The first optical light from the supernova remnant G182.4+4.3 located in the Galactic anticentre region

Abstract

We report the discovery of optical filamentary and diffuse emission from G182.4+4.3 using the 1.5‐m Russian–Turkish telescope. We present the optical CCD images obtained with the Hα filter, revealing the presence of mainly filamentary structure to the north‐west and filamentary and diffuse structure in the centre, south and north regions of the remnant. The bright optical filaments located in the north‐west and south regions are well correlated with the prominent radio shell of the remnant, strongly suggesting an association. From the flux‐calibrated CCD imaging, the average [S ii]/Hα ratio is found to be ∼0.9 and ∼1.1 for south and north‐west regions, respectively, which clearly indicates that the emission originates from shock‐heated gas. We also present the results of X‐ray data obtained from XMM–Newton, showing diffuse emission with a very low luminosity of ∼7.3 × 1031 erg s−1 at a distance of 3 kpc in the 0.3–10 keV energy band. Furthermore, we find a surprisingly low age of ∼4400 yr for this remnant, given its large radius of ∼22 pc.

Detection of extensive optical emission from the extremely radio faint Galactic supernova remnant G182.4+4.3

“…Moreover, if the remnant had a shock velocity of ∼2000 km s −1 , one would also expect to find widespread nonradiative Balmer dominated filament emissions like those seen in the remnants of Tycho's SNR (SN 1572) and SN 1006 (Kirshner et al 1987;Ghavamian et al 2002) especially along it limbs. Instead we find, as did Sezer et al (2012), ordinary shocked SNR optical emission filaments with strong emission from low ionization states such as [N II] and [S II].…”

“…The presence of strong [S II] and [N II] emissions but weak or absent [O III] emission is a signature of relatively low velocity shocks (≤70 km s −1 ) (Raymond 1979;Shull & McKee 1979;Hartigan et al 1987). However, such a conclusion is contrary to earlier estimates for G182.4+4.3's properties where it has been suggested to be a relatively young SNR with a shock velocity around 2000 km s −1 (Kothes et al 1998;Sezer et al 2012).…”

“…Knowledge of G182.4+4.3 true physical size would greatly aid in determining its evolutionary phase but this is unknown due to its uncertain distance. Kothes et al (1998) With an angular diameter of appromiately 43 based on our optical images, G182.4+4.3 would have a linear diameter of around 38 pc if placed at its initial estimated minimum distance of 3 kpc (Kothes et al 1998;Sezer et al 2012). However, a distance in excess of 3 kpc seems likely.…”

“…The optical filaments exhibited [S II]/Hα ratios of 0.9 to 1.1 ±0.1 based on flux-calibrated images, well above the standard SNR [S II]/Hα ratio criteria of 0.4 (Mathewson & Clarke 1972;D'Odorico et al 1980;Blair et al 1981;Dopita et al 1984), confirming the shocked nature of the detected optical emission. Sezer et al (2012) also reported finding associated X-ray emission based on XMM-Newton data and estimated a relatively young age of just 4400 yr assuming a distance of 3 kpc.…”

“…Optical emission associated with the G182.4+4.3 was first reported by Sezer et al (2012). Four 13.5 × 13.5 regions were imaged using on and off Hα and [S II] 6716,6731 narrow passband filters.…”