Hubble Deep Fields

Abstract

The Hubble space telescope observations of the northern Hubble deep field, and more recently its counterpart in the south, provide detections and photometry for stars and field galaxies to the faintest levels currently achievable, reaching magnitudes V ∼ 30. Since 1995, the northern Hubble deep field has been the focus of deep surveys at nearly all wavelengths. These observations have revealed many properties of high redshift galaxies, and have contributed to important data on the stellar mass function in the Galactic halo. Part 1: Observations, Measurements, and PhenomenologyThe HDFs were carefully selected to be free of bright stars, radio sources, nearby galaxies, etc., and to have low Galactic extinction. The HDF-S selection criteria included finding a quasi-stellar object (QSO) that would be suitable for studies of absorption lines along the line of sight. Field selection was limited to the "continuous viewing zone" around δ = ±62 • , because these declinations allow HST to observe, at suitable orbit phases, without interference by earth -3occultations. Apart from these criteria, the HDFs are typical high-galactic-latitude fields; the statistics of field galaxies or faint Galactic stars should be free from a priori biases. The HDF-N observations were taken in December 1995 and the HDF-S in October 1998. Both were reduced and released for study within 6 weeks of the observations. Many groups followed suit and made data from follow-up observations publicly available through the world wide web.Details of the HST observations are set out in Williams et al. (1996), for HDF-N and in a series of papers for the southern field (Williams et al. 2000;Ferguson et al. 2000;Gardner et al. 2000;Casertano et al. 2000;Fruchter et al. 2000;Lucas et al. 2000). The HDF-N observations primarily used the WFPC2 camera, whereas the southern observations also took parallel observations with the new instruments installed in 1997: the near-infrared camera and multi-object spectrograph (NICMOS) and the space telescope imaging spectrograph (STIS). The area of sky covered by the observations is small: 5.3 arcmin 2 in the case of WFPC2 and 0.7 arcmin 2 in the case of STIS and NICMOS for HDF-S. The WFPC2 field subtends about 4.6 Mpc at z ∼ 3 (comoving, for Ω M , Ω Λ , Ω tot = 0.3, 0.7, 1.0). This angular size is small relative to scales relevant for large-scale structure.The WFPC2 observing strategy was driven partly by the desire to identify high-redshift galaxies via the Lyman-break technique , and partly by considerations involving scattered light within HST (Williams et al. 1996). The images were taken in four very broad bandpasses (F300W, F450W, F606W, and F814W), spanning wavelengths from 2500 to 9000Å. Although filter bandpasses and zeropoints are well calibrated, 2 no standard photometric system has emerged for the HDF. In this review, we use the notation U 300 , B 450 , V 606 and I 814 to denote magnitudes in the HST passbands on the AB system (Oke 1974). On this system m(AB) = −2.5 log f ν (nJy) + 31.4. Where we drop the subscrip...

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