Submillimeter observations of molecular gas interacting with the supernova remnant W28

Abstract

Context: Supernovae (SNe) inject large amounts of energy and chemically enriched materials into their surrounding interstellar medium and, in some instances, into molecular clouds (MCs). The interaction of a supernova remnant (SNR) with a MC plays a crucial role in the evolution of the cloud's physical and chemical properties. Despite their importance, only a handful of studies have been made addressing the molecular richness in MCs impacted by SNRs. (Sub)millimter wavelength observations of SNR-MC can be used to build a census of their molecular richness, which in turn can motivate various chemical and physical models aimed at explaining the chemical evolution of the clouds. Aims: We carried out multi-molecule/multi-transition observations toward the region F abutting the SNR W28. We used the detected lines to constrain the physical conditions of this region. Methods: We used the APEX Telescope to observe molecular lines in the frequency from $213-374\text{GHz}$. We used non-LTE RADEX modeling to interpret the observational data. Results: We detected emission from multiple molecular species, namely CH${}_3$OH, H${}_2$CO, SO, SiO, CN, CCH, NO, CS, HCO${}^{+}$, HCN, HNC, N${}_2$H${}^{+}$, CO, and from isotopologues of some of them. We report the first detection of thermally excited (non-maser) CH${}_3$OH emission toward a SNR. Employing non-LTE RADEX modeling of multiple H${}_2$CO and CH${}_3$OH lines, we constrain the kinetic temperature from 60 to 100K and the gas density from $9\times 10^5$ to $5\times 10^6\mathrm{c}{\mathrm{m}}^{-3}$. We obtained an ortho-para ratio $\sim$2 for H${}_2$CO, which indicates that formaldehyde is most likely formed on dust grain surfaces. Conclusions: Our results show that molecules as complex as H${}_2$CO and CH${}_3$OH can be detected in SNR-MC interactions. This could motivate chemical modelling to explore their formation pathways.

19 pages, 13 figures, 6 tables, accepted to A&A

References in corpus (13)

• Non-thermal desorption from interstellar dust grains via exothermic surface reactions
• SiO line emission from C-type shock waves : interstellar jets and outflows
• A New Reference Chemical Composition for TMC-1
• AGILE detection of GeV gamma-ray emission from the SNR W28
• Spitzer spectral line mapping of supernova remnants: I. Basic data and principal component analysis
• Galactic H2CO Densitometry I: Pilot survey of Ultracompact HII regions and methodology
• Kinetic temperature of massive star forming molecular clumps measured with formaldehyde
• Kinetic temperature of massive star forming molecular clumps measured with formaldehyde. II. The Large Magellanic Cloud
• APEX observations of supernova remnants - I. Non-stationary MHD-shocks in W44
• Sub-mm/mm studies of the molecular gas in the Galactic disk; the TeV gamma ray SNR RXJ1713.7-3946 and the W28 high mass star forming region
• Localized SiO emission triggered by the passage of the W51C SNR shock
• Interstellar anatomy of the TeV gamma-ray peak in the IC443 supernova remnant
• Shocked Molecular Hydrogen and Broad CO lines from the Interacting Supernova Remnant HB 3

Cited by in corpus (2)

• Kinetic temperature of massive star-forming molecular clumps measured with formaldehyde V. The massive filament DR21
• A Complete X-ray View of Supernova Remnant W28 with Einstein Probe: Spatial Distribution of Parameters and Origin of the Thermal-Composite Morphology