EUVE Science Highlights -
January 20, 2000
EUVE Science Highlights -
January 20, 2000
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Slide 5 of 11
Contributed by Dr. Barry Welsh, University of California at Berkeley Based on paper: Welsh, B.Y., D.M. Sfeir, M.M. Sirk, and R. Lallement, "EUV Mapping of the Local Interstellar Medium: the Local Chimney Revealed?", A&A, 352, 308, 1999.
Using new, accurate Hipparcos distance estimates, the space distribution of 450 (of the potential 1153) sources detected by the EUVE satellite has been plotted. Late type stars dominate the nearby (d < 50 pc) source distribution, whereas hot white dwarf stars represent 60% of sources detected with a distance > 50pc. The galactic distribution of all detected EUV sources is non-uniform with number enhancements seen towards both the Hyades cluster (d = 44 pc), and in the line-of-sight along the beta CMa interstellar tunnel to ~200 pc. A comparison of the galactic distribution of EUV sources has been made with that of the distribution of cold, neutral NaI gas observed within 300 pc (Sfeir et al 1999). This neutral gas boundary essentially defines the extent of the hot Local Bubble region. We find that 95% of the EUV sources are contained within this neutral boundary - not surprising since EUV radiation is heavily absorbed by neutral H gas At high galactic latitudes the neutral absorption boundary of the Local Bubble seems "open-ended". This is confirmed by the detection of 20 extragalactic EUV sources along these high latitude lines-of-sight. This suggests that the Local Bubble is infact an "interstellar chimney" that extends into the local galactic halo. Interstellar chimneys are believed to be formed when supernova remnants expand away from the galactic plane and burst into the halo. The hot interstellar gas then acts like a galactic fountain which rises up away from the galactic plane and then cools and "rains" back down from the halo onto the galaxy. It appears that this Local Chimney is pointing perpendicularly to the plane of the Gould's Belt association of OB stars and is aimed directly at the two regions of enhanced soft X-ray emission discovered by the ROSAT satellite at high galactic latitudes.
References
Sfeir, D.M. et al., A&A, 346, 785S, 1999.