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we present initial results from the cosmic ultraviolet baryon survey (cubs). cubs is designed to map diffuse baryonic structures at redshift z ≲ 1 using absorption-line spectroscopy of 15 uv-bright qsos with matching deep galaxy survey data. cubs qsos are selected based on their nuv brightness to avoid biases against t... | the cosmic ultraviolet baryon survey (cubs) - i. overview and the diverse environments of lyman limit systems at z < 1 |
we present basic data and modeling for a survey of the cool, photoionized circumgalactic medium (cgm) of low-redshift galaxies using far-uv qso absorption-line probes. this survey consists of “targeted” and “serendipitous” cgm subsamples, originally described in stocke et al. (paper i). the targeted subsample probes lo... | characterizing the circumgalactic medium of nearby galaxies with hst/cos and hst/stis absorption-line spectroscopy. ii. methods and models |
the recent measurement of an ionising mean free path $\lambda_{\text{mfp}}<1$ pmpc at $z=6$ challenges our understanding of the small-scale structure of the intergalactic medium (igm) at the end of reionisation. we introduce a new method to constrain \mfp at $z=6$ by using lower limits on the individual free paths o... | constraints on the mean free path of ionising photons at $z\\sim6$ using limits on individual free paths |
outflows driven by active galactic nuclei (agns) are often invoked as agents of the long-sought agn feedback. yet, characterizing and quantifying the impact on their host galaxies has been challenging. we present gemini multi-object spectrograph integral field unit data of six local (z \lt 0.1) and luminous (l{}[{{o}{{... | unraveling the complex structure of agn-driven outflows. i. kinematics and sizes |
we present a self-consistent prediction from a large-scale cosmological simulation for the population of “wandering” supermassive black holes (smbhs) of mass greater than 106 m ⊙ on long-lived, kpc-scale orbits within milky way (mw)-mass galaxies. we extract a sample of mw-mass halos from the romulus25 cosmological sim... | wandering supermassive black holes in milky-way-mass halos |
we present an x-ray point-source catalogue from the xmm-large scale structure (xmm-lss) survey region, one of the xmm-spitzer extragalactic representative volume survey (xmm-servs) fields. we target the xmm-lss region with 1.3 ms of new xmm-newton ao-15 observations, transforming the archival x-ray coverage in this reg... | the xmm-servs survey: new xmm-newton point-source catalogue for the xmm-lss field |
a supramassive, strongly magnetized millisecond neutron star (ns) has been proposed to be the candidate central engine of at least some short gamma-ray bursts (sgrbs), based on the "internal plateau" commonly observed in the early x-ray afterglow. while a previous analysis shows a qualitative consistency between this s... | internal x-ray plateau in short grbs: signature of supramassive fast-rotating quark stars? |
the observational evidence that super-massive black holes (m• ∼ 109-10 m⊙) are already in place less than 1 gyr after the big bang poses stringent time constraints on the growth efficiency of their seeds. among proposed possibilities, the formation of massive (∼103-6 m⊙) seeds and/or the occurrence of super-eddington (... | the growth efficiency of high-redshift black holes |
we report on the acceleration properties of 329 features in 95 blazar jets from the mojave very long baseline array program. nearly half the features and three-quarters of the jets show significant changes in speed and/or direction. in general, apparent speed changes are distinctly larger than changes in direction, ind... | mojave. xii. acceleration and collimation of blazar jets on parsec scales |
observations show a prevalence of high-redshift galaxies with large stellar masses and predominantly passive stellar populations. a variety of processes have been suggested that could reduce the star formation in such galaxies to observed levels, including quasar mode feedback, virial shock heating, or galactic winds d... | the argo simulation - i. quenching of massive galaxies at high redshift as a result of cosmological starvation |
we confirm two new local massive relic galaxies, i.e. untouched survivors of the early universe massive population: mrk 1216 and pgc 032873. both show early and peaked formation events within very short time-scales (<1 gyr) and thus old mean mass-weighted ages (∼13 gyr). their star formation histories remain virtual... | two new confirmed massive relic galaxies: red nuggets in the present-day universe |
we examine the distribution of radio emission from ~42 000 quasars from the sloan digital sky survey, as measured in the lofar two-metre sky survey (lotss). we present a model of the radio luminosity distribution of the quasars that assumes that every quasar displays a superposition of two sources of radio emission: ac... | the radio loudness of sdss quasars from the lofar two-metre sky survey: ubiquitous jet activity and constraints on star formation |
in this paper, we use the latest observations of quasars covering the redshift range of 0.04 <z <5.1 to investigate a series of chaplygin gas models as candidates for unified dark matter and dark energy. based on different combinations of available standard candle and standard ruler data, we put constraints on th... | revisiting chaplygin gas cosmologies with the recent observations of high-redshift quasars |
context. positions and proper motions of gaia sources are expressed in a reference frame that ideally should be non-rotating relative to distant extragalactic objects, coincident with the international celestial reference system (icrs), and consistent across all magnitudes. for sources fainter than 16th magnitude, this... | the gaia reference frame for bright sources examined using vlbi observations of radio stars |
we present a systematic investigation of physical conditions and elemental abundances in four optically thick lyman-limit systems (llss) at z = 0.36-0.6 discovered within the cosmic ultraviolet baryon survey (cubs). because intervening llss at z < 1 suppress far-uv (ultraviolet) light from background qsos, an unbias... | the cosmic ultraviolet baryon survey (cubs) - iii. physical properties and elemental abundances of lyman-limit systems at z < 1 |
context. the damped random walk (drw) stochastic process is nowadays frequently used to model aperiodic light curves of active galactic nuclei (agns). a number of correlations between the drw model parameters, the signal decorrelation timescale and amplitude, and the physical agn parameters, such as the black hole mass... | limitations on the recovery of the true agn variability parameters using damped random walk modeling |
the radio galaxy 0402+379 is believed to host a supermassive black hole binary (smbhb). the two compact-core sources are separated by a projected distance of 7.3 pc, making it the most (spatially) compact resolved smbhb known. we present new multi-frequency vlbi observations of 0402+379 at 5, 8, 15, and 22 ghz and comb... | constraining the orbit of the supermassive black hole binary 0402+379 |
we present time-delay measurements for the new quadruple imaged quasar des j0408-5354, the first quadruple imaged quasar found in the dark energy survey (des). our result is made possible by implementing a new observational strategy using almost daily observations with the mpia 2.2 m telescope at la silla observatory a... | cosmograil: the cosmological monitoring of gravitational lenses. xvi. time delays for the quadruply imaged quasar des j0408-5354 with high-cadence photometric monitoring |
motivated by the claimed detection of a large population of faint active galactic nuclei (agns) at high redshift, recent studies have proposed models in which agns contribute significantly to the z > 4 h i ionizing background. in some models, agns are even the chief sources of reionization. if proved true, these mod... | on the contribution of active galactic nuclei to the high-redshift metagalactic ionizing background |
research over the past decade has shown diminishing evidence for major galaxy mergers being a dominant mechanism for the growth of supermassive black holes (bhs) in galaxies and the triggering of optically or x-ray-selected active galactic nuclei (agns). for the first time we test whether such a connection exists at le... | major mergers are not the dominant trigger for high-accretion agns at z ∼ 2 |
we compare cosmological hydrodynamical simulations combined with the homogeneous metagalactic uv background (uvb) of haardt & madau (hereafter hm2012) to observations of the lyman α forest that are sensitive to the thermal and ionization state of the intergalactic medium (igm). the transition from optically thick t... | the photoheating of the intergalactic medium in synthesis models of the uv background |
this paper presents a survey of x-ray-selected active galactic nuclei (agns) with optical spectroscopic follow-up in a ∼ 18 deg2 area of the equatorial xmm-xxl north field. a sample of 8445 point-like x-ray sources detected by xmm-newton above a limiting flux of f_{0.5-10 kev} > 10^{-15} erg cm^{-2} s^{-1} was match... | a spectroscopic survey of x-ray-selected agns in the northern xmm-xxl field |
we report results of a spectroscopic campaign carried out at the 10 m gran telescopio canarias for a sample of 22 bl lac objects detected (or candidates) at tev energies, aiming to determine or constrain their redshift. this is of fundamental importance for the interpretation of their emission models and for population... | on the redshift of tev bl lac objects |
binary supermassive black holes (bsbhs) are expected to be a generic byproduct from hierarchical galaxy formation. the final coalescence of bsbhs is thought to be the loudest gravitational wave (gw) siren, yet no confirmed bsbh is known in the gw-dominated regime. while periodic quasars have been proposed as bsbh candi... | discovery of a candidate binary supermassive black hole in a periodic quasar from circumbinary accretion variability |
we report the detection (>4σ) of a quasi-periodic oscillation (qpo) in the gamma-ray light curve of 3c 454.3 along with a simultaneous marginal qpo detection (>2.4σ) in the optical light curves. periodic flux modulations were detected in both of these wavebands with a dominant period of ~47 d. the gamma-ray qpo l... | multiwaveband quasi-periodic oscillation in the blazar 3c 454.3 |
we study the frequently used assumption in multi-messenger astrophysics that the gamma-ray and neutrino fluxes are directly connected because they are assumed to be produced by the same photohadronic production chain. an interesting candidate source for this test is the flat-spectrum radio quasar pks b1424-418, which r... | on the direct correlation between gamma-rays and pev neutrinos from blazars |
ratios of different ions of the same element encode ionization information independently from relative abundances in quasar absorption line systems, crucial for understanding the multiphase nature and origin of absorbing gas, particularly at z > 6 where h i cannot be observed. observational considerations have limit... | heavy element absorption systems at 5.0 < z < 6.8: metal-poor neutral gas and a diminishing signature of highly ionized circumgalactic matter |
active galactic nuclei can be copious extragalactic emitters of mev-gev-tev γ rays, a phenomenon linked to the presence of relativistic jets powered by a super-massive black hole in the center of the host galaxy. most of γ-ray emitting active galactic nuclei, with more than 1500 known at gev energies, and more than 60 ... | active galactic nuclei at gamma-ray energies |
we calibrate here cosmological radiative transfer simulations with aton/ramses with a range of measurements of the ly α opacity from quasi-stellar objects (qso) absorption spectra. we find the ly α opacity to be very sensitive to the exact timing of hydrogen reionization. models reproducing the measured evolution of th... | calibrating cosmological radiative transfer simulations with ly α forest data: evidence for large spatial uv background fluctuations at z ∼ 5.6-5.8 due to rare bright sources |
we present the first discoveries from a survey of z ≳ 6 quasars using imaging data from the decam legacy survey (decals) in the optical, the ukirt deep infrared sky survey (ukidss) and a preliminary version of the ukirt hemisphere survey (uhs) in the near-ir, and allwise in the mid-ir. decals will image 9000 deg2 of sk... | first discoveries of z > 6 quasars with the decam legacy survey and ukirt hemisphere survey |
high-redshift quasars are important tracers of structure and evolution in the early universe. however, they are very rare and difficult to find when using color selection because of contamination from late-type dwarfs. high-redshift quasar surveys based on only optical colors suffer from incompleteness and low identifi... | a survey of luminous high-redshift quasars with sdss and wise. i. target selection and optical spectroscopy |
radio-loud quasars (rlqs) are more x-ray luminous than predicted by the x-ray-optical/uv relation (i.e. $l_\mathrm{x}\propto l_\mathrm{uv}^\gamma$) for radio-quiet quasars (rqqs). the excess x-ray emission depends on the radio-loudness parameter (r) and radio spectral slope (αr). we construct a uniform sample of 729 op... | the lx-luv-lradio relation and corona-disc-jet connection in optically selected radio-loud quasars |
we used 3.1 million spectroscopically labelled sources from the sloan digital sky survey (sdss) to train an optimised random forest classifier using photometry from the sdss and the widefield infrared survey explorer. we applied this machine learning model to 111 million previously unlabelled sources from the sdss phot... | identifying galaxies, quasars, and stars with machine learning: a new catalogue of classifications for 111 million sdss sources without spectra |
the broad mg ii line in quasars has distinct variability properties compared with broad balmer lines: it is less variable and usually does not display a “breathing” mode, the increase in the average cloud distance when luminosity increases. we demonstrate that these variability properties of mg ii can be reasonably wel... | understanding broad mg ii variability in quasars with photoionization: implications for reverberation mapping and changing-look quasars |
powerful radio galaxies exist as either compact or extended sources, with the extended sources traditionally classified by their radio morphologies as fanaroff-riley (fr) type i and ii sources. fri/frii and compact radio galaxies have also been classified by their optical spectra into two different types: high excitati... | the nuclear properties and extended morphologies of powerful radio galaxies: the roles of host galaxy and environment |
we construct a supervised classifier based on gaussian mixture models to probabilistically classify objects in gaia data release 2 (gdr2) using only photometric and astrometric data in that release. the model is trained empirically to classify objects into three classes - star, quasar, galaxy - for g ≥ 14.5 mag down to... | quasar and galaxy classification in gaia data release 2 |
we present a systematic x-ray and multiwavelength study of a sample of 47 active galactic nuclei (agns) with reverberation mapping measurements. this sample includes 21 super-eddington accreting agns and 26 sub-eddington accreting agns. using high-state observations with simultaneous x-ray and uv/optical measurements, ... | on the observational difference between the accretion disk-corona connections among super- and sub-eddington accreting active galactic nuclei |
quasar absorption systems encode a wealth of information about the abundances, ionization structure, and physical conditions in intergalactic and circumgalactic media. simple (often single-phase) photoionization models are frequently used to decode such data. using five discrete absorbers from the cos absorption survey... | the cos absorption survey of baryon harbors: unveiling the physical conditions of circumgalactic gas through multiphase bayesian ionization modelling |
the concurrent growth of supermassive black holes (smbhs) and their host galaxies remains to be fully explored, especially at high redshift. while often understood as a consequence of self-regulation via agn feedback, it can also be explained by alternative smbh accretion models. here, we expand on previous work by stu... | black hole-galaxy scaling relations in fire: the importance of black hole location and mergers |
high-redshift quasars (z > 5) that also shine brightly at radio wavelengths are unique signposts of supermassive black hole activity in the early universe. however, bright radio sources at z ≥ 5 are extremely rare and therefore we have started a campaign to search for new high-z quasars by combining an optical dropo... | discovery of 24 radio-bright quasars at 4.9 ≤ z ≤ 6.6 using low-frequency radio observations |
peculiar motion of the solar system, determined from the dipole anisotropy in the cosmic microwave background radiation (cmbr), has given a velocity 370 km s-1 along ra = 168°, dec. = -7°. subsequent peculiar motion determinations from the number counts, sky brightness, or redshift dipoles observed in large samples of ... | peculiar motion of solar system from the hubble diagram of supernovae ia and its implications for cosmology |
the recent advanced ligo/virgo detections of gravitational waves (gws) from stellar binary black hole (bbh) mergers, in particular gw190521, which is potentially associated with a quasar, have stimulated renewed interest in active galactic nuclei as factories of merging bbhs. compact objects evolving from massive stars... | accretion-modified stars in accretion disks of active galactic nuclei: gravitational-wave bursts and electromagnetic counterparts from merging stellar black hole binaries |
recent analyses of the planck data and quasars at high redshifts have suggested possible deviations from the flat λ cold dark matter model (λcdm), where λ is the cosmological constant. here we use machine learning methods to investigate any possible deviations from λcdm at both low and high redshifts by using the lates... | hints of dark energy anisotropic stress using machine learning |
we have designed, developed, and applied a convolutional neural network (cnn) architecture using multi-task learning to search for and characterize strong h i lyα absorption in quasar spectra. without any explicit modelling of the quasar continuum or application of the predicted line profile for lyα from quantum mechan... | deep learning of quasar spectra to discover and characterize damped lyα systems |
measuring the proximity effect and the damping wing of intergalactic neutral hydrogen in quasar spectra during the epoch of reionization requires an estimate of the intrinsic continuum at rest-frame wavelengths of λ rest ∼ 1200-1260 å. in contrast to previous works which used composite spectra with matched spectral pro... | predicting quasar continua near lyα with principal component analysis |
context. the physical characteristics of the material closest to supermassive black holes (smbhs) are primarily studied through x-ray observations. however, the origins of the main x-ray components such as the soft x-ray excess, the fe kα line complex, and the hard x-ray excess are still hotly debated. this is particul... | a deep x-ray view of the bare agn ark 120. iv. xmm-newton and nustar spectra dominated by two temperature (warm, hot) comptonization processes |
we have utilized high-resolution optical hubble space telescope images and deep, ground-based near-infrared images to examine the host galaxies of 37 active galactic nuclei (agns) with reverberation-based black hole masses. using two-dimensional image decompositions, we have separated the host galaxy from the bright ce... | black hole-galaxy scaling relationships for active galactic nuclei with reverberation masses |
we present the ultraviolet (uv) spectroscopic evolution of a tidal disruption event (tde) for the first time. after the discovery of the nearby tde iptf16fnl, we obtained a series of observations with the space telescope imaging spectrograph (stis) onboard the hubble space telescope (hst). the dominant emission feature... | the ultraviolet spectroscopic evolution of the low-luminosity tidal disruption event iptf16fnl |
we have analysed the differences in positions of 9081 matched sources between the gaia data release 2 (dr2) and very long baseline interferometry (vlbi) catalogues. the median position uncertainty of matched sources in the vlbi catalogue is a factor of two larger than the median position uncertainty in gaia dr2. there ... | a quantitative analysis of systematic differences in the positions and proper motions of gaia dr2 with respect to vlbi |
we present the results of a model-independent investigation of the rest-frame uv spectra from a comprehensive sample of 394 quasars in the redshift range 1.5 ≤ z ≤ 7.5. we fit the main broad emission lines (bels) in the rest-frame range 1280 å ≤ λ ≤ 3000 å (o i, c ii, si iv, c iii], c iv, and mg ii) with a lightly supe... | new constraints on quasar evolution: broad-line velocity shifts over 1.5 ≲ z ≲ 7.5 |
we resolve the host galaxies of seven gravitationally lensed quasars at redshift 1.5-2.8 using observations with the atacama large (sub)millimetre array. using a visibility plane lens modelling technique, we create pixellated reconstructions of the dust morphology, and co line morphology and kinematics. we find that th... | the rocky road to quiescence: compaction and quenching of quasar host galaxies at z ∼ 2 |
we present the effective-field theory (eft-)based cosmological full-shape analysis of the anisotropic power spectrum of eboss quasars at the effective redshift zeff=1.48 . we perform extensive tests of our pipeline on simulations, paying particular attention to the modeling of observational systematics, such as redshif... | cosmological constraints from the power spectrum of eboss quasars |
general relativity reproduces main current cosmological observations, assuming the validity of the cosmic distance duality relation (cddr) at all scales and epochs. however, cddr is poorly tested in the redshift interval between the farthest observed type ia supernovae and that of the cosmic microwave background. we pr... | multiple measurements of quasars acting as standard probes: exploring the cosmic distance duality relation at higher redshift |
we derive predictions from state-of-the-art cosmological galaxy simulations for the spatial distribution of the hot circumgalactic medium (cgm, [0.1-1]r200c) through its emission lines in the x-ray soft band ([0.3-1.3] kev). in particular, we compare illustristng, eagle, and simba and focus on galaxies with stellar mas... | x-ray metal line emission from the hot circumgalactic medium: probing the effects of supermassive black hole feedback |
understanding the growth of the supermassive black holes (smbh) powering luminous quasars, their co-evolution with host galaxies, and impact on the surrounding intergalactic medium (igm) depends sensitively on the duration of quasar accretion episodes. unfortunately, this time-scale, known as the quasar lifetime, tq, i... | the first measurement of the quasar lifetime distribution |
we present a novel, few-body computational framework designed to shed light on the likelihood of forming intermediate-mass (im) and supermassive (sm) black holes (bhs) in nuclear star clusters (nscs) through successive bh mergers, initiated with a single bh seed. using observationally motivated nsc profiles, we find th... | growing black holes through successive mergers in galactic nuclei - i. methods and first results |
aims: modelling the low-ionisation lines (lils) in active galactic nuclei (agns) still faces problems in explaining the observed equivalent widths (ews) when realistic covering factors are used and the distance of the broad-line region (blr) from the centre is assumed to be consistent with the reverberation mapping mea... | the cafe project: optical fe ii and near-infrared ca ii triplet emission in active galaxies: simulated ews and the co-dependence of cloud size and metal content |
we study the genesis and evolution of supermassive black hole (smbh) seeds through different formation channels, from popiii remnants to massive seeds, modelled within the l-galaxies semi-analytic code. we run the model on the millennium-ii simulation (mr-ii) merger trees, as their halo-mass resolution ($m_{\rm vir,res... | multiflavour smbh seeding and evolution in cosmological environments |
the physical properties of galactic winds are one of the keys to understand galaxy formation and evolution. these properties can be constrained thanks to background quasar lines of sight (los) passing near star-forming galaxies (sfgs). we present the first results of the muse gas flow and wind survey obtained from two ... | muse gas flow and wind (megaflow). i. first muse results on background quasars |
the completed extended baryon oscillation spectroscopic survey (eboss) catalogues contain redshifts of 344 080 quasars at 0.8 < z < 2.2, 174 816 luminous red galaxies between 0.6 < z < 1.0, and 173 736 emission-line galaxies over 0.6 < z < 1.1 in order to constrain the expansion history of the univers... | the completed sdss-iv extended baryon oscillation spectroscopic survey: pairwise-inverse probability and angular correction for fibre collisions in clustering measurements |
the australian dark energy survey (ozdes) is a five-year, 100-night, spectroscopic survey on the anglo-australian telescope, whose primary aim is to measure redshifts of approximately 2500 type ia supernovae host galaxies over the redshift range 0.1 < z < 1.2, and derive reverberation-mapped black hole masses for... | ozdes multifibre spectroscopy for the dark energy survey: first-year operation and results |
we introduce a new method for determining the influence of galaxies and active galactic nuclei (agn) on the intergalactic medium (igm) at high redshift and illustrate its potential via a first application to the field of the z = 6.42 qso j1148+5251. correlating spatial positions lyman break galaxies (lbgs) with the lym... | the role of galaxies and agn in reionizing the igm - i. keck spectroscopy of 5 < z < 7 galaxies in the qso field j1148+5251 |
we study h i and metal-line absorption around z ≈ 2 star-forming galaxies by comparing an analysis of data from the keck baryonic structure survey to mock spectra generated from the evolution and assembly of galaxies and their environments (eagle) cosmological, hydrodynamical simulations. we extract sightlines from the... | a comparison of observed and simulated absorption from h i, c iv, and si iv around z ≈ 2 star-forming galaxies suggests redshift-space distortions are due to inflows |
a new estimation of the isotropic diffuse γ -ray background (igrb) observed by the large area telescope (lat) on board the fermi gamma-ray space telescope (fermi) has been presented for 50 months of data, in the energy range 100 mev-820 gev and for different modelings of the galactic foreground. we attempt here the int... | composition of the fermi-lat isotropic gamma-ray background intensity: emission from extragalactic point sources and dark matter annihilations |
we present two catalogues of active galactic nucleus (agn) candidates selected from the latest data of two all-sky surveys - data release 2 of the gaia mission and the unwise catalogue of the wide-field infrared survey explorer (wise). we train a random forest classifier to predict the probability of each source in the... | catalogues of active galactic nuclei from gaia and unwise data |
we carry out a series of deep karl g. jansky very large array (vla) s-band observations of a sample of 21 quasars at z ∼ 6. the new observations expand the searches of radio continuum emission to the optically faint quasar population at the highest redshift with rest-frame $4400\,\mathring{\rm a} $ luminosities down to... | constraining the quasar radio-loud fraction at z ∼ 6 with deep radio observations |
the high redshift lyman-α forest, in particular the gunn-peterson trough, is the most unambiguous signature of the neutral to ionized transition of the intergalactic medium (igm) taking place during the epoch of reionization. recent studies have shown that reproducing the observed lyman-α opacity distributions after ov... | lyman-alpha opacities at z = 4-6 require low mass, radiatively-suppressed galaxies to drive cosmic reionization |
we study the physical properties of a homogeneous sample of 157 optically thick absorption line systems at redshifts ∼1.8-4.4, selected from a high-dispersion spectroscopic survey of lyman limit systems (llss). by means of multiple ionization models and bayesian techniques, we derive the posterior probability distribut... | the physical properties of z > 2 lyman limit systems: new constraints for feedback and accretion models |
outbursts from gamma-ray quasars provide insights on the relativistic jets of active galactic nuclei and constraints on the diffuse radiation fields that fill the universe. the detection of significant emission above 100 gev from a distant quasar would show that some of the radiated gamma-rays escape pair-production in... | gamma-rays from the quasar pks 1441+25: story of an escape |
context. the reionisation of the universe is a process that is thought to have ended around z ~ 6, as inferred from spectroscopy of distant bright background sources, such as quasars (qso) and gamma-ray burst (grb) afterglows. furthermore, spectroscopy of a grb afterglow provides insight in its host galaxy, which is of... | vlt/x-shooter spectroscopy of the afterglow of the swift grb 130606a. chemical abundances and reionisation at z ~ 6 |
radio-loud active galactic nuclei at z∼ 2-4 are typically located in dense environments and their host galaxies are among the most massive systems at those redshifts, providing key insights for galaxy evolution. finding radio-loud quasars at the highest accessible redshifts (z∼ 6) is important to the study of their pro... | constraining the radio-loud fraction of quasars at z > 5.5 |
observations of high-redshift quasars at z > 6 indicate that they harbour supermassive black holes (smbhs) of a billion solar masses. the direct collapse scenario has emerged as the most plausible way to assemble smbhs. the nurseries for the direct collapse black holes are massive primordial haloes illuminated with ... | how realistic uv spectra and x-rays suppress the abundance of direct collapse black holes |
we use time-domain optical spectroscopy to distinguish between broad emission lines powered by accreting black holes (bhs) and stellar processes (i.e., supernovae) for 16 galaxies identified as active galactic nucleus (agn) candidates by reines et al (2013). our study is primarily focused on those objects with narrow e... | multi-epoch spectroscopy of dwarf galaxies with agn signatures: identifying sources with persistent broad hα emission |
we present the results of a dust-reverberation survey of quasars at redshifts z < 0.6. we found a delayed response of the k-band flux variation after the optical flux variation in 25 out of 31 targets, and obtained the lag time between them for 22 targets. combined with the results for nearby seyfert galaxies, we pr... | reverberation measurements of the inner radii of the dust tori in quasars |
we explore whether an independent determination of the distance−redshift relation, and hence cosmological model parameters, can be obtained from the apparent correlations between two different wave-band luminosities or fluxes, as has been claimed in recent works using the x-ray and ultraviolet luminosities and fluxes o... | can the distance−redshift relation be determined from correlations between luminosities? |
we present a new x-ray spectroscopic study of 22 luminous (2 × 1045 ≲ lbol/erg s−1 ≲ 2 × 1046) active galactic nuclei (agns) at intermediate redshifts (0.1 ≲ z ≲ 0.4), as part of the supermassive black hole winds in the x-rays (subways) sample, mostly composed of quasars and type 1 agns. here, 17 targets were observed ... | supermassive black hole winds in x-rays: subways. i. ultra-fast outflows in quasars beyond the local universe |
the james webb space telescope (jwst) will open a new window into the most distant universe and unveil the early growth of supermassive black holes (bhs) in the first galaxies. in preparation for deep jwst imaging surveys, it is crucial to understand the color selection of high-redshift accreting seed bhs. we model the... | the age of discovery with the james webb space telescope: excavating the spectral signatures of the first massive black holes |
we use measurements of 59/58 quasars (qsos), over a redshift range 0.0041 ≤ z ≤ 1.686, to do a comparative study of the radius-luminosity (r - l) and x-ray-uv luminosity (lx - luv) relations and the implication of these relations for cosmological parameter estimation. by simultaneously determining r - l or lx - luv rel... | quasar uv/x-ray relation luminosity distances are shorter than reverberation-measured radius-luminosity relation luminosity distances |
the cosmological principle (cp) is part of the foundation that underpins the standard model of the universe. in the era of precision cosmology, when stress tests of the standard model are uncovering various tensions and possible anomalies, it is critical to check the viability of this principle. a key test is the consi... | theoretical systematics in testing the cosmological principle with the kinematic quasar dipole |
the active galactic nucleus (agn) phenomenon results from a supermassive black hole accreting its surrounding gaseous and dusty material. the infrared (ir) regime provides most of the information to characterize the dusty structures that bridge from the galaxy to the black hole, providing clues to the black hole growth... | infrared spectral energy distribution and variability of active galactic nuclei: clues to the structure of circumnuclear material |
we have conducted an extensive x-ray spectral variability study of a sample of 20 compton-thin type ii galaxies using broadband spectra from xmm-newton, chandra, and suzaku. the aim is to study the variability of the neutral intrinsic x-ray obscuration along the line of sight and investigate the properties and location... | the variable and non-variable x-ray absorbers in compton-thin type ii active galactic nuclei |
every star-forming galaxy has a halo of metal-enriched gas that extends out to at least 100 kiloparsecs, as revealed by the absorption lines that this gas imprints on the spectra of background quasars. however, quasars are sparse and typically probe only one narrow beam of emission through the intervening galaxy. close... | a clumpy and anisotropic galaxy halo at redshift 1 from gravitational-arc tomography |
aims: our goal is to study molecular gas properties in nuclei and large scale outflows/winds from active galactic nuclei (agns) and starburst galaxies.methods: we obtained high resolution (0.̋25 to 0.̋90) observations of hcn and hco+j = 3 → 2 of the ultraluminous qso galaxy mrk 231 with the iram plateau de bure interfe... | high resolution observations of hcn and hco+j = 3-2 in the disk and outflow of mrk 231. detection of vibrationally excited hcn in the warped nucleus |
ultra-light dark matter (uldm) refers to a class of theories, including ultra-light axions, in which particles with mass $m_{\psi } \lt 10^{-20}\, \rm {ev}$ comprise a significant fraction of the dark matter. a galactic scale de broglie wavelength distinguishes these theories from cold dark matter (cdm), suppressing th... | quantum fluctuations masquerade as haloes: bounds on ultra-light dark matter from quadruply imaged quasars |
the non-linear relation between the x-ray and ultraviolet (uv) luminosity in quasars has been used to derive quasar distances and to build a hubble diagram at redshifts up to z ∼ 7. this cosmological application is based on the assumption of independence of the relation on redshift and luminosity. we want to test the r... | quasars as high-redshift standard candles |
the idea that dark matter can be made of intermediate-mass primordial black holes (pbhs) in the 10 m ⊙ ≲ m ≲ 200 m ⊙ range has recently been reconsidered, particularly in the light of the detection of gravitational waves by the ligo experiment. the existence of even a small fraction of dark matter in black holes should... | limits on the mass and abundance of primordial black holes from quasar gravitational microlensing |
the most robust way for determining the distance of quasar absorption outflows is the use of troughs from ionic excited states. the column density ratio between the excited and resonance states yields the outflow number density. combined with a knowledge of the outflow’s ionization parameter, a distance from the centra... | evidence that 50% of balqso outflows are situated at least 100 pc from the central source |
we present atacama large millimeter/submillimeter array band 8 observations of the [o iii] 88 μm line and the underlying thermal infrared continuum emission in the z = 6.08 quasar cfhqs j2100-1715 and its dust-obscured starburst companion galaxy (projected distance: ∼60 kpc). each galaxy hosts dust-obscured star format... | no evidence for enhanced [o iii] 88 μm emission in a z ∼ 6 quasar compared to its companion starbursting galaxy |
direct-collapse black holes (dcbhs) of mass $\sim 10^4$-$10^5 {m}_\odot$ that form in hi-cooling halos in the early universe are promising progenitors of the $\gtrsim 10^9 {m}_\odot$ supermassive black holes that fuel observed $z \gtrsim 7$ quasars. efficient accretion of the surrounding gas onto such dcbh seeds may re... | a search for high-redshift direct-collapse black hole candidates in the pearls north ecliptic pole field |
we report 6 yr monitoring of distant bright quasar cts c30.10 (z = 0.90052) with the southern african large telescope. we measured the rest-frame time lag of {562}-68+116 days between the continuum variations and the response of the mg ii emission line, using six different methods. this time delay, combined with other ... | time delay measurement of mg ii line in cts c30.10 with salt |
we separately assess elemental abundances in active galactic nuclei's (agns) broad and narrow emission line regions (blr and nlr), based on a critical assessment of published results together with new photoionization models. we find (1) he/h enhancements in some agn, exceeding what can be explained by normal chemical e... | metal enrichment due to embedded stars in agn discs |
context. the precise determination of the present-day expansion rate of the universe, expressed through the hubble constant h0, is one of the most pressing challenges in modern cosmology. assuming flat λcdm, h0 inference at high redshift using cosmic microwave background data from planck disagrees at the 4.4σ level wit... | the hubble constant determined through an inverse distance ladder including quasar time delays and type ia supernovae |
galight is a python-based open-source package that can be used to perform two-dimensional model fitting of optical and near-infrared images to characterize the light distribution of galaxies with components including a disk, bulge, bar, and quasar. the decomposition of stellar components has been demonstrated in publis... | galaxy shapes of light (galight): a 2d modeling of galaxy images |
negative feedback from accreting supermassive black holes is considered crucial in suppressing star formation and quenching massive galaxies. however, several models and observations suggest that black hole feedback may have a positive effect, triggering star formation by compressing interstellar medium gas to higher d... | local positive feedback in the overall negative: the impact of quasar winds on star formation in the fire cosmological simulations |
announcing the final release, v8, of the milliquas (million quasars) quasar catalogue which presents all published quasars to 30 june 2023, including quasars from the first releases of the dark energy spectroscopic instrument (desi) and the sdss-dr18 black hole mapper. its totals are 907,144 type-i qsos/agn and 66,026 ... | the million quasars (milliquas) catalogue, v8 |
the origin of ultracompact dwarfs (ucds), a class of compact stellar systems discovered two decades ago, still remains a matter of debate. recent discoveries of central supermassive black holes in ucds likely inherited from their massive progenitor galaxies provide support for the tidal stripping hypothesis. at the sam... | a 3.5 million solar masses black hole in the centre of the ultracompact dwarf galaxy fornax ucd3 |
the direct collapse model for the formation of massive black holes has gained increased support as it provides a natural explanation for the appearance of bright quasars already less than a billion years from the big bang. in this paper we review a recent scenario for direct collapse that relies on multi-scale gas infl... | the route to massive black hole formation via merger-driven direct collapse: a review |
the dynamics of the broad line region (blr) in active galaxies is an open question; direct observational constraints suggest a predominantly keplerian motion, with possible traces of inflow or outflow. in this paper we study in detail the physically motivated blr model of czerny & hryniewicz based on the radiation ... | the picture of blr in 2.5d frado: dynamics and geometry |
we discuss a novel window to probe the origin of our universe via the mass functions of primordial black holes (pbhs). the mass functions of pbhs are simply estimated using the conventional press-schechter formalism for two paradigms of cosmic origin, including inflationary $\lambda$cdm and bounce cosmology. the standa... | primordial black hole mass functions as a probe of cosmic origin |
if $z > 6$ quasars reside in rare, massive haloes, $\lambda$cdm cosmology predicts they should be surrounded by an anomalously high number of bright companion galaxies. in this paper, i show that these companion galaxies should also move unusually fast. using a new suite of cosmological, `zoom-in' hydrodynamic simul... | the host dark matter haloes of the first quasars |
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