This is a description of an older version of the Hubble Source Catalog.
The current version is preferred for most purposes.

Version 2.1 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 source lists in the Hubble Legacy Archive (HLA) into a single master catalog.

Version 2.1 was released on January 25, 2017 and includes relatively minor additions which should not affect most users. The additions are:

1.Tables have been made available via HSC CASJOBS providing MEDIAN rather than MEAN values for magnitudes from the summary form (i.e., SumMagAper2Med for magaper2 values and SumMagAutoMed for magauto values).


2.A table has been made available via HSC CASJOBS providing cross-matching between Version 1 - Version 2 sources (i.e., xMatchV1).


3.Spectroscopic matches for COS, FOS, and GHRS observations have been added for Version 2 sources that do not have Version 1 counterparts.

Version 2 includes:

• Four additional years of ACS source lists (i.e., through June 9, 2015). All ACS source lists go deeper than in version 1. See current HLA holdings for details.
• One additional year of WFC3 source lists (i.e., through June 9, 2015).
• Cross-matching between HSC sources and spectroscopic COS, FOS, and GHRS observations.
• Availability of magauto values through the MAST Discovery Portal. The maximum number of sources displayed has increased from 10,000 to 50,000.

The HSC v2 contains members of the WFPC2, ACS/WFC, WFC3/UVIS and WFC3/IR Source Extractor source lists from HLA version DR9.1 (data release 9.1). 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. The relative astrometry is supported by using Pan-STARRS, SDSS, and 2MASS as the astrometric backbone for initial corrections. In addition, the catalog includes source nondetections. The crossmatching algorithms and the properties of the initial (Beta 0.1) catalog are described in Budavari & Lubow (2012).

Interfaces

There are currently three ways to access the HSC as described below. We are working towards having these interfaces consolidated into one primary interface, the MAST Discovery Portal.

• The MAST Discovery Portal provides a one-stop web access to a wide variety of astronomical data. To access the Hubble Source Catalog v2 through this interface, select Hubble Source Catalog v2 in the Select Collection dropdown, enter your search target, click search and you are on your way. Please try Use Case Using the Discovery Portal to Query the HSC
• The HSC CasJobs interface permits you to run large and complex queries, phrased in the Structured Query Language (SQL).
• HSC Home Page
  - 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).

Five things you should know about the HSC

1.Detailed Use Cases and Videos are available to you.

2. Coverage can be very non-uniform (unlike surveys such as SDSS).

3. Current WFPC2, ACS/WFC and WFC3 source lists are of variable quality.

4. The default is to show all HSC objects. This may include a large number of artifacts. You can request Numimages > 1 (or more) to filter out many artifacts.

5. The default is to use mag_aper2 Source Extractor values for magnitudes (in the ABMAG system) . You will need to request mag_auto if desired.

Current Limitations

• About 5% of the ACS/WFC, WFPC2, and WFC3 images are not included in the catalog due to image quality and other issues.
• About 25% of the source lists (white-light images) in the HSC do not have an astrometric correction due to the lack of an overlapping image and other factors.
• About 30% of the sources could not be crosssmatched with sources in other visits. Such single sources are included in the catalog.

Help and Acknowledgment

More detailed information can be found on the Frequently Asked Questions page. Several Use Cases are available to give you step by step instructions. There is also a video available.

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

HSC Data Use Policy:

The HSC is based on data from the Hubble Legacy Archive (HLA). Refereed publications making use of the HSC should therefore include this footnote in the acknowledgements.

Authors are also asked to acknowledge the "Hubble Source Catalog" in the text of the paper, and consider a reference to the Whitmore et al.(2016) paper describing the HSC.