135 research outputs found
Environmental dependence of 8 μm luminosity functions of galaxies at z ~ 0.8: Comparison between RXJ1716.4+6708 and the AKARI NEP-deep field
Aims. We aim to reveal environmental dependence of infrared luminosity functions (IR LFs) of galaxies at z ~ 0.8 using the AKARI
satellite. AKARI’s wide field of view and unique mid-IR filters help us to construct restframe 8 μm LFs directly without relying on
SED models.
Methods. We construct restframe 8 μm IR LFs in the cluster region RXJ1716.4+6708 at z = 0.81, and compare them with a blank
field using the AKARI north ecliptic pole deep field data at the same redshift. AKARI’s wide field of view (10' × 10') is suitable to
investigate wide range of galaxy environments. AKARI’s 15 μm filter is advantageous here since it directly probes restframe 8 μm at
z ~ 0.8, without relying on a large extrapolation based on a SED fit, which was the largest uncertainty in previous work.
Results. We have found that cluster IR LFs at restframe 8 μm have a factor of 2.4 smaller L^∗ and a steeper faint-end slope than that
of the field. Confirming this trend, we also found that faint-end slopes of the cluster LFs becomes flatter and flatter with decreasing
local galaxy density. These changes in LFs cannot be explained by a simple infall of field galaxy population into a cluster. Physics
that can preferentially suppress IR luminous galaxies in high density regions is required to explain the observed results
Field-dependent dynamics of the Anderson impurity model
Single-particle dynamics of the Anderson impurity model in the presence of a
magnetic field are considered, using a recently developed local moment
approach that encompasses all energy scales, field and interaction strengths.
For strong coupling in particular, the Kondo scaling regime is recovered. Here
the frequency () and field ()
dependence of the resultant universal scaling spectrum is obtained in large
part analytically, and the field-induced destruction of the Kondo resonance
investigated. The scaling spectrum is found to exhibit the slow logarithmic
tails recently shown to dominate the zero-field scaling spectrum. At the
opposite extreme of the Fermi level, it gives asymptotically exact agreement
with results for statics known from the Bethe ansatz. Good agreement is also
found with the frequency and field-dependence of recent numerical
renormalization group calculations. Differential conductance experiments on
quantum dots in the presence of a magnetic field are likewise considered; and
appear to be well accounted for by the theory. Some new exact results for the
problem are also established
A Bose-Einstein condensation model for high-temperature superconductivity
I propose that a dopant charge singlet bonding state may arise from the
hybridization of molecular orbitals in a cluster containing 13 Cu atoms in the
CuO2 plane of the superconducting cuprates. This singlet state forms a
pre-formed pair with low binding energy that is spatially bounded and weakly
interacting, and that can undergo Bose-Einstein condensation. I show that this
model is able to account, in a quantitative and natural way, for many of the
thermodynamic and electronic characteristics of the superconducting cuprates,
including many of the key experimental ARPES, muSR and microwave results on the
temperature and doping dependencies of both the superfluid density and the
pairing strengths (superconducting gap, leading-edge-midpoint and psuedogap) in
these high-temperature superconductors.Comment: 28 pages, 9 figures, submitted to Phys. Rev.
Differential postural effects of plantar-flexor muscles fatigue under normal, altered and improved vestibular and neck somatosensory conditions
The aim of the present study was to assess the effects of plantar-flexor
muscles fatigue on postural control during quiet standing under normal, altered
and improved vestibular and neck somatosensory conditions. To address this
objective, young male university students were asked to stand upright as still
as possible with their eyes closed in two conditions of No Fatigue and Fatigue
of the plantar-flexor muscles. In Experiment 1 (n=15), the postural task was
executed in two Neutral head and Head tilted backward postures, recognized to
degrade vestibular and neck somatosensory information. In Experiment 2 (n=15),
the postural task was executed in two conditions of No tactile and Tactile
stimulation of the neck provided by the application of strips of adhesive
bandage to the skin over and around the neck. Centre of foot pressure
displacements were recorded using a force platform. Results showed that (1) the
Fatigue condition yielded increased CoP displacements relative to the No
Fatigue condition (Experiment 1 and Experiment 2), (2) this destabilizing
effect was more accentuated in the Head tilted backward posture than Neutral
head posture (Experiment 1) and (3) this destabilizing effect was less
accentuated in the condition of Tactile stimulation than that of No tactile
stimulation of the neck (Experiment 2). In the context of the multisensory
control of balance, these results suggest an increased reliance on vestibular
and neck somatosensory information for controlling posture during quiet
standing in condition of altered ankle neuromuscular function
Modelling the Pan-Spectral Energy Distribution of Starburst Galaxies: IV The Controlling Parameters of the Starburst SED
We combine the the stellar spectral synthesis code Starburst99, the nebular
modelling code MAPPINGSIII, and a 1-D dynamical evolution model of HII regions
around massive clusters of young stars to generate improved models of the
spectral energy distribution (SED) of starburst galaxies. We introduce a
compactness parameter, C, which characterizes the specific intensity of the
radiation field at ionization fronts in HII regions, and which controls the
shape of the far-IR dust re-emission, often referred to loosely as the dust
``temperature''. We also investigate the effect of metallicity on the overall
SED and in particular, on the strength of the PAH features. We provide
templates for the mean emission produced by the young compact HII regions, the
older (10 - 100 Myr) stars and for the wavelength-dependent attenuation
produced by a foreground screen of the dust used in our model. We demonstrate
that these components may be combined to produce a excellent fit to the
observed SEDs of star formation dominated galaxies which are often used as
templates (Arp 220 and NGC 6240). This fit extends from the Lyman Limit to
wavelengths of about one mm. The methods presented in both this paper and in
the previous papers of this series allow the extraction of the physical
parameters of the starburst region (star formation rates, star formation rate
history, mean cluster mass, metallicity, dust attenuation and pressure) from
the analysis of the pan-spectral SED.Comment: 35 pages, 21 figures, accepted for publication in ApJS full-res
available at http://www.strw.leidenuniv.nl/~brent/publications/SEDIV.pd
Modelling the Pan-Spectral Energy Distribution of Starburst Galaxies: I. The role of ISM pressure & the Molecular Cloud Dissipation Timescale
In this paper, we combine the stellar spectral synthesis code STARBURST 99,
the nebular modelling code MAPPINGS IIIq, a 1-D dynamical evolution model of
\HII regions around massive clusters of young stars and a simplified model of
synchrotron emissivity to produce purely theoretical self-consistent synthetic
spectral energy distributions (SEDs) for (solar metallicity) starbursts lasting
some years. These SEDs extend from the Lyman Limit to beyond 21 cm. We
find that two ISM parameters control the form of the SED; the pressure in the
diffuse phase of the ISM (or, equivalently, its density), and the molecular
cloud dissipation timescale. We present detailed SED fits to Arp 220 and NGC
6240, and we give the predicted colors for starburst galaxies derived from our
models for the IRAS and the Spitzer Space Observatory MIPS and IRAC
instruments. Our models reproduce the spread in observed colors of starburst
galaxies. Finally, we present absolute calibrations to convert observed fluxes
into star formation rates in the UV (GALEX), at optical wavelengths
(H), and in the IR (IRAS or the Spitzer Space Observatory). (Abstract
Truncated)Comment: 56 pages, 16 figures, accepted by The Apstrophysical Journal For
version with full, colour figures go to
http://www.mso.anu.edu.au/~bgroves/starburst
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