J/ApJ/844/78 The high-redshift COBRA survey: IRAC obs. (Paterno-Mahler+, 2017)
The high-redshift Clusters Occupied by Bent Radio AGN (COBRA) Survey: the
Spitzer catalog.
Paterno-Mahler R., Blanton E.L., Brodwin M., Ashby M.L.N., Golden-Marx E.,
Decker B., Wing J.D., Anand G.
<Astrophys. J., 844, 78 (2017)>
=2017ApJ...844...78P 2017ApJ...844...78P
ADC_Keywords: Clusters, galaxy ; Photometry, infrared ; Redshifts ;
Radio continuum ; QSOs
Keywords: galaxies: clusters: general; galaxies: evolution;
galaxies: high-redshift; infrared: galaxies; radio continuum: galaxies
Abstract:
We present 190 galaxy cluster candidates (most at high redshift) based
on galaxy overdensity measurements in the Spitzer/IRAC imaging of the
fields surrounding 646 bent, double-lobed radio sources drawn from the
Clusters Occupied by Bent Radio AGN (COBRA) Survey. The COBRA sources
were chosen as objects in the Very Large Array FIRST survey that lack
optical counterparts in the Sloan Digital Sky Survey to a limit of
mr=22, making them likely to lie at high redshift. This is confirmed
by our observations: the redshift distribution of COBRA sources with
estimated redshifts peaks near z=1 and extends out to z∼3. Cluster
candidates were identified by comparing our target fields to a
background field and searching for statistically significant
(≥2σ) excesses in the galaxy number counts surrounding the
radio sources; 190 fields satisfy the ≥2σ limit. We find that
530 fields (82.0%) have a net positive excess of galaxies surrounding
the radio source. Many of the fields with positive excesses but below
the 2σ cutoff are likely to be galaxy groups. Forty-one COBRA
sources are quasars with known spectroscopic redshifts, which may be
tracers of some of the most distant clusters known.
Description:
The Spitzer Infrared Array Camera (IRAC) observations of the Clusters
Occupied by Bent Radio AGN (COBRA) sources were carried out as a
Snapshot Program during Cycle 8 (PID 80161, PI Blanton). All 646
sources were imaged at 3.6um. We also observed 135 sources at 4.5um.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 108 646 COBRA cluster survey catalog
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See also:
VII/4 : Abell and Zwicky Clusters of Galaxies (Abell+ 1974)
II/294 : SDSS Photometric Catalog, Release 7 (Adelman-McCarthy+, 2009)
VIII/92 : The FIRST Survey Catalog, Version 2014Dec17 (Helfand+ 2015)
J/A+A/461/823 : Candidate Lyα emitting galaxies (Venemans+, 2007)
J/ApJ/684/905 : z>1 gal. clusters from IRAC Shallow Survey (Eisenhardt+, 2008)
J/ApJ/686/966 : Spitzer-FLS catalog of clusters of galaxies (Muzzin+, 2008)
J/AJ/141/88 : Galaxy cluster environments of radio sources (Wing+, 2011)
J/ApJ/769/79 : Spitzer obs. of radio-loud AGNs (CARLA) (Wylezalek+, 2013)
J/ApJS/213/25 : WISE Massive & Distant Clusters (MaDCoWS) II. (Stanford+, 2014)
J/ApJ/786/17 : Luminosity functions for 1.3<z<3.2 galaxies (Wylezalek+, 2014)
J/ApJS/218/33 : Spitzer-CANDELS catalog within 5 deep fields (Ashby+, 2015)
J/ApJS/216/27 : Galaxy clusters discovered in the SPT-SZ survey (Bleem+, 2015)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 1 I1 --- Type [1/3] Source selection type (1)
3- 7 A5 --- --- [COBRA]
8- 22 A15 --- COBRA Radio source name (HHMMSS.s+DDMMSS; J2000)
24- 25 I2 h RAh ? Hour of Right Ascension (J2000) (2)
27- 28 I2 min RAm ? Minute of Right Ascension (J2000) (2)
30- 34 F5.2 s RAs ? Second of Right Ascension (J2000) (2)
36 A1 --- DE- Sign of the Declination (J2000) (2)
37- 38 I2 deg DEd ? Degree of Declination (J2000) (2)
40- 41 I2 arcmin DEm ? Arcminute of Declination (J2000) (2)
43- 46 F4.1 arcsec DEs ? Arcsecond of Declination (J2000) (2)
48- 53 F6.1 mJy S20 [2/1503] FIRST survey 20cm flux density
55- 59 F5.2 mag 3.6mag [12.7/23.8]? Host Spitzer/IRAC 3.6um band mag
as determined by SExtractor.
61- 65 F5.2 mag 3.6-4.5 [-0.6/0.7]? Host Spitzer/IRAC 3.6-4.5um band
color index
67 A1 --- f_3.6-4.5 Flag on 3.6-4.5 (3)
69- 73 F5.3 --- z [0/3]? Redshift (4)
75 A1 --- f_z Flag on z (5)
77- 81 F5.1 --- DelN1 [-14/50] Overdensity within 1 arcmin
83- 85 F3.1 --- e_DelN1 [3/9] Uncertainty in DelN1 (6)
87- 91 F5.2 --- Sig1 [-2.2/7.8] Significance within 1 arcmin (7)
93- 97 F5.1 --- DelN2 [-45/120] Overdensity within 2 arcmin
99-102 F4.1 --- e_DelN2 [8/16] Uncertainty in DelN2 (6)
104-108 F5.2 --- Sig2 [-3.1/8.1] Significance within 2 arcmin (7)
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Note (1): Source type as follows:
1 = 3.6 micron band only;
2 = 3.6 and 4.5 micron (103 occurrences);
3 = Quasars (40 occurrences).
Note (2): Of the optical/IR host, which in some cases differs from that
of the radio source (see text). A blank indicates that no host
could be identified.
Note (3): Flag as follows:
g = The listed coordinates of the radio source are not those of the
identified host. The identified host of the radio source was not at
the center of the search radius used to calculate an overdensity.
h = Color could not be determined due to nearby saturated pixels.
i = Object identified as host is identified as a star in SDSS.
Note (4): Photometric redshift available in SDSS, unless otherwise noted.
Quasar redshifts are spectroscopically determined.
Note (5): Flag as follows:
c = Spectroscopic redshift from SDSS (69 occurrences).
d = Redshift is derived from the color of the source associated with the
radio contours (35 occurrences). See text for more details.
e = While the listed color is too red to determine a redshift based on our
models, examining the surrounding sources yields the listed redshift.
f = Identified in the SDSS Digital Release 6 Galaxy Clusters Catalog.
j = Spectroscopically determined redshift from
Blanton+ (2003AJ....125.1635B 2003AJ....125.1635B). Redshift from the color is 0.99.
k = Source observed at 3.6 micron only later identified as a quasar.
Note (6): Including Poisson noise contributions from both the cluster and
background subtraction.
Note (7): Computed using Equation 2 (Significance=ΔN/σSpUDS),
which relates the overdensity to the standard deviation of the
Spitzer UKIDSS Ultra Deep Survey (SpUDS, PI: J. Dunlop) field in each
aperture size.
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDs] 05-Mar-2018