Red star

Abstract: We present a wide-field H-alpha imaging survey of the rich cluster CL0939+4713 (Abell 851) at z=0.41 with Suprime-Cam on the Subaru Telescope, using the narrow-band filter NB921. The survey is sensitive to active galaxies with star formation rates down to ~0.3Msun/yr throughout the 27'x27' field, and we identified 445 H-alpha emitters along the large-scale structures around the cluster. Using this sample, we find that (1) the fraction of H-alpha emitters is a strong function of environment and shows a clear decline toward the cluster central region. We also find that (2) the color of H-alpha emitters is clearly dependent on environment. The majority of the H-alpha emitters have blue colors with B-I<2, but we find H-alpha emitters with red colors as well. Such red emitters are very rare in the cluster center or its immediate surrounding regions, while they are most frequently found in groups located far away from the cluster center. These groups coincide with the environment where a sharp transition in galaxy color distribution is seen. This may suggest that dusty star formation activity tends to be involved in galaxy truncation processes that are effective in groups, and it is probably related to the "pre-processing" that generates present-day cluster S0 galaxies. Finally, we confirm that (3) the mass-normalized integrated star formation rate in clusters (i.e. the total star formation rate within 0.5xR200 from the cluster center divided by the cluster dynamical mass) rapidly increases with look-back time following approximately ~(1+z)^6, and it is also correlated with the cluster mass.

Abstract: Surprisingly little known, the Polish-Soviet War of 1919-20 was to change the course of twentieth-century history. In White Eagle, Red Star, Norman Davies gives a full account of the War, with its dramatic climax in August 1920 when the Red Army - sure of victory and pledged to carry the Revolution across Europe to 'water our horses on the Rhine' - was crushed by a devastating Polish attack. Since known as the 'miracle on the Vistula', it remains one of the most decisive battles of the Western world. Drawing on both Polish and Russian sources, Norman Davies illustrates the narrative with documentary material which hitherto has not been readily available and shows how the War was far more an 'episode' in East European affairs, but largely determined the course of European history for the next twenty years or more.