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The isolated elliptical (IE) NGC 7796 is accompanied by an interestingearly-type dwarf galaxy, named NGC7796-DW1. It exhibits a tidal tail, very boxyisophotes, and multiple nuclei or regions (A, B, and C) that are bluer than thebulk population of the galaxy, indicating a younger age. These properties aresuggestive of a dwarf-dwarf merger remnant. We use the Multi-Unit SpectroscopicExplorer (MUSE) at the VLT to investigate NGC 7796-DW1. We extractcharacteristic spectra to which we apply the STARLIGHT population synthesissoftware to obtain ages and metallicities of the various population componentsof the galaxy. The galaxy's main body is old and metal-poor. A surprisingresult is the extended line emission in the galaxy, forming a ring-likestructure with a projected diameter of 2.2 kpc. The line ratios fall into theregime of HII-regions, although OB-stellar populations cannot be identified byspectral signatures. Nucleus A is a relatively old (7 Gyr or older) andmetal-poor super star cluster, most probably the nucleus of the dwarf, nowdisplaced. The star-forming regions B and C show younger and distinctly moremetal-rich components. The emission line ratios of regions B and C indicate analmost solar oxygen abundance, if compared with radiation models of HIIregions. NGC7796-DW1 occupies a particular role in the group of transition-typegalaxies with respect to its origin and current evolutionary state, being thecompanion of an IE. The dwarf-dwarf merger scenario is excluded because of themissing metal-rich merger component. A viable alternative is gas accretion froma reservoir of cold, metal-rich gas. NGC7796 has to provide this gas within itsX-ray bright halo. As illustrated by NGC7796-DW1, cold accretion may be ageneral solution to the problem of extended star formation histories intransition dwarf galaxies. (abridged)

The curious case of the companion: evidence for cold accretion onto a dwarf satellite near the isolated elliptical NGC 7796