The Redshift Evolution of Bulges and Disks of Spiral Galaxies in COSMOS

Abstract

We present a preliminary analysis of the bulge and disk properties for a sample of over 4000 L* spiral galaxies at z < 0.84 from the COSMOS 2 square degree survey. We find that for early Hubble type spiral galaxies (Sa–Sb), the bulge-to-disk ratio is roughly constant over the last 7 Gyr of lookback time. This suggests that bulges of early type spirals were in place early on, consistent with other downsizing signatures. There is a monotonic increase in the bulge-to-disk ratios of late type spirals but that likely reflects the well-known decline in the star formation rate from z ~ 1 to the present. For this sample of L* spirals, we also find that the median exponential scale length of disks remains unchanged at 3.1 kpc from z = 0.0 to z = 0.84.

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