2019A&A...627A..20B


Query : 2019A&A...627A..20B

2019A&A...627A..20B - Astronomy and Astrophysics, volume 627A, 20-20 (2019/7-1)

A population of high-velocity absorption-line systems residing in the Local Group.

BOUMA S.J.D., RICHTER P. and FECHNER C.

Abstract (from CDS):

Aims. We investigated the ionisation conditions and distances of Galactic high-velocity clouds (HVCs) in the Galactic halo and beyond in the direction of the Local Group (LG) barycentre and anti-barycentre, by studying spectral data of 29 extragalactic background sources obtained with the Cosmic Origins Spectropgraph (COS) installed on the Hubble Space Telescope (HST). Methods. We model column-densities of low, intermediate, and high ions such as SiII, CII, SiIII, SiVI, and CIV, and use these data to construct a set of Cloudy ionisation models. Results. In total, we found 69 high-velocity absorption components along the 29 lines of sight. The components in the direction of the LG barycentre span the entire range of studied velocities, 100≤|vLSR|≤400km/s, while those in the anti-barycentre sample have velocities up to about 300km/s. For 49 components, we infer the gas densities. In the direction of the LG barycentre, the gas densities exhibit a wide range from log nH=-3.96 to -2.55, while in the anti-barycentre direction the densities are systematically higher, lognH>-3.25. The barycentre absorbers can be split into two groups based on their density: a high-density group with log nH>-3.54, which can be affected by the Milky Way radiation field, and a low-density group (lognH←3.54). The latter has very low thermal pressures of P/k<7.3K/cm3. Conclusions. Our study shows that part of the absorbers in the LG barycentre direction trace gas at very low gas densities and thermal pressures. These properties indicate that the absorbers are located beyond the virial radius of the Milky Way. Our study also confirms results from earlier, single-sightline studies, suggesting the presence of a metal-enriched intragroup medium filling the LG near its barycentre.

Abstract Copyright: © ESO 2019

Journal keyword(s): Galaxy: halo - Galaxy: structure - Galaxy: evolution - ISM: kinematics and dynamics - techniques: spectroscopic - ultraviolet: ISM

Simbad objects: 37

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Number of rows : 37
N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2024
#notes
1 ICRF J000559.2+160949 Sy1 00 05 59.2378545384 +16 09 49.021968096   16.51 16.40     ~ 291 1
2 Mrk 335 Sy1 00 06 19.5372339024 +20 12 10.617404076   14.19 13.85     ~ 1255 0
3 2MASX J00122399-1022269 Sy1 00 12 24.0235889448 -10 22 26.551199748   17.59 17.25     ~ 58 0
4 LEDA 1790 Sy1 00 29 13.7012449608 +13 16 03.947778264   15.70 15.41     ~ 446 0
5 NAME Magellanic Stream HVC 00 32 -30.0           ~ 973 1
6 LEDA 3095439 Sy1 00 36 23.0055058008 +43 16 40.155340080   17.2       ~ 17 0
7 PB 8488 QSO 00 42 22.2911404848 -10 37 43.821166980   16.83 16.61     ~ 44 0
8 M 31 AGN 00 42 44.330 +41 16 07.50 4.86 4.36 3.44     ~ 12678 1
9 2MASS J00481898+3941116 Sy1 00 48 18.9838647792 +39 41 11.718147912   16.2       ~ 54 0
10 2MASS J01013117+4229356 Sy1 01 01 31.1691112200 +42 29 35.590782768   16.7       ~ 23 0
11 LBQS 0107-0235 QSO 01 10 13.1603515272 -02 19 52.838715144   18.39 17.80 17.61   ~ 91 1
12 NAME Magellanic Clouds GrG 03 00 -71.0           ~ 7084 0
13 NAME HVC Complex A HVC 08 36 +64.4           ~ 133 0
14 QSO J1216+0712 QSO 12 16 40.5697104672 +07 12 24.225610932   16.95 16.91     ~ 39 0
15 RMB 221 Sy1 12 18 50.5204079496 +10 15 54.283624488   17.76 17.63     ~ 48 0
16 2MASS J12201843+0641196 Sy1 12 20 18.4414889616 +06 41 19.609635012   17.67 17.49     ~ 48 0
17 2MASSI J1221024+155446 Sy1 12 21 02.5018070808 +15 54 47.033436960   18.55 18.09     ~ 44 0
18 RMB 219 Sy1 12 23 12.1662684816 +09 50 17.776788360   18.36 18.12     ~ 37 0
19 2MASS J12231781+0923066 Sy1 12 23 17.7936603552 +09 23 06.953012232   17.83 17.74     ~ 54 0
20 2MASS J12305003+0115226 Sy1 12 30 50.0331165552 +01 15 22.598028288   14.44 14.42     ~ 98 0
21 LBQS 1230-0015 QSO 12 33 04.0514120328 -00 31 34.179576564   18.02 17.87 16.8   ~ 74 0
22 QSO J1234+0724 QSO 12 34 26.8071006240 +07 24 11.316291516   16.7 17.41 16.3   ~ 27 0
23 QSO J1315+1525 QSO 13 15 45.2115924624 +15 25 56.328044052   17.80 17.67     ~ 39 0
24 NAME HVC Complex C HVC 16 34.8 +63 07           ~ 260 1
25 NAME Galactic Center reg 17 45 39.60213 -29 00 22.0000           ~ 14463 0
26 Mrk 509 Sy1 20 44 09.7504483224 -10 43 24.727155528   13.35 13.12 10.7   ~ 1279 0
27 Mrk 1513 Sy1 21 32 27.8162556672 +10 08 19.252365396   14.92 14.64     ~ 614 0
28 NAME Outer Arm PoG 21 48 +69.4           ~ 319 0
29 PHL 1811 Sy1 21 55 01.5124437432 -09 22 24.349496808   13.9 16.8 14.1   ~ 187 1
30 QSO B2155-304 BLL 21 58 52.0652249880 -30 13 32.118447792   13.36 13.09 12.62   ~ 1739 1
31 Mrk 304 Sy1 22 17 12.2637639888 +14 14 20.917852980   15.02 14.66     ~ 356 0
32 UGC 12163 Sy1 22 42 39.3363009144 +29 43 31.302092640   14.86 14.16     ~ 699 1
33 3C 454.3 Bla 22 53 57.7480438728 +16 08 53.561508864   16.57 16.10 15.22   ~ 2856 2
34 NAME MR 2251-178 Sy1 22 54 05.8858611984 -17 34 55.402233708   14.99 14.36 15.12   ~ 436 3
35 QSO J2257+1340 QSO 22 57 38.2067032296 +13 40 45.501519396   17.25 17.15     ~ 45 0
36 NGC 7469 Sy1 23 03 15.6 +08 52 26 12.60 13.00 12.34     ~ 2101 3
37 NAME Local Group GrG ~ ~           ~ 8415 0

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