1,969 research outputs found
The Calibration of the WISE W1 and W2 Tully-Fisher Relation
In order to explore local large-scale structures and velocity fields,
accurate galaxy distance measures are needed. We now extend the well-tested
recipe for calibrating the correlation between galaxy rotation rates and
luminosities -- capable of providing such distance measures -- to the all-sky,
space-based imaging data from the Wide-field Infrared Survey Explorer (WISE) W1
(m) and W2 (m) filters. We find a linewidth to absolute
magnitude correlation (known as the Tully-Fisher Relation, TFR) of
(0.54
magnitudes rms) and (0.56 magnitudes rms) from 310 galaxies in 13 clusters. We update the
I-band TFR using a sample 9% larger than in Tully & Courtois (2012). We derive
(0.46 magnitudes
rms). The WISE TFRs show evidence of curvature. Quadratic fits give
(0.52 magnitudes rms) and (0.55
magnitudes rms). We apply an I-band -- WISE color correction to lower the
scatter and derive
and (both 0.46
magnitudes rms). Using our three independent TFRs (W1 curved, W2 curved and
I-band), we calibrate the UNION2 supernova Type Ia sample distance scale and
derive (stat) (sys) kms Mpc with 4%
total error.Comment: 22 page, 21 figures, accepted to ApJ, Table 1 data at
http://spartan.srl.caltech.edu/~neill/tfwisecal/table1.tx
Secondary phi meson peak as an indicator of QCD phase transition in ultrarelativistic heavy ion collisions
In a previous paper, we have shown that a double phi peak structure appears
in the dilepton invariant mass spectrum if a first order QCD phase transition
occurs in ultrarelativistic heavy ion collisions. Furthermore, the transition
temperature can be determined from the transverse momentum distribution of the
low mass phi peak. In this work, we extend the study to the case that a smooth
crossover occurs in the quark-gluon plasma to the hadronic matter transition.
We find that the double phi peak structure still exists in the dilepton
spectrum and thus remains a viable signal for the formation of the quark-gluon
plasma in ultrarelativistic heavy ion collisions.Comment: 8 pages, 9 uuencoded postscript figures included, Latex, LBL-3572
Challenges in shrimp aquaculture due to viral diseases: distribution and biology of the five major penaeid viruses and interventions to avoid viral incidence and dispersion
What's Decidable About Sequences?
We present a first-order theory of sequences with integer elements,
Presburger arithmetic, and regular constraints, which can model significant
properties of data structures such as arrays and lists. We give a decision
procedure for the quantifier-free fragment, based on an encoding into the
first-order theory of concatenation; the procedure has PSPACE complexity. The
quantifier-free fragment of the theory of sequences can express properties such
as sortedness and injectivity, as well as Boolean combinations of periodic and
arithmetic facts relating the elements of the sequence and their positions
(e.g., "for all even i's, the element at position i has value i+3 or 2i"). The
resulting expressive power is orthogonal to that of the most expressive
decidable logics for arrays. Some examples demonstrate that the fragment is
also suitable to reason about sequence-manipulating programs within the
standard framework of axiomatic semantics.Comment: Fixed a few lapses in the Mergesort exampl
Anomaly Detection & Behavior Prediction: Higher-Level Fusion Based on Computational Neuroscientific Principles
Cryptotomography: reconstructing 3D Fourier intensities from randomly oriented single-shot diffraction patterns
We reconstructed the 3D Fourier intensity distribution of mono-disperse
prolate nano-particles using single-shot 2D coherent diffraction patterns
collected at DESY's FLASH facility when a bright, coherent, ultrafast X-ray
pulse intercepted individual particles of random, unmeasured orientations. This
first experimental demonstration of cryptotomography extended the
Expansion-Maximization-Compression (EMC) framework to accommodate unmeasured
fluctuations in photon fluence and loss of data due to saturation or background
scatter. This work is an important step towards realizing single-shot
diffraction imaging of single biomolecules.Comment: 4 pages, 4 figure
Diffusion processes and growth on stepped metal surfaces
We study the dynamics of adatoms in a model of vicinal (11m) fcc metal
surfaces. We examine the role of different diffusion mechanisms and their
implications to surface growth. In particular, we study the effect of steps and
kinks on adatom dynamics. We show that the existence of kinks is crucially
important for adatom motion along and across steps. Our results are in
agreement with recent experiments on Cu(100) and Cu(1,1,19) surfaces. The
results also suggest that for some metals exotic diffusion mechanisms may be
important for mass transport across the steps.Comment: 3 pages, revtex, complete file available from
ftp://rock.helsinki.fi/pub/preprints/tft/ or at
http://www.physics.helsinki.fi/tft/tft_preprints.html (to appear in Phys.
Rev. B Rapid Comm.
Competing mechanisms for step meandering in unstable growth
The meander instability of a vicinal surface growing under step flow
conditions is studied within a solid-on-solid model. In the absence of edge
diffusion the selected meander wavelength agrees quantitatively with the
continuum linear stability analysis of Bales and Zangwill [Phys. Rev. B {\bf
41}, 4400 (1990)]. In the presence of edge diffusion a local instability
mechanism related to kink rounding barriers dominates, and the meander
wavelength is set by one-dimensional nucleation. The long-time behavior of the
meander amplitude differs in the two cases, and disagrees with the predictions
of a nonlinear step evolution equation [O. Pierre-Louis et al., Phys. Rev.
Lett. {\bf 80}, 4221 (1998)]. The variation of the meander wavelength with the
deposition flux and with the activation barriers for step adatom detachment and
step crossing (the Ehrlich-Schwoebel barrier) is studied in detail. The
interpretation of recent experiments on surfaces vicinal to Cu(100) [T.
Maroutian et al., Phys. Rev. B {\bf 64}, 165401 (2001)] in the light of our
results yields an estimate for the kink barrier at the close packed steps.Comment: 8 pages, 7 .eps figures. Final version. Some errors in chapter V
correcte
Extinction law variations and dust excitation in the spiral galaxy NGC 300
We investigate the origin of the strong radial gradient in the
ultraviolet-to-infrared ratio in the spiral galaxy NGC 300, and emphasize the
importance of local variations in the interstellar medium geometry, concluding
that they cannot be neglected with respect to metallicity effects. This
analysis is based upon a combination of maps from GALEX and Spitzer, and from
the ground (UBVRI, Halpha and Hbeta). We select ionizing stellar clusters
associated with HII regions of widely varying morphologies, and derive their
fundamental parameters from population synthesis fitting of their spectral
energy distributions, measured to eliminate local backgrounds accurately. From
these fits, we conclude that the stellar extinction law is highly variable in
the line of sight of young clusters of similar ages. In the particular model
geometry that we consider most appropriate to the sampled regions, we checked
that our findings are not significantly altered by the correct treatment of
radiative transfer effects. The variations are systematic in nature: extinction
laws of the Milky Way or LMC type are associated with compact HII regions (the
compacity being quantified in two different ways), while clusters surrounded by
diffuse HII regions follow extinction laws of the 30 Doradus or SMC type. The
Calzetti starburst attenuation law, although most often degenerate with the 30
Doradus extinction law, overpredicts ionizing photon fluxes by large amounts.
We also find that the extinction law variations are correlated with the column
density of dust species emitting in the near- and mid-infrared. Finally, we
briefly discuss the nebular to stellar extinction ratios, and the excitation of
aromatic band carriers, invalidating their claimed association with cold dust.Comment: accepted for publication in ApJ -- figure 6 abridged her
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