| Type |
Conference Paper |
| Names |
Alex S. Hill, R. J. Reynolds, R. A. Benjamin, L. M. Haffner |
| Conference Name |
Bulletin of the American Astronomical Society |
| Volume |
38 |
| Pages |
923 |
| Date |
December 1, 2006 |
| URL |
http://adsabs.harvard.edu/abs/2006AAS...209.1723H |
| Library Catalog |
NASA ADS |
| Abstract |
Observations of Hα emission measures and pulsar dispersion
measures at high Galactic latitude (|b| > 10°) provide
information about the density and distribution of the diffuse warm
ionized medium (WIM). We use data from the Wisconsin H-Alpha Mapper
(WHAM) Northern Sky Survey. We have removed sightlines that intersect
classical HII regions, leaving a sample of only the diffuse WIM. The
diffuse WIM has a lognormal distribution of EM sin |b|, which is
consistent with a density structure established by isothermal
turbulence. A comparison of pulsar dispersion measures with emission
measures shows that the H+ responsible for most of the emission along
high-EM sightlines is clumped in high density (> 0.2 cm^-3) regions
that occupy only of order 10 parsecs along the line of sight and
contribute little to the total H+ column density, while the H+ along
low-EM sightlines occupies hundreds of parsecs with densities of 0.03
0.1 cm^-3. We find an approximate power law relationship between local
density of the gas and occupation length.
WHAM is supported by NSF grant AST 02-04973. |