1. Specific Star Formation Rates to z=1.5
Amanda E. Bauer
N. Drory, G. Hill
University of Texas at Austin
July 7, 2005

2. Where and when does stellar mass build?
Lilly-Madau Diagram
• High mass galaxies exist early in the universe!
• 50% stellar mass in place by z=1
• Is declining SFR since z=1 universal for all galaxies?
Pérez-González et al. 2005
Mass Function
Must combine MF and SFR information
Drory et al. 2005

3. FORS Deep Field and the Munich Near-Infrared Cluster Survey
50-75% of current spectroscopic samples are forming stars.
SFR increases with redshift
Redshift Log (SFR) (Msun/yr)
Bauer et al. 2005

4. Specific Star Formation Rate (SSFR)
Log ( Specific SFR ) (yr-1)
Log M* ( Msun )
• SSFR decreases with increasing M* at all z
• SF contributes more to growth of low mass galaxies
• Turnover mass increases with redshift
• Upper envelop decrease matches Lilly-Madau plot
Bauer et al. 2005

5. Possible Evolutionary Paths in SSFR
Red points show starting point for evolution of Msun galaxy.
Black points show possible end point.
Log ( Specific SFR ) (yr-1)
Log M* ( Msun )

6. Ongoing Work Analyzing HST/ACS I-band data of FDF galaxies
red / near-IR spectroscopy of massive galaxies from FDF and MUNICS.

7. Summary
There exists a ridge in SSFR that runs parallel to lines of constant SFR.
The SSFR from mass-selected samples replicates Lilly-Madau plot evidence for factor of 10 decrease in SFR density since z=1
The decrease occurs simultaneously for galaxies of different stellar masses.