J/MNRAS/435/1928 Dwarf galaxy planes in Local Group (Pawlowski+, 2013)
Dwarf galaxy planes: the discovery of symmetric structures in the Local Group.
Pawlowski M.S., Kroupa P., Jerjen H.
<Mon. Not. R. Astron. Soc., 435, 1928-1957 (2013)>
=2013MNRAS.435.1928P 2013MNRAS.435.1928P
ADC_Keywords: Galaxies, nearby
Keywords: Galaxy: halo - galaxies: dwarf - galaxies: individual: M31 -
galaxies: kinematics and dynamics - Local Group - Magellanic Clouds
Abstract:
Both major galaxies in the Local Group (LG) are surrounded by thin
planes of mostly co-orbiting satellite galaxies, the vast polar
structure (VPOS) around the Milky Way (MW) and the Great Plane of
Andromeda (GPoA) around M31. We summarize the current knowledge
concerning these structures and compare their relative orientations by
re-determining their properties in a common coordinate system. The
existence of similar, coherent structures around both major LG
galaxies motivates an investigation of the distribution of the more
distant non-satellite galaxies in the LG. This results in the
discovery of two planes (diameters of 1-2Mpc) which contain almost all
nearby non-satellite galaxies. The two LG planes are surprisingly
symmetric. They are inclined by only 20° relative to the galactic
disc of M31, are similarly thin (heights of ~60kpc) and have
near-to-identical offsets from the MW and from M31. They are inclined
relative to each other by 35°. Comparing the plane orientations
with each other and with additional features reveals indications for
an intimate connection between the VPOS and the GPoA. They are both
polar with respect to the MW, have similar orbital directions and are
inclined by about 45°±7° relative to each other. The
Magellanic Stream approximately aligns with the VPOS and the GPoA, but
also shares its projected position and line-of-sight velocity trend
with a part of the dominating structure of non-satellite dwarf
galaxies. In addition, the recent proper motion measurement of M31
indicates a prograde orbit of the MW-M31 system, the VPOS and the
GPoA. The alignment with other features such as the Supergalactic
Plane and the overdensity in hypervelocity stars are discussed as
well. We end with a short summary of the currently proposed scenarios
trying to explain the LG galaxy structures as either originating from
cosmological structures or from tidal debris of a past galaxy
encounter. We emphasize that there currently exists no full detailed
model which satisfactorily explains the existence of the thin
symmetric LG planes.
Description:
The analysis presented in the following is based on the catalogue of
nearby galaxies as compiled by McConnachie (2012AJ....144....4M 2012AJ....144....4M,
Cat. J/AJ/144/4) (see also Mateo, 1998ARA&A..36..435M 1998ARA&A..36..435M). It includes
information on all known galaxies within 3Mpc from the Sun, which
have distance estimates based on resolved stellar populations. We use
the galaxy positions, radial distances and line-of-sight velocities of
the LG galaxies as provided by the most recent online version of the
tables by McConnachie (2012AJ....144....4M 2012AJ....144....4M,
https://www.astrosci.ca/users/alan/Nearby_Dwarfs_Database.html,
Version 2013/Jun/17).
To this we add the recently published line-of-sight velocity for
Andromeda XXIX (Tollerud et al., 2013ApJ...768...50T 2013ApJ...768...50T) for which no
velocities are provided in the catalogue yet.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table4.dat 114 78 Distances and offsets (minimum distance) of
galaxies from the MW, M31 and the galaxy planes
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See also:
J/AJ/144/4 : Properties of dwarf galaxies in Local Group (McConnachie+, 2012)
Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
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1- 18 A18 --- Name Galaxy name
20- 25 F6.1 kpc dMW Galaxy distance from the centre of the MW
28- 33 F6.1 kpc dM31 Galaxy distance from the centre of M31
36- 43 A8 --- Cat Galaxy category (1)
47- 51 F5.1 kpc dVPOS Offset to all vast polar structure plane (2)
53- 56 F4.1 kpc e_dVPOS rms uncertainty on dVPOS
57 A1 --- n_dVPOS [*] * : galaxy to which the offset are fitted
58- 62 F5.1 kpc dVPOS-3 Offset to the VPOS-3 plane (2)
64- 67 F4.1 kpc e_dVPOS-3 rms uncertainty on dVPOS-3
68 A1 --- n_dVPOS-3 [*] * : galaxy to which the offset are fitted
69- 74 F6.1 kpc dGPoA Offset to Great Plane of Andromeda (2)
76- 79 F4.1 kpc e_dGPoA rms uncertainty on dGPoA
80 A1 --- n_dGPoA [*] * : galaxy to which the offset are fitted
81- 86 F6.1 kpc dLGP1 Offset to Local Group Plane 1 (LGP1) (2)
88- 91 F4.1 kpc e_dLGP1 rms uncertainty on dLGP1
92 A1 --- n_dLGP1 [*] * : galaxy to which the offset are fitted
93- 97 F5.1 kpc dLGP2 Offset to Local Group Plane 2 (LGP2) (2)
99-102 F4.1 kpc e_dLGP2 rms uncertainty on dLGP2
103 A1 --- n_dLGP2 [*] * : galaxy to which the offset are fitted
104-108 F5.1 kpc dM31p Offset to M31 disc plane
110-113 F4.1 kpc e_dM31p rms uncertainty on dM31p
114 A1 --- n_dM31p [*] * : galaxy to which the offset are fitted
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Note (1): Categories are:
host = galaxy is considered a host (only the MW and M31)
MW sat. = an MW satellite (dMW<300kpc)
M31 sat. = M31 satellite (dM31<300kpc)
non-sat. = a non-satellite (both dMW and dM31 >300kpc)
Note (2): Planes are defined as:
VPOS = Vast POlar Structure of satellite objects around the Milky Way.
VPOS-3 = VPOS except Leo I, Hercules and Ursa Major
GPoA = Great Plane of Andromeda
LGP1 = Local Group galaxies UGC 4879, Leo A, Leo T, Phoenix, Tucana,
Cetus, WLM, IC 1613 and Andromeda XVI
LGP2 = Local Group galaxies NGC 6822, Sagittarius dIrr, Aquarius,
Andromeda XXVIII and Andromeda XVIII
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History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 26-Sep-2014