2021A&A...646A..16R


Query : 2021A&A...646A..16R

2021A&A...646A..16R - Astronomy and Astrophysics, volume 646A, 16-16 (2021/2-1)

Discovery of O stars in the tidal Magellanic Bridge. Stellar parameters, abundances, and feedback of the nearest metal-poor massive stars and their implication for the Magellanic System ecology.

RAMACHANDRAN V., OSKINOVA L.M. and HAMANN W.-R.

Abstract (from CDS):

The Magellanic Bridge, stretching between the Small and the Large Magellanic Cloud (SMC and LMC), is the nearest tidally stripped intergalactic environment. The Bridge has a significantly low average metallicity of Z≤0.1Z. Here we report the first discovery of O-type stars in the Magellanic Bridge. Three massive O stars were identified thanks to the archival spectra obtained by the ESO's Very Large Telescope FLAMES instrument. We analyze the spectra of each star using the Potsdam Wolf-Rayet (PoWR) non-local thermodynamic equilibrium model atmosphere code, which provides the physical parameters, ionizing photon fluxes, and surface abundances. The ages of the newly discovered O stars suggest that star formation in the Bridge is ongoing. Furthermore, the discovery of O stars in the Bridge implies that tidally stripped galactic tails containing low-density but highly dynamical gas are capable of producing massive O stars. The multi-epoch spectra indicate that all three O stars are binaries. Despite their spatial proximity to one another, these O stars are chemically distinct. One of them is a fast-rotating giant with nearly LMC-like abundances. The other two are main-sequence stars that rotate extremely slowly and are strongly metal depleted. We discover the most nitrogen-poor O star known to date. Taking into account the previous analyses of B stars in the Bridge, we interpret the various metal abundances as the signature of a chemically inhomogeneous interstellar medium (ISM), suggesting that the Bridge gas might have accreted during multiple episodes of tidal interaction between the Clouds. Attributing the lowest derived metal content to the primordial gas, the time of the initial formation of the Bridge may date back several billion years. Using the Gaia and Galex color-magnitude diagrams, we roughly estimate the total number of O stars in the Bridge and their total ionizing radiation. Comparing this with the energetics of the diffuse ISM, we find that the contribution of the hot stars to the ionizing radiation field in the Bridge is less than 10% and conclude that the main sources of ionizing photons are leaks from the LMC and SMC. We estimate a lower limit for the fraction of ionizing radiation that escapes from these two dwarf galaxies.

Abstract Copyright: © ESO 2021

Journal keyword(s): stars: massive - stars: fundamental parameters - stars: abundances - Magellanic Clouds - techniques: spectroscopic - stars: atmospheres

Simbad objects: 17

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Number of rows : 17
N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2022
#notes
1 NAME SMC G 00 52 38.0 -72 48 01   2.79 2.2     ~ 10197 1
2 NGC 346 Cl* 00 59 05.090 -72 10 33.24           ~ 459 0
3 DEM S 160 HII 01 23 22.4 -73 21 59           ~ 6 0
4 DEM S 167 HII 01 29 09.9 -73 24 50           ~ 15 0
5 DEM S 169 HII 02 11 07 -74 09.9           ~ 5 0
6 [DI91] 719 * 02 11 55.0316078496 -74 12 37.098702756   14.83 15.24     ~ 2 0
7 Gaia EDR3 4637562032451492608 * 02 12 04.8203745744 -74 11 57.706054728           ~ 1 0
8 DEM S 168 HII 02 12 24 -74 11.0           ~ 5 0
9 [MSZ2003] 105 sh 02 13 39 -73 51.7           ~ 2 0
10 [DI91] 842 * 02 14 11.8544083536 -74 04 42.808802772   13.98 14.26     ~ 2 0
11 IDK B005 HS* 02 57 11.8275811104 -72 52 54.184544508 13.04 14.09 14.30 14.55   sdB+F 20 0
12 NAME Magellanic Clouds GrG 03 00 -71.0           ~ 6280 1
13 NAME Magellanic Bridge HI 03 11 -77.5           ~ 381 1
14 NAME LMC G 05 23 34.6 -69 45 22     0.4     ~ 15993 1
15 NAME Sex A H2G 10 11 00.5 -04 41 30 12.48 12.13 11.93 11.78   ~ 690 2
16 NAME Leo P BiC 10 21 45.123 +18 05 16.89           ~ 184 0
17 NAME Sgr dIG G 19 29 59.0 -17 40 41   15.5 13.6     ~ 291 1

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2022.05.24-10:48:27

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