NOAO >   Observing Info >   Approved Programs >   2002B-0344

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Proposal Information for 2002B-0344


PI: James Rhoads, STScI, rhoads@stsci.edu
Address: 3700 San Martin Drive, Baltimore, MD 21218, USA

CoI: Sangeeta Malhotra, STScI
CoI: Arjun Dey, NOAO
CoI: Buell Jannuzi, NOAO
CoI: Michael Brown, NOAO

Title: A Census of z > 4 Galaxies

Abstract: Although recent discoveries have yielded galaxies with redshifts up to z~ 6.6, statistical samples of galaxies at these redshifts are limited. Recent evidence for reionization near z \appx 6 makes this redshift range interesting for studying galaxy formation and evolution. We propose to specroscopically confirm and characterize a statistically useful sample of 4<z<7 galaxies. The candidates for spectroscopy are selected using two criteria: (1) Strong \lya line emission from the Large Area Lyman Alpha (LALA) survey at z=4.5 & 5.7 and (2) Lyman break colors from the NOAO Deep Wide-Field Survey (NDWFS). These two selection methods are complementary and using both will yield the most complete optically selected galaxy sample. Ly-(alpha) selected galaxies typically have low luminosities and high \lya\ equivalent widths, indicating young stellar populations (\le 10^7 years old) with little or no dust. Lyman-break galaxies are typically more luminous, with weak \lya emission or absorption, and may be more evolved. We will use the spectroscopic sample to refine photometric classification methods, in order to leverage much larger samples from LALA and NDWF surveys and extend redshift determinations to lower luminosities. The sample will be used to study galaxy evolution between z=4-7. We will determine luminosity functions, star formation rates, and clustering properties of the sample as a whole, the Lyman-break and \lya populations seperately and will study the relationship between the two. We will determine whether these two kinds of galaxies are different evolutionary stages or whether the lower bolometric luminosities of the line-selected samples imply correspondingly lower halo masses by comparing clustering of the two samples.


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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