ALMA CO Observations of Gamma-Ray Supernova Remnant N132D in the Large Magellanic Cloud: Possible Evidence for Shocked Molecular Clouds Illuminated by Cosmic-Ray Protons

Abstract

N132D is the brightest gamma-ray supernova remnant (SNR) in the Large Magellanic Cloud (LMC). We carried out ${}^{12}$CO($J$ = 1-0, 3-2) observations toward the SNR using the Atacama Large Millimeter/submillimeter Array (ALMA) and Atacama Submillimeter Telescope Experiment. We find diffuse CO emission not only at the southern edge of the SNR as previously known, but also inside the X-ray shell. We spatially resolved nine molecular clouds using ALMA with an angular resolution of $5^{\prime \prime }$, corresponding to a spatial resolution of $\sim$1 pc at the distance of the LMC. Typical cloud sizes and masses are $\sim$2.0 pc and $\sim$100 $M_{\odot }$, respectively. High-intensity ratios of CO $J$ = 3-2 / 1-0 $>1.5$ are seen toward the molecular clouds, indicating that shock-heating has occurred. Spatially resolved X-ray spectroscopy reveals that thermal X-rays in the center of N132D are produced not only behind a molecular cloud, but also in front of it. Considering the absence of a thermal component associated with the forward shock towards one molecular cloud located along the line of sight to the center of the remnant, this suggests that this particular cloud is engulfed by shock waves and is positioned on the near side of remnant. If the hadronic process is the dominant contributor to the gamma-ray emission, the shock-engulfed clouds play a role as targets for cosmic-rays. We estimate the total energy of cosmic-ray protons accelerated in N132D to be $\sim$0.5-$3.8\times 10^{49}$ erg as a conservative lower limit, which is similar to that observed in Galactic gamma-ray SNRs.

18 pages, 2 tables, 11 figures, accepted for publication in The Astrophysical Journal (ApJ)

References in corpus (18)

• HI4PI: A full-sky HI survey based on EBHIS and GASS
• An eclipsing binary distance to the Large Magellanic Cloud accurate to 2 per cent
• Multi-Scale CLEAN deconvolution of radio synthesis images
• On the use of C-stat in testing models for X-ray spectra
• Dust Destruction in Fast Shocks of Core-Collapse Supernova Remnants in the Large Magellanic Cloud
• The Bubble-like Interior of the Core-Collapse Supernova Remnant Cassiopeia A
• Cosmic ray production in supernovae
• Sparsity and adaptivity for the blind separation of partially correlated sources
• Interstellar protons in the TeV gamma-ray SNR HESS J1731-347:Possible evidence for the coexistence of hadronic and leptonic gamma-rays
• X-Ray Emitting Ejecta of Supernova Remnant N132D
• A detailed study of the interstellar protons toward the TeV $\gamma$-ray SNR RX J0852.0$-$4622 (G266.2$-$1.2, Vela Jr.); a third case of the $\gamma$-rays and ISM spatial correspondence
• Dense Clumps in Giant Molecular Clouds in the Large Magellanic Cloud: Density and Temperature Derived from ${}^{13}$CO($J=3-2$) Observations
• Evidence for Shocked Molecular Gas in the Galactic SNR CTB 109 (G109.1-1.0)
• Three-Dimensional Kinematic Reconstruction of the Optically-Emitting, High-Velocity, Oxygen-Rich Ejecta of Supernova Remnant N132D
• A novel method for component separation of extended sources in X-ray astronomy
• Spatially Resolved Chandra Spectroscopy of the Large Magellanic Cloud Supernova Remnant N132D
• Dust destruction in non-radiative shocks
• A Preliminary Chandra X-ray Spectroscopy of the Supernova Remnant N132D

Cited by in corpus (19)

• ALMA CO Observations of the Mixed-Morphology Supernova Remnant W49B: Efficient Production of Recombining Plasma and Hadronic Gamma-rays via Shock-Cloud Interactions
• New Optically Identified Supernova Remnants in the Large Magellanic Cloud
• TeV cosmic ray nuclei acceleration in shell-type supernova remnants with hard $\gamma$-ray spectra
• ALMA CO Observations of the Gamma-Ray Supernova Remnant RX J1713.7-3946: Discovery of Shocked Molecular Cloudlets and Filaments at 0.01 pc scales
• The interstellar medium in young supernova remnants: key to the production of cosmic X-rays and $\gamma$-rays
• An Expanding Shell of Neutral Hydrogen Associated with SN 1006: Hints for the Single-Degenerate Origin and Faint Hadronic Gamma-Rays
• Forbidden Line Emission from Type Ia Supernova Remnants Containing Balmer-Dominated Shells
• New ASKAP Radio Supernova Remnants and Candidates in the Large Magellanic Cloud
• LMC N132D: A mature supernova remnant with a power-law gamma-ray spectrum extending beyond 8 TeV
• Molecular and Atomic Clouds Associated with the Gamma-Ray Supernova Remnant Puppis A
• Using Anisotropies as a Forensic Tool for Decoding Supernova Remnants
• High resolution X-ray study of supernova remnant J0453.6$-$6829 with unusually high forbidden-to-resonance ratio
• Supernova remnant G46.8-0.3, a new case of interaction with molecular material
• HST Proper Motion Measurements of Supernova Remnant N132D: Center of Expansion and Age
• Infrared Ejecta and Cold Dust in the Young Supernova Remnant N132D
• Measurement of the Forward Shock Velocities of the Supernova Remnant N132D Based on the Thermal X-ray Emission
• XMM-Newton Observations of the High Temperature Plasma in the Large Magellanic Cloud Supernova Remnant N132D
• IRAM 30 m CO-line Observation toward PeVatron Candidate G106.3+2.7: Direct Interaction between the Shock and the Molecular Cloud Remains Uncertain
• LMC N132D: a mature supernova remnant with a youthful gamma-ray spectrum