6 research outputs found
Clustering Properties of restframe UV selected galaxies I: the correlation length derived from GALEX data in the local Universe
We present the first measurements of the angular correlation function of
galaxies selected in the far (1530 A) and near (2310 A) Ultraviolet from the
GALEX survey fields overlapping SDSS DR5 in low galactic extinction regions.
The area used covers 120 sqdeg (GALEX - MIS) down to magnitude AB = 22,
yielding a total of 100,000 galaxies. The mean correlation length is ~ 3.7 \pm
0.6 Mpc and no significant trend is seen for this value as a function of the
limiting apparent magnitude or between the GALEX bands. This estimate is close
to that found from samples of blue galaxies in the local universe selected in
the visible, and similar to that derived at z ~ 3 for LBGs with similar rest
frame selection criteria. This result supports models that predict anti-biasing
of star forming galaxies at low redshift, and brings an additional clue to the
downsizing of star formation at z<1.Comment: Accepted for publication in GALEX Special ApJs, December 200
The On-Orbit Performance of the Galaxy Evolution Explorer
We report the first year on-orbit performance results for the Galaxy
Evolution Explorer (GALEX), a NASA Small Explorer that is performing a survey
of the sky in two ultraviolet bands. The instrument comprises a 50 cm diameter
modified Ritchey-Chretien telescope with a 1.25 degree field of view,
selectable imaging and objective grism spectroscopic modes, and an innovative
optical system with a thin-film multilayer dichroic beam splitter that enables
simultaneous imaging by a pair of photon counting, microchannel plate, delay
line readout detectors. Initial measurements demonstrate that GALEX is
performing well, meeting its requirements for resolution, efficiency,
astrometry, bandpass definition and survey sensitivity.Comment: This paper will be published as part of the Galaxy Evolution Explorer
(GALEX) Astrophysical Journal Letters Special Issu
Statistical Properties of the GALEX/SDSS matched source catalogs, and classification of the UV sources
We use the Galaxy Evolution Explorer (GALEX) Medium and All-Sky-Imaging
Survey (MIS & AIS) data from the first public data release (GR1), matched to
the Sloan Digital Sky Survey (SDSS) DR3 catalog, to perform source
classification. The GALEX surveys provide photometry in far- and near-UV bands
and the SDSS in five optical bands (u,g,r,i,z). The GR1/DR3 overlapping areas
are 363[83]deg^2 for the GALEX AIS[MIS], for sources within the 0.5deg central
area of the GALEX fields. Our sample covers mostly |b|>30deg galactic
latitudes. We present statistical properties of the GALEX/SDSS matched sources
catalog, containing >2x10^6 objects detected in at least one UV band. We
classify the matched sources by comparing the seven-band photometry to model
colors constructed for different classes of astrophysical objects. For sources
with photometric errors <0.3 mag, the corresponding typical AB-magnitude limits
are m_FUV~21.5, m_NUV~22.5 for AIS, and m_FUV~24, m_NUV~24.5 for MIS. At AIS
depth, the number of Galactic and extragalactic objects are comparable, but the
latter predominate in the MIS. Based on our stellar models, we estimate the
GALEX surveys detect hot White Dwarfs throughout the Milky Way halo (down to a
radius of 0.04 R_sun at MIS depth), providing an unprecedented improvement in
the Galactic WD census. Their observed surface density is consistent with Milky
Way model predictions. We also select low-redshift QSO candidates, extending
the known QSO samples to lower magnitudes, and providing candidates for
detailed z~1 follow-up investigations. SDSS optical spectra available for a
large subsample confirm the classification for the photometrically selected
candidates with 97% purity for single hot stars, ~45%(AIS)/31%(MIS) for
binaries containing a hot star and a cooler companion, and about 85% for QSOs.Comment: 33 pages, 11 figures, accepted for the GALEX special issue of ApJS.
For a version with full resolution figures see
http://dolomiti.pha.jhu.edu/publgoto.htm