293 research outputs found
A Migration Study of \u3ci\u3eStelidota Geminata\u3c/i\u3e (Coleoptera: Nitidulidae)
The strawberry sap beetle, Stelidota geminata (Say), is a major pest of strawberries in the northeastern United States. Further knowledge of the migratory habits of this insect pest can enhance the effectiveness of pest management strategies. This nitidulid was shown to migrate from its overwintering sites to one of its primary reproductive sites, strawberry fields, in late May. The beetle population peaked in the third week in July, 1993 in the strawberry field and then gradually declined. In 1994, the peak, as well as the total population, was much greater than in 1993. Furthermore, S. geminata was concentrated in the transition areas surrounding the strawberry fields prior to the ripening of the fruit
Evolution of the Stellar Mass--Metallicity Relation - I: Galaxies in the z~0.4 Cluster Cl0024
We present the stellar mass-stellar metallicity relationship (MZR) in the
Cl0024+1654 galaxy cluster at z~0.4 using full spectrum stellar population
synthesis modeling of individual quiescent galaxies. The lower limit of our
stellar mass range is , the lowest galaxy mass at which
individual stellar metallicity has been measured beyond the local universe. We
report a detection of an evolution of the stellar MZR with observed redshift at
dex per Gyr, consistent with the predictions from
hydrodynamical simulations. Additionally, we find that the evolution of the
stellar MZR with observed redshift can be explained by an evolution of the
stellar MZR with their formation time, i.e., when the single stellar population
(SSP)-equivalent ages of galaxies are taken into account. This behavior is
consistent with stars forming out of gas that also has an MZR with a
normalization that decreases with redshift. Lastly, we find that over the
observed mass range, the MZR can be described by a linear function with a
shallow slope, (). The slope suggests
that galaxy feedback, in terms of mass-loading factor, might be
mass-independent over the observed mass and redshift range.Comment: 22 pages, 10 figures. Accepted for publication in Ap
How to make a traversable wormhole from a Schwarzschild black hole
The theoretical construction of a traversable wormhole from a Schwarzschild
black hole is described, using analytic solutions in Einstein gravity. The
matter model is pure phantom radiation (pure radiation with negative energy
density) and the idealization of impulsive radiation is employed.Comment: 4 pages, 4 figure
The Dynamical Distinction between Elliptical and Lenticular Galaxies in Distant Clusters: Further Evidence for the Recent Origin of S0 Galaxies
We examine resolved spectroscopic data obtained with the Keck II telescope
for 44 spheroidal galaxies in the fields of two rich clusters, Cl0024+16
(z=0.40) and MS0451-03 (z=0.54), and contrast this with similar data for 23
galaxies within the redshift interval 0.3<z<0.65 in the GOODS northern field.
For each galaxy we examine the case for systemic rotation, derive central
stellar velocity dispersions sigma and photometric ellipticities, epsilon.
Using morphological classifications obtained via Hubble Space Telescope imaging
as the basis, we explore the utility of our kinematic quantities in
distinguishing between pressure-supported ellipticals and
rotationally-supported lenticulars (S0s). We demonstrate the reliability of
using the v/(1-epsilon) vs sigma and v/sigma vs epsilon distributions as
discriminators, finding that the two criteria correctly identify 63%+-3% and
80%+-2% of S0s at z~0.5, respectively, along with 76%+8-3% and 79%+-2% of
ellipticals. We test these diagnostics using equivalent local data in the Coma
cluster, and find that the diagnostics are similarly accurate at z=0. Our
measured accuracies are comparable to the accuracy of visual classification of
morphologies, but avoid the band-shifting and surface brightness effects that
hinder visual classification at high redshifts. As an example application of
our kinematic discriminators, we then examine the morphology-density relation
for elliptical and S0 galaxies separately at z~0.5. We confirm, from kinematic
data alone, the recent growth of rotationally-supported spheroidals. We discuss
the feasibility of extending the method to a more comprehensive study of
cluster and field galaxies to z~1, in order to verify in detail the recent
density-dependent growth of S0 galaxies.Comment: 7 pages, 4 figures, updated with version accepted to Ap
Evolution of the Stellar MassâMetallicity Relation. II. Constraints on Galactic Outflows from the Mg Abundances of Quiescent Galaxies
We present the stellar massâ[Fe/H] and massâ[Mg/H] relation of quiescent galaxies in two galaxy clusters at z ~ 0.39 and z ~ 0.54. We derive the age, [Fe/H], and [Mg/Fe] for each individual galaxy using a full-spectrum fitting technique. By comparing with the relations for z ~ 0 Sloan Digital Sky Survey galaxies, we confirm our previous finding that the massâ[Fe/H] relation evolves with redshift. The massâ[Fe/H] relation at higher redshift has lower normalization and possibly steeper slope. However, based on our sample, the massâ[Mg/H] relation does not evolve over the observed redshift range. We use a simple analytic chemical evolution model to constrain the average outflow that these galaxies experience over their lifetime, via the calculation of mass-loading factor. We find that the average mass-loading factor η is a power-law function of galaxy stellar mass, η â M*^(â0.21±0.09). The measured mass-loading factors are consistent with the results of other observational methods for outflow measurements and with the predictions where outflow is caused by star formation feedback in turbulent disks
Comment on "Failure of standard conservation laws at a classical change of signature"
Hellaby & Dray (gr-qc/9404001) have recently claimed that matter conservation
fails under a change of signature, compounding earlier claims that the standard
junction conditions for signature change are unnecessary. In fact, if the field
equations are satisfied, then the junction conditions and the conservation
equations are satisfied. The failure is rather that the authors did not make
sense of the field equations and conservation equations, which are singular at
a change of signature.Comment: 3 pages, Te
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