Extragalactic stellar photometry and the blending problem

CARLOS FEINSTEIN; GUSTAVO BAUME; MARIA JIMENA RODRIGUEZ; MARCELA VERGNE

Maryland

Congreso; The 28th annual international Astronomical Data Analysis Software & Systems; 2018

The images provided by the Advanced Camera for Surveys at the HubbleSpace Telescope (ACS/HST) have the amazing spacial resolution of 0".05/pixel. Therefore, it is possible to resolve individual stars in nearby galaxies and, in particular, youngblue stars in associations and open clusters of the recent starburst. These data are useful for studies of the extragalactic young population using color magnitude diagrams(CMD) of the stellar groups. However, even with the excellent indicated spatial resolution, the blending of several stars in crowded fields can change the shape of the CMDs.Some of the blendings could be handled in the cases they produce particular featureson the stellar PSF profile (e.g. abnormal sharpness, roundness, etc). But in some cases,the blend could be difficult to detect, this is the case, were a pair or several stars are inthe same line of sight (e.g. observed in the same pixel). In this work, we investigatedthe importance of the blending effect in several crowded regions, using both numericalsimulations and real ACS/HST data. In particular, we evaluated the influence of thiseffect over the CMDs, luminosity functions (LFs) and reddening estimations obtainedfrom the observations.