NOAO >   Observing Info >   Approved Programs >   2006A-0580

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Proposal Information for 2006A-0580


PI: Mark Dickinson, NOAO, med@noao.edu
Address: 950 N. Cherry Ave., Tucson, AZ 85719, United States

CoI: Ranga-Ram Chary, SSC
CoI: Emanuele Daddi, NOAO
CoI: David Elbaz, CEA/Saclay
CoI: Emily MacDonald, NOAO
CoI: Casey Papovich, Steward Observatory
CoI: Daniel Stern, JPL

Title: A survey of galaxy mass assembly at \mathbf 1.5 < z < 3 via faint GOODS \mathbf24(micron) sources

Abstract: Current evidence strongly points to the redshift range 1 < z < 3 as the era when most of the stars in the Universe were formed. The GOODS Spitzer Legacy program is mapping this process, with observations at 3-8 (micron) to measure the stellar masses of galaxies, and the deepest MIPS 24(micron) data to study dusty star formation with much greater sensitivity than is possible at other wavelengths. We have recently shown that a large fraction (> 50%) of massive (stellar M_\ast ~ 10^11 M_\odot) galaxies at 1.5 < z < 3 are detected by Spitzer at 24(mu)m, with implied \langle L_IR \rangle > 10^12 L_\odot, or average star formation rates > 170 M_\odot/year. The high fraction implies a large duty cycle: massive galaxies were growing rapidly in that era. However, at present this result relies mainly on color selection and photometric redshifts. Spectroscopic redshifts are essential due to the complex k-corrections arising from the very strong mid-IR emission & absorption bands. We propose to measure redshifts for ~ 180 non-Xray 24(micron) sources at z > 1.5, which will more than triple the sample now known, and enable us to compare the MIPS measurements against radio & other multiwavelength data in order to calibrate 24(mu)m-derived star formation rates.


National Optical Astronomy Observatory, 950 North Cherry Avenue, P.O. Box 26732, Tucson, Arizona 85726, Phone: (520) 318-8000, Fax: (520) 318-8360



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