The Sloan Digital Sky Survey Reverberation Mapping Project: Composite Lags at z ≤ 1

Jennifer Li, Yue Shen, Keith Horne, W. N. Brandt, Jenny E. Greene, C. J. Grier, Luis C. Ho, Chris Kochanek, Donald P. Schneider, Jonathan R. Trump, Kyle S. Dawson, Kaike Pan, Dmitry Bizyaev, Daniel Oravetz, Audrey Simmons, Elena Malanushenko

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Abstract

We present composite broad-line region (BLR) reverberation mapping lag measurements for Hα, Hβ, He ii λ4686, and Mg ii for a sample of 144, z ≲ 1 quasars from the Sloan Digital Sky Survey Reverberation Mapping (SDSS-RM)roject. Using only the 32-epoch spectroscopic light curves in the first six-month season of SDSS-RM observations, we compile correlation function measurements for individual objects and then coadd them to allow the measurement of the average lags for our sample at mean redshifts of 0.4 (for Hα) and ∼0.65 (for the other lines). At similar quasar luminosities and redshifts, the sample-averaged lag decreases in the order of Mg ii, Hα, Hβ, and He ii. This decrease in lags is accompanied by an increase in the mean line width of the four lines, and is roughly consistent with the virialized motion for BLR gas in photoionization equilibrium. These are among the first RM measurements of stratified BLR structure at z > 0.3. Dividing our sample by luminosity, Hα shows clear evidence of increasing lags with luminosity, consistent with the expectation from the measured BLR size-luminosity relation based on Hβ. The other three lines do not show a clear luminosity trend in their average lags due to the limited dynamic range of luminosity probed and the poor average correlation signals in the divided samples, a situation that will be improved with the incorporation of additional photometric and spectroscopic data from SDSS-RM. We discuss the utility and caveats of composite lag measurements for large statistical quasar samples with reverberation mapping data.

Original languageEnglish (US)
Article number79
JournalAstrophysical Journal
Volume846
Issue number1
DOIs
StatePublished - Sep 1 2017

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reverberation
time lag
luminosity
composite materials
quasars
project
light curve
dynamic range
photoionization
time measurement
trends
gas
gases

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

Cite this

Li, Jennifer ; Shen, Yue ; Horne, Keith ; Brandt, W. N. ; Greene, Jenny E. ; Grier, C. J. ; Ho, Luis C. ; Kochanek, Chris ; Schneider, Donald P. ; Trump, Jonathan R. ; Dawson, Kyle S. ; Pan, Kaike ; Bizyaev, Dmitry ; Oravetz, Daniel ; Simmons, Audrey ; Malanushenko, Elena. / The Sloan Digital Sky Survey Reverberation Mapping Project : Composite Lags at z ≤ 1. In: Astrophysical Journal. 2017 ; Vol. 846, No. 1.
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title = "The Sloan Digital Sky Survey Reverberation Mapping Project: Composite Lags at z ≤ 1",
abstract = "We present composite broad-line region (BLR) reverberation mapping lag measurements for Hα, Hβ, He ii λ4686, and Mg ii for a sample of 144, z ≲ 1 quasars from the Sloan Digital Sky Survey Reverberation Mapping (SDSS-RM)roject. Using only the 32-epoch spectroscopic light curves in the first six-month season of SDSS-RM observations, we compile correlation function measurements for individual objects and then coadd them to allow the measurement of the average lags for our sample at mean redshifts of 0.4 (for Hα) and ∼0.65 (for the other lines). At similar quasar luminosities and redshifts, the sample-averaged lag decreases in the order of Mg ii, Hα, Hβ, and He ii. This decrease in lags is accompanied by an increase in the mean line width of the four lines, and is roughly consistent with the virialized motion for BLR gas in photoionization equilibrium. These are among the first RM measurements of stratified BLR structure at z > 0.3. Dividing our sample by luminosity, Hα shows clear evidence of increasing lags with luminosity, consistent with the expectation from the measured BLR size-luminosity relation based on Hβ. The other three lines do not show a clear luminosity trend in their average lags due to the limited dynamic range of luminosity probed and the poor average correlation signals in the divided samples, a situation that will be improved with the incorporation of additional photometric and spectroscopic data from SDSS-RM. We discuss the utility and caveats of composite lag measurements for large statistical quasar samples with reverberation mapping data.",
author = "Jennifer Li and Yue Shen and Keith Horne and Brandt, {W. N.} and Greene, {Jenny E.} and Grier, {C. J.} and Ho, {Luis C.} and Chris Kochanek and Schneider, {Donald P.} and Trump, {Jonathan R.} and Dawson, {Kyle S.} and Kaike Pan and Dmitry Bizyaev and Daniel Oravetz and Audrey Simmons and Elena Malanushenko",
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Li, J, Shen, Y, Horne, K, Brandt, WN, Greene, JE, Grier, CJ, Ho, LC, Kochanek, C, Schneider, DP, Trump, JR, Dawson, KS, Pan, K, Bizyaev, D, Oravetz, D, Simmons, A & Malanushenko, E 2017, 'The Sloan Digital Sky Survey Reverberation Mapping Project: Composite Lags at z ≤ 1', Astrophysical Journal, vol. 846, no. 1, 79. https://doi.org/10.3847/1538-4357/aa845d

The Sloan Digital Sky Survey Reverberation Mapping Project : Composite Lags at z ≤ 1. / Li, Jennifer; Shen, Yue; Horne, Keith; Brandt, W. N.; Greene, Jenny E.; Grier, C. J.; Ho, Luis C.; Kochanek, Chris; Schneider, Donald P.; Trump, Jonathan R.; Dawson, Kyle S.; Pan, Kaike; Bizyaev, Dmitry; Oravetz, Daniel; Simmons, Audrey; Malanushenko, Elena.

In: Astrophysical Journal, Vol. 846, No. 1, 79, 01.09.2017.

Research output: Contribution to journalArticle

TY - JOUR

T1 - The Sloan Digital Sky Survey Reverberation Mapping Project

T2 - Composite Lags at z ≤ 1

AU - Li, Jennifer

AU - Shen, Yue

AU - Horne, Keith

AU - Brandt, W. N.

AU - Greene, Jenny E.

AU - Grier, C. J.

AU - Ho, Luis C.

AU - Kochanek, Chris

AU - Schneider, Donald P.

AU - Trump, Jonathan R.

AU - Dawson, Kyle S.

AU - Pan, Kaike

AU - Bizyaev, Dmitry

AU - Oravetz, Daniel

AU - Simmons, Audrey

AU - Malanushenko, Elena

PY - 2017/9/1

Y1 - 2017/9/1

N2 - We present composite broad-line region (BLR) reverberation mapping lag measurements for Hα, Hβ, He ii λ4686, and Mg ii for a sample of 144, z ≲ 1 quasars from the Sloan Digital Sky Survey Reverberation Mapping (SDSS-RM)roject. Using only the 32-epoch spectroscopic light curves in the first six-month season of SDSS-RM observations, we compile correlation function measurements for individual objects and then coadd them to allow the measurement of the average lags for our sample at mean redshifts of 0.4 (for Hα) and ∼0.65 (for the other lines). At similar quasar luminosities and redshifts, the sample-averaged lag decreases in the order of Mg ii, Hα, Hβ, and He ii. This decrease in lags is accompanied by an increase in the mean line width of the four lines, and is roughly consistent with the virialized motion for BLR gas in photoionization equilibrium. These are among the first RM measurements of stratified BLR structure at z > 0.3. Dividing our sample by luminosity, Hα shows clear evidence of increasing lags with luminosity, consistent with the expectation from the measured BLR size-luminosity relation based on Hβ. The other three lines do not show a clear luminosity trend in their average lags due to the limited dynamic range of luminosity probed and the poor average correlation signals in the divided samples, a situation that will be improved with the incorporation of additional photometric and spectroscopic data from SDSS-RM. We discuss the utility and caveats of composite lag measurements for large statistical quasar samples with reverberation mapping data.

AB - We present composite broad-line region (BLR) reverberation mapping lag measurements for Hα, Hβ, He ii λ4686, and Mg ii for a sample of 144, z ≲ 1 quasars from the Sloan Digital Sky Survey Reverberation Mapping (SDSS-RM)roject. Using only the 32-epoch spectroscopic light curves in the first six-month season of SDSS-RM observations, we compile correlation function measurements for individual objects and then coadd them to allow the measurement of the average lags for our sample at mean redshifts of 0.4 (for Hα) and ∼0.65 (for the other lines). At similar quasar luminosities and redshifts, the sample-averaged lag decreases in the order of Mg ii, Hα, Hβ, and He ii. This decrease in lags is accompanied by an increase in the mean line width of the four lines, and is roughly consistent with the virialized motion for BLR gas in photoionization equilibrium. These are among the first RM measurements of stratified BLR structure at z > 0.3. Dividing our sample by luminosity, Hα shows clear evidence of increasing lags with luminosity, consistent with the expectation from the measured BLR size-luminosity relation based on Hβ. The other three lines do not show a clear luminosity trend in their average lags due to the limited dynamic range of luminosity probed and the poor average correlation signals in the divided samples, a situation that will be improved with the incorporation of additional photometric and spectroscopic data from SDSS-RM. We discuss the utility and caveats of composite lag measurements for large statistical quasar samples with reverberation mapping data.

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