59,372 research outputs found
A General Formulation of the Source Confusion Statistics and Application to Infrared Galaxy Surveys
Source confusion has been a long-standing problem in the astronomical
history. In the previous formulation, sources are assumed to be distributed
homogeneously on the sky. This fundamental assumption is not realistic in many
applications. In this work, by making use of the point field theory, we derive
general analytic formulae for the confusion problems with arbitrary
distribution and correlation functions. As a typical example, we apply these
new formulae to the source confusion of infrared galaxies. We first calculate
the confusion statistics for power-law galaxy number counts as a test case.
When the slope of differential number counts, \gamma, is steep, the confusion
limits becomes much brighter and the probability distribution function (PDF) of
the fluctuation field is strongly distorted. Then we estimate the PDF and
confusion limits based on the realistic number count model for infrared
galaxies. The gradual flattening of the slope of the source counts makes the
clustering effect rather mild. Clustering effects result in an increase of the
limiting flux density with \sim 10%. In this case, the peak probability of the
PDF decreases up to \sim 15% and its tail becomes heavier.Comment: ApJ in press, 21 pages, 9 figures, using aastex.cls, emulateapj5.sty.
Abstract abridge
The Phoenix Deep Survey: Extremely Red Galaxies and Cluster Candidates
We present the results of a study of a sample of 375 Extremely Red Galaxies
(ERGs) in the Phoenix Deep Survey, 273 of which constitute a subsample which is
80% complete to K_s = 18.5 over an area of 1160 arcmin^2. The angular
correlation function for ERGs is estimated, and the association of ERGs with
faint radio sources explored. We find tentative evidence that ERGs and faint
radio sources are associated at z > 0.5. A new overdensity-mapping algorithm
has been used to characterize the ERG distribution, and identify a number of
cluster candidates, including a likely cluster containing ERGs at 0.5 < z < 1.
Our algorithm is also used in an attempt to probe the environments in which
faint radio sources and ERGs are associated. We find limited evidence that the
I - K_s > 4 criterion is more efficient than R - K_s > 5 at selecting dusty
star-forming galaxies, rather than passively evolving ERGs.Comment: 14 emulateapj pages, 15 figures, 1 table, accepted for publication in
Astronomical Journal. A version with full resolution figures is available at
http://www.physics.usyd.edu.au/~asmith/research/ERGpaper.pd
- …