The epoch of star formation for th e most massive galaxies Sarah Brough (AAO)

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Transcript of The epoch of star formation for th e most massive galaxies Sarah Brough (AAO)

GAMA From little blue fuzzies to massive red monsters

The epoch of star formation for the most massive galaxiesSarah Brough (AAO)

Executive Summary1. Massive galaxies are an important test of models of galaxy formation.2. We need to understand observationally how massive galaxies form.3. Current models predict that massive galaxies formed quickly at early times. 4. ALMA can observe massive galaxies in the epoch they form stars.5. We can use this information to test the current models.In the standard model of galaxy formation more massive galaxies assemble from mergers of smaller galaxiesThe most massive galaxies are the extreme limit of this process. They form an important test of any simulation of galaxy formation. Their formation and growth need to be understood observationally.

Massive Red Monsters


de Lucia & Blaizot 200750% stars formed50% mass assembledI generally work in the optical where observing galaxies at these epochs is really hard.5

Thomas et al. (2010)Clearly need to observe these galaxies during the time in which they form their stars; form a between the systems observed then and what we observe now.6Where does ALMA come in?During the periods when galaxies formed their stars, they are brighter in the millimetre than in the optical/UV due to the re-processing of optical/UV by interstellar dust. Also, the characteristic spectral energy distribution of galaxies means that the increasing distance is balanced by the increasing intrinsic luminosity. The consequence is that the galaxys flux density is approximately independent of redshift.

The top row shows the number of low and high redshift (z>1.5) galaxies expected from a simulated deep ALMA observation. The bottom row shows that with an optical image, such as the Hubble Deep Field, most of the detections are of galaxies with z