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public:seminar_abstracts [2018/10/30 15:31]
Mark Magee
public:seminar_abstracts [2019/04/15 11:23] (current)
Krishna Prasad
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-====== ARC Seminar Abstracts ======+ ====== ARC Seminar Abstracts ====== 
 +===Century-Long,​ multi-wavelength solar database from kodaikanal solar observatory=== 
 + 
 +** Prof. Dipankar Banerjee ** (IIA, Bangalore, India)- ARC Seminar Wednesday 17 April 2019 11 am 
 + 
 +The Kodaikanal observatory has been obtaining solar images since 1904 in broad band white light, narrow band Ca-K 393.37 nm and H-alpha 656.3 nm wavelengths. Many of these observations are still continuing. The historical data which were on photographic plates has been digitized. The calibration of the Ca-K, white light and H-alpha images have been completed. The digitized data are available through an online portal. Cross calibration between different data sources as collected from observatory across the globe is underway. Some new results from this multiwavelength database will be presented. I will also  briefly talk about two National Solar projects, namely NLST and ADITYA where Indian Solar community are engaged now.  
 + 
 +===Exploring the outer solar system: A window into our past=== 
 + 
 +** Dr. Marc Buie ** (SWRI & New Horizons Team)- ARC Seminar Monday 15 April 2019 1 pm 
 + 
 +Following the successful flyby of Pluto in 2015, New Horizons continued 
 +out into the Kuiper Belt to pursue its mission of explorations of the 
 +outer reaches of the solar system. ​ The next chapter in this exploration 
 +is being written through the encounter with (486958) 2014MU69, nicknamed 
 +"​Ultima Thule" that occurred on 2019 Jan 1.  This phase of the mission 
 +was very challenging but worth all of that effort as we see the new 
 +data continuing to be received from the spacecraft. ​ This chapter that 
 +New Horizons is now writing would not have been possible without broad 
 +support from the community and formidable ground-based and space-based 
 +telescopes we have at our disposal. ​ However, there is a special synergy 
 +between New Horizons, the Hubble Space Telescope, and ESA's Gaia Mission 
 +and the people behind these missions. My presentation will provide a glimpse into the work that began in 
 +2004 and culminating in the first ever flyby of a cold-classical Kuiper 
 +Belt object. ​ I will present a summary of what it took to get there as 
 +well as an update on the current scientific results from the mission. 
 + 
 +===TRAPPIST:​ a robotic telescope to study planetary systems: A window into our past=== 
 +** Dr. Emmanuel Jehin ** (Liege University)- ARC Seminar Monday 10 April 2019 1 pm 
 + 
 +TRAPPIST- for TRAnsiting Planets and PlanetesImals Small Telescope - is a 60 cm robotic telescope operated remotely by the Liège University in La Silla since June 2010. It is devoted exclusively to the study of planetary systems through two approaches: the detection and characterisation of exoplanets and the study of comets and other small bodies of the Solar System. We will review 8 years of operations and the main science results, showing that relatively small and dedicated telescopes can still play an important rôle, especially from excellent observing sites like la Silla.  
 + 
 +=== Exploring the Atmospheres of Uranus and Neptune === 
 +** Dr Leigh N.Fletcher** (@leighfletcher)Associate Professor in planetary Sciences, University of Leicester 
 + 
 +Uranus and Neptune are our closest and best representatives of a class of worlds that may be commonplace in our universe. ​ The Ice Giants are intermediate in size between the gas giants and the terrestrial planets; enhanced in heavy elements compared to their gas-giant cousins; possess magnetospheres unlike anywhere else in our Solar System; display extremes in atmospheric processes governed by the balance between seasonal changes in the weak sunlight and powerful (Neptune) or minimal (Uranus) internal heat sources; and are attended by both natural icy satellites (Uranus) and captured Kuiper Belt Objects (Neptune). ​ Previous robotic exploration by Voyager 2 has barely scratched the surface. ​ Following the successes of gas giant exploration with Galileo, Cassini, Juno, and ultimately JUICE, the international community now sees the Ice Giants as a top priority for future exploration in the 2020s and 2030s. 
 +  
 +This presentation will explore how our knowledge of Ice Giant atmospheres has evolved since the Voyager era, using ground-based facilities and space-based telescopes to explore their evolving clouds, temperatures,​ and composition. ​ A new and complex picture of Ice Giant circulation patterns is beginning to emerge that will be tested in the 2020s using the James Webb Space Telescope. ​ Ultimately, long-lived orbiters, coupled with in situ measurements by entry probes, will be necessary to fully understand how – and why - the Ice Giants differ from the other worlds in our Solar System. 
 + 
 + 
 +=== Molecular Astronomy: Cool stars and exoplanets ===== 
 +** Prof. Peter Bernath ** (ODU)- ARC Seminar Friday 8 March 2019 10 am 
 + 
 +The spectra of “cool” astronomical objects such as low mass stars, brown dwarfs and exoplanets are dominated by molecular absorption features. Of particular interest are methane, water, ammonia and diatomic hydrides at high temperatures. An overview of this area of molecular astronomy will be presented from a spectroscopic perspective. The talk will include emission and absorption laboratory measurements of hot molecules by Fourier transform spectroscopy related to exoplanets. Comparisons with the latest theoretical predictions will be presented.  
 + 
 +=== Revisiting the HST archive: the search for Transneptunian Binaries (and more!) ===== 
 +** Richard Smith ** (QUB)- ARC Seminar Wednesday 6 March 2019 3 pm 
 + 
 +While the New Horizons flybys of Pluto in 2015 and 2014MU69 at the start of 2019 have answered some important questions about the Transneptunian Region, there is a great deal still to be learned. One prevailing question concerns the number and characteristics of binary objects. Out of more than 2,500 Transneptunian Objects now identified, only 85 are known to be binaries. My work aims to increase the number of known Transneptunian Binaries by reprocessing HST archive data using a robust emcee-based PSF-fitting algorithm. This constitutes the first large-scale attempt at applying a consistent method to HST observations of Transneptunian Objects in search of binarity, allowing for the confirmation and discovery of binary candidates. I will detail how the fitting process works and present the results obtained so far, including objects of interest. I will also discuss the future application of the algorithm to search for cometary fragmentation in archive data.  
 + 
 +=== Understanding the early stages of stellar and planetary system evolution ===== 
 +** Dr. Edward Gillen ** (Cambridge)- ARC Seminar Wednesday 27 February 2019 3 pm 
 + 
 +Young open clusters are fruitful astrophysical laboratories because their members possess a common age, composition and distance. Combining information from clusters at different ages offers a powerful tool to understand the early evolution of stellar and planetary systems. Significant advances have been made in this area during recent years. I will begin by presenting successful efforts to detect transiting planets in young open clusters with Kepler/K2, before highlighting some of the interesting serendipitous discoveries made during this work. I will then present the Next Generation Transit Survey (NGTS), highlight some of our recently-discovered planets, and introduce our new clusters program, which is already providing novel insight into early stellar and planetary system evolution. 
 + 
 +=== How the Chromosphere responds to a flare-initiated Sunquake ===== 
 +** Sean Quinn ** (QUB)- ARC Seminar Wednesday 20 February 2019 3 pm 
 + 
 +Active region 12673 produced a number of solar flares in September 2017, including the largest of solar cycle 24, an X9.3 flare on September 6th. Using data form the Swedish 1-m Solar Telescope (SST), a co-spatial and co-temporal chromospheric component of one of the Photospheric sunquakes has been detected. In this presentation I will describe the analysis of such a response, using the co-alignment of SST and HMI LOS data, as well as using the spectroscopic capabilities of the SST to investigate the line profiles of the wavefronts created by the sunquake. Finally, I will discuss the use of the NICOLE inversion code in helping us understand the creation of such a chromospheric response. 
 + 
 +=== von Karman decay and intermittent dissipation in Corona and solar wind plasmas ===== 
 +** Dr. Penny Wu ** (QUB)- ARC Seminar Wednesday 13 February 2019 3 pm 
 + 
 +Collisionless plasma turbulence may be described by magnetohydrodynamics (MHD) at large scales, but requires kinetic description at ion and electron scales in order to include dissipative processes that terminate the cascade. We performed the first kinetic demonstration of von Karman similarity decay (in a formulation adapted to MHD from hydrodynamics) for 2.5-D collisionless plasmas. The profound implication is that decay/​dissipation rate is determined in the outer scale by energy containing eddies, independent of the microscopic viscosity, resistivity,​ and details of dissipation mechanisms.  
 + 
 +Kurtosis of magnetic field increments indicates that kinetic scale coherent structures are present, with some suggestion of incoherent wave activity near ion scales. Proton temperature distributions suggest heating associated with coherent (non-Gaussian) structures: intermittent heating. Further, simulations render that at small turbulence amplitudes the electrons are preferentially heated, whilst at larger amplitudes proton heating is the dominant effect. In the corona and the solar wind the protons are typically hotter, suggesting that these natural systems are in the large amplitude turbulence regime. ​  
 + 
 + 
 +===Taking the Temperature of Solar System Airless Bodies: Insights from the NASA’s LRO and OSIRIS-REx missions ===== 
 +** Dr. Kerri Donaldson Hanna** (Oxford)- ARC Seminar Wednesday 30 January 2019 1 pm 
 + 
 +Thermal infrared observations of Solar System bodies provide key insights into the physical and compositional properties of their surfaces. ​ Thermal physical properties include surface temperatures,​ regolith and rock properties, and thermal inertia. ​ Thermal infrared spectral measurements can be used to identify compositional units on planetary surfaces as rocks and minerals have diagnostic features across this wavelength region. ​ In this talk, I will provide an overview of current spacecraft observations of the Moon (NASA’s Lunar Reconnaissance Orbiter; LRO) and asteroids (NASA’s Origins, Spectral Interpretation,​ Resource Identification,​ Security, Regolith-Explorer;​ OSIRIS-REx) and what these observations tell us about Solar System airless bodies. ​ In addition I will discuss how laboratory spectral measurements across the thermal infrared spectral region are necessary for the interpretation of current and future thermal infrared observations of Solar System airless bodies. ​  
 + 
 + 
 +===Wave Mechanics and Cosmic Structure ===== 
 +** Prof. Peter Coles** (Maynooth)- ARC Seminar Wednesday 23 January 2019 1 pm 
 + 
 +The Standard Model of Cosmology involves the assumption that galaxies and large-scale cosmic structures form through the gravitational instability of a distribution of collisionless cold dark matter which is usually treated as classical particles. In this talk I will outline some of the problems with this picture and discuss the possibility that dark matter might behave quantum mechanically (e.g. if it comprises a very light axion-like particle). Following on from a seminal paper by Widrow & Kaiser (1992) I will further discuss why it can be advantageous for some purposes (e.g. reconstruction problems) to treat the growth of cosmic structure as a wave rather than particle phenomenon anyway, even if dark matter does not have this peculiar form.    
 + 
 + 
 + 
 +===Energetic particles and star formation ===== 
 +** Dr Donna Rodgers-Lee** (Hertfordshire)- ARC Seminar Wednesday 16 January 2019 3 pm 
 + 
 +There is a growing body of observational evidence to suggest that energetic particles are produced during the low-mass star formation process. Both the young low-mass stars themselves and the jets they power appear to be capable of accelerating particles up to ~GeV energies. These low-energy cosmic rays may be important in determining the ionisation rate in star-forming regions and subsequently the chemical and dynamic evolution of protoplanetary disks. 
 + 
 +Here, based on the assumption that young low-mass stars accelerate protons to ~GeV energies, I will discuss our recent work focusing on the ionising effect of these energetic particles in protoplanetary disks, as well as further ways of investigating their transport properties. I will also describe on-going observational efforts to identify further evidence of non-thermal emission from young stellar objects. ​   
 + 
 +===Revealing the Evolution of Comet Nuclei with Ground Photometric Observations ===== 
 +** Dr Rosita Kokotanekova** (ESO)- ARC Seminar Wednesday 12 December 2018 3 pm 
 + 
 +The complex nature of comets has earned them a spot among the most interesting objects in the Solar System. Comets are believed to still preserve information about the physical conditions in the protoplanetary disk. At the same time, they also bear signatures of the epoch of planetary migration ~4 billion years ago, of the time spent in the outer solar system, as well as of their recent activity. In the past three decades, a great progress in untangling the intricate history of comets has come from the in-situ studies during a series of space missions which culminated with the Rosetta mission between 2014 and 2016. However, with no plans for space missions to further comets in the next couple of decades, we have to rely more heavily on telescope observations to reveal new clues on the unanswered questions in cometary science.  
 +In this talk, I will present results from our effort to study Jupiter-family comet nuclei and their source populations in the Centaur region and the Kuiper Belt from the ground. This work has demonstrated that photometric observations of the rotation and surface properties of comet nuclei can be key for understanding their evolution. 
 + 
 + 
 + 
 +===Internal Gravity Waves in Massive Stars ===== 
 +** Dr Tamara Rogers** (Newcastle University)- ARC Seminar Wednesday 05 December 2018 1 pm 
 + 
 +Internal Gravity Waves (IGW) can lead to angular momentum transport and chemical mixing in stellar interiors. In this talk I will  present numerical simulations of these waves in massive stars and discuss how they might contribute to the understanding of a variety of observational mysteries. ​  
 + 
 + 
 + 
 +===Unveiling extreme dusty star-formation in the distant Universe ===== 
 +** Dr Julie Wardlow** (Lancaster University)- ARC Seminar Wednesday 28 November 2018 3.30 pm 
 + 
 +In recent years the high-redshift Universe has been increasingly opened to scrutiny at far-infrared wavelengths,​ where cool dust emission from star-formation dominates. The dusty star-forming galaxies (DSFGs), selected at these wavelengths likely represent an important, but short-lived phase in the growth of massive galaxies. These DSFGs often have star-formation rates in excess of ~1000 solar masses per year and are confirmed beyond z~6, although their redshifts and high dust contents make them faint and difficult to study at other wavelengths. I will present results probing their nature and the triggering mechanisms of their immense star-formation rates, using data from ALMA and other leading facilities. 
 + 
 +===Transverse Wave Induced Kelvin-Helmholtz Rolls in Spicules ===== 
 +** Dr Patrick Antolin** (University of St. Andrews)- ARC Seminar Wednesday 21 November 2018 3pm 
 + 
 +In addition to their jet-like dynamic behavior, spicules usually exhibit strong transverse speeds, multi-stranded structure, and heating from chromospheric to transition region temperatures. In this work we first analyze Hinode and IRIS observations of spicules and find different behaviors in terms of their Doppler velocity evolution and collective motion of their sub-structure. Some have a Doppler shift sign change that is rather fixed along the spicule axis, and lack coherence in the oscillatory motion of strand-like structure, matching rotation models, or long- wavelength torsional Alfvén waves. Others exhibit a Doppler shift sign change at maximum displacement and coherent motion of their strands, suggesting a collective magnetohydrodynamic (MHD) wave.  
 +By comparing with an idealized 3D MHD simulation combined with radiative transfer modeling, we analyze the role of transverse MHD waves and associated instabilities in spicule-like features. We find that transverse wave induced Kelvin– Helmholtz (TWIKH) rolls lead to coherence of strand-like structure in imaging and spectral maps, as seen in some observations. The rapid transverse dynamics and the density and temperature gradients at the spicule boundary lead to ring-shaped Mg II k and Ca II H source functions in the transverse cross-section,​ potentially allowing IRIS to capture the Kelvin–Helmholtz instability dynamics. Twists and currents propagate along the spicule at Alfvénic speeds, and the temperature variations within TWIKH rolls, produce the sudden appearance/​disappearance of strands seen in Doppler velocity and in Ca II H intensity. However, only a mild intensity increase in higher-temperature lines is obtained, suggesting there is an additional heating mechanism at work in spicules.  
 + 
  
  
Line 641: Line 755:
 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.1540913488.txt.gz · Last modified: 2018/10/30 15:31 by Mark Magee

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