7.5 Catalogue statistics and plots

7.5.1 Introduction

Author(s): Raúl Borrachero and Frédéric Arenou

The data fields of the main table of the Gaia Catalogue and a short description of these fields are indicated Table 7.4. A more extensive description of these fields is available where all other tables concerning variability and crossmatch are also described.

The TGAS subset has the same content plus two more fields, Hipparcos and Tycho-2_id which are respectively the Hipparcos identifier and the Tycho-2 identifier.

A summary of statistics and plots by Gaia analysis Tool (GAT) on these fields for the 1 142 679 769 sources is shown Table 7.5 and following pages.

Table 7.4: Data fields of the main Catalogue.
Name Description Type Units
solution_id Solution Identifier long
source_id Unique source identifier long
random_index Random index used to select subsets long
ref_epoch Reference epoch double Julian Year
ra Right ascension double deg
ra_error Standard error of right ascension double mas
dec Declination double deg
dec_error Standard error of declination double mas
parallax Parallax double mas
parallax_error Standard error of parallax double mas
pmra Proper motion in right ascension direction double mas/year
pmra_error Standard error of proper motion in right ascension direction double mas/year
pmdec Proper motion in declination direction double mas/year
pmdec_error Standard error of proper motion in declination direction double mas/year
ra_dec_corr Correlation between right ascension and declination float
ra_parallax_corr Correlation between right ascension and parallax float
ra_pmra_corr Correlation between right ascension and p.m. in r.a. float
ra_pmdec_corr Correlation between right ascension and p.m. in declination float
dec_parallax_corr Correlation between declination and parallax float
dec_pmra_corr Correlation between declination and p.m. in right ascension float
dec_pmdec_corr Correlation between declination and p.m. in declination float
parallax_pmra_corr Correlation between parallax and p.m. in right ascension float
parallax_pmdec_corr Correlation between parallax and p.m. in declination float
pmra_pmdec_corr Correlation between p.m. in r.a. and p.m. in declination float
astrometric_n_obs_al Total number of observations AL int
astrometric_n_obs_ac Total number of observations AC int
astrometric_n_good_obs_al Number of good observations AL int
astrometric_n_good_obs_ac Number of good observations AC int
astrometric_n_bad_obs_al Number of bad observations AL int
astrometric_n_bad_obs_ac Number of bad observations AC int
astrometric_delta_q Hipparcos/Gaia discrepancy (Hipparcos TGAS subset only) float
astrometric_excess_noise Excess noise of the source double mas
astrometric_excess_noise_sig Significance of excess noise double
astrometric_primary_flag Primary or seconday boolean
astrometric_relegation_factor Relegation factor float
astrometric_weight_al Mean astrometric weight of the source float mas -2
astrometric_weight_ac Mean astrometric weight of the source float mas -2
astrometric_priors_used Type of prior used in in the astrometric solution int
matched_observations Amount of observations matched to this source short
duplicated_source Source with duplicate sources boolean
scan_direction_strength_k1 Degree of concentration of scan directions across the source float
scan_direction_strength_k2 Degree of concentration of scan directions across the source float
scan_direction_strength_k3 Degree of concentration of scan directions across the source float
scan_direction_strength_k4 Degree of concentration of scan directions across the source float
scan_direction_mean_k1 Mean position angle of scan directions across the source float deg
scan_direction_mean_k2 Mean position angle of scan directions across the source float deg
scan_direction_mean_k3 Mean position angle of scan directions across the source float deg
scan_direction_mean_k4 Mean position angle of scan directions across the source float deg
phot_g_n_obs Number of observations contributing to G photometry int
phot_g_mean_flux G band mean flux double e - s -1
phot_g_mean_flux_error Error on G band mean flux double e - s -1
phot_g_mean_mag G band mean magnitude double mag
phot_variable_flag Photometric variability flag string
l Galactic longitude double deg
b Galactic latitude double deg
ecl_lon Ecliptic longitude double deg
ecl_lat Ecliptic latitude double deg
Table 7.5: The following table contains the minimum and maximum values, mean and standard deviation for all the Catalogue fields, and the number of sources not represented in the following plots. AL (resp. AC) designate the Gaia along-scan (resp. across-scan) measurements. gMeanMagError is σG, the uncertainty on G, computed using phot_g_mean_flux_error and phot_g_mean_flux.
Field name Null values Not plotted Minimum Mean Maximum Std. dev.
ra 0 0 8.26E-7 221.86 360.000 83.1590
ra_error 0 128523480 0.01710 4.82573 99.9911 7.9581
dec 0 0 -89.993 -15.777 89.9901 39.0775
dec_error 0 98728634 0.02259 4.10143 99.9965 6.67577
parallax 1140622719 6410 -24.820 2.47763 295.804 2.91018
parallax_error 1140622719 0 0.20397 0.38501 1.00000 0.16993
pmra 1140622719 6519 -3259.4 -1.7409 2890.43 25.1755
pmra_error 1140622719 465 0.01183 1.40340 18.3433 1.02779
pmdec 1140622719 5796 -3159.3 -5.2517 1858.53 23.5580
pmdec_error 1140622719 0 0.01184 1.09591 18.8544 0.88851
astrometric_n_obs_ac 0 5994239 0.0 0.69548 1977.0 9.55682
astrometric_n_obs_al 0 1400018 1.0 89.2145 2066.0 60.1374
astrometric_n_good_obs_ac 5729106 0 0.0 0.65793 1920.0 9.10076
astrometric_n_good_obs_al 3614313 0 1.0 88.6508 2062.0 59.8077
astrometric_n_bad_obs_ac 0 90335 0.0 0.03755 118.0 0.52450
astrometric_n_bad_obs_al 0 193803 0.0 0.56369 1981.0 1.46788
astrometric_delta_q 1142586134 1182 3.77E-5 9.37448 20437.8 99.9191
astrometric_excess_noise 0 104663428 0.0 1.00344 20.0000 1.56895
astrometric_excess_noise_sig 0 51843782 -2E-14 3.95E15 3.48E24 1.07E20
astrometric_relegation_factor 0 19118253 1.0 3.11314 193.843 5.17666
astrometric_weight_al 0 1717 10.0E-7 2.01162 556.866 2.82490
astrometric_weight_ac 1128060126 12563484 9.49E-7 0.35711 6.96892 0.55396
scan_direction_strength_k1 0 2514 4.26E-6 0.42473 1.0 0.19349
scan_direction_strength_k2 0 2456 3.10E-7 0.46240 1.0 0.23594
scan_direction_strength_k3 0 3525 2.48E-7 0.42299 1.0 0.21000
scan_direction_strength_k4 0 4239 1.13E-6 0.64740 1.0 0.26781
scan_direction_mean_k1 0 20 -180.0 -39.253 180.0 95.6541
scan_direction_mean_k2 0 9 -90.0 -12.351 90.0 43.0841
scan_direction_mean_k3 0 17 -60.0 -7.1549 60.0 32.1176
scan_direction_mean_k4 0 105 -45.0 -1.3543 45.0 33.0508
ra_dec_corr 0 0 -1.0000 -0.0085 0.99997 0.56875
ra_parallax_corr 1140622719 0 -0.9985 -0.0220 0.99772 0.54093
ra_pmra_corr 1140622719 0 -0.9999 -0.5910 0.99894 0.35991
ra_pmdec_corr 1140622719 0 -0.9994 -0.0070 0.99938 0.55113
dec_parallax_corr 1140622719 0 -0.9962 0.13186 0.99795 0.49861
dec_pmra_corr 1140622719 0 -0.9991 -3.8E-4 0.99923 0.56926
dec_pmdec_corr 1140622719 0 -0.9996 -0.4677 0.99890 0.40947
parallax_pmra_corr 1140622719 0 -0.9986 0.02463 0.99876 0.64020
parallax_pmdec_corr 1140622719 0 -0.9969 -0.1596 0.99626 0.48475
pmra_pmdec_corr 1140622719 0 -0.9998 0.00319 0.99972 0.62182
phot_g_mean_flux 0 14697952 0.05818 6705.78 8.872E8 292347.
phot_g_mean_mag 0 520 3.15463 18.6551 28.6129 1.60472
gMeanMagError 0 0 9.71E-6 0.01040 0.43107 0.00951

7.5.2 Sky Density

Figure 7.11: HEALPix map of total density count in ecliptic coordinates (larger), logarithmic counts (larger), and in galactic coordinates (larger), logarithmic counts (larger).

7.5.3 Magnitude

Figure 7.12: Histogram of the mean G magnitude (larger), σG (larger), mean G flux (larger).
Figure 7.13: Histogram 2D of the mean G magnitude as a function of the σG magnitude (larger), and as a function of the number of observations (larger).
Figure 7.14: HEALPix map in ecliptic coordinates of median values of mean G magnitude (larger), median values of σG (larger), standard deviation of mean G magnitude (larger) and standard deviation of σG (larger).

7.5.4 Positions

Figure 7.15: Histogram of α (larger), and σα⁣* (larger).
Figure 7.16: Histogram 2D of σα⁣* as a function of α (larger), as a function of the G magnitude (larger), and as a function of the number of observations (larger).
Figure 7.17: HEALPix map in ecliptic coordinates of σα⁣*, median value (larger), and standard deviation (larger).
Figure 7.18: Histogram of δ (larger), and of σδ (larger).
Figure 7.19: Histogram 2D of σδ as a function of δ (larger), as a function of the G magnitude (larger), and as a function of the number of observations (larger).
Figure 7.20: HEALPix map in ecliptic coordinates of σδ: median values (larger), and standard deviation (larger).

7.5.5 Parallaxes

Figure 7.21: Histogram of ϖ (larger), and σϖ (larger).
Figure 7.22: Histogram 2D of σϖ as a function of ϖ (larger), as a function of G magnitude (larger), and as a function of the number of observations along-scan (larger).
Figure 7.23: HEALPix map in ecliptic coordinates of median values of ϖ (larger), median values of σϖ (larger), and standard deviation of σϖ (larger).

7.5.6 Proper motions

Figure 7.24: Histogram of μα⁣* (larger), of σμα⁣*: linear scale (larger), and log scale (larger).
Figure 7.25: Histogram 2D of σμα⁣* as a function of μα⁣* (larger), as a function of G magnitude (larger), and as a function of the number of observations along-scan (larger).
Figure 7.26: HEALPix map in ecliptic coordinates of the median value of μα⁣* (larger), median value of σμα⁣* (larger), standard deviation of σμα⁣* (larger).
Figure 7.27: Histogram of μδ (larger), of σμδ: linear scale (larger), and log scale (larger).
Figure 7.28: Histogram 2D of σμδ as a function of μδ (larger), as a function of G magnitude (larger), and as a function of the number of observations (larger).
Figure 7.29: HEALPix map in ecliptic coordinates of the median value of μδ (larger), of the median value of σμδ (larger), and of the standard deviation of σμδ (larger).

7.5.7 Astrometric correlations

Figure 7.30: Histogram of correlation between α and δ (larger), between α and ϖ (larger), between α and μα⁣* (larger), and between α and μδ (larger).
Figure 7.31: Histogram of correlation between δ and ϖ (larger), between δ and μα⁣* (larger), between δ and μδ (larger), and between ϖ and μα⁣* (larger).
Figure 7.32: Histogram of correlation between ϖ and μδ (larger), Histogram of correlation between μα⁣* and μδ (larger).
Figure 7.33: HEALPix map in ecliptic coordinates of correlation between α and δ: mean value (larger), and standard deviation (larger); correlation between α and ϖ: mean value (larger), and standard deviation (larger).
Figure 7.34: HEALPix map in ecliptic coordinates of correlation between α and μα⁣*: mean value (larger), and standard deviation (larger); correlation between α and μδ: mean value (larger), and standard deviation (larger).
Figure 7.35: HEALPix map in ecliptic coordinates of correlation between δ and ϖ: mean value (larger), and standard deviation (larger); correlation between δ and μα⁣*: mean value (larger), and standard deviation (larger).
Figure 7.36: HEALPix map in ecliptic coordinates of correlation between δ and μδ: mean value (larger), and standard deviation (larger); correlation between ϖ and μα⁣*: mean value (larger), and standard deviation (larger).
Figure 7.37: HEALPix map in ecliptic coordinates of correlation between ϖ and μδ: mean value (larger), and standard deviation (larger); correlation between μα⁣* and μδ: mean value (larger), and standard deviation (larger).

7.5.8 Astrometry: number of observations

Figure 7.38: Histogram of the number of good observations: along-scan (larger), and across-scan (larger); Histogram 2D of the number of good observations as a function of G magnitude: along-scan (larger), and across-scan (larger).
Figure 7.39: HEALPix map in ecliptic coordinates of the mean value of the number of good observations: along-scan (larger), and across-scan (larger); standard deviation of the number of good observations: along-scan (larger), and across-scan (larger).
Figure 7.40: HEALPix map in ecliptic coordinates of the mean value of the fraction of good observations: along-scan (larger), and across-scan (larger).
Figure 7.41: Histogram of the number of bad observations: along-scan (larger), and across-scan (larger); Histogram 2D of the number of bad observations as a function of G magnitude: along-scan (larger), and across-scan (larger).
Figure 7.42: HEALPix map in ecliptic coordinates of the mean value of the number of bad observations: along-scan (larger), and across-scan (larger); standard deviation of the number of bad observations: along-scan (larger), and across-scan (larger).
Figure 7.43: HEALPix map in ecliptic coordinates of the mean value of the fraction of bad observations: along-scan (larger), and across-scan (larger).
Figure 7.44: Histogram of the number of transits per CCD: along-scan (larger), and across-scan (larger); HEALPix map in ecliptic coordinates of the number of transits per CCD: along-scan (larger), and across-scan (larger).

7.5.9 Astrometry: quality of the solution

Figure 7.45: Histogram of excess noise (larger), and of excess noise significance (larger).
Figure 7.46: Histogram 2D of excess noise as a function of G magnitude (larger), and as a function of the number of observations (larger); excess noise significance as a function of G magnitude (larger), and as a function of the number of observations (larger).
Figure 7.47: HEALPix map in ecliptic coordinates of the excess noise: mean value (larger), and standard deviation (larger); excess noise significance: mean value (larger), and standard deviation (larger).
Figure 7.48: Histogram of deltaQ (larger); Histogram 2D of deltaQ as a function of G magnitude (larger), and as a function of the number of observations (larger).
Figure 7.49: HEALPix map in ecliptic coordinates of deltaQ: mean value (larger), and standard deviation (larger).
Figure 7.50: Histogram of the astrometric weight: along-scan (larger), and across-scan (larger).
Figure 7.51: Histogram 2D of the astrometric weight as a function of G magnitude: along-scan (larger), and across-scan (larger); Histogram 2D of the astrometric weight as a function of the number of observations: along-scan (larger), and across-scan (larger).
Figure 7.52: HEALPix map in ecliptic coordinates of the mean value of the astrometric weight: along-scan (larger), and across-scan (larger); HEALPix map in ecliptic coordinates of the standard deviation of the astrometric weight: along-scan (larger), and across-scan (larger).
Figure 7.53: Histogram of the relegation factor (larger); Histogram 2D of the relegation factor as a function of G magnitude (larger), and as a function of the number of observations (larger).
Figure 7.54: HEALPix map in ecliptic coordinates of the relegation factor: mean value (larger), and standard deviation (larger).
Figure 7.55: Histogram of the scan direction mean K1 (larger), mean K2 (larger), mean K3 (larger), and mean K4 (larger).
Figure 7.56: HEALPix map in ecliptic coordinates of the mean value of the scan direction mean K1 (larger), mean K2 (larger), mean K3 (larger), mean K4 (larger).
Figure 7.57: Histogram of the scan direction strength K1 (larger), strength K2 (larger), strength K3 (larger), strength K4 (larger).
Figure 7.58: HEALPix map in ecliptic coordinates of the mean value of the scan direction strength K1 (larger), strength K2 (larger), strength K3 (larger), strength K4 (larger).