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Statistical Properties of the GALEX-SDSS Matched Source Catalogs, and Classification of the UV Sources

Bianchi, Luciana and Rodriguez-Merino, Lino and Viton, Maurice and Laget, Michel and Efremova, Boryana and Herald, James and Conti, Alberto and Shiao, Bernie and Gil de Paz, Armando and Salim, Samir and Thakar, A. and Friedman, Peter G. and Rey, Soo-Chang and Thilker, David and Barlow, Tom A. and Budavári, Tamás and Donas, José and Forster, Karl and Heckman, Timothy M. and Lee, Young-Wook and Madore, Barry F. and Martin, D. Christopher and Milliard, Bruno and Morrissey, Patrick and Neff, Susan G. and Rich, R. Michael and Schiminovich, David and Seibert, Mark and Small, Todd and Szalay, Alex S. and Wyder, Ted K. and Welsh, Barry Y. and Yi, Sukyoung K. (2007) Statistical Properties of the GALEX-SDSS Matched Source Catalogs, and Classification of the UV Sources. Astrophysical Journal Supplement Series, 173 (2). 659-672 . ISSN 0067-0049.

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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) deg^2 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 × 10^6 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. 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.

Item Type:Article
Related URLs:
URLURL TypeDescription
Bianchi, Luciana0000-0001-7746-5461
Gil de Paz, Armando0000-0001-6150-2854
Salim, Samir0000-0003-2342-7501
Thilker, David0000-0002-8528-7340
Forster, Karl0000-0001-5800-5531
Madore, Barry F.0000-0002-1576-1676
Martin, D. Christopher0000-0002-8650-1644
Morrissey, Patrick0000-0001-8177-1023
Rich, R. Michael0000-0003-0427-8387
Seibert, Mark0000-0002-1143-5515
Additional Information:© 2007 American Astronomical Society. Received 2006 July 21; accepted 2006 October 26. GALEX (Galaxy Evolution Explorer) is a NASA Small Explorer, launched in 2003 April. We gratefully acknowledge NASA’s support for construction, operation, and science analysis of the GALEX mission, developed in cooperation with the Centre National d’Etudes Spatiales of France and the Korean Ministry of Science and Technology. We are grateful to John Hutchings, Wei Zheng, and Gordon Richards for discussions about QSO issues and clarifications about the QSO SDSS catalogs and templates, to Alessandro Bressan for providing the yet unpublished SSP models and for extremely useful discussions, and (with Olga Vega) for assistance in calculations of the galaxy template, to Paula Szkody and Knox Long for illuminating discussions about CVs and for the CV templates. Facilities: GALEX, Sloan
Group:Space Radiation Laboratory, Space Astrophysics Laboratory
Subject Keywords:Galaxy: stellar content; quasars: general; stars: statistics; surveys; ultraviolet: stars; white dwarfs
Issue or Number:2
Record Number:CaltechAUTHORS:20100430-103413888
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Official Citation:Luciana Bianchi et al 2007 ApJS 173 659 doi: 10.1086/516648
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:18086
Deposited By: Jason Perez
Deposited On:03 May 2010 18:18
Last Modified:09 Mar 2020 21:07

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