Issue |
A&A
Volume 678, October 2023
|
|
---|---|---|
Article Number | L9 | |
Number of page(s) | 7 | |
Section | Letters to the Editor | |
DOI | https://doi.org/10.1051/0004-6361/202347233 | |
Published online | 20 October 2023 |
Letter to the Editor
The [CII] 158 μm emission line as a gas mass tracer in high redshift quiescent galaxies
1
Instituto de Astrofísica de Canarias, C. Vía Láctea, s/n, 38205 La Laguna, Tenerife, Spain
e-mail: cdeugenio@iac.es
2
Universidad de La Laguna, Dpto. Astrofísica, 38206 La Laguna, Tenerife, Spain
3
Université Paris-Saclay, Université Paris Cité, CEA, CNRS, AIM, 91191 Gif-sur-Yvette, France
4
Max Planck Institute for Astronomy, Königstuhl 17, 69117 Heidelberg, Germany
5
Instituto de Física, Pontificia Universidad Católica de Valparaíso, Casilla, 4059 Valparaíso, Chile
Received:
19
June
2023
Accepted:
15
September
2023
A great deal of effort has been made in recent years to probe the gas fraction evolution of massive quiescent galaxies (QGs); however, a clear picture has not yet been established. Recent spectroscopic confirmations at z > 3 offer the chance to measure the residual gas reservoirs of massive galaxies a few hundred Myr after their death and to study how fast quenching proceeds in a highly star-forming Universe. Even so, stringent constraints at z > 2 remain hardly accessible with the Atacama Large Millimeter/submillimeter Array (ALMA) when adopting molecular gas tracers commonly used for the quenched population. In this Letter we propose overcoming this impasse by using the carbon [CII] 158 μm emission line to systematically probe the gaseous budget of unlensed QGs at z > 2.8, when these galaxies could still host non-negligible star formation on an absolute scale and when the line becomes best observable with ALMA (Bands 8 and 7). Predominantly used for star-forming galaxies to date, this emission line is the best choice to probe the gas budget of spectroscopically confirmed QGs at z > 3, reaching 2–4 and 13–30 times deeper than dust continuum emission (ALMA band 7) and CO(2–1)/(1–0) (Very Large Array, VLA, K − Kα bands), respectively, at fixed integration time. Exploiting archival ALMA observations, we place conservative 3σ upper limits on the molecular gas fraction (fmol = MH2/M⋆) of ADF22-QG1 (fmol < 21%) and ZF-COS-20115 (fmol < 3.2%), two of the best-studied high-z QGs in the literature, and GS-9209 (fmol < 72%), the most distant massive QG discovered to date. The deep upper limit found for ZF-COS-20115 is three times lower than previously anticipated for high-z QGs suggesting, at best, the existence of a large scatter in the fmol distribution of the first QGs. Lastly, we discuss the current limitations of the method and propose ways to mitigate some of them by exploiting ALMA bands 9 and 10.
Key words: galaxies: evolution / galaxies: high-redshift / galaxies: elliptical and lenticular / cD / galaxies: ISM
© The Authors 2023
Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
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