A Survey of O VI, C III, and H I in Highly Ionized High-Velocity Clouds

Details A Survey of O VI, C III, and H I in Highly Ionized High-Velocity Clouds A Survey of O VI, C III, and H I in Highly Ionized High-Velocity Clouds

2006-04-05

arxiv.org/abs/astro-ph/0604091v1

Astronomy and Astrophysics

Astrophysics

36 pages, 14 figures (3 in color), accepted to ApJS. Some figures downgraded to limit file size

Scientific paper

10.1086/504800

(ABRIDGED) We present a Far-Ultraviolet Spectroscopic Explorer survey of highly ionized high-velocity clouds (HVCs) in 66 extragalactic sight lines. We find a total of 63 high-velocity O VI absorbers, 16 with 21 cm-emitting H I counterparts and 47 ``highly ionized'' absorbers without 21 cm emission. 11 of these high-velocity O VI absorbers are positive-velocity wings (broad O VI features extending asymmetrically to velocities of up to 300 km/s). The highly ionized HVC population is characterized by =38+/-10 km/s and =13.83+/-0.36. We find that 81% (30/37) of high-velocity O VI absorbers have clear accompanying C III absorption, and 76% (29/38) have accompanying H I absorption in the Lyman series. The lower average width of the high-velocity H I absorbers implies the H I lines arise in a separate, lower temperature phase than the O VI. We find that the shape of the wing profiles is well reproduced by a radiatively cooling, vertical outflow. However, the outflow has to be patchy and out of ionization equilibrium. An alternative model, consistent with the observations, is one where the highly ionized HVCs represent the low N(H I) tail of the HVC population, with the O VI formed at the interfaces around the embedded H I cores. Though we cannot rule out a Local Group explanation, we favor a Galactic origin. This is based on the recent evidence that both H I HVCs and the million-degree gas detected in X-ray absorption are Galactic phenomena. Since the highly ionized HVCs appear to trace the interface between these two Galactic phases, it follows that highly ionized HVCs are Galactic themselves. However, the non-detection of high-velocity O VI in halo star spectra implies that any Galactic high-velocity O VI exists at z-distances beyond a few kpc.

Affiliated with

Also associated with

No associations

Rating

A Survey of O VI, C III, and H I in Highly Ionized High-Velocity Clouds does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.

If you have personal experience with A Survey of O VI, C III, and H I in Highly Ionized High-Velocity Clouds, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and A Survey of O VI, C III, and H I in Highly Ionized High-Velocity Clouds will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-418052