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Direct Physical Diagnostics of Triggered Star Formation

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.

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Direct Physical Diagnostics of Triggered Star Formation

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  1. 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

  2. triggered star formation in HII regions • the expansion of HII regions can trigger star formation • ~20 % of HII region bubbles (sufficiently resolved at 870 μm) show evidence for massive star formation (Deharveng et al. 2010) • this work • analyse tracers of low-density, high-density and ionized gas in a set of HII regions • e.g. NH3observations 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

  3. targets 3.5μm,8.0 μm, 24μm G41.1+0.2 G41.9+0.0 • set of 4 HII regions • D ~ 4 – 5 kpc • associated 13CO (GRS) • evidence for triggered SF (IRAC/MIPS, masers) • GBT NH3 (1,1) – (4,4) inversion transitions • Spitzer IRS – 6.9 μm – 36 μm • + GLIMPSE, MIPSGAL (Spitzer IRAC, MIPS), GRS (13CO), MAGPIS (20 cm), BGPS (1.1 mm) G44.3+0.1 G44.3-0.8

  4. census of YSOs 3.5μm,8.0 μm, 24μm G41.1+0.2 G41.9+0.0 Class II protostar M = 7 MSun 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 I protostar M = 0.3 Msun

  5. GBT NH3 results & analysis 3.5μm,8.0 μm, 24μm G44.3+0.1 G44.3-0.8 G41.1+0.2 3 NH3 (1,1), (2,2), map extents NH3 (1,1) 2 • NH3 emission follows infrared-dark areas • Self-consistent fitting of the (1,1) and (2,2) line profiles: • vlsrconsistent with shell 13CO (GRS) – dense gas associated with HII regions • evidence of local heating near embedded protostars, but TK ~ 15 - 25 K • supersonic line widths ~ 1.3 – 2.3 km s-1, some asymmetric line wings NH3 (2,2) 1 NH3 (3,3) x 3 0 40 80 60

  6. NH3 (1,1), 1.1 mm G41.10: molecular gas NH3 (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 Mo - TK ~ 14 – 25 K - N(H2) ~ 6 x 1022 cm-2 - M/Mvir~ 1 ~ 3

  7. NH3 (1,1) contours G41.10: ionized gas Spitzer IRS maps: - fine structure lines reveal the physical conditions in the ionized gas - photoionization modeling to determine ionized gas and PDR properties Top RB: [SIII] (33.5 μm)+ [SIII] (18.7 μm) - can determine ne from ratio of [SIII] lines (Dudik et al. 2007) - Pe TK = 25 K NH3 TK H2 emission shows shocked molecular gas Bottom RGB: [H2] + [SIII] + [8 μm] - H2 emission, ionized gas surrounds one clump - warmer with no internal heat source TK = 14 K TK = 19 K

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

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