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Astronomy Tea Talks at Caltech

Mondays, Robinson 106
Tea:  4.00pm
Talk: 4.15pm

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2007 - 2008 season:
3 March 2008 Vernesa Smolcic (Caltech)

"The dust-unbiased cosmic star formation history derived from the faint radio population"


The major advantage of using radio observations for determining the star
formation history of the universe is no need for uncertain dust-extinction
corrections. Radio emission at 1.4 GHz (20cm) is dominated by the emission
from active-galactic nuclei (AGN) and star-forming (SF) galaxies, hence a
reliable SF/AGN separation is one of the main pre-requisites for a robust
determination of star-formation rates using radio-data.
The VLA-COSMOS survey with ~3,600 detected radio sources at 1.4GHz, with
1.5" resolution and high sensitivity (rms = 10 uJy/beam), provides enough
targets to allow for the first time for a robust systematic
characterization of the 'cosmological mix' of faint radio sources.
Utilizing the entire COSMOS multi-wavelength (X-ray to radio) data set I
will present our newly developed method which separates the radio
population into SF and AGN galaxies. We find that SF galaxies are not the
dominant radio population at faint flux densities (<1 mJy) as previously
suspected, but rather have a fairly constant contribution with decreasing
fluxes. Selecting the SF galaxies within the VLA-COSMOS population, we
derive their star formation rates and present the dust-unbiased cosmic
star-formation history out to z=1.3, for the first time based on radio
observations of a large, contiguous field with unprecedented sensitivity.
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