The grey extinction of the ionizing cluster in NGC 3603 from ultraviolet to optical wavelengths

Abstract

We use photometry in the F220W, F250W, F330W, F435W filters from the High Resolution Channel of the Advanced Camera for Surveys and photometry in the F555W, F675W, and F814W filters from the Wide Field and Planetary Camera 2 aboard the Hubble Space Telescope to derive individual stellar reddenings and extinctions for stars in the HD 97950 cluster in the giant HII region NGC 3603. The mean line-of-sight reddening for about a hundred main-sequence member stars inside the cluster is $E(F435W-F555W)=1.33\pm 0.12$ mag. After correcting for foreground reddening, the total to selective extinction ratio is $R_{F555W}=3.75\pm 0.87$ in the cluster. Within the standard deviation associated with $E(\lambda -F555W)/E(F435W-F555W)$ in each filter, the cluster extinction curve at ultraviolet wavelengths tends to be greyer than the average Galactic extinction laws from Cardelli et al. (1989) and Fitzpatrick et al. (1999). It is closer to the extinction law derived by Calzetti et al. (2000) for starburst galaxies, where the 0.2175 $\mu \mathrm{m}$ bump is absent. This indicates an anomalous extinction in the HD 97950 cluster, which may due to the clumpy dust distribution within the cluster, and the size of dust grains being larger than the average Galactic ISM.

24 pages, 11 figures, accepted for publication in AJ

References in corpus (8)

• An Analysis of the Shapes of Interstellar Extinction Curves. V. The IR-Through-UV Curve Morphology
• The Initial Mass Function of the Massive Star-forming Region NGC 3603 from Near-Infrared Adaptive Optics observations
• An Analysis of the Shapes of Interstellar Extinction Curves. VI. The Near-IR Extinction Law
• The Massive Star Content of NGC 3603
• UV dust attenuation in spiral galaxies: the role of age-dependent extinction and of the IMF
• On the Origin of Mass Segregation in NGC 3603
• PAH Strength and the Interstellar Radiation Field around the Massive Young Cluster NGC3603
• Emission from Very Small Grains and PAH Molecules in Monte Carlo Radiation Transfer Codes: Application to the Edge-On Disk of Gomez's Hamburger

Cited by in corpus (4)

• Optical-NIR dust extinction towards Galactic O stars
• The deep OB star population in Carina from the VST Photometric H$\alpha$ Survey (VPHAS+)
• Spectral characterisation of the extinction properties of NGC 3603 using JWST NIRSpec
• Exploring non-thermal emission from the star-forming region NGC 3603 through a realistic modelling of its environment