The environment of supernova remnant VRO 42.05.01 as probed with IRAM 30m molecular line observations

Abstract

Context. The environment of supernova remnants (SNRs) is a key factor in their evolution, particularly at later stages of their existence. Mixed-morphology (MM) SNRs have a peculiar centre-filled X-ray shape that remains enigmatic. It is often assumed that they evolve in very dense environments, and that the X-ray morphology is due to interactions between the SNRs and their surroundings. Aims. We aim to determine whether VRO 42.05.01 is embedded in, and interacting with, a dense molecular environment. We also aim to understand the multi-wavelength emission from the environment of this SNR, and whether the interstellar material can be responsible for the the MM nature of the source, and for its strange radio and optical shape. Methods. We used the IRAM telescope in Pico Veleta, Spain, to search for signs of interaction between the SNR and neighbouring molecular clouds. We observed a region of 26 × 14 towards the west of VRO 42.05.01 and a region of 8 × 4 towards the north of the remnant in the 12 CO J = 1 − 0, 13 CO J = 1 − 0, and 12 CO J = 2 − 1 transitions with the EMIR receiver. We made maps of the properties of the observed molecular clouds (peak temperatures, central velocities, velocity dispersions), as well as maps of column density along the line of sight, and ratio of the 12 CO J = 2 − 1 to 12 CO J = 1 − 0 transitions. We also analyse archival optical, infrared, and radio spectroscopic data for other hints on the nature of the medium. Results. We do not find conclusive physical proof that the SNR is interacting with the few, clumpy molecular clouds that surround it in the region of our observations, although there is some suggestion of such interaction (in a region outside our map) from infrared emission. We find that there is a velocity gradient in one of the molecular clouds that is consistent with a stellar wind blown by a 12−14 M progenitor star. We reassess the literature distance to VRO 42.05.01, and propose that it has a local standard of rest velocity of −6 km s −1 , and that it is located 1.0 ± 0.4 kpc away (the earlier distance value was 4.5 ± 1.5 kpc). We find that a dust sheet intersects VRO 42.05.01 and is possibly related to its double shell-shaped morphology.

IRAM 30 m CO-line Observation toward PeVatron Candidate G106.3+2.7: Direct Interaction between the Shock and the Molecular Cloud Remains Uncertain

“…Therefore, we suggest that the expanding structure and the velocity gradient of the molecular gas could be due to the progenitor wind of G106.3+2.7. We note that similar structures due to progenitor winds have also been found in a few other SNRs, such as Tycho (Zhou et al 2016;Chen et al 2017), N132D (Sano et al 2020), and VRO 42.05.01 (Arias et al 2019).…”

VRO 42.05.01: A supernova remnant resulted by a supersonic, mass losing progenitor star

“…However, the wind properties are determined by the natural size of VRO, which in turn is determined by the distance of the object. Given that VRO distance is not well defined (Landecker et al, 1989;Arias et al, 2019a), the properties of the anisotropic wind that shaped the cavity around VRO, and thus the nature of the progenitor star, are up to date, not well constrained. A sequence of papers relevant to VRO will be published soon (VRO's optical observations; Boumis et al (2019) and VRO's 3D morphokinematical modeling; Derlopa et al 2019) that are expected to limit the parameter space of the remnant's physical quantities and consequently provide vital insights on the unknown nature of VRO 42.05.01.…”

“…Subsequently, the interaction of the SNR with the surrounding Mach cone formed the triangular-shaped 'wing'. However, recent observations of VRO and its environment did not reveal any physical proof of an interaction between the remnant and a non-homogeneous surrounding medium (Arias et al, 2019a). This fact in combination with the lack of any detailed modeling of VRO retains its origin largely unknown.…”

First 3D Morpho-Kinematic model of Supernova Remnants. The case of VRO 42.05.01 (G 166.0+4.3)

“…That means that the "shell" goes inwards the page, while the "hat" component goes outwards from the page. Concerning the "wing" component, the model showed that its northern part is bent with respect to its eastern counterpart, implying a possible interaction with a denser ambient medium at this part of the remnant (see also Arias et al 2019b). In addition, a part of the "wing" penetrates the central region of the "shell" at its front side (see Fig.…”

“…The part of the remnant that evolved into the denser region created the "shell" component, while the rest diffused into a hotter and tenuous medium and shaped the "wing" component. However, according to the recent results presented by Arias et al (2019b), there is no physical proof of an interaction of the remnant with the surrounding molecular clouds and they attributed the almost triangular shape of the "wing" to a Mach cone cavity which was created by a supersonically moving progenitor star and was filled out by the SN ejecta. Finally, Chiotellis et al (2019) modeled the observed morphology of VRO with 2D hydrodynamic simulations, suggesting that the remnant is currently interacting with the density wall of a wind bubble sculptured by the equatorial confined mass outflows of a supersonically moving progenitor star.…”