethe (b ≡ {10}51 erg) and increasing at 0.03, 0.15, 0.19, and 0.52 {\text{b s}}-1, respectively, for the 12, 15, 20, and 25 {m}⊙models at the endpoint of this report. we examine the growth of the explosion energy in our models through detailed analyses of the energy sources and flows. we discuss how the explosion energies may be subject to stochastic variations as exemplfied by the effect of the explosion geometry of the 20 {m}⊙model in reducing its explosion energy. we compute the proto-neutron star masses and kick velocities. we compare our results for the explosion energies and ejected {}56{ni} masses against some observational standards despite the large error bars in both models and observations. | the development of explosions in axisymmetric ab initio core-collapse supernova simulations of 12-25 m stars |
we develop a new phenomenological model that addresses current tensions between observations of the early and late universe. our scenario features: (i) a decaying dark energy fluid (dde) with a transition at z ∼5 ,000 , to raise today's value of the hubble parameter, and (ii) an ultralight axion (ula), which starts oscillating at z ≳104, to suppress the matter power spectrum. our markov chain monte carlo analyses show that such a dark sector model fits a combination of cosmic microwave background (cmb), baryon acoustic oscillations, and large scale structure (lss) data slightly better than the λ cdm model, while importantly reducing both the h0 and s8 tensions with late universe probes (≲3 σ ). combined with measurements from cosmic shear surveys, we find that the discrepancy on s8 is reduced to the 1.4 σ level. adding local supernovae measurements, we find that the h0 and s8 tensions are reduced to the 1.4 σ and 1.2 σ levels respectively, with a significant improvement δ χ2≃-18 compared to the λ cdm model. with this complete dataset, the dde and ula are detected at ≃4 σ and ≃2 σ , respectively. we discuss a possible particle physics realization of this model, with a dark confining gauge sector and its associated axion, although embedding the full details within microphysics remains an urgent open question. our scenario will be decisively probed with future cmb and lss surveys. | dark sector to restore cosmological concordance |
we present a suite of 3d multiphysics mhd simulations following star formation in isolated turbulent molecular gas discs ranging from 5 to 500 parsecs in radius. these simulations are designed to survey the range of surface densities between those typical of milky way giant molecular clouds (gmcs) ({∼ } 10^2 {m_{\odot } pc^{-2}}) and extreme ultraluminous infrared galaxy environments ({∼ } 10^4 {m_{\odot } pc^{-2}}) so as to map out the scaling of the cloud-scale star formation efficiency (sfe) between these two regimes. the simulations include prescriptions for supernova, stellar wind, and radiative feedback, which we find to be essential in determining both the instantaneous per-freefall (ɛff) and integrated (ɛint) star formation efficiencies. in all simulations, the gas discs form stars until a critical stellar surface density has been reached and the remaining gas is blown out by stellar feedback. we find that surface density is a good predictor of ɛint, as suggested by analytic force balance arguments from previous works. sfe eventually saturates to ∼1 at high surface density. we also find a proportional relationship between ɛff and ɛint, implying that star formation is feedback-moderated even over very short time-scales in isolated clouds. these results have implications for star formation in galactic discs, the nature and fate of nuclear starbursts, and the formation of bound star clusters. the scaling of ɛff with surface density is not consistent with the notion that ɛff is always ∼ 1 per cent on the scale of gmcs, but our predictions recover the ∼ 1 per cent value for gmc parameters similar to those found in spiral galaxies, including our own. | when feedback fails: the scaling and saturation of star formation efficiency |
it has been speculated for a long time that neutrinos from a supernova (sn) may undergo fast flavor conversions near the collapsed stellar core. we perform a detailed study of this intriguing possibility, for the first time analyzing two time-dependent state-of-the-art three-dimensional (3d) sn models of 9 m⊙ and 20 m⊙ from recent papers of glas et al. both models were computed with multidimensional three-flavor neutrino transport based on a two-moment solver, and both exhibit the presence of the so-called lepton-number emission self-sustained asymmetry (lesa). the transport solution does not provide the angular distributions of the flavor-dependent neutrino fluxes, which are crucial to track the fast flavor instability. to overcome this limitation, we use a recently proposed approach based on the angular moments of the energy-integrated electron lepton-number distribution up to second order, i.e., angle-energy integrals of the difference between νe and ν¯e phase-space distributions multiplied by corresponding powers of the unit vector of the neutrino velocity. with this method we find the possibility of fast neutrino flavor instability at radii smaller than ∼20 km , which is well interior to the neutrinosphere where neutrinos are still in the diffusive and near-equilibrium regime. our results confirm recent observations in a two-dimensional (2d) (axisymmetric) sn model and in 2d and 3d models with a fixed matter background, which were computed with boltzmann neutrino transport. however, the flavor unstable locations are not isolated points as discussed previously, but thin skins surrounding volumes where ν¯e are more abundant than νe. these volumes grow with time and appear first in the convective layer of the proto-neutron star (pns), where a decreasing electron fraction and high temperatures favor the occurrence of regions with negative neutrino chemical potential. since the electron fraction remains higher in the lesa dipole direction, where convective lepton-number transport out from the nonconvective pns core slows down the deleptonization, flavor unstable conditions become more widespread in the opposite hemisphere. this interesting phenomenon deserves further investigation, since its impact on sn modeling and possible consequences for sn dynamics and neutrino observations are presently unclear. | fast neutrino flavor instability in the neutron-star convection layer of three-dimensional supernova models |
collective pair conversion νeν¯ e↔νxν¯ x by forward scattering, where x =μ or τ , may be generic for supernova neutrino transport. depending on the local angular intensity of the electron lepton number carried by neutrinos, the conversion rate can be "fast," i.e., of the order of √{2 }gf(nνe-nν¯e)≫δ matm2/2 e . we present a novel approach to understand these phenomena: a dispersion relation for the frequency and wave number (ω ,k ) of disturbances in the mean field of νeνx flavor coherence. runaway solutions occur in "dispersion gaps," i.e., in "forbidden" intervals of ω and/or k where propagating plane waves do not exist. we stress that the actual solutions also depend on the initial and/or boundary conditions, which need to be further investigated. | fast pairwise conversion of supernova neutrinos: a dispersion relation approach |
turbulence is ubiquitous in molecular clouds (mcs), but its origin is still unclear because mcs are usually assumed to live longer than the turbulence dissipation time. interstellar medium (ism) turbulence is likely driven by supernova (sn) explosions, but it has never been demonstrated that sn explosions can establish and maintain a turbulent cascade inside mcs consistent with the observations. in this work, we carry out a simulation of sn-driven turbulence in a volume of (250 pc)3, specifically designed to test if sn driving alone can be responsible for the observed turbulence inside mcs. we find that sn driving establishes a velocity scaling consistent with the usual scaling laws of supersonic turbulence, suggesting that previous idealized simulations of mc turbulence, driven with a random, large-scale volume force, were correctly adopted as appropriate models for mc turbulence, despite the artificial driving. we also find that the same scaling laws extend to the interiors of mcs, and that the velocity-size relation of the mcs selected from our simulation is consistent with that of mcs from the outer-galaxy survey, the largest mc sample available. the mass-size relation and the mass and size probability distributions also compare successfully with those of the outer galaxy survey. finally, we show that mc turbulence is super-alfvénic with respect to both the mean and rms magnetic-field strength. we conclude that mc structure and dynamics are the natural result of sn-driven turbulence. | supernova driving. i. the origin of molecular cloud turbulence |
the question of what ingredients characterize the quasisteady state of fast neutrino-flavor conversion (ffc) is one of the longstanding riddles in neutrino oscillation. addressing this issue is necessary for accurate modeling of neutrino transport in core-collapse supernova and binary neutron star merger. recent numerical simulations of ffc have shown, however, that the quasisteady state is sensitively dependent on boundary conditions in space, and the physical reason for the dependence is not clear at present. in this study, we provide a physical interpretation of this issue based on arguments with stability and conservation laws. the stability can be determined by the disappearance of electron neutrino-lepton number-heavy-leptonic one (eln-xln) angular crossings, and we also highlight two conserved quantities characterizing the quasisteady state of ffc: (1) lepton number conservation along each neutrino trajectory and (2) conservation law associated with angular moments, depending on boundary conditions, for each flavor of neutrinos. we present an analytic prescription that matches the results of the nonlinear simulations presented in this work. this study represents a major step forward to a unified picture determining asymptotic states of ffcs. | characterizing quasisteady states of fast neutrino-flavor conversion by stability and conservation laws |
in this work, we study a cosmological model of bianchi type-i universe in teleparallel gravity for a perfect fluid. to obtain the cosmological solution of the model, we assume that the deceleration parameter (dp) is a linear function of the hubble parameter h i.e. q = -1 + βh (where β as a positive constant). consequently, we get a model of our universe, where it goes from the initial phase of deceleration to the current phase of acceleration. we have discussed some physical and geometric properties such as hubble parameter, dp, energy density, pressure, and equation of state parameter and study their behavior graphically in terms of redshift and compare it with observational data such as type ia supernovae. we also discussed the behavior of other parameters such as the jerk parameter, statefinder parameters and we tested the validity of the model by studying the stability analysis and energy conditions. | stability analysis of anisotropic bianchi type-i cosmological model in teleparallel gravity |
we present updated constraints on the variation of the fine structure constant, αem, and effective electron rest mass, me, during the cosmological recombination era. these two fundamental constants directly affect the ionization history at redshift z ≃ 1100 and, thus, modify the temperature and polarization anisotropies of the cosmic microwave background (cmb) measured precisely with planck . the constraints on αem tighten slightly due to improved planck 2018 polarization data but otherwise remain similar to previous cmb analysis. however, a comparison with the 2015 constraints reveals a mildly discordant behaviour for me, which from cmb data alone is found below its local value. adding baryon acoustic oscillation data brings me back to the fiducial value, m_e=(1.0078± 0.0067) m_e,0, and also drives the hubble parameter to h0 = 69.1 ± 1.2(in units of {km s^{-1} mpc^{-1} }). further adding supernova data yields m_e=(1.0190± 0.0055) m_e,0 with h0 = 71.24 ± 0.96. we perform several comparative analyses using the latest cosmological recombination calculations to further understand the various effects. our results indicate that a single-parameter extension allowing a slightly increased value of me (≃3.5σ above me, 0) could play a role in the hubble tension. | updated fundamental constant constraints from planck 2018 data and possible relations to the hubble tension |
the study of stellar-remnant black holes (bh) in dense stellar clusters is now in the spotlight, especially due to their intrinsic ability to form binary black holes (bbh) through dynamical encounters, which potentially coalesce via gravitational-wave (gw) radiation. in this work, which is a continuation from a recent study (paper i), additional models of compact stellar clusters with initial masses ≲ 105 m⊙ and also those with small fractions of primordial binaries (≲ 10 per cent) are evolved for long term, applying the direct n-body approach, assuming state-of-the-art stellar-wind and remnant-formation prescriptions. that way, a substantially broader range of computed models than that in paper i is achieved. as in paper i, the general-relativistic bbh mergers continue to be mostly mediated by triples that are bound to the clusters rather than happen among the ejected bbhs. in fact, the number of such in situ bbh mergers, per cluster, tends to increase significantly with the introduction of a small population of primordial binaries. despite the presence of massive primordial binaries, the merging bbhs, especially the in situ ones, are found to be exclusively dynamically assembled and hence would be spin-orbit misaligned. the bbhs typically traverse through both the lisa's and the ligo's detection bands, being audible to both instruments. the 'dynamical heating' of the bhs keeps the electron-capture-supernova (ecs) neutron stars (ns) from effectively mass segregating and participating in exchange interactions; the dynamically active bhs would also exchange into any ns binary within ≲1 gyr. such young massive and open clusters have the potential to contribute to the dynamical bbh merger detection rate to a similar extent as their more massive globular-cluster counterparts. | stellar-mass black holes in young massive and open stellar clusters and their role in gravitational-wave generation - ii |
previously we used the nearby supernova factory sample to show that type ia supernovae (sne ia) having locally star-forming environments are dimmer than sne ia having locally passive environments. here we use the constitution sample together with host galaxy data from galex to independently confirm that result. the effect is seen using both the salt2 and mlcs2k2 lightcurve fitting and standardization methods, with brightness differences of 0.094 ± 0.037 mag for salt2 and 0.155 ± 0.041 mag for mlcs2k2 with rv = 2.5. when combined with our previous measurement the effect is 0.094 ± 0.025 mag for salt2. if the ratio of these local sn ia environments changes with redshift or sample selection, this can lead to a bias in cosmological measurements. we explore this issue further, using as an example the direct measurement of h 0. galex observations show that the sne ia having standardized absolute magnitudes calibrated via the cepheid period-luminosity relation using the hubble space telescope originate in predominately star-forming environments, whereas only ~50% of the hubble-flow comparison sample have locally star-forming environments. as a consequence, the h 0 measurement using sne ia is currently overestimated. correcting for this bias, we find a value of h_0{corr}= 70.6 ± 2.6 km s-1 mpc-1 when using the lmc distance, milky way parallaxes, and the ngc 4258 megamaser as the cepheid zero point, and 68.8 ± 3.3 km s-1 mpc-1 when only using ngc 4258. our correction brings the direct measurement of h 0 within ~1 σ of recent indirect measurements based on the cosmic microwave background power spectrum. | confirmation of a star formation bias in type ia supernova distances and its effect on the measurement of the hubble constant |
we report the discovery of asassn-15lh (sn 2015l), which we interpret as the most luminous supernova yet found. at redshift z = 0.2326, asassn-15lh reached an absolute magnitude of mu,ab = -23.5 ± 0.1 and bolometric luminosity lbol = (2.2 ± 0.2) × 1045 ergs s-1, which is more than twice as luminous as any previously known supernova. it has several major features characteristic of the hydrogen-poor super-luminous supernovae (slsne-i), whose energy sources and progenitors are currently poorly understood. in contrast to most previously known slsne-i that reside in star-forming dwarf galaxies, asassn-15lh appears to be hosted by a luminous galaxy (mk ≈ -25.5) with little star formation. in the 4 months since first detection, asassn-15lh radiated (1.1 ± 0.2) × 1052 ergs, challenging the magnetar model for its engine. | asassn-15lh: a highly super-luminous supernova |
time-domain science has undergone a revolution over the past decade, with tens of thousands of new supernovae (sne) discovered each year. however, several observational domains, including sne within days or hours of explosion and faint, red transients, are just beginning to be explored. here we present the young supernova experiment (yse), a novel optical time-domain survey on the pan-starrs telescopes. our survey is designed to obtain well-sampled griz light curves for thousands of transient events up to z ≈ 0.2. this large sample of transients with four-band light curves will lay the foundation for the vera c. rubin observatory and the nancy grace roman space telescope, providing a critical training set in similar filters and a well-calibrated low-redshift anchor of cosmologically useful sne ia to benefit dark energy science. as the name suggests, yse complements and extends other ongoing time-domain surveys by discovering fast-rising sne within a few hours to days of explosion. yse is the only current four-band time-domain survey and is able to discover transients as faint as ∼21.5 mag in gri and ∼20.5 mag in z, depths that allow us to probe the earliest epochs of stellar explosions. yse is currently observing approximately 750 deg2 of sky every 3 days, and we plan to increase the area to 1500 deg2 in the near future. when operating at full capacity, survey simulations show that yse will find ∼5000 new sne per year and at least two sne within 3 days of explosion per month. to date, yse has discovered or observed 8.3% of the transient candidates reported to the international astronomical union in 2020. we present an overview of yse, including science goals, survey characteristics, and a summary of our transient discoveries to date. | the young supernova experiment: survey goals, overview, and operations |
large-scale outflows in star-forming galaxies are observed to be ubiquitous and are a key aspect of theoretical modeling of galactic evolution, the focus of the simulating multiscale astrophysics to understand galaxies (smaug) project. gas blown out from galactic disks, similar to gas within galaxies, consists of multiple phases with large contrasts of density, temperature, and other properties. to study multiphase outflows as emergent phenomena, we run a suite of rougly parsec-resolution local galactic disk simulations using the tigress framework. explicit modeling of the interstellar medium (ism), including star formation and self-consistent radiative heating plus supernova feedback, regulates ism properties and drives the outflow. we investigate the scaling of outflow mass, momentum, energy, and metal loading factors with galactic disk properties, including star formation rate (sfr) surface density (σsfr ∼ 10-4 - 1 m⊙ kpc-2 yr-1), gas surface density ( ${{\rm{\sigma }}}_{\mathrm{gas}}\sim 1\mbox{--}100\,{m}_{\odot }\,{\mathrm{pc}}^{-2}$ ), and total midplane pressure (or weight; ${p}_{\mathrm{mid}}\approx { \mathcal w }\sim {10}^{3}\mbox{--}{10}^{6}\,{k}_{b}\,{\mathrm{cm}}^{-3}\,{\rm{k}}$ ). the main components of outflowing gas are mass-delivering cool gas (t ∼ 104 k) and energy/metal-delivering hot gas (t ≳ 106 k). cool mass outflow rates measured at outflow launch points (one or two scale heights $\sim 300\,\mathrm{pc}\mbox{--}1\,\mathrm{kpc}$ ) are 1-100 times the sfr (decreasing with σsfr), although in massive galaxies most mass falls back owing to insufficient outflow velocity. the hot galactic outflow carries mass comparable to 10% of the sfr, together with 10%-20% of the energy and 30%-60% of the metal mass injected by sn feedback. importantly, our analysis demonstrates that in any physically motivated cosmological wind model it is crucial to include at least two distinct thermal wind components. | first results from smaug: characterization of multiphase galactic outflows from a suite of local star-forming galactic disk simulations |
separating the components of redshift due to expansion and peculiar motion in the nearby universe (z < 0.1) is critical for using type ia supernovae (sne ia) to measure the hubble constant (h 0) and the equation-of-state parameter of dark energy (w). here, we study the two dominant "motions" contributing to nearby peculiar velocities: large-scale, coherent-flow (cf) motions and small-scale motions due to gravitationally associated galaxies deemed to be in a galaxy group. we use a set of 584 low-z sne from the pantheon+ sample, and evaluate the efficacy of corrections to these motions by measuring the improvement of sn distance residuals. we study multiple methods for modeling the large and small-scale motions and show that, while group assignments and cf corrections individually contribute to small improvements in hubble residual scatter, the greatest improvement comes from the combination of the two (relative standard deviation of the hubble residuals, rel. sd, improves from 0.167 to 0.157 mag). we find the optimal flow corrections derived from various local density maps significantly reduce hubble residuals while raising h 0 by ~0.4 km s-1 mpc-1 as compared to using cmb redshifts, disfavoring the hypothesis that unrecognized local structure could resolve the hubble tension. we estimate that the systematic uncertainties in cosmological parameters after optimally correcting redshifts are 0.06-0.11 km s-1 mpc-1 in h 0 and 0.02-0.03 in w which are smaller than the statistical uncertainties for these measurements: 1.5 km s-1 mpc-1 for h 0 and 0.04 for w. | the pantheon+ analysis: evaluating peculiar velocity corrections in cosmological analyses with nearby type ia supernovae |
muons can be created in nascent neutron stars (nss) due to the high electron chemical potentials and the high temperatures. because of their relatively lower abundance compared to electrons, their role has so far been ignored in numerical simulations of stellar core collapse and ns formation. however, the appearance of muons softens the ns equation of state, triggers faster ns contraction, and thus leads to higher luminosities and mean energies of the emitted neutrinos. this strengthens the postshock heating by neutrinos and can facilitate explosions by the neutrino-driven mechanism. | muon creation in supernova matter facilitates neutrino-driven explosions |
recent analyses suggest that distance residuals measured from type ia supernovae (sne ia) are correlated with local host galaxy properties within a few kiloparsecs of the sn explosion. however, the well-established correlation with global host galaxy properties is nearly as significant, with a shift of 0.06 mag across a low to high mass boundary (the mass step). here, with 273 sne ia at z < 0.1, we investigate whether the stellar masses and rest-frame u - g colors of regions within 1.5 kpc of the sn ia explosion site are significantly better correlated with sn distance measurements than global properties or properties measured at random locations in sn hosts. at ≲2σ significance, local properties tend to correlate with distance residuals better than properties at random locations, though despite using the largest low-z sample to date, we cannot definitively prove that a local correlation is more significant than a random correlation. our data hint that sne observed by surveys that do not target a pre-selected set of galaxies may have a larger local mass step than sne from surveys that do, an increase of 0.071 ± 0.036 mag (2.0σ). we find a 3σ local mass step after global mass correction, evidence that sne ia should be corrected for their local mass, but we note that this effect is insignificant in the targeted low-z sample. only the local mass step remains significant at >2σ after global mass correction, and we conservatively estimate a systematic shift in h 0 measurements of -0.14 km s-1 mpc-1 with an additional uncertainty of 0.14 km s-1 mpc-1, ∼10% of the present uncertainty. | should type ia supernova distances be corrected for their local environments? |
we study gravitational waves (gws) from a set of 2d multigroup neutrino radiation hydrodynamic simulations of core-collapse supernovae (ccsne). our goal is to systematize the current knowledge about the post-bounce ccsn gw signal and recognize the templatable features that could be used by the ground-based laser interferometers. we demonstrate that, starting from ∼400 ms after core bounce, the dominant gw signal represents the fundamental quadrupole (l = 2) oscillation mode (f-mode) of the proto-neutron star (pns), which can be accurately reproduced by a linear perturbation analysis of the angle-averaged pns profile. before that, in the time interval between ∼200 and ∼400 ms after bounce, the dominant mode has two radial nodes and represents a g-mode. we associate the high-frequency noise in the gw spectrograms above the main signal with p-modes, while below the dominant frequency there is a region with very little power. the collection of models presented here summarizes the dependence of the ccsn gw signal on the progenitor mass, equation of state, many-body corrections to the neutrino opacity, and rotation. weak dependence of the dominant gw frequency on the progenitor mass motivates us to provide a simple fit for it as a function of time, which can be used as a prior when looking for ccsn candidates in the ligo data. | the gravitational wave signal from core-collapse supernovae |
we study a power-law f (r) gravity with an early dark energy term, that can describe both the early-time and the late-time acceleration of the universe. we confront this scenario with recent observational data including the pantheon type ia supernovae, measurements of the hubble parameter h (z) (cosmic chronometers), data from baryon acoustic oscillations and standard rulers data from the cosmic microwave background (cmb) radiation. the model demonstrates some achievements in confronting with these observations and can be compared with the λ-cold-dark-matter model. in particular, in both models we obtain very close estimates for the hubble constant h0, but it is not true for ωm0 . the early dark energy term supports viability of the considered f (r) gravity model. | early dark energy with power-law f(r) gravity |
we present the results from a search for gravitational-wave transients associated with core-collapse supernovae observed optically within 30 mpc during the third observing run of advanced ligo and advanced virgo. no gravitational wave associated with a core-collapse supernova has been identified. we then report the detection efficiency for a variety of possible gravitational-wave emissions. for neutrino-driven explosions, the distance at which we reach 50% detection efficiency is up to 8.9 kpc, while more energetic magnetorotationally-driven explosions are detectable at larger distances. the distance reaches for selected models of the black hole formation, and quantum chromodynamics phase transition are also provided. we then constrain the core-collapse supernova engine across a wide frequency range from 50 hz to 2 khz. the upper limits on gravitational-wave energy and luminosity emission are at low frequencies down to $10^{-4}\,m_\odot c^2$ and $5 \times 10^{-4}\,m_\odot c^2$/s, respectively. the upper limits on the proto-neutron star ellipticity are down to 5 at high frequencies. finally, by combining the results obtained with the data from the first and second observing runs of ligo and virgo, we improve the constraints of the parameter spaces of the extreme emission models. specifically, the proto-neutron star ellipticities for the long-lasting bar mode model are down to 1 for long emission (1 s) at high frequency. | an optically targeted search for gravitational waves emitted by core-collapse supernovae during the third observing run of advanced ligo and advanced virgo |
we report the first search result for the flux of astrophysical electron antineutrinos for energies ${ \mathcal o }(10)\,\mathrm{mev}$ in the gadolinium-loaded super-kamiokande (sk) detector. in 2020 june, gadolinium was introduced to the ultrapure water of the sk detector in order to detect neutrons more efficiently. in this new experimental phase, sk-gd, we can search for electron antineutrinos via inverse beta decay with efficient background rejection thanks to the high efficiency of the neutron tagging technique. in this paper, we report the result for the initial stage of sk-gd, during 2020 august 26, and 2022 june 1 with a 22.5 × 552 kton · day exposure at 0.01% gd mass concentration. no significant excess over the expected background in the observed events is found for the neutrino energies below 31.3 mev. thus, the flux upper limits are placed at the 90% confidence level. the limits and sensitivities are already comparable with the previous sk result with pure water (22.5 × 2970 kton · day) owing to the enhanced neutron tagging. operation with gd increased to 0.03% started in 2022 june. | search for astrophysical electron antineutrinos in super-kamiokande with 0.01% gadolinium-loaded water |
we present observations of sn 2021csp, the second example of a newly identified type of supernova (sn) hallmarked by strong, narrow, p cygni carbon features at early times (type icn). the sn appears as a fast and luminous blue transient at early times, reaching a peak absolute magnitude of -20 within 3 days due to strong interaction between fast sn ejecta (v ≈ 30,000 km s-1) and a massive, dense, fast-moving c/o wind shed by the wc-like progenitor months before explosion. the narrow-line features disappear from the spectrum 10-20 days after explosion and are replaced by a blue continuum dominated by broad fe features, reminiscent of type ibn and iin supernovae and indicative of weaker interaction with more extended h/he-poor material. the transient then abruptly fades ~60 days post-explosion when interaction ceases. deep limits at later phases suggest minimal heavy-element nucleosynthesis, a low ejecta mass, or both, and imply an origin distinct from that of classical type ic sne. we place sn 2021csp in context with other fast-evolving interacting transients, and discuss various progenitor scenarios: an ultrastripped progenitor star, a pulsational pair-instability eruption, or a jet-driven fallback sn from a wolf-rayet (w-r) star. the fallback scenario would naturally explain the similarity between these events and radio-loud fast transients, and suggests a picture in which most stars massive enough to undergo a w-r phase collapse directly to black holes at the end of their lives. | the type icn sn 2021csp: implications for the origins of the fastest supernovae and the fates of wolf-rayet stars |
using spectral line observations of hnco, n2h+, and hnc, we investigate the kinematics of dense gas in the central ∼250 pc of the galaxy. we present scouse (semi-automated multi-component universal spectral-line fitting engine), a line-fitting algorithm designed to analyse large volumes of spectral line data efficiently and systematically. unlike techniques which do not account for complex line profiles, scouse accurately describes the {l, b, vlsr} distribution of central molecular zone (cmz) gas, which is asymmetric about sgr a* in both position and velocity. velocity dispersions range from 2.6 km s-1 < σ < 53.1 km s-1. a median dispersion of 9.8 km s-1, translates to a mach number, m_3d≥28. the gas is distributed throughout several `streams', with projected lengths ∼100-250 pc. we link the streams to individual clouds and sub-regions, including sgr c, the 20 and 50 km s-1 clouds, the dust ridge, and sgr b2. shell-like emission features can be explained by the projection of independent molecular clouds in sgr c and the newly identified conical profile of sgr b2 in {l, b, vlsr} space. these features have previously invoked supernova-driven shells and cloud-cloud collisions as explanations. we instead caution against structure identification in velocity-integrated emission maps. three geometries describing the 3d structure of the cmz are investigated: (i) two spiral arms; (ii) a closed elliptical orbit; (iii) an open stream. while two spiral arms and an open stream qualitatively reproduce the gas distribution, the most recent parametrization of the closed elliptical orbit does not. finally, we discuss how proper motion measurements of masers can distinguish between these geometries, and suggest that this effort should be focused on the 20 km s-1 and 50 km s-1 clouds and sgr c. | molecular gas kinematics within the central 250 pc of the milky way |
we explore the influence of non-axisymmetric modes on the dynamics of the collapsed core of rotating, magnetized high-mass stars in three-dimensional simulations of a rapidly rotating star with an initial mass of $m_{\rm {\small zams}} = 35 \, \mathrm{m}_{\odot }$ endowed with four different pre-collapse configurations of the magnetic field, ranging from moderate to very strong field strength and including the field predicted by the stellar evolution model. the model with the weakest magnetic field achieves shock revival due to neutrino heating in a gain layer characterized by a large-scale, hydrodynamic m = 1 spiral mode. later on, the growing magnetic field of the proto neutron star launches weak outflows into the early ejecta. their orientation follows the evolution of the rotational axis of the proto neutron star, which starts to tilt from the original orientation due to the asymmetric accretion flows impinging on its surface. the models with stronger magnetization generate mildly relativistic, magnetically driven polar outflows propagating over a distance of 104 km within a few $100 \, \textrm {ms}$ . these jets are stabilized against disruptive non-axisymmetric instabilities by their fast propagation and by the shear of their toroidal magnetic field. within the simulation times of around $1 \, \textrm {s}$ , the explosions reach moderate energies and the growth of the proto neutron star masses ceases at values substantially below the threshold for black hole formation, which, in combination with the high rotational energies, might suggest a possible later proto-magnetar activity. | magnetorotational core collapse of possible grb progenitors - iii. three-dimensional models |
we discuss new methods to integrate the cosmic ray (cr) evolution equations coupled to magnetohydrodynamics on an unstructured moving mesh, as realized in the massively parallel arepo code for cosmological simulations. we account for diffusive shock acceleration of crs at resolved shocks and at supernova remnants in the interstellar medium (ism) and follow the advective cr transport within the magnetized plasma, as well as anisotropic diffusive transport of crs along the local magnetic field. cr losses are included in terms of coulomb and hadronic interactions with the thermal plasma. we demonstrate the accuracy of our formalism for cr acceleration at shocks through simulations of plane-parallel shock tubes that are compared to newly derived exact solutions of the riemann shock-tube problem with cr acceleration. we find that the increased compressibility of the post-shock plasma due to the produced crs decreases the shock speed. however, cr acceleration at spherically expanding blast waves does not significantly break the self-similarity of the sedov-taylor solution; the resulting modifications can be approximated by a suitably adjusted, but constant adiabatic index. in first applications of the new cr formalism to simulations of isolated galaxies and cosmic structure formation, we find that crs add an important pressure component to the ism that increases the vertical scaleheight of disc galaxies and thus reduces the star formation rate. strong external structure formation shocks inject crs into the gas, but the relative pressure of this component decreases towards halo centres as adiabatic compression favours the thermal over the cr pressure. | simulating cosmic ray physics on a moving mesh |
we study the evolution of the binary black hole (bbh) mass distribution across cosmic time. the second gravitational-wave transient catalog (gwtc-2) from ligo/virgo contains bbh events out to redshifts z ∼ 1, with component masses in the range ∼5-80 m⊙. in this catalog, the biggest bbhs, with m1 ≳ 45 m⊙, are only found at the highest redshifts, z ≳ 0.4. we ask whether the absence of high-mass observations at low redshift indicates that the mass distribution evolves: the biggest bbhs only merge at high redshift, and cease merging at low redshift. modeling the bbh primary-mass spectrum as a power law with a sharp maximum mass cutoff (truncated model), we find that the cutoff increases with redshift (> 99.9% credibility). an abrupt cutoff in the mass spectrum is expected from (pulsational) pair-instability supernova simulations; however, gwtc-2 is only consistent with a truncated mass model if the location of the cutoff increases from ${45}_{-5}^{+13}\,{m}_{\odot }$ at z < 0.4 to ${80}_{-13}^{+16}\,{m}_{\odot }$ at z > 0.4. alternatively, if the primary-mass spectrum has a break in the power law (broken power law) at ${38}_{-8}^{+15}\,{m}_{\odot }$ , rather than a sharp cutoff, the data are consistent with a nonevolving mass distribution. in this case, the overall rate of mergers, at all masses, increases with redshift. future observations will distinguish between a sharp mass cutoff that evolves with redshift and a nonevolving mass distribution with a gradual taper, such as a broken power law. after ∼100 bbh merger observations, a continued absence of high-mass, low-redshift events would provide a clear signature that the mass distribution evolves with redshift. | when are ligo/virgo's big black hole mergers? |
we present constraints on extensions to the λ cdm cosmological model from measurements of the e -mode polarization autopower spectrum and the temperature-e -mode cross-power spectrum of the cosmic microwave background (cmb) made using 2018 spt-3g data. the extensions considered vary the primordial helium abundance, the effective number of relativistic degrees of freedom, the sum of neutrino masses, the relativistic energy density and mass of a sterile neutrino, and the mean spatial curvature. we do not find clear evidence for any of these extensions, from either the spt-3g 2018 dataset alone or in combination with baryon acoustic oscillation and planck data. none of these model extensions significantly relax the tension between hubble-constant, h0, constraints from the cmb and from distance-ladder measurements using cepheids and supernovae. the addition of the spt-3g 2018 data to planck reduces the square-root of the determinants of the parameter covariance matrices by factors of 1.3-2.0 across these models, signaling a substantial reduction in the allowed parameter volume. we also explore cmb-based constraints on h0 from combined spt, planck, and act dr4 datasets. while individual experiments see some indications of different h0 values between the t t , t e , and e e spectra, the combined h0 constraints are consistent between the three spectra. for the full combined datasets, we report h0=67.49 ±0.53 km s-1 mpc-1 , which is the tightest constraint on h0 from cmb power spectra to date and in 4.1 σ tension with the most precise distance-ladder-based measurement of h0. the spt-3g survey is planned to continue through at least 2023, with existing maps of combined 2019 and 2020 data already having ∼3.5 ×lower noise than the maps used in this analysis. | constraints on λ cdm extensions from the spt-3g 2018 e e and t e power spectra |
we simulate the scientific performance of the nancy grace roman space telescope high latitude survey (hls) on dark energy and modified gravity. the 1.6-yr hls reference survey is currently envisioned to image 2000 deg2 in multiple bands to a depth of ~26.5 in y, j, h and to cover the same area with slit-less spectroscopy beyond z = 3. the combination of deep, multiband photometry and deep spectroscopy will allow scientists to measure the growth and geometry of the universe through a variety of cosmological probes (e.g. weak lensing, galaxy clusters, galaxy clustering, bao, type ia supernova) and, equally, it will allow an exquisite control of observational and astrophysical systematic effects. in this paper, we explore multiprobe strategies that can be implemented, given the telescope's instrument capabilities. we model cosmological probes individually and jointly and account for correlated systematics and statistical uncertainties due to the higher order moments of the density field. we explore different levels of observational systematics for the hls survey (photo-z and shear calibration) and ultimately run a joint likelihood analysis in n-dim parameter space. we find that the hls reference survey alone can achieve a standard dark energy fom of >300 when including all probes. this assumes no information from external data sets, we assume a flat universe however, and includes realistic assumptions for systematics. our study of the hls reference survey should be seen as part of a future community-driven effort to simulate and optimize the science return of the roman space telescope. | cosmology with the roman space telescope - multiprobe strategies |
asteroseismology has grown from its beginnings three decades ago to a mature field teeming with discoveries and applications. this phenomenal growth has been enabled by space photometry with precision 10-100 times better than ground-based observations, with nearly continuous light curves for durations of weeks to years, and by large-scale ground-based surveys spanning years designed to detect all time-variable phenomena. the new high-precision data are full of surprises, deepening our understanding of the physics of stars. this review explores asteroseismic developments from the past decade primarily as a result of light curves from the kepler and transiting exoplanet survey satellite space missions for massive upper main sequence obaf stars, pre-main-sequence stars, peculiar stars, classical pulsators, white dwarfs and subdwarfs, and tidally interacting close binaries. the space missions have increased the numbers of pulsators in many classes by an order of magnitude. asteroseismology measures fundamental stellar parameters and stellar interior physics-mass, radius, age, metallicity, luminosity, distance, magnetic fields, interior rotation, angular momentum transfer, convective overshoot, core-burning stage-supporting disparate fields such as galactic archeology, exoplanet host stars, supernovae progenitors, gamma-ray and gravitational wave precursors, close binary star origins and evolution, and standard candles. stars are the luminous tracers of the universe. asteroseismology significantly improves models of stellar structure and evolution on which all inference from stars depends. | asteroseismology across the hertzsprung-russell diagram |
recent modeling of hydrogen-rich type ii supernova (sn ii) light curves suggests the presence of dense circumstellar material (csm) surrounding the exploding progenitor stars. this has important implications for the activity and structure of massive stars near the end of their lives. since previous work focused on just a few events, here we expand to a larger sample of 20 well-observed sne ii. for each event we are able to constrain the progenitor zero-age main-sequence (zams) mass, explosion energy, and the mass and radial extent of the dense csm. we then study the distribution of each of these properties across the full sample of sne. the inferred zams masses are found to be largely consistent with a salpeter distribution with minimum and maximum masses of 10.4 and 22.9 m ⊙, respectively. we also compare the individual zams masses we measure with specific sne ii that have pre-explosion imaging to check their consistency. our masses are generally comparable to or higher than the pre-explosion imaging masses, potentially helping ease the red supergiant problem. the explosion energies vary from (0.1-1.3) × 1051 erg, and for ∼70% of the sne we obtain csm masses in the range between 0.18 and 0.83 m ⊙. we see a potential correlation between the csm mass and explosion energy, which suggests that pre-explosion activity has a strong impact on the structure of the star. this may be important to take into account in future studies of the ability of the neutrino mechanism to explode stars. we also see a possible correlation between the csm radial extent and zams mass, which could be related to the time with respect to explosion when the csm is first generated. | measuring the progenitor masses and dense circumstellar material of type ii supernovae |
the explosive death of a star as a supernova is one of the most dramatic events in the universe. supernovae have an outsized impact on many areas of astrophysics: they are major contributors to the chemical enrichment of the cosmos and significantly influence the formation of subsequent generations of stars and the evolution of galaxies. here we review the observational properties of thermonuclear supernovae—exploding white dwarf stars resulting from the stellar evolution of low-mass stars in close binary systems. the best known objects in this class are type-ia supernovae (sne ia), astrophysically important in their application as standardizable candles to measure cosmological distances and the primary source of iron group elements in the universe. surprisingly, given their prominent role, sn ia progenitor systems and explosion mechanisms are not fully understood; the observations we describe here provide constraints on models, not always in consistent ways. recent advances in supernova discovery and follow-up have shown that the class of thermonuclear supernovae includes more than just sne ia, and we characterize that diversity in this review. | observational properties of thermonuclear supernovae |
several large neutrino telescopes, operating at various sites around the world, have as their main objective the first detection of neutrinos emitted by a gravitational collapse in the milky way. the success of these observation programs depends on the rate of supernova core collapse in the milky way, r. in this work, standard statistical techniques are used to combine several independent results. their consistency is discussed and the most critical input data are identified. the inference on r is further tested and refined by including direct information on the occurrence rate of gravitational collapse events in the milky way and in the local group, obtained from neutrino telescopes and electromagnetic surveys. a conservative treatment of the errors yields a combined rate r = 1.63 ± 0.46 (100 yr)-1; the corresponding time between core collapse supernova events turns out to be t = 61-14+24 yr. the importance to update the analysis of the stellar birthrate method is emphasized. | on the rate of core collapse supernovae in the milky way |
star-forming gas clouds are strongly magnetized, and their ionization fractions are high enough to place them close to the regime of ideal magnetohydrodyamics on all by the smallest size scales. in this review we discuss the effects of magnetic fields on the star formation rate (sfr) in these clouds, and on the mass spectrum of the fragments that are the outcome of the star formation process, the stellar initial mass function (imf). current numerical results suggest that magnetic fields by themselves are fairly minor players in setting either the sfr or the imf, changing outcomes only at the factor of 2-3 level compared to non-magnetized flows. however, the possibility remains that the indirect effects of magnetic fields, via their interaction with star formation feedback in the form of jets, photoionization, radiative heating, and supernovae, could have significantly larger effects. we explore hints at that direction in current simulations, and suggest avenues for future exploration, both in simulations and observations. | the role of magnetic fields in setting the star formation rate and the initial mass function |
we report on the detection of seven bursts from the periodically active, repeating fast radio burst (frb) source frb 180916.j0158+65 in the 300-400 mhz frequency range with the green bank telescope (gbt). emission in multiple bursts is visible down to the bottom of the gbt band, suggesting that the cutoff frequency (if it exists) for frb emission is lower than 300 mhz. observations were conducted during predicted periods of activity of the source, and had simultaneous coverage with the low frequency array (lofar) and the frb backend on the canadian hydrogen intensity mapping experiment (chime) telescope. we find that one of the gbt-detected bursts has potentially associated emission in the chime band (400-800 mhz) but we detect no bursts in the lofar band (110-190 mhz), placing a limit of $\alpha \gt -1.0$ on the spectral index of broadband emission from the source. we also find that emission from the source is severely band-limited with burst bandwidths as low as ∼40 mhz. in addition, we place the strictest constraint on observable scattering of the source, <1.7 ms at 350 mhz, suggesting that the circumburst environment does not have strong scattering properties. additionally, knowing that the circumburst environment is optically thin to free-free absorption at 300 mhz, we find evidence against the association of a hyper-compact h ii region or a young supernova remnant (age <50 yr) with the source. | detection of repeating frb 180916.j0158+65 down to frequencies of 300 mhz |
as a long gamma-ray burst (grb) jet propagates within the stellar atmosphere it creates a cocoon composed of an outer newtonian shocked stellar material and an inner (possibly relativistic) shocked jet. the jet deposits {10}51{--}{10}52 erg into this cocoon. this is comparable to the energies of the grb and of the accompanying supernova, yet the cocoon’s signature has been largely ignored. the cocoon radiates a fraction of this energy as it expands, following the breakout from the star, and later as it interacts with the surrounding matter. we explore the possible signatures of this emission and outline a framework to calculate them from the conditions of the cocoon at the time of the jet breakout. the cocoon signature depends strongly on the, currently unknown, mixing between the shocked jet and shocked stellar material. with no mixing the γ-ray emission from the cocoon is so bright that it should have been already detected. the lack of such detections indicates that some mixing must take place. for partial and full mixing the expected signals are weaker than regular grb afterglows. however, the latter are highly beamed while the former are wider. future optical, uv, and x-ray transient searches, like lsst, ztf, ultrasat, iss-lobster, and others, will most likely detect such signals, providing a wealth of information on the progenitors and jets of grbs. while we focus on long grbs, analogous (but weaker) cocoons may arise in short grbs. their signatures might be the most promising electromagnetic counterparts for gravitational wave signals from compact binary mergers. | the observable signatures of grb cocoons |
interactions with neutrons and protons play a crucial role for the neutrino opacity of matter in the supernova core. their current implementation in many simulation codes, however, is rather schematic and ignores not only modifications for the correlated nuclear medium of the nascent neutron star, but also free-space corrections from nucleon recoil, weak magnetism, or strange quarks, which can easily add up to changes of several 10% for neutrino energies in the spectral peak. in the garching supernova simulations with the prometheus-vertex code, such sophistications have been included for a long time except for the strange-quark contributions to the nucleon spin, which affect neutral-current neutrino scattering. we demonstrate on the basis of a 20 {m}⊙progenitor star that a moderate strangeness-dependent contribution of {g}{{a}}{{s}}=-0.2 to the axial-vector coupling constant {g}{{a}}≈ 1.26 can turn an unsuccessful three-dimensional (3d) model into a successful explosion. such a modification is in the direction of current experimental results and reduces the neutral-current scattering opacity of neutrons, which dominate in the medium around and above the neutrinosphere. this leads to increased luminosities and mean energies of all neutrino species and strengthens the neutrino-energy deposition in the heating layer. higher nonradial kinetic energy in the gain layer signals enhanced buoyancy activity that enables the onset of the explosion at ∼300 ms after bounce, in contrast to the model with vanishing strangeness contributions to neutrino-nucleon scattering. our results demonstrate the close proximity to explosion of the previously published, unsuccessful 3d models of the garching group. | neutrino-driven explosion of a 20 solar-mass star in three dimensions enabled by strange-quark contributions to neutrino-nucleon scattering |
context. persistent tension between low-redshift observations and the cosmic microwave background radiation (cmb), in terms of two fundamental distance scales set by the sound horizon rd and the hubble constant h0, suggests new physics beyond the standard model, departures from concordance cosmology, or residual systematics.aims: the role of different probe combinations must be assessed, as well as of different physical models that can alter the expansion history of the universe and the inferred cosmological parameters.methods: we examined recently updated distance calibrations from cepheids, gravitational lensing time-delay observations, and the tip of the red giant branch. calibrating the baryon acoustic oscillations and type ia supernovae with combinations of the distance indicators, we obtained a joint and self-consistent measurement of h0 and rd at low redshift, independent of cosmological models and cmb inference. in an attempt to alleviate the tension between late-time and cmb-based measurements, we considered four extensions of the standard λcdm model.results: the sound horizon from our different measurements is rd = (137 ± 3stat. ± 2syst.) mpc based on absolute distance calibration from gravitational lensing and the cosmic distance ladder. depending on the adopted distance indicators, the combined tension in h0 and rd ranges between 2.3 and 5.1 σ, and it is independent of changes to the low-redshift expansion history. we find that modifications of λcdm that change the physics after recombination fail to provide a solution to the problem, for the reason that they only resolve the tension in h0, while the tension in rd remains unchanged. pre-recombination extensions (with early dark energy or the effective number of neutrinos neff = 3.24 ± 0.16) are allowed by the data, unless the calibration from cepheids is included.conclusions: results from time-delay lenses are consistent with those from distance-ladder calibrations and point to a discrepancy between absolute distance scales measured from the cmb (assuming the standard cosmological model) and late-time observations. new proposals to resolve this tension should be examined with respect to reconciling not only the hubble constant but also the sound horizon derived from the cmb and other cosmological probes. | cosmic dissonance: are new physics or systematics behind a short sound horizon? |
the stochastic gravitational-wave backgrounds (sgwbs) for current detectors are dominated by binary black-hole (bbh) and binary neutron-star (bns) coalescences. the sensitivity of current networks of gravitational-wave (gw) detectors allows only a small fraction of bbhs and bnss to be resolved and subtracted, but previous work indicated that the situation should significantly improve with next-generation (xg) observatories. we revisit these conclusions by taking into account waveform-modeling uncertainties, updated astrophysical models, and (crucially) the full set of parameters that must be estimated to remove the resolved sources. compared to previous studies, we find that the residual background from bbhs and bnss is large even with xg detector networks. new data analysis methods will thus be required to observe the sgwb from cosmic supernovae or contributions from early-universe phenomena like cosmic strings, stiff post-inflation fluids, or axion inflation. | compact binary foreground subtraction in next-generation ground-based observatories |
core-collapse supernovae are among the most powerful explosions in the universe, emitting thermal neutrinos that carry away the majority of the gravitational binding energy released. these neutrinos create a diffuse supernova neutrino background (dsnb), one of the largest energy budgets among all radiation backgrounds. detecting the dsnb is a crucial goal of modern high-energy astrophysics and particle physics, providing valuable insights in both core-collapse modeling, neutrino physics, and cosmic supernova rate history. in this review, we discuss the key ingredients of dsnb calculation and what we can learn from future detections, including black-hole formation and non-standard neutrino interactions. additionally, we provide an overview of the latest updates in neutrino experiments, which could lead to the detection of the dsnb in the next decade. with the promise of this breakthrough discovery on the horizon, the study of dsnb holds enormous potential for advancing our understanding of the universe. | diffuse neutrino background from past core collapse supernovae |
recent first-principles approaches to semiconductors are reviewed, with an emphasis on theoretical insight into emerging materials and in silico exploration of as-yet-unreported materials. as relevant theory and methodologies have developed, along with computer performance, it is now feasible to predict a variety of material properties ab initio at the practical level of accuracy required for detailed understanding and elaborate design of semiconductors; these material properties include (i) fundamental bulk properties such as band gaps, effective masses, dielectric constants, and optical absorption coefficients; (ii) the properties of point defects, including native defects, residual impurities, and dopants, such as donor, acceptor, and deep-trap levels, and formation energies, which determine the carrier type and density; and (iii) absolute and relative band positions, including ionization potentials and electron affinities at semiconductor surfaces, band offsets at heterointerfaces between dissimilar semiconductors, and schottky barrier heights at metal-semiconductor interfaces, which are often discussed systematically using band alignment or lineup diagrams. these predictions from first principles have made it possible to elucidate the characteristics of semiconductors used in industry, including group iii-v compounds such as gan, gap, and gaas and their alloys with related al and in compounds; amorphous oxides, represented by in-ga-zn-o transparent conductive oxides (tcos), represented by in2o3, sno2, and zno; and photovoltaic absorber and buffer layer materials such as cdte and cds among group ii-vi compounds and chalcopyrite cuinse2, cugase2, and cuin1- x ga x se2 (cigs) alloys, in addition to the prototypical elemental semiconductors si and ge. semiconductors attracting renewed or emerging interest have also been investigated, for instance, divalent tin compounds, including sno and sns; wurtzite-derived ternary compounds such as znsnn2 and cugao2; perovskite oxides such as srtio3 and basno3; and organic-inorganic hybrid perovskites, represented by ch3nh3pbi3. moreover, the deployment of first-principles calculations allows us to predict the crystal structure, stability, and properties of as-yet-unreported materials. promising materials have been explored via high-throughput screening within either publicly available computational databases or unexplored composition and structure space. reported examples include the identification of nitride semiconductors, tcos, solar cell photoabsorber materials, and photocatalysts, some of which have been experimentally verified. machine learning in combination with first-principles calculations has emerged recently as a technique to accelerate and enhance in silico screening. a blend of computation and experimentation with data science toward the development of materials is often referred to as materials informatics and is currently attracting growing interest. | design and exploration of semiconductors from first principles: a review of recent advances |
we use hydrodynamical simulations to study the milky way's central molecular zone (cmz). the simulations include a non-equilibrium chemical network, the gas self-gravity, star formation, and supernova feedback. we resolve the structure of the interstellar medium at sub-parsec resolution while also capturing the interaction between the cmz and the bar-driven large-scale flow out to $r\sim 5\, {\rm kpc}$. our main findings are as follows: (1) the distinction between inner (r ≲ 120 pc) and outer (120 ≲ r ≲ 450 pc) cmz that is sometimes proposed in the literature is unnecessary. instead, the cmz is best described as single structure, namely a star-forming ring with outer radius r ≃ 200 pc which includes the 1.3° complex and which is directly interacting with the dust lanes that mediate the bar-driven inflow. (2) this accretion can induce a significant tilt of the cmz out of the plane. a tilted cmz might provide an alternative explanation to the ∞-shaped structure identified in herschel data by molinari et al. (3) the bar in our simulation efficiently drives an inflow from the galactic disc (r ≃ 3 kpc) down to the cmz (r ≃ 200 pc) of the order of $1\rm \, m_\odot \, yr^{-1}$, consistent with observational determinations. (4) supernova feedback can drive an inflow from the cmz inwards towards the circumnuclear disc of the order of ${\sim}0.03\, \rm m_\odot \, yr^{-1}$. (5) we give a new interpretation for the 3d placement of the 20 and 50 km s-1 clouds, according to which they are close (r ≲ 30 pc) to the galactic centre, but are also connected to the larger scale streams at r ≳ 100 pc. | simulations of the milky way's central molecular zone - i. gas dynamics |
we investigate an interacting dark sector scenario in which the vacuum energy is free to interact with cold dark matter (cdm), which itself is assumed to cluster under the sole action of gravity, i.e. it is in freefall (geodesic), as in λcdm. the interaction is characterized by a dimensionless coupling qv(z), in general a function of redshift. aiming to reconstruct the evolution of the coupling, we use cosmic microwave background data from planck 2015, along with baryon acoustic oscillation, redshift space distortion, and type ia supernova measurements to constrain various parametrizations of qv(z). we present the full linear perturbation theory of this interacting scenario and use monte carlo markov chains (mcmc) sampling to study five different cases: two cases in which we have λcdm evolution in the distant past, until a set redshift ztrans, below which the interaction switches on and qv is the single-sampled parameter, with ztrans fixed at ztrans = 3000 and 0.9, respectively; a case where we allow this transition redshift to vary along with qv; a case in which the vacuum energy is zero for z > ztrans and then begins to grow once the interaction switches on; and the final case in which we bin qv(z) in four redshift bins to investigate the possibility of a dynamical interaction, reconstructing the redshift evolution of the function using gaussian processes. we find that, in all cases where the high-redshift evolution is not modified, the results are compatible with a vanishing coupling, thus finding no significant deviation from λcdm. | constraints on the interacting vacuum-geodesic cdm scenario |
using the new state-of-the-art core-collapse supernova (ccsn) code fornax, we have simulated the three-dimensional dynamical evolution of the cores of 9-, 10-, 11-, 12-, and 13-m⊙ stars from the onset of collapse. stars from 8 to 13 m⊙ constitute roughly 50 per cent of all massive stars, so the explosive potential for this mass range is important to the overall theory of ccsne. we find that the 9-, 10-, 11-, and 12-m⊙ models explode in 3d easily, but that the 13-m⊙ model does not. from these findings, and the fact that slightly more massive progenitors seem to explode, we suggest that there is a gap in explodability near 12 to 14 m⊙ for non-rotating progenitor stars. factors conducive to explosion are turbulence behind the stalled shock, energy transfer due to neutrino-matter absorption and neutrino-matter scattering, many-body corrections to the neutrino-nucleon scattering rate, and the presence of a sharp silicon-oxygen interface in the progenitor. our 3d exploding models frequently have a dipolar structure, with the two asymmetrical exploding lobes separated by a pinched waist where matter temporarily continues to accrete. this process maintains the driving neutrino luminosity, while partially shunting matter out of the way of the expanding lobes, thereby modestly facilitating explosion. the morphology of all 3d explosions is characterized by multiple bubble structures with a range of low-order harmonic modes. though much remains to be done in ccsn theory, these and other results in the literature suggest that, at least for these lower mass progenitors, supernova theory is converging on a credible solution. | three-dimensional supernova explosion simulations of 9-, 10-, 11-, 12-, and 13-m⊙ stars |
knowing the late time evolution of the universe and finding out the causes for this evolution are the important challenges of modern cosmology. in this work, we adopt a model-independent cosmographic approach and approximate the hubble parameter considering the pade approximation which works better than the standard taylor series approximation for z > 1. with this, we constrain the late time evolution of the universe considering low-redshift observations coming from supernova type ia, baryon acoustic oscillation, h(z), h0, strong-lensing time-delay as well as the megamaser observations for angular diameter distances. we confirm the tensions with λ cold dark matter model for low-redshifts observations. the present value of the equation of state for the dark energy has to be phantom-like and for other redshifts, it has to be either phantom or should have a phantom crossing. for lower values of ωm0, multiple phantom crossings are expected. this poses serious challenges for single, non-interacting scalar field models for dark energy. we derive constraints on the statefinders (r, s) and these constraints show that a single dark energy model cannot fit data for the whole redshift range 0 ≤ z ≤ 2: in other words, we need multiple dark energy behaviours for different redshift ranges. moreover, the constraint on sound speed for the total fluid of the universe, and for the dark energy fluid (assuming them being barotropic), rules out the possibility of a barotropic fluid model for unified dark sector and barotropic fluid model for dark energy, as fluctuations in these fluids are unstable as c_{ s}^2 < 0 due to constraints from low-redshift observations. | model-independent constraints on dark energy evolution from low-redshift observations |
recently, a full-shape analysis of large-scale structure (lss) data was employed to provide new constraints on a class of early dark energy models. in this paper, we derive similar constraints on new early dark energy (nede) using the publicly available pybird code, which makes use of the effective field theory of lss. we study the nede base model with the fraction of nede and the trigger field mass as two additional parameters allowed to vary freely, while making simplifying assumptions about the decaying fluid sector. including the full-shape analysis of lss together with measurements of the cosmic microwave background, baryonic acoustic oscillations, and supernovae data, we report h0=71.2 ±1.0 km s-1 mpc-1 (68% c.l.) together with an approximate 4 σ evidence for a nonvanishing fraction of nede. this is an insignificant change to the value previously found without full-shape lss data, h0=71.4 ±1.0 km s-1 mpc-1 (68% c.l.). as a result, while the nede fit cannot be improved upon the inclusion of additional lss data, it is also not adversely affected by it, making it compatible with current constraints from lss data. in fact, we find evidence that the effective field theory of lss acts in favor of nede. | new early dark energy is compatible with current lss data |
we utilize high-resolution cosmological simulations to reveal that high-redshift galaxies tend to undergo a robust 'wet compaction' event when near a 'golden' stellar mass of $\sim \!\!10^{10}\, \rm m_\odot$ . this is a gaseous shrinkage to a compact star-forming phase, a 'blue nugget' (bn), followed by central quenching of star formation to a compact passive stellar bulge, a 'red nugget' (rn), and a buildup of an extended gaseous disc and ring. such nuggets are observed at cosmic noon and seed today's early-type galaxies. the compaction is triggered by a drastic loss of angular momentum due to, e.g. wet mergers, counter-rotating cold streams, or violent disc instability. the bn phase marks drastic transitions in the galaxy structural, compositional, and kinematic properties. the transitions are from star forming to quenched inside-out, from diffuse to compact with an extended disc or ring and a stellar envelope, from dark matter to baryon central dominance, from prolate to oblate stellar shape, from pressure to rotation support, from low to high metallicity, and from supernova to agn feedback. the central black hole growth, first suppressed by supernova feedback when below the golden mass, is boosted by the compaction, and the black hole keeps growing once the halo is massive enough to lock in the supernova ejecta. | wet compaction to a blue nugget: a critical phase in galaxy evolution |
a longstanding problem in the study of supernovae (sne) has been the relationship between the type iip and type iil subclasses. whether they come from distinct progenitors or they are from similar stars with some property that smoothly transitions from one class to another has been the subject of much debate. here, using one-dimensional radiation-hydrodynamic sn models, we show that the multi-band light curves of sne iil are well fit by ordinary red supergiants surrounded by dense circumstellar material (csm). the inferred extent of this material, coupled with a typical wind velocity of ∼ 10{--}100 {km} {{{s}}}-1, suggests enhanced activity by these stars during the last ~months to ∼years of their lives, which may be connected with advanced stages of nuclear burning. furthermore, we find that, even for more plateau-like sne, dense csm provides a better fit to the first ∼ 20 days of their light curves, indicating that the presence of such material may be more widespread than previously appreciated. here we choose to model the csm with a wind-like density profile, but it is unclear whether this just generally represents some other mass distribution, such as a recent mass ejection, thick disk, or even inflated envelope material. better understanding the exact geometry and density distribution of this material will be an important question for future studies. | unifying type ii supernova light curves with dense circumstellar material |
we present the first systematic investigation of spectral properties of 17 type ic supernovae (sne ic), 10 broad-lined sne ic (sne ic-bl) without observed gamma-ray bursts (grbs), and 11 sne ic-bl with grbs (sn-grbs) as a function of time in order to probe their explosion conditions and progenitors. using a number of novel methods, we analyze a total of 407 spectra, which were drawn from published spectra of individual sne as well as from the densely time-sampled spectra of modjaz et al (2014). in order to quantify the diversity of the sn spectra as a function of sn subtype, we construct average spectra of sne ic, sne ic-bl without grbs, and sne ic-bl with grbs. we find that sn 1994i is not a typical sn ic, contrasting the general view, while the spectra of sn 1998bw/grb 980425 are representative of mean spectra of sne ic-bl. we measure the ejecta absorption and width velocities using a new method described here and find that sne ic-bl with grbs, on average, have quantifiably higher absorption velocities, as well as broader line widths than sne without observed grbs. in addition, we search for correlations between sn-grb spectral properties and the energies of their accompanying grbs. finally, we show that the absence of clear he lines in optical spectra of sne ic-bl, and in particular of sn-grbs, is not due to them being too smeared-out due to the high velocities present in the ejecta. this implies that the progenitor stars of sn-grbs are probably free of the he-layer, in addition to being h-free, which puts strong constraints on the stellar evolutionary paths needed to produce such sn-grb progenitors at the observed low metallicities. | the spectral sn-grb connection: systematic spectral comparisons between type ic supernovae and broad-lined type ic supernovae with and without gamma-ray bursts |
protogalaxies forming in low-mass dark matter haloes are thought to provide the majority of ionizing photons needed to reionize the universe, due to their high escape fractions of ionizing photons. we study how the escape fraction in high-redshift galaxies relates to the physical properties of the halo in which the galaxies form, by computing escape fractions in more than 75 000 haloes between redshifts 27 and 6 that were extracted from the first billion years project, high-resolution cosmological hydrodynamical simulations of galaxy formation. we find that the main constraint on the escape fraction is the gas column density in a radius of 10 pc around the stellar populations, causing a strong mass dependence of the escape fraction. the lower potential well in haloes with m200 ≲ 108 m⊙ results in low column densities that can be penetrated by radiation from young stars (age <5 myr). in haloes with m200 ≳ 108 m⊙ supernova feedback is important, but only ∼30 per cent of the haloes in this mass range have an escape fraction higher than 1 per cent. we find a large range of escape fractions in haloes with similar properties, caused by different distributions of the dense gas in the halo. this makes it very hard to predict the escape fraction on the basis of halo properties and results in a highly anisotropic escape fraction. the strong mass dependence, the large spread and the large anisotropy of the escape fraction may strongly affect the topology of reionization and is something current models of cosmic reionization should strive to take into account. | the first billion years project: the escape fraction of ionizing photons in the epoch of reionization |
almost all massive stars explode as supernovae and form a black hole or neutron star. the remnant mass and the impact of the chemical yield on subsequent star formation and galactic evolution strongly depend on the internal physics of the progenitor star, which is currently not well understood. the theoretical uncertainties of stellar interiors accumulate with stellar age, which is particularly pertinent for the blue supergiant phase. stellar oscillations represent a unique method of probing stellar interiors, yet inference for blue supergiants is hampered by a dearth of observed pulsation modes. here we report the detection of diverse variability in blue supergiants using the k2 and tess space missions. the discovery of pulsation modes or an entire spectrum of low-frequency gravity waves in these stars allow us to map the evolution of hot massive stars towards the ends of their lives. future asteroseismic modelling will provide constraints on ages, core masses, interior mixing, rotation and angular momentum transport. the discovery of variability in blue supergiants is a step towards a data-driven empirical calibration of theoretical evolution models for the most massive stars in the universe. | low-frequency gravity waves in blue supergiants revealed by high-precision space photometry |
we present results of three-dimensional (3d), radiation-magnetohydrodynamics (mhd) simulations of core-collapse supernovae in full general relativity (gr) with spectral neutrino transport. in order to study the effects of the progenitor's rotation and magnetic fields, we compute three models, where the precollapse rotation rate and magnetic fields are included parametrically to a 20 m⊙ star. while we find no shock revival in our two nonmagnetized models during our simulation times (∼500 ms after bounce), the magnetorotational (mr) driven shock expansion immediately initiates after bounce in our rapidly rotating and strongly magnetized model. we show that the expansion of the mr-driven flows toward the polar directions is predominantly driven by the magnetic pressure, whereas the shock expansion toward the equatorial direction is supported by neutrino heating. our detailed analysis indicates that the growth of the so-called kink instability may hinder the collimation of jets, resulting in the formation of broader outflows. furthermore, we find a dipole emission of lepton number, only in the mr explosion model, whose asymmetry is consistent with the explosion morphology. although it is similar to the lepton number emission self-sustained asymmetry (lesa), our analysis shows that the dipole emission occurs not from the proto-neutron star convection zone but from above the neutrino sphere, indicating that it is not associated with the lesa. we also report several unique neutrino signatures, which are significantly dependent on both the time and the viewing angle, if observed, possibly providing rich information regarding the onset of the mr-driven explosion. | magnetorotational explosion of a massive star supported by neutrino heating in general relativistic three-dimensional simulations |
in this paper, we investigate the cosmological viability of a double scalar field model motivated by warm inflation. to this end, we first set up the theoretical framework in which dark energy, dark matter and inflation are accounted for in a triple unification scheme. we then compute the overall dynamics of the model, analyzing the physical role of coupling parameters. focussing on the late-time evolution, we test the model against current data. specifically, using the low-redshift pantheon supernovae ia and hubble cosmic chronometers measurements, we perform a bayesian analysis through the monte carlo markov chains method of integration on the free parameters of the model. we find that the mean values of the free parameters constrained by observations lie within suitable theoretical ranges, and the evolution of the scalar fields provides a good resemblance to the features of the dark sector of the universe. such behaviour is confirmed by the outcomes of widely adopted selection criteria, suggesting a statistical evidence comparable to that of the standard λcdm cosmology. we finally discuss the presence of large uncertainties over the free parameters of the model and we debate about fine-tuning issues related to the coupling constants. | cosmological viability of a double field unified model from warm inflation |
twenty years after the discovery that the expansion of the universe is accelerating, a new finding is now challenging our understanding of the cosmos. recent studies have shown that the hubble constant, the speed of expansion measured today, provides values in significant tension when measured from the cosmic microwave background in the primordial universe or from cepheids and supernovae type ia in the local universe. whether this tension is hinting towards new physics or some issue in the measurements, is still under debate; but it is clearly calling for new independent cosmological probes to provide additional pieces of evidence to solve this puzzle. this chapter introduces the method of cosmic chronometers, a new emerging cosmological probe that can provide cosmology-independent estimates of the universe's expansion history. this method is based on the fact that the expansion rate of the universe can be directly derived from measuring how much the universe has changed in age between two different redshifts, i.e. by estimating the slope of the age--redshift relation. first, the main ingredients of the method will be discussed, presenting the main equations involved and how to estimate from the observables the needed quantities. after, it will be presented how to reliably select a sample of tracers to map the age evolution of the universe coherently. next, different methods to robustly measure the differential age of a population, the fundamental quantity involved in the method, will be reviewed. finally, the main measurements obtained will be presented, providing forecasts for future surveys and discussing how these data can provide useful feedback to address the hubble tension. | addressing the hubble tension with cosmic chronometers |
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