A Deep Submillimeter Survey of Lensing Clusters: A New Window on Galaxy Formation and Evolution

Abstract

We present the first results of a sub-millimeter survey of distant clusters using the new Sub-mm Common-User Bolometer Array (SCUBA) on the James Clerk Maxwell Telescope. We have mapped fields in two massive, concentrated clusters, A370 at z = 0.37 and Cl 2244−02 at z = 0.33, at wavelengths of 450 and 850 µm. The resulting continuum maps cover a total area of about 10 arcmin 2 to 1σ noise levels less than 14 and 2 mJy beam −1 at the two wavelengths, 2-3 orders of magnitude deeper than was previously possible. We have concentrated on lensing clusters to exploit the amplification of all background sources by the cluster, improving the sensitivity by a factor of 1.3-2 as compared with a blank-field survey. A cumulative source surface density of (2.4 ± 1.0) × 10 3 degree −2 is found to a 50% completeness limit of ∼ 4 mJy at 850 µm. The sub-mm spectral properties of these sources indicate that the majority lie at high redshift, z > 1. Without correcting for lens amplification, our observations limit the blank-field counts at this depth. The surface density is 3 orders of magnitude greater than the expectation of a non-evolving model using the local IRAS 60 µm luminosity function. The observed source counts thus require a substantial increase in the number density of strongly star-forming galaxies in the high-redshift Universe and suggest that optical surveys may have substantial underestimated the star formation density in the distant Universe. Deeper sub-mm surveys with SCUBA should detect large numbers of star-forming galaxies at high redshift, and so provide strong constraints on the formation of normal galaxies.

Dusty star-forming galaxies at high redshift

“…Smail et al, 1997;Hughes et al, 1998;Barger et al, 1998), although their properties were hard to study due to the large beamsize of Scuba's observations (∼15 at 850µm; at cosmological redshifts, roughly 120 kpc) and the difficulty in identifying multi-wavelength counterparts. However, at the time it was already thought that these submillimeter sources would be predominantly located at high-redshift.…”

“…The first few submillimeter deep-field maps which were published (e.g. Smail et al, 1997;Barger et al, 1998;Hughes et al, 1998) detected several galaxies at 850µm within several square arcminutes. A Figure 5: A schematic spectral energy distribution for a dusty star forming galaxy at z = 2.…”

“…While the early submm surveys were limited to smaller sky areas, the advent of wide-field surveys, especially with Herschel and SPT, at sub/millimeter wavelengths have allowed detections of large samples of lensed DSFGs that can be followed up with a host of radio and submm/mm-wave interferometers. Similarly, and pre-dating the large area survey work, important targets of lensed DSFGs have come from submm/mm-wave imaging of known massive lensing galaxy clusters Smail et al (1997).…”

The nature of the [C ii] emission in dusty star-forming galaxies from the SPT survey

“…Smail et al 1997;Hughes et al 1998;Barger et al 1998) fundamentally changed our view of galaxy formation and evolution. DSFGs are massive (M * ∼ 10 11 M ; e.g.…”

ISO deep far-infrared survey in the “Lockman Hole”

“…The sub-millimeter common-user bolometer array (SCUBA) on the 15 m James Clerk Maxwell Telescope (JCMT) is now able to resolve a substantial fraction of the CIB at 0.85 mm into luminous IR galaxies most of which appear to lie at high redshift, z > 1 (Smail et al 1997;Hughes et al 1998;Barger et al 1998;Scott et al 2002;Sato et al 2002). In the midand far-infrared, various surveys have been conducted with the European Space Agency (ESA) Infrared Space Telescope (ISO: Kessler 1996), which was in operation between 1995 and 1998.…”