Observations of H II Regions in M81 Virtual Observatory Resource

Authors
  1. Hill J.K.
  2. Cheng K.-P.
  3. Bohlin R.C.
  4. Cornett R.H.
  5. Hintzen P.M.N.,Robert M.S.
  6. O'Connell R.W.
  7. Roberts M.S.,Smith A.M.
  8. Smith E.P.,Stecher T.P.
  9. Published by
    CDS
Abstract

Images of the type Sab spiral galaxy M81 were obtained in far-UV and near-UV bands by the Ultraviolet Imaging Telescope (UIT) during the Astro-1 Spacelab mission of 1990 December. Magnitudes in the two UV bands are determined for 52 H II regions from the catalog of Petit, Sivan, & Karachentsev (1988A&AS...74..475P). Fluxes of the H-alpha and H-beta emission lines are determined from CCD images. Extinctions for the brightest H II regions are determined from observed Balmer decrements. Fainter H II regions are assigned the average of published radio-H-alpha extinctions for several bright H II regions. The radiative transfer models of Witt, Thronson, & Capuano (1992, ApJ, 393, 611) are shown to predict a relationship between Balmer Decrement and H-alpha extinction consistent with observed line and radio fluxes for the brightest 7 H II regions and are used to estimate the UV extinction. Ratios of Lyman continuum flux (computed from the extinction corrected H-alpha flux) to the extinction corrected far-UV flux are compared with ratios predicted by model spectra computed for IMF slope equal to -1.0 and stellar masses ranging from 5 to 120 Msun. Ages and masses are estimated by comparing the H-alpha and far-UV fluxes and their ratio with the models. The total of the estimated stellar masses for the 52 H II regions is 1.4x10^5^ Msun. The star-formation rate inferred for M81 from the observed UV and H-alpha fluxes is low for a spiral galaxy at ~0.13 Msun/yr, but consistent with the low star-formation rates obtained by Kennicutt (1983ApJ...272...54K) and Caldwell et al. (1991ApJ...370..526C) for early-type spirals.

Keywords
  1. h-ii-regions
  2. ultraviolet-astronomy
Bibliographic source Bibcode
1995ApJ...438..181H
See also HTML
https://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJ/438/181
IVOA Identifier IVOID
ivo://CDS.VizieR/J/ApJ/438/181
Document Object Identifer DOI
doi:10.26093/cds/vizier.14380181

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History

1997-12-09T20:51:30Z
Resource record created
1997-12-09T19:51:33Z
Updated
1997-12-09T20:51:30Z
Created

Contact

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CDS support team
Postal Address
CDS, Observatoire de Strasbourg, 11 rue de l'Universite, F-67000 Strasbourg, France
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cds-question@unistra.fr