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Eight E+A Galaxies Located Inside A Large-Scale Filament In The Coma Cluster

Presentation #341.05 in the session “Galaxy Quenching”.

Published onJan 11, 2021
Eight E+A Galaxies Located Inside A Large-Scale Filament In The Coma Cluster

E+A galaxies are post-starburst galaxies that have recently undergone complete quenching of their star formation, making them a valuable source for studying the evolution of galaxies and their environments. Bluer E+A galaxies tend to be younger, giving us a picture of how young galaxies transform into E+A galaxies. Using data from DR16 of the Sloan Digital Sky Survey (SDSS), we analyzed a color-selected sample of 1,520 galaxies within 3 degrees of the center of the Coma Cluster (SDSS J125950.40+280000.00) with spectra in the SDSS catalog. We identified 134 E+A galaxies and candidates using their optical spectra, based on their spectral shape, u-r color, lack of Hα emission, and hydrogen Balmer absorption. We manually measured the equivalent widths of the Balmer absorption lines using PyRAF and Python. Of these 134 E+A galaxies, we classified 13 as “blue” based on their color magnitudes and spectral appearance. Using 3-D mapping and Unity interactive visualization (virtual reality) techniques, We found that 8 of these blue E+A galaxies were located inside a large-scale filament, mapped by Malavasi et al. (2020, A&A 634, A30), emanating from the center of the Coma Cluster. The location of these blue E+A galaxies suggests that their unusual density continues along the filament, although our data do not reach that extent. Galaxies in dense environments can be stripped of their gas content by ram pressure, so these E+A galaxies could potentially have been formed in this way within this filament. Conversely, these E+A galaxies could have been formed through mergers because of the increased density of galaxies within the filament. This work was supported by the Alfred P. Sloan Foundation via the SDSS-IV Faculty and Student Team (FaST) initiative, ARC Agreement SSP483, and by NSF grants AST-1852355, 1852360, 1460939, and 1460860 to the American Museum of Natural History and CUNY College of Staten Island.


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