[Paper Review] Observations of the Planetary Nebula SMP LMC 058 with the JWST MIRI Medium Resolution Spectrometer

Olivia Jones, Javier Álvarez-Márquez+22 more|arXiv (Cornell University)|Jan 30, 2023

Astro and Planetary Science4 citations

TL;DR

This study presents the first medium-resolution mid-infrared spectroscopy of the planetary nebula SMP LMC 058 using the James Webb Space Telescope's MIRI Medium-Resolution Spectrometer (MRS), confirming its spectral resolving power between R = 1500 and 4000 across sub-bands. The data reveal previously undetected emission lines, confirm the presence of silicon carbide (SiC) dust, and show no significant time evolution in dust or line strengths over 17 years, demonstrating the MRS’s high sensitivity and capability for probing circumstellar and interstellar material in nearby galaxies.

ABSTRACT

During the commissioning of {\em JWST}, the Medium-Resolution Spectrometer (MRS) on the Mid-Infrared Instrument (MIRI) observed the planetary nebula SMP LMC 058 in the Large Magellanic Cloud. The MRS was designed to provide medium resolution (R = $λ$/$Δλ$) 3D spectroscopy in the whole MIRI range. SMP LMC 058 is the only source observed in {\em JWST} commissioning that is both spatially and spectrally unresolved by the MRS and is a good test of {\em JWST's} capabilities. The new MRS spectra reveal a wealth of emission lines not previously detected in this planetary nebula. From these lines, the spectral resolving power ($λ$/$Δλ$) of the MRS is confirmed to be in the range R $=$ 4000 to 1500, depending on the MRS spectral sub-band. In addition, the spectra confirm that the carbon-rich dust emission is from SiC grains and that there is little to no time evolution of the SiC dust and emission line strengths over a 17-year epoch. These commissioning data reveal the great potential of the MIRI MRS for the study of circumstellar and interstellar material.

Motivation & Objective

• To test the performance and capabilities of the JWST MIRI Medium-Resolution Spectrometer (MRS) on a spatially and spectrally unresolved source.
• To investigate the mid-infrared spectral characteristics of the planetary nebula SMP LMC 058 in the Large Magellanic Cloud.
• To determine the composition and evolutionary stability of dust and emission lines in this carbon-rich nebula.
• To assess the resolving power and sensitivity of the MRS across its spectral bands.
• To demonstrate the potential of the MIRI MRS for future studies of circumstellar and interstellar material in nearby galaxies.

Proposed method

• The MIRI Medium-Resolution Spectrometer (MRS) on the James Webb Space Telescope observed SMP LMC 058 during the telescope’s commissioning phase.
• The MRS is an integral field unit (IFU) that provides 3D spectroscopy across the 4.9–27.9 μm wavelength range with a field of view of 3.2"×3.7" to 6.6"×7.7".
• Spectral resolving power (R = λ/Δλ) was measured from the observed line profiles across different sub-bands of the MRS.
• Emission lines in the spectra were identified and analyzed to determine the chemical and dust composition of the nebula.
• The observed spectra were compared with archival data from Spitzer/IRS to assess time evolution over a 17-year baseline.
• The presence of silicon carbide (SiC) dust was confirmed by the detection of characteristic emission features at 11.3 μm and 21.2 μm.

Experimental results

Research questions

• RQ1 What is the actual spectral resolving power of the MIRI MRS across its different sub-bands?
• RQ2 What new emission lines are revealed in the mid-infrared spectrum of SMP LMC 058 using JWST?
• RQ3 What is the composition of the dust in SMP LMC 058, and is it consistent with silicon carbide (SiC)?
• RQ4 Are the strengths of the emission lines and dust features stable over a 17-year timescale?
• RQ5 To what extent can the MIRI MRS resolve and characterize circumstellar and interstellar material in extragalactic sources?

Key findings

• The MIRI MRS achieved a spectral resolving power of R ≈ 4000 in the short-wavelength sub-band and R ≈ 1500 in the long-wavelength sub-band.
• The spectra revealed a wealth of previously undetected emission lines, including features from high-excitation ions and molecular species.
• The presence of silicon carbide (SiC) dust was confirmed by the detection of characteristic emission features at 11.3 μm and 21.2 μm.
• No significant time evolution was observed in the SiC dust emission or in the strengths of the detected emission lines over a 17-year baseline.
• The lack of high-excitation lines in the spectrum supports the stability of SiC grains, as such lines would indicate a hard radiation field that could destroy them.
• The commissioning data demonstrate the MIRI MRS’s exceptional sensitivity and resolving power for studying solid-state features, molecular lines, and ionized gas in circumstellar and interstellar environments.