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Title: 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 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 ismore » 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.« less

Authors:
 [1]; ; ;  [2];  [3]; ;  [4]; ;  [5]; ;  [6];  [7];  [8];  [9]; ; ; ; ; ;  [10] more »; « less
  1. Kavli Institute for Theoretical Physics, University of California, Santa Barbara, CA 93106 (United States)
  2. Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)
  3. Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08544 (United States)
  4. Department of Astronomy, University of Illinois at Urbana-Champaign, Urbana, IL 61801 (United States)
  5. Department of Astronomy, University of Washington, Box 351580, Seattle, WA 98195 (United States)
  6. Department of Astronomy and Astrophysics, The Pennsylvania State University, University Park, PA 16802 (United States)
  7. Max Planck Institute for Astronomy, Königstuhl 17, D-69117 Heidelberg (Germany)
  8. Institute for Applied Computational Science, John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138 (United States)
  9. Astrophysics, Imperial College London, Blackett Laboratory, London SW7 2AZ (United Kingdom)
  10. Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu HI 96822 (United States)
Publication Date:
OSTI Identifier:
22667720
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 836; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ACCRETION DISKS; DETECTION; EMISSION; GALAXIES; GALAXY NUCLEI; LUMINOSITY; METALLICITY; PHOTONS; QUASARS; RED SHIFT; ULTRAVIOLET RADIATION; VISIBLE RADIATION; WAVELENGTHS

Citation Formats

Jiang, Yan-Fei, Green, Paul J., Pancoast, Anna, MacLeod, Chelsea L., Greene, Jenny E., Morganson, Eric, Shen, Yue, Anderson, Scott F., Ruan, John J., Brandt, W. N., Grier, C. J., Rix, H.-W., Protopapas, Pavlos, Scott, Caroline, Burgett, W. S., Hodapp, K. W., Huber, M. E., Kaiser, N., Kudritzki, R. P., Magnier, E. A., and and others. Detection of Time Lags between Quasar Continuum Emission Bands Based On Pan-STARRS Light Curves. United States: N. p., 2017. Web. doi:10.3847/1538-4357/AA5B91.
Jiang, Yan-Fei, Green, Paul J., Pancoast, Anna, MacLeod, Chelsea L., Greene, Jenny E., Morganson, Eric, Shen, Yue, Anderson, Scott F., Ruan, John J., Brandt, W. N., Grier, C. J., Rix, H.-W., Protopapas, Pavlos, Scott, Caroline, Burgett, W. S., Hodapp, K. W., Huber, M. E., Kaiser, N., Kudritzki, R. P., Magnier, E. A., & and others. Detection of Time Lags between Quasar Continuum Emission Bands Based On Pan-STARRS Light Curves. United States. doi:10.3847/1538-4357/AA5B91.
Jiang, Yan-Fei, Green, Paul J., Pancoast, Anna, MacLeod, Chelsea L., Greene, Jenny E., Morganson, Eric, Shen, Yue, Anderson, Scott F., Ruan, John J., Brandt, W. N., Grier, C. J., Rix, H.-W., Protopapas, Pavlos, Scott, Caroline, Burgett, W. S., Hodapp, K. W., Huber, M. E., Kaiser, N., Kudritzki, R. P., Magnier, E. A., and and others. Mon . "Detection of Time Lags between Quasar Continuum Emission Bands Based On Pan-STARRS Light Curves". United States. doi:10.3847/1538-4357/AA5B91.
@article{osti_22667720,
title = {Detection of Time Lags between Quasar Continuum Emission Bands Based On Pan-STARRS Light Curves},
author = {Jiang, Yan-Fei and Green, Paul J. and Pancoast, Anna and MacLeod, Chelsea L. and Greene, Jenny E. and Morganson, Eric and Shen, Yue and Anderson, Scott F. and Ruan, John J. and Brandt, W. N. and Grier, C. J. and Rix, H.-W. and Protopapas, Pavlos and Scott, Caroline and Burgett, W. S. and Hodapp, K. W. and Huber, M. E. and Kaiser, N. and Kudritzki, R. P. and Magnier, E. A. and and others},
abstractNote = {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 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.},
doi = {10.3847/1538-4357/AA5B91},
journal = {Astrophysical Journal},
number = 2,
volume = 836,
place = {United States},
year = {Mon Feb 20 00:00:00 EST 2017},
month = {Mon Feb 20 00:00:00 EST 2017}
}