 PublicationsPublications (125) Article A method we developed recently for the reconstruction of the initial density field in the nearby Universe is applied to the Sloan Digital Sky Survey Data Release 7. A high-resolution N-body constrained simulation (CS) of the reconstructed initial condition, with $3072^3$ particles evolved in a 500 Mpc/h box, is carried out and analyzed in terms of...
Article Full-text available Simulating the evolution of the local universe is important for studying galaxies and the intergalactic medium in a way free of cosmic variance. Here we present a method to reconstruct the initial linear density field from an input non-linear density field, employing the Hamiltonian Markov Chain Monte Carlo (HMC) algorithm combined with Particle Me... Estimating Black Hole Masses in Active Galactic Nuclei Using the Mg II λ2800 Emission Line Article Full-text available We investigate the relationship between the linewidths of broad Mg II λ2800 and Hβ in active galactic nuclei (AGNs) to refine them as tools to estimate black hole (BH) masses. We perform a detailed spectral analysis of a large sample of AGNs at intermediate redshifts selected from the Sloan Digital Sky Survey, along with a smaller sample of archiva... Internal properties and environments of dark matter halos Article We use seven high-resolution N-body simulations to study the correlations among different halo properties (assembly time, spin, shape and substructure), and how these halo properties are correlated with the large-scale environment in which haloes reside. The large-scale tidal field estimated from haloes above a mass threshold is used as our primary...
Metallicity and Quasar Outflows Article Full-text available Correlations are investigated of the outflow strength of quasars, as measured by the blueshift and asymmetry index (BAI) of the CIV line (Wang et al. 2011), with intensities and ratios of broad emission lines, based on composite quasar spectra built from the Sloan Digital Sky Survey. We find that most of the line ratios of other ions to CIV promine... MAHGIC: A Model Adapter for the Halo-Galaxy Inter-Connection Preprint Full-text available We develop a model to establish the interconnection between galaxies and their dark matter halos. We use Principal Component Analysis (PCA) to reduce the dimensionality of both the mass assembly histories of halos/subhalos and the star formation histories of galaxies, and Gradient Boosted Decision Trees (GBDT) to transform halo/subhalo properties i... Hosts and triggers of AGNs in the Local Universe Article Based on the spectroscopic and shear catalogs for SDSS galaxies in the local Universe, we compared optically selected active galactic nuclei (AGNs) with control star-forming and quiescent galaxies on galactic and inter-halo scales, and larger. We find that AGNs are preferentially found in two specific stages of galaxy evolution: in the starburst an...
Secondary bias of dark matter halos: Perspective in the linear density field Preprint Full-text available Using two sets of large $N$-body simulations, we study the origin of the correlations of halo assembly time ($z_{\rm f}$), concentration ($v_{\rm max}/v_{\rm 200}$) and spin ($\lambda$) with the large-scale density field around halos. We find that the correlations of the three halo properties with the large-scale density at $z=0$ are the secondary... An Extended Halo-based Group/Cluster Finder: Application to the DESI Legacy Imaging Surveys DR8 Article The Breakdown Scale of H I Bias Linearity Article An Extended Halo-based Group/Cluster finder: application to the DESI legacy imaging surveys DR8 Preprint We extend the halo-based group finder developed by Yang et al. (2005b) to use data {\it simultaneously} with either photometric or spectroscopic redshifts. A mock galaxy redshift surveys constructed from a high-resolution N-body simulation is used to evaluate the performance of this extended group finder. For galaxies with magnitude ${\rm z\le 21}$...
Host and Trigger of AGNs in local Universe Preprint Full-text available Based on the spectroscopic and shear catalogs for SDSS galaxies in the local Universe, we compare optically-selected active galactic nuclei (AGNs) with control star-forming and quiescent galaxies on galactic, inter-halo and larger scales. We find that AGNs are preferentially found in two specific stages of galaxy evolution: star-burst and `green va... Characteristic Mass in Galaxy Quenching: Environmental versus Internal Effects Article Elucidating Galaxy Assembly Bias in SDSS Preprint We investigate the level of galaxy assembly bias in the Sloan Digital Sky Survey (SDSS) main galaxy redshift survey using ELUCID, a state-of-the-art constrained simulation that accurately reconstructed the initial density perturbations within the SDSS volume. On top of the ELUCID haloes, we develop an extended HOD model that includes the assembly b...
Relating the Structure of Dark Matter Halos to Their Assembly and Environment Article Full-text available The Formation History of Subhalos and the Evolution of Satellite Galaxies Article Characteristic masses in galaxy quenching: environmental versus internal effects Preprint A clear transition of galaxy quenching is identified in the multi-parameter space of stellar mass ($M_*$), bulge to total mass ratio ($B/T_{\rm m}$), halo mass ($M_{\rm h}$) and halo-centric distance ($r/r_{180}$). For a given halo mass, the characteristic stellar mass ($M_{*, \rm c}$) for the transition is about one-fifth of the stellar mass of th...
Relating the structure of dark matter halos to their assembly and environment Preprint Full-text available We use the ELUCID N-Body simulation to study the relation of structural properties of dark matter halos to their assembly history and environment. We find that the complexity of halo assembly histories can be well described by a small number of principal components. Using decision trees built with the random ensemble method, we find that the correl... Probing Primordial Chirality with Galaxy Spins Article Chiral symmetry is maximally violated in weak interactions [1], and such microscopic asymmetries in the early Universe might leave observable imprints on astrophysical scales without violating the cosmological principle. In this Letter, we propose a helicity measurement to detect primordial chiral violation. We point out that observations of halo-g... Detection of Missing Baryons in Galaxy Groups with Kinetic Sunyaev–Zel’dovich Effect Article Article The Formation History of Subhalos and the Evolution of Satellite Galaxies Preprint Satellites constitute an important fraction of the overall galaxy population and are believed to form in dark matter subhalos. Here we use the cosmological hydrodynamic simulation TNG100 to investigate how the formation histories of subhalos affect the properties and evolution of their host galaxies. We use a scaled formation time ($a_{\rm nf}$) to... Detection of missing baryons in galaxy groups with kinetic Sunyaev-Zel'dovich effect Preprint We present the detection of the kinetic Sunyaev-Zel'dovich effect (kSZE) signals from groups of galaxies as a function of halo mass down to $\log (M_{500}/{\rm M_\odot}) \sim 12.3$, using the {\it Planck} CMB maps and stacking about $40,000$ galaxy systems with known positions, halo masses, and peculiar velocities. The signals from groups of differ... Preprint As demonstrated in Paper I, the quenching properties of central and satellite galaxies are quite similar as long as both stellar mass and halo mass are controlled. Here we extend the analysis to the size and bulge-to-total light ratio (B/T) of galaxies. In general central galaxies have size-stellar mass and B/T-stellar mass relations different from... Screening maps of the local Universe I – Methodology Article We introduce the LOCal Universe Screening Test Suite (locusts) project, an effort to create ‘screening maps’ in the nearby Universe to identify regions in our neighbourhood which are screened, i.e. regions where deviations from General Relativity (GR) are suppressed, in various modified gravity (MG) models. In these models, deviations from the GR f...
Preprint Full-text available IRAS F11119+3257 is a quasar-dominated Ultra-Luminous InfraRed Galaxy, with a partially obscured narrow-line seyfert 1 nucleus. In this paper, we present the NIR spectroscopy of F11119+3257, in which we find unusual Paschen emission lines, and metastable He I* $\lambda$10830 absorption associated with the previously reported atomic sodium and molec... Article Fast Inflow Directly Feeding Black Hole Accretion Disk in Quasars Preprint Full-text available Quasars are high-luminosity active galactic nuclei believed to be powered by accretion of interstellar matter onto a super-massive black hole (SMBH) therein. Most of the observed energy is released in an accretion disk of inspiralling gas surrounding the SMBH. An enormous amount of fueling material is expected to be transported inwards. However, ba...
Fast inflows as the adjacent fuel of supermassive black hole accretion disks in quasars Article Full-text available Quasars, which are exceptionally bright objects at the centres (or nuclei) of galaxies, are thought to be produced through the accretion of gas into disks surrounding supermassive black holes1–3. There is observational evidence at galactic and circumnuclear scales⁴ that gas flows inwards towards accretion disks around black holes, and such an inflo... Screening maps of the local Universe I -- Methodology Preprint We introduce the LOCal Universe Screening Test Suite (LOCUSTS) project, an effort to create 'screening maps' in the nearby Universe to identify regions in our neighbourhood which are screened, i.e., regions where deviations from General Relativity (GR) are suppressed, in various modified gravity (MG) models. In these models, deviations from the GR... The Morphological Transformation and the Quenching of Galaxies Article The morphological transformation and the quenching of galaxies Preprint We study the morphological transformation from late types to early types and the quenching of galaxies with the seventh Data Release (DR7) of the Sloan Digital Sky Survey (SDSS). Both early type galaxies and late type galaxies are found to have bimodal distributions on the star formation rate versus stellar mass diagram ($\lg SFR - \lg M_*$). We th... The clustering of galaxies with pseudo-bulge and classical bulge in the local Universe Article We investigate the clustering properties and close neighbour counts for galaxies with different types of bulges and stellar masses. We select samples of 'pseudo' bulges, as well as 'bulge-less' pure disc galaxies, based on the bulge/disc decomposition catalogue of SDSS galaxies provided by Simard et al. (2011). For a given galaxy sample we estimate... Probing primordial chirality with galaxy spins Preprint Chiral symmetry is maximally violated in weak interactions. In this letter, we propose a helicity measurement to detect primordial chiral violation. We point out that observations of galaxy angular momentum directions (spins), which are frozen in during the galaxy formation process, provide a fossil chiral observable. From the clustering-mode of la... Article We use a sample of ∼3000 galaxies from the MaNGA MPL-7 internal data release to study the α abundance distribution within low-redshift galaxies. We use the Lick index ratio Mgb/ as an α abundance indicator to study relationships between the α abundance distribution and galaxy properties such as effective stellar velocity dispersion within 0.3 effec...
The properties of broad absorption line outflows based on a large sample of quasars Article Full-text available Quasar outflows carry mass, momentum and energy into the surrounding environment, and have long been considered a potential key factor in regulating the growth of supermassive black holes and the evolution of their host galaxies1–4. A crucial parameter for understanding the origin of these outflows and measuring their influence on their host galaxi...
ELUCID. VI. Cosmic Variance of the Galaxy Distribution in the Local Universe Article Full-text available Halo merger trees are constructed from ELUCID, a constrained N-body simulation in the Sloan Digital Sky Survey (SDSS) volume. These merger trees are used to populate dark matter halos with galaxies according to an empirical model of galaxy formation. Mock catalogs in the SDSS sky coverage are constructed, which can be used to study the spatial dist... Preprint Following Cui et al. 2018 (hereafter Paper I) on the classification of large-scale environments (LSE) at z = 0, we push our analysis to higher redshifts and study the evolution of LSE and the baryon distributions in them. Our aim is to investigate how baryons affect the LSE as a function of redshift. In agreement with Paper I, the baryon models hav... SDSS-IV MaNGA: Environmental dependence of the Mgb/ -sigma_* relation for nearby galaxies Preprint We use a sample of ~3000 galaxies from the MaNGA MPL-7 internal data release to study the alpha abundance distribution within low-redshift galaxies. We use the Lick index ratio Mgb/ as an alpha abundance indicator to study relationships between the alpha abundance distribution and galaxy properties such as effective stellar velocity dispersion with... Can HI gas trace the matter density distribution linearly on large scales? Preprint It is customary to assume that HI gas traces the matter density distribution linearly on large scales. However, nonlinear effects which modulate HI gas in halos might spoil this. We employ three approaches to generate the mock HI density from an N-body simulation at low redshifts, and demonstrate, for the first time, that the HI linearity assumptio...
Article Full-text available The properties of broad absorption line outflows based on a large sample of quasars Preprint Quasar outflows carry mass, momentum and energy into the surrounding environment, and have long been considered a potential key factor in regulating the growth of supermassive black holes and the evolution of their host galaxies. A crucial parameter for understanding the origin of these outflows and measuring their influence on their host galaxies... ELUCID. VI: Cosmic variance of galaxy distribution in the local Universe Preprint Halo merger trees are constructed from ELUCID, a constrained $N$-body simulation in the Sloan Digital Sky Survey (SDSS) volume. These merger trees are used to populate dark matter halos with galaxies according to an empirical model of galaxy formation. Mock catalogs in the SDSS sky coverage are constructed, which can be used to study the spatial di... Article As we demonstrated in Paper I, the quenched fractions of central and satellite galaxies as a function of halo mass are extremely similar, as long as one controls for stellar mass. The same holds for the quenched fractions as a function of central velocity dispersion, which is tightly correlated with black hole mass, as long as one controls for both... Exploring the thermal energy contents of the intergalactic medium with the Sunyaev-Zel’dovich effect Article We examine the thermal energy contents of the intergalactic medium (IGM) over three orders of magnitude in both mass density and gas temperature using thermal Sunyaev-Zel’dovich effect (tSZE). The analysis is based on Planck tSZE map and the cosmic density field, reconstructed in the SDSS DR7 volume and sampled on a grid of cubic cells of (1h⁻¹Mpc)... Preprint As we demonstrated in Paper I, the quenched fractions of central and satellite galaxies as function of halo mass are extremely similar, as long as one controls for stellar mass. The same holds for the quenched fractions as a function of central velocity dispersion, which is tightly correlated with black hole mass, as long as one controls for both s... Article We extend the real-space mapping method developed in Shi et al. so that it can be applied to flux-limited galaxy samples. We use an ensemble of mock catalogs to demonstrate the reliability of this extension, showing that it allows for an accurate recovery of the real-space correlation functions and galaxy biases. We also demonstrate that, using an... Article We investigate the quenching properties of central and satellite galaxies, utilizing the halo masses and central-satellite identifications from the Sloan Digital Sky Survey galaxy group catalog of Yang et al. We find that the quenched fractions of centrals and satellites of similar stellar masses have similar dependence on host halo mass. The simil... The clustering of galaxies with pseudo bulge and classical bulge in the local Universe Preprint We investigate the clustering properties and close neighbour counts for galaxies with different types of bulges and stellar masses. We select samples of "classical" and "pseudo" bulges, as well as "bulge-less" disk galaxies, based on the bulge/disk decomposition catalog of SDSS galaxies provided by Simard et al. (2011). For a given galaxy sample we... Preprint We investigate the quenching properties of central and satellite galaxies, utilizing the halo masses and central-satellite identifications from the SDSS galaxy group catalog of Yang et al. We find that the quenched fractions of centrals and satellites of similar stellar masses have similar dependence on host halo mass. The similarity of the two pop... Exploring the thermal energy contents of the intergalactic medium with the Sunyaev-Zel'dovich effect Preprint We examine the thermal energy contents of the intergalactic medium (IGM) over three orders of magnitude in both mass density and gas temperature using thermal Sunyaev-Zel'dovich effect (tSZE). The analysis is based on {\it Planck} tSZE map and the cosmic density field, reconstructed for the SDSS DR7 volume and sampled on a grid of cubic cells of $(...
Article Full-text available The intrinsic alignment of galaxies is an important systematic effect in weak-lensing surveys, which can affect the derived cosmological parameters. One direct way to distinguish different alignment models and quantify their effects on the measurement is to produce mocked weak-lensing surveys. In this work, we use full-sky ray-tracing technique to... The detection of missing baryons in galaxy halos with kinetic Sunyaev-Zel'dovich effect Article One unsettled problem in cosmology is that the baryon fractions identified as stars and cold gas in halos of galaxies and galaxy groups are lower than the universal fraction. The detection of the missing baryon component and the study of its properties are crucial for understanding how physical processes produce the galaxy population we observe. Nu...
Preprint Full-text available We extend the real-space mapping method developed in Shi et al. (2016) so that it can be applied to flux-limited galaxy samples. We use an ensemble of mock catalogs to demonstrate the reliability of this extension, showing that it allows for an accurate recovery of the real-space correlation functions and galaxy biases. We also demonstrate that, us... Article We extend the real-space mapping method developed in [Shi16] so that it can be applied to flux-limited galaxy samples. We use an ensemble of mock catalogs to demonstrate the reliability of this extension, showing that it allows for an accurate recovery of the real-space correlation functions and galaxy biases. We also demonstrate that, using an ite... ELUCID V. Lighting dark matter halos with galaxies Article Full-text available In a recent study, using the distribution of galaxies in the north galactic pole of SDSS DR7 region enclosed in a 500$\mpch$ box, we carried out our ELUCID simulation (Wang et al. 2016, ELUCID III). Here we {\it light} the dark matter halos and subhalos in the reconstructed region in the simulation with galaxies in the SDSS observations using a nov...
Bimodal Formation Time Distribution for Infall Dark Matter Halos Article Full-text available We use a high-resolution N-body simulation to study the mass accretion history of infall dark matter halos before they are accreted by larger halos. We find that their formation time distribution is bimodal. Infall halos are dominated by a young population at high redshift and by an old population at low redshift. This bimodal distribution is found...
Gas Contents of Galaxy Groups from Thermal Sunyaev–Zel’dovich Effects Article Full-text available A matched filter technique is applied to the Planck all-sky Compton y-parameter map to measure the thermal Sunyaev-Zel'dovich (tSZ) effect produced by galaxy groups of different halo masses selected from large redshift surveys in the low-z Universe. Reliable halo mass estimates are available for all the groups, which allows us to bin groups of simi...
ELUCID IV: Galaxy Quenching and its Relation to Halo Mass, Environment, and Assembly Bias Article Full-text available We examine the quenched fraction of central and satellite galaxies as a function of galaxy stellar mass, halo mass, and the matter density of their large scale environment. Matter densities are inferred from our ELUCID simulation, a constrained simulation of the local Universe, sampled by the Sloan Digital Sky Survey (SDSS), while halo masses and t... Mid-infrared Flare of TDE Candidate PS16dtm: Dust Echo and Implications for the Spectral Evolution Article Full-text available PS16dtm was classified as a candidate tidal disruption event (TDE) in a dwarf Seyfert 1 galaxy with low-mass black hole ($\sim10^6M\odot$) and has presented various intriguing photometric and spectra characteristics. Using the archival WISE and the newly released NEOWISE data, we found PS16dtm is experiencing a mid-infrared (MIR) flare which starte...
The Properties of Massive Star-forming galaxies with Outside-in Assembly Mode Article Full-text available Previous findings show that massive ($> 10^{10} M_{sun}$) star-forming (SF) galaxies usually have an inside-out stellar mass assembly mode. In this paper, we have for the first time selected a sample of 77 massive SF galaxies with an outside-in assembly mode (called targeted sample) from the Mapping Nearby Galaxies at the Apache Point Observatory (...
Halo Intrinsic Alignment: Dependence on Mass, Formation Time, and Environment Article Full-text available In this paper we use high-resolution cosmological simulations to study halo intrinsic alignment and its dependence on mass, formation time and large-scale environment. In agreement with previous studies using N-body simulations, it is found that massive halos have stronger alignment. For given mass, older halos have stronger alignment than younger...
Angular Momentum of Early and Late Type Galaxies: Nature or Nurture? Article Full-text available We investigate the origin, the shape, the scatter, and the cosmic evolution in the observed relationship between specific angular momentum $j_\star$ and the stellar mass $M_\star$ in early-type (ETGs) and late-type galaxies (LTGs). Specifically, we exploit the observed star-formation efficiency and chemical abundance to infer the fraction $f_{\rm i... Galaxy groups in the low-redshift Universe Article Full-text available We apply a halo-based group finder to four large redshift surveys, the 2MRS, 6dFGS, SDSS and 2dFGRS, to construct group catalogs in the low-redshift Universe. The group finder is based on that of Yang et al. but with an improved halo mass assignment so that it can be applied uniformly to various redshift surveys of galaxies. Halo masses are assigne... Article Full-text available The ELUCID project aims to build a series of realistic cosmological simulations that reproduce the spatial and mass distribution of the galaxies as observed in the Sloan Digital Sky Survey (SDSS). This requires powerful reconstruction techniques to create constrained initial conditions. We test the reconstruction method by applying it to several $N... Revealing the Cosmic Web-dependent Halo Bias Article Full-text available Halo bias is the one of the key ingredients of the halo models. It was shown at a given redshift to be only dependent, to the first order, on the halo mass. In this study, four types of cosmic web environments: clusters, filaments, sheets and voids are defined within a state of the art high resolution $N$-body simulation. Within those environments,... Article Broad emission-line outflows of active galactic nuclei (AGNs) have been proposed for many years but are very difficult to quantitatively study because of the coexistence of the gravitationally-bound and outflow emission. We present detailed analysis of a heavily reddened quasar, SDSS J000610.67+121501.2, whose normal ultraviolet (UV) broad emission... MAPPING the REAL-SPACE DISTRIBUTIONS of GALAXIES in SDSS DR7. I. TWO-POINT CORRELATION FUNCTIONS Article Using a method to correct redshift-space distortion (RSD) for individual galaxies, we mapped the real-space distributions of galaxies in the Sloan Digital Sky Survey (SDSS) Data Release 7 (DR7). We use an ensemble of mock catalogs to demonstrate the reliability of our method. Here, in the first paper in a series, we focus mainly on the two-point co... SDSS-IV MaNGA: Environmental dependence of stellar age and metallicity gradients in nearby galaxies Article We present a study on the stellar age and metallicity distributions for 1105 galaxies using the STARLIGHT software on MaNGA integral field spectra. We derive age and metallicity gradients by fitting straight lines to the radial profiles, and explore their correlations with total stellar mass M*, NUV-r colour and environments, as identified by both... Article The accretion of interstellar medium onto the central super massive black holes is widely accepted as the source of the gigantic energy released by the active galactic nuclei. But few pieces of observational evidence have been confirmed directly demonstrating the existence of the inflows. The absorption line system in the spectra of quasar SDSS J11...
The real space clustering of galaxies in SDSS DR7: I. Two point correlation functions Article Full-text available Using a method to correct redshift space distortion (RSD) for individual galaxies, we present the measurements of real space two-point correlation functions (2PCFs) of galaxies in the Sloan Digital Sky Survey (SDSS) Data Release 7 (DR7). Galaxy groups selected from the SDSS are used as proxies of dark matter halos to correct the virial motions of g... Galaxy groups in the 2MASS Redshift Survey Article A galaxy group catalog is constructed from the 2MASS Redshift Survey (2MRS) with the use of a halo-based group finder. The halo mass associated with a group is estimated using a `GAP' method based on the luminosity of the central galaxy and its gap with other member galaxies. Tests using mock samples shows that this method is reliable, particularly... Evidence for Fluorescent Fe II Emission from Extended Low Ionization Outflows in Obscured Quasars Article Recent studies have shown that outflows in at least some broad absorption line (BAL) quasars are extended well beyond the putative dusty torus. Such outflows should be detectable in obscured quasars. We present four WISE selected infrared red quasars with very strong and peculiar ultraviolet Fe ii emission lines: strong UV Fe ii UV arising from tra... An empirical model to form and evolve galaxies in dark matter halos Article Based on the star formation histories (SFH) of galaxies in halos of different masses, we develop an empirical model to grow galaxies in dark mattet halos. This model has very few ingredients, any of which can be associated to observational data and thus be efficiently assessed. By applying this model to a very high resolution cosmological $N$-body... Article SDSS J095253.83+011422.0 (J0952+0114) was reported by Hall et al. as an exotic quasar at zem = 3.020. In contrast to prominent broad metal-line emission with FWHM ∼ 9000 km s-1, only a narrow Lyα emission line is present with FWHM ∼ 1000 km s-1. The absence of a broad Lyα emission line has been a mystery for more than a decade. In this paper, we de... Alignments of dark matter halos with large-scale tidal fields: mass and redshift dependence Article Large scale tidal field estimated directly from the distribution of dark matter halos is used to investigate how halo shapes and spin vectors are aligned with the cosmic web. The major, intermediate and minor axes of halos are aligned with the corresponding tidal axes, and halo spin axes tend to be parallel with the intermediate axes and perpendicu... Differences in Halo-Scale Environments between Type 1 and Type 2 AGNs at Low Redshift Article Using samples of AGNs, normal galaxies and groups of galaxies selected from the Sloan Digital Sky Survey (SDSS), we study the environments of type 1 and type 2 AGNs both on small and large scales. Comparisons are made for samples matched in redshift, r-band luminosity, and [OIII] luminosity, and separately for central and satellite galaxies. We fin...
Evidence for Photoionization Driven Broad Absorption Line Variability Article Full-text available We present a qualitative analysis of the variability of quasar broad absorption lines using the large multi-epoch spectroscopic dataset of the Sloan Digital Sky Survey Data Release 10. We confirm that variations of absorption lines are highly coordinated among different components of the same ion or the same absorption component of different ions f... Article Full-text available The existence of intermediate-width emission line regions (IELRs) in active galactic nuclei has been discussed for over two decades. A consensus, however, is yet to be arrived at due to the lack of convincing evidence for their detection. We present a detailed analysis of the broadband spectrophotometry of the partially obscured quasar OI 287. The...
Article Full-text available Neutral Helium multiplets, HeI*3189,3889,10830 are very useful diagnostics to the geometry and physical conditions of the absorbing gas in quasars. So far only a handful of HeI* detections have been reported. Using a newly developed method, we detected HeI*3889 absorption line in 101 sources of a well-defined sample of 285 MgII BAL quasars selected...
Article Full-text available We report the identification of an unusual absorption line system in the quasar SDSS J080248.18$+$551328.9 and present a detailed study of the system, incorporating follow-up optical and NIR spectroscopy. A few tens of absorption lines are detected, including He I*, Fe II* and Ni II* that arise from metastable or excited levels, as well as resonant...
An observational proxy of halo assembly time and its correlation with galaxy properties Article Full-text available We show that the ratio between the stellar mass of central galaxy and the mass of its host halo, fc ≡ M*,c/Mh, can be used as an observable proxy of halo assembly time, in that galaxy groups with higher fc assembled their masses earlier. Using SDSS groups of Yang et al., we study how fc correlates with galaxy properties such as colour, star formati...
Article Full-text available We study how halo intrinsic dynamical properties are linked to their formation processes, and how both are affected by the large scale tidal field in which halo resides. Halo merger trees obtained from cosmological N-body simulations are used to identify infall halos that are about to merge with their hosts. We find that local tidal field can signi...
Spin alignments of spiral galaxies within the large-scale structure from SDSS DR7 Article Full-text available Using a sample of spiral galaxies selected from the Sloan Digital Sky Survey Data Release 7 (SDSS DR7) and Galaxy Zoo 2 (GZ2), we investigate the alignment of spin axes of spiral galaxies with their surrounding large scale structure, which is characterized by the large-scale tidal field reconstructed from the data using galaxy groups above a certai...
Strong Variability of Overlapping Iron Broad Absorption Lines in Five Radio-selected Quasars Article Full-text available We present the results of a variability study of broad absorption lines (BALs) in a uniformly radio-selected sample of 28 BAL quasars using the archival data from the first bright quasar survey (FBQS) and the Sloan Digital Sky Survey (SDSS), as well as those obtained by ourselves, covering time scales $\sim 1-10$ years in the quasar's rest-frame. T... Outflow and hot dust emission in broad absorption line quasars Article Full-text available We have investigated a sample of 2099 broad absorption line (BAL) quasars with z=1.7-2.2 built from the Sloan Digital Sky Survey Data Release Seven and the Wide-field Infrared Survey. This sample is collected from two BAL quasar samples in the literature, and refined by our new algorithm. Correlations of outflow velocity and strength with hot dust...
Outflow and hot dust emission in high redshift quasars Article Full-text available Correlations of hot dust emission with outflow properties are investigated, based on a large z~2 non-broad absorption lines quasar sample built from the Wide-field Infrared Survey and the Sloan Digital Sky Survey data releases. We use the near infrared slope and the infrared to UV luminosity ratio to indicate the hot dust emission relative to the e...
Alignments of galaxies within cosmic filaments from SDSS DR7 Article Full-text available Using a sample of spiral galaxies selected from the Sloan Digital Sky Survey Data Release 7 (SDSS DR7) and Galaxy Zoo 2 (GZ2), we investigate the alignment of spin axes of spiral galaxies with their surrounding large scale structure, which is characterized by the large-scale tidal field reconstructed from the data using galaxy groups above a certai...
Strong Variability of Overlapping Iron Broad Absorption Lines in Five Radio-selected Quasars Article Full-text available We present the results of a variability study of broad absorption lines (BALs) in a uniformly radio-selected sample of 28 BAL quasars using the archival data from the first bright quasar survey (FBQS) and the Sloan Digital Sky Survey (SDSS), as well as those obtained by ourselves, covering time scales $\sim 1-10$ years in the quasar's rest-frame. T... Outflow and hot dust emission in broad absorption line quasars Article Full-text available We have investigated a sample of 2099 broad absorption line (BAL) quasars with z=1.7-2.2 built from the Sloan Digital Sky Survey Data Release Seven and the Wide-field Infrared Survey. This sample is collected from two BAL quasar samples in the literature, and refined by our new algorithm. Correlations of outflow velocity and strength with hot dust...
Outflow and hot dust emission in high redshift quasars Article Full-text available Correlations of hot dust emission with outflow properties are investigated, based on a large z~2 non-broad absorption lines quasar sample built from the Wide-field Infrared Survey and the Sloan Digital Sky Survey data releases. We use the near infrared slope and the infrared to UV luminosity ratio to indicate the hot dust emission relative to the e...
Alignments of galaxies within cosmic filaments from SDSS DR7 Article Full-text available Using a sample of galaxy groups selected from the Sloan Digital Sky Survey Data Release 7 (SDSS DR7), we examine the alignment between the orientation of galaxies and their surrounding large scale structure in the context of the cosmic web. The latter is quantified using the large-scale tidal field, reconstructed from the data using galaxy groups a...
Quasar-Galaxy Clustering through Projected Galaxy Counts at z=0.6-1.2 Article Full-text available We investigate the spatial clustering of galaxies around quasars at redshifts from 0.6 to 1.2 using the photometric data from Sloan Digital Sky Survey (SDSS) Stripe 82. The quasar and galaxy cross-correlation functions are measured through the projected galaxy number density n(r_p) on scales $0.05<r_p<20 h^-1 Mpc around quasars for a sample of 2300... Data
Reconstructing the Initial Density Field of the Local Universe: Method and Test with Mock Catalogs Article Full-text available Our research objective in this paper is to reconstruct an initial linear density field, which follows the multivariate Gaussian distribution with variances given by the linear power spectrum of the current cold dark matter model and evolves through gravitational instabilities to the present-day density field in the local universe. For this purpose,...
Anomalously Steep Reddening Law in Quasars: An Exceptional Example Observed in IRAS14026+4341 Article Full-text available A fraction of the heavily reddened quasars require a reddening curve which is even steeper than that of the Small Magellanic Cloud. In this paper, we thoroughly characterize the anomalously steep reddening law in quasars, via an exceptional example observed in IRAS 14026+4341. By comparing the observed spectrum to the quasar composite spectrum, we... Dust reddening in star-forming galaxies Article We present empirical relations between the global dust reddening and other physical galaxy properties including the Hα luminosity, Hα surface brightness, metallicity and axial ratio for star-forming disc galaxies. The study is based on a large sample of ∼22 000 well-defined star-forming galaxies selected from the Sloan Digital Sky Survey. The redde...
Article Full-text available We report the discovery of an unusual, extremely dust-rich and metal-strong damped Lyα absorption system (DLA) at a redshift za = 2.4596 toward the quasar SDSS J115705.52+615521.7 with an emission-line redshift ze = 2.5125. The quasar spectrum, taken in the Sloan Digital Sky Survey, shows a very red color and a number of metal absorption lines, inc... Article [abridge]Cosmic velocity and tidal fields are important for the understanding of the cosmic web and the environments of galaxies, and can also be used to constrain cosmology. In this paper, we reconstruct these two fields in SDSS volume from dark matter halos represented by galaxy groups. Detailed mock catalogues are used to test the reliability of... Dust reddening in star-forming galaxies Article Full-text available Dust is a crucial component of galaxies in modifying the observed properties of galaxies. Previous studies have suggested that dust reddening in star-forming galaxies is correlated with star formation rate (SFR), luminosity, gas-phase metallicity (Z), stellar mass (M*) and inclination. In this work we investigate the fundamental relations between d... Resolving Subhaloes' Lives with the Hierarchical Bound-Tracing Algorithm Article We develop a new code, the Hierarchical Bound-Tracing (hbt for short) code, to find and trace dark matter subhaloes in simulations based on the merger hierarchy of dark matter haloes. Application of this code to a recent benchmark test of finding subhaloes demonstrates that hbt stands as one of the best codes to trace the evolutionary history of su...
Extreme Coronal Line Emitters: Tidal Disruption of Stars by Massive Black Holes in Galactic Nuclei? Article Full-text available Tidal disruption of stars by supermassive black holes at the centers of galaxies is expected to produce unique emission-line signatures, which have not yet been explored adequately. Here we report the discovery of extremely strong coronal lines from [Fe X] up to [Fe XIV] in a sample of seven galaxies (including two recently reported cases), which w...
Discovery of Balmer Broad Absorption Lines in the Quasar LBQS 1206+1052 Article Full-text available We report the discovery of Balmer broad absorption lines (BALs) in the quasar LBQS 1206+1052 and present a detailed analysis of the peculiar absorption line spectrum. Besides Mg II $\lambda \lambda 2796, 2803$ doublet, BALs are also detected in He I* multiplet at $\lambda \lambda 2946, 3189, 3889$ \AA arising from metastable helium $2^3S$ level, an...
Article Full-text available There are mutually contradictory views in the literature of the kinematics and structure of high-ionization line (e.g., C IV) emitting regions in active galactic nuclei (AGNs). Two kinds of broad emission line region (BELR) models have been proposed, outflow and gravitationally-bound BELR, which are supported, respectively, by blueshift of the C IV... Publications (125)
Discovery of a variable broad absorption line in the BL Lac object PKS B0138-097 Article Full-text available We report the discovery of a broad absorption line (BAL) of ~ 104 km s-1 in width in the previously known BL Lac object PKS 0138-097, which we tentatively identified as an Mg II BAL. This is the first detection of a BAL, which is sometimes seen in powerful quasars with high accretion rates, in a BL Lac object. The BAL was clearly detected in its sp...
The Prevalence of Narrow Optical Fe II Emission Lines in Type 1 Active Galactic Nuclei Article Full-text available From detailed spectral analysis of a large sample of low-redshift active galactic nuclei (AGNs) selected from the Sloan Digital Sky Survey, we demonstrate---statistically for the first time---that narrow optical Fe II emission lines, both permitted and forbidden, are prevalent in type 1 AGNs. Remarkably, these optical lines are completely absent in... On the Physical Mechanism Underlying PC1 and Baldwin Effect in Quasars Article Full-text available Recent work (Baskin & Laor 2004; Dong et al. 2009a, b) suggests that the Eddington ratio (l ≡ L/LEdd) is the origin of all the significant first-order object-to-object variations of quasar spectral properties from the zeroth-order similarity of AGN spectra; specifically, this includes the PC1 of Boroson & Green (1992), the classic or inverse Baldwi...
Low-z Mg II Broad Absorption-line Quasars from the Sloan Digital Sky Survey Article Full-text available We present a sample of 68 low-z Mg II low-ionization broad absorption-line (loBAL) quasars. The sample is uniformly selected from the Sloan Digital Sky Survey Data Release 5 according to the following criteria: (1) redshift 0.4 < z ≤ 0.8, (2) median spectral S/N>7 pixel–1, and (3) Mg II absorption-line width Δvc ≥ 1600 km s–1. The last criterion is...
On the Scattering Enhancement of N V λ1240 Emission Line of Quasi-stellar Objects Article Full-text available The N V emission line of active galactic nuclei shows peculiar behavior in the line-continuum correlation, which may be indicative of an extra line component in addition to that from the normal broad emission line region. In this paper, we investigate possible contribution to the N V emission via resonant scattering of both continuum and Lyalpha in... The Spin and Orientation of Dark Matter Halos Within Cosmic Filaments Article Full-text available Clusters, filaments, sheets and voids are the building blocks of the cosmic web. In this study, we present and compare two distinct algorithms for finding cosmic filaments and sheets, a task which is far less well established than the identification of dark matter halos or voids. One method is based on the smoothed dark matter density field, the ot... Estimating Black Hole Masses in Active Galactic Nuclei Using the MgII 2800 Emission Line Article Full-text available We investigate the relationship between the linewidths of broad Mg II \lambda2800 and Hbeta in active galactic nuclei (AGNs) to refine them as tools to estimate black hole (BH) masses. We perform a detailed spectral analysis of a large sample of AGNs at intermediate redshifts selected from the Sloan Digital Sky Survey, along with a smaller sample o...
Eddington Ratio Governs the Equivalent Width of Mg II Emission Line in Active Galactic Nuclei Article Full-text available We have investigated the ensemble regularities of the equivalent widths (EWs) of Mg II λ2800 emission line of active galactic nuclei (AGNs), using a uniformly selected sample of 2092 Seyfert 1 galaxies and quasars at 0.45 ≤ z ≤ 0.8 in the spectroscopic data set of the Sloan Digital Sky Survey Fourth Data Release. We find a strong correlation betwee... The distribution of ejected subhalos and its implication for halo assembly bias Article Using a high-resolution cosmological N-body simulation, we identify the ejected population of subhaloes, which are haloes at redshift z= 0 but were once contained in more massive ‘host’ haloes at high redshifts. The fraction of the ejected subhaloes in the total halo population of the same mass ranges from 9 to 4 per cent for halo masses from ∼1011...
The origin and physical mechanism of the ensemble Baldwin effect Article Full-text available We have conducted a systematic investigation of the origin and underlying physics of the line--line and line--continuum correlations of AGNs, particularly the Baldwin effect. Based on the homogeneous sample of Seyfert 1s and QSOs in the SDSS DR4, we find the origin of all the emission-line regularities is Eddington ratio (L/Ledd). The essential phy...
What controls the Fe II strength in active galactic nuclei? Article Full-text available We used a large, homogeneous sample of 4178 z ≤ 0.8 Seyfert 1 galaxies and QSOs selected from the Sloan Digital Sky Survey to investigate the strength of Fe II emission and its correlation with other emission lines and physical parameters of active galactic nuclei. We find that the strongest correlations of almost all the emission-line intensity ra... Reconstructing the cosmic density field with the distribution of dark matter halos Article We develop a new method to reconstruct the cosmic density field from the distribution of dark matter haloes above a certain mass threshold. Our motivation is that well-defined samples of galaxy groups/clusters, which can be used to represent the dark halo population, can now be selected from large redshift surveys of galaxies, and our ultimate goal...
The correlation between X-ray and UV properties of BAL QSOs Article Full-text available We compile a large sample of broad absorption line (BAL) quasars with X-ray observations from the XMM-Newton archive data and Sloan Digital Sky Survey Data Release 5. The sample consists of 41 BAL QSOs. Among 26 BAL quasars detected in X-ray, spectral analysis is possible for 12 objects. X-ray absorption is detected in all of them. Complementary to...
Unsaturated Low-Ionization Broad Absorption Lines in the Quasar SDSS J144842.45+042403.1 Article Full-text available We present a detailed analysis of the exceptional low-ionization broad absorption line (LoBAL) quasar SDSS J144842.45+042403.1. The C iv absorption trough, which is likely saturated, has a box-shaped bottom at a flux level of 2% Y5% of the unabsorbed flux. A large fraction of at least 80% of the C iv and Fe ii emission-line fluxes are obliterated b...
XMM-Newton Observations of Broad Absorption Line Quasars with Polar Outflows Article Full-text available We have selected a sample of broad absorption line (BAL) quasars which show significant radio variations, indicating the presence of polar BAL outflows. We obtained snapshot XMM observations of four polar BAL QSOs, to check whether strong X-ray absorption, one of the most prominent characteristics of most BAL QSOs, also exists in polar outflows. Tw... XMM observations of BAL Quasars with polar outflows Article We have selected a sample of broad absorption line (BAL) quasars which show significant radio variations, indicating the presence of polar BAL outflows. We obtained snapshot XMM observations of four polar BAL QSOs, to check whether strong X-ray absorption, one of the most prominent characteristics of most BAL QSOs, also exist in polar outflows. Two... Environmental Dependence of Cold Dark Matter Halo Formation Article We use a high-resolution N-body simulation to study how the formation of cold dark matter haloes is affected by their environments, and how such environmental effects produce the age dependence of halo clustering observed in recent N-body simulations. We estimate, for each halo selected at redshift z= 0, an ‘initial’ mass Mi defined to be the mass...
SDSS J160531.84+174826.1: A dwarf disk galaxy with an intermediate-mass black hole Article Full-text available We report the discovery of a dwarf Seyfert 1 active galactic nucleus (AGN) with a candidate intermediate-mass black hole, hosted by the dwarf galaxy SDSS J160531.84+174826.1 at z = 0.032. A broad component of the H alpha line with FWHM = 781 km s(-1) is detected in its optical spectrum, and a bright, pointlike nucleus is evident from a Hubble Space...
Polarization of Quasars: Resonant Line Scattering in the Broad Absorption Line Region Article Full-text available Recent works showed that the absorbing material in broad absorption line (BAL) quasars is optically thick to major resonant absorption lines. This material may contribute significantly to the polarization in the absorption lines. In this paper, we present a detailed study of the resonant line scattering process using Monte-Carlo method to constrain...
Broad-line AGNs with Candidate Intermediate-mass Black holes in the Sloan Digital Sky Survey Article Full-text available We have conducted a systematic search of AGNs with IMBHs from the SDSS DR4. As results we found 245 candidates of broad-line AGN with M_{BH}<10^6 \Msun estimated from the luminosity and width of the broad Halpha component. Compared to the pioneer Greene & Ho (2004) sample of 19 IMBH AGNs, our sample has improved in covering a larger range of the Ed... Polarization of Quasars: Rotated and Funnel-shaped Outflow Article Full-text available Polarization is a useful probe to investigate the geometries and dynamics of outflow in BAL QSOs. We perform a Monte-Carlo simulation to calculate the polarization produced by resonant and electron scattering in BALR. We find: 1)A rotated and funnel-shaped outflow is preferred to explain many observed polarization features. 2)The resonant scatterin...
Polar Outflows in Six Broad Absorption Line Quasars Article Full-text available Using the radio observations by FIRST and NVSS, we build a sample of 151 radio variable quasars selected from the Sloan Digital Sky Survey Data Release 3 (SDSS DR3). Six (probably another two) among them are classified as broad absorption line (BAL) quasars, with radio flux variations of a few 10 percent within 1.5-5 years. Such large amplitudes of... The phase-space distribution of infalling dark matter subhalos Article We use high-resolution numerical simulations to study the physical properties of subhaloes when they merge into their host haloes. An improved algorithm is used to identify the subhaloes. We then examine their spatial and velocity distributions in spherical and triaxial halo models. We find that the accretion of satellites preferentially occurs alo...
Polarization of Quasars: Electronic Scattering in the Broad Absorption Line Region Article Full-text available It is widely accepted that the broad absoption line region (BALR) exists in most (if not all) quasars with a small covering factor. Recent works showed that the BALR is optically thick to soft and even medium energy X-rays, with a typical hydrogen column density of a few 1023 to > 1024 cm−2. The electronic scattering in the thick absorber might con...
Polarization of Quasars: Electron Scattering in the Broad Absorption Line Region Article Full-text available It is widely accepted that the broad absorption line region (BALR) exists in most (if not all) quasars with a small covering factor. Recent works showed that the BALR is optically thick to soft and even medium energy X-rays, with a typical hydrogen column density of a few 10$^{23}$ to $>$ 10$^{24}$ cm$^{-2}$. The electron scattering in the thick ab... |
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