射电天文研究室知识库

We derive the Sun's offset from the local mean Galactic plane (z(circle dot)) using the observed z-distribution of young pulsars. Pulsar distances are obtained from measurements of annual parallax, HI absorption spectra or associations where available and otherwise from the observed pulsar dispersion and a model for the distribution of free electrons in the Galaxy. We fit the cumulative distribution function for a sech(2)(z)-distribution function, representing an isothermal self-gravitating disc, with uncertainties being estimated using the bootstrap method. We take pulsars having characteristic age tau(c) less than or similar to 10(6.5) yr and located within 4.5 kpc of the Sun, omitting those within the local spiral arm and those significantly affected by the Galactic warp, and solve for z(circle dot) and the scaleheight, H, for different cut-offs in tau(c). We compute these quantities using just the independently determined distances and these together with dispersion measure (DM)-based distances separately using the YMW16 and NE2001 Galactic electron density models. We find that an age cut-off at 10(5.75) yr with YMW16 DM distances gives the best results with a minimum uncertainty in z(circle dot) and an asymptotically stable value for H showing that, at this age and below, the observed pulsar z-distribution is dominated by the dispersion in their birth locations. From this sample of 115 pulsars, we obtain z(circle dot) = 13.4 +/- 4.4 pc and H = 56.9 +/- 6.5 pc, similar to estimated scaleheights for OB stars and open clusters. Consistent results are obtained using the independent-only distances and using the NE2001 model for the DM-based distances.