Search for differences between radio-loud and radio-quiet gamma-ray pulsar populations with Fermi-LAT data

Abstract

Observations by Fermi LAT enabled us to explore the population of non-recycled gamma-ray pulsars with the set of 89 objects. It was recently noted that there are apparent differences in properties of radio-quiet and radio-loud subsets. In particular, average observed radio-loud pulsar is younger than radio-quiet one and is located at smaller galactic latitude. Even so, the analysis based on the full list of pulsars may suffer from selection effects. Namely, most of radio-loud pulsars are first discovered in the radio-band, while radio-quiet ones are found using the gamma-ray data. In this work we perform a blind search for gamma-ray pulsars using the Fermi LAT data alone using all point sources from 3FGL catalog as the candidates. Unlike preceding blind search, the present catalog is constructed with novel semi-coherent method and covers the full range of characteristic ages down to 1 kyr. The search resulted in the catalog of 40 non-recycled pulsars, 26 of which are radio-quiet. There are no statistically significant differences in age and galactic latitude distributions for the radio-loud and radio-quiet pulsars, while the rotation period distributions are marginally different with $2.4\sigma$ pre-trial statistical significance. The fraction of radio-quiet pulsars is estimated as $\epsilon_{RQ}=63\pm 8\%$. The results are in agreement with the predictions of the outer magnitosphere models, while the Polar cap models are disfavored.