Hubble Source Catalog Search Help
This page describes how to use the Hubble Source Catalog Search form
and describes the individual fields in that form.
Use this form to search the Hubble Source Catalog
by object name, position, and Detection level.
Other fields can also be searched using the "user-specified field" options.
The Hubble Source Catalog contains information about sources detected
in many of the WFPC2 and ACS images. The sources are detections based
on combined images that are each for a particular filter, detector,
and visit (Hubble Space Telescope (HST) pointing).
Please visit our Use Cases for step by step instructions.
Please visit our FAQ page for additional information.
- Detection Options
- For target searches (i.e., cone searches) only,
one may specify 3 different detection options:
- Level 0 returns source detections only (no nondetections).
- Level 1 returns source detections and color dropouts (nondetections).
Color dropouts are inferred from the HLA source list processing
that takes place in two steps. First, within each visit and for
each detector, Source Extractor is run on a white light detection
image, a filter-combined drizzled image for the detector and visit.
The software identifies each source and its position. Second, the
combined drizzled image for each filter used in the detection image
is searched for a source at each position indicated by the detection
image. If a source is detected, then its properties are entered into
the HLA source list. We infer a color dropout from the absence of a
source detection in a filter at the source position covered by the
detection image. We then obtain certain properties of the nondetection,
including the image name, exposure time, filter. The source position
of the dropout is taken as the detection image source position.
Certain properties such as fluxes and
magnitudes are not determined and are left blank on the search
form (represented in the database as null).
- Level 2 returns source detections, color dropouts,
and white light nondetections. We infer white light image nondetections
by searching for images with source lists that cover
the position search being made, but are not included in any results
based on a Level 1 search.
These nondetections have image information, but have blank (null)
source positions, fluxes, and magnitudes. Through this scheme, we
provide complete information on a position search
that includes for each filter all detected sources, color dropouts,
and white light nondetections for all HLA ACS/WFC and WFPC2 source lists.
Therefore, every image with a source list that could cover a position
search is reported on,
independent of whether the image has sources within the search range.
- Match ID
- Integer ID. Catalog entries with the same value of MatchID match together.