Speaker: Piotr Sybilski

Abstract: The alignment of spin-orbit in binary stars is a very common assumption in modeling of such objects. Still this is not always the case and recent publications prove the significance of misalignment on observables and models. In my presentation I describe a plan to observe spectroscopically a selected sample of bright eclipsing binaries to discover and subsequently characterize the spin-orbit alignment with the RossiterMcLaughlin effect.

The second part of my presentation covers the Project Solaris. The primary aims of this project are to detect circumbinary planets and achieve high precision results regarding fundamental stars parameters. This will be achieved by a network of automatic, photometric, 0.5 m telescopes. The first one arrived to South Africa last week.

 

Speaker: Andrew Mason

Abstract: The precise form of the equation of state (EOS) for neutron stars (NS) has long been an outstanding problem within astrophysics.  There have been numerous theoretically derived EOS proposed over the previous few decades, each of which define a NS mass-radius relation and predict a maximum NS mass. In order to eliminate some of the contending theories we must however turn to observations.

Within this talk I will describe our ongoing work within the area of High Mass X-ray Binaries (HMXB) in which we have attempted to determine the upper mass limit for neutron stars.  The systems in which this can be achieved are rare, and the main part of this talk will comprise our work on 3 HMXB systems containing an eclipsing X-ray pulsar : OAO 1657-415, EXO 1722-363  and IGR J18027-2016.

The companion massive star in each of these systems is extremely obscured and is only observable in the near-infrared (NIR). Observations obtained over the last two years from ESO VLT and the NIR spectrograph ISSAC  has allowed the construction of an orbital solution and a corresponding NS mass range determination for each system, the first time this has been achieved in the NIR.    

Additionally, I will also discuss a relatively new class of HMXB system, (that has only in the past few years been identified by the ESA's gamma-ray observatory INTEGRAL) the Supergiant Fast X-ray Transients (SFXTs). Knowledge regarding the orbital parameters and modes of accretion for SFXTs is currently limited and is an ongoing field of research, for which I have been granted observational time using the 1.9m Radcliffe telescope at SAAO Sutherland.

Speaker: Yabebal Tadesse Fantaye

Abstract: Primordial gravitational waves are a key prediction and test of models of the early universe. We discuss the prospects for detecting them from future ground and balloon CMB experiments such as EBEX and POLARBEAR. Since this will require detection and precision mapping of the CMB polarisation we discuss complications arising from foregrounds such as synchrotron and dust in our galaxy.

Speaker: Se-Heon Oh

Abstract: I present a direct comparison of dark matter distributions between fully cosmological simulations of dwarf galaxies and sample dwarf galaxies from “The HI Nearby Galaxy Survey” (THINGS). The simulations form bulgeless galaxies with a dark matter core, and include the effect of baryonic feedback processes, such as gas cooling, star formation, cosmic UV background heating and most importantly physically motivated gas outflows driven by supernovae. Analyzing the simulations in exactly the same way as the observational sample allows us to address directly the so-called "cusp/core" problem in the Lambda CDM model. The derived rotation curve shape and the inner density slopes of the simulated dwarf galaxies show a good agreement with those of the THINGS dwarf galaxies. This result confirms that the baryonic feedback processes included in the new simulations are efficiently able to make the initial cusps predicted from dark-matter-only simulations shallower, and induce dark matter halos with a central mass distribution similar to that observed in nearby dwarf galaxies.

Speaker: Darragh O' Donoghue

Abstract: Since its Inauguration, SALT has not reached its potential as a telescope due to two major problems: poor image quality and poor efficiency in the RSS spectrograph. The latter problem has been fixed and the instrument is ready to go back on the telescope. Image quality has been worked on by removing the spherical aberration corrector (SAC) from the telescope and carrying out repairs and re-alignment of the optics. This talk will describe the repairs and re-alignment and give an update on the status of the work.

Speaker: Marcel Agüeros

Abstract: X-ray emission traces the strength of a star's magnetic dynamo, and is tightly linked to the star's age and rotation. X-ray observations find that the X-ray luminosity decreases steadily as stars move from the pre-main sequence into the old disk population. This result relies heavily on observations of open clusters, whose homogeneous, coeval populations provide an ideal laboratory in which to study the age-activity-rotation relation. However, there are few nearby open clusters, and fewer still have the high quality optical data needed to fully characterize their X-ray emitters. Much of what we know about the age-activity-rotation relation is based on a handful of stars in a small number of well-studied benchmark clusters--particularly the Hyades, whose proximity (~50 pc) has facilitated observations of its members at many wavelengths. Praesepe is a rich (~1000 members), nearby (~170 pc) open cluster whose properties are very similar to those of the Hyades. But Praesepe has consistently surprised those who expected to observe levels of stellar activity similar to those seen in the Hyades: Praesepe stars are under-luminous in the X-ray relative to the Hyads. Recent optical studies of Praesepe have improved and expanded the census of cluster members, while optical monitoring by the Palomar Transient Factory (PTF) is providing a new diagnosis of stellar rotation within the cluster. Combining these datasets with archival X-ray observations, we are undertaking a new analysis of Praesepe's X-ray luminosity function (XLF), and examining the degree to which its anomalous XLF is a product of the cluster's activity-rotation relation. Praesepe is the first target for our Columbia/Cornell/Caltech PTF Survey of open clusters, which aims to measure rotations in a half dozen clusters of varying ages in order to map out the relationship between stellar rotation and activity in unprecedented detail.

Speaker: Benne Holwerda

Abstract: The MeerKAT UltraDeep HI Survey aims to observe the 21 cm line emission out to a redshift of z=1 and beyond. From both direct detections and stacked signal, we will address the HI mass function, the cosmic hydrogen density of the Universe (OmegaHI) and their evolution over cosmic times, as well as galaxy evolution via e.g., the Tully-Fisher relation, the relation between HI mass and Hubble Type or stellar mass, and the Schmidt-Kennicutt star-formation law. We propose to observe two fields, the COSMOS and Chandra Deep Field South (CDF-S) for 1000 hours, adding an additional 4000 hours to one of these fields in 2015 when the full instantaneous bandwidth of MeerKAT (0.58-2.5 GHz) will be realised. The CDF-S presents an unique opportunity for SA's premier astronomical instruments, MeerKAT and SALT to collaborate on a combined legacy dataset.

Speaker: Andres Escala

Abstract: In this talk I will discuss gravitational instabilities in disks, with special attention to the most massive clumps that form because they are expected to be the progenitors of massive clusters. The maximum unstable mass is set by rotation, it depends only on the surface density and orbital frequency of the disk, and is  proposed to be related to the formation of massive clusters in galaxies. Also, I will discuss the role of this largest scale in galaxies not stabilised by rotation, in the triggering of star formation at galactic scale.

Speaker: Ed Olson

Abstract: Star formation is a major driver of galaxy evolution.  A galaxy's luminosity, colours, metallicity and gas content are all controlled by its star formation activity.  A quantitative assessment of galactic-scale star formation and its links to the global properties of the ISM therefore serves as an important step towards understanding the life-cycles of galaxies.  Nearby galaxies serve as ideal laboratories in which to study star formation.  In this talk I present new, high-quality ultraviolet, infrared and HI imaging of two nearby dwarfs, NGC 2915 and NGC 1705.  These are atypical star-forming systems, each having a small stellar disk embedded in a large, extended HI disk.  It is not clear why star formation should only occur near the very centre of each galaxy's HI disk.  A suite of star formation models is examined for the galaxies in order to relate their star-forming properties to those of their inter-stellar media, with the aim of better understanding the interplay between the key properties of the ISM that regulate the star formation activity.  The star formation threshold of each galaxy is shown not to be a local phenomenon, depending on global kinematics as well as the stellar and dark matter potentials.  Treating ~10^9 solar masses of dark matter as being distributed within the HI disk of each galaxy leads to gravitational instabilities that are consistent with observations.  Alternatively, adopting the rotational shear as a characterization of the global ISM kinematics allows for accurate descriptions of the star-forming cores of the galaxies. These results therefore suggest that dark matter could play a potentially important role in regulating a galaxy's star formation activity, and that rotational shear can largely prevent star formation in the outer, differentially-rotating disks of late-type systems.

Speaker: Juan Gutierrez-Soto

Abstract: Be stars are non-supergiant B-type main sequence stars whose spectrum has or had at some time one or more Balmer lines in emission, due to the presence of a circumstellar disk. The interest of these stars is enormous: the yet unknown mechanism(s) to eject the material from the star to the disk, the presence of non-radial pulsations and/or clouds attached to the star, the relationship with other B-type pulsators such as beta Cep or SPB stars, the high-rotational velocity, the presence of a magnetic field, etc.  In order to understand the star as a whole we need a very high-precision, very long duration and high duty-cycle photometric monitoring, which can only be provided by the new space missions such as CoRoT or Kepler.

In this talk I will show you the recent results obtained from the study of the high-precision light curves of the Be stars observed by COROT and Kepler.

Speaker: Dr Amanda Weltman

Abstract: Dark energy makes up nearly 75% of the total energy budget of the universe and is the agent responsible for the observed accelerated expansion of the universe. This is a polite way of quantifying how very little we actually know about what makes up the universe and what is causing it to expand ever faster. Despite the spectacular improvements in observational cosmology to date - pinning down the detailed nature of dark energy is notoriously difficult with cosmological surveys alone. In this talk we will discuss the dark energy problem and its possible solutions. In particular we will focus on an exciting proposal - chameleon dark energy - and the possibility that we can learn about the large scale features of our universe within the fairly small scale setting of the laboratory.

Speaker: Dr Torsten Böhm

Abstract: In this talk, I will present the open question of the origin of the tremendous activity in pre-main sequence Herbig Ae/Be stars. Different approaches to understand this problem are presented. Eventually, the most promising analysis tool - the astroseismology of this group of stars based on high-resolution ground-based spectroscopy is introduced.

Speaker: Gerhardt R. Meurer

Abstract: Star formation is complex, involving processes ranging from atomic reactions to the gravitational stability of entire galaxies. This makes it very hard to model even with the fastest computers. Instead, computer simulations of galaxy evolution usually resort to emprical based prescriptions to set the amount of ISM that is converted into stars (the Star Formation Law - SFL) and the mass distribution of stars formed (the Initial Mass Function - IMF). These "laws" have proved remarkably resilient, having been proposed over 50 years ago. I will show results and ongoing work from the Survey of Ionization in Neutral Gas Galaxies (SINGG) and the Survey of Ultraviolet emission in Neutral Gas Galaxies (SUNGG) which survey the star formation properties of galaxies as traced by H-alpha and Ultraviolet emission. Our simple neutral hydrogen (HI) only selection criteria results in a sample that captures all types of star forming galaxies, while the use of two star formation tracers and integrated HI fluxes provide new constraints on both the SFL and IMF. We find strong correlations between the Halpha/FUV flux ratio and the optical surface brightness of galaxies. The only plausible explanation of this result is that the IMF is not constant. This result has enormous implications for galaxy evolution. Meanwhile strong correlations between the HI, star-formation, and old stellar population properties of galaxies are tighter than the Kennicutt-Schmidt Star Formation Law. The existence of an HI - star formation connection has been somewhat of a mystery since stars form in the molecular not the neutral ISM, while the highest mass stars and the HI have very different distributions in galaxies. I will argue that the IMF and the other star formation scaling relations result from pressure-regulated star-formation in a disk maintained at near critical dynamical stability.

 

 

Speaker: Andrzej Zdziarski

Abstract: Cyg X-3 is the only known X-ray binary in the Galaxy with a Wolf-Rayet companion, and its spectral and timing properties are different from those of X-ray binaries with either black hole or neutron star compact objects. For example, its X-ray spectra in the hard state show a high energy cutoff at energies much lower than those seen in other accreting X-ray binaries. Also, the power spectra show a high-frequency cutoff at an unusally low frequency. I will discuss a model explaining well the uniquness of both the spectral and temporal properties as an effect of a single physical process. Also, I will present some other results on modelling the stellar wind, the radio/X-ray correlation, and the GeV emission observed by Fermi.

Speaker: Amanda Weltman

Abstract: Dark energy makes up nearly 75% of the total energy budget of the universe and is the agent responsible for the observed accelerated expansion of the universe. This is a polite way of quantifying how very little we actually know about what makes up the universe and what is causing it to expand ever faster. Despite the spectacular improvements in observational cosmology to date - pinning down the detailed nature of dark energy is notoriously difficult with cosmological surveys alone. In this talk we will discuss the dark energy problem and its possible solutions. In particular we will focus on an exciting proposal - chameleon dark energy - and the possibility that we can learn about the large scale features of our universe within the fairly small scale setting of the laboratory.

Speaker: Alexander Kaiser

Abstract: BRITE-Constellation consists of UniBRITE and BRITE-AUSTRIA (TUG-SAT1), two 20 cm cube nanosatellites. Each will fly a small aperture telescope with a CCD camera to perform high-precision two-color photometry of the brightest stars in the sky (≤ 4th mag) continuously for up to several years. The primary science goals are studies of massive and luminous stars in our neighbourhood, representing objects which dominate the ecology of our Universe, and also evolved stars (giants) to probe the future development of our Sun. The wide field cameras (24°) will also obtain data from other scientifically interesting stars to investigate their stellar structure and evolution. All of that is enabled by innovative technology currently developed in collaboration between Canada and Austria. A launch of UniBRITE and BRITE-AUSTRIA in early 2011 in envisioned.

 

Speaker: Renee Hlozek

Abstract: The Atacama Cosmology Telescope (ACT) has mapped the microwave sky down to arcminute scales. We will present the recent measurement from ACT of the angular power spectrum of the microwave background radiation observed at 148GHz. After introducing the telescope and observing strategy, we will discuss the map-making procedures and tests of the ACT spectrum and analysis pipeline. Finally, we will describe constraints on parameters of the small-scale power spectrum, including the emission of unresolved point sources and diffuse emission from the Sunyaev-Zel’dovich (SZ) effect of galaxy clusters.

Speaker: A. Pigulski

Abstract: The study of Beta Cephei stars, hot, massive, main-sequence pulsators, has already over a hundred years-long history with a significant contribution of the SAAO astronomers. The asteroseismology of these stars seems to be very promising and may help to solve important problems related to the evolution of massive stars, their rotation and even the input physics (opacites). I will summarize the recent discoveries made using the All Sky Automated Survey (ASAS) photometry: nearly 300 Beta Cephei stars were discovered in this photometry, constituting an excellent sample of bright pulsators of this type for the follow-up study and statistical considerations.

Speaker: Prof Shuji Sato

Abstract: I will present a brief review and the current activities of IRSF (Infrared Survey Facility at SAAO), which was commissioned in 2000 together with SIRIUS (NIR 3-ch camera) at Sutherland. I will show statistics of visiting observers, obtained PhDs and publications from IRSF for these nine years.

Polarimetric mode was installed in 2006, simply by adding two pieces; a half-wave plate and a wire-grid polarizer, called “SIRPOL = SIRIUS+POLARIMETER”. Since then, polarimetry has been carried out for star forming regions, dark clouds and the inner regions of the Galaxy. I will talk on some recent topics, based on “Near-InfraRed Polarimetric Survey toward the Galactic Center”. In previous studies, starlight transmitting through interstellar space is polarized due to non-spherical dust grains aligned in magnetic field. These observations in optical wavelengths suffered heavy extinction by dust grains, so reached only to distances of ~3 kpc from the Sun. We carried out polarimetric survey in the direction of the Galactic central region of b~±1x l~±2 deg in NIR wavelengths, being capable to reach to GC of ~ 8 kpc. NIR polarization angles,?, manifest a regular configuration of interstellar magnetic field running along the Galactic plane, in a similar way to the optical pattern so far revealed. Both p?and E(H-Ks) show steep decrease to the latitude of b~±1 deg from Galactic plane. However, polarization efficiency,? defined as pKs/E(H-Ks), is by one-thirds smaller than that expected from the neighborhood to Sun and does not show any trends with l or b. We found that it anti-correlates spatially with dispersion of polarization angle;?=??. We infer that overlapping of magnetic fields in the clouds along line-of-sight cause the low efficiency and the anti-correlation. Violent phenomena, such as star formations, SNRs, HII regions and so on, may disorder regular magnetic fields in the interior of the Galaxy.

Speaker: Gerald Handler

Abstract: Designed for finding Earth-like planets in the habitable zone around solar-like stars with the transit method, the Kepler space mission allocates a fraction of its observing time to asteroseismology. The motivation stems from the capability of determining the radii of solar-like stars, and thus of their transiting planets, to high accuracy by asteroseismic means. (Asteroseismology uses stellar oscillations as seismic waves to determine interior structure properties.) We give an overview of the Kepler mission, a brief introduction to the Kepler Asteroseismic Investigation, and present a some initial results from the first months of science operations.

Speaker: Dr. Thijs Kouwenhoven

Abstract: Observations have indicated that the vast majority of stars form in clusters, and that a large fraction forms in a binary or multiple system. In order to understand star formation, is it of crucial importance to recover the outcome of star formation, i.e., the properties of the newly formed stellar population: the IMF and the properties of binary systems. This is not an easy task, as dynamical interactions and stellar evolution alter the binary population quickly after the stars have formed. Observational selection effects associated with surveys for multiplicity introduce further complications. In this colloquium I will discuss the formation and early evolution of the binary population in star clusters, and how observations can be used to constrain the star formation process.

Speaker:  Dr. Simon Pustilnik

Abstract: Galaxies with gas metallicity Zo/50 < Z < Zo/10 (Zo - is Sun's value) are very rare in the local Metagalaxy. The observational properties of a part of such galaxies allow to assign them as the best proxies of evolutionary young galaxies in the early Universe (redshifts of 5-10). Therefore one hopes that the studies of rare local cousins of cosmologically young galaxies can shed new light on star formation and its feedback at metallicities much lower than typical ones of the current epoch. This, in partcular, causes a continuing interest to search for and detailed studies of these atypical objects. The very existence of the most metal-poor gas-rich galaxies in the Local Volume seems to be a challenge to modern galaxy evolution models. I will briefly and subjectively overview the 40-years history of research in this area, including the most interesting results in different spectral domains. The accent will be done on my collaborators and my results, obtained during the last decade. In particular, I will emphasize the properties of a small subgroup of the most metal-poor galaxies
(Zo/50 < Z < Zo/30) and the relation of very metal-poor galaxies to the large scale structures in the Universe.

Speaker: Dr K Sheth

Abstract: The redshift evolution of galaxy morphology provides crucial information on the formation and evolution of galaxies. Using the 2-sq degree COSMOS survey, we have studied the evolution of bars, bulges and disks from the present day to z~1. Over the last 7 Gyr of lookback time, we have measured in detail the rapidly declining bar fraction in L* spiral galaxies; it declines from its local value 65% to < 25% at z~0.85. This bar fraction, however, is strongly dependent on the host galaxy properties. At z~0.85, the most massive (> 10¹¹ Msun), red and bulge dominated systems already had a high bar fraction ( > 50%). With the COSMOS data we are able to quantify the precise rate at which galaxies "matured", became sufficiently massive and cold to host bars and arrived on the Hubble sequence. The results are robust against a host of selection and completeness effects which typically plague studies of high redshift galaxy morphology. Other studies of galaxy morphology with COSMOS have been aimed at understanding the evolution of the morphology density relationship. We confirm that while the relationship is present to z~1, there may be a critical mass above which the environment is less important in shaping a galaxy. I will also review several other results from a host of galaxy morphology studies with COSMOS & DEEP2.

References for students: Sheth, et al. 2008, ApJ, 675, 1141 and references therein,

See also:  Menéndez-Delmestre, Sheth, Schinnerer, Jarrett, Scoville, 2007, ApJ, 657, 790
Sheth, Regan, Scoville, Strubbe, 2003, ApJL, 592, 13

Speaker: Alan Penny

Abstract: This is not a research colloquium, but an undergraduate-level review of how we measure the distances to astronomical objects.

Brush up your hazy knowledge of matters including what Archimedes did, how Henderson let down the Royal Observatory Cape by failing to reduce his measures, how the Planck satellite will determine the Hubble Constant, and what the distance of "the edge of the Universe' (Hubble sphere, event horizon, particle horizon?) means.

Of interest to graduate students and, I dare say, more advanced people.

Speaker: Alan Penny

Abstract: Polaris is a four-day Cepheid which in 1900 had an amplitude of 0.10 mag. By 1995 this had fallen to 0.02 mag. Starting in 2003 the SMEI space camera was monitoring Polaris (along with all other bright stars), and Polaris was also being monitored in radial velocity by a ground-based telescope. We expected it to switch off.

However, it turns out that the amplitude is now increasing and has now reached 0.04 mag. It seems that Polaris may be a double mode Cepheid with a beat period of some 200 or so years. Monitoring is continuing, and our team is now using Kepler to look at other double mode Cepheids.

Speaker: Prof David Williams

Abstract: I shall try to discuss three examples of how molecular astrophysics can help us to understand galaxies and their evolution. These are (1) the CO to H2 conversion factor; (2) the identification of molecular probes of the physical conditions in galaxies; and (3) a discussion of how molecular astrophysics controls the IMF and allows a prediction of conditions in (and tracers of) galaxies with top-heavy IMFs.

Speaker: Helene Sol

Abstract: During the last few years, current ground-based Cherenkov telescopes proved their capability to analyse in detail very high energy (VHE) cosmic sources and revealed the richness of our universe in the TeV gamma-ray range. About hundred sources of several types are now expected at such high energies, with several tens of supernovae remants, pulsar nebulae, binary systems in our Galaxy, and a sample of active galactic nuclei (and the recently discovered starburst galaxies) in the extragalactic space. The atmospheric Cherenkov detectors provide reliable VHE spectra, monitor variable sources down to the minute scale, map the extended ones, and even obtain bi-dimensional spectroscopy. The next generation of detectors, with the projects CTA and AGIS, should widely contribute to advances in astroparticle physics, astrophysics and cosmology.

Speaker: Mikako Matsuura

Abstract: One of the key inputs to understand galactic chemical evolution is the gas and dust ejected from dying stars. However, it has been difficult to measure the actual gas and dust production from asymptotic giant branch (AGB) stars and supernovae (SNe) on a galaxy scale. Recent Spitzer Space Telescope observations have provided a unique opportunity to study almost the whole population of AGB stars in the Large Magellanic Cloud. We have analysed these data set to measure gas and dust ejected from AGB stars into the interstellar medium (ISM) of the LMC. We found that AGB stars can be important gas and dust sources in the LMC.

We further detected amorphous dust grains in AGB stars in nearby dwarf spheroidal galaxies, which have very low metallicity. This shows that AGB stars can make dust grains even at very low metallicities, because carbon atoms are synthesised in these stars. We argue that AGB stars could have contributed to the dust formation in high-z galaxies as young as 0.2 Giga years old.

Speaker: Chris Clarkson

Abstract: I consider some of the issues we face in trying to understand and reconstruct dark energy.  Huge fluctuations in the unknown dark energy equation of state can be hidden in distance data, so I argue that model-independent tests which signal if the cosmological constant is wrong are valuable. These can be constructed to remove degeneracies with the cosmological parameters. Gravitational effects can play an important role. Even small inhomogeneity clouds our ability to say something definite about dark energy. I discuss how the averaging problem affects our potential understanding of dark energy by considering the backreaction from density perturbations to second-order in the concordance model: this effect leads to at least a 10\% increase in the deceleration parameter, and could be significantly higher. Large Hubble-scale inhomogeneity has not been investigated in detail, and could conceivably be the cause of apparent cosmic acceleration. I consider void models which defy the Copernican principle, and describe how we can potentially rule out these models.

Speaker: Andreas Faltenbacher

Abstract: The ongoing Arecibo Legacy Fast ALFA (ALFALFA) survey will probe the local HI universe with high accuracy. I discuss a comparison of the HI galaxy mass function derived  from the early ALFALFA data release with theoretical predictions based on constrained cold and warm dark matter simulations.

Speaker: Luis Balona

Abstract: I will summarize a few recent developments in stellar pulsation as presented in a recent conference "Challenges for Theory and Observation".  Results from large-scale surveys and the MOST and CoRoT space missions have opened fresh perspectives on the subject.  The topics discussed covered all fields of stellar pulsation, but in the limited time available I will concentrate on a few of the most interesting developments. 

Speaker: Govind Swarup 

Abstract: During the last few decades many great discoveries have been made by radio astronomers, such as radio galaxies, quasars, pulsars, cosmic microwave background radiation that have revolutionized our understanding of the Universe. After a brief introduction to radio astronomy, I plan to describe the Giant Metrewave Radio Telescope  in India that is being used to explore many key questions today by hundreds of astronomers from India and 22 countries.

The GMRT consists of 30 fully steerable parabolic dishes of 45m diameter each placed in an array of about 25 km in extent. It operates in 5 frequency bands from ~ 130 MHz to 1430 MHz. It is the largest radio telescope in the world operating in the above frequency range. After a brief introduction to the GMRT, I will describe some recent results concerning pulsars, nearby galaxies, radio galaxies, HI observations of a variety of objects, GMRT observations of the Extreme Cold Spot of the Comic Microwave Background and search for Ultra High Energy Neutrinos. Finally, I will describe briefly plans for GMRT's major upgrade.  

Speaker: Theodoros Nakos 

Abstract: The James Webb Space Telescope is an infrared telescope due to launch in 2014. It is a collaborative project between NASA, the European and Canadian Space Agencies. JWST, HST's successor, will be the largest telescope ever launched into space. This talk aims at giving a general description of the project (spacecraft, instrument characteristics, project planning) and a summary of its scientific objectives, with more emphasis on the area of Active Galactic Nuclei.  

Speaker: Jean-Philippe Uzan, Institut d'Astrophysique de Paris, CNRS

Abstract: Recent observations of quasar absorption spectra have restarted a debate initiated by Paul Dirac in 1937 on the constancy of the fundamental constants, and in particular of the fine structure constant. In this talk, I will explain the role that the constants are playing in the theories of physics and show that such tests of their constancy are tests of the Einstein equivalence principle. I will then concentrate on the fine structure constant and describe the various methods used to test its constancy. In particular the recent quasar results will be discussed. To finish, I will discuss theoretical theories that can account for dynamical constants.  

Speaker: Shazrene Mohamed, Oxford University, UK 

Abstract: Symbiotic binaries consist of a compact star, typically a white dwarf, accreting from the dense stellar wind of an evolved giant companion. As it is often possible to resolve and study individual components, these interacting binaries are ideal candidates for testing mass-transfer theories. I will present 3D hydrodynamical simulations of a new mass-transfer mode - wind Roche-lobe overflow (RLOF) - that can occur when the wind acceleration region of the evolved star occurs at several stellar radii (as, e.g., in Mira variables). If this region is relatively close to the Roche-lobe, wind material fills the giant's Roche-lobe and is transferred to the hot component through the inner Lagrangian point (similar to standard RLOF). The resulting accretion rate can be 100 times larger than the rate expected from standard Bondi-Hoyle accretion, and the mass loss from the system tends to be strongly concentrated towards the binary orbital plane. I will discuss the implications of this study for the shaping of planetary nebulae, the origin of barium stars and for symbiotic binaries as potential Type Ia supernova progenitors.  

Speaker: Dr. R. Johnston, UWC

Abstract: Estimation of the luminosity function (LF) of extragalactic objects presents a considerable challenge due to the impact of selection effects caused by detection thresholds in apparent magnitude, colour and surface brightness, coupled with systematics and/or evolutionary effects. In order to overcome these effects numerous parametric and non-parametric statistical methods have been devised, including the Schmidt (1968) 1/Vmax estimator, the Lynden-Bell (1971) C-method and various Maximum Likelihood Estimators (e.g. Sandage et al. 1979), where a parametric form of the LF is assumed.  However, in all of these methods the survey catalogue is assumed to be 'complete' and the LF assumed to be independent of the spatial distribution.

I will talk about  robust statistical tools that we have been developing that explore apparent magnitude completeness limits of current galaxy redshift surveys and therefore for the first time allow us to test the validity of the assumption that the LF and spatial distribution are independent.  Our test statistics, therefore, probe the above contributing factors which render a galaxy survey incomplete, or otherwise influence the statistical properties of those galaxies which are observable.  

Speaker: Dr. I Loubser

Abstract: I will present the results of an investigation of a large sample of brightest cluster galaxies (BCGs), their kinematic and stellar population properties and the relationships between these and the properties of the host clusters. We have obtained high signal-to-noise, long-slit spectra of 49 BCGs in the nearby Universe with the Gemini and WHT telescopes. From this, we have measured the radial velocity and velocity dispersion profiles, and used the Lick/IDS system of absorption indices to derive Single Stellar Population (SSP)-equivalent ages, metallicities and alpha-abundance ratios. The results were systematically compared with those of large samples of ordinary elliptical galaxies in the same mass range. In addition, the derived properties were tested for possible correlations with the internal properties of the galaxies (mass, rotation and luminosity) and the properties of the host clusters (density, mass, distance to X-ray peak and the presence of cooling flows). I will address the following questions: how the kinematic and stellar population properties differ from those of ordinary giant elliptical galaxies; and whether these properties are more influenced by the internal parameters of the BCGs or the properties of the host cluster.  

Speaker: Dr. Benne Holwerda, UCT

Abstract: The upcoming new perspective of the high redshift Universe in the 21 cm line of atomic hydrogen opens possibilities to explore topics of spiral disk evolution, hitherto reserved for other wavelengths.

Morphology of disks is quantified over Cosmic time using star-formation dominated wavelengths. In studies of deep Hubble Space Telescope fields, the rest-frame optical or UV morphology of high-redshift objects have been characterised using a few quantities: concentration (C), asymmetry (A), smoothness (S), second-order-moment (M20), the GINI coefficient (G), and Ellipticity (E).

I present these parameter for the The HI Nearby Galaxy Survey (THINGS) and the Westerborg HI Spiral Project (WHISP). We used the multi-wavelength data to compare the morphology of star-formation to that of HI. I will discuss the suitability of HI morphology to detect interaction and mergers. The future goal is to determine a merger rate in the local Universe with MeerKAT and later a merger history with SKA.

 

Speaker: Dr. Antoine Bouchard, UCT

Abstract: I will present ULySS (Université de Lyon Spectroscopic analysis Software), a new Full-Spectrum Fitting software tool and explore one of its uses, i.e. measuring star formation history from integrated spectra. Contrary to other commonly used methods (e.g. Lick indices), ULySS uses all available information by fitting a linear combination of spectral templates onto an observed spectrum. This method is applied to NGC404, a nearly face-on nearby low-luminosity lenticular (dS0) galaxy. Probing its internal kinematics and the spatial distribution of the star formation history provides a wealth of information on possible evolution processes affecting dS0 galaxies. More precisely, NGC404 shows evidence of a double stellar radial velocity inversion (counter-rotating cores) along its major axis, along with 4 distinct stellar populations of radially varying relative importance. It seems that NGC404 used to be a spiral galaxy about 1 Gyr ago and that (two) merger events have triggered a morphological transition leading it to the currently observed dS0 morphology.  

Speaker: A Kniazev

Abstract: The nearest galaxies are an excellent laboratory for studies of stellar populations and evolution. Their stellar populations can be characterised using color-magnitude diagrams of resolved stars. However, the star formation; histories are model-dependent and should be compared with other, additional, observational data that can be obtained for these galaxies. In particular, individual HII regions, planetary nebulae (PNe) and different types of emission-line stars are available for spectroscopy in the Local Group (LG) galaxies with present-day large telescopes and can then be used as independent kinematics, metallicity and evolution tracers of different stellar opulations. I will present some latest results of our studies PNe and HII regions in some LG galaxies.

Speaker: M Hilton

Abstract: The XMM Cluster Survey (XCS) is a serendipitous galaxy cluster survey being conducted using publicly available X-ray data from the XMM-Newton Science Archive. I will present an update on the status of the survey, discuss the expected cosmological constraints, and describe recent results from studies of galaxy evolution in z > 1 clusters conducted under the umbrella of the XCS project. 

Speaker: Prof N Katz

Abstract: There are two ways that a galaxy can acquire gas to form stars: the accretion of smaller galaxies that contain gas or the smooth accretion of gas not in galaxies. I will use hydrodynamical simulations of a Lambda dominated CDM Universe to investigate these issues. Perhaps surprisingly, most material enters galaxies through smooth accretion and not through merging. It is commonly believed that gas is shock heated to the virial emperature as it enters a dark halo and that the rate that smooth gas accretes onto the galaxy is regulated by the cooling time from the virial temperature. I will show that there are actually two channels by which gas can smoothly accrete onto a galaxy: the standard one just mentioned and one where the gas remains cool and its accretion rate is dominated by dynamical processes. It is this second process that dominates overall, particularly at higher redshifts. I will discuss how different feedback processes should interact differently with these different accretion modes.

Speaker: Warrick Lawson

Abstract: A talk in two parts: the first reviewing recent Spitzer disk results and our understanding of the so-called 'transitional' disks seen around low mass PMS stars, the second on the use of optical spectrophotometry to aid in overcoming one of the most uncertain elements of PMS evolution, the age of PMS systems.

Speaker: Chris Koen

Abstract: I'll present  outlines of a few projects, both completed and in progress.
The former includes
(1) assessment of the correlation between GRB peak energy, and the undelying supernova peak brightness; and
(2) disentangling the effects of seeing and true variability in CCD photometry of blended star images.
To-be-completed work includes
(1) The estimation of mode lifetime for stochastically-excited pulsations (or quasi-periodicities) when only a few cycles of variation are observed;
(2) The Nyquist frequency for observations with slight irregularities in times between measurements;
(3) Testing for evolution in the Tully-Fisher relation.

Speaker: S Littlefair

Abstract: The eclipse shape of dwarf novae possesses sufficient information to derive the mass and radius of the donor star, given minimal assumptions about the system. This allows the donor star mass and radius to be derived, even if the donor is too faint to detect directly. Using this fact, we present system parameters for a small sample of short period, eclipsing CVs taken from the Sloan Digital Sky Survey. Three out of seven of the systems possess brown dwarf donor stars and have thus evolved past the orbital period minimum. The donor star masses and radii are inconsistent with model predictions, unless enhanced angular momentum loss is invoked. However, the mass transfer rates as deduced from white dwarf effective temperatures are not consistent with enhanced mass transfer rates.  We discuss possible solutions to this conundrum.

Speaker: Kevin Crause

Abstract: Rock art in South Africa is a national treasure that belongs to all, it is a wealth beyong measure and it is slowly but inexorably disappearing. Natural forces of denudation, fire, vandalism, ndiscriminate recreational activities and development are destroying this fragile heritage.  Given the near impossibility of protecting the many thousands of rock art sites, the art must at the very least, be accurately and systematically preserved in digital form for future generations.  Combining 23 years of skills in graphics and animation, 3D visualisation, virtual reality, image processing and multimedia authoring and with a passion for photography and the outdoors, Kevin has formulated a powerful toolset for capturing, processing, enhancing and displaying ultra-high resolution images of rock art and its context.  With these new techniques, it is possible to recover detail practically invisible to the naked eye and even to resolve superimposition, thus opening up exciting research opportunities and possibly challenging current interpretations.

Speaker: P Gillingham

Abstract: Peter Gillingham has worked in astronomical instrumentation since 1968, mostly with the Anglo-Australian Observatory but also for the first five years of Keck operation as its Operations Director. Since 1986, he has been promoting optical/infrared astronomy in Antarctica, especially to take advantage of the exceptional seeing which was hypothesised to occur there. Seeing tests in this decade from the Italian/French base at Dome C have suggested that such sites could give median seeing diameters about half those of Mauna Kea, i.e. about 0.25 arcsec.  A group at University of NSW has led in conducting winter-time site testing at Dome C and more recently at the highest point on the plateau, thanks to Chinese expeditions to Dome A.  UNSW and the AAO last year completed a feasibility study for a 2.5 m optical/infrared telescope for Dome C.  Funding for the follow-up detailed design has not yet been granted but an international telescope of about that size is bound to be built there soon.  For many types of observation, it should be fully competitive with an 8 m telescope on Mauna Kea.

Speaker: Prof. R Strom

Abstract: In 1944, the student H.C. van de Hulst predicted that the 21-cm line of atomic hydrogen might be detectable with a sensitive radio receiver. This marked the beginning of radio astronomy in the Netherlands. Using original source material from the Oort archive and the Foundation for Radio Astronomy, I will fill in some gaps in our knowledge regarding the line's prediction, how Oort organised the Dutch effort to detect the line, and what was required to get the necessary equipment up and running. Oort used his network of academic colleagues to bridge gaps in expertise which he and his fellow astronomers lacked. I will describe how these efforts were brought to a successful conclusion, and discuss some of the lessons which may be instructive to organizers of other large scientific projects.

Speaker: Dr. R Hickox

Abstract: The last decade in astrophysics has shown that the evolution of galaxies is linked remarkably strongly to the growth of their central supermassive black holes as active galactic nuclei (AGN). It is also clear that galaxy and black hole evolution is strongly affected by large-scale environments and the masses of their host dark matter halos. We have used data from the wide-field, 9 square degree Bootes multiwavelength survey to study the host galaxies, environments, and evolution of AGN. First, I will discuss an analysis of the three-dimensional clustering and host galaxies of AGN at z~0.5 selected in different bands (WSRT radio, Chandra X-ray, and Spitzer infrared), and discuss the results in terms of a simple model of black hole and galaxy evolution. Second, I will outline a technique that uses Spitzer IRAC data to detect dust-obscured quasars at z~1, and show that the spatial clustering of obscured quasars and galaxies on small scales may show evidence for fueling by major galaxy mergers.

Speaker: Dr D Russell

Abstract: Synchrotron emission from jets produced by X-ray binaries can be detected at optical and infrared (IR) frequencies in addition to the traditional radio. I show that optical/IR colour-magnitude diagrams of the outbursts of X-ray binaries can successfully separate thermal disc emission from non-thermal jet emission, in both black hole and neutron star sources. A heated single-temperature blackbody is able to reproduce the observed relations between colour and magnitude, except when excursions are made to a redder colour than expected, which is due to jet emission since it is correlated with radio and X-ray state. The general picture that is developed is then incorporated into the unified picture of disc-jet behaviour in black hole X-ray binaries. At a given position of a source in the X-ray hardness-intensity diagram, the radio, IR and optical properties can be inferred. Similarly, it is possible in some cases to predict the X-ray and radio luminosities and spectral states from optical/IR monitoring.

 

Speaker: R de Grijs

Abstract: I review the long-term survival chances of young massive star clusters (YMCs), hallmarks of intense starburst episodes often associated with violent galaxy interactions. I address the key question as to whether at least some of these YMCs can be considered proto-globular clusters (GCs), in which case these would be expected to evolve into counterparts of the ubiquitous old GCs believed to be among the oldest galactic building blocks. In the absence of significant external perturbations, the key factor determining a cluster's long-term survival chances is the shape of its stellar initial mass function (IMF). It is, however, not straightforward to assess the IMF shape in unresolved extragalactic YMCs. I discuss in detail the promise of using high-resolution spectroscopy to make progress towards this goal, as well as the numerous pitfalls associated with this approach. I also discuss the latest progress in worldwide efforts to better understand the evolution of entire cluster systems, the disruption processes they are affected by, and whether we can use recently gained insights to determine the nature of at least some of the YMCs observed in extragalactic starbursts as proto-GCs. I conclude that there is an increasing body of evidence that GC formation appears to be continuing until today; their long-term evolution, however, crucially depends on their environmental conditions.

Speaker: I. Baraffe

Abstract: I will present current uncertainties in the modelling of young low mass stars and brown dwarfs. I will discuss in particular the effects of accretion on their structure and evolution. Young brown dwarfs are predicted to oscillate during the deuterium burning phase, and I will describe this process and its observational signatures.

Speaker: M. Hajduk

Abstract: About 10% of nuclei of planetary nebulae are known to be close binaries. Six eclipsing systems have been discovered so far. In two more cases, eclipses by non-stellar bodies have been observed. Photometric variations in NGC 2346 and M 2-29 are best explained in terms of an eclipsing dusty cloud or occultation by dust. I will discuss photometric and spectroscopic observations of M 2-29.

Speaker: Dr. Gilles Chabrier

Abstract: I will review the basic foundation of modern star and planet formation theory and present recent results in connection with the existing or planed observational surveys devoted to this field.

Speaker: Zdenek Mikulasek

Abstract: Analyzing all available photometric and spectroscopic observations of the famous helium-strong magnetic chemically peculiar star V901 Ori (HD 37776) we find that its 1.5387 d rotational period has lengthened by a remarkable 17.7 sec over the past 31 years. The record- breaking period increase among all known main sequence stars is interpreted as a consequence of the momentum loss through events or processes in the extended stellar magnetosphere.

Speaker: Miloslav Zejda

Abstract: TW Draconis is one of the most well-known Algol-type eclipsing binaries. There is significant evidence for miscellaneous interacting physical processes in the system, which manifest themselves as e.g. period and light curve changes. Using 561 available minima timings accumulated over the past 150 years we compile an extended O-C diagram analysis. We applied weighting nonlinear robust regression with iteratively determined weights of individual types of minima. The timing residuals (according to the linear ephemeris) display two stages of differing behaviour in 1858-2007. The first part is characterised by more or less smooth linear/parabolic course of timing residuals. Since 1942, the system has been showing alternating and shortening period changes with the length of a cycle of about two decades, modulated by short-term periodic variations. The latter small variations with the period 6.5 years are caused by the light-time effect due to the presence of a third low-mass body in the system. Major oscillations can be explained as consequences of quadrupole moment variation in the system.

Speaker: Marek Chrastina

Abstract: During the last outburst of symbiotic prototype Z and spectral features of collimated bipolar jets were detected as never before. Also rapid photometric variations appeared. Observed photometric and spectroscopic features and their evolution during the last outburst can be interpreted as transient jets from a warping and tilting accretion disk. Masaryk University Observatory will be briefly introduced, as well.

Speaker: Ido Finkelman, Tel Aviv University

Abstract: Recent surveys indicate that many early-type galaxies show dark lanes or dark patches, presumably produced by dust extinction in a large fraction of such galaxies. This light extinction by the dust grains is wavelength-dependent and is commonly known as the "extinction law". The smoothly-varying underlying light distribution of early-type
galaxies provides a method to determine the dust extinction law. In
most cases, the derived extinction curves is similar to the Galactic
extinction law, indicating that the dust grains in such galaxies may
not differ significantly from those in the Galaxy.

In my lecture I will present the method of determining the
extragalactic extinction law in early-type galaxies and the first
results of an ongoing study of dust lane early-type galaxies with SALT
and other telescopes. I will also discuss the dust grain properties in
view of their striking similarity with Galactic dust, and will briefly
address the question of the dust origin.

 

Speaker: Enrico Olivier, SAAO/UWC

Abstract: It has been proposed that Luminous Red Galaxies can be used as "cosmic chronometers" for cosmological studies. One possible implementation of this is the South-African-proposed SCALPEL project to measure the Hubble parameter at z~0.5. In this talk, I will briefly review the SCALPEL project and its underlying assumptions. I will then present ongoing work to explore these assumptions using physically realistic starformation histories from the Millennium Simulation.

Speaker: Mariusz Gromadzki, Nicolaus Copernicus Astron Centre

Abstract: R Aqr is one of the closest symbiotic binaries and the only D-type system with radial velocity data suitable for orbital parameters estimation.  We have used available radial velocity data to derive a reliable spectroscopic orbit of the Mira component, and to establish connections between the orbital motion and other phenomena shown by R Aqr.

Speaker: Dr Alan Penny, St Andrews

Abstract: A SETI (Search for Extraterrestrial Intelligence) project is
in the design phase for the European LOFAR telescope. This
will be the first modern search for artificial radiation in
the 30-240 MHz range.

While there disadvantages for SETI in this frequency range,
such as the galactic background and radio interference, the
opening up of a new frequency range is always exciting.

The rationale and status of this SETI project and its planned
performance together with the results from a project workshop
this June at Dwingeloo will be discussed.

Speaker: John Menzies, SAAO

Abstract: I will present a summary of a long-term programme with the IRSF that was conducted by Michael Feast, Patricia Whitelock and myself together with several Japanese colleagues. The aim was to search for long period variables and to characterise the AGB sequences in all the Local Group galaxies accessible from Sutherland. The galaxies Leo I, Phoenix and Fornax (in each of which Mira variables have been found) will be considered in detail, while preliminary results will be presented for some others.

Speaker: Dr Benne Holwerda, UCT

Abstract: The distribution of dust in spiral disks affects ever measurement of the spiral's properties (e.g., estimates of star-formation and history, and distance scales). Dust extinction as a function of galactic radius, arm or interarm region, and Hubble type are useful both to correct measurements of disks and to trace the cold, dusty ISM. The distribution of dust extinction in spirals could very well evolve over the lifetime of spiral disks.

The current project is to probe the distribution and variance of disk opacity out to a redshift of 1 using the same types of objects: spiral galaxies overlapping a more distant galaxy, preferably elliptical. In those cases, one can measure the extinction in the spiral in the overlap region. The dominant assumption is symmetry of both galaxies.

In order to accurately determine the opacity of spiral disks as a function of radius, redshift and Hubble type, a large sample of occulting pairs is needed. Until recently, only few were known and these had already been extensively studied. We obtained a first larger sample from the SDSS spectra, selecting elliptical galaxy spectra with lower-redshift emission lines. This netted 86 bona-fide pairs to a redshift of z = 0.2.  The radial dependence of the disk opacity can be directly compared to that of local galaxies.

Recently, the team found a pair serendipitously imaged with the Hubble Space Telescope.  The data-quality and favorable geometry of this pair has led us to use it as a test case for the analysis of occulting pairs, resulting in an extinction map and the effective extinction law through a spiral disk.  Now that we know of many more pairs, I will briefly discuss future work using occulting pairs and what we hope to learn from these.

Speaker: Erwin de Blok

Abstract: I will give an overview of The HI Nearby Galaxy Survey (THINGS), a high spectral (<= 5.2 km/s) and spatial (6") resolution survey of HI emission in 34 nearby galaxies obtained using the NRAO Very Large Array (VLA). The overarching scientific goal of THINGS is to investigate at sub-kpc resolution fundamental characteristics of the interstellar medium (ISM) related to galaxy morphology, star formation and mass distribution across the Hubble sequence. Unique characteristics of the THINGS database are the homogeneous sensitivity as well as spatial and velocity resolution of the HI data which is at the limit of what can be achieved with the VLA for a significant number of galaxies. THINGS has been combined with similar large-scale surveys in the UV (GALEX) and the IR (Spitzer), and I use the combined data to address issues such as the small-scale structure of the ISM, the (dark) matter distribution in THINGS galaxies, and the processes leading to star formation.

Speaker: Sudhanshu Barway

Abstract: The Virtual Observatory (VO) is a concept (or type of a scientific organisation) for the era of exponential growth of astronomical data, driven by the progress in information technology. Digital sky surveys and large ground- and space-based telescopes are generating many terabytes (and soon petabytes) of information, of an ever increasing complexity. This data richness is enabling us to ask new kinds of questions about the universe, but it also poses significant challenges. The Virtual Observatory (VO) is a response to these challenges and opportunities; it is a general, distributed, web-based research environment for astronomy with massive and complex data sets and numerical simulations. In my talk, I will present an overview on virtual observatory and describe some of the software tools and astronomy web-services that are being developed to use large astronomical archives. I will also describe few applications developed by the Virtual Observatory-India project.

Speaker: Amanda Gulbis

Abstract: At the edge of our observable Solar System there exists a large population of small, icy bodies known as the Kuiper Belt. The first Kuiper Belt object (KBO) was discovered in 1992, making this region one of the newest frontiers in planetary science. Since that time, more than 1300 KBOs have sufficiently observed orbits to be designated by the Minor Planet Center. In this talk I present some of the findings of the Deep Ecliptic Survey, which has discovered nearly 500 designated KBOs.  A strength of this survey is that it provides a consistent database for removal of observational biases and study of KBO orbital parameters.  Here, I focus on the observed inclination distributions of different classes of KBOs. Such investigations are the key to understanding the evolution of the outer Solar System.

 

Speaker: David Buckley, SALT

Abstract: ALT is now nearing its three years since inauguration and is still not in full science operations mode. Why? How? When? I will discuss the various issues that we have been facing in getting SALT and its instruments properly completed and commissioned and attempt to show that there is some reason for optimism.

Speaker: Yabebal Fantaye

Abstract: We present measurements of the angular two and three point correlation functions for the largest photometric galaxy catalogue currently available (MegaZ) consisting of several hundred thousand luminous red galaxies at redshifts of 0.4 to 0.7. This allows us to place constraints on primordial non-Gaussianity and galaxy bias. We will also present Fisher4cast, a new public toolbox and GUI for computing Fisher matrices in cosmology that is useful both in education and research (available from http://www.cosmology.org.za/).

Speaker: Kate Su

Abstract: Debris disks form when asteroidal-scale bodies collide or star-grazing comets evaporate,  generating fine dust through collisional cascades. Therefore, debris disks are the most visible signposts of other planetary systems. Due to its large emitting surface area, the dusty disk, mostly identified through infrared excesses around stars, is the most easily observable component of other planetary systems. The record of events in the planetary forming zones traced by the study of debris disks around stars at various evolutionary stages offers a great opportunity to study planet formation in real time and to observe processes that may have operated in our solar system. I will present recent results from Spitzer observations of debris disks around main-sequence stars and white dwarfs with the ultimate goal of connecting them with theories for the evolution of our solar system.

Speaker: Ian Glass

Abstract: South Africa can claim a unique astronomical distinction: the first ever measurement of the distance to a star. In 1833 Alpha Centauri was the first star to have had its distance measured and it stayed the nearest star known until 82 years later when a closer one was found. The new champion, another South African discovery, was Proxima Centauri. To this day it remains the record holder and Alpha the runner-up.  This lecture tells the story of the discoveries and the curious characters involved in making them, starting with the first suggestion that the distance to a star might be measurable and continuing right up to the present-day investigations of Alpha and Proxima.

Speaker: Oozeer Nadeem

Abstract: We present the results of a study of a sub-sample of radio sources using the Giant Meter wave Radio Telescope (GMRT). The sample consists of 117 radio sources which is a sub set taken from a complete set of sources selected from the Molonglo Radio Catalogue (MRC) at 408 MHz. This is part of the multi frequency observations carried out using the MRT at 1280, 610 and 244 MHz respectively, to obtain spectra, detailed maps and also to complete the MRC-1Jy sample. The observations were focused on 3 short observations of about 5 min snapshots each. We carried out a morphological classification of the sources as well as positional statistics by comparing with the NVSS.

By overlaying the GMRT 618 MHz radio images on digital optical plates as obtained from the SuperCOSMOS, new optical positions for 40 corresponding radio sources are given. We also checked for the infra red (IR) counterparts using the 2MASS and the DENIS surveys. A sub-sample of 49 Optically/ IR identified sources from the MRC/1Jy-B sample is chosen and preliminary results such as: effective distance, overall linear size, volume of individual components of the sources, radio power, radio luminosity and finally the estimated minimum total energy are presented. The redshift of some of our sources was estimated using the k-z relationship.

Two of the radio sources observed have also been observed by the Chandra X-ray Telescope. Using the X-ray data available from the public domain, we show the X-ray analysis; spectra, images at different energies and fitted physical parameters to the spectra at different radii from the core centre.

We finally show some interesting sources which have been observed for the first time at 1280 MHz with suficient resolution to produce images which provide details of their structure. These are potential candidates to follow up for more detailed analysis. New Giant Radio Galaxies (GRGs) have also been detected in our sample together with some new sources in cluster environment.

Speaker: Philip Lah

Abstract: It is known that the rate at which stars are produced in galaxies has dropped by a factor of ten in the last 9 billion years (from z ~ 1.0). However, the gas content of galaxies - the fuel supply for star-formation - is only poorly constrained by observations during this period of time.

Quantifying the atomic neutral hydrogen gas (HI) content of galaxies using 21 cm emission from distant galaxies (z > 0.1) is difficult with current radio telescopes.  However, the average HI content of galaxies at moderate redshifts can be measured by coadding the HI signal from multiple galaxies with known optical positions and redshifts.  Our group has been pioneering this technique using the Giant Metrewave Radio Telescope (GMRT) and the Anglo-Australian Telescope (AAT).

I will present our current results for the average neutral hydrogen gas content in star forming field galaxies at a redshift 0.24 (look-back time of 2.8 Gyr) and the gas content of galaxies surrounding the galaxy cluster Abell 370 at a redshift of 0.37 (look-back time of 4.0 Gyr).  I will also discuss the use of the HI coadding technique with the SKA pathfinders of MeerKAT and ASKAP and show that they can be used to quantify the average HI content of galaxies out to redshifts of 1.0.

Speaker: Tom Jarrett

Abstract: Our view of the local universe has come into sharp focus with the dual combination of large area photometric surveys and target-dedicated redshift surveys.  We find the local universe is graced with colossal filaments and voids that harken back to the origin of matter and structure.  And yet even after decades of committed effort, our view of the local universe remains incomplete due to the presence of our own Galaxy blocking ~30% of the sky.  Among several superclusters of galaxies that extend into the Zone of Avoidance, one of the most important dynamical structures, the Great Attractor, lies largely hidden by the Milky Way; and thus our understanding of the mass density field of the local universe remains outstanding as we grapple for clarity through the Galactic haze of stars, gas and dust. In this talk I will review the current state of our understanding of the distribution of galaxies, presenting all-sky 3-D views of galaxies, clusters and large scale structures.  And in this context, present a new multi-wavelength project to pierce the most heavily obscured region of the Great Attractor, the "heart" of the Norma Wall of galaxies that stretches across the plane of the Milky Way from Norma in the south to Centaurus in the north. I will also discuss future long-wavelength surveys that are particularly adept at unveiling what lurks behind the Milky Way, including the Wide Field Infrared Survey Explorer (WISE), an all-sky mapping space telescope that will launch in 2009.

Speaker: Michael Feast

Abstract: This will be a review of the Type II Cepheids which are evolved, low-mass pulsating variables.  They are found both in the field and globular clusters. The composition of their atmopheres, which shows evidence of contamination by nuclear processed material from the interior as well gas-dust separation, is not properly understood. The short period variables in the field throw some light on the "third-parameter" problem in globular clusters. An infrared period-luminosity relation has recently been calibrated using Dave Laney's pulsation parallaxes and leads to new distances to the LMC and the Galactic Centre. Present uncertainties will be outlined and current work on these stars and their shorter period cousins, the RR Lyrae variables, will be outlined.

Speaker: Kailash Sahu

Abstract: The exoplanets discovered so far have been mostly around relatively nearby and bright stars. As a result, the host stars are mostly (i) in the Galactic disk, (ii) relatively massive, and (iii) relatively metal rich. After a review of the current status of exoplanets, I will describe the SWEEPS project which was aimed at extending our knowledge to stars which (i) are in a different part of the Galaxy, (ii) have low masses, and (iii) have a large range of metallicities.  We used the Hubble Space Telescope to monitor 180,000 F, G, K, and M dwarfs in the Galactic bulge continuously for 7 days in order to look for transiting planets. We discovered 16 candidate transiting extrasolar planets with periods of 0.6 to 4.2 days, including a new class of ultra-short period planets (USPPs) with P <1 day. Radial velocity observations of two brightest candidates support the planetary nature. These results suggest that planets are equally abundant in the Galactic bulge and around low-mass stars, and the metallicity distribution holds even for the stars in the Galactic bulge. The microlensing results suggest that terrestrial planets may be more common than the Jovian planets.

Speaker: Thebe Medupe

Abstract: I have developed a computer code to solve radial pulsation equations in the atmospheres of A stars. The code uses radiative transfer equation to model the effects of radiation on the oscillations. In this talk I show some of the results of this code when applied to the atmospheres of stars in the temperature range 6500 up to 9500 kelvins. For example, I find that the opacity flactuations play a very important role in relationship between fluctuations in effective temperature and surface flux. I will also discuss the new boundary condition that we derived for radial modes in the upper part of the atmosphere.

 

Speakers: Thomas Widemann and Francois Colas

Abstract: Last month Triton's atmosphere has been successfully observed from stations in Namibia and La Reunion Island on May 21, 2008, while in South Africa the shadow missed stations or was clouded out (SAAO/Sutherland 1.0, 1.9 and SALT/Salticam, Springbok,SAAO/Cape Town)  Preliminary analysis shows that the event lasted ~3mn 30s, from~01h 39m10s to ~01h 42m 40s  at Namibia/ Hakos. The event at La Reunion (located ~265 km north of Hakos, in the sky plane) recorded a ~5mn 10s event, from ~01h  48m 30s to ~01h 53m 40s. Beside ephemeris corrections and updates, one of the main scientific issues is now to see whether Triton's atmosphere has experienced drastic changes since 1997, knowing that the satellite reached an "extreme" southern summer solstice in 2000. Then, the sub-solar latitude reached ~50 deg S. This happens every 600 years or so, and may have significantly heated up the Nitrogen ice cap, triggering enhanced geyser activity in the south polar regions of Triton.  The Pluto/Charon event of 22/23 June will be observed from Austral Africa, La Reunion and Australia. We will comment on our observing strategy, as well as science objectives, instrumental and timing methodology.

Speaker: Lisa Crause

Abstract: My second of three contiguous 2007/2008 winters was spent at the University of Wisconsin - Madison, playing with optical equipment in Matt Bershady's fibre(fiber?!) lab. Various fibre types were tested to evaluate their throughput and focal ratio degradation properties to assess suitability for use in SALT's High Resolution Spectrograph and other fibre-fed instruments. This talk describes our experiment – including the test bench set-up, data collection, analysis, conclusions and plans for future work.