Bibcode
DOI
Alonso-Herrero, Almudena; Knapen, Johan H.
Referencia bibliográfica
The Astronomical Journal, Volume 122, Issue 3, pp. 1350-1364.
Fecha de publicación:
9
2001
Número de citas
39
Número de citas referidas
31
Descripción
We analyze the statistical properties of the circumnuclear H II regions
of a sample of 52 nearby galaxies (v<1000 km s-1) from
archival HST/NICMOS H-band and Paα (1.87 μm) observations at
unprecedented spatial resolutions of between 1 and 30 pc. We catalog H
II regions from the continuum-subtracted Paα images and find H II
regions in the central regions of most galaxies, and more than a hundred
in each of eight galaxies. In contrast to disk H II regions, the
physical properties (luminosity and size) of individual circumnuclear H
II regions do not vary strongly with the morphological type of the host
galaxy, nor does the number of circumnuclear H II regions per unit area.
The Hα luminosity within the central kiloparsec, as derived from H
II region emission, is significantly enhanced in early-type (S0/a-Sb)
galaxies. We find evidence that bars increase the circumnuclear star
formation, presumably by funneling gas from the disk toward the nucleus.
Barred galaxies exhibit enhanced luminosities of the brightest H II
region, the central kiloparsec Hα luminosities (an effect mostly
due to the early-type galaxies in our sample), and the star formation
rates per unit stellar mass (which could also be understood as the
integral equivalent widths of Paα) over the central kiloparsec
with respect to nonbarred galaxies. We fit the luminosity functions
(LFs) and diameter distributions of the circumnuclear H II regions in
eight galaxies where we can catalog enough H II regions to do so in a
meaningful way. We use power laws and find that the fitted slopes of the
H II region LF are exactly in the previously found ranges and even
confirm a trend with steeper slopes in galaxies of earlier morphological
type. This implies that the physical processes giving rise to enhanced
star formation in the circumnuclear regions of galaxies must be similar
to those in disks. Based on observations with the NASA/ESA Hubble Space
Telescope, obtained from the data archive at the Space Telescope Science
Institute, which is operated by the Association of Universities for
Research in Astronomy, Inc., under NASA contract NAS 5-26555.