Dwarf spheroidal galaxies and resonant orbital coupling

Kuhn, Jeffrey R.; Miller, Richard H.

doi:10.1086/185453

Cited by 73 publications

(82 citation statements)

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“…While this is partly due to technical differences in interpretation of even the same databases (e.g., Wilkinson et al 2004;xokas et al 2005;Muñoz et al 2005), in general most studies are finding flat dSph velocity dispersion profiles to be the norm. As discussed several times here, such profiles are produced naturally in dSph models undergoing tidal disruption (see also Kuhn & Miller 1989;Kroupa 1997;Mayer et al 2002;Fleck & Kuhn 2003;Read et al 2006;M06). However, rather than settling the issue, these rather flat velocity dispersion profiles have prompted the development of even more extreme, two-component, extended dark halo dSph models with substantially higher bound masses and total M /L, exceeding 400 or even 1000 (M/L) (e.g., xokas 2002; Kleyna et al 2002;Walker et al 2006).…”

Section: Summary and Discussionmentioning

confidence: 76%

“…The prime observational evidence to support this claim is the relatively high measured central velocity dispersions that, coupled with an assumption of dynamical equilibrium, imply masses far in excess of that inferred by the luminous component. Alternatively, (2) dSph's have also been discussed as systems partly or completely out of virial equilibrium (Hodge & Michie 1969;Kuhn & Miller 1989;Kuhn 1993;Kroupa 1997;Gómez-Flechoso et al 1999;Fleck & Kuhn 2003). Such an assertion seeks to explain the large central velocity dispersions of dSph's through inflation by tidal heating or other dynamical effects, allowing for much more modest dSph masses, consistent with no dark matter.…”

Section: Summary and Discussionmentioning

confidence: 99%

“…Flat dispersion profiles arise naturally in tidal disruption models (Kuhn & Miller 1989;Kroupa 1997;Fleck & Kuhn 2003) even if large amounts of dark matter are present and the central parts of dSph's are bound and in equilibrium (Mayer et al 2002;Sohn et al 2006). As we show in M06, a single-component, mass-follows-light, tidally disrupting dSph model gives a good representation for both the density and velocity dispersion profile for the Carina dSph we have derived here.…”

Section: Velocity Dispersion Trend Of Carina Starsmentioning

confidence: 99%

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Exploring Halo Substructure with Giant Stars. XI. The Tidal Tails of the Carina Dwarf Spheroidal Galaxy and the Discovery of Magellanic Cloud Stars in the Carina Foreground

Muñoz

Majewski

Zaggia

et al. 2006

ApJ

166

114

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A new large-area Washington M, T 2 +DDO51 filter survey of more than 10 deg 2 around the Carina dSph galaxy reveals a spectroscopically confirmed power-law radial density ''break'' population of Carina giant stars extending several degrees beyond the central King profile. Magellan telescope MIKE spectroscopy establishes the existence of Carina stars to at least 4.5 times its central King limiting radius, r lim , and primarily along Carina's major axis. To keep these stars bound to the dSph would require a global Carina mass-to-light ratio of M /L ! 6300 (M/L) . The MIKE velocities, supplemented with $950 additional Carina field velocities from archived VLT+GIRAFFE spectra with r P r lim , demonstrate a nearly constant Carina velocity dispersion ( v ) to just beyond r ¼ r lim and both a rising v and a velocity shear at still larger radii. Together, the observational evidence suggests that the discovered extended Carina population represents tidal debris from the dSph. Of 65 giant candidates at large angular radii from the Carina center for which MIKE spectra have been obtained, 94% are associated with either Carina or a second, newly discovered diffuse, but strongly radial velocity-coherent ( v ¼ 9:8 km s À1 ), foreground halo system. The 15 stars in this second, retrograde velocity population have (1) a mean metallicity $1 dex higher than that of Carina and (2) colors and magnitudes consistent with the red clump of the LMC. Additional spectroscopy of giant star candidates in fields linking Carina and the LMC shows a smooth velocity gradient between the LMC and the retrograde Carina moving group. We conclude that we have found Magellanic stars almost twice as far (22 ) from the LMC center than previously known.

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Section: Summary and Discussionmentioning

confidence: 76%

Section: Summary and Discussionmentioning

confidence: 99%

Section: Velocity Dispersion Trend Of Carina Starsmentioning

confidence: 99%

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Exploring Halo Substructure with Giant Stars. XI. The Tidal Tails of the Carina Dwarf Spheroidal Galaxy and the Discovery of Magellanic Cloud Stars in the Carina Foreground

Muñoz

Majewski

Zaggia

et al. 2006

ApJ

166

114

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“…Models related to this idea have been studied by Kuhn (1993). Moreover, resonant orbital coupling can periodically inflate kinematically measured M/L values (Kuhn & Miller 1989;Kuhn et al 1996). Fully self-consistent Newtonian N-body models have demonstrated that unphysically high M/L ratios arise indeed if TDGs are allowed to orbit a host galaxy sufficiently long such that the remaining stellar population within the ancient TDG adopts a highly non-isotropic phase-space distribution function (Kroupa 1997;Klessen & Kroupa 1998;).…”

Section: The Evolution Of Tdgsmentioning

confidence: 99%

Local-Group tests of dark-matter concordance cosmology

Kroupa

Famaey

Boer

et al. 2010

A&A

229

301

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Predictions of the concordance cosmological model (CCM) of the structures in the environment of large spiral galaxies are compared with observed properties of Local Group galaxies. Five new, most probably irreconcilable problems are uncovered: 1) A wide variety of published CCM models consistently predict some form of relation between dark-matter-mass and luminosity for the Milky Way (MW) satellite galaxies, but none is observed.2) The mass function of luminous sub-haloes predicted by the CCM contains too few satellites with dark matter (DM) mass ≈10 7 M within their innermost 300 pc than in the case of the MW satellites.3) The Local Group galaxies and data from extragalactic surveys indicate there is a correlation between bulge-mass and the number of luminous satellites that is not predicted by the CCM. 4) The 13 new ultra-faint MW satellites define a disc-of-satellites (DoS) that is virtually identical to the DoS previously found for the 11 classical MW satellites, implying that most of the 24 MW satellites are correlated in phase-space. 5) The occurrence of two MW-type DM halo masses hosting MW-like galaxies is unlikely in the CCM. However, the properties of the Local Group galaxies provide information leading to a solution of the above problems. The DoS and bulge-satellite correlation suggest that dissipational events forming bulges are related to the processes forming phase-space correlated satellite populations. These events are well known to occur since in galaxy encounters energy and angular momentum are expelled in the form of tidal tails, which can fragment to form populations of tidal-dwarf galaxies (TDGs) and associated star clusters. If Local Group satellite galaxies are to be interpreted as TDGs then the substructure predictions of the CCM are internally in conflict. All findings thus suggest that the CCM does not account for the Local Group observations and that therefore existing as well as new viable alternatives have to be further explored. These are discussed and natural solutions for the above problems emerge.

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“…They are the two closest galaxies to the Milky Way among our set, as well as the two of lowest luminosity. Because of these properties, it is often suggested that Draco and UMi are victims of tidal stripping (Kuhn & Miller 1989;Kuhn 1993;Kroupa 1997;Fleck & Kuhn 2003;Gómez-Flechoso & Martínez-Delgado 2003;Muñoz et al 2005). For example, Muñoz et al (2005) argue that this galaxy is not a simple, dynamically relaxed system because of the unphysically large inferred mass (implying ) based on their measurement of a large j far M/L 1 900 from UMi's core.…”

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confidence: 99%

Local Group Dwarf Galaxies and the Fundamental Manifold of Spheroids

Zaritsky

Gonzalez

Zabludoff

2006

ApJ

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The fundamental manifold (FM), an extension of the fundamental plane formalism, incorporates all spheroiddominated stellar systems from dwarf ellipticals up to the intracluster stellar populations of galaxy clusters by accounting for the continuous variation of the mass-to-light ratio within the effective radius with scale.Here r e we find that Local Group dwarf spheroidal and dwarf elliptical galaxies, which probe the FM relationship roughly one decade lower in than previous work, lie on the extrapolation of the FM. When combined with the earlier r e data, these Local Group dwarfs demonstrate the validity of the empirical manifold over nearly 4 orders of magnitude in . The continuity of the galaxy locus on the manifold and, more specifically, the overlap on the r e FM of dwarf ellipticals like M32 and dwarf spheroidals like Leo II, imply that dwarf spheroidals belong to the same family of spheroids as their more massive counterparts. The only significant outliers are Ursa Minor and Draco. We explore whether the deviation of these two galaxies from the manifold reflects a breakdown in the coherence of the empirical relationship at low luminosities or rather the individual dynamical peculiarities of these two objects. We discuss some implications of our results for how the lowest mass galaxies form.

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Dwarf spheroidal galaxies and resonant orbital coupling

Cited by 73 publications

References 0 publications

Exploring Halo Substructure with Giant Stars. XI. The Tidal Tails of the Carina Dwarf Spheroidal Galaxy and the Discovery of Magellanic Cloud Stars in the Carina Foreground

Exploring Halo Substructure with Giant Stars. XI. The Tidal Tails of the Carina Dwarf Spheroidal Galaxy and the Discovery of Magellanic Cloud Stars in the Carina Foreground

Local-Group tests of dark-matter concordance cosmology

Local Group Dwarf Galaxies and the Fundamental Manifold of Spheroids

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