Multiple gas phases in supernova remnant IC 443: mapping shocked H2 with VLT/KMOS

Abstract

Supernovae and their remnants provide energetic feedback to the ambient interstellar medium (ISM), which is often distributed in multiple gas phases. Among them, warm molecular hydrogen (H2) often dominates the cooling of the shocked molecular ISM, which has been observed with the H2 emission lines at near-infrared wavelengths. Such studies, however, were either limited in narrow filter imaging or sparsely sampled mid-infrared spectroscopic observations with relatively poor angular resolutions. Here we present near-infrared (H- and K-band) spectroscopic mosaic observations towards the A, B, C, and G regions of the supernova remnant (SNR) IC 443, with the K-band Multi-Object Spectrograph (KMOS) onboard the Very Large Telescope (VLT). We detected 20 ro-vibrational transitions of H2, one H line (Brγ), and two [Fe ii] lines, which dominate broadband images at both H- and K-band. The spatial distribution of H2 lines at all regions are clumpy on scales from ∼0.1 pc down to ∼0.008 pc. The fitted excitation temperature of H2 is between 1500 K and 2500 K, indicating warm shocked gas in these regions. The multi-gas-phase comparison shows stratified shock structures in all regions, which explains the co-existence of multiple types of shocks in the same regions. Last, we verify the candidates of young stellar objects previously identified in these regions with our spectroscopic data, and find none of them are associated with young stars. This sets challenges to the previously proposed scenario of triggered star formation by SNR shocks in IC 443.

Criss-cross Nebula: A Case Study of Shock Regions with Resolved Microstructures at Scales of ∼1000 au

“…There have also been many studies of nearby shocked regions, such as the Crab Nebula at ∼2 kpc (Chevalier & Gull 1975;Clark & Stephenson 1977;Davidson & Fesen 1985;Nomoto 1987;Fesen et al 1997;Hester 2008;Martin et al 2021) and IC443 at ∼2 kpc (Carpenter et al 1995;Jones et al 1998;Rho & Petre 1998;Chevalier 1999;Olbert et al 2001;Troja et al 2008;Alarie & Drissen 2019;Deng et al 2023), which usually present regular shell-like structures and have high shock velocities and electron densities. In this work, we study the Criss-cross Nebula (CCN), which has different structures and physical conditions, compared with other wellstudied nearby shock regions.…”