32 research outputs found
CMBPol Mission Concept Study: Foreground Science Knowledge and Prospects
We report on our knowledge of Galactic foregrounds, as well as on how a CMB
satellite mission aiming at detecting a primordial B-mode signal (CMBPol) will
contribute to improving it. We review the observational and analysis techniques
used to constrain the structure of the Galactic magnetic field, whose presence
is responsible for the polarization of Galactic emissions. Although our current
understanding of the magnetized interstellar medium is somewhat limited,
dramatic improvements in our knowledge of its properties are expected by the
time CMBPol flies. Thanks to high resolution and high sensitivity instruments
observing the whole sky at frequencies between 30 GHz and 850 GHz, CMBPol will
not only improve this picture by observing the synchrotron emission from our
galaxy, but also help constrain dust models. Polarized emission from
interstellar dust indeed dominates over any other signal in CMBPol's highest
frequency channels. Observations at these wavelengths, combined with
ground-based studies of starlight polarization, will therefore enable us to
improve our understanding of dust properties and of the mechanism(s)
responsible for the alignment of dust grains with the Galactic magnetic field.
CMBPol will also shed new light on observations that are presently not well
understood. Morphological studies of anomalous dust and synchrotron emissions
will indeed constrain their natures and properties, while searching for
fluctuations in the emission from heliospheric dust will test our understanding
of the circumheliospheric interstellar medium. Finally, acquiring more
information on the properties of extra-Galactic sources will be necessary in
order to maximize the cosmological constraints extracted from CMBPol's
observations of CMB lensing. (abridged)Comment: 43 pages, 7 figures, 2 table
VALES I: the molecular gas content in star-forming dusty H-ATLAS galaxies up to z = 0.35
We present an extragalactic survey using observations from the Atacama Large Millime- ter/submillimeter Array (ALMA) to characterize galaxy populations up to z = 0.35: the ValparaŽıso ALMA Line Emission Survey (VALES). We use ALMA Band-3 CO(1â0) obser- vations to study the molecular gas content in a sample of 67 dusty normal star-forming galaxies selected from the Herschel Astrophysical Terahertz Large Area Survey (H-ATLAS). We have spectrally detected 49 galaxies at >5Ï significance and 12 others are seen at low significance in stacked spectra. CO luminosities are in the range of (0.03â1.31) Ă 1010 K km sâ1 pc2, equivalent to log(Mgas/M) = 8.9â10.9 assuming an αCO= 4.6 (K km sâ1 pc2)â1, which perfectly complements the parameter space previously explored with local and high-z normal galaxies. We compute the optical to CO size ratio for 21 galaxies resolved by ALMA at âŒ3.5 arcsec resolution (6.5 kpc), finding that the molecular gas is on average ⌠0.6 times more compact than the stellar component. We obtain a global SchmidtâKennicutt relation, given by log[:ESFR/(Myrâ1 kpcâ2)] = (1.26 ± 0.02) Ă log[:EMH2/(Mpcâ2)] â (3.6 ± 0.2). We find a significant fraction of galaxies lying at âintermediate efficienciesâ between a long-standing mode of star formation activity and a starburst, specially at LIR = 1011â12 L. Combining our observations with data taken from the literature, we propose that star formation
efficiencies can be parametrized by log [SFR/MH2 ] = 0.19 Ă (log LIR â 11.45) â 8.26 â0.41 Ă arctan[â4.84 (log LIR â 11.45)]. Within the redshift range we explore (z < 0.35), we identify a rapid increase of the gas content as a function of redshift
CMB-S4: Forecasting Constraints on Primordial Gravitational Waves
CMB-S4---the next-generation ground-based cosmic microwave background (CMB)
experiment---is set to significantly advance the sensitivity of CMB
measurements and enhance our understanding of the origin and evolution of the
Universe, from the highest energies at the dawn of time through the growth of
structure to the present day. Among the science cases pursued with CMB-S4, the
quest for detecting primordial gravitational waves is a central driver of the
experimental design. This work details the development of a forecasting
framework that includes a power-spectrum-based semi-analytic projection tool,
targeted explicitly towards optimizing constraints on the tensor-to-scalar
ratio, , in the presence of Galactic foregrounds and gravitational lensing
of the CMB. This framework is unique in its direct use of information from the
achieved performance of current Stage 2--3 CMB experiments to robustly forecast
the science reach of upcoming CMB-polarization endeavors. The methodology
allows for rapid iteration over experimental configurations and offers a
flexible way to optimize the design of future experiments given a desired
scientific goal. To form a closed-loop process, we couple this semi-analytic
tool with map-based validation studies, which allow for the injection of
additional complexity and verification of our forecasts with several
independent analysis methods. We document multiple rounds of forecasts for
CMB-S4 using this process and the resulting establishment of the current
reference design of the primordial gravitational-wave component of the Stage-4
experiment, optimized to achieve our science goals of detecting primordial
gravitational waves for at greater than , or, in the
absence of a detection, of reaching an upper limit of at CL.Comment: 24 pages, 8 figures, 9 tables, submitted to ApJ. arXiv admin note:
text overlap with arXiv:1907.0447
CMB-S4: Forecasting Constraints on Primordial Gravitational Waves
Abstract: CMB-S4âthe next-generation ground-based cosmic microwave background (CMB) experimentâis set to significantly advance the sensitivity of CMB measurements and enhance our understanding of the origin and evolution of the universe. Among the science cases pursued with CMB-S4, the quest for detecting primordial gravitational waves is a central driver of the experimental design. This work details the development of a forecasting framework that includes a power-spectrum-based semianalytic projection tool, targeted explicitly toward optimizing constraints on the tensor-to-scalar ratio, r, in the presence of Galactic foregrounds and gravitational lensing of the CMB. This framework is unique in its direct use of information from the achieved performance of current Stage 2â3 CMB experiments to robustly forecast the science reach of upcoming CMB-polarization endeavors. The methodology allows for rapid iteration over experimental configurations and offers a flexible way to optimize the design of future experiments, given a desired scientific goal. To form a closed-loop process, we couple this semianalytic tool with map-based validation studies, which allow for the injection of additional complexity and verification of our forecasts with several independent analysis methods. We document multiple rounds of forecasts for CMB-S4 using this process and the resulting establishment of the current reference design of the primordial gravitational-wave component of the Stage-4 experiment, optimized to achieve our science goals of detecting primordial gravitational waves for r > 0.003 at greater than 5Ï, or in the absence of a detection, of reaching an upper limit of r < 0.001 at 95% CL
Genomic investigations of unexplained acute hepatitis in children
Since its first identification in Scotland, over 1,000 cases of unexplained paediatric hepatitis in children have been reported worldwide, including 278 cases in the UK1. Here we report an investigation of 38 cases, 66 age-matched immunocompetent controls and 21 immunocompromised comparator participants, using a combination of genomic, transcriptomic, proteomic and immunohistochemical methods. We detected high levels of adeno-associated virus 2 (AAV2) DNA in the liver, blood, plasma or stool from 27 of 28 cases. We found low levels of adenovirus (HAdV) and human herpesvirus 6B (HHV-6B) in 23 of 31 and 16 of 23, respectively, of the cases tested. By contrast, AAV2 was infrequently detected and at low titre in the blood or the liver from control children with HAdV, even when profoundly immunosuppressed. AAV2, HAdV and HHV-6 phylogeny excluded the emergence of novel strains in cases. Histological analyses of explanted livers showed enrichment for T cells and B lineage cells. Proteomic comparison of liver tissue from cases and healthy controls identified increased expression of HLA class 2, immunoglobulin variable regions and complement proteins. HAdV and AAV2 proteins were not detected in the livers. Instead, we identified AAV2 DNA complexes reflecting both HAdV-mediated and HHV-6B-mediated replication. We hypothesize that high levels of abnormal AAV2 replication products aided by HAdV and, in severe cases, HHV-6B may have triggered immune-mediated hepatic disease in genetically and immunologically predisposed children
A new mouse model of Canavan leukodystrophy displays hearing impairment due to central nervous system dysmyelination
Canavan disease is a leukodystrophy caused by mutations in the ASPA gene. This gene encodes the enzyme that converts N-acetylaspartate into acetate and aspartic acid. In Canavan disease, spongiform encephalopathy of the brain causes progressive mental retardation, motor deficit and death. We have isolated a mouse with a novel ethylnitrosourea-induced mutation in Aspa. This mutant, named deaf14, carries a c.516T>A mutation that is predicted to cause a p.Y172X protein truncation. No full-length ASPA protein is produced in deaf14 brain and there is extensive spongy degeneration. Interestingly, we found that deaf14 mice have an attenuated startle in response to loud noise. The first auditory brainstem response peak has normal latency and amplitude but peaks II, III, IV and V have increased latency and decreased amplitude in deaf14 mice. Our work reveals a hitherto unappreciated pathology in a mouse model of Canavan disease, implying that auditory brainstem response testing could be used in diagnosis and to monitor the progression of this disease