the disk of ab aurigae

The disk of AB Aurigae

Dmitry Semenov (MPIA, Heidelberg, Germany)

Yaroslav Pavluchenko (INASAN, Moscow, Russia)

Katharina Schreyer (AIU, Jena, Germany)

Thomas Henning (MPIA, Heidelberg, Germany)

Kees Dullemond (MPA, Garching, Germany)

Aurore Bacmann (Observatoire de Bordeaux, France)

Ringberg April 15

Ringberg April 15

The disk of AB Aurigae

Chemical modeling

Dmitry Semenov

Observations

Aurore Bacmann(Observatoire de Bordeaux, France)

Katharina Schreyer (AIU Jena)

(MPIA Heidelberg)

Radiative transfer Lines:

Yaroslav Pavluchenko(INASAN, Moscow, Russia)

Continuum: Kees Dullemond

(MPA, Garching, Germany)

Outline• Motivation• General Properties• Observations & Results• a) IRAM 30m & b) PdBI• The Model of the AB Aurigae system• Chemical modeling • Line radiative transfer simulations • Modeling results • Conclusions

3/18

MotivationWhy AB Aurigae ?

One of the best-studied Herbig Ae(/Be) stars: A0 Ve+sh D = 144 +23 pc, M = 2.4 ± 0.2 M, age = 2−5 Myr

(e.g. van den Ancker et al. 1997, Manning & Sargent 1997, Grady et al. 1999, deWarf et al. 2003, Fukagawa et al. 2004)

circumstellar structure:

compact disk (Rdisk ≈ 450 pc, Mdisk ≈ 0.02 M,

i, poorly defined) (Mannings & Sargent 1997, Henning et al. 1998)

+ extended, low-density envelope (R > 1000 pc, optically thin, AV = 0.5m

internal structure + extent not well determined)

-17

well suitable object to study the chemistry of the disk

R-band image, University of Hawaii2.2m telescope(Grady et al. 1999)

10″

8

AB Aur: General PropertiesThe envelope

IRAS 60μm

IRAS 60 μm map

Renvelope = 4’ ≈ 35 000 AU

SED Modeling (Miroshnichenko

et al. 1999) Renvelope ≈ 5000 AU

extended asymmetrical nebulosity, inhomogeneous spherical envelope,

Renvelope ≈ 1300 AU ( = 10″) i < 45o

HST visual image (Grady et al. 1999)

N

E

AB Aurigae: General Properties - The disk

Subaru H-band image(Fukagawa et al. 2004):mass supply from the envelope contributesto the spiral instability

8″

8″

Main velocities13CO (10) OVRO

5″ 5 0 -5arcsec 4

.5

5

5.5

6

6

.5

v

LS

R

(km

s-1)

(Mannings & Sargent, 1997, OVRO) Keplerian rotation, a/b 110 AU / 450 AU i 76o

HST image (Grady et al. 1999)

non-detections N2H+, CH3CN, HDCO, C2H, SO, SO2

AB Aur - Our observational results:IRAM 30m

CO 21 C18O 21

DCO+ 21

HCN 10

CS 54

HCO+ 10 HCO+ 32

CS 21

SiO 21 H2CO 31,221,1

Tm

b [

K]

vLSR [km/s]

0 5 100 5 10

HNC 10

0 10 20

CN 10

0 5 100 5 10

-10 0 10 20 0 5 10 -5 0 5 10 15

0 5 10 0 5 10 0 5 100 5 10

7/18

2000-2001 beamsizes: 10″ − 30″

Results: detected species: HCO+, CS, CO, C18O, HCN, HNC, ~3: SiO, H2CO, CN, DCO+

Observations:

sum

HST image: Grady et al. 1999

HCO+ J=1-0Beam6.5″ x 5″

34SO 3221

HCN 10

SO2 73,582,6

S[

Jy

]

AB Aur - Our observational results: PdB Interferometer

4.5

5.5

6

.5

v

LS

R

(km

s-1)

Main velocities Results:

HCO+ map, ~3: 34SO, SO2, HCN, C2H, …

Observations:2002, beams ~ 5″ x 7″

C2H 10 3/2-1/2 F=2-1

velocity [km/s]

9/18

SED

AB Aurigae

The model of the AB Aur system(Dullemond & Dominik, 2004)

2D continuum radiative transfer code

passive flared disk model

low-density cones have the open angle shadowed part of the envelope is denser and cooler

R

Disk: 2D passive disk with vertical temperature gradient,

(r) = o·(r / Ro)p, p = −1.5, Mdisk = 3 (± 0.5) 10-2 M,

Rin = Ro = 0.7 AU, Rout = 400 AU, vertical hight = 0.3 … 350 AU

i = 17˚±3˚, = 80˚ +10˚, Tdisk = 35 ... 1500 K

ndisk = 10-24 ... 10-9 g cm-3,

Keplerian rotation, Vturb = 0.2 km/s

Envelope: Rin = 0 / 400 AU, Rout = 2100 AU,

(r) = o·(r / Rin )p, p = −1.0,

low-density cones: = 25˚, olobe = 9.4 10-20 g cm-3, Tenv = 100 K

shadowed torus: olobe = 5.5 10-19 g cm-3, Tenv = 35 K

Menv 4 · 10-3 M, ad = 0.1 μm, AV ≈ 0.5m, Vturb = 0.2 km/s,

stationary accretion, V(r) 1 / r (0.2 km/s at r = Rin),

dynamical timescale is ~ 107 yrs

−30˚

ad = 0.3 μm

10/18

The model of the AB Aur system

T = 35 K

T = 100 K

400 AU

a gas-phase chemistry (UMIST95) with a surface reaction set

(Hasegawa et al. 1992)

a deuterated chemical network from Bergin et al. 1999

self- & mutual-shielding of H2 (Draine & Bertoldi 1996) and

CO (Lee et al. 1996)

the 1D slab model to compute UV- and CR-dissociation and

ionization rates depending on vertical height

ionization by the decay of radionuclides (disk)

thermal, photo-, and CR-desorption of surface species back

in the gas-phase

initial abundances: chemical evolution of a molecular cloud (low-metal

set, T = 10 K, n = 2·104 cm-3, time span = 1Myr, Wiebe et al. 2003)

(Semenov et al., 2004)

11/18

AB Aur – Chemical Modeling

Results : 2D-distribution of column densities and molecular abundances for 3 Myr evolutionary time span

Modeling of the chemistry with reduced chemical network (in total 560 species made of 13 elements, involved in 5335 reactions)

On the basis of the fractional ionisation, disk divided into three layers:

(i) dark dense mid-plane (chemical network of ~ ten species & reactions)

(ii) intermediate layer (chemistry of the fractional ionization driven by the stellar X-rays)

(iii) unshielded low-density surface layer (photoionisation-recombination processes)

12/18

AB Aur – Chemical Modeling

AB Aur - Line radiative transfer(Pavluchenkov & Shustov, 2004)

2D URAN NLTE code: further development of the public 1D code by Hogerheijde & van der Tak (2000)

solution of the system of radiative transfer equations using the Accelerated –Iteration (ALI) method

the mean intensities are calculated with the Accelerated Monte Carlo algorithm

the same model as obtained by the continuum radiative transfer

synthetic line profiles, beam-convolved13/18

Results:

Modeling Results: НСО+(1-0) disk map

Inverse P Cygni profile a possible evidence for the accretion at distances ~ 600 AU

-4 -3 -2 -1 0 1 2 3 4 arcsec

4

3

2

1

0

-1

-2

-3

-4

14/18

AB Aurigae

Disk model: R = 400 AU

4

3

2

1

0

-1

-2

-3

-4

Modeling Results: НСО+(1-0) disk map

15/18

Subaru H-band image

disk model

Fukagawa et al. 2004

sub-component structures possibly stem from the spirals

AB Aurigae

-4 -3 -2 -1 0 1 2 3 4 arcsec

inclination angle of the disk i = 17˚± 3˚

position angle = 80˚+10˚

Modeling Results: Estimate of i and

−30˚ = 40o = 80o = 120o

1 2 1 2 1 2 arcsec

i = 10o i = 15o i = 20o

16/18

AB Aurigae

Tm

b [

K]

AB Aur -ModelingResults:Line profiles

of different species

Fit for three cases:

Left:

Middle:

Right:

only the disk

only the envelope

disk + envelope

17/18

AB Aurigae - Conclusions

There is an evidence for the accretion at distances of

about 600 AU from the star

It is shown that the IRAM single-dish spectra can be adequately described by the «disk-in-envelope» model

The coupled dynamical, chemical, and radiative transfer

simulation is an effective tool to find a consistent model

18/18

Based on observational data a suitable model of the AB Aurigae system is acquired mass, size, geometry and dynamical structure temperature and density distribution

AB Aur - Our observations

IRAMIRAM 30m:

2000-2001, beam sizes 10″ - 30″detected different transitions of HCO+, CS, CO, C18O, HCN, HNC, ~3: SiO, H2CO, CN, DCO+

non-detections: N2H+, CH3CN, HDCO, C2H, SO, SO2

Plateau de Bure Interferometer:

2002, synthezied beam sizes 5″×7″detected HCO+ (& ~ 3: 34SO, SO2, HCN, C2H, …)

PdBI

7/19

AB Aurigae - Conclusions • About a dozen molecular spectra as well as the HCO+(1-0)

interferometric map of AB Aurigae are acquired

• There is an evidence for the accretion at distances of about 600 AU from the star

• The mass, size, geometry and dynamical structure of the disk are constrained

• The temperature and density distribution of the envelope are estimated

• It is shown that the IRAM single-dish spectra can be adequately described by the «disk-in-envelope» model

• Further investigations are needed18/18

AB Aur - Line radiative transfer

• System of equations including the equation of radiative transfer and statistical equations for the level populations

• Mean intensity in every cell is calculated by the accelerated Monte-Carlo technique (AMC)

• Level populations are iteratively calculated using the Accelerated Lambda Iteration (ALI) scheme

• Global iterations are finished after a requested accuracy in level populations is achieved

(Pavluchenkov & Shustov, 2004)

• 2D URAN NLTE code: further development of the public 1D code by Hogerheijde & van der Tak (2000)

13/18

rayi

ds

Icell boundaries

1 2 3 N

1. Geometry

VVVVV

RfRf

RR ,,0,0,

,

1D model 2D model

iR 1iR

i

1i

0

Grid

cell

er

e

e

N

CMBd

NNN

ddd

dd

d

II

eIeeSII

eeSII

eeSII

eSI

N

1

1

1

1

1

)(323

212

11

213

12

1

Back-up integration:First calculation Second calculation

Comparison of the level populations for each cell to estimate Monte-Carlo error

3. Estimation of the error in level populations

2. Integration of transfer

equation

-4 -3 -2 -1 0 1 2 3 4 arcsec

4

3

2

1

0

-1

-2

-3

-4 sub-component structures possibly stem from the spirals

Modeling Results: НСО+(1-0) disk map Subaru R-band image

Fukagawa et al. 2004

15/18

AB Aurigae

30.01.2004 Friday-seminar talk at AIU Jena 24

HCO+(1-0) [29’’]

Disk Envelope Both

Line wings disk, central peak envelope


HCO+(3-2) [9.3’’]

Disk Envelope Both

Beam is smaller contribution from the disk is larger


CO(2-1) [11’’]

Disk Envelope Both

Line is optically thick, 12}max{ 1)-CO(2


C18O(2-1) [11’’]

Disk Envelope Both

Line is optically thin, 2

1)-O(2C103}max{ 18


CS(2-1) [26’’]

Disk Envelope Both


Mass of the disk

HCO+(1-0) is optically thin

chemistry) , ,Gas

Dust(}max{ ddiskHCOmb aMNT


Mass of the disk • Dependence on the grain size:

• Dependence on the chemical network:

• Dependence on the gas-to-dust ratio: ?• Dependence on the disk structure: ?

)μm 3.0(5.1μm) 0.1( diskdisk MM

)UMIST95(3.1)NSM( diskdisk MM


AB Aurigae: General properties• Star:

• Disk:

• Envelope:

Myr) 52( sequence-main-pre

,50,5.2~,5.2 K, 10000

,5.0 AU), 1451( pc 145 sh,A0Ve

SunSunSun

mV

t

LLMMRRT

Ar

definedpoorly are and

rotation, Keplerian ,10~AU, 450 Sun2

i

MMR

understood not well are properties physical and dynamical

D/IR),(visual/SE AU 35000/5000/1300~ R


The AB Aurigae system: IR

IRAS 60m map radius of the envelope ~ 35000 AU

8


The AB Aurigae system: visual

Scattered light image extended asymmetrical nebulosity

(Grady et al. ApJ, 523, 151, 1999)

HST K-band image (Grady et al. 1999): inhomogeneous spherical envelope, Rdisk 1300 AU i < 45o

AB Aur: General Properties - The envelope


The AB Aurigae system: 10m

The shape of the 10m-silicate band implies that ad<1m (Bouwman et al. A&A, 375, 950, 2001)

Keplerian rotation, positional angle 90 ?

Results: PdB Interferometer


Chemical processes in space

Grain

Desorption

Accretion

Surface reaction

Gas-phase reaction

UV, CR, X-ray

Mantle

Grain


Disk positional angle

Positional angle of the disk oo 3080 = 40o = 80o = 120o

HCO+(1-0) [29’’]

Line wings disk, central peak envelope

Temperature of the envelope

Envelope temperature (r 800 AU) 35Kkinmb TT

T = 15K T = 25K T = 35K

8″

8″

HST image (Grady et al. 1999)

AB Aurigae: General Properties - The disk

Subaru H-band image(Fukagawa et al. 2004):mass supply from the envelope contributesto the spiral instability

(Mannings & Sargent, 1997) Keplerian rotation, a/b 110 AU / 450 AU i 76o

Main velocities13CO (1-0) OVRO

5″ 5 0 -5arcsec 4

.5

5

5.5

6

6

.5

v

LS

R (

km s

-1)

sum

HST image: Grady et al. 1999

HCO+ J=1-0Beam6.5″ x 5″

34SO 3221

HCN 10

SO2 73,582,6

S[

Jy

]

Main velocities

Keplerian rotation, position angle 90 ?

4.5

5

5

.5

6

6.5

v

LS

R (

km s

-1)

AB Aur - Our observational results: PdB Interferometer

9/18

SED

AB Aurigae

The model of the AB Aur system(Dullemond & Dominik, 2004)

R

2D continuum radiative transfer code

passive flared disk model

low-density cones have the open angle shadowed part of the envelope is denser and cooler

the disk of ab aurigae

Documents

disk rband image

au sed modeling miroshnichenko

observational results

d passive disk

lowdensity envelope

hco map

ab aur systemdullemond

o hst image grady