Cosmic Relations and Dark Matter

Through their observations of the sky, astrophysicists try to determine the distance of cosmic objects like stars and galaxies from Earth and the relationship of these objects to one another. But the task is not always easy. Viewed in a 2D image created by a telescope, stars may look close together because they overlap in the image, when in fact they exist at great distances from each other in space.

Using data gathered by two space telescopes, NYU Abu Dhabi rising senior Sumit Dahal, with his advisor, NYUAD Assistant Professor of Physics Joseph Gelfand, determined that two objects that researchers have thought were related are actually not. Dahal's poster presentation on the topic, "Is SNR G12.8-0.0 really associated with the star forming region W33?," won second prize at the joint meeting of the New York State Section of the American Physical Society and the Astronomy Society of New York.

One of the brightest sources of high-energy photons in the Milky Way, G12.8-0.0 is a pulsar wind nebula, a cloud composed of extremely high-energy particles generated by the rotational energy of a pulsar: the extremely small (literally the size of the island of Abu Dhabi), dense, magnetized remnant of a massive star that emits a beam of electromagnetic radiation (light) as it spins rapidly around its own axis, similar to a lighthouse casting light across the ocean. (A pulsar seems to "pulse" because from Earth we can only observe the beam of radiation when it is pointed in our direction, which happens once a rotation period.)

It was thought that the pulsar inside G12.8-0.0 had been created by the death of a star that was associated with the star cluster of W33. But Dahal's research shows that that is not the case. This work may encourage astronomers to look elsewhere for the origin of the star whose death created the pulsar that powers the nebula G12.8-0.0.

Pulsars are believed to result from the gravitational collapse of the most massive stars. But we are interested to know if the properties of a pulsar are related to the properties of the star that formed it.

Joseph Gelfand, NYUAD assistant professor of Physics

Gelfand provided background on the significance of the project. "Pulsars are believed to result from the gravitational collapse of the most massive stars. But we are interested to know if the properties of a pulsar are related to the properties of the star that formed it. And if so, how are they related?" To address these questions, researchers must determine the properties of the star that turned into the pulsar. This is complicated because the star no longer exists and researchers must determine the characteristics of the former star based on evidence of its existence that remains in the sky.

Dahal's work has further implications for better understanding the pulsar wind nebula. Astronomers make a distinction between the amount of light an object produces, called "luminosity," and the amount of light produced by an object that can be seen on Earth, called "flux." Dahal's paper shows that the pulsar wind nebula being studied is further away than researchers had thought; therefore, the luminosity of the nebula is in fact much higher.

Dahal conducted research for his prize-winning poster in the summer of 2013 in New York at NYU's Center for Cosmology and Particle Physics (CCPP), where he was able to attend seminars, lectures, and workshops, and conduct hands-on research: "That experience gave me an opportunity to use the theory and equations that seem extremely complicated when we are introduced to them in lectures," Dahal said.

Now, Dahal is working as an undergraduate researcher in the XENON Dark Matter Project in the Gran Sasso National Laboratory (LNGS) in Italy, which he described as "the largest underground laboratory in the world, shielded under more than a kilometer of rock." The XENON experiment is "trying to detect dark matter, an elusive hypothesized particle believed to have made more than a quarter of our entire universe."

A double major in Physics and Mathematics with a minor in Astronomy, Dahal has always held an interest in the sky, but he mentioned a talk by NASA astronaut Mike Massimino that was given at NYUAD's Downtown Campus that had a great impact on him. "Meeting people like Mike Massimino has always motivated me to pursue my dreams, be passionate about my work, and to never give up, no matter how hard situations get."