A measurement of the absolute flux from Vega at wavelength of 2.250 microns by comparison with a standard source is presented. The result is 3.86 10 to the -10 W/sq m micron, with a probable error of 4 percent, in fair agreement with other determinations made by this method.

Current observational constraints on anisotropies in the cosmic microwave background (CMB) and on the clustering of galaxies have considerably narrowed the range of acceptable models for galaxy formation. Observations of these anisotropies on intermediate and large angular scales provide the best constraint on the amplitude of very long wavelength

Highly ionized large scale structures have recently been observed in many active galaxies. There is evidence that photoionization by the active nucleus may be the most relevant mechanism, responsible of the excitation of the gas. The authors use a simple model for a thick accretion disk around a supermassive black hole and a photoionization code to

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Observations of the nucleus of M82 obtained with the 12-m Kitt Peak antenna show that the CO J = 1 to 2 peak temperature structure possesses a dual-core morphology similar to that found at J = 1 to 0. The results indicate that the predominant regime of low opacity gas is located to the north of the star-burst zone, suggesting that material to the

This paper reports on extensive spectroscopic observations of the WR-ring nebulae NGC 2359 and RCW 78, respectively, excited by the WN5 stars HD 56925 and WN8 HD 117688. For the first object, abundances were determined for O/H, Ne/H, N/H, and He/H in many different positions, including the ionized gas in the bubble, inside the optical shell