We have used the Arecibo Telescope and the Green Bank Telescope to carry outa deep search for H{\sc i}~21\,cm emission from a large sample of Green Peagalaxies, yielding 19 detections, and 21 upper limits on the H{\sc i} mass. Weobtain H{\sc i} masses of $\rm M_{HI} \approx (4-300) \times 10^8 \, \rmM_\odot$ for the detections, with a median H{\sc i} mass of $\approx 2.6 \times10^9 \, \rm M_\odot$; for the non-detections, the median $3\sigma$ upper limiton the H{\sc i} mass is $\approx 5.5 \times 10^8 \, \rm M_\odot$. These are thefirst estimates of the atomic gas content of Green Pea galaxies. We find thatthe H{\sc i}-to-stellar mass ratio in Green Peas is consistent with trendsidentified in star-forming galaxies in the local Universe. However, the medianH{\sc i} depletion timescale in Green Peas is $\approx 0.6$~Gyr, an order ofmagnitude lower than that obtained in local star-forming galaxies. This impliesthat Green Peas consume their atomic gas on very short timescales. Asignificant fraction of the Green Peas of our sample lie $\gtrsim 0.6$~dex($2\sigma$) above the local $\rm M_{HI} - M_B$ relation, suggesting recent gasaccretion. Further, $\approx 30$\% of the Green Peas are more than $\pm2\sigma$ deviant from this relation, suggesting possible bimodality in theGreen Pea population. We obtain a low H{\sc i}~21\,cm detection rate in theGreen Peas with the highest O32~$\equiv$~[O{\sc iii}]$\lambda$5007/[O{\scii}]$\lambda$3727 luminosity ratios, O32~$> 10$, consistent with the highexpected Lyman-continuum leakage from these galaxies.

We report the discovery of large amounts of previously undetected coldneutral atomic hydrogen (\HI) around the core triplet galaxies in the nearbyNGC~7232 galaxy group with MeerKAT. With a physical resolution of $\sim$1 kpc,we detect a complex web of low surface brightness \HI\ emission down to a4$\sigma$ column density level of $\sim$1 $\times$ 10$^{19}$ cm$^{-2}$ (over 44\kms ). The newly discovered H\,{\sc i} streams extend over $\sim$20 arcmincorresponding to 140~kpc in projection. This is $\sim$3 times the \HI\ extentof the galaxy triplet (52 kpc). The \HI\ debris has an \HI\ mass of $\sim$6.6$\times 10^9$~M$_{\odot}$, more than 50\% of the total \HI\ mass of thetriplet. Within the galaxy triplet, NGC~7233 and NGC~7232 have lost asignificant amount of \HI\ while NGC~7232B appears to have an excess of \HI.The \HI\ deficiency in NGC~7232 and NGC~7233 indicates that galaxy-galaxyinteraction in the group concentrates on this galaxy pair while the other discgalaxies have visited them over time. In comparison to the AMIGA sample ofisolated galaxies we find that with regards to its total \HI\ mass theNGC~7232/3 galaxy triplet is not \HI\ deficient. Despite the many interactionsassociated to the triplet galaxies, no \HI\ seems to have been lost from thegroup (yet).

We present an ultra-violet study of two nearby dwarf irregular galaxies WLMand IC~2574, using the Far-UV and Near-UV data from the Ultra-Violet ImagingTelescope (UVIT). We used the F148W band Far-UV images and identified 180 and782 young star-forming clumps in WLM and IC~2574, respectively. The identifiedclumps have sizes between 7 - 30 pc in WLM and 26 - 150 pc in IC~2574. Wenoticed more prominent hierarchical splitting in the structure of star-formingregions at different flux levels in IC~2574 than WLM. We found that themajority of the clumps have elongated shapes in the sky plane with ellipticity($\epsilon$) greater than 0.6 in both the galaxies. The major axis of theidentified clumps is found to show no specific trend of orientation in IC~2574,whereas in WLM the majority are aligned along south-west to north-eastdirection. We estimated (F148W$-$N242W) colour for the clumps identified in WLMand noticed that the younger ones (with (F148W$-$N242W) $<-0.5$) are smaller insize ($<10$ pc) and are located mostly in the southern half of the galaxybetween galactocentric radii 0.4 - 0.8 kpc.

We present PHANGS-ALMA, the first survey to map CO J=2-1 line emission at ~1"~ 100pc spatial resolution from a representative sample of 90 nearby (d<~20Mpc) galaxies that lie on or near the z=0 "main sequence" of star-forminggalaxies. CO line emission traces the bulk distribution of molecular gas, whichis the cold, star-forming phase of the interstellar medium. At the resolutionachieved by PHANGS-ALMA, each beam reaches the size of a typical individualgiant molecular cloud (GMC), so that these data can be used to measure thedemographics, life-cycle, and physical state of molecular clouds across thepopulation of galaxies where the majority of stars form at z=0. This paperdescribes the scientific motivation and background for the survey, sampleselection, global properties of the targets, ALMA observations, andcharacteristics of the delivered ALMA data and derived data products. As theALMA sample serves as the parent sample for parallel surveys with VLT/MUSE,HST, AstroSat, VLA, and other facilities, we include a detailed discussion ofthe sample selection. We detail the estimation of galaxy mass, size, starformation rate, CO luminosity, and other properties, compare estimates usingdifferent systems and provide best-estimate integrated measurements for eachtarget. We also report the design and execution of the ALMA observations, whichcombine a Cycle~5 Large Program, a series of smaller programs, and archivalobservations. Finally, we present the first 1" resolution atlas of CO emissionfrom nearby galaxies and describe the properties and contents of the firstPHANGS-ALMA public data release.

The PHANGS program is building the first dataset to enable the multi-phase,multi-scale study of star formation across the nearby spiral galaxy population.This effort is enabled by large Treasury programs with ALMA, VLT/MUSE, and HST,with which we have obtained CO(2-1) imaging, optical spectroscopic mapping, andhigh resolution UV-optical imaging, respectively. Here, we present PHANGS-HST,which is obtaining five band NUV-U-B-V-I imaging of the disks of 38 spiralgalaxies at distances of 4-23 Mpc, and parallel V and I band imaging of theirhalos, to provide a census of tens of thousands of compact star clusters andassociations. The combination of HST, ALMA, and VLT/MUSE observations willyield an unprecedented joint catalog of the observed and physical properties of$\sim$100,000 star clusters, associations, HII regions, and molecular clouds.With these basic units of star formation, PHANGS will systematically chart theevolutionary cycling between gas and stars, across a diversity of galacticenvironments found in nearby galaxies. We discuss the design of the PHANGS-HSTsurvey, and provide an overview of the HST data processing pipeline and firstresults, highlighting new methods for selecting star cluster candidates,morphological classification of candidates with convolutional neural networks,and identification of stellar associations over a range of physical scales witha watershed algorithm. We describe the cross-observatory imaging, catalogs, andsoftware products to be released, which will seed a broad range of communityscience, in particular, upcoming JWST study of dust embedded star formation andISM physics.

The Milky Way disk consists of two prominent components - a thick,alpha-rich, low-metallicity component and a thin, metal-rich, low-alphacomponent. External galaxies have been shown to contain thin and thick diskcomponents, but whether distinct components in the [$\alpha$/Fe]-[Z/H] planeexist in other Milky Way-like galaxies is not yet known. We present VLT-MUSEobservations of UGC 10738, a nearby, edge-on Milky Way-like galaxy. Wedemonstrate through stellar population synthesis model fitting that UGC 10738contains alpha-rich and alpha-poor stellar populations with similar spatialdistributions to the same components in the Milky Way. We discuss how thefinding that external galaxies also contain chemically distinct disk componentsmay act as a significant constraint on the formation of the Milky Way's ownthin and thick disk.