Is there a redshift cutoff for submillimetre galaxies?

TL;DR

This study investigates the redshift distribution of submillimetre galaxies, finding no cutoff in the 1.1 mm selected sample but a decline at higher redshifts in 850 μm samples, indicating different evolutionary behaviors.

Contribution

It provides new photometric redshifts for 1.1 mm sources and compares their evolution with 850 μm sources, revealing distinct redshift distributions and sub-population evolution.

Findings

High-redshift 1.1 mm sources are more common than in 850 μm surveys.

No evidence for a redshift cutoff in the 1.1 mm sample.

Existence of two sub-populations with different luminosity evolution.

Abstract

We present new optical and infrared photometry for a statistically complete sample of seven 1.1 mm selected sources with accurate Submillimetre Array coordinates. We determine photometric redshifts for four of the seven sources of 4.47, 4.50, 1.49 and 0.64. Of the other three sources two are undetected at optical wavelengths down to the limits of very deep Subaru and Canada-France-Hawaii Telescope images ($\sim$27 mag AB, i band) and the photometry of the remaining source is corrupted by a bright nearby galaxy. The sources with the highest redshifts are at higher redshifts than all but one of the $\sim$200 sources taken from the largest recent 850 $\mu$m surveys, which may indicate that 1.1 mm surveys are more efficient at finding sources at very high redshifts than 850 $\mu$m surveys. We investigate the evolution of the number density with redshift of our sample using a banded $V_{e}/V_{a}$ analysis and find no evidence for a redshift cutoff, although the number of sources is very small. We also perform the same analysis on a statistically complete sample of 38 galaxies selected at 850$\mu$m from the GOODS-N field and find evidence for a drop-off in the number density beyond $z\sim1$ and 2 for hot and cold dust dominated SMGs respectively, confirming the earlier conclusion of Wall, Pope & Scott. We also find strong evidence for the existence of two differently evolving sub-populations separated in luminosity, with a higher relative density of the high luminosity galaxies at higher redshifts.