ATLAS-REFCAT2 is an all-sky reference catalog containing nearly one billion stars down to apparent magnitude m ~19. The catalog includes PanSTARRS DR1, ATLAS Pathfinder, ATLAS re-flattened APASS, SkyMapper DR1, APASS DR9, Tycho-2, and the Yale Bright Star Catalog. Gaia DR2 serves as the source of the astrometric solution for ATLAS-REFCAT2, with typical systematic errors of < 5 mmag RMS, although this can be as much as 20 mmag near the Galactic plane. The ATLAS Pathfinder telescope was used to collect g,r,i photometry for stars brighter than the 14th magnitude bright limit of PanSTARRS, and to extend the reference system below -30 declination. You can refer to the full collection of ATLAS-REFCAT2 data products in papers or webpages using the DOI http://dx.doi.org/10.17909/t9-2p3r-7651.
The ATLAS-REFCAT2 catalog is split into multiple .csv files on disk, organized into zones of declination. The database tables are also available in the MAST CasJobs interface to enable SQL queries and to cross-match the ATLAS-REFCAT2 catalog with numerous other catalogs available at MAST.
The ATLAS-REFCAT2 catalog is available in bzip2 tar files with columns stored as scaled integers (as described in Tonry et al. 2018). It is also provided as gzipped .csv files, with the columns converted to standard astronomical units as described above. Those files are split into zones of declination.
Original Format, Scaled Integer Columns
The ATLAS-REFCAT2 catalog is available in the format described in Tonry et al 2018, organized into magnitude chunks. These are compressed tarballs of 64800 CSV files for each coordinate square degree. A program refcat.c with man page refcat.man are provided by J. Tonry to Refcat2 data files in a directory and return all the stars within a distance of a given coordinate. Note this software is provided "as-is" from the author, and is not maintained by MAST.
MAST Format, Astronomical Units
The Refcat2 data are also available as gzipped CSV files in Dec zones, with columns converted to standard astronomical units. The units for the columns in the MAST version have been converted to slightly different units than what is documented in Tonry et al. 2018: coordinates are converted into degrees, parallax and proper motions are converted into milliarcseconds and milliarcseconds per year, respectively, magnitudes are given in full magnitude, χ2/DOF values are not scaled, and the bitmasks have been "collapsed" into integer representations. The full column information for the MAST version of the catalog can be found in the README file, and also in the table notes section in MAST CasJobs under MyDB: select "HLSP_ATLAS_REFCAT2" from the Context drop-down, then click on the "NOTES" button in the table display on the right of the page. The tutorial section below demonstrates how to convert the bitmask integers into the corresponding set flags.
SQL Access Via MAST CasJobsIt is also available on MAST CasJobs, see below for some example queries and helpful tutorials. The below examples show SQL commands you can enter in the "Query" tab once you sign into CasJobs.
Converting "Contrib" Integers To BitMask Values
You can see the contents of the look-up table by issuing this query:This query should result in a table that looks like the following: You can translate the various "Contrib" values to see which bits were set with the following function: You can select sources that have a given bit set in a given "Contrib" column by doing something like the following, which uses a stored procedure called "fGetgrizContribFlagsValue" available in the ATLAS-REFCAT2 Context:
Box Search Using RA and Dec.
This search conducts a box search between an RA of 0.0 and 0.2 degrees and a Declination between +0.0 and +0.2 degrees on the sky.
Box Search Using RA and Dec. Via Stored Procedure
This search conducts a box search between an RA of 0.0 and 0.2 degrees and a Declination between +0.0 and +0.2 degrees on the sky using a stored procedure called "fGetObjFromRect". In most situations it is likely faster to do the query directly. The parameter list for "fGetObjFromRect" is (ra1, ra2, dec1, dec2), all in degrees.
Cone Search Using RA and Dec. Via Stored Procedure
This search conducts a cone search centered on an (RA, Dec) coorindate of (0.0, 0.0) degrees using a 5 arcminute search radius. This makes use of the "fGetNearbyObjEq" stored procedure, which accepts as parameters the RA and Dec. of the search center in degrees, and a search radius (also in degrees). This query also sorts the return results by distance from search center, so that objects closest to the cone search center are returned first.
Cross-Match Against An Uploaded Table
If you upload a table containing targets with positions, you can perform a spatial cross-match (or any other cross-match on columns that contain the same info). This example shows how to perform a spatial cross-match. First, create an upload table that looks like this:Upload this file into MyDB (for this tutorial, we will call it "MySources") using the Import tool in CasJobs. Then, run the following query to obtain the ATLAS-REFCAT2 catalog entries within a 1 arcminute radius of each source in your table (remember "fGetNearbyObjEq" uses a search radius in degrees):
Cross-Match Against GALEX GR7
You can cross-match tables with any other database table availble in MAST CasJobs. For instance, here we will show how to cross-match ATLAS-REFCAT2 with GALEX GR7 (the last data release) to get candidate matches to add UV flux information. Note that this example requires setting the Context drop-down menu in the top left to "gale_gr6Plus7", because one can not call "fGetNearbyObjEq" by adding the Context to the function call. Also note that the "fGetNearbyObjEq" stored procedure in the GALEX Context accepts the search radius in arcminutes, not degrees. In this example, the match radius is set to 10 arcseconds in the call to fGetNearbyObjEq (converted to arcminutes as required by the stored procedure).