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A.P.S. Crotts (Columbia U.), J. Bechtold (U.~of Arizona)
We present new spectra for several close pairs of QSOs spanning Ly \alpha forest redshifts from z<1 to z>3. All of these pairs are between about 0.5 and 1.5 arcmin angular separation, hence about 240 to 710~kpc transverse proper separation (assuming q0 = 0.2 and H0 = 65~km~s-1~Mpc-1), so span the indicated range for proper sizes of Ly \alpha forest absorbers seen at z\approx 2. All of these objects are studied with spectra of 1.5-2Å\ resolution obtained on the CTIO 4-meter and MMT telescopes. At lower redshifts, HST FOS spectra are also used. These spectra represent a large increment over published QSO pair data in terms of redshift range covered and number of lines detected, especially at these small QSO pair separations. They are useful in showing whether absorbers are collapsing, expanding or evaporating with cosmic time, and serve as a powerful test of numerical models of the evolution of intergalactic gas and small overdensities at intermediate redshifts. Since these structures are predicted to contain most of the baryons in the Universe at these redshifts, their size evolution is a powerful constraint on the fate of normal matter.
The author(s) of this abstract have provided an email address for comments about the abstract: arlin@astro.columbia.edu