From fuel to fireworks: the MeerKAT view of converting gas to stars across cosmic time

• Applicant: Professor Dr. Joseph Mohr, since 10/2022
• Subject Area: Astrophysics and Astronomy
• Term: since 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 500825193

A key ingredient missing from the multi-wavelength census of galaxy evolution is the neutral hydrogen (HI) gas, which is the reservoir of fuel from which stars form. The availability of this fuel underlies the diversity of galaxies we observe, but observations have until now been restricted to the local Universe due to the intrinsic faintness of the signal. The research proposed here will add the HI to the observational census, providing a crucial missing piece of the puzzle that will lead to revolutionary new insights into how galaxies fuel their star formation and build their stellar mass over cosmic time. The proposed work is based on data from the Large Survey Project MIGHTEE, undertaken with the SKA precursor radio telescope MeerKAT. We will use the transformational HI data to probe the gas content of galaxies to unprecedented depths spanning unexplored cosmic time.A primary objective of this proposal is to investigate how HI is consumed and converted into stellar mass, by parameterising the Kennicutt-Schmidt scaling relation. Current HI-based work focuses on the nearby Universe, but due to the sensitivity and resolution of MeerKAT, we can extend the relation over the past billion years of cosmic time. The results will serve as vital input for cosmological simulations, which rely on this relation for the conversion of gas into stars.Our work also includes the HI-poor galaxy population. Galaxies have a bimodal colour distribution, with blue galaxies being HI-rich and star forming, while red galaxies have exhausted their gas reservoir and are passively evolving. Underlying this bimodality is the availability of HI, but the mechanisms for transitioning from blue to red are not well understood. With the superior sensitivity of the MeerKAT data, we can probe galaxies with moderate HI content. Only by observing the full galaxy ensemble, and by including their HI properties, can we understand the bimodal population and the associated transition mechanisms.As the new data encompass a large cosmic volume, we are sensitive to the rare, most gas-rich galaxies. We expect to detect several of these massive galaxies at distancesthat have remained unprobed by HI observations. At the other end of the mass scale, with the exceptional sensitivity, new discovery space to the smallest galaxies is opened. We will search for the elusive 'dark' galaxies, predicted by simulations to be HI-rich. Discovery of such objects will strongly influence cosmological simulations. Searching for these rare objects at low masses and high redshifts requires robust and reliable source finding, another key goal of this proposal.With data from the world-class MeerKAT facility already in hand, we are in an excellent position to advance our understanding of the fuel for star formation beyond the local Universe for the first time.

• DFG Programme: Research Grants
• Ehemalige Antragstellerin: Dr. Natasha Maddox, until 9/2022