Formation and evolution of dwarf early-type galaxies in the Virgo cluster I. Internal kinematics

Astronomy and Astrophysics (Impact Factor: 4.48). 11/2010; DOI: 10.1051/0004-6361/201015344
Source: arXiv

ABSTRACT We present new medium resolution kinematic data for a sample of 21 dwarf early-type galaxies (dEs) mainly in the Virgo cluster, obtained with the WHT and INT telescopes at the Roque de los Muchachos Observatory (La Palma, Spain). These data are used to study the origin of the dwarf elliptical galaxy population inhabiting clusters. We confirm that dEs are not dark matter dominated galaxies, at least up to the half-light radius. We also find that the observed galaxies in the outer parts of the cluster are mostly rotationally supported systems with disky morphological shapes. Rotationally supported dEs have rotation curves similar to those of star forming galaxies of similar luminosity and follow the Tully-Fisher relation. This is expected if dE galaxies are the descendant of low luminosity star forming systems which recently entered the cluster environment and lost their gas due to a ram pressure stripping event, quenching their star formation activity and transforming into quiescent systems, but conserving their angular momentum. Comment: 24 pages, 15 figures and 7 tables. Replaced to match the journal version

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    ABSTRACT: We present the dynamical analysis of a sample of 12 dwarf elliptical (dE) galaxies for which we have obtained SAURON large-scale two-dimensional spectroscopic data. We construct Jeans axisymmetric models and obtain total dynamical masses enclosed within one effective radius. We use the obtained values to show that the validity of the dynamical scaling relations of massive early-type galaxies can be extended to these low-mass systems, except that dEs seem to contain relatively larger fraction of dark matter in their inner parts. We then demonstrate that dE galaxies have lower angular momenta than the present-day analogues of their presumed late-type progenitors and we show that dE circular velocity curves are steeper than the rotation curves of galaxies with equal and up to an order of magnitude higher luminosity. This requires a transformation mechanism that is not only able to lower the angular momentum but also one that needs to account for increased stellar concentration. Additionally, we match the dark matter fraction of our galaxies to their location in the Virgo Cluster and see that galaxies in the cluster outskirts tend to have a higher dark-to-stellar matter ratio. Transformation due to tidal harassment is able to expain all of the above, unless the dE progenitors were already compact and had lower angular momenta at higher redshifts.
    Monthly Notices of the Royal Astronomical Society 12/2013; 439(1). · 5.23 Impact Factor
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    ABSTRACT: We present evidence for kinematically decoupled cores (KDCs) in two dwarf early-type (dE) galaxies in the Virgo cluster, VCC 1183 and VCC 1453, studied as part of the SMAKCED stellar absorption-line spectroscopy and imaging survey. These KDCs have radii of 1.8'' (0.14 kpc) and 4.2'' (0.33 kpc), respectively. Each of these KDCs is distinct from the main body of its host galaxy in two ways: (1) inverted sense of rotation; and (2) younger (and possibly more metal-rich) stellar population. The observed stellar population differences are probably associated with the KDC, although we cannot rule out the possibility of intrinsic radial gradients in the host galaxy. We describe a statistical analysis method to detect, quantify the significance of, and characterize KDCs in long-slit rotation curve data. We apply this method to the two dE galaxies presented in this paper and to five other dEs for which KDCs have been reported in the literature. Among these seven dEs, there are four significant KDC detections, two marginal KDC detections, and one dE with an unusual central kinematic anomaly that may be an asymmetric KDC.The frequency of occurence of KDCs and their properties provide important constraints on the formation history of their host galaxies. We discuss different formation scenarios for these KDCs in cluster environments and find that dwarf-dwarf wet mergers or gas accretion can explain the properties of these KDCs. Both of these mechanisms require that the progenitor had a close companion with a low relative velocity. This suggests that KDCs were formed in galaxy pairs residing in a poor group environment or in isolation whose subsequent infall into the cluster quenched star formation.
    The Astrophysical Journal 01/2014; 783(2). · 6.28 Impact Factor
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    ABSTRACT: Galaxy clusters are populated by thousands of low-mass galaxies, with hundreds of them already within stellar masses of 108 < M* ≤ 109.5M⊙ and magnitudes of –16 < Mr < –19 mag. While objects in this regime are commonly termed “dwarfs”, they are not as faint and diffuse as many of the known Milky Way satellites. Their observed complexity, particularly regarding the dominant early-type dwarf population, is still poorly understood and requires models and simulations of environmental influence on dwarfs. Studying cluster dwarf galaxies at the current time is motivated by two facts: (i) for nearby clusters, multicolour observational samples exist that are complete in the above luminosity range and cover a substantial portion of the cluster; (ii) state-of-the-art semi-analytic models based on high-resolution N-body simulations, reaching down to dwarf masses, have recently become available. Here I show how comparisons of models and observations can serve as a tool for studying the evolutionary history of low-mass galaxy populations in today's clusters (© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
    Astronomische Nachrichten 06/2012; 333(5‐6). · 1.12 Impact Factor

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