Ultraviolet Imaging Telescope: Globular Clusters in M31

Previous abstract Next abstract

Session 50 -- Globular Clusters
Display presentation, Wednesday, 9:20-6:30, Pauley Room

[50.08] Ultraviolet Imaging Telescope: Globular Clusters in M31

R.C.Bohlin, E.W.Deutsch, K.A.McQuade (STSciI), J.K.Hill, W.B.Landsman (Hughes STX), R.W.O'Connell (UVa), M.S.Roberts (NRAO), A.M. Smith, T.P.Stecher (NASA/GSFC)

Two 40$'$ fields of M31 observed with the Ultraviolet Imaging Telescope (UIT) during the Astro-1 mission in December 1990 are searched for known globular clusters. The fluxes of 20 clusters in the nucleus field and 23 clusters in the disk field are measured in a near ultraviolet (NUV $\sim$2500 \AA) bandpass. In the far ultraviolet (FUV $\sim$1500 \AA), only 4 clusters are detected with certainty, and 6 others are possible detections.

The NUV photometry of the M31 globulars that are detected by UIT shows that they do not have a UV excess in comparison to their Galactic counterparts. The spectral energy distributions of the globular clusters from the NUV to V fall within the range of predictions of the Buzzoni models for a 15 Gyr old population. However, two of the three classical globular clusters with red NUV and visible colors that are detected in the FUV have a "UV upturn" with fluxes that are greater in the FUV than in the NUV. The other seven FUV detections have optical colors that are too blue for classical globular clusters and are probably the nuclei of compact OB associations.

Wednesday program listing