The Sloan Digital Sky Survey Reverberation Mapping Project: Comparison of Lag Measurement Methods with Simulated Observations

Jennifer I.Hsiu Li, Yue Shen, W. N. Brandt, C. J. Grier, P. B. Hall, L. C. Ho, Y. Homayouni, K. Horne, D. P. Schneider, J. R. Trump, D. A. Starkey

Research output: Contribution to journalArticle

1 Citation (Scopus)

Abstract

We investigate the performance of different methodologies that measure the time lag between broad-line and continuum variations in reverberation mapping data using simulated light curves that probe a range of cadence, time baseline, and signal-to-noise ratio in the flux measurements. We compare three widely adopted lag-measuring methods: the interpolated cross-correlation function (ICCF), the z-transformed discrete correlation function (ZDCF), and the Markov chain Monte Carlo code JAVELIN, for mock data with qualities typical of multiobject spectroscopic reverberation mapping (MOS-RM) surveys that simultaneously monitor hundreds of quasars. We quantify the overall lag-detection efficiency, the rate of false detections, and the quality of lag measurements for each of these methods and under different survey designs (e.g., observing cadence and depth) using mock quasar light curves. Overall JAVELIN and ICCF outperform ZDCF in essentially all tests performed. Compared with ICCF, JAVELIN produces higher quality lag measurements, is capable of measuring more lags with timescales shorter than the observing cadence, is less susceptible to seasonal gaps and signal-to-noise ratio degradation in the light curves, and produces more accurate lag uncertainties. We measure the Hβ broad-line region size-luminosity (R-L) relation with each method using the simulated light curves to assess the impact of selection effects of the design of MOS-RM surveys. The slope of the R-L relation measured by JAVELIN is the least biased among the three methods and is consistent across different survey designs. These results demonstrate a clear preference for JAVELIN over the other two nonparametric methods for MOS-RM programs, particularly in the regime of limited light-curve quality as expected from most MOS-RM programs.

Original languageEnglish (US)
Article number119
JournalAstrophysical Journal
Volume884
Issue number2
DOIs
StatePublished - Oct 20 2019

Fingerprint

measurement method
reverberation
time lag
light curve
survey design
cross correlation
signal-to-noise ratio
quasars
signal to noise ratios
flux measurement
luminosity
Markov chain
Markov chains
probe
comparison
project
timescale
monitors
methodology
method

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

Cite this

Li, Jennifer I.Hsiu ; Shen, Yue ; Brandt, W. N. ; Grier, C. J. ; Hall, P. B. ; Ho, L. C. ; Homayouni, Y. ; Horne, K. ; Schneider, D. P. ; Trump, J. R. ; Starkey, D. A. / The Sloan Digital Sky Survey Reverberation Mapping Project : Comparison of Lag Measurement Methods with Simulated Observations. In: Astrophysical Journal. 2019 ; Vol. 884, No. 2.
@article{ea13fd1d862e46d4a2f8b0137d9a8803,
title = "The Sloan Digital Sky Survey Reverberation Mapping Project: Comparison of Lag Measurement Methods with Simulated Observations",
abstract = "We investigate the performance of different methodologies that measure the time lag between broad-line and continuum variations in reverberation mapping data using simulated light curves that probe a range of cadence, time baseline, and signal-to-noise ratio in the flux measurements. We compare three widely adopted lag-measuring methods: the interpolated cross-correlation function (ICCF), the z-transformed discrete correlation function (ZDCF), and the Markov chain Monte Carlo code JAVELIN, for mock data with qualities typical of multiobject spectroscopic reverberation mapping (MOS-RM) surveys that simultaneously monitor hundreds of quasars. We quantify the overall lag-detection efficiency, the rate of false detections, and the quality of lag measurements for each of these methods and under different survey designs (e.g., observing cadence and depth) using mock quasar light curves. Overall JAVELIN and ICCF outperform ZDCF in essentially all tests performed. Compared with ICCF, JAVELIN produces higher quality lag measurements, is capable of measuring more lags with timescales shorter than the observing cadence, is less susceptible to seasonal gaps and signal-to-noise ratio degradation in the light curves, and produces more accurate lag uncertainties. We measure the Hβ broad-line region size-luminosity (R-L) relation with each method using the simulated light curves to assess the impact of selection effects of the design of MOS-RM surveys. The slope of the R-L relation measured by JAVELIN is the least biased among the three methods and is consistent across different survey designs. These results demonstrate a clear preference for JAVELIN over the other two nonparametric methods for MOS-RM programs, particularly in the regime of limited light-curve quality as expected from most MOS-RM programs.",
author = "Li, {Jennifer I.Hsiu} and Yue Shen and Brandt, {W. N.} and Grier, {C. J.} and Hall, {P. B.} and Ho, {L. C.} and Y. Homayouni and K. Horne and Schneider, {D. P.} and Trump, {J. R.} and Starkey, {D. A.}",
year = "2019",
month = "10",
day = "20",
doi = "10.3847/1538-4357/ab41fb",
language = "English (US)",
volume = "884",
journal = "Astrophysical Journal",
issn = "0004-637X",
publisher = "IOP Publishing Ltd.",
number = "2",

}

The Sloan Digital Sky Survey Reverberation Mapping Project : Comparison of Lag Measurement Methods with Simulated Observations. / Li, Jennifer I.Hsiu; Shen, Yue; Brandt, W. N.; Grier, C. J.; Hall, P. B.; Ho, L. C.; Homayouni, Y.; Horne, K.; Schneider, D. P.; Trump, J. R.; Starkey, D. A.

In: Astrophysical Journal, Vol. 884, No. 2, 119, 20.10.2019.

Research output: Contribution to journalArticle

TY - JOUR

T1 - The Sloan Digital Sky Survey Reverberation Mapping Project

T2 - Comparison of Lag Measurement Methods with Simulated Observations

AU - Li, Jennifer I.Hsiu

AU - Shen, Yue

AU - Brandt, W. N.

AU - Grier, C. J.

AU - Hall, P. B.

AU - Ho, L. C.

AU - Homayouni, Y.

AU - Horne, K.

AU - Schneider, D. P.

AU - Trump, J. R.

AU - Starkey, D. A.

PY - 2019/10/20

Y1 - 2019/10/20

N2 - We investigate the performance of different methodologies that measure the time lag between broad-line and continuum variations in reverberation mapping data using simulated light curves that probe a range of cadence, time baseline, and signal-to-noise ratio in the flux measurements. We compare three widely adopted lag-measuring methods: the interpolated cross-correlation function (ICCF), the z-transformed discrete correlation function (ZDCF), and the Markov chain Monte Carlo code JAVELIN, for mock data with qualities typical of multiobject spectroscopic reverberation mapping (MOS-RM) surveys that simultaneously monitor hundreds of quasars. We quantify the overall lag-detection efficiency, the rate of false detections, and the quality of lag measurements for each of these methods and under different survey designs (e.g., observing cadence and depth) using mock quasar light curves. Overall JAVELIN and ICCF outperform ZDCF in essentially all tests performed. Compared with ICCF, JAVELIN produces higher quality lag measurements, is capable of measuring more lags with timescales shorter than the observing cadence, is less susceptible to seasonal gaps and signal-to-noise ratio degradation in the light curves, and produces more accurate lag uncertainties. We measure the Hβ broad-line region size-luminosity (R-L) relation with each method using the simulated light curves to assess the impact of selection effects of the design of MOS-RM surveys. The slope of the R-L relation measured by JAVELIN is the least biased among the three methods and is consistent across different survey designs. These results demonstrate a clear preference for JAVELIN over the other two nonparametric methods for MOS-RM programs, particularly in the regime of limited light-curve quality as expected from most MOS-RM programs.

AB - We investigate the performance of different methodologies that measure the time lag between broad-line and continuum variations in reverberation mapping data using simulated light curves that probe a range of cadence, time baseline, and signal-to-noise ratio in the flux measurements. We compare three widely adopted lag-measuring methods: the interpolated cross-correlation function (ICCF), the z-transformed discrete correlation function (ZDCF), and the Markov chain Monte Carlo code JAVELIN, for mock data with qualities typical of multiobject spectroscopic reverberation mapping (MOS-RM) surveys that simultaneously monitor hundreds of quasars. We quantify the overall lag-detection efficiency, the rate of false detections, and the quality of lag measurements for each of these methods and under different survey designs (e.g., observing cadence and depth) using mock quasar light curves. Overall JAVELIN and ICCF outperform ZDCF in essentially all tests performed. Compared with ICCF, JAVELIN produces higher quality lag measurements, is capable of measuring more lags with timescales shorter than the observing cadence, is less susceptible to seasonal gaps and signal-to-noise ratio degradation in the light curves, and produces more accurate lag uncertainties. We measure the Hβ broad-line region size-luminosity (R-L) relation with each method using the simulated light curves to assess the impact of selection effects of the design of MOS-RM surveys. The slope of the R-L relation measured by JAVELIN is the least biased among the three methods and is consistent across different survey designs. These results demonstrate a clear preference for JAVELIN over the other two nonparametric methods for MOS-RM programs, particularly in the regime of limited light-curve quality as expected from most MOS-RM programs.

UR - http://www.scopus.com/inward/record.url?scp=85075146201&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=85075146201&partnerID=8YFLogxK

U2 - 10.3847/1538-4357/ab41fb

DO - 10.3847/1538-4357/ab41fb

M3 - Article

AN - SCOPUS:85075146201

VL - 884

JO - Astrophysical Journal

JF - Astrophysical Journal

SN - 0004-637X

IS - 2

M1 - 119

ER -