Fakultät für Physik und Astronomie
STEPHEN PHILLIPS hostreviews.co.uk / UNSPLASH

The growth of spiral galaxies over cosmic time

Richard Tuffs , MPI for Nuclear Physics (Heidelberg)

A growing body of photometric, imaging and spectroscopic measurements of the distant galaxy population over the last decade have led to a concensus that the stars that we see today in the local Universe predominantly formed over the past 10Gyr in rotationally-supported and secularly evolving disk-dominated galaxies. Although this observational picture of the evolution of star formation with cosmic time is now well established, observational constraints on how the growth of galaxian disks is modulated (with respect to the overall evolution of the density of the Universe) by the non-linear growth of the parent dark matter (DM) haloes of galaxies have hitherto been limited to indirect statistical treatments, which moreover have been agnostic to galaxy morphology. After an introductory review, I will present results obtained using the Galaxy And Mass Assembly (GAMA) spectroscopic survey, of the so-called "Main Sequence" (MS) relation between SFR and stellar mass for morphologically-selected disk-dominated galaxies in the local Universe. These results are used to examine how the MS relation depends (at fixed stellar mass) on the mass of the host DM halo, as measured through kinematic and weak lensing data. I will also examine the dependence of the relation on cosmic time over the past Gyr - from which the present-day time-derivative of the light curve of galaxy disks in the UV as a function of their stellar mass will be inferred - and the effect on the MS relation and its scatter of whether a galaxy is a dominant central galaxy or is a satellite orbiting within the halo. The overall picture given by this analysis is one in which the efficiency of the condensation of baryons in the intergalactic medium into stars in galaxy disks as a function of halo mass varies according to a simple time-independent power law relation. Overall, this picture suggests that the present day diversity of the galaxy population, in particular the well-known propensity of red/blue galaxies to inhabit more/less dense regions of the cosmic web, and the rapidity at which the star formation activity of the Universe is being extinguished, is driven mainly by the transformation of morphology from disks to spheroids in different environments, rather than by variations of the cooling and accretion of the intergalactic medium onto galaxies as a function of environment.

Heidelberg Joint Astronomical Colloquium
13 Nov 2018, 16:15
Philosophenweg 12, Großer Hörsaal

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