A Spectroscopic Study of the Star-Forming Properties of the Center of NGC 4194

We have obtained Space Telescope Imaging Spectrograph long-slit spectra of the central region of the advanced merger NGC 4194. The spectra cover the wavelength ranges 1150-1750 A in the UV and 2900-10270 A in the visible. Results from the study of the properties of 14 star-forming regions (knots) are presented. If the [N II] contribution is 40% of the combined H alpha + [N II] flux, then the average E(B - V) = 0.7 mag. The metal abundances are approximately solar, with individual knot abundances ranging from log(O/H) + 12 = 8.1 ± 0.5 to 8.9 ± 0.4. The H alpha luminosities of the 14 observed knots yield a total star formation rate (SFR) of ~46 M yr-1. The sizes of the H II regions associated with the knots were determined from L(H beta ) and range from ~28 to ~119 pc when a filling factor of 0.1 is assumed. The sizes are a factor of ~2.15 smaller for a filling factor of 1. Using Starburst99, the EW(H alpha + [N II]), and EW(H beta ), we estimate the ages of the star-forming regions to be 5.5-10.5 Myr. From ground-based spectra the effective temperatures of the H II regions are found to be ~11,000 K, and the electron densities are determined to be ~530 cm-3. We find that eight of the knots probably formed with a Salpeter initial mass function truncated at an upper mass of 30 M, and one of the knots likely formed with a standard Salpeter initial mass function. We suggest that the knots in our sample are the precursors of globular clusters. Two of the knots are in a region of flowing gas and are among the most massive, are the largest in radius, have the highest SFR, and are among the youngest of the knots.