G321.3-3.9: A new supernova remnant observed with multi-band radio data and in the SRG/eROSITA All-Sky Surveys (2401.17294v2)

Abstract: G321.3-3.9 was first identified as a partial shell at radio frequencies a few decades ago. Although it continued to be observed, no additional studies were undertaken until recently. In this paper we present results from a large selection of radio and X-ray data that cover the position of G321.3-3.9. We confirmed G321.3-3.9 as a new supernova remnant (SNR) using data collected by several radio surveys, spanning a frequency range from 200 to 2300 MHz. Stacked eROSITA data from four consecutive all-sky surveys (eRASS:4) provide spectro-imaging information in the energy band 0.2 - 8.0 keV. G321.3-3.9 has an elliptical shape with major and minor axes of approximately 1.7 deg x 1.1 deg. From CHIPASS and S-PASS data, we calculate a spectral index {\alpha} = -0.8 +- 0.2, consistent with synchrotron emission from an expanding shell in the radiative phase. The eROSITA data show an X-ray diffuse structure filling almost the entire radio shell. Based on our spectral analysis, we found the temperature to be approximately 0.6 keV and the column absorption density about 10^21 cm^-2. Comparing this absorption density to optical extinction maps, we estimated the distance to fall within the range of (1.0 - 1.7) kpc, considering the 1{\sigma} uncertainty range.

• The paper confirms G321.3-3.9 as a supernova remnant using multi-band radio and eROSITA X-ray observations that reveal an elliptical shell structure.
• The study calculates a synchrotron spectral index of -0.8±0.2, supporting the identification of the remnant in its radiative phase.
• The paper estimates the remnant’s distance to be between 1.0 and 1.7 kpc, providing key insights into its galactic context and chemical enrichment roles.

Analysis of G321.3-3.9: Confirmation as a Supernova Remnant

The paper "G321.3--3.9: A new supernova remnant observed with multi-band radio data and in the SRG/eROSITA All-Sky Surveys" provides an in-depth examination and confirmation of the astronomical object G321.3-3.9 as a supernova remnant (SNR). Utilizing multi-band radio and X-ray data, this research delineates a path towards understanding the composition and morphology of G321.3-3.9, alongside placing constraints on its physical parameters including shape, spectral index, and distance.

Key Findings and Methodology

1. Multi-band Confirmatory Approach: The identification of G321.3-3.9 as a SNR is achieved using data from several radio surveys operating across a wide frequency range from 200 MHz to 2300 MHz. These radio observations present an elliptical shell structure with dimensions approximately 1.7° by 1.1°. Additionally, data from the eROSITA X-ray telescope corroborates the radio observations by revealing diffuse X-ray emissions that encompass much of the radio shell, suggesting a mixed morphology indicative of SNRs.
2. Spectral Index and Emission Analysis: The researchers calculate a spectral index of $\alpha = -0.8 \pm 0.2$ based on data from CHIPASS and S-PASS surveys. This value is consistent with synchrotron emission linked to SNRs in a radiative phase, further strengthening the classification of G321.3-3.9 as a supernova remnant.
3. Distance Estimations: The eROSITA data provide an estimate of the remnant's distance as falling within 1.0 to 1.7 kpc, based on column density and extinction correlations with optical maps. These well-founded distance constraints afford better insights into the spatial context and potential origins of the remnant within the Milky Way.
4. Spectral Analysis and Element Abundance: X-ray spectral analysis exhibits certain elemental abundance patterns and temperatures. The temperature is estimated around 0.6 keV, and the abundance measurements, while exhibiting large uncertainties due to photon statistics, suggest an ironic depletion of elements such as Ne and Mg. This phenomenon could potentially hint at a thermonuclear supernova origin, although confirmation requires further analysis.

Implications and Future Directions

The confirmation of G321.3-3.9 as a SNR presents several direct implications for the broader field of astrophysics:

• Understanding of Galactic Chemical Evolution: As supernova remnants are key sources in dispersing elements through the interstellar medium, studies like this contribute to understanding the chemical evolution within the galaxy.
• Role in Cosmic Ray Production: The nonthermal synchrotron emission is indicative of ongoing particle acceleration, aligning with theories that SNRs are significant contributors to cosmic ray populations.
• Pacing Future Observations: The paper highlights the need for deeper surveys across multiple wavelengths to identify and confirm more such objects, which are instrumental in piecing together the history of supernova activities and their remnants in the galaxy.

Conclusion

This paper offers a comprehensive confirmation of the G321.3-3.9 as a supernova remnant utilizing both radio and X-ray data across various bands. The methodologies employed and the corroborative findings are reflective of a detailed and systematically conducted classification process. With the parameters established, G321.3-3.9 stands as a valuable case paper for advancing theoretical models of SNR aging, dynamics, and chemical enrichment influence in the galactic environment. Future research can build upon this work by integrating more extensive sky surveys and possibly resolving some of the uncertainties regarding elemental abundance and morphological anomalies in such remnants.