Broad absorption line disappearance and emergence using multiple-epoch spectroscopy from the Sloan Digital Sky Survey


MCGRAW S. M., Brandt W. N., GRIER C. J., Ak N., Hall P. B., Schneider D. P., ...More

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, vol.469, no.3, pp.3163-3184, 2017 (SCI-Expanded) identifier identifier

  • Publication Type: Article / Article
  • Volume: 469 Issue: 3
  • Publication Date: 2017
  • Doi Number: 10.1093/mnras/stx1063
  • Journal Name: MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
  • Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus
  • Page Numbers: pp.3163-3184
  • Keywords: galaxies: active, quasars: absorption lines, quasars: general, SUPERMASSIVE BLACK-HOLES, ACTIVE GALACTIC NUCLEI, DRIVEN DISK WINDS, AGN FEEDBACK, OBSERVATIONAL EVIDENCE, SHOOTER OBSERVATIONS, TIME VARIABILITY, SPACE-TELESCOPE, QUASAR OUTFLOWS, ACCRETION DISK
  • Erciyes University Affiliated: Yes

Abstract

We investigate broad absorption line (BAL) disappearance and emergence using a 470 BAL-quasar sample over <= 0.10-5.25 rest-frame years with at least three spectroscopic epochs for each quasar from the Sloan Digital Sky Survey. We identify 14 disappearing BALs over <= 1.73-4.62 rest-frame years and 18 emerging BALs over <= 1.46-3.66 rest-frame years associated with the C IV lambda 1548,1550 and/or Si IV lambda lambda 1393,1402 doublets, and report on their variability behaviour. BAL quasars in our data set exhibit disappearing/emerging C IV BALs at a rate of 2.3(-0.7)(+0.9) and 3.0(-0.8)(+1.0) per cent, respectively, and the frequency for BAL to non-BAL quasar transitions is 1.7(-0.6)(+0.8) per cent. We detect four re-emerging BALs over <= 3.88 rest-frame years on average and three re-disappearing BALs over <= 4.15 rest-frame years on average, the first reported cases of these types. We infer BAL lifetimes along the line of sight to be nominally less than or similar to 100-1000 yr using disappearing C IV BALs in our sample. Interpretations of (re-) emerging and (re-) disappearing BALs reveal evidence that collectively supports both transverse-motion and ionization-change scenarios to explain BAL variations. We constrain a nominal C IV/Si IV BAL-outflow location of less than or similar to 100 pc from the central source and a radial size of greater than or similar to 1x 10(-7) pc (0.02 au) using the ionization-change scenario, and constrain a nominal outflow location of less than or similar to 0.5 pc and a transverse size of similar to 0.01 pc using the transverse-motion scenario. Our findings are consistent with previous work, and provide evidence in support of BALs tracing compact flow geometries with small filling factors.