J/ApJ/817/119 Spitzer/IRAC variability survey of Bootes field (Kozlowski+, 2016)
Quasar variability in the mid-infrared.
Kozlowski S., Kochanek C.S., Ashby M.L.N., Assef R.J., Brodwin M.,
Eisenhardt P.R., Jannuzi B.T., Stern D.
<Astrophys. J., 817, 119 (2016)>
=2016ApJ...817..119K 2016ApJ...817..119K (SIMBAD/NED BibCode)
ADC_Keywords: QSOs ; Photometry, infrared ; Surveys ; Active gal. nuclei
Keywords: cosmology: observations; galaxies: active; infrared: galaxies;
quasars: general
Abstract:
The Decadal IRAC Bootes Survey is a mid-IR variability survey of the
∼9deg2 of the NDWFS Bootes Field and extends the time baseline of
its predecessor, the Spitzer Deep, Wide-Field Survey (SDWFS), from 4
to 10 years. The Spitzer Space Telescope visited the field five times
between 2004 and 2014 at 3.6 and 4.5µm. We provide the difference
image analysis photometry for a half a million mostly extragalactic
sources. In mid-IR color-color plane, sources with quasar colors
constitute the largest variability class (75%), 16% of the variable
objects have stellar colors and the remaining 9% have the colors of
galaxies. Adding the fifth epoch doubles the number of variable active
galactic nuclei (AGNs) for the same false positive rates as in SDWFS,
or increases the number of sources by 20% while decreasing the false
positive rates by factors of 2-3 for the same variability amplitude.
We quantify the ensemble mid-IR variability of ∼1500 spectroscopically
confirmed AGNs using single power-law structure functions (SFs), which
we find to be steeper (index γ∼0.45) than in the optical
(γ∼0.3), leading to much lower amplitudes at short time-lags.
This provides evidence for large emission regions, smoothing out any
fast UV/optical variations, as the origin of infrared quasar
variability. The mid-IR AGN SF slope γ seems to be uncorrelated
with both the luminosity and rest-frame wavelength, while the
amplitude shows an anti-correlation with the luminosity and a
correlation with the rest-frame wavelength.
Description:
A detailed description of Spitzer Deep Wide-Field Survey (SDWFS) is
presented in Ashby et al. (2009, see J/ApJ/716/530). The first epoch
was taken on 2004 January 10-14 as the IRAC Shallow Survey (Eisenhardt
et al. 2004ApJS..154...48E 2004ApJS..154...48E). Then, we added three more epochs on 2007
August 8-13, 2008 February 2-6, and 2008 March 6-10 as the SDWFS
(Ashby et al. 2009, see J/ApJ/716/530; D. Stern PI, PID 40839). The
new, fifth epoch was taken on 2014 April 23-29 as the Decadal IRAC
Bootes Survey (DIBS; M.L.N. Ashby PI, PID 10088). The intervals
between any two epochs span the range from 1 month to 10 years.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 90 514974 The 3.6 micron light curves for the Decadal IRAC
Bootes Survey (DIBS) variability catalog
table2.dat 90 514974 The 4.5 micron light curves for the Decadal IRAC
Bootes Survey (DIBS) variability catalog
table3.dat 169 514974 Decadal IRAC Bootes Survey (DIBS) variability catalog
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See also:
J/MNRAS/453/1562 : CRTS close supermassive black hole binaries (Graham+, 2015)
J/ApJ/806/128 : Space telescope RM project. I. NGC5548 (De Rosa+, 2015)
J/ApJ/804/27 : NIR photometry of hot dust-obscured galaxies (Assef+, 2015)
J/ApJ/801/127 : 3.6um, 4.5um, B & V light curves of NGC 6418 (Vazquez+, 2015)
J/MNRAS/441/715 : Mid-infrared study of RR Lyrae stars (Gavrilchenko+, 2014)
J/MNRAS/439/1648 : Subarcsecond mid-infrared atlas of local AGN (Asmus+, 2014)
J/ApJ/772/26 : AGN with WISE. II. The NDWFS Bootes field (Assef+, 2013)
J/ApJ/755/60 : Reverberation mapping for 5 Seyfert 1 galaxies (Grier+, 2012)
J/ApJ/754/45 : IR properties of Swift/BAT X-ray AGNs (Ichikawa+, 2012)
J/ApJS/200/8 : AGES: the AGN and Galaxy Evolution Survey (Kochanek+, 2012)
J/ApJ/728/26 : QSO selection based on photom. variability (Macleod+, 2011)
J/ApJ/717/1181 : Spitzer power-law galaxies in EGS (Park+, 2010)
J/ApJ/716/530 : Mid-IR variability from the SDWFS (Kozlowski+, 2010)
J/ApJ/713/970 : Low-resolution SED templates for AGNs & gal. (Assef+, 2010)
J/ApJ/709/572 : COSMOS 70um sources (Kartaltepe+, 2010)
J/ApJ/701/428 : The Spitzer Deep, Wide-Field Survey (SDWFS) (Ashby+, 2009)
J/ApJ/698/895 : Variations in QSOs optical flux (Kelly+, 2009)
J/ApJ/660/167 : Spitzer AGN candidates in CDFN (Donley+, 2007)
J/ApJS/166/470 : SDSS-Spitzer type I QSOs IR photometry (Richards+, 2006)
J/ApJ/641/140 : Optical counterparts in the NDWFS Bootes field (Brand+, 2006)
J/AJ/123/1784 : 1.4 GHz imaging of the Bootes field (de Vries+, 2002)
J/ApJS/95/1 : Atlas of Quasar Energy Distributions (Elvis+ 1994)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 10 F10.6 deg RAdeg Right Ascension in decimal degrees (J2000)
12- 20 F9.6 deg DEdeg Declination in decimal degrees (J2000)
22- 27 F6.3 mag 3.6mag1 [10.9/20.5]?=99.999 Epoch 1 Spitzer/IRAC 3.6um
band magnitude (G1)
29- 34 F6.3 mag 3.6mag2 ?=99.999 Epoch 2 Spitzer/IRAC 3.6um band mag (G1)
36- 41 F6.3 mag 3.6mag3 ?=99.999 Epoch 3 Spitzer/IRAC 3.6um band mag (G1)
43- 48 F6.3 mag 3.6mag4 ?=99.999 Epoch 4 Spitzer/IRAC 3.6um band mag (G1)
50- 55 F6.3 mag 3.6mag5 ?=99.999 Epoch 5 Spitzer/IRAC 3.6um band mag (G1)
57- 62 F6.3 mag e_3.6mag1 ?=99.999 The Epoch 1 1σ error in 3.6mag
64- 69 F6.3 mag e_3.6mag2 [0.01/0.6]?=99.999 The Epoch 2 1σ error
in 3.6mag
71- 76 F6.3 mag e_3.6mag3 ?=99.999 The Epoch 3 1σ error in 3.6mag
78- 83 F6.3 mag e_3.6mag4 ?=99.999 The Epoch 4 1σ error in 3.6mag
85- 90 F6.3 mag e_3.6mag5 ?=99.999 The Epoch 5 1σ error in 3.6mag
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 10 F10.6 deg RAdeg Right Ascension in decimal degrees (J2000)
12- 20 F9.6 deg DEdeg Declination in decimal degrees (J2000)
22- 27 F6.3 mag 4.5mag1 ?=99.999 Epoch 1 Spitzer/IRAC 4.5um band mag (G1)
29- 34 F6.3 mag 4.5mag2 ?=99.999 Epoch 2 Spitzer/IRAC 4.5um band mag (G1)
36- 41 F6.3 mag 4.5mag3 ?=99.999 Epoch 3 Spitzer/IRAC 4.5um band mag (G1)
43- 48 F6.3 mag 4.5mag4 [10.5/20.5]?=99.999 Epoch 4 Spitzer/IRAC 4.5um
band magnitude (G1)
50- 55 F6.3 mag 4.5mag5 ?=99.999 Epoch 5 Spitzer/IRAC 4.5um band mag (G1)
57- 62 F6.3 mag e_4.5mag1 ?=99.999 The Epoch 1 1σ error in 4.5mag
64- 69 F6.3 mag e_4.5mag2 [0.01/0.6]?=99.999 The Epoch 2 1σ error
in 4.5mag
71- 76 F6.3 mag e_4.5mag3 ?=99.999 The Epoch 3 1σ error in 4.5mag
78- 83 F6.3 mag e_4.5mag4 ?=99.999 The Epoch 4 1σ error in 4.5mag
85- 90 F6.3 mag e_4.5mag5 ?=99.999 The Epoch 5 1σ error in 4.5mag
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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- 4 A4 --- --- [DIBS]
6- 24 A19 --- DIBS Object name (JHHMMSS.ss+DDMMSS.s)
26- 35 F10.6 deg RAdeg Right Ascension in decimal degrees (J2000)
37- 45 F9.6 deg DEdeg Declination in decimal degrees (J2000)
47- 52 F6.3 mag 3.6mag [9.2/19.8] Spitzer/IRAC 3.6um band magnitude (1)
54- 58 F5.3 mag e_3.6mag [0/0.4] The 1σ error in 3.6mag
60- 65 F6.3 mag 4.5mag [8.3/25.9] Spitzer/IRAC 4.5um band magnitude (1)
67- 71 F5.3 mag e_4.5mag [0/5.2] The 1σ error in 4.5mag
73- 78 F6.3 mag 5.8mag [5.9/22]?=99.999 Spitzer/IRAC 5.8um band
magnitude (1)
80- 85 F6.3 mag e_5.8mag [0/5.2]?=99.999 The 1σ error in 5.8mag
87- 92 F6.3 mag 8.0mag [6.4/20.3]?=99.999 Spitzer/IRAC 8.0um band
magnitude (1)
94- 99 F6.3 mag e_8.0mag [0/5.2]?=99.999 The 1σ error in 8.0mag
101 I1 --- Ne1 [0/5] Number of epochs used in channel 1
103-107 F5.3 mag nu1 [0/3.5] Channel 1 dispersion
109-114 F6.3 --- Sig1 [-1.2/51.5] Channel 1 significance (2)
116 I1 --- Ne2 [0/5] Number of epochs used in channel 2
118-122 F5.3 mag nu2 [0/3] Channel 2 dispersion
124-129 F6.3 --- Sig2 [-2.2/60]?=99.999 Channel 2 significance (2)
131 I1 --- Ne [0/5] Common number of available epochs
133-138 F6.3 mag nu3.6 [0.001/4]?=99.999 Dispersion in channel 1
for common number of epochs
140-145 F6.3 mag nu4.5 [0/3.6]?=99.999 Dispersion in channel 2
for common number of epochs
147-152 F6.3 mag2 C12 [-3.6/2.2]?=99.999 Covariance between
channels 1 and 2
154-159 F6.3 --- r ?=99.999 Correlation between channels 1 and 2
161-167 F7.3 --- Sig12 [0.002/101]?=99.999 joint significance in
channels 1 and 2
169 I1 --- mask [0/1]? Mask code (3)
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Note (1): The Vega magnitudes presented in the table are measured in 4 arcsec
apertures; see Ashby et al. 2009, J/ApJ/701/428
Note (2): The variability significance with respect to the median
variability (ν-νm)/σ.
Note (3): Mask code as follows:
0 = bright star with 2MASS K-band magnitude within 260(1-K/11) arcsec
affecting the measurement;
1 = no bright star with 2MASS K-band magnitude within 260(1-K/11) arcsec
affecting the measurement.
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Global note:
Note (G1): See the "Description" section above for the explanations of Epoch:
1 = 2004 January 10-14 (IRAC Shallow Survey)
2 = 2007 August 8-13 (SDWFS)
3 = 2008 February 2-6 (SDWFS)
4 = 2008 March 6-10 (SDWFS)
5 = 2014 April 23-29 (DIBS)
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 18-Apr-2016