0 Assigned ID: 1713 ----- Attempting Submission 1 (Fri Mar 01 20:04:01 GMT 2013) ----- HST Phase I Proposal 1713 (hstcy21spiral_APT.apt) successfully submitted. ----- Attempting Submission 2 (Sat Mar 02 00:24:52 GMT 2013) ----- With the superb imaging capability of HST, we can see the detailed features of the current state of star formation and evolution in nearby galaxies, where their stars and star clusters are often resolved into individual stars. For galaxies at higher redshift (0.5<z<1.5), the best we can do is to study their integrated flux by spectroscopy or the SED fitting technique. With sub-arcsecond HST imaging, the broad-band SEDs of intermediate redshift galaxies can be fit on a pixel-by-pixel (pSED) basis. Due to the difference in the physical spatial resolution in images of galaxies at low and intermediate redshifts, blending of stellar populations makes the interpretation of the pSED analysis difficult, and these effects need to be studied in further detail. Therefore, we propose to assess the resolution limit of the pSED fitting technique for intermediate redshift galaxies, and study the effects of stellar population mixing. We will compare properties (e.g., stellar mass, age, star-formation rate, metallicity) of the resolved stellar populations in nearby galaxies (<12 Mpc) to those of unresolved stellar populations in galaxies at intermediate redshift (0.5<z<1.5). With a carefully selected sample of galaxies at low and intermediate redshifts, we will 1) Perform a resolved stellar population study on six nearby galaxies from the Archive. 2) Apply the pSED method to artificially redshifted versions of these galaxies. 3) Quantify the size-scale where the pSED technique breaks down by relating the results of (1) and (2) 4) Use this result to better interpret the pSED fits on a sample of >100 intermediate redshift galaxies from CANDELS-GOODS Archival data. RESOLVED STELLAR POPULATIONS Default Medium false true false false false SUPPORTED