Determining Properties of the Interstellar Medium through Scintillation of 166 Pulsars

Radiation from galactic and intergalactic radio sources (i.e., pulsars and fast radio bursts) is affected by the ionized interstellar medium (ISM) along the line-of-sight. However, the prevailing Galactic electron density models for the ISM, including NE2001 and YMW16, provide predictions which can differ from each other, and from derived observational values, by up to an order of magnitude. Scintillation, the modulation of radio intensity in time and frequency due to the ISM, can be measured for steady radio sources such as pulsars and used to infer corrections to the electron density models. In this work, the research team at the Penn State Pulsar Search Collaboratory is measuring pulsar scintillation bandwidths in archival drift-scan radio data from the Arecibo 305-m telescope. We have identified 166 pulsars, with a total of 217 observations, with predicted NE2001 scintillation bandwidths that should be resolvable in the drift scan data across the bandwidth of the 327 MHz receiver. We are using PRESTO, PSRCHIVE, and PyPulse software tools on these observations to generate dynamic spectra and apply an autocorrelation analysis to measure scintillation bandwidths, and we have analyzed about 35% of the dataset so far. Once these measurements are complete, we can compare them to existing models of the ISM and identify discrepancies; this will allow for improved ISM models in the future, leading to, i.e., more accurate measurements of pulsar and fast radio burst distances via their dispersion measures.