A HIGH-METALLICITY, HIGH-VELOCITY CLOUD ALONG THE Mrk 421 SIGHT LINE: A TRACER OF COMPLEX M?

Journal Article · Thu Feb 10 04:00:00 EST 2011 · Astrophysical Journal Letters

DOI:https://doi.org/10.1088/2041-8205/728/1/L16· OSTI ID:21560504

Yangsen, Yao; Shull, J Michael

We present a new measurement, 0.85-3.5 Z{sub sun}, of the metallicity of high-velocity cloud (HVC) Complex M by analyzing ultraviolet spectroscopic observations of the blazar Mrk 421 taken with the Cosmic Origins Spectrograph on the Hubble Space Telescope and the Far-Ultraviolet Spectroscopic Explorer. Although an HVC at V{sub LSR} = -131 km s{sup -1} is not visible in 21 cm emission (log N{sub H{sub I}} < 18.38; 3{sigma}), it is detected in ultraviolet absorption lines of C II, N I, O I, O VI, Si II, Si III, Si IV, Fe II, and H I. By referencing velocities to the intermediate-velocity cloud at -60 km s{sup -1} and jointly analyzing H I absorption from high-order H I Lyman lines, we measure log N{sub H{sub I}} = 16.84{sup +0.34}{sub -0.13} (1{sigma}) in the HVC. Comparing H I and O I, we find an HVC metallicity [O/H] =0.32{sup +0.22}{sub -0.39}. Because the sight line passes {approx}4{sup 0} from the HVCs in Complex M, the detected HVC may represent the highest velocity component of the Complex, and our measurements provide a lower limit to its metallicity. The high, possibly super-solar metallicity, together with the low distance, z < 3.5 kpc, above the Galactic plane suggests that Complex M is condensed returning gas from a Galactic fountain.

• OSTI ID: 21560504
• Journal Information: Astrophysical Journal Letters, Journal Name: Astrophysical Journal Letters Journal Issue: 1 Vol. 728; ISSN 2041-8205
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
ABSORPTION
ABUNDANCE
CLOUDS
ELECTROMAGNETIC RADIATION
ELEMENT ABUNDANCE
EMISSION
FAR ULTRAVIOLET RADIATION
LYMAN LINES
RADIATIONS
SORPTION
ULTRAVIOLET RADIATION
VELOCITY