Far-Ultraviolet Imaging of the Large Magellanic Cloud Populous Cluster NGC 1978 with WFPC2

Creators: Cole, Andrew A.; Mould, Jeremy R.; Gallagher, John S., III; Clarke, John T.; Trauger, John T.; Ballester, Gilda E.; Burrows, Christopher J.; Casertano, Stefano; Crisp, David; Griffiths, Richard; Hester, J. Jeff; Hoessel, John G.; Holtzman, Jon A.; Scowen, Paul A.; Stapelfeldt, Karl R.; Westphal, James A.

Abstract

We have imaged the ~2.2 billion-year-old Large Magellanic Cloud populous cluster NGC 1978 in the far-ultraviolet and visible with the second Wide Field/Planetary Camera (WFPC2) on the Hubble Space Telescope. The far-ultraviolet images show a sparse stellar field with little apparent density enhancement in the cluster core. The visible images are dominated by the cluster's first-ascent and second-ascent red giants, which are completely invisible to the far-ultraviolet filter. No evidence for a hot horizontal branch population of core-helium-burning stars is seen; nor is there any apparent indication of a significant blue straggler population. These results suggest that the presence of a rich, young population of field stars in the NGC 1978 region is responsible for the unusual location of the cluster in the integrated light color-color plots produced by IUE.

Additional Information

© 1997 American Astronomical Society. Provided by the NASA Astrophysics Data System. Received 1997 June 18; revised 1997 August 4; accepted 5 August 1997. Based on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. This research was carried out by the WFPC2 Investigation Definition Team for JPL and was sponsored by NASA through Contract No. NAS 7-1260. A preliminary version of these results was presented in poster format at the VIII Canary Islands Winter School: "Stellar Astrophysics For the Local Group," which was held in La Laguna, Spain, during 1996 December 2-13. A.A.C. would like to thank the participants in the Winter School for many critical readings, questions, and suggestions which improved the discussion of the results as presented in this paper.

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Published - 1997AJ____114_1945C.pdf

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