BROAD ABSORPTION LINE DISAPPEARANCE ON MULTI-YEAR TIMESCALES IN A LARGE QUASAR SAMPLE

Journal Article · Mon Oct 01 04:00:00 EDT 2012 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/757/2/114· OSTI ID:22092213

Filiz Ak, N.; Brandt, W. N.; Schneider, D. P. ^[1]; Hall, P. B. ^[2]; Anderson, S. F.; Gibson, R. R. ^[3]; Lundgren, B. F. ^[4]; Myers, A. D. ^[5]; Petitjean, P. ^[6]; Ross, Nicholas P. ^[7]; Yue, Shen ^[8]; York, D. G. ^[9]; Bizyaev, D.; Brinkmann, J.; Malanushenko, E.; Oravetz, D. J.; Pan, K.; Simmons, A. E. ^[10]

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1. Department of Astronomy and Astrophysics, Pennsylvania State University, University Park, PA 16802 (United States)
2. Department of Physics and Astronomy, York University, 4700 Keele St., Toronto, Ontario M3J 1P3 (Canada)
3. Astronomy Department, University of Washington, Seattle, WA 98195 (United States)
4. Department of Physics, Yale University, New Haven, CT 06511 (United States)
5. Department of Physics and Astronomy, University of Wyoming, Laramie, WY 82071 (United States)
6. Institut d'Astrophysique de Paris, Universite Paris 6, F-75014, Paris (France)
7. Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 92420 (United States)
8. Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, MS-51, Cambridge, MA 02138 (United States)
9. Department of Astronomy and Astrophysics, and Enrico Fermi Institute, University of Chicago, 5640 S. Ellis Ave., Chicago, IL 60637 (United States)
10. Apache Point Observatory, P.O. Box 59, Sunspot, NM 88349-0059 (United States)

We present 21 examples of C IV broad absorption line (BAL) trough disappearance in 19 quasars selected from systematic multi-epoch observations of 582 bright BAL quasars (1.9 < z < 4.5) by the Sloan Digital Sky Survey-I/II (SDSS-I/II) and SDSS-III. The observations span 1.1-3.9 yr rest-frame timescales, longer than have been sampled in many previous BAL variability studies. On these timescales, Almost-Equal-To 2.3% of C IV BAL troughs disappear and Almost-Equal-To 3.3% of BAL quasars show a disappearing trough. These observed frequencies suggest that many C IV BAL absorbers spend on average at most a century along our line of sight to their quasar. Ten of the 19 BAL quasars showing C IV BAL disappearance have apparently transformed from BAL to non-BAL quasars; these are the first reported examples of such transformations. The BAL troughs that disappear tend to be those with small-to-moderate equivalent widths, relatively shallow depths, and high outflow velocities. Other non-disappearing C IV BALs in those nine objects having multiple troughs tend to weaken when one of them disappears, indicating a connection between the disappearing and non-disappearing troughs, even for velocity separations as large as 10,000-15,000 km s{sup -1}. We discuss possible origins of this connection including disk-wind rotation and changes in shielding gas.

• OSTI ID: 22092213
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 2 Vol. 757; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
ABSORPTION SPECTRA
ABSORPTION SPECTROSCOPY
ASTRONOMY
ASTROPHYSICS
CARBON IONS
QUASARS
ROTATION
STELLAR WINDS