Information on Service 'SDSS DR16 Selection'

[Use this service from your browser]

Further access options are discussed below

This is a redacted version of the SDSS DR16 table prepared for VizieR (V/154/sdss16). It is mainly here to facilitate local matches; for original SDSS-related research, it is probably better to somewhere else. Over VizieR and SDSS, we are keeping most of the per-band values in arrays to keep the column list manageable. Note that in ADQL, array indexes are 1-based. We are trying to orient our column names on SDSS but use underscores instead of camel-casing (e.g. spec_obj_id instead of SpecObjID), since mixed-case identifiers in SQL is asking for trouble. To save space, we do not keep psf-based classifications, per-band offsets, spectrum metadata, and USNO-related information in this table. Let the operators know if you need any of that.

For a list of all services and tables belonging to this service's resource, see Information on resource 'SDSS DR16 Selection'

Overview

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.

Spatial Coverage

Input Fields

The following fields are available to provide input to the service (with some renderers, some of these fields may be unavailable):

NameTable Head DescriptionUnitUCD
DEC Delta (ICRS) Declination (ICRS decimal) deg pos.eq.dec
g G Model magnitude in g filter AB scale mag phot.mag;em.opt.V
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
i I Model magnitude in i filter AB scale mag phot.mag;em.opt.I
maxrec Match limit Maximum number of records returned. Pass 0 to retrieve service parameters. N/A N/A
obj_id Obj_id SDSS unique object identifier N/A meta.id;meta.main
r R Model magnitude in r filter AB scale 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
spec_z Spec_z Spectroscopic final redshift (when SpObjID>0) N/A src.redshift
SR Search Radius Search radius deg N/A
u U Model magnitude in u filter AB scale mag phot.mag;em.opt.U
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
z Z Model magnitude in z filter AB scale mag phot.mag;em.opt.I

Default Output Fields

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.

NameTable Head DescriptionUnitUCD
_r Dist. Distance to cone center deg pos.distance
class Class Type of object (3=galaxy, 6=star) Note 2 N/A src.class
clean Clean Clean photometry flag (1=clean; 0=unclean) N/A meta.code
dec Dec Declination of the object (ICRS) deg pos.eq.dec;meta.main
dec_err Dec_err Mean error on dec arcsec stat.error;pos.eq.dec
dev_abs Dev_abs Array of de Vaucouleurs fit b/a ratios, in ugriz sequence N/A phys.size.axisRatio
dev_phi Dev_phi Array of position angles of de Vaucouleurs fits in ugriz sequence (warning: anything smaller than 0 in here must be considered NULL). deg pos.posAng
dev_rads Dev_rads Array of de Vaucouleurs fit radii, in ugriz sequence arcsec phys.angSize;src
e_pm_ra E_pm_ra Mean error on pmra Note 11 mas/yr stat.error;pos.pm;pos.eq.ra
err_g Err_g Model magnitude in g filter AB scale mag phot.mag;em.opt.V
err_i Err_i Model magnitude in i filter AB scale mag phot.mag;em.opt.I
err_r Err_r Model magnitude in r filter AB scale mag phot.mag;em.opt.R
err_u Err_u Model magnitude in u filter AB scale mag phot.mag;em.opt.U
err_z Err_z Model magnitude in z filter AB scale mag phot.mag;em.opt.I
field_id Field_id The field this object is in. N/A meta.note
field_mjds Field_mjds Array of dates of observation per ugriz band Note 13 d time.epoch
field_quality Field_quality Quality of the observation: 1=bad; 2=barely acceptable; 3=good Note 13 N/A meta.code.qual;obs.param;obs
flags Flags Array of detection flags, in ugriz sequence Note 3 N/A meta.code
g G Model magnitude in g filter AB scale Note 7 mag phot.mag;em.opt.V
i I Model magnitude in i filter AB scale Note 7 mag phot.mag;em.opt.I
mode Mode Photo mode (1=primary, 2=secondary, 3=family, 4=outside) N/A meta.code.class
obj_id Obj_id SDSS unique object identifier Note 1 N/A meta.id;meta.main
parent_id Parent_id Pointer to parent (if object deblended) N/A meta.id.parent
petmags Petmags Array of Petrosian magnitudes, in ugriz sequence Note 4 mag phot.mag
petrad_errs Petrad_errs Array of Petrosian radii, in ugriz sequence arcsec stat.error;phys.angSize;src
petrads Petrads Array of Petrosian radii, in ugriz sequence arcsec phys.angSize;src
photo_flags Photo_flags Photo Object Attribute flags Note 3 N/A meta.code.error
photoz_chisq Photoz_chisq Chi-square value for the minimum chi-square template fit Note 12 N/A stat.value
photoz_nn_avg_z Photoz_nn_avg_z Average redshift of the nearest neighbors; if significantly different from photoz_z this might be a better estimate than photoz_z N/A src.redshift.phot
photoz_z Photoz_z Photometric redshift estimated by robust fit to nearest neighbors in a reference set Note 12 N/A src.redshift
photoz_z_err Photoz_z_err Estimated error of the photometric redshift Note 12 N/A stat.error
pm_dec Pm_dec Proper motion along Declination Note 11 mas/yr pos.pm;pos.eq.dec
pm_dec_err Pm_dec_err Mean error on pmDE. mas/yr stat.error;pos.pm;pos.eq.dec
pm_ra Pm_ra Proper motion along Right Ascension Note 11 mas/yr pos.pm;pos.eq.ra
pm_sig_dec Pm_sig_dec RMS residual of proper motion fit in Dec. mas stat.fit.residual
pm_sig_ra Pm_sig_ra RMS residual of proper motion fit in RA. Note 11 mas stat.fit.residual
psfmags Psfmags Array of PSF magnitudes, in ugriz sequence Note 4 mag phot.mag
r R Model magnitude in r filter AB scale Note 7 mag phot.mag;em.opt.R
ra Ra Right Ascension of the object (ICRS) deg pos.eq.ra;meta.main
ra_err Ra_err Mean error on ra arcsec stat.error;pos.eq.ra
sdss_id Sdss_id SDSS object identifier (run-rerun-camcol-field-object) Note 1 N/A meta.id
spec_class Spec_class Spectroscopic class: "GALAXY"; "QSO"; "STAR" Note 6 N/A meta.code.class;pos.parallax.spect
spec_sn_median Spec_sn_median Median signal-to-noise over all good pixels. Note 6 N/A em.wl.central;stat.median
spec_sub_class Spec_sub_class Spectroscopic subclass. Note 10 N/A src.class
spec_vel_disp Spec_vel_disp Velocity dispersion Note 6 km/s phys.veloc.dispersion
spec_vel_disp_err Spec_vel_disp_err Mean error on spec_vel_disp Note 6 km/s stat.error
spec_z Spec_z Spectroscopic final redshift (when SpObjID>0) Note 6 N/A src.redshift
spec_z_err Spec_z_err Mean error on spec_z (negative for bad fit) Note 6 N/A stat.error
spec_z_warning Spec_z_warning Warning flag on redshift. Note 9 N/A meta.code
spectral_id Spectral_id Spectroscopic Plate-MJD-Fiber identifier (plate-mjd-fiberID) N/A meta.id
types Types Array of phototypes (6=Star ; 3=galaxy) in ugriz sequence Note 2 N/A src.class.starGalaxy
u U Model magnitude in u filter AB scale Note 7 mag phot.mag;em.opt.U
z Z Model magnitude in z filter AB scale Note 7 mag phot.mag;em.opt.I

VOTable Output Fields

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.

NameTable Head DescriptionUnitUCD Verb. Level
obj_id Obj_id SDSS unique object identifier Note 1 N/A meta.id;meta.main 1
ra Ra Right Ascension of the object (ICRS) deg pos.eq.ra;meta.main 1
dec Dec Declination of the object (ICRS) deg pos.eq.dec;meta.main 1
dec_err Dec_err Mean error on dec arcsec stat.error;pos.eq.dec 1
pm_ra Pm_ra Proper motion along Right Ascension Note 11 mas/yr pos.pm;pos.eq.ra 1
pm_dec Pm_dec Proper motion along Declination Note 11 mas/yr pos.pm;pos.eq.dec 1
pm_sig_dec Pm_sig_dec RMS residual of proper motion fit in Dec. mas stat.fit.residual 1
u U Model magnitude in u filter AB scale Note 7 mag phot.mag;em.opt.U 1
err_u Err_u Model magnitude in u filter AB scale mag phot.mag;em.opt.U 1
g G Model magnitude in g filter AB scale Note 7 mag phot.mag;em.opt.V 1
err_g Err_g Model magnitude in g filter AB scale mag phot.mag;em.opt.V 1
r R Model magnitude in r filter AB scale Note 7 mag phot.mag;em.opt.R 1
err_r Err_r Model magnitude in r filter AB scale mag phot.mag;em.opt.R 1
i I Model magnitude in i filter AB scale Note 7 mag phot.mag;em.opt.I 1
err_i Err_i Model magnitude in i filter AB scale mag phot.mag;em.opt.I 1
z Z Model magnitude in z filter AB scale Note 7 mag phot.mag;em.opt.I 1
err_z Err_z Model magnitude in z filter AB scale mag phot.mag;em.opt.I 1
field_id Field_id The field this object is in. N/A meta.note 1
flags Flags Array of detection flags, in ugriz sequence Note 3 N/A meta.code 1
types Types Array of phototypes (6=Star ; 3=galaxy) in ugriz sequence Note 2 N/A src.class.starGalaxy 1
parent_id Parent_id Pointer to parent (if object deblended) N/A meta.id.parent 1
spec_z Spec_z Spectroscopic final redshift (when SpObjID>0) Note 6 N/A src.redshift 1
spec_z_err Spec_z_err Mean error on spec_z (negative for bad fit) Note 6 N/A stat.error 1
spec_z_warning Spec_z_warning Warning flag on redshift. Note 9 N/A meta.code 1
spec_class Spec_class Spectroscopic class: "GALAXY"; "QSO"; "STAR" Note 6 N/A meta.code.class;pos.parallax.spect 1
spec_sub_class Spec_sub_class Spectroscopic subclass. Note 10 N/A src.class 1
spec_vel_disp Spec_vel_disp Velocity dispersion Note 6 km/s phys.veloc.dispersion 1
spec_vel_disp_err Spec_vel_disp_err Mean error on spec_vel_disp Note 6 km/s stat.error 1
spec_sn_median Spec_sn_median Median signal-to-noise over all good pixels. Note 6 N/A em.wl.central;stat.median 1
photoz_z Photoz_z Photometric redshift estimated by robust fit to nearest neighbors in a reference set Note 12 N/A src.redshift 1
photoz_z_err Photoz_z_err Estimated error of the photometric redshift Note 12 N/A stat.error 1
photoz_nn_avg_z Photoz_nn_avg_z Average redshift of the nearest neighbors; if significantly different from photoz_z this might be a better estimate than photoz_z N/A src.redshift.phot 1
photoz_chisq Photoz_chisq Chi-square value for the minimum chi-square template fit Note 12 N/A stat.value 1
field_quality Field_quality Quality of the observation: 1=bad; 2=barely acceptable; 3=good Note 13 N/A meta.code.qual;obs.param;obs 1
field_mjds Field_mjds Array of dates of observation per ugriz band Note 13 d time.epoch 1
sdss_id Sdss_id SDSS object identifier (run-rerun-camcol-field-object) Note 1 N/A meta.id 1
spectral_id Spectral_id Spectroscopic Plate-MJD-Fiber identifier (plate-mjd-fiberID) N/A meta.id 1
_r Dist. Distance to cone center deg pos.distance 10
ra_err Ra_err Mean error on ra arcsec stat.error;pos.eq.ra 15
e_pm_ra E_pm_ra Mean error on pmra Note 11 mas/yr stat.error;pos.pm;pos.eq.ra 15
pm_dec_err Pm_dec_err Mean error on pmDE. mas/yr stat.error;pos.pm;pos.eq.dec 15
pm_sig_ra Pm_sig_ra RMS residual of proper motion fit in RA. Note 11 mas stat.fit.residual 15
mode Mode Photo mode (1=primary, 2=secondary, 3=family, 4=outside) N/A meta.code.class 15
class Class Type of object (3=galaxy, 6=star) Note 2 N/A src.class 15
clean Clean Clean photometry flag (1=clean; 0=unclean) N/A meta.code 15
photo_flags Photo_flags Photo Object Attribute flags Note 3 N/A meta.code.error 15
psfmags Psfmags Array of PSF magnitudes, in ugriz sequence Note 4 mag phot.mag 15
petmags Petmags Array of Petrosian magnitudes, in ugriz sequence Note 4 mag phot.mag 15
petrads Petrads Array of Petrosian radii, in ugriz sequence arcsec phys.angSize;src 15
petrad_errs Petrad_errs Array of Petrosian radii, in ugriz sequence arcsec stat.error;phys.angSize;src 15
dev_rads Dev_rads Array of de Vaucouleurs fit radii, in ugriz sequence arcsec phys.angSize;src 15
dev_abs Dev_abs Array of de Vaucouleurs fit b/a ratios, in ugriz sequence N/A phys.size.axisRatio 15
dev_phi Dev_phi Array of position angles of de Vaucouleurs fits in ugriz sequence (warning: anything smaller than 0 in here must be considered NULL). deg pos.posAng 15
psfmag_errs Psfmag_errs Array of the errors of the PSF magnitudes, in ubriz sequence mag stat.error;phot.mag 25
petmag_errs Petmag_errs Array of the errors Petrosian magnitudes, in ugriz sequence mag phot.mag 25

Please see http://www.sdss.org/collaboration/citing-sdss/ for the authors' requests on how to cite this material.

VOResource XML (that's something exclusively for VO nerds)

Note 1

The SDSS identifier is composed of the 5 numbers run, rerun (301), camcol (1-6), field (11-1001) and object (1-16000). The SDSS-ID is written run-rerun-cam-field-obj (5 numbers and 4 dashes).

The objID is also combined from these numbers (the ≪n operator represents the left shift of n bits, i.e. a multiplication by 2n):

objID = skyVersion << 59 + rerun << 48 + run << 32
        + camcol<<29 + field<<16 + obj

(objID is in the range 1237645876861272065-1237680531356583125).

Note 10

The spectroscopic subclass includes:

  • for GALAXY classes: BROADLINE, STARFORMING, STARBURST, AGN
  • for STAR classes: MK spectral sub-classes, CV=Catataclysmic Variable, Carbon stars (Carbon, Carbon_lines), white dwarfs (WD, WDcooler, WDhotter, WDmagnetic, CarbonWD, CalciumWD)
Note 11

Columns from the ProperMotions table.

Note 12

Columns from the Photoz table

Note 13

Columns from the Field table

Note 2

The type (class) is numbered as follows:

0:Unknown: Object type is not known.
1:Cosmic-ray track (not used).
2:Defect (not used)
3:Galaxy: An extended object composed of many stars and other matter
4:Ghost: Object created by reflected or refracted light. (not used)
5:KnownObject: Object came from some other catalog (not yet used)
6:Star: A a self-luminous gaseous celestial body
7:Trail: A satellite or asteroid or meteor trail. (not yet used)
8:Sky: Blank sky spectrogram (no objects in this arcsecond area).
Note 3

Flags written in hexadecimal (full description)

0000000000000001 CANONICAL_CENTER Measurements used the center in r*
0000000000000002 BRIGHT Object detected in bright object-finding
0000000000000004 EDGE Object is too close to edge of frame
0000000000000008 BLENDED Multiple peaks detected
0000000000000010 CHILD Product of deblending a BLENDED object.
0000000000000020 PEAKCENTER Position of peak pixel rather than ML
0000000000000040 NODEBLEND No deblending attempted on BLENDED object
0000000000000080 NOPROFILE Radial profile could not be estimated
0000000000000100 NOPETRO No valid Petrosian radius found
0000000000000200 MANYPETRO More than one Petrosian radius found.
0000000000000400 NOPETRO_BIG Petrosian radius beyond radial profile.
0000000000000800 DEBLENDTOOMANY_PEAKS More than 25 peaks in this object
0000000000001000 COSMIC_RAY Contains a pixel part of a cosmic ray.
0000000000002000 MANYR50 More than one 50% light radius.
0000000000004000 MANYR90 More than one 90% light radius.
0000000000008000 BAD_RADIAL Some points in radial profile S/N<0
0000000000010000 INCOMPLETE_PROFILE Petrosian radius intersects frame edge
0000000000020000 INTERP Pixel(s) determined by interpolation.
0000000000040000 SATURATED Saturated pixel(s)
0000000000080000 NOTCHECKED Not checked for local peaks
0000000000100000 SUBTRACTED BRIGHT object, wings subtracted
0000000000200000 NOSTOKES No measured Stokes params
0000000000400000 BADSKY Sky level so bad that highest pixel <0.
0000000000800000 PETROFAINT Petrosian radius(es) rejected for low SB
0000000001000000 TOO_LARGE Object too large to measure its profile
0000000002000000 DEBLENDEDASPSF Deblender treated obj as PSF
0000000004000000 DEBLEND_PRUNED At least one child was removed
0000000008000000 ELLIPFAINT Object center fainter than the isophote
0000000010000000 BINNED1 Object detected in 1x1 binned image
0000000020000000 BINNED2 Object detected in 2x2 binned image
0000000040000000 BINNED4 Object detected in 4x4 binned image
0000000080000000 MOVED Possibly moving object
0000000100000000 DEBLENDEDASMOVING A MOVED object treated as moving.
0000000200000000 NODEBLEND_MOVING A MOVED object not treated as moving.
0000000400000000 TOOFEWDETECTIONS Too few detections to deblend as moving.
0000000800000000 BADMOVINGFIT Moving fit too poor to be believable.
0000001000000000 STATIONARY Object consistent with being stationary.
0000002000000000 PEAKSTOOCLOSE Some peaks merged into a single peak.
0000004000000000 MEDIAN_CENTER Center given is of median-smoothed image.
0000008000000000 LOCAL_EDGE Center too close to an edge.
0000010000000000 BADCOUNTSERROR Too few good pixels, error underestimated
0000020000000000 BADMOVINGFIT_CHILD Moving child's velocity fit too poor
0000040000000000 DEBLENDUNASSIGNEDFLUX After deblending flux not assigned
0000080000000000 SATUR_CENTER Center is close to saturated pixel(s)
0000100000000000 INTERP_CENTER Center is close to interpolated pixel(s)
0000200000000000 DEBLENDEDATEDGE Object close to edge was deblended
0000400000000000 DEBLEND_NOPEAK No detected peak within this child
0000800000000000 PSFFLUXINTERP PSF flux from interpolated pixels > 20%
0001000000000000 TOOFEWGOOD_DETECTIONS Too few good detections
0002000000000000 CENTEROFFAIMAGE At least one peak's center lay off image
0004000000000000 DEBLEND_DEGENERATE Identical candidate children, 1 retained
0008000000000000 BRIGHTESTGALAXYCHILD Brightest member classified as galaxy
0010000000000000 CANONICAL_BAND Band chosen as 'Canonical', generally r
0020000000000000 AMOMENT_FAINT Object too faint to measure moments
0040000000000000 AMOMENT_SHIFT Centroid shift too large
0080000000000000 AMOMENT_MAXITER Maximum number of iterations exceeded
0100000000000000 MAYBE_CR Object could actually be a cosmic ray
0200000000000000 MAYBE_EGHOST Object could actually be a ghost
0400000000000000 NOTCHECKED_CENTER Object center in a region not searched
0800000000000000 OBJECT2HASSATUR_DN Trails included in estimated flux.
1000000000000020 OBJECT2DEBLENDPEEPHOLE Deblend modified by peephole
2000000000000020 GROWN_MERGED Growing led to a merger
4000000000000020 HAS_CENTER Object has a canonical center
8000000000000020 RESERVED Not used
Note 4

We have retained the CDS practice of setting PSF and Petrosian magnitudes to NaN values when corresponding errors>100; errors >100 have been set to NaN values.

Note 6

Columns from the SpecObjAll table

Note 7

The response curves of the SDSS filters (u g r i z) can be found on the SDSS page http://classic.sdss.org/dr7/instruments/imager The central wavelength and FWHM are:

(nm) u' g' r' i' z'
lambda 354.3 477.0 623.1 762.5 913.4
FWHM 56.7 138.7 137.3 152.6 95.0

Note that the ugriz magnitudes are not exactly on the AB scale for the u-band (uAB = u0.04) and z-band (zAB = z + 0.02) (http://www.sdss.org/dr16/algorithms/fluxcal/#SDSStoAB)

Note 9

This flag is a number consisting of the following bits:

1 sky fiber
2 too little wavelength coverage
4 chi-squared of best fit is too close to that of second best
8 synthetic spectrum is negative
16 fraction of points more than 5 σ away from best model is too large (>5%)
32 chi-squared minimum at edge of the redshift fitting range
64 a QSO line exhibits negative emission
128 the fiber was unplugged, so no spectrum obtained

The flag 64 is only triggered in QSO spectra if CIV, CIII, MgII, Hβ, or Hα has
textrmlineArea + 3⋅(
textrmlineArea) < 0.

See also http://skyserver.sdss.org/dr16/en/help/browser/browser.aspx#&&history=search+SpeczWarning