# 12.5.1 gaia_source_simulation

Table of sources realised according to the Gaia Object Generator (GOG) simulation. Observed attributes are given with simulated observational uncertainties.
This table contains the output of GOG. The values are obtained after adding the corresponding uncertainty (based on the error models) to the true values in table gaia_universe_model. Both the values and the uncertainties are provided.

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 where 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

source_id : Long Identifier (long)

A unique source identifier composed by the type of source, the sky region where the source is located and a sequential number inside this region (see the source_extended_id in gaia_universe_model table).

In the source_id information is coded within the 64 bit long integer. The celestial position is encoded via a level 12 Hierarchical Triangular Mesh, covering roughly one square arc minute size on the average:

• The 4 most significant bits contain the object type: (0: Unknown; 1: Stellar; 2: Galaxy; 3: QSO; 4: Supernova; 5: Exoplanet; 6: Noise or PPE; 7: Cluster; 8: Planetary Nebulae; 9: HII Region; 10: GRB; 11: Asteroid; 12: Comet; 13: Planet; 14: Satellite; 15: User Source; -1: Not identified)

• The 28 following bits contain the HTM index at level 12 (note the use of HTM as opposed to HEALPix in source_id in gaia_source)

• One bit indicates the variability,

• One bit indicates whether this is a multiple system (i.e. not a component).

• The 4 next groups of 3 bits are the 4 hierarchical levels for a multiple system. It is based on the fact that the maximum multiplicity of a hierarchical multiple system currently known is 7 (i.e. 3 bits are needed) with a 4 levels depth. The components in a level are sequential (i.e. non-hierarchical).

• The 18 least significant bits concern the object number in the region.

ra : Right Ascension (double, Angle[deg])

GOG simulation of the right ascension of the barycentre at J2010 reference epoch in ICRS frame

ra_error : Right Ascension error (float, Angle[mas])

GOG simulation of the standard error of right ascension

dec : Declination (double, Angle[deg])

GOG simulation of the declination of the barycentre at J2010 reference epoch in ICRS frame

dec_error : Declination error (float, Angle[mas])

GOG simulation of the standard error of declination

parallax : Parallax (float, Angle[mas])

GOG simulation of the parallax of the source. The inverse of the parallax is the distance from the barycenter of the Solar System to the barycenter of the source at J2010 reference epoch

parallax_error : Parallax error (float, Angle[mas])

GOG simulation of the standard error of parallax

pmra : Proper motion in RA (float, Angular Velocity[mas/year])

GOG simulation of the proper motion along right ascension at J2010 reference epoch: $\mu_{\alpha*}\equiv\mu_{\alpha}\cos\delta$. This is the local tangent plane projection of the proper motion vector in the direction of increasing right ascension.

pmra_error : Error in RA proper motion (float, Angular Velocity[mas/year])

GOG simulation of the standard error of proper motion in right ascension direction

pmdec : Proper motion in dec (float, Angular Velocity[mas/year])

GOG simulation of the proper motion along declination at J2010 reference epoch. This is the projection of the proper motion vector in the direction of increasing declination.

pmdec_error : Error in dec. proper motion (float, Angular Velocity[mas/year])

GOG simulation of the standard error of proper motion in declination direction

n_obs_al : Number of AL observations (int)

AL number of accepted observations

n_outliers_al : Number of outliers AL observations (int)

AL number of outliers observations

phot_g_mean_flux : Mean G flux (float, Flux[e-/s])

GOG simulation of the mean flux in the G band.

phot_g_mean_flux_error : Mean G flux error (float, Flux[e-/s])

GOG simulation of the mean G-band flux error

phot_g_mean_mag : Mean G magnitude (float, Magnitude[mag])

GOG simulation of the apparent mean magnitude in the G band in the Vega scale.

phot_bp_mean_flux : Mean BP flux (float, Flux[e-/s])

GOG simulation of the mean flux in the BP band

phot_bp_mean_flux_error : Mean BP flux error (float, Flux[e-/s])

GOG simulation of the mean BP flux error

phot_bp_mean_mag : Mean BP magnitude (float, Magnitude[mag])

GOG simulation of the mean apparent magnitude in the integrated BP band in the Vega scale.

phot_rp_mean_flux : Mean RP flux (float, Flux[e-/s])

GOG simulation of the mean flux in the RP band.

phot_rp_mean_flux_error : Mean RP flux error (float, Flux[e-/s])

GOG simulation of the mean RP flux error

phot_rp_mean_mag : Mean RP magnitude (float, Magnitude[mag])

GOG simulation of the mean apparent magnitude in the integrated RP band in the Vega scale.

phot_rvs_mean_flux : Mean RVS flux (float, Flux[e-/s])

GOG simulation of the mean flux in the RVS band.

phot_rvs_mean_flux_error : Mean RVS flux error (float, Flux[e-/s])

GOG simulation of the mean RVS flux error

phot_rvs_mean_mag : Mean RVS magnitude (float, Magnitude[mag])

GOG simulation of the mean apparent magnitude in the integrated RVS band in the Vega scale.

radial_velocity : Radial velocity (float, Velocity[km/s])

GOG simulation of the spectroscopic radial velocity in the solar barycentric reference frame at J2010 reference epoch.

radial_velocity_error : Radial velocity error (float, Velocity[km/s])

GOG simulation of the radial velocity error

teff : Effective temperature (float, Temperature[K] )

GOG simulation of the star effective temperature

teff_error : Effective temperature error (float, Temperature[K] )

GOG simulation of the star effective temperature error

vsini : v sin i (float, Velocity[km/s])

GOG simulation of the rotational velocity

vsini_error : v sin i error (float, Velocity[km/s] )

GOG simulation of the rotational velocity error

a0 : Extinction at 550 nm (float, Magnitude[mag])

GOG simulation of the extinction at 550 nm

a0_error : Extinction at 550 nm error (float, Magnitude[mag])

GOG simulation of the extinction at 550 nm error

feh : Iron abundance (float, Abundances[dex] )

GOG simulation of the iron abundance

feh_error : Iron abundance error (float, Abundances[dex] )

GOG simulation of the iron abundance error

logg : Surface gravity (float, GravitySurface[log cgs])

GOG simulation of the log10 of the surface gravity (log cgs)

logg_error : Surface gravity Error (float, GravitySurface[log cgs])

GOG simulation of the log10 of the surface gravity error