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neutron stars (nss) which could contain exotic degrees of freedom in the core and the self-bound quark stars (qss) made purely of absolutely stable deconfined quark matter are still two main candidates for the compact objects observed in pulsars and gravitational wave (gw) events in binary star mergers. we perform a ba... | neutron star vs quark star in the multimessenger era |
we present new measurements of the flux power-spectrum p(k) of the z < 0.5 h i lyman-α forest spanning scales k ∼ 0.001-0.1 s km^{-1}. these results were derived from 65 far-ultraviolet quasar spectra (resolution r ∼ 18 000) observed with the cosmic origin spectrograph (cos) on board the hubble space telescope. the ... | the power spectrum of the lyman-α forest at z < 0.5 |
we present a new method to study the contribution of faint sources to the ultraviolet background using the 1d correlation of metal absorbers with the intergalactic medium transmission in a quasi-stellar object (qso) sightline. we take advantage of a sample of 25 high signal-to-noise ratio qso spectra to retrieve 150 tr... | the role of galaxies and agns in reionizing the igm - ii. metal-tracing the faint sources of reionization at 5 ≲ z ≲ 6 |
in the standard active galactic nucleus (agn) reverberation-mapping model, variations in broad-line region (blr) fluxes are predicted from optical continuum variability (taken as a proxy for the ionizing continuum) convolved with a response function that depends on the geometry. however, it has long been known that blr... | anomalous broad-line region responses to continuum variability in active galactic nuclei - i. hβ variability |
i study the location of the γ-ray emission in blazar jets by creating a compton-scattering approximation that is valid for all anisotropic radiation fields in the thomson through klein-nishina regimes, is highly accurate, and can speed up numerical calculations by up to a factor of ∼10. i apply this approximation to sy... | external compton scattering in blazar jets and the location of the gamma-ray emitting region |
context. the vera rubin observatory will provide an unprecedented set of time-dependent observations of the sky. the planned legacy survey of space and time (lsst), operating for ten years, will provide dense light curves for thousands of active galactic nuclei (agn) in deep drilling fields (ddfs) and less dense light ... | expectations for time-delay measurements in active galactic nuclei with the vera rubin observatory |
we study the structure of quark stars (qss) adopting homogeneously confined matter inside the star with a 3-flavor neutral charge and a fixed strange quark mass ms. we explore the internal structure, and the physical properties of specific classes of qss in the recently proposed energy-momentum squared gravity (emsg). ... | the mass-radius relation for quark stars in energy-momentum squared gravity |
the size of the dust torus in active galactic nuclei (agns) and their high-luminosity counterparts, quasars, can be inferred from the time delay between uv/optical accretion disk continuum variability and the response in the mid-infrared (mir) torus emission. this dust reverberation mapping (rm) technique has been succ... | dust reverberation mapping in distant quasars from optical and mid-infrared imaging surveys |
the correlation between neutral hydrogen (h i) in the intergalactic medium (igm) and galaxies attracts great interest. we select four fields that include several coherently strong lyα absorption systems at z ∼ 2.2 detected using background quasars from the whole sdss/(e) baryon oscillation spectroscopic survey (boss) d... | statistical correlation between the distribution of lyα emitters and intergalactic medium h i at z ∼ 2.2 mapped by the subaru/hyper suprime-cam |
the masses of supermassive black holes at the centres of local galaxies appear to be tightly correlated with the mass and velocity dispersions of their galactic hosts. however, the local mbh-mstar relation inferred from dynamically measured inactive black holes is up to an order-of-magnitude higher than some estimates ... | probing black hole accretion tracks, scaling relations, and radiative efficiencies from stacked x-ray active galactic nuclei |
observational studies are increasingly finding evidence against major mergers being the dominant mechanism responsible for triggering an active galactic nucleus (agn). after studying the connection between major mergers and agns with the highest eddington ratios at z = 2, we here expand our analysis to $z\lt 0.2$ , exp... | a significant excess in major merger rate for agns with the highest eddington ratios at z < 0.2 |
dirac, in 1937, proposed the potential variation of coupling constants derived from his large numbers hypothesis. efforts have continued since then to constrain their variation by various methods, including astrophysical and cosmological observations. we briefly discuss several methods used for the purpose while focusi... | constraining coupling constants' variation with supernovae, quasars, and grbs |
hot dust-obscured galaxies (dogs) are hyperluminous (l8-1000 μm > 1013 l⊙) infrared galaxies with extremely high (up to hundreds of k) dust temperatures. the sources powering both their extremely high luminosities and dust temperatures are thought to be deeply buried and rapidly accreting supermassive black holes (s... | heavy x-ray obscuration in the most luminous galaxies discovered by wise |
the scaling relations between supermassive black holes and their host galaxy properties are of fundamental importance in the context black hole-host galaxy co-evolution throughout cosmic time. in this work, we use a novel algorithm that identifies smooth trends in complex data sets and apply it to a sample of 2000 type... | black hole mass estimation for active galactic nuclei from a new angle |
early-type galaxies (etgs) frequently show emission from warm ionized gas. these low-ionization emission regions (liers) were originally attributed to a central, low-luminosity active galactic nucleus. however, the recent discovery of spatially extended lier emission suggests ionization by both a central source and an ... | self-consistent predictions for lier-like emission lines from post-agb stars |
numerous observations indicate that galaxies need a continuous gas supply to fuel star formation and explain the star formation history. however, direct observational evidence of gas accretion remains rare. using the eagle cosmological hydrodynamic simulation suite, we study cold gas accretion onto galaxies and the obs... | how gas accretion feeds galactic disks |
we report on a spectroscopic program to search for dual quasars using subaru hyper suprime-cam (hsc) images of sdss quasars, which represent an important stage during galaxy mergers. using subaru/focas and gemini-n/gmos, we identify three new physically associated quasar pairs having projected separations less than 20 ... | optical spectroscopy of dual quasar candidates from the subaru hsc-ssp program |
active galactic nuclei (agn) produce copious amounts of x-rays through the corona, the region of hot gas that lies close to the accretion disk. the temperature of the corona can be accurately determined by the cut-off signature in the x-ray spectrum. owing to the high temperatures in the corona, observations well above... | distribution of the coronal temperature in seyfert 1 galaxies |
so far large and different data sets revealed the accelerated expansion rate of the universe, which is usually explained in terms of dark energy. the nature of dark energy is not yet known, and several models have been introduced: a non zero cosmological constant, a potential energy of some scalar field, effects relate... | prospects of high redshift constraints on dark energy models with the ep- eiso correlation in long gamma ray bursts |
strong gravitationally lensed quasars provide a powerful means to study galaxy evolution and cosmology. we use chitah, which is an algorithm used to hunt for new lens systems, particularly lensed quasars, in the hyper suprime-cam subaru strategic program (hsc ssp) s16a. we present 46 lens candidates, of which 3 are pre... | survey of gravitationally lensed objects in hsc imaging (sugohi). iv. lensed quasar search in the hsc survey |
the final fate of gravitational collapse of massive stars has been a subject of interest for a long time since such a collapse may lead to black holes and naked singularities alike. since, the formation of naked singularities is forbidden by the cosmic censorship conjecture, exploring their observational differences fr... | imprints of the janis-newman-winicour spacetime on observations related to shadow and accretion |
our ancestors, such as cro-magnon, always looked up at the stars and wished to understand the mysteries of the universe, but their view of the universe was probably quite simple: the stars are inlaid on the inner surface of the sky, and they are very small. however, now we know that stars and galaxies are actually extr... | a novel method of measuring cosmological distances using broad-line regions of quasars |
the relation between the mass of the supermassive black hole (smbh) in the center of galaxies and their bulge mass or central velocity dispersion is well known. this suggests a coevolution between the smbhs and their galaxy hosts. our aim is to study this relation, specifically, for radio loud galaxies, and as a functi... | black hole and galaxy co-evolution in radio-loud active galactic nuclei at z ∼ 0.3-4 |
about 70 luminous quasars discovered at z > 6.5 are strongly biased toward the bright end, thus not providing a comprehensive view of quasar abundance beyond the cosmic dawn. we present the predicted results of the roman/rubin high-redshift quasar survey, yielding 3 times more, 2-4 mag deeper quasar samples, probing... | predicting the yields of z > 6.5 quasar surveys in the era of roman and rubin |
the flat spectrum radio quasar (fsrq) pks 1510−089 is known for its complex multiwavelength behaviour and it is one of only a few fsrqs detected in very-high-energy (vhe, e > 100 gev) γ rays. the vhe γ-ray observations with h.e.s.s. and magic in late may and early june 2016 resulted in the detection of an unpreceden... | h.e.s.s. and magic observations of a sudden cessation of a very-high-energy γ-ray flare in pks 1510−089 in may 2016 |
we utilize recent nustar observations (co-added depth ≈55-120 ks) of pg 1001+054, pg 1254+047, and phl 1811 to constrain their hard x-ray (≳5 kev) weakness and spectral shapes and thus to investigate the nature of their extreme x-ray weakness. these quasars showed very weak soft x-ray emission, and they were proposed t... | nustar observations of intrinsically x-ray weak quasar candidates: an obscuration-only scenario |
tension between cosmic microwave background-based and distance ladder-based determinations of the hubble constant h 0 motivates the pursuit of independent methods that are not subject to the same systematic effects. a promising alternative, proposed by refsdal in 1964, relies on the inverse scaling of h 0 with the dela... | hubble constant measurement from three large-separation quasars strongly lensed by galaxy clusters |
context. sdss j2222+2745, at z = 0.489, is one of the few currently known lens clusters with multiple images (six) of a background (z = 2.801) quasar with measured time delays between two image pairs (with a sub-percent relative error for the longer time delay). systems of this kind can be exploited as alternative cosm... | new strong lensing modelling of sdss j2222+2745 enhanced with vlt/muse spectroscopy |
the origin of jets is one of the most important issues concerning active galactic nuclei, yet it has remained obscure. in this work, we made use of information from emission lines, spectral energy distributions, and fermi-lat γ-ray emission to construct a blazar sample that contains 667 sources. we note that jet power ... | the relativistic jet and central engine of fermi blazars |
observations of z ≳ 6 quasars provide information on the early phases of the most massive black holes (mbhs) and galaxies. current observations at sub-mm wavelengths trace cold and warm gases, and future observations will extend information to other gas phases and the stellar properties. the goal of this study is to ex... | high-redshift quasars and their host galaxies - ii. multiphase gas and stellar kinematics |
water vapor (h2o) is one of the brightest molecular emitters after carbon monoxide (co) in galaxies with high infrared (ir) luminosity, allowing us to investigate the warm and dense phase of the interstellar medium (ism) where star formation occurs. however, due to the complexity of its radiative spectrum, h2o is not f... | unveiling the warm and dense ism in z > 6 quasar host galaxies via water vapor emission |
we study the impact of active galactic nuclei (agns) on the co spectral line energy distribution (sled) of high-z galaxies. in particular, we want to assess if the co sled can be used as a probe of agn activity. to this purpose, we develop a semi-analytical model that takes into account the radiative transfer and the c... | impact of x-rays on co emission from high-z galaxies |
various unification schemes interpret the complex phenomenology of quasars and luminous active galactic nuclei (agn) in terms of a simple picture involving a central black hole, an accretion disc and an associated outflow. here, we continue our tests of this paradigm by comparing quasar spectra to synthetic spectra of ... | testing quasar unification: radiative transfer in clumpy winds |
in order to study the circumgalactic medium (cgm) of galaxies we develop an automated pipeline to estimate the optical continuum of quasars and detect intervening metal absorption line systems with a matched kernel convolution technique and adaptive s/n criteria. we process ~ one million quasars in the latest data rele... | characterizing the abundance, properties, and kinematics of the cool circumgalactic medium of galaxies in absorption with sdss dr16 |
we present the results of a pilot hubble space telescope (hst) imaging study of the host galaxies of ten quasars from the sloan digital sky survey reverberation mapping (sdss-rm) project. probing more than an order of magnitude in black hole (bh) and stellar masses, our sample is the first statistical sample to study t... | the sloan digital sky survey reverberation mapping project: the mbh-host relations at 0.2 ≲ z ≲ 0.6 from reverberation mapping and hubble space telescope imaging |
the active galactic nucleus (agn) re j1034+396 displays the most significant x-ray quasi-periodic oscillation (qpo) detected so far. we perform a detailed spectral-timing analysis of our recent simultaneous xmm-newton, nustar, and swift observations. we present the energy dependence of the qpo's frequency, rms, coheren... | re-observing the nls1 galaxy re j1034+396 - ii. new insights on the soft x-ray excess, qpo, and the analogy with grs 1915+105 |
gaia used a large sample of photometrically selected active galactic nuclei (agns) and quasars to remove the residual spin of its global proper motion system in order to achieve a maximally inertial reference frame. a small fraction of these reference objects have statistically significant astrometric proper motions in... | quasars with proper motions and the link to double and multiple agns |
context. thanks to the cross-identification between the gaia edr3 (e-data release 3) catalogue and the quasars' compiled catalogue lqac-5 (large quasar astrometric catalogue-5), accurate astrometric parameters as well as photometric measurements were available for a set of 416 113 quasars.aims: after analysing the astr... | quasars with large proper motions: a selection from the lqac-5 catalogue combined with gaia edr3. focusing on astrometric and photometric properties |
with the distance sum rule in the friedmann-lemaître-robertson-walker metric, model-independent constraints on both the hubble constant h0 and spatial curvature ${{\rm{\omega }}}_{k}$ can be obtained using strong lensing time-delay data and type ia supernovae (sne ia) luminosity distances. this method is limited by the... | cosmology-independent estimate of the hubble constant and spatial curvature using time-delay lenses and quasars |
context. when can an active galactic nucleus (agn) be considered radio loud (rl)? following the established view of the agns inner workings, an agn is rl if associated with relativistic ejections emitting a radio synchrotron spectrum (i.e., it is a "jetted" agn). in this paper we exploit the agn main sequence that offe... | radio loudness along the quasar main sequence |
the masses of supermassive black holes (bhs) in broad-line active galactic nuclei (agns) can be measured through reverberation mapping, but this method currently cannot be applied to very large samples or to high-redshift agns. as a practical alternative, one can devise empirical scaling relations, based on the correla... | a revised calibration of the virial mass estimator for black holes in active galaxies based on single-epoch hβ spectra |
the spectroscopy of background qso sightlines passing close to foreground galaxies is a potent technique for studying the circumgalactic medium (cgm). however, qsos are effectively point sources, limiting their potential to constrain the size of circumgalactic gaseous structures. here we present the first large keck/lo... | galaxies probing galaxies in primus. i. sample, spectroscopy, and characteristics of the z\\sim 0.5 mg ii-absorbing circumgalactic medium |
we study the relation between the metallicity of quasar broad line region (blr) and black hole (bh) mass (10^{7.5}{-}10^{10} m_{⊙}) and quasar bolometric luminosity (10^{44.6}{-}10^{48} { erg s^{-1}}) using a sample of ∼130 000 quasars at 2.25 ≤ z ≤ 5.25 from sloan digital sky survey data release 12 (dr12). we generate... | the evolution of chemical abundance in quasar broad line region |
context. multiply imaged gravitationally lensed quasars are among the most interesting and useful observable extragalactic phenomena. because their study constitutes a unique tool in various fields of astronomy, they are highly sought, but difficult to find. even in this era of all-sky surveys, discovering them remains... | gaia gral: gaia dr2 gravitational lens systems. i. new quadruply imaged quasar candidates around known quasars |
while theoretical arguments predict that most of the early growth of supermassive black holes (smbhs) happened during heavily obscured phases of accretion, current methods used for selecting z > 6 quasars (qsos) are strongly biased against obscured qsos, thus considerably limiting our understanding of accreting smbh... | discovery of the first heavily obscured qso candidate at z > 6 in a close galaxy pair |
we present rest-frame near-ultraviolet (nuv) spectroscopy of star-forming galaxies (sfgs) at 0.6 < z < 1.2 from the extended baryon oscillation spectroscopic survey (eboss) in sdss-iv. one of the eboss programs is to obtain 2″ (about 15 kpc) fiber spectra of about 200,000 emission-line galaxies (elgs) at redshift... | near-ultraviolet spectroscopy of star-forming galaxies from eboss: signatures of ubiquitous galactic-scale outflows |
we investigate the relationship between x-ray and optical line emission in 340 nearby (z ≃ 0.04) agn selected above 10 kev using swift bat. we find a weak correlation between the extinction corrected [o iii] and hard x-ray luminosity (l_[o iii]^{int} ∝ l_{14-195}) with a large scatter (rpear = 0.64, σ = 0.62 dex) and a... | bat agn spectroscopic survey-ii. x-ray emission and high-ionization optical emission lines |
the inner regions of active galaxies host the most extreme and energetic phenomena in the universe including, relativistic jets, supermassive black hole binaries, and recoiling supermassive black holes. however, many of these sources cannot be resolved with direct observations. i review how strong gravitational lensing... | gravitational lenses as high-resolution telescopes |
observations of metal absorption systems in the spectra of distant quasars allow one to constrain a possible variation of the fine-structure constant throughout the history of the universe. such a test poses utmost demands on the wavelength accuracy and previous studies were limited by systematics in the spectrograph w... | fundamental physics with espresso: towards an accurate wavelength calibration for a precision test of the fine-structure constant |
we present a study of the distribution of radio jet position angles of radio galaxies over an area of 1 square degree in the elais n1 field. elais n1 was observed with the giant metrewave radio telescope at 612 mhz to an rms noise level of 10 μjy and angular resolution of 6 arcsec × 5 arcsec. the image contains 65 reso... | alignments of radio galaxies in deep radio imaging of elais n1 |
we investigated, using spectral-timing analysis, the characterization of highly ionized outflows in seyfert galaxies, the so-called warm absorbers. here, we present our results of the extensive 600 ks of xmm-newton archival observations of the bright and highly variable seyfert 1 galaxy ngc 4051 whose spectrum has reve... | timing the warm absorber in ngc 4051 |
we present the results of a search for cold gas at high redshift along quasar lines of sight carried out without any a priori assumption on the neutral atomic-hydrogen content of the absorption-line systems. to do this, we systematically looked for neutral-carbon (c i) λλ1560, 1656 transition lines in 41 696 low-resolu... | neutral atomic-carbon quasar absorption-line systems at z> 1.5. sample selection, h i content, reddening, and 2175 å extinction feature |
we investigate how uncertainties in the chemical and cooling rate coefficients relevant for a metal-free gas influence our ability to determine the critical ultraviolet field strength required to suppress h2 cooling in high-redshift atomic cooling haloes. the suppression of h2 cooling is a necessary prerequisite for th... | simulating the formation of massive seed black holes in the early universe - ii. impact of rate coefficient uncertainties |
time domain optical surveys have discovered roughly a dozen candidate stellar tidal disruption flares in the last five years, and future surveys like the large synoptic survey telescope will likely find hundreds to thousands more. these tidal disruption events (tdes) present an interesting puzzle: a majority of the cur... | an enhanced rate of tidal disruptions in the centrally overdense e+a galaxy ngc 3156 |
inverse compton cooling limits the brightness temperature of the radiating plasma to a maximum of 1011.5 k. relativistic boosting can increase its observed value, but apparent brightness temperatures much in excess of 1013 k are inaccessible using ground-based very long baseline interferometry (vlbi) at any wavelength.... | radioastron observations of the quasar 3c273: a challenge to the brightness temperature limit |
we have monitored the quasar 3c 273 in the optical v, r, and i bands from 2005 to 2016. intraday variability (idv) is detected on seven nights. the variability amplitudes on most of the nights are less than 10%, and on four nights, more than 20%. when considering the nights with time spans >4 hr, the duty cycle (dc)... | multicolor optical monitoring of the quasar 3c 273 from 2005 to 2016 |
galaxy mergers and gas accretion from the cosmic web drove the growth of galaxies and their central black holes at early epochs. we report spectroscopic imaging of a multiple merger event in the most luminous known galaxy, wise j224607.56-052634.9 (w2246-0526), a dust-obscured quasar at redshift 4.6, 1.3 billion years ... | the multiple merger assembly of a hyperluminous obscured quasar at redshift 4.6 |
in modern astrophysics, machine learning has increasingly gained popularity with its incredibly powerful ability to make predictions or calculated suggestions for large amounts of data. we describe an application of the supervised machine-learning algorithm, random forests (rf), to the star/galaxy/qso classification an... | machine learning applied to star-galaxy-qso classification and stellar effective temperature regression |
we study the redshift evolution of the quasar (qso) uv luminosity function (lf) for 0.5 < z < 6.5, by collecting the most up to date observational data and, in particular, the recently discovered population of faint active galactic nuclei (agns). we fit the qso lf using either a double power-law function or a sch... | quasar uv luminosity function evolution up to z = 8 |
we present the results of photometric and spectroscopic monitoring campaigns of the changing look agn ngc 3516 carried out in 2018 to 2020 covering the wavelength range from the x-ray to the optical. the facilities included the telescopes of the cmo sai msu, the 2.3-m wiro telescope, and the xrt and uvot of swift. we f... | multiwavelength monitoring and reverberation mapping of a changing look event in the seyfert galaxy ngc 3516 |
we present the results from the search for lyman alpha emitters (laes) in the proximity of 11 c iv absorption systems at z > 4.7 in the spectrum of the qso j1030+0524, using data from multi-unit spectroscopic explorer. we have found multiple lae candidates close to four c iv systems at $z_{{\rm{c {\small iv}}}}=4.94... | faint laes near z > 4.7 c iv absorbers revealed by muse |
the bright emission from high-redshift quasars completely conceals their host galaxies in the rest-frame ultraviolet/optical, with detection of the hosts in these wavelengths eluding even the hubble space telescope (hst) using detailed point spread function (psf) modelling techniques. in this study, we produce mock ima... | observing the host galaxies of high-redshift quasars with jwst: predictions from the bluetides simulation |
since its launch in 1999, the chandra x-ray observatory has discovered several dozen x-ray jets associated with powerful quasars. in many cases, the x-ray spectrum is hard and appears to come from a second spectral component. the most popular explanation for the kpc-scale x-ray emission in these cases has been inverse-... | fermi non-detections of four x-ray jet sources and implications for the ic/cmb mechanism |
the bimodal absorption system imaging campaign (basic) aims to characterize the galaxy environments of a sample of 36 h i-selected partial lyman limit systems (pllss) and lyman limit systems (llss) in 23 qso fields at z ≲ 1. these pllss/llss provide a unique sample of absorbers with unbiased and well-constrained metall... | the bimodal absorption system imaging campaign (basic). i. a dual population of low-metallicity absorbers at z < 1 |
quasars (qsos) hosting supermassive black holes are believed to reside in massive halos harboring galaxy overdensities. however, many observations revealed average or low galaxy densities around z ≳ 6 qsos. this could be partly because they measured galaxy densities in only tens of arcmin2 around qsos and might have ov... | large-scale environment of a z = 6.61 luminous quasar probed by lyα emitters and lyman break galaxies |
we present a method of selecting quasars up to redshift ≈6 with random forests, a supervised machine-learning method, applied to pan-starrs1 and wise data. we find that, thanks to the increasing set of known quasars, we can assemble a training set that enables supervised machine-learning algorithms to become a competit... | random forests as a viable method to select and discover high-redshift quasars |
small angle scattering by dust grains causes a significant contribution to the total interstellar extinction for any x-ray instrument with sub-arcminute resolution (chandra, swift, xmm-newton). however, the dust-scattering component is not included in the current absorption models: phabs, tbabs, and tbnew. we simulate ... | the dust-scattering component of x-ray extinction: effects on continuum fitting and high-resolution absorption edge structure |
supernovae are considered as prime sources of dust in space. observations of local supernovae over the past couple of decades have detected the presence of dust in supernova ejecta. the reddening of the high redshift quasars also indicate the presence of large masses of dust in early galaxies. considering the top heavy... | dust in supernovae and supernova remnants i: formation scenarios |
the european space agency is studying two large-class missions bound to operate in the decade of the 30s, and aiming at investigating the most energetic and violent phenomena in the universe. athena is poised to study the physical conditions of baryons locked in large-scale structures from the epoch of their formation,... | chasing supermassive black hole merging events with athena and lisa |
we present luminosity functions derived from a spectroscopic survey of active galactic nuclei (agns) selected from spitzer space telescope imaging surveys. selection in the mid-infrared is significantly less affected by dust obscuration. we can thus compare the luminosity functions of obscured and unobscured agns in a ... | the spitzer mid-infrared agn survey. ii. the demographics and cosmic evolution of the agn population |
rapid gamma-ray flares pose an astrophysical puzzle, requiring mechanisms both to accelerate energetic particles and to produce fast observed variability. these dual requirements may be satisfied by collisionless relativistic magnetic reconnection. on the one hand, relativistic reconnection can energize gamma-ray emitt... | kinetic beaming in radiative relativistic magnetic reconnection: a mechanism for rapid gamma-ray flares in jets |
the tidal disruption of a star by a supermassive black hole can result in transient radio emission. the electrons producing these synchrotron radio flares could either be accelerated inside a relativistic jet or externally by shocks resulting from an outflow interacting with the circumnuclear medium. until now, evidenc... | discovery of a time lag between the soft x-ray and radio emission of the tidal disruption flare asassn-14li: evidence for linear disk-jet coupling |
we report an identification of sdss j141324+530527.0 (sbs 1411+533) at z = 0.456344 as a new “changing-look” quasar with a “turn-on” spectral type transition from type-1.9/2 to type-1 within a rest-frame timescale of 1-10 yr by a comparison of our new spectroscopic observation and the sloan digital sky survey (sdss) ar... | identification of sdss j141324.27+530527.0 as a new “changing-look” quasar with a “turn-on” transition |
observing the light emitted by the first accreting black holes (bhs) would dramatically improve our understanding of the formation of quasars at z > 6, possibly unveiling the nature of their supermassive black hole (smbh) seeds. in previous works, we explored the relative role of the two main competing bh seed forma... | chasing the observational signatures of seed black holes at z > 7: candidate observability |
the {m}\bullet {--}σ relation establishes a connection between central black holes (bhs) and their host spheroids. supported by observations at {m}\bullet ≳ {10}5 {m}⊙ , there is limited data on its validity at lower masses. employing a semi-analytical model to simulate the combined evolution of bhs and their host gala... | glimmering in the dark: modeling the low-mass end of the m •-σ relation and of the quasar luminosity function |
we present the detection of the average h2 absorption signal in the overall population of neutral gas absorption systems at z∼ 3 using composite absorption spectra built from the sloan digital sky survey-iii damped lyman α catalogue. we present a new technique to directly measure the h2 column density distribution func... | constraining the h2 column density distribution at z ∼ 3 from composite dla spectra |
we report on a hubble space telescope search for rest-frame ultraviolet emission from the host galaxies of five far-infrared-luminous z ≃ 6 quasars and the z = 5.85 hot-dust-free quasar sdss j0005-0006. we perform 2d surface brightness modeling for each quasar using a markov chain monte carlo estimator, to simultaneous... | limits to rest-frame ultraviolet emission from far-infrared-luminous z ≃ 6 quasar hosts |
the imaging channel on the mid-infrared instrument (miri) is equipped with four coronagraphs that provide high contrast imaging capabilities for studying faint point sources and extended emission that would otherwise be overwhelmed by a bright point-source in its vicinity. such bright sources might include stars that a... | the mid-infrared instrument for the james webb space telescope, v: predicted performance of the miri coronagraphs |
substantial evidence points to dusty, geometrically thick tori obscuring the central engines of active galactic nuclei (agns), but so far no mechanism satisfactorily explains why cool dust in the torus remains in a puffy geometry. near-eddington infrared (ir) and ultraviolet (uv) luminosities coupled with high dust opa... | radiation-driven outflows from and radiative support in dusty tori of active galactic nuclei |
we present a search for h i in the circumgalactic medium (cgm) of 21 massive (< {log}{m}\star > ∼ 11.4), luminous red galaxies (lrgs) at z ∼ 0.5. using uv spectroscopy of qso sightlines projected within 500 kpc (∼{r}vir}) of these galaxies, we detect h i absorption in 11/21 sightlines, including two partial lyman... | the red dead redemption survey of circumgalactic gas about massive galaxies. i. mass and metallicity of the cool phase |
context. most investigations of the x-ray variability of active galactic nuclei (agn) have been concentrated on the detailed analyses of individual, nearby sources. a relatively small number of studies have treated the ensemble behaviour of the more general agn population in wider regions of the luminosity-redshift pla... | ensemble x-ray variability of active galactic nuclei. ii. excess variance and updated structure function |
the boss quasar sample is used to study cosmic homogeneity with a 3d survey in the redshift range 2.2 < z < 2.8. we measure the count-in-sphere, n(< r), i.e. the average number of objects around a given object, and its logarithmic derivative, the fractal correlation dimension, d2(r). for a homogeneous distribu... | a 14 h-3 gpc3 study of cosmic homogeneity using boss dr12 quasar sample |
we report on the identification of a new γ-ray-emitting narrow-line seyfert 1 (nls1) galaxy, sdss j122222.55+041315.7, which increases the number of known objects of this remarkable but rare type of active galactic nuclei to seven. its optical spectrum, obtained in the sloan digital sky survey-baryon oscillation spectr... | identification of a new γ-ray-emitting narrow-line seyfert 1 galaxy, at redshift ∼1 |
since the beginning of the new millennium, more than 100 z 6 quasars have been discovered through several surveys and followed-up with multi-wavelength observations. these data provided a large amounts of information on the growth of supermassive black holes at the early epochs, the properties of quasar host galaxies a... | physical properties of the first quasars |
as setti and woltjer noted back in 1973, one can use quasars to construct the hubble diagram; however, the actual application of the idea was not that straightforward. it took years to implement the proposition successfully. most ways to employ quasars for cosmology now require an advanced understanding of their struct... | accretion disks, quasars and cosmology: meandering towards understanding |
using new ultraviolet (uv) spectra of five background quasars from the cosmic origins spectrograph on the hubble space telescope, we analyze the low-latitude ( $| b| =20^\circ \mbox{--}30^\circ $ ) regions of the fermi bubbles, the giant gamma-ray-emitting lobes at the galactic center. we combine these data with previo... | mapping outflowing gas in the fermi bubbles: a uv absorption survey of the galactic nuclear wind |
we report on three redshift z > 2 quasars with dramatic changes in their c iv emission lines, the first sample of changing-look quasars (clqs) at high redshift. this is also the first time the changing-look behaviour has been seen in a high-ionization emission line. sdss j1205+3422, j1638+2827, and j2228 + 2201 show... | the first high-redshift changing-look quasars |
context. time-delay lensing is a powerful tool for measuring the hubble constant h0. however, in order to obtain an accurate estimate of h0 from a sample of time-delay lenses, very good knowledge of the mass structure of the lens galaxies is needed. strong lensing data on their own are not sufficient to break the degen... | statistical strong lensing. ii. cosmology and galaxy structure with time-delay lenses |
we present atacama large millimeter/submillimeter array (alma) observations of six radio-loud quasar host galaxies at z = 1.4-2.3. we combine the kiloparsec-scale resolution alma observations with high spatial resolution adaptive optics integral field spectrograph data of the ionized gas. we detect molecular gas emissi... | multiphase outflows in high-redshift quasar host galaxies |
measuring the density of the intergalactic medium using quasar sight lines in the epoch of reionization is challenging due to the saturation of lyα absorption. near a luminous quasar, however, the enhanced radiation creates a proximity zone observable in the quasar spectra where the lyα absorption is not saturated. in ... | measuring the density fields around bright quasars at z 6 with xqr-30 spectra |
the discovery of changing-look active galactic nuclei (clagns) with a significant change in optical broad emission lines (optical clagns) and/or strong variation of line-of-sight column densities (x-ray clagns) challenges the orientation-based agn unification model. we explore mid-infrared (mid-ir) properties for a sam... | wise view of changing-look active galactic nuclei: evidence for a transitional stage of agns |
aims: in this work we present a new catalogue of cosmic filaments obtained from the latest sloan digital sky survey (sdss) public data.methods: in order to detect filaments, we implement a version of the subspace-constrained mean-shift algorithm that is boosted by machine learning techniques. this allows us to detect c... | a novel cosmic filament catalogue from sdss data |
we report the discovery of giant (50-100 kpc) [o ii] emitting nebulae with muse in the field of txs 0206-048, a luminous quasar at z = 1.13. "down-the-barrel" uv spectra of the quasar show absorption at velocities coincident with those of the extended nebulae, enabling new insights into inflows and outflows around the ... | directly tracing cool filamentary accretion over >100 kpc into the interstellar medium of a quasar host at z = 1 |
we analyze a sample of 25 [ne v] (λ3426) emission-line galaxies at 1.4 < z < 2.3 using hubble space telescope/wide field camera 3 g102 and g141 grism observations from the candels lyα emission at reionization (clear) survey. [ne v] emission probes extremely energetic photoionization (creation potential of 97.11 e... | clear: high-ionization [ne v] λ3426 emission-line galaxies at 1.4 < z < 2.3 |
we develop a thermodynamical model of fermionic dark matter halos at finite temperature. statistical equilibrium states may be justified by a process of violent collisionless relaxation in the sense of lynden-bell or from a collisional relaxation of nongravitational origin if the fermions are self-interacting. the most... | predictive model of fermionic dark matter halos with a quantum core and an isothermal atmosphere |
the quasar target selection for the upcoming survey of the dark energy spectroscopic instrument (desi) will be fixed for the next 5 yr. the aim of this work is to validate the quasar selection by studying the impact of imaging systematics as well as stellar and galactic contaminants, and to develop a procedure to mitig... | angular clustering properties of the desi qso target selection using dr9 legacy imaging surveys |
we examine massive black hole (mbh) mergers and their associated gravitational wave signals from the large-volume cosmological simulation astrid . astrid includes galaxy formation and black hole models recently updated with an mbh seed population between 3 × 104h-1m⊙ and 3 × 105h-1m⊙ and a sub-grid dynamical friction (... | massive black hole mergers with orbital information: predictions from the astrid simulation |
the observed lensed fraction of high-redshift quasars (~0.2%) is significantly lower than previous theoretical predictions (≳4%). we revisit the lensed fraction of high-redshift quasars predicted by theoretical models, where we adopt recent measurements of galaxy velocity dispersion functions (vdfs) and explore a wide ... | revisiting the lensed fraction of high-redshift quasars |
the baryon acoustic oscillation feature in the clustering of galaxies or quasars provides a `standard ruler' for distance measurements in cosmology. in this work, we report a 2-3σ signal of the baryon acoustic oscillation dip feature in the galaxy density-ellipticity cross-correlation functions using the spectroscopic ... | evidence for baryon acoustic oscillations from galaxy-ellipticity correlations. |
we present the first empirical constraints on the turbulent velocity field of the diffuse circumgalactic medium around four luminous quasi-stellar objects (qsos) at z ≈ 0.5-1.1. spatially extended nebulae of ≈50-100 physical kpc in diameter centred on the qsos are revealed in [o ii] $\lambda \lambda \, 3727,3729$ and/o... | empirical constraints on the turbulence in qso host nebulae from velocity structure function measurements |
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