A Systematic Study of Associations between Supernova Remnants and Molecular Clouds

Abstract

We universally search for evidence of kinematic and spatial correlation of supernova remnant (SNR) and molecular cloud (MC) associations for nearly all SNRs in the coverage of the Milky Way Imaging Scroll Painting CO survey, i.e., 149 SNRs, 170 SNR candidates, and 18 pure pulsar wind nebulae in 1° < l < 230° and −5.°5 < b < 5.°5. Based on high-quality and unbiased 12CO/13CO/C18O (J = 1–0) survey data, we apply automatic algorithms to identify broad lines and spatial correlations for molecular gas in each SNR region. The 91% of SNR–MC associations detected previously are identified in this paper by CO line emission. Overall, there could be as high as 80% of SNRs associated with MCs. The proportion of SNRs associated with MCs is high within the Galactic longitude less than ∼50°. Kinematic distances of all SNRs that are associated with MCs are estimated based on systemic velocities of associated MCs. The radii of SNRs associated with MCs follow a lognormal distribution, which peaks at ∼8.1 pc. The progenitor initial mass of these SNRs follows a power-law distribution with an index of ∼−2.3 that is consistent with the Salpeter index of −2.35. We find that SNR–MC associations are mainly distributed in a thin disk along the Galactic plane, while a small number are distributed in a thick disk. With the height of these SNRs from the Galactic plane below ∼45 pc, the distribution of the average radius relative to the height of them is roughly flat, and the average radius increases with the height when above ∼45 pc.

Cannonball or Bowling Ball: Proper Motion and Parallax for PSR J0002+6216

“…The proper motion, now reduced in magnitude but with substantially less uncertainty, combined with the expansion of CTB 1 seem to be indicative of a fairly large ISM density. The implied value would be beyond the low density (∼0.1-1.0 cm −3 ) which has typically been inferred from the remnant's relatively weak Hα emission (Landecker et al 1982) or from the nondetection of tracers such as CO (Zhou et al 2023). While this can be somewhat mitigated if one assumes a weaker supernova energy (E 51 < 1), the collimation of the pulsar's bow shock is decoupled from this term and still requires a higher density given this lower velocity.…”

An X-Ray Synchrotron Shell and a Pulsar: The Peculiar Supernova Remnant G32.4+0.1

“…Various distances d to the shell have been quoted: Yamaguchi et al (2004) divided their N H value of 5.2 × 10 22 cm −2 by an assumed mean interstellar medium hydrogen density of 1 cm −3 to obtain d = 17 kpc, while Kilpatrick et al (2016) used the velocity of broadened CO J = 2 -1 emission (∼+45 km s −1 ) seen toward the eastern shell of G32.4+0.1 to obtain 11.8-18.5 kpc from rotation curves. A cavity in 12 CO (1 -0) emission at a velocity of 10.8 km s −1 surrounding G32.4+0.1 was identified in a survey of firstquadrant SNRs (Sofue et al 2021), but the survey by Zhou et al (2023) found broad CO (1 -0) line features associated with G32.4+0.1 at a velocity giving d = 10.1 ± 0.4 kpc. Though an association of the shell and the pulsar is subject to question (see below), we shall use the pulsar distance of 11 kpc as the distance to the shell.…”

Cloud Formation by Supernova Implosion

“…To our knowledge, there are no instances of SN implosions reported in observations. This might, however, simply attest to the fact that radiative SNRs, in particular those close to merging with the ISM, are very dim and thus are often difficult to observe (Green 2019; Koo et al 2020;Zhou et al 2023). Moreover, the fact that the morphology of imploding SNRs differs qualitatively from traditional SNRs might have led to a misclassification of imploding SNRs as something other than an SNR.…”