3,161 research outputs found
Algebraic Torsion in Contact Manifolds
We extract a nonnegative integer-valued invariant, which we call the "order
of algebraic torsion", from the Symplectic Field Theory of a closed contact
manifold, and show that its finiteness gives obstructions to the existence of
symplectic fillings and exact symplectic cobordisms. A contact manifold has
algebraic torsion of order zero if and only if it is algebraically overtwisted
(i.e. has trivial contact homology), and any contact 3-manifold with positive
Giroux torsion has algebraic torsion of order one (though the converse is not
true). We also construct examples for each nonnegative k of contact 3-manifolds
that have algebraic torsion of order k but not k - 1, and derive consequences
for contact surgeries on such manifolds. The appendix by Michael Hutchings
gives an alternative proof of our cobordism obstructions in dimension three
using a refinement of the contact invariant in Embedded Contact Homology.Comment: 53 pages, 4 figures, with an appendix by Michael Hutchings; v.3 is a
final update to agree with the published paper, and also corrects a minor
error that appeared in the published version of the appendi
High Velocity Line Emission in the NLR of NGC 4151
Narrow-band imaging of the nuclear region of NGC 4151 with the Hubble Space
Telescope is presented. The filter bandpasses isolate line emission in various
high velocity ranges in several ions. Slitless and long-slit spectra of the
region with the Space Telescope Imaging Spectrograph also indicate the
locations of high velocity gas. These emission regions are faint and are
interspersed among the bright emission clouds seen in direct images. They have
radial velocities up to 1400 km/s relative to the nucleus, and are found in
both approach and recession on both sides of the nucleus. This contrasts
strongly with the bright emission line clouds which have been discussed
previously as showing bidirectional outflow with velocities within 400 km/s of
the nucleus. We discuss the possible connections of the high velocity material
with the radio jet and the nuclear radiation.Comment: 12 pages plus 6 figures, to be published in A
Printing stable liquid tracks on a surface with finite receding contact angle.
We have used high-speed imaging to study the formation of liquid tracks on a surface with nonzero receding contact angle, by the sequential deposition of liquid drops. For small drop spacing we found good agreement with the track morphology predicted by an existing line stability model. In addition, we confirmed definitively the preferential drop-to-bead fluid flow and the predicted drop spreading variation in the scalloped line and paired bead formation regimes. However, we found that without accounting for drop impact inertia, the model underestimated the maximum drop spreading radii and, hence, the instantaneous track width. In addition, the printed track became stable at larger drop spacing, in contrast to the expected behavior. We believe that the destabilizing effect of a receding contact line may be minimized when track radii, as predicted by volume conservation and drop-bead coalescence dynamics, converge as the drop spacing increases. An increase in viscous dissipation and a reduction of the capillary-driven flow may be the additional stabilization mechanisms. The latter may also be responsible for achieving a stable and symmetrical track when printing with a shorter interval (higher print frequency) at a given drop spacing.This project was supported by the UK Engineering and
Physical Sciences Research Council and industrial partners in
the Programme Grant number EP/H018913/1 âInnovation in
Industrial Inkjet Technologyâ.This is the final published version. It first appeared at http://pubs.acs.org/doi/abs/10.1021/la502490p
FUSE Spectra of the Black Hole Binary LMC X-3
Far-ultraviolet spectra of LMC X-3 were taken covering photometric phases
0.47 to 0.74 in the 1.7-day orbital period of the black-hole binary (phase zero
being superior conjunction of the X-ray source). The continuum is faint and
flat, but appears to vary significantly during the observations. Concurrent
RXTE/ASM observations show the system was in its most luminous X-ray state
during the FUSE observations. The FUV spectrum contains strong terrestrial
airglow emission lines, while the only stellar lines clearly present are
emissions from the O VI resonance doublet. Their flux does not change
significantly during the FUSE observations. These lines are modelled as two
asymmetrical profiles, including the local ISM absorptions due to C II and
possibly O VI. Velocity variations of O VI emission are consistent with the
orbital velocity of the black hole and provide a new constraint on its mass.Comment: 12 pages including 1 table, 4 diagrams To appear in A
Spatially resolved spectra of 3C galaxy nuclei
We present and discuss visible-wavelength long-slit spectra of four low
redshift 3C galaxies obtained with the STIS instrument on the Hubble Space
Telescope. The slit was aligned with near-nuclear jet-like structure seen in
HST images of the galaxies, to give unprecedented spatial resolution of the
galaxy inner regions. In 3C 135 and 3C 171, the spectra reveal clumpy emission
line structures that indicate outward motions of a few hundred km s
within a centrally illuminated and ionised biconical region. There may also be
some low-ionisation high-velocity material associated with 3C 135. In 3C 264
and 3C 78, the jets have blue featureless spectra consistent with their
proposed synchrotron origin. There is weak associated line emission in the
innermost part of the jets with mild outflow velocity. These jets are bright
and highly collimated only within a circumnuclear region of lower galaxy
luminosity, which is not dusty. We discuss the origins of these central regions
and their connection with relativistic jets.Comment: 15 pages incl Tables, 12 diagrams, To appear in A
STIS Longslit Spectroscopy Of The Narrow Line Region Of NGC 4151. I. Kinematics and Emission Line Ratios
Longslit spectra of the Seyfert galaxy NGC 4151 from the UV to near infrared
have been obtained with STIS to study the kinematics and physical conditions in
the NLR. The kinematics show evidence for three components, a low velocity
system in normal disk rotation, a high velocity system in radial outflow at a
few hundred km/s relative to the systemic velocity and an additional high
velocity system also in outflow with velocities up to 1400 km/s, in agreement
with results from STIS slitless spectroscopy (Hutchings et al., 1998, Kaiser et
al., 1999, Hutchings et al., 1999) We have explored two simple kinematic models
and suggest that radial outflow in the form of a wind is the most likely
explanation. We also present evidence indicating that the wind may be
decelerating with distance from the nucleus.
We find that the emission line ratios along our slits are all entirely
consistent with photoionization from the nuclear continuum source. A decrease
in the [OIII]5007/H-beta and [OIII]5007/[OII]3727 ratios suggests that the
density decreases with distance from the nucleus. This trend is borne out by
the [SII] ratios as well. We find no strong evidence for interaction between
the radio jet and the NLR gas in either the kinematics or the emission line
ratios in agreement with the results of Kaiser et al. (1999) who find no
spatial coincidence of NLR clouds and knots in the radio jet. These results are
in contrast to other recent studies of nearby AGN which find evidence for
significant interaction between the radio source and the NLR gas.Comment: 32 pages, 13 figures, accepted for publication in The Astrophysical
Journa
Mapping the Kinematics of the Narrow-Line Region in the Seyfert Galaxy NGC 4151
Using The Hubble Space Telescope's Space Telescope Imaging Spectrograph HST's
STIS, observations of the OIII emission from the narrow-line region (NLR) of
NGC 4151 were obtained and radial velocities determined. Five orbits of HST
time were used to obtain spectra at five parallel slit configurations, at a
position angle of 58 degrees, with spatial resolution 0.2 arcseconds across and
0.1 arcseconds along each slit. A spectral resolving power of ~ 9,000 with the
G430M grating gave velocity measurements accurate to ~ 34 km/s. A kinematic
model was generated to match the radial velocities, for comparison to previous
kinematic models of biconical radial outflow developed for low-dispersion
spectra at two slit positions. The new high-resolution spectra permit the
measurement of accurate velocity dispersions for each radial-velocity
component. The full-width at half-maximum (FWHM) reaches a maximum of 1000 km/s
near the nucleus, and generally decreases with increasing distance to about 100
km/s in the extended narrow-line region (ENLR), starting at about 6 arcseconds
from the nucleus. In addition to the bright emission knots, which generally fit
our model, there are faint high velocity clouds which do not fit the biconical
outflow pattern of our kinematic model. These faint clouds occur at the
turnover points of the outflowing bright clouds. We suggest possible scenarios
that could explain these rogue clouds: (1) backflow resulting from shocks and
(2) outflow outside of the bicones, although the latter does not explain how
the knots are ionized and accelerated. A comparison of our observations with a
high-resolution radio map shows that there is no evidence that the kinematics
of the NLR clouds are affected by the radio lobes that comprise the inner jet.Comment: 30 pages, 15 figures (some color), accepted for publication in the
Astronomical Journal. Downloadable versions of the paper with high resolution
figures/images are available here:
http://www.chara.gsu.edu/~crenshaw/NGC4151_kinematics.pdf <--PDF Version
http://www.chara.gsu.edu/~crenshaw/NGC4151_kinematics.ps <--PS Versio
Probing the Kinematics of the Narrow-Line Region in Seyfert Galaxies with Slitless Spectroscopy: Observational Results
We present slitless spectra of 10 Seyfert galaxies observed with the Space
Telescope Imaging Spectrograph on the Hubble Space Telescope. The spectra cover
the [OIII] 4959, 5007 emission lines at a spectral resolving power of ~9000 and
a spatial resolution of 0.1". We compare the slitless spectra with previous HST
narrow-band images to determine the velocity shifts and dispersions of the
bright emission-line knots in the narrow-line regions (NLRs) of these Seyferts.
Many knots are spatially resolved with sizes of tenths of arcsecs,
corresponding to tens of pcs, and yet they appear to move coherently with
radial velocities between zero and +/- 1200 km/s with respect to the systemic
velocities of their hostgalaxies. The knots also show a broad range in velocity
dispersion, ranging from ~30 km/s (the velocity resolution) to ~1000 km/s FWHM.
Most of the Seyfert galaxies in this sample show an organized flow pattern,
with radial velocities near zero at the nucleus (defined by the optical
continuum peak) and increasing to maximum blueshifts and redshifts within ~1''
of the nucleus, followed by a decline to the systemic velocity. The
emission-line knots also follow a general trend of decreasing velocity
dispersion with increasing distance. In the Seyfert 2 galaxies, the presence of
blueshifts and redshifts on either side of the nucleus indicates that rotation
alone cannot explain the observed radial velocities, and that radial outflow
plays an important role. Each of the Seyfert galaxies in this sample (with the
exception of Mrk 3) shows a bright, compact (FWHM < 0.5") [O III] knot at the
position of its optical nucleus. These nuclear emission-line knots have
radial-velocity centroids near zero, but they typically have the highest
velocity dispersions.Comment: 28 pages, 5 figures (on 9 pages), accepted for A
A Kinematic Model for the Narrow-Line Region in NGC 4151
We present a simple kinematic model for the narrow-line region (NLR) of the
Seyfert 1 galaxy NGC 4151, based on our previous observations of extended [O
III] emission with the Space Telescope Imaging Spectrograph (STIS). The model
is similar to a biconical radial outflow model developed for the Seyfert 2
galaxy NGC 1068, except that the bicone axis is tilted much more into our line
of sight (40 degrees out of the plane of the sky instead of 5 degrees), and the
maximum space velocities are lower (750 km/s instead of 1300 km/s. We find
evidence for radial acceleration of the emission-line knots to a distance of
160 pc, followed by deceleration that approaches the systemic velocity at a
distance of 290 pc (for a distance to NGC 4151 of 13.3 Mpc). Other similarities
to the kinematics of NGC 1068 are: 1) there are a number of high-velocity
clouds that are not decelerated, suggesting that the medium responsible for the
deceleration is patchy, and 2) the bicone in NGC 4151 is at least partially
evacuated along its axis. Together, these two Seyfert galaxies provide strong
evidence for radial outflow (e.g., due to radiation and/or wind pressure) and
against gravitational motion or expansion away from the radio jets as the
principal kinematic component in the NLR.Comment: 31 pages, Latex, includes 11 figures in postscript, Figures
5a,5b,6a,6b in color, to appear in the Astronomical Journa
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