165 research outputs found
A family of Prym-Tyurin varieties of exponent 3
We investigate a family of correspondences associated to \'etale coverings of
degree 3 of hyperelliptic curves. They lead to Prym-Tyurin varieties of
exponent 3. We identify these varieties and derive some consequences.Comment: names of authors correcte
Near-Infrared Imaging of Early-Type Galaxies III. The Near-Infrared Fundamental Plane
Near-infrared imaging data on 251 early-type galaxies in clusters and groups
are used to construct the near-infrared Fundamental Plane (FP) r_eff ~
sigma_0^1.53 _eff^-0.79. The slope of the FP therefore departs from
the virial expectation of r_eff ~ sigma_0^2 _eff^-1 at all optical and
near-infrared wavelengths, which could be a result of the variation of M/L
along the elliptical galaxy sequence, or a systematic breakdown of homology
among the family of elliptical galaxies. The slope of the near-infrared FP
excludes metallicity variations as the sole cause of the slope of the FP. Age
effects, dynamical deviations from a homology, or any combination of these
(with or without metallicity), however, are not excluded. The scatter of both
the near-infrared and optical FP are nearly identical and substantially larger
than the observational uncertainties, demonstrating small but significant
intrinsic cosmological scatter for the FP at all wavelengths. The lack of a
correlation of the residuals of the near-infrared FP and the residuals from the
Mg_2-sigma relation indicates that the thickness of these relations cannot be
ascribed only to age or metallicity effects. Due to this metallicity
independence, the small scatter of the near-infrared FP excludes a model in
which age and metallicity effects ``conspire'' to keep the optical FP thin. All
of these results suggest that the possible physical origins of the FP relations
are complicated due to combined effects of variations of stellar populations
and structural parameters among elliptical galaxies.Comment: to appear in The Astronomical Journal; 35 pages, including 13
Postscript figures and 1 table; uses AAS LaTeX style file
Effect of the Milky Way on Magellanic Cloud structure
A combination of analytic models and n-body simulations implies that the
structural evolution of the Large Magellanic Cloud (LMC) is dominated by its
dynamical interaction with the Milky Way. Although expected at some level, the
scope of the involvement has significant observational consequences. First, LMC
disk orbits are torqued out of the disk plane, thickening the disk and
populating a spheroid. The torque results from direct forcing by the Milky Way
tide and, indirectly, from the drag between the LMC disk and its halo resulting
from the induced precession of the LMC disk. The latter is a newly reported
mechanism that can affect all satellite interations. However, the overall
torque can not isotropize the stellar orbits and their kinematics remains
disk-like. Such a kinematic signature is observed for nearly all LMC
populations. The extended disk distribution is predicted to increase the
microlensing toward the LMC. Second, the disk's binding energy slowly decreases
during this process, puffing up and priming the outer regions for subsequent
tidal stripping. Because the tidally stripped debris will be spatially
extended, the distribution of stripped stars is much more extended than the HI
Magellanic Stream. This is consistent with upper limits to stellar densities in
the gas stream and suggests a different strategy for detecting the stripped
stars. And, finally, the mass loss over several LMC orbits is predicted by
n-body simulation and the debris extends to tens of kiloparsecs from the tidal
boundary. Although the overall space density of the stripped stars is low,
possible existence of such intervening populations have been recently reported
and may be detectable using 2MASS.Comment: 15 pages, color Postscript figures, uses emulateapj.sty. Also
available from http://www-astro.phast.umass.edu/~weinberg/weinberg-pubs.htm
Complete moduli of cubic threefolds and their intermediate Jacobians
The intermediate Jacobian map, which associates to a smooth cubic threefold
its intermediate Jacobian, does not extend to the GIT compactification of the
space of cubic threefolds, not even as a map to the Satake compactification of
the moduli space of principally polarized abelian fivefolds. A much better
"wonderful" compactification of the space of cubic threefolds was constructed
by the first and fourth authors --- it has a modular interpretation, and
divisorial normal crossing boundary. We prove that the intermediate Jacobian
map extends to a morphism from the wonderful compactification to the second
Voronoi toroidal compactification of the moduli of principally polarized
abelian fivefolds --- the first and fourth author previously showed that it
extends to the Satake compactification. Since the second Voronoi
compactification has a modular interpretation, our extended intermediate
Jacobian map encodes all of the geometric information about the degenerations
of intermediate Jacobians, and allows for the study of the geometry of cubic
threefolds via degeneration techniques. As one application we give a complete
classification of all degenerations of intermediate Jacobians of cubic
threefolds of torus rank 1 and 2.Comment: 56 pages; v2: multiple updates and clarification in response to
detailed referee's comment
The Near-Infrared Fundamental Plane of Elliptical Galaxies
We present results from a near-infrared -band imaging survey of 59
elliptical galaxies in five nearby clusters. We measure photometric parameters
for each galaxy using surface photometry and draw velocity dispersions from the
literature. Three observables define a near-infrared Fundamental Plane (FP) of
elliptical galaxies with . The scatter in the near-infrared relation is small at
\% in distance, which is equivalent to, or less than, the scatter of the
optical FP. We suggest that the small deviation of the near-infrared FP
relation from the optical FP is due to the reduction of metallicity effects in
the near-infrared bandpass. While the small scatter of the optical FP could be
consistent with compensating effects of age and metallicity, the similarly
small scatter of the near-infrared FP is nearly independent of metallicity and
hence places a strong constraint on possible age spreads among elliptical
galaxies at every point along the FP. We suggest that the departure of the
near-infrared FP from the pure virial form , and the corresponding observed relation , may be explained by slight systematic departures of
the structure and dynamics of elliptical galaxies from a homology.Comment: to appear in The Astrophysical Journal (Letters); 12 pages, including
2 Postscript figures and 1 table; uuencoded, compressed format; the paper is
also available in various formats from
http://astro.caltech.edu/~map/map.bibliography.refereed.htm
The Discovery and Nature of Optical Transient CSS100217:102913+404220
We report on the discovery and observations of the extremely luminous optical
transient CSS100217:102913+404220 (CSS100217 hereafter). Spectroscopic
observations show this transient was coincident with a galaxy at redshift
z=0.147, and reached an apparent magnitude of V ~ 16.3. After correcting for
foreground Galactic extinction we determine the absolute magnitude to be M_V
=-22.7 approximately 45 days after maximum light. Based on our unfiltered
optical photometry the peak optical emission was L = 1.3 x 10^45 erg s^-1, and
over a period of 287 rest-frame days had an integrated bolometric luminosity of
1.2 x 10^52 erg. Analysis of the pre-outburst SDSS spectrum of the source shows
features consistent with a Narrow-line Seyfert1 (NLS1) galaxy. High-resolution
HST and Keck followup observations show the event occurred within 150pc of
nucleus of the galaxy, suggesting a possible link to the active nuclear region.
However, the rapid outburst along with photometric and spectroscopic evolution
are much more consistent with a luminous supernova. Line diagnostics suggest
that the host galaxy is undergoing significant star formation. We use extensive
follow-up of the event along with archival CSS and SDSS data to investigate the
three most likely sources of such an event; 1) an extremely luminous supernova;
2) the tidal disruption of a star by the massive nuclear black hole; 3)
variability of the central AGN. We find that CSS100217 was likely an extremely
luminous type IIn supernova that occurred within range of the narrow-line
region of an AGN. We discuss how similar events may have been missed in past
supernova surveys because of confusion with AGN activity.Comment: submitted to Ap
Vasorelaxant activity of Euphorbia furcillata Kunth mainly by activation of NO/cGMP pathway and calcium channel blockade
The aim of current study was to determinate ex vivo and chromatographic fingerprint by HPLC of four extracts of Euphorbia furcillata K. Ethyl acetate extract of Euphorbia furcillata (EaEEf) was the most effective and potent extract (Emax=98.69±1.24%) and its effect was partially endothelium-dependent. Functional vasorelaxant mechanism of action of EaEEf was determinate, EaEEf showed efficient relaxation of KCl [80 mM]-induced contraction and norepinephrine and CaCl2 contraction curves showed diminution of maximal contraction in the presence of EAEEf and EaEEf-relaxation curve was shifted to the right in the presence of L-NAME (nitric oxide synthase inhibitor) and ODQ (guanylate cyclase inhibitor). Chromatographic fingerprints analysis suggests presence of diterpenoid such as abietane, tigliane, and ingenane skeletons. Our experiments suggest the EaEEf vasorelaxant activity could be attributed to diterpenoid molecules whose mechanism involves nitric oxide production and calcium channel blockade
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