Finding distant galactic H ii regions

Journal Article · Tue Dec 01 04:00:00 EST 2015 · Astrophysical Journal, Supplement Series

DOI:https://doi.org/10.1088/0067-0049/221/2/26· OSTI ID:22872400

Anderson, L. D.; Armentrout, W. P.; Johnstone, B. M.; Cunningham, V. ^[1]; Bania, T. M. ^[2]; Balser, Dana S. ^[3]; Wenger, Trey V. ^[4]

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1. Department of Physics and Astronomy, West Virginia University, Morgantown, WV 26506 (United States)
2. Institute for Astrophysical Research, Department of Astronomy, Boston University, 725 Commonwealth Avenue, Boston, MA 02215 (United States)
3. National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA 22903-2475 (United States)
4. Astronomy Department, University of Virginia, P.O. Box 3818, Charlottesville, VA 22903-0818 (United States)

The WISE Catalog of Galactic H ii Regions contains ∼2000 H ii region candidates lacking ionized gas spectroscopic observations. All candidates have the characteristic H ii region mid-infrared morphology of WISE 12 μm emission surrounding 22 μm emission, and additionally have detected radio continuum emission. We here report Green Bank Telescope hydrogen radio recombination line and radio continuum detections in the X-band (9 GHz; 3 cm) of 302 WISE H ii region candidates (out of 324 targets observed) in the zone 225{sup ∘}⩾ℓ⩾−20{sup ∘}, |b|⩽6{sup ∘}. Here we extend the sky coverage of our H ii region Discovery Survey, which now contains nearly 800 H ii regions distributed across the entire northern sky. We provide LSR velocities for the 302 detections and kinematic distances for 131 of these. Of the 302 new detections, 5 have (ℓ,b,v) coordinates consistent with the Outer Scutum–Centaurus Arm (OSC), the most distant molecular spiral arm of the Milky Way. Due to the Galactic warp, these nebulae are found at Galactic latitudes >1° in the first Galactic quadrant, and therefore were missed in previous surveys of the Galactic plane. One additional region has a longitude and velocity consistent with the OSC but lies at a negative Galactic latitude (G039.183−01.422; −54.9 km s{sup −1}). With Heliocentric distances >22 kpc and Galactocentric distances >16 kpc, the OSC H ii regions are the most distant known in the Galaxy. We detect an additional three H ii regions near ℓ≃150{sup ∘} whose LSR velocities place them at Galactocentric radii >19 kpc. If their distances are correct, these nebulae may represent the limit to Galactic massive star formation.

• OSTI ID: 22872400
• Journal Information: Astrophysical Journal, Supplement Series, Journal Name: Astrophysical Journal, Supplement Series Journal Issue: 2 Vol. 221; ISSN 0067-0049; ISSN APJSA2
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
CATALOGS
DETECTION
GHZ RANGE
HYDROGEN
INTERMEDIATE INFRARED RADIATION
MILKY WAY
MORPHOLOGY
NEBULAE
RADIOWAVE RADIATION
RECOMBINATION
SKY
STARS
TELESCOPES