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Today's Colloquium (4PM!): HI properties of massive galaxies

Submitter: Colloquium
Description: Speaker: Barbara Catinella (MPA Garching)

The main obstacle to understand the formation and evolution of galaxies is our limited knowledge of the role played by gas. In particular we still lack measurements of the HI gas, which is the reservoir for future starformation, for large and unbiased samples for which ancillary data on stellar and star formation properties are also available. To this end we are carrying out the GALEX Arecibo SDSS Survey (GASS), an ambitious program to assemble the first unbiased inventory of atomic hydrogen in massive galaxies. Using the Arecibo radio telescope, we are acquiring HI spectra for ~1000 galaxies selected uniquely bystellar mass (>10^10 Msolar) and redshift (0.025<z<0.05), covered by both SDSS spectroscopic and GALEX imaging surveys. Our selected stellar mass range allows us to probe the interesting region where galaxies transition from blue and star-forming to red and passively evolving.

In this talk I will discuss how the gas content of massive systems depends on their structural and star formation properties, and will show how gas fraction scaling relations can be used to identify objects that might be transitioning between blue, star-forming cloud and red sequence. In particular, objects with HI excess are good candidates for systems that might have recently accreted gas from the surrounding medium. I will also illustrate a relation between baryonic mass and velocity for massive systems that does not involve morphological pruning, and thus is more suited to comparison with theoretical models. Lastly, I will discuss the relevance of HI scaling relations for the future surveys that will be carried out with the SKA precursors. As an example, I will compare the properties of GASS galaxies with those of a unique sample of very HI-rich disks at redshift z~0.2 detected with Arecibo.
Copyright: Barbara Catinella
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