Reconstructing the Mass Assembly of Galaxy Disks over the last 12 Billion Years with ALMA, HST and Spitzer
Bars are a key signpost in the evolutionary history of a disk galaxy. When a disk is sufficiently massive, dynamically cold and rotationally supported, and sufficient time has elapsed for the baryonic matter to exchange energy and angular momentum with the dark matter halo or the outer disk, the formation of a bar is inevitable. Therefore understanding the evolution of the bar fraction as a function of the host galaxy properties and as a function of redshift provides important clues to the evolutionary history of galaxies. I will present the latest results on local bars from the Spitzer Survey of Stellar Structure in Galaxies (S4G) and discuss the observations for the declining bar fraction with redshift from the COSMOS survey. A plausible reason for the decline in the bar fraction may be that galaxy disks were too dynamically hot to host bars at higher redshift which we have investigated using the DEEP2 / AEGIS data. Together these data are beginning to provide a coherent and consistent picture for the assembly history of disks on the Hubble sequence. The star formation in these disks is also now being understood with the latest results from ALMA. I will show the latest results on the cosmological evolution of the molecular gas content in a mass-selected sample of galaxies at three epochs, z=2.2, z=1, and z=0.3 and discuss planned Cycle 1 observations of the molecular gas environment in the prototypical barred spiral NGC 1097.
Kartik Sheth (NASA)