A photodissociation region in HII region N55 of the LMC Naslim Neelamkodan Academia Sinica Institute of Astronomy and Astrophysics Ciska Kemper, Sacha Hony, Suzanne Madden, Margaret Meixner, Karl Gordon, Frank Israel, Frederic Galliano, Caroline Bot, Jacco Van Loon, Aigen Li, Annie Hughes, Oscar Morata, Vienney Lebouteiller, Remy Indebetouw. SuperSuper GiantGiant Shells Shells in in the the LMC LMC HI LMC 4 N55 H-alpha Mearburn et al 1980 have identified nine super giant shells in the LMC. Among them, LMC 4 is the largest. N55 is a remnant left inside the shell and has been strongly affected by the expanding shell. Israel et al. (2003), Yamaguchi et al. (2001) HII region N55 The eighth note nebula N55 - is located inside the LMC 4, at the north-eastern edge of SGS 14 - powered by the OB association LH72. - HI kinematic studies show an expansion with a velocity 15km/s. Olsen et al 2001. Photodissociation region in N55 PAH 15 Pc H2 l This PDR is likely to be powered by the brightest star O6 V in LH72, S133 which is located within 5pc from the bar. ( G0 = 500) l IRAC 8µm emission, PAH, of this PDR is filamentary and appears as a bar parallel to the lower lobe. H2 emission in ISM of the LMC H2 emission in ISM of the LMC The H2 warm gas physical parameters strongly correlate with average starlight intensity. The warm H2 might be photo-processed in PDRs. Naslim+ 2015 H2 emission in ISM of the LMC Naslim+ 2015, Roussel+ 2007 H2 emission in N55 PDR Warm H2 gas : Text = 140±37 K 20 -2 Ntot = 4.2±0.3X10 cm M = 1000±450 Msun Gordon+ 2014 Naslim+2015 Stratification in N55 PDR IRAC 8.0µm PAH, H2 and Si emission appear to peak at same location. At an angular resolution 3”, the stratification in the LMC is hard to resolve. Naslim+ 2015, in prep ALMA observation of dense molecular gas H-alpha Band 3 (Angular resolution 3”) 13 l CO (1-0) + l HCO (1-0) l HCN (1-0) l CS (2-1) l C2H Band 6 (Angular resolution 1.5”) 13 l CO (2-1) 18 l C O 12 l CO (2-1) We plan to determine the properties of dense gas and its association with star formation. Velocity integrated intensity maps of 13CO, HCO+, HCN and CS Velocity integrated intensity maps of 13CO, HCO+, HCN and CS Stratification HCN, CS, HCO+ and CS emission, all peak at same place. Two velocity components in line profiles 1 + 13CO HCO 2 3 CS HCN Two velocity components in 13CO, HCO+ and CS -active starformation? -detected YSOs in clump 1 & 2 (Gruendl & Chu, 2009) -overlap of two kinematically distinct clump? Hyperfine components in HCN 13CO channel map of big molecular complex 286-287km/s HCO+ channel map of big molecular complex -3.3km/s -1.8km/s -0.2km/s 1.5km/s Position-velocity cuts HCO+ (1-0) HCN (1-0) CS (2-1) Position-velocity cuts are taken diagonal to the bigger molecular complex along clump 1 and 2 Clump properties 1 4 2 3 Clump Size pc M (13CO) M (HCO+) M (HCN) M(CS) 3 3 3 3 10 Msun 10 Msun 10 Msun 10 Msun 1 1.2 3.87+/-0.5 2.0+/-0.2 1.2+/-0.3 2.2+/-0.4 2 1.0 4.30+/-0.5 3.8+/-0.5 2.3+/-0.5 3.0+/-0.5 3 1.1 0.856+/-0.2 2.7+/-0.7 1.0+/-0.2 2.5+/-0.3 4 0.8 1.0+/-0.3 1.3+/-0.5 0.7+/-0.2 1.2+/-0.2 Summary l Spatial distribution of H2 28µm and PAH emission show a PDR in N55 l At an angular resolution 3”, the PDR stratification is not resolved. Higher angular resolution observation of PDR tracers arr needed. l The ALMA observation of N55 PDR resolves clumpy molecular cloud with massive star formation. l The emission maps of 13CO, HCO+, HCN and CS show clumps with similar spatial distribution with massive cores l The size of clumps range from 0.8-1.5 pc and mass ranging 3 0.8-5.0X10 Msun .