WHAM Observations of Hα Emission from High‐Velocity Clouds in the M, A, and C Complexes
| Autor: | Ronald J. Reynolds, L. M. Haffner, S. L. Tufte |
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| Rok vydání: | 1998 |
| Předmět: |
Physics
010504 meteorology & atmospheric sciences Astrophysics (astro-ph) FOS: Physical sciences Astronomy and Astrophysics Astrophysics Photoionization 01 natural sciences High-velocity cloud 13. Climate action Space and Planetary Science Ionization 0103 physical sciences Hydrogen line H-alpha Halo Emission spectrum 010303 astronomy & astrophysics Astrophysics::Galaxy Astrophysics 0105 earth and related environmental sciences Line (formation) |
| Zdroj: | The Astrophysical Journal. 504:773-784 |
| ISSN: | 1538-4357 0004-637X |
| Popis: | The first observations of the recently completed Wisconsin H-Alpha Mapper (WHAM) facility include a study of emission lines from high velocity clouds in the M, A, and C complexes, with most of the observations on the M I cloud. We present results including clear detections of H-alpha emission from all three complexes with intensities ranging from 0.06 R to 0.20 R. In every observed direction where there is significant high velocity H I gas seen in the 21 cm line we have found associated ionized hydrogen emitting the H-alpha line. The velocities of the H-alpha and 21 cm emission are well correlated in every case except one, but the intensities are not correlated. There is some evidence that the ionized gas producing the H-alpha emission envelopes the 21 cm emitting neutral gas but the H-alpha "halo", if present, is not large. If the H-alpha emission arises from the photoionization of the H I clouds, then the implied Lyman continuum flux F_{LC} at the location of the clouds ranges from 1.3 to 4.2 x 10^5 photons cm^{-2} s^{-1}. If, on the other hand, the ionization is due to a shock arising from the collision of the high-velocity gas with an ambient medium in the halo, then the density of the pre-shocked gas can be constrained. We have also detected the [S II] 6716 angstrom line from the M I cloud and have evidence that the [S II] to H-alpha ratio varies with location on the cloud. 32 pages, 18 figures, to appear in ApJ (Sept. 10, 1998) |
| Databáze: | OpenAIRE |
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