3,487 research outputs found
Isomonodromic deformations of connections with singularities of parahoric formal type
In previous work, the authors have developed a geometric theory of
fundamental strata to study connections on the projective line with irregular
singularities of parahoric formal type. In this paper, the moduli space of
connections that contain regular fundamental strata with fixed combinatorics at
each singular point is constructed as a smooth Poisson reduction. The authors
then explicitly compute the isomonodromy equations as an integrable system.
This result generalizes work of Jimbo, Miwa, and Ueno to connections whose
singularities have parahoric formal type.Comment: 32 pages. One of the main theorems (Theorem 5.1) has been
significantly strengthened. It now states that the isomonodromy equations
give rise to an integrable system on the moduli space of framed connections
with fixed combinatorics instead of only on a principal GL_n bundle over this
space. Sections 5 and 6 have been substantially rewritte
The Archean crust in the Wawa-Chapleau-Timmins region. A field guidebook prepared for the 1983 Archean Geochemistry-Early Crustal Genesis Field Conference
This guidebook describes the characteristics and interrelationships of Archean greenstone-granite and high-grade gneiss terrains of the Superior Province. A 300-km long west to east transect between Wawa and Timmins, Ontario will be used to illustrate regional-scale relationships. The major geological features of the Superior Province are described
The Nature of Nearby Counterparts to Intermediate Redshift Luminous Compact Blue Galaxies II. CO Observations
We present the results of a single-dish beam-matched survey of the three
lowest rotational transitions of CO in a sample of 20 local (D < 70 Mpc)
Luminous Compact Blue Galaxies (LCBGs). These ~L*, blue, high surface
brightness, starbursting galaxies were selected with the same criteria used to
define LCBGs at higher redshifts. Our detection rate was 70%, with those
galaxies having Lblue<7e9 Lsun no detected. We find the H2 masses of local
LCBGs range from 6.6e6 to 2.7e9 Msun, assuming a Galactic CO-to-H2 conversion
factor. Combining these results with our earlier HI survey of the same sample,
we find that the ratio of molecular to atomic gas mass is low, typically 5-10%.
Using a Large Velocity Gradient model, we find that the average gas conditions
of the entire ISM in local LCBGs are similar to those found in the centers of
star forming regions in our Galaxy, and nuclear regions of other galaxies. Star
formation rates, determined from IRAS fluxes, are a few solar masses per year,
much higher per unit dynamical mass than normal spirals. If this rate remains
constant, the molecular hydrogen depletion time scales are short, 10-200 Myr.Comment: accepted for publication in the ApJ (vol 625
Girl, Just Pray ...”: Factors that Influence Breast and Cervical Cancer Among Black Women in Rochester, MN
Coupled surface plasmon-polariton mediated photoluminescence from a top-emitting organic light-emitting structure
Copyright © 2004 American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics. The following article appeared in Applied Physics Letters 85 (2004) and may be found at http://link.aip.org/link/?APPLAB/85/182/1We report strong photoluminescence from a top-emitting organic light-emitting structure where emission takes place through a thin (55 nm) silver film. We show that this emission is mediated via coupled surface plasmon-polariton modes. Our results show that the addition of a dielectric grating to otherwise planar structures, such as surface-emitting organic light-emitting diodes, may offer a way to increase the external efficiency of top-emitting organic light-emitting diodes
Non-linear Dependence of L(B) on L(FIR) and M(H2) among Spiral Galaxies and Effects of Tidal Interaction
Through the study of a carefully selected sample of isolated spiral galaxies,
we have established that two important global physical quantities for tracing
star forming activities, L(FIR) and M(H2), have non-linear dependence on
another commonly cited global quantity L(B). Furthermore we show that simple
power law relations can effectively describe these non-linear relations for
spiral galaxies spanning four orders of magnitude in FIR and M(H2) and nearly
three orders of magnitude in L(B). While the existence of non-linear dependence
of M(H2) (assuming a constant CO-to-H2 conversion) and L(FIR) on optical
luminosity L(B) has been previously noted in the literature, an improper
normalization of simple scaling by L(B) has been commonly used in many previous
studies to claim enhanced molecular gas content and induced activities among
tidally interacting and other types of galaxies. We remove these non-linear
effects using the template relations derived from the isolated galaxy sample
and conclude that strongly interacting galaxies do not have enhanced molecular
gas content, contrary to previous claims. With these non-linear relations among
L(B), L(FIR) and M(H2) properly taken into account, we confirm again that the
FIR emission and the star formation efficiency L(FIR)/M(H2) are indeed enhanced
by tidal interactions. Virgo galaxies show the same level of M(H2) and L(FIR)
as isolated galaxies. We do not find any evidence for enhanced star forming
activity among barred galaxies.Comment: 19 pages and 5 figures, requires AAS style files, ApJ, accepte
The Cool ISM in S0 Galaxies. I. A Survey of Molecular Gas
Lenticular galaxies remain remarkably mysterious as a class. Observations to
date have not led to any broad consensus about their origins, properties and
evolution, though they are often thought to have formed in one big burst of
star formation early in the history of the Universe, and to have evolved
relatively passively since then. In that picture, current theory predicts that
stellar evolution returns substantial quantities of gas to the interstellar
medium; most is ejected from the galaxy, but significant amounts of cool gas
might be retained. Past searches for that material, though, have provided
unclear results. We present results from a survey of molecular gas in a
volume-limited sample of field S0 galaxies, selected from the Nearby Galaxies
Catalog. CO emission is detected from 78 percent of the sample galaxies. We
find that the molecular gas is almost always located inside the central few
kiloparses of a lenticular galaxy, meaning that in general it is more centrally
concentrated than in spirals. We combine our data with HI observations from the
literature to determine the total masses of cool and cold gas. Curiously, we
find that, across a wide range of luminosity, the most gas rich galaxies have
about 10 percent of the total amount of gas ever returned by their stars. That
result is difficult to understand within the context of either monolithic or
hierarchical models of evolution of the interstellar medium.Comment: 26 pages of text, 15 pages of tables, 10 figures. Accepted for
publication in the Astrophysical Journa
Discovery of Recent Star Formation in the Extreme Outer Regions of Disk Galaxies
We present deep Halpha images of three nearby late-type spiral galaxies
(NGC628, NGC1058 and NGC6946), which reveal the presence of HII regions out to,
and beyond, two optical radii (defined by the 25th B-band isophote). The
outermost HII regions appear small, faint and isolated, compared to their inner
disk counterparts, and are distributed in organized spiral arm structures,
likely associated with underlying HI arms and faint stellar arms. The
relationship between the azimuthally--averaged Halpha surface brightness
(proportional to star formation rate per unit area) and the total gas surface
density is observed to steepen considerably at low gas surface densities. We
find that this effect is largely driven by a sharp decrease in the covering
factor of star formation at large radii, and not by changes in the rate at
which stars form locally. An azimuthally--averaged analysis of the
gravitational stability of the disk of NGC6946 reveals that while the existence
of star formation in the extreme outer disk is consistent with the Toomre-Q
instability model, the low rates observed are only compatible with the model
when a constant gaseous velocity dispersion is assumed. We suggest that
observed behaviour could also be explained by a model in which the star
formation rate has an intrinsic dependence on the azimuthally-averaged gas
volume density, which decreases rapidly in the outer disk due to the vertical
flaring of the gas layer.Comment: 10 pages, 2 embedded postscript files, 3 jpeg images; accepted for
publication in ApJ Letter
School resources, resource allocation and risk of physical assault against Minnesota educators
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