Year: 1998
Type: preprint
Abstract: Optical emission lines provide an important new window on the HVCs. Recent studies of the H-alpha line reveal that ionized gas is pervasively associated with the neutral hydrogen in HVCs. The Wisconsin H-Alpha Mapper (WHAM) instrument has so far detected H-alpha from high-velocity clouds in the M, A, and C complexes. We find a close spatial correspondence between the neutral and ionized portions of the HVCs with some evidence that the ionized gas envelopes the neutral part of the clouds. The velocities of the H-alpha and 21-cm detections are well correlated, but the intensities are not. If the clouds are photoionized, the H-alpha intensity is a direct measure of the Lyman continuum flux in the Galactic halo. Forthcoming observations of the H-alpha line in combination with other emission lines will give new insights into the high-velocity cloud phenomena and will also probe the physical conditions of their environment.
Source: arXiv (Cornell University)
Authors: Tufte, S. L., Reynolds, R. J., Haffner, L. M.
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W1949538099