J/ApJ/836/186 Continuum-band lags in SDSS QSOs from PS1 obs. (Jiang+, 2017)
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.
<Astrophys. J., 836, 186-186 (2017)>
=2017ApJ...836..186J 2017ApJ...836..186J (SIMBAD/NED BibCode)
ADC_Keywords: QSOs ; Photometry, ugriz ; Redshifts ; Surveys
Keywords: accretion, accretion disks; galaxies: active; galaxies: nuclei;
quasars: general
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 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.
Description:
We have chosen to study quasars in the Medium Deep Fields of the
Pan-STARRS1 (PS1) survey. The PS1 survey used a wide-field f/4.4
optical telescope system designed for survey mode operation at the
Haleakala Observatory on the island of Maui in Hawaii. The PS1
photometric system is described in Tonry+ (2012, J/ApJ/750/99), and
passband shapes are detailed in Stubbs+ (2010ApJS..191..376S 2010ApJS..191..376S).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 107 240 Sample summary
table3.dat 51 39 Rest frame lags for the subsample cLD (quasars
with significant detections; see section 4.1)
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See also:
V/147 : The SDSS Photometric Catalogue, Release 12 (Alam+, 2015)
VII/279 : SDSS quasar catalog: twelfth data release (Paris+, 2017)
J/ApJ/613/682 : AGN central masses & broad-line region sizes (Peterson+, 2004)
J/ApJ/622/129 : Lag-luminosity relationship in AGN (Sergeev+, 2005)
J/ApJ/633/638 : Variable quasar sample from SDSS (Wilhite+, 2005)
J/ApJ/698/895 : Variations in QSOs optical flux (Kelly+, 2009)
J/ApJS/194/45 : QSO properties from SDSS-DR7 (Shen+, 2011)
J/A+A/536/A84 : X-ray variability of AGN (Vagnetti+, 2011)
J/A+A/542/A83 : CAIXA. II. AGNs from excess variance analysis (Ponti+, 2012)
J/ApJ/750/99 : The Pan-STARRS1 photometric system (Tonry+, 2012)
J/ApJ/788/48 : X-ray through NIR photometry of NGC 2617 (Shappee+, 2014)
J/ApJS/217/26 : Lick AGN monitoring 2011: light curves (Barth+, 2015)
J/ApJ/806/129 : Space telescope RM project. II. Swift data (Edelson+, 2015)
J/ApJS/216/4 : SDSS-RM project: technical overview (Shen+, 2015)
J/ApJ/821/56 : Space telescope RM project. III. (Fausnaugh+, 2016)
J/ApJ/818/30 : Lag measurements for z<0.8 QSOs from the SDSS-RM (Shen+, 2016)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 19 A19 --- SDSS SDSS identifier
21- 28 F8.4 deg RAdeg Right Ascension in decimal degrees (J2000)
30- 36 F7.4 deg DEdeg Declination in decimal degrees (J2000)
38- 41 F4.2 --- z [0.1/1.1] Spectroscopic redshift
43- 47 F5.2 mag gmag [15.6/24.1] Pan-STARRS1 apparent
g band magnitude
49- 52 F4.2 mag e_gmag [0/0.5] Uncertainty in gmag
54- 58 F5.2 mag rmag [15.4/22.2] Pan-STARRS1 apparent
r band magnitude
60- 63 F4.2 mag e_rmag [0/0.2] Uncertainty in rmag
65- 69 F5.2 mag imag [15.4/22.1] Pan-STARRS1 apparent
i band magnitude
71- 74 F4.2 mag e_imag [0/0.2] Uncertainty in imag
76- 80 F5.2 mag zmag [15.2/23.4] Pan-STARRS1 apparent
z band magnitude
82- 85 F4.2 mag e_zmag [0.01/0.8] Uncertainty in zmag
87- 91 F5.2 [10-7W] logL [0/47] Log luminosity; erg/s
93- 97 F5.2 [solMass] logMBH [0/10] Log blackhole mass
99-107 A9 --- sigma2 Normalized g band excess variance
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 19 A19 --- SDSS SDSS identifier (JHHMMSS.ss+DDMMSS.s)
21- 25 F5.2 d dt(g-r) [-1.5/5.6] Rest frame lag Δtg-r
27- 30 F4.2 d e_dt(g-r) [0.2/5.3] dt(g-r) uncertainty
32- 35 F4.2 d dt(g-i) [0.8/9.3] Rest frame lag Δtg-i
37- 40 F4.2 d e_dt(g-i) [0.2/6.3] dt(g-i) uncertainty
42- 46 F5.2 d dt(g-z) [1.7/14.4] Rest frame lag Δtg-z
48- 51 F4.2 d e_dt(g-z) [0.2/3.8] dt(g-z) uncertainty
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 06-Oct-2017