James Webb Space Telescope Feed Post

Date: 5/15/2024

Arxiv: Spectral characterisation of the extinction properties of NGC 3603 using JWST NIRSpec Published: 5/14/2024 12:11:17 PM Updated: 5/14/2024 12:11:17 PM

Paper abstract: Context. A necessary ingredient in understanding the star formation historyof a young cluster is knowledge of the extinction towards the region. This hastypically been done by making use of the colour-difference method withphotometry, or similar methods utilising the colour-colour diagram. Aims. Thecolour-excess can be independently determined by studying the decrements of therecombination lines produced by the nebular gas. Having access to manyrecombination lines from the same spectral series removes the need of adoptingan extinction curve. Methods. Using the Micro-Shutter Assembly (MSA) on boardthe Near InfraRed Spectrograph (NIRSpec), multi-object spectroscopy wasperformed, yielding 600 nebular spectra from the Galactic massive starformation region NGC 3603. The recombination line intensity ratios were used todetermine independent values of colour-excess. Results. The extinctioncharacteristics of NGC 3603 are similar to other Galactic HII regions likeOrion, as well as starburst regions such 30 Doradus in the Large MagellanicCloud, in that we find a relatively large value of total-to-selectiveextinction of 4.8 \pm 1.06, larger than the Galactic average of 3.1. We finda typical value for the colour-excess of 0.64 \pm 0.27, significantly lowerthan values determined in previous studies. We also present a stacked nebularspectrum with a typical continuum S/N = 70. This spectrum highlights therecombination lines of the HII region, several s-process elements such as KrIII and Se IV, and molecular H2 emission lines. Conclusions. Using ratios ofhydrogen recombination lines, we calculated the total-to-selective extinction,colour-excess and visual extinction for > 200 lines of sight across NGC 3603.An extinction curve with a total-to-selective extinction of 4.8 \pm 1.06 wasfound, corresponding to a colour-excess of 0.64 \pm 0.27.