37 research outputs found
The role of previous generations of stars in triggering star formation and driving gas dynamics
We present hydrodynamic and magnetohydrodynamic (MHD) simulations of sub
galactic regions including photoionising and supernova feedack. We aim to
improve the initial conditions of our region extraction models by including an
initial population of stars. We also investigate the reliability of extracting
regions in simulations, and show that with a good choice of region, results are
comparable with using a larger region for the duration of our simulations.
Simulations of star formation on molecular cloud scales typically start with a
turbulent cloud of gas, from which stars form and then undergo feedback. In
reality, a typical cloud or region within a galaxy may already include, or
reside near some population of stars containing massive stars undergoing
feedback. We find the main role of a prior population is triggering star
formation, and contributing to gas dynamics. Early time supernova from the
initial population are important in triggering new star formation and driving
gas motions on larger scales above 100 pc, whilst the ionising feedback
contribution from the initial population has less impact, since many members of
the initial population have cleared out gas around them in the prior model. In
terms of overall star formation rates though, the initial population has a
relatively small effect, and the feedback does not for example suppress
subsequent star formation. We find that MHD has a relatively larger impact than
initial conditions, reducing the star formation rate by a factor of 3 at later
times.Comment: 12 pages, 10 figure
Observational Bias and Young Massive Cluster Characterisation II. Can Gaia accurately observe young clusters and associations?
Observations of clusters suffer from issues such as completeness, projection
effects, resolving individual stars and extinction. As such, how accurate are
measurements and conclusions are likely to be? Here, we take cluster
simulations (Westerlund2- and Orion- type), synthetically observe them to
obtain luminosities, accounting for extinction and the inherent limits of Gaia,
then place them within the real Gaia DR3 catalogue. We then attempt to
rediscover the clusters at distances of between 500pc and 4300pc. We show the
spatial and kinematic criteria which are best able to pick out the simulated
clusters, maximising completeness and minimising contamination. We then compare
the properties of the 'observed' clusters with the original simulations. We
looked at the degree of clustering, the identification of clusters and
subclusters within the datasets, and whether the clusters are expanding or
contracting. Even with a high level of incompleteness (e.g. stellar
members identified), similar qualitative conclusions tend to be reached
compared to the original dataset, but most quantitative conclusions are likely
to be inaccurate. Accurate determination of the number, stellar membership and
kinematic properties of subclusters, are the most problematic to correctly
determine, particularly at larger distances due to the disappearance of cluster
substructure as the data become more incomplete, but also at smaller distances
where the misidentification of asterisms as true structure can be problematic.
Unsurprisingly, we tend to obtain better quantitative agreement of properties
for our more massive Westerlund2-type cluster. We also make optical style
images of the clusters over our range of distances.Comment: 19 pages, 10 figures, 6 tables. Accepted for publication in MNRA
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Biodegradation of the herbicide mecoprop-p with soil depth and its relationship with class III tfdA genes
Mecoprop-p [(R)-2-(4-chloro-2-methylphenoxy) propanoic acid) is widely used 37 in agriculture and poses an environmental concern because of its susceptibility to leach 38 from soil to water. We investigated the effect of soil depth on mecoprop-p 39 biodegradation and its relationship with the number and diversity of tfdA related genes, 40 which are the most widely known genes involved in degradation of the 41 phenoxyalkanoic acid group of herbicides by bacteria. Mecoprop-p half-life (DT50) was 42 approximately 12 days in soil sampled from <30 cm depth, and increased progressively 43 with soil depth, reaching over 84 days at 70-80 cm. In sub-soil there was a lag period of 44 between 23 and 34 days prior to a phase of rapid degradation. No lag phase occurred in 45 top-soil samples prior to the onset of degradation. The maximum degradation rate was 46 the same in top-soil and sub-soil samples. Although diverse tfdAα and tfdA genes were 47 present prior to mecoprop-p degradation, real time PCR revealed that degradation was 48 associated with proliferation of tfdA genes. The number of tfdA genes and the most 49 probable number of mecoprop-p degrading organisms in soil prior to mecoprop-p 50 addition were below the limit of quantification and detection respectively. Melting 51 curves from the real time PCR analysis showed that prior to mecoprop-p degradation 52 both class I and class III tfdA genes were present in top- and sub-soil samples. However 53 at all soil depths only tfdA class III genes proliferated during degradation. Denaturing 54 gradient gel electrophoresis confirmed that class III tfdA genes were associated with 55 mecoprop-p degradation. Degradation was not associated with the induction of novel 56 tfdA genes in top- or sub-soil samples, and there were no apparent differences in tfdA 57 gene diversity with soil depth prior to or following degradation
New constraints on oscillation parameters from Ve appearance and Vu disappearance in the NOvA experiment
For full abstract please refer to Official URL link”, or if there is a document attached which contains the abstract, “For full abstract please refer to attached documen
Search for multimessenger signals in NOvA coincident with LIGO/Virgo detections
Using the NOvA neutrino detectors, a broad search has been performed for any signal coincident with 28 gravitational wave events detected by the LIGO/Virgo Collaboration between September 2015 and July 2019. For all of these events, NOvA is sensitive to possible arrival of neutrinos and cosmic rays of GeV and higher energies. For five (seven) events in the NOvA Far (Near) Detector, timely public alerts from the LIGO/Virgo Collaboration allowed recording of MeV-scale events. No signal candidates were found
Search for multimessenger signals in NOvA coincident with LIGO/Virgo detections
Using the NOvA neutrino detectors, a broad search has been performed for any signal coincident with 28 gravitational wave events detected by the LIGO/Virgo Collaboration between September 2015 and July 2019. For all of these events, NOvA is sensitive to possible arrival of neutrinos and cosmic rays of GeV and higher energies. For five (seven) events in the NOvA Far (Near) Detector, timely public alerts from the LIGO/Virgo Collaboration allowed recording of MeV-scale events. No signal candidates were found
Measurement of neutrino-induced neutral-current coherent π⁰ production in the NOvA near detector
The cross section of neutrino-induced neutral-current coherent π⁰ production on a carbon-dominated target is measured in the NOvA near detector. This measurement uses a narrow-band neutrino beam with an average neutrino energy of 2.7 GeV, which is of interest to ongoing and future long-baseline neutrino oscillation experiments. The measured, flux-averaged cross section is σ = 13.8±0.9(stat)±2.3(syst)×10⁻⁴⁰ cm²/nucleus, consistent with model prediction. This result is the most precise measurement of neutral-current coherent π⁰ production in the few-GeV neutrino energy region