Dust and metals in galaxies at Cosmic Noon
Abstract
At the peak epoch of cosmic star formation activity, z ∼ 2, the obscured star-formation rate (SFR) density of our Universe traced by infrared light is ∼ 4 to 8 times higher than the unobscured SFR density traced by the UV luminosity. This observation demonstrates that dust is ubiquitous in the interstellar medium (ISM) of high-redshift galaxies and must play a key role in galaxy physics. However, studying dust at high redshifts has been challenging due to limits in instrumentation, and our current knowledge is primarily restricted to exceptionally massive and luminous objects. Although there are measurements of dust and gas at low redshifts, the differences in the ISM conditions in high-redshift galaxies compared to those in the local universe, such as higher gas fractions and SFR surface densities, underscore the importance of studying the properties of ISM dust at high redshifts. A key galaxy property closely tied to the build-up of dust in galaxies is metallicity. For example, the relation between the dust-to-gas ratio of galaxies and their metallicity provides key constraints for the physics and timescales governing the buildup and destruction of dust in galaxies. Unfortunately, samples of galaxies at z~2 for which metalliciy and dust-continuum information is available are limited.
To remedy this, we used ALMA to observe the 870 micron emission of 27 redshift two main-sequence galaxies for which metallicity information is available from the MOSFIRE Deep Evolution Field survey (MOSDEF), with metallicities ranging from 0.5 solar to solar. After introducing the current theoretical picture of dust in galaxies at cosmic noon I will present the results of this effort. I will specifically focus on how the shape of the dust-continuum spectral energy distribution (SED) of galaxies at z~2 changes as a function of various galaxy properties, what this implies for the properties of the dust in these galaxies, and draw conclusions on the relative amount of obscured star-formation in main-sequence galaxies as a function of their metallicity. I will then present the dust masses we can infer from the z~2 galaxies, how they compare to their stellar masses and the relation we obtain between the dust-to-gas ratio of galaxies and their metalliciy. These results will all be placed in the context of redshift zero observations to constrain the evolution of the dust properties of galaxies and in the context of theoretical model predictions. I will finish by discussing what future observations and technology will be necessary to push the study of dust and dust-obscured star-formation in sub-solar metallicity galaxies at cosmic noon forward.