Hopkins Ultraviolet Telescope Observations of Six E and S0 Galaxies

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Session 20 -- Astro 2
Display presentation, Tuesday, June 13, 1995, 9:20am - 6:30pm

[20.04] Hopkins Ultraviolet Telescope Observations of Six E and S0 Galaxies

T.M.Brown (JHU), H.C.Ferguson (STScI), A.F.Davidsen (JHU)

In order to better understand the hot stellar populations of E and S0 galaxies, we observed six objects using the Hopkins Ultraviolet Telescope. Through our 11\arcsec\ $\times$ 60\arcsec\ aperture, we obtained one observation each of M~49 (1346~s), M~87 (950~s), M~89 (1682~s), and NGC~3115 (1634~s), two observations of NGC~3379 (3074~s), and four observations of M~60 (5824~s). The far-ultraviolet (FUV) spectra were obtained during orbital night as part of the Astro-2 mission on the space shuttle \it Endeavor \rm in March 1995, and cover the spectral range of 912 \AA\ to 1850 \AA\ with a resolution of 2--4 \AA. This sample quadruples the number of early-type galaxies studied to the Lyman limit.

After correcting for geocoronal emission and interstellar extinction in our own Galaxy, all the spectra are similar, even though the ``UV upturn'' strength, as characterized by the parameter $m_{1550}-V$, varies over the range of 2.04~mag to 3.86~mag for these galaxies. Comparison with models of evolved stellar populations confirms the conclusion from Astro-1 data that the FUV flux can be explained by stars with a narrow range of temperature and envelope mass on the extreme horizontal branch (EHB).

This work was supported by NASA contract NAS 5-27000 to the Johns Hopkins University.

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