We present a procedure for obtaining the mean density of clusters and their associated structures in a very general type of distribution. We first consider the one-dimensional case, and then use it to develop the procedure according to the d-dimensional case. These procedures require the probability that a randomly placed body should contain no

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We have acquired CO J=1->0 mapping of a region 2x2arcmin^2^ about the cometary nebula and jet outflow source 1548c27. We find little evidence for interaction between the jet and molecular cloud, although it is found that the reflection nebula is embedded within a neutral condensation of size =~10^2^arcsec. Kinematic variations across the source

Aims. We aimed at finding a physical explanation for the occurrence of macroturbulence in the atmospheres of hot massive stars, a phenomenon found in observations for more than a decade but that remains unexplained. Methods: We computed time series of line profiles for evolved massive stars broadened by rotation and by hundreds of low-amplitude

Collisional excitation of neutral hydrogen atoms can significantly increase the intensity of Balmer lines with respect to pure recombination. If this effect is not taken into account, the abundance analysis of these objects returns biased values, and the bias may be significant if accuracies better than a few percent are required. The most affected

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