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High Velocity Gas in the Halos of Spiral Galaxies

Published online by Cambridge University Press:  26 May 2016

Filippo Fraternali ,
Tom Oosterloo ,
Rense Boomsma ,
Rob Swaters  and
Renzo Sancisi
Filippo Fraternali
Affiliation:
ASTRON, Dwingeloo, The Netherlands
Tom Oosterloo
Affiliation:
ASTRON, Dwingeloo, The Netherlands
Rense Boomsma
Affiliation:
Kapteyn Institute, Groningen, The Netherlands
Rob Swaters
Affiliation:
Johns Hopkins University, Baltimore, USA
Renzo Sancisi
Affiliation:
INAF, Osserv. Astron. Bologna, I & Kapteyn Institute, Groningen, The Netherlands

Abstract

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Recent, high sensitivity, HI observations of nearby spiral galaxies show that their thin ‘cold’ disks are surrounded by thick layers (halos) of neutral gas with anomalous kinematics. We present results for three galaxies viewed at different inclination angles: NGC 891 (edge-on), NGC 2403 (i=60°), and NGC 6946 (almost face-on). These studies show the presence of halo gas up to distances of 10-15 kpc from the plane. Such gas has a mean rotation 25-50 km s−1 lower than that of the gas in the plane, and some complexes are detected at very high velocities, up to 200-300 km s−1. The nature and origin of this halo gas are poorly understood. It can either be the result of a galactic fountain or of accretion from the intergalactic medium. It is probably analogous to some of the High Velocity Clouds (HVCs) of the Milky Way.

Type
Part 2. Origin
Information
Symposium - International Astronomical Union , Volume 217: Recycling Intergalactic and Interslettar Matter , 2004 , pp. 136 - 141
Copyright
Copyright © Astronomical Society of the Pacific 2004 

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