Journal article
Very blue UV-continuum slope β of low luminosity z∼7 galaxies from WFC3/IR: Evidence for extremely low metallicities?
RJ Bouwens, GD Illingworth, PA Oesch, M Trenti, M Stiavelli, CM Carollo, M Franx, PG Van Dokkum, I Labbé, D Magee
Astrophysical Journal Letters | Published : 2010
Abstract
We use the ultra-deep WFC3/IR data over the Hubble Ultra Deep Field and the Early Release Science WFC3/IR data over the CDF-South GOODS field to quantify the broadband spectral properties of candidate star-forming galaxies at z∼7. We determine the UV-continuum slope β in these galaxies, and compare the slopes with galaxies at later times to measure the evolution in β. For luminous L* z=3 galaxies, we measure a mean UV-continuum slope β of -2.0 0.2, which is comparable to the β -2 derived at similar luminosities at z∼5-6. However, for the lower luminosity 0.1L* z=3 galaxies, we measure a mean β of ≫-3.0±0.2. This is substantially bluer than is found for similar luminosity galaxies at z∼4, jus..
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Funding Acknowledgements
We thank Daniel Schaerer for helpful conversations. We are grateful to all those at NASA, STScI, and throughout the community who have worked so diligently to make Hubble the remarkable observatory that it is today. We acknowledge the support of NASA grant NAG5-7697 and NASA grant HST-GO-11563.01. Based on observations made with the NASA/ESA Hubble Space Telescope, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. These observations are associated with programs #11563, 9797.