The Cygnus X region XXIII. Is 18P87 galactic or extragalactic?

TL;DR

This paper investigates whether the radio source 18P87 is a galactic microquasar or an extragalactic radio galaxy, using multi-wavelength observations and HI absorption data, suggesting it is likely a Galactic jet.

Contribution

It provides new high-resolution radio imaging and multi-wavelength analysis to reclassify 18P87 as a Galactic microquasar rather than an extragalactic source.

Findings

18P87 has a core-jet structure in VLA maps.

HI absorption indicates a Galactic origin.

Archival data favor a microquasar interpretation.

Abstract

The radio source 18P87, previously thought to be a point source, has been serendipitously found to be resolved into a core-jet geometry in VLA maps. HI absorption of continuum emission (in data from the Canadian Galactic Plane Survey) appears in gas with radial velocities > +2 km/s but not in brightly emitting gas at lower radial velocity. Examination of further archival observations at radio, infrared and optical wavelengths suggests that the "obvious" interpretation as a radio galaxy requires a rather unusual object of this kind and a highly unusual local line of sight. We argue that 18P87 may be a Galactic object, a local astrophysical jet. If this is correct it could have arisen from outbursts of a microquasar.