Master Thesis defense by David Blanquez-Serse (DTU Space)

Title: Tracing the Interstellar Medium of Quiescent Galaxies across Cosmic Time with ALMA


Gas plays a paramount role in the galactic life cycle and is one of the main drivers of galaxy evolution. While gas mass reservoirs (Mgas) of star forming galaxies (SFGs) are routinely measured out to the highest redshifts, this is a very challenging feat for high redshift quiescent galaxies (QG). The limited existing attempts so far yield contradictory or inconclusive results regarding the gas fraction (fgas = Mgas/Mstas) of these systems and its evolution with time primarily due to technical limitations or biased sample selections. To address this issue in this project we attempt to measure the fgas for representative samples of massive (Mstar > 1010 Mo), 1<z<3 QGs. Our samples are selected in the GOODS-South field taking advantage of the existing ZFOURGE UV to mid-IR multi-wavelength catalogues and are complemented by the new GOODS-S ALMA 1.1mm map that covers 72.42 arcmin^2 of the field.  By selecting QGs based on their UVJ colours or their distance to the main sequence (MS) we measure the rest frame dust emission (or upper the corresponding upper limits) in the the R-J tail of the populations through ALMA stacking and infer their fgas using a range of techniques. We find that galaxies residing in the envelop below the MS (1/5 < deltaMS <1/2) have an average fgas that range from 67.54 +/- to 14.84% to 30.86 +/- 5.75 %  while UVJ selected QGs have fgas < 18.85 % The inferred estimates, comply with previously estimated fgas and support the current understanding that quiescent galaxies have lower gas fractions than main sequence galaxies at their correspondent redshifts while at the same time suggesting higher fgas in high-z QGs compared to those in the local universe. A more sophisticated stacking approach in the UV-plane this time is the next step forward aiming to boost the stacked signal and fully characterise the fgas of high-z QGs and get a better insight into the quenching mechanisms in the early universe. 

Georgios Magdis, DTU SPACE/Niels Bohr Institute, DAWN

Johan Peter Uldall Fynbo, Niels Bohr Insitute, DAWN