Updated radio Σ - D relation for galactic supernova remnants - II

Abstract

In this paper we present the updated empirical radio surface-brightness-to-diameter (Σ-D) relation for Galactic supernova remnants (SNRs) calibrated using 110 SNRs with reliable distances. We apply orthogonal fitting procedure and kernel density smoothing in Σ − D plane and compare the results with the latest theoretical Σ − D relations derived from simulations of radio evolution of SNRs. We argue that the best agreement between the empirical and simulated Σ − D relations is achieved if the mixed-morphology SNRs and SNRs of both, low brightness and small diameter, are filtered out from the calibration sample. The distances to 5 newly discovered remnants and 27 new candidates for shell SNRs are estimated from our full and filtered calibration samples.

Unexpected circular radio objects at high Galactic latitude

“…To quantify this, we use a subset of SNRs with measured distances (Vukotić et al 2019) to construct a model of the SNR distribution in the Galaxy. The distribution of z values (the distance from the mid-plane) of these SNRs is roughly Gaussian with a mean of 3.7 pc and a standard deviation of 127 pc.…”

Distances to the supernova remnants in the inner disk

“…The discrepancies of the other seven SNRs are larger than 2.0 kpc, and the most substantial difference even reaches 6.4 kpc. The recent works of Stafford et al (2019) and Vukotić et al (2019) also presented a tabulation of the distances for a large group of SNRs. We compare these distances with the radio-surface-brightness distances as well.…”

“…SNR G351.7+0.8 is a shell-like SNR, whose distance is estimated to be 13.2 ± 0.5 kpc based on an associated HI emission by Tian et al (2007), and 5.4 kpc using the radio surface-brightness-diameter relationship by Pavlović et al (2013). In Vukotić et al (2019), the adopted distances to G15.1-1.6, G73.9+0.9, G359.1-0.5 are 2.2, 1.25, 8.5 kpc, respectively, also apparently different from their d rad distances from Pavlović et al (2013) being 4.2, 4.0, 4.0 kpc. Moreover, the distances to some SNRs are still controversial, such as SNR G359.1-0.5.…”

“…( f ) The distances listed in this column d other are mainly kinematic distances fromGreen (2019b). The symbols , , •, , , ×, •, and denote distances determined by different methods fromVukotić et al (2019),Lee et al (2019),Ranasinghe & Leahy (2018),Misanovic et al (2010),Shan et al (2018),Kilpatrick et al (2016),Jackson et al (2008), andSuzuki et al (2020), respectively.…”

Energy Conservation in the Thin-Layer Approximation: V. The Surface Brightness in Supernova Remnants

“…The astrophysical approach to the Σ-D has always mixed the observations with the theory and the statistics. We select some items among others: a catalog of 25 SNRs has been compiled by [7] with the conclusion that SNRs in the galactic halo have diameters greater than those in the disk, the evolutionary properties of SNRs have been deduced from observations with the Molonglo and Parkes radio telescopes [8], the Σ-D relationship was used to fix the scale for distances of SNRs [9], the diameters, luminosities, surface brightness, galactic heights for 231 SNRs were processed in the framework of the Sedov solution [10], a new high-latitude SNR [11] was analysed, an updated radio Σ-D relationship was derived [12] and the phases of some supernova remnant have been determined from the observations [13]. In order to derive the Σ-D relationship, some hypotheses on the single equation of motion should be made, e.g., the conservation of the momentum [14].…”