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Astronomical colloquia.

These form an important part of a research facility, often as a sort of prepublication discussion or a discussion of an individual's current research, and as such it is virtually impossible to "publish" this material. However by recording the topics discussed in the form below does indicate to those, who are unable to attend, what current trends are and who has visited to do research: it keeps everyone 'in the loop' so to speak

Also included in this section are the colloquia/seminars at the SAAO, NASSP, UWC and the Astrophysics, Cosmology and Gravity Centre at UCT, ACGC. Also included are the SAAO Astro-coffees which are 15-20min informal discussions on just about any topic including but not limited to: recent astro-ph papers, seminal/classic publications, education/outreach ideas and initiatives, preliminary results, student progress reports, conference/workshop feedback and skills-transfer.



Title: H2 Line-Cooling as a Beacon of Active Transformation within Compact Groups.

Speaker: Michelle Cluver (AAO)

Date: 25 October 2012

Time: 11:00

Venue: SAAO Auditorium

Abstract: Stephan's Quintet (SQ) is a Hickson Compact Group (HCG) experiencing a group-wide shock due to the high velocity collision of an intruder galaxy with the intragroup medium. We find in SQ abundant excited molecular hydrogen, efficiently dominating the cooling of this system. But is SQ unusual or just at the extreme end of HCG behaviour? HCGs are strongly interacting and show a distinctive gap in mid-infrared colour-colour space, suggesting rapid evolution from late types with copious star formation, to early-type systems dominated by S0's) with little star forming activity. I will present results from a Spitzer spectroscopy study of a sample of 23 HCGs where we observe enhanced H2 emission in galaxies lying at intermediate mid-IR colour (and specific star formation) with "green valley" optical colours. We propose that interactions with previously stripped material may be accelerating the transition from actively star forming to passively evolving systems dominated by an old stellar population.

Title: HST Observations of Globular Clusters and Metal-Poor Stars

Speaker: Prof BC Chaboyer (Dartmouth, Scientific Editor--The Astrophysical Journal)

Venue: SAAO Auditorium

Date: 12 November 2012

Time: 12:00

Abstract: Results from two large HST programs on globular clusters and metal-poor stars will be discussed. The ACS Survey of Galactic Globular Clusters obtained deep, uniform photometry of the central 3 arcminutes of 65 galactic globular clusters. I will highlight some important results from this survey, including the discovery of multiple stellar populations in some globular clusters, constraints on the three-dimensional orientation of the Sagittarius dwarf galaxy and the relative ages of the 65 clusters. Initial results from an on-going HST program which uses the fine guidance sensors to obtain accurate parallaxes of metal-poor ([Fe/H] < -1.5) main sequence field stars will also be presented. These stars are used to test stellar evolution models and as standard candles to determine distances to metal-poor globular clusters.

Title: Modelling the Variability of Luminous Red Giant Stars

Speaker: Peter Wood

Venue: 1896 Building

Date: 7 November 2012

Time: 11:00

Abstract: The luminous red giant stars on the AGB and ip of the RGB vary with amplitudes that can be detected with ground-based telescope. Long-term photometric monitoring by microlensing experiments such as MACHO and OGLE has provided data which shows that the luminous red giants fall on approximately twelve period-luminosity (PL) sequences of different origin. Nine of these sequences are almost certainly of pulsation origin. I will discuss the nature of these sequences and the latest attempts to model them. One of the PL sequences consists of close binary systems containing a red giant. I will show how modelling this population can give a reliable estimate of the formation rate of planetary nebulae, binary and single. The other two sequences consist of red giants with long secondary periods. I wish I could model them, but I haven't a clue where to start!

Title: Studying the Blue Sky at Night--SAAO's Potential Contribution to Solar Energy Research

Speaker: Hartmut Winkler

Venue: 1896 Building

Date: 8 November 2012

Time: 11:00

Abstract: Astronomical data from Sutherland constitutes possibly the best calibrated set of measurements of the interplay between extra-terrestrial light and the Earth's atmosphere over southern Africa. Thousands of readings of standard star brightness and adjacent background sky illuminance have been collected over the decades, enabling one, in theory at least, to develop a detailed sky brightness profile as a function of wavelength, zenith angle, lunar phase and position, and atmospheric conditions. The presenter will describe preliminary results of a multi-filter photometric 20-inch observing run that aimed to systematically measure the brightness profile of the sky dome in the presence of the Moon. This profile is analysed in terms of light scattering theory, and its applicability to the estimation of the daytime sky dome profile is assessed. The talk concludes by exploring the significance of the data, as well as SAAO archival data, for photovoltaic solar energy installations, which will scheduled to be erected on a massive scale in the Northern Cape over the years to come.

Title: Proposing an "i-band Wide-field Camera" for the SAAO 0.75-m Telescope

Speaker: Shuji Sato (Nagoya University)

Venue: SAAO Auditorium

Date: 22 November 2012

Time: 11:00

Abstract: We are planning a polarization survey project by developing a dedicated i-band (680~830nm) camera which covers ~1/2 degree square at one-shot and ~several degrees in one-night. We have finished the optical design for the camera (CCD pixel scale 15?m x4k format) on the SAAO 75cm telescope, so we will present two layouts of the cameras and telescope, lens system, and spot diagrammes; plan "A" and "B". Plan "A" is to convert F15 to F5.5 with five lenses at around the Cassegrain focus, while Plan "B" to convert F3.5 to F5.5 with four lenses at around the primary focus. "A" shows the spot diagram of 8.2?m (~0.4") at the worst RMS over the field of view, while "B" achieves 5.6?m(~0.3") with distortions less than +-0.6% (<10"). This camera can be used for the r'-(620nm) and possibly for the g'-(480nm), as well as for the i'-band. From the viewpoint of the optical design and fabrication, "B" is more simple, feasible and economical, being preferable to "A". However, "B" may interfere with the existing secondary mirror. We estimate the limiting magnitudes to be ~17 mag in i'-bands with [SN~10] for 60 s integration for photometry with this camera on the telescope/F5.5. Last year, we obtained the limiting magnitudes g'~17.2, r'~17.1 and i'~16.5 mag for 60 s by using TRIPOL-1 on the SAAO 75cm/F15. For polarimetry, we expect the limiting to be ~15 mag with ?p < 0.3% for 60 s. We plan the schedule; 1) optical design will be fixed by the end of 2012, and 2) camera will be developed by the middle of 2013, then 3) we will install and test survey in the late of 2013. 4) Survey of dark clouds will be executed in 2014 and we will delineate magnetic field configurations in the peripheries of dark clouds.


Title: Late-type distance indicators

Speaker: Mr Marek Gorski, University of Warsaw

Venue: RW James Building Lecture Theatre C.

Date: 9 November 2012

Time: 13:00

Abstract: Why Local Group Galaxies are so important in terms of the Hubble constant, and how can we improve the cosmic distance scale? I will present some goals and results achieved by the project Araucaria--the main objective of which is to analyse and improve the cosmic distance scale indicators.


Title: Clusters of Galaxies: crossroads of Astro and Particle Physics

Speaker: Prof Sergio Colafrancesco (SKA SARChI Chair)

Venue: RW James Lecture Theatre C

Date: 22 November 2012

Time: 12h30

Abstract: Galaxy clusters are the largest laboratories for Astro and Particle physics in the universe: they contain baryons (in diffuse gas and condensed, e.g. galaxy, forms), high-E and relativistic plasmas, cosmic rays, magnetic fields, Black Holes, Dark Matter. The study of their formation and evolution requires complementary information and synergies from both Astrophysics and Particle physics, and an approach that combines multi-disciplinary physics and multi-frequency observations. This is a challenging but scientifically rewarding task that will be able to return a vast amount of information on: the nature of Dark Matter, the origin of cosmic rays, the evolution of magnetic fields, the feedback of BHs and their jets. We discuss how this challenge can be tackled by using either a multi-experiment approach (i.e. combining observations obtainable from radio to gamma-ray observatories) or a single (multi-purpose) experimental technique.

Title: Testing galaxy formation with gravitational lensing

Speaker: Dr John McKean (ASTRON).

Venue: Lecture Theatre C, RW James Building, UCT

Date: 23 November 2012

Time: 12:00

Abstract: will review some of the recent results that have been obtained on the mass structure of galaxies at intermediate red-shit, as probed using strong gravitational lens systems. In particular, I will discuss how the observed mass slopes and the level of low-mass substructure within galaxy-scale dark mater haloes compares with the expectations from cold dark mater models for galaxy formation. Initial results suggest that the level of substructure observed in dark matter haloes is higher, with a flatter mass function, than to what is expected from simulations of galaxy formation.

Title: Exascale computing in the Square Kilometre Array

Speaker: Chris Broekma (Astron, NL).

Venue: LT303, 3rd Floor Computer Science Building (18 University Avenue), UCT

Date: Tue 11 December 2012

Time: 12:00

Abstract: The Square Kilometer Array (SKA) is an international project that aims to build a distributed radio telescope with a maximum baseline in the order of 3000 km, either in South Africa or Western Australia. Although the estimated processing requirements sill vary wildly, these are clearly beyond the capabilities of even the most modern supercomputers. The first phase of the SKA, scheduled for first operations in 2018, requires anywhere from several to several hundred petaflop/s, while the full SKA, which we expect to build after 2020, is well on its way to require far in excess of an exaflop/ s. Additionally, the I/O requirements run firmly into the scary range of several terabytes/s. It is clear that the SKA project is critically dependant on improvements in high-performance computing, and the ability of the project to efficiently leverage these improvements. It is also obvious that the unique requirements of the SKA instrument mean that we cannot expect a tailored solution to just appear a few years from now. I will outline the SKA project and the experiences we've had building some of the pathfinder instruments. I'll also look at the processing requirements demanded by the SKA, how these match onto the projected developments in high-performance computing and where we can expect them to fall short.


Title: Quasars and super-massive black holes

Speaker: Dr Stephen Fine, UWC

Venue: Rm 135, Physics Department

Date: 2 November 1012

Time: 13:00

Abstract: Since the realisation that quasars are distant, highly-luminous objects accretion onto a super-massive black hole has been considered a likely power source. While the sphere of influence of the SMBHs is spatially unresolvable, studies of broad lines in quasar spectra appear to be able to measure the mass of SMBHs to within a factor of ~3. I will discuss how these estimators work and give some contrasting reasons to be both positive and negative about their potential. I will show some examples of how they have been applied to measure the SMBH mass function and to constrain semi-analytic models of galaxy evolution, and outline what further work is being carried out to improve quasar BH studies.

Title: Evolution, Nucleosynthesis and Mass Loss in Low and Intermediate-Mass Stars

Speaker: Peter Wood

Venue: Rm 135, Physics Department

Date: 9 November 1012

Time: 14:00

Abstract: Low and intermediate mass stars have initial masses less than about 8 MSUN. When they finally die, they leave a white dwarf star of about 0.6-1.0 MSUN: the remainder of their initial mass is ejected back into the interstellar medium. The ejected material is enriched in carbon, nitrogen and s-process elements as a result of nucleosynthesis in the stellar interior and dredge-up processes that bring the enriched material to the stellar surface. I will describe the various mixing, nucleosynthesis and mass loss processes that occur in low and intermediate mass stars, noting the large uncertainties that exist in modelling them.


Title: Using Blending Effects: A Challenge to Study Super Star Clusters in a Sample of Extragalactic Systems at z>0.01.

Speaker: Zara Randriamanakoto

Venue: 1896 Building

Date: 17 October 2012

Time: 11:00

Abstract: For nearby extragalactic systems located at distances beyond ~40Mpc, the literature agrees that photometric biases are expected in a crowded-field of CCD imaging. However, little has been done so far to quantify the effects of blending. In this talk, I will present our findings from a deeper investigation of the effects on the photometric analysis of super star clusters (SSC) in our sample. A simulation aimed to record any change in the values of the SSC luminosity function slopes has been performed as well as a photometric follow-up of SSC of a nearby system (~19Mpc) when it is moved to a larger distance.


Title: Exposing the hidden side of GAMA.

Speaker: Dr Michelle Cluver

Venue: RW James Lecture Hall D

Date: 17 October 1012

Time: 13:00

Abstract: The mid-infrared is key to disentangling the composition and dusty metabolism of a galaxy as it evolves. By harnessing the power of the Galaxy and Mass Assembly (GAMA) multi-wavelength photometric and (opical) spectroscopic survey, combined with WISE (the Wide-field Infrared Survey Explorer), we can investigate key empirical relationships, in turn revealing the intrinsic physics of vast galaxy populations. This talk will focus on preliminary results from a detailed WISE study of the GAMA G15 field, as well as discuss other applications of GAMA and WISE science.

Title: Activities and Opportunities in Space Science at the South African National Space Agency

Speakers: Dr John Bosco Habarulema, Dr Jeanne de Villiers, Dr Elijah Oyeyemi and Ms Mpho Tshisaphungo from the South African National Space Agency (SANSA)

Venue: Duncan Elliot Rm., RW James Building

Date: 17 October 1012

Time: 12:00-13:00

Abstract: The South African National Space Agency (SANSA) was established under the SANSA Act, No. 36 of 2008, as a public entity with independent, impartial and objective decision-making authority to serve local and international stakeholders and coordinate the country's space -related initiatives. SANSA has four directorates: SANSA Space Science, Earth Observations, Space Operations and Space Engineering. SANSA became fully operational on 01 April 2011, and as a new public entity we have a responsibility to inform the South African people about the current and future activities of SANSA and encourage collaborations with SANSA. SANSA's presentation aims to expose the staff and students to the available SANSA facilities, postgraduate projects, and collaboration and job opportunities. In addition, we hope that this interaction will create an opportunity for staff and students to ask questions and receive information on SANSA and our plans for the advancement of Space Science and Technology in South Africa. We hope that this will result in active engagements in the form of collaborations (research in space science and student training) between SANSA Space Science and UCT.
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Title Annotation:colloquia
Publication:Monthly Notes of the Astronomical Society of Southern Africa
Date:Dec 1, 2012
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