745 research outputs found
Probing the Reionization History of the Universe using the Cosmic Microwave Background Polarization
The recent discovery of a Gunn--Peterson (GP) trough in the spectrum of the
redshift 6.28 SDSS quasar has raised the tantalizing possibility that we have
detected the reionization of the universe. However, a neutral fraction (of
hydrogen) as small as 0.1% is sufficient to cause the GP trough, hence its
detection alone cannot rule out reionization at a much earlier epoch. The
Cosmic Microwave Background (CMB) polarization anisotropy offers an alternative
way to explore the dark age of the universe. We show that for most models
constrained by the current CMB data and by the discovery of a GP trough
(showing that reionization occurred at z > 6.3), MAP can detect the
reionization signature in the polarization power spectrum. The expected 1-sigma
error on the measurement of the electron optical depth is around 0.03 with a
weak dependence on the value of that optical depth. Such a constraint on the
optical depth will allow MAP to achieve a 1-sigma error on the amplitude of the
primordial power spectrum of 6%. MAP with two years (Planck with one year) of
observation can distinguish a model with 50% (6%) partial ionization between
redshifts of 6.3 and 20 from a model in which hydrogen was completely neutral
at redshifts greater than 6.3. Planck will be able to distinguish between
different reionization histories even when they imply the same optical depth to
electron scattering for the CMB photons.Comment: ApJ version. Added Figure 2 and reference
Social behavioral impairments in SYNGAP1-related intellectual disability
IntroductionDevelopmental synaptopathies are neurodevelopmental disorders caused by genetic mutations disrupting the development and function of neuronal synapses.MethodsWe administered the validated Social Responsiveness Scale, Second Edition (SRS-2) to investigate the phenotypic presentation of social-behavioral impairments for the developmental synaptopathyâSYNGAP1-related Intellectual Disability (SYNGAP1-ID) (nâ=â32) compared with a phenotypically similar disorder Phelan-McDermid syndrome (PMD) (nâ=â27) and healthy controls (nâ=â43). A short form SRS-2 analysis (nâ=â85) was also conducted.ResultsBoth SYNGAP1-ID and PMD had significantly elevated total and subcategory T-scores, with no significant score differences between SYNGAP1-ID and PMD, consistent between the full and short form. Mild to severe deficiencies in reciprocal social behavior were found in 100% of PMD individuals and 87.1% of SYNGAP1-ID individuals. Surprisingly, a positive correlation between age and total score was discovered for SYNGAP1-ID participants and not found in individuals with PMD or healthy controls.DiscussionThe short form demonstrated greater utility for SYNGAP1-ID participants due to lower item-omission rates. In conclusion, significant impairment in reciprocal social behaviors is highly prevalent in SYNGAP1-ID
On the Angular Correlation Function of SZ Clusters : Extracting cosmological information from a 2D catalog
We discuss the angular correlation function of Sunyaev-Zel'dovich
(SZ)-detected galaxy clusters as a cosmological probe. As a projection of the
real-space cluster correlation function, the angular function samples the
underlying SZ catalog redshift distribution. It offers a way to study cosmology
and cluster evolution directly with the two-dimensional catalog, even before
extensive follow-up observations, thereby facilitating the immediate scientific
return from SZ surveys. As a simple illustration of the information content of
the angular function, we examine its dependence on the parameter pair Om_m,
sigma_8 in flat cosmologies. We discuss sources of modeling uncertainty and
consider application to the future Planck SZ catalog, showing how these two
parameters and the normalization of the SZ flux-mass relation can be
simultaneously found when the local X-ray cluster abundance constraint is
included.Comment: 11 pages, 5 figures. A&A, 410, 767; corrected typo, published versio
Sleep abnormalities in the synaptopathiesâSYNGAP1-related intellectual disability and PhelanâMcDermid syndrome
Neurodevelopmental disorders are frequently associated with sleep disturbances. One class of neurodevelopmental disorders, the genetic synaptopathies, is caused by mutations in genes encoding proteins found at the synapse. Mutations in these genes cause derangement of synapse development and function. We utilized a validated sleep instrument, Childrenâs Sleep Habits Questionnaire (CSHQ) to examine the nature of sleep abnormalities occurring in individuals with two synaptopathiesâPhelanâMcDermid syndrome (PMD) (N = 47, male = 23, female = 24, age 1â46 years) and SYNGAP1-related intellectual disability (SYNGAP1-ID) (N = 64, male = 31, female = 33, age 1â64 years), when compared with unaffected siblings (N = 61, male = 25, female = 36, age 1â17 years). We found that both PMD and SYNGAP1-ID have significant sleep abnormalities with SYNGAP1-ID having greater severity of sleep disturbance than PMD. In addition, sleep disturbances were more severe for PMD in individuals 11 years and older compared with those less than 11 years old. Individuals with either disorder were more likely to use sleep aids than unaffected siblings. In conclusion, sleep disturbances are a significant phenotype in the synaptopathies PMD and SYNGAP1-ID. Improved sleep is a viable endpoint for future clinical trials for these neurodevelopmental disorders
Search for High Energy Gamma Rays from an X-ray Selected Blazar Sample
Our understanding of blazars has been greatly increased in recent years by
extensive multi-wavelength observations, particularly in the radio, X-ray and
gamma-ray regions. Over the past decade the Whipple 10m telescope has
contributed to this with the detection of 5 BL Lacertae objects at very high
gamma-ray energies. The combination of multi-wavelength data has shown that
blazars follow a well-defined sequence in terms of their broadband spectral
properties. Together with providing constraints on emission models, this
information has yielded a means by which potential sources of TeV emission may
be identified and predictions made as to their possible gamma-ray flux. We have
used the Whipple telescope to search for TeV gamma-ray emission from eight
objects selected from a list of such candidates. No evidence has been found for
VHE emission from the objects in our sample, and upper limits have been derived
for the mean gamma-ray flux above 390GeV. These flux upper limits are compared
with the model predictions and the implications of our results for future
observations are discussed.Comment: 15 pages, 2 figures, Accepted for publication in Ap
Detection of the BL Lac Object H1426+428 at TeV Gamma Ray Energies
A very high energy (VHE) gamma-ray signal has been detected at the 5.4 sigma
level from H1426+428, an x-ray selected BL Lacertae object at a redshift of
0.129. The object was monitored from 1995 - 1998 with the Whipple 10m imaging
atmospheric Cherenkov telescope as part of a general blazar survey; the results
of these observations, although not statistically significant, were
consistently positive. X-ray observations of H1426+428 during 1999 with the
BeppoSAX instrument revealed that the peak of its synchrotron spectrum occurs
at > 100 keV, leading to the prediction of observable TeV emission from this
object. H1426+428 was monitored extensively at the Whipple Observatory during
the 1999, 2000, and 2001 observing seasons. The strongest TeV signals were
detected in 2000 and 2001. During 2001, an integral flux of 2.04 +/- 0.35
x10e-11 cm-2 s-1 above 280 GeV was recorded from H1426+428. The detection of
H1426+428 supports the idea that, as also seen in Markarian 501 and
1ES2344+514, BL Lacertae objects with extremely high synchrotron peak
frequencies produce gamma rays in the TeV range.Comment: 35 pages, 7 figures, accepted by ApJ Two upper limits in Table 3
(upper limits for 1995 and 1997) are different from the ApJ versio
A Search for TeV Gamma-Ray Emission from High-Peaked Flat Spectrum Radio Quasars Using the Whipple Air-Cherenkov Telescope
Blazars have traditionally been separated into two broad categories based
upon their optical emission characteristics; BL Lacs, with faint or no emission
lines, and flat spectrum radio quasars (FSRQs) with prominent, broad emission
lines. The spectral energy distribution of FSRQs has generally been thought of
as being more akin to the low-peaked BL Lacs, which exhibit a peak in the
infrared region of the spectrum, as opposed to high-peaked BL Lacs (HBLs),
which exhibit a peak in UV/X-ray region of the spectrum. All blazars currently
confirmed as sources of TeV emission are HBLs. Recent surveys have found
several FSRQs exhibiting spectral properties similar to HBLs, particularly the
synchrotron peak frequency. These objects are potential sources of TeV emission
according to several models of blazar jet emission and blazar evolution.
Measurements of TeV flux or upper limits could impact existing theories
explaining the links between different blazar types and could have a
significant impact on our understanding of the nature of objects that are
capable of TeV emission. In particular, the presence (or absence) of TeV
emission from FSRQs could confirm (or cast doubt upon) recent evolutionary
models that expect intermediate objects in a transitionary state between FSRQ
and BL Lac. The Whipple 10 meter imaging air-Cherenkov gamma-ray telescope is
well suited for TeV gamma-ray observations. Using the Whipple telescope, we
have taken data on a small selection of nearby(z<0.1 in most cases),
high-peaked FSRQs. Although one of the objects, B2 0321+33, showed marginal
evidence of flaring, no significant emission was detected. The implications of
this paucity of emission and the derived upper limits are discussed.Comment: accepted for publication in Astrophysical Journa
A Multi-wavelength View of the TeV Blazar Markarian 421: Correlated Variability, Flaring, and Spectral Evolution
We report results from a multi-wavelength monitoring campaign on Mrk 421 over
the period of 2003-2004. The source was observed simultaneously at TeV and
X-ray energies, with supporting observations frequently carried out at optical
and radio wavelengths. The large amount of simultaneous data has allowed us to
examine the variability of Mrk 421 in detail. The variabilities are generally
correlated between the X-ray and gamma-ray bands, although the correlation
appears to be fairly loose. The light curves show the presence of flares with
varying amplitudes on a wide range of timescales both at X-ray and TeV
energies. Of particular interest is the presence of TeV flares that have no
coincident counterparts at longer wavelengths, because the phenomenon seems
difficult to understand in the context of the proposed emission models for TeV
blazars. We have also found that the TeV flux reached its peak days before the
X-ray flux during a giant flare in 2004. Such a difference in the development
of the flare presents a further challenge to the emission models. Mrk 421
varied much less at optical and radio wavelengths. Surprisingly, the normalized
variability amplitude in optical seems to be comparable to that in radio,
perhaps suggesting the presence of different populations of emitting electrons
in the jet. The spectral energy distribution (SED) of Mrk 421 is seen to vary
with flux, with the two characteristic peaks moving toward higher energies at
higher fluxes. We have failed to fit the measured SEDs with a one-zone SSC
model; introducing additional zones greatly improves the fits. We have derived
constraints on the physical properties of the X-ray/gamma-ray flaring regions
from the observed variability (and SED) of the source. The implications of the
results are discussed. (Abridged)Comment: 32 pages, 12 figures, to appear in Ap
Very-high energy gamma-ray astronomy: A 23-year success story in high-energy astroparticle physics
Very-high energy (VHE) gamma quanta contribute only a minuscule fraction -
below one per million - to the flux of cosmic rays. Nevertheless, being neutral
particles they are currently the best "messengers" of processes from the
relativistic/ultra-relativistic Universe because they can be extrapolated back
to their origin. The window of VHE gamma rays was opened only in 1989 by the
Whipple collaboration, reporting the observation of TeV gamma rays from the
Crab nebula. After a slow start, this new field of research is now rapidly
expanding with the discovery of more than 150 VHE gamma-ray emitting sources.
Progress is intimately related with the steady improvement of detectors and
rapidly increasing computing power. We give an overview of the early attempts
before and around 1989 and the progress after the pioneering work of the
Whipple collaboration. The main focus of this article is on the development of
experimental techniques for Earth-bound gamma-ray detectors; consequently, more
emphasis is given to those experiments that made an initial breakthrough rather
than to the successors which often had and have a similar (sometimes even
higher) scientific output as the pioneering experiments. The considered energy
threshold is about 30 GeV. At lower energies, observations can presently only
be performed with balloon or satellite-borne detectors. Irrespective of the
stormy experimental progress, the success story could not have been called a
success story without a broad scientific output. Therefore we conclude this
article with a summary of the scientific rationales and main results achieved
over the last two decades.Comment: 45 pages, 38 figures, review prepared for EPJ-H special issue "Cosmic
rays, gamma rays and neutrinos: A survey of 100 years of research
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