Official Intel ISEF 2019 Abstract and Certification

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5/15/2019 7:12:28 PM

Applications of Helium-4 Doubly Forbidden Singlet-Triplet TransitionLines in Astronomical Spectroscopy PHYS030

Physics and AstronomyChristine Ye

Eastlake High School, Sammamish, WA

Helium-4, the most common isotope of helium, is difficult to detect in the interstellar medium, as classicaltransitions are moderately rare; however, Helium-4 also can undergo forbidden transitions. One of these,between metastable states of Helium-4 in the 2s energy level, occurs experimentally at 1557nm in thenear-infrared range; it is lower in energy and less subject to dust extinction, making it an excellent choicefor the cold and warm neutral mediums. A sample of 50 nearby spiral galaxies were chosen for the study,a mostly homogeneous population. Near-infrared and radio spectra were processed, reduced, andanalyzed through an independently developed procedure to correct errors, and to determine the spectralflux of the Doppler-broadened 1557nm line using a Gaussian line fit and a polynomial backgroundapproximation. Overall, in 31 of the 50 galaxies, the line was detected at a statistically significant level withhigh confidence, and in 6, it was detected with moderate confidence. In addition, in the sample galaxies,as expected, the spectral line flux correlated with overall H-band magnitude as defined by theastronomical magnitude system, confirming the accuracy and potential of this spectral line. Preliminarywork has been undertaken for the study of the 1557nm spectral line in main sequence and post-MS stars,including the development of a procedure to adjust for errors and perform a Voigt approximation, as wellas some spectral analysis. Forbidden transition spectroscopy in Helium-4, in the future, may serve as auseful tool for mapping and tracing states and masses of helium in the universe, leading to a variety ofinsights. As a proof of concept, a set of equations have been derived to calculate the mass of Helium-4 inthe galaxy from spectral flux.

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