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T. Robishaw, L. Blitz (University of California at Berkeley)
We present a complete, unbiased catalog of high-velocity clouds (HVCs) found in the Leiden/Dwingeloo Survey (LDS) of Galactic HI. We designed an automated routine to search for emission features in each of the >206,000 spectra in the LDS and employed a nonlinear least squares method to fit all detected features with Gaussian profiles. From our compilation of fit parameters, spatial and velocity criteria were used to collect high-velocity features into clouds. The LDS uniformly samples the full sky north of \delta=-30\circ and has twice the spatial and ~10 times the velocity resolution of the HI survey used to compile the 1991 all-sky HVC catalog of Wakker and van Woerden. Our catalog is produced with the intent of providing a large sample of HVCs for comparison with observations of other galactic systems. We measure dN(H)/dN and d\Omega/dN, examine the distribution of angular size as a function of vGSR, and determine beam-corrected values of radius and column density for the sample. The catalog will allow us to investigate whether the distribution dN(H)/dN can be directly compared with the same quantity for the Lyman limit systems seen in QSO spectra, and thereby assess whether the HVC properties are consistent with their being extragalactic objects. We also use these data to evaluate the reliability and completeness of previous HVC surveys.
This research was partially supported by the National Science Foundation.