AAS 195th Meeting, January 2000
Session 9. Evolution of Galaxies, Galaxy Surveys
Display, Wednesday, January 12, 2000, 9:20am-6:30pm, Grand Hall

## [9.20] The Two-Point Correlation Function of the Local Ly\alpha Forest

S.V. Penton, J.T. Stocke (CU/CASA), J.M. Shull (CU/CASA,JILA)

We combine our recent HST/GHRS/G160M results (Penton, Shull, & Stocke, 2000; 15 sightlines) with 13 new HST/STIS low-z (z < 0.07) sightlines to determine the linear two-point correlation function (TPCF, \xi(\Delta v)) of the low column density (12.5 \leq\ log[NH I] \leq 14.5) local Ly\alpha forest. Careful accounting of the sensitivity function of each HST spectrum allows us to probe velocity separations (\Delta v) as low as 50 km s-1. The new STIS/G140M data roughly doubles the number of existing low-z sightlines, and more importantly increases the pathlength per sightline to establish a better baseline" for any potential excess TPCF power at \Delta v< 150~km s-1. The new STIS data allows us to check the reality of the \xi(\Delta v) < 150~km s-1 3.3 \sigma excess seen in GHRS data, and to test whether any of the tentative features" (1.5-2.5\sigma) seen at larger velocity separations (\Delta v ~ 850 and 1,700 km s-1; which may be related to the velocity widths of supercluster filaments and voids) are real. This z~ TPCF will be compared with similar data at z\geq2 obtained from ground-based telescopes to determine whether these local, low-column density clouds are plausibly the direct descendents of the high-z Ly\alpha forest.

This work is based on observations with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc. under NASA contract No. NAS5-26555. This research was supported by HST guest observer grant GO-06593.01-95A.