Multiwavelength Study of the Starburst Galaxy NGC 7714. II. The Balance between Young, Intermediate‐Age, and Old Stars

We combine existing multiwavelength data (incl. an HST/GHRS UV spectrum, anoptical spectrum, far-IR, Xray and radio fluxes) with new HST/WFPC2 images,near-IR photometry and K band spectroscopy. We use these data to constrain theyoung, the intermediate age and the old stellar populations in the central 330pc of the starburst galaxy NGC 7714. [...] We find that the young burst responsible for the UV light is only a smallpart of an extended episode of enhanced star formation (SF) [...]. The mass ofyoung and intermediate age stars thus formed equals at least 10% of the masslocked in pre-existing stars of the underlying galaxy nucleus [...]. Thespectrophotometric SF timescale is long compared to the ~110 Myr elapsed sinceclosest contact with NGC 7715. The trigger of the starburst remains elusive. NGC 7714 owes its brightness in the UV to a few low extinction lines of sighttowards young stars. [...] The different extinction estimates obtained fromdifferent indicators result naturally from the coexistence of populations withvarious ages and obscurations. The near-IR continuum image looks smoothest, asa consequence of lower sensitivity to extinction and of a larger contributionof old stars. We compare the nuclear properties of NGC 7714 with results fromstudies in larger apertures. We emphasize that the global properties ofstarburst galaxies are the result of the averaging over many lines of sightwith diverse properties in terms of obscuration and stellar ages.Comment: 29 pages (+20 figures and tables), Latex2e (figs. included), uses aastex.cls. To be published in ApJ (May 2001 issue