2018AJ....155..233I


Query : 2018AJ....155..233I

2018AJ....155..233I - Astron. J., 155, 233-233 (2018/June-0)

Smooth H I low column density outskirts in nearby galaxies.

IANJAMASIMANANA R., WALTER F., DE BLOK W.J.G., HEALD G.H. and BRINKS E.

Abstract (from CDS):

The low column density gas at the outskirts of galaxies as traced by the 21 cm hydrogen line emission (H I) represents the interface between galaxies and the intergalactic medium, i.e., where galaxies are believed to get their supply of gas to fuel future episodes of star formation. Photoionization models predict a break in the radial profiles of H I at a column density of ∼5 x 1019 cm–2 due to the lack of self-shielding against extragalactic ionizing photons. To investigate the prevalence of such breaks in galactic disks and to characterize what determines the potential edge of the H I disks, we study the azimuthally averaged H I column density profiles of 17 nearby galaxies from the H I Nearby Galaxy Survey and supplemented in two cases with published Hydrogen Accretion in LOcal GAlaxieS data. To detect potential faint H I emission that would otherwise be undetected using conventional moment map analysis, we line up individual profiles to the same reference velocity and average them azimuthally to derive stacked radial profiles. To do so, we use model velocity fields created from a simple extrapolation of the rotation curves to align the profiles in velocity at radii beyond the extent probed with the sensitivity of traditional integrated H I maps. With this method, we improve our sensitivity to outer-disk H I emission by up to an order of magnitude. Except for a few disturbed galaxies, none show evidence of a sudden change in the slope of the H I radial profiles: the alleged signature of ionization by the extragalactic background.

Abstract Copyright: © 2018. The American Astronomical Society. All rights reserved.

Journal keyword(s): galaxies: evolution - galaxies: halos - galaxies: ISM - radio lines: 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 - 2021
#notes
1 M 33 GiG 01 33 50.904 +30 39 35.79 6.17 6.27 5.72     ~ 5340 1
2 NGC 925 H2G 02 27 16.913 +33 34 43.97   10.69 10.12 9.55   ~ 718 1
3 NGC 2366 H2G 07 28 51.85 +69 12 31.1 12.25 11.86 11.39 11.33   ~ 717 0
4 NGC 2403 AGN 07 36 51.396 +65 36 09.17 9.31 8.84 8.38 8.19   ~ 1654 1
5 NGC 2841 LIN 09 22 02.655 +50 58 35.32 10.43 10.09 9.22     ~ 1013 1
6 NGC 2905 H2G 09 32 10.111 +21 30 02.99 10.44 9.75 9.07 8.68   ~ 1027 3
7 NGC 2976 GiP 09 47 15.458 +67 54 58.97 11.77 11.03 10.16 9.51   ~ 604 1
8 M 81 Sy2 09 55 33.17306143 +69 03 55.0609270   7.89 6.94     ~ 4078 5
9 M 82 IG 09 55 52.430 +69 40 46.93 9.61 9.30 8.41     ~ 5478 6
10 NGC 3077 GiP 10 03 19.0965510921 +68 44 01.556166166 11.23 10.85 10.14 9.74   ~ 707 0
11 NGC 3198 EmG 10 19 54.990 +45 32 58.88 10.83 10.87 10.33     ~ 839 1
12 IC 2574 G 10 28 23.6204574649 +68 24 43.441365350 11.70 11.07 10.87 10.74   ~ 618 1
13 NGC 3521 LSB 11 05 48.5676206040 -00 02 09.228156576 10.06 9.83 9.02 10.1 9.6 ~ 733 2
14 NGC 3621 AGN 11 18 16.300 -32 48 45.36 10.10 9.44 9.56 8.07 10.1 ~ 509 3
15 M 66 GiP 11 20 15.026 +12 59 28.64 9.85 9.65 8.92     ~ 1213 4
16 M 94 SyG 12 50 53.148 +41 07 12.55 9.15 8.96 8.24 7.78   ~ 1268 2
17 UGC 8024 GiC 12 54 05.248 +27 08 58.67 14.37 14.23 13.95 13.84   ~ 551 1
18 M 64 SyG 12 56 43.696 +21 40 57.57   9.36 8.52     ~ 845 2
19 M 63 LIN 13 15 49.2738527699 +42 01 45.726078017   9.34 8.59 8.35   ~ 1105 2
20 M 83 SBG 13 37 00.919 -29 51 56.74 8.85 8.11 7.52 7.21   ~ 2316 2
21 NGC 6946 H2G 20 34 52.332 +60 09 13.24   10.5       ~ 2325 2
22 NGC 7331 LIN 22 37 04.102 +34 24 57.31 10.65 10.35 9.48     ~ 1145 2
23 NGC 7793 GiG 23 57 49.7533807411 -32 35 27.708304655 10.26 9.74 9.28 9.06 9.7 ~ 976 2

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2021.09.19-06:10:25

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