Distances, Radial Distribution, and Total Number of Galactic Supernova Remnants

Abstract

We present a table of 215 supernova remnants (SNRs) with distances. New distances are found to SNR G51.26 + 0.11 of 6.6 ± 1.7 kpc using H i absorption spectra and to five other SNRs using maser/molecular cloud associations. We recalculate the distances and errors to all SNRs using a consistent rotation curve and provide errors where they were not previously estimated. This results in a significant distance revisions for 20 SNRs. Because of observational constraints and selection effects, there is an apparent deficit of observed number of Galactic SNRs. To investigate this, we employ two methods. The first method applies correction factors for the selection effects to derive the radial density distribution. The second method compares functional forms for the SNR surface density and selection function against the data to find which functions are consistent with the data. The total number of SNRs in the Galaxy is ∼3500 (Method 1) or in the range from ∼2400 to ∼5600 (Method 2). We conclude that the current observed number of SNRs is not yet complete enough to give a well-determined total SNR number or radial density function.

A Systematic Study of Associations between Supernova Remnants and Molecular Clouds

“…Therefore, we suggest that the SNRC is associated with the +54.6 km s −1 component. Considering the presence of H I absorption up to the tangent point velocity shown by Ranasinghe & Leahy (2022), its kinematic distance is estimated as 5.8 ± 0.5 kpc.…”

“…(see also Table1inRanasinghe & Leahy 2022, for a summary of known SNR distances). For known SNRs, about 60% of them were found to be associated…”

A Statistical Analysis of Galactic Radio Supernova Remnants

“…The distances for this study are literature estimations (see Ranasinghe & Leahy 2022; the methods of the distance estimations and references therein). We have added six more SNRs (uncertain) to the list with distances bringing the total number of sources with distances to 221.…”

“…Green (2019) gives the current total of Galactic SNRs as 294. While the predicted total number of Galactic SNRs is a few thousand (Supan et al 2018;Ranasinghe & Leahy 2022), observations and identification of SNRs are greatly affected by selection effects.…”

EMU Detection of a Large and Low Surface Brightness Galactic SNR G288.8–6.3

“…The census of the Galactic supernova remnant (SNR) population is well understood to be underrepresented (Foster et al 2013;Dokara et al 2021;Ball et al 2023). Only ∼300 such objects are confirmed (Green 2022;Ferrand & Safi-Harb 2012), with expectations that up to an almost order of magnitude more could exist in the Milky Way (Ranasinghe & Leahy 2022). Most of the missing Galactic SNRs are expected to be low surface brightness or in complex regions where clear distinctions from other source types (e.g., H II regions) are challenging.…”