A Submillimetre Survey of the Hubble Deep Field: Unveiling Dust-Enshrouded Star Formation in the Early Universe

TL;DR

This paper presents a deep submillimetre survey of the Hubble Deep Field revealing dust-enshrouded star formation in distant galaxies, significantly contributing to the cosmic sub-mm background and indicating high star-formation rates at redshifts 2-4.

Contribution

It provides the deepest sub-mm survey of the HDF, detecting multiple sources and resolving a large fraction of the sub-mm background, highlighting the importance of dust-obscured star formation in the early universe.

Findings

Detected 5 reliable sub-mm sources above 2 mJy.

Resolved 30-50% of the sub-mm background with these sources.

Star-formation density at redshifts 2-4 is at least five times higher than UV-based estimates.

Abstract

The advent of sensitive sub-mm array cameras now allows a proper census of dust-enshrouded massive star-formation in very distant galaxies, previously hidden activity to which even the deepest optical images are insensitive. We present the deepest sub-mm survey, taken with the SCUBA camera on the James Clerk Maxwell Telescope (JCMT) and centred on the Hubble Deep Field (HDF). The high source density on this image implies that the survey is confusion-limited below a flux density of 2 mJy. However within the central 80 arcsec radius independent analyses yield 5 reproducible sources with S(850um) > 2 mJy which simulations indicate can be ascribed to individual galaxies. These data lead to integral source counts which are completely inconsistent with a no evolution model, whilst the combined brightness of the 5 most secure sources in our map is sufficient to account for 30-50% of the previously unresolved sub-mm background, and statistically the entire background is resolved at about the 0.3 mJy level. Four of the five brightest sources appear to be associated with galaxies which lie in the redshift range 2 < z < 4. With the caveat that this is a small sample of sources detected in a small survey area, these submm data imply a star-formation density over this redshift range that is at least five times higher than that inferred from the rest-frame ultraviolet output of HDF galaxies.