Detection of Time Lags Between Quasar Continuum Emission Bands based on Pan-STARRS Light-curves

Abstract

We study the time lags between the continuum emission of quasars at different wavelengths, based on more than four years of multi-band ($g$, $r$, $i$, $z$) light-curves in the Pan-STARRS Medium Deep Fields. As photons from different bands emerge from different radial ranges in the accretion disk, the lags constrain the sizes of the accretion disks. We select 240 quasars with redshifts $z\approx 1$ or $z\approx 0.3$ that are relatively emission line free. The light curves are sampled from day to month timescales, which makes it possible to detect lags on the scale of the light crossing time of the accretion disks. With the code JAVELIN, we detect typical lags of several days in the rest frame between the $g$ band and the $riz$ bands. The detected lags are $\sim 2-3$ times larger than the light crossing time estimated from the standard thin disk model, consistent with the recently measured lag in NGC5548 and micro-lensing measurements of quasars. The lags in our sample are found to increase with increasing luminosity. Furthermore, the increase in lags going from $g-r$ to $g-i$ and then to $g-z$ is slower than predicted in the thin disk model, particularly for high luminosity quasars. The radial temperature profile in the disk must be different from what is assumed. We also find evidence that the lags decrease with increasing line ratios between ultraviolet FeII lines and MgII, which may point to changes in the accretion disk structure at higher metallicity.

18 pages, 17 Figures, 3 Tables, submitted to ApJ

References in corpus (11)

• A Catalog of Quasar Properties from SDSS DR7
• Modeling the Time Variability of SDSS Stripe 82 Quasars as a Damped Random Walk
• Space Telescope and Optical Reverberation Mapping Project. II. Swift and HST Reverberation Mapping of the Accretion Disk of NGC 5548
• Testing thermal reprocessing in AGN accretion discs
• Black hole masses and enrichment of z ~ 6 SDSS quasars
• Quasar Accretion Disks Are Strongly Inhomogeneous
• The Sloan Digital Sky Survey Reverberation Mapping Project: Technical Overview
• The Lick AGN Monitoring Project 2011: Spectroscopic Campaign and Emission-Line Light Curves
• Swift monitoring of NGC 5548: X-ray reprocessing and short term UV/optical variability
• On the variability of quasars: a link between Eddington ratio and optical variability?
• Correlated X-ray and Optical Variability in Mkn 509

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