Variability of Narrow, Associated Absorption Lines in Moderate- and Low-Redshift Quasars

Abstract

We present the results of a search for variability in the equivalent widths (EWs) of narrow, associated (Delta v < 5,000 km/s) absorption lines found in the UV spectra of z < 1.5 quasars. The goal of this search was to use variability as a means of identifying absorption lines arising in gas that is intrinsic to the quasar central engine. We have compared archival HST/FOS spectra of quasars with recent spectra obtained as part of our own snapshot survey of the same objects with STIS. The intervals between observations are 4-10 years. We primarily focused on the C IV absorption lines, although we also studied other lines available in the same spectra (e.g., Ly-alpha, N V, O VI). Our main result is that 4 out of 15 quasars, or 4 out of 19 associated absorption systems, contained variable narrow absorption lines, which are indicative of intrinsic absorption. We conclude that a minimum of 21% of the associated absorption-line systems are variable. Because not all systems will have necessarily varied, this is a lower limit on this fraction and it is consistent with previous estimates based on variability, partial coverage analysis, or statistical arguments. If we interpret the upper limits on the variability time scale as upper limits on the recombination time of the absorber, we constrain the density of the absorber to be n_e > 3000 cm^{-3} and its distance from the ionizing source to be R < 100pc. Moreover, we are now able to pick out specific intrinsic absorption-line systems to be followed up with high-dispersion spectroscopy in order to constrain the geometry, location, and physical conditions of the absorber. We briefly illustrate how followup studies can yield such constraints by means of a simulation.

arXiv comment42 pages, including 2 tables and 8 figures. To appear in ApJ, vol. 613, 20 Sep. 2004

References in corpus (14)

• Reverberation Measurements for 17 Quasars and the Size-Mass-Luminosity Relations in Active Galactic Nuclei
• Dynamics of line-driven disk winds in Active Galactic Nuclei
• On the Nature of Soft X-ray Weak Quasi-Stellar Objects
• Keck High Resolution Spectroscopy of PKS 0123+257: Intrinsic Absorption in a Radio Loud Quasar
• Conference Summary: AGN Physics with the Sloan Digital Sky Survey
• The Hubble Space Telescope Quasar Absorption Line Key Project XIII. A Census of Absorption Line Systems at Low Redshift
• On the Origin of Intrinsic Narrow Absorption Lines in z<1 QSOs
• Variability Tests for Intrinsic Absorption Lines in Quasar Spectra
• Accurate Redshifts and Classifications for 110 Radio-Loud AGNs
• A uniform analysis of the Lyman alpha forest at z = 0-5: III. HST FOS Spectral Atlas
• Determining the Fraction of Intrinsic CIV Absorption in Quasi-Stellar Object Absorption Line Systems
• Variable UV Absorption in the Spectrum of MRC 2251-178
• The Nature and Origin of z_a~z_e Absorption Lines in the Redshift 0.20 Quasar, PKS 2135-147
• The Identification of Quasars Behind Elliptical Galaxies and Clusters of Galaxies

Cited by in corpus (39)

• On the Fraction of Quasars with Outflows
• Quasar Broad Absorption Line Variability on Multi-Year Time Scales
• Variability in Quasar Broad Absorption Line Outflows I. Trends in the Short-Term versus Long-Term Data
• Outflows and the Physical Properties of Quasars
• A Census of Intrinsic Narrow Absorption Lines in the Spectra of Quasars at z=2-4
• Broad Absorption Line Variability in Repeat Quasar Observations from the Sloan Digital Sky Survey
• Multi-wavelength study of the gravitational lens system RXS J1131-1231: III. Long slit spectroscopy: micro-lensing probes the QSO structure
• Variability in quasar broad absorption line outflows II. Multi-epoch monitoring of SiIV and CIV BAL variability
• The Role of Galactic Winds on Molecular Gas Emission from Galaxy Mergers
• The Quasar-frame Velocity Distribution of Narrow CIV Absorbers
• The nature of proximate damped Lyman alpha systems
• Results of Monitoring the Dramatically Variable C IV Mini-BAL System in the Quasar HS 1603+3820
• Time-Variable Complex Metal Absorption Lines in the Quasar HS1603+3820
• Probing the Origins of the CIV and Fe Kalpha Baldwin Effect
• Monitoring the Variability of Intrinsic Absorption Lines in Quasar Spectra
• High-Resolution Absorption Spectroscopy of Multi-phase, High-Metallicity Gas Associated with the Luminous Quasar HE 0226-4110
• Unusual high-redshift radio BAL quasar 1624+3758
• Metal Absorption Systems in Spectra of Pairs of QSOs
• Discovery of the Transition of a Mini-Broad Absorption Line into Broad Absorption in the SDSS Quasar J115122.14+020426.3
• Narrow absorption line variability in repeat quasar observations from the Sloan Digital Sky Survey
• Narrow absorption lines with two observations of Sloan Digital Sky Survey
• The Physical Conditions of the Intrinsic N V Narrow Absorption Line Systems of Three Quasars
• Evidence for photoionization-driven variability in narrow absorption lines
• The Gaseous Environments of Quasars: Associate Absorption Lines with Density and Distance Constraints
• Emergences of C IV narrow absorption troughs in the quasar SDSS J095254.10+021932.8
• The correlated variations of C IV narrow absorption lines and quasar continuum
• Resolving the Clumpy Structure of the Outflow Winds in the Gravitationally Lensed Quasar SDSS J1029+2623
• Spectroscopy along Multiple, Lensed Sightlines through Outflowing Winds in the Quasar SDSS J1029+2623
• Disappearance of a narrow Mg II absorption system with a measured velocity up to $166,000km{\mathrm{s}}^{-1}$
• Time variations of narrow absorption lines in high resolution quasar spectra
• Search for intrinsic NALs in BAL/mini-BAL quasar spectra
• Hubble Space Telescope Ultraviolet Spectroscopy of Fourteen Low-Redshift Quasars
• A Spectropolarimetric Test of the Structure of the Intrinsic Absorbers in the Quasar HS1603+3820
• Multi-Sightline Observation of Narrow Absorption Lines in Lensed Quasar SDSS J1029+2623
• Narrow C IV absorption doublets on quasar spectra of the Baryon Oscillation Spectroscopic Survey
• The disappearance of a narrow Mg II absorption system in quasar SDSS J165501.31+260517.4
• On The Fine Tuning and Physical Origin of Line-Locked Absorption Systems in Active Galaxies
• Nature and Origins of Rich Complexes of C IV Associated Absorption Lines
• Spectroscopic Observations of the Outflowing Wind in the Lensed Quasar SDSS J1001+5027