Документ взят из кэша поисковой машины. Адрес оригинального документа : http://www.eso.org/~rsiebenm/FTP/PPT/pah.pdf Дата изменения: Thu May 27 20:03:21 2010 Дата индексирования: Fri Feb 28 11:27:22 2014 Кодировка: Поисковые слова: http www.badastronomy.com phpbb index.php

Frank Heymann (PhD) Endrik Krgel

Dust model of the ISM PAH bands in starburst nuclei Monte Carlo radiative transfer

PAH destruction in T Tauri disks

Ralf Siebenmorgen

Toulouse June'10


dust'1990

Ralf Siebenmorgen

Toulouse June'10


1: polarisation

spheroids

Voshchinnikov (2004)

Ralf Siebenmorgen

Toulouse June'10


2: `'2200" bump +

3: PAH absorption
Vertraete et al. 1992 Malloci et al. 2007 Schutte et al. 1993

gr

PAH

Ralf Siebenmorgen

Toulouse June'10


extinction'2010

Si + aC Graphite PAH ISM [g]
Ralf Siebenmorgen

: 60е < a < 0.2-0.3µm, ~a: 5е < a < 80 е , : 30, 200 C ~a

3.5

-3.5

: 0.66Si + 0.22aC + 0.07gr + 0.05 PAH [g]

Toulouse June'10


mean I S R F

Ralf Siebenmorgen

Toulouse June'10


4: abundance +

5: PAH bands

"Carbon crisis"

abundances [ppm]:
Ralf Siebenmorgen

31Si + 150aC + 50gr + 30PAH
Toulouse June'10


dust'2010

Ralf Siebenmorgen

Toulouse June'10


ISO

HD97300

Boulanger et al. (1998)
Ralf Siebenmorgen Siebenmorgen et al. (1998) Toulouse June'10


Radiative transfer in SB

NGC1808

Siebenmorge gen Ralf Siebenmorn et al. (2001)

Toulouse June'10


post ISO

Ralf Siebenmorgen

17 features

Toulouse June'10


post ISO

Si f Siebenmorgen Ralebenmorgen et al. (2001)

Toulouse June'10


post Spitzer

SED model grid:
· luminosity

· size
· mass

Ralf Siebenmorn et al. (2007) Siebenmorge gen

Toulouse June'10


high z

Efs Siebenmo gen Ralf tathiou r& Siebenmorgen (2009)

Toulouse June'10


Monte Carlo


Arbitrary dust distribution Pseudo adaptive mesh



1.

geometry

Ralf Siebenmorgen

Original code by Krgel (2006)

Toulouse June'10


Monte Carlo


Source emits "photon packages" of equal energy

1.

geometry source

2.

Ralf Siebenmorgen

Toulouse June'10


Monte Carlo
= - ln()


absorption / scattering / no interaction

1.

geometry source inter-action dust temperature

2.

3.

4.

Ralf Siebenmorgen

Toulouse June'10


Monte Carlo


Photons escape model cloud

1.

geometry source inter-action temperature detection
Toulouse June'10

2.

3.

4.

5.

Ralf Siebenmorgen


Monte Carlo
+ PAH



store PAH absorption

events of each cell


compute PAH emission neglect PAH self absorption



Ralf Siebenmorgen

Toulouse June'10


MC
parallelization
·

Multiple photons at a time:
1. Cell locked when hit by photon
2. Parallel random number

generator (Mersene Twister)
3. Computer games Graphical

Processing Units (CUDA)

Ralf Siebenmorgen

Toulouse June'10


1D benchmark sphere

Iveciz (99)

Ralf Siebenmorgen

Toulouse June'10


1D benchmark sphere
1

T* = 2500K (r) = const.
AV=10 100 1000 mag

~5% for 0

Ralf Siebenmorgen

Toulouse June'10


MC
methods

Method

Parallelization YES (but floating)

Advantage

Time
Benchmark sphere ~1000)

Lucy Bjorkman & Wood our

Optical thin No iteration GPU

>1h 5min <1min

Partly (not independent)
YES

Ralf Siebenmorgen

Toulouse June'10


Monte Carlo
+ PAH

Ralf Siebenmorgen

Toulouse June'10


2D benchmark

Pascucci et al (2004)

Disk:
T* = 5800K L * = Lsun (r) : hydro static equilibrium (Chiang & Goldreich 1997)
Toulouse June'10

Ralf Siebenmorgen


2D benchmark disk

1= 10

face-on

edge-on

100

~10% for 0

Ralf Siebenmorgen

Toulouse June'10


3D proto-planetary disk + spiral

T* = 5800K L * = Lsun Av =10mag

MHD (Fargo)

density

8au 3au

Ralf Siebenmorgen

Toulouse June'10


3D proto-planetary disk + spiral

Ralf Siebenmorgen

Toulouse June'10


ELT 42m
PAH imaging

Ralf Siebenmorgen

Toulouse June'10


ELT 42m
PAH imaging

D = 50pc 50mas at 11.3m dual band + coronograph PSF

Ralf Siebenmorgen

Toulouse June'10


PAH imaging

gap

D = 50pc 50mas at 11.3m
/px

Ralf Siebenmorgen

Toulouse June'10


T Tauri stars

PAH detection rate:
Herbig AeBe 60% TTS 10%
Ralf Siebenmorgen Toulouse June'10


T Tauri stars

Ralf Siebenmorgen

Toulouse June'10


Ralf Siebenmorgen

Toulouse June'10


PAH in a mono-energetic heating bath

if | Uf ­ Ui ­ h | < Ѕ Uf : Afi = K F / h
Ralf Siebenmorn & Krgel (2010) Siebenmorge gen Toulouse June'10


PAH destruction
Eo
T [K]

Unimolecular dissociation:
Arrhenius form: t
dis

tcool
time

~ exp(Eo/kT) /

0

«t

cool/f

~ 1s

t

abs

~ 1h

T

min

= Eo/k ln(0) ~2000K; ~ 0.1 Nc.E

Eb ~ 5eV; 0 = 1013Hz => Nc < 2 E /[eV] (PAH unstable)

E = 3Nc kT

min

o

Omont (1986); Micedlotta et al. (2010); Tielens (2005) Ralf Siebenmorgen To

ulouse June'10


PAH destruction
Eo

Unimolecular dissociation:
t
dis min

~ exp(Eo/kT) /

0

«t

cool/f

~ 1s

T

= Eo/k ln(0) ~2000K; ~ 0.1 Nc.E

Eo ~ 5eV => Nc < 2 E /[eV] (PAH unstable)

E = 3Nc kT

min

o

1) single hard photon : independent of distance 2) many soft photons : ~ 1AU

Ralf Siebenmorgen

Toulouse June'10


Stationary disk
z

Sufficient X-ray photons?




=1
I

}

top surface layer = /

# C in PAH = h 4r2/L # hard absorption/sec

,,PAH removal time
Ralf Siebenmorgen

<< TT phase
Toulouse June'10


PAH replenishment
Vertical mixing in disk?

/v = t

exp

> NC t

abs

Ralf Siebenmorn & Krgel (2010) Siebenmorge gen

Toulouse June'10


Future
MC model of T Tauri disks Heating: photosph.+FEUV + X-rays Dust + Gas Density structure PAH emission + destruction

Ralf Siebenmorgen

Toulouse June'10


Conclusion

?
Ralf Siebenmorgen Toulouse June'10