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Detection of Time Lags between Quasar Continuum Emission Bands Based On Pan-STARRS Light Curves

Jiang, Y.-F.; Green, P.J.; Greene, J.E.; Morganson, E.; Shen, Y.; Pancoast, A.; MacLeod, C.L.; Anderson, S.F.; Brandt, W.N.; Grier, C.J.; Rix, H.-W.; Ruan, J.J.; Protopapas, P.; Scott, C.; Burgett, W.S.; Hodapp, K.W.; Huber, M.E.; Kaiser, N.; Kudritzki, R.P.; Magnier, E.A.; Metcalfe, N.; Tonry, J.T.; Wainscoat, R.J.; Waters, C.

Detection of Time Lags between Quasar Continuum Emission Bands Based On Pan-STARRS Light Curves Thumbnail


Authors

Y.-F. Jiang

P.J. Green

J.E. Greene

E. Morganson

Y. Shen

A. Pancoast

C.L. MacLeod

S.F. Anderson

W.N. Brandt

C.J. Grier

H.-W. Rix

J.J. Ruan

P. Protopapas

C. Scott

W.S. Burgett

K.W. Hodapp

M.E. Huber

N. Kaiser

R.P. Kudritzki

E.A. Magnier

J.T. Tonry

R.J. Wainscoat

C. Waters



Abstract

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 of z ≈ 1 or z ≈ 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 ~2–3 times larger than the light crossing time estimated from the standard thin disk model, consistent with the recently measured lag in NGC 5548 and microlensing 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 Fe ii lines and Mg ii, which may point to changes in the accretion disk structure at higher metallicity.

Citation

Jiang, Y., Green, P., Greene, J., Morganson, E., Shen, Y., Pancoast, A., …Waters, C. (2017). Detection of Time Lags between Quasar Continuum Emission Bands Based On Pan-STARRS Light Curves. Astrophysical Journal, 836(2), Article 186. https://doi.org/10.3847/1538-4357/aa5b91

Journal Article Type Article
Acceptance Date Jan 13, 2017
Online Publication Date Feb 21, 2017
Publication Date Feb 21, 2017
Deposit Date Mar 30, 2017
Publicly Available Date Mar 31, 2017
Journal Astrophysical Journal
Print ISSN 0004-637X
Electronic ISSN 0571-7248
Publisher American Astronomical Society
Peer Reviewed Peer Reviewed
Volume 836
Issue 2
Article Number 186
DOI https://doi.org/10.3847/1538-4357/aa5b91

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Copyright Statement
© 2017. The American Astronomical Society. All rights reserved.





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