Compact Elliptical Galaxies

Nieto, J. L.; Prugniel, Philippe

doi:10.1007/978-94-009-3971-4_8

Cited by 30 publications

(48 citation statements)

References 13 publications

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“…Thus a possible source for the star pile is obviously the CBCG itself or rather the compact dwarf cE, likely stripped by interaction with the CBCG. In fact, compact elliptical galaxies are though to form through tidal stripping (Nieto & Prugniel 1987;Bekki et al 2001).…”

Section: Star Pile and Merging Scenariomentioning

confidence: 99%

Internal dynamics of the galaxy cluster Abell 545

Barrena

Girardi²,

Boschin³

et al. 2011

A&A

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Context. The mechanisms giving rise to diffuse radio emission in galaxy clusters, and in particular their connection with cluster mergers, are still debated. Aims. We seek to explore the internal dynamics of the cluster Abell 545, which has been shown to host a radio halo. Abell 545 is also peculiar for hosting in its center a very bright, red, diffuse intracluster light due to an old, presumably metal-rich stellar population, so bright to be named as "star pile". Methods. Our analysis is mainly based on redshift data for 110 galaxies acquired at the Telescopio Nazionale Galileo. We identify 95 cluster members and analyze the cluster internal dynamics by combining galaxy velocities and positions. We also use both multiband photometric data acquired at the Isaac Newton Telescope and X-ray data from the XMM-Newton Science Archive. Results. We estimate the cluster redshift, z = 0.1580, a large line-of-sight (LOS) velocity dispersion σ V ∼ 1200 km s −1 , and ICM temperature kT X ∼ 8 keV. Our optical and X-ray analyses detect substructures. Optical data reveal three main galaxy clumps (one at the center hosting the peak of X-ray emission; one at NNW, and one at NE); and possibly a fourth clump at South. There is not a dominant galaxy and the four brightest galaxies avoid the cluster core -> ∼ 0.4 h −1 70 Mpc distant from the cluster center -and are > ∼ 1500 km s −1 far from the mean cluster velocity. Two of these brightest galaxies are located in the NNW and NE clumps. The analysis of the X-ray surface brightness distribution provides us evidence of a disturbed dynamical phase: the strong NNW-SSE elongation, a western excess, and a sharp discontinuity in the northern region which is the likely signature of a shock. Located in the star pile region there is the brightest galaxy of the cluster core (CBCG) and a very compact elliptical galaxy, likely a M32-like dwarf. We show that the star pile, which has a previously determined redshift, has a similar redshift to that of the CBCG. Both the star pile and the CBCG are at rest in the cluster rest frame. The elongation of the star pile and its relative position with respect to the CBCG indicate the same direction pointed out by the NE clump. Conclusions. The emerging picture of Abell 545 is that of a massive, M(R < 1.6 h 70 M , very complex cluster with merging occurring along two directions. Abell 545 gives another proof in the favor of the connection between cluster merger and extended, diffuse radio emission. The star pile, likely due to the process of a brightest galaxy forming in the cluster core, is related to the accretion along the NE direction. Abell 545 represents a textbook cluster where to study the simultaneous formation of a galaxy system and its brightest galaxy.

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Section: Star Pile and Merging Scenariomentioning

confidence: 99%

Internal dynamics of the galaxy cluster Abell 545

Barrena

Girardi²,

Boschin³

et al. 2011

A&A

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“…It is under discussion, whether environmental effects such as tidal stripping have shaped their present appearance (e.g. Faber 1973) or whether these galaxies just represent the low-luminosity end of the giant ellipticals (Nieto & Prugniel 1987). E.g., M 32 itself is a companion of the Andromeda galaxy (M 31).…”

Section: Introductionmentioning

confidence: 99%

The central region of the Fornax cluster

Hilker

Infante²,

Vieira³

et al. 1999

Astron. Astrophys. Suppl. Ser.

243

270

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Abstract. Radial velocities of 94 galaxies brighter than about V tot = 20 mag in the direction of the central Fornax cluster have been measured1 . Except for 8 Fornax members, all galaxies lie in the background. Among the 8 members, there are 5 nucleated dwarf ellipticals that are already listed in the FCC (Ferguson 1989). Two of the 3 "new" members are very compact and have surface brightnesses comparable to globular clusters, however their luminosities are in the range of dwarf elliptical nuclei.The measured line indices (especially Mg2, Hβ, and iron) of the brighter of the compact objects suggest a solar metallicity, whereas the fainter compact object as well as the dE, Ns have line indices that are similar to those of old metal-poor globular clusters (GCs). However, with these data it is not possible to clearly classify the compact objects either as very bright globular clusters, isolated nuclei of dE, Ns, or even compact ellipticals.A background galaxy cluster at z = 0.11 has been found just behind the center of the Fornax cluster. This explains the excess population of galaxies reported in Paper I. The brightest galaxy of the background cluster lies only 1. 1 south of NGC 1399 and is comparable in absolute luminosity with the central Fornax galaxy itself.Key words: galaxies: clusters: Fornax clustergalaxies: distances and redshifts -galaxies: abundances -galaxies: dwarf Send offprint requests to: M. Hilker 1 Table 2 containing the position, magnitude and velocity of all galaxies is also available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/Abstract.html

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“…INTRODUCTION The 32nd object in the catalog of Messier (1850) has come to be known as the archetype of high surface brightness, lowluminosity, compact elliptical galaxies (de Vaucouleurs 1961). It has been proposed that they may be the dense cores of tidally truncated, or at least modified, ordinary elliptical galaxies (King 1962;Faber 1973;Nieto & Prugniel 1987;Choi, Guhathakurta, & Johnston 2002 and references therein). It has also been suggested that M32 (NGC 221) may in fact never have been an elliptical galaxy but is instead the bulge of a (partially) stripped disk galaxy (Bekki et al 2001; see also Nieto 1990 r ral galaxy, and knowing its SMBH mass, allows one to decipher which scenario is more probable.…”

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confidence: 99%

Evidence for an Outer Disk in the Prototype “Compact Elliptical” Galaxy M32

Graham

2002

The Astrophysical Journal

107

138

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M32 is the prototype for the relatively rare class of galaxies referred to as compact ellipticals. It has been suggested that M32 may be a tidally disturbed elliptical galaxy or the remnant bulge of a disk-stripped early-1/4 r type spiral galaxy. This Letter reveals that the surface brightness profile, the velocity dispersion measurements, and the estimated supermassive black hole mass in M32 are inconsistent with the galaxy having, and probably ever having had, an light profile. Instead, the radial surface brightness distribution of M32 resembles an 1/4 r almost perfect (bulgeϩexponential disk) profile; this is accompanied by a marked increase in the ellipticity profile and an associated change in the position angle profile where the "disk" starts to dominate. Compelling evidence that this bulge/disk interpretation is accurate comes from the best-fitting bulge model, which has a Sérsic 1/n r index of , in agreement with the recently discovered relation between a bulge's Sérsic index and the n p 1.5 mass of a bulge's supermassive black hole. An index of would also be inconsistent with the stellar velocity n ≥ 4 dispersion of M32. The bulge-to-disk size ratio equals 0.20, and the logarithm of the bulge-to-disk luminosity r /h e ratio equals 0.22, typical of Sf galaxies. The effective radius of the bulge is 27Љ (∼100 pc), while the log (B/D) scale length of the disk is less well determined: owing to possible tidal stripping of the outer profile beyond 220Љ-250Љ, the scale length may be as large as 1.3 kpc. M32 is a relatively face-on, nucleated dwarf galaxy with a low surface brightness disk and a high surface brightness bulge. This finding brings into question the very existence of the compact elliptical class of galaxies.

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Compact Elliptical Galaxies

Cited by 30 publications

References 13 publications

Internal dynamics of the galaxy cluster Abell 545

Internal dynamics of the galaxy cluster Abell 545

The central region of the Fornax cluster

Evidence for an Outer Disk in the Prototype “Compact Elliptical” Galaxy M32

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