STScI logoThe Hubble Deep Field South

Project Description


In December, 1995 the Hubble Space Telescope pointed at an undistinguished high-galactic latitude patch of sky in the northern hemisphere, and observed for 10 straight days. The result was the deepest optical image of the sky yet obtained: The Hubble Deep Field (HDF) (henceforth referred to as the Hubble Deep Field North, or HDF-N). The images allow detection of sources as faint as V = 30 in four bandpasses spanning the near-UV to the near-IR (Williams et al. 1996). The data were released to the community within one month of the observations and have been used in a wide variety of projects and publications, ranging from studies of the star-formation rate as a function of redshift, to studies of faint M dwarfs in the Galactic halo.

A second Hubble Deep Field campaign was carried out between late September and October of 1998. The raw, pipeline calibrated and reprocessed data were released to the community on November 23, 1998. The rationale for undertaking a second deep field campaign followed from the wealth of information that has come out of HDF-N, and from the desire to provide a point of focus for similar studies of the distant universe from southern-hemisphere facilities. The wide public access to the HDF-N data stimulated extensive followup observations across the electromagnetic spectrum, both from major ground-based observatories and from other satellites. A similar level of effort is anticipated for HDF-S. We are maintaining a `clearinghouse' for supporting and follow-up observations of the HDF-S.

Test observations of the HDF-S field were obtained in October, 1997. The primary purpose of the test was to ensure that the guide stars to be used for the full campaign were acceptable, but an initial reconnaissance of the field was also carried out.

The HDF-S campaign differs from the HDF-N campaign in several important areas:

The actual observations of the HDF-S were similar in spirit to the original HDF. As was the case for HDF-N, approximately 150 consecutive orbits were devoted to a single telescope pointing. Additional flanking field observations were made surrounding the deep STIS, WFPC2 and NICMOS fields.

HDF-S Field Layout

Layout Main Fields

The figure shows the position of the HDF-S overlayed on a deep ground-based image. The image is a 3000s R-band exposure from the CTIO 4m telescope (courtesy of Alistair Walker). North is up and East is left. The WFPC2 region is to the West, the STIS region is to the East and NICMOS region is to the South. The STIS field is centered on the quasar at z ~ 2.24.

Note that the figure is for illustrative purposes only. The overlaid positions of the STIS and WFPC2 fields is accurate only to a few arcsec. The overlaid positions of the NICMOS fields are accurate only at the ~ 10 arcsec level. Use the calibrated J2000 coordinates of the HDF-S) when higher accuracy overlays are required.

Click on the image to get a larger scale view of the field.

HDFS Flanking Fields Layout

Layout Flanking Fields

As with the HDF-N, some time during the HDF-S campaign was devoted to obtaining WFPC2 single-band images of a larger, contiguous area around the primary imaging field (the "flanking fields"), to a typical depth of I_AB ~ 25.5. The current plan is to observe a region about 7 arcmin in diameter, defined so as to include both the STIS and the NICMOS primary target regions. The goals of the wide-area imaging are to provide a large contiguous area for angular correlation studies, especially interesting near the QSO; to yield better statistics for less numerous, brighter galaxies; and to provide optical morphologies for galaxies in the larger fields typical of ground-based multi-object spectrographs.

The figure shows the tentative HDF-S flanking field arrangement as laid out several months before the campaign, overlaid on an image extracted from the Digitized Sky Survey. Note that the figure is for illustrative purposes only. The arrangement used for the actual campaign may have been slightly different, due to late changes in the observing strategy. Consult the actual Observing logs or the header information of the data files for more detailed information.

The red field is the main HDF-S WFPC2 field. The green fields are flanking fields for the WFPC2 with the F814W filter. The blue fields are the STIS CCD fields associated with the flanking fields, and the yellow are flanking-fields for the NIC3 parallels with the F160W filter. The main NIC3 field was observed for 9 orbits with the STIS CCD (no filter). The right-most WFPC2 flanking field is the parallel frame associated with that exposure.

Click on the image to get an overlay of the same flanking field arrangement on the deeper R-band ground-based CTIO image.

Observing strategy

Discussions about the observing strategy for the HDF-S focussed primarily on the questions:

A detailed but outdated discussion of the observing strategy for each of the individual instruments is available:

These discussions describe various general issues, as well as the planned observing strategy as of July 1998. The strategy used for the actual campaign was somewhat different, due to late changes in the observing strategy. Consult the actual Observing logs or the header information of the data files for more accurate and up-to-date information on the observing strategy.

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This page was last updated on November 23, 1998.
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