Shock-induced Molecular Astrochemistry in Dense

Clouds

Jeonghee Rho SOFIA Science Center Universities Space Research Association NASA Ames Research Center, CA Collaborators J. Hewitt (NASA/GSFC), M. Anderson (ESA, ESTEC, Netherland), A.

Tappe (CfA, Harvard Smithsonian), W. T. Reach (SOFIA SMO/NASA Ames), and J. P. Bernard (CNRS, Toulouse)

Interaction with CSM/ISMradiative shock in dense gas

heating, chemistry, dust processing

Massive Stars form in GMC Young adiabatic SNR >8 Msol dies within cloud lifetime

(~40% SNe in the field)expanding in wind cavity

ejecta mixing, dust creation,cosmic ray accel

SNR merges into ISMSuperbubble / Chimney release of cosmic rays

W44, enveloped by a molecular cloudRadiative signatures:• IR-bright => shock cooling in

relatively dense gas (>103 cm-3)• Broad molecular lines (eg. CO 2-1)

Supernova Remnants Interacting with Clouds

Spitzer IRAC color image (Reach, Rho et al. 2006):

Shocked H2 (4.5 μm, green), PAH and dust (8 μm, red)

Reach, Rho, Jarrett (2005)

12CO(2-1), ΔV=40 km/s)

IC 443 : prototype of interacting SNR • Optical, radio are shell-like• X-rays: shell + bright inside• Interaction with clouds: Near-IR H2 image (Burton et al. 1988)

CO broad lines (van Dishoeck et al.)

• 2MASS images: bright K emission (H2) in the southern ridge and J,H emission ([Fe II]) in the northern rim

• H2 lines; 1-0 S(1) in K, 1-0 S(7) in H, 2-1 S(1) in J

(Rho et al. 2001)

[Fe II]

H2

• Spitzer GLIMPSE survey detected 18 IR-bright SNRs

• Colors hint at dominant cooling lines and shock type.

However... Color-typing shows large scatter, even within the same SNR

IR spectroscopy is clearly needed

Supernova Remnants Interacting with Clouds

from Reach et al. 2006

Molecular

Ionic

PAH

Must explain mix of IR lines: H2 S(0)-S(7) [Fe II], [Ne II], [Si II], [S III] PAHs, Dust continuum

• brightest IR clumps in 14 SNRs• long-slit: remove Galactic emission

Hewitt et al. 2009, Andersen et al. (submitted)

Spitzer 5 to 95 μm Spectroscopy

G349.7

Kes 17

IRAC 3-color images

Spitzer IRS SL/LL 5-35μm R~100

Complements IRS mapping 4 SNRs (Neufeld et al.)

• Two H2 components (warm, hot) T(H2)= 320 1150 K OPR = 1.0 3.0● H2 fitting with shock models (Le Bourlot 2002)

VS = 10, 40 km/s nH = 105, 104 cm-3 PS = 1x10-6, 3x10-7 dyne cm-2

over-pressure in warm, dense clumps

Multi-shock fitting:

BEST FIT

H2 Excitation in Kes 69

Rho, Hewitt, Jarrett et al.(in prep.)

H2 Excitation in G348.5-0.0● Spitzer IRS + near-IR with AAT

● H2 2-1 S(1)/1-0 S(1) Ratio [=X] ~ 7

Shock: X=12-15 (IC 443), UV pumping: X=2-4

=> shock + UV pumping (Chang & Martin 1991)

NIR H2 lines

Para-to-ortho H2 conversion via reactions with atomic-H:

τconv ≈ 3000 yrs [100 cm-3/n(H)] EA/k ~ 4000 K

Ortho-to-Para Ratio in Equilibrium

H2 Excitation: Ortho-to-Para

warm H2: OPR ~ 0.4-3equilibrium: OPRLTE ~ 3

Para-to-ortho H2 conversion via reactions with atomic-H:

τconv ≈ 3000 yrs [100 cm-3/n(H)] EA/k ~ 4000 K

Ortho-to-Para Ratio in Equilibrium

H2 Excitation: Ortho-to-Para

warm H2: OPR ~ 0.4-3equilibrium: OPRLTE ~ 3

OPR < 3 in TH2 = 250-600 K requires τshock < τconv

=> slow C-shocks into cold, quiescent clouds; no significant pre-heating of MC

Kes 69

3C396

G346.6

G348.5

G349.7

Kes 17

Excitation of ionic species: Fe+, Ne+, Ne++, Si+, S++

requires VS >100 km/s, ne ~102-3 cm-3

Ionic emission spatially segregated from H2 along the IRS slit. => multiple shocks

Fast, Dissociative ShocksNeon Line Ratio

Good fits obtained for Dust. TBB = 35-50 K

Relative grain abundances: SNRs MW YVSG/BG 0.23-1.0 0.13 YPAH/BG 0.01-0.2 0.004

=> Processing of grain size distribution by SNR shock

Dust Emission from SNRs

IRS SL/LL

MIPS SED

Dust continuum modeling (DUSTEM, Campiegne et al. 2008, Poster #35) Parameters: Big Grains, Very Small Grains, PAHs, and Radiation Field

0.01-0.2 μm 0.001-0.01μm

line-subtracted spectrum

Milky Way Value

VS > 60 km/sVS < 60 km/s

Sputtering efficient for fast shocks,affecting all grain sizes

Shattering in dense/slow shocks,destroys BGs, but not VSG/PAHs

Observe VSG/BG consistent with shattering, increasing with VS

from Borkowski et al. 1995

Dust Processing by SNR shocks

Dust Heating by SNR shocks

fitted ISRF ~ 20-100

Dust continuum is a significant coolant!

Fit Radiation Field, case B H-recomb. (normalized to ISRF)

Milky Way Value

SNRs have even higher UV radiation from H-recomb (fast shocks, [Fe II])

100 LΘ1 L

Θ

10 4 LΘ

Radiative Cooling: SNR/MCs

G349.7

Kes20A

Kes17

LH2 is ~0.6-6% of LDust in SNR/MCs

[O I] 63μm line detected in 10/14 SNRs, L[OI]/LDust ~ 1-7%What are other coolings?

Fermi γ-ray detections of SNR/MCsMaser SNR subset: interaction, distance, cloud mass, n=105 cm-3

• For π0-decay origin (Drury et al. 1994)

Fγ ~ Mcloud dkpc-2 ωCR

• Given Mcloud, dkpc : determines CR ionization rate ζCR ≈ ωCR ζlocal

• Maser SNRs have ωCR ~ 10-50 enhanced over local density

• Significant ionization, >10-16 s-1

Kes69G16.7

12/24 SNRs detected by Fermi

(Hewitt et al. 2011)

enhances n(H,e)/n(H2) in C-shocks

Fermi image of W44

Far-infrared Spectroscopy

• Abundances of Fe: 99% locked in grains => dust vaporized by shocks• Febry-Perot spectrum of [OI] shows resolved broad line V~100 km/s. • H2O, OH, CO lines are detected <= from warm, dense (105cm-3) gas O + H2 => OH (T>400K) OH + H2 => H2O

Fe IIISO

Reach & Rho 1996

[O I] 63μm

[Fe II] 26μm

Water abundance was smaller than expected relative to OH or CO

Herschel/SOFIA Observations of MSNRs• 18 hours of Herschel

time is granted• 3 brightest molecular

interacting SNRs• What is the post-shock

abundance and excitation of water, hydroxyl, CO and atomic oxygen??

• What mechanism produces the observed non-equilibrium oxygen chemistry?

Hershel: PACS, SPIRE, HIFIComplement with SOFIA: GREAT (1hr)

The violent lives of Supernova Remnants

SNR shocks are a spectacular probe of molecular clouds

Future directions

Non-equilibrium chemistry, driven by enhanced ionization and radiation field?Both collisional and radiative coolingChemistry. Water chemistry. Shock-induced molecule cooling and astrochemical processes• Challenges of molecular astrochemistry modeling

• Multiple shocks, through a multi-phase cloud trace thermal history of the cloud (OPR)

• Radiative cooling: dust continuum, IR lines• Enhanced radiation field ~20-100 x ISRF evidenced

by Dust heating, H2 UV excitation• Grain processing: shattering decreases large grain size • Accelerate cosmic rays yielding up to few % ESN

3 km/s

300km/s

SOFIA Observations of Shocks/PDRs

Molecular lines: CO, OH, H2O

Shock cooling, Ionic lines

Dust Sputtering: Fe, Si

[OI] [CII] velocity and mapping

Shock processed PAHs

Maps of dust processing

GREAT GREAT First Light

April 6, 2011

German REceiver for Astronomy at Teraherz Frequencies (GREAT)

PI: Rolf Güsten, MPIfR in Bonn

M17 (Omega Nebula) CO (J=13-12, green) and [C II] (white) spectra

Velocity (x-axis): from -10 to 50 km/s

GREAT Spectral resolution is between 106 and 108.

Efficient Scan mapping capability.

GREAT

OB (yellow) stars, [CII] (green) contours on VLA image (ionizing flux). Inserted CO (J=13-12) image with [CII] contours.

[CII] is ionized gas at the boundary of dense warm CO.

(Perez-Beaupuits, Güsten, and GREAT team, in preparation)

Lee et al. 1996

VLA image

[CII] image

CO (13-12) contours

GREAT

OB (yellow) stars, [CII] (green) contours on VLA image (ionizing flux). Inserted CO (J=13-12) image with [CII] contours.

[CII] is ionized gas at the boundary of dense warm CO.

(Perez-Beaupuits, Güsten, and GREAT team, in preparation)

Lee et al. 1996

VLA image

[CII] image

CO (13-12) contours

Comparison between Herschel and SOFIA far-IR instrumentsPACS

specFIFI-LS HIFI GREAT PACS

imagerHAWC

Wavelength range (μm)

55-210 42-110,110-220

157-213, 240-625

60, 110-125, 156-165, 200-240

55-210 53, 89, 115, 216

Field of View

47’’x47’’ 30’’x30’’60’’x60’’

Single pixel

Single pixel (7 pixels in future)

47’’x47’’ 27’’x72’’, 42’’x112’’, 72’’x192’’,96’’x256’’

Pixel size 9’’ 6’’, 12’’ 13’’, 39’’ 20’’ 9’’ 2.3’’,3.5’’, 6’’, 8’’

Sensitivity 2-5x10-18

Wm-2

100-250mJy

Similar to PACSspec within a factor of 3-5, but efficient mapping

A few to 100 mK

Similar to HIFI with a factor of 2-8, but efficient mapping

2-5x10-18

Wm-2

100-250mJy

60-120mJy

SpectralResolution

2600-5400 (55-72μm)900-3000

1000-5000

1000-107 106-108 2600-5400 (55-72μm)900-3000

None

Current Schedule• GREAT Short Science Flights: April 2011 • FORCAST Basic Science Flights: May to June 2011• GREAT Basic Science Flights: July and September 2011• FLITECAM Verification flights: Aug 2011

Draft AO for 2nd Generation Instruments• Draft AO: http://soma.larc.nasa.gov/SOFIA/sofiapbtelecon_agenda.html• Anticipated proposal announcement: Mid- 2011 (it is coming soon)• Asilomar meeting proceedingshttp://www.sofia.usra.edu/Science/workshops/asilomar.html

Next Science Proposal Call • Fall to Winter 2011, 300 hours observing time: open internationally• FORCAST(w/grism), GREAT, FLITECAM and HIPO are scheduled to be included.• Data Analysis funding is available for US Investigators

W44, enveloped by a molecular cloudRadiative signatures:• IR-bright => shock cooling in

relatively dense gas (>103 cm-3)• Broad molecular lines (eg. CO 2-1)• OH(1720 MHz) Masers (Hewitt et al. 2008, 2010)

Catalog of SNR/MCs (Jiang et al. 2009)• 34 confirmed (24 w/Masers)• 11 probable• 19 possible

64 of 274 Galactic SNRs (~23%) expect ~40% of SNe in field

Supernova Remnants Interacting with Clouds

20cm Radio

Recent Spitzer IR surveys have made the largest contribution(Reach et al. 2006; Hewitt, Rho et al. 2009; Anderson, Rho et al. 2011)

• Spitzer GLIMPSE survey detected 18 IR-bright SNRs

• Colors hint at dominant cooling lines and shock type.

Supernova Remnants Interacting with Clouds

from Reach et al. 2006

Shocks into multi-phase Molecular Clouds

(Chevalier 1999, Cox et al. 1999, Reach et al. 2005)

How to reconcile different IR lines? multiple shocks in a multi-phase medium

What about dust emission?

Dense Clump

Atomic Gas

Dust Heating by SNR shocks

Collisional Heating dominatesthrough collisions with electrons Hcoll ≈ 5.4E-18 a2 ne T3/2 [erg/s]

Radiative Heating dominatesthrough H recomb. emission

[Fe II] emitting gas: ne~100-1000 cm-3, T=5-10x103 K

Above assumes radiative field is = ISRF

SNRs have even higher UV radiation from H-recomb (fast shocks, [Fe II])

Maser-emitting SNRsYoung SNR