========================================================================== J/ApJ/438/181 Observations of H II Regions in M81 (Hill+ 1995) The following files can be converted to FITS (extension .fit .fit.Z .fgz) table2.dat ========================================================================== Query from: http://vizier.u-strasbg.fr/cgi-bin/VizieR?-source=J/ApJ/438/181 ==========================================================================
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Beginning of ReadMe : J/ApJ/438/181 Observations of H II Regions in M81 (Hill+ 1995) ================================================================================ Ultraviolet Imaging Telescope and Optical Emission-Line Observations of H II Regions in M81 Hill J.K., Cheng K.-P., Bohlin R.C., Cornett R.H., Hintzen P.M.N., Robert M.S., O'Connell R.W., Roberts M.S.,Smith A.M., Smith E.P., Stecher T.P. <Astrophys. J. 438, 181 (1995)> =1995ApJ...438..181H ================================================================================ ADC_Keywords: H II regions ; Ultraviolet ; Keywords: dust, extinction - galaxies: individual (M81) - galaxies: stellar content - H II regions - ultraviolet: galaxies 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.