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The Australia Telescope National Facility Colloquium
15:00-16:00 Wed 08 Aug 2012

Marsfield Lecture Theatre

Carlos de Breuck


First ALMA results on lensed and unlensed submm galaxies-- Carlos de Breuck Colloquium

I will present first results from four ALMA Cycle 0 projects on submm galaxies (SMGs). A sample of 120 SMGs uniformally selected from the LABOCA ECDFS submm survey (LESS) were observed in band 7 (PI Smail). The results show that arcsec resolution dust continuum imaging is required
to get reliable identifications, and previous 1.4 GHz identifications turn out to be unreliable or incomplete in many cases. A significant fraction of sources also splits up into multiple components, which changes the bright end of the 850um source counts. In 2 sources, we also
detect the [CII] line, providing the first redshift of these targets and an estimate of the [CII] luminisity function.

Follow-up observations of a z=4.76 SMG (PI Nagao) detect the [NII] 205um line. When combined with an APEX [CII] and an ATCA CO(2-1) detection, this provides evidence that this distant SMG must already have close to solar metallicity.

In the second part of my presentation, I will present results on a population of strongly lensed SMGs selected from the south pole telescope (SPT). Using ALMA band 3, we performed the first ALMA blind redshift search on 26 SPT SMGs (PI Weiss). We detect lines in all but 2 targets, and derive reliable (multi-line) redshifts for half of our
targets, with the remaining one-line redshifts strongly constrained by the FIR SEDs. Our results show a much more pronounced high redshift tail of the SMGs than assumed before, which may be due to the prior radio identification. The band 6 imaging (PI Marrone) provides clear morphological evidence that these SPT SMGs are indeed strongly amplified by gravitational lensing.

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Ryan Shannon

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