New optically identified supernova remnants in the Large Magellanic Cloud

Abstract

We present a new optical sample of three Supernova Remnants (SNRs) and 16 Supernova Remnant (SNR) candidates in the Large Magellanic Cloud (LMC). These objects were originally selected using deep Hα, [S ii] and [O iii] narrow-band imaging. Most of the newly found objects are located in less dense regions, near or around the edges of the LMC’s main body. Together with previously suggested MCSNR J0541–6659, we confirm the SNR nature for two additional new objects: MCSNR J0522–6740 and MCSNR J0542–7104. Spectroscopic follow-up observations for 12 of the LMC objects confirm high [S ii]/Hα emission-line ratios ranging from 0.5 to 1.1. We consider the candidate J0509–6402 to be a special example of the remnant of a possible type Ia Supernova (SN) which is situated some 2○ (∼1.75 kpc) north from the main body of the LMC. We also find that the SNR candidates in our sample are significantly larger in size than the currently known LMC SNRs by a factor of ∼2. This could potentially imply that we are discovering a previously unknown but predicted, older class of large LMC SNRs that are only visible optically. Finally, we suggest that most of these LMC SNRs are residing in a very rarefied environment towards the end of their evolutionary span where they become less visible to radio and X-ray telescopes.

Radio continuum sources behind the Large Magellanic Cloud

“…These matches are most likely intrinsic to the LMC (see e.g. Yew et al 2021). Radio sources with optical counterparts as detected in MCELS have been excluded from further analysis in this work.…”

“…The LMC is currently ∼50 kpc (Pietrzyński et al 2013(Pietrzyński et al , 2019Riess et al 2019) from the centre of the MW, while the SMC is further away at a distance of ∼60 kpc (Hilditch, Howarth & Harries 2005). In addition, this well-known distance and motion of the LMC allow for accurate calculations of the total energy that has been released from supernova remnants (SNRs; E-mail: m.filipovic@uws.edu.au Maggi et al 2016Maggi et al , 2019Bozzetto et al 2017;Leahy et al 2019;Yew et al 2021). A detailed optical study of 715 LMC Planetary Nebulae (PNe) is presented by Reid & Parker (2013) and Reid (2014).…”

Radio Continuum Sources behind the Large Magellanic Cloud

“…Additionally, extensive cross checking with the Magellanic Cloud Emission Line Survey (MCELS) in H𝛼, [S ], and [O ] images presented by Smith & MCELS Team (1998) has been performed to identify sources in both the optical and radio bands. These matches are most likely intrinsic to the LMC (see for example Yew et al 2021). Radio sources with optical counterparts as detected in MCELS have been excluded from further analysis in this work.…”

“…The LMC is currently ∼50 kpc (Pietrzyński et al 2013(Pietrzyński et al , 2019Riess et al 2019) from the centre of the MW, while the SMC is further away at a distance of ∼60 kpc (Hilditch et al 2005). In addition, this well-known distance and motion of the LMC allows for accurate calculations of the total energy that has been released from Supernova Remnants (SNRs) (Maggi et al 2016;Bozzetto et al 2017;Maggi et al 2019;Leahy et al 2019;Yew et al 2021). A detailed optical study of 715 LMC Planetary Nebulae (PNe) is presented by Reid & Parker (2013) and Reid (2014).…”

Polarization of fluorescence lines: tracing magnetic field from circumstellar medium to early universe

“…The optical emission lines from elements such as Sulfur, Oxygen, Carbon, and even heavier Iron, Chromium, have been broadly utilized in astronomy. For decades, the emission lines have been used to study the universe near and far: comet and satellite in our solar system (Decock et al 2015;Trauger et al 1997), circumstellar regions in Magellanic Cloud (Smith & MCELS Team 1999;Hung et al 2021), chemistry of supernova remnant (Sahu et al 2011;Yew et al 2021), and even other galaxies (Dopita et al 2000;Kewley et al 2001), etc.…”