0 Assigned ID: 4620 ----- Attempting Submission 1 (Wed May 24 20:41:09 GMT 2023) ----- We will produce an HST/SDSS Atlas and Morphological Catalog of 7000 SDSS galaxies serendipitously imaged by HST and study a subset of 2000 galaxies at z<0.3 to elucidate the morphological transformation associated with star formation quenching. SDSS in conjunction with GALEX has revealed the different stages of galaxy evolution from star-forming to transitional to quenched. However, limits in resolution and depth prevent a full accounting of features like bars, rings, faint arms and merger signatures, leading to an overly simplified picture of late- to early-type transition as one from spiral-arm dominated disks to pure spheroids. An incomplete census of galaxy substructure as well as the imprecision in structural parameter estimation from ground-based images directly affects our understanding of quenching. To address these limitations while taking full advantage of SDSS's statistical power and the wealth of ancillary data, we will perform a large-scale optical study of HST/SDSS galaxies spanning the full range of activity from star-forming to quenched. We will lift the veil from ostensibly featureless galaxies, robustly quantify and qualify internal structure using various morphology software tools, and map the morphological transition from late- to early-type at resolutions 10x better than available from the ground. Combining HST-based morphologies with SDSS ancillary data, the relative importance of different quenching mechanisms will be constrained. The HST/SDSS Atlas & Morphological Catalog will also provide legacy value for a wide variety of studies that would benefit from the combination of the SDSS's statistical power and the HST's resolving power and sensitivity. The PI, Samir Salim, is an assistant professor in the Department of Astronomy at Indiana University. As part of the GALEX Science Team he has contributed to the early characterization of the main sequence of star formation and the green valley (Salim et al. 2007). He has used HST/ACS-SBC far-UV imaging of the green valley early-type galaxies to show that the UV emission is indeed from star formation, rather than the UV upturn or a UV excess from an AGN (Salim & Rich 2010, Salim et al. 2012). With C. Charlot, G. Kauffmann and J. Brinchmann he helped pioneer Bayesian SED (Spectral Energy Distribution) fitting (Salim et al. 2005) which is the basis for the largest catalog of SED fitting parameters of low-z galaxies (GALEX-SDSS-WISE Legacy Catalog; Salim et al. 2016). Recently, he and his collaborators have contributed to the understanding of the diversity and physical underpinning of the dust attenuation in galaxies (Salim, Lee & Boquien 2018; Salim & Narayanan 2020, ARA&A). In addition to the aforementioned HST program (HST-GO-11158), he was involved in an HST program to obtain high-resolution imaging of nearby Lyman Break Galaxy analogs. The Co-I, Chandler Osborne, is a 5th year (at time of submission) PhD student at Indiana University working under Dr. Samir Salim (PI). Chandler has extensive experience in galaxy morphology, image processing, and modelling galaxy properties. He has recently authored a paper which focused on the connection between star formation and morphology for both low (z = 0) and high-redshift (z = 0.8-2.5) galaxies (Osborne et al. 2020). As part of this paper, he made use of imaging data from SDSS, GALEX, and HST (CANDELS) alongside many ancillary catalogs. Using the GALEX and SDSS images, Chandler performed visual morphological classification for all (~500) of the local galaxies in their sample. Beyond this, he is currently leading the effort to analyze the discrepancies in UV-optical and IR star-formation rates among galaxies from the HST/CANDELS survey in Osborne et al. (in prep). Galaxies 0 Regular false false false false false false SUPPORTED