2000A&A...361..500H


C.D.S. - SIMBAD4 rel 1.7 - 2019.12.16CET00:17:08

2000A&A...361..500H - Astronomy and Astrophysics, volume 361, 500-506 (2000/9-2)

Extensive molecular gas in the tidal arms near NGC 3077 - birth of a dwarf galaxy?

HEITHAUSEN A. and WALTER F.

Abstract (from CDS):

Using the IRAM 30m radio telescope we have mapped the tidal arm feature south-east of NGC 3077 where we recently detected molecular gas in the CO (J=1-0) and (2-1) transitions. We find that the molecular gas is much more extended than previously thought (several kpc). The CO emission can be separated into at least 3 distinct complexes with equivalent radii between 250pc and 700pc and all well confined over a narrow range in velocity - the newly detected complexes therefore range among the largest molecular complexes in the local universe. For one complex we have also obtained a CO (3-2) spectrum using the KOSMA 3m radio telescope; utilizing an LVG model we find that the kinetic temperature for this complex must be about 10K, and the H2 volume density between 600 and 10000cm–3. Mass estimates based on virialization yield a total mass for the complexes of order 2-4x107M, i.e. more than the estimated molecular mass within NGC 3077 itself. This implies that interactions between galaxies can efficiently remove heavy elements and molecules from a galaxy and enrich the intergalactic medium. A comparison of the distribution of HI and CO shows no clear correlation. However, CO is only found in regions where the HI column density exceeds 1.1x1021cm–2. HI masses for the molecular complexes mapped are of the same order as the corresponding molecular masses. Because the intergalactic pressure is most likely too low to confine the complexes we conclude that they are gravitationally bound. Since the tidal arm with its molecular complexes has all the ingredients to form stars in the future, we are thus presumably witnessing the birth of a dwarf galaxy. This process could be important for the formation of dwarf galaxies especially at larger look-back times in the universe where galaxy interactions may have been more frequent.

Abstract Copyright:

Journal keyword(s): ISM: molecules - galaxies: dwarf - galaxies: formation - galaxies: individual: NGC 3077 - galaxies: ISM - radio lines: ISM

Nomenclature: Table 1: [HW2000] N (Nos 1-4).

Simbad objects: 18

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Number of rows : 18

N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2020
#notes
1 NGC 185 Sy2 00 38 57.970 +48 20 14.56   9.10 9.2     ~ 714 1
2 M 110 GiG 00 40 22.0544552438 +41 41 07.496294862   8.92 8.07     ~ 1186 1
3 M 31 G 00 42 44.330 +41 16 07.50 4.86 4.36 3.44     ~ 10616 1
4 NAME LMC G 05 23 34.6 -69 45 22     0.4     ~ 14392 1
5 RMC 136 Cl* 05 38 42.396 -69 06 03.36   9.63 9.50     ~ 1681 2
6 NGC 2782 Sy2 09 14 05.120 +40 06 49.68 12.29 12.30 11.63     ~ 429 3
7 M 81 Sy2 09 55 33.17306143 +69 03 55.0609270   7.89 6.94     ~ 3901 5
8 M 82 IG 09 55 52.430 +69 40 46.93 9.61 9.30 8.41     ~ 5239 6
9 NAME Molecular Complex in NGC 3077 ? 10 03 14 +68 44.0           ~ 2 0
10 NGC 3077 GiP 10 03 19.0965510921 +68 44 01.556166166 11.23 10.85 10.14 9.74   ~ 672 0
11 [HW2000] 2 Cld 10 03 56.0 +68 40 52           ~ 1 0
12 [HW2000] 1 Cld 10 03 56.0 +68 42 42           ~ 1 0
13 [HW2000] 3 Cld 10 04 16.5 +68 42 12           ~ 1 0
14 [HW2000] 4 Cld 10 04 32.8 +68 42 42           ~ 1 0
15 NGC 4038 GiP 12 01 53.002 -18 52 03.32   10.91   9.74 11.0 ~ 1265 1
16 NAME Antennae IG 12 01 53.170 -18 52 37.92           ~ 1537 0
17 NGC 4039 GiP 12 01 53.8 -18 53 06   11.08   9.77   ~ 1124 1
18 NGC 4438 LIN 12 27 45.652 +13 00 30.92 11.37 11.02 10.17     ~ 565 3

    Equat.    Gal    SGal    Ecl

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2019.12.16-00:17:08

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