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 H ii region NGC 3603 .
The mean line-of-sight reddening for about a hundred main-sequence member stars inside the cluster is E ( F 435 W - F 555 W ) = 1.33 \pm 0.12 mag .
After correcting for foreground reddening , the total to selective extinction ratio is R _ { F 555 W } = 3.75 \pm 0.87 in the cluster .
Within the standard deviation associated with E ( \lambda - F 555 W ) / E ( F 435 W - F 555 W ) 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 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 .