1994A&A...291..425V -
Astronomy and Astrophysics, volume 291, 425-438 (1994/11-2)
Interstellar and intergalactic gas towards SN1993J in M81: a study of optical and 21cm spectra.
VLADILO G., CENTURION M., DE BOER K.S., KING D.L., LIPMAN K., STEGERT J.S.W., UNGER S.W. and WALTON N.A.
Abstract (from CDS):
We present a study of the interstellar and intergalactic clouds located in the direction of the recent supernova 1993J in M81 based on the analysis of optical and 21cm spectra obtained during the first nights after its discovery. The optical spectra were taken at high spectral resolution (FWHM 4 to 6km/s) using the 4.2m William Herschel Telescope (La Palma, Spain), covering the resonance lines of CN, CaII, CaI, CH+, CH, NaI, LiI and KI. We also observed in CaII a sample of foreground Galactic stars in the field of the supernova. The 21cm spectra were taken with the 100 m Effelsberg Radiotelescope (beam FWHM≃9') at the position of SN1993J and in 6 positions around the supernova, at 10' separation. We find numerous absorption lines in the velocity range -139km/s<vlsr<+172km/s, which fall into 3 distinct groups, representing absorption by gas within our Galaxy and its halo, within M81 itself and in the intergalactic space within the M 81 group of galaxies. The nearby clouds, close to rest velocity, are located at d≃100 pc, beyond a low density region of the local interstellar medium; one of these belongs to the population of high-latitude molecular clouds. In the lower halo of our Galaxy (0.5kpc≲d≲3kpc) we find gas at vlsr≃-50 km/s with low depletion, local interstellar abundance and relatively cold temperature; these properties make this cloud a good candidate for cooling gas in a galactic fountain model. In the interstellar gas of M81 we find two components with properties of cold gas near rest velocity with respect to the rotating disk of that galaxy. We also detect two low density components at -110km/s and -100km/s which probably represent gas infalling at moderate velocity onto the disk of M81. We do not find evidence of neutral gas outflowing from the disk. The group of intergalactic absorptions falls in the range +125km/s≤vlsr≤+172km/s. Two of these components show properties of cold, metal-rich gas and are detected in KI and CaI, the first detections of this type in intergalactic space. The other intergalactic components have low density and originate in warm gas. This complex of gas is most likely the result of a smooth tidal interaction of M81 with a companion galaxy of its group. Kinematical considerations suggest that the material does not arise from M81 but probably from M82. The presence of a stellar component co-existing with such intergalactic structure is consistent with our data.
Abstract Copyright:
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Journal keyword(s):
Galaxy: halo - galaxies: individual: M 81 - ISM: intergalactic: medium - ISM: general - supernovae: individual: SN 1993J
Simbad objects:
11
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