6,155 research outputs found
Superwind-driven Intense H Emission in NGC 6240 II: Detailed Comparison of Kinematical and Morphological Structures of the Warm and Cold Molecular Gas
We report on our new analysis of the spatial and kinematical distribution of
warm and cold molecular gas in NGC 6240, which was undertaken to explore the
origin of its unusually luminous H emission. By comparing three-dimensional
emission-line data (in space and velocity) of CO (J=2-1) in the radio and H
in the near infrared, we are able to study the H emitting efficiency,
defined in terms of the intensity ratio of H to CO [(H)/(CO)], as
a function of velocity. The integrated H emitting efficiency is calculated
by integrating the velocity profile of H emitting efficiency in blue, red,
and total (blue + red) velocity regions of the profile. We find that (1) both
the total H emitting efficiency and the blue-to-red ratio of the efficiency
are larger in regions surrounding the CO and H intensity peaks, and (2) the
H emitting efficiency and the kinematical conditions in the warm molecular
gas are closely related to each other. A collision between the molecular gas
concentration and the external superwind outflow from the southern nucleus
seems plausible to explain these characteristics, since it can reproduce the
enhanced emitting efficiency of blueshifted H around the molecular gas
concentration, if we assume that the superwind blows from the southern nucleus
toward us, hitting the entire gas concentration from behind. In this model,
internal cloud-cloud collisions within the molecular gas concentration are
enhanced by the interaction with the superwind outflow, and efficient and
intense shock-excited H emission is expected as a result of the
cloud-crushing mechanism.Comment: 12 pages, 6 figures, accepted for publication in A
Understanding the Entrepreneur: An Index of Entrepreneurial Success
A measure of entrepreneur success is important to identify current and future successful ventures, to further our understanding of the entrepreneurial process and to guide public policies to improve the success rate of start-ups. In this paper we propose an index of entrepreneur success that accommodates multiple inputs and outputs, that is predicated on inputs and that mitigates the impact of outliers. We relate the index to characteristics of the entrepreneur and the venture: age, experience, gender, race, competitive advantage, education, and birthplace. The data are from the Kauffman Firm Survey. The index is calculated for 2,863 firms in 2006.entrepreneur, Kauffman Survey, Financial Economics, Productivity Analysis,
The Impact of Age on the Ability to Perform under Pressure: Golfers on the PGA Tour
This paper is about aging and the ability to perform under pressure on the PGA tour. Performance increases with golfing skill, but may first increase and then decrease with age as experience interacts with changes in physical condition. Similarly, mental fortitude or the ability of a golfer to perform under pressure may first increase and then decrease with age as experience interacts with changes in the ability to concentrate. Net performance on the tour is the result of both physical golfing skill and the ability to perform under pressure. We control for changes in physical skill and focus on the mental side of the game. The role of experience suggests an inverted U shaped relationship between age and mental performance that could vary significantly across golfers. We use Order-m FDH to calculate a measure of performance under pressure, and we confirm an inverted U-shaped curve with age. Along the way, we examine the ability to perform under pressure at the level of the individual golfer.age, efficiency, order-m FDH, golf, performance under pressure, Productivity Analysis,
Determination of complex dielectric functions of ion implanted and implanted‐annealed amorphous silicon by spectroscopic ellipsometry
Measuring with a spectroscopic ellipsometer (SE) in the 1.8–4.5 eV photon energy region we determined the complex dielectric function (ϵ = ϵ1 + iϵ2) of different kinds of amorphous silicon prepared by self‐implantation and thermal relaxation (500 °C, 3 h). These measurements show that the complex dielectric function (and thus the complex refractive index) of implanted a‐Si (i‐a‐Si) differs from that of relaxed (annealed) a‐Si (r‐a‐Si). Moreover, its ϵ differs from the ϵ of evaporated a‐Si (e‐a‐Si) found in the handbooks as ϵ for a‐Si. If we use this ϵ to evaluate SE measurements of ion implanted silicon then the fit is very poor. We deduced the optical band gap of these materials using the Davis–Mott plot based on the relation: (ϵ2E2)1/3 ∼ (E− Eg). The results are: 0.85 eV (i‐a‐Si), 1.12 eV (e‐a‐Si), 1.30 eV (r‐a‐Si). We attribute the optical change to annihilation of point defects
About the morphology of dwarf spheroidal galaxies and their dark matter content
The morphological properties of the Carina, Sculptor and Fornax dwarfs are
investigated using new wide field data with a total area of 29 square degrees.
The stellar density maps are derived, hinting that Sculptor possesses tidal
tails indicating interaction with the Milky Way. Contrary to previous studies
we cannot find any sign of breaks in the density profiles for the Carina and
Fornax dwarfs. The possible existence of tidal tails in Sculptor and of King
limiting radii in Fornax and Carina are used to derive global M/L ratios,
without using kinematic data. By matching those M/L ratios to kinematically
derived values we are able to constrain the orbital parameters of the three
dwarfs. Fornax cannot have M/L smaller than 3 and must be close to its
perigalacticon now. The other extreme is Sculptor that needs to be on an orbit
with an eccentricity bigger than 0.5 to be able to form tidal tails despite its
kinematic M/L.Comment: 9 pages, 7 figures, accepted by A&
A Side of Mercury Not Seen By Mariner 10
More than 60,000 images of Mercury were taken at ~29 deg elevation during two
sunrises, at 820 nm, and through a 1.35 m diameter off-axis aperture on the
SOAR telescope. The sharpest resolve 0.2" (140 km) and cover 190-300 deg
longitude -- a swath unseen by the Mariner 10 spacecraft -- at complementary
phase angles to previous ground-based optical imagery. Our view is comparable
to that of the Moon through weak binoculars. Evident are the large crater
Mozart shadowed on the terminator, fresh rayed craters, and other albedo
features keyed to topography and radar reflectivity, including the putative
huge ``Basin S'' on the limb. Classical bright feature Liguria resolves across
the northwest boundary of the Caloris basin into a bright splotch centered on a
sharp, 20 km diameter radar crater, and is the brightest feature within a
prominent darker ``cap'' (Hermean feature Solitudo Phoenicis) that covers the
northern hemisphere between longitudes 140-250 deg. The cap may result from
space weathering that darkens via a magnetically enhanced flux of the solar
wind, or that reddens low latitudes via high solar insolation.Comment: 7 pages, 4 PDF figures, pdfLaTeX, typos corrected, Fig. 2 modified
slightly to add crater diameters not given in published versio
Closed surface bundles of least volume
Since the set of volumes of hyperbolic 3-manifolds is well ordered, for each
fixed g there is a genus-g surface bundle over the circle of minimal volume.
Here, we introduce an explicit family of genus-g bundles which we conjecture
are the unique such manifolds of minimal volume. Conditional on a very
plausible assumption, we prove that this is indeed the case when g is large.
The proof combines a soft geometric limit argument with a detailed
Neumann-Zagier asymptotic formula for the volumes of Dehn fillings.
Our examples are all Dehn fillings on the sibling of the Whitehead manifold,
and we also analyze the dilatations of all closed surface bundles obtained in
this way, identifying those with minimal dilatation. This gives new families of
pseudo-Anosovs with low dilatation, including a genus 7 example which minimizes
dilatation among all those with orientable invariant foliations.Comment: 22 pages, 4 figures. V2: Corrected Table 1.9; V3: Added Table 1.10;
V4: Minor edits; V5: Corrected Figure 2.1. To appear in AG&
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