J/MNRAS/454/952 Chandra Deep Field-South ATLAS 5.5GHz DR2 (Huynh+, 2015)
The ATLAS 5.5 GHz survey of the extended Chandra Deep Field-South:
the second data release.
Huynh M.T., Bell M.E., Hopkins A.M., Norris R.P., Seymour N.
<Mon. Not. R. Astron. Soc., 454, 952-972 (2015)>
=2015MNRAS.454..952H 2015MNRAS.454..952H (SIMBAD/NED BibCode)
ADC_Keywords: Surveys ; Galaxy catalogs ; Radio sources ; Morphology
Keywords: galaxies: evolution; radio continuum: galaxies
Abstract:
We present a new image of the 5.5GHz radio emission from the extended
Chandra Deep Field South. Deep radio observations at 5.5GHz were
obtained in 2010 and presented in the first data release. A further
76h of integration has since been obtained, nearly doubling the
integration time. This paper presents a new analysis of all the data.
The new image reaches 8.6µJy rms, an improvement of about 40% in
sensitivity. We present a new catalogue of 5.5GHz sources, identifying
212 source components, roughly 50% more than were detected in the
first data release. Source counts derived from this sample are
consistent with those reported in the literature for S5.5GHz>0.1mJy
but significantly lower than published values in the lowest flux
density bins (S5.5GHz<0.1mJy), where we have more detected sources
and improved statistical reliability. The 5.5GHz radio sources were
matched to 1.4GHz sources in the literature and we find a mean
spectral index of -0.35±0.10 for S5.5GHz>0.5mJy, consistent with
the flattening of the spectral index observed in 5GHz sub-mJy samples.
The median spectral index of the whole sample is αmed=-0.58,
indicating that these observations may be starting to probe the
star-forming population. However, even at the faintest levels
(0.05<S5.5GHz<0.1mJy), 39% of the 5.5GHz sources have flat or
inverted radio spectra. Four flux density measurements from our data,
across the full 4.5-6.5GHz bandwidth, are combined with those from
literature and we find 10% of sources (S5.5GHz≳0.1mJy) show
significant curvature in their radio spectral energy distribution
spanning 1.4-9GHz.
Description:
The eCDFS was observed with the CABB on the ATCA with the full 2048
MHz bandwidth centred at 5.5GHz. We chose a 42 pointing hexagonal
mosaic with spacings of 5-arcmin (approximately 0.5FWHM of the
primary beam) to uniformly sample the full 30-arcminx30-arcmin
eCDFS region, centred approximately at RA=3:32:22 and DE=-27:48:37
(J2000). The 20h in 2009 and 144h in 2010 were allocated under ATCA
observing programme C2028. This data resulted in a rms sensitivity of
11.9uJy and synthesized beam size of 4.9-arcsecx2.0-arcsec (Huynh et
al., 2012, Cat. J/MNRAS/426/2342, H12), under hereafter Epoch 1 and
Data Release 1 (DR1).
Further observations were obtained in 2012 via ATCA programme C2670.
The C2670 programme was conceived as a blind search for sub-mJy level
sources that are variable on time-scales of months to roughly a year,
with a secondary goal of testing the Variables and Slow Transients
(VAST) data pipeline. A total of 54h in 2012 May-June (Epoch 2) and
47h in 2012 August (Epoch 3) was allocated to C2670, and the data was
taken using the mosaicking strategy of H12.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table2.dat 99 212 The ATLAS 5.5GHz DR2 catalogue
table4.dat 29 167 The 1.4-5.5GHz spectral index of the ATCA 5.5GHz
sample
table5.dat 58 59 Summary of radio SED fitting results
--------------------------------------------------------------------------------
See also:
J/MNRAS/426/2342 : Chandra Deep Field South ATLAS 5.5GHz survey (Huynh+, 2012)
Byte-by-byte Description of file: table2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 3 I3 --- Seq Sequential number
4 A1 --- m_Seq [ABCD] Multiplicity index on Seq Column
(indicates a component of a multiple source)
6- 12 A7 --- --- [ATCDFS5]
14- 33 A20 --- ATCDFS5 Source ATCDFS5 IAU name (JHHMM.ss+DDMMSS.s)
35- 36 I2 h RAh Right ascension (J2000)
38- 39 I2 min RAm Right ascension (J2000)
41- 45 F5.2 s RAs Right ascension (J2000)
47 A1 --- DE- Declination sign (J2000)
48- 49 I2 deg DEd Declination (J2000)
51- 52 I2 arcmin DEm Declination (J2000)
54- 57 F4.1 arcsec DEs Declination (J2000)
59- 63 I5 uJy Speak Point source flux density at 5.5GHz (peak flux
density for deconvolved sources)
65- 67 I3 uJy e_Speak Uncertainty in point source flux density or
peak flux density for deconvolved sources
69- 73 I5 uJy Sint ?=0 Integrated flux density at 5.5GHz (1)
75- 77 I3 uJy e_Sint ?=0 Uncertainty in integrated flux density (1)
79- 83 F5.2 arcsec Bmaj ?=0 Deconvolved major axis (2)
85- 88 F4.2 arcsec Bmin ?=0 Deconvolved minor axis (2)
90- 94 F5.1 deg PA []?=0 Deconvolved position angle,
measured from north through east (2)
96- 99 F4.1 uJy rms ?=0 Local noise level, rms
--------------------------------------------------------------------------------
Note (1): Zero indicates source is not successfully deconvolved and hence no
integrated flux density is given.
Note (2): Zero indicates source is not successfully deconvolved.
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table4.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 3 I3 --- Seq Sequential number
5- 9 I5 uJy S5.5GHz Flux density at 5.5GHz
12- 18 F7.1 uJy S1.4GHz Flux density at 1.4GHz
20- 24 F5.2 --- alpha 1.4-5.5GHz spectral index
26- 29 F4.2 --- e_alpha rms uncertainty on alpha
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table5.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 3 I3 --- Seq Sequential number
5- 9 F5.2 --- gammal gamma for log-linear fit (1)
11- 14 F4.2 --- e_gammal rms uncertainty on gammal (1)
16- 20 F5.2 --- alphal alpha for log-linear fit (1)
22- 25 F4.2 --- e_alphal rms uncertainty on alpha (1)
27- 31 F5.2 --- gammaq gamma for log-quadratic fit (1)
33- 36 F4.2 --- e_gammaq rms uncertainty on gammaq (1)
38- 42 F5.2 --- alphaq alpha for log-quadratic fit (1)
44- 47 F4.2 --- e_alphaq rms uncertainty on alphaq (1)
49- 53 F5.2 --- betaq beta for log-quadratic fit (1)
55- 58 F4.2 --- e_betaq rms uncertainty on log-quadratic fit (1)
--------------------------------------------------------------------------------
Note (1): We fitted the SEDs in log space with first- and second-order
polynomials of the form:
logS = γ + αlogν + β(logν)2
with units of S in mJy and ν in GHz.
The first order polynomial fit (β=0) is the commonly assumed power law
S∝ν^α, with α as the spectral index. We refer to the
first order polynomial fit as the log-linear fit and the second order
polynomial fit as the log-quadratic fit.
--------------------------------------------------------------------------------
History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 28-Jun-2016