Intrinsic narrow absorption lines in keck hires spectra of a sample of six quasars

Rajib Ganguly, Michael Eracleous, Jane Camilla Charlton, Christopher W. Churchill

Research output: Contribution to journalArticle

74 Citations (Scopus)

Abstract

In the course of a large survey of intervening Mg II absorbers in the spectra of quasars, the C IV emission lines of six of the target objects (three radio-loud and three radio-quiet) were observed serendipitously. In four of these six quasars, we detected "associated" narrow absorption lines with velocities within 5000 km s-1 of the quasar emission-line redshift (three of these four quasars are radio quiet while the other is radio loud). As a result of the original target selection, the small sample of six quasars is unbiased toward finding associated absorption lines. In three of these four cases, the absorption-line optical-depth ratios deviate from the prediction based on atomic physics, suggesting that the background photon source(s) are only partially covered by the absorbing medium and, by extension, that the absorption lines are intrinsic to the quasar. We have used the method of Barlow & Sargent to determine the effective coverage fraction of background source(s) and we have extended it to constrain the coverage fraction of the continuum and broad emission-line sources separately. We have also applied this refined method to the narrow intrinsic absorption lines in three additional quasars for which the necessary data were available from the literature. We find that in two objects from our sample, the continuum source must be partially covered regardless of the covering factor of the emission-line source. We discuss these results in the context of the properties of absorption lines observed in different types of active galaxies and related outflow phenomena. We cannot distinguish between possible mechanisms for the origin of the partial coverage signature, although we do consider possible observational tests. Finally, we speculate on how the gas responsible for the narrow lines may be related to the accretion disk wind that may be responsible for the broad absorption lines observed in some quasars.

Original languageEnglish (US)
Pages (from-to)2594-2607
Number of pages14
JournalAstronomical Journal
Volume117
Issue number6
DOIs
StatePublished - Jan 1 1999

Fingerprint

quasars
radio
continuums
active galaxies
atomic physics
optical depth
accretion disks
optical thickness
outflow
physics
accretion
absorbers
coverings
signatures
prediction
gas
photons
predictions
gases

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

Cite this

@article{469e9928f2a046ecad470df76398cbb8,
title = "Intrinsic narrow absorption lines in keck hires spectra of a sample of six quasars",
abstract = "In the course of a large survey of intervening Mg II absorbers in the spectra of quasars, the C IV emission lines of six of the target objects (three radio-loud and three radio-quiet) were observed serendipitously. In four of these six quasars, we detected {"}associated{"} narrow absorption lines with velocities within 5000 km s-1 of the quasar emission-line redshift (three of these four quasars are radio quiet while the other is radio loud). As a result of the original target selection, the small sample of six quasars is unbiased toward finding associated absorption lines. In three of these four cases, the absorption-line optical-depth ratios deviate from the prediction based on atomic physics, suggesting that the background photon source(s) are only partially covered by the absorbing medium and, by extension, that the absorption lines are intrinsic to the quasar. We have used the method of Barlow & Sargent to determine the effective coverage fraction of background source(s) and we have extended it to constrain the coverage fraction of the continuum and broad emission-line sources separately. We have also applied this refined method to the narrow intrinsic absorption lines in three additional quasars for which the necessary data were available from the literature. We find that in two objects from our sample, the continuum source must be partially covered regardless of the covering factor of the emission-line source. We discuss these results in the context of the properties of absorption lines observed in different types of active galaxies and related outflow phenomena. We cannot distinguish between possible mechanisms for the origin of the partial coverage signature, although we do consider possible observational tests. Finally, we speculate on how the gas responsible for the narrow lines may be related to the accretion disk wind that may be responsible for the broad absorption lines observed in some quasars.",
author = "Rajib Ganguly and Michael Eracleous and Charlton, {Jane Camilla} and Churchill, {Christopher W.}",
year = "1999",
month = "1",
day = "1",
doi = "10.1086/300882",
language = "English (US)",
volume = "117",
pages = "2594--2607",
journal = "Astronomical Journal",
issn = "0004-6256",
publisher = "IOP Publishing Ltd.",
number = "6",

}

Intrinsic narrow absorption lines in keck hires spectra of a sample of six quasars. / Ganguly, Rajib; Eracleous, Michael; Charlton, Jane Camilla; Churchill, Christopher W.

In: Astronomical Journal, Vol. 117, No. 6, 01.01.1999, p. 2594-2607.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Intrinsic narrow absorption lines in keck hires spectra of a sample of six quasars

AU - Ganguly, Rajib

AU - Eracleous, Michael

AU - Charlton, Jane Camilla

AU - Churchill, Christopher W.

PY - 1999/1/1

Y1 - 1999/1/1

N2 - In the course of a large survey of intervening Mg II absorbers in the spectra of quasars, the C IV emission lines of six of the target objects (three radio-loud and three radio-quiet) were observed serendipitously. In four of these six quasars, we detected "associated" narrow absorption lines with velocities within 5000 km s-1 of the quasar emission-line redshift (three of these four quasars are radio quiet while the other is radio loud). As a result of the original target selection, the small sample of six quasars is unbiased toward finding associated absorption lines. In three of these four cases, the absorption-line optical-depth ratios deviate from the prediction based on atomic physics, suggesting that the background photon source(s) are only partially covered by the absorbing medium and, by extension, that the absorption lines are intrinsic to the quasar. We have used the method of Barlow & Sargent to determine the effective coverage fraction of background source(s) and we have extended it to constrain the coverage fraction of the continuum and broad emission-line sources separately. We have also applied this refined method to the narrow intrinsic absorption lines in three additional quasars for which the necessary data were available from the literature. We find that in two objects from our sample, the continuum source must be partially covered regardless of the covering factor of the emission-line source. We discuss these results in the context of the properties of absorption lines observed in different types of active galaxies and related outflow phenomena. We cannot distinguish between possible mechanisms for the origin of the partial coverage signature, although we do consider possible observational tests. Finally, we speculate on how the gas responsible for the narrow lines may be related to the accretion disk wind that may be responsible for the broad absorption lines observed in some quasars.

AB - In the course of a large survey of intervening Mg II absorbers in the spectra of quasars, the C IV emission lines of six of the target objects (three radio-loud and three radio-quiet) were observed serendipitously. In four of these six quasars, we detected "associated" narrow absorption lines with velocities within 5000 km s-1 of the quasar emission-line redshift (three of these four quasars are radio quiet while the other is radio loud). As a result of the original target selection, the small sample of six quasars is unbiased toward finding associated absorption lines. In three of these four cases, the absorption-line optical-depth ratios deviate from the prediction based on atomic physics, suggesting that the background photon source(s) are only partially covered by the absorbing medium and, by extension, that the absorption lines are intrinsic to the quasar. We have used the method of Barlow & Sargent to determine the effective coverage fraction of background source(s) and we have extended it to constrain the coverage fraction of the continuum and broad emission-line sources separately. We have also applied this refined method to the narrow intrinsic absorption lines in three additional quasars for which the necessary data were available from the literature. We find that in two objects from our sample, the continuum source must be partially covered regardless of the covering factor of the emission-line source. We discuss these results in the context of the properties of absorption lines observed in different types of active galaxies and related outflow phenomena. We cannot distinguish between possible mechanisms for the origin of the partial coverage signature, although we do consider possible observational tests. Finally, we speculate on how the gas responsible for the narrow lines may be related to the accretion disk wind that may be responsible for the broad absorption lines observed in some quasars.

UR - http://www.scopus.com/inward/record.url?scp=0040921025&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0040921025&partnerID=8YFLogxK

U2 - 10.1086/300882

DO - 10.1086/300882

M3 - Article

AN - SCOPUS:0040921025

VL - 117

SP - 2594

EP - 2607

JO - Astronomical Journal

JF - Astronomical Journal

SN - 0004-6256

IS - 6

ER -