Jul 28, 2014

Longevity of Dark Matter Substructures in Abell 3827


Our Universe matter content today is dominated by Dark Matter.If it is called dark matter, it is because we don’t know much about its nature.Abell 3827 is an exceptional massive galaxy cluster not too far from us. Its core is formed by four massive galaxies, that are still in the process of merging together.This configuration is really rare and makes Abell 3827 a primary target to study the evolution of dark matter.With these observations, we will be able to see where the stars (luminous matter) and the dark matter are situated with a really high accuracy.This is mandatory to understand the history of this rare and exceptional galaxy cluster, but not only ! By looking at the location of the stars compared to the dark matter, we will be able to derive clues on the properties of dark matter particles.

Jul 22, 2014

Constraining dark matter in the centres of clusters


We are using SALT to observe the dominant galaxies in the centres of clusters to learn about the dark matter in the cluster. Dark matter can not be directly observed, but observations of the random motions of stars in these galaxies can be used to describe the dark matter in the cluster if the data is combined with other observations from the Hubble Space Telescope and X-ray observatories.

Jul 21, 2014

Spin-up of the O Companions in WR+O binaries


We propose to measure the spin rates (vsini) of 16 O stars in WR + O binaries. Theory predicts that the mass transfer from their WR companions will have boosted many to nearly breakup velocity. Only two systems are well studied (V444 Cyg and HD 186943); both are very rapidly rotating. The observed vsini distribution will be critical to constrain mass transfer theory, and binary massive star evolution.

Jul 19, 2014

Fundamental Properties of Peculiar Hot Subdwarfs


Stars approaching the end of their lives expand and, in many cases, exchange material with close companions. This has a radical effect on their evolutionand surface composition, producing a zoo of rare but highly exotic stars. By exploring the propertiesof thes pathological cases, we are endeavouring to understand the ways in which stars exhange matter and evolve towardstheir final fate as white dwarfs or supernovae. The stars in this programme are perfect examples — all of them have completelylost their surface hydogen, for reasons still to be explained. These observations will tell us about the abundances of otherelements — previously we have discovered huge overabundances of exotic species such as lead and zirconium.

Jul 15, 2014

Calibrating RINGS: RSS Imaging and Spectroscopy Nearby Galaxy Survey (phase II)


We will measure the orbital speeds of hydrogen gas cloudsin nearby galaxies like our own Milky Way, and we will use them to derive the total mass distribution of each system. By comparing this mass to those of the gas and the stars in each system, we can map its dark matter content. Our main scientific goal is to compare this dark matter content to theoretical models developed from computer simulations of the evolution of the Universe: are our observationsconsistent with predictions from the standard cosmological model input into the simulations, or is our understanding of cosmology and/or galaxy formation incomplete?

Jul 12, 2014

Optical Spectroscopy of YSO candidates in N81, N88 and N113


We aim to probe the environments of 3 star forming regions in the Magellanic Clouds using the Robert Stobie Spectrograph on SALT. This will allow us to compare how star forming regions differ in areas with low levels of dust and strong tidal forces compared to those in our own galaxy.

Jul 9, 2014

Pseudobulges in S0 Galaxies


The galaxies being observed here are special. They are known to contain central parts, called bulges, of a very specific kind, called pseudobulges. We believe that pseudobulges have formed very slowly by rearranging the material in the disk part of the galaxy but a lot remains unknown about them. Using observations of the spectra of these special set of galaxies, we hope to perform various studies which will help us come one step closer to understanding them.

Jul 1, 2014

Ringed early type galaxies: origins of weirdness


When we think of “jewelry” what comes to mind are gold or silver rings studded with diamonds and other precious stones. These tiny adornments fetch huge prices at public sales, but they are not the most beautiful rings astronomers know of. One particularly interesting kind of galaxy looks like just the jewelry ring; a ring of stars and gas that shine brightly in the darkness of the Universe. The empty ring we are studying is tens of thousands of light-years across. The luminous band also carries a very bright “ruby”; a huge collection of young and older stars, and very hot gas. Astronomers do not yet know how such galaxies are formed and into which form they will evolve. This is the reason to study the celestial ring that goes by the mundane name “ESO 474-G040”.

Jun 29, 2014

Excitation of Pulsation Modes in Rapidly Rotating Early-Type Stars


Using asteroseismology (the study of pulsations in stars) we can learn a lot about the insides of stars. βCephei stars are a class of pulsating stars that often exhibit multiple pulsation modes that orginate atdifferent depths of these stars. By looking at the entire set of pulsations visible in a particular β Cepheistar, we can calculate basic physical parameters (for this project, mostly rotation rate) at different depthsof these stars.

Jun 28, 2014

Tracing the stellar mass build-up of BCGs via mergers


Brightest cluster galaxies (BCGs) are the most massive and luminous galaxies in the Universe. These galaxies are exceedinglydifficult to observe and therefore, not much is known about the stellar mass build-up of these galaxies. We are therefore forced to use galaxy formation models to study the mass build-up of BCGs. From these models is appears that BCGs areformed through repeated mergers of less massive galaxies, more specifically major mergers appear to be the dominant contributors to the mass growth of BCGs.In this proposal we observe BCGs that are likely to experience a major merge with its companion galaxy in the near future and therefore measure the merger pair fraction of BCGs. At low redshifts (z ~0.2-0.4) the merger rate can spectroscopicallydetermined from homogenous data publically available from SDSS, however at redshifts above this the spectroscopic completeness in SDSS drops significantly. For this reason, we aim to use SALT to significantly contribute to the statistics at z =0.4–0.5 in order to maximally constrain the merger rate throughout different epochs.