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Dr. Kartik Sheth, ALMA, and SKA March 19, 2013

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by JC Holbrook

National Society of Black Physicists members Eric Wilcots and Kartik Sheth were part of a new initiative to foster radio astronomy collaborations with South African astronomers and students. Last week marked the official inauguration of ALMA, the Atacama Large Millimeter/Submillimeter Array, in the high altitude Atacama desert of Chile, South America. I was able to sit down with Dr. Sheth to discuss the broader issue of radio astronomy and South Africa.

“I think this celebration was the culmination of thirty years worth of work from a lot of different people. The inauguration of the array was a chance for us to celebrate how much hard work has gone into it.” Dr. Sheth said of the inauguration ceremony in Chile. “We started science operations September 30th of 2011. We have been collecting data for over two and a half years, because even with a small ALMA it is still the most powerful [millimeter/submillimeter] telescope in the world.”

Since ALMA is an array of dishes similar to the radio dishes of the Very Large Array in New Mexico, even during construction as each dish was put into place and connected, the astronomers were already using what was available to collect data. Thus, the months of science data collection with ALMA before the official inauguration.

I pointed out, “You were not even there!”

Dr. Sheth laughed, “Only the dignitaries were invited, so a lot of people from the political arena in the twenty-five plus countries that are part of ALMA. President Piñera inaugurated ALMA…For me it doesn’t mean much… but I’m kinda sad that I’m not there because I really wanted to be there. But I knew that I wasn’t going to be invited, so coming here [to South Africa] really was driven by the NASSP deadline for Master’s proposals.” NASSP is the National Astrophysics and Space Sciences Programme in South Africa. In 2010, I began writing a book about NASSP. The program is a dramatic success story about educating underrepresented groups in astrophysics and space sciences. NASSP include one honor year and a two year masters of science degree. Nearly all NASSP students are funded by the program.

Dr. Sheth explained, “The idea is to foster bridges between the faculty here that are taking on students who eventually want to work with MeerKat and SKA. But MeerKAT and SKA are not built, yet. So, what we would really like the faculty to do is to think about including radio data from existing telescopes and NRAO operates four of them.”

The SKA is currently under construction, yet the South African astronomy students need to learn everything about radio astronomy and the analysis of radio data. Dr. Sheth along with other American radio astronomers is here to encourage South African astronomers and their students the opportunity to learn by working with the existing facilities and their archival data. The four facilities are ALMA, the Robert C. Byrd Greenbank telescope a single dish in West Virginia, the Jansky Very Large Array (JVLA or EVLA) which is the enhanced VLA in New Mexico, and the Very Large Baseline Array (VLBA) which is spread across the Northern Hemisphere. Thus, the visit before the NASSP deadline for submitting Masters of Science thesis proposals. Dr. Sheth hopes that a few NASSP students will propose radio astronomy projects including using NRAO facilities for their Masters work.

According to Dr. Sheth the JVLA is the Northern Hemisphere equivalent of what MeerKat will be. MeerKat is the precursor to the SKA, the Square Kilometer Array.  It is a new state of the art radio observatory currently being built in South Africa. The SKA array itself will consist of 3000 dishes spread across nine African countries: South Africa, Namibia, Botswana, Mozambique, Madagascar, Mauritius, Zambia, Ghana, and Kenya. The SKA Africa headquarters are in Cape Town, South Africa, and they will be coordinating all of the African construction. A question I thought would be uppermost in the minds of South Africans was: Will ALMA be competition for SKA?

His response, “No, not at all. ALMA operates at higher frequencies than what the SKA will operate at. They are not looking at the same part of the electromagnetic spectrum but they will be looking at the same type of objects. EVLA is a mini version of SKA. With the SKA, it will be observing thermal emission and synchrotron emission from sources…” In an email he added, “We are looking at electrons energy as they cool around star forming regions or zip around magnetic fields. So you can get a real idea of the magnetic field that pervades the Milky Way and with the SKA across cosmic time. ALMA cannot really look at atomic gas unless its at very high red shift (i.e. the lines are red shifted into the regime that ALMA can observe) and only using atomic gas tracers like ionized carbon, nitrogen, or oxygen. ALMA cannot look at the atomic hydrogen gas which is emitting in the wavelengths that MeerKat and SKA will work at. So SKA & Meerkat are looking at the atomic gas from which molecular gas forms. And the molecular gas is what ALMA looks at which from stars form. And the stars are what HST and JWST look at. So it is a nice transition.  Together these are giving you the full picture of what the universe looks like. Additionally there is a lot about magnetic fields and transient phenomena — these are also MeerKat and SKA’s core strengths. For instance, these will be excellent instruments for looking at the timing of pulsars.”

Trying to put it altogether I asked, “So, anything that is hot and has electrons moving around will be able to be studied by SKA?”

Kartik Sheth clarified, “No, I wouldn’t call it ‘hot’. The atomic gas is quite cold as well. It is hotter than the molecular gas but not hot compared to stars.”

As a student of astronomy, I had always had a fascination with the connection between wavelengths of light or color, physical properties, chemistry, and celestial bodies. Planetary nebulae, which are mentioned in my last Vector blog, in visible light appear greenish in color. The color is the result of a specific atomic transition in the oxygen atom that occurs under very low density conditions. First the oxygen has to be ionized twice, i.e. it has to have lost two electrons, then it is through collisions that the transitions producing the characteristic green lines emit. A rule-of-thumb temperature for planetary nebulae is 10,000 degrees Kelvin. Thus, if there is a celestial body that appears ‘green’ in visible light you can conclude that it might include oxygen especially if it is a nebula which tends to have low density and it should be around 10,000 degrees Kelvin. Hydrogen is also found in planetary nebulae and the strongest transition line, known as H-alpha, occurs when its electron goes from an excited state to a less excited state releasing energy in the form of red light.

In the case of ALMA and SKA, they are probing two different sections of the electromagnetic spectrum similar to studying green light or red light. In the fullness of time, SKA will cover the same wavelengths and types of celestial bodies as the EVLA but focused on the Southern sky rather than the Northern, but also be more sensitive revealing more physical details. ALMA will add to our understanding of the same region of the sky but is studying different physical properties of celestial bodies. Both will add to our understanding of the Milky Way and the Universe.

NSBP members visit South Africa to strengthen ties March 15, 2013

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NSBP members Kartik Sheth and Eric Wilcots along with National Radio Astronomy Observatory (NRAO) astronomer Scott Ransom have been in South Africa to cement linkages for a NRAO’s faculty bridge program. NSBP, the South African Institute of Physics (SAIP), NRAO and others are working together on the science dimension of the US-South Africa Bilateral Strategic Dialogue.

The visit is intended to foster partnerships in multi-wavelength astronomy research.  Last week they had meetings with astronomers and cosmologists at University of Cape Town, University of Western Cape, SAAO, the SKA Africa Project Office and the African Institute of Mathematical Sciences (AIMS).  This week they will also meet with high energy astrophysicists at the Potchefstroom campus of North-West University, University of Johannesburg, and University of Witswatersrand, as well as astronomers at the North-West University campus in Mafikeng, and the Hartebeesthoek Radio Astronomy Observatory (HartRAO).

As South Africa builds a second NASSP site, teaching and research partnerships with NRAO will be beneficial on both sides of the Atlantic. NRAO currently operates four premier radio astronomy observatories: ALMA, JVLA, GBT and the VLBA.  NRAO is likely to also be a partner in helping to train scientists across the continent to be operators and users of the African VLBI Network (AVN). The AVN project consists of converting large, redundant telecommunications dishes across Africa for radio astronomy. The AVN will become part of the global VLBI network.

In addition to major radio astronomy successes, South Africa’s strategic plan for astronomy calls for its institutions to be active in multiple wavelengths including radio, optical, gamma/x-ray, and near IR. South Africa is the host of the Southern Africa Large Telescope (SALT), the largest optical telescope in the southern hemisphere. Wilcots is a member of the SALT board. South Africa is also supporting the Namibian bid to host the Cherenkov Telescope Array (CTA), the next generation success to the H.E.S.S telescope that has been in Namibia since 2002. Following an exchange at the 2011 NSBP conference, South Africa and the LIGO Collaboration have begun exploring opportunities in gravitational wave astronomy. Already LIGO and SAIP have convened a faculty workshop and a student summer school, both in Pretoria.

In a separate but simultaneous visit, Jim Gates participated in South Africa’s National Science Festival (SciFest), giving talks at several venues around the country on science policy and supersymmetry.  ScieFest was established in 1996 to promote the public awareness, understanding and appreciation of science, technology, engineering, mathematics and innovation. The main event in Grahamstown, held in March every year, attracts 72,000 visitors from South Africa, Botswana, Lesotho, Mozambique, Namibia, Swaziland and Zimbabwe. Several government departments, listed companies, museums, NGOs, research facilities, science centers, science councils, universities, as well as small, medium and micro enterprises, both from South Africa and abroad contribute to the success of the event.

Gates was on the same program as South Africa’s Minister of Science and Technology, Derek Hanekom.  Each discussed science and innovation policy and gave their perspectives on aligning science with national priorities. Additionally Gates participated in three formal policy meetings, including one with Simphiwe Duma, CEO of the Technology Innovation Agency, and two more informal policy meetings.  In a lecture at the University of South Africa (UNISA) he and Dr. Rob Adam, former head to South Africa’s National Research Foundation, spoke on the efficacy of policy-formation surrounding STEM fields and the innovation cycle.

In other events around the country Gates met 45 students spanning the 8th through 11th grade levels at the Mae Jemison Science Reading Room in the Mamelodi township.  At Nelson Mandela Metropolitan University and the University of Johannesburg he gave talks on the strange mathematical objects found in the equations of supersymmetry.

These meetings and exchanges involving NSBP and South African colleagues are all part of the evolution from ideas put into motion by the Nobel Laureate, Abdus Salaam, and the founders of the Edward Bouchet-Abdus Salaam Institute (EBASI). Over a decade ago former NSBP president, Charles McGruder, traveled to South Africa to explore possible linkages between astronomers.  That visit led to Khotso Mokhele’s participation in the 2004 NSBP conference.  At the time he was the head of South Africa’s National Research Foundation. Later NSBP won a grant from the WK Kellogg Foundation to support NSBP’s participation the NASSP program. In the year’s since, NSBP has partnered with SAIP on a number of projects, and the relationship was codified in at MOU signed at the 2011 NSBP conference and witnessed by Minister Naledi Pandor.  The relationships between NSBP, SAIP as well as colleagues across the entire continent continue to evolve and vistas are opening up in the realms of geophysics, biophysics and medical physics, nuclear and particle physics, mathematical and computational physics, as well as physics education at all levels.

Unfinished Business in Astronomy March 11, 2013

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JC Holbrook

My master’s thesis in astronomy at San Diego State University focused on the electron temperature structure of the ionized gas of planetary nebulae. I focused on two planetary nebulae: NGC 6572 and NGC 6543. I observed using the one meter telescope at Mt. Laguna Observatory with a CCD detector. Planetary nebula are created as low mass stars throw off their atmosphere during their transition to white dwarfs. My observations and analysis of NGC 6572 revealed a knot of high temperature gas well away from but connected to the nebula. I could not explain what the knot was but submitted the paper in 1992 to ApJ with my advisor Theodore Daub. The referee reports insisted that we take spectra of the knot. JPL’s Trina Ray took spectra but we still could not identify the hot knot. The project was left behind as I left SDSU for NASA and a doctorate. However, a week ago I looked up images of NGC 6572 and got a big surprise! The Hubble Space Telescope image showed a far bigger nebula than what we could detect twenty years ago! Though it has been several years, looking at the contours I estimate that the hot spot I found, which at that point was at the edge of the nebula, I have marked with a circle in the second image. The structure of NGC 6572 is much more complicated than what I was working with and it is clear that some of the assumptions that went into the temperature would need to be updated to fully determine if the knot was indeed as hot as calculated. Certainly, some eager young astronomy student has already unraveled this bit of unfinished business!