409 research outputs found
Do Proto-Jovian Planets Drive Outflows?
We discuss the possibility that gaseous giant planets drive strong outflows
during early phases of their formation. We consider the range of parameters
appropriate for magneto-centrifugally driven stellar and disk outflow models
and find that if the proto-Jovian planet or accretion disk had a magnetic field
of >~ 10 Gauss and moderate mass inflow rates through the disk of less than
10^-7 M_J/yr that it is possible to drive an outflow. Estimates based both on
scaling from empirical laws observed in proto-stellar outflows and the
magneto-centrigugal disk and stellar+disk wind models suggest that winds with
mass outflow rates of 10^-8 M_J/yr and velocities of order ~ 20 km/s could be
driven from proto-Jovian planets. Prospects for detection and some implications
for the formation of the solar system are briefly discussed.Comment: AAS Latex, accepted for Ap
The Distribution of Dark Matter in a Ringed Galaxy
Outer rings are located at the greatest distance from the galaxy center of
any feature resonant with a bar. Because of their large scale, their morphology
is sensitive to the distribution of the dark matter in the galaxy. We introduce
here how study of these rings can constrain the mass-to-light ratio of the bar,
and so the percentage of dark matter in the center of these galaxies. We
compare periodic orbits integrated in the ringed galaxy NGC 6782 near the outer
Lindblad resonance to the shape of the outer ring. The non-axisymmetric
component of the potential resulting from the bar is derived from a
near-infrared image of the galaxy. The axisymmetric component is derived
assuming a flat rotation curve. We find that the pinched non-self-intersecting
periodic orbits are more elongated for higher bar mass-to-light ratios and
faster bars. The inferred mass-to-light ratio of the bar depends on the assumed
inclination of the galaxy. With an assumed galaxy inclination of i=41 degrees,
for the orbits to be consistent with the observed ring morphology the
mass-to-light ratio of the bar must be high, greater than 70% of a maximal disk
value. For i=45 degrees, the mass-to-light ratio of the bar is of
the maximal disk value. Since the velocity field of these rings can be used to
constrain the galaxy inclination as well as which periodic orbit is represented
in the ring, further study will yield tighter constraints on the mass-to-light
ratio of the bar. If a near maximal disk value for the bar is required, then
either there would be little dark matter within the bar, or the dark matter
contained in the disk of the galaxy would be non-axisymmetric and would rotate
with the bar.Comment: AAS Latex + jpg Figures, Accepted for publication in Ap
Manin products, Koszul duality, Loday algebras and Deligne conjecture
In this article we give a conceptual definition of Manin products in any
category endowed with two coherent monoidal products. This construction can be
applied to associative algebras, non-symmetric operads, operads, colored
operads, and properads presented by generators and relations. These two
products, called black and white, are dual to each other under Koszul duality
functor. We study their properties and compute several examples of black and
white products for operads. These products allow us to define natural
operations on the chain complex defining cohomology theories. With these
operations, we are able to prove that Deligne's conjecture holds for a general
class of operads and is not specific to the case of associative algebras.
Finally, we prove generalized versions of a few conjectures raised by M. Aguiar
and J.-L. Loday related to the Koszul property of operads defined by black
products. These operads provide infinitely many examples for this generalized
Deligne's conjecture.Comment: Final version, a few references adde
The Evolution of Protoplanetary Disk Edges
We investigate gap formation in gaseous protostellar disks by a planet in a
circular orbit in the limit of low disk viscosity. This regime may be
appropriate to an aging disk after the epoch of planet formation. We find that
the distance of planet to the gap outer boundary can be between the location of
the and outer Lindblad resonances. This distance is weakly
dependent upon both the planet's mass and disk viscosity. We find that the
evolution of the disk edge takes place on two timescales. The first timescale
is set by the spiral density waves driven by the planet. The second timescale
depends on the viscosity of the disk. The disk approaches a state where the
outward angular momentum flux caused by the disk viscosity is balanced by the
dissipation of spiral density waves which are driven at the Lindblad
resonances. This occurs inefficiently however because of the extremely low gas
density near the planet. We find that the distance between the planet and the
peak density at the disk outer edge is only weakly dependent on the viscosity
and planet mass, however the ratio of the gas density near the planet to that
in the disk (or the slope of density along the disk edge) is strongly dependent
upon both quantities. We find that the disk density profile along the edge
scales approximately with disk viscosity divided by the square of the planet
mass. We account for this behavior with a simple scenario in which the
dissipation of angular momentum from the spiral density waves is balanced
against diffusion in the steep edge of the disk.Comment: Accepted for publication in ApJ, 11 figures, 13 page
Homotopy Theoretic Models of Type Theory
We introduce the notion of a logical model category which is a Quillen model
category satisfying some additional conditions. Those conditions provide enough
expressive power that one can soundly interpret dependent products and sums in
it. On the other hand, those conditions are easy to check and provide a wide
class of models some of which are listed in the paper.Comment: Corrected version of the published articl
The Warped Circumstellar Disk of HD100546
We propose that the two armed spiral features seen in visible Hubble Space
Telescope images of scattered light in HD100546's circumstellar disk are caused
by the illumination of a warped outer disk. A tilt of 6-15 degrees from the
symmetry plane can cause the observed surface brightness variations providing
the disk is very twisted (highly warped) at radii greater than 200 AU where the
spiral features are seen. Dust lanes are due in part to shadowing in the
equatorial plane from the inner disk within a radius of 100 AU. HD100546's
outer disk, if viewed edge-on, would appear similar to that of Beta Pictorus. A
disk initially misaligned with a planetary system, becomes warped due to
precession induced by planetesimal bodies and planets. However, the twistedness
of HD100546's disk cannot be explained by precession during the lifetime of the
system induced by a single Jovian mass planet within the clearing at ~13 AU.
One possible explanation for the corrugated disk is that precession was induced
by massive of bodies embedded in the disk at larger radius. This would require
approximately a Jupiter mass of bodies well outside the central clearing at 13
AU and within the location of the spiral features or at radii approximately
between 50-200 AU.Comment: submitted to Ap
Disentangling the Circumnuclear Environs of Centaurus A: III. An Inner Molecular Ring, Nuclear Shocks and the CO to warm H2 interface
We present the distribution and kinematics of the molecular gas in the
circumnuclear disk (CND, 400 pc x 200 pc) of Centaurus A with resolutions of ~5
pc (0.3 arcsec) and shed light onto the mechanism feeding the Active Galactic
Nucleus (AGN) using CO(3-2), HCO+(4-3), HCN(4-3), and CO(6-5) observations
obtained with ALMA. Multiple filaments or streamers of tens to a hundred parsec
scale exist within the CND, which form a ring-like structure with an
unprojected diameter of 9 x 6 arcsec (162pc x 108pc) and a position angle PA =
155deg. Inside the nuclear ring, there are two leading and straight filamentary
structures with lengths of about 30-60pc at PA = 120deg on opposite sides of
the AGN, with a rotational symmetry of 180deg and steeper position-velocity
diagrams, which are interpreted as nuclear shocks due to non-circular motions.
Along the filaments, and unlike other nearby AGNs, several dense molecular
clumps present low HCN/HCO+(4-3) ratios (~0.5). The filaments abruptly end in
the probed transitions at r = 20pc from the AGN, but previous near-IR H2
(J=1-0) S(1) maps show that they continue in an even ~1000 K), winding up in
the form of nuclear spirals, and forming an inner ring structure with another
set of symmetric filaments along the N-S direction and within r = 10pc. The
molecular gas is governed primarily by non-circular motions, being the
successive shock fronts at different scales where loss of angular momentum
occurs, a mechanism which may feed efficiently powerful radio galaxies down to
parsec scales.Comment: 46 pages. Accepted for publication in Ap
Discovery of a 500 pc shell in the nucleus of Centaurus A
Spitzer Space Telescope mid-infrared images of the radio galaxy Centaurus A
reveal a shell-like, bipolar, structure 500 pc to the north and south of the
nucleus. This shell is seen in 5.8, 8.0 and 24 micron broad-band images. Such a
remarkable shell has not been previously detected in a radio galaxy and is the
first extragalactic nuclear shell detected at mid-infrared wavelengths. We
estimate that the shell is a few million years old and has a mass of order
million solar masses. A conservative estimate for the mechanical energy in the
wind driven bubble is 10^53 erg. The shell could have created by a small few
thousand solar mass nuclear burst of star formation. Alternatively, the
bolometric luminosity of the active nucleus is sufficiently large that it could
power the shell. Constraints on the shell's velocity are lacking. However, if
the shell is moving at 1000 km/s then the required mechanical energy would be
100 times larger.Comment: submitted to ApJ Letter
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