Recent Talks
List of all the talks in the archive, sorted by date.
Abstract
The 3.8m optical and infrared telescope, which is Japan's first segmented mirror telescope, is now being constructed using the world's first super high precision, high speed grinding technology and the world's first truss structure drive system. This is the joint project between Kyoto University, Nagoya University, National Astronomical Observatory, and Nano-Optonics Energy (private company) with the budget of the Nnao-Optonics Energy and Dr Hiroshi Fujiwara (CEO of the Nano-Optonics Energy). The telescope will be completed in 2012 and installed in Okayama, and will become the biggest optical and infrared telescope in east Asia. The technologies for making this telescope such as (1) grinding technology, (2) segmented mirror, and (3) truss structure drive system are also basic technologies for the future extremely large telescope such as the 30m telescope. The scientific objective of the telescope is the search for the transient objects (gamma ray bursts, black hole binaries, stellar flares) and the extra solar planets. How this project has emerged and developed will be discussed in detail, including also the discussion about the possible future international collaboration.Abstract
I will present grid-adaptive computational studies of both magnetized and unmagnetized jet flows, with significantly relativistic bulk speeds, as appropriate for AGN jets. Our relativistic jet studies shed light on the observationally established classification of Fanaroff-Riley galaxies, where the appearance in radio maps distinguishes two types of jet morphologies. We investigate how density changes in the external medium can induce one-sided jet decelerations, explaining the existence of hybrid morphology radio sources. Our simulations explore under which conditions highly energetic FR II jets may suddenly decelerate and continue with FR I characteristics. In a related investigation, we explore the role of dynamically important, organized magnetic fields in the collimation of the relativistic jet flows. In that study, we concentrate on morphological features of the bow shock and the jet beam, for various jet Lorentz factors and magnetic field helicities. We show that the helicity of the magnetic field is effectively transported down the beam, with compression zones in between diagonal internal cross-shocks showing stronger toroidal field regions. For the high speed jets considered, significant jet deceleration only occurs beyond distances exceeding hundred jet radii, as the axial flow can reaccelerate downstream to internal cross-shocks. This reacceleration is magnetically aided, due to field compression across the internal shocks which pinch the flow.Abstract
Galaxies are the basic building blocks of the Universe, and understanding their formation and evolution is crucial to many areas of current astrophysical research. Nearby galaxies, being the 'fossil record' of the evolution of galaxies, provide a wealth of detail to test extensively the current models of galaxy formation and evolution. A galaxy's structure is linked to both its mass and evolutionary history. Probing galactic structure requires understanding the distribution of stars among galaxies of all types and luminosities across the full range of environments. We are performing a complete volume-limited (d < 40 Mpc) survey of over 2200 nearby spiral, elliptical and dwarf galaxies at 3.6 and 4.5 μ in the Spitzer Warm Mission to address fundamental questions of galactic structure that are united by the common need for deep, uniform, unbiased maps of the stellar mass in galaxies. I will introduce the survey, give examples of images and of the science that can be done, and explain how other researchers at the IAC can become involved in analysing these exciting data.Abstract
ΛCDM-based numerical simulations predict a scenario consistent with observational evidence in Milky Way-like halos. However, less clear is the role of low-mass galaxies in the big picture. The best way to answer this question is to study the nearest example of a dwarf spiral galaxy, M33. We will use star clusters to understand the structure, kinematics and stellar populations of this galaxy. We will present our current status and future plans of a comprehensive study of the star cluster system of M33. This study will provide key insights into the star formation history, composition and kinematics of low-mass galaxies as well as place M33 within the context of galaxy formation process.Abstract
For a long time radiative MHD simulations of entire sunspots from first principles were out of reach due to insufficient computing resources. Over the past 4 years simulations have evolved from 6x6x2 Mm size domains focusing on the details of umbral dots to simulations covering a pair of opposite polarity sunspots in a 100x50x6 Mm domain. In this talk I will discuss the numerical challenges encountered in comprehensive radiative MHD simulations of active regions and summarize the recent progress. Numerical simulations point toward a common magnetoconvective origin of umbral dots and filaments in the inner and outer penumbra. Most recent simulations also capture the processes involved in the formation of an extended outer penumbra with strong horizontal outflows averaging around 5 km/s in the photosphere. I will discuss in detail the magneto convective origin of penumbral fine structure as well as the Evershed flow. I will conclude with a brief summary of recent helioseismic studies based on realistic MHD simulations as well as inferences on the sub surface structure of sunspots.Abstract
The window of very high energy (VHE) gamma-ray astronomy was only opened 20 years ago by the first observation of TeV gamma-rays from the CRAB nebula. Since then the field is rapidly expanding and we are approaching the first 100 VHE sources. In contrast to the many orders of magnitude larger flux of charged VHE Cosmic Rays, gamma-rays can be extrapolated back to their sources, the high energy particle processes mostly in stellar environments and thus allows us to retrieve basic information about the ultra-relativistic universe. In my talk I will shortly describe the gamma-ray production mechanisms related to these ultra relativistic processes, losses during the transport of gamma-rays through the universe and the detection methods. This is followed by a review of classes of gamma ray emitters and the relation to multi-wavelength respectively multi-messenger observations. Because of the very rich findings of the past years some restriction to highlight observations have to be made. The talk concludes with an outlook for the next years including possible prospects to build the so-called North-CTA (Cherenkov Telescope Array) on the Canary Islands.
Abstract
Ultra Compact Binaries are predicted to be the strongest known sources of gravitational waves in the LISA pass-band. Since they are at the short period end of the orbital period distribution (<70 mins), their number is a sensitive test of binary evolutionary models. The best method to detect these short period systems, whose optical light is dominated by an accretion disk and show optical intensity variations on timescales close to their orbital period, is through deep, wide-field, fast-cadence photometric surveys. The RaTS (Rapid Temporal Survey) project is unique in that it is sensitive to variability on timescales as short as 2 mins and systems with V~22. Our strategy and initial results will be presented.Abstract
Long suspected on theoretical grounds and supported by tantalising observational evidence, the connection between supernovae and gamma-ray bursts was definitely established in 2003. Since then, a number of events have forced us to revise what we thought we knew about SNe and GRBs. This SN/GRB connection went from tentative to definitive, to maybe not, to maybe in most cases. I will briefly review the major milestones along this road and describe the situation as it is today.Abstract
The Hubble Space Telescope has been given new life with the successful Servicing Mission 4 (SM4). The goal of each servicing mission to the telescope has been to replace instruments and other system components that would enable better science productivity and enlightenment. But never before has the notion of repairing existing broken instruments in the telescope been considered because of the complexity of such an activity... until now. During SM4, two new scientific instruments were installed – the Cosmic Origins Spectrograph (COS) and Wide Field Camera 3 (WFC3); two failed instruments, the Space Telescope Imaging Spectrograph (STIS) and the Advanced Camera for Surveys (ACS), were brought back to life by the first ever on-orbit repairs; and, the spacecraft original batteries were replaced with new ones that will keep HST powered well into the next decade. But what will the scientific observations look like? The evidence is here with the release of the early observations from each instrument, and the news is wonderful!Abstract
History: astroparticle physics emerged from particle physics and connects it to astrophysics. Early particle physics was based on cosmic ray studies. The 1930s and 1940s were dominated by the discovery of new particles (positron, muon, pion) and the problems of their identification. In the 1950s, the era of the big accelerators began. Recent astroparticle physics started in the 1980s, with solar neutrino measurements and the investigation of cosmic rays by means of particle detectors.
Upcoming talks
- Coloquio con Isabel Pérez Grande (AEE)Dr. Isabel Pérez GrandeTuesday November 26, 2024 - 10:30 GMT (Aula)
- Revisiting mass transfer and accretion in symbiotic binaries in the Gaia eraDr. Jaroslav MercThursday November 28, 2024 - 10:30 GMT (Aula)