Structural and spectral properties of Galactic plane variable radio sources
Journal article, 2022

In the time domain, the radio sky in particular along the Galactic plane direction may vary significantly because of various energetic activities associated with stars, stellar, and supermassive black holes. Multi-epoch Very Large Array surveys of the Galactic plane at 5.0 GHz enabled the finding of a catalogue of 39 variable radio sources in the flux density range 1-70 mJy. To probe their radio structures and spectra, we observed 17 sources with the very-long-baseline interferometric (VLBI) imaging technique and collected additional multifrequency data from the literature. We detected all of the sources at 5 GHz with the Westerbork Synthesis Radio Telescope, but only G23.6644-0.0372 with the European VLBI Network (EVN). Together with its decadal variability and multifrequency radio spectrum, we interpret it as an extragalactic peaked-spectrum source with a size of less than or similar to 10 pc. The remaining sources were resolved out by the long baselines of the EVN because of either strong scatter broadening at the Galactic latitude < 1 degrees or intrinsically very extended structures on centi-arcsec scales. According to their spectral and structural properties, we find that the sample has a diverse nature. We notice two young H ii regions and spot a radio star and a candidate planetary nebula. The rest of the sources are very likely associated with radio active galactic nuclei (AGNs). Two of them also display arcsec-scale faint jet activity. The sample study indicates that AGNs are common place even among variable radio sources in the Galactic plane.

Hii regions

scattering

Galaxy: general

radio continuum: galaxies

radio continuum: stars

Author

Jun Yang

Chalmers, Space, Earth and Environment, Onsala Space Observatory

Joint Institute for VLBI in Europe (JIVE)

Yongjun Chen

Chinese Academy of Sciences

Gurvits

Delft University of Technology

Joint Institute for VLBI in Europe (JIVE)

Zsolt Paragi

Joint Institute for VLBI in Europe (JIVE)

Aiyuan Yang

Max-Planck Institute for Radio Astronomy

Xiaolong Yang

Chinese Academy of Sciences

Zhiqiang Shen

Chinese Academy of Sciences

Monthly Notices of the Royal Astronomical Society

0035-8711 (ISSN) 1365-2966 (eISSN)

Vol. 511 1 280-294

Subject Categories

Astronomy, Astrophysics and Cosmology

DOI

10.1093/mnras/stab3804

More information

Latest update

10/10/2023