Dwarf elliptical galaxies

Abstract

Dwarf elliptical (dE) galaxies, with blue absolute magnitudes typically fainter than M B = 16, are the most numerous type of galaxy in the nearby universe. Tremendous advances have been made over the past several years in delineating the properties of both Local Group satellite dE's and the large dE populations of nearby clusters. We review some of these advances, with particular attention to how w ell currently available data can constrain (a) models for the formation of dE's, (b) the physical and evolutionary connections between dierent t ypes of galaxies (nucleated and nonnucleated dE's, compact E's, irregulars, and blue compact dwarfs) that overlap in the same portion of the mass-spectrum of galaxies, (c) the contribution of dE's to the galaxy luminosity functions in clusters and the eld, (d) the star-forming histories of dE's and their possible contribution to faint galaxy counts, and (e) the clustering properties of dE's.In addressing these issues, we highlight the extent to which selection eects temper these constraints, and outline areas where new data would be particularly valuable.

Scale-invariance of galaxy clustering

“…An observation that is particularly important from a theoretical point of view is the behavior of the giant-to-dwarf ratio as a function of the local density: we ask whether dwarf galaxies exist in low density regions, where giants are rare, or if they are only found as satellites of giants so that the giants-to-dwarfs ratio does not depend on environmental density. There is a clear experimental indication that the dwarf-to-giant ratio depends on the local density [164,168,169].…”

“…Various studies [167][168][169] of the spatial distribution of dwarf galaxies show that these galaxies fall into the structures defined by the luminous ones and that there is no evidence of segregation of bright and faint galaxies on large scale: dwarf galaxies are not more uniformly distributed than giants and the dwarfs, as the giants, belong to clouds, groups or clusters. There is evidence that the dwarfs fall well into the large scale patterns suggested by the giants consisting of filaments, walls and arcs.…”

The Next Generation Virgo Cluster Survey Xvi: The Angular Momentum of Dwarf Early-Type Galaxies From Globular Cluster Satellites

“…These three dEs are ∼1mag fainter than the brightest dEs, which have M V ∼−18, (e.g., Ferguson & Binggeli 1994). They are very round, with ellipticities of ò  0.1, and they do not show any disk-like structures, such as bars, spiral arms, or irregular features, in the NGVS deep images (see Figure 10), confirming the lack of substructure found by Lisker et al (2006aLisker et al ( , 2007 based on the much shallower Sloan Digital Sky Survey images (SDSS; Adelman-McCarthy et al 2008).…”

Structural properties of dwarf ellipticals and the connection with (ordinary) elliptical galaxies

“…This is the case for the M -µ e and R e -µ e diagram (Capaccioli, Caon & D'Onofrio 1992, their figure 4;Binggeli & Ferguson 1994; their section 2.2.2), and also for the Fundamental Plane (Djorgovski & Davis 1987) when constructed using effective surface brightnesses (e.g., Geha, Guhathakurta & van der Marel 2002).…”