Pulsars, transients and relativistic astrophysics

Abstract:

Using a sample of 67 galaxies from the MeerKAT International GigaHertz Tiered Extragalactic Exploration Survey Early Science data, we study the H i-based baryonic Tully-Fisher relation (bTFr), covering a period of ∼1 billion years (0 ≤ z ≤ 0.081). We consider the bTFr based on two different rotational velocity measures: The width of the global H i profile and Vout, measured as the outermost rotational velocity from the resolved H i rotation curves. Both relations exhibit very low intrinsic scatter orthogonal to the best-fitting relation (σ⊥ = 0.07 ± 0.01), comparable to the SPARC sample at z 0. The slopes of the relations are similar and consistent with the z 0 studies (3.66+0.35-0.29 for W50 and 3.47+0.37-0.30 for Vout). We find no evidence that the bTFr has evolved over the last billion years, and all galaxies in our sample are consistent with the same relation independent of redshift and the rotational velocity measure. Our results set-up a reference for all future studies of the H i-based bTFr as a function of redshift that will be conducted with the ongoing deep SKA pathfinders surveys.

Abstract:

We report on a timing programme of 74 young pulsars that have been observed by the Parkes 64-m radio telescope over the past decade. Using modern Bayesian timing techniques, we have measured the properties of 124 glitches in 52 of these pulsars, of which 74 are new. We demonstrate that the glitch sample is complete to fractional increases in spin-frequency greater than $\Delta\nu^{90\%}_{g}/\nu \approx 8.1 \times 10^{-9}$. We measure values of the braking index, $n$, in 33 pulsars. In most of these pulsars, their rotational evolution is dominated by episodes of spin-down with $n > 10$, punctuated by step changes in the spin-down rate at the time of a large glitch. The step changes are such that, averaged over the glitches, the long-term $n$ is small. We find a near one-to-one relationship between the inter-glitch value of $n$ and the change in spin-down of the previous glitch divided by the inter-glitch time interval. We discuss the results in the context of a range of physical models.