1995A&A...293..703M -
Astronomy and Astrophysics, volume 293, 703-709 (1995/1-3)
The outflow in the halo of M 82.
McKEITH C.D., GREVE A., DOWNES D. and PRADA F.
Abstract (from CDS):
New observations of emission and absorption lines along M 82's minor axis yield detailed radial velocity-position curves tracing the blowout of the superwind from the starburst region. The new velocity data provide good evidence for the acceleration of the wind in the energy input region (z<300pc), for the wind becoming supersonic about 300pc above and below the galactic plane, and tending to a constant velocity in the free wind zone at z>300pc. Inflexion points in the velocity curves suggest that the blowout region has an hourglass shape, that is, the profile is cylindrical for z<300pc, and flares out to a conical shape for z>300pc. While most of the line emission comes from ionized gas moving on the surfaces of the blowout cones, some of it may be scattered, appearing near the systemic velocity. The stellar Ca II IR absorption lines appear near the systemic velocity at all distances along the minor axis. These lines may come mainly from late-type stars in the disk, with the radiation scattered by dust in the halo. Although a contribution from scattered light is definitely present, any explanation for the emission lines wholly in terms of scattered radiation from dust in a giant bipolar reflection nebula is immediately ruled out by a) the large blue shifts (-300 to -450km/s) relative to the systemic velocity of the galaxy, b) the monotonic variations of the velocity as a function of height above the galactic plane, c) the non-shifted, non-split, scattered stellar CaII IR lines, and d) the variation of the extinction-independent [SII] line ratios, which indicate a rapid decrease of electron density with height above the galactic plane. The superwind model accounts for these facts both qualtitatively and quantitatively.
Abstract Copyright:
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Journal keyword(s):
galaxies: individual: M 82 - galaxies: interstellar matter - galaxies: kinematics and dynamics - galaxies: nuclei
VizieR on-line data:
<Available at CDS (J/A+A/293/703): table2 table3>
Simbad objects:
1
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