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.

Super Giant Shells in the LMC

LMC 4

Super Giant Shells in the LMC

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)

N55 HI

H-alpha

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.

HII region N55

Photodissociation region in N55

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.

PAH H2

15 Pc

H2 emission in ISM of the LMC

H2 emission in ISM of the LMC

Naslim+ 2015

The H2 warm gas physical parameters strongly correlate with average starlight intensity. The warm H2 might be photo-processed in PDRs.

H2 emission in ISM of the LMC

Naslim+ 2015, Roussel+ 2007

H2 emission in N55 PDR

Warm H2 gas : Text = 140±37 K Ntot = 4.2±0.3X1020 cm-2

M = 1000±450 Msun

Naslim+2015 Gordon+ 2014

Stratification in N55 PDR

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

IRAC 8.0µm

ALMA observation of dense molecular gas

Band 3 (Angular resolution 3”)

l 13CO (1-0)

l  HCO+ (1-0) l  HCN (1-0) l  CS (2-1) l  C2H

Band 6 (Angular resolution 1.5”) l 

13CO (2-1) l  C18O l 

12CO (2-1)

We plan to determine the properties of dense gas and its association with star formation.

H-alpha

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

Hyperfine components in HCN

13CO HCO+

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?

1 2

3

13CO channel map of big molecular complex

286-287km/s

-3.3km/s -1.8km/s

-0.2km/s 1.5km/s

HCO+ channel map of big molecular complex

Position-velocity cuts

Position-velocity cuts are taken diagonal to the bigger molecular complex along clump 1 and 2

HCO+ (1-0) HCN (1-0)

CS (2-1)

Clump Size pc M (13CO) 103 Msun

M (HCO+) 103 Msun

M (HCN) 103 Msun

M(CS) 103 Msun

1 2 3 4

1.2 1.0 1.1 0.8

3.87+/-0.5 4.30+/-0.5

0.856+/-0.2 1.0+/-0.3

2.0+/-0.2 3.8+/-0.5 2.7+/-0.7 1.3+/-0.5

1.2+/-0.3 2.3+/-0.5 1.0+/-0.2 0.7+/-0.2

2.2+/-0.4 3.0+/-0.5 2.5+/-0.3 1.2+/-0.2

Clump properties

1

2 3

4

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

0.8-5.0X103 Msun

Summary