203 research outputs found
XMM-Newton view of the N 206 superbubble in the Large Magellanic Cloud
We perform an analysis of the X-ray superbubble in the N 206 HII region in
the Large Magellanic Cloud using current generation facilities to gain a better
understanding of the physical processes at work in the superbubble and to
improve our knowledge of superbubble evolution. We used XMM-Newton observations
of the N 206 region to produce images and extract spectra of the superbubble
diffuse emission. Morphological comparisons with Halpha images from the
Magellanic Cloud Emission Line Survey were performed, and spectral analysis of
the diffuse X-ray emission was carried out. We derived the physical properties
of the hot gas in the superbubble based on the results of the spectral
analysis. We also determined the total energy stored in the superbubble and
compared this to the expected energy input from the stellar population to
assess the superbubble growth rate discrepancy for N 206. We find that the
brightest region of diffuse X-ray emission is confined by a Halpha shell,
consistent with the superbubble model. In addition, faint emission extending
beyond the Halpha shell was found, which we attribute to a blowout region. The
spectral analysis of both emission regions points to a hot shocked gas as the
likely origin of the emission. We determine the total energy stored in the
bubble and the expected energy input by the stellar population. However, due to
limited data on the stellar population, the input energy is poorly constrained
and, consequently, no definitive indication of a growth rate discrepancy is
seen. Using the high-sensitivity X-ray data from XMM-Newton and optical data
from the Magellanic Cloud Emission Line Survey has allowed us to better
understand the physical properties of the N 206 superbubble and address some
key questions of superbubble evolution.Comment: 12 pages, 7 figures. Accepted for publication in A&
Digging for Dark Matter: Spectral Analysis and Discovery Potential of Paleo-Detectors
Paleo-detectors are a recently proposed method for the direct detection of
Dark Matter (DM). In such detectors, one would search for the persistent damage
features left by DM--nucleus interactions in ancient minerals. Initial
sensitivity projections have shown that paleo-detectors could probe much of the
remaining Weakly Interacting Massive Particle (WIMP) parameter space. In this
paper, we improve upon the cut-and-count approach previously used to estimate
the sensitivity by performing a full spectral analysis of the background- and
DM-induced signal spectra. We consider two scenarios for the systematic errors
on the background spectra: i) systematic errors on the normalization only, and
ii) systematic errors on the shape of the backgrounds. We find that the
projected sensitivity is rather robust to imperfect knowledge of the
backgrounds. Finally, we study how well the parameters of the true WIMP model
could be reconstructed in the hypothetical case of a WIMP discovery.Comment: 14 pages, 5 figures, code available at
https://github.com/tedwards2412/paleo_detectors/ . v2: Added additional
analysis theory details, matches version published in PR
Effect of Pre-and Post-weaning Nutrition and Management on Performance of Weaned Pigs to circa 35 kg.
End of Project ReportThe objective of this project was to examine the factors
affecting performance (growth rate, appetite, feed conversion efficiency)
of pigs in the stage from weaning to 35 kg liveweight.
The study involved three stages, creep feeding during the suckling
period, management during the first weaner stage (c. 4 weeks
from weaning or 6 kg to 15 kg liveweight) and management during
the second weaner stage (c. 15 kg to 35 kg liveweight.
Creep feed intake before weaning was low c. 2.5 to 3.0 kg
per litter but where it was consumed the response in terms of feed
conversion efficiency was good with litter weight increasing in
weight by about 1.1 kg for each 1 kg creep consumed. Milk
replacer in liquid form was very readily consumed but its preparation
and feeding is very laborious. Weaning weight was poorly
related to post weaning performance and weaning age seemed to
be more critical which is probably a reflection of the greater
maturity of older animals.
In the first weaner stage, feeding of cooked cereal containing
diets was found to have little benefit in pig performance.
Acidification of feeds is likely to have only a minor influence on
pig performance. An experiment on choice feeding of starter and
link feeds did not confirm that smaller pigs require a higher quality
diet and, in a choice situation will eat a greater proportion of the
more nutrient dense diet.
In the second weaner stage, comparison of three commercial
weaner feeds with a cereal based control diet showed good performance
on all four diets. Pigs fed a high lysine weaner diet grew
better in the weaner stage but by slaughter those pigs fed the low
lysine weaner diet, after all pigs were fed a common finisher diet,
had overtaken them. The high lysine group did, however, have
leaner carcasses.
Residual effects of early nutrition need to be investigated in
more detail including the effect of pregnancy feeding on prenatal
development and the relationship between prenatal growth and
postnatal growth, in particular development of muscle.European Union Structural Funds (EAGGF
Paleo-Detectors for Galactic Supernova Neutrinos
Paleo-detectors are a proposed experimental technique in which one would
search for traces of recoiling nuclei in ancient minerals. Natural minerals on
Earth are as old as Gyr and, in many minerals, the damage
tracks left by recoiling nuclei are also preserved for timescales long compared
to 1 Gyr once created. Thus, even reading out relatively small target samples
of order 100 g, paleo-detectors would allow one to search for very rare events
thanks to the large exposure, . Here, we explore the potential of paleo-detectors to
measure nuclear recoils induced by neutrinos from galactic core collapse
supernovae. We find that they would not only allow for a direct measurement of
the average core collapse supernova rate in the Milky Way, but would also
contain information about the time-dependence of the local supernova rate over
the past 1 Gyr. Since the supernova rate is thought to be directly
proportional to the star formation rate, such a measurement would provide a
determination of the local star formation history. We investigate the
sensitivity of paleo-detectors to both a smooth time evolution and an
enhancement of the core collapse supernova rate on relatively short timescales,
as would be expected for a starburst period in the local group.Comment: 15 pages, 5 figures. code available at
https://github.com/tedwards2412/SN-paleology (archived at
https://doi.org/10.5281/zenodo.3066206 ) v2: matches the published versio
Multi-frequency study of DEM L299 in the Large Magellanic Cloud
We have studied the HII region DEM L299 in the Large Magellanic Cloud to
understand its physical characteristics and morphology in different
wavelengths. We performed a spectral analysis of archived XMM-Newton EPIC data
and studied the morphology of DEM L299 in X-ray, optical, and radio
wavelengths. We used H alpha, [SII], and [OIII] data from the Magellanic Cloud
Emission Line Survey and radio 21 cm line data from the Australia Telescope
Compact Array (ATCA) and the Parkes telescope, and radio continuum data from
ATCA and the Molonglo Synthesis Telescope. Our morphological studies imply
that, in addition to the supernova remnant SNR B0543-68.9 reported in previous
studies, a superbubble also overlaps the SNR in projection. The position of the
SNR is clearly defined through the [SII]/H alpha flux ratio image. Moreover,
the optical images show a shell-like structure that is located farther to the
north and is filled with diffuse X-ray emission, which again indicates the
superbubble. Radio 21 cm line data show a shell around both objects. Radio
continuum data show diffuse emission at the position of DEM L299, which appears
clearly distinguished from the HII region N 164 that lies south-west of it. We
determined the spectral index of SNR B0543-68.9 to be alpha=-0.34, which
indicates the dominance of thermal emission and therefore a rather mature SNR.
We determined the basic properties of the diffuse X-ray emission for the SNR,
the superbubble, and a possible blowout region of the bubble, as suggested by
the optical and X-ray data. We obtained an age of 8.9 (3.5-18.1) kyr for the
SNR and a temperature of 0.64 (0.44-1.37) keV for the hot gas inside the SNR,
and a temperature of the hot gas inside the superbubble of 0.74 (0.44-1.1) keV.
We conclude that DEM L299 consists of a superposition of SNR B0543-68.9 and a
superbubble, which we identified based on optical data.Comment: Accepted for publication in Astronomy and Astrophysics. 17 pages, 16
figure
Human stem cell osteoblastogenesis mediated by novel glycogen synthase kinase 3 inhibitors induces bone formation and a unique bone turnover biomarker profile in rats
AbstractWnt activation by inhibiting glycogen synthase kinase 3 (GSK-3) causes bone anabolism in rodents making GSK-3 a potential therapeutic target for osteoporotic and osteolytic metastatic bone disease. To understand the wnt pathway related to human disease translation, the ability of 3 potent inhibitors of GSK-3 (AZD2858, AR79, AZ13282107) to 1) drive osteoblast differentiation and mineralisation using human adipose-derived stem cells (hADSC) in vitro; and 2) stimulate rat bone formation in vivo was investigated. Bone anabolism/resorption was determined using clinically relevant serum biomarkers as indicators of bone turnover and bone formation assessed in femurs by histopathology and pQCT/μCT imaging.GSK-3 inhibitors caused β-catenin stabilisation in human and rat mesenchymal stem cells, stimulated hADSC commitment towards osteoblasts and osteogenic mineralisation in vitro. AZD2858 produced time-dependent changes in serum bone turnover biomarkers and increased bone mass over 28days exposure in rats. After 7days, AZD2858, AR79 or AZ13282107 exposure increased the bone formation biomarker P1NP, and reduced the resorption biomarker TRAcP-5b, indicating increased bone anabolism and reduced resorption in rats. This biomarker profile was differentiated from anabolic agent PTH1–34 or the anti-resorptive Alendronate-induced changes. Increased bone formation in cortical and cancellous bone as assessed by femur histopathology supported biomarker changes. 14 day AR79 treatment increased bone mineral density and trabecular thickness, and decreased trabecular number and connectivity assessed by pQCT/μCT.GSK-3 inhibition caused hADSC osteoblastogenesis and mineralisation in vitro. Increased femur bone mass associated with changes in bone turnover biomarkers confirmed in vivo bone formation and indicated uncoupling of bone formation and resorption
A JWST/MIRI and NIRCam Analysis of the Young Stellar Object Population in the Spitzer I region of NGC 6822
We present an imaging survey of the Spitzer~I star-forming region in NGC 6822
conducted with the NIRCam and MIRI instruments onboard JWST. Located at a
distance of 490 kpc, NGC 6822 is the nearest non-interacting low-metallicity
(0.2 ) dwarf galaxy. It hosts some of the brightest known HII
regions in the local universe, including recently discovered sites of
highly-embedded active star formation. Of these, Spitzer I is the youngest and
most active, and houses 90 color-selected candidate young stellar objects
(YSOs) identified from Spitzer Space Telescope observations. We revisit the YSO
population of Spitzer~I with these new JWST observations. By analyzing
color-magnitude diagrams (CMDs) constructed with NIRCam and MIRI data, we
establish color selection criteria and construct spectral energy distributions
(SEDs) to identify candidate YSOs and characterize the full population of young
stars, from the most embedded phase to the more evolved stages. In this way, we
have identified 129 YSOs in Spitzer I. Comparing to previous Spitzer studies of
the NGC 6822 YSO population, we find that the YSOs we identify are fainter and
less massive, indicating that the improved resolution of JWST allows us to
resolve previously blended sources into individual stars.Comment: 17 pages, 9 figures, 2 tables, to be submitted to ApJ, comments
welcom
The nature of point source fringes in mid-infrared spectra acquired with the James Webb Space Telescope
The constructive and destructive interference in different layers of the
James Webb Space Telescope (JWST) Mid-Infrared Instrument (MIRI) detector
arrays modulate the detected signal as a function of wavelength. Additionally,
sources of different spatial profiles show different fringe patterns. Dividing
by a static fringe flat could hamper the scientific interpretation of sources
whose fringes do not match that of the fringe flat. We find point source
fringes measured by the MIRI Medium-Resolution Spectrometer (MRS) to be
reproducible under similar observing conditions. We want, thus, to identify the
variables, if they exist, that would allow for a parametrization of the signal
variations induced by point source fringe modulations. We do this by analyzing
MRS detector plane images acquired on the ground. We extracted the fringe
profile of multiple point source observations and studied the amplitude and
phase of the fringes as a function of field position and pixel sampling of the
point spread function of the optical chain. A systematic variation in the
amplitude and phase of the point source fringes is found over the wavelength
range covered by the test sources (4.9-5.8 m). The variation depends on
the fraction of the point spread function seen by the detector pixel. We
identify the non-uniform pixel illumination as the root cause of the reported
systematic variation. We report an improvement after correction of 50% on the
1 standard deviation of the spectral continuum. A 50% improvement is
also reported in line sensitivity for a benchmark test with a spectral
continuum of 100 mJy. The improvement in the shape of weak lines is illustrated
using a T Tauri model spectrum. Consequently, we verify that fringes of
extended sources and potentially semi-extended sources and crowded fields can
be simulated by combining multiple point source fringe transmissions.Comment: 17 pages, 31 figure
Deep XMM-Newton observations of the northern disk of M31 II: Tracing the hot interstellar medium
Aims: We use new deep XMM-Newton observations of the northern disk of M 31 to
trace the hot interstellar medium (ISM) in unprecedented detail and to
characterise the physical properties of the X-ray emitting plasmas. Methods: We
used all XMM-Newton data up to and including our new observations to produce
the most detailed image yet of the hot ISM plasma in a grand design spiral
galaxy such as our own. We compared the X-ray morphology to multi-wavelength
studies in the literature to set it in the context of the multi-phase ISM. We
performed spectral analyses on the extended emission using our new observations
as they offer sufficient depth and count statistics to constrain the plasma
properties. Data from the Panchromatic Hubble Andromeda Treasury were used to
estimate the energy injected by massive stars and their supernovae. We compared
these results to the hot gas properties. Results: The brightest emission
regions were found to be correlated with populations of massive stars, notably
in the 10 kpc star-forming ring. The plasma temperatures in the ring regions
are ~0.2 keV up to ~0.6 keV. We suggest this emission is hot ISM heated in
massive stellar clusters and superbubbles. We derived X-ray luminosities,
densities, and pressures for the gas in each region. We also found large
extended emission filling low density gaps in the dust morphology of the
northern disk, notably between the 5 kpc and 10 kpc star-forming rings. We
propose that the hot gas was heated and expelled into the gaps by the
populations of massive stars in the rings. Conclusions. It is clear that the
massive stellar populations are responsible for heating the ISM to X-ray
emitting temperatures, filling their surroundings, and possibly driving the hot
gas into the low density regions. Overall, the morphology and spectra of the
hot gas in the northern disk of M 31 is similar to other galaxy disks.Comment: 23 pages, 14 figures, accepted for publication in Astronomy &
Astrophysic
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