Large format imaging spectrograph for the Large Submillimeter Telescope (LST)

TL;DR

This paper proposes a large-format imaging spectrograph for the LST and AtLAST telescopes, enabling the detection of early galaxies and star formation in the universe's first billion years through advanced superconducting detector technology.

Contribution

It introduces a novel 3-band, medium-resolution imaging spectrograph with 1.5 million detectors based on the KATANA concept, tailored for high-redshift galaxy observations.

Findings

Design of a 3-band (200, 255, 350 GHz) spectrograph with R=2000

Capability to detect [O III] and [C II] emitters at z=8--9 and z>12

Projected survey to constrain early universe luminosity functions

Abstract

We present a conceptual study of a large format imaging spectrograph for the Large Submillimeter Telescope (LST) and the Atacama Large Aperture Submillimeter Telescope (AtLAST). Recent observations of high-redshift galaxies indicate the onset of earliest star formation just a few 100 million years after the Big Bang (i.e., z = 12--15), and LST/AtLAST will provide a unique pathway to uncover spectroscopically-identified first forming galaxies in the pre-reionization era, once it will be equipped with a large format imaging spectrograph. We propose a 3-band (200, 255, and 350 GHz), medium resolution (R = 2,000) imaging spectrograph with 1.5 M detectors in total based on the KATANA concept (Karatsu et al. 2019), which exploits technologies of the integrated superconducting spectrometer (ISS) and a large-format imaging array. A 1-deg2 drilling survey (3,500 hr) will capture a large number of [O III] 88 um (and [C II] 158 um) emitters at z = 8--9, and constrain [O III] luminosity functions at z > 12.