THOR survey in northern Galactic plane

After removing spurious source detections caused by the sidelobes of the synthesised beam, we classified 10387 sources as reliable detections.We smoothed the images to a common resolution of 25" and extracted the peak flux density of each source in each spectral window (SPW) to determine the spectral indices {alpha} (assuming I(nu){prop.to}nu^alpha^). By cross-matching with catalogs of HII regions, SNRs, PNe, and pulsars, we found radio counterparts for 840 HII regions, 52 SNRs, 164 PNe, and 38 pulsars.

We found 79 continuum sources that are associated with X-ray sources. We identified 699 ultrasteep spectral sources (alpha<-1.3) that could be high-redshift galaxies. Around 9000 of the sources we extracted are not classified specifically, but based on their spatial and spectral distribution, a large fraction of them is likely to be extragalactic background sources.

More than 7750 sources do not have counterparts in the SIMBAD database, and more than 3760 sources do not have counterparts in the NED database. Studying the long wavelengths cm continuum emission and the associated spectral indices allows us to characterize a large fraction of Galactic and extragalactic radio sources in the area of the northern inner Milky Way. This database will be extremely useful for future studies of a diverse set of astrophysical objects.