Observations

Apr 29, 2017

HRS Observations of RGBs in NGC 6584 and NGC 7099

2016-2-SCI-002

Globular clusters, groups of ~100,000 stars thought to be formed at the same time from the same material, are among the oldest objects in our Galaxy. However, the assumption that their stars have the same chemical makeup is not holding up to current observations. It is becoming clear that globular clusters are composed of several generations of stars. What is unclear is whether or not these generations are distinct in their chemical compositions or if the distribution is a continuous spread. We aim to answer this question by studying the brightest stars in the globular clusters NGC 6584 and NGC 7099 and obtaining the most accurate abundance measurements possible.

Spectroscopic investigations of Cepheids and stars belonging to Galactic open clusters and associations

2017-1-MLT-005

Spectroscopic investigations of Cepheids and stars belonging to Galactic open clusters and associations

Long-Slit Kinematics of Galaxies for the RESOLVE Survey

2017-1-SCI-034

Galaxies are the luminous markers of a vast cosmic web, whose filaments and clusters condense under gravity while spacetime expands in voids between them. Gas and dark matter are the presumed lifeblood of this multi-scale organism, flowing along its filaments and feeding the growth of its galaxy cells. Yet much of the gas is undetected, and its relationship to invisible dark matter is unknown. To meet this challenge, the RESOLVE Survey combines state-of-the-art optical and radio/millimeter spectroscopy with multi-wavelength photometry to construct an unprecedented integrated view of gas, dark matter, and stars, spanning nearly five orders of magnitude in spatial scale. RESOLVE will disentangle dark matter and undetected gas to relate invisible mass to cosmic structure, illuminating mysteries such as the dramatic large-scale variation of the dwarf-galaxy inventory and the surprising abundance of galaxies like our own, with profound implications for galaxy evolution and cosmology.

Spectroscopic investigation of southern lambda Boo – type stars.

2017-1-SCI-010

When talking about stars, we very often refer to the Sun which is the most extensively studied star in the sky. In the Universe, however, there are plenty of stars. Some are cooler than the Sun, others are hotter, but for most of them the elemental abundance of the constituent material is very close to solar. There are, however, exceptions. Among stars that are hotter than the Sun, there is a small group of stars called lambda Boo type which are chemically peculiar. Their peculiarity is characterised by moderate to high- surface underabundances of heavy elements like magnesium, aluminium, manganese, nickel or iron and near-solar abundances of carbon, nitrogen, oxygen and sulphur. The origin of these anomalies is not clear. It is generally accepted that lambda Boo stars are young and that their chemical peculiarities result from accretion of metal-poor material from the interstellar medium or from the interaction of the star with protoplanetary disks or planets. However, there is no agreement which of these two theories is correct. We do not know if the chemical peculiarities are limited to the surface or continue into the depth of the stars, and we are not sure if the lambda Boo phenomenon is limited to young stars, as suggested by a lot of observational evidence.The keys to the understanding of the origin, structure, and evolutionary status of lambda Boo stars lie in the studies of high-resolution, high signal-to-noise spectroscopic observations and high-precision photometric data that are planned in this proposal. Our spectroscopic observations will be used by us to derive detailed pattern of abundances of chemical elements in lambda Boo stars. Those will then be used as an input in asteroseismic analysis of the photometric observations which will be delivered by the TESS space mission within a few years.Our study will allow us not only to address the questions of the origin and composition of lambda Boo stars, but also investigate larger problems of formation and evolution of stars , and interactions between stars, planets, and planetary disks.

SALT Supernova Followup

2016-1-MLT-007

Observations of supernovae, near and far.

Technology demonstration of SETI using the BVIT on SALT

2016-2-SCI-011

The question as to whether life forms exists elsewhere in the Universe has fascinated mankind for centuries. Over the past 50 years, since it was realized that “earthlings” have been advertising their presence through radio and TV emitted signals, we have been searching for similar signalsemitted by extra-terrestrails (ET). The search for ET intelligence (SETI) gained initial fame in the 1970’s through Carl Sagan and the Voyager Spacecraft. Now, with the BVIT detector collecting photons with the 10m SALT mirror array, we have developed a unique method to record signals generated by laser communications from advanced ET civilizations that are located within 1000 light years of Earth. The detection technique is only limited by two factors: (1) Whether an ET civilization is sufficiently advanced to generate powerful laser signals, and (2) the size of the mirror collecting area on earth (i.e., SALT). The present observations of 3 earth-like exoplanets each residing in the habitable zone of their respective host stars, will act as a technology demonstration for SETI that may be utilized on far larger, future 30 meter-plus sized telecopes.

Observing the Transient Universe

2016-2-LSP-001

This large SALT program is aimed at studying “things that go bang in the night”, namely transient objects in the Universe which either are newly discovered objects, or known objects who suddenly change their appeatance. Such things include binary stars with accreting compact companions, many of them X-ray or gamma ray sources, eruptive stars which suddenly brighten, black holes systems, including active galaxies powered by them, and all manner of explosions including the most energetic of all, gamma ray bursts.

Apr 28, 2017

Technology demonstration of SETI using the BVIT on SALT

2016-2-SCI-011

The question as to whether life forms exists elsewhere in the Universe has fascinated mankind for centuries. Over the past 50 years, since it was realized that “earthlings” have been advertising their presence through radio and TV emitted signals, we have been searching for similar signalsemitted by extra-terrestrails (ET). The search for ET intelligence (SETI) gained initial fame in the 1970’s through Carl Sagan and the Voyager Spacecraft. Now, with the BVIT detector collecting photons with the 10m SALT mirror array, we have developed a unique method to record signals generated by laser communications from advanced ET civilizations that are located within 1000 light years of Earth. The detection technique is only limited by two factors: (1) Whether an ET civilization is sufficiently advanced to generate powerful laser signals, and (2) the size of the mirror collecting area on earth (i.e., SALT). The present observations of 3 earth-like exoplanets each residing in the habitable zone of their respective host stars, will act as a technology demonstration for SETI that may be utilized on far larger, future 30 meter-plus sized telecopes.

THE SALT GRAVITATIONAL LENSING LEGACY SURVEY

2015-2-MLT-006

Everything in the universe warps space – even you, right now, are warping the space around you. This is too tiny to see in everyday objects but entire galaxies are big enough for the warps to be measurable. You can see the warps if you have a chance alignment of a foreground and a background galaxy: the background looks warped and stretched and magnified because of the warped space around the foreground galaxy. However, finding these alignments of foreground and background galaxies has been tricky. We have made a breakthrough and discovered an extremely efficient method of finding these chance alignments of galaxies using the Herschel infrared space telescope. Some galaxies appear to be unexpectedly bright in infrared light, and this is because of the magnification from a foreground galaxy. Our project on SALT aims to measure the distances to these foreground galaxies, so we can work out the geometry of the lenses and make inferences about the geometry of the Universe, the shape of the invisible dark matter, and shed light on why the expansion of the Universe is accelerating.

Multi-slit spectroscopy of edge-on galaxies: solving a puzzle of the thick disc formation

2016-1-MLT-005

Multi-slit spectroscopy of edge-on galaxies