We report JWST MIRI/MRS observations of the H2 S(1) 17.04 micron transition in two regions in the boundary of the Taurus Molecular Cloud. The two regions, denoted Edge (near the relatively sharp boundary of the 13CO J=1-0 emission) and Peak (the location of the strongest H2 emission observed with Spitzer), have average intensities of 14.5 MJy/sr and 32.1 MJy/sr, respectively. We find small scale structures of characteristic size 1.0 to 2.5 arcseconds, corresponding to 140 AU to 350 AU, with characteristic intensity above the extended background of 10 MJy/sr, corresponding to a J = 3 column density of 1.6x1017/cm2. The most plausible explanation for the observed intensities from level 845 K above the J = 1 ortho-H2 ground state level is excitation by collisions with H2 molecules (the hydrogen in this region being predominantly molecular). Two mechanisms, turbulent dissipation and shocks, have been proposed for heating of localized regions of the ISM to temperatures ~1000 K to explain abundances of and emission from particular molecules. While we cannot determine unique values of density and kinetic temperature, the solutions in best agreement with predictions of shock models are H2 density = 370 /cm3 and kinetic temperature = 1000 K. The total H2 column density of the small-scale structures under these conditions is ~8x1017/cm2. This first direct detection of heated tiny scale structure in the quiescent molecular interstellar medium has significant implications for the physical structure of this phase of the ISM and maintaining supersonic motions within it.
The evolution of dust in core-collapse supernovae (SNe), in general, is poorly constrained owing to a lack of infrared observations after a few years from explosion. Most theories of dust formation in SNe heavily rely only on SN 1987A. In the last two years, the James Webb Space Telescope (JWST) has enabled us to probe the dust evolution in decades-old SNe, such as SN 2004et, SN 2005ip, and SN 1980K. In this paper, we present two decades of dust evolution in SN 2005af, combining early-time infrared observations with Spitzer Space Telescope and recent detections by JWST. We have used a chemical kinetic model of dust synthesis in SN ejecta to develop a template of dust evolution in SN 2005af. Moreover, using this approach, for the first time, we have separately quantified the dust formed in the pre-explosion wind that survived after the explosion, and the dust formed in the metal-rich SN ejecta post-explosion. We report that in SN 2005af, predominantly carbon-rich dust is formed in the ejecta, where the total mass of ejecta dust is about 0.02-0.03 Msun, while in the circumstellar medium the amount of surviving oxygen-rich dust is 0.001-0.004 Msun.