We study the dust content of galaxies from z = 0 to z = 9 in semi-analytic models of galaxy formation that include new recipes to track the production and destruction of dust. We include condensation of dust in stellar ejecta, the growth of dust in the interstellar medium (ISM), the destruction of dust by supernovae and in the hot halo, and dusty winds and inflows. The rate of dust growth in the ISM depends on the metallicity and density of molecular clouds. Our fiducial model reproduces the relation between dust mass and stellar mass from z = 0 to z = 7, the number density of galaxies with dust masses less than 10 8.3 M , and the cosmic density of dust at z = 0. The model accounts for the double power-law trend between dust-togas (DTG) ratio and gas-phase metallicity of local galaxies and the relation between DTG ratio and stellar mass. The dominant mode of dust formation is dust growth in the ISM, except for galaxies with M * < 10 7 M , where condensation of dust in supernova ejecta dominates. The dust-to-metal ratio of galaxies depends on the gasphase metallicity, unlike what is typically assumed in cosmological simulations. Model variants including higher condensation efficiencies, a fixed timescale for dust growth in the ISM, or no growth at all reproduce some of the observed constraints, but fail to simultaneously reproduce the shape of dust scaling relations and the dust mass of high-redshift galaxies.

We use the results from the ALMA large program ASPECS, the spectroscopic survey in the Hubble Ultra Deep Field (HUDF), to constrain CO luminosity functions of galaxies and the resulting redshift evolution of ρ(H 2 ). The broad frequency range covered enables us to identify CO emission lines of different rotational transitions in the HUDF at z > 1. We find strong evidence that the CO luminosity function evolves with redshift, with the knee of the CO luminosity function decreasing in luminosity by an order of magnitude from ∼2 to the local universe. Based on Schechter fits, we estimate that

We study the evolution of atomic and molecular gas in galaxies in semi-analytic models of galaxy formation that include new modeling of the partitioning of cold gas in galactic discs into atomic, molecular, and ionised phases. We adopt two scenarios for the formation of molecules: one pressure-based and one metallicity-based. We find that both recipes successfully reproduce the gas fractions and gas-to-stellar mass ratios of Hi and H 2 in local galaxies, as well as the Hi and H 2 disc sizes up to z 2. We reach good agreement with the locally observed Hi and H 2 mass function, although both recipes slightly overpredict the low-mass end of the Hi mass function. Both of our models predict that the high-mass end of the Hi mass function remains nearly constant at redshifts z < 2.0. The metallicity-based recipe yields a higher cosmic density of cold gas and much lower cosmic H 2 fraction over the entire redshift range probed than the pressure based recipe. These strong differences in Hi mass function and cosmic density between the two recipes are driven by low mass galaxies (log (M * /M ⊙ ) 7) residing in low mass halos (log (M vir /M ⊙ ) 10). Both recipes predict that galaxy gas fractions remain high from z ∼ 6 − 3 and drop rapidly at lower redshift. The galaxy H 2 fractions show a similar trend, but drop even more rapidly. We provide predictions for the CO J = 1 − 0 luminosity of galaxies, which will be directly comparable with observations with sub-mm and radio instruments.

We present ALMA Band 9 observations of the [C II]158µ m emission for a sample of 10 main-sequence galaxies at redshift z∼2, with typical stellar masses (log M /M ∼10.0-10.9) and star formation rates (∼35-115 M yr −1 ). Given the strong and well understood evolution of the interstellar medium from the present to z = 2, we investigate the behaviour of the [C II] emission and empirically identify its primary driver. We detect [C II] from six galaxies (four secure, two tentative) and estimate ensemble averages including non detections. The [C II]-to-infrared luminosity ratio (L [C II] /L IR ) of our sample is similar to that of local main-sequence galaxies (∼ 2 × 10 −3 ), and ∼ 10 times higher than that of starbursts. The [C II] emission has an average spatial extent of 4 -7 kpc, consistent with the optical size. Complementing our sample with literature data, we find that the [C II] luminosity correlates with galaxies' molecular gas mass, with a mean absolute deviation of 0.2 dex and without evident systematics: the [C II]-to-H 2 conversion factor (α [C II] ∼ 30 M /L ) is largely independent of galaxies' depletion time, metallicity, and redshift. [C II] seems therefore a convenient tracer to estimate galaxies' molecular gas content regardless of their starburst or main-sequence nature, and extending to metal-poor galaxies at low-and high-redshifts. The dearth of [C II] emission reported for z > 6-7 galaxies might suggest either a high star formation efficiency or a small fraction of UV light from star formation reprocessed by dust.

We present new measurements of the cosmic cold molecular gas evolution out to redshift 6 based on systematic mining of the ALMA public archive in the COSMOS deep field (A 3 COSMOS). Our A 3 COSMOS dataset contains ∼ 700 galaxies (0.3 z 6) with high-confidence ALMA detections in the (sub-)millimeter continuum and multi-wavelength spectral energy distributions (SEDs). Multiple gas mass calibration methods are compared and biases in band conversions (from observed ALMA wavelength to rest-frame Rayleigh-Jeans(RJ)-tail continuum) have been tested. Combining our A 3 COSMOS sample with ∼ 1, 000 CO-observed galaxies at 0 z 4 (75% at z < 0.1), we parameterize galaxies' molecular gas depletion time (τ depl ) and molecular gas to stellar mass ratio (µ molgas ) each as a function of the stellar mass (M ), offset from the star-forming main sequence (∆MS) and cosmic age (or redshift). Our proposed functional form provides a statistically better fit to current data (than functional forms in the literature), and implies a "downsizing" effect (i.e., more-massive galaxies evolve earlier than less-massive ones) and "mass-quenching" (gas consumption slows down with cosmic time for massive galaxies but speeds up for low-mass ones). Adopting galaxy stellar mass functions and applying our µ molgas function for gas mass calculation, we for the first time infer the cosmic cold molecular gas density evolution out to redshift 6 and find agreement with CO blind surveys as well as semi-analytic modeling. These together provide a coherent picture of cold molecular gas, SFR and stellar mass evolution in galaxies across cosmic time.