Updated 1430223003 Assigned ID: 2260 ----- Attempting Submission 1 (Fri Apr 09 21:10:48 GMT 2021) ----- HST Phase I Proposal 2260 successfully submitted. Receipt: # 2260-1 ----- Attempting Submission 2 (Fri Apr 09 23:28:53 GMT 2021) ----- We propose an archival program to identify, catalog, and characterize the striking dust extinction features visible in HST multi-band imaging of nearby galaxies. Recent studies of the Milky Way suggest that extended, coherent filaments of dense gas form the backbone of the cold interstellar medium in galaxies. Extinction mapping with HST offers almost the only way to achieve the < 10 pc resolution needed to identify dense filamentary structures in galaxies beyond the Local Group, and by eye inspection HST imaging suggests that such features are pervasive. To test this, we will combine HST's outstanding resolution and color information with advanced image-processing / machine learning techniques to identify coherent dust features and quantify the distribution of extinction across a sample of 38 nearby galaxies with public NUV-U-B-V-I imaging. Crucially, all of our targets also have public ALMA CO imaging, though at much lower resolution than achieved by HST. This will allow us to validate the extinction mapping as a tracer of molecular gas and compare the orientation and structure of dust features to the large scale morphology of the molecular gas. We also will directly compare our observed extinction features to synthetic observations from leading theoretical simulations. Lastly, in addition to providing cutting-edge data products to the community, our program will provide a strong test of whether this new view of the Milky Way's ISM is a general feature of galaxies or restricted to specific environments like spiral arms or stellar bars. Dr. David Thilker (PI, JHU) is an expert in multiwavelength observational characterization of star formation in nearby galaxies and radio imaging of neutral hydrogen (HI) in circumgalactic environments. He specializes in ultraviolet imaging from HST and GALEX, with emphasis on star formation occurring at low density. He is credited with the discovery of extended UV disks (XUV disks). Dr. Thilker has extensive experience with PSF fitting, and clump based photometry. Rupali Chandar is an expert at dealing with stellar population and star clusters in nearby star-forming galaxies, particularly using HST observations. Sinan Deger is a postdoctoral researcher specializing in star formation in both nearby and distant galaxies, analysis of morphological features on both the galactic and resolved stellar population level, and the applications of state of the art machine learning techniques in astronomy research. Simon Glover is a theorist who has extensive experience with numerical simulations of the cold ISM and with the production of synthetic observations. He will assist with the theoretical interpretation of the observations and with the comparison of observations with simulations. Ralf Klessen is full professor for theoretical astrophysics at Heidelberg University. His research interests focus on the formation of stars at present days and inthe early universe, on the dynamics of the interstellar medium, on astrophysical turbulence, and on the development of numerical methods for computational astrophysics. Eric Koch is an expert on filamentary structures in the neutral ISM using cm- and mm-interferometry, and is the author of the FilFinder algorithm. Diederik Kruijssen is an expert in the multi-wavelength and theoretical studies of star formation, stellar feedback, and star cluster formation and evolution. Janice Lee is an expert on star formation in nearby galaxies, and ground- and space-based observations of galaxies spanning from the UV to the IR. She is PI of the PHANGS-HST and PHANGS-JWST Treasury programs. Adam Leroy is an expert on dust molecular gas and dust in galaxies, and will contribute to the comparison with ALMA and scientific interpretation of results. Adam has experience with ISM feature identification via image segmentation and the combined use of dust and CO emission to trace molecular gas in the Milky Way, the Local Group, and nearby galaxies. Erik Rosolowsky specializes in using image processing methods to characterizing the structure in the interstellar medium and relate that structure to the regulation of star formation. He and his research group have developed the pyCPROPS algorithm for measuring molecular cloud properties, FilFinder for simple characterization of filamentary structures in two- and three-dimensions, and TurbuStat for measuring the properties of turbulence from images of the ISM. Eva Schinnerer's research experience covers the analysis of optical to radio observational data of nearby and distant star-forming galaxies. She is an expert in the analysis of molecular gas observations and large-scale dynamics. Brad Whitmore has extensive expertise working with HST data, age-dating and classifying star clusters, and making comparisons between manual and machine learning determinations. All members of the team will participate at varying degrees in the analysis and paper preparation. Galaxies Stellar Populations and the Interstellar Medium 0 Regular false false false false true SUPPORTED