2010A&A...515A..63O


Query : 2010A&A...515A..63O

2010A&A...515A..63O - Astronomy and Astrophysics, volume 515, A63-63 (2010/6-1)

The dark matter halo shape of edge-on disk galaxies. IV. UGC 7321.

O'BRIEN J.C., FREEMAN K.C. and VAN DER KRUIT P.C.

Abstract (from CDS):

This is the fourth paper in a series in which we attempt to put constraints on the flattening of dark halos in disk galaxies. We observed for this purpose the HI in edge-on galaxies, where it is in principle possible to measure the force field in the halo vertically and radially from gas layer flaring and rotation curve decomposition respectively. As reported in earlier papers in this series we have for this purpose analysed the HI channel maps to accurately measure all four functions that describe as a function of galactocentric radius the planar HI kinematics and 3D HI distribution of a galaxy: the radial HI surface density, the HI vertical thickness, the rotation curve and the HI velocity dispersion. In this paper we analyse these data for the edge-on galaxy UGC 7321. We measured the stellar mass distribution (M=3x108M with M/LR≲0.2), finding that the vertical force of the gas disk dominates the stellar disk at all radii. Measurements of both the rotation curve and the vertical force field showed that the vertical force puts a much stronger constraint on the stellar mass-to-light ratio than rotation curve decomposition. Fitting of the vertical force field derived from the flaring of the HI layer and HI velocity dispersion revealed that UGC 7321 has a spherical halo density distribution with a flattening of q=c/a=1.0±0.1. However, the shape of the vertical force field showed that a non-singular isothermal halo was required, assuming a vertically isothermal HI velocity dispersion. A pseudo-isothermal halo and a gaseous disk with a declining HI velocity dispersion at high latitudes may also fit the vertical force field of UGC 7321, but to date there is no observational evidence that the HI velocity dispersion declines away from the galactic plane. We compare the halo flattening of UGC 7321 with other studies in the literature and discuss its implications. Our result is consistent with new n-body simulations which show that inclusion of hydrodynamical modelling produces more spherical halos.

Abstract Copyright:

Journal keyword(s): galaxies: structure - galaxies: kinematics and dynamics - galaxies: halos - galaxies: ISM

Simbad objects: 23

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Number of rows : 23
N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2023
#notes
1 NAME Magellanic Stream HVC 00 32 -30.0           ~ 917 1
2 M 31 G 00 42 44.330 +41 16 07.50 4.86 4.36 3.44     ~ 12022 1
3 NAME SMC G 00 52 38.0 -72 48 01   2.79 2.2     ~ 10458 1
4 M 74 G 01 36 41.7451236624 +15 47 01.107512304 10.52 10.00 9.46 9.16   ~ 1595 1
5 2MASX J01385522-0745553 GiC 01 38 55.2336829296 -07 45 55.565640144   15.62       ~ 69 0
6 NAME Sagittarius Stream St* 02 22 +00.0           ~ 789 0
7 NGC 891 H2G 02 22 32.907 +42 20 53.95 11.08 10.81 9.93 7.86   ~ 1607 2
8 ESO 415-26 G 02 28 20.1024142368 -31 52 51.628774224   14.6   13.14   ~ 74 0
9 NAME LMC G 05 23 34.6 -69 45 22     0.4     ~ 16400 1
10 NGC 2905 H2G 09 32 10.111 +21 30 02.99 10.44 9.75 9.07 8.68   ~ 1067 3
11 NGC 4013 GiG 11 58 31.417 +43 56 49.28   12.4       ~ 403 1
12 NGC 4244 GiG 12 17 29.659 +37 48 25.60   10.71   9.99   ~ 538 1
13 UGC 7321 EmG 12 17 34.021 +22 32 23.35   14.07   13.21   ~ 244 0
14 NGC 4565 LIN 12 36 20.804 +25 59 14.61   13.61 12.43     ~ 924 0
15 ESO 322-69 GiG 12 44 49.0352044176 -40 42 51.691570488   14.12 13.58 13.29 13.9 ~ 190 0
16 NGC 4753 GiG 12 52 22.112 -01 11 58.88 11.26 10.85 9.95     ~ 265 1
17 UGC 8024 GiC 12 54 05.248 +27 08 58.67 14.37 14.23 13.95 13.84   ~ 568 1
18 NGC 5023 EmG 13 12 11.8036148808 +44 02 17.328663600   13.2       ~ 240 0
19 ESO 274-1 G 15 14 13.429 -46 48 33.12   12.00   10.97 11.3 ~ 100 0
20 NAME Galactic Center reg 17 45 39.60213 -29 00 22.0000           ~ 13320 0
21 NAME SDG G 18 55 03.1 -30 28 42   4.5 3.6     ~ 2017 2
22 2MASX J20235495-5039063 GiG 20 23 54.9120351168 -50 39 06.848951112   14.72   13.59   ~ 56 0
23 NAME Galactic Bulge reg ~ ~           ~ 3967 0

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2022.12.01-20:19:19

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