7,393 research outputs found
The Meaning of Probability of Default for Asset-backed Loans
The authors examine the concept of probability of default for asset-backed
loans. In contrast to unsecured loans it is shown that probability of default
can be defined as either a measure of the likelihood of the borrower failing to
make required payments, or as the likelihood of an insufficiency of collateral
value on foreclosure. Assuming expected loss is identical under either
definition, this implies a corresponding pair of definitions for loss given
default. Industry treatment of probability of default for asset-backed loans
appears to inconsistently blend the two types of definition.
The authors develop a mathematical treatment of asset-backed loans which
consistently applies each type of definition in a framework to produce the same
expected loss and allows translation between the two frameworks.Comment: 28 pages, 13 figure
The Intrinsic Ellipticity of Spiral Disks
We have measured the distribution of intrinsic ellipticities for a sample of
28 relatively face-on spiral disks. We combine H-alpha velocity fields and R
and I-band images to determine differences between kinematic and photometric
inclination and position angles, from which we estimate intrinsic ellipticities
of galaxy disks. Our findings suggest disks have a log-normal distribution of
ellipticities (mean epsilon =0.06) and span a range from epsilon= 0 (circular)
to epsilon=0.2. We are also able to construct a tight Tully-Fisher relation for
our face-on sample. We use this to assess the contribution of disk ellipticity
on the observed Tully-Fisher scatter.Comment: 4 pages, 2 figures, to appear in "Disks of Galaxies: Kinematics,
Dynamics and Perturbations" (ASP Conference Series), eds E.Athanassoula and
A. Bosm
Sky coverage modeling for the whole sky for laser guide star multiconjugate adaptive optics
The scientific productivity of laser guide star adaptive optics systems strongly depends on the sky coverage, which describes the probability of finding natural guide stars for the tip/tilt wavefront sensor(s) to achieve a certain performance. Knowledge of the sky coverage is also important for astronomers planning their observations. In this paper, we present an efficient method to compute the sky coverage for the laser guide star multiconjugate adaptive optics system, the Narrow Field Infrared Adaptive Optics System (NFIRAOS), being designed for the Thirty Meter Telescope project. We show that NFIRAOS can achieve more than 70% sky coverage over most of the accessible sky with the requirement of 191 nm total rms wavefront
WIYN Integral-Field Kinematics of Disk Galaxies
We have completed a new fiber array, SparsePak, optimized for
low-surface-brightness studies of extended sources on the WIYN telescope. We
are now using this array as a measuring engine of velocity and
velocity-dispersion fields of stars and ionized gas in disk galaxies from high
to low surface-brightness. Here we present commissioning data on the velocity
ellipsoids, surface densities and mass-to-light ratios in two blue, high
surface-brightness, yet small disks. If our preliminary results survive further
observation and more sophisticated analysis, then NGC 3949 has sigma_z/sigma_R
>> 1, implying strong vertical heating, while NGC 3982's disk is substantially
sub-maximal. These galaxies are strikingly unlike the Milky Way, and yet would
be seen more easily at high redshift.Comment: to appear in Disk Galaxies: Kinematics, Dynamics and Perturbations,
eds. E. Athanassoula and A. Bosma, ASP Conference Series; 4 pages with 4
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