J/MNRAS/431/194 Selecting IRAC counterparts to SMGs (Alberts+, 2013)
Submm/mm galaxy counterpart identification using a characteristic density
distribution.
Alberts S., Wilson G.W., Lu Y., Johnson S., Yun M.S., Scott K.S., Pope A.,
Aretxaga I., Ezawa H., Hughes D.H., Kawabe R., Kim S., Kohno K., Oshima T.
<Mon. Not. R. Astron. Soc., 431, 194-209 (2013)>
=2013MNRAS.431..194A 2013MNRAS.431..194A
ADC_Keywords: Galaxies, IR ; Galaxies, radio ; Cross identifications
Keywords: methods: data analysis - techniques: photometric -
galaxies: high-redshift - infrared: galaxies -
radio continuum: galaxies - submillimetre: galaxies
Abstract:
We present a new submm/mm galaxy counterpart identification technique
which builds on the use of Spitzer Infrared Array Camera (IRAC)
colours as discriminators between likely counterparts and the general
IRAC galaxy population. Using 102 radio- and Submillimeter
Array-confirmed counterparts to AzTEC sources across three fields
[Great Observatories Origins Deep Survey-North, -South and Cosmic
Evolution Survey (COSMOS)], we develop a non-parametric IRAC
colour-colour characteristic density distribution, which, when
combined with positional uncertainty information via likelihood
ratios, allows us to rank all potential IRAC counterparts around
submillimetre galaxies (SMGs) and calculate the significance of each
ranking via the reliability factor. We report all robust and tentative
radio counterparts to SMGs, the first such list available for
AzTEC/COSMOS, as well as the highest ranked IRAC counterparts for all
AzTEC SMGs in these fields as determined by our technique. We
demonstrate that the technique is free of radio bias and thus
applicable regardless of radio detections. For observations made with
a moderate beam size (∼18"), this technique identifies ∼85% of SMG
counterparts. For much larger beam sizes (≳30"), we report
identification rates of 33-49%. Using simulations, we demonstrate that
this technique is an improvement over using positional information
alone for observations with facilities such as AzTEC on the Large
Millimeter Telescope and Submillimeter Common User Bolometer Array 2
on the James Clerk Maxwell Telescope.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablea1.dat 108 374 *Training and radio counterpart set: this table
contains the radio counterparts to AzTEC SMGs
in GOODS-N, GOODS-S and COSMOS
tablea2.dat 108 107 *Multiple Radio Set: list of SMGs in GOODS-N,
GOODS-S, and COSMOS that have multiple radio
detections
tablea3.dat 71 301 Radio-undetected SMG set: list of SMGs without
radio detections
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Note on tablea1.dat: Sources are included in the training set if the radio
counterpart was detected in the original radio catalogues (non-extended,
see Section 5.3) and if there is a corresponding IRAC detection to the
radio counterpart that is detected in all four bands. For COSMOS, radio
detections which were found in the extended catalogue (see Section 5.3)
are indicated. Three additional radio-undetected SMA-confirmed IRAC
counterparts are listed and included in the training set.
Note on tablea2.dat: For COSMOS, radio detections which were found in the
extended catalog (see Section 5.3) are indicated. Some AzTEC/COSMOS SMGs
were single systems in the unextended radio catalog, but are multiple
systems in the extended catalog.
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See also:
J/MNRAS/379/1571 : SCUBA Half-Degree Extragalactic Survey. IV (Aretxaga+, 2007)
J/MNRAS/423/529 : AzTEC deep-field observations (Downes+, 2012)
Byte-by-byte Description of file: tablea[12].dat
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Bytes Format Units Label Explanations
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1- 7 A7 --- Field Field name (COSMOS, GOODS-N or GOODS-S)
9- 18 A10 --- AzTEC AzTEC ID (G1)
19 A1 --- n_AzTEC [defgj] Individual note on source (1)
22- 25 F4.1 arcsec RS ? Distance from radio source
27- 46 A20 --- Radio Radio counterpart name (JHHMMSS.ss+DDMMSS.s)
47 A1 --- n_Radio [hd] Note on radio counterpart (1)
49- 53 F5.3 --- Pstat ? P-statistic at 1.4GHz (best when Pstat≤0.05)
55- 74 A20 --- IRAC IRAC counterpart name (JHHMMSS.ss+DDMMSS.s) (2)
75 A1 --- n_IRAC [fi] Note on near-UD counterpart (1)
77- 80 A4 --- Rank Rank (N/NN) (best when Rank = 1/N)
82- 87 F6.2 --- LR ? Likelihood ratio of IRAC association
89- 92 F4.1 --- e_LR ? rms uncertainty on LR
94- 97 F4.2 --- Rel [0/1]? Reliability factor (best when Rel≥0.8)
99-108 A10 --- OID Other IDs (G2)
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Note (1): Notes as follows:
d = Radio counterpart is identified in the extended 3σ radio
catalogue (see Section 5.3)
e = AzTEC source is cross-listed with Table A2
f = IRAC counterpart is not detected in all four bands
g = IRAC counterparts identified via the SMA (Younger et al.
2007ApJ...671.1531Y 2007ApJ...671.1531Y, 2009ApJ...704..803Y 2009ApJ...704..803Y). These include two
radio-undetected SMGs (AzTEC/C4 and AzTEC/C10) and one multiple system
(AzTEC/C42) for which the SMA identified the correct counterpart and
which is cross-listed with the two tables. Two SMA sources,
AzTEC7 (Younger et al. 2007ApJ...671.1531Y 2007ApJ...671.1531Y) and AzTEC10
(Younger et al. 2009ApJ...704..803Y 2009ApJ...704..803Y) do not match any SMGs in our AzTEC
catalogues and so their IRAC fluxes were taken from their respective
papers.
h = The true radio counterpart for AzTEC/GN14 is undetected in our radio
catalogues. The radio source listed here is unassociated with the submm
emission (Barger et al. 2012ApJ...761..145B 2012ApJ...761..145B).
i = IRAC detection is within 2" of both radio detections
j = AzTEC source is cross-listed with Table A1
Note (2): In tablea1.dat.
For each source, the IRAC counterpart (if available) is listed on the same
line as the radio counterpart, along with its rank, likelihood ratio and
reliability factor. The next two highest ranked IRAC galaxies are
additionally listed (if available). Some AzTEC sources in COSMOS are
cross-listed with Table A2 due to having an additional nearby radio source
in the extended radio catalogue, making them multiple systems
(see Section 5.3).
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Byte-by-byte Description of file: tablea3.dat
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Bytes Format Units Label Explanations
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1- 7 A7 --- Field Field name (COSMOS, GOODS-N or GOODS-S)
9- 18 A10 --- AzTEC AzTEC ID (G1)
20- 23 F4.1 arcsec RS ? Distance from radio source
25- 44 A20 --- IRAC IRAC counterpart name (JHHMMSS.ss+DDMMSS.s) (1)
45- 49 F5.2 --- LR ? Likelihood ratio of IRAC association
51- 54 F4.1 --- e_LR ? rms uncertainty on LR
56- 59 F4.2 --- Rel [0/1]? Reliability factor (best for Rel≥0.8)
61- 71 A11 --- OID Other IDs (G2)
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Note (1): For each AzTEC source, the likelihood ratios and reliability factors
for the top three ranked potential IRAC counterparts are listed.
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Global notes:
Note (G1): AzTEC IDs correspond to the IDs from
* Downes et al. (2012, Cat. J/MNRAS/423/529) for the GOODS fields
(AzTEC/GNnnn and AzTEC/GSnnn) and
* Aretxaga et al. (2011MNRAS.415.3831A 2011MNRAS.415.3831A) for COSMOS (AzTEC/Cnnn,
<[AWA2011] AzTEC/Cnnn> in Simbad).
Note (G2):
* "AzTECxx" correspond to the IDs from Younger et al. (2007ApJ...671.1531Y 2007ApJ...671.1531Y,
2009ApJ...704..803Y 2009ApJ...704..803Y) for SMA observations,
* "COSLA-xx" correspond to IDs from Smolcic et al. (2012A&A...548A...4S 2012A&A...548A...4S) for
PdBI observations of AzTEC sources in the COSMOS field and
* "GOODS850-x" correspond to IDs from Barger et al. (2012ApJ...761..145B 2012ApJ...761..145B) for
SMA observations of SCUBA/AzTEC sources in GOODS-N.
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History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 09-May-2014