The UV Sky

NEW! The latest catalogs of GALEX UV sources are published: (available below)

More than 200 million UV source measurements in two UV bands, far-UV (1344-1786Ang) and near-UV (1771-2831Ang). This is the legacy of GALEX, the first mission to perform sky surveys in the Ultraviolet. What are these sources? How many of them are Milky Way stars, and how many extragalactic objects? How are they distributed over the sky, and in color, magnitude, luminosity? How to extract samples of UV sources by astrophysical class? Are there peculiar classes of objects discovered from the GALEX data? The "UV sky" project and the series of papers below seek to answer these questions.

  1. relevant publications describing data, catalogs and science tools
  2. final catalogs of unique UV (GALEX) sources (and matched catalogs)
  3. catalogs of hot stars selected from GALEX-SDSS matched catalogs (GR5) [goes to a different page]
  4. catalogs of 19000 QSO candidates around redshift 1 from GALEX-SDSS matched catalogs
  5. catalog of matched GALEX AIS with GSC2 [goes to a different page]
  6. GALEX photometry of Magellanic Cloud stars

1) Relevant publications:

* An Invited Review of GALEX data
Bianchi, L. 2014, in "Challenges in UV Astronomy", Proceedings NUVA/ESO Conference (Oct. 2013), ApSS, in press; DOI: 10.1007/s10509-014-1935-6 ; arXiv:1404.4882
The Galaxy Evolution Explorer (GALEX). Its legacy of UV surveys, and science highlights
you may download pdf manuscript here or see the Springer online article here (open source)

* The latest version of the GALEX catalogs of UV sources, including GR7 additions:
Bianchi, L., Conti, A., and Shiao, B. 2014, J. Adv. Space Res. 53 (2014), pp. 900-912, DOI: http://dx.doi.org/10.1016/j.asr.2013.07.045 ; astro-ph 1312.3281
The ultraviolet sky: An overview from the GALEX surveys. link to ASR article or download manuscript pdf or go to astro-ph 1312.3281

* Catalog of UV (GALEX) serendipitous variables:
Conti, A., Bianchi, L., Chopra, N., Orio, M., and Shiao, B. 2014, J. Adv. Space Res. 53 (2014), pp. 967-972; DOI: http://dx.doi.org/10.1016/j.asr.2013.07.022
A database of UV Variables from the GALEX survey link to online article in Advances in Space Research or download pdf here

* Catalog of UV sources in the Magellanic Clouds : (part I)
Simons, R., Thilker, D., and Bianchi, L., 2014, J. Adv. Space Res. 53 (2014), pp.939-949 ; DOI: http://dx.doi.org/10.1016/j.asr.2013.07.016
The Ultraviolet View of the Magellanic Clouds from GALEX: A First Look at the LMC Source Catalog. link to online article in Advances in Space Research or download pdf here

* Includes useful tables for converting magntiudes, and for extinction corrections, for GALEX, SDSS, and other systems, and a summary of some GALEX results
Bianchi, L., 2011, ApSS, 335, 51; DOI: 10.1007/s10509-011-0612-2 ( download pdf )
this is an invited review in "The UV Universe 2010" (St. Petersburg June 2010), editors B. Shustov, A.I. Gomez de Castro, and M. Sachkov
"GALEX and star formation"

* First version of the UV source catalogs (and description of recipes and caveats) (available at this site or MAST or Vizier ;) it describes the matches GALEX_SDSS catalogs, and analysis hot-star sub-catalogs with Milky Way models:
Bianchi, L., Efremova, B., Herald, J., Girardi, L, Zabot, A., Marigo, P., Martin, C, 2011, MNRAS, 411, 2770, ( doi:10.1111/j.1365-2966.2010.17890.x) , (astro-ph: http://arxiv.org/abs/1011.1733 )
Catalogs of Milky Way Hot White Dwarf Candidates from GALEX's Ultraviolet Sky Surveys. Constraining Stellar Evolution.
download manuscript pdf or get the published paper: link to MNRAS paper or go to preprint in ADS (http://arxiv.org/abs/1011.1733 )

* Additional statistical properties of the UV catalogs, biases of sample selections, GALEX-GSC2 matched catalog:
Bianchi, L. , Herald, J., Efremova, B., Girardi, L., Zabot, A., Marigo, P., Conti, A., Shiao, B. 2011, ApSS, 335, 161, DOI: 10.1007/s10509-010-0581-x, ``GALEX Catalogs of UV sources: Statistical properties and sample science applications: Hot White Dwarfs in the Milky Way'' link to paper in ADS or go to ApSS link download pdf here

* Catalog of z~1 QSO candidates extracted from the Bianchi+2011 catalogs:
Hutchings, J.B., and Bianchi, L. , 2010, AJ, 140, 1987
A sample of 19000 QSO Caldidates with redshift 0.5 to 2.0 download pdf or link to the AJ catalog

* Overview of GALEX's UV surveys and source classification by astrophysical class:
Bianchi, L. 2009, in "Space Astronomy: The UV Window to the Universe", APSS, 320, 11 ( DOI: 10.1007/s10509-008-9761-3 )
The Ultraviolet Sky Surveys: Filling the Gap in our View of the Universe
download the poscript file or the pdf file or get the article from www.spirngerlink.com

* Discovery of QSOs with anomalous FUV-NUV color: Ly_alpha enhanced?
Bianchi, L., Hutchings, J.B., Efremova, B. et al. 2009, AJ, 137, 3761 ( astro-ph arXiv:0901.1896 )
Ultraviolet Quasi Stellar Objects download pdf file

* Early analysis of the Bianchi et al. 2011 MNRAS sample:
Bianchi, L., Efremova, B., Herald, J. et al. 2009, in "Future Directions in Ultraviolet Spectroscopy", eds.Van Steenberg et al AIPC, 1135, 326
The UV sky surveys: a roadmap for future UV missions download ps file

* On the classification of GALEX UV sources (several color-color diagrams):
Bianchi, L., et al. 2007, ApJS, 173, 659
Statistical Properties of the GALEX/SDSS Matched Source Catalogs, and Classification of the UV Sources
download: [paper ps gzip file]

* First work on classification of GALEX UV sources from early data release:
Bianchi, L. et al. 2005, ApJ, 619, L27 [pdf file] or [link to ApJ]
Classification and Characterization of Objects from the Galaxy Evolution Explorer Survey and the Sloan Digital Sky Survey

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2) GALEX CATALOGS of UV SOURCES :

To estimate density of certain sources across the sky, or number of sources with given magnitude or color range, you need a catalog in which each astronomical source is counted only once. The MAST GALEX database includes all existing GALEX measurements, and same sources have repeated measurements (useful to search for variability, for example). We constructed catalogs of clean, unique (i.e. only one entry for each object) sources You also need to weed out artfacts and bad measurements: flags are included.
Catalogs were constructed for the two GALEX surveys with the largest sky coverge (see maps):
MIS (Medium Imaging Survey, depth about 22.7 ABmag in FUV/NUV)
AIS (All-Sky Imaging Survey, depth about 19.9/20.8 FUV/NUV ABmag).

GALEX SKY COVERAGE
Figures above: Final (GR6+GR7) sky coverage of GALEX AIS and MIS surveys (figures from Bianchi et al. 2014, J. ASR 53, 900; astro-ph 1312.3281 )

Criteria for constructing the catalogs: (for more details, see the original papers: Bianchi et al. 2014, J. ASR 53, 900; Bianchi, L. et al. 2011, MNRAS, 411, 2770)
1) only observations with both FOV and NUV detectors turned on are included. This is useful for any science analysis where the fraction of sources with a given FUV-NUV color is of interest, or to estimate the fraction of sources with significant detection in both FUV and NUV over the total number of NUV detections. Note that the basic GALEX database gives FUV magnitude = -999 in both cases when the FUV detector was off, or the FUV detector was on but the source's FUV flux is below detection threshold.
More observations exist in the GALEX archive taken with one detector off (mostly FUV); those can be found in the galex.stsci.edu MAST database.

2) only sources within 0.5 degree of the field center are included, to avoid sources with poor photometry/astrometry near the edge, and rim artifacts. This makes the catalogs useful for statistical analysis of sources with homogeneous quality, without great loss of area coverage (also considering that overlap exist among several fields). Users interested in a particular source that happens to fall on the rim of a GALEX filed, should obtain its measurements from the main database and carefully examine the quality.

3) we retained sources with NUV magnitude errors less or equal 0.5mag (see Figure 4 of Bianchi et al. 2011 MNRAS , and Figures 2--4 of Bianchi et al. 2011 ApSS for effects of error cuts on the resulting sample statistics).

4) The general GALEX database contains all measurements for sources with repeated observations. We removed duplicate measurements to produce a unique source catalog as follows. GALEX sources within 2.5'' of each other, but from different observations, were considered duplicates. In such cases the object from the observation with the longest NUV exposure time was retained, and - in cases of equal exposure times - the object closest to the center of the field of view.

See also these review articles for useful information on GALEX data: Bianchi, L. 2009, 320, 11, DOI: 10.1007/s10509-008-9761-3 ; Bianchi, L. 2011 ApSS, 335, 51; DOI: 10.1007/s10509-011-0612-2 ) )

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Final catalogs of UV sources (BCScat); include all GALEX data:
Reference: Bianchi, L., Conti, A., and Shiao, B. 2014, J. Adv. Space Res. Vol. 53 (2014), 900; DOI: 10.1016/j.asr.2013.07.045 ; astro-ph 1312.3281
The ultraviolet sky: An overview from the GALEX surveys. link to ASR article (open access, i.e. free) or download manuscript pdf or go to astro-ph 1312.3281

How to get the catalogs :

CATALOGS of UV sources( " BCScat" AIS and MIS )
==> download the catalogs HERE in csv files, or fits files:
==> from MAST casjobs : galex.stsci.edu/casjobs (Context: GALEXCatalogs, Tables: bcscat_ais, bcscat_mis )
==> from Vizier (coming very soon)

MATCHED CATALOGS UV-optical-IR
==> MATCHED with SDSS DR10: catalogs READY, will be posted soon
==> MATCHED with 2MASS: testing in progress, coming soon
==> MATCHED with GSC2: planned
==> MATCHED with Pan-STARRS: in progress

=> SUBCATALOGS: sources with significant detection in both FUV and NUV, from the above catalogs

Area coverage of BCScat and matched BCScatXoptical catalogs
Table with area coverage, total and at different latitudes
Compute area in sky regions of your choice

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Previous Catalogs, from GALEX fifth data release (GR5)
The previous version of the final catalogs available above; these also include matched GALEXxSDSS catalogs, GALEXxGSC2 catalogs and extracted catalogs of hot stars and QSOs: go to the GR5 catalogs

Source/ reference: Catalogs can be used citing this ref.
Bianchi, L. et al. MNRAS, 2011 411, 2770 (open access) 2011, Catalogs of Milky Way Hot White Dwarf Candidates from GALEX's Ultraviolet Sky Surveys. Constraining Stellar Evolution.


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4) CATALOG OF 19000 QSOs candidates around redshift 1

Hutchings, J.B., and Bianchi, L., 2010, AJ, 140, 1987
A sample of 19000 QSO Candidates with redshift 0.5 to 2.0 download pdf or link to the AJ catalog

QSOs with normal optical properties and unusual UV properties:

Bianchi, L., Hutchings, J.B., Efremova, B. et al. 2009, AJ, 137, 3761 ( astro-ph arXiv:0901.1896 )
Ultraviolet Quasi Stellar Objects download pdf file

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GALEX photometry of Magellanic Cloud stars :

Simons, R., Thilker, D., and Bianchi, L.,, 2013, J. Adv. Space Res. (2013), DOI: http://dx.doi.org/10.1016/j.asr.2013.07.016
The Ultraviolet View of the Magellanic Clouds from GALEX: A First Look at the LMC Source Catalog. link to online article in Advances in Space Research or download pdf here

Catalogs will be posted here
Custom photometry has been performed in the GALEX fields in the periphery of the MC (Thilker et al., in preparation), within 15 and 10 deg of each galaxy, respectively. Safety constraints prohibited observing the bright central regions of the LMC and SMC during the main GALEX mission, but the survey will be extended in the last phase of the mission. The sources in these fields are often very crowded and standard pipeline photometry is not ideal.
Current coverage with both FUV and NUV measurements includes ~550 square degrees in 1460 overlapping GALEX tiles with exposures typically at AIS depth, but occasionally reaching MIS level. The typical magnitude limit is therefore 19.9[20.8] ABmag in the FUV[NUV] band. The catalogued GALEX detections have been matched to visible source catalogs (primarily NOMAD) to produce a multi-wavelength database for over 2 million objects of which MC stars are a large subset.

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