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one of the most unique phenomena in the galactic center region is the existence of numerous long and narrow filamentary structures within a few hundred parsecs of sgr a⋆. while more than 100 radio filaments have been revealed by meerkat, only about two dozen x-ray filaments have been discovered so far. in this article, we report our analysis of deep chandra and nustar observations of a nonthermal x-ray filament, g0.13-0.11, which is located adjacent to the radio arc. chandra revealed a unique morphology of g0.13-0.11, which is an elongated (0.1 pc in width and 3.2 pc in length) structure slightly bent toward the radio arc. a pulsar candidate (γ ∼ 1.4) is detected in the middle of the filament, with a tail of diffuse nonthermal x-ray emission on one side of the filament. the filament is detected by nustar up to 79 kev, with the hard x-ray centroid consistent with the pulsar candidate. we found that the x-ray intensity decays along the filament farther away from the pulsar candidate, dropping to half of its peak value 2.2 pc away. this system is most likely a pulsar wind nebula (pwn) interacting with the ambient interstellar magnetic field, where the filaments are kinetic jets from the pwn as recently proposed. the nature of this filament adds to the complex origin of x-ray filaments, which serve as powerful tools for probing local and global powerful particle accelerators in the galactic center. | nustar and chandra observations of the galactic center nonthermal x-ray filament g0.13-0.11: a pulsar-wind-nebula-driven magnetic filament |
this paper aims to provide new insights on the origin of the tev source ver j1907+062 through new high-quality radio observations. we used the karl g. jansky very large array (vla) to observe the whole extension of ver j1907+062 at 1.5 ghz with a mosaicking technique and the psr j1907+0602 in a single pointing at 6 ghz. these data were used together with 12co and atomic hydrogen observations obtained from public surveys to investigate the interstellar medium in the direction of ver j1907+062. the new radio observations do not show any evidence of a pulsar wind nebula (pwn) driven by the pulsars present in the field and no radio counterpart to the proposed x-ray pwn powered by psr j1907+0602 is seen in the new vla image at 6 ghz down to a noise level of 10 μjy beam-1. molecular clouds were discovered over the eastern, southern, and western borders of the radio shell of g40.5-0.5, suggesting an association with this supernova remnant. we explored several scenarios for the origin of ver j1907+062. we propose as the most probable scenario one in which the tev emission is produced by two separated γ-ray sources located at different distances: one of leptonic origin and associated with a pwn powered by psr j1907+0602 at ∼3.2 kpc and another of hadronic origin and produced by the interaction between g40.5-0.5 and the surrounding molecular gas at ∼8.7 kpc. | radio study of the extended tev source ver j1907+062 |
we calculate the effective temperature (teff) of ionizing star(s), the oxygen abundance of the gas phase (o/h), and the ionization parameter u for a sample of h ii regions located in the discs of 59 spiral galaxies in the redshift range 0.005 < z < 0.03. we use spectroscopic data taken from the califa data release 3 (dr3) and theoretical (for teff and u) and empirical (for o/h) calibrations based on strong emission lines. we consider the spatial distribution and radial gradients of these parameters in each galactic disc for the objects in our sample. most of the galaxies in our sample (∼70 per cent) show positive teff radial gradients, although some exhibit negative or flat ones. the median value of the teff radial gradient is 0.762 kk/r25. we find that the radial gradients of both log u and teff depend on the oxygen abundance gradient, in the sense that the gradient of log u increases as the log (o/h) gradient increases while there is an anti-correlation between the gradient of teff and the oxygen abundance gradient. moreover, galaxies with flat oxygen abundance gradients tend to have flat log u and teff gradients as well. although our results are in agreement with the idea of the existence of positive teff gradients along the disc of the majority of spiral galaxies, it seems that this is not a universal property for these objects. | effective temperature of ionizing stars in extragalactic h ii regions - ii. nebular parameter relationships based on califa data |
we obtained six observations of psr j1741-2054 using the chandra acis-s detector totaling ∼300 ks. by registering this new epoch of observations to an archival observation taken 3.2 yr earlier using x-ray point sources in the field of view, we have measured the pulsar proper motion at μ =109+/- 10 mas y{{r}-1} in a direction consistent with the symmetry axis of the observed hα nebula. we investigated the inferred past trajectory of the pulsar but find no compelling association with ob associations in which the progenitor may have originated. we confirm previous measurements of the pulsar spectrum as an absorbed power law with photon index γ = 2.68 ± 0.04, plus a blackbody with an emission radius of (4.5-2.5+3.2){{d}0.38} km, for a dm-estimated distance of 0.38{{d}0.38} kpc and a temperature of 61.7 ± 3.0 ev. emission from the compact nebula is well described by an absorbed power law model with a photon index of γ = 1.67 ± 0.06, while the diffuse emission seen as a trail extending northeast of the pulsar shows no evidence of synchrotron cooling. we also applied image deconvolution techniques to search for small-scale structures in the immediate vicinity of the pulsar, but found no conclusive evidence for such structures. | x-ray analysis of the proper motion and pulsar wind nebula for psr j1741-2054 |
due to its youth, proximity and richness, the orion nebula cloud (onc) is an ideal testbed to obtain a comprehensive view on the initial mass function (imf) down to the planetary mass regime. using the hawk-i camera at the vlt, we have obtained an unprecedented deep and wide near-infrared jhk mosaic of the onc (90 per cent completeness at k ∼ 19.0 mag, 22 × 28 arcmin2). applying the most recent isochrones and accounting for the contamination of background stars and galaxies, we find that onc's imf is bimodal with distinct peaks at about 0.25 and 0.025 m⊙ separated by a pronounced dip at the hydrogen burning limit (0.08 m⊙), with a depth of about a factor of 2-3 below the log-normal distribution. apart from ∼920 low-mass stars (m < 1.4 m⊙) the imf contains ∼760 brown dwarf candidates and ∼160 isolated planetary mass object candidates with m > 0.005 m⊙, hence about 10 times more substellar candidates than known before. the substellar imf peak at 0.025 m⊙ could be caused by brown dwarfs and isolated planetary mass objects which have been ejected from multiple systems during the early star formation process or from circumstellar discs. | the bimodal initial mass function in the orion nebula cloud |
we use integral field spectroscopic (ifs) observations from the gemini multi-object spectrograph north (gmos-n) to study the central h ii region in a nearby blue compact dwarf (bcd) galaxy ngc 4449. the ifs data enable us to explore the variation of physical and chemical conditions of the star-forming region and the surrounding gas on spatial scales as small as 5.5 pc. our kinematical analysis shows possible signatures of shock ionization and shell structures in the surroundings of the star-forming region. the metallicity maps of the region, created using direct te and indirect strong line methods (r23, o3n2 and n2), do not show any chemical variation. from the integrated spectrum of the central h ii region, we find a metallicity of 12 + log(o/h) = 7.88 ± 0.14 ({∼ }0.15^{+0.06}_{-0.04} z⊙) using the direct method. comparing the central h ii region metallicity derived here with those of h ii regions throughout this galaxy from previous studies, we find evidence of increasing metallicity with distance from the central nucleus. such chemical inhomogeneities can be due to several mechanisms, including gas loss via supernova blowout, galactic winds or metal-poor gas accretion. however, we find that the localized area of decreased metallicity aligns spatially with the peak of star-forming activity in the galaxy, suggesting that gas accretion may be at play here. spatially resolved ifs data for the entire galaxy are required to confirm the metallicity inhomogeneity found in this study and determine its possible cause. | a gmos-n ifu study of the central h ii region in the blue compact dwarf galaxy ngc 4449: kinematics, nebular metallicity and star formation |
stellar bow shocks are observed in a variety of interstellar environments and shaped by the conditions of gas in the interstellar medium (ism). in situ measurements of turbulent density fluctuations near stellar bow shocks are only achievable with a few observational probes, including hα-emitting bow shocks and the voyager interstellar mission (vim). in this paper, we examine density variations around the guitar nebula, an hα bow shock associated with psr b2224+65, in tandem with density variations probed by vim near the boundary of the solar wind and ism. high-resolution hubble space telescope observations of the guitar nebula taken between 1994 and 2006 trace density variations over scales from hundreds to thousands of au, while vim density measurements made with the voyager 1 plasma wave system constrain variations from thousands of meters to tens of au. the power spectrum of density fluctuations constrains the amplitude of the turbulence wavenumber spectrum near the guitar nebula to ${\mathrm{log}}_{10}{c}_{{\rm{n}}}^{2}=-0.8\pm 0.2$ m-20/3 and for the very local ism probed by voyager to ${\mathrm{log}}_{10}{c}_{{\rm{n}}}^{2}=-1.57\pm 0.02$ m-20/3. spectral amplitudes obtained from multiepoch observations of four other hα bow shocks also show significant enhancements from values that are considered typical for the diffuse, warm ionized medium, suggesting that density fluctuations near these bow shocks may be amplified by shock interactions with the surrounding medium or selection effects that favor hα emission from bow shocks embedded in denser media. | an in situ study of turbulence near stellar bow shocks |
we use the measured fluxes of polycyclic aromatic hydrocarbon (pah) emission features at 6.2, 7.7, 8.6, 11.0, and 11.2 μm in the reflection nebula ngc 2023 to carry out a principal component analysis (pca) as a means to study previously reported variations in the pah emission. we find that almost all of the variations (99 per cent) can be explained with just two parameters - the first two principal components (pcs). we explore the characteristics of these pcs and show that the first pc (pc1), which is the primary driver of the variation, represents the amount of emission of a mixture of pahs with ionized species dominating over neutral species. the second pc (pc2) traces variations in the ionization state of the pahs across the nebula. correlations of the pcs with various pah ratios show that the 6.2 and 7.7 μm bands behave differently than the 8.6 and 11.0 μm bands, thereby forming two distinct groups of ionized bands. we compare the spatial distribution of the pcs to the physical conditions, in particular to the strength of the radiation field, g0, and the g0/nh ratio and find that the variations in pc2, i.e. the ionization state of pahs are strongly affected by g0 whereas the amount of pah emission (as traced by pc1) does not depend on g0. | a principal component analysis of polycyclic aromatic hydrocarbon emission in ngc 2023 |
we have performed very large and high-resolution cosmological hydrodynamic simulations in order to investigate detectability of nebular lines in the rest-frame ultraviolet (uv) to optical wavelength range from galaxies at z > 7. we find that the expected line fluxes are very well correlated with the apparent uv magnitudes. the c iv 1549 å and c iii] 1909 å lines of galaxies brighter than 26 ab magnitudes are detectable with current facilities such as the very large telescope (vlt) xshooter and the keck multi-object spectrometer for infra-red exploration (mosfire). metal lines such as c iv 1549 å, c iii] 1909 å, [o ii] 3727 å and [o iii] 4959/5007 å are good targets for spectroscopic observation with the thirty-metre telescope (tmt), european extremely large telescope (e-elt), giant magellan telescope (gmt) and james webb space telescope (jwst). we also expect hα and hβ lines to be detectable with these telescopes. additionally, we predict the detectability of nebular lines for z > 10 galaxies, which will be found with jwst, the wide-field infrared survey telescope (wfirst) and first light and reionization explorer (flare) (11 ≤ z ≤ 15). we conclude that the c iv 1549 å, c iii] 1909 å, [o iii] 4959/5007 å and hβ lines from even z ∼15 galaxies could be strong targets for tmt, e-elt and jwst. we also find that magnification by gravitational lensing is of great help in detecting such high-z galaxies. according to our model, the c iii] 1909 å line in z > 9 galaxy candidates is detectable even using current facilities. | nebular line emission from z > 7 galaxies in a cosmological simulation: rest-frame uv to optical lines |
we present follow-up radio observations of eso 243-49 hlx-1 from 2012 using the australia telescope compact array (atca) and the karl g. jansky very large array (vla). we report the detection of radio emission at the location of hlx-1 during its hard x-ray state using the atca. assuming that the `fundamental plane' of accreting black holes is applicable, we provide an independent estimate of the black hole mass of m_{bh}≤ 2.8^{+7.5}_{-2.1} × 106 m⊙ at 90 per cent confidence. however, we argue that the detected radio emission is likely to be doppler-boosted and our mass estimate is an upper limit. we discuss other possible origins of the radio emission such as being due to a radio nebula, star formation, or later interaction of the flares with the large-scale environment. none of these were found adequate. the vla observations were carried out during the x-ray outburst. however, no new radio flare was detected, possibly due to a sparse time sampling. the deepest, combined vla data suggest a variable radio source and we briefly discuss the properties of the previously detected flares and compare them with microquasars and active galactic nuclei. | on the radio properties of the intermediate-mass black hole candidate eso 243-49 hlx-1 |
polarimetric observations of celestial sources in the hard x-ray band stand to provide new information on emission mechanisms and source geometries. pogo+ is a compton scattering polarimeter (20-150 kev) optimised for the observation of the crab (pulsar and wind nebula) and cygnus x-1 (black hole binary), from a stratospheric balloon-borne platform launched from the esrange space centre in summer 2016. prior to flight, the response of the polarimeter has been studied with polarised and unpolarised x-rays allowing a geant4-based simulation model to be validated. the expected modulation factor for crab observations is found to be mcrab = (41.75 ± 0.85) % , resulting in an expected minimum detectable polarisation (mdp) of 7.3% for a 7 day flight. this will allow a measurement of the crab polarisation parameters with at least 5 σ statistical significance assuming a polarisation fraction ∼ 20 % - a significant improvement over the pogolite pathfinder mission which flew in 2013 and from which the pogo+ design is developed. | calibration and performance studies of the balloon-borne hard x-ray polarimeter pogo+ |
the w50/ss433 system is an unusual galactic outflow-driven object of debatable origin. we have used the australia telescope compact array to observe a new 198 pointing mosaic, covering 3° × 2°, and present the highest-sensitivity full-stokes data of w50 to date using wide-field, wide-band imaging over a 2 ghz bandwidth centred at 2.1 ghz. we also present a complementary hα mosaic created using the isaac newton telescope photometric hα survey of the northern galactic plane. the magnetic structure of w50 is consistent with the prevailing hypothesis that the nebula is a reanimated shell-like supernova remnant (snr), which has been re-energized by the jets from ss433. we observe strong depolarization effects that correlate with diffuse hα emission, likely due to spatially varying faraday rotation measure (rm) fluctuations of ≥48-61 rad m-2 on scales ≤4.5-6 pc. we also report the discovery of numerous, faint, hα filaments that are unambiguously associated with the central region of w50. these thin filaments are suggestive of an snr's shock emission, and almost all have a radio counterpart. furthermore, an rm-gradient is detected across the central region of w50, which we interpret as a loop magnetic field with a symmetry axis offset by ≈90° to the east-west jet-alignment axis, and implying that the evolutionary processes of both the jets and the snr must be coupled. a separate rm-gradient is associated with the termination shock in the eastern ear, which we interpret as a ring-like field located where the shock of the jet interacts with the circumstellar medium. future optical observations will be able to use the new hα filaments to probe the kinematics of the shell of w50, potentially allowing for a definitive experiment on w50's formation history. | interacting large-scale magnetic fields and ionized gas in the w50/ss433 system |
we report on the discovery and timing observations of 29 distant long-period pulsars found in the ongoing arecibo l-band feed array pulsar survey. following discovery with the arecibo telescope, confirmation and timing observations of these pulsars over several years at jodrell bank observatory have yielded high-precision positions and measurements of rotation and radiation properties. we have used multi-frequency data to measure the interstellar scattering properties of some of these pulsars. most of the pulsars have properties that mirror those of the previously known pulsar population, although four show some notable characteristics. psrs j1907+0631 and j1925+1720 are young and are associated with supernova remnants or plerionic nebulae: j1907+0631 lies close to the center of snr g40.5-0.5, while j1925+1720 is coincident with a high-energy fermi γ-ray source. one pulsar, j1932+1500, is in a surprisingly eccentric, 199 day binary orbit with a companion having a minimum mass of 0.33 m⊙. several of the sources exhibit timing noise, and two, psrs j0611+1436 and j1907+0631, have both suffered large glitches, but with very different post-glitch rotation properties. in particular, the rotational period of psr j0611+1436 will not recover to its pre-glitch value for about 12 years, a far greater recovery timescale than seen following any other large glitches. | timing of 29 pulsars discovered in the palfa survey |
we present a spectral analysis of cool and cooling gas in 45 cool-core clusters and groups of galaxies obtained from reflection grating spectrometer (rgs) xmm-newton observations. the high-resolution spectra show fe xvii emission in many clusters, which implies the existence of cooling flows. the cooling rates are measured between the bulk intracluster medium temperature and 0.01 kev and are typically weak, operating at less than a few tens of m_{⊙} yr^{-1} in clusters and less than 1 m_{⊙} yr^{-1} in groups of galaxies. they are 10-30 {{ per cent}} of the classical cooling rates in the absence of heating, which suggests that active galactic nucleus feedback has a high level of efficiency. if cooling flows terminate at 0.7 kev in clusters, the associated cooling rates are higher, and have a typical value of a few to a few tens of m_{⊙} yr^{-1}. since the soft x-ray emitting region, where the temperature kt < 1 kev, is spatially associated with h α nebulosity, we examine the relation between the cooling rates above 0.7 kev and the h α nebulae. we find that the cooling rates have enough energy to power the total ultraviolet-optical luminosities, and are 5 to 50 times higher than the observed star formation rates for low-luminosity objects. in four high-luminosity clusters, the cooling rates above 0.7 kev are not sufficient and an inflow at a higher temperature is required. further residual cooling below 0.7 kev indicates very low complete cooling rates in most clusters. | searching for cool and cooling x-ray emitting gas in 45 galaxy clusters and groups |
the distribution of ejecta in young supernova remnants offers a powerful observational probe of their explosions and progenitors. here we present a 3d reconstruction of the ejecta in snr 0540-69.3, which is an o-rich remnant with a pulsar wind nebula located in the lmc. we use observations from the very large telescope (vlt)/muse to study hβ, [o iii] λ λ4959, 5007, hα, [s ii] λ λ6717, 6731, [ar iii] λ7136, and [s iii] λ9069. this is complemented by 2d spectra from vlt/x-shooter, which also cover [o ii] λ λ3726, 3729, and [fe ii] λ12567. we identify three main emission components: (i) clumpy rings in the inner nebula (≲1000 km s-1) with similar morphologies in all lines; (ii) faint extended [o iii] emission dominated by an irregular ring-like structure with radius ~1600 km s-1 and inclination ~40°, but with maximal velocities reaching ~3000 km s-1; and (iii) a blob of hα and hβ located southeast of the pulsar at velocities ~1500-3500 km s-1. we analyze the geometry using a clump-finding algorithm and use the clumps in the [o iii] ring to estimate an age of 1146 ± 116 yr. the observations favor an interpretation of the [o iii] ring as ejecta, while the origin of the h-blob is more uncertain. an alternative explanation is that it is the blown-off envelope of a binary companion. from the detection of balmer lines in the innermost ejecta we confirm that snr 0540 was a type ii supernova and that hydrogen was mixed down to low velocities in the explosion. | clumps and rings of ejecta in snr 0540-69.3 as seen in 3d |
the mammoth-1 nebula at z = 2.317 is an enormous lyα nebula (elan) extending to a ~440 kpc scale at the center of the extreme galaxy overdensity boss 1441. in this paper, we present observations of the co(3 - 2) and 250 ghz dust-continuum emission from mammoth-1 using the iram northern extended millimeter array. our observations show that co(3 - 2) emission in this elan has not extended widespread emission into the circum- and inter-galactic media. we also find a remarkable concentration of six massive galaxies in co(3 - 2) emission in the central ~100 kpc region of the elan. their velocity dispersions suggest a total halo mass of m 200c~ 1013.1 m ⊙, marking a possible protocluster core associated with the elan. the peak position of the co(3 - 2) line emission from the obscured agn is consistent with the location of the intensity peak of mammoth-1 in the rest-frame uv band. its luminosity line ratio between the co(3 - 2) and co(1 - 0)r 3,1 is 0.61 ± 0.17. the other five galaxies have co(3 - 2) luminosities in the range of (2.1-7.1) × 109 k km s-1 pc2, with the star-formation rates derived from the 250 ghz continuum of (<36)-224 m ⊙ yr-1. follow-up spectroscopic observations will further confirm more member galaxies and improve the accuracy of the halo mass estimation. | discovery of a protocluster core associated with an enormous lya nebula at z = 2.3 |
deep near-infrared photometric surveys are efficient in identifying high-redshift galaxies, however, they can be prone to systematic errors in photometric redshift. this is particularly salient when there is limited sampling of key spectral features of a galaxy's spectral energy distribution (sed), such as for quiescent galaxies where the expected age-sensitive balmer/4000 å break enters the k-band at z > 4. with single-filter sampling of this spectral feature, degeneracies between sed models and redshift emerge. a potential solution to this comes from splitting the k band into multiple filters. we use simulations to show an optimal solution is to add two medium-band filters, k blue (λ cen = 2.06 μm, δλ = 0.25 μm) and k red (λ cen = 2.31 μm, δλ = 0.27 μm), that are complementary to the existing k s filter. we test the impact of the k-band filters with simulated catalogs comprised of galaxies with varying ages and signal-to-noise. the results suggest that the k-band filters do improve photometric redshift constraints on z > 4 quiescent galaxies, increasing precision and reducing outliers by up to 90%. we find that the impact from the k-band filters depends on the signal-to-noise, the redshift, and the sed of the galaxy. the filters we designed were built and used to conduct a pilot of the flamingos-2 extragalactic near-infrared k-band split survey. while no new z > 4 quiescent galaxies are identified in the limited area pilot, the k blue and k red filters indicate strong balmer/4000 å breaks in existing candidates. additionally, we identify galaxies with strong nebular emission lines, for which the k-band filters increase photometric redshift precision and in some cases indicate extreme star formation. | introducing the flamingos-2 split-k medium-band filters: the impact on photometric selection of high-z galaxies in the feniks-pilot survey |
observations and modelling of stars with near-solar masses in their early phases of evolution are critical for a better understanding of how dynamos of solar-type stars evolve. we examine the chemical composition and the spot distribution of the pre-main-sequence solar analogue ek dra. using spectra from the hermes spectrograph (la palma), we obtain the abundances of 23 elements with respect to the solar ones, which lead to a [fe/h] = 0.03, with significant overabundance of li and ba. the s-process elements sr, y, and ce are marginally overabundant, while co, ni, cu, zn are marginally deficient compared to solar abundances. the overabundance of ba is most likely due to the assumption of depth-independent microturbulent velocity. li abundance is consistent with the age and the other abundances may indicate distinct initial conditions of the pre-stellar nebula. we estimate a mass of 1.04 m⊙ and an age of $27^{+11}_{-8}$ myr using various spectroscopic and photometric indicators. we study the surface distribution of dark spots, using 17 spectra collected during 15 nights using the cafe spectrograph (calar alto). we also conduct flux emergence and transport (feat) simulations for ek dra's parameters and produce 15-d-averaged synoptic maps of the likely starspot distributions. using doppler imaging, we reconstruct the surface brightness distributions for the observed spectra and feat simulations, which show overall agreement for polar and mid-latitude spots, while in the simulations there is a lack of low-latitude spots compared to the observed image. we find indications that cross-equatorial extensions of mid-latitude spots can be artefacts of the less visible southern-hemisphere activity. | observing and modelling the young solar analogue ek draconis: starspot distribution, elemental abundances, and evolutionary status |
we reconsider the commonly held assumption that warm debris disks are tracers of terrestrial planet formation. the high occurrence rate inferred for earth-mass planets around mature solar-type stars based on exoplanet surveys (∼20%) stands in stark contrast to the low incidence rate (≤2%-3%) of warm dusty debris around solar-type stars during the expected epoch of terrestrial planet assembly (∼10 myr). if earth-mass planets at au distances are a common outcome of the planet formation process, this discrepancy suggests that rocky planet formation occurs more quickly and/or is much neater than traditionally believed, leaving behind little in the way of a dust signature. alternatively, the incidence rate of terrestrial planets has been overestimated, or some previously unrecognized physical mechanism removes warm dust efficiently from the terrestrial planet region. a promising removal mechanism is gas drag in a residual gaseous disk with a surface density ≳10-5 of the minimum-mass solar nebula. | rocky planet formation: quick and neat |
aims: star-forming galaxies with nebular he ii emission contain very energetic ionizing sources of radiation, which can be considered as analogs to the major contributors of the reionization of the universe in early epochs. it is therefore of great importance to provide a reliable absolute scale for the equivalent effective temperature (t*) for these sources.methods: we study a sample of local (z < 0.2) star-forming galaxies showing optical nebular he ii emission using the so-called softness diagrams, involving emission lines of two elements in two consecutive stages of ionization (e.g., [s ii]/[s iii] vs. [o ii]/[o iii]). we use for the first time the he i/he ii ratio in these diagrams in order to explore the higher range of t* expected in these objects, and to investigate the role of possible mechanisms driving the distribution of galaxy points in these diagrams. we build grids of photoionization models covering different black-body temperatures, model cluster atmospheres, and density-bounded geometries to explain the conditions observed in the sample.results: we verified that the use of the softness diagrams including the emission-line ratio he i/he ii combined with black-body photoionization models can provide an absolute scale of t* for these objects. the application of a bayesian-like code indicates t* in the range 50-80 kk for the sample of galaxies, with a mean value higher than 60 kk. the average of these high temperature values can only be reproduced using cluster model populations with nearly metal-free stars, although such ionizing sources cannot explain either the highest t* values, beyond 1σ, or the dispersion observed in the softness diagrams. according to our photoionization models, most sample galaxies could be affected to some extent by ionizing photon leaking, presenting a mean photon absorption fraction of 26% or higher depending on the metallicity assumed for the ionizing cluster. the entire range of he i/he ii, [s ii]/[s iii], and [o ii]/[o iii] ratios for these heii-emitting galaxies is reproduced with our models, combining nearly metal-free ionizing clusters and photon leaking under different density-bounded conditions. observed and derived properties of the sample of galaxies 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/643/a80 | photon leaking or very hard ionizing radiation? unveiling the nature of he ii-emitters using the softness diagram |
the microwave radiometer on board the juno spacecraft provided a measurement of the water abundance found to range between ~1 and 5.1 times the protosolar abundance of oxygen in the near-equatorial region of jupiter. here, we aim to combine this up-to-date oxygen determination, which is likely to be more representative of the bulk abundance than the galileo probe subsolar value, with the other known measurements of elemental abundances in jupiter, to derive the formation conditions and initial composition of the building blocks agglomerated by the growing planet, and that determine the heavy element composition of its envelope. we investigate several cases of formation of icy solids in the protosolar nebula (psn), from the condensation of pure ices to the crystallization of mixtures of pure condensates and clathrates in various proportions. each of these cases corresponds to a distinct solid composition whose amount is adjusted in the envelope of jupiter to match the o abundance measured by juno. the volatile enrichments can be matched by a wide range of planetesimal compositions, from solids exclusively formed from pure condensates or from nearly exclusively clathrates, the latter case providing a slightly better fit. the total mass of volatiles needed in the envelope of jupiter to match the observed enrichments is within the ~4.3-39 m⊕ range, depending on the crystallization scenario considered in the psn. a wide range of masses of heavy elements derived from our fits is found to be compatible with the envelope's metallicity calculated from current interior models. | the nature and composition of jupiter's building blocks derived from the water abundance measurements by the juno spacecraft |
giant star-forming regions (clumps) are widespread features of galaxies at z ≈ 1-4. theory predicts that they can play a crucial role in galaxy evolution, if they survive to stellar feedback for >50 myr. numerical simulations show that clumps' survival depends on the stellar feedback recipes that are adopted. up to date, observational constraints on both clumps' outflows strength and gas removal time-scale are still uncertain. in this context, we study a line-emitting galaxy at redshift z ≃ 3.4 lensed by the foreground galaxy cluster abell 2895. four compact clumps with sizes ≲280 pc and representative of the low-mass end of clumps' mass distribution (stellar masses ≲2 × 108 m⊙) dominate the galaxy morphology. the clumps are likely forming stars in a starbursting mode and have a young stellar population (~10 myr). the properties of the lyman-α (lyα) emission and nebular far-ultraviolet absorption lines indicate the presence of ejected material with global outflowing velocities of ~200-300 km s-1. assuming that the detected outflows are the consequence of star formation feedback, we infer an average mass loading factor (η) for the clumps of ~1.8-2.4 consistent with results obtained from hydrodynamical simulations of clumpy galaxies that assume relatively strong stellar feedback. assuming no gas inflows (semiclosed box model), the estimates of η suggest that the time-scale over which the outflows expel the molecular gas reservoir (≃7 × 108 m⊙) of the four detected low-mass clumps is ≲50 myr. | stellar feedback in a clumpy galaxy at z 3.4 |
we report the detection of very high energy gamma-ray emission from the blazar s3 1227+25 (ver j1230+253) with the very energetic radiation imaging telescope array system (veritas). veritas observations of the source were triggered by the detection of a hard-spectrum gev flare on 2015 may 15 with the fermi-large area telescope (lat). a combined 5 hr veritas exposure on may 16 and 18 resulted in a strong 13σ detection with a differential photon spectral index, γ = 3.8 ± 0.4, and a flux level at 9% of the crab nebula above 120 gev. this also triggered target-of-opportunity observations with swift, optical photometry, polarimetry, and radio measurements, also presented in this work, in addition to the veritas and fermi-lat data. a temporal analysis of the gamma-ray flux during this period finds evidence of a shortest variability timescale of τ obs = 6.2 ± 0.9 hr, indicating emission from compact regions within the jet, and the combined gamma-ray spectrum shows no strong evidence of a spectral cutoff. an investigation into correlations between the multiwavelength observations found evidence of optical and gamma-ray correlations, suggesting a single-zone model of emission. finally, the multiwavelength spectral energy distribution is well described by a simple one-zone leptonic synchrotron self-compton radiation model. | veritas discovery of very high energy gamma-ray emission from s3 1227+25 and multiwavelength observations |
context. future and ongoing infrared and radio observatories such as jwst, metis, and alma will increase the amount of rest-frame ir spectroscopic data for galaxies by several orders of magnitude. while studies of the chemical composition of the interstellar medium (ism) based on optical observations have been widely spread over decades for star-forming galaxies (sfgs) and, more recently, for active galactic nuclei (agn), similar studies need to be performed using ir data. in the case of agn, this regime can be especially useful given that it is less affected by temperature and dust extinction, traces higher ionic species, and can also provide robust estimations of the chemical abundance ratio n/o.aims: we present a new tool based on a bayesian-like methodology (hii-chi-mistry-ir) to estimate chemical abundances from ir emission lines in agn. we use a sample of 58 agn with ir spectroscopic data retrieved from the literature, composed by 43 seyferts, eight ultraluminous infrared galaxies (ulirgs), four luminous infrared galaxies (lirgs), and three low-ionization nuclear emission line regions (liners), to probe the validity of our method. the estimations of the chemical abundances based on ir lines in our sample are later compared with the corresponding abundances derived from the optical emission lines in the same objects.methods: hii-chi-mistry-ir takes advantage of photoionization models, characterized by the chemical abundance ratios o/h and n/o, and the ionization parameter u, to compare their predicted emission-line fluxes with a set of observed values. instead of matching single emission lines, the code uses some specific emission-line ratios that are sensitive to the above free parameters.results: we report mainly solar and also subsolar abundances for o/h in the nuclear region for our sample of agn, whereas n/o clusters are around solar values. we find a discrepancy between the chemical abundances derived from ir and optical emission lines, the latter being higher than the former. this discrepancy, also reported by previous studies of the composition of the ism in agn from ir observations, is independent of the gas density or the incident radiation field to the gas, and it is likely associated with dust obscuration and/or temperature stratification within the gas nebula. full tables a.1-a.4 are only available at the cds via anonymous ftp to cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/cat/j/a+a/666/a115 | measuring chemical abundances in agn from infrared nebular lines: hii-chi-mistry-ir for agn |
using deep near-infrared keck/mosfire observations, we analyze the rest-optical spectra of eight star-forming galaxies in the cosmos and goods-n fields. we reach integration times of ~10 hr in the deepest bands, pushing the limits on current ground-based observational capabilities. the targets fall into two redshift bins, of five galaxies at z ~ 1.7 and three galaxies at z ~ 2.5, and were selected as likely to yield significant auroral-line detections. even with long integration times, detection of the auroral lines remains challenging. we stack the spectra together into subsets based on redshift, improving the signal-to-noise ratio on the [o iii]λ4364 auroral emission line and, in turn, enabling a direct measurement of the oxygen abundance for each stack. we compare these measurements to commonly employed strong-line ratios alongside measurements from the literature. we find that the stacks fall within the distribution of z > 1 literature measurements, but a larger sample size is needed to robustly constrain the relationships between strong-line ratios and oxygen abundance at high redshift. we additionally report detections of [o i]λ6302 for nine individual galaxies and composite spectra of 21 targets in the mosfire pointings. we plot their line ratios on the [o iii]λ5008/hβ versus [o i]λ6302/hα diagnostic diagram, comparing our targets to local galaxies and h ii regions. we find that the [o i]/hα ratios in our sample of galaxies are consistent with being produced in gas ionized by α-enhanced massive stars, as has been previously inferred for rapidly forming galaxies at early cosmic times. | ultra-deep keck/mosfire spectroscopic observations of z 2 galaxies: direct oxygen abundances and nebular excitation properties |
the evolution and lifetime of protoplanetary disks (ppds) play a central role in the formation and architecture of planetary systems. astronomical observations suggest that ppds evolve in two timescales, accreting onto the star for up to several million years (myr) followed by gas dissipation within ≲1 myr. because solar nebula magnetic fields are sustained by the gas of the protoplanetary disk, we can use paleomagnetic measurements to infer the lifetime of the solar nebula. here, we use paleomagnetic measurements of meteorites to constrain this lifetime and investigate whether the solar nebula had a two-timescale evolution. we report on paleomagnetic measurements of bulk subsamples of two co carbonaceous chondrites: allan hills a77307 and dominion range 08006. if magnetite in these meteorites can acquire a crystallization remanent magnetization that recorded the ambient field during aqueous alteration, our measurements suggest that the local magnetic field strength at the co parent body location was <0.9 μt at some time between 2.7 and 5.1 myr after the formation of calcium-aluminum-rich inclusions. coupled with previous paleomagnetic studies, we conclude that the dissipation of the solar nebula in the 3-7 au region occurred <1.5 myr after the dissipation of the nebula in the 1-3 au region, suggesting that protoplanetary disks go through a two-timescale evolution in their lifetime, consistent with dissipation by photoevaporation and/or magnetohydrodynamic winds. we also discuss future directions necessary to obtain robust records of solar nebula fields using bulk chondrites, including obtaining ages from meteorites and experimental work to determine how magnetite acquires magnetization during chondrite parent body alteration. | lifetime of the outer solar system nebula from carbonaceous chondrites |
while there is now a consensus that x-ray binaries (xrbs) are the dominant x-ray sources in the early universe and play a significant role during the epoch of heating of the intergalactic medium (igm), recent studies report contradicting results regarding their contribution in the nebular emission of local universe galaxies. ultraluminous x-ray sources (ulxs), which dominate the x-ray budget of normal galaxies, may be important interstellar-medium (ism) ionizing sources. however, their output in the extreme-ultraviolet (euv) and soft x-ray part of the spectrum remains observationally unconstrained. in this paper, we predict the ionizing and heating power from ulx populations under the geometrical beaming scenario, and three models describing the emission from super-critical accretion disks. we find that our theoretical spectra for ulx populations cannot (can) explain the he ii (ne v) emission observed in some galaxies, with their contribution being less (more) important than the underlying stellar population. stochastic fluctuations in the number of ulxs may allow for equal contributions in the he ii emission, in a fraction of galaxies. we provide average spectra of ulx populations as an input to local, and early-universe studies. we find that the soft x-ray emission arising from super-critical accretion is significant for the heating of the igm, and consistent with recent constraints from the 21-cm cosmic signal. based on the dependence on the adopted compact-object (co) mass and accretion model, we encourage efforts in modeling ulx spectra via simulations, and their combination with detailed binary population synthesis models. full table 1 is only available at the cds via anonymous ftp to cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/cat/j/a+a/665/a28 | the ionizing and heating power of ultraluminous x-ray sources under the geometrical beaming model |
young stellar objects are known to exhibit strong radio variability on timescales of weeks to months, and a few reports have documented extreme radio flares with at least an order of magnitude change in flux density on timescales of hours to days. however, there have been few constraints on the occurrence rate of such radio flares or on the correlation with pre-main sequence x-ray flares, although such correlations are known for the sun and nearby active stars. here we report simultaneous deep vla radio and chandra x-ray observations of the orion nebula cluster, targeting hundreds of sources to look for the occurrence rate of extreme radio variability and potential correlation with the most extreme x-ray variability. we identify 13 radio sources with extreme radio variability, with some showing an order of magnitude change in flux density in less than 30 minutes. all of these sources show x-ray emission and variability, but we find clear correlations with extreme radio flaring only on timescales <1 hr. strong x-ray variability does not predict the extreme radio sources and vice versa. radio flares thus provide us with a new perspective on high-energy processes in ysos and the irradiation of their protoplanetary disks. finally, our results highlight implications for interferometric imaging of sources violating the constant-sky assumption. | extreme radio flares and associated x-ray variability from young stellar objects in the orion nebula cluster |
efforts over 40 yr still leave the source of astronomical infrared emission bands largely unidentified. here, we report the first laboratory infrared (6-25 μm) spectra of gas-phase fullerene-metal complexes, [c60-metal]+ (metal = fe, v) and show with density functional theory calculations that complexes of c60 with cosmically abundant metals, including li, na, k, mg, ca, al, v, and fe, all have similar spectral patterns. comparison with observational infrared spectra from several fullerene-rich planetary nebulae demonstrates a strong positive linear cross-correlation. the infrared features of [c60-metal]+ coincide with four bands attributed earlier to neutral c60 bands and in addition also with several bands unexplained to date. abundance and collision theory estimates indicate that [c60-metal]+ could plausibly form and survive in astrophysical environments. hence, [c60-metal]+ are proposed as promising carriers, in supplement to c60, of observational bands, potentially representing the largest molecular species in space other than c60, c60 +, and c70. | buckyball-metal complexes as potential carriers of astronomical unidentified infrared emission bands |
we investigated the stable isotope fractionation of chromium (cr) for a panorama of chondrites, including eh and el enstatite chondrites and their chondrules and different phases (by acid leaching). we observed that chondrites have heterogeneous δ 53cr values (per mil deviation of the 53cr/52cr from the nist srm 979 standard), which we suggest reflect different physical conditions in the different chondrite accretion regions. chondrules from a primitive eh3 chondrite (sah 97096) possess isotopically heavier cr relative to their host bulk chondrite, which may be caused by cr evaporation in a reduced chondrule-forming region of the protoplanetary disk. enstatite chondrites show a range of bulk δ 53cr values that likely result from variable mixing of isotopically different sulfide-silicate-metal phases. the bulk silicate earth (δ 53cr = -0.12 ± 0.02‰, 2se) has a lighter cr stable isotope composition compared to the average δ 53cr value of enstatite chondrites (-0.05 ± 0.02‰, 2se, when two samples out of 19 are excluded). if the bulk earth originally had a cr isotopic composition that was similar to the average enstatite chondrites, this cr isotope difference may be caused by evaporation under equilibrium conditions from magma oceans on earth or its planetesimal building blocks, as previously suggested to explain the magnesium and silicon isotope differences between earth and enstatite chondrites. alternatively, chemical differences between earth and enstatite chondrite can result from thermal processes in the solar nebula and the enstatite chondrite-earth, which would also have changed the cr isotopic composition of earth and enstatite chondrite parent body precursors. | chromium stable isotope panorama of chondrites and implications for earth early accretion |
context. ngc 2264 is a young cluster whose accretion properties can be investigated in detail by taking advantage of the flames data in the context of the gaia-eso survey. in fact, the analysis of the hα emission line profile can provide us with information about the accretion and ejection activity of young stars. however, a strong nebular emission that contributes to the hα emission can alter the profiles, with consequences for their physical interpretation.aims: our study is aimed at investigating the accretion and ejection properties of ngc 2264 by applying a proper treatment of the sky contribution to the hα and forbidden emission lines (fels; [sii] and [nii] doublets).methods: we developed a tool, the ohαna-method, to handle the strong nebular contribution and spectra with spurious profiles of the hα and fels, namely altered hα profiles or absorption features artificially created where emission lines (fels) are expected. we derived the quantitative measurements of relevant parameters to describe the accretion and ejection processes in young members of ngc 2264, focusing on reliable quantities derived from the width of the lines, which is relatively unaffected by the nebular emission, unlike the intensity peak, which can be altered significantly.results: we derive the quantitative measurements related to the hα emission line and discuss the comparison between the original and sky-subtracted spectra. we thus reveal possible profile alterations with consequences for their physical interpretation. furthermore, we show the analysis of the variability for multi-epoch observations, also deriving the velocity of the infalling and outflowing plasma from the wings of the broad hα emission line (in accreting stars). we also explore the mass accretion rate versus full width at zero intensity of the hα line, namely ṁ versus fwzi(hα), a correlation based on the width of the emission line, which is expected to be more robust with respect to any measurement derived from the peak (e.g., hα10%) and possibly altered by the nebular contribution.conclusions: we are able to ascertain that more than 20% of the confirmed accretors, which have already been identified in ngc 2264, are affected by the alteration of their line profiles due to the contribution of the nebular emission. therefore, this is an important issue to consider when investigating accretion and ejection processes in young stellar clusters. while a small fraction of spectra can be unequivocally classified as either unaffected by nebular emission or dominated by nebular emission, the majority (> 90%) represent intermediate cases whose spectral features have to be investigated in detail to derive reliable measurements of the relevant parameters and their physical implications. full tables 1, a.1, and a.2 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/642/a56 | the gaia-eso survey: a new diagnostic for accretion and outflow activity in the young cluster ngc 2264 |
enormous lyα nebulae, extending over 300-500 kpc around quasars, represent the pinnacle of galaxy and cluster formation. here we present iram plateau de bure interferometer observations of the enormous lyα nebulae "slug" (z = 2.282) and "jackpot" (z = 2.041). our data reveal bright, synchrotron emission associated with the two radio-loud active galactic nuclei embedded in the targeted nebulae as well as molecular gas, as traced via the co(3-2) line, in three galaxies (two sources in slug, and one in jackpot). all of the co emission is associated with galaxies detected in their rest-frame uv stellar emission. the total mass in molecular gas of these three galaxies [∼(3 - 5) × 1010 m⊙] is comparable with the total ionized gas mass responsible for the diffuse nebular emission. our observations place limits on the molecular gas emission in the nebulae: the molecular gas surface density is σh2 < 12 - 25 m⊙ pc-2 for the slug nebula and σh2 < 34 - 68 m⊙ pc-2 for the jackpot nebula. these are consistent with the expected molecular gas surface densities, as predicted via photoionization models of the rest-frame uv line emission in the nebulae, and via lyα absorption in the jackpot nebula. compared to other radio-loud quasars at z > 1 and high-redshift radio-loud galaxies, we do not find any strong trends relating the molecular gas reservoirs, the radio power, and the lyα luminosities of these systems. the significant step in sensitivity required to achieve a detection of the molecular gas from the nebulae, if present, will require a substantial time investment with jvla, noema, or alma. | a search for dust and molecular gas in enormous lyα nebulae at z ≈ 2 |
the alkali element k is moderately volatile and fluid mobile; thus, it can be influenced by both primary processes (evaporation and recondensation) in the solar nebula and secondary processes (thermal and aqueous alteration) in the parent body. since these primary and secondary processes would induce different isotopic fractionations, k isotopes could become a potential tracer to distinguish them. using recently developed methods with improved precision (0.05‰, 95% confidence interval), we systematically measured the k isotopic compositions and major/trace elemental compositions of chondritic components (18 chondrules, 3 cais, 2 matrices, and 5 bulks) in the carbonaceous chondrite fall allende. among all the components analyzed in this study, cais, which formed initially under high temperature conditions in the solar nebula and were dominated by nominally k free refractory minerals, have the highest k2o content (average 0.53 wt%) and have k isotope compositions most enriched in heavy isotopes (δ41k: -0.30 to -0.25‰). such an observation is consistent with previous petrologic studies that show cais in allende have undergone alkali enrichment during metasomatism. in contrast, chondrules contain lower k2o content (0.003-0.17 wt%) and generally lighter k isotope compositions (δ41k: -0.87‰ to -0.24‰). the matrix and bulks are nearly identical in k2o content and k isotope compositions (0.02-0.05 wt%; δ41k: -0.62 to - 0.46‰), which are, as expected, right in the middle of cais and chondrules. this strongly indicates that most of the chondritic components of allende suffered aqueous alteration and their k isotopic compositions are the ramification of allende parent body processing instead of primary nebular signatures. nevertheless, we propose the small k isotope fractionations observed (< 1‰) among allende components are likely similar to the overall range of k isotopic fractionation that occurred in nebular environment. furthermore, the k isotope compositions seen in the components of allende in this study are consistent with mc icp ms analyses of the components in ordinary chondrites, which also show an absence of large (10‰) isotope fractionations. this is not expected as evaporation experiments in nebular conditions suggest there should be large k isotopic fractionations. nevertheless, possible nebular processes such as chondrules back exchanging with ambient gas when they formed could explain this lack of large k isotopic variation. | early solar system aqueous activity: k isotope evidence from allende |
we present extensive ground-based and hubble space telescope (hst) photometry of the highly reddened, very nearby sn ia 2014j in m82, covering the phases from 9 days before to about 900 days after the b-band maximum. sn 2014j is similar to other normal sne ia near the maximum light, but it shows flux excess in the b band in the early nebular phase. this excess flux emission can be due to light scattering by some structures of circumstellar materials located at a few 1017 cm, consistent with a single-degenerate progenitor system or a double-degenerate progenitor system with mass outflows in the final evolution or magnetically driven winds around the binary system. at t ∼ +300 to ∼+500 days past the b-band maximum, the light curve of sn 2014j shows a faster decline relative to the 56ni decay. that feature can be attributed to the significant weakening of the emission features around [fe iii] λ4700 and [fe ii] λ5200 rather than the positron escape, as previously suggested. analysis of the hst images taken at t > 600 days confirms that the luminosity of sn 2014j maintains a flat evolution at the very late phase. fitting the late-time pseudobolometric light curve with radioactive decay of 56ni, 57ni, and 55fe isotopes, we obtain the mass ratio 57ni/56ni as 0.035 ± 0.011, which is consistent with the corresponding value predicted from the 2d and 3d delayed-detonation models. combined with early-time analysis, we propose that delayed-detonation through the single-degenerate scenario is most likely favored for sn 2014j. | observations of type ia supernova 2014j for nearly 900 days and constraints on its progenitor system |
the tight correlation between turbulence and luminosity in giant hii regions (ghrs) is not well understood. while the luminosity is due to the uv radiation from the massive stars in the ionizing clusters, it is not clear what powers the turbulence. observations of the two prototypical ghrs in the local universe, 30 doradus and ngc 604, show that part of the kinetic energy of the nebular gas comes from the combined stellar winds of the most massive stars, the cluster winds, but not all. we present a study of the kinematics of 30 doradus based on archival vlt flames/giraffe data and new high-resolution observations with harps. we find that the nebular structure and kinematics are shaped by a hot cluster wind and not by the stellar winds of individual stars. the cluster wind powers most of the turbulence of the nebular gas, with a small contribution from the combined gravitational potential of stars and gas. we estimate the total mass of 30 doradus and we argue that the region does not contain significant amounts of neutral (hi) gas, and that the giant molecular cloud 30 dor-10, which is close to the center of the nebula in projection, is in fact an inflating cloud tens of parsecs away from r136, the core of the ionizing cluster. we rule out a kolmogorov-like turbulent kinetic energy cascade as the source of supersonic turbulence in ghrs. partly based on observations made with eso telescopes at the la silla paranal observatory under programmes 072.c-0348; 182.d-0222; and 60.a-9700(g), and programme id 076.c-0888, processed and released by the eso vos/adp group. | supersonic turbulence in giant hii regions: clues from 30 doradus |
we present a detailed analysis of ic 4776, a planetary nebula displaying a morphology believed to be typical of central star binarity. the nebula is shown to comprise a compact hourglass-shaped central region and a pair of precessing jet-like structures. time-resolved spectroscopy of its central star reveals a periodic radial velocity variability consistent with a binary system. whilst the data are insufficient to accurately determine the parameters of the binary, the most likely solutions indicate that the secondary is probably a low-mass main-sequence star. an empirical analysis of the chemical abundances in ic 4776 indicates that the common-envelope phase may have cut short the asymptotic giant branch evolution of the progenitor. abundances calculated from recombination lines are found to be discrepant by a factor of approximately 2 relative to those calculated using collisionally excited lines, suggesting a possible correlation between low-abundance discrepancy factors and intermediate-period post-common-envelope central stars and/or wolf-rayet central stars. the detection of a radial velocity variability associated with the binarity of the central star of ic 4776 may be indicative of a significant population of (intermediate-period) post-common-envelope binary central stars that would be undetected by classic photometric monitoring techniques. | the planetary nebula ic 4776 and its post-common-envelope binary central star |
the first repeating fast radio burst (frb), frb 121102, was found to be associated with a spatially coincident, persistent nonthermal radio source, but the origin of the persistent emission remains unknown. in this paper, we propose that the persistent emission is produced via a synchrotron-heating process by multiple bursts of frb 121102 in a self-absorbed synchrotron nebula. with a population of bursts of the repeating frb absorbed by the synchrotron nebula, the energy distribution of electrons in the nebula will change significantly. as a result, the spectrum of the nebula will show a hump steadily. for the persistent emission of frb 121102, the total energy of bursts injecting into the nebula is required to be about 3.3 × 1049 erg, the burst injection age is over 6.7 × 104 yr, the nebula size is ∼0.02 pc, and the electron number is about 3.2 × 1055. we predict that as more bursts inject, the brightness of the nebula would be brighter than the current observation, and meanwhile, the peak frequency would become higher. due to the synchrotron absorption of the nebula, some low-frequency bursts would be absorbed, which may explain why most bursts were detected above ∼1 ghz. | persistent radio emission from synchrotron heating by a repeating fast radio burst source in a nebula |
n103b is a type ia supernova remnant (snr) projected in the outskirts of the superbubble around the rich cluster ngc 1850 in the large magellanic cloud (lmc). we have obtained hα and continuum images of n103b with the hubble space telescope (hst) and high-dispersion spectra with the 4 m and 1.5 m telescopes at cerro tololo inter-american observatory. the hst hα image exhibits a complex system of nebular knots inside an incomplete filamentary elliptical shell that opens to the east, where x-ray and radio emission extends farther out. electron densities of the nebular knots, determined from the [s ii] doublet, reach 5300 cm-3, indicating an origin of circumstellar medium, rather than interstellar medium. the high-dispersion spectra reveal three kinematic components in n103b: (1) a narrow component with [n ii] λ6583/hα ∼ 0.14 from the ionized interstellar gas associated with the superbubble of ngc 1850 in the background, (2) a broader hα component with no [n ii] counterpart from the snr’s collisionless shocks into a mostly neutral ambient medium, and (3) a broad component, {{δ }}v ∼ 500 km s-1, in both hα and [n ii] lines from shocked material in the nebular knots. the balmer-dominated filaments can be fitted by an ellipse, and we adopt its center as the site of sn explosion. we find that the star closest to this explosion center has colors and luminosity consistent with a 1 {m}⊙surviving subgiant companion as modeled by podsiadlowski. follow-up spectroscopic observations are needed to confirm this star as the sn’s surviving companion. | physical structures of the type ia supernova remnant n103b |
for pulsars born in supernovae, the expansion of the shocked pulsar wind nebula is initially in the freely expanding ejecta of the supernova. while the nebula is in the inner flat part of the ejecta density profile, the swept-up, accelerating shell is subject to the rayleigh-taylor instability. we carried out two- and three-dimensional simulations showing that the instability gives rise to filamentary structure during this initial phase but does not greatly change the dynamics of the expanding shell. the flow is effectively self-similar. if the shell is powered into the outer steep part of the density profile, the shell is subject to a robust rayleigh-taylor instability in which the shell is fragmented and the shocked pulsar wind breaks out through the shell. the flow is not self-similar in this phase. for a wind nebula to reach this phase requires that the deposited pulsar energy be greater than the supernova energy, or that the initial pulsar period be in the ms range for a typical 1051 erg supernova. these conditions are satisfied by some magnetar models for type i superluminous supernovae. we also consider the crab nebula, which may be associated with a low energy supernova for which this scenario applies. | pulsar wind bubble blowout from a supernova |
we report the discovery of an ∼100 kpc ionized nebula associated with the radio-quiet type 2 quasar (qso2) nicknamed the `teacup' (z = 0.085). the giant nebula is among the largest known around active galaxies at any z. we propose that it is part of the circumgalactic medium (cgm) of the qso2 host, which has been populated with tidal debris by galactic interactions. this rich gaseous medium has been rendered visible due to the illumination by the powerful active nucleus (agn). subsolar abundances (∼0.5 z⊙) are tentatively favoured by agn photoionization models. we also report the detection of coronal emission (fe+6) from the ne bubble, at ∼9 kpc from the agn. the detection of coronal lines at such large distances from the agn and the [n ii] λ6583/hα, [s ii] λλ6716,6731/hα, [o i] λ6300/hα optical emission-line ratios of the giant nebula are consistent with the fading quasar scenario proposed by gagne et al. the fading rate appears to have been faster in the last ∼46 000 yr. deep wide field integral field spectroscopy of giant nebulae around powerful agn such as the `teacup's' with instruments such as muse on vlt opens up a way to detect and study the elusive material from the cgm around massive active galaxies thanks to the illumination by the luminous agn. | a 100 kpc nebula associated with the `teacup' fading quasar |
vela x is a prototypical example of a pulsar wind nebula whose morphology and detailed structure have been affected by interaction with the reverse shock of its host supernova remnant. the resulting complex of filamentary structure and mixed-in ejecta embedded in a nebula that is offset from the pulsar provides the best example we have of this middle-age state that characterizes a significant fraction of composite supernova remnants (snrs), and perhaps all of the large-diameter pulsar wind nebulae (pwne) seen as tev sources. here, we report on an xmm-newton (hereafter xmm) large project study of vela x, supplemented by additional chandra observations. through broad spectral modeling, as well as detailed spectral investigations of discrete emission regions, we confirm previous studies that report evidence for ejecta material within vela x, and show that equivalent-width variations of o vii and o viii are consistent with temperature maps within the pwn that show low-temperature regions where the projected snr emission appears to dominate emission from the ejecta. we identify spectral variations in the nonthermal emission, with hard emission being concentrated near the pulsar. we carry out investigations of the vela x “cocoon” structure, and with hydrodynamical simulations, show that its overall properties are consistent with structures formed in the late-phase evolution of a composite snr expanding into a surrounding medium with a density gradient, with ejecta material being swept beyond the pulsar and compressed into an elongated structure in the direction opposite the high external density. | investigating the structure of vela x |
the famous rosette nebula has an evacuated central cavity formed from the stellar winds ejected from the 2-6 myr old codistant and comoving central star cluster ngc 2244. however, with upper age estimates of less than 110 000 yr, the central cavity is too young compared to ngc 2244 and existing models do not reproduce its properties. a new proper motion study herein using gaia data reveals the ejection of the most massive star in the rosette, hd 46223, from ngc 2244 occurred 1.73 (+0.34, -0.25) myr (1σ uncertainty) in the past. assuming this ejection was at the birth of the most massive stars in ngc 2244, including the dominant centrally positioned hd 46150, the age is set for the famous ionized region at more than 10 times that derived for the cavity. here, we are able to reproduce the structure of the rosette nebula, through simulation of mechanical stellar feedback from a 40 m⊙ star in a thin sheet-like molecular cloud. we form the 135 000 m⊙ cloud from thermally unstable diffuse interstellar medium (ism) under the influence of a realistic background magnetic field with thermal/magnetic pressure equilibrium. properties derived from a snapshot of the simulation at 1.5 myr, including cavity size, stellar age, magnetic field, and resulting inclination to the line of sight, match those derived from observations. an elegant explanation is thus provided for the stark contrast in age estimates based on realistic diffuse ism properties, molecular cloud formation and stellar wind feedback. | a new mechanical stellar wind feedback model for the rosette nebula |
protostars and young stars are strongly spatially 'clustered' or 'correlated' within their natal giant molecular clouds. we demonstrate that such clustering leads to the conclusion that the incident bolometric radiative flux upon a random young star/disc is enhanced (relative to volume-averaged fluxes) by a factor that increases with the total stellar mass of the complex. because the galactic cloud mass function is top-heavy, the typical star in our galaxy experienced a much stronger radiative environment than those forming in well-observed nearby (but relatively small) clouds, exceeding fluxes in the orion nebular cluster by factors of ≳30. heating of the circumstellar disc around a median young star is dominated by this external radiation beyond ∼ 50 au. and if discs are not well shielded by ambient dust, external ultraviolet irradiation can dominate over the host star down to sub-au scales. another consequence of stellar clustering is an extremely broad galaxy-wide distribution of incident flux (spanning >10 decades), with half the galactic star formation in a substantial 'tail' towards even more intense background radiation. we also show that the strength of external irradiation is amplified superlinearly in high-density environments such as the galactic centre, starbursts, or high-redshift galaxies. | most stars (and planets?) are born in intense radiation fields |
ehwc j2019+368 is one of the sources emitting γ-rays with energies higher than 100 tev based on the recent measurement with the high altitude water cherenkov observatory (hawc), and the origin is still in debate. the pulsar psr j2021+3651 is spatially coincident with the tev source. we investigate theoretically whether the multiband non-thermal emission of ehwc j2019+368 can originate from the pulsar wind nebula (pwn) g75.2+0.1 powered by psr j2021+3651. in the model, the spin-down power of the pulsar is transferred to high-energy particles and magnetic field in the nebula. as the particles with an energy distribution of either a broken power law or a power law continually injected into the nebula, the multiband non-thermal emission is produced via synchrotron radiation and inverse compton scattering. the spectral energy distribution of the nebula from the model with the reasonable parameters is generally consistent with the detected radio, x-ray, and tev γ-ray fluxes. our study supports that the pwn has the ability to produce the tev γ-rays of ehwc j2019+368, and the most energetic particles in the nebula have energies up to about 0.4 pev. | investigating the multiband non-thermal emission of the 100 tev source ehwc j2019+368 with a pulsar wind nebula scenario |
nu ori is a massive spectroscopic and visual binary in the orion nebula cluster, with four components: aa, ab, b, and c. the b0.5 primary (aa) is one of the most massive b-type stars reported to host a magnetic field. we report the detection of a spectroscopic contribution from the c component in high-resolution espadons spectra, which is also detected in a very large telescope interferometer data set. radial velocity (rv) measurements of the inner binary (designated aab) yield an orbital period of 14.3027(7) d. the orbit of the third component (designated c) was constrained using both rvs and interferometry. we find c to be on a mildly eccentric 476(1) d orbit. thanks to spectral disentangling of mean line profiles obtained via least-squares deconvolution, we show that the zeeman stokes v signature is clearly associated with c, rather than aa as previously assumed. the physical parameters of the stars were constrained using both orbital and evolutionary models, yielding maa = 14.9 ± 0.5 m⊙, mab = 3.9 ± 0.7 m⊙, and mc = 7.8 ± 0.7 m⊙. the rotational period obtained from longitudinal magnetic field <bz> measurements is prot = 1.09468(7) d, consistent with previous results. modelling of <bz> indicates a surface dipole magnetic field strength of ∼8 kg. nu ori c has a magnetic field strength, rotational velocity, and luminosity similar to many other stars exhibiting magnetospheric hα emission, and we find marginal evidence of emission at the expected level (∼1 per cent of the continuum). | nu ori: a hierarchical triple system with a strongly magnetic b-type star |
type ia supernovae are vital to our understanding of the universe due to their use in measuring cosmological distances and their significance in enriching the interstellar medium with heavy elements. they are understood to be the thermonuclear explosions of white dwarfs, but the exact mechanism(s) leading to these explosions remains unclear. the two competing models are the single degenerate scenario, wherein a white dwarf accretes material from a companion star and explodes when it reaches the chandrasekhar limit, and the double degenerate scenario, wherein the explosion results from a merger of two white dwarfs. here, we report results which rule out hot, luminous progenitors consistent with the single degenerate scenario for four young type ia supernova remnants in the large magellanic cloud. using the integral field spectrograph wifes, we have searched these remnants for relic nebulae ionized by the progenitor, which would persist for up to 105 yr after the explosion. we detected no such nebula around any of the remnants. by comparing our upper limits with photoionization simulations performed using cloudy, we have placed stringent upper limits on the luminosities of the progenitors of these supernova remnants. our results add to the growing evidence disfavouring the single degenerate scenario. | excluding supersoft x-ray sources as progenitors for four type ia supernovae in the large magellanic cloud |
a particularly intriguing recent result from γ-ray astronomy missions is the detection of powerful flares from the crab nebula, which challenges the current understanding of pulsar wind nebulae and acceleration mechanisms. to search for the production site(s) of these flares, we conducted a multi-wavelength observing campaign using keck, the hubble space telescope (hst), and the chandra x-ray observatory. as the short timescales of the γ-ray flares (≲ 1 day) suggest a small emitting region, the crab’s inner knot (about 0.6 arcsec from the pulsar) is a candidate site for such flaring. this paper describes observations of the inner knot, seeking to understand its nature and possible relationship with γ-ray flares. using singular-value decomposition, analysis of the hst images yielded results consistent with traditional methods while substantially reducing some uncertainties. these analyses show that the knot’s intrinsic properties (especially size and brightness) are correlated with its (projected) separation from the pulsar. this characterization of the inner knot helps in constraining standard shock model parameters, under the assumption that the knot lies near the shocked surface. while the standard shock model gives good agreement in several respects, two puzzles persist: (a) the observed angular size of the knot relative to the pulsar-knot separation is much smaller than expected; and (b) the variable high degree of polarization (reported by others) is difficult to reconcile with a highly relativistic downstream flow. however, the ir-optical flux of the inner knot is marginally consistent with the shock accelerating most of the nebula’s optical-emitting particles. | characterization of the inner knot of the crab: the site of the gamma-ray flares? |
re-observations with the hess telescope array of the very high-energy (vhe) source hess j1018-589 a that is coincident with the fermi-lat γ-ray binary 1fgl j1018.6-5856 have resulted in a source detection significance of more than 9σ and the detection of variability (χ2/ν of 238.3/155) in the emitted γ-ray flux. this variability confirms the association of hess j1018-589 a with the high-energy γ-ray binary detected by fermi-lat and also confirms the point-like source as a new vhe binary system. the spectrum of hess j1018-589 a is best fit with a power-law function with photon index γ = 2.20 ± 0.14stat ± 0.2sys. emission is detected up to ~20 tev. the mean differential flux level is (2.9 ± 0.4) × 10-13 tev-1 cm-2 s-1 at 1 tev, equivalent to ~1% of the flux from the crab nebula at the same energy. variability is clearly detected in the night-by-night light curve. when folded on the orbital period of 16.58 days, the rebinned light curve peaks in phase with the observed x-ray and high-energy phaseograms. the fit of the hess phaseogram to a constant flux provides evidence of periodicity at the level of nσ> 3σ. the shape of the vhe phaseogram and measured spectrum suggest a low-inclination, low-eccentricity system with amodest impact from vhe γ-ray absorption due to pair production (τ ≲ 1 at 300 gev). | discovery of variable vhe γ-ray emission from the binary system 1fgl j1018.6-5856 |
the second gravitational-wave transient catalog reported on 39 compact binary coalescences observed by the advanced ligo and advanced virgo detectors between 1 april 2019 15:00 utc and 1 october 2019 15:00 utc. we present gwtc-2.1, which reports on a deeper list of candidate events observed over the same period. we analyze the final version of the strain data over this period with improved calibration and better subtraction of excess noise, which has been publicly released. we employ three matched-filter search pipelines for candidate identification, and estimate the astrophysical probability for each candidate event. while gwtc-2 used a false alarm rate threshold of 2 per year, we include in gwtc-2.1, 1201 candidates that pass a false alarm rate threshold of 2 per day. we calculate the source properties of a subset of 44 high-significance candidates that have an astrophysical probability greater than 0.5. of these candidates, 36 have been reported in gwtc-2. if the 8 additional high-significance candidates presented here are astrophysical, the mass range of events that are unambiguously identified as binary black holes (both objects $\geq 3m_\odot$) is increased compared to gwtc-2, with total masses from $\sim 14 m_\odot$ for gw190924_021846 to $\sim 182 m_\odot$ for gw190426_190642. the primary components of two new candidate events (gw190403_051519 and gw190426_190642) fall in the mass gap predicted by pair instability supernova theory. we also expand the population of binaries with significantly asymmetric mass ratios reported in gwtc-2 by an additional two events (the mass ratio is less than $0.65$ and $0.44$ at $90\%$ probability for gw190403_051519 and gw190917_114630 respectively), and find that 2 of the 8 new events have effective inspiral spins $\chi_\mathrm{eff} > 0$ (at $90\%$ credibility), while no binary is consistent with $\chi_\mathrm{eff} < 0$ at the same significance. | gwtc-2.1: deep extended catalog of compact binary coalescences observed by ligo and virgo during the first half of the third observing run |
on may 21, 2019 at 03:02:29 utc advanced ligo and advanced virgo observed a short duration gravitational-wave signal, gw190521, with a three-detector network signal-to-noise ratio of 14.7, and an estimated false-alarm rate of 1 in 4900 yr using a search sensitive to generic transients. if gw190521 is from a quasicircular binary inspiral, then the detected signal is consistent with the merger of two black holes with masses of 8 5-14+21 m⊙ and 6 6-18+17 m⊙ (90% credible intervals). we infer that the primary black hole mass lies within the gap produced by (pulsational) pair-instability supernova processes, with only a 0.32% probability of being below 65 m⊙. we calculate the mass of the remnant to be 14 2-16+28 m⊙ , which can be considered an intermediate mass black hole (imbh). the luminosity distance of the source is 5.3-2.6+2.4 gpc , corresponding to a redshift of 0.82-0.34+0.28 . the inferred rate of mergers similar to gw190521 is 0.13-0.11+0.30 gpc-3 yr-1 . | gw190521: a binary black hole merger with a total mass of 150 m⊙ |
the preponderance of matter over antimatter in the early universe, the dynamics of the supernovae that produced the heavy elements necessary for life, and whether protons eventually decay -- these mysteries at the forefront of particle physics and astrophysics are key to understanding the early evolution of our universe, its current state, and its eventual fate. dune is an international world-class experiment dedicated to addressing these questions as it searches for leptonic charge-parity symmetry violation, stands ready to capture supernova neutrino bursts, and seeks to observe nucleon decay as a signature of a grand unified theory underlying the standard model. the dune far detector technical design report (tdr) describes the dune physics program and the technical designs of the single- and dual-phase dune liquid argon tpc far detector modules. volume ii of this tdr, dune physics, describes the array of identified scientific opportunities and key goals. crucially, we also report our best current understanding of the capability of dune to realize these goals, along with the detailed arguments and investigations on which this understanding is based. this tdr volume documents the scientific basis underlying the conception and design of the lbnf/dune experimental configurations. as a result, the description of dune's experimental capabilities constitutes the bulk of the document. key linkages between requirements for successful execution of the physics program and primary specifications of the experimental configurations are drawn and summarized. this document also serves a wider purpose as a statement on the scientific potential of dune as a central component within a global program of frontier theoretical and experimental particle physics research. thus, the presentation also aims to serve as a resource for the particle physics community at large. | deep underground neutrino experiment (dune), far detector technical design report, volume ii: dune physics |
the preponderance of matter over antimatter in the early universe, the dynamics of the supernovae that produced the heavy elements necessary for life, and whether protons eventually decay—these mysteries at the forefront of particle physics and astrophysics are key to understanding the early evolution of our universe, its current state, and its eventual fate. the deep underground neutrino experiment (dune) is an international world-class experiment dedicated to addressing these questions as it searches for leptonic charge-parity symmetry violation, stands ready to capture supernova neutrino bursts, and seeks to observe nucleon decay as a signature of a grand unified theory underlying the standard model. the dune far detector technical design report (tdr) describes the dune physics program and the technical designs of the single- and dual-phase dune liquid argon tpc far detector modules. this tdr is intended to justify the technical choices for the far detector that flow down from the high-level physics goals through requirements at all levels of the project. volume i contains an executive summary that introduces the dune science program, the far detector and the strategy for its modular designs, and the organization and management of the project. the remainder of volume i provides more detail on the science program that drives the choice of detector technologies and on the technologies themselves. it also introduces the designs for the dune near detector and the dune computing model, for which dune is planning design reports. volume ii of this tdr describes dune's physics program in detail. volume iii describes the technical coordination required for the far detector design, construction, installation, and integration, and its organizational structure. volume iv describes the single-phase far detector technology. a planned volume v will describe the dual-phase technology. | volume i. introduction to dune |
previous detections of individual astrophysical sources of neutrinos are limited to the sun and the supernova 1987a, whereas the origins of the diffuse flux of high-energy cosmic neutrinos remain unidentified. on 22 september 2017, we detected a high-energy neutrino, icecube-170922a, with an energy of ~290 tera-electron volts. its arrival direction was consistent with the location of a known γ-ray blazar, txs 0506+056, observed to be in a flaring state. an extensive multiwavelength campaign followed, ranging from radio frequencies to γ-rays. these observations characterize the variability and energetics of the blazar and include the detection of txs 0506+056 in very-high-energy γ-rays. this observation of a neutrino in spatial coincidence with a γ-ray-emitting blazar during an active phase suggests that blazars may be a source of high-energy neutrinos. | multimessenger observations of a flaring blazar coincident with high-energy neutrino icecube-170922a |
the jiangmen underground neutrino observatory (juno) is a 20 kton liquid scintillator detector in a laboratory at 700-m underground. an excellent energy resolution and a large fiducial volume offer exciting opportunities for addressing many important topics in neutrino and astro-particle physics. with six years of data, the neutrino mass ordering can be determined at a 3-4 σ significance and the neutrino oscillation parameters sin2θ12 , δ m212 , and | δ m322 | can be measured to a precision of 0.6% or better, by detecting reactor antineutrinos from the taishan and yangjiang nuclear power plants. with ten years of data, neutrinos from all past core-collapse supernovae could be observed at a 3 σ significance; a lower limit of the proton lifetime, 8 . 34 × 1033 years (90% c.l.), can be set by searching for p → ν ̄ k+ ; detection of solar neutrinos would shed new light on the solar metallicity problem and examine the vacuum-matter transition region. a typical core-collapse supernova at a distance of 10 kpc would lead to ∼ 5000 inverse-beta-decay events and ∼ 2000 (300) all-flavor neutrino-proton (electron) elastic scattering events in juno. geo-neutrinos can be detected with a rate of ∼ 400 events per year. construction of the detector is very challenging. in this review, we summarize the final design of the juno detector and the key r&d achievements, following the conceptual design report in 2015 (djurcic et al., 2015). all 20-inch pmts have been procured and tested. the average photon detection efficiency is 28.9% for the 15,000 mcp pmts and 28.1% for the 5000 dynode pmts, higher than the juno requirement of 27%. together with the > 20 m attenuation length of the liquid scintillator achieved in a 20-ton pilot purification test and the > 96% transparency of the acrylic panel, we expect a yield of 1345 photoelectrons per mev and an effective relative energy resolution of 3 . 02% /√{ e(mev) } in simulations (abusleme et al., 2021). to maintain the high performance, the underwater electronics is designed to have a loss rate < 0 . 5% in six years. with degassing membranes and a micro-bubble system, the radon concentration in the 35 kton water pool could be lowered to < 10 mbq/m3. acrylic panels of radiopurity < 0 . 5 ppt u/th for the 35.4-m diameter liquid scintillator vessel are produced with a dedicated production line. the 20 kton liquid scintillator will be purified onsite with alumina filtration, distillation, water extraction, and gas stripping. together with other low background handling, singles in the fiducial volume can be controlled to ∼ 10 hz . the juno experiment also features a double calorimeter system with 25,600 3-inch pmts, a liquid scintillator testing facility osiris, and a near detector tao. | juno physics and detector |
rayleigh-taylor (rt) and richtmyer-meshkov (rm) instabilities play an important role in a wide range of engineering, geophysical, and astrophysical flows. they represent a triggering event that, in many cases, leads to large-scale turbulent mixing. much effort has been expended over the past 140 years, beginning with the seminal work of lord rayleigh, to predict the evolution of the instabilities and of the instability-induced mixing layers. the objective of part i of this review is to provide the basic properties of the flow, turbulence, and mixing induced by rt, rm, and kelvin-helmholtz (kh) instabilities. historical efforts to study these instabilities are briefly reviewed, and the significance of these instabilities is discussed for a variety of flows, particularly for astrophysical flows and for the case of inertial confinement fusion. early experimental efforts are described, and analytical attempts to model the linear, and nonlinear regimes of these mixing layers are examined. these analytical efforts include models for both single-mode and multi-mode initial conditions, as well as multi-scale models to describe the evolution. comparisons of these models and theories to experimental and simulation studies are then presented. next, attention is paid to the issue of the influence of stabilizing mechanisms (e.g., viscosity, surface tension, and diffuse interface) on the evolution of these instabilities, as well as the limitations and successes of numerical methods. efforts to study these instabilities and mixing layers using group-theoretic ideas, as well as more formal notions of turbulence cascade processes during the later stages of the induced mixing layers, are inspected. a key element of the review is the discussion of the late-time self-similar scaling for the rt and rm growth factors, α and θ. these parameters are influenced by the initial conditions and much of the observed variation can be explained by this. in some cases, these instabilities induced flows can transition to turbulence. both the spatial and temporal criteria to achieve the transition to turbulence have been examined. finally, a description of the energy-containing scales in the mixing layers, including energy "injection" and cascade processes are presented in greater detail. part ii of this review is designed to provide a much broader and in-depth understanding of this critical area of research (zhou, 2017. physics reports, 723-725, 1-160). | rayleigh-taylor and richtmyer-meshkov instability induced flow, turbulence, and mixing. i |
rayleigh-taylor (rt) and richtmyer-meshkov(rm) instabilities are well-known pathways towards turbulent mixing layers, in many cases characterized by significant mass and species exchange across the mixing layers (zhou, 2017. physics reports, 720-722, 1-136). mathematically, the pathway to turbulent mixing requires that the initial interface be multimodal, to permit cross-mode coupling leading to turbulence. practically speaking, it is difficult to experimentally produce a non-multi-mode initial interface. numerous methods and approaches have been developed to describe the late, multimodal, turbulent stages of rt and rm mixing layers. this paper first presents the initial condition dependence of rt mixing layers, and introduces parameters that are used to evaluate the level of "mixedness" and "mixed mass" within the layers, as well as the dependence on density differences, as well as the characteristic anisotropy of this acceleration-driven flow, emphasizing some of the key differences between the two-dimensional and three-dimensional rt mixing layers. next, the rm mixing layers are discussed, and differences with the rt mixing layer are elucidated, including the rm mixing layers dependence on the mach number of the initiating shock. another key feature of the rm induced flows is its response to a reshock event, as frequently seen in shock-tube experiments as well as inertial confinement events. a number of approaches to modeling the evolution of these mixing layers are then described, in order of increasing complexity. these include simple buoyancy-drag models, reynolds-averaged navier-stokes models of increased complexity, including k- ɛ, k-l, and k- l- a models, up to full reynolds-stress models with more than one length-scale. multifield models and multiphase models have also been implemented. additional complexities to these flows are examined as well as modifications to the models to understand the effects of these complexities. these complexities include the presence of magnetic fields, compressibility, rotation, stratification and additional instabilities. the complications induced by the presence of converging geometries are also considered. finally, the unique problems of astrophysical and high-energy-density applications, and efforts to model these are discussed. | rayleigh-taylor and richtmyer-meshkov instability induced flow, turbulence, and mixing. ii |
the dark energy camera is a new imager with a 2.°2 diameter field of view mounted at the prime focus of the victor m. blanco 4 m telescope on cerro tololo near la serena, chile. the camera was designed and constructed by the dark energy survey collaboration and meets or exceeds the stringent requirements designed for the wide-field and supernova surveys for which the collaboration uses it. the camera consists of a five-element optical corrector, seven filters, a shutter with a 60 cm aperture, and a charge-coupled device (ccd) focal plane of 250 μm thick fully depleted ccds cooled inside a vacuum dewar. the 570 megapixel focal plane comprises 62 2k × 4k ccds for imaging and 12 2k × 2k ccds for guiding and focus. the ccds have 15 μm × 15 μm pixels with a plate scale of 0.″263 pixel-1. a hexapod system provides state-of-the-art focus and alignment capability. the camera is read out in 20 s with 6-9 electron readout noise. this paper provides a technical description of the camera's engineering, construction, installation, and current status. | the dark energy camera |
the cherenkov telescope array, cta, will be the major global observatory for very high energy gamma-ray astronomy over the next decade and beyond. the scientific potential of cta is extremely broad: from understanding the role of relativistic cosmic particles to the search for dark matter. cta is an explorer of the extreme universe, probing environments from the immediate neighbourhood of black holes to cosmic voids on the largest scales. covering a huge range in photon energy from 20 gev to 300 tev, cta will improve on all aspects of performance with respect to current instruments. the observatory will operate arrays on sites in both hemispheres to provide full sky coverage and will hence maximize the potential for the rarest phenomena such as very nearby supernovae, gamma-ray bursts or gravitational wave transients. with 99 telescopes on the southern site and 19 telescopes on the northern site, flexible operation will be possible, with sub-arrays available for specific tasks. cta will have important synergies with many of the new generation of major astronomical and astroparticle observatories. multi-wavelength and multi-messenger approaches combining cta data with those from other instruments will lead to a deeper understanding of the broad-band non-thermal properties of target sources. the cta observatory will be operated as an open, proposal-driven observatory, with all data available on a public archive after a pre-defined proprietary period. scientists from institutions worldwide have combined together to form the cta consortium. this consortium has prepared a proposal for a core programme of highly motivated observations. the programme, encompassing approximately 40% of the available observing time over the first ten years of cta operation, is made up of individual key science projects (ksps), which are presented in this document. | science with the cherenkov telescope array |
we predict enormous, anisotropic piezoelectric effects in intrinsic monolayer group iv monochalcogenides (mx, m=sn or ge, x=se or s), including snse, sns, gese, and ges. using first-principle simulations based on the modern theory of polarization, we find that their piezoelectric coefficients are about one to two orders of magnitude larger than those of other 2d materials, such as mos2 and gase, and bulk quartz and aln which are widely used in industry. this enhancement is a result of the unique "puckered" c2v symmetry and electronic structure of monolayer group iv monochalcogenides. given the achieved experimental advances in the fabrication of monolayers, their flexible character, and ability to withstand enormous strain, these 2d structures with giant piezoelectric effects may be promising for a broad range of applications such as nano-sized sensors, piezotronics, and energy harvesting in portable electronic devices. | giant piezoelectricity of monolayer group iv monochalcogenides: snse, sns, gese, and ges |
we report on international gamma-ray astrophysics laboratory (integral) observations of the soft γ-ray repeater sgr 1935+2154 performed between 2020 april 28 and may 3. several short bursts with fluence of $\sim {10}^{-7}\mbox{--}{10}^{-6}$ erg cm-2 were detected by the imager on-board integral (ibis) instrument in the 20-200 kev range. the burst with the hardest spectrum, discovered and localized in real time by the integral burst alert system, was spatially and temporally coincident with a short and very bright radio burst detected by the canadian hydrogen intensity mapping experiment (chime) and survey for transient astronomical radio emission 2 (stare2) radio telescopes at 400-800 mhz and 1.4 ghz, respectively. its lightcurve shows three narrow peaks separated by ∼29 ms time intervals, superimposed on a broad pulse lasting ∼0.6 s. the brightest peak had a delay of 6.5 ± 1.0 ms with respect to the 1.4 ghz radio pulse (that coincides with the second and brightest component seen at lower frequencies). the burst spectrum, an exponentially cutoff power law with photon index ${\rm{\gamma }}={0.7}_{-0.2}^{+0.4}$ and peak energy ${e}_{p}=65\pm 5\,\mathrm{kev}$ , is harder than those of the bursts usually observed from this and other magnetars. by the analysis of an expanding dust-scattering ring seen in x-rays with the neil gehrels swift observatory x-ray telescope (xrt) instrument, we derived a distance of ${4.4}_{-1.3}^{+2.8}$ kpc for sgr 1935+2154, independent of its possible association with the supernova remnant g57.2+0.8. at this distance, the burst 20-200 kev fluence of $(6.1\pm 0.3)\times {10}^{-7}$ erg cm-2 corresponds to an isotropic emitted energy of $\sim 1.4\times {10}^{39}$ erg. this is the first burst with a radio counterpart observed from a soft γ-ray repeater and it strongly supports models based on magnetars that have been proposed for extragalactic fast radio bursts. | integral discovery of a burst with associated radio emission from the magnetar sgr 1935+2154 |
the preponderance of matter over antimatter in the early universe, the dynamics of the supernovae that produced the heavy elements necessary for life, and whether protons eventually decay—these mysteries at the forefront of particle physics and astrophysics are key to understanding the early evolution of our universe, its current state, and its eventual fate. dune is an international world-class experiment dedicated to addressing these questions as it searches for leptonic charge-parity symmetry violation, stands ready to capture supernova neutrino bursts, and seeks to observe nucleon decay as a signature of a grand unified theory underlying the standard model. central to achieving dune's physics program is a far detector that combines the many tens-of-kiloton fiducial mass necessary for rare event searches with sub-centimeter spatial resolution in its ability to image those events, allowing identification of the physics signatures among the numerous backgrounds. in the single-phase liquid argon time-projection chamber (lartpc) technology, ionization charges drift horizontally in the liquid argon under the influence of an electric field towards a vertical anode, where they are read out with fine granularity. a photon detection system supplements the tpc, directly enhancing physics capabilities for all three dune physics drivers and opening up prospects for further physics explorations. the dune far detector technical design report (tdr) describes the dune physics program and the technical designs of the single- and dual-phase dune liquid argon tpc far detector modules. volume iv presents an overview of the basic operating principles of a single-phase lartpc, followed by a description of the dune implementation. each of the subsystems is described in detail, connecting the high-level design requirements and decisions to the overriding physics goals of dune. | volume iv. the dune far detector single-phase technology |
neutrino-nuclear responses associated with astro-neutrinos, single beta decays and double beta decays are crucial in studies of neutrino properties of interest for astro-particle physics. the present report reviews briefly recent studies of the neutrino-nuclear responses from both experimental and theoretical points of view in order to obtain a consistent understanding of the many facets of the neutrino-nuclear responses. subjects discussed in this review include (i) experimental studies of neutrino-nuclear responses by means of single beta decays, charge-exchange nuclear reactions, muon- photon- and neutrino-nuclear reactions, and nucleon-transfer reactions, (ii) implications of and discussions on neutrino-nuclear responses for single beta decays, for astro-neutrinos, and for astro-neutrino nucleosynthesis, (iii) theoretical aspects of neutrino-nuclear responses for beta and double beta decays, for nuclear muon capture and for neutrino-nucleus scattering, and (iv) critical discussions on nucleonic and non-nucleonic spin-isospin correlations and renormalization (quenching or enhancement) effects on the axial weak coupling. remarks are given on perspectives of experimental and theoretical studies of the neutrino-nuclear responses and on future experiments of double beta decays. | neutrino-nuclear responses for astro-neutrinos, single beta decays and double beta decays |
2d van der waals ferroelectrics have emerged as an attractive building block with immense potential to provide multifunctionality in nanoelectronics. although several accomplishments have been reported in ferroelectric switching for out-of-plane ferroelectrics down to the monolayer, a purely in-plane ferroelectric has not been experimentally validated at the monolayer thickness. herein, an in-plane ferroelectricity is demonstrated for micrometer-size monolayer sns at room temperature. sns has been commonly regarded to exhibit the odd-even effect, where the centrosymmetry breaks only in the odd-number layers to exhibit ferroelectricity. remarkably, however, a robust room temperature ferroelectricity exists in sns below a critical thickness of 15 layers with both an odd and even number of layers, suggesting the possibility of controlling the stacking sequence of multilayer sns beyond the limit of ferroelectricity in the monolayer. this work will pave the way for nanoscale ferroelectric applications based on sns as a platform for in-plane ferroelectrics. | purely in-plane ferroelectricity in monolayer sns at room temperature |
pair-instability supernovae are thought to restrict the formation of black holes in the mass range $\sim 50\mbox{--}135\,{m}_{\odot }$ . however, black holes with masses within this "high mass gap" are expected to form as the remnants of binary black hole mergers. these remnants can merge again dynamically in densely populated environments such as globular clusters. the hypothesis that the binary black hole merger gw190521 formed dynamically is supported by its high mass. orbital eccentricity can also be a signature of dynamical formation, since a binary that merges quickly after becoming bound may not circularize before merger. in this work, we measure the orbital eccentricity of gw190521. we find that the data prefer a signal with eccentricity $e\geqslant 0.1$ at 10 hz to a nonprecessing, quasi-circular signal, with a log bayes factor $\mathrm{ln}{ \mathcal b }=5.0$ . when compared to precessing, quasi-circular analyses, the data prefer a nonprecessing, $e\geqslant 0.1$ signal, with log bayes factors $\mathrm{ln}{ \mathcal b }\approx 2$ . using injection studies, we find that a nonspinning, moderately eccentric (e = 0.13) gw190521-like binary can be mistaken for a quasi-circular, precessing binary. conversely, a quasi-circular binary with spin-induced precession may be mistaken for an eccentric binary. we therefore cannot confidently determine whether gw190521 was precessing or eccentric. nevertheless, since both of these properties support the dynamical formation hypothesis, our findings support the hypothesis that gw190521 formed dynamically. | gw190521: orbital eccentricity and signatures of dynamical formation in a binary black hole merger signal |
in diverse areas of science and technology, including inertial confinement fusion (icf), astrophysics, geophysics, and engineering processes, turbulent mixing induced by hydrodynamic instabilities is of scientific interest as well as practical significance. because of the fundamental roles they often play in icf and other applications, three classes of hydrodynamic instability-induced turbulent flows-those arising from the rayleigh-taylor, richtmyer-meshkov, and kelvin-helmholtz instabilities-have attracted much attention. icf implosions, supernova explosions, and other applications illustrate that these phases of instability growth do not occur in isolation, but instead are connected so that growth in one phase feeds through to initiate growth in a later phase. essentially, a description of these flows must encompass both the temporal and spatial evolution of the flows from their inception. hydrodynamic instability will usually start from potentially infinitesimal spatial perturbations, will eventually transition to a turbulent flow, and then will reach a final state of a true multiscale problem. indeed, this change in the spatial scales can be vast, with hydrodynamic instability evolving from just a few microns to thousands of kilometers in geophysical or astrophysical problems. these instabilities will evolve through different stages before transitioning to turbulence, experiencing linear, weakly, and highly nonlinear states. the challenges confronted by researchers are enormous. the inherent difficulties include characterizing the initial conditions of such flows and accurately predicting the transitional flows. of course, fully developed turbulence, a focus of many studies because of its major impact on the mixing process, is a notoriously difficult problem in its own right. in this pedagogical review, we will survey challenges and progress, and also discuss outstanding issues and future directions. | turbulent mixing and transition criteria of flows induced by hydrodynamic instabilities |
the group-iv monochalcogenides sns, snse, ges, and gese form a family within the wider group of semiconductor "phosphorene analogues." here, we used first-principles calculations to investigate systematically their structural, electronic, and optical properties, analyzing the changes associated with the reduction of dimensionality, from bulk to monolayer or bilayer form. we show that all those binary phosphorene analogues are semiconducting, with band-gap energies covering part of the infrared and visible range, and in most cases higher than phosphorene. further, we found that they have multiple valleys in the valence and conduction band, the latter with spin-orbit splitting of the order of 19-86 mev. | phosphorene analogues: isoelectronic two-dimensional group-iv monochalcogenides with orthorhombic structure |
thermoelectric technology allows conversion between heat and electricity. many good thermoelectric materials contain rare or toxic elements, so developing low-cost and high-performance thermoelectric materials is warranted. here, we report the temperature-dependent interplay of three separate electronic bands in hole-doped tin sulfide (sns) crystals. this behavior leads to synergistic optimization between effective mass (m*) and carrier mobility (μ) and can be boosted through introducing selenium (se). this enhanced the power factor from ~30 to ~53 microwatts per centimeter per square kelvin (μw cm-1 k-2 at 300 k), while lowering the thermal conductivity after se alloying. as a result, we obtained a maximum figure of merit zt (ztmax) of ~1.6 at 873 k and an average zt (ztave) of ~1.25 at 300 to 873 k in sns0.91se0.09 crystals. our strategy for band manipulation offers a different route for optimizing thermoelectric performance. the high-performance sns crystals represent an important step toward low-cost, earth-abundant, and environmentally friendly thermoelectrics. | high thermoelectric performance in low-cost sns0.91se0.09 crystals |
collisionless shocks can be produced as a result of strong magnetic fields in a plasma flow, and therefore are common in many astrophysical systems. the weibel instability is one candidate mechanism for the generation of sufficiently strong fields to create a collisionless shock. despite their crucial role in astrophysical systems, observation of the magnetic fields produced by weibel instabilities in experiments has been challenging. using a proton probe to directly image electromagnetic fields, we present evidence of weibel-generated magnetic fields that grow in opposing, initially unmagnetized plasma flows from laser-driven laboratory experiments. three-dimensional particle-in-cell simulations reveal that the instability efficiently extracts energy from the plasma flows, and that the self-generated magnetic energy reaches a few percent of the total energy in the system. this result demonstrates an experimental platform suitable for the investigation of a wide range of astrophysical phenomena, including collisionless shock formation in supernova remnants, large-scale magnetic field amplification, and the radiation signature from gamma-ray bursts. | observation of magnetic field generation via the weibel instability in interpenetrating plasma flows |
in order to improve super-kamiokande's neutron detection efficiency and to thereby increase its sensitivity to the diffuse supernova neutrino background flux, 13 tons of gd2(so4)3 ⋅8h2 o (gadolinium sulfate octahydrate) was dissolved into the detector's otherwise ultrapure water from july 14 to august 17, 2020, marking the start of the sk-gd phase of operations. during the loading, water was continuously recirculated at a rate of 60 m3/h, extracting water from the top of the detector and mixing it with concentrated gd2(so4)3 ⋅8h2 o solution to create a 0.02% solution of the gd compound before injecting it into the bottom of the detector. a clear boundary between the gd-loaded and pure water was maintained through the loading, enabling monitoring of the loading itself and the spatial uniformity of the gd concentration over the 35 days it took to reach the top of the detector. during the subsequent commissioning the recirculation rate was increased to 120 m3/h, resulting in a constant and uniform distribution of gd throughout the detector and water transparency equivalent to that of previous pure-water operation periods. using an am-be neutron calibration source the mean neutron capture time was measured to be 115 ± 1 μs , which corresponds to a gd concentration of 111 ± 2 ppm, as expected for this level of gd loading. this paper describes changes made to the water circulation system for this detector upgrade, the gd loading procedure, detector commissioning, and the first neutron calibration measurements in sk-gd. | first gadolinium loading to super-kamiokande |
grb 221009a has been referred to as the brightest of all time (boat). we investigate the veracity of this statement by comparing it with a half century of prompt gamma-ray burst observations. this burst is the brightest ever detected by the measures of peak flux and fluence. unexpectedly, grb 221009a has the highest isotropic-equivalent total energy ever identified, while the peak luminosity is at the ~99th percentile of the known distribution. we explore how such a burst can be powered and discuss potential implications for ultralong and high-redshift gamma-ray bursts. by geometric extrapolation of the total fluence and peak flux distributions, grb 221009a appears to be a once-in-10,000-year event. thus, it is almost certainly not the boat over all of cosmic history; it may be the brightest gamma-ray burst since human civilization began. | grb 221009a: the boat |
tin selenide (snse) and tin sulfide (sns) have recently attracted particular interest due to their great potential for large-scale thermoelectric applications. a complete prediction of the thermoelectric performance and the understanding of underlying heat and charge transport details are the key to further improvement of their thermoelectric efficiency. we conduct comprehensive investigations of both thermal and electrical transport properties of snse and sns using first-principles calculations combined with the boltzmann transport theory. due to the distinct layered lattice structure, snse and sns exhibit similarly anisotropic thermal and electrical behaviors. the cross-plane lattice thermal conductivity κl is 40 -60 % lower than the in-plane values. extremely low κl is found for both materials because of high anharmonicity, while the average κl of sns is ∼8 % higher than that of snse from 300 to 750 k. it is suggested that nanostructuring would be difficult to further decrease κl because of the short mean free paths of dominant phonon modes (1-30 nm at 300 k), while alloying would be efficient in reducing κl considering that the relative κl contribution (∼65 %) of optical phonons is remarkably large. on the electrical side, the anisotropic electrical conductivities are mainly due to the different effective masses of holes and electrons along the a , b , and c axes. this leads to the highest optimal zt values along the b axis and lowest ones along the a axis in both p -type materials. however, the n -type ones exhibit the highest zt s along the a axis due to the enhancement of power factor when the chemical potential gradually approaches the secondary conduction band valley that causes significant increase in electron mobility and density of states. owing to the larger mobility and smaller κl along the given direction, snse exhibits larger optimal zts compared with sns in both p - and n -type materials. for both materials, the peak zt s of n -type materials are much higher than those of p -type ones along the same direction. the predicted highest zt values at 750 k are 1.0 in snse and 0.6 in sns along the b axis for the p -type doping, while those for the n -type doping reach 2.7 in snse and 1.5 in sns along the a axis, rendering them among the best bulk thermoelectric materials for large-scale applications. our calculations show reasonable agreements with the experimental results and quantitatively predict the great potential in further enhancing the thermoelectric performance of snse and sns, especially for the n -type materials. | first-principles study of anisotropic thermoelectric transport properties of iv-vi semiconductor compounds snse and sns |
a central concept in the modern understanding of turbulence is the existence of cascades of excitations from large to small length scales, or vice versa. this concept was introduced in 1941 by kolmogorov and obukhov, and such cascades have since been observed in various systems, including interplanetary plasmas, supernovae, ocean waves and financial markets. despite much progress, a quantitative understanding of turbulence remains a challenge, owing to the interplay between many length scales that makes theoretical simulations of realistic experimental conditions difficult. here we observe the emergence of a turbulent cascade in a weakly interacting homogeneous bose gas—a quantum fluid that can be theoretically described on all relevant length scales. we prepare a bose-einstein condensate in an optical box, drive it out of equilibrium with an oscillating force that pumps energy into the system at the largest length scale, study its nonlinear response to the periodic drive, and observe a gradual development of a cascade characterized by an isotropic power-law distribution in momentum space. we numerically model our experiments using the gross-pitaevskii equation and find excellent agreement with the measurements. our experiments establish the uniform bose gas as a promising new medium for investigating many aspects of turbulence, including the interplay between vortex and wave turbulence, and the relative importance of quantum and classical effects. | emergence of a turbulent cascade in a quantum gas |
in the past few years, f(q) theories have drawn a lot of research attention in replacing einstein's theory of gravity successfully. the current study examines the novel cosmological possibilities emerging from two specific classes of f(q) models using the parametrization form of the equation of state (eos) parameter as ω (z )=-1/1 +3 β (1+z )3 , which displays quintessence behavior with the evolution of the universe. we do statistical analyses using the markov chain monte carlo (mcmc) method and background datasets like type ia supernovae (sne ia) luminosities and direct hubble datasets (from cosmic clocks), and baryon acoustic oscillations (bao) datasets. this lets us compare these new ideas about the universe to the λ cdm model in a number of different possible ways. we have come to the conclusion that, at the current level of accuracy, the values of their specific parameters are the best fits for our f(q) models. to conclude the accelerating behavior of the universe, we further study the evolution of energy density, pressure, and deceleration parameter for these f(q) models. | observational constraints on two cosmological models of f(q) theory |
low-dimensional multiferroic materials hold great promises in miniaturized device applications such as nanoscale transducers, actuators, sensors, photovoltaics, and nonvolatile memories. here, using first-principles theory we predict that two-dimensional (2d) monolayer group iv monochalcogenides including ges, gese, sns, and snse are a class of 2d semiconducting multiferroics with giant strongly-coupled in-plane spontaneous ferroelectric polarization and spontaneous ferroelastic lattice strain that are thermodynamically stable at room temperature and beyond, and can be effectively modulated by elastic strain engineering. their optical absorption spectra exhibit strong in-plane anisotropy with visible-spectrum excitonic gaps and sizable exciton binding energies, rendering the unique characteristics of low-dimensional semiconductors. more importantly, the predicted low domain wall energy and small migration barrier together with the coupled multiferroic order and anisotropic electronic structures suggest their great potentials for tunable multiferroic functional devices by manipulating external electrical, mechanical, and optical field to control the internal responses, and enable the development of four device concepts including 2d ferroelectric memory, 2d ferroelastic memory, and 2d ferroelastoelectric nonvolatile photonic memory as well as 2d ferroelectric excitonic photovoltaics. | two-dimensional multiferroics in monolayer group iv monochalcogenides |
large neutrino event numbers in future experiments measuring coherent elastic neutrino nucleus scattering allow precision measurements of standard and new physics. we analyze the current and prospective limits of a light scalar particle coupling to neutrinos and quarks, using coherent and conus as examples. both lepton number conserving and violating interactions are considered. it is shown that current (future) experiments can probe for scalar masses of a few mev couplings down to the level of 10-4 (10-6). scalars with masses around the neutrino energy allow to determine their mass via a characteristic spectrum shape distortion. our present and future limits are compared with constraints from supernova evolution, big bang nucleosynthesis and neutrinoless double beta decay. we also outline uv-complete underlying models that include a light scalar with coupling to quarks for both lepton number violating and conserving coupling to neutrinos. | probing neutrino coupling to a light scalar with coherent neutrino scattering |
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 |
maximizing the discovery potential of increasingly precise neutrino experiments will require an improved theoretical understanding of neutrino-nucleus cross sections over a wide range of energies. low-energy interactions are needed to reconstruct the energies of astrophysical neutrinos from supernovae bursts and search for new physics using increasingly precise measurement of coherent elastic neutrino scattering. higher-energy interactions involve a variety of reaction mechanisms including quasi-elastic scattering, resonance production, and deep inelastic scattering that must all be included to reliably predict cross sections for energies relevant to dune and other accelerator neutrino experiments. this white paper discusses the theoretical status, challenges, required resources, and path forward for achieving precise predictions of neutrino-nucleus scattering and emphasizes the need for a coordinated theoretical effort involved lattice qcd, nuclear effective theories, phenomenological models of the transition region, and event generators. | theoretical tools for neutrino scattering: interplay between lattice qcd, efts, nuclear physics, phenomenology, and neutrino event generators |
one of the greatest uncertainties in any modeling of the inner engine of core-collapse supernova (ccsn) is neutrino-flavor conversions driven by neutrino self-interactions. we carry out large-scale numerical simulations of a multienergy, multiangle, three-flavor framework and general relativistic quantum kinetic neutrino transport in spherical symmetry with an essential set of neutrino-matter interactions under a realistic fluid profile of ccsn. our result suggests that the neutrino heating in the gain region is reduced by ∼40 % due to fast neutrino-flavor conversion (ffc). we also find that the total luminosity of neutrinos is enhanced by ∼30 %, for which the substantial increase of heavy-leptonic neutrinos by ffcs are mainly responsible. this study provides evidence that ffc has a significant impact on the delayed neutrino-heating mechanism. | roles of fast neutrino-flavor conversion on the neutrino-heating mechanism of core-collapse supernova |
typical microseismic data recorded by surface arrays are characterized by low signal-to-noise ratios (s/ns) and highly nonstationary noise that make it difficult to detect small events. currently, array or crosscorrelation-based approaches are used to enhance the s/n prior to processing. we have developed an alternative approach for s/n improvement and simultaneous detection of microseismic events. the proposed method is based on the synchrosqueezed continuous wavelet transform (ss-cwt) and custom thresholding of single-channel data. the ss-cwt allows for the adaptive filtering of time- and frequency-varying noise as well as offering an improvement in resolution over the conventional wavelet transform. simultaneously, the algorithm incorporates a detection procedure that uses the thresholded wavelet coefficients and detects an arrival as a local maxima in a characteristic function. the algorithm was tested using a synthetic signal and field microseismic data, and our results have been compared with conventional denoising and detection methods. this technique can remove a large part of the noise from small-amplitudes signal and detect events as well as estimate onset time. | automatic microseismic denoising and onset detection using the synchrosqueezed continuous wavelet transform |
astrophysical neutrinos are excellent probes of astroparticle physics and high-energy physics. with energies far beyond solar, supernovae, atmospheric, and accelerator neutrinos, high-energy and ultra-high-energy neutrinos probe fundamental physics from the tev scale to the eev scale and beyond. they are sensitive to physics both within and beyond the standard model through their production mechanisms and in their propagation over cosmological distances. they carry unique information about their extreme non-thermal sources by giving insight into regions that are opaque to electromagnetic radiation. this white paper describes the opportunities astrophysical neutrino observations offer for astrophysics and high-energy physics, today and in coming years. | high-energy and ultra-high-energy neutrinos: a snowmass white paper |
cosmography is an ideal tool to investigate the cosmic expansion history of the universe in a model-independent way. the equations of motion in modified theories of gravity are usually very complicated; cosmography may select practical models without imposing arbitrary choices a priori. we use the model-independent way to derive f (z ) and its derivatives up to fourth order in terms of measurable cosmographic parameters. we then fit those functions into the luminosity distance directly. we perform the mcmc analysis by considering three different sets of cosmographic functions. using the largest supernovae ia pantheon sample, we derive the constraints on the hubble constant h0 and the cosmographic functions, and find that the former two terms in taylor expansion of luminosity distance work dominantly in f (q ) gravity. | cosmography in f (q ) gravity |
new classes of two-dimensional (2d) materials beyond graphene, including layered and non-layered, and their heterostructures, are currently attracting increasing interest due to their promising applications in nanoelectronics, optoelectronics and clean energy, where thermal transport is a fundamental physical parameter. in this paper, we systematically investigated the phonon transport properties of the 2d orthorhombic group iv-vi compounds of ges, gese, sns and snse by solving the boltzmann transport equation (bte) based on first-principles calculations. despite their similar puckered (hinge-like) structure along the armchair direction as phosphorene, the four monolayer compounds possess diverse anisotropic properties in many aspects, such as phonon group velocity, young's modulus and lattice thermal conductivity (κ), etc. especially, the κ along the zigzag and armchair directions of monolayer ges shows the strongest anisotropy while monolayer sns and snse show almost isotropy in phonon transport. the origin of the diverse anisotropy is fully studied and the underlying mechanism is discussed in details. with limited size, the κ could be effectively lowered, and the anisotropy could be effectively modulated by nanostructuring, which would extend the applications to nanoscale thermoelectrics and thermal management. our study offers fundamental understanding of the anisotropic phonon transport properties of 2d materials, and would be of significance for further study, modulation and applications in emerging technologies. | diverse anisotropy of phonon transport in two-dimensional group iv-vi compounds: a comparative study |
we explore the thermoelectric and phonon transport properties of two-dimensional monochalcogenides (snse, sns, gese, and ges) using density functional theory combined with boltzmann transport theory. we studied the electronic structures, seebeck coefficients, electrical conductivities, lattice thermal conductivities, and figures of merit of these two-dimensional materials, which showed that the thermoelectric performance of monolayer of these compounds is improved in comparison compared to their bulk phases. high figures of merit (zt) are predicted for snse (zt = 2.63, 2.46), sns (zt = 1.75, 1.88), gese (zt = 1.99, 1.73), and ges (zt = 1.85, 1.29) at 700 k along armchair and zigzag directions, respectively. phonon dispersion calculations confirm the dynamical stability of these compounds. the calculated lattice thermal conductivities are low while the electrical conductivities and seebeck coefficients are high. thus, the properties of the monolayers show high potential toward thermoelectric applications. | thermoelectric and phonon transport properties of two-dimensional iv-vi compounds |
we revise the bound from the supernova sn1987a on the coupling of ultralight axion-like particles (alps) to photons. in a core-collapse supernova, alps would be emitted via the primakoff process, and eventually convert into gamma rays in the magnetic field of the milky way. the lack of a gamma-ray signal in the grs instrument of the smm satellite in coincidence with the observation of the neutrinos emitted from sn1987a therefore provides a strong bound on their coupling to photons. due to the large uncertainty associated with the current bound, we revise this argument, based on state-of-the-art physical inputs both for the supernova models and for the milky-way magnetic field. furthermore, we provide major amendments, such as the consistent treatment of nucleon-degeneracy effects and of the reduction of the nuclear masses in the hot and dense nuclear medium of the supernova. with these improvements, we obtain a new upper limit on the photon-alp coupling: | revisiting the sn1987a gamma-ray limit on ultralight axion-like particles |
we present ground-based and swift photometric and spectroscopic observations of the candidate tidal disruption event (tde) asassn-14li, found at the centre of pgc 043234 (d ≃ 90 mpc) by the all-sky automated survey for supernovae (asas-sn). the source had a peak bolometric luminosity of l ≃ 1044 erg s-1 and a total integrated energy of e ≃ 7 × 1050 erg radiated over the ∼6 months of observations presented. the uv/optical emission of the source is well fitted by a blackbody with roughly constant temperature of t ∼ 35 000 k, while the luminosity declines by roughly a factor of 16 over this time. the optical/uv luminosity decline is broadly consistent with an exponential decline, l∝ e^{-t/t_0}, with t0 ≃ 60 d. asassn-14li also exhibits soft x-ray emission comparable in luminosity to the optical and uv emission but declining at a slower rate, and the x-ray emission now dominates. spectra of the source show broad balmer and helium lines in emission as well as strong blue continuum emission at all epochs. we use the discoveries of asassn-14li and asassn-14ae to estimate the tde rate implied by asas-sn, finding an average rate of r ≃ 4.1 × 10-5 yr-1 per galaxy with a 90 per cent confidence interval of (2.2-17.0) × 10-5 yr-1 per galaxy. asas-sn found roughly 1 tde for every 70 type ia supernovae in 2014, a rate that is much higher than that of other surveys. | six months of multiwavelength follow-up of the tidal disruption candidate asassn-14li and implied tde rates from asas-sn |
hydrodynamic instabilities such as rayleigh-taylor (rt) and richtmyer-meshkov (rm) instabilities usually appear in conjunction with the kelvin-helmholtz (kh) instability and are found in many natural phenomena and engineering applications. they frequently result in turbulent mixing, which has a major impact on the overall flow development and other effective material properties. this can either be a desired outcome, an unwelcome side effect, or just an unavoidable consequence, but must in all cases be characterized in any model. the rt instability occurs at an interface between different fluids, when the light fluid is accelerated into the heavy. the rm instability may be considered a special case of the rt instability, when the acceleration provided is impulsive in nature such as that resulting from a shock wave. in this pedagogical review, we provide an extensive survey of the applications and examples where such instabilities play a central role. first, fundamental aspects of the instabilities are reviewed including the underlying flow physics at different stages of development, followed by an overview of analytical models describing the linear, nonlinear and fully turbulent stages. rt and rm instabilities pose special challenges to numerical modeling, due to the requirement that the sharp interface separating the fluids be captured with fidelity. these challenges are discussed at length here, followed by a summary of the significant progress in recent years in addressing them. examples of the pivotal roles played by the instabilities in applications are given in the context of solar prominences, ionospheric flows in space, supernovae, inertial fusion and pulsed-power experiments, pulsed detonation engines and scramjets. progress in our understanding of special cases of rt/rm instabilities is reviewed, including the effects of material strength, chemical reactions, magnetic fields, as well as the roles the instabilities play in ejecta formation and transport, and explosively expanding flows. the article is addressed to a broad audience, but with particular attention to graduate students and researchers who are interested in the state-of-the-art in our understanding of the instabilities and the unique issues they present in the applications in which they are prominent. | rayleigh-taylor and richtmyer-meshkov instabilities: a journey through scales |
the primary goal of the coherent collaboration is to measure and study coherent elastic neutrino-nucleus scattering (cevns) using the high-power, few-tens-of-mev, pulsed source of neutrinos provided by the spallation neutron source (sns) at oak ridge national laboratory (ornl). the coherent collaboration reported the first detection of cevns [akimov:2017ade] using a csi[na] detector. at present the collaboration is deploying four detector technologies: a csi[na] scintillating crystal, p-type point-contact germanium detectors, single-phase liquid argon, and nai[tl] crystals. all detectors are located in the neutron-quiet basement of the sns target building at distances 20-30 m from the sns neutrino source. the simultaneous measurement in all four coherent detector subsystems will test the $n^2$ dependence of the cross section and search for new physics. in addition, coherent is measuring neutrino-induced neutrons from charged- and neutral-current neutrino interactions on nuclei in shielding materials, which represent a non-negligible background for cevns as well as being of intrinsic interest. the collaboration is planning as well to look for charged-current interactions of relevance to supernova and weak-interaction physics. this document describes concisely the coherent physics motivations, sensitivity, and next plans for measurements at the sns to be accomplished on a few-year timescale. | coherent 2018 at the spallation neutron source |
recent observations using the atacama cosmology telescope (act) have provided ground-based cosmic microwave background (cmb) maps with higher angular resolution than the planck satellite. these have the potential to put interesting constraints on models resolving the "hubble tension." in this paper we fit two models of early dark energy (ede) (an increase in the expansion rate around matter/radiation equality) to the combination of act data with large-scale measurements of the cmb either from the wmap or the planck satellite (including lensing), along with measurements of the baryon acoustic oscillations and uncalibrated supernovae luminosity distance. we study a phenomenological axionlike potential ("axede") and a scalar field experiencing a first-order phase transition ("nede"). we find that for both models the "planck-free" analysis yields nonzero ede at ≳2 σ and an increased value for h0∼70 - 74 km /s /mpc , compatible with local measurements, without the inclusion of any prior on h0. on the other hand, the inclusion of planck data restricts the ede contribution to an upper limit only at 95% c.l. for axede, the combination of planck and act leads to constraints 30% weaker than with planck alone, and there is no residual hubble tension. on the other hand, nede is more strongly constrained in a p l a n c k +act analysis, and the hubble tension remains at ∼3 σ , illustrating the ability for cmb data to distinguish between different ede models. we further explore the apparent inconsistency between the planck and act data and find that it comes (mostly) from a slight tension between the temperature power spectrum at multipoles around ∼1000 and ∼1500 . finally, through a mock analysis of act data, we demonstrate that the preference for ede is not driven by a lack of information at high ℓ when removing planck data, and that a λ cold dark matter fit to the fiducial ede cosmology results in a significant bias on {h0,ωcdm}. more accurate measurements of the tt cmb power spectra above ℓ∼2500 and ee between ℓ∼300 - 500 will play a crucial role in differentiating between ede models. | dark energy at early times and act data: a larger hubble constant without late-time priors |
we present here up-to-date neutrino mass limits exploiting the most recent cosmological data sets. by making use of the cosmic microwave background temperature fluctuation and polarization measurements, supernovae ia luminosity distances, baryon acoustic oscillation observations and determinations of the growth rate parameter, we are able to set the most constraining bound to date, ∑mν<0.09 ev at 95% c.l. this very tight limit is obtained without the assumption of any prior on the value of the hubble constant and highly compromises the viability of the inverted mass ordering as the underlying neutrino mass pattern in nature. the results obtained here further strengthen the case for very large multitracer spectroscopic surveys as unique laboratories for cosmological relics, such as neutrinos: that would be the case of the dark energy spectroscopic instrument survey and of the euclid mission. | most constraining cosmological neutrino mass bounds |
new measurements of the expansion rate of the universe have plunged the standard model of cosmology into a severe crisis. in this letter, we propose a simple resolution to the problem that relies on a first order phase transition in a dark sector in the early universe, before recombination. this will lead to a short phase of a new early dark energy (nede) component and can explain the observations. we model the false vacuum decay of the nede scalar field as a sudden transition from a cosmological constant source to a decaying fluid with constant equation of state. the corresponding fluid perturbations are covariantly matched to the adiabatic fluctuations of a sub-dominant scalar field that triggers the phase transition. fitting our model to measurements of the cosmic microwave background (cmb), baryonic acoustic oscillations (bao, and supernovae (sne) yields a significant improvement of the best-fit compared with the standard cosmological model without nede. we find the mean value of the present hubble parameter in the nede model to be $h_0=71.4 \pm 1.0 ~\textrm{km}\, \textrm{s}^{-1}\, \textrm{mpc}^{-1}$ ($68\, \%$ c.l.). | new early dark energy |
numerical simulations are a versatile tool for providing insight into the complicated process of structure formation in cosmology. this process is mainly governed by gravity, which is the dominant force on large scales. at present, a century after the formulation of general relativity, numerical codes for structure formation still employ newton’s law of gravitation. this approximation relies on the two assumptions that gravitational fields are weak and that they originate from non-relativistic matter. whereas the former seems well justified on cosmological scales, the latter imposes restrictions on the nature of the `dark’ components of the universe (dark matter and dark energy), which are, however, poorly understood. here we present the first simulations of cosmic structure formation using equations consistently derived from general relativity. we study in detail the small relativistic effects for a standard lambda cold dark matter cosmology that cannot be obtained within a purely newtonian framework. our particle-mesh n-body code computes all six degrees of freedom of the metric and consistently solves the geodesic equation for particles, taking into account the relativistic potentials and the frame-dragging force. this conceptually clean approach is very general and can be applied to various settings where the newtonian approximation fails or becomes inaccurate, ranging from simulations of models with dynamical dark energy or warm/hot dark matter to core collapse supernova explosions. | general relativity and cosmic structure formation |
we propose a novel model in the framework of f (q) gravity, which is a gravitational modification class arising from the incorporation of non-metricity. the model has general relativity as a particular limit, it has the same number of free parameters to those of λcdm, however at a cosmological framework it gives rise to a scenario that does not have λcdm as a limit. nevertheless, confrontation with observations at both background and perturbation levels, namely with supernovae type ia (snia), baryonic acoustic oscillations (bao), cosmic chronometers (cc), and redshift space distortion (rsd) data, reveals that the scenario, according to aic, bic and dic information criteria, is in some datasets slightly preferred comparing to λcdm cosmology, although in all cases the two models are statistically indiscriminate. finally, the model does not exhibit early dark energy features, and thus it immediately passes bbn constraints, while the variation of the effective newton's constant lies well inside the observational bounds. | first evidence that non-metricity f(q) gravity could challenge λcdm |
gw190521 is the first confident observation of a binary black hole merger with total mass $m\gt 100\,{m}_{\odot }$ . given the lack of observational constraints at these masses, we analyze gw190521 considering two different priors for the binary's masses: uniform in mass ratio and source-frame total mass, and uniform in source-frame component masses. for the uniform in mass-ratio prior, we find that the component masses are ${m}_{1}^{\mathrm{src}}={168}_{-61}^{+15}\,{m}_{\odot }$ and ${m}_{2}^{\mathrm{src}}={16}_{-3}^{+33}\,{m}_{\odot }$ . the uniform in component-mass prior yields a bimodal posterior distribution. there is a low-mass-ratio mode ( $q\lt 4$ ) with ${m}_{1}^{\mathrm{src}}={100}_{-18}^{+17}\,{m}_{\odot }$ and ${m}_{2}^{\mathrm{src}}={57}_{-16}^{+17}\,{m}_{\odot }$ and a high-mass-ratio mode ( $q\geqslant 4$ ) with ${m}_{1}^{\mathrm{src}}={166}_{-35}^{+16}\,{m}_{\odot }$ and ${m}_{2}^{\mathrm{src}}={16}_{-3}^{+14}\,{m}_{\odot }$ . although the two modes have nearly equal posterior probability, the maximum-likelihood parameters are in the high-mass-ratio mode, with ${m}_{1}^{\mathrm{src}}=171\,{m}_{\odot }$ and ${m}_{2}^{\mathrm{src}}=16\,{m}_{\odot }$ , and a signal-to-noise ratio of 16. these results are consistent with the proposed "mass gap" produced by pair-instability in supernovae. our results differ from those published in abbott et al. we find that a combination of the prior used and the constraints applied may have prevented that analysis from sampling the high-mass-ratio mode. an accretion flare in agn j124942.3+344929 was observed in possible coincidence with gw190521 by the zwicky transient facility. we report parameters assuming a common origin; however, the spatial agreement of gw190521 and the electromagnetic flare alone does not provide convincing evidence for the association ( $\mathrm{ln}{ \mathcal b }\gtrsim -4$ ). | gw190521 may be an intermediate-mass ratio inspiral |
in this paper we present new constraints on the hubble parameter h0 using: (i) the available data on h(z) obtained from cosmic chronometers (cch); (ii) the hubble rate data points extracted from the supernovae of type ia (snia) of the pantheon compilation and the hubble space telescope (hst) candels and clash multy-cycle treasury (mct) programs; and (iii) the local hst measurement of h0 provided by riess et al. (2018), h0hst=(73.45±1.66) km/s/mpc. various determinations of h0 using the gaussian processes (gps) method and the most updated list of cch data have been recently provided by yu, ratra & wang (2018). using the gaussian kernel they find h0=(67.42± 4.75) km/s/mpc. here we extend their analysis to also include the most released and complete set of snia data, which allows us to reduce the uncertainty by a factor ~ 3 with respect to the result found by only considering the cch information. we obtain h0=(67.06± 1.68) km/s/mpc, which favors again the lower range of values for h0 and is in tension with h0hst. the tension reaches the 2.71σ level. we round off the gps determination too by taking also into account the error propagation of the kernel hyperparameters when the cch with and without h0hst are used in the analysis. in addition, we present a novel method to reconstruct functions from data, which consists in a weighted sum of polynomial regressions (wpr). we apply it from a cosmographic perspective to reconstruct h(z) and estimate h0 from cch and snia measurements. the result obtained with this method, h0=(68.90± 1.96) km/s/mpc, is fully compatible with the gps ones. finally, a more conservative gps+wpr value is also provided, h0=(68.45± 2.00) km/s/mpc, which is still almost 2σ away from h0hst. | h0 from cosmic chronometers and type ia supernovae, with gaussian processes and the novel weighted polynomial regression method |
we present an analysis of 15 type ia supernovae (sne ia) at redshift z> 1 (9 at 1.5< z< 2.3) recently discovered in the candels and clash multi-cycle treasury programs using wfc3 on the hubble space telescope. we combine these sne ia with a new compilation of ∼1050 sne ia, jointly calibrated and corrected for simulated survey biases to produce accurate distance measurements. we present unbiased constraints on the expansion rate at six redshifts in the range 0.07< z< 1.5 based only on this combined sn ia sample. the added leverage of our new sample at z> 1.5 leads to a factor of ∼3 improvement in the determination of the expansion rate at z = 1.5, reducing its uncertainty to ∼20%, a measurement of h(z=1.5)/{h}0 = {2.69}-0.52+0.86. we then demonstrate that these six derived expansion rate measurements alone provide a nearly identical characterization of dark energy as the full sn sample, making them an efficient compression of the sn ia data. the new sample of sne ia at z> 1.5 usefully distinguishes between alternative cosmological models and unmodeled evolution of the sn ia distance indicators, placing empirical limits on the latter. finally, employing a realistic simulation of a potential wide-field infrared survey telescope sn survey observing strategy, we forecast optimistic future constraints on the expansion rate from sne ia. | type ia supernova distances at redshift >1.5 from the hubble space telescope multi-cycle treasury programs: the early expansion rate |
we use observational data from supernovae (snia) pantheon sample, as well as from direct measurements of the hubble parameter from the cosmic chronometers (cc) sample, in order to extract constraints on the scenario of barrow holographic dark energy. the latter is a holographic dark energy model based on the recently proposed barrow entropy, which arises from the modification of the black-hole surface due to quantum-gravitational effects. we first consider the case where the new deformation exponent δ is the sole model parameter, and we show that although the standard value δ =0 , which corresponds to zero deformation, lies within the 1 σ region, a deviation is favored. in the case where we let both δ and the second model parameter to be free we find that a deviation from standard holographic dark energy is preferred. additionally, applying the akaike, bayesian and deviance information criteria, we conclude that the one-parameter model is statistically compatible with λ cdm paradigm, and preferred comparing to the two-parameter one. finally, concerning the present value of the hubble parameter we find that it is close to the planck value. | observational constraints on barrow holographic dark energy |
inferring high-fidelity constraints on the spatial curvature parameter, ωk, under as few assumptions as possible, is of fundamental importance in cosmology. we propose a method to non-parametrically infer ωk from late-universe probes alone. using gaussian processes (gps) to reconstruct the expansion history, we combine cosmic chronometers (ccs) and type ia supernovae (sne ia) data to infer constraints on curvature, marginalized over the expansion history, calibration of the cc and sne ia data, and the gp hyper-parameters. the obtained constraints on ωk are free from parametric model assumptions for the expansion history and are insensitive to the overall calibration of both the cc and sne ia data (being sensitive only to relative distances and expansion rates). applying this method to pantheon sne ia and the latest compilation of ccs, we find ωk = -0.03 ± 0.26, consistent with spatial flatness at the $\mathcal {o}(10^{-1})$ level, and independent of any early-universe probes. applying our methodology to future baryon acoustic oscillations and sne ia data from upcoming stage iv surveys, we forecast the ability to constrain ωk at the $\mathcal {o}(10^{-2})$ level. | non-parametric spatial curvature inference using late-universe cosmological probes |
the zwicky transient facility (ztf) is performing a three-day cadence survey of the visible northern sky (∼3π) with newly found transient candidates announced via public alerts. the ztf bright transient survey (bts) is a large spectroscopic campaign to complement the photometric survey. bts endeavors to spectroscopically classify all extragalactic transients with mpeak ≤ 18.5 mag in either the gztf or rztf filters, and publicly announce said classifications. bts discoveries are predominantly supernovae (sne), making this the largest flux-limited sn survey to date. here we present a catalog of 761 sne, classified during the first nine months of ztf (2018 april 1-2018 december 31). we report bts sn redshifts from sn template matching and spectroscopic host-galaxy redshifts when available. we analyze the redshift completeness of local galaxy catalogs, the redshift completeness fraction (rcf; the ratio of sn host galaxies with known spectroscopic redshift prior to sn discovery to the total number of sn hosts). of the 512 host galaxies with sne ia, 227 had previously known spectroscopic redshifts, yielding an rcf estimate of 44% ± 4%. the rcf decreases with increasing distance and decreasing galaxy luminosity (for z < 0.05, or ∼200 mpc, rcf ≈ 0.6). prospects for dramatically increasing the rcf are limited to new multifiber spectroscopic instruments or wide-field narrowband surveys. existing galaxy redshift catalogs are only ∼50% complete at r ≈ 16.9 mag. pushing this limit several magnitudes deeper will pay huge dividends when searching for electromagnetic counterparts to gravitational wave events or sources of ultra-high-energy cosmic rays or neutrinos. | the zwicky transient facility bright transient survey. i. spectroscopic classification and the redshift completeness of local galaxy catalogs |
a constant early dark energy (ede) component contributing a fraction fede(zc)∼10 % of the energy density of the universe around zc≃3500 and diluting as or faster than radiation afterwards, can provide a simple resolution to the hubble tension, the ∼5 σ discrepancy—in the λ cdm context—between the h0 value derived from early- and late-universe observations. however, it has been pointed out that including large-scale structure (lss) data, which are in ∼3 σ tension with λ cdm and ede cosmologies, might break some parameter degeneracy and alter these conclusions. we reassess the viability of the ede against a host of high- and low-redshift measurements, by combining lss observations from recent weak lensing (wl) surveys with cmb, baryon acoustic oscillation (bao), growth function (fs) and supernova ia (snia) data. introducing a model whose only parameter is fede(zc), we report in agreement with past work a ∼2 σ preference for nonzero fede(zc) from planck cmb data alone, while the tension with the local h0 measurement from sh0es is reduced below 2 σ . adding bao, fs and snia does not affect this conclusion, while the inclusion of a prior on h0 from sh0es increase the preference for ede over λ cdm to the ∼3.6 σ level. after checking the ede nonlinear matter power spectrum as predicted by standard semi-analytical algorithms via a dedicated set of n -body simulations, we test the 1-parameter ede cosmology against wl data. we find that it does not significantly worsen the fit to the s8 measurement as compared to λ cdm , and that current wl observations do not exclude the ede resolution to the hubble tension. we also caution against the interpretation of constraints obtained from combining statistically inconsistent datasets within the λ cdm cosmology. in light of the cmb lensing anomalies, we show that the lensing-marginalized cmb data also favor nonzero fede(zc) at ∼2 σ , predicts h0 in 1.4 σ agreement with sh0es and s8 in 1.5 σ and 0.8 σ agreement with kids-viking and des respectively. there still exists however a ∼2.5 σ tension with the joint results from kids-viking and des. with an eye on occam's razor, we finally discuss promising extensions of the ede cosmology that could allow us to fully restore cosmological concordance. | early dark energy resolution to the hubble tension in light of weak lensing surveys and lensing anomalies |
in this work, we provide updated constraints on coupled dark energy (cde) cosmology with peebles-ratra (pr) potential and constant coupling strength β . this modified gravity scenario introduces a fifth force between dark matter particles, mediated by a scalar field that plays the role of dark energy. the mass of the dark matter particles does not remain constant, but changes with time as a function of the scalar field. here we focus on the phenomenological behavior of the model, and assess its ability to describe updated cosmological datasets that include the planck 2018 cosmic microwave background (cmb) temperature, polarization and lensing, baryon acoustic oscillations, the pantheon compilation of supernovae of type ia, data on h (z ) from cosmic chronometers, and redshift-space distortions. we also study the impact of the local measurement of h0 from sh0es and the strong-lensing time delay data from the h0licow collaboration on the parameter that controls the strength of the interaction in the dark sector. we find a peak corresponding to a coupling β >0 and to a potential parameter α >0 , more or less evident depending on the dataset combination. we show separately the impact of each dataset and remark that cmb lensing is especially the one dataset that shifts the peak the most towards λ cdm . when a model selection criterion based on the full bayesian evidence is applied, however, λ cdm is still preferred in all cases, due to the additional parameters introduced in the cde model. | update on coupled dark energy and the h0 tension |
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