We present the Virgo Environment Traced in CO (VERTICO) survey, a new effort to map 12 CO (2-1), 13 CO (2-1), and C 18 O (2-1) in 51 Virgo Cluster galaxies with the Atacama Compact Array, part of the Atacama Large Millimeter/submillimeter Array. The primary motivation of VERTICO is to understand the physical mechanisms that perturb molecular gas disks, and therefore star formation and galaxy evolution, in dense environments. This first paper contains an overview of VERTICOʼs design and sample selection, 12 CO (2-1) observations, and data reduction procedures. We characterize global 12 CO (2-1) fluxes and molecular gas masses for the 49 detected VERTICO galaxies, provide upper limits for the two nondetections, and produce resolved 12 CO (2-1) data products (median resolution = 8″ ≈ 640 pc). Azimuthally averaged 12 CO (2-1) radial intensity profiles are presented along with derived molecular gas radii. We demonstrate the scientific power of VERTICO by comparing the molecular gas size-mass scaling relation for our galaxies with a control sample of field galaxies, highlighting the strong effect that radius definition has on this correlation. We discuss the drivers of the form and scatter in the size-mass relation and highlight areas for future work. VERTICO is an ideal resource for studying the fate of molecular gas in cluster galaxies and the physics of environment-driven processes that perturb the star formation cycle. Upon public release, the survey will provide a homogeneous legacy data set for studying galaxy evolution in our closest cluster.

We present the calibration between the dust continuum luminosity and interstellar gas content obtained from the Valparaíso ALMA Line Emission Survey (VALES) sample of 67 main-sequence star-forming galaxies at 0.02 < z < 0.35. We use CO(1-0) observations from the Atacama Large Millimetre/submillimetre Array (ALMA) to trace the molecular gas mass, M H 2 , and estimate the rest-frame monochromatic luminosity at 850 µm, L ν 850 , by extrapolating the dust continuum from MAGPHYS modelling of the far-ultraviolet to submillimetre spectral energy distribution sampled by the Galaxy And Mass Assembly (GAMA) survey. Adopting α CO = 6.5 (K km s −1 pc 2 ) −1 , the average ratio of L ν 850 /M H 2 = (6.4±1.4)×10 19 erg s −1 Hz −1 M −1 , in excellent agreement with literature values. We obtain a linear fit of log 10 M H 2 /M = (0.92 ± 0.02) log 10 (L ν 850 /erg s −1 Hz −1 ) − (17.31 ± 0.59). We provide relations between L ν 850 , M H 2 and M ISM when combining the VALES and literature samples, and adopting a Galactic α CO value.

We present an extragalactic survey using observations from the Atacama Large Millimeter/submillimeter Array (ALMA) to characterise galaxy populations up to z = 0.35: the Valparaíso ALMA Line Emission Survey (VALES). We use ALMA Band-3 CO(1-0) observations to study the molecular gas content in a sample of 67 dusty normal star-forming galaxies selected from the Herschel Astrophysical Terahertz Large Area Survey (H-ATLAS). We have spectrally detected 49 galaxies at > 5σ significance and 12 others are seen at low significance in stacked spectra. CO luminosities are in the range of (0.03 − 1.31) × 10 10 K km s −1 pc 2 , equivalent to log(M gas /M ) = 8.9 − 10.9 assuming an α CO = 4.6 (K km s −1 pc 2 ) −1 , which perfectly complements the parameter space previously explored with local and high-z normal galaxies. We compute the optical to CO size ratio for 21 galaxies resolved by ALMA at ∼ 3. 5 resolution (6.5 kpc), finding that the molecular gas is on average ∼ 0.6 times more compact than the stellar component. We obtain a global Schmidt-Kennicutt relation, givenWe find a significant fraction of galaxies lying at 'intermediate efficiencies' between a long-standing mode of star-formation activity and a starburst, specially at L IR = 10 11−12 L . Combining our observations with data taken from the literature, we propose that star formation efficiencies can be parameterised by

In this VERTICO early science paper we explore in detail how environmental mechanisms, identified in H i, affect the resolved properties of molecular gas reservoirs in cluster galaxies. The molecular gas is probed using ALMA ACA (+TP) observations of 12CO(2–1) in 51 spiral galaxies in the Virgo cluster (of which 49 are detected), all of which are included in the VIVA H i survey. The sample spans a stellar mass range of 9 ≤ log M ⋆ / M ⊙ ≤ 11 . We study molecular gas radial profiles, isodensity radii, and surface densities as a function of galaxy H i deficiency and morphology. There is a weak correlation between global H i and H2 deficiencies, and resolved properties of molecular gas correlate with H i deficiency: galaxies that have large H i deficiencies have relatively steep and truncated molecular gas radial profiles, which is due to the removal of low-surface-density molecular gas on the outskirts. Therefore, while the environmental mechanisms observed in H i also affect molecular gas reservoirs, there is only a moderate reduction of the total amount of molecular gas.

We measure the star formation rate (SFR) per unit gas mass and the star formation efficiency (SFEgas for total gas, SFEmol for the molecular gas) in 81 nearby galaxies selected from the EDGE-CALIFA survey, using 12CO (J = 1–0) and optical IFU data. For this analysis we stack CO spectra coherently by using the velocities of Hα detections to detect fainter CO emission out to galactocentric radii r gal ∼ 1.2r 25 (∼3R e) and include the effects of metallicity and high surface densities in the CO-to-H2 conversion. We determine the scale lengths for the molecular and stellar components, finding a close to 1:1 relation between them. This result indicates that CO emission and star formation activity are closely related. We examine the radial dependence of SFEgas on physical parameters such as galactocentric radius, stellar surface density Σ⋆, dynamical equilibrium pressure P DE, orbital timescale τ orb, and the Toomre Q stability parameter (including star and gas Q star+gas). We observe a generally smooth, continuous exponential decline in the SFEgas with r gal. The SFEgas dependence on most of the physical quantities appears to be well described by a power law. Our results also show a flattening in the SFEgas–τ orb relation at log [ τ orb ] ∼ 7.9 – 8.1 and a morphological dependence of the SFEgas per orbital time, which may reflect star formation quenching due to the presence of a bulge component. We do not find a clear correlation between SFEgas and Q star+gas.