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Neutral gas content in the ISM at the cosmic noon: a millimeter-based assessment

Hugo Messias
ALMA, Chile

In the last decade, thanks to millimeter-based observing facilities such as ALMA and NOEMA the community was able to measure the evolution of the molecular gas mass density (rho_H2). Between targeted observations and deep surveys, it is now clear that rho_H2 peaks between redshift 1 and 3. This is very much in line with the evolution observed for the star formation rate density. However, the same is not seen for the neutral Hydrogen (HI) mass density (rho_HI) which is observed to be constant throughout most cosmic time (as estimated via [sub-]Damped Lyman_alpha systems). Linking these two results has been a difficult task, partially related to the different scales probed by different techniques, but it is mostly due to the fact that detecting HI in the inter-stellar medium (ISM) of galaxies has mostly been limited to within the last 4.3Gyr of cosmic time. Here, we give a step toward solving this problem. We make use of the empirical relation between dust continuum and ISM gas mass proposed in Orellana et al. (2017) to extract the HI content in the ISM of galaxies. This statistical study puts together a large sample of mm-continuum- and CO-selected galaxies extracted from ALMA, VLA, and NOEMA surveys. Such sample already shows that, overall, the depletion times commonly quoted in the literature considering molecular gas alone in mm-selected galaxies are underestimated by a factor of almost two. Specifically focusing on the sample extracted from ASPECS, COLDz, and Birkin et al. (2021) we also show that this technique already recovers at least about a third of the HI cosmological content at redshifts between 2 and 3 (a fifth if one limits the sample to galaxies with Lum_IR greater than 1e11 Lsun). Also, the major difference in HI content is seen at the massive end when comparing the sample at redshifts between 2 and 3, and that between 1 and 2. This archival statistical study thus shows the impact of millimeter-based observing facilities in preparing the community to HI-survey machines such as SKA and ngVLA.

2023 July 13, 13:30

Observatório Astronómico de Lisboa (Seminar room)
Tapada da Ajuda, 1349-018 Lisboa

Faculdade de Ciências da Universidade de Lisboa Universidade do Porto Faculdade de Ciências e Tecnologia da Universidade de Coimbra
Fundação para a Ciência e a Tecnologia COMPETE 2020 PORTUGAL 2020 União Europeia