2Mass Star Counts For Gaia Tgas Selection Function

This file contains star counts from the 2MASS point-source catalog (Skrutskie et al. 2006) for the purpose of determining the selection function of the Gaia DR1 Tycho-Astrometric Solution (Gaia collaboration et al. 2016; Lindegren et al. 2016). Counts are computed as a function of sky position (at HEALPix level 5 in RA, Dec), J-Ks color and a custom magnitude [J_T = J + (J − Ks )^2 + 2.5 (J − Ks )]. This file is designed to be used with the https://github.com/jobovy/gaia_tools package.

The counts were performed using the following SQL query on a database that contains the full 2MASS PSC and a table that contains the HEALPix index of all stars in the 2MASS PSC at HEALPix level 12 in Ra, Dec (keys hp12index and pts_key in table twomass_psc_hp12):

select floor((j_m+(j_m-k_m)*(j_m-k_m)+2.5*(j_m-k_m))*10), \

floor((j_m-k_m+0.05)/1.05*3), floor(hp12index/16384), count(*) as count \

from twomass_psc, twomass_psc_hp12 \

where (twomass_psc.pts_key = twomass_psc_hp12.pts_key \

AND (ph_qual like 'A__' OR (rd_flg like '1__' OR rd_flg like '3__')) \

AND (ph_qual like '__A' OR (rd_flg like '__1' OR rd_flg like '__3')) \

AND use_src='1' AND ext_key is null \

AND (j_m-k_m) > -0.05 AND (j_m-k_m) < 1.0 AND j_m < 13.5 AND j_m > 2) \

group by floor((j_m+(j_m-k_m)*(j_m-k_m)+2.5*(j_m-k_m))*10), \

floor((j_m-k_m+0.05)/1.05*3),floor(hp12index/16384) \

order by floor((j_m+(j_m-k_m)*(j_m-k_m)+2.5*(j_m-k_m))*10) ASC;