April 2026
Estimating ionization fractions in SILCC simulations (Lennart Buhlmann)
OBSERVATION OF SUPERNOVA REMNANT INTERACTING WITH MOLECULAR CLOUD
It is rare to find supernova remnants (SNRs) interacting with their nascent clouds despite the short lifetimes of massive stars. This is due to the fact that supernovae are typically clustered and the first supernova will clear the molecular cloud; subsequent supernovae then explode in the rarefied post-shock gas. One example of a SNR interacting with a giant molecular cloud (GMC) is CTB 109. CTB 109 is an X-ray luminous SNR, located at a distance of 3.2 kpc in the Perseus arm. Due to its semicircular morphology in both X-ray and radio, it is thought that the SNR shock has encountered the GMC and been stopped. Parts of the GMC extend in-front of CTB 109 and are seen in absorption in the X-rays, the most prominent being the "CO-arm" (Figure 1). Thus CTB 109 is an excellent site to study the impact a SNR shock has on an extended high column density cloud.
We have observed the easternmost tip of the CO arm using the IRAM 30m telescope. Our observations include the CO (J=1-0) and (J=2-1) lines for the 3 main isotopologues, HCN (J=1-0), HNC (J=1-0), HCO+ (J=1-0), N2H+ (J=1-0) and SiO (J=2-1) and (J=5-4). The moment zero map of 12CO (1-0) is shown in figure 2. Using the 13CO (2-1) / 13CO (1-0) ratio and the 13CO (2-1) / 12CO (2-1) ratio we are able to constrain the physical properties of the emitting gas along each line-of-sight using the RADEX code. We find that there exists a thick layer of hot (>100 K) dense CO-bright gas at the edge of the cloud. Chemical and thermodynamic modelling using our X-ray code suggests that to achieve temperatures above 100 K at these densities, while maintaining a high fractional abundance of CO, the UV flux must be very low (< 0.001 G0) for CO not to be dissociated, while the cosmic ray ionisation rate is high (~10−14 s-1) or the X-ray flux is very high (~ 0.1 erg/cm2/s) to heat the gas. Thus, the heating cannot be due to the background interstellar radiation field but due to the high cosmic ray and/or X-ray flux produced by CTB 109.
Monthly Highlights
March 2026
1D protostellar disk sub-grid model for star formation 3D MHD simulations (Anaïs Pauchet)
January 2026
Protostellar Outflows: From Simulations to Synthetic Observations (Taishi Ushirogi)
December 2025
Prestellar Core Formation in Colliding Gas Flows: Simulations and Synthetic Observations (Felix Rauprich)
November 2025
Measuring the Velocity Dispersion of the Warm Neutral Medium of the Milky Way at Galactic Scale using the Code FLASH (Wajdee Chayeb)
October 2025
Higher-order finite volume method for modelling shock waves in the interstellar medium (Mervin Yap)
June 2025
Simulating [CII] emission in high-redshift galaxies and their halos (Clarissa Immisch)
May 2025
Episodic Accretion onto Low Mass Protostars (Christian Riesop)
April 2025
Molecular cloud formation: Impact of metallicity, far-UV and CR heating using SILCC-Zoom simulations (Sanjit Pal)
March 2025
Modelling Protostellar Outflows in ISM Simulations (Michael Weis)
February 2025
Multi-band ray-tracing of ionizing photons (Sebastian Vider)
December 2024
Simulating the ISM and its processes (Sebastian Vider)