Structural and spectral properties of Galactic plane variable radio sources
Artikel i vetenskaplig tidskrift, 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.

Galaxy: general

radio continuum: stars

Hii regions

radio continuum: galaxies



Jun Yang

Chalmers, Rymd-, geo- och miljövetenskap, Onsala rymdobservatorium

Joint Institute for VLBI ERIC

Yongjun Chen

Chinese Academy of Sciences


Joint Institute for VLBI in Europe (JIVE)

TU Delft

Zsolt Paragi

Joint Institute for VLBI in Europe (JIVE)

Aiyuan Yang

Max-Planck Institut für Radioastronomie

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


Astronomi, astrofysik och kosmologi



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