Effect of errors on arm asymmetry of doubles

TL;DR

This paper investigates how measurement errors and resolution issues affect the observed distribution of arm asymmetry in double radio sources, revealing both random and systematic biases that influence the inferred hotspot separation speeds.

Contribution

It quantifies the impact of measurement errors and resolution limitations on the distribution of arm asymmetry and hotspot speeds in double radio sources.

Findings

Errors broaden the arm asymmetry distribution g(x).

Errors shift the hotspot speed distribution p(v) to higher values.

Systematic overestimation occurs due to peak recognition errors.

Abstract

Measured values of arm asymmetry parameter x = (theta> - theta<)/(theta> + theta<) of a double have appreciable random errors due to errors in positions of radio peaks & of the optically identified galaxy or quasar. These broaden the monotonic decreasing x-distribution g(x). In addition, finite resolution & blending of complex structure leads to errors in recognizing peaks leading to systematic overestimate of x. Thus both random & systematic errors broaden g(x), & consequently broaden the distribution p(v) of derived hotspot separation speed v, & shift its peak to larger v, since p(v) = -v.g'(v). Keywords: active galaxies - double radio sources - bilateral symmetry - arm asymmetry