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L.P. Crosthwaite (Astute Networks), J.L. Turner (Dept. of Physics and Astronomy, UCLA), S.C. Beck (Dept. of Physics and Astronomy, Tel Aviv University), D.S. Meier (Dept of Astronomy, University of Illinois, Urbana)
The gas-rich nucleus of barred spiral galaxy, M83, is a hotbed of star formation, with a total infrared luminosity of 4 X 109 Lo. We have observed the nucleus of M83 with the near infrared spectrometer, NIRSPEC, on Keck 2 to obtain high resolution Br\gamma recombination line spectra of the nucleus. Simultaneous imaging with the SCAM camera in a broadband K filter shows the position of the slit on the near-infrared galaxy. This allows us to map the nucleus with a continuum reference. The SCAM image shows a bright peak at the nucleus and a complex semi-circular arc of emission to the southwest. We stepped the 0.5'' X 24'' length slit in small declination increments to map a 20'' X 20'' region just west of the nucleus. Individual spectra were used to form a ra-dec-lambda cube and an integrated intensity map of Br\gamma.
A total of 1.1 X 10-16 W m-2 of Br\gamma emission is detected in the map, in good agreement with previous low resolution observations (Turner, Ho, & Beck 1987, ApJ, 313, 644). This is not corrected for extinction within the molecular clouds in M83 or to the nebulae themselves and is therefore a lower limit to the true Br\gamma flux. Extinction is estimated to be at least a magnitude in the near-IR as measured in larger (4'') beams (Turner et al.) The bulk of the Br\gamma emission extends along the northern portion of the near-IR continuum semi-circle. Twenty percent of the total Br\gamma emission comes from single a 3'' (FWHM) source located 5'' west of the near-IR nucleus.
The complementary NIRSPEC Br\alpha data we have obtained will eventually allow us to evaluate the near-IR extinction on subarcsecond sizescales and obtain an extinction-corrected estimate of the Lyman continuum rate and therefore the number of ionizing stars.
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Bulletin of the American Astronomical Society, 36 5
© 2004. The American Astronomical Society.