NGC 4382 (also known as Messier 85, M85, UGC 07508, PGC 40515), NGC 4394, IC 3292 in the Coma Berenices

NGC 4382 (M85) is a S0 galaxy with an interacting companion NGC 4394, which together with several other nearby galaxies (VCC 797=PGC 40512, IC 3292) form a galaxy group RSCG 54 (Barton et al. 1996). Since NGC 4382 has somewhat bluer colors than are typical for a S0, and its disk shows a spiral pattern, it is classified as a S0-a. The distance to NGC 4382 is 17.9 Mpc (58.4 Mly), calculated assuming a Hubble constant of H0 = 70 km s-1 Mpc-1 (Cappellari et al. 2010; Gebhardt et al. 2011).

The early-type galaxies (ETGs, ellipticals E and lenticulars S0) have played a central role in our understanding of galaxy evolution. Observations of high-redshift galaxies and the cosmic microwave background (Spergel et al. 2007) have revealed the Universe to be dominated by dark matter and dark energy (Riess et al. 1998; Perlmutter et al. 1999). Early-type (elliptical E and lenticular S0) galaxies (ETGs) are especially useful for observations as they are old, have smaller levels of star formation and limited amount of dust. Star formation in ETGs only happens in fast rotators and follows two distinct modes: in disks or widespread (Shapiro et al. 2010).

A shell galaxy as NGC 4382 is a normal elliptical or S0 galaxy showing faint ripples or ellipsoidal, sharp-edged features in its outer regions. Shells are likely to be 3D in geometry, not parts of a disk. Schweizer & Seitzer (1988) considered the term ‘shell’ as imposing an unjustified interpretation on the shapes of the features, and suggested the term ‘ripples’ instead. The best theory suggests that shells/ripples are remnants of a minor merger between a massive E galaxy and a small, cold, disk-shaped galaxy (e.g., Quinn 1984). In the case of NGC 4382, the fine structure appears to be “Malin shells,” which can be the result of gas-poor, primarily stellar, mergers (Malin & Carter 1980; Quinn 1984). As a core elliptical this galaxy is expected to be a mostly gas-poor merger (Lauer et al. 2007b; Kormendy et al. 2009).

Charts and image details obtained from Astrometry.net

Image and FOV details

RC 12" Astrograph (IRIDA South dome)

Imaging details