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public:seminar_abstracts [2018/06/11 10:04]
Samuel Grant
public:seminar_abstracts [2018/06/11 10:17] (current)
Samuel Grant
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 I will present results from both recent simulations and observations of molecular clouds in spiral galaxies. I will focus on the importance of stellar feedback and galaxtic structure. I will discuss the role of feedback in controlling molecular cloud evolution and the overall star formation rate in galaxies. I will also show results on molecular cloud lifetimes, and what determines cloud lifetimes. The relevance of galactic spiral structure to molecular cloud properties has long been unclear. Both simulations and observations indicate that cloud properties vary between arm and inter-arm regions. The exact nature of spiral arms does not have a huge effect on molecular clouds and star formation, although tidally induced galaxies tend to exhibit more massive GMCs which has a disproportionate effect on the star formation rate. I will present results from both recent simulations and observations of molecular clouds in spiral galaxies. I will focus on the importance of stellar feedback and galaxtic structure. I will discuss the role of feedback in controlling molecular cloud evolution and the overall star formation rate in galaxies. I will also show results on molecular cloud lifetimes, and what determines cloud lifetimes. The relevance of galactic spiral structure to molecular cloud properties has long been unclear. Both simulations and observations indicate that cloud properties vary between arm and inter-arm regions. The exact nature of spiral arms does not have a huge effect on molecular clouds and star formation, although tidally induced galaxies tend to exhibit more massive GMCs which has a disproportionate effect on the star formation rate.
 +
 +==== Shocking Events in the Solar Atmosphere ===
 +**Scott Houston ** (QUB) - ARC Seminar Wed 16th May 2018 3pm
 +
 +Previous research has documented the ubiquitous presence of non-linear shocks that are introduced by upwardly propagating magneto-acoustic waves in sunspot umbral atmospheres. In recent years, extensive analyses have been undertaken to examine the effect of these shocks on the surrounding magnetically-dominated plasma, with previous work identifying line-of-sight modulations of the magnetic field strengths and temperature enhancements on the order of several hundred degrees Kelvin. We employ simultaneous slit-based spectro-polarimetry and spectral imaging observations of the chromospheric He I 10830Å and Ca II 8542Å lines to examine full vector fluctuations in the umbral magnetic field caused by the steepening of magneto-acoustic waves into umbral flashes. Following the application of the HAZEL inversion routine, we find evidence to support the scenario that umbral shock events cause expansion of the embedded magnetic field lines due to the increased adiabatic pressure, hence providing increased transversal magnetic field fluctuations up to ~600 Gauss. Through comparisons with non-linear force-free field extrapolations,​ we demonstrate how the development of umbral flashes can deflect the quiescent magnetic field geometry by up to 8 degrees in both inclination and azimuthal directions.
 +
 +==== Characterising the atmosphere of a benchmark Hot Jupiter ===
 +**Dr Tom Evans ** (Exeter University) - ARC Seminar Wed 9th May 2018 2pm
 +
 +Only about 1% of FGK dwarfs have a hot Jupiter. Despite being relatively rare, the hot Jupiters are our key to understanding the complex physics and chemistry of tidally-locked atmospheres,​ for which we have no solar system analogs. This is important, for instance, because all terrestrial planets in the habitable zone of M dwarfs should be tidally-locked within 1Gyr. If we do not understand the atmospheres of hot Jupiters, we have little hope of understanding these more challenging targets, which will become an increasing priority over the next decade. In this talk I will present our latest efforts to observationally characterise the atmosphere of the benchmark hot Jupiter, WASP-121b. The dayside thermal emission implies a hot stratosphere,​ while the transmission spectrum reveals a rich array of features. The latter includes evidence of a strong NUV absorber, not currently accounted for by models, and which we speculate may be a product of sulfur photochemistry.
 +
 +==== Transit Visibility Zones of the Solar System Planets ===
 +**Robert Wells ** (QUB) - ARC Seminar Wed 2nd May 2018 3pm
 +
 +The detection of thousands of extrasolar planets by the transit method naturally raises the question of whether potential extrasolar observers could detect the transits of the Solar system planets, and in particular those of the Earth. In this talk I will present an analysis of the regions in the sky from where transit events of the Solar system planets can be detected - named "​transit zones"​. I will discuss how probable it is to detect one or more Solar system planet, the timescales over which they are valid, plus the prospects of finding temperate extrasolar planets which could observe transits of Earth. I will also report on a habitable zone candidate situated in one of the transit zones - a super-Earth near the inner-edge of the HZ of an early M-dwarf. Lastly, I will outline the search for more systems with the ongoing Kepler-K2 mission, including the hunt for "​monster"​ planets.
 +
 +==== Supernovae in the Era of High Cadence Sky Surveys ===
 +**Peter Clark ** (QUB) - ARC Seminar Wed 25th April 2018 3pm
 +
 +Supernovae continue to play a key role our comprehension of the fundamental physical processes of our universe. Whether through modelling of high mass element nucleosynthesis or through Type Ia supernovae observations,​ supernovae are ideal tools to map the expansion history of the universe and explore the effect of dark energy at high redshift.
 +I will discuss the fundamentals of supernova identification and classification with particular focus on the new options provided by current and upcoming high cadence surveys as well as detailing my own current work into the unusual ‘fast’ evolving transient LSQ13ddu.
  
 ==== Spirals, rings, gaps and asymmetries:​ using disc structure to infer planet formation processes === ==== Spirals, rings, gaps and asymmetries:​ using disc structure to infer planet formation processes ===
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 The infrared (IR) spectra of objects associated with dust and gas – including evolved stars, reflection nebulae, the interstellar medium (ISM), star-forming regions, and galaxies out to redshifts of z ∼ 3 – are dominated by emission bands at 3.3, 6.2, 7.7, 8.6 and 11.2 μm, the so-called unidentified infrared (UIR) bands. They are generally attributed to the IR fluorescence of Polycyclic Aromatic Hydrocarbon molecules (PAHs) UV pumped by nearby massive stars. Hence, the UIR band strengths are used to determine the star formation rate in galaxies, one of the key indicators for understanding galaxy formation and evolution. To date, PAHs are among the largest and most complex molecules known in space and emit up to 10% of the total power output of star-forming galaxies. The infrared (IR) spectra of objects associated with dust and gas – including evolved stars, reflection nebulae, the interstellar medium (ISM), star-forming regions, and galaxies out to redshifts of z ∼ 3 – are dominated by emission bands at 3.3, 6.2, 7.7, 8.6 and 11.2 μm, the so-called unidentified infrared (UIR) bands. They are generally attributed to the IR fluorescence of Polycyclic Aromatic Hydrocarbon molecules (PAHs) UV pumped by nearby massive stars. Hence, the UIR band strengths are used to determine the star formation rate in galaxies, one of the key indicators for understanding galaxy formation and evolution. To date, PAHs are among the largest and most complex molecules known in space and emit up to 10% of the total power output of star-forming galaxies.
 Space-based telescopes such as the Infrared Space Observatory (ISO) and the Spitzer Space Telescope revealed the richness of the PAH spectrum and provided extensive evidence for significant variability in the PAH spectrum from source to source and spatially within sources. In this talk, I will focus on the PAH properties in the reflection nebula NGC2023. I will present spectral maps of NGC2023 obtained with the SL and SH mode of the Infrared Spectrograph (IRS) on board the Spitzer Space Telescope. These observations clearly illustrate that the detailed characteristics of the PAH emission features vary across the reflection nebula and that different sets of PAH bands correlate spatially across the nebula. In particular, we conclude that at least 2 spatially distinct components contribute to the 7–9 μm PAH emission. We interpret these differences in spatial behavior in terms of variations in PAH characteristics such as size, charge and structure with the changing environment across the nebula. Space-based telescopes such as the Infrared Space Observatory (ISO) and the Spitzer Space Telescope revealed the richness of the PAH spectrum and provided extensive evidence for significant variability in the PAH spectrum from source to source and spatially within sources. In this talk, I will focus on the PAH properties in the reflection nebula NGC2023. I will present spectral maps of NGC2023 obtained with the SL and SH mode of the Infrared Spectrograph (IRS) on board the Spitzer Space Telescope. These observations clearly illustrate that the detailed characteristics of the PAH emission features vary across the reflection nebula and that different sets of PAH bands correlate spatially across the nebula. In particular, we conclude that at least 2 spatially distinct components contribute to the 7–9 μm PAH emission. We interpret these differences in spatial behavior in terms of variations in PAH characteristics such as size, charge and structure with the changing environment across the nebula.
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public/seminar_abstracts.txt · Last modified: 2018/06/11 10:17 by Samuel Grant

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