Table information for 'alerce_tap.ztf_dataquality'

General

Table Description:

Detailed data quality metrics for ZTF detections including image position, PSF-fit quality (chi-square, FWHM), SExtractor properties, pixel statistics, photometric calibration parameters, and signal-to-noise measurements.

This table is available for ADQL queries and through the TAP endpoint.

Resource Description:

Multi-survey astronomical object catalog containing astrometric and statistical information from multiple surveys. This table provides aggregated properties for astronomical objects including position, detection statistics, and temporal coverage.

For a list of all services and tables belonging to this table's resource, see Information on resource 'ALeRCE Multi-Survey Object Catalog'

Citing this table

To cite the table as such, we suggest the following BibTeX entry:

@MISC{vo:alerce_tap_ztf_d,
  year=2026,
  title={{ZTF} Data Quality Metrics},
  author={{ALeRCE} Team},
  url={http://tap.alerce.online/tableinfo/alerce_tap.ztf_dataquality},
  howpublished={{VO} resource provided by the {ALeRCE} {TAP} service}
}

Columns

Sorted by DB column index. [Sort alphabetically]

NameTable Head DescriptionUnitUCD
oid Oid Unique identifier for this object N/A meta.id;src
measurement_id Measurement_id Unique identifier for the subtraction candidate N/A meta.id
xpos Xpos X-image position of candidate on CCD pix pos.cartesian.x
ypos Ypos Y-image position of candidate on CCD pix pos.cartesian.y
chipsf Chipsf Reduced chi-square for PSF-fit N/A stat.fit.goodness
sky Sky Local sky background estimate [DN] N/A instr.skyLevel
fwhm Fwhm Full Width Half Maximum assuming a Gaussian core, from SExtractor pix instr.obsty.seeing
classtar Classtar Star/Galaxy classification score from SExtractor N/A src.class.starGalaxy
mindtoedge Mindtoedge Distance to nearest edge in image pix phys.angSize
seeratio Seeratio Ratio: difffwhm / fwhm N/A stat.fit.goodness
aimage Aimage Windowed profile RMS along major axis from SExtractor pix phys.angSize.smajAxis
bimage Bimage Windowed profile RMS along minor axis from SExtractor pix phys.angSize.sminAxis
aimagerat Aimagerat Ratio: aimage / fwhm N/A arith.ratio
bimagerat Bimagerat Ratio: bimage / fwhm N/A arith.ratio
nneg Nneg Number of negative pixels in a 5 x 5 pixel stamp N/A meta.number
nbad Nbad Number of prior-tagged bad pixels in a 5 x 5 pixel stamp N/A meta.number
sumrat Sumrat Ratio: sum(pixels) / sum(abs(pixels)) in a 5 x 5 pixel stamp where stamp is first median-filtered to mitigate outliers N/A arith.ratio
scorr Scorr Peak-pixel signal-to-noise ratio in point source matched-filtered detection image N/A stat.correlation
dsnrms Dsnrms Ratio: D/stddev(D) on event position where D = difference image N/A stat.stdev
ssnrms Ssnrms Ratio: S/stddev(S) on event position where S = image of convolution: D (x) PSF(D) N/A stat.stdev
magzpsci Magzpsci Magnitude zero point for photometry estimates mag phot.calib
magzpsciunc Magzpsciunc Magnitude zero point uncertainty (in magzpsci) mag stat.error;phot.calib
magzpscirms Magzpscirms RMS (deviation from average) in all differences between instrumental photometry and matched photometric calibrators from science image processing mag stat.stdev;phot.calib
nmatches Nmatches Number of PS1 photometric calibrators used to calibrate science image from science image processing N/A meta.number
clrcoeff Clrcoeff Color coefficient from linear fit from photometric calibration of science image N/A arith.factor
clrcounc Clrcounc Color coefficient uncertainty from linear fit (corresponding to clrcoeff) N/A stat.error;arith.factor
zpclrcov Zpclrcov Covariance in magzpsci and clrcoeff from science image processing [mag^2] N/A stat.covariance
zpmed Zpmed Magnitude zero point from median of all differences between instrumental photometry and matched photometric calibrators from science image processing mag phot.calib;stat.median
clrmed Clrmed Median color of all PS1 photometric calibrators used from science image processing: for filter (fid) = 1, 2, 3, PS1 color used = g-r, g-r, r-i respectively N/A stat.median
clrrms Clrrms RMS color (deviation from average) of all PS1 photometric calibrators used from science image processing N/A stat.stdev
exptime Exptime Integration time of camera exposure s time.duration;obs.exposure
created_date Created_date Date record was created N/A time.creation

Columns that are parts of indices are marked like this.

VOResource

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