Original article can be found at: http://adsabs.harvard.edu/ Copyright American Astronomical Society. DOI: 10.1086/192193 [Full text of this article is not available in the UHRA]We have conducted a directed search for intergalactic H I clouds, using H II galaxies as pointers to fields on the sky likely to contain such clouds. This extends our previous survey (Taylor et al. 1993) by using the VLA to map in the 21 cm line of H I a complete, volume-limited sample of H II galaxies. We detected 20 of the 21 galaxies in our sample and find that 14 have nearby H I companions. Some H II galaxies have multiple companions, and we have discovered a total of 19 companions, or a frequency of occurrence of companions of 0.67. This detection rate is statistically consistent with a lower limit of the companion frequency of 0.46, assuming that no companions are present outside of the spatial and velocity ranges searched by our VLA observations. The companion population is not a homogeneous one but is comprised of H II galaxies, cataloged and previously uncataloged dwarfs, and several objects for which there are no known optical counterparts. These latter objects may be intergalactic H I clouds. Here we present our H I maps and R-band optical images of the H II galaxy and companion systems, along with physical properties determined from these data. We compare our sample to samples of H II galaxies from the literature, finding that the literature samples over-represent the more massive, more luminous H II galaxies. Our total mass estimates imply that H II galaxies are dominated by dark matter, in agreement with observations of dwarf irregular galaxies. We also find a tendency for H II galaxies to be characterized by dense central H I concentrations surrounded by less dense envelopes. Detailed analysis of the H II galaxy/companion systems will appear in subsequent papers

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We present photometry and spectroscopy of SN 1992am for five months following its discovery by the Calan/CTIO SN search. These data show SN 1992am to be type II-P, displaying hydrogen in its spectrum and the typical shoulder in its light curve. The photometric data and the distance from our own analysis are used to construct the supernova's bolometric light curve. Using the bolometric light curve, we estimate SN 1992am ejected approximately 0.30. i# o °f 56 Ni, an amount four times larger than that of other well studied SNe II. SN 1992amis; host galaxy lies at a redshift of cz = 14 600 km s -1 , making it one of the most distant SNe II discovered, and an important application of the Expanding Photosphere Method. Since z=0.05 is large enough for redshift-dependent effects to matter, we develop the technique to derive luminosity distances with the Expanding Photosphere Method at any redshift, and apply this method to SN 1992am. The derived distance, D=180Í25 Mpc, is independent of all other rungs in the extragalactic distance ladder. The redshift of SN Jl992am's host galaxy is sufficiently large that uncertainties due to perturbations in the smooth Hubble flo\^ should be smaller than 10%. The Hubble ratio derived from the distance and redshift of this single object is H 0 =Slt\l km s -1 Mpc -1 . In the future, with more of these distant objects, we hope to establish an independent and statistically robust estimate of H 0 based solely on type II supernovae. * I Ä v^bTt)'(2)

The Stratospheric Observatory for Infrared Astronomy (SOFIA) has recently concluded a set of engineering flights for Observatory performance evaluation. These in-flight opportunities are viewed as a first comprehensive assessment of the Observatory's performance and are used to guide future development activities, as well as to identify additional Observatory upgrades. Pointing stability was evaluated, including the image motion due to rigid-body and flexible-body telescope modes as well as possible aero-optical image motion. We report on recent improvements in pointing stability by using an active mass damper system installed on the telescope. Measurements and characterization of the shear layer and cavity seeing, as well as image quality evaluation as a function of wavelength have also been performed. Additional tests targeted basic Observatory capabilities and requirements, including pointing accuracy, chopper evaluation and imager sensitivity. This paper reports on the data collected during these flights and presents current SOFIA Observatory performance and characterization.