Description of the Boston University HII Region Catalog

This catalog contains all 298 Galactic HII regions with measured radio recombination lines over the extent of the Galactic Ring Survey (l = 15-57°, |b| ≤ 1°. We compiled this catalog from the catalogs of ultra compact (UC) regions (Araya et al. 2002, Watson et al. 2003, Sewilo et al. 2004), classical regions (Lockman 1989), and regions that are truly diffuse (Lockman, Pisano, & Howard 1996). All sources were verified as being HII regions based on the infrared (MIPSGAL and GLIMPSE) and 20cm continuum (MAGPIS) emission. Below we describe the columns presented on the main page.


  1. Name

    The names are constructed from the l and b values from the recombination line measurements. The first letter refers to our three classes of HII regions, U:ultra compact regions, C:compact, classical regions, D:diffuse regions

  2. l

    Galactic Longitude of the recombination line measurements. If, in examining the continuum of a source, we determined that this position was off, this value was adjusted.

  3. b

    Ditto for Galactic Latitude.

  4. RA

    Right Ascension (J2000) calculated from the position in Galactic coordinates.

  5. Dec

    Declination (J2000) calculated from the position in Galactic coordintes.

  6. VLSR

    The LSR velocity from the recombination line measurements.

  7. Ellipse l

    The Galactic longitude of the fitted ellipse centroid.

  8. Ellipse b

    The Galactic latitude of the fitted ellipse centroid.

  9. Size

    This is the geometric mean of the semimajor and semiminor axes of the fitted ellipse.

  10. Semimajor

    The semimajor axis of the fitted ellipse.

  11. Semimajor

    The semimajor axis of the fitted ellipse.

  12. PA

    The position angle of the fitted ellipse.

  13. V

    The center of the fitted line.

  14. σ V

    The 1σ error in the fitted line.

  15. T

    The peak line intensity of the fitted line.

  16. σ T

    The 1σ error in the fitted line peak intensity.

  17. Δ V

    The FWHM of the fitted line.

  18. σ(Δ V)

    The 1σ error in the fitted FWHM.

  19. Tex

    The excitation temperature calculated using the University of Massachusetts - Stoney Brook 12CO survey.

  20. σ Tex

    The 1σ error in Tex

  21. N(13CO)

    Column density estimate calculated using the method in Rohlf's & Wilsons' Tools of Radio Astronomy

  22. CP

    Our qualitative criteria for the confidence parameter are as follows: A: no ambiguity in position or velocity; B: either offset somewhat in position or velocity, or in a complex region of molecular gas; C: either offset in position or velocity or in a complex region, but fainter than a B source and offset further; D: diffuse emission near the correct position and velocity, but uncharacterizable due to low intensity or ambiguous morphology; E: nothing apparent at position and RRL velocity.