Printer Friendly

Astronomical colloquia.

These form an important part of a research facility, often as a sort of pre-publication 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. Ed

At SAAO

Title: The SEDs of 250um selected galaxies in the Herschel-ATLAS

Date: 6 October 2011

Time: 12:30

Venue: 1896 Building

Speaker: Dan Smith (University of Hertfordshire)

Abstract: I will present the results of applying a panchromatic SED-fitting technique to a sample of 1404 local galaxies selected at 250um in data from the Herschel ATLAS project. I will discuss our results, including the determination of dust luminosities and masses, star formation rates, and a variety of other physical parameters. I will also present the results obtained by using our large sample to create a new set of empirical template SEDs for these galaxies, binned according to their physical properties, and show their differences from other currently-available panchromatic SED template libraries.

Title: New capabilities of IRSF and a simultaneous optical g'r'i' camera TRIPOL

Date: 13 October 2011

Time: 12:30

Venue: 1896 Building

Speaker: Takahiro Nagayama (Nagoya University)

Abstract: IRSF is a Japanese 1.4m telescope with a near infrared JHK simultaneous camera SIRIUS working from November 2000 at Sutherland. Recently, we have performed two upgrades to IRSF/SIRIUS; multi-bandpass filters and accurate photometry mode.

The new multi-bandpass filters have two transparency bands; one in the J band and another in the Ks band, and so we can obtain two narrow band images, for example, Pa Beta and Br Gamma simultaneously. The filters are installed just before the entrance window of SIRIUS camera, and so it is very easy to exchange the filters. Some images taken these filters and currently available filters are shown in my talk.

The accurate photometry mode is realized by a special self-guiding software which keeps a target at the same position on detector arrays. This software works both on-focused and defocused objects, and the target is normally kept within a pixel. Photometry relative to a reference star in the same field of view is stable within 0.002 mag for the J and H bands, and 0.003 mag for the Ks band (rms), and an 0.015 mag

eclipse due to ex-planet was easily detected. Our simultaneous milli-magnitude photometry of JHKs band will be very useful to monitor very small change of colours (J-H, H-Ks).

Finally, I also introduce our new instrument TRIPOL, a simultaneous optical g'r'i' camera. The test observation is planed from 28 September to 11 October at the SAAO 0.75m telescope, and I show some results taken in this observation. I believe that a simultaneous g'r'i' milli-magnitude photometry with TRIPOL on the 0.75m telescope will be available by the same method done with IRSF/SIRIUS in a near future. Our final goal is simultaneous 6-bands (g'r'i'JHKs) milli-magnitude photometry coordinated with IRSF/SIRIUS and TRIPOL/0.75m. It will be fantastic for all kind of astronomy.

Title: Disks, bulges, and the origin of lenticular galaxies

Date: 20 October 2011

Time: 12:30

Venue: 1896 Building

Speaker: Olga K Sil'chenko (Sternberg Astronomical Institute of the Lomonosov Moscow State University)

By undertaking deep long-slit spectroscopy with the focal reducer SCORPIO of the Russian 6m telescope, we have studied the stellar population properties along the radius beyond several scalelengths in the large-scale stellar disks of 15 S0 galaxies spread over a range of luminosities and settling in different environments. For the outer disks of the galaxies, we have found SSP-equivalent metallicities from the solar one down to [Z/H]=-0.4-0.7, rather high magnesium-to-iron ratios, [Mg/Fe]> +0.2, and mostly old SSP-equivalent ages. Nine of 15 (60%) galaxies have the outer disks older than 10 Gyr, and those are the galaxies in dense environments. The isolated galaxies possess intermediate-age stellar disks, of 7-8 Gyr old. Only two galaxies reveal the young SSP-equivalent ages of their disks of 2-3 Gyr. Just both young disks have appeared to be thin, while the other, old, disks have the scaleheights typical for thick stellar disks. The bulges at are on the contrary more metal-rich than the solar abundance and homogeneously distributed over all ages from 2 to 15 Gyr, being almost always younger than the disks. I conclude that the S0 galaxies are the primary type of disk galaxies completely shaped at z=1.5-2; they could not form in groups at z=0.4 as it is thought now. The Butcher-Oemler effect observed in the clusters at z=0.4 reflects probably some rejuvenation events confined mostly to the galaxies' bulges.

Title: Herschel-ATLAS: The relationship between accretion luminosity and star formation in QSO hosts

Date: 27 October 2011

Time: 12:30

Venue: 1896 Building

Speaker: Dr Dave Bonfield (University of Hertfordshire)

Abstract: We use the science demonstration field data of the Herschel-ATLAS to study how star formation, traced by the far-infrared Herschel data, is related to both the accretion luminosity of quasars selected from the Sloan Digital Sky Survey and the 2SLAQ survey. We find evidence that the star-formation in quasar hosts is correlated with both redshift and quasar accretion luminosity. Assuming a relationship of the form L_IR~L_QSO[and]theta.(1+z)[and] zeta, we find theta = 0.22 +/- 0.08. This shallow power-law slope in the relationship between star formation rate and quasar accretion rate is consistent with several other recent measurements, but conflicts with a suggestion (based on FIR-flux-limited samples) that a steeper slope, with theta=0.8, describes powerful quasars, which are expected to be triggered by major mergers. I will briefly discuss ways in which a shallow, non-linear relationship between star formation and black hole accretion can arise in the context of the merger paradigm.

Title: Mass Assembly of Galaxies over the last 10 Gyr

Date: 17 November 2011

Time: 12:30

Venue: SAAO Auditorium

Presenter: Philippe Amram (Laboratoire d'Astrophysique de Marseille)

Abstract: Understanding how galaxies evolve and assemble their mass across cosmic time is sill a fundamental unsolved issue. Processes driving mass assembly are expected to evolve on different timescales along cosmic time. A transition might happen around z=1 as the cosmic star formation rate starts its decrease. To get insight into the various processes of galaxy mass assembly, the Mass Assembly Survey with SINFONI in VVDS (MASSIV) aims at probing the kinematical and chemical properties of a significant and representative sample of high-redshift (0.9 < z < 1.8) star-forming galaxies. This sample contains 84 star-forming galaxies, selected from the VIMOS VLT Deep Survey (VVDS) and observed with the SINFONI integral-field spectrograph at the VLT. The MASSIV selection function, based on star formation criteria provides a good representation of "normal" star-forming galaxies. I will present preliminary results of this survey.

At NASSP

Title: The new South African Space Agency (SANSA): Space Weather--what's up?

Date: Wednesday, 5 October 2011

Time: 13:00

Venue: RW James C

Presenter: Dr Pierre Cilliers. Research Physicist in the Space Science Directorate of the South African Space Agency (previously the Hermanus Magnetic Observatory)

Abstract: SANSA was appointed in June 2007 as the African Regional Space Weather Warning Centre for Space Weather of the International Space Environment Service (ISES). The vulnerability of modern communications and electrical power distribution technology to space weather events is one of the reasons for SANSA's research on Space Weather and for South Africa's cooperation with various institutions on the design and development of a space weather payloads for satellites.

Dr Pierre Cilliers participated in an Antarctic expedition in December 2007 and an expedition to Marion Island in April 2010 to promote international research on Space Weather and is currently the SANSA PI for a project on Geomagnetically induced currents.

Dr Cilliers will present challenges and opportunities for research in Space Physics and

Engineering which relate to the following areas :

* space weather observations inter alia in Antarctica, on Marion Island, on Gough Island, with an emphasis on recent intense solar events.

* the prediction and mitigation of space weather impacts on technology, particularly on electrical power systems,

* the development of space weather sensors for CubeSats

Title: The Cold Gas in Early-Type Galaxies: Past, Present, and Future.

Date: Wednesday, 12 October 2011

Time: 13:00

Venue: RW James C

Speaker: Danielle Lucero. Danielle Lucero is one of the new SKA SARChI Postdoctoral Fellows here at UCT. She obtained her PhD in Physics (dissertation in Astrophysics) at the New Mexico Institute of Mining and Technology in March of this year. Her research interests include the interstellar medium and star formation in early-type galaxies.

Abstract: The process by which early-type galaxies form remains a key issue in the general theory of galaxies. The traditional view is that early-type galaxies are old systems that formed at high redshit, passively evolving until the present without further star formation activity. In recent years a wide variety of observational work has suggested that the formation of early-type galaxies is in actuality a very intricate process; it has been drawn out over most of a Hubble time and it is even continuing at some reduced level now. For instance, GALEX observations find UV emission from current star formation in up to 30% of nearby ellipticals. Some of the early-type galaxies have stellar population age gradients, with the central stars of the galaxy several Gyr younger than the outer stars. Many early-type galaxies also have internal structures with kinematic properties that are dramatically different from the rest of the galaxy; these kinematically decoupled cores are probably the result of a dramatic merger or accretion event. It is clear that the cold gas in early-type galaxies holds important clues to their evolutionary history---it serves as a tracer of past accretion or interactions. It is now well established that many early-type galaxies contain detectable amounts of cold gas, sometimes settled in a disc, and recent star formation. In this talk I will discuss what the current observational evidence suggests about the origin of early-type galaxies and their gas contents.

Title: A Search for Intermediate-Mass Black Holes at the Centres of Nearby Dwarf Galaxies

Date: Wednesday, 19 October 2011

Time: 13:00

Venue: RW James C

Speaker: Bonita De Swardt. Bonita obtained her PhD from UCT in 2009 and is currently a postdoctoral research fellow at the SAAO. Her research interests include studying the properties and characteristics of the faintest galaxies--broadly known as dwarf galaxies--that we observe in the nearby universe.

Abstract: The correlation between black hole (BH) mass and the bulge velocity dispersion is well established for early-type galaxies having a supermassive BH in the centres. The extrapolation of this relation to the lower BH-mass regime is strongly dependent on the existence of BHs in the mass range of 10A3-10A6MSun--called the "intermediate-mass" black hole (IMBH). The BH mass versus velocity dispersion relation infers the existence of IMBHs in dense stellar environments having dispersion in the range of 20-100km/s. Dwarf galaxies are well known to have central velocity dispersions in this range making them ideal candidates for hosting an IMBH. In this talk, I will present an ambitious project for the search of IMBHs using the Southern African Large Telescope (SALT). In particular, the results of a pilot study in the search of these objects at the centre of nearby dwarf galaxies using the SALT spectrograph will be shown. Even though the presence of an IMBH in the galaxy centre remains inconclusive with the current data, these results do however give a great deal of insight into the capabilities and limitations of SALT in our search for the elusive IMBH.

Title: Technological applications of Geomagnetic field measurements at SANSA Space Science

Date: Wednesday, 26 October 2011

Time: 13:00

Venue: RW James C

Speaker: Elda Saunderson

Abstract: We all know that the Earth is surrounded by a relatively weak magnetic field which protects us from radiation from the Sun and in that capacity makes life possible on Earth. This geomagnetic field is not stationary but changes all the time. We can't significantly change this field, nor can we switch it off or control it, however, we can measure it and use it to our advantage.

Geomagnetic measurements have been used for centuries by seafarers to navigate with a magnetic compass, but today we use measurements of the geomagnetic field for navigation and orientation control of satellites, some as small as 10[cm.sup.3], unmanned aerial vehicles such as spy-planes, weapon systems, underwater unmanned rovers and many more. We can also use measurements of the geomagnetic field to find magnetic objects (both stationary and fast moving objects), or to hide magnetic objects from someone else ... We are even attempting to predict Earthquakes with super cooled magnetic sensors!
COPYRIGHT 2011 Astronomical Society of Southern Africa
No portion of this article can be reproduced without the express written permission from the copyright holder.
Copyright 2011 Gale, Cengage Learning. All rights reserved.

Article Details
Printer friendly Cite/link Email Feedback
Title Annotation:colloquia
Publication:Monthly Notes of the Astronomical Society of Southern Africa
Date:Dec 1, 2011
Words:2142
Previous Article:Photographing the moon's parallax.
Next Article:Lepus--a storybook rabbit.

Terms of use | Privacy policy | Copyright © 2019 Farlex, Inc. | Feedback | For webmasters