J/ApJ/716/530 Mid-IR variability from the SDWFS (Kozlowski+, 2010)
Mid-infrared variability from the Spitzer deep wide-field survey.
Kozlowski S., Kochanek C.S., Stern D., Ashby M.L.N., Assef R.J., Bock J.J.,
Borys C., Brand K., Brodwin M., Brown M.J.I., Cool R., Cooray A., Croft S.,
Dey A., Eisenhardt P.R., Gonzalez A., Gorjian V., Griffith R., Grogin N.,
Ivison R., Jacob J., Jannuzi B.T., Mainzer A., Moustakas L., Rottgering H.,
Seymour N., Smith H.A., Stanford S.A., Stauffer J.R., Sullivan I.S.,
van Breugel W., Willner S.P., Wright E.L.
<Astrophys. J., 716, 530-543 (2010)>
=2010ApJ...716..530K 2010ApJ...716..530K
ADC_Keywords: Photometry, infrared ; Surveys ; Active gal. nuclei
Keywords: cosmology: observations - galaxies: active - infrared: galaxies -
quasars: general
Abstract:
We use the multi-epoch, mid-infrared Spitzer Deep Wide-Field Survey
(SDWFS; Ashby et al. 2009, Cat. J/ApJ/701/428) to investigate the
variability of objects in 8.1deg2 of the NOAO Deep Wide Field Survey
Bootes field (NDWFS; Jannuzi & Dey 1999ASPC..191..111J 1999ASPC..191..111J). We perform a
Difference Image Analysis of the four available epochs between 2004
and 2008, focusing on the deeper 3.6 and 4.5um bands. Out of 474, 179
analyzed sources, 1.1% meet our standard variability selection
criteria that the two light curves are strongly correlated (r>0.8) and
that their joint variance (σ12) exceeds that for all sources
with the same magnitude by 2σ. We then examine the mid-IR colors
of the variable sources and match them with X-ray sources from the
XBootes survey (Murray et al. 2005ApJS..161....1M 2005ApJS..161....1M), radio catalogs
(FIRST (Becker et al., Cat. VIII/71) and WSRT (de Vries et al. 2002,
Cat. J/AJ/123/1784)), 24um selected active galactic nucleus (AGN)
candidates (see Houck et al. 2005ApJ...622L.105H 2005ApJ...622L.105H), and spectroscopically
identified AGNs from the AGN and Galaxy Evolution Survey (AGES; C. S.
Kochanek et al. 2010, in prep). Based on their mid-IR colors, most of
the variable sources are AGNs (76%), with smaller contributions from
stars (11%), galaxies (6%), and unclassified objects, although most of
the stellar, galaxy, and unclassified sources are false positives. For
our standard selection criteria, 11%-12% of the mid-IR counterparts to
X-ray sources, 24um AGN candidates, and spectroscopically identified
AGNs show variability.
Description:
Counting the original IRAC Shallow Survey (Eisenhardt et al.
2004ApJS..154...48E 2004ApJS..154...48E) as epoch 1, the Spitzer Deep Wide-Field Survey
(SDWFS) data (Ashby et al. 2009, Cat. J/ApJ/701/428) span a period of
four years between 2004 and 2008, where the intervals between the
epochs are approximately 3.5yr, 0.5yr, and 1 month (observations were
done on 2004 January 10-14, 2007 August 8-13, 2008 February 2-6, and
2008 March 6-10). For each individual observation of a patch of the
sky (256x256 pixels), there is only a ∼40s offset between the channel
1/3 and 2/4 observations.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 174 515055 SDWFS-DIA (Spitzer Deep Wide Field Survey -
Difference Image Analysis) variability catalog
table2.dat 76 515055 The light curves for the SDWFS-DIA variability
catalog
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See also:
VIII/71 : The FIRST Survey Catalog, Version 03Apr11 (Becker+ 2003)
J/ApJ/701/428 : The Spitzer Deep, Wide-Field Survey (SDWFS) (Ashby+, 2009)
J/ApJ/641/140 : Optical counterparts in the NDWFS Bootes field (Brand+, 2006)
J/ApJS/161/9 : X-ray survey of the NDWFS Bootes field (Kenter+, 2005)
J/ApJ/634/L1 : 16µm sources in the NOAO Bootes field (Kasliwal+, 2005)
J/AJ/123/1784 : 1.4 GHz imaging of the Bootes field (de Vries+, 2002)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 5 A5 --- --- [SDWFS]
7- 25 A19 --- SDWFS Object name (JHHMMSS.ss+DDMMSS.s)
27- 36 F10.6 deg RAdeg Right Ascension in decimal degrees (J2000)
38- 46 F9.6 deg DEdeg Declination in decimal degrees (J2000)
48- 53 F6.3 mag [3.6] Spitzer/IRAC 3.6 micron band magnitude (1)
55- 59 F5.3 mag e_[3.6] The 1σ error in 3.6mag
61- 66 F6.3 mag [4.5] Spitzer/IRAC 4.5 micron band magnitude (1)
68- 72 F5.3 mag e_[4.5] The 1σ error in 4.5mag
74- 79 F6.3 mag [5.8] ?=99.999 Spitzer/IRAC 5.8 micron band magnitude
(1)
81- 86 F6.3 mag e_[5.8] ?=99.999 The 1σ error in 5.8mag
88- 93 F6.3 mag [8.0] ?=99.999 Spitzer/IRAC 8.0 micron band magnitude
(1)
95-100 F6.3 mag e_[8.0] ?=99.999 The 1σ error in 8.0mag
102 I1 --- Ne1 [0,4] Number of epochs used in channel 1
104-109 F6.3 mag nu1 ?=99.999 Channel 1 dispersion
111-117 F7.3 --- Sig1 ?=99.999 Channel 1 variability significance (2)
119 I1 --- Ne2 [0,4] Number of epochs used in channel 2
121-126 F6.3 mag nu2 ?=99.999 Channel 2 dispersion
128-133 F6.3 --- Sig2 ?=99.999 Channel 2 variability significance (2)
135 I1 --- Ne [0,4] Common number of available epochs
137-142 F6.3 mag nu3.6 ?=99.999 Dispersion in channel 1 for common
number of epochs
144-149 F6.3 mag nu4.5 ?=99.999 Dispersion in channel 2 for common
number of epochs
151-157 F7.3 mag2 C12 ?=99.999 Covariance between channels 1 and 2
159-164 F6.3 --- r ?=99.999 Correlation between channels 1 and 2
166-172 F7.3 --- Sig12 ?=99.999 joint significance in channels 1 and 2
174 I1 --- mask [0/1] Mask code for neighbour bright star (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, Cat. J/ApJ/701/428).
Note (2): The variability significance with respect to the median
variability (ν-νm)/σ.
Note (3): 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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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 [3.6]1 ?=99.999 Epoch 1 Spitzer/IRAC 3.6 micron band mag
29- 34 F6.3 mag [3.6]2 ?=99.999 Epoch 2 Spitzer/IRAC 3.6 micron band mag
36- 41 F6.3 mag [3.6]3 ?=99.999 Epoch 3 Spitzer/IRAC 3.6 micron band mag
43- 48 F6.3 mag [3.6]4 ?=99.999 Epoch 4 Spitzer/IRAC 3.6 micron band mag
50- 55 F6.3 mag [4.5]1 ?=99.999 Epoch 1 Spitzer/IRAC 4.5 micron band mag
57- 62 F6.3 mag [4.5]2 ?=99.999 Epoch 2 Spitzer/IRAC 4.5 micron band mag
64- 69 F6.3 mag [4.5]3 ?=99.999 Epoch 3 Spitzer/IRAC 4.5 micron band mag
71- 76 F6.3 mag [4.5]4 ?=99.999 Epoch 4 Spitzer/IRAC 4.5 micron band mag
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History:
From electronic version of the journal
References:
Ashby et al. Paper I. 2009ApJ...701..428A 2009ApJ...701..428A Cat. J/ApJ/701/428
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 06-Sep-2011