Legacy Survey - Data Access

The Legacy Survey data and database are accessible from the Astro Data Lab, and from the Legacy Survey team website. Explore the dataset interactively using the Sky Viewer.

Data Lab Table Access Protocol (TAP) service

TAP provides a convenient access layer to the Legacy Survey catalog database. TAP-aware clients (such as TOPCAT) can point to https://datalab.noirlab.edu/tap. DR9, DR8, DR7, DR6, DR5, DR4 and DR3 databases are respectively named ls_dr9, ls_dr8, ls_dr7, ls_dr6, ls_dr5, ls_dr4, and ls_dr3. Select a database in order to see the tables it contains as well as their descriptions. Please note that the data model has changed slightly between DR9 and between other releases so the tables and columns are not identical.

Another way to view the tables is through the Data Lab Query Interface (https://datalab.noirlab.edu/query.php). From the Column Information tab, select ls_dr9 from the left-hand menu to see the list of tables for DR9, respectively. Clicking on a table will show the column names and description. For example, ls_dr9.tractor, ls_dr9.tractor_n, ls_dr9.tractor_s correspond to the main Tractor photometry tables covering, respectively, to the full combined footprint, the North footprint (_n), and the South footprint (_s).

Data Lab Query Manager

The Query Manager is available as part of the Data Lab software distribution. The Query Manager client provides a Python API to Data Lab database services. For the Legacy Survey, these services include anonymous, and authenticated access through synchronous or asynchronous queries of the catalog made directly to the database. Additional Data Lab services for registered users include personal database storage, and storage through the Data Lab VOSpace.

The Query Manager can be called from a Jupyter Notebook on the Data Lab Notebook server. Example notebooks are provided to users upon creation of their user account (https://datalab.noirlab.edu/register.php)

Image cutouts

The Data Lab Simple Image Access (SIA) service provide users with a fast way to retrieve cutouts from Legacy Survey images.

In addition, sections of the Legacy Survey can be obtained as JPEGs or FITS files using the Legacy Survey team cutout service, as follows:

JPEG:   https://www.legacysurvey.org/viewer/cutout.jpg?ra=199.1111&dec=17.7009&layer=ls-dr9&pixscale=1.00&bands=grz

FITS:   https://www.legacysurvey.org/viewer/cutout.fits?ra=199.1111&dec=17.700&layer=ls-dr9&pixscale=0.25

where "bands" is a string such as "grz","gz","g", etc. This will merge the northern (MzLS+BASS) and equatorial (DECam) images at the Dec=32.375 line. Replacing layer=ls-dr9 with layer=ls-dr9-model or layer=ls-dr9-resid will instead return cutouts for the model and residual images, respectively. For more options, see the Legacy Survey page describing the Viewer URL Formats.

JPEG:   http://legacysurvey.org/viewer/jpeg-cutout/?ra=190.1086&dec=1.2005&layer=dr8&pixscale=0.27&bands=grz

FITS:   http://legacysurvey.org/viewer/fits-cutout/?ra=190.1086&dec=1.2005&layer=dr8&pixscale=0.27&bands=grz

where "bands" is a string such as "grz","gz","g", etc. This will merge the northern (MzLS+BASS) and equatorial (DECam) images at the Dec=32.375 line. Replacing layer=dr8 with layer=dr8-model or layer=dr8-resid will instead return cutouts for the model and residual images, respectively.

In addition to ls-dr9, and dr8, a subset of previous layers are still accessible: decals-dr5, mzls+bass-dr6, and decals-dr7.

The NSF’s NOIRLab Science Archive access

The NSF’s NOIRLab Science Archive portal can be used to retrieve raw, and calibrated Legacy Survey images, as well as the Tractor catalogs. The DR1-DR8 collections are still posted on the legacy NOAO version of the Science Archive as described below. This will be updated as we have been migrating to our new NOIRLab domain. The DR9 collection is not yet available.

  • Query the NSF’s NOIRLab Science Archive.
  • From the menu of "Available Collections" on the left, select the desired data release (e.g. Legacy Survey-DR8).
  • Under "Data products - Raw data" check "Object".
  • Optionally, you may select data from specific filters, or restrict the search by other parameters such as sky coordinates, observing date, or exposure time.
  • Click "Search".
  • In the DR8 (or DR7, DR5, DR3) collection, refine the search by Proposal ID (2014B-0404) in the "Refine" tab in order to obtain DECaLS only images.

There is a direct link for the LS DR8 collection. Similarly, the previous DR7 and DR6 collections also have a direct link.

The Results page offers several different ways to download the data. See the Tutorials page for details.