# 20.2.4 total_galactic_extinction_map_opt

This table provides an optimum version of the Total Galactic Extinction map, derived from the table total_galactic_extinction_map at a single HEALPix level 9. For this, the mean effective total Galactic extinction and related uncertainties have been selected from the optimal HEALPix level of the four offered in total_galactic_extinction_map. For further details see Section 11.3.11 of the online documentation.

Columns description:

solution_id : Solution Identifier (long)

All Gaia data processed by the Data Processing and Analysis Consortium comes tagged with a solution identifier. This is a numeric field attached to each table row that can be used to unequivocally identify the version of all the subsystems that were used in the generation of the data as well as the input data used. It is mainly for internal DPAC use but is included in the published data releases to enable end users to examine the provenance of processed data products. To decode a given solution ID visit https://gaia.esac.esa.int/decoder/solnDecoder.jsp.

healpix_id : HEALPix identification (long)

The unique HEALPix index number for which the total Galactic extinction parameters are estimated. For further details on the HEALPix scheme used by Gaia, see Bastian and Portell (2020).

a0 : Median A${}_{0}$ extinction parameter (float, Magnitude[mag] )

The median $A_{0}$ of the selected extinction tracers (giants) as estimated by GSP-Phot from BP/RP spectra, apparent $G$ magnitude and parallax (i.e. azero_gspphot in table gaia_source). $A_{0}$ is the extinction parameter in the adopted Fitzpatrick extinction law (Fitzpatrick 1999), taken as the monochromatic extinction at 541.4 nm. Here the $A_{0}$ value is taken from the optimum HEALPix in table total_galactic_extinction_map.

a0_uncertainty : Uncertainty for the mean A${}_{0}$ (float, Magnitude[mag] )

The uncertainty of the mean $A_{0}$ for selected extinction tracers in the HEALPix. Here the value is taken from the optimum HEALPix in table total_galactic_extinction_map.

num_tracers_used : Number of tracers used (int)

The number of extinction tracers (selected giants) used for calculating the extinction parameters for this HEALPix. Here the value is taken from the optimum HEALPix in table total_galactic_extinction_map.

status : Exit status for TGE (short)

Indicates the exit status of TGE.

0: Nominal processing.

1: Insufficient number of tracers, after validation of input for each source (Step 0).

2: Insufficient number of tracers, after ($T_{\rm eff}$, $M_{G}$) selection (Step 1).

3: Insufficient number of tracers, after check on the distance (Step 2).

4: Insufficient number of tracers, after outlier rejection (Step 3).

5: Insufficient number of tracers, after rejection of tracers with large $A_{0}$ errors (Step 4).

99: Unknown error flag.

optimum_hpx_level : Number indicating which HEALPix level was chosen to populate this HEALPix (byte)

The HEALPix level (6-9) of the optimum HEALPix: The TotalGalalcticExtinctionMap HEALPix at highest resolution (highest HEALPix level) with at least 10 tracers in the direction of this HEALPix, as indicated by the optimum_hpx_flag, and used to populate the values in this HEALPix. As the optimum HEALPix may be at a lower HEALPix level than this map (level 9), the values in this level 9 HEALPix will be the same as neighboring HEALPix pixels if optimum_hpx_level is less than 9.