Submillimetre-wavelength detection of dusty star-forming galaxies at high redshift

Abstract

The global star formation rate in high redshift galaxies, based on optical surveys, shows a strong peak at a redshift of z ∼ 1.5, which implies that we have already seen most of the formation. High redshift galaxies may, however, emit most of their energy at submillimeter wavelengths if they contain substantial amounts of dust. The dust would absorb the starlight and reradiate it as far-infrared light, which would be redshifted to the submillimeter range. Here we report a deep survey of two blank regions of sky performed at submillimeter wavelengths (450 and 850µm). If the sources we detect in the 850µm band are powered by star formation, then each must be converting more than 100 solar masses of gas per year into stars, which is larger than the maximum star formation rates inferred for most optically-selected galaxies. The total amount of high redshift star formation is essentially fixed by the level of background light, but where the peak occurs in redshift for the submillimeter is not yet established. However, the background light contribution from only the sources detected at 850µm is already comparable to that from the optically-selected sources. Establishing the main epoch of star formation will therefore require a combination of optical and submillimeter studies.In recent years high redshift optical galaxy searches have become increasingly successful at uncovering significant populations of galaxies that are likely to be in early phases of evolution. However, the global star formation rate (SFR) inferred 1, 3, 4 omits the many fainter sources that are now being detected. 5,6 Furthermore, the effects of dust can cause the SFRs in the detected UV-bright objects to be grossly underestimated (see, e.g., ref. 7), and many rapid star forming galaxies may even be omitted from the optical samples.Nearby star forming galaxies emit a large fraction of their bolometric luminosity in the far infrared waveband, which for distant sources is redshifted into the submillimeter waveband. Because the spectra of these star forming galaxies are very steep, if they are at large redshifts their flux density decreases much less rapidly with increasing redshift

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.…”

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.…”