Infrared Supernova Remnants in the Large Magellanic Cloud

INFRARED SUPERNOVA REMNANTS

IN THE LARGE MAGELLANIC CLOUD

Ji Yeon SeokSeoul National University

Contents Part I: IR survey of the LMC SNRs

1. Introduction2. Data & Approach3. Result 4. Discussion: Origin of IR emission

Part II: PAH emission from a SNR1. Introduction 2. Object & Data3. Result: PAH properties4. Discussion: PAH emission mechanism in a SNR

Summary

2012. 2. 27.The Second AKARI Conference: Legacy of AKARI: A Panoramic View of the Dusty Universe

2012 February 27-29, Ramada Plaza Hotel, Jeju, KOREA 2

The Large Magellanic Cloud Different environment from the Milky Way

Lower metallicity: 1/3 of MW (Pei 92)Lower dust-to-gas ratio: 1/5 of MW (Pei 92)SN rate: 0.5 SNe /100 yr, Ia : CC (II+Ib) = 1 : 11

(Tamman+94)○ c.f. , MW: 2.5 SNe /100 yr, Ia : CC = 1 : 6

Advantages to study LMC SNRsWell-known distance and close to look details (~50

kpc)Uniform and non-biased samples (~50 known SNRs

in the LMC) Far from the galactic plane to avoid back/foreground

confusion of other IR emission2012. 2. 27.

The Second AKARI Conference: Legacy of AKARI: A Panoramic View of the Dusty Universe2012 February 27-29, Ramada Plaza Hotel, Jeju, KOREA 3

Part I: 1. Introduction

Previous IR surveys of SNRs



Galactic SNRs LMC SNRs

IRAS

• 51 IR SNRs out of 157 (Arendt 89)• 35 IR SNRs/ 9 candidates out of 161 (Saken+92)

• 3 IR SNRs out of 4 IR sources (Graham+87), 5 with IR emission out of 25 LMC SNRs (Schwering 89)• IR & radio comparison for 21 SNRs (including 9 candidates, Filipovic+98a)

Spitzer

• GLIMPSE & MIPSGAL survey (10<|l|<65, |b|<1)– 18 NIR SNRs out of 95 (Reach+06), 16 NIR SNRs out of 100 (H. Lee 05)– 39 MIR SNRs out of 121 (Pinheiro Goncalves+11)

• 39 LMC SNR imaging survey – 4 Type Ia by Borkowski+06 – 4 CC by B. Williams+06• 4 out of 6 SNRs with IR emission (R. Williams+06)

Limitation

Confusion with other Galactic sources is a big problem!!

More statistical study for IR LMC SNRs is essential!!

Part I: 1. Introduction

AKARI & Spitzer Survey of the LMC

AKARI LMC survey (Ita+08) Area: ~10 deg2

N3, S7, S11, L15, L24 21 SNRs included (Seok+08)

Spitzer SAGE survey (Meixner+06)

Area:~77 IRAC (3.4, 4.5, 5.8, 8.0)+ MIPS

(24, 70) All known SNRs covered + Several pointed observations

Data approach Visual inspection to 45 known

LMC SNRs (Desai+10) Comparison with multi-wave-

length data ATCA radio, MCELS, Chandra X-

ray Images in literatures (e.g., R.

Williams+06)2012. 2. 27.


Part I: 2. Data & Approach

MCELS optical Ha, [SII], [OIII] (Seok+in prep.)

O: SNR

28 out of 45 SNRs detected in the AKARI and/or Spitzer bands! 13 IR SNRs are firstly identified in several IR bands.

Catalog of LMC SNRs (Seok+in prep.) General information: name, position, size, SN type, age +

AKARI/Spitzer detection AKARI & Spitzer fluxes

○ Mostly detected at 24 um, and half of SNRs seen at shorter wave-lengths

Measurement of IR LMC SNRs



Part I: 3. Result

Seok+08



IR morphology of 28 LMC SNRsPart I: 3. Result

AKARI L24 (Seok+08)

Spitzer images (Seok+in prep.)

IR origin and its correlationN/MIR origin: IRAC CCD (Reach+06) Ionic/molecular line emission PAH emission, Synchrotron emission

24 & 70 um Correlation: good regard-less of MIR origins!

Comparison with modified BB Tdust: 50-100 K, Mdust: 0.1-100?? M Overestimation due to other contribution (e.g.,

0.4 M in N49, Otsuka+10) Mixture of multi-component dust (hot dust +

cold dust) In general, SNRs interacting with MCs are

bright in MIR.MIR color-color diagram Dust emission: significantly low 8/24 um ra-

tio Ionic/molecular line & PAH emission contri-

bution High 8/24 ratio, but not clearly separated in the

diagram Rough linear correlation similar to Galactic

SNRs (Pinheiro Goncalves+11)



Part I: 4. Discussion

IR vs X-ray: Tightly correlated. Both emission mechanisms are physically re-

lated. Dust collisionally heated by hot plasma good

spatial agreement

IR visibility Equilibrium Tdust with Te & ne of hot plasma

(Dwek+08) No IR emission detected from SNRs with Tdust

<~40 K Higher 24/70 um ratio located at higher Tdust

Comparison to X-ray



Seok+08


IR X-ray IR X-ray

B. Williams+06

Statistical properties of IR SNRs




IR detection rate: 62% (28 out of 45) c.f., MIPSGAL survey: 32% (39 out of 121, Pinheiro

Goncalves+11) Extrinsic aspect

Much severe IR confusion by Galactic disk Biased survey of Galactic SNRs (|b|<1)

Any intrinsic reason? Lower dust-to-gas ratio than that of the MW Dust composition (graphite to silicate ratio rc/rs, Pei 92)

○ LMC: rc/rs= 0.22, but MW: rc/rs, =0.9-0.95

Dwek+96

PAH emission from SNRs



Part II: 1. Introduction

Theoretical expectation PAH formation by a shock (Jones+96) Complete destruction by a fast shock (>150 km/s)

(Micelotta+10a) Entrainment of dense clumps in a hot post shock gas

for PAH survival (Micelotta+10b)

Few observational evidences Four Galactic SNRs categorized by IRAC colors (Reach+06) Mostly undetected due to destruction by a fast shock

(e.g., Williams+06) The first detection of PAH emission in SNR N132D

(Tappe+06) Large PAH clusters attribute to 15-20 um hump No major features by smaller PAHs due to destruction

N63A: Spitzer IRAC Ch3

Chandra X-ray

N49: AKARI N3

CO emission 6-cm radio continuum

AKARI NIR Spectroscopy: N49 & N63A

Phase 3 IRC NG spectroscopy for NIR bright LMC SNRs



The 3.3 um PAH features are detected in N49 & N63A for the first time (details of N49: Seok+12).

Part II: 2. Object & Data

Distribution of PAH emission Overall similar to both H2 & Br (H: contour) Differences in locality

Band ratio: fraction of ionized PAHs PAH features at 6.2, 7.7, and 11.3 um also de-

tected at Spitzer IRS spectrum I6.2/I11.3=0.630.31, I7.7/I11.3=1.250.26 Follow the universal linear relation between

the ratios In dense MCs, PAHs in neutral and anionic

charge state are dominant (Le Page+03). High I6.2/I7.7 (=0.50.27) & I3.3/I11.3 (=0.3-0.43)

Presence of small PAHs (Draine & Li 01, Mori+12) Consistent with PAH formation from larger grains

but NOT with preferential destruction of small PAHs by shocks

Characteristics of PAHs in N49



Part II: 3. Result

Neutral

Ionic

PAH emission mechanism in N49

Condition for PAH to exist and radiate in a SNR: Ambient dense medium + Sufficient heating

source2012. 2. 27.


Part II: 4. Discussion

Too hot (T~7106

K): rapid

destruction

PAHs swept up by retarded shocks or

unshocked with UV

heating: emit PAH features

PAH outside a

SNR heated by radiative precursor

Summary Using IR survey data of the LMC, we examine

all known LMC SNRs and find IR emission from 28 SNRs (detection rate: 62%).

IR properties and its origins are investigated based on the IR colors.

X-ray properties (ne, Te) can be a good indica-tor of IR emission from a SNR.

PAH features are detected in SNR N49 & N63A. Ambient dense medium and sufficient heating

sources are most likely required to observe PAH emission from a SNR.



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Infrared Supernova Remnants in the Large Magellanic Cloud