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Publication Details
AFRICAN RESEARCH NEXUS
SHINING A SPOTLIGHT ON AFRICAN RESEARCH
earth and planetary sciences
The Hubble ultra deep field
Astronomical Journal, Volume 132, No. 5, Year 2006
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Description
This paper presents the Hubble Ultra Deep Field (HUDF), a 1 million s exposure of an 11 arcmin2 region in the southern sky with the Advanced Camera for Surveys on the Hubble Space Telescope using Director's Discretionary Time. The exposure time was divided among four filters, F435W (B435), F606W (F606), F775W (i 775), and F850LP (z850), to give approximately uniform limiting magnitudes m AB ∼ 29 for point sources. The image contains at least 10,000 objects, presented here as a catalog, the vast majority of which are galaxies. Visual inspection of the images shows few if any galaxies at redshifts greater than ∼4 that resemble present-day spiral or elliptical galaxies. The image reinforces the conclusion from the original Hubble Deep Field that galaxies evolved strongly during the first few billion years in the infancy of the universe. Using the Lyman break dropout method to derive samples of galaxies at redshifts between 4 and 7, it is possible to study the apparent evolution of the galaxy luminosity function and number density. Examination of the catalog for dropout sources yields 504 S435 dropouts, 204 V 606 dropouts, and 54 i775 dropouts. The i775 dropouts are most likely galaxies at redshifts between 6 and 7. Using these samples, which are at different redshifts but derived from the same data, we find no evidence for a change in the characteristic luminosity of galaxies but some evidence for a decrease in their number densities between redshifts of 4 and 7. Assessing the factors needed to derive the luminosity function from the data suggests that there is considerable uncertainty in parameters from samples discovered with different instruments and derived using independent assumptions about the source populations. This assessment calls into question some of the strong conclusions of recently published work on distant galaxies. The ultraviolet luminosity density of these samples is dominated by galaxies fainter than the characteristic luminosity, and the HUDF reveals considerably more luminosity than shallower surveys. The apparent ultraviolet luminosity density of galaxies appears to decrease from redshifts of a few to redshifts greater than 6, although this decrease may be the result of faint-end incompleteness in the most distant samples. The highest redshift samples show that star formation was already vigorous at the earliest epochs at which galaxies have been observed, less than 1 billion years after the big bang. © 2006. The American Astronomical Society. All rights reserved.
Authors & Co-Authors
Koekemoer, Anton M.
United States, Baltimore
Space Telescope Science Institute
Caldwell, John A.R.
United States, Baltimore
Space Telescope Science Institute
United States, Austin
The University of Texas at Austin
Ferguson, Henry C.
United States, Baltimore
Space Telescope Science Institute
Lucas, Ray A.
United States, Baltimore
Space Telescope Science Institute
Jogee, Shardha
United States, Baltimore
Space Telescope Science Institute
United States, Austin
The University of Texas at Austin
Panagia, Nino
France, Paris
European Space Agency - Esa
Robberto, Massimo
France, Paris
European Space Agency - Esa
Somerville, Rachel S.
United States, Baltimore
Space Telescope Science Institute
Germany, Heidelberg
Max Planck Institute for Astronomy
Statistics
Citations: 639
Authors: 8
Affiliations: 8
Identifiers
Doi:
10.1086/507302
ISSN:
00046256
Study Design
Cross Sectional Study