Kinematics, structure and environment of three dwarf spheroidal galaxies

Abstract

AbstractWe explore the environmental status of three low surface brightness dwarf spheroidal galaxies (dSphs) KKH65, KK180 and KK227 using the results of our long slit spectroscopic observations at the 6m telescope of the Russian Academy of Sciences and surface photometry on the Sloan Digital Sky Survey (SDSS) images. The objects were selected by Karachentseva in 2010 as presumably isolated galaxies. The obtained surface brightness profiles demonstrate that our sample dSphs are less centrally concentrated than the objects of the same morphological type in the Virgo cluster (VC). Using the derived kinematic data we searched for possible neighbours of the dSphs within the projected distances from them Rproj > 500 kpc and with the differences in radial velocities |Δ V| > 500 kms−1. We applied the group finding algorithm by Makarov and Karachentsev to the selected sample. Our analysis shows that the dwarf galaxies of our study are not isolated. KKH65 and KK227 belong to the groups NGC3414 and NGC5371, respectively. KK180 is in the VC infall region. We conclude that it is not possible at the moment to justify the existence of isolated dSphs outside the Local Volume. The searches are complicated due to the lack of the accurate distances to the galaxies farther than 10 Mpc.