I/347          Distances to 1.33 billion stars in Gaia DR2 (Bailer-Jones+, 2018)

Estimating distances from parallaxes. IV. Distances to 1.33 billion stars in Gaia data release 2. Bailer-Jones C.A.L., Rybizki J., Fouesneau M., Mantelet G., Andrae R. <Astron. J. 156, 58 (2018)> =2018AJ....156...58B =2018yCat.1347....0B
ADC_Keywords: Surveys ; Stars, distances Keywords: catalogs - Galaxy: structure - methods: statistical - stars: distances Abstract: For the majority of stars in the second Gaia data release, reliable distances cannot be obtained by inverting the parallax. A correct inference procedure must instead be used to account for the nonlinearity of the transformation and the asymmetry of the resulting probability distribution. Here we infer distances to almost all 1.33 billion stars with parallaxes published in the second Gaia data release. This is done using a weak distance prior that varies smoothly as a function of Galactic longitude and latitude according to a Galaxy model. The irreducible uncertainty in the distance estimate is characterized by the lower and upper bounds of an asymmetric confidence interval. Although more precise distances can be estimated for a subset of the stars using additional data (such as photometry), our goal is to provide purely geometric distance estimates, independent of assumptions about the physical properties of, or interstellar extinction towards, individual stars. We analyze the characteristics of the catalog and validate it using clusters. Description: The catalog can be queried using ADQL at http://gaia.ari.uni-heidelberg.de/tap.html (which also hosts the Gaia catalog) and downloaded from http://www.mpia.de/~calj/gdr2_distances.html. Each file contains 200000 sources (except the last one) with a single header line. Total size of all files is 114GB. File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file gaia2dis.sam 143 1000 Estimating distances from parallaxes (1331909727 sources)
See also: I/337 : Gaia DR1 (Gaia Collaboration, 2016) I/345 : Gaia DR2 (Gaia Collaboration, 2018) J/ApJ/833/119 : Distances of Gaia DR1 TGAS sources (Astraatmadja+, 2016) Byte-by-byte Description of file: gaia2dis.sam
Bytes Format Units Label Explanations
1- 19 I19 --- Source Source identifier, identical to the Gaia-DR2 source_id (id) 21- 35 F15.11 deg RAdeg Barycentric right ascension (ICRS) at Ep=2015.5 (ra) 37- 51 F15.11 deg DEdeg Barycentric declination (ICRS) at Ep=2015.5 (dec) 53- 73 F21.15 pc rest ? Estimated distance (r_est) 75- 95 F21.15 pc b_rest ? Lower bound on the confidence interval of the estimated distance (r_lo) 101-121 F21.15 pc B_rest ? Upper bound on the confidence interval of the estimated distance (r_hi) 124-139 F16.12 pc rlen Length scale used in the prior for the distance estimation (r_len) 141 A1 --- ResFlag [0-2] Result flag (result_flag) (1) 143 I1 --- ModFlag [1/2] Number of modes in the posterior (modality_flag)
Note (1): Result flag as follows: 0 = failed estimate (r_est, r_lo, r_hi are all NaN) 1 = rest is the mode (highest if the posterior is bimodal); brest/Brest define the lower/upper limits of the highest density interval (HDI) containing 68% of the posterior probability 2 = rest is the median; brest/Brest define the lower/upper limits of the equal-tailed interval (ETI), containing 68% of the posterior probability
Acknowledgements: Coryn Bailer-Jones, calj(at)mpia.de References: Bailer-Jones C.A.L., Paper I 2015PASP..127..994B Astraatmadja & Bailer-jones, Paper II 2016ApJ...832..137A Astraatmadja & Bailer-jones, Paper III 2016ApJ...833..119A, Cat. J/ApJ/833/119
(End) Coryn Bailer-Jones [MPIA], Patricia Vannier [CDS] 07-Jun-2018
The document above follows the rules of the Standard Description for Astronomical Catalogues; from this documentation it is possible to generate f77 program to load files into arrays or line by line

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