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Abstract

We present the function J as a morphological descriptor for point patterns formed by the distribution of galaxies in the universe. This function was recently introduced in the Ðeld of spatial statistics, and is based on the nearest-neighbor distribution and the void probability function. The J descriptor allows us to distinguish clustered (i.e., correlated) from regular (i.e., anticorrelated) point distributions. We outline the theoretical foundations of the method, perform tests with a cluster process as an idealized Mate rn model of galaxy clustering, and apply the descriptor to galaxies and loose groups in the Perseus-Pisces Survey. A comparison with mock samples extracted from a mixed dark matter simulation shows that the J descriptor can be proÐtably used to constrain (or in this case reject) viable models of cosmic structure formation.

Chemodynamical Simulations of the Milky Way Galaxy

“…Chemical enrichment must be solved as well as energy feedback. Supernova feedback is also important for solving the angular momentum problem (Steinmetz & Navarro 1999;Sommer-Larsen et al 2003) and the missing satellite problem (Moore et al 1999), and for explaining the existence of heavy elements in intracluster medium (Renzini et al 1993) and intergalactic medium, and possibly the mass-metallicity relation of galaxies (Kobayashi et al 2007, hereafter K07).…”

Are Nonthermal Velocities in Active Region Coronal Loops Anisotropic?

“…This assumption is unavoidable, as there are not enough measurables to extract possible actual variations in v nt,⊥ , v nt,∥ , and T i simultaneously. This assumption is also made in other studies, such as Hara & Ichimoto (1999) and Hara et al (2008) mentioned in the Introduction. Here, we have investigated some factors that might limit the validity of this assumption by examining how the parameters of interest vary with distance along the loop.…”

“…In order to help resolve these issues of variation along the loop and the limited dynamic range of angles, we plan to analyze an observation at the solar limb. At the limb, we expect to observe face-on and edge-on loops, much as was seen by Hara & Ichimoto (1999), but with the advantage of using our improved magnetic field diagnostics to remove the ambiguity as to the actual magnetic field direction.…”

“…Only a few existing measurements have attempted to measure the anisotropy of v nt , but the results are ambiguous. Hara & Ichimoto (1999) observed loops at the solar limb and characterized them as being either face-on or edge-on. For faceon loops the line of sight is perpendicular to the magnetic field everywhere, while for edge-on loops the line of sight is perpendicular to the loop near the base and parallel near the loop top.…”

“…For faceon loops the line of sight is perpendicular to the magnetic field everywhere, while for edge-on loops the line of sight is perpendicular to the loop near the base and parallel near the loop top. Based on their measurements, Hara & Ichimoto (1999) concluded that line widths were 3-5 km s −1 broader in the perpendicular direction than in the parallel direction, so v nt,⊥ > v nt,∥ .…”