ALMA and the First Galaxies

TL;DR

ALMA will revolutionize the study of primordial galaxies by enabling the detection of numerous lower-luminosity sources, providing high-resolution observations, and clarifying star formation efficiency evolution at high redshifts.

Contribution

This paper highlights ALMA's capabilities in detecting and analyzing early galaxies, emphasizing its potential to overcome current observational biases and complement other telescopes.

Findings

ALMA will detect at least 100 times more sources than current instruments.

High spatial resolution will reduce confusion in observations.

ALMA will determine redshifts of obscured objects via CO lines.

Abstract

ALMA will become fully operational in a few years and open a new window on primordial galaxies. The mm and submm domain is privileged, since the peak of dust emission between 60 and 100 microns is redshifted there for z= 5-10, and the continuum benefits from a negative K-correction. At least 100 times more sources than with present instruments could be discovered, so that more normal galaxies, with lower luminosities than huge starbursts and quasars will be surveyed. The high spatial resolution will suppress the confusion, which plagues today single dish bolometer surveys. Several CO lines detected in broad-band receivers will determine the redshift of objects too obscured to be seen in the optical. With the present instrumentation, only the most massive and gas rich objects have been detected in CO at high z, most of them being ultra-luminous starbursts with an extremely high star formation efficiency. However, selection biases are omni-present in this domain, and ALMA will statistically clarify the evolution of star formation efficiency, being fully complementary to JWST and ELTs.