Three high-redshift millimeter sources and their radio and near-infrared identifications

TL;DR

This study reports millimeter detections of three faint high-redshift starburst galaxy candidates, combining radio and near-infrared data to estimate their redshifts and analyze their properties.

Contribution

First millimeter interferometric detection of a high-redshift candidate with multi-wavelength identification, expanding understanding of faint starburst galaxies at z>2.

Findings

One source unresolved at 2.5'' resolution with IRAM

Two sources with fluxes ~4 mJy and radio counterparts

Majority of faint mm/sub-mm sources likely at redshift z>2

Abstract

We present millimeter wavelength detections of three faint sources that are most likely high-redshift starburst galaxies. For one of the sources, which was previously discovered with SCUBA at 850 mu m, we present a detection with the IRAM interferometer at 240 GHz (1.25 mm) that shows the object unresolved at an angular resolution of 2.''5, and coincident within 1'' with a radio source and a galaxy detected in the near-infrared. The two other sources were discovered in a deep 250 GHz (1.2 mm) survey with the Max-Planck Millimeter Bolometer (MAMBO) array at the IRAM 30m telescope. Both have fluxes of ~4 mJy and radio counterparts with a 1.4 GHz flux density of ~75 muJy. Their radio-to-mm flux ratios suggest redshifts larger than 2. Both sources are faint in the optical and near-infrared, one showing a 20.5 mag K-band counterpart. From our data and that available in the literature, we estimate the redshift distribution of twenty-two faint mm and sub-mm sources and conclude that the majority of them are likely to be at z>2.