434 research outputs found
Probing the Primordial Power Spectrum with Cluster Number Counts
We investigate how well galaxy cluster number counts can constrain the
primordial power spectrum. Measurements of the primary anisotropies in the
cosmic microwave background (CMB) may be limited, by the presence of
foregrounds from secondary sources, to probing the primordial power spectrum at
wave numbers less than about 0.30 h Mpc^{-1}. We break up the primordial power
spectrum into a number of nodes and interpolate linearly between each node.
This allows us to show that cluster number counts could then extend the
constraints on the form of the primordial power spectrum up to wave numbers of
about 0.45 h Mpc^{-1}. We estimate combinations of constraints from PLANCK and
SPT primary CMB and their respective SZ surveys. We find that their
constraining ability is limited by uncertainties in the mass scaling relations.
We also estimate the constraint from clusters detected from a SNAP like
gravitational lensing survey. As there is an unambiguous and simple
relationship between the filtered shear of the lensing survey and the cluster
mass, it may be possible to obtain much tighter constraints on the primordial
power spectrum in this case.Comment: Clarifications added and a few minor corrections made. Matches
version to appear in PR
High Resolution STIS/HST and HIRES/Keck Spectra of Three Weak MgII Absorbers Toward PG 1634+706
High resolution optical (HIRES/Keck) and UV (STIS/HST) spectra, covering a
large range of chemical transitions, are analyzed for three single-cloud weak
MgII absorption systems along the line of sight toward the quasar PG 1634+706.
Weak MgII absorption lines in quasar spectra trace metal-enriched environments
that are rarely closely associated with the most luminous galaxies (>0.05L^*).
The two weak MgII systems at z=0.81 and z=0.90 are constrained to have >=solar
metallicity, while the metallicity of the z=0.65 system is not as
well-constrained, but is consistent with >1/10th solar. These weak MgII clouds
are likely to be local pockets of high metallicity in a lower metallicity
environment. All three systems have two phases of gas, a higher density region
that produces narrower absorption lines for low ionization transitions, such as
MgII, and a lower density region that produces broader absorption lines for
high ionization transitions, such as CIV. The CIV profile for one system (at
z=0.81) can be fit with a single broad component (b~10 km/s), but those for the
other two systems require one or two additional offset high ionization clouds.
Two possible physical pictures for the phase structure are discussed: one with
a low-ionization, denser phase embedded in a lower density surrounding medium,
and the other with the denser clumps surrounding more highly ionized gas.Comment: 32 pages, 4 figures; to appear in ApJ on May 20, 200
Forecast Constraints on Inflation from Combined CMB and Gravitational Wave Direct Detection Experiments
We study how direct detection of the inflationary gravitational wave
background constrains inflationary parameters and complements CMB polarization
measurements. The error ellipsoids calculated using the Fisher information
matrix approach with Planck and the direct detection experiment, BBO (Big Bang
Observer), show different directions of parameter degeneracy, and the
degeneracy is broken when they are combined. For a slow-roll parameterization,
we show that BBO could significantly improve the constraints on the
tensor-to-scalar ratio compared with Planck alone. We also look at a quadratic
and a natural inflation model. In both cases, if the temperature of reheating
is also treated as a free parameter, then the addition of BBO can significantly
improve the error bars. In the case of natural inflation, we find that the
addition of BBO could even partially improve the error bars of a cosmic
variance-limited CMB experiment.Comment: 12 pages, 5 figures; matches version to appear in PRD; typos
correcte
Primordial helium recombination III: Thomson scattering, isotope shifts, and cumulative results
Upcoming precision measurements of the temperature anisotropy of the cosmic
microwave background (CMB) at high multipoles will need to be complemented by a
more complete understanding of recombination, which determines the damping of
anisotropies on these scales. This is the third in a series of papers
describing an accurate theory of HeI and HeII recombination. Here we describe
the effect of Thomson scattering, the He isotope shift, the contribution of
rare decays, collisional processes, and peculiar motion. These effects are
found to be negligible: Thomson and He scattering modify the free electron
fraction at the level of several . The uncertainty in the
rate is significant, and for conservative estimates gives
uncertainties in of order . We describe several convergence
tests for the atomic level code and its inputs, derive an overall
error budget, and relate shifts in to the changes in , which
are at the level of 0.5% at . Finally, we summarize the main
corrections developed thus far. The remaining uncertainty from known effects is
in .Comment: 19 pages, 15 figures, to be submitted to PR
Individual differences in self-affirmation: distinguishing self-affirmation from positive self-regard
Research into self-affirmation has almost exclusively employed experimental manipulations. In this paper we address individual differences in the tendency to respond to threats with self-affirming cognitions and distinguish this from two overlapping constructs: habitual positive self-thought and trait self-esteem. Items we designed to measure self-affirmation were represented by three first-order factors and loaded on a higher-order factor, creating the Spontaneous Self-Affirmation Measure (SSAM). The SSAM correlated moderately with self-esteem and habitual positive self-thought. In competitive analyses, the SSAM was an independent predictor of a large number of outcomes. The studies provide evidence about the correlates of individual differences in reported spontaneous self-affirmation in response to threat and the contribution made to this response by habitual positive self-thought and trait self-esteem
Prenatal development is linked to bronchial reactivity: epidemiological and animal model evidence
Chronic cardiorespiratory disease is associated with low birthweight suggesting the importance of the developmental environment. Prenatal factors affecting fetal growth are believed important, but the underlying mechanisms are unknown. The influence of developmental programming on bronchial hyperreactivity is investigated in an animal model and evidence for comparable associations is sought in humans. Pregnant Wistar rats were fed either control or protein-restricted diets throughout pregnancy. Bronchoconstrictor responses were recorded from offspring bronchial segments. Morphometric analysis of paraffin-embedded lung sections was conducted. In a human mother-child cohort ultrasound measurements of fetal growth were related to bronchial hyperreactivity, measured at age six years using methacholine. Protein-restricted rats' offspring demonstrated greater bronchoconstriction than controls. Airway structure was not altered. Children with lesser abdominal circumference growth during 11-19 weeks' gestation had greater bronchial hyperreactivity than those with more rapid abdominal growth. Imbalanced maternal nutrition during pregnancy results in offspring bronchial hyperreactivity. Prenatal environmental influences might play a comparable role in humans
A Quadruple-Phase Strong Mg II Absorber at z~0.9902 Toward PG 1634+706
The z=0.9902 system along the quasar PG 1634+706 line of sight is a strong
MgII absorber (W(2796)>0.3A) with only weak CIV absorption (it is
``CIV-deficient''). To study this system, we used high-resolution spectra from
both HST/STIS (R=30,000) and Keck/HIRES (R=45,000). These spectra cover key
transitions, such as MgI, MgII, FeII, SiII, CII, SiIII, CIII, SiIV, and CIV.
Assuming a Haardt and Madau extragalactic background spectrum, we modeled the
system with a combination of photoionization and collisional ionization. Based
on a comparison of synthetic spectra to the data profiles, we infer the
existence of the following four phases of gas: i) Seven MgII clouds have sizes
of 1-1000pc and densities of 0.002-0.1/cm^3, with a gradual decrease in density
from blue to red. The MgII phase gives rise to most of the CIV absorption and
resembles the warm, ionized inter-cloud medium of the Milky Way; ii) Instead of
arising in the same phase as MgII, MgI is produced in separate, narrow
components with b~0.75km/s. These small MgI pockets (~100AU) could represent a
denser phase (~200/cm^3) of the interstellar medium (ISM), analogous to the
small-scale structure observed in the Milky Way ISM; iii) A ``broad phase''
with a Doppler parameter, b~60km/s, is required to consistently fit Ly-alpha,
Ly-beta, and the higher-order Lyman-series lines. A low metallicity (log Z <=
-2) for this phase could explain why the system is ``CIV-deficient'', and also
why NV and OVI are not detected. This phase may be a galactic halo or it could
represent a diffuse medium in an early-type galaxy; iv) The strong absorption
in SiIV relative to CIV could be produced in an extra, collisionally ionized
phase with a temperature of T~60,000K. The collisional phase could exist in
cooling layers that are shock-heated by supernovae-related processes.Comment: 25 pages, 4 figures; to appear in ApJ, April 20, 200
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