1,070 research outputs found
The Origin of \lya Absorption Systems at ---Implications from the Hubble Deep Field
The Hubble Deep Field images have provided us with a unique chance to relate
statistical properties of high-redshift galaxies to statistical properties of
\lya absorption systems. Combining an {\em empirical} measure of the galaxy
surface density versus redshift with an {\em empirical} measure of the gaseous
extent of galaxies, we predict the number density of \lya absorption systems
that originate in extended gaseous envelopes of galaxies versus redshift. We
show that at least 50% and as much as 100% of observed \lya absorption systems
of W\apg0.32 \AA can be explained by extended gaseous envelops of galaxies.
Therefore, we conclude that known galaxies of known gaseous extent must produce
a significant fraction and perhaps all of \lya absorption systems over a large
redshift range.Comment: 12 pages, 3 figures, accepted for publication in the Astrophysical
Journal, April 10, 2000 issu
Photometry and Photometric Redshifts of Faint Galaxies in the Hubble Deep Field South NICMOS Field
We present a catalog of photometry and photometric redshifts of 335 faint
objects in the HDF-S NICMOS field. The analysis is based on (1) infrared images
obtained with the Hubble Space Telescope (HST) using the Near Infrared Camera
and Multi-Object Spectrograph (NICMOS) with the F110W, F160W, and F222M
filters, (2) an optical image obtained with HST using the Space Telescope
Imaging Spectrograph (STIS) with no filter, and (3) optical images obtained
with the European Southern Observatory (ESO) Very Large Telescope (VLT) with U,
B, V, R, and I filters. The primary utility of the catalog of photometric
redshifts is as a survey of faint galaxies detected in the NICMOS F160W and
F222M images. The sensitivity of the survey varies significantly with position,
reaching a limiting depth of AB(16,000) ~ 28.7 and covering 1.01 arcmin^2 to
AB(16,000) = 27 and 1.05 arcmin^2 to AB(16,000) = 26.5. The catalog of
photometric redshifts identifies 21 galaxies (or 6% of the total) of redshift z
> 5, 8 galaxies (or 2% of the total) of redshift z > 10, and 11 galaxies (or 3%
of the total) of best-fit spectral type E/S0, of which 5 galaxies (or 1% of the
total) are of redshift z > 1.Comment: 33 pages, 10 figures, accepted for publication in the Astrophysical
Journal, August 1, 2000 issu
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