8,238 research outputs found
On the Anomalous Temperature Distribution of the Intergalactic Medium in the NGC 3411 Group of Galaxies
We present XMM, Chandra and VLA observations of the USGC S152 group and its
central elliptical NGC 3411. Imaging of the group X-ray halo suggests it is
relaxed with little apparent structure. We investigate the temperature and
metal abundance structure of the group halo, and find that while the abundance
distribution is fairly typical, the temperature profile is highly unusual,
showing a hot inner core surrounded by a cool shell of gas with a radius of
\~20-40 kpc, at the center of the larger group halo. Spectral mapping confirms
an irregular ring of gas ~0.15 keV cooler than its surroundings. We estimate
the total mass, entropy and cooling time profiles within ~200 kpc, and find
that the cool shell contains ~9x10^9 Msun of gas. VLA observations at 1.4, 5
and 8 GHz reveal a relatively weak nuclear radio source, with a core radio
luminosity L_R=2.7x10^38 erg/s, and a diffuse component extended on scales of a
few arcseconds (or more). A lack of evidence for activity at optical or X-ray
wavelengths supports the conclusion that the central black hole is currently in
a quiescent state. We discuss possible mechanisms for the formation of
temperature features observed in the halo, including a previous period of AGN
activity, and settling of material stripped from the halo of one of the other
group member galaxies.Comment: 15 pages, 8 postscript figures, accepted for publication in ApJ
version with high resolution figures available at
http://hea-www.harvard.edu/~ejos/files/N3411_hires.pd
Introduction
This book emerged from conversations with colleagues from across the world and is intended to contribute to our understanding of pedagogical leadership in early childhood education (ECE). In this book, colleagues from academic, policy and practice organisations discuss pedagogical leadership, how it is defined and delivered in a range of international contexts. This chapter highlights gaps and weaknesses in the existing literature on pedagogical leadership and explains how the contributors to this book respond to these and in doing so, how they advance the field
Robust quantum state engineering through coherent localization in biased-coin quantum walks
We address the performance of a coin-biased quantum walk as a generator for
non-classical position states of the walker. We exploit a phenomenon of
coherent localisation in the position space --- resulting from the choice of
small values of the coin parameter and assisted by post-selection --- to
engineer large-size coherent superpositions of distinguishable position states
of the walker. The protocol that we design appears to be remarkably robust
against both the actual value taken by the coin parameter and strong
dephasing-like noise acting on the spatial degree of freedom. We finally
illustrate a possible linear-optics implementation of our proposal, suitable
for both bulk and integrated-optics platforms.Comment: 7 pages, 7 figure
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