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Young Photodissociation Complexes in NGC 6822: Stars and PDRs

Event Details

Event Dates: 

Friday, November 1, 2013 - 12:00pm

Seminar Location: 

  • CASA Conference Room C324

Speaker Name(s): 

Lynn Carlson

Speaker Affiliation(s): 

Seminar Type/Subject

Scientific Seminar Type: 

  • Astrophysics Lunch Seminar

Event Details & Abstract: 

I examine Photodissociation Region (PDR) properties in relation to stellar populations in three regions of NGC 6822. This Local Group dwarf galaxy has a metallicity less than half Solar and lies 490kpc away. It is close enough that stellar populations are resolved as are nebular structures of evolving young HII regions; we can see that these regions are being driven by O/B stars. We model the radiation field directly from the stellar content and find that it matches the radiation structure determined from far-infrared (FIR) line ratios from Herschel/PACS spectral maps (in [CII], [OI] 63micron, and [OIII] 88micron) and derived total FIR maps from dust spectral energy distribution fitting. This allows us to constrain the radiation and density structure of the PDR. With imaging from HST and HII region modeling, we characterize the expansion of young HII regions. Finally, with mid-IR [SIII] line ratios, we map the ionized gas density. At this distance, Spitzer images are insufficient to confirm continuing star formation in these regions via the identification of Young Stellar Objects (YSOs), but the evolutionary picture and ISM density distribution indicate that we are likely to find YSOs with the advent of JWST.