Beta Version 0.2 of the
Hubble Source Catalog

The Hubble Source Catalog (HSC) is designed to optimize science from the Hubble Space Telescope by combining the tens of thousands of visit-based, general purpose, source lists in the Hubble Legacy Archive (HLA) into a single master catalog.

Search with Summary Form now (one row per match)
Search with Detailed Form now (one row per source)

Beta Version 0.2 of the HSC contains all members of the ACS/WFC and WFPC2 Source Extractor source lists in HLA version DR7.1 (data release 7.1) that are considered to be valid detections. WFC3 source lists will be included in a future HSC release that is tentatively planned for fall 2013. Please visit our HSC Walkthrough for a step by step example of how to use the interfaces.

The crossmatching process involves adjusting the relative astrometry of overlapping images so as to minimize positional offsets between closely aligned sources in different images. After correction, the astrometric residuals of crossmatched sources are significantly reduced, to typically less than 10 mas. In addition, the catalog includes source nondetections. The crossmatching algorithms and the properties of the catalog are described in Budavari & Lubow (2012) .

Interfaces

- The HSC Summary Search Form displays a single row entry for each object, as defined by a set of detections that have been cross-matched and hence are believed to be a single object. Averaged values for magnitudes and other relevant parameters are provided.

- The HSC Detailed Search Form displays an entry for each separate detection (or nondetection if nothing is found at that position) using all the relevant Hubble observations for a given object (i.e., different filters, detectors, separate visits).

In the future a more general SQL query interface will be provided for more complex and longer running searches through a CasJobs system.

Five things you should know about the HSC

1. Coverage can be very non-uniform (unlike surveys like SDSS).

2. Current WFPC2, ACS/WFC (and soon WFC3) source lists are of variable quality.

3. The default is to show all objects in the catalog. This may include a large number of artifacts. You can request "NumImages > 0" or larger to filter out many of the artifacts.

4. The default is to use MagAuto source extractor values for magnitudes (in the ABMAG system) . You will need to request MagAper2 if you would like to use aperture magnitudes instead.

5. When you display HSC positions (obtained from a combination of images), they may not line up well on the specific image you are looking at.

Current Limitations

This is a Beta version of the HSC; you can expect some rough edges and a larger fraction of artifacts than will be present in the Version 1 release. In addition, the database may change without warning since we are working to make improvements on a variety of issues, including the following,

• About 1/3 of the ACS/WFC and WFPC2 images are not included in the catalog due to image quality and other issues.
• About 1/3 of the source lists in the HSC do not an have astrometric correction due to the lack of an overlapping image and other factors.
• About 1/2 the sources could not be crosssmatched with sources in other visits. Such single sources are included in the catalog.

We are interested in your feedback. If you have questions, or items to bring to our attention, please send them to: archive help.

Help

More detailed information can be found on the Frequently Asked Questions page. In addition, there are Training Exercises with step-by-step instructions here. You-Tube videos will be produced in the future.