Estimating Distance from Parallaxes (gdr2_contrib.geometric_distance)
The catalogue provides distances estimates (and uncertainties therein) for 1.33 billion stars over the whole sky brighter than about G=20.7. These have been estimated using the parallaxes (and their uncertainties) from Gaia data release 2. A Bayesian procedure was used involving a prior with a single parameter L(l,b), which varies smoothly with Galactic longitude and latitude according to a Galaxy model. The posterior is summarized with a point estimate (usually the mode) and a confidence interval (usually the 68% highest density interval). The estimation procedure is described in detail in the accompanying paper (link), which also analyses the catalogue content.
|source_id||long||meta.id||Source identifier, identical to the Gaia-DR2 source_id|
|pc||Lower bound on the confidence interval of the estimated distance|
|pc||Upper bound on the confidence interval of the estimated distance|
|r_len||double||pos.distance||pc||Length scale used in the prior for the distance estimation|
|result_flag||short||=0 failed estimate (none of r_est, r_lo, r_hi are defined) =1 r_est is the mode (highest if the posterior is bimodal); r_lo/r_hi define the lower/upper limits of the highest density interval (HDI) containing 68% of the posterior probability =2 r_est is the median; r_lo/r_hi define the lower/upper limits of the equal-tailed interval (ETI), containing 68% of the posterior probability|
|modality_flag||short||no. of modes in the posterior (1 or 2)|