The JWST-NIRCam View of Sagittarius C. III. The Extinction Curve

Abstract

Determining the infrared extinction curve towards the Galactic centre is crucial for accurately correcting observed data and deriving the underlying stellar populations. However, extinction curves reported in the literature often show discrepancies. We aim to derive the infrared extinction curve towards the Galactic centre based on JWST-NIRCam data for the first time, using observations of the Sagittarius C region in the 1-5 $\mu$m range. We determined extinction ratios using two different methods, both based on measuring the reddening vector using the slope of red clump stars, whose intrinsic properties are well known, in observed colour-magnitude diagrams. The extinction curve derived in this work is in good agreement with previous results in the literature. We obtained the following extinction ratios relative to F162M: $A_{F115W}:A_{F162M}:A_{F182M}:A_{F212N}:A_{F360M}:A_{F405N}:A_{F470N}:A_{F480M}=1.84\pm 0.03:1.00:0.789\pm 0.005:0.607\pm 0.014:0.306\pm 0.011:0.248\pm 0.017:0.240\pm 0.019:0.21\pm 0.03$. Besides, we found different values of the extinction index for the short- ($\lambda \sim 1-2.5\mu$m, $\alpha \sim 2$) and long-wavelength ($\lambda \sim 2.5-5\mu$m, $\alpha \sim 1.4$) regimes, with the extinction curve flattening at longer wavelengths. Comparison with extinction curves derived both inside and outside the Galactic centre suggests that the infrared extinction curve does not significantly vary in the central regions, and shows no significant evidence for variations between different lines of sight beyond the inner Galaxy within the uncertainties.

14 pages, 11 figures, accepted version

References in corpus (16)

• The Astropy Project: Sustaining and Growing a Community-oriented Open-source Project and the Latest Major Release (v5.0) of the Core Package
• Interstellar Extinction Law toward the Galactic Center II: V, J, H, and Ks Bands
• The Astrodust+PAH Model: A Unified Description of the Extinction, Emission, and Polarization from Dust in the Diffuse Interstellar Medium
• The nuclear cluster of the Milky Way: Our primary testbed for the interaction of a dense star cluster with a massive black hole
• Extinction ratios in the inner Galaxy as revealed by the VVV survey
• Extinction law in the range 0.4-4.8 $\mu$m and the 8620 $\mathring{A}$ DIB towards the stellar cluster Westerlund 1
• GALACTICNUCLEUS: A high-angular-resolution JHKs imaging survey of the Galactic centre III. Evidence for wavelength dependence of the extinction curve in the near-infrared
• GALACTICNUCLEUS: A high-angular-resolution $JH{K}_s$ imaging survey of the Galactic centre. IV. Extinction maps and de-reddened photometry
• Galactic extinction laws: I. A global NIR analysis with 2MASS photometry
• Observations of the Onset of Complex Organic Molecule Formation in Interstellar Ices
• M-Band Spectra of Dust Embedded Sources at the Galactic Center
• 2MASS J17112318-2724315: A Deeply-Embedded Low-Mass Protostellar System in the B59 Molecular Cloud
• Extending the extinction law in 30 Doradus to the infrared with JWST
• JWST reveals widespread CO ice and gas absorption in the Galactic Center cloud G0.253+0.016
• Constraining Spatial Densities of Early Ice Formation in Small Dense Molecular Cores from Extinction Maps
• The JWST-NIRCam View of Sagittarius C. II. Evidence for Magnetically Dominated HII Regions in the CMZ