KPNO IRIM Observations of the Hubble Deep Field

During the course of ten nights of observing (UT 27 April - 6 May 1996), the KPNO Mayall 4m Telescope was used to image the Hubble Deep Field in the near infrared. The IRIM camera employs a 256 x 256 Rockwell NICMOS-3 HgCdTe array, with a scale of approximately 0".6/pixel at the 4m f/15 Cassegrain focus. This provides a field of view approximately 2.5 arcmin on a side, well matched to that of the WFPC2.

Uncannily, the weather remained clear throughout the run. A small amount of time was lost one night due to telescope closure for smoke from the forest fires happening elsewhere in Arizona. Some cirrus was present during the first three nights, but thereafter conditions were largely photometric. Warm weather resulted in an unfortunately bright K-band background.

Altogether, 22.9 hours of data were collected in the K-band, along with 11.0 hours at J and 11.3 hours at H. Net image quality in the combined images produced on-line at the telescope is 1.0 arcsec FWHM. Formal 5-sigma limiting magnitudes for the HDF/IRIM images, computed from the measured sky noise within a 2 arcsecond diameter circular aperture, are 23.45 at J, 22.29 at H, and 21.92 at K.

In addition, about half the flanking field area was covered with 24 minute K-band exposures. Fields to the east and north of the central HDF were observed.

Some pictures:

Version 1 data release

The Version 1 release of the HDF/IRIM images is now available here. This release consists of the summed J, H and K images, geometrically transformed into registration with the mosaiced HDF/WFPC2 data. Exposure maps are also provided which indicate how much exposure time went into each pixel of the infrared images.

In addition, newly produced HDF WFPC2 mosaics are now available. These are fits images produced by drizzling the HDF version 2 reductions onto a very large (4096x4096) pixel grid. The KPNO IRIM images have been geometrically transformed into registration with this mosaic grid, and then rebinned (with appropriate pixel weighting) back down to a more manageable 1024x1024 format. For convenience, we also provide a link here to rebinned (1024x1024) versions of the HDF WFPC2 mosaic.

At present, the flanking field images have not yet been reduced.

Version 2 data release

Sometime in the future, we will be releasing an improved rereduction of the HDF/IRIM data. We anticipate that the version 2 release will have somewhat improved image quality. We are taking particular care to remove the geometric distortion of the IRIM camera at an early stage in the reduction process, to more accurately register the individual exposures, and to screen out some intervals of poorer seeing. We also anticipate an improved photometric calibration of the data. More details about Version 2 will be available here as the reduction progresses.

Catalogs and Publications

Photometric catalogs of the HDF/IRIM images will be made available at this URL soon. A paper on the HDF/IRIM data (observations, reductions, catalogs and basic analysis) is in preparation, titled "Near Infrared Properties of the Hubble Deep Field" by Dickinson et al. In addition, several papers analyzing various aspects of this data set are in preparation. Results from these projects which may be of general interest may be posted here at this URL in the future.

Using this data

We encourage general use of these IR images by the research community, and welcome any comments, questions, or suggestions about the data; please contact the PI (

All use of this data should reference the basic data paper which is currently in preparation: "Near Infrared Properties of the Hubble Deep Field" by Dickinson et al. 1997 (in preparation). Further details about this paper will be posted here in the near future.

In addition, publications making use of this data should include a footnote to the title citing the use of KPNO data. This footnote should read:

Based on observations made at the Kitt Peak National Observatory, National Optical Astronomy Observatories, which is operated by the Association of Universities for Research in Astronomy, Inc. (AURA) under cooperative agreement with the National Science Foundation.


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Copyright © 1997 The Association of Universities for Research in Astronomy, Inc. All Rights Reserved.

Mark Dickinson: 10/24/96