70 research outputs found
Regional differences in the spatial and temporal heterogeneity of oceanographic habitat used by Steller sea lions
Over the past three decades, the decline and altered spatial distribution of the western stock of Steller sea lions (Eumetopias jubatus) in Alaska have been attributed to changes in the distribution or abundance of their prey due to the cumulative effects of fisheries and environmental perturbations. During this period, dietary prey occurrence and diet diversity were related to population decline within metapopulation regions of the western stock of Steller sea lions, suggesting that environmental conditions may be variable among regions. The objective of this study, therefore, was to examine regional differences in the spatial and temporal heterogeneity of oceanographic habitat used by Steller sea lions within the context of recent measures of diet diversity and population trajectories. Habitat use was assessed by deploying satellite-depth recorders and satellite relay data loggers on juvenile Steller sea lions (n = 45) over a five-year period (2000–2004) within four regions of the western stock, including the western, central, and eastern Aleutian Islands, and central Gulf of Alaska. Areas used by sea lions during summer months (June, July, and August) were demarcated using satellite telemetry data and characterized by environmental variables (sea surface temperature [SST] and chlorophyll a [chl a]), which possibly serve as proxies for environmental processes or prey. Spatial patterns of SST diversity and Steller sea lion population trends among regions were fairly consistent with trends reported for diet studies, possibly indicating a link between environmental diversity, prey diversity, and distribution or abundance of Steller sea lions. Overall, maximum spatial heterogeneity coupled with minimal temporal variability of SST appeared to be beneficial for Steller sea lions. In contrast, these patterns were not consistent for chl a, and there appeared to be an ecological threshold. Understanding how Steller sea lions respond to measures of environmental heterogeneity will ultimately be useful for implementing ecosystem management approaches and developing additional conservation strategies
Improved Constraints on the Gravitational Lens Q0957+561. I. Weak Lensing
Attempts to constrain the Hubble constant using the strong gravitational lens
system Q0957+561 are limited by systematic uncertainties in the mass model,
since the time delay is known very precisely. One important systematic effect
is the mass sheet degeneracy, which arises because strong lens modeling cannot
constrain the presence or absence of a uniform mass sheet , which
rescales by the factor . In this paper we present new
constraints on the mass sheet derived from a weak-lensing analysis of the
Hubble Space Telescope imaging of a 6 arcmin square region surrounding the
lensed quasar. The average mass sheet within a circular aperture (the strong
lens model region) is constrained by integrating the tangential weak
gravitational shear over the surrounding area. We find the average convergence
within a radius around the lens galaxy to be ( confidence level), normalized to the quasar redshift.
This includes contributions from both the lens galaxy and the surrounding
cluster. We also constrain a few other low-order terms in the lens potential by
applying a multipole aperture mass formalism to the gravitational shear in an
annulus around the strong lensing region. Implications for strong lens models
and the Hubble constant are discussed in an accompanying paper.Comment: 13 pages, 8 figures, accepted for publication in Ap
Third quantization of -type gravity
We examine the third quantization of -type gravity, based on its
effective Lagrangian in the case of a flat Friedmann-Lemaitre-Robertson-Walker
metric. Starting from the effective Lagrangian, we execute a suitable change of
variable and the second quantization, and we obtain the Wheeler-DeWitt
equation. The third quantization of this theory is considered. And the
uncertainty relation of the universe is investigated in the example of
-type gravity, where . It is shown, when the time is late
namely the scale factor of the universe is large, the spacetime does not
contradict to become classical, and, when the time is early namely the scale
factor of the universe is small, the quantum effects are dominating.Comment: 9 pages, Arbitrary constants in (4.19) are changed to arbitrary
functions of . Conclusions are not changed. References are added.
Typos are correcte
Near-Infrared K and L' Flux Ratios in Six Lensed Quasars
We examine the wavelength dependence of flux ratios for six gravitationally
lensed quasars using K and L' images obtained at the Gemini North 8m telescope.
We select lenses with source redshifts z_s < 2.8 so that K-band images probe
rest-frame optical emission from accretion disks, while L'-band images probe
rest-frame near-infrared flux emitted (in part) from the more extended
surrounding torus. Since the observations correspond to different source sizes,
the K and L' flux ratios are sensitive to structure on different scales and may
be useful for studying small-structure in the lens galaxies. Four of the six
lenses show differences between K and L' flux ratios. In HE 0435$-1223, SDSS
0246-0825, and HE 2149-2745 the differences may be attributable to known
microlensing and/or intrinsic variability. In SDSS 0806+2006 the wavelength
dependence is not easily attributed to known variations, and may indicate the
presence of substructure. By contrast, in Q0142-100 and SBS 0909+523 the K and
L' flux ratios are consistent within the uncertainties. We discuss the utility
of the current data for studying chromatic effects related to microlensing,
dust extinction, and dark matter substructure.Comment: 19 pages, 4 Figures, 4 Tables, AJ accepte
LBT and Spitzer Spectroscopy of Star-Forming Galaxies at 1 < z < 3: Extinction and Star Formation Rate Indicators
We present spectroscopic observations in the rest-frame optical and near- to
mid-infrared wavelengths of four gravitationally lensed infrared (IR) luminous
star-forming galaxies at redshift 1 < z < 3 from the LUCIFER instrument on the
Large Binocular Telescope and the Infrared Spectrograph on Spitzer. The sample
was selected to represent pure, actively star-forming systems, absent of active
galactic nuclei. The large lensing magnifications result in high
signal-to-noise spectra that can probe faint IR recombination lines, including
Pa-alpha and Br-alpha at high redshifts. The sample was augmented by three
lensed galaxies with similar suites of unpublished data and observations from
the literature, resulting in the final sample of seven galaxies. We use the IR
recombination lines in conjunction with H-alpha observations to probe the
extinction, Av, of these systems, as well as testing star formation rate (SFR)
indicators against the SFR measured by fitting spectral energy distributions to
far-IR photometry. Our galaxies occupy a range of Av from ~0 to 5.9 mag, larger
than previously known for a similar range of IR luminosities at these
redshifts. Thus, estimates of SFR even at z ~ 2 must take careful count of
extinction in the most IR luminous galaxies. We also measure extinction by
comparing SFR estimates from optical emission lines with those from far-IR
measurements. The comparison of results from these two independent methods
indicates a large variety of dust distribution scenarios at 1 < z < 3. Without
correcting for dust extinction, the H-alpha SFR indicator underestimates the
SFR; the size of the necessary correction depends on the IR luminosity and dust
distribution scenario. Individual SFR estimates based on the 6.2 micron PAH
emission line luminosity do not show a systematic discrepancy with extinction,
although a considerable, ~0.2 dex scatter is observed.Comment: Accepted for publication in The Astrophysical Journal; 14 pages, 8
figure
Substructure in the lens HE 0435-1223
We investigate the properties of dark matter substructure in the
gravitational lens HE 0435-1223 (z_l=0.455) via its effects on the positions
and flux ratios of the quadruply-imaged background quasar (z_s=1.689). We start
with a smooth mass model, add individual, truncated isothermal clumps near the
lensed images, and use the Bayesian evidence to compare the quality of
different models. Compared with smooth models, models with at least one clump
near image A are strongly favored. The mass of this clump within its Einstein
radius is log(Mein/Msun) = 7.65 +0.87/-0.84. The Bayesian evidence provides
weaker support for a second clump near image B, with log(Mein/Msun) = 6.55
+1.01/-1.51. We also examine models with a full population of substructure, and
find the mass fraction in substructure at the Einstein radius to be f_sub >
0.00077, assuming the total clump masses follow a mass function dN/dM
proportional to M^(-1.9) over the range M = 10^7-10^10 Msun. Few-clump and
population models produce similar Bayesian evidence values, so neither type of
model is objectively favored.Comment: 18 pages, 12 figures, 4 tables. MNRAS accepte
Dissecting the Gravitational Lens B1608+656. II. Precision Measurements of the Hubble Constant, Spatial Curvature, and the Dark Energy Equation of State
Strong gravitational lens systems with measured time delays between the
multiple images provide a method for measuring the "time-delay distance" to the
lens, and thus the Hubble constant. We present a Bayesian analysis of the
strong gravitational lens system B1608+656, incorporating (i) new, deep Hubble
Space Telescope (HST) observations, (ii) a new velocity dispersion measurement
of 260+/-15 km/s for the primary lens galaxy, and (iii) an updated study of the
lens' environment. When modeling the stellar dynamics of the primary lens
galaxy, the lensing effect, and the environment of the lens, we explicitly
include the total mass distribution profile logarithmic slope gamma' and the
external convergence kappa_ext; we marginalize over these parameters, assigning
well-motivated priors for them, and so turn the major systematic errors into
statistical ones. The HST images provide one such prior, constraining the lens
mass density profile logarithmic slope to be gamma'=2.08+/-0.03; a combination
of numerical simulations and photometric observations of the B1608+656 field
provides an estimate of the prior for kappa_ext: 0.10 +0.08/-0.05. This latter
distribution dominates the final uncertainty on H_0. Compared with previous
work on this system, the new data provide an increase in precision of more than
a factor of two. In combination with the WMAP 5-year data set, we find that the
B1608+656 data set constrains the curvature parameter to be -0.031 < Omega_k <
0.009 (95% CL), a level of precision comparable to that afforded by the current
Type Ia SNe sample. Asserting a flat spatial geometry, we find that, in
combination with WMAP, H_0 = 69.7 +4.9/-5.0 km/s/Mpc and w=-0.94 +0.17/-0.19
(68% CL), suggesting that the observations of B1608+656 constrain w as tightly
as do the current Baryon Acoustic Oscillation data. (abridged)Comment: 24 pages, 8 figures, revisions based on referee's comments, accepted
for publication in Ap
Black Hole Mass Estimates Based on CIV are Consistent with Those Based on the Balmer Lines
Using a sample of high-redshift lensed quasars from the CASTLES project with
observed-frame ultraviolet or optical and near-infrared spectra, we have
searched for possible biases between supermassive black hole (BH) mass
estimates based on the CIV, Halpha and Hbeta broad emission lines. Our sample
is based upon that of Greene, Peng & Ludwig, expanded with new near-IR
spectroscopic observations, consistently analyzed high S/N optical spectra, and
consistent continuum luminosity estimates at 5100A. We find that BH mass
estimates based on the FWHM of CIV show a systematic offset with respect to
those obtained from the line dispersion, sigma_l, of the same emission line,
but not with those obtained from the FWHM of Halpha and Hbeta. The magnitude of
the offset depends on the treatment of the HeII and FeII emission blended with
CIV, but there is little scatter for any fixed measurement prescription. While
we otherwise find no systematic offsets between CIV and Balmer line mass
estimates, we do find that the residuals between them are strongly correlated
with the ratio of the UV and optical continuum luminosities. Removing this
dependency reduces the scatter between the UV- and optical-based BH mass
estimates by a factor of approximately 2, from roughly 0.35 to 0.18 dex. The
dispersion is smallest when comparing the CIV sigma_l mass estimate, after
removing the offset from the FWHM estimates, and either Balmer line mass
estimate. The correlation with the continuum slope is likely due to a
combination of reddening, host contamination and object-dependent SED shapes.
When we add additional heterogeneous measurements from the literature, the
results are unchanged.Comment: Accepted for publication in The Astrophysical Journal. 37 text pages
+ 8 tables + 23 figures. Updated with comments by the referee and with a
expanded discussion on literature data including new observation
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