A3^{3}COSMOS: Dissecting the gas content of star-forming galaxies across the main sequence at 1.2 ≤z\leq z < 1.6

We aim to understand the physical mechanisms that drive star formation in a sample of mass-complete (>10$^{9.5}M_{\odot}$) star-forming galaxies (SFGs) at 1.2 $\leq z$ < 1.6. We selected SFGs from the COSMOS2020 catalog and applied a $uv$-domain stacking analysis to their archival Atacama Large Millimeter/submillimeter Array (ALMA) data. Our stacking analysis provides precise measurements of the mean molecular gas mass and size of SFGs. We also applied an image-domain stacking analysis on their \textit{HST} $i$-band and UltraVISTA $J$- and $K_{\rm s}$-band images. Correcting these rest-frame optical sizes using the $R_{\rm half-stellar-light}$-to-$R_{\rm half-stellar-mass}$ conversion at rest 5,000 angstrom, we obtain the stellar mass size of MS galaxies. Across the MS (-0.2 < $\Delta$MS < 0.2), the mean molecular gas fraction of SFGs increases by a factor of $\sim$1.4, while their mean molecular gas depletion time decreases by a factor of $\sim$1.8. The scatter of the MS could thus be caused by variations in both the star formation efficiency and molecular gas fraction of SFGs. The majority of the SFGs lying on the MS have $R_{\rm FIR}$ $\approx$ $R_{\rm stellar}$. Their central regions are subject to large dust attenuation. Starbursts (SBs, $\Delta$MS>0.7) have a mean molecular gas fraction $\sim$2.1 times larger and mean molecular gas depletion time $\sim$3.3 times shorter than MS galaxies. Additionally, they have more compact star-forming regions ($\sim$2.5~kpc for MS galaxies vs. $\sim$1.4~kpc for SBs) and systematically disturbed rest-frame optical morphologies, which is consistent with their association with major-mergers. SBs and MS galaxies follow the same relation between their molecular gas mass and star formation rate surface densities with a slope of $\sim1.1-1.2$, that is, the so-called KS relation.Comment: 20 pages, 17 figure

A3^{3}COSMOS: A census on the molecular gas mass and extent of main-sequence galaxies across cosmic time

To constrain for the first time the mean mass and extent of the molecular gas of a mass-complete sample of $>10^{10}$M$_{\odot}$ main-sequence (MS) galaxies at $0.4<z<3.6$. We apply an innovative $uv$-based stacking analysis to a large set of archival Atacama Large Millimeter/submillimeter Array (ALMA) observations. This stacking analysis provides measurements of the mean mass and extent of the molecular gas of galaxy populations. The molecular gas mass of MS galaxies evolves with redshift and stellar mass. At all stellar masses, the molecular gas fraction decreases by a factor of 24 from $z\sim3.2$ to $z\sim0$. At a given redshift, the molecular gas fraction of MS galaxies decreases with stellar mass, at roughly the same rate as their specific star formation rate decreases. The molecular gas depletion time of MS galaxies remains roughly constant at $z>0.5$ with a value of 300--500 Myr, but increases by a factor of 3 from $z\sim0.5$ to $z\sim0$. This evolution of the molecular gas depletion time of MS galaxies can be predicted from the evolution of their molecular gas surface density and a seemingly universal MS-only $\Sigma_{M_{\rm mol}}-\Sigma_{\rm SFR}$ relation with an inferred slope of 1.13, i.e., the so-called KS relation. The far-infrared size of MS galaxies shows no significant evolution with redshift or stellar mass, with a mean circularized half-light radius of 2.2 kpc. Finally, our mean molecular gas masses are lower than previous estimates, likely caused by the fact that literature studies were biased towards individually-detected MS galaxies with massive gas reservoirs. To first order, the molecular gas content of MS galaxies regulates their star formation across cosmic time, while variation of their star formation efficiency plays a secondary role. Despite a large evolution of their gas content and SFRs, MS galaxies evolved along a seemingly universal MS-only KS relation.Comment: 27 pages, 19 figure

CCAT-prime Collaboration: Science Goals and Forecasts with Prime-Cam on the Fred Young Submillimeter Telescope

We present a detailed overview of the science goals and predictions for the Prime-Cam direct-detection camera-spectrometer being constructed by the CCAT-prime collaboration for dedicated use on the Fred Young Submillimeter Telescope (FYST). The FYST is a wide-field, 6 m aperture submillimeter telescope being built (first light in late 2023) by an international consortium of institutions led by Cornell University and sited at more than 5600 m on Cerro Chajnantor in northern Chile. Prime-Cam is one of two instruments planned for FYST and will provide unprecedented spectroscopic and broadband measurement capabilities to address important astrophysical questions ranging from Big Bang cosmology through reionization and the formation of the first galaxies to star formation within our own Milky Way. Prime-Cam on the FYST will have a mapping speed that is over 10 times greater than existing and near-term facilities for high-redshift science and broadband polarimetric imaging at frequencies above 300 GHz. We describe details of the science program enabled by this system and our preliminary survey strategies