Intrinsic Absorption Lines Research Articles

Spectral Signatures of Quasar Ages at z ≈ 3

Abstract Insight into quasar ages may be obtained from the proximity effect, but so far only in a limited number of bright quasars. Based on ∼2600 Sloan Digital Sky Survey quasar spectra at 2.5 ≤ z ≤ 3.5, a search for spectral voids between Lyα forest lines finds proximity zones over a wide range of radial distances. The majority of zone sizes are less than 5 Mpc, with their numbers decreasing exponentially toward larger distances. After a normalization by luminosities, the zone sizes are distributed with an e-folding scale of 0.64 as compared with the anticipated values. A group of quasars are selected for their large proximity zones of ≳10 Mpc. Their composite spectrum displays strong narrow cores and large equivalent widths in Lyα and other major UV emission lines. If the proximity zones along lines of sight are indicative of quasar ages, these features may be the signatures of old quasars. Another group of quasars are selected as they show no proximity zone and exhibit intrinsic absorption lines at z ab > z em . They are likely young quasars and exhibit weaker narrow emission-line components. The significant difference of spectral features between the two groups may reflect an evolution pattern over quasars’ lifetimes.

A Wind-based Unification Model for NGC 5548: Spectral Holidays, Nondisk Emission, and Implications for Changing-look Quasars

Abstract The 180 day Space Telescope and Optical Reverberation Mapping campaign on NGC 5548 discovered an anomalous period, the broad-line region (BLR) holiday, in which the emission lines decorrelated from the continuum variations. This is important since the correlation between the continuum-flux variations and the emission-line response is the basic assumption for black hole (BH) mass determinations through reverberation mapping. During the BLR holiday the high-ionization intrinsic absorption lines also decorrelated from the continuum as a result of the variable covering factor of the line-of-sight (LOS) obscurer. The emission lines are not confined to the LOS, so this does not explain the BLR holiday. If the LOS obscurer is a disk wind, its streamlines must extend down to the plane of the disk and the base of the wind would lie between the BH and the BLR, forming an equatorial obscurer. This obscurer can be transparent to ionizing radiation, or can be translucent, blocking only parts of the spectral energy distribution, depending on its density. An emission-line holiday is produced if the wind density increases only slightly above its transparent state. Both obscurers are parts of the same wind, so they can have associated behavior in a way that explains both holidays. A very dense wind would block nearly all ionizing radiation, producing a Seyfert 2 and possibly providing a contributor to the changing-look active galactic nucleus phenomenon. Disk winds are very common and we propose that the equatorial obscurers are too, but mostly in a transparent state.

Space Telescope and Optical Reverberation Mapping Project. X. Understanding the Absorption-line Holiday in NGC 5548

Abstract The Space Telescope and Optical Reverberation Mapping Project (AGN STORM) on NGC 5548 in 2014 is one of the most intensive multiwavelength AGN monitoring campaigns ever. For most of the campaign, the emission-line variations followed changes in the continuum with a time lag, as expected. However, the lines varied independently of the observed UV-optical continuum during a 60–70 day “holiday,” suggesting that unobserved changes to the ionizing continuum were present. To understand this remarkable phenomenon and to obtain an independent assessment of the ionizing continuum variations, we study the intrinsic absorption lines present in NGC 5548. We identify a novel cycle that reproduces the absorption line variability and thus identify the physics that allows the holiday to occur. In this cycle, variations in this obscurer’s line-of-sight covering factor modify the soft X-ray continuum, changing the ionization of helium. Ionizing radiation produced by recombining helium then affects the level of ionization of some ions seen by the Hubble Space Telescope. In particular, high-ionization species are affected by changes in the obscurer covering factor, which does not affect the optical or UV continuum, and thus appear as uncorrelated changes, a “holiday.” It is likely that any other model that selectively changes the soft X-ray part of the continuum during the holiday can also explain the anomalous emission-line behavior observed.

Hunting for metals using XQ-100 Legacy Survey composite spectra

We investigate the NV absorption signal along the line of sight of background quasars, in order to test the robustness of the use of this ion as criterion to select intrinsic (i.e. physically related to the quasar host galaxy) narrow absorption lines (NALs). We build composite spectra from a sample of $\sim$ 1000 CIV absorbers, covering the redshift range 2.55 < z < 4.73, identified in 100 individual sight lines from the XQ-100 Legacy Survey. We detect a statistical significant NV absorption signal only within 5000 km s$^{-1}$ of the systemic redshift, z$\rm_{em}$. This absorption trough is $\sim$ 15$\sigma$ when only CIV systems with N(CIV) > 10$^{14}$ cm$^{-2}$ are included in the composite spectrum. This result confirms that NV offers an excellent statistical tool to identify intrinsic systems. We exploit the stacks of 11 different ions to show that the gas in proximity to a quasar exhibits a considerably different ionization state with respect to gas in the transverse direction and intervening gas at large velocity separations from the continuum source. Indeed, we find a dearth of cool gas, as traced by low-ionization species and in particular by MgII, in the proximity of the quasar. We compare our findings with the predictions given by a range of Cloudy ionization models and find that they can be naturally explained by ionization effects of the quasar.

THE WIDE-ANGLE OUTFLOW OF THE LENSED z = 1.51 AGN HS 0810+2554

ABSTRACT We present results from X-ray observations of the gravitationally lensed z = 1.51 active galactic nucleus (AGN) HS 0810+2554 performed with the Chandra X-ray Observatory and XMM-Newton. Blueshifted absorption lines are detected in both observations at rest-frame energies ranging between ∼1 and 12 keV at ≳99% confidence. The inferred velocities of the outflowing components range between ∼0.1c and ∼0.4c. A strong emission line at ∼6.8 keV that is accompanied by a significant absorption line at ∼7.8 keV is also detected in the Chandra observation. The presence of these lines is a characteristic feature of a P-Cygni profile supporting the presence of an expanding, outflowing, highly ionized iron absorber in this quasar. Modeling of the P-Cygni profile constrains the covering factor of the wind to be ≳0.6, assuming disk shielding. A disk-reflection component is detected in the XMM-Newton observation accompanied by blueshifted absorption lines. The XMM-Newton observation constrains the inclination angle to be &lt;45° at 90% confidence, assuming that the hard excess is due to blurred reflection from the accretion disk. The detection of an ultrafast and wide-angle wind in an AGN with intrinsic narrow absorption lines (NALs) would suggest that quasar winds may couple efficiently with the intergalactic medium and provide significant feedback if ubiquitous in all NAL and broad absorption line (BAL) quasars. We estimate the mass-outflow rate of the absorbers to lie in the range of 1.5–3.4 M ⊙ yr−1 for the two observations. We find that the fraction of kinetic to electromagnetic luminosity released by HS 0810+2554 is large (ϵ k = 9 ), which suggests that magnetic driving is likely a significant contributor to the acceleration of this outflow.

MONITORING THE VARIABILITY OF INTRINSIC ABSORPTION LINES IN QUASAR SPECTRA, ,

We have monitored 12 intrinsic narrow absorption lines (NALs) in five quasars and seven mini-broad absorption lines (mini-BALs) in six quasars for a period of 4-12 years (1-3.5 years in the quasar rest-frame). We present the observational data and the conclusions that follow immediately from them, as a prelude to a more detailed analysis. We found clear variability in the equivalent widths (EWs) of the mini-BAL systems but no easily discernible changes in their profiles. We did not detect any variability in the NAL systems nor in narrow components that are often located at the center of mini-BAL profiles. Variations in mini-BAL EWs are larger at longer time intervals, reminiscent of the trend seen in variable broad absorption lines. If we assume that the observed variations result from changes in the ionization state of the mini-BAL gas, we infer lower limits to the gas density $\sim$ 10$^3$-10$^5$ cm$^{-3}$ and upper limits on the distance of the absorbers from the central engine of order a few kpc. Motivated by the observed variability properties, we suggest that mini-BALs can vary because of fluctuations of the ionizing continuum or changes in partial coverage while NALs can vary primarily because of changes in partial coverage.

THE ALFALFA H I ABSORPTION PILOT SURVEY: A WIDE-AREA BLIND DAMPED Lyα SYSTEM SURVEY OF THE LOCAL UNIVERSE

We present the results of a pilot survey for neutral hydrogen (HI) 21 cm absorption in the Arecibo Legacy Fast Arecibo L-Band Feed Array (ALFALFA) Survey. This project is a wide-area "blind" search for HI absorption in the local universe, spanning -650 km/s < cz < 17,500 km/s and covering 517.0 square degrees (7% of the full ALFALFA survey). The survey is sensitive to HI absorption lines stronger than 7.7 mJy (8983 radio sources) and is 90% complete for lines stronger than 11.0 mJy (7296 sources). The total redshift interval sensitive to all damped Lyman alpha (DLA) systems (N_HI >= 2x10^20 cm^-2) is Delta z = 7.0 (129 objects, assuming T_s = 100 K and covering fraction unity); for super-DLAs (N_HI >= 2x10^21 cm^-2) it is Delta z= 128.2 (2353 objects). We re-detect the intrinsic HI absorption line in UGC 6081 but detect no intervening absorption line systems. We compute a 95% confidence upper limit on the column density frequency distribution function f(N_HI,X) spanning four orders of magnitude in column density, 10^19 (T_s/100 K)(1/f) cm^-2 < N_HI < 10^23 (T_s/100 K)(1/f) cm^-2, that is consistent with previous redshifted optical damped Ly alpha surveys and the aggregate HI 21 cm emission in the local universe. The detection rate is in agreement with extant observations. This pilot survey suggests that an absorption line search of the complete ALFALFA survey --- or any higher redshift, larger bandwidth, or more sensitive survey, such as those planned for Square Kilometer Array pathfinders or a low frequency lunar array --- will either make numerous detections or will set a strong statistical lower limit on the typical spin temperature of neutral hydrogen gas.

GALACTIC-SCALE ABSORPTION OUTFLOW IN THE LOW-LUMINOSITY QUASAR IRAS F04250–5718:HUBBLE SPACE TELESCOPE/COSMIC ORIGINS SPECTROGRAPH OBSERVATIONS

We present absorption line analysis of the outflow in the quasar IRAS F04250–5718. Far-ultraviolet data from the Cosmic Origins Spectrograph on board the Hubble Space Telescope reveal intrinsic narrow absorption lines from high ionization ions (e.g., C IV, N V, and O VI) as well as low ionization ions (e.g., C II and Si III). We identify three kinematic components with central velocities ranging from ~–50 to ~–230 km s–1. Velocity-dependent, non-black saturation is evident from the line profiles of the high ionization ions. From the non-detection of absorption from a metastable level of C II, we are able to determine that the electron number density in the main component of the outflow is 30 cm–3. Photoionization analysis yields an ionization parameter log U H ~ –1.6 ± 0.2, which accounts for changes in the metallicity of the outflow and the shape of the incident spectrum. We also consider solutions with two ionization parameters. If the ionization structure of the outflow is due to photoionization by the active galactic nucleus, we determine that the distance to this component from the central source is 3 kpc. Due to the large distance determined for the main kinematic component, we discuss the possibility that this outflow is part of a galactic wind.

THE PHYSICAL CONDITIONS OF THE INTRINSIC N V NARROW ABSORPTION LINE SYSTEMS OF THREE QUASARS

We employ detailed photoionization models to infer the physical conditions of intrinsic narrow absorption line systems found in high resolution spectra of three quasars at z=2.6-3.0. We focus on a family of intrinsic absorbers characterized by N V lines that are strong relative to the Ly-alpha lines. The inferred physical conditions are similar for the three intrinsic N V absorbers, with metallicities greater than 10 times the solar value (assuming a solar abundance pattern), and with high ionization parameters (log U ~ 0). Thus, we conclude that the unusual strength of the N V lines results from a combination of partial coverage, a high ionization state, and high metallicity. We consider whether dilution of the absorption lines by flux from the broad-emission line region can lead us to overestimate the metallicities and we find that this is an unlikely possibility. The high abundances that we infer are not surprising in the context of scenarios in which metal enrichment takes place very early on in massive galaxies. We estimate that the mass outflow rate in the absorbing gas (which is likely to have a filamentary structure) is less than a few solar masses per year under the most optimistic assumptions, although it may be embedded in a much hotter, more massive outflow.

MASS OUTFLOW IN THE SEYFERT 1 GALAXY NGC 5548

We present a study of the intrinsic UV absorption and emission lines in an historically low-state spectrum of the Seyfert 1 galaxy NGC 5548, which we obtained in 2004 February at high spatial and spectral resolution with the Space Telescope Imaging Spectrograph (STIS) on the Hubble Space Telescope. We isolate a component of emission with a width of 680 km/s (FWHM) that arises from an "intermediate line region" (ILR), similar to the one we discovered in NGC 4151, at a distance of ~1 pc from the central continuum source. From a detailed analysis of the five intrinsic absorption components in NGC 5548 and their behavior over a span of 8 years, we present evidence that most of the UV absorbers only partially cover the ILR and do not cover an extended region of UV continuum emission, most likely from hot stars in the circumnuclear region. We also find that four of the UV absorbers are at much greater distances (>70 pc) than the ILR, and none have sufficient N V or C IV column densities to be the ILR in absorption. At least a portion of the UV absorption component 3, at a radial velocity of -530 km/s, is likely responsible for most of the X-ray absorption, at a distance < 7 pc from the central source. The fact that we see the ILR in absorption in NGC 4151 and not in NGC 5548 suggests that the ILR is located at a relatively large polar angle (~45 degrees) with respect to the narrow-line region outflow axis.

Exploratory Study of the X‐Ray Properties of Quasars with Intrinsic Narrow Absorption Lines

We have used archival Chandra and XMM-Newton observations of quasars hosting intrinsic narrow UV absorption lines (intrinsic NALs) to carry out an exploratory survey of their X-ray properties. Our sample consists of three intrinsic NAL quasars and one mini-BAL quasar, plus four quasars without intrinsic absorption lines for comparison. These were drawn in a systematic manner from an optical/UV-selected sample. The X-ray properties of intrinsic NAL quasars are indistinguishable from those of normal quasars. We do not find any excess absorption in quasars with intrinsic NALs, with upper limits of -->NH few × 1022 cm −2. We compare the X-ray and UV properties of our sample quasars by plotting the equivalent width and blueshift velocity of the intrinsic NALs and the X-ray spectral index against the optical-to-X-ray slope, -->αox. When BAL quasars and other AGNs with intrinsic NALs are included, the plots suggest that intrinsic NAL quasars form an extension of the BAL sequences and tend to bridge the gap between BAL and normal quasars. Observations of larger samples of intrinsic NAL quasars are needed to verify these conclusions. We also test two competing scenarios for the location of the NAL gas in an accretion disk wind. Our results strongly support a location of the NAL gas at high latitudes above the disk, closer to the disk axis than the dense BAL wind. We detect excess X-ray absorption only in Q0014+8118, which does not host intrinsic NALs. The absorbing medium very likely corresponds to an intervening system at -->z = 1.1, which also produces strong absorption lines in the rest-frame UV spectrum of this quasar. In an appendix we discuss the connection between UV and X-ray attenuation and its effect on -->αox.

A Survey of Intrinsic Absorption in Active Galaxies using theFar Ultraviolet Spectroscopic Explorer

We present a survey of 72 Seyfert galaxies and quasars observed by the it Far Ultraviolet Spectroscopic Explorer (FUSE). We have determined that 72 of 253 available active galactic nuclei (AGN) targets are viable targets for detection of intrinsic absorption lines. We examined these spectra for signs of intrinsic absorption in the O VI doublet (lambda 1031.9, 1037.6) and Lyman beta (lambda 1025.7). The fraction of Seyfert 1 galaxies and low-redshift quasars at z < 0.15 that show evidence of intrinsic UV absorption is ~50%, which is slightly lower than Crenshaw et al. (1999) found (60%) based on a smaller sample of Seyfert 1 galaxies observed with the Hubble Space Telescope (HST). With this new fraction we find a global covering factor of the absorbing gas with respect to the central nucleus of ~0.4. Our survey is to date the largest searching for intrinsic UV absorption with high spectral resolution, and is the first step toward a more comprehensive study of intrinsic absorption in low-redshift AGN.

A Census of Intrinsic Narrow Absorption Lines in the Spectra of Quasars at z = 2–4

We use Keck HIRES spectra of 37 optically bright quasars at z = 2-4 to study narrow absorption lines that are intrinsic to the quasars (intrinsic NALs, produced in gas that is physically associated with the quasar central engine). We identify 150 NAL systems, which contain 124 C IV, 12 N V, and 50 Si IV doublets, of which 18 are associated systems (within 5000 km s-1 of the quasar redshift). We use partial coverage analysis to separate intrinsic NALs from NALs produced in cosmologically intervening structures. We find 39 candidate intrinsic systems (28 reliable determinations and 11 that are possibly intrinsic). We estimate that 10%-17% of C IV systems at blueshifts of 5000-70,000 km s-1 relative to quasars are intrinsic. At least 32% of quasars contain one or more intrinsic C IV NALs. Considering N V and Si IV doublets showing partial coverage as well, at least 50% of quasars host intrinsic NALs. This result constrains the solid angle subtended by the absorbers to the background source(s). We identify two families of intrinsic NAL systems, those with strong N V absorption and those with negligible absorption in N V but with partial coverage in the C IV doublet. We discuss the idea that these two families represent different regions or conditions in accretion disk winds. Of the 26 intrinsic C IV NAL systems, 13 have detectable low-ionization absorption lines at similar velocities, suggesting that these are two-phase structures in the wind rather than absorbers in the host galaxy. We also compare possible models for quasar outflows, including radiatively accelerated disk-driven winds, magnetocentrifugally accelerated winds, and pressure-driven winds, and we discuss ways of distinguishing between these models observationally.

Results of Monitoring the Dramatically Variable CivMini–Broad Absorption Line System in the Quasar HS 1603+3820

We present six new and two previously published high-resolution spectra of the quasar HS 1603+3820 (z_em = 2.542) taken over an interval of 4.2 years (1.2 years in the quasar rest frame). The observations were made with the High-Dispersion Spectrograph on the Subaru telescope and Medium-Resolution Spectrograph on the Hobby-Eberly Telescope. The purpose was to study the narrow absorption lines (NALs). We use time variability as well as coverage fraction analysis to separate intrinsic absorption lines, which are physically related to the quasar, from intervening absorption lines. By fitting models to the line profiles, we derive the parameters of the respective absorbers as a function of time. Only the mini-BAL system at z_abs ~ 2.43 (v_off ~ 9,500 km/s) shows both partial coverage and time variability, although two NAL systems possibly show evidence of partial coverage. We find that all the troughs of the mini-BAL system vary in concert and its total equivalent width variations resemble those of the coverage fraction. However, no other correlations are seen between the variations of different model parameters. Thus, the observed variations cannot be reproduced by a simple change of ionization state nor by motion of a homogeneous parcel of gas across the cylinder of sight. We propose that the observed variations are a result of rapid continuum fluctuations, coupled with coverage fraction fluctuations caused by a clumpy screen of variable optical depth located between the continuum source and the mini-BAL gas. An alternative explanation is that the observed partial coverage signature is the result of scattering of continuum photons around the absorber, thus the equivalent width of the mini-BAL can vary as the intensity of the scattered continuum changes.

Time‐Variable Complex Metal Absorption Lines in the Quasar HS 1603+3820

We present a new spectrum of the quasar HS 1603+3820 taken 1.28 yr (0.36 yr in the quasar rest frame) after a previous observation with Subaru+HDS. The new spectrum enables us to search for time variability as an identifier of intrinsic narrow absorption lines (NALs). This quasar shows a rich complex of C IV NALs within 60,000 km s-1 of the emission redshift. On the basis of covering factor analysis, Misawa et al. found that the C IV NAL system at zabs = 2.42-2.45 (system A, at a shift velocity of vsh = 8300-10,600 km s-1 relative to the quasar) was intrinsic to the quasar. With our new spectrum, we perform time variability analysis, as well as covering factor analysis, to separate intrinsic NALs from intervening NALs for eight C IV systems. Only system A, which was identified as an intrinsic system in the earlier paper by Misawa et al., shows a strong variation in line strength (Wobs ≈ 10.4 → 19.1 Å). We speculate that a broad absorption line (BAL) could be forming in this quasar (i.e., many narrower lines will blend together to make a BAL profile). We illustrate the plausibility of this suggestion with the help of a simulation in which we vary the column densities and covering factors of the NAL complex. Under the assumption that a change of ionization state causes the variability, a lower limit can be placed on the electron density (ne ≳ 3 × 104 cm-3) and an upper limit on the distance from the continuum source (r ≤ 6 kpc). On the other hand, if the motion of clumpy gas causes the variability (a more likely scenario), the crossing velocity and the distance from the continuum source are estimated to be vcross > 8000 km s-1 and r < 3 pc. In this case, the absorber does not intercept any flux from the broad emission line region, but only flux from the UV continuum source. If we adopt the dynamical model of Murray et al., we can obtain a much more strict constraint on the distance of the gas parcel from the continuum source, r < 0.2 pc.

Emission Line Properties of Active Galactic Nuclei from a Post‐COSTARHubble Space TelescopeFaint Object Spectrograph Spectral Atlas

We present consistent emission-line measurements for active galactic nuclei (AGNs), useful for reliable statistical studies of emission line properties. This paper joins a series including similar measurements of 993 spectra from the Large Bright Quasar Survey and 174 spectra of AGNs obtained from the Faint Object Spectrograph (FOS) on the Hubble Space Telescope (HST) prior to the installation of COSTAR. This time we concentrate on 220 spectra obtained with the FOS after the installation of COSTAR, completing the emission line analysis of all FOS archival spectra. We use the same automated technique as in previous papers, which accounts for Galactic extinction, models blended optical and UV iron emission, includes Galactic and intrinsic absorption lines, and models emission lines using multiple Gaussians. We present UV and optical emission line parameters (equivalent widths, fluxes, FWHM, and line positions) for a large number (28) of emission lines including upper limits for undetected lines. Further scientific analyses will be presented in subsequent papers.

Variability Tests for Intrinsic Absorption Lines in Quasar Spectra

Quasar spectra have a variety of absorption lines whose origins range from energetic winds expelled from the central engines to unrelated, intergalactic clouds. We present multiepoch, medium-resolution spectra of eight quasars at z ~ 2 that have narrow associated absorption lines (AALs, within ±5000 km s-1 of the emission redshift). Two of these quasars were also known previously to have high-velocity mini-broad absorption lines (mini-BALs). We use these data, spanning ~17 yr in the observed frame with 2-4 observations per object, to search for line-strength variations as an identifier of absorption that occurs physically near (intrinsic to) the central active galactic nucleus. Our main results are the following: Two out of the eight quasars with narrow AALs exhibit variable AAL strengths. Two out of two quasars with high-velocity mini-BALs exhibit variable mini-BAL strengths. We also marginally detect variability in a high-velocity narrow absorption line system, blueshifted ~32,900 km s-1 with respect to the emission lines. No other absorption lines in these quasars appeared to vary. The outflow velocities of the variable AALs are 3140 and 1490 km s-1. The two mini-BALs identify much higher velocity outflows of ~28,400 and ~52,000 km s-1. Our temporal sampling yields upper limits on the variation timescales from 0.28 to 6.1 yr in the quasar rest frames. The corresponding minimum electron densities in the variable absorbers, based on the recombination timescale, are ~40,000 to ~1900 cm-3. The maximum distances of the absorbers from the continuum source, assuming photoionization with no spectral shielding, range from ~1.8 to ~7 kpc.

Multiwavelength studies of the Seyfert 1 galaxy NGC 7469 I. Far UV observations with FUSE

We obtained far-ultraviolet spectra of the Seyfert 1 galaxy NGC 7469 using the Far Ultraviolet Spectroscopic Explorer on 1999 December 6. Our spectra cover the wavelength range 990-1187 A with a resolution of0:05 A. We see broad emission lines of Ciii ,N iii ,O vi ,a nd Heii as well as intrinsic absorption lines in the O vi1032; 1038 resonance doublet. The absorption arises in two distinct kinematic components at systemic velocities of 569 km s 1 and 1898 km s 1 . Both components are very highly ionized - no significant Ly absorption is present. The higher blueshift component is not quite saturated, and it has a total O vi column density of 8 10 14 cm 2 . It covers more than 90% of the continuum and broad- line emission. The lower blueshift component is heavily saturated and covers only 50% of the continuum and broad-line emission. It too has a column density of 8 10 14 cm 2 , but this is less certain due to the high saturation. We set an upper limit of<1:5 10 18 cm 2 on the O vi column density of this component. Its line depth is consistent with coverage of only the continuum, and thus this component may lie interior to the broad emission-line gas. The component at 569 km s 1 has a velocity comparable to the high-ionization X-ray absorption lines seen in the XMM-Newtongrating spectrum of NGC 7469, and photoionization models show that the observed column densities of O vi and H i are compatible with their formation in the same gas as that causing the X-ray absorption. The gas at 1898 km s 1 has lower ionization and column density, and no

Subaru High-Resolution Spectroscopy of Complex Metal Absorption Lines of the Quasar HS 1603+3820

We present a high-resolution spectrum of the quasar HS 1603+3820 (zem = 2.542), observed with the High Dispersion Spectrograph on the Subaru Telescope. This quasar, first discovered in the Hamburg/CfA Quasar Survey, has 11 C IV lines at 1.96 2.29 and resolves some of them into multiple narrow components with b 65 km s-1). We use three properties of C IV lines, specifically, time variability, covering factor, and absorption-line profile, to classify them into quasar intrinsic absorption lines (QIALs) and spatially intervening absorption lines (SIALs). The C IV lines at 2.42 < zabs < 2.45 are classified as QIALs in spite of their large velocity shifts from the quasar. Perhaps they are produced by gas clouds ejected from the quasar with velocity vej = 8000–10,000 km s-1. On the other hand, three C IV lines at 2.48 < zabs < 2.55 are classified as SIALs, which suggests there exist intervening absorbers near the quasar. We, however, cannot rule out QIALs for the two lines at zabs ~ 2.54 and 2.55, because their velocity shifts, 430 km s-1 blueward and 950 km s-1 redward of the quasar, are very small. The C IV line at zabs ~ 2.48 consists of many narrow components and also has corresponding low-ionization metal lines (Al II, Si II, and Fe II). The velocity distribution of these low-ionization ions is concentrated at the center of the system compared with that of the high-ionization C IV ion. Therefore we ascribe this system of absorption lines to an intervening galaxy.

Emission Line Properties of Active Galactic Nuclei from a Pre‐COSTAR Faint Object Spectrograph Hubble Space Telescope Spectral Atlas

UV/optical emission lines offer some of the most detailed information obtainable about the intrinsic properties of quasars. Studies of the density, ionization and metal abundance of gas near the accreting black hole are probed through an intriguing but poorly understood complex of correlations between emission lines and overall quasar spectral energy distributions that has long suffered from a lack of large, consistently measured samples. As part of a broader effort to expand and systematize the data upon which these studies are built, we present measurements of the UV/optical emission line parameters in a sample of 158 active galactic nuclei observed with the Faint Object Spectrograph on the Hubble Space Telescope (HST), prior to the installation of COSTAR. We use an automated technique that accounts for galactic reddening, includes iron emission blends, galactic and intrinsic absorption lines, and performs multicomponent fits to the emission line profiles. We present measured line parameters (equivalent width and FWHM) for a large number (28) of different UV/optical lines, including upper limits for undetected lines. We also study the relations between the emission line equivalent widths and luminosity (the Baldwin effect), as well as redshift (evolution). We compare results from this HST FOS sample with our previous measurements of 993 QSOs in the Large Bright Quasar Survey using the same analysis technique and sum the samples to achieve better coverage of the luminosity-redshift plane. We confirm a significant Baldwin effect for UV iron emission from Green et al. and find that evolution dominates the effect for iron and for Si IV emission. The values of the Baldwin effect slopes for all UV emission lines and the dependence of the slopes on the sample's luminosity range point to a change of the SED as the cause of the Baldwin effect in the FOS sample.