570 research outputs found
CMB observations using the SKA
We examine the prospects for observations of CMB anisotropy with the SKA; we
discuss the advantages of interferometric SKA imaging, observing strategies,
calibration issues and the achievable sensitivity. Although the SKA will
probably operate at cm wavelengths, where discrete source confusion dominates
the CMB anisotropy, its extreme sensitivity to point sources will make it
possible to subtract the source contamination at these wavelengths and thereby
image the low surface brightness CMB anisotropies on small angular scales. The
SKA, operating at 10-20 GHz, may usefully make high-l observations of the CMB
anisotropy spectrum and survey the sky for Sunyaev-Zeldovich decrements.Comment: 4 pages. invited talk presented at the XXVIIth General Assembly of
the URSI, 17-24 Aug 2002, Maastricht, The Netherland
ATLBS: the Australia Telescope Low-brightness Survey
We present a radio survey carried out with the Australia Telescope Compact
Array. A motivation for the survey was to make a complete inventory of the
diffuse emission components as a step towards a study of the cosmic evolution
in radio source structure and the contribution from radio-mode feedback on
galaxy evolution. The Australia Telescope low-brightness survey (ATLBS) at 1388
MHz covers 8.42 sq deg of the sky in an observing mode designed to yield images
with exceptional surface brightness sensitivity and low confusion. The ATLBS
radio images, made with 0.08 mJy/beam rms noise and 50" beam, detect a total of
1094 sources with peak flux exceeding 0.4 mJy/beam. The ATLBS source counts
were corrected for blending, noise bias, resolution, and primary beam
attenuation; the normalized differential source counts are consistent with no
upturn down to 0.6 mJy. The percentage integrated polarization Pi_0 was
computed after corrections for the polarization bias in integrated polarized
intensity; Pi_0 shows an increasing trend with decreasing flux density.
Simultaneous visibility measurements made with longer baselines yielded images,
with 5" beam, of compact components in sources detected in the survey. The
observations provide a measurement of the complexity and diffuse emission
associated with mJy and sub-mJy radio sources. 10% of the ATLBS sources have
more than half of their flux density in extended emission and the fractional
flux in diffuse components does not appear to vary with flux density, although
the percentage of sources that have complex structure increases with flux
density. The observations are consistent with a transition in the nature of
extended radio sources from FR-II radio source morphology, which dominates the
mJy population, to FR-I structure at sub-mJy flux density. (Abridged)Comment: 18 pages, 8 figues, 6 tables, accepted for publication in MNRA
A deep survey of the low-surface-brightness radio sky
We have made a radio survey--the Australia Telescope Low Brightness Survey
(ATLBS)--of 8.4 square degrees sky area, using the Australia Telescope Compact
Array in the 20-cm band, in an observing mode designed to provide wide-field
images with exceptional sensitivity in surface brightness, and thereby explore
a new parameter space in radio source populations. The goals of this survey are
to quantify the distribution in angular sizes, particularly at weak surface
brightness levels: this has implications for the confusion in deep surveys with
the SKA. The survey is expected to lead to a census of the radio emission
associated with low-power radio galaxies at redshifts 1-3, without any missing
extended emission, and hence a study of the cosmic evolution of low-power radio
galaxies to higher redshift and a comprehensive study of the AGN feedback
during the intense black hole growth phase during this redshift range.Comment: 5 pages, includes 2 figures and 1 table. To appear in the proceedings
of "From Planets to Dark energy: the modern radio universe" in the online
journal Proceedings of Science - Po
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