2025A&A...698A.178M

Query : 2025A&A...698A.178M

2025A&A...698A.178M - Astronomy and Astrophysics, volume 698A178 (2025/6-1)

The frozen outskirts: A cold Hubble flow and the mass of the Local Group.

MAKAROV D., MAKAROV D., MAKAROVA L. and LIBESKIND N.

Abstract (from CDS):

We analyze the velocity field of peripheral members of the Local Group. The Hubble flow at distances from 400 to 1400 kpc, formed by 7 of 11 nearby galaxies, is characterized by an extremely small line-of-sight velocity dispersion of 15 km s–1, which differs significantly from the predictions of cosmological simulations of about 70 km s–1. This fact allows us to determine the total mass of the Local Group as MLG = (2.47 ± 0.15)×1012 M⊙ using an analytical model of the Hubble flow around a spherical overdensity in the standard flat ΛCDM Universe. The practical equality of this mass to the sum of the masses of our Galaxy and the Andromeda Galaxy, as well as the absence of mass growth in the range of distances under consideration, gives us grounds to conclude that the entire mass of the Local Group is confined within the virial radii around its two main galaxies. The barycenter, found from the minimal scatter of mass estimates, corresponds to the mass ratio of the Milky Way and the Andromeda Galaxy equal to MMW/MM31 = 0.74 ± 0.10. The velocity of our Galaxy to the barycenter turns out to be 62.6 ± 2.6 km s–1. This allows us to determine the apex of the Sun relative to the barycenter of the Local Group to be (l, b, V) = (+94.0° ±0.7° , - 2.7° ±0.3° ,301 ± 3 km s–1) in Galactic coordinates.

Abstract Copyright: © The Authors 2025

Journal keyword(s): Local Group - dark matter

Simbad objects: 42

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Number of rows : 42
N Identifier Otype ICRS (J2000)
RA 		ICRS (J2000)
DEC 		Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2026 		#notes
1 NAME Andromeda XVIII G 00 02 14.5 +45 05 20     16.0     ~ 129 0
2 NAME Cetus Dwarf Galaxy G 00 26 10.8 -11 03 14     13.2     ~ 257 0
3 M 31 AGN 00 42 44.330 +41 16 07.50 4.86 4.36 3.44     ~ 13622 1
4 NAME M31 Group GrG 00 47 28.6 +40 17 23           ~ 65 0
5 NGC 253 SyG 00 47 33.134 -25 17 19.68   8.03   6.94 8.1 ~ 3588 2
6 IC 1613 GiC 01 04 48.4071 +02 07 10.185   10.42 10.01 9.77   ~ 1316 2
7 NAME Tri III G 01 21 40.5 +26 23 24           ~ 9 0
8 M 33 GiG 01 33 50.8965749232 +30 39 36.630403128 6.17 6.27 5.72     ~ 6226 1
9 NAME Phoenix Dwarf Galaxy Sy1 01 51 06.3 -44 26 41   13.48 13.2 12.69   ~ 575 2
10 LEDA 9140 G 02 24 40.9 -73 30 48   16.0       ~ 41 0
11 NAME Andromeda XXXIII G 03 01 23.6 +40 59 18           ~ 43 0
12 NAME Eridanus II G 03 44 21.1 -43 32 00           ~ 216 0
13 IC 342 AGN 03 46 48.514 +68 05 45.98   10.5       ~ 1579 1
14 NAME LMC G 05 23 34.6 -69 45 22     0.4     ~ 19090 0
15 Z 264-88 AG? 09 16 02.0195908968 +52 50 42.051257412   14.0 13.2     ~ 141 0
16 NAME Leo K Dwarf Galaxy LSB 09 24 06.1 +16 30 38           ~ 8 0
17 NAME Leo T G 09 34 53.4 +17 03 05     15.1     ~ 434 0
18 NAME Antlia B G 09 48 56.08 -25 59 24.0           ~ 41 0
19 M 81 Sy2 09 55 33.1726556496 +69 03 55.062505368   7.89 6.94     ~ 4725 3
20 Z 153-10 G 09 59 26.46 +30 44 47.0 14.08 13.54 13.26 13.33   ~ 652 0
21 NGC 3109 AG? 10 03 06.877 -26 09 34.46 11.10 10.42 10.04 9.91   ~ 825 2
22 Z 64-73 G 10 08 28.12 +12 18 23.4   11.3 10.0     ~ 1284 1
23 MCG-01-26-030 H2G 10 11 00.5 -04 41 30 12.48 12.13 11.93 11.78   ~ 789 2
24 NAME Leo M Dwarf Galaxy LSB 11 05 21.43 +25 20 43.0           ~ 8 0
25 NAME Virgo Cluster ClG 12 30 47.8 +12 23 07           ~ 7107 0
26 NAME Local Supercluster SCG 12 31 +12.4           ~ 566 0
27 M 94 SyG 12 50 53.0737971432 +41 07 12.900884628 9.15 8.96 8.24 7.78   ~ 1476 2
28 NAME Centaurus A BLL 13 25 27.61521044 -43 01 08.8050291   8.18 6.84 6.66   ~ 4774 3
29 LEDA 2801026 LSB 16 13 47.504 +54 22 08.25     15.9     ~ 115 0
30 NAME Sgr A* X 17 45 40.03599 -29 00 28.1699           ~ 4970 3
31 IRAS 18339-0714 IR 18 36 41.8 -07 12 24           ~ 7 0
32 NAME Sgr dIG G 19 29 59.0 -17 40 41   15.5 13.6     ~ 323 1
33 NGC 6822 G 19 44 56.199 -14 47 51.29   18 8.1     ~ 1661 0
34 MCG-02-53-003 G 20 46 51.7 -12 50 54 15.75 15.18 14.83 14.46   ~ 470 1
35 NAME Andromeda XXVIII G 22 32 41.20 +31 12 58.2     15.6     ~ 88 0
36 ESO 468-20 G 22 40 43.6 -30 47 55   15.88   15.13   ~ 45 0
37 NAME Tuc Galaxy G 22 41 49.6 -64 25 10   15.7 15.2     ~ 324 0
38 Z 431-72 G 23 28 35.2 +14 44 35 13.85 13.16 12.52     ~ 499 1
39 NAME Peg dSph GiG 23 51 46.3 +24 34 57   14.5 13.2     ~ 250 2
40 NAME Pegasus W Dwarf Galaxy G 23 53 14.99560 +22 06 07.0928           ~ 8 0
41 NAME Laniakea Supercluster SCG ~ ~           ~ 61 0
42 NAME Local Group GrG ~ ~           ~ 9325 0

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