A key to understanding quasar unification paradigms is the emission properties of broad absorption line quasars (BALQs). The fact that only a small fraction of quasar spectra exhibit deep absorption troughs blueward of the broad permitted emission lines provides a crucial clue to the structure of quasar emitting regions. To learn whether it is possible to discriminate between the BALQ and non-BALQ populations given the observed spectral properties of a quasar, we employ two approaches: one based on statistical methods and the other supervised machine learning classification, applied to quasar samples from the Sloan Digital Sky Survey. The features explored include continuum and emission line properties, in particular the absolute magnitude, redshift, spectral index, line width, asymmetry, strength, and relative velocity offsets of high-ionisation CIV $λ1549$ and low-ionisation MgII $λ2798$ lines.
We consider a complete population of quasars, and assume that the statistical distributions of properties represent all angles where the quasar is viewed without obscuration. The distributions of the BALQ and non-BALQ sample properties show few significant differences. None of the observed continuum and emission line features are capable of differentiating between the two samples. Most published narrow disk-wind models are inconsistent with these observations, and an alternative disk-wind model is proposed. The key feature of the proposed model is a disk-wind filling a wide opening angle with multiple radial streams of dense clumps.
Randomly oriented flattened spheroids have been used to describe a broad range of astrophysical phenomena. Here we use this geometric approach to derive equations representing lines of sight through quasar absorption clouds to constrain cloud sizes.
We study large-scale UV background inhomogeneity in three-dimensions associated with the observed quasar populations at high redshift. We do this by measuring metal absorption through quasar absorption spectrum stacking as a function distance to closest quasar in SDSS-IV/eBOSS on 10s of comoving megaparsec scales. We study both intergalactic medium absorbers and mixed circumgalactic medium absorbers and probe absorption in O VI, C IV, and Si IV, and Si III. Overall stronger high ionization species absorption is seen closer to quasars at $2.4<z<3.1$. O VI absorption shows a particularly strong …
In the early Universe, most of the cold neutral gas that will later form into individual stars and galaxies is practically invisible to us. These neutral gas reservoirs can, however, be illuminated by bright cosmic lightsources such as gamma-ray bursts (GRBs) and quasars. The aim of this thesis is to use these luminous objects as tools to study the environments of intervening or host galaxy absorption systems through cosmic time. Part I is dedicated to examining the gas, dust and metals in the immediate region surrounding GRBs. Part II presents a search for and the study of cold and molecular …
Enhanced ionizing radiation in close proximity to redshift $z\gtrsim 6$ quasars creates short windows of intergalactic Ly$α$ transmission blueward of the quasar Ly$α$ emission lines. The majority of these Ly$α$ near-zones are consistent with quasars that have optically/UV bright lifetimes of $t_{\rm Q}\sim 10^{5}-10^{7}\rm\,yr$. However, lifetimes as short as $t_{\rm Q}\lesssim 10^{4}\rm\,yr$ appear to be required by the smallest Ly$α$ near-zones. These short lifetimes present an apparent challenge for the growth of $\sim 10^{9}\rm\,M_{\odot}$ black holes at $z\gtrsim 6$. Accretion over longer…
GBT Detection of Polarization-dependent HI Absorption and HI Outflows in Local ULIRGs and Quasars
本文介绍了用罗伯特C。伯德格林班克望远镜（GBT）这些残骸是从类星体/ULIRG演化研究（QUEST）的超亮红外星系（ULIRG; L $_{8-1000 μm} > 10^{12}$ L $_\odot$）和类星体样本中选择的;我们的目标都是由活动星系核（AGN）控制的，并且是建议的ULIRG到类星体演化序列的后期阶段的样本。我们发现HI吸收（发射）的流行率是100%（29%）在ULIRG与HI检测，100%（88%）在FIR强类星体，和63%（100%）在FIR弱类星体。吸收功能与强大的中性外流，从主要驱动的恒星形成ULIRGs被驱动的类星体的活动星系核。在某些情况下，这些流出物的速度超过1500 km s $^{-1}$。出乎意料的是，我们在57%的光谱中发现了偏振相关的HI吸收（分别为88%和63%的FIR强和FIR弱类星体）。我们将这一结果归因于前景HI云对这些源的偏振连续辐射的吸收。在显示偏振光谱的类星体中，约有60%是射电强的，远高于在活动星系核中观测到的$\sim$ 10%。这种差异表明，射电喷流在塑造这些星系的环境方面起着重要作用。这些系统可能代表了一个过渡阶段，在丰富的气体合并到“成熟”的射电星系的演变。
Quasars that exhibit blue-shifted, broad absorption lines (BAL QSOs) are an important probe of black hole feedback on galaxy evolution. Yet the presence of BALs is also a complication for large, spectroscopic surveys that use quasars as cosmological probes because the BAL features can affect redshift measurements and contaminate information about the matter distribution in the Lyman-$α$ forest. We present a new BAL QSO catalog for quasars in the Sloan Digital Sky Survey (SDSS) Data Release 14 (DR14). As the SDSS DR14 quasar catalog has over 500,000 quasars, we have developed an automated BAL c…
On time variability and other complications in studying the UV broad absorption lines of quasars: results from numerical simulations of radiation driven disk winds
Determining the distance of quasar absorption outflows from the central source (R) and their kinetic luminosity are crucial for understanding their contribution to active galactic nucleus (AGN) feedback. Here we summarize the results for a sample of nine luminous quasars that were observed with the Hubble Space Telescope. We find that the outflows in more than half of the objects are powerful enough to be the main agents for AGN feedback, and that most outflows are found at R>100 pc. The sample is representative of the quasar absorption outflow population as a whole and is unbiased towards spe…
Quasars with PV broad absorption in BOSS data release 9
宽吸收线（BALs）在类星体光谱的重要部分中发现，识别可能存在于所有类星体中的高速外流，并且可能是星系演化反馈的主要因素。理解这些流动的性质需要进一步限制其物理性质，包括其柱密度，对于这些物理性质，由于饱和效应，诸如CIV 1548、1551的充分研究的BALs通常仅提供下限。低丰度线，如PV 1118，1128，表明大柱密度，这意味着流出比单独测量CIV更强大。我们搜索了2694个BAL类星体的样本，从SDSS-III/BOSS DR 9类星体目录的这种吸收，我们确定了81个“明确的”和86个“可能的”检测PV广泛的吸收，产生一个坚定的下限为3.0-6.2%的发生率之间的吸收BAL类星体。PV探测到的类星体往往具有更强的CIV和SiIV吸收，以及比整体BAL类星体更高的LoBAL吸收率。许多PV检测到的类星体都有CIV槽，这些槽没有达到零强度（在检测到PV的速度下），这证实了外流气体只是部分覆盖了UV连续源。PV在非PV检测到的BAL类星体的复合光谱中显着出现，表明PV吸收（和大柱密度）比我们的搜索结果更常见。我们的PV检测样本显著增加了已知PV检测的数量，为后续研究提供了更好地了解BAL流出能量学的机会。
We aim to find out the reason why there exists an anisotropic HI absorption around quasars; i.e., the environments around quasars are highly biased toward producing strong HI absorption in transverse direction while there exists a significant deficit of HI absorption within a few Mpc of quasars along line-of-sight. The most plausible explanation for this opposite trend is that the transverse direction is shadowed from the quasar UV radiation due to dust torus. However, a critical weakness of this idea is that we have no information on inclination angle of our sightline relative to the torus. I…
We investigate the connection between the intrinsic C IV absorption line variability and the continuum flux changes of broad absorption line (BAL) quasars using a sample of 78 sources in the Stripe 82 region. The absorption trough variability parameters are measured using the archival multi-epoch spectroscopic data from the Sloan Digital Sky Survey (SDSS), and the continuum flux variability parameters are estimated from the photometric light curves obtained by the SDSS and the Catalina Real-Time Survey (CRTS) surveys. We find evidence for weak correlations (ρ~ 0.3) between the intrinsic C IV a…
We present results from our search for HI 21-cm and OH 18-cm absorption at z~1-1.4 towards red quasars showing strong MgII absorption using uGMRT. The quasars J1501+1822 and J1521+5508 show multiple strong associated MgII absorption at z~1.1 and signature of reddening in their optical spectra. We report the detection of HI 21-cm absorption towards J1521+5508 at the systemic redshift of the quasar, with N(HI) =(1.2 +/- 0.2) x 10^{20} cm^{-2} for spin temperature of 100 K and unit covering factor. The HI 21-cm absorption is offset from the blueshifted strong MgII absorbers by >~1500 km/s. We do …
The early stage of massive galaxy evolution often involves outflows driven by a starburst or a central quasar plus cold mode accretion (infall), which adds to the mass build-up in the galaxies. To study the nature of these infall and outflows in the quasar environments, we have examined the correlation of narrow absorption lines (NALs) at positive and negative velocity shifts to other quasar properties, such as their broad absorption-line (BAL) outflows and radio-loudness, using spectral data from SDSS-BOSS DR12. Our results show that the incidence of associated absorption lines (AALs) and out…
Broad absorption line (BAL) features in quasar spectra reveal an unambiguous signature of energetic outflows from central supermassive black holes, and thus BAL quasars are prime targets for investigating the potential process of luminous quasar feedback on galaxies. We analyzed the rest-UV spectrum of an "overlapping trough" iron low-ionization broad absorption line quasar (FeLoBAL) SDSS J135246.37+423923.5 using the novel spectral synthesis code SimBAL (Leighly et al. 2018) and discovered an extraordinarily fast and energetic BAL outflow. Our analysis revealed outflow velocities reaching $\s…
We find multiple Mg II absorption systems at redshift z=1.66, 2.069, and 2.097 in the spatially resolved spectra of the quadruply gravitationally lensed quasar H1413+1143 utilizing the Kyoto tridimensional spectrograph II (Kyoto 3DII) spectrograph on board the Subaru telescope. Here we present the first measurement of differences in Mg II absorption strength of the multiple intervening absorbers, which include ones identified as damped Lyman alpha (DLA) absorption systems. Our detection of the significant Mg II absorptions in the spatially resolved spectra reveals the inhomogeneous chemical en…
We report, for the first time, a synchronized velocity shift of Mg II and Al III broad absorption lines (BALs) in quasar SDSS J134444.33+315007.6 (hereafter J1344+3150). We found this quasar from a sample of 134 Mg II BAL quasars with multi-epoch observations. This quasar contains three low-ionization BAL systems, the fastest of which at $\sim$$-17, 000\,\rm km\,s^{-1}$ shows a kinematic shift of $\sim$$-1101\,\rm km\,s^{-1}$ and $\sim$$-1170\,\rm km\,s^{-1}$ in its Mg II and Al III ions, respectively, during a rest-frame time of about 3.21 yr. Meanwhile, this quasar also shows other various v…
Observational evidence revealing the main mechanisms that accelerate quasar outflows has proven difficult to obtain, due to the complexity of the absorption features that this gas produces in the spectra of the emission sources. We build 36 composite outflow spectra, covering a large range of outflow and quasar parameters, by stacking broad ($>450\,{\rm km\,s^{-1}}$) absorption line systems in the spectra of SDSS-III/BOSS DR12 quasars. The two lines of the atomic doublet of CIV, with a separation of $\approx 497\,{\rm km\,s^{-1}}$, as well as those of other species appear well resolved in most…
We report a synchronized kinematic shift of CIV and SiIV broad absorption lines (BAL) in a high-ionization, radio-loud, and X-ray bright quasar SDSS-J092345+512710 (at $z_{em} \sim 2.1627$). This quasar shows two broad absorption components (blue component at $v \sim 14,000\ km\ s^{-1}$, and red component at $v \sim 4,000\ km\ s^{-1}$ with respect to the quasars systemic redshift). The absorption profiles of CIV and SiIV BAL of the blue component show decrease in outflow velocity with an average deceleration rate of $-1.62_{-0.05}^{+0.04}\ cm\ s^{-2}$ and $-1.14^{+0.21}_{-0.22}\ cm\ s^{-2}$ ov…
Using a sample of $\simeq$144,000 quasars from the Sloan Digital Sky Survey data release 14 we investigate the outflow properties, evident both in absorption and emission, of high-ionization Broad Absorption Line (BAL) and non-BAL quasars with redshifts 1.6 $\lesssim z \leq$ 3.5 and luminosities 45.3 $< \log_{10}(L_{bol}) < $ 48.2 erg s$^{-1}$. Key to the investigation is a continuum and emission-line reconstruction scheme, based on mean-field independent component analysis, that allows the kinematic properties of the CIV$λ$1550 emission line to be compared directly for both non-BAL and BAL qu…
We analyze the VLT/UVES spectrum of the quasar SDSS J143907.5-010616.7, retrieved from the UVES Spectral Quasar Absorption Database. We identify two outflow systems in the spectrum: a mini broad absorption line (mini-BAL) system and a narrow absorption line (NAL) system. We measure the ionic column densities of the mini-BAL ($v=-1550$ km s$^{-1}$) outflow, which has excited state absorption troughs of Fe II. We determine that the electron number density $\log{n_e}=3.4^{+0.1}_{-0.1}$ based on the ratios between the excited and ground state abundances of Fe II, and find the kinetic luminosity of…
We present a new set of 84 Broad absorption line (BAL) quasars ( 1.7 $<$ \zem $<$ 4.4) exhibiting an appearance of \civ BAL troughs over 0.3$-$4.8 rest-frame years by comparing the Sloan Digital Sky Survey Data Release (SDSSDR)-7, SDSSDR-12, and SDSSDR-14 quasar catalogs. We contrast the nature of BAL variability in this appearing BAL quasar sample with a disappearing BAL quasar sample studied in literature by comparing the quasar's intrinsic, BAL trough, and continuum parameters between the two samples. We find that appearing BAL quasars have relatively higher redshift and smaller probed time…
Photoionization-driven Absorption Lines Variability in Balmer Absorption Line Quasar LBQS 1206+1052
在本文中，我们提出了一个小型BAL类星体LBQS 1206+1052的吸收线的变化分析。SDSS谱表明，吸收槽相对于类星体静止坐标系可分为$\sim$ 700 km s $^{-1}$和$\sim$ 1400 km s $^{-1}$两个蓝移速度分量.前者表现出罕见的巴耳末吸收，这是高密度吸收气体的指示，因此该类星体值得进行后续的光谱观测。我们使用MMT，YFOSC，TripleSpec和DBSP的后续光学和近红外光谱显示，两种组分的吸收线的强度不同，而速度不变。我们重现所有的光谱数据，假设只有电离状态的吸收气体是可变的，所有其他的物理性质是不变的。从V波段光变曲线上看，电离度的变化与光连续谱的变化是一致的。此外，我们不能通过假设可变性是由于吸收气体的运动来解释数据。因此，我们的分析强烈表明LBQS 1206+1052中的吸收线可变性是光电离驱动的。如从光电离模拟所示，具有$\sim$ 700 km s $^{-1}$的蓝移速度的吸收气体具有在$10^9$至$10^{10}$ cm $^{-3}$的范围内的密度和$\sim$ 1 pc的距离，并且具有$\sim$ 1400 km s $^{-1}$的蓝移速度的气体具有$10^3$ cm $^{-3}$的密度和$\sim$ 1 kpc的距离。
Wind Acceleration as a Driver of Detached Blueshifted Absorption in Quasar Disk Winds
University of Nevada, Las Vegas（内华达大学拉斯维加斯分校）；Nevada Center for Astrophysics（内华达天体物理中心）；Physical Sciences Division, School of STEM University of Washington Bothell（华盛顿大学博塞尔校区理学院STEM学部）
We present ten metallicity measurements for quasar absorbers near $z=1.2$ that were selected for having unusually significant ZnII absorption in their SDSS spectra. Follow-up UV space spectroscopy of the Ly$α$ region shows that all ten have damped Ly$α$ (DLA) absorption, corresponding to neutral hydrogen column densities in the range $2.4\times 10^{20}$ $\le$ N(HI) $\le$ $2.5\times 10^{21}$ atoms cm$^{-2}$, and indicating that the gas is very optically thick and essentially neutral. The sample is a very small subset of systems compiled by searching the University of Pittsburgh catalog of $\app…
A key assumption in quasar absorption line studies of the circumgalactic medium (CGM) is that each absorption component maps to a spatially isolated "cloud" structure that has single valued properties (e.g. density, temperature, metallicity). We aim to assess and quantify the degree of accuracy underlying this assumption. We used adaptive mesh refinement hydrodynamic cosmological simulations of two $z=1$ dwarf galaxies and generated synthetic quasar absorption-line spectra of their CGM. For the SiII $λ1260$ transition, and the CIV $λ\lambda1548, 1550$ and OVI $λ\lambda1031, 1037$ fine-structur…
Circumgalactic medium of quasar host galaxies at 0.4<z<0.8 probed by strong Mg II absorption
Central University of Himachal Pradesh（喜马偕尔邦中央大学）；Inter-University Centre for Astronomy and Astrophysics（大学间天文学与天体物理学中心）；Indian Institute of Astrophysics（印度天体物理研究所）
We investigate the correlation between rest-frame UV flux variability of broad absorption line (BAL) quasars and their variability in BAL equivalent widths (EWs) in a various timescale from $<10$~days to a few years in the quasar rest-frame. We use the data sets of BAL EWs taken by the Sloan Digital Sky Survey Reverberation Mapping (SDSS-RM) project and photometric data taken by the intermediate Palomar Transient Factory (iPTF) in $g$ and $R$-bands and the Panoramic Survey Telescope and Rapid Response System (Pan-STARRS) in $grizy$ bands. Our results are summarized as below; (1) the distributi…
