Publications (5)19.48 Total impact
-
Article: Statistical Properties of the GALEX-SDSS Matched Source Catalogs, and Classification of the UV Sources
[show abstract] [hide abstract]
ABSTRACT: We use the Galaxy Evolution Explorer (GALEX) Medium and All-Sky Imaging Survey (MIS and 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 (86) deg2 for the GALEX AIS (MIS), for sources within the 0.5° central area of the GALEX fields. Our sample covers mostly |b| > 30° Galactic latitudes. We present statistical properties of the GALEX-SDSS matched sources catalog, containing >2 × 106 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 mFUV ~ 21.5, mNUV ~ 22.5 for AIS, and mFUV ~ 24, mNUV ~ 24.5 for MIS. At AIS depth, the number of Galactic and extragalactic objects are comparable, but the latter predominate in the MIS. On the basis of 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☉ 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 z ≈ 1 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) or 31% (MIS) for binaries containing a hot star and a cooler companion, and about 85% for QSOs.The Astrophysical Journal Supplement Series 12/2008; 173(2):659. · 13.46 Impact Factor -
Article: Large-Amplitude Ultraviolet Variations in the RR Lyrae Star ROTSE-I J143753.84+345924.8
[show abstract] [hide abstract]
ABSTRACT: The NASA Galaxy Evolution Explorer (GALEX) satellite has obtained simultaneous near-ultraviolet (NUV) and far-ultraviolet (FUV) light curves of the ROTSE-I Catalog RR Lyrae type ab variable star J143753.84+345924.8. A series of 38 GALEX Deep Imaging Survey observations well distributed in phase within the star's 0.56432 day period shows an AB = 4.9 mag variation in the FUV (1350-1750 Å) band and an AB = 1.8 mag variation in the NUV (1750-2750 Å) band, compared with only a 0.8 mag variation in the broad, unfiltered ROTSE-I (≈4500-10,000 Å) band. These GALEX UV observations are the first to reveal a large RR Lyrae amplitude variation at wavelengths below 1800 Å. We compare the GALEX and ROTSE-I observations to predictions made by recent Kurucz stellar atmosphere models. We use published physical parameters for the comparable period (0.57433 days), well-observed RR Lyrae star WY Antliae to compute predicted FUV, NUV, and ROTSE-I light curves for J143753.84+345924.8. The observed light curves agree with the Kurucz predictions for [Fe/H] = -1.25 to within AB = 0.2 mag in the GALEX NUV and ROTSE-I bands and to within 0.5 mag in the FUV. At all metallicities between solar and 1/100 solar, the Kurucz models predict 6-8 mag of variation at wavelengths between 1000 and 1700 Å. Other variable stars with similar temperature variations, such as Cepheids, should also have large-amplitude FUV light curves, observable during the ongoing GALEX imaging surveys.The Astrophysical Journal 12/2008; 619(1):L123. · 6.02 Impact Factor -
Article: Clustering Properties of restframe UV selected galaxies I: the correlation length derived from GALEX data in the local Universe
[show abstract] [hide abstract]
ABSTRACT: 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 200710/2007; -
Article: 2D analytical modeling of distortion and sky background in multi-fiber spectrographs: the case of the Norris spectrograph at Palomar Mountain
[show abstract] [hide abstract]
ABSTRACT: A method for optimal reduction of data taken with multi-fiber spectrographs is described, based on global correction of their geometrical distortion. Though it was specifically developed for reducing observations performed at Palomar Mountain using the Norris fiber spectrograph, this method can be adapted to other types of multi-object spectrographs such as the multi-slit ones. Combined with a 2D analytical interpolation of sky-background that accounts for non-uniform spectral resolution, the Norris software package achieves very high accuracy in airglow subtraction, even in the near infrared (7000-9000A) where molecular band-emissions commonly induce strong artefacts that preclude clean sky subtraction whenever standard image processing techniques are used. Correlatively, an improvement by a factor of 2 on the precision of radial velocities is achievable. Throughout the paper possible improvements to the method are suggested for those devising similar packages for other instruments. Comment: 12 pages LateX, 4 PS figures, accepted for PASP (February 2003)11/2002; -
Article: Clustering Properties of Rest-Frame UV-Selected Galaxies. I. the Correlation Length Derived from GALEX Data in the Local Universe
[show abstract] [hide abstract]
ABSTRACT: We present the first measurements of the angular correlation function of galaxies selected in the far (1530 Å) and near (2310 Å) ultraviolet from the GALEX survey fields overlapping SDSS DR5 in low Galactic extinction regions. The area used covers 120 deg^2 (GALEX Medium Imaging Survey) down to magnitude AB = 22, yielding a total of 100,000 galaxies. The mean correlation length is ~3.7 ± 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 antibiasing of star-forming galaxies at low redshift and brings an additional clue to the downsizing of star formation at z < 1.
