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Session 6 - HII Regions & Massive Star Formation.
Display session, Wednesday, January 07
We examine the massive star formation region NGC 6334 in the near-, mid-, and far-infrared in order to investigate the dust properties at each of 8 sites of massive star formation in the cloud: NGC 6334 A, C, D, E, F, V, I(N) and G351.20+0.70.
We have obtained LWS full-grating scans toward 7 of the sites in NGC 6334 and SWS full-grating scans toward 2 of the sites. With full-grating scans toward the sites of massive star formation and examining the fine-structure lines from ionic species, we determine the hardnesses of the UV fields, and thus derive the ZAMS spectral types. This independent measure of the spectral types is compared to the known radio and FIR spectral types, which often disagree in this cloud. To determine the gas density and UV field strength based on PDR models, we use the [Si II] 35 \mum line, along with the [C II] 158 \mum and [O I] 145 \mum lines from the ISO LWS full-grating scans. Because the [O I] 63 \mum is anomalously faint toward at least two of the sources in NGC 6334, probably due to self-absorption, the optically thin [S II] 35 \mum line is essential for testing the model predictions. We investigate the dependence on the hardness of the UV field of the UIR features at 6.3, 7.7, 8.6 and 11.3 \mum. We also examine the relative strength of ice vs. silicate features and their dependence on the hardness of the UV field.
We have also imaged 6 of the sites with ISOCAM through 4 settings of the CVF filter (5.8, 6.3, 6.8, and 14.8 \mum). The CVF filter is used to avoid saturation due to the extreme brightness of the sources. By imaging the well-isolated 6.3 \mum UIR feature at each site, we examine the survivability of small grains in hard/intense UV fields. In order to separate the UIR feature from the continuum emission, we have taken images at 5.8 and 6.8 \mum. These continuum images, plus the fourth CVF filter setting at 14.8 \mum, allow us to determine the dust opacity, a crucial input parameter for PDR models.
Program listing for Wednesday