SEARCHING FOR DIFFUSE LIGHT IN THE M96 GALAXY GROUP

摘要

We present deep, wide-field imaging of the M96 galaxy group (also known as the Leo I Group). Down to surface brightness limits of μ B = 30.1 and μ V = 29.5, we find no diffuse, large-scale optical counterpart to the "Leo Ring," an extended H I ring surrounding the central elliptical M105 (NGC?3379). However, we do find a number of extremely low surface brightness (μ B 29) small-scale streamlike features, possibly tidal in origin, two of which may be associated with the Ring. In addition, we present detailed surface photometry of each of the group's most massive members—M105, NGC?3384, M96 (NGC?3368), and M95 (NGC?3351)—out to large radius and low surface brightness, where we search for signatures of interaction and accretion events. We find that the outer isophotes of both M105 and M95 appear almost completely undisturbed, in contrast to NGC?3384 which shows a system of diffuse shells indicative of a recent minor merger. We also find photometric evidence that M96 is accreting gas from the H I ring, in agreement with H I data. In general, however, interaction signatures in the M96 Group are extremely subtle for a group environment, and provide some tension with interaction scenarios for the formation of the Leo H I Ring. The lack of a significant component of diffuse intragroup starlight in the M96 Group is consistent with its status as a loose galaxy group in which encounters are relatively mild and infrequent.