## Mission Overview

### The ATLAS All-Sky Stellar Reference Catalog ("ATLAS-REFCAT2")

Primary Investigator: J. L. Tonry

HLSP AuthorsJ. L. Tonry

Released: 2018-09-17

Updated: 2018-09-17

Primary Reference(s): Tonry et al. 2018

## Overview

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.

## Data Products

The ATLAS-REFCAT2 catalog is available in two formats: the original format by Tonry et al. and gzipped CSV format by MAST. The latter 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 original catalog formats are organized into magnitude chunks, as described in Tony et al. 2018. These are compressed tarballs of 64800 CSV files for each coordinate square degree. A program refcat.c with man page refcat.man is provided by J. Tonry to Refcat2 data files in a directory, and returns all the stars within a distance of a given coordinate. Note this software is provided "as-is" by the author and is not maintained by MAST. The original catalog has the following name convention:

hlsp_atlas-refcat2_atlas_ccd_<lower_mag>-m-<upper_mag>_multi_v1_cat.tbz

where:

• <lower_mag> = lower limit of magnitudes {g,r,i}
• <upper_mag> = upper limit of magnitudes {g,r,i}

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.

The MAST gzipped CSV version of the catalog has the following name convention:

hlsp_atlas-refcat2_atlas_ccd_<lower_Dec>-<upper_Dec>_multi_v1_cat.csv.gz

where:

• <lower_Dec>  = lower limit of Declination, e.g., m53
• <upper_Dec> = upper limit of Declination e.g., p19
• 'm' and 'p' represent negative and positive values respectively. e.g., m53 = -53º, p19 = +19º

## Data Access

There are three ways to access the ATLAS-REFCAT2 catalog:  direct downloads of  1) bzip2 tar files with columns stored as scaled integers (as described in Tonry et al. 2018) and 2) gzipped .csv files, with the columns converted to standard astronomical units described above and 3) SQL access the MAST CasJobs interface.

#### Original Format, Scaled Integer Columns

.tbz File

Range

Size

hlsp_atlas-refcat2_atlas_ccd_00-m-16_multi_v1_cat.tbz

{g,r,i} < 16

5.9 GB

hlsp_atlas-refcat2_atlas_ccd_16-m-17_multi_v1_cat.tbz

16 < {g,r,i} < 17

5.6 GB

hlsp_atlas-refcat2_atlas_ccd_17-m-18_multi_v1_cat.tbz

17 < {g,r,i} < 18

9.8 GB

hlsp_atlas-refcat2_atlas_ccd_18-m-19_multi_v1_cat.tbz

18 < {g,r,i} < 19

17 GB

hlsp_atlas-refcat2_atlas_ccd_19-m-20_multi_v1_cat.tbz

{g,r,i} > 19

8.7 GB

#### MAST Format, Astronomical Units

.csv.gz File

Range

Size

hlsp_atlas-refcat2_atlas_ccd_m90-m53_multi_v1_cat.csv.gz

-90 < Dec. (º) < -53

17 GB

hlsp_atlas-refcat2_atlas_ccd_m53-m33_multi_v1_cat.csv.gz

-53 < Dec. (º) < -33

17 GB

hlsp_atlas-refcat2_atlas_ccd_m33-m15_multi_v1_cat.csv.gz

-33 < Dec. (º) < -15

19 GB

hlsp_atlas-refcat2_atlas_ccd_m15-p19_multi_v1_cat.csv.gz

-15 < Dec. (º) < +19

19 GB

hlsp_atlas-refcat2_atlas_ccd_p19-p90_multi_v1_cat.csv.gz

+19 < Dec. (º) < +90

19 GB

### CasJobs

The catalog is also available through in the "HLSP_ATLAS_VAR" Context within MAST CasJobs. The "detection" table (all ATLAS photometric measurements of all the candidate variables) is only available via the MAST CasJobs SQL interface.

MAST CasJobs

A web-based SQL interface to query and cross-match between catalogs. Export tables, saved queries, long query submissions.

The below examples show SQL commands you can enter in the "Query" tab once you sign into CasJobs.

#### Tutorial 1: Converting "Contrib" Integers To BitMask Values

You can see the contents of the look-up table by issuing this query:

select * from grizContribFlags

This query should result in a table that looks like the following:

name                             hexadecimal      value       description
-------------------------------- ---------------- ----------- ----------------------------------------------
Gaia DR2                          0x00000000      0           Gaia DR2 contributed to griz magnitude
GMP                               0x00000001      1           GMP contributed to griz magnitude.
Pan-STARRS                        0x00000002      2           Pan-STARRS contributed to griz magnitude.
SkyMapper                         0x00000004      4           SkyMapper contributed to griz magnitude.
Pathfinder                        0x00000008      8           Pathfinder contributed to griz magnitude.
APASS                             0x00000010      16          APASS contributed to griz magnitude.
APASS DR9                         0x00000020      32          APASS DR9 contributed to griz magnitude.
Tycho-2/BSC                       0x00000040      64          Tycho-2/BSC contributed to griz magnitude.

You can translate the various "Contrib" values to see which bits were set with the following function:

;WITH cteExample
as
(
select top 100
dbo.fGetgrizContribFlagsName(gContrib) as gContribs,
dbo.fGetgrizContribFlagsName(rContrib) as rContribs,
dbo.fGetgrizContribFlagsName(iContrib) as iContribs,
dbo.fGetgrizContribFlagsName(zContrib) as zContribs,
gContrib, rContrib, iContrib, zContrib,
objid, RA, Dec, plx, dplx, pmra,
dpmra, pmdec, dpmdec, Gaia, dGaia, BP,
dBP, RP, dRP, Teff, AGaia, dupvar,
Ag, rp1, r1, r10, g, dg,
gchi, r, dr, rchi, i, di,
ichi, z, dz, zchi, nstat,
J, dJ, H, dH, K, dK
from refcat2
)
select * from cteExample
order by zContrib desc

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:

select top 10 dbo.fGetgrizContribFlagsName(gContrib) as gContribs,*
from refcat2
where gContrib & dbo.fGetgrizContribFlagsValue('GMP') > 0

#### Tutorial 2: 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.

select * from refcat2
where ra between 0 and 0.2
and dec between 0 and 0.2

#### Tutorial 3: 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.

select r.*
from refcat2 as r
inner join fGetObjFromRect(0,0.2,0,0.2) as nb on r.objid=nb.objid

#### Tutorial 4: 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 the search center, so that objects closest to the cone search center are returned first.

select n.distance as dstDegrees, r.*
from fGetNearbyObjEq(0,0,5.0/60.0) as n
inner join refcat2 as r on n.objid=r.objid
order by n.distance

#### Tutorial 5: 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:

ID, RA, DEC
1, 1.58851, -0.07845
2, 5.53825, -1.51730
3, 6.33772, -12.34491

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):

select nb.distance as dstDegrees, nb.distance*3600.0 as dstArcSec,r.*
from MyDB.MySources s
cross apply fGetNearbyObjEq(s.ra,s.dec,1.0/60.0) nb
inner join refcat2 as r on nb.objid=r.objid

#### Tutorial 6: Cross-Match Against GALEX GR7

You can cross-match tables with any other database table available in MAST CasJobs. For instance, we show here 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 "GALEX_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).

## Citations

Please remember to cite the appropriate paper(s) below and the DOI if you use these data in a published work.

Note: These HLSP data products are licensed for use under CC BY 4.0.