Direct Physical Diagnostics of Triggered Star Formation Rachel Friesen NRAO Postdoctoral Fellow North American ALMA Science Center C. Brogan, R. Indebetouw, C. Cyganowski, E. Churchwell, M. Wolfire, B. Whitney, C. Watson, W. Dirienzo

triggered star formation in H II regions this work - analyse tracers of low-density, high-density and ionized gas in a set of H II regions - e.g. NH 3 observations reveal the temperature and kinematics of the cold molecular gas in shell - compare with predictions of collect-and-collapse, radiation driven implosion models of triggered star formation - the expansion of H II regions can trigger star formation - ~20 % of H II region bubbles (sufficiently resolved at 870 μm) show evidence for massive star formation (Deharveng et al. 2010)

targets - set of 4 HII regions - D ~ 4 – 5 kpc - associated 13 CO (GRS) - evidence for triggered SF (IRAC/MIPS, masers) - GBT NH 3 (1,1) – (4,4) inversion transitions - Spitzer IRS – 6.9 μm – 36 μm + GLIMPSE, MIPSGAL (Spitzer IRAC, MIPS), GRS ( 13 CO), MAGPIS (20 cm), BGPS (1.1 mm) 3.5μm, 8.0 μm, 24μm G G G G

census of YSOs Protostar properties: Class 1 Class II based on SED fitting of IRAC/MIPS data (Dirienzo et al. in prep, SED models by Robitaille et al. 2006, 2007) ¾ detections Class II protostar M = 7 M Sun 3.5μm, 8.0 μm, 24μm G G Class I protostar M = 0.3 M sun

GBT NH 3 results & analysis - NH 3 emission follows infrared-dark areas 3.5μm, 8.0 μm, 24μm NH 3 (1,1), (2,2), map extents G G G NH 3 (1,1) NH 3 (2,2) NH 3 (3,3) x 3 Self-consistent fitting of the (1,1) and (2,2) line profiles: - v lsr consistent with shell 13 CO (GRS) – dense gas associated with H II regions - evidence of local heating near embedded protostars, but T K ~ K - supersonic line widths ~ 1.3 – 2.3 km s -1, some asymmetric line wings

NH 3 (1,1) emission correlates with 1.1 mm (Bolocam GPS; Aguirre et al. 2010) 3D clump analysis finds 4 distinct clumps - R ~ 0.9 – 1.5 pc, elongated along shell - M ~ 1000 – 3000 M o - T K ~ 14 – 25 K - N(H 2 ) ~ 6 x cm -2 - M/M vir ~ 1 ~ 3 G41.10: molecular gas NH 3 (1,1), 1.1 mm

H 2 emission shows shocked molecular gas Bottom RGB: [H 2 ] + [SIII] + [8 μm] - H 2 emission, ionized gas surrounds one clump - warmer with no internal heat source Top RB: [SIII] (33.5 μm)+ [SIII] (18.7 μm) - can determine n e from ratio of [SIII] lines (Dudik et al. 2007) - P e Spitzer IRS maps: - fine structure lines reveal the physical conditions in the ionized gas - photoionization modeling to determine ionized gas and PDR properties G41.10: ionized gas NH 3 T K T K = 25 K T K = 19 K T K = 14 K NH 3 (1,1) contours

.. ongoing summary - existing and new datasets allows characterization of - low density gas - high density gas - ionized gas - current YSO population towards 4 H II regions with ongoing, active star formation in their shells - compare directly measurements with predictions of triggering scenarios stay tuned…