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This is a description of the current version of the Hubble Source
You may still access
HSC version 2 and the
documentation for HSC version 1.
Version 3.1 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)
single master catalog.
2019 September 24:
The Hubble Catalog of Variables (HCV),
a major new High-Level Science Product derived from the HSC, was released.
The HCV is the first homogeneous catalog of variable sources found in the HSC.
It includes variable stars in our Galaxy and nearby galaxies, as
well as transients and variable active galactic nuclei. The HCV
contains 84,428 candidate variable sources (out of 3.7 million HSC
sources that were searched for variability) with V <= 27 mag; for
11,115 of them the variability is detected in more than one filter.
The number of data points in a light curve range from 5 to 120, and the
time baseline ranges from under a day to over 15 years.
The released data includes both variable objects and objects identified as
The HCV was created from HSCv3 in a 4 year ESA-funded project at the National Observatory of
Athens (PI: Alceste Bonanos). It is available for download via the
HLSP page and is also fully integrated with the
MAST user interfaces for the HSC, including the
HSC CasJobs and
VO TAP database query interfaces and the
MAST catalogs simple form interface and query API.
There are Python Jupyter notebooks available that show how to access the
data in scripts. The ESAC Science Data Centre
has created the HCV Explorer, a new online web tool to access, visualize, and
interactively explore the HCV.
Note that the HCV includes improved magnitudes with local corrections for objects that were searched
for variability (those with at least 5 epochs available in some HST filter), so this data may also be useful
for projects that are not primarily focused on variability.
See the HCV journal paper (Bonanos et al., 2019, A&A, 630, A92)
for more details on the project.
2019 August 15:
A new search interface for the HSC was
released as part of the MAST catalogs access tools. This interface allows
searching multiple tables and releases of the HSC in a single web form.
Searches can optionally be filtered by catalog parameters (such as magnitudes
and available filters). An API can be used for scripted queries of the catalogs,
and Python Jupyter notebooks show some examples
demonstrating the use of the API for simple and complex queries.
2019 June 26:
HSC version 3.1 was released. It
adds to the current HSC version 3.0
by providing proper motions of over 400,000 objects in the augmented Sagittarius Window Eclipsing Extrasolar Planet Search (SWEEPS) HST field.
This field is within a few degrees of the Galactic center, and most of the stars belong to the Galactic bulge.
The field has been observed by ACS and WFC3 with a time baseline as long as 12 years.
The proper motion information is available in the form of database tables within the HSCv3 context of the STScI CasJobs interface.
The data can be readily queried by means of SQL through that interface. In addition, we provide a
Python Jupyter notebook
that runs on Python 3.6.
The notebook provides statistical information about the photometry and proper motions and includes some science use cases.
More details are found here.
2018 July 5:
HSC version 3 was released. It includes
many improvements in the photometry and astrometry along with a significant increase in the
number of objects and measurements.
Highlights from Version 3
25% more ACS/WFC images and more than twice as many
WFC3 images compared with the HSC v2 release. ACS and WFC3 data that were public as of 2017 October 1 are included.
See notes on the HLA DR10 data release and on the
current HLA holdings for details.
Improved photometric quality in the source lists due both to the alignment algorithm used to match exposures and filters in the HLA
image processing and to improved algorithms for Source Extractor photometry (particularly near the edges of images).
The scatter in magnitudes is measured using the median absolute deviation (MAD) of the differences
from the median magnitude. This is more robust and less sensitive to outliers than the RMS used in
Cross-matching between HSC sources and spectroscopic COS, STIS, FOS, and GHRS observations.
Properties of the HSC
The HSC v3 contains members of the
WFPC2, ACS/WFC, WFC3/UVIS and WFC3/IR
source lists from HLA version DR10 (data release 10). The cross-matching 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 cross-matched sources are significantly
reduced, with median errors less than 8 mas.
The absolute astrometry is calibrated using Gaia DR1, Pan-STARRS, SDSS, and 2MASS as the astrometric backbone for initial corrections.
In addition, the catalog includes source nondetections. The cross-matching algorithms and the properties of the initial (Beta 0.1) catalog are described in
Budavari & Lubow (2012),
and the Version 1 catalog is described in Whitmore et al. (2016).
There are currently four ways to access the HSC as described below.
The MAST catalogs interface provides a simple but powerful
search interface for the HSC and other catalogs (including Pan-STARRS). It includes a user interface for
searches at a sky position with optional filtering by catalog parameters and customization of the columns.
It also incorporates an API for scripted queries of the catalogs.
The new HSC search interface has a single web form
that allows searching different tables chosen from either the v3 or v2 releases of the HSC catalog.
This single page replaces four different web forms from the older HSC search interface.
Select the HSC Summary Table to display 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. Median values for
magnitudes, positions, and other relevant parameters are provided.
Select the HSC Detailed Table to display 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).
2. Sky coverage can be very non-uniform (unlike surveys such as SDSS) due to the highly variable HST observing patterns.
3. Current WFPC2, ACS/WFC and WFC3 source lists are of
variable quality. In particular, the WFPC2 source lists are of poorer quality than the ACS and WFC3 source lists.
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 can request mag_auto if desired.
About 30% of the ACS/WFC, WFC3, and WFPC2 images are not included in the catalog due to image quality and other issues
(e.g., moving targets, grism observations, cosmic ray contamination, etc.)
About 6% of the source lists (white-light images) in the HSC do not have an astrometric correction
from either an external catalog (e.g. Gaia) or from overlapping HST images. (Note this is much improved from the
About 19% of the sources could not be cross-matched with sources in other visits.
Such single sources are nonetheless 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.
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:
Based on observations made with the NASA/ESA Hubble Space Telescope, and obtained from the Hubble Legacy Archive, which is a collaboration between the Space Telescope Science Institute (STScI/NASA), the Space Telescope European Coordinating Facility (ST-ECF/ESAC/ESA) and the Canadian Astronomy Data Centre (CADC/NRC/CSA).
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.