Narrow band imaging in [OIII] and Halpha to search for ICPNe in the Virgo cluster

We have identified intracluster planetary nebulae in a Virgo cluster core field by imaging with the Subaru Suprime-Cam through two narrow band filters centered at the redshifted wavelengths of the [OIII] $\lambda=5007$ \AA and the H$\alpha$ $\lambda = 6563$ \AA lines; broad-band images in V and R were acquired to check for emission in the adjacent continuum. Emission line objects in Virgo are then selected from the two-color diagram ([OIII] -- Halpha) vs. ([OIII] -- (V+R)), which is calibrated using PNe in M84 (Jacoby et al. 1990). Using both [OIII] and Halpha allows us to distinguish bona-fide planetary nebulae from high redshift emission-line galaxies at the bright end of the [OIII] luminosity function. Spectroscopic observations of a subsample of these objects were made at the TNG and at the VLT, in a region around M84 and in an intracluster field respectively. The observations confirm the efficiency of the combined [OIII]+H$\alpha$ imaging to identify true PNe. We also obtained the first spectrum of an intracluster PN which shows the [OIII] doublet with S/N > 10 and its Halpha emission. From the results based on the spectroscopic follow-up, we derive a lower limit to the fraction of the Virgo cluster light contributed by the intracluster stars at the surveyed position in the cluster core: it amounts to 10%.Comment: 32 pages,11 figures, in press on AJ, February 200

Collisionless evaporation from cluster elliptical galaxies

We describe a particular aspect of the effects of the parent cluster tidal field (CTF) on stellar orbits inside cluster Elliptical galaxies. In particular we discuss, with the aid of a simple numerical model, the possibility that collisionless stellar evaporation from elliptical galaxies is an effective mechanism for the production of the recently discovered intracluster stellar populations. A preliminary investigation, based on very idealized galaxy density profiles (Ferrers density distributions), showed that over an Hubble time, the amount of stars lost by a representative galaxy may sum up to the 10% of the initial galaxy mass, a fraction in interesting agreement with observational data. The effectiveness of this mechanism is due to the fact that the galaxy oscillation periods near equilibrium configurations in the CTF are comparable to stellar orbital times in the external galaxy regions. Here we extend our previous study to more realistic galaxy density profiles, in particular by adopting a triaxial Hernquist model.Comment: 6 pages, 2 figures. To appear on "Lecture Notes in Physics", proceedings of the Workshop on "Galaxies and Chaos. Theory and Observations", Athens (September 16-19, 2002), G. Contopoulos and N. Voglis, ed

Enhancements of Bayesian Blocks; Application to Large Light Curve Databases

Bayesian Blocks are optimal piecewise linear representations (step function fits) of light-curves. The simple algorithm implementing this idea, using dynamic programming, has been extended to include more data modes and fitness metrics, multivariate analysis, and data on the circle (Studies in Astronomical Time Series Analysis. VI. Bayesian Block Representations, Scargle, Norris, Jackson and Chiang 2013, ApJ, 764, 167), as well as new results on background subtraction and refinement of the procedure for precise timing of transient events in sparse data. Example demonstrations will include exploratory analysis of the Kepler light curve archive in a search for "star-tickling" signals from extraterrestrial civilizations. (The Cepheid Galactic Internet, Learned, Kudritzki, Pakvasa1, and Zee, 2008, arXiv: 0809.0339; Walkowicz et al., in progress)

"Classical" methods of social work and social pedagogy in Germany

В данной статье представлены основные методы социальной работы и социальной педагогики в ФРГ. Рассмотрены особенности каждого из классических методов

Identification of a strong emission line at 2.8935 mu in the spectrum of the Orion Nebula

A strong emission line at 2.8935 mu discovered by Rubin et al. (2001) in an ISO SWS02 spectrum of the Orion Nebula is identified as the 4p - 4s multiplet of the O I triplets. Line formation is due to de-excitation cascades following UV-pumping of high triplet terms and occurs in the O I zone immediately behind the Hydrogen ionization front. This cascade mechanism also accounts for permitted O I triplet lines in the optical spectrum (Grandi 1975). An escape probability treatment of the O I cascades accounts for the strength of the 2.89 mu line and suggests interesting diagnostic possibilities for the optical lines.Comment: Minor changes. Accepted by MNRA

Reform pedagogics - a reconstruction and reception problem

Die deutsche Reformpädagogik (bzw. die Reformpädagogische Bewegung) hat sich selber synchron reflektiert (in der Abteilung „Aus der Pädagogischen Bewegung" in der Zeitschrift „Die Erziehung") und vor 1933 kodifiziert (vor allem im „Handbuch der Pädagogik" von Nohl und Pallat) . Sie hat sich nach 1945 mehrfach traditionalisiert, vor allem in der Quellensammlung von W. Flitner und G. Kudritzki sowie in den Darstellungen von W. Scheibe und H. Rohrs (Herrmann 1991). Eine Selbsthistorisierung, wie sie W. Flitner vorgenommen hat, war eher die Ausnahme. Kontrovers wurde die Beschäftigung mit der deutschen Reformpädagogik, als sie sowohl für die Epoche vor 1914 als auch nach 1933 sowie international kontextualisiert wurde, und entsprechend ambivalent oder die bisherige Sichtweise kritisch-korrigierend fielen die Revisionen und Bilanzen aus (Ullrich 1990; Oelkers 1993; Grunder 1993 a,b; Koerrenz 1993; Schmitt 1993). [Dieses Heft setzt die Debatte fort] mit Beiträgen zur Rekonstruktion „der" Reformpädagogik bzw. unserer Sichtweise(n) auf ihre zentralen Annahmen und Aussagen (Oelkers, Koerrenz, Tenorth). (DIPF/Orig.