Searching for diffuse light in the M96 Group

TL;DR

Deep imaging of the M96 galaxy group reveals no large-scale diffuse light associated with the Leo Ring, but uncovers faint tidal features and provides insights into galaxy interactions and gas accretion within the group.

Contribution

This study provides the first deep, wide-field imaging analysis of the M96 Group, setting limits on diffuse light and identifying subtle interaction signatures.

Findings

No diffuse optical counterpart to the Leo Ring down to μ_B=30.1.

Detection of low surface-brightness tidal features possibly related to the Ring.

Evidence of gas accretion onto M96 from the HI ring.

Abstract

We present deep, wide-field imaging of the M96 galaxy group (also known as the Leo I Group). Down to surface brightness limits of $\mu_{B}=30.1$ and $\mu_{V}=29.5$, we find no diffuse, large-scale optical counterpart to the "Leo Ring", an extended HI ring surrounding the central elliptical M105 (NGC 3379). However, we do find a number of extremely low surface-brightness ($\mu_{B} \gtrsim 29$) 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 HI ring, in agreement with HI 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 HI 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.