The disk of AB Aurigae

1
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
2
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)
Ringberg April 15
3
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
4
Motivation

• Why AB Aurigae ?
• One of the best-studied Herbig Ae(/Be) stars A0
  Vesh
• D 144 23 pc, M? 2.4 0.2 M8, 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 M8,
• i,f poorly defined)
• (Mannings Sargent 1997,
  Henning et al. 1998)
• extended, low-density envelope
• (R gt 1000 pc, optically
  thin, AV 0.5m
• internal
  structure extent not well determined)

? ?
-17
? well suitable object to study the chemistry of
the disk
5
R-band image, University of Hawaii 2.2m
telescope (Grady et al. 1999)
AB Aur General Properties The envelope
IRAS 60µm
?

• ? extended
• asymmetrical
• nebulosity,
• inhomogeneous
• spherical
• envelope,
• Renvelope
• 1300 AU ( 10?)
• i lt 45o

HST visual image (Grady et al. 1999)

• ? IRAS 60 µm map
• ? Renvelope 4 35 000 AU
• SED Modeling (Miroshnichenko
• et al. 1999) ? Renvelope 5000 AU

N E
10?
6
AB Aurigae General Properties - The disk
13CO (1?0) OVRO
Main velocities
Subaru H-band image (Fukagawa et al. 2004) mass
supply from the envelope contributes to the
spiral instability
4.5 5 5.5 6
6.5 vLSR (km s-1)
5?
5 0
-5 arcsec
(Mannings Sargent, 1997, OVRO) Keplerian
rotation, a/b ? 110 AU / 450 AU ? i ? 76o
8?
8?
HST image (Grady et al. 1999)
7
AB Aur - Our observational results IRAM 30m

Observations

• 2000-2001
• beamsizes
• 10? - 30?
• Results
• detected
• species
• HCO, CS,
• CO, C18O,
• HCN, HNC,
• 3? SiO,
• H2CO, CN,
• DCO

CS 5?4
CO 2?1
C18O 2?1
CS 2?1
0 5 10
0 5 10
0 5 10
0 5 10
HCO 1?0
HCO 3?2
Tmb K
0 10 20
-10 0 10 20
0 5 10
-5 0 5 10 15
SiO 2?1
H2CO 31,2?21,1
CN 1?0
? non-detections N2H, CH3CN, HDCO, C2H,
SO, SO2
0 5 10
0 5 10
0 5 10
0 5 10
vLSR km/s
7/18
8
AB Aur - Our observational results
PdB Interferometer
sum
HCO J1-0
Beam 6.5? x 5?
Observations 2002, beams 5? x 7?
Main velocities
Results HCO map, 3? 34SO, SO2, HCN,
C2H,
HST image Grady et al. 1999
34SO 32?21
SO2 73,5?82,6
S?Jy
HCN 1?0
velocity km/s
9
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
9/18
10
The model of the AB Aur system
Disk 2D passive disk with vertical
temperature gradient, ?(r) ?o(r / Ro)p,
p -1.5, Mdisk 3 ( 0.5) 10-2 M8, Rin
Ro 0.7 AU, Rout 400 AU, vertical hight
0.3 350 AU i 173, ? 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
M8, 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
ad 0.3 µm
-30
400 AU
10/18
11
AB Aur Chemical Modeling
(Semenov et al., 2004)

• ? 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 2104 cm-3, time
  span 1Myr, Wiebe et al. 2003)

11/18
12
AB Aur Chemical Modeling

• 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
• 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)

? ?
Results
2D-distribution of column densities and
molecular abundances for 3 Myr evolutionary
time span
12/18
13
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-convolved

Results
13/18
14
Modeling Results ???(1-0) disk map
AB Aurigae
4 3 2 1 0 -1 -2 -3 -4

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

Disk model R 400 AU
-4 -3 -2 -1
0 1 2 3 4

arcsec
14/18
15
Modeling Results ???(1-0) disk map
AB Aurigae
Subaru H-band image
disk model Fukag
awa et al. 2004
4 3 2 1 0 -1 -2 -3 -4
? sub-component structures possibly stem from
the spirals
-4 -3 -2 -1
0 1 2 3 4

arcsec
15/18
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Modeling Results Estimate of i and ?
i 10o i 15o
i 20o
AB Aurigae
? inclination angle of the disk ?
i 17 3 ? position angle ? ?
8010
? 40o ? 80o
? 120o
-30

• 2 1
  2 1
  2
• 
  arcsec

16/18
17
AB Aur -Modeling Results Line profiles
of different species Fit for three
cases Left Middle Right
Tmb K
only the disk only the envelope disk
envelope
? ?
? ?
(J2-1)
17/18
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AB Aurigae - Conclusions

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

• 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
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AB Aur - Our observations
IRAM 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
IRAM
Plateau de Bure Interferometer 2002, synthezied
beam sizes 5?7? detected HCO ( 3? 34SO,
SO2, HCN, C2H, )
PdBI
7/19
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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 needed

18/18
23
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)

• 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

13/18
24
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Modeling Results ???(1-0) disk map
AB Aurigae
Subaru R-band image Fukagawa et al.
2004
4 3 2 1 0 -1 -2 -3 -4
? sub-component structures possibly stem from
the spirals
-4 -3 -2 -1
0 1 2 3 4

arcsec
15/18
26
HCO(1-0) 29
24
27
HCO(3-2) 9.3
Disk Envelope
Both
25
28
CO(2-1) 11
Disk Envelope
Both
26
29
C18O(2-1) 11
Disk Envelope
Both
27
30
CS(2-1) 26
Disk Envelope
Both
28
31
Mass of the disk
21
32
Mass of the disk
22
33
AB Aurigae General properties

• Star
• Disk
• Envelope

3
34
The AB Aurigae system IR
IRAS 60?m map ? radius of the envelope 35000 AU
4
35
The AB Aurigae system visual
(Grady et al. ApJ, 523, 151, 1999)
Scattered light image ? extended asymmetrical
nebulosity
5
36
AB Aur General Properties - The envelope
HST K-band image (Grady et al. 1999)
inhomogeneous spherical envelope, Rdisk ? 1300
AU ? i lt 45o
37
The AB Aurigae system 10?m
The shape of the 10?m-silicate band implies that
adlt1?m (Bouwman et al. AA, 375, 950, 2001)
8
38
Results PdB Interferometer
Keplerian rotation, positional angle ? ? 90? ?
39
Chemical processes in space
Grain
15
40
Disk positional angle
20
41
HCO(1-0) 29
42
Temperature of the envelope
43
AB Aurigae General Properties - The disk
Subaru H-band image (Fukagawa et al. 2004) mass
supply from the envelope contributes to the
spiral instability
(Mannings Sargent, 1997) Keplerian rotation,
a/b ? 110 AU / 450 AU ? i ? 76o
8?
8?
HST image (Grady et al. 1999)
44
AB Aur - Our observational results
PdB Interferometer
Main velocities
4.5 5 5.5 6
6.5 vLSR (km s-1)
Keplerian rotation, position angle ? ? 90? ?
34SO 32?21
SO2 73,5?82,6
S?Jy
HCN 1?0
45
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
9/18