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Report

Teaser, summary, work performed and final results

Periodic Reporting for period 1 - Cosmic_Gas (Mapping the Cosmic Gas Supply with ALMA)

Teaser

Summary

The molecular gas phase is the material in galaxies out of which stars form. As such, it is the quantity that controls the star formation rate of a galaxy, thereby the overall stellar mass build-up, and ultimately galaxy evolution through cosmic times. In contrast to studies of the stellar mass and star formation, characterizing this fuel supply in galaxies as a function of cosmic epoch is still in its infancy. The ALMA facility now redefines our ability to map out the cosmic cold gas supply. This ERC program is based on extensive observational ALMA programs led by the PI: ASPECS is the first-ever approved ALMA large (150h) program, aimed at providing a comprehensive view of the baryon cycle from gas to stars over cosmic time. ASPECS provides 3D molecular scans in two ALMA bands of the Hubble Ultra Deep Field -- the iconic cosmological deep field. A second focus is the detailed characterization of the gas content at z>6 in host galaxies of the most distant quasars. This will assess the role of cold gas in the build-up of the first (t_Universe<1 Gyr) massive cosmic structures in the Universe. This project capitalizes on the unparalleled capabilities of ALMA and other facilities (e.g. VLT/MUSE) to map out the cosmic gas supply through cosmic history, and will provide crucial insights to define observational strategies for JWST. The final goal of this program is to define the global state-of-the-art in cosmological galaxy evolution through high-redshift ISM studies.

Work performed

Much of the focus in this reporting period was on the analysis of the ALMA data of the Large Program ASPECS, as well an ALMA survey of distant quasars, as originally envisioned. A key to this success was the instalment of a new server / storage system that is critical to deal with the large amount of data that is being analysed as part of this ERC program. ASPECS is the first extragalactic large ALMA program ever approved, and has already resulted in key results. In this large international collaboration led by the PI, a number of papers have already been submitted to the peer-reviewed â€˜The Astrophysical Journalâ€™ and additional papers are currently in preparation. A first ASPECS workshop / team meeting was held at the PIâ€™s host institution end of March 2019, in which important strategies for the future exploitation of the ALMA data have been discussed. Regarding the quasars, a number of papers have recently been submitted, focusing on the gas properties of the most distant quasars known (using ALMA and MUSE). There are an additional 3 quasar papers planned for submission later this year. Overall the project is well on track and group (and affiliated) members travelled significantly to strengthen the ties between the PIâ€™s group and international efforts. One unforeseen issue that is beyond the control of the PI is the delayed launch (by 2 years) of the JWST space mission. This has significant impact on the PIâ€™s research plans (in particular in the latter years of the program).

Final results

In the next steps the program will focus on the full characterisation of the ALMA Large Program ASPECS, and to define the next steps beyond this large initiative. A Ringberg team meeting is planned towards the end of 2019 to discuss these questions in detail. The ALMA and NOEMA facilities will be used further to investigate the environment of newly found quasars at z~7.5 -- pushing the quasar redshift barrier to the extreme. Eventually, JWST will provide observing capabilities beyond what is possible currently to characterise some of the earliest cosmic structures known. A breakthrough result would be the first detection of the stellar components of the first quasar host galaxies using JWST