High School Intern Measures Milky Way Rotation Curve

Sep 05, 2013

Through the High School Science Research Internship Program, Madison West High School student Shauna Jacob worked as an intern this summer with Professor Snezana Stanimirovic’s research group. She measured the Milky Way rotation curve using the 2.3-meter Small Radio Telescope (SRT) constructed at the Pine Bluff Observatory in December 2012 (see department news story).

Before conducting her observations, Shauna had to calibrate the telescope. First, she calibrated the telescope’s noise diode to provide accurate brightness temperature measurements of hydrogen emission. This was done by taking hydrogen (HI) spectra of different Galactic locations and comparing the observed brightness temperature to measurements from the Leiden/Dwingeloo Survey. Then she modified Carl Heiles’ (UC Berkeley) method of measuring the telescope gain as a function of frequency and applying it on individual spectra to correct for the bandpass fluctuations.  

Once this was done, she took HI spectra at galactic longitudes 20˚ to 75˚, in 5˚ intervals, at latitude 0˚. After basic calibration, she applied the tangent point method (where the velocity of HI clouds closest to the Galactic center is measured from the spectra) to determine a set of orbital velocities as a function of the distance from the Galactic center. The resultant curve is in excellent agreement with observations obtained by McClure-Griffiths & Dickey (2007) and Brand & Blitz (1993) using much larger radio telescopes.

The High School Science Research Internship Program is an informal partnership between the Madison Metropolitan School District (MMSD) and the University of Wisconsin-Madison. Students from MMSD are partnered with researchers at UW-Madison each summer. The goal of the program is to provide an authentic science research experience for the intern.

UW-Madison Astronomy Home