A Search for Far-UV Emission from Hot Gas in the Halo of NGC~4631

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

[20.05] A Search for Far-UV Emission from Hot Gas in the Halo of NGC~4631

H. Ferguson (STScI), A.F. Davidsen, W.V. Dixon (JHU)

During the Astro-2 mission in March of 1995, the Hopkins Ultraviolet Telescope (HUT) was used to conduct a sensitive search for far-UV emission lines from hot gas in the halo of NGC~4631. This galaxy has a strong radio continuum emission, extended ${\rm H} \alpha$ emission, and soft X-ray emission from an extended halo. Recent ROSAT observations indicate that much of the X-ray emission comes from a very soft component, with temperature less than $6 \times 10^5$ K. Gas cooling through this temperature range should show emission in the prominent O~VI $\lambda\lambda 1032,1038$ and C~IV $\lambda\lambda 1548,1550$ lines.

The HUT observations probe a portion of the halo 39 arcseconds (corresponding to 1.4 kpc for at distance of 7.5 Mpc) south of the disk, through a $11 \times 56^{\prime\prime}$ aperture. Neither emission line was detected. Implications for galactic fountain models will be discussed.

This work was supported by NASA contract NAS 5-27000 to the Johns Hopkins University and through grant HF1043 awarded by the STScI which is operated by AURA, Inc., for NASA under contract NAS5-26555.

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