We present the results of a Keck-ESI spectroscopic study of six dwarf elliptical (dE) galaxies in the Perseus Cluster core, and confirm two dwarfs as cluster members for the first time. All six dEs follow the size-magnitude relation for dE/dSph galax
ies. Central velocity dispersions are measured for three Perseus dwarfs in our sample, and all lie on the $sigma$-luminosity relation for early-type, pressure supported systems. We furthermore examine SA 0426-002, a unique dE in our sample with a bar-like morphology surrounded by low-surface brightness wings/lobes ($mu_{B} = 27$ mag arcsec$^{-2}$). Given its morphology, velocity dispersion ($sigma_{0} = 33.9 pm 6.1 $ km s$^{-1}$), velocity relative to the brightest cluster galaxy NGC 1275 (2711 km s$^{-1}$), size ($R_{e} =2.1 pm 0.10$ kpc), and Sersic index ($n= 1.2 pm 0.02$), we hypothesise the dwarf has morphologically transformed from a low mass disc to dE via harassment. The low-surface brightness lobes can be explained as a ring feature, with the bar formation triggered by tidal interactions via speed encounters with Perseus Cluster members. Alongside spiral structure found in dEs in Fornax and Virgo, SA 0426-002 provides crucial evidence that a fraction of bright dEs have a disc infall origin, and are not part of the primordial cluster population.
We present the results of a Keck/DEIMOS survey of Ultra Compact Dwarfs (UCDs) in the Perseus Cluster core. We confirm cluster membership for 14 UCDs, with radial velocities ~5300 km s$^{-1}$. Two of these confirmed Perseus UCDs have extremely blue co
lours ($B-R < 0.6$ mag), reside in star forming filaments surrounding NGC 1275, and have likely formed as massive star clusters in the last ~100 Myr. We also measure a central velocity dispersion of a third, UCD13 ($sigma_0 = 38 pm 8$ km s$^{-1}$), the most extended UCD in our sample. We determine it to have radius $R_{e} = 85 pm 1.1$ pc, a dynamical mass of ($2.3 pm 0.8)times10^{8}$ M$_{odot}$, and a metallicity [Z/H]$= -0.52^{+0.33}_{-0.29}$ dex. UCD13 and the clusters central galaxy, NGC 1275, have a projected separation of 30 kpc and a radial velocity difference of ~20 km s$^{-1}$. Based on its size, red colour, internal velocity dispersion, dynamical mass, metallicity and proximity to NGC 1275, we argue that UCD13 is likely the remnant nucleus of a tidally stripped dE, with this progenitor dE having $M_{B} approx -16$ mag and mass $sim10^{9}$ M$_{odot}$.
Using deep B band imaging down to mu_{B} = 26 mag arcsec^{-2}, we present evidence for tidal tails in the Antlia Dwarf galaxy, one of the most distant members of the Local Group. This elongation is in the direction of Antlias nearest neighbor, the Ma
gellanic-type NGC 3109. The tail is offset by less than 10 degrees from a vector linking the centers of the two galaxies, indicative of interactions between the pair. Combined with the warped disc previously identified in NGC 3109, Antlia and NGC 3109 must be at a small separation for tidal features to be present in Antlia. We calculate that Antlia cannot be completely disrupted by NGC 3109 in a single interaction unless its orbit pericenter is less than 6 kpc, however multiple interactions could significantly alter its morphology. Therefore despite being located right at the edge of the Local Group, environmental effects are playing an important role in Antlias evolution.
We present the results of the first search for Ultra Compact Dwarfs (UCDs) in the Perseus Cluster core, including the region of the cluster around the unusual Brightest Cluster Galaxy (BCG) NGC 1275. Utilising Hubble Space Telescope Advanced Camera f
or Surveys imaging, we identify a sample of 84 UCD candidates with half-light radii 10 pc < r_e < 57 pc out to a distance of 250 kpc from the cluster centre, covering a total survey area of ~70 armin^2. All UCDs in Perseus lie in the same size-luminosity locus seen for confirmed UCDs in other regions of the local Universe. The majority of UCDs are brighter than M_R = -10.5, and lie on an extrapolation of the red sequence followed by the Perseus Cluster dwarf elliptical population to fainter magnitudes. However, three UCD candidates in the vicinity of NGC 1275 are very blue, with colours (B-R)_0 < 0.6 implying a cessation of star formation within the past 100 Myr. Furthermore, large blue star clusters embedded in the star forming filaments are highly indicative that both proto-globular clusters (GCs) and proto-UCDs are actively forming at the present day in Perseus. We therefore suggest star forming filaments as a formation site for some UCDs, with searches necessary in other low redshift analogues of NGC 1275 necessary to test this hypothesis. We also suggest that tidal disruption of dwarf galaxies is another formation channel for UCD formation in the core of Perseus as tidal disruption is ongoing in this region as evidenced by shells around NGC 1275. Finally, UCDs may simply be massive GCs based on strong similarities in the colour trends of the two populations.
