990 research outputs found
Chandra Detection of X-ray Absorption Associated with a Damped Lyman Alpha System
We have observed three quasars, PKS 1127-145, Q 1331+171 and Q0054+144, with
the ACIS-S aboard the Chandra X-ray Observatory, in order to measure soft X-ray
absorption associated with intervening 21-cm and damped Ly absorbers.
For PKS 1127-145, we detect absorption which, if associated with an intervening
z_{abs}=0.312 absorber, implies a metallicity of 23% solar. If the absorption
is not at z_{abs}=0.312, then the metallicity is still constrained to be less
than 23% solar. The advantage of the X-ray measurement is that the derived
metallicity is insensitive to ionization, inclusion of an atom in a molecule,
or depletion onto grains. The X-ray absorption is mostly due to oxygen, and is
consistent with the oxygen abundance of 30% solar derived from optical nebular
emission lines in a foreground galaxy at the redshift of the absorber.
For Q1331+171 and Q 0054+144, only upper limits were obtained, although the
exposure times were intentionally short, since for these two objects we were
interested primarily in measuring flux levels to plan for future observations.
The imaging results are presented in a companion paper.Comment: 23 pages, 6 figures, accepted for publication in the Astrophysical
Journa
The energy dependence of charge exchange reactions favourably used in Lambshift type ion sources
A Proto-Galaxy Candidate at z=2.7 Discovered by Its Young Stellar Population
A protogalaxy candidate at z=2.72 has been discovered serendipitously by the
CNOC cluster redshift survey. The candidate is an extremely luminous (V=20.5
mag, absolute mag -26) and well resolved disk-like galaxy. The redshift is
identified from a dozen strong UV absorption lines. No emission lines are found
between 1000 and 2000A (rest), including Ly alpha. The photometric data fit the
spectral energy distributions of a stellar population from 400 million years to
an arbitrarily young age, dependent on the amount of dust extinction. However,
the presence of a strong P-Cygni profile in CIV~indicates that a very
substantial component of the stellar population must be younger than ~ 10 Myr.
We interpret this object as an early-type galaxy observed within about 100
million years of the initial burst of star formation which created most of its
stellar mass. Because of the resolved, regular, and smooth nature of the
object, it is unlikely that the high luminosity is due to gravitational
lensing.Comment: 31 page, Latex file with 9 encapsulated figures, requiring aasppt.sty
and epsf.sty (included). Full uuencoded ps file available from:
http://manaslu.astro.utoronto.ca/~carlberg/cnoc/general.html Accepted by
Astronomical Journal, in press, May 199
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