Deep coadd

The combination of multiple processed, calibrated, and background-subtracted images, for a patch of sky, for each of the six LSST filters.

Citation: NSF-DOE Vera C. Rubin Observatory (2025); Legacy Survey of Space and Time Data Preview 1: deep_coadd dataset type DOI Logo https://doi.org/10.71929/rubin/2570313

Access

The deep coadd images are accessible via the Butler, SIA, and TAP services.

Butler

  • Dataset type: (‘deep_coadd’, {band, skymap, tract, patch}, ExposureF)

  • Format: FITS

  • Number of Butler datasets: 2,644

SIA and TAP

Schema: ObsCore table

IVOA calibration level: 3

Dataproduct subtype: lsst.deep_coadd

Description

A DP1 visit image must have a PSF FWHM < 1.7 arcseconds to be selected as an input image to the coadd. A mean stacking algorithm, weighted by inverse variance, combines selected exposures.

Each individual deep coadd image covers a single patch of the sky: a quadrilateral sub-region of the overall skymap that covers approximately 79 square arcminutes. Patches slightly overlap at their edges. Deep coadd images are for a single filter.

Processing

The deep coadd images are the result of Image coaddition.

Pixel data

The deep coadd images have three planes of pixel data.

Image: sky pixel data in flux units of nJy.

Variance: uncertainty (noise) in the flux in units of nJy^2.

Mask: an integer bitmask of representative flag values that indicate processing status or issues, similar to the SDSS bitmasks.

Metadata

The metadata for deep coadd images retrieved from the Butler include a list of the input visit images, and the derived PSF, photometric calibration, and WCS.

Tutorials

See the 200-level notebook or 200-level portal tutorials demonstrating how to access the deep coadd images.