Discs of satellites: the new dwarf spheroidals

Metz, Manuel; Kroupa, Pavel; Jerjen, Helmut

doi:10.1111/j.1365-2966.2009.14489.x

Cited by 116 publications

(118 citation statements)

References 60 publications

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“…Andromeda may also have a DoS (Koch & Grebel 2006; see also Fig. 4 in Metz et al 2009a) 11 suggesting that these satellite distributions may not be uncommon among MW-type DM halos.…”

Section: The Dos -Discussionmentioning

confidence: 98%

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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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“…Andromeda may also have a DoS (Koch & Grebel 2006; see also Fig. 4 in Metz et al 2009a) 11 suggesting that these satellite distributions may not be uncommon among MW-type DM halos.…”

Section: The Dos -Discussionmentioning

confidence: 98%

“…An updated list of all currently known satellites is provided in Table 2 upon which the following analysis is based. and Metz et al (2009a) employed a sophisticated fitting routine to find the DoS. Here, an intuitive plane-fitting algorithm and a new disc-test are introduced.…”

Section: The Disc Of Satellites (Dos) and Invariant Baryonic Galaxiesmentioning

confidence: 99%

Local-Group tests of dark-matter concordance cosmology

Kroupa

Famaey

Boer

et al. 2010

A&A

229

301

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“…A possible explaination to the phase-space correlation problem of Milky Way satellites Metz et al 2009a), has been proposed in terms of a "group infall" of subhalos (Li & Helmi 2008;D'Onghia & Lake 2008;D'Onghia et al 2009). Alternately, dwarf galaxies may form along dark matter filaments (Ricotti et al 2008).…”

Section: How Did the Knots Form?mentioning

confidence: 99%

VLT observations of NGC 1097's “dog-leg” tidal stream

Galianni¹,

Patat²,

Higdon³

et al. 2010

A&A

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Aims. We investigate the structure and stellar population of two large stellar condensations (knots A & B) along one of the faint optical "jet-like" tidal streams associated with the spiral NGC 1097, with the goal of establishing their physical association with the galaxy and their origin. Methods. We use the VLT/FORS2 to get deep V-band imaging and low-resolution optical spectra of two knots along NGC 1097's northeast "dog-leg" tidal stream. With this data, we explore their morphology and stellar populations. Results. Spectra were obtained for eleven sources in the field surrounding the tidal stream. The great majority of them turned out to be background or foreground sources, but the redshift of knot A (and perhaps of knot B) is consistent with that of NGC 1097. Using the V-band image of the "dog-leg" tidal feature we find that the two knots match the photometric scaling relations of canonical dwarf spheroidal galaxies (dSph) very well. Spectral analysis shows that knot A is mainly composed of stars near G-type, with no signs of ongoing star formation. Comparing its spectrum with a library of high resolution spectra of galactic globular clusters (GCs), we find that the stellar population of this dSph-like object is most similar to intermediate to metal rich galactic GCs. We find moreover, that the tidal stream shows an "S" shaped inflection as well as a pronounced stellar overdensity at knot A's position. This suggests that knot A is being tidally stripped, and populating the stellar stream with its stars. Conclusions. We have discovered that two knots along NGC 1097's northeast tidal stream share most of their spectral and photometric properties with ordinary dwarf spheroidal galaxies (dSph). Moreover, we find strong indications that the "dog-leg" tidal stream arises from the tidal disruption of knot A. Since it has been demonstrated that tidally stripping dSph galaxies need to loose most of their dark matter before starting to loose stars, we suggest that knot A is at present a CDM-poor object.

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“…Hence, Kunkel & Demers (1976) and Lynden-Bell (1976) termed this phenomenon the "Magellanic plane". As more MW satellites were discovered, e.g., Sextans and those dwarf galaxies in the footprint of the Sloan Digital Sky Survey, they were found to lie close to this plane too (Kroupa, Theis & Boily 2005;Metz, Kroupa & Jerjen 2009).…”

Section: Introductionmentioning

confidence: 96%

The new Milky Way satellites: alignment with the VPOS and predictions for proper motions and velocity dispersions

Pawlowski

McGaugh

Jerjen

2015

Mon. Not. R. Astron. Soc.

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The evidence that stellar systems surrounding the Milky Way (MW) are distributed in a Vast Polar Structure (VPOS) may be observationally biased by satellites detected in surveys of the northern sky. The recent discoveries of more than a dozen new systems in the southern hemisphere thus constitute a critical test of the VPOS phenomenon. We report that the new objects are located close to the original VPOS, with half of the sample having offsets less than 20 kpc. The positions of the new satellite galaxy candidates are so well aligned that the orientation of the revised best-fitting VPOS structure is preserved to within 9 degrees and the VPOS flattening is almost unchanged (31 kpc height). Interestingly, the shortest distance of the VPOS plane from the MW center is now only 2.5 kpc, indicating that the new discoveries balance out the VPOS at the Galactic center. The vast majority of the MW satellites are thus consistent with sharing a similar orbital plane as the Magellanic Clouds, confirming a hypothesis proposed by Kunkel & Demers and Lynden-Bell almost 40 years ago. We predict the absolute proper motions of the new objects assuming they orbit within the VPOS. Independent of the VPOS results we also predict the velocity dispersions of the new systems under three distinct assumptions: that they (i) are dark-matter-free star clusters obeying Newtonian dynamics, (ii) are dwarf satellites lying on empirical scaling relations of galaxies in dark matter halos, and (iii) obey MOND.

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Discs of satellites: the new dwarf spheroidals

Cited by 116 publications

References 60 publications

Local-Group tests of dark-matter concordance cosmology

Local-Group tests of dark-matter concordance cosmology

VLT observations of NGC 1097's “dog-leg” tidal stream

The new Milky Way satellites: alignment with the VPOS and predictions for proper motions and velocity dispersions

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