AAS 205th Meeting, 9-13 January 2005
Session 94 From Protogalaxies to Large Surveys: Tracing the Galaxy Evolution
Poster, Wednesday, January 12, 2005, 9:20am-6:30pm, Exhibit Hall

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[94.19] Spectroscopic Confirmation of z~6 i-band Dropout Galaxies in the RDCSJ1252-2927 and UDF-Parallel ACS Fields

C. Dow-Hygelund, G. Illingworth, B. Holden, R. Bouwens (UC Santa Cruz), A. van der Wel, M. Franx (U of Leiden)

We have selected a sample of 22 potential z~6 galaxies from HST ACS imaging using the Lyman break technique. We present deep LRIS and FORS2 spectroscopy for these objects, with exposures of up to 24 hours. For our brightest galaxy (z850,AB=24.3, z=5.515), there is clear evidence for significant metal absorption line features similar to starbursting galaxies at lower redshifts. We believe this to be the highest redshift absorption spectrum acquired to date of a Lyman break galaxy. Furthermore, a continuum spectrum of another object (z850,AB=25.6, z=5.8) will also be shown and it similarly lacks a strong Lyman-alpha emission component. Two significant trends seen in our sample are (i) objects that possess strong Lyman-alpha emission have relatively low star formation rates, and (ii) these objects compose approximately 25% of the LBG's at z~6. Lyman-alpha emitters appear to be a poor representation of the star-forming populace at this epoch, implying that broadband selection techniques are critical for obtaining statistically relevant samples of z~6 objects.

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© 2004. The American Astronomical Society.