The Nature of the Strong 24 micron Spitzer Source J222557+601148: Not a Young Galactic Supernova Remnant

TL;DR

This study re-evaluates the nature of the nebula J222557+601148, concluding it is a planetary nebula rather than a supernova remnant based on optical spectra, morphology, and multi-wavelength observations.

Contribution

The paper provides a comprehensive multi-wavelength analysis that challenges previous classification, identifying the nebula as a planetary nebula instead of a supernova remnant.

Findings

Optical spectra show narrow emission lines with no high-velocity features.

Absence of shock-heated gas indicators and X-ray/radio emissions.

Elliptical morphology consistent with planetary nebulae.

Abstract

The nebula J222557+601148, tentatively identified by Morris et al. (2006) as a young Galactic supernova remnant (SNR) from Spitzer Galactic First Look Survey images and a follow-up mid-infrared spectrum, is unlikely to be a SNR remnant based on Halpha, [O III], [S II] images and low dispersion optical spectra. The object is seen in Halpha and [O III] 5007 images as a faint, roughly circular ring nebula with dimensions matching that seen in 24 micron Spitzer images. Low-dispersion optical spectra show it to have narrow Halpha and [N II] 6548, 6583 line emissions with no evidence of broad or high-velocity (v > 300 km/s) line emissions. The absence of any high-velocity optical features, the presence of relatively strong [N II] emissions, a lack of detected [S II] emission which would indicate the presence of shock-heated gas, plus no coincident X-ray or nonthermal radio emissions indicate the nebula is unlikely to be a SNR, young or old. Instead, it is likely a faint, high-excitation planetary nebula (PN) as its elliptical morphology would suggest, lying at a distance of approximately 2 - 3 kpc with unusual but not extraordinary mid-IR colors and spectrum. We have identified a m_r' = 22.4 +/- 0.2 star as a PN central star candidate.