ORIGIN(S) OF THE HIGHLY IONIZED HIGH-VELOCITY CLOUDS BASED ON THEIR DISTANCES

Journal Article · Mon Feb 01 04:00:00 EST 2010 · Astrophysical Journal Letters

DOI:https://doi.org/10.1088/2041-8205/709/2/L138; COUNTRY OF INPUT: INTERNATIONAL ATOMIC ENERGY AGENCY (IAEA)· OSTI ID:21301366

Lehner, N; Howk, J C ^[1]

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1. Department of Physics, University of Notre Dame, 225 Nieuwland Science Hall, Notre Dame, IN 46556 (United States)

Previous Hubble Space Telescope and FUSE observations have revealed highly ionized high-velocity clouds (HVCs) or more generally low H I column HVCs along extragalactic sight lines over 70%-90% of the sky. The distances of these HVCs have remained largely unknown hindering from distinguishing a 'Galactic' origin (e.g., outflow, inflow) from a 'Local Group' origin (e.g., warm-hot intergalactic medium). We present the first detection of highly ionized HVCs in the Cosmic Origins Spectrograph spectrum of the early-type star HS 1914+7134 (l = 103 deg., b = +24 deg.) located in the outer region of the Galaxy at d {approx_equal} 14.9 kpc. Two HVCs are detected in absorption at v {sub LSR} = -118 and -180 km s{sup -1} in several species, including C IV, Si IV, Si III, Al II, C II, Si II, O I, but H I 21 cm emission is only seen at -118 km s{sup -1}. Within 17 deg. of HS 1914+7134, we found HVC absorption of low and high ions at similar velocities toward five extragalactic sight lines, suggesting that these HVCs are related. The component at -118 km s{sup -1} is likely associated with the outer arm of the Milky Way. The highly ionized HVC at -180 km s{sup -1} is possibly an HVC plunging at high speed onto the thick disk of the Milky Way. This is the second detection of highly ionized HVCs toward Galactic stars, supporting a 'Galactic' origin for at least some of these low H I column density HVCs.

• OSTI ID: 21301366
• Journal Information: Astrophysical Journal Letters, Journal Name: Astrophysical Journal Letters Journal Issue: 2 Vol. 709; ISSN 2041-8205
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
99 GENERAL AND MISCELLANEOUS
ABSORPTION
COSMOLOGY
DENSITY
DISTANCE
EMISSION
MILKY WAY
SPECTRA
STARS
TELESCOPES