The spatial distribution of the Milky Way and Andromeda satellite galaxies

By M. Metz, Pavel Kroupa, H. Jerjen. 2006

167 citations recorded by the source corpus.

There are two fundamentally different physical origins of faint satellite galaxies: cosmological sub-structures that contain shining baryons and the fragmentation of gas-rich tidal arms thrown out from interacting galaxies during hierarchical structure formation. The latter tidal-dwarf galaxies (TDG) may form populations with correlated orbital angular momenta about their host galaxies. The existence of TDGs is a stringent necessity because they arise as a result of fundamental physical principals. We determine the significance of the apparent disc-like distribution of Milky Way (MW) satellite galaxies. The distribution of the MW satellites is found to be inconsistent with an isotropic or prolate DM sub-structure distribution at a 99.5 per cent level including the recently discovered UMa and CVn dwarf spheroidal galaxies. The distribution is extremely oblate and inclined by about 88 ◦ with respect to the the MW disc. We also apply the methods to Andromeda’s (M31) satellite galaxies using two recently published data-sets. It can not be excluded that the whole population of M31 companions is drawn randomly from an isotropic parent distribution. However, two subsamples of Andromeda satellites are identified which have disc-like features. A kinematically motivated subsample of eight Andromeda satellites forms a pronounced disc-like distribution in both data-sets. The existence of this disc would be inconsistent with a CDM parent distribution of subhaloes if the disc is rotationally supported. The M31 satellite distribution is inclined by about 59 ◦ with respect to the M31 disc, and has virtually the same orientation as the disc derived for the whole M31 satellite sample. We present a new geometric method to set restrictions on possible locations of angular momentum vectors for Andromeda satellites. Our conclusion is that both, the MW and M31, may indeed have satellite galaxies derived from TDGs. Further, both host-discs and both identified discs-of-satellites are highly inclined relative to the supergalactic plane. The discs-of-satellites therefore cannot be created from individual accretion events from the supergalactic plane further supporting the possibility that they are of TDG origin.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/7d9d0f9e670b3e93ebbdc837700b51c068a52e0a

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Citations in the corpus

The Dark Matter Crisis: Falsification of the Current Standard Model of Cosmology (2012, background): “The sky coverage is not complete, but the coverage extends over most part of the northern hemisphere therewith being a cone rather than a slab with small regions having also been surveyed in the southern Galactic hemisphere (see figure 1 in Metz et al. 2007).”
Dwarf galaxy planes: the discovery of symmetric structures in the Local Group (2013, methodology): “Therefore, an apparent agreement of the simulated and observed flattening as measured via rthick/rcut is no indication that MW-like satellite systems are present in the simulation (see also Kang et al. 2005; Metz et al. 2007).”
The Luminosity Function of the Milky Way Satellites (2007, background): “…since DR5 does not contain dwarfs brighter than MV ∼ −11, we have also included in Figure 14 the estimate of the luminosity function (filled points) for the bright satellites of the Milky Way sampled over the full sky, together with the bright M31 satellites within 280kpc from Metz et al. (2007).”
The VPOS: a vast polar structure of satellite galaxies, globular clusters and streams around the Milky Way (2012, methodology): “1 Method l[◦] b[◦] Objects Reference DoS 2007 square (vertical) positions 157.3 -12.7 11 classical satellites Metz et al. (2007) DoS 2009 not plotted positions 149.6 -5.3 22 satellites Metz et al. (2009) DoS 2009 (w/o Her) not plotted positions 159.7 -6.8 21 satellites Metz et al. (2009) DoS open…”
Modified Newtonian Dynamics (MOND): Observational Phenomenology and Relativistic Extensions (2011, background): “Whether or not this phase-space correlation would be unique to the Milky Way should also be carefully checked, the evidence in M31 being currently much less convincing, with a richer and more complex satellite population [289].”
Hundreds of Milky Way Satellites? Luminosity Bias in the Satellite Luminosity Function (2008, background): “…whether satellite galaxies are preferentially oriented (either parallel or perpendicular) with respect to galaxy disks (Kroupa et al. 2005; Metz et al. 2007; Kuhlen et al. 2007; Wang et al. 2008; Faltenbacher et al. 2008) and equally contradictory claims regarding how disks are oriented…”
The Velocity Dispersion Profile of the Remote Dwarf Spheroidal Galaxy Leo I: A Tidal Hit and Run? (2007, background): “But to probe the satellites and study their DM halos in detail, we need to account for the effects of interactions, since these can strongly alter our conclusions regarding the properties of the halos (Klessen & Kroupa 1998; Fleck & Kuhn 2003; Metz et al. 2007).”
Co-orbiting satellite galaxy structures are still in conflict with the distribution of primordial dwarf galaxies (2014, background): “…satellite galaxies and determine which of all possible combinations of eight of these poles for a given satellite system have the smallest spherical standard distance∆std (Metz et al. 2007; Pawlowski et al. 2012) from their average direction〈n̂〉, ∆std= √ ∑8 i=1 [arccos(〈n̂〉 · n̂i )] 2 8 =min.”
Local-Group tests of dark-matter concordance cosmology - Towards a new paradigm for structure formation (2010, methodology): “This is in excellent agreement with the results of Metz et al. (2007).”
Galaxies as simple dynamical systems: observational data disfavor dark matter and stochastic star formation (2014, methodology): “[85] have developed statistics tools from the mathematical literature to assess the degree of clustering of data distributed on the sphere in terms of strength and shape parameters.”
Luminosity function and radial distribution of Milky Way satellites in a ΛCDM Universe (2009, methodology): “Distances for bright satellites are taken from Metz et al. (2007), while we use results compiled in MdJR08 for faint galaxies (MV > −9).”
THE INVISIBLES: A DETECTION ALGORITHM TO TRACE THE FAINTEST MILKY WAY SATELLITES (2008, background): “Studies of the spatial distributions of Milky Way and M31 dwarf galaxy companions have also highlighted possible discrepancies between ΛCDM theory and observations (Kroupa et al. 2005; Kang et al. 2005; Metz et al. 2007).”
The Orbital Poles of Milky Way Satellite Galaxies: A Rotationally Supported Disk of Satellites (2008, methodology): “In x 2.2 we analyze, using the techniques developed in Metz et al. (2007), the spatial distribution of a set of simulated luminous CDMhalos published with the claim of being a solution to the disk-of-satellites problem.”
Small scale problems of the $\Lambda$CDM model: a short review (2016, background): “[83] to conclude on the tidal origin (i.”
THE SAGITTARIUS DWARF GALAXY: A MODEL FOR EVOLUTION IN A TRIAXIAL MILKY WAY HALO (2010, background): “…great circle has a pole (l, b) = (135◦,−2.9◦) (Lynden-Bell 1982; see also Kunkel & Demers 1976; Majewski 1994; Fusi Pecci et al. 1995), and a recent update (Metz et al. 2007, 2009) including the faint new dwarfs discovered in the SDSS gives a revised satellite pole (l, b) = (159.7,−6.8).”