Trey V. Wenger

The WISE Catalog of Galactic H II Regions

Using data from the all-sky Wide-Field Infrared Survey Explorer (WISE) satellite, we made a catalog of over 8000 Galactic HII regions and HII region candidates by searching for their characteristic mid-infrared (MIR) morphology. WISE has sufficient sensitivity to detect the MIR emission from HII regions located anywhere in the Galactic disk. We believe this is the most complete catalog yet of regions forming massive stars in the Milky Way. Of the ∼ 8000 cataloged sources, ∼ 1500 have measured radio recombination line (RRL) or Hα emission, and are thus known to be HII regions. This sample improves on previous efforts by resolving HII region complexes into multiple sources and by removing duplicate entries. There are ∼ 2500 candidate HII regions in the catalog that are spatially coincident with radio continuum emission. Our group’s previous RRL studies show that ∼ 95% of such targets are HII regions. We find that ∼ 500 of these candidates are also positionally associated with known HII region complexes, so the probability of their being bona fide HII regions is even higher. At the sensitivity limits of existing surveys, ∼ 4000 catalog sources show no radio continuum emission. Using data from the literature, we find distances for ∼ 1500 catalog sources, and molecular velocities for ∼ 1500 HII region candidates.

AZIMUTHAL METALLICITY STRUCTURE IN THE MILKY WAY DISK

Elemental abundance patterns in the Galactic disk constrain theories of the formation and evolution of the Milky Way. H ii region abundances are the result of billions of years of chemical evolution. We made radio recombination line and continuum measurements of 21 H ii regions located between Galactic azimuth Az = 90??130?, a previously unexplored region. We derive the plasma electron temperatures using the line-to-continuum ratios and use them as proxies for the nebular [O/H] abundances, because in thermal equilibrium the abundance of the coolants (O, N, and other heavy elements) in the ionized gas sets the electron temperature, with high abundances producing low temperatures. Combining these data with our previous work produces a sample of 90 H ii regions with high-quality electron temperature determinations. We derive kinematic distances in a self-consistent way for the entire sample. The radial gradient in [O/H] is for Az = 90??130?, about a factor of 2 higher than the average value between Az = 0??60?. Monte Carlo simulations show that the azimuthal structure we reported for Az = 0??60? is not significant because kinematic distance uncertainties can be as high as 50% in this region. Nonetheless, the flatter radial gradients between Az = 0??60? compared with Az = 90??130? are significant within the uncertainty. We suggest that this may be due to radial mixing from the Galactic Bar whose major axis is aligned toward Az ? 30?.

FINDING DISTANT GALACTIC H ii REGIONS

The WISE Catalog of Galactic HII Regions contains

Untangling the Recombination Line Emission from H II Regions with Multiple Velocity Components

\sim2000

High-Mass Star Formation in the Outer Scutum-Centaurus Arm

HII region candidates lacking ionized gas spectroscopic observations. All candidates have the characteristic HII region mid-infrared morphology of WISE

The Southern H II Region Discovery Survey (SHRDS): pilot survey

12\,\,\mu\,m

Kinematic Distances: A Monte Carlo Method

emission surrounding

Hydrogen Radio Recombination Line Emission from M51 and NGC 628

22\,\mu\,m

Diffuse Ionized Gas in the Milky Way Disk

emission, and additionally have detected radio continuum emission. We here report Green Bank Telescope (GBT) hydrogen radio recombination line (RRL) and radio continuum detections at X-band (9GHz; 3cm) of 302 WISE HII region candidates (out of 324 targets observed) in the zone

Carbon Monoxide Observations toward Star-forming Regions in the Outer Scutum–Centaurus Spiral Arm

225^{\circ} > l > -20^{\circ}