Table information for 'xpparams.main'

Example: A Dust Map

As an example of what one can do with this data, consider the following ADQL query to generate an all-sky extinction map for stars at a distance between 400 pc and 600 pc:

select source_id/140737488355328 as hpx, avg(ext) as meanext
from xpparams.main
where
mod_parallax between 1.67 and 2.5
        and quality_flags < 8
        and mod_parallax/err_mod_parallax > 5
        and err_ext < 0.2
group by hpx

This exploits the fact that Gaia source ids can be converted to HEALPixes to produce a map and shows how to do useful quality cuts that allow relatively careless use of the data.

If you use TOPCAT to execute this on the GAVO DC TAP service (select Asynchronous mode and make sure you set Max Rows to something more than 50000, because that is how many pixels our map will have), you can do a sphere plot, then add a Healpix control. In it, select the table resulting from this query, manually set the HEALPix level to 6 and configure the Axis to Aitoff projection in the Galactic system to arrive at a plot like this:

Example: Metallicity of a Globular Cluster

Try the following query yielding data on Omega Cen and illustrating how to match with the local Gaia DR3 catalogue in order to constrain proper motions:

SELECT
        xpp.*,
        g.pmra, g.pmdec, g.phot_g_mean_mag, g.phot_bp_mean_mag,
        g.phot_rp_mean_mag
FROM xpparams.main as xpp JOIN gaia.edr3lite as g USING (source_id)
WHERE
        distance(xpp.ra, xpp.dec, 201.697, -47.479472)<0.5
        AND distance(g.pmra, g.pmdec, -3.24, -6.73)<1.25
        AND xpp.quality_flags < 8
        AND xpp.mod_parallax/xpp.err_mod_parallax > 5.
        AND xpp.feh_confidence > 0.5
        AND xpp.err_fe_h < 0.2

Again in TOPCAT, try a 3d plot of RA, Dec and 1/mod_parallax. You will want to manually cut the parallax axis a bit to get rid of (presumably spurious) background stars. Make fe_h the aux axis in the “Form“ tab. If you look “from above“, you will see that the quality cuts have punched a hole into the cluster. If you look from the side, you can see that the cluster stars are (by and large) rather metal-poor compared to foreground stars: