Deep Submillimeter Surveys: Luminous Infrared Galaxies at High Redshift

Deep surveys at 850μm from Mauna Kea using the SCUBA camera on the JCMT appear to have discovered a substantial population of ultraluminous infrared galaxies (ULIGs: Lir > 10 L⊙) 3 at high redshift (z ∼ 1−4). The cumulative space density of these sources (∼ 10 deg with S850 > 1mJy) is sufficient to account for nearly all of the extragalactic background light at submillimeter wavelengths. Current estimates of the redshift distribution suggest a peak in the comoving space density of SCUBA sources at z = 1 − 3, similar to what is observed for QSOs and radio galaxies. The luminosity density in the far-infrared/submillimeter exceeds that in the UV by factors of 3–10 over this redshift range, implying that as much as 80–90% of the “activity” in galaxies at z ∼ < 4 is hidden by dust. The SCUBA sources plausibly represent the primary epoch in the formation of spheroids and massive black holes triggered by major mergers of gas-rich disks.