High Galactic Latitude Interstellar Neutral Hydrogen Structure and Associated (WMAP) High‐Frequency Continuum Emission

Abstract

Spatial associations have been found between interstellar neutral hydrogen ( H i) emission morphology and smallscale structure observed by the Wilkinson Microwave Anisotropy Probe (WMAP) in an area bounded by l ¼ 60 , 180and b ¼ 30 , 70 , which was the primary target for this study. This area is marked by the presence of highly disturbed local H i and a preponderance of intermediate-and high-velocity gas. The H i distribution toward the brightest peaks in the WMAP Internal Linear Combination (ILC) map for this area is examined, and by comparing with a second area on the sky it is demonstrated that the associations do not appear to be the result of chance coincidence. Close examination of several of the associations reveals important new properties of diffuse interstellar neutral hydrogen structure. In the case of the high-velocity cloud MI, the H i and WMAP ILC morphologies are similar, and an excess of soft X-ray emission and H emission have been reported for this feature. It is suggested that the small angular scale, highfrequency continuum emission observed by WMAP may be produced at the surfaces of H i features interacting one another, or at the interface between moving H i structures and regions of enhanced plasma density in the surrounding interstellar medium. It is possible that dust grains play a role in producing the emission. However, the primary purpose of this report is to draw attention to these apparent associations, without offering an unambiguous explanation as to the relevant emission mechanism(s).

FIVE-YEAR WILKINSON MICROWAVE ANISOTROPY PROBE OBSERVATIONS: GALACTIC FOREGROUND EMISSION

“…There has been some discussion in the literature of correlation between CMB maps and neutral hydrogen (Verschuur 2007), but this result was not found to be statistically significant (Land & Slosar 2007).…”

Tests and Problems of the Standard Model in Cosmology

“…This unknown radiation of galactic origin might take place in the surface of Galactic HI structures moving through interstellar space and/or interacting with one another [271]. The spatial association on scales of 1-2 degrees between interstellar neutral hydrogen [271], integrated in maps over ranges of 10 km/s and CMBR maps cleaned of foreground contamination through the ILC methods, is especially significant for the present discussion too. Several extended areas of excess emission at high galactic latitudes (b > 30…”

On the existence of young embedded clusters at high Galactic latitude

“…But high latitude H I gas is not uncommon. In many cases, Galactic H I clouds are coincident with warm spots in the WMAP and PLANCK surveys (Verschuur 2007), although the latter are somewhat less than 1 • in diameter, rather than the few arcminutes of the Camargo groups, and generally attributed to acoustic bubbles in the cosmic microwave background radiation (Hu & White 1996). Other mechanisms may also explain their origin (e.g., Verschuur & Schmelz 2016).…”