arXiv:0909.3669v2 [astro-ph.CO] 18 Jan 2010
The ATLAS Survey of the CDFS and ELAIS-S1 Fields
Emil Lenc∗, Ray Norris
Australia Telescope National Facility
E-mail: Emil.Lenc@csiro.au, Ray.Norris@csiro.au
Chris Hales, Kate Randall
University of Sydney
Andrew Hopkins, Rob Sharp
E-mail: email@example.com, firstname.lastname@example.org
Infrared Processing and Analysis Center
University of Tasmania
Astronomisches Institut, Ruhr-Universität Bochum
The first phase of the ATLAS (Australia Telescope Large Area Survey) project surveyed a total
7 square degrees down to 30 µJy rms at 1.4 GHz and is the largest sensitive radio survey ever
attempted. We report on the scientific achievements of ATLAS to date and plans to extend the
project as a path finder for the proposed EMU (Evolutionary map of the Universe) project which
has been designed to use ASKAP (Australian Square Kilometre Array Pathfinder).
Panoramic Radio Astronomy: Wide-field 1-2 GHz research on galaxy evolution
June 2-5 2009
Groningen, the Netherlands
c ? Copyright owned by the author(s) under the terms of the Creative Commons Attribution-NonCommercial-ShareAlikeLicence.
ATLAS (Australia Telescope Large Area Survey)
The first phase of the ATLAS (Australia Telescope Large Area Survey) project has surveyed a
total 7 square degrees down to 30 µJy rms at 1.4 GHz and is the largest sensitive radio survey ever
attempted. The survey has observed an area surrounding the CDFS (Chandra Deep Field South)
and ELAIS-S1 (European Large Area ISO Survey - South 1) regions with the ATCA (Australia
Telescope Compact Array). The survey areas were chosen to cover the Southern SWIRE fields,
which have deep optical, near-infrared, and far-infrared (and in some parts of the field, deep X-
ray) data, so that this combined SWIRE/ATLAS survey may be the most comprehensive multi-
wavelength survey yet attempted.
The broad scientific goal of ATLAS is to understand the evolution of galaxies in the early
Universe. The radio observations are important as they penetrate the heavy dust extinction found
in the most active galaxies at all redshifts  and are particularly effective at detecting AGN buried
within dusty galaxies (Figure 1).
Figure 1: ATLAS contains unusual sources, such as these Powerful Radio Objects Nested in Galaxies with
Star formation (PRONGS). These sources have the radio appearance of an AGN (left), but have a spectral
energy density typical of classical star-forming galaxies (right), with no hint of an AGN .
The ATLAS team have already achieved the following:
• The first CDFS and ELAIS-S1 survey results have been published [3, 4].
• A new and unexpected class of object, Infrared-Faint Radio Sources (IFRS), have been dis-
covered , catalogued and analysed , and observed using VLBI [6, 7].
• Discovered and explained a change in slope of the FIR-radio correlation at S1.4< 1 mJy
• Discovered a z ∼ 0.2 cluster through the presence of a wide-angled tail ATLAS radio source
ATLAS (Australia Telescope Large Area Survey)
• Begun analyses on the evolution of radio sources , and to optimise discrimination be-
tween AGN and star forming galaxies .
• Produced images and catalogues of source polarisation which we will use to investigate in-
dividual sources. By using the rotation measure grid we hope to measure or put limits on the
intergalactic magnetic field .
3. Current Status
The CDFS and ELAIS-S1 fields have been imaged down to 30 µJy rms at 1.4 GHz yielding
a total of ∼ 2000 radio sources. Catalogues of these sources have been made publicly available
through NED (the NASA/IPAC Extragalactic Database) and work is currently underway to provide
VO (Virtual Observatory) access to the catalogues also.
Figure2: (a)Left,imageofconfusingsourcefromfirst ATLASdatarelease. (b)Right,imagewithimproved
source modelling applied.
The 30 µJy rms limit of the first ATLAS data release was generally imposed by observational
sensitivity, however, itwasclear that further observations would be limited by ourability to mitigate
the effects of bright sources in each field (Figure 2a). We have recently been successful in removing
these limitations in onepointing ofthe CDFSregion bymodelling bright confusing sources intheu-
v plane. This enabled self-calibration to converge on a more optimal solution, and after subsequent
deconvolution, allowed the theoretical signal-to-noise to be achieved throughout the entire field
(Figure 2b). We anticipate releasing an updated catalogue, utilising this improved imaging, by
We are now in the process of continuing observations of both ATLAS fields to achieve the
originally proposed goal of 10 µJy rms over the full 7 sq. deg. These observations will make use
of the Compact Array Broadband Back-end (CABB) which provides a continuous 0.5 GHz band
at 1.4 GHz. We estimate the detection of 10000 radio sources with these observations.
ATLAS (Australia Telescope Large Area Survey) Download full-text
4. ATLAS as an ASKAP Path-finder
EMU (Evolutionary Map of the Universe) is a proposed radio sky survey project designed to
use the new ASKAP (Australian Square Kilometre Array Pathfinder) telescope. The EMU-wide
project, will make a deep (∼ 10 µJy rms) radio continuum survey covering the entire Southern Sky
as far North as 30◦. As a result, it will be able to probe star forming galaxies up to z= 1, AGNs
to the edge of the Universe, and will undoubtedly uncover new classes of object. Similarly, the
EMU-deep project will aim to observe a smaller region of the sky (∼ 30 sq. degrees) down to an
rms of about ∼ 1 µJy.
It is envisaged that by pushing the ATLAS fields down to 10 µJy rms we will be using it as a
design study for ASKAP EMU-wide. This will result in a better characterisation of the challenges
faced by deep surveys, such as EMU-wide and EMU-deep e.g. the effects of confusion. Subse-
quently, ATLAS will drive the development of new advanced calibration and imaging algorithms
that will ultimately be used for future instruments such as ASKAP. The ATLAS project also plans
to set up a pipeline for the automatic multi-wavelength cross-identification of radio sources. The
output of this pipeline will be placed in the public domain in the form of images and source cat-
alogues. Finally, ATLAS will provide the first preview of the science that can be achieved with
surveys such as EMU. So watch this space, ATLAS has a great deal to offer over the next few
 S. C. Chapman, et al. 2003, ApJ, 585, 57
 R. P. Norris, E. Middelberg, & B. J. Boyle 2008, arXiv:0804.3998
 R. P. Norris, et al. 2006, AJ, 132, 2409
 E. Middelberg, et al. 2008a, AJ, 135, 1276
 M. T. Huynh, et al. 2009, AJ, submitted
 R. P. Norris, E. Middelberg, & B. J. Boyle 2007, Deepest Astronomical Surveys, 380, 229
 E. Middelberg, et al. 2008b, AAP, 491, 435
 R. P. Norris, et al. 2010, in prep.
 B. J. Boyle, et al. 2007, MNRAS, 376, 1182
 M. Mao, et al. 2009, AJ, submitted.
 M. Mao, et al. 2009 in “Starburst-AGN Connection”, Shanghai, ASPC
 K. Randall, et al. 2009 in “Starburst-AGN Connection”, Shanghai, ASPC
 C. A. Hales, et al. 2010, in prep.