HI Line Measurements of Pulsars towards the Gum Nebula and the Carina Arm
Simon Johnston (
RCfTA ), Bärbel Koribalski (ATNF),
Joel Weisberg
( Carlton College , USA),
and Warrick Wilson (ATNF)
Abstract. We have observed 21-cm absorption and emission spectra in the direction of 7 southern pulsars with the Parkes telescope to derive their kinematic distances and to study the interstellar medium. In each case we thoroughly investigate the environment of each pulsar as well as sources along the line of sight which may contribute to the pulsars' dispersion measure. For the first time we have successfully obtained HI absorption measurements for PSRs J0942-5552, J1048-5832, J1224-6424 and J1401-6357. We have also significantly improved the sensitivity and resolution on PSRs J0738-4042, J0837-4135 and J1157-6224, whose spectra have been measured previously, and measured the transverse velocities of PSRs J0837-4135 and J0942-5552 by analysing their scintillation properties. These 7 pulsars fall into two groups, those which lie behind the Gum Nebula and those which are in the direction of the Carina spiral arm. We present our absorption and emission spectra for these pulsars, derive kinematic distances and electron densities along their lines of sight where possible, and compare our results with previous work. We show that the Taylor & Cordes distance-model works reasonably well for pulsars located behind the Gum Nebula. Following from our earlier work, we show further evidence for strong deviations from a simple Galactic rotation law in the velocities of the HI gas towards the Carina Arm.
headings: general - radio lines: stars - stars: distances, luminosities, supernova remnants