Further access options are discussed below
For a list of all services and tables belonging to this service's resource, see Information on resource 'Selections from Gaia Data Release 2 (DR2)'
You can access this service using:
This service is published as follows:
local means it is listed on our front page, ivo_managed means it has a record in the VO registry.
Other services provided on the underlying data include:
The following fields are available to provide input to the service (with some renderers, some of these fields may be unavailable):
Name | Table Head | Description | Unit | UCD |
---|---|---|---|---|
DEC | Delta (ICRS) | Declination (ICRS decimal) | deg | pos.eq.dec |
hscs_pos | Position/Name | Coordinates (as h m s, d m s or decimal degrees), or SIMBAD-resolvable object | N/A | N/A |
hscs_sr | Search radius | Search radius in arcminutes | N/A | N/A |
MAXREC | Match limit | Maximum number of records returned. Pass 0 to retrieve service parameters. | N/A | N/A |
parallax | Parallax | Absolute barycentric stellar parallax of the source at the reference epoch ref_epoch. If looking for a distance, consider joining with gdr2dist.main and using the distances from there. | mas | pos.parallax |
phot_bp_mean_mag | Mag BP | Mean magnitude in the integrated BP band. This is computed from the BP-band mean flux applying the magnitude zero-point in the Vega scale. No error is provided for this quantity as the error distribution is only symmetric in flux space. For errors small compared to the flux (less than 10%, say), the magnitude error is well approximated by 1.09*flux/flux_err. | mag | phot.mag;em.opt.B |
phot_g_mean_mag | m_G | Mean magnitude in the G band. This is computed from the G-band mean flux applying the magnitude zero-point in the Vega scale. | mag | phot.mag;em.opt;stat.mean |
phot_rp_mean_mag | Mag RP | Mean magnitude in the integrated RP band. This is computed from the RP-band mean flux applying the magnitude zero-point in the Vega scale. No error is provided for this quantity as the error distribution is only symmetric in flux space. For errors small compared to the flux (less than 10%, say), the magnitude error is well approximated by 1.09*flux/flux_err. | mag | phot.mag;em.opt.R |
RA | Alpha (ICRS) | Right Ascension (ICRS decimal) | deg | pos.eq.ra |
RESPONSEFORMAT | Output Format | File format requested for output. | N/A | meta.code.mime |
SR | Search Radius | Search radius | deg | N/A |
VERB | Verbosity | Exhaustiveness of column selection. VERB=1 only returns the most important columns, VERB=2 selects the columns deemed useful to the average user, VERB=3 returns a table with all available columns. | N/A | N/A |
The following fields are contained in the output by default. More fields may be available for selection; these would be given below in the VOTable output fields.
Name | Table Head | Description | Unit | UCD |
---|---|---|---|---|
_r | Dist. | Distance to cone center | deg | pos.distance |
astrometric_gof_al | GoF | Goodness-of-fit statistic of the astrometric solution for the source in the along-scan direction (you probably want to use RUWE instead of this). Note gof | N/A | stat.fit.goodness |
astrometric_params_solved | PS | This is a binary code indicating which astrometric parameters were estimated for the source. A set bit means the parameter was estimated. The least-significant bit represents α, the next bits δ, parallax, PM(RA) and PM(De). For Gaia DR2 the only relevant values are 31 (all five parameters solved) and 3 (only positions). | N/A | meta.code |
dec | Dec (ICRS) | Barycentric Declination in ICRS at ref_epoch | deg | pos.eq.dec;meta.main |
dec_error | Err. Dec | Standard error of dec | mas | stat.error;pos.eq.dec |
parallax | Parallax | Absolute barycentric stellar parallax of the source at the reference epoch ref_epoch. If looking for a distance, consider joining with gdr2dist.main and using the distances from there. | mas | pos.parallax |
parallax_error | Parallax_error | Standard error of parallax | mas | stat.error;pos.parallax |
phot_bp_mean_flux | Flux BP | Mean flux in the integrated BP band. Note phot | s**-1 | phot.flux;em.opt.B |
phot_bp_mean_flux_error | Err. Fl. BP | Error in the mean flux in the integrated BP band. Errors are computed from the dispersion about the weighted mean of the input calibrated photometry. | s**-1 | stat.error;phot.flux;em.opt.B |
phot_bp_mean_mag | Mag BP | Mean magnitude in the integrated BP band. This is computed from the BP-band mean flux applying the magnitude zero-point in the Vega scale. No error is provided for this quantity as the error distribution is only symmetric in flux space. For errors small compared to the flux (less than 10%, say), the magnitude error is well approximated by 1.09*flux/flux_err. Note phot | mag | phot.mag;em.opt.B |
phot_bp_rp_excess_factor | BP/RP excess | BP/RP excess factor estimated from the comparison of the sum of integrated BP and RP fluxes with respect to the flux in the G band. This measures the excess of flux in the BP and RP integrated photometry with respect to the G band. This excess is believed to be caused by background and contamination issues affecting the BP and RP data. Therefore a large value of this factor for a given source indicates systematic errors in the BP and RP photometry. | N/A | stat.fit.goodness |
phot_g_mean_flux | Flux_G | G-band mean flux as electrons per second. Note phot | s**-1 | phot.flux;em.opt;stat.mean |
phot_g_mean_flux_error | Err. Flux(G) | Error on phot_g_mean_flux | s**-1 | stat.error;phot.flux;em.opt;stat.mean |
phot_g_mean_mag | m_G | Mean magnitude in the G band. This is computed from the G-band mean flux applying the magnitude zero-point in the Vega scale. Note phot | mag | phot.mag;em.opt;stat.mean |
phot_rp_mean_flux | Flux RP | Mean flux in the integrated RP band. Note phot | s**-1 | phot.flux;em.opt.R |
phot_rp_mean_flux_error | Err. Fl. RP | Error in the mean flux in the integrated RP band. Errors are computed from the dispersion about the weighted mean of the input calibrated photometry. | s**-1 | stat.error;phot.flux;em.opt.R |
phot_rp_mean_mag | Mag RP | Mean magnitude in the integrated RP band. This is computed from the RP-band mean flux applying the magnitude zero-point in the Vega scale. No error is provided for this quantity as the error distribution is only symmetric in flux space. For errors small compared to the flux (less than 10%, say), the magnitude error is well approximated by 1.09*flux/flux_err. Note phot | mag | phot.mag;em.opt.R |
pmdec | µ(Dec) | Proper motion in declination at ref_epoch. | mas/yr | pos.pm;pos.eq.dec |
pmdec_error | Err. PM(Dec) | Standard error of pmdec | mas/yr | stat.error;pos.pm;pos.eq.dec |
pmra | µ(RA) | Proper motion in right ascension of the source in ICRS at ref_epoch. This is the projection of the proper motion vector in the direction of increasing right ascension. | mas/yr | pos.pm;pos.eq.ra |
pmra_error | Err. PM(RA) | Standard error of pmra | mas/yr | stat.error;pos.pm;pos.eq.ra |
ra | RA (ICRS) | Barycentric Right Ascension in ICRS at ref_epoch | deg | pos.eq.ra;meta.main |
ra_error | Err. RA | Standard error of ra (with cos δ applied). | mas | stat.error;pos.eq.ra |
radial_velocity | RV | Spectroscopic radial velocity in the solar barycentric reference frame. The radial velocity provided is the median value of the radial velocity measurements at all epochs. Warning: in the vicinity of bright stars, DR2 RVs can be grossly wrong. See arXiv:1901.10460 for details. | km/s | spect.dopplerVeloc |
radial_velocity_error | Err. RV | The radial velocity error is the error on the median to which a constant noise floor of 0.11 km/s has been added in quadrature to take into account the calibration contribution. | km/s | stat.error;spect.dopplerVeloc |
random_index | Random | Random index that can be used to deterministically select subsets | N/A | meta.code |
ruwe | RUWE | Renormalized Unit Weight Error; this is a revised measure for the overall consistency of the solution as defined by GAIA-C3-TN-LU-LL-124-01. A suggested cut on this is RUWE <1.40) See the note for details. Note ruwe | N/A | stat.weight |
source_id | Source Id | Unique source identifier. Note that this *cannot* be matched against the DR1 source_id. Note id | N/A | meta.id;meta.main |
The following fields are available in VOTable output. The verbosity level is a number intended to represent the relative importance of the field on a scale of 1 to 30. The services take a VERB argument. A field is included in the output if their verbosity level is less or equal VERB*10.
Name | Table Head | Description | Unit | UCD | Verb. Level |
---|---|---|---|---|---|
source_id | Source Id | Unique source identifier. Note that this *cannot* be matched against the DR1 source_id. Note id | N/A | meta.id;meta.main | 1 |
ra | RA (ICRS) | Barycentric Right Ascension in ICRS at ref_epoch | deg | pos.eq.ra;meta.main | 1 |
dec | Dec (ICRS) | Barycentric Declination in ICRS at ref_epoch | deg | pos.eq.dec;meta.main | 1 |
pmra | µ(RA) | Proper motion in right ascension of the source in ICRS at ref_epoch. This is the projection of the proper motion vector in the direction of increasing right ascension. | mas/yr | pos.pm;pos.eq.ra | 1 |
pmdec | µ(Dec) | Proper motion in declination at ref_epoch. | mas/yr | pos.pm;pos.eq.dec | 1 |
parallax | Parallax | Absolute barycentric stellar parallax of the source at the reference epoch ref_epoch. If looking for a distance, consider joining with gdr2dist.main and using the distances from there. | mas | pos.parallax | 1 |
phot_g_mean_mag | m_G | Mean magnitude in the G band. This is computed from the G-band mean flux applying the magnitude zero-point in the Vega scale. Note phot | mag | phot.mag;em.opt;stat.mean | 1 |
phot_rp_mean_mag | Mag RP | Mean magnitude in the integrated RP band. This is computed from the RP-band mean flux applying the magnitude zero-point in the Vega scale. No error is provided for this quantity as the error distribution is only symmetric in flux space. For errors small compared to the flux (less than 10%, say), the magnitude error is well approximated by 1.09*flux/flux_err. Note phot | mag | phot.mag;em.opt.R | 1 |
phot_bp_mean_mag | Mag BP | Mean magnitude in the integrated BP band. This is computed from the BP-band mean flux applying the magnitude zero-point in the Vega scale. No error is provided for this quantity as the error distribution is only symmetric in flux space. For errors small compared to the flux (less than 10%, say), the magnitude error is well approximated by 1.09*flux/flux_err. Note phot | mag | phot.mag;em.opt.B | 1 |
radial_velocity | RV | Spectroscopic radial velocity in the solar barycentric reference frame. The radial velocity provided is the median value of the radial velocity measurements at all epochs. Warning: in the vicinity of bright stars, DR2 RVs can be grossly wrong. See arXiv:1901.10460 for details. | km/s | spect.dopplerVeloc | 1 |
ruwe | RUWE | Renormalized Unit Weight Error; this is a revised measure for the overall consistency of the solution as defined by GAIA-C3-TN-LU-LL-124-01. A suggested cut on this is RUWE <1.40) See the note for details. Note ruwe | N/A | stat.weight | 5 |
_r | Dist. | Distance to cone center | deg | pos.distance | 10 |
ra_error | Err. RA | Standard error of ra (with cos δ applied). | mas | stat.error;pos.eq.ra | 20 |
dec_error | Err. Dec | Standard error of dec | mas | stat.error;pos.eq.dec | 20 |
pmra_error | Err. PM(RA) | Standard error of pmra | mas/yr | stat.error;pos.pm;pos.eq.ra | 20 |
pmdec_error | Err. PM(Dec) | Standard error of pmdec | mas/yr | stat.error;pos.pm;pos.eq.dec | 20 |
parallax_error | Parallax_error | Standard error of parallax | mas | stat.error;pos.parallax | 20 |
phot_g_mean_flux | Flux_G | G-band mean flux as electrons per second. Note phot | s**-1 | phot.flux;em.opt;stat.mean | 20 |
phot_g_mean_flux_error | Err. Flux(G) | Error on phot_g_mean_flux | s**-1 | stat.error;phot.flux;em.opt;stat.mean | 20 |
phot_rp_mean_flux | Flux RP | Mean flux in the integrated RP band. Note phot | s**-1 | phot.flux;em.opt.R | 20 |
phot_rp_mean_flux_error | Err. Fl. RP | Error in the mean flux in the integrated RP band. Errors are computed from the dispersion about the weighted mean of the input calibrated photometry. | s**-1 | stat.error;phot.flux;em.opt.R | 20 |
phot_bp_mean_flux | Flux BP | Mean flux in the integrated BP band. Note phot | s**-1 | phot.flux;em.opt.B | 20 |
phot_bp_mean_flux_error | Err. Fl. BP | Error in the mean flux in the integrated BP band. Errors are computed from the dispersion about the weighted mean of the input calibrated photometry. | s**-1 | stat.error;phot.flux;em.opt.B | 20 |
phot_bp_rp_excess_factor | BP/RP excess | BP/RP excess factor estimated from the comparison of the sum of integrated BP and RP fluxes with respect to the flux in the G band. This measures the excess of flux in the BP and RP integrated photometry with respect to the G band. This excess is believed to be caused by background and contamination issues affecting the BP and RP data. Therefore a large value of this factor for a given source indicates systematic errors in the BP and RP photometry. | N/A | stat.fit.goodness | 20 |
radial_velocity_error | Err. RV | The radial velocity error is the error on the median to which a constant noise floor of 0.11 km/s has been added in quadrature to take into account the calibration contribution. | km/s | stat.error;spect.dopplerVeloc | 20 |
astrometric_gof_al | GoF | Goodness-of-fit statistic of the astrometric solution for the source in the along-scan direction (you probably want to use RUWE instead of this). Note gof | N/A | stat.fit.goodness | 20 |
astrometric_params_solved | PS | This is a binary code indicating which astrometric parameters were estimated for the source. A set bit means the parameter was estimated. The least-significant bit represents α, the next bits δ, parallax, PM(RA) and PM(De). For Gaia DR2 the only relevant values are 31 (all five parameters solved) and 3 (only positions). | N/A | meta.code | 20 |
random_index | Random | Random index that can be used to deterministically select subsets | N/A | meta.code | 20 |
If you use public Gaia DR2 data in a paper, please take note of ESAC's guide on how to acknowledge and cite it.
VOResource XML (that's something exclusively for VO nerds)
This is the “gaussianized chi-square”, which for good fits should approximately follow a normal distribution with zero mean value and unit standard deviation. Values exceeding, say, +3 thus indicate a bad fit to the data.
This statistic is computed according to the formula
gof = sqrt(9ν/2) [(χ²/ν)^(1/3) + 2/(9ν) − 1],
where χ² (astrometric_chi2_al) is the AL chi-square statistic and ν = (astrometric_n_good_obs_al − 5) is the number of degrees of freedom for a source update. Here, 5 is the number of astrometric parameters. Note that only “good” (i.e. not strongly downweighted) observations are included in χ² and ν.
An alternative indicator of bad fits is the astrometric excess noise. In AGIS the source update deals with bad fits by adding astrometric excess noise to the formal observation noise. This reduces the weight of the observations and inflates the covariance of the estimated astrometric parameters correspondingly. However, the chi-square values used to calculate astrometric_gof_al do not take into account the astrometric excess noise, and astrometric_gof_al can therefore always be used as a goodness-of-fit indicator of the source solution in AGIS.
For the contents of Gaia DR1 (and hence TGAS), which does not include Solar System objects, the source ID consists of a 64-bit integer, least significant bit = 1 and most significant bit = 64, comprising:
This means that the HEALpix index level 12 of a given source is contained in the most significant bits. HEALpix index of 12 and lower levels can thus be retrieved as follows:
Note that several systematics have been found for both Gaia G and BP photometry on the level of 10s of mmags. See 2018A&A...616A..17A and 2018A&A...616A...4E for a description of the problem as well as some proposed empirical corrections. For sources brighter than 16.5, see also 2018MNRAS.479L.102C and 2018A&A...617A.138W, where the latter also discusses systematics in BP.
The Renormalized Unit Weight Error (RUWE) is defined in L. Lindegren: Re-normalising the astrometric chi-square in Gaia DR2 (Gaia tech note GAIA-C3-TN-LU-LL-124-01). This is essentially the astrometric_chi2 from the DR2 release, but corrected for its strong dependency on magnitude and colour. For quality cuts, this is the recommended quantity to use. Lindegren suggests using RUWE<1.4 as a quality cut for “good” solutions based on the shape of the distribution.
The values given here were calculated independently of DPAC and do not use interpolation on the grids provided by Lindegren et al. Thus, minor differences from the “official” RUWE values are expected. As Lindegren et al point out, such differences should not matter in science applications, though.