X-RAY MORPHOLOGY, KINEMATICS, AND GEOMETRY OF THE ERIDANUS SOFT-X-RAYENHANCEMENT

We present mosaics of X-ray intensity maps and spectral fit results fo r selected regions of the Eridanus soft X-ray enhancement (EXE), as we ll as kinematics of the X-ray-absorbing clouds in the EXE region and g eometrical properties of this X-ray-emitting bubble. The work is based on pointed observations with the ROSAT Position Sensitive Proportiona l Counter, 21 cm observations with the NRAO 140 foot telescope at Gree n Bank and interstellar Na D line observations with the NOAO Coude Fee d telescope at Kitt Peak. The ROSAT pointed observations examine two r egions of the EXE. The first is an X-ray absorption lane produced by a n IR filament which is located at galactic coordinates of about (200 d egrees, -47 degrees). The second is in the vicinity of the northern (g alactic) boundary of the 1/4 keV EXE, at galactic coordinates of about (202 degrees, -25 degrees). Both our spatial and spectral analysis su ggest that variations in emission measure and N-H are primarily respon sible for the observed variations of the X-ray intensity. Using 100 mu m intensities obtained from IRAS maps and N-H column densities obtain ed from our X-ray spectral fits, we find 100 mu m/N-H ratios across th e IR filament that are compatible with typical high-latitude values. M aps of the X-ray-absorbing clouds in the EXE region at 21 cm reveal th at these clouds may belong to two different expanding systems, with on e possibly associated with our Local Bubble and the other with the bou ndary of the EXE. Based on 21 cm data and Na D observations in the dir ection (l, b) similar to (200 degrees, -47 degrees), our best estimate of the distance to the near side of the Orion-Eridanus bubble is 159 +/- 16 pc. We estimate the center of the bubble in this direction to b e about 226 pc away, with much larger uncertainty. The density and the thermal pressure found for this X-ray-emitting superbubble are 0.015 cm(-3) and 4.9 x 10(4) cm(-3) K.