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DOI: 10.1086/175063
¤ OpenAccess: Bronze
This work has “Bronze” OA status. This means it is free to read on the publisher landing page, but without any identifiable license.

Ultraviolet imaging telescope and optical emission-line observations of H II regions in M81

J. K. Hill,K. P. Cheng,R. C. Bohlin,R. H. Cornett,P. Hintzen,R. W. O’Connell,M. S. Roberts,Andrew M. Smith,Eric P. Smith,T. P. Stecher

Physics
Astrophysics
Balmer series
1995
view Abstract Citations (30) References (24) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Ultraviolet Imaging Telescope and Optical Emission-Line Observations of H II Regions in M81 Hill, Jesse K. ; Cheng, K. -P. ; Bohlin, Ralph C. ; Cornett, Robert H. ; Hintzen, P. M. N. ; O'Connell, Robert W. ; Roberts, Morton S. ; Smith, Andrew M. ; Smith, Eric P. ; Stecher, Theodore P. 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 (1988). Fluxes of the Hα and Hβ 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-Hα extinctions for several bright H II regions. The radiative transfer models of Witt, Thronson, & Capuano (1992) are shown to predict a relationship between Balmer Decrement and Hα 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 Hα 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 M_sun_. Ages and masses are estimated by comparing the Hα and far-UV fluxes and their ratio with the models. The total of the estimated stellar masses for the 52 H II regions is 1.4 x 10^5^ M_sun_. The star-formation rate inferred for M81 from the observed UV and Hα fluxes is low for a spiral galaxy at ~0.13 M_sun_ yr^-1^, but consistent with the low star- formation rates obtained by Kennicutt (1983) and Caldwell et al. (1991) for early-type spirals. Publication: The Astrophysical Journal Pub Date: January 1995 DOI: 10.1086/175063 Bibcode: 1995ApJ...438..181H Keywords: H Alpha Line; H Ii Regions; Light Emission; Spiral Galaxies; Ultraviolet Astronomy; Ultraviolet Photography; Visible Spectrum; Astronomical Catalogs; Flux Density; H Beta Line; Interstellar Extinction; Radiative Transfer; Stellar Spectra; Ultraviolet Telescopes; Astronomy; GALAXIES: INDIVIDUAL MESSIER NUMBER: M81; GALAXIES: STELLAR CONTENT; ISM: DUST; EXTINCTION; ISM: H II REGIONS; ULTRAVIOLET: GALAXIES full text sources ADS | data products SIMBAD (51) NED (1) MAST (1) CDS (1)
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    Ultraviolet imaging telescope and optical emission-line observations of H II regions in M81” is a paper by J. K. Hill K. P. Cheng R. C. Bohlin R. H. Cornett P. Hintzen R. W. O’Connell M. S. Roberts Andrew M. Smith Eric P. Smith T. P. Stecher published in 1995. It has an Open Access status of “bronze”. You can read and download a PDF Full Text of this paper here.