the disk of ab aurigae
DESCRIPTION
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). - PowerPoint PPT PresentationTRANSCRIPT
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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
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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)
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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
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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
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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
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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)
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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:
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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]
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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
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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
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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
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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
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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:
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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
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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
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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
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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
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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
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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
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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 needed18/18
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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
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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
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-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
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30.01.2004 Friday-seminar talk at AIU Jena 24
HCO+(1-0) [29’’]
Disk Envelope Both
Line wings disk, central peak envelope
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30.01.2004 Friday-seminar talk at AIU Jena 25
HCO+(3-2) [9.3’’]
Disk Envelope Both
Beam is smaller contribution from the disk is larger
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30.01.2004 Friday-seminar talk at AIU Jena 26
CO(2-1) [11’’]
Disk Envelope Both
Line is optically thick, 12}max{ 1)-CO(2
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30.01.2004 Friday-seminar talk at AIU Jena 27
C18O(2-1) [11’’]
Disk Envelope Both
Line is optically thin, 2
1)-O(2C103}max{ 18
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30.01.2004 Friday-seminar talk at AIU Jena 28
CS(2-1) [26’’]
Disk Envelope Both
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30.01.2004 Friday-seminar talk at AIU Jena 21
Mass of the disk
HCO+(1-0) is optically thin
chemistry) , ,Gas
Dust(}max{ ddiskHCOmb aMNT
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30.01.2004 Friday-seminar talk at AIU Jena 22
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
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30.01.2004 Friday-seminar talk at AIU Jena 3
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
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30.01.2004 Friday-seminar talk at AIU Jena 4
The AB Aurigae system: IR
IRAS 60m map radius of the envelope ~ 35000 AU
8
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30.01.2004 Friday-seminar talk at AIU Jena 5
The AB Aurigae system: visual
Scattered light image extended asymmetrical nebulosity
(Grady et al. ApJ, 523, 151, 1999)
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HST K-band image (Grady et al. 1999): inhomogeneous spherical envelope, Rdisk 1300 AU i < 45o
AB Aur: General Properties - The envelope
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30.01.2004 Friday-seminar talk at AIU Jena 8
The AB Aurigae system: 10m
The shape of the 10m-silicate band implies that ad<1m (Bouwman et al. A&A, 375, 950, 2001)
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Keplerian rotation, positional angle 90 ?
Results: PdB Interferometer
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30.01.2004 Friday-seminar talk at AIU Jena 15
Chemical processes in space
Grain
Desorption
Accretion
Surface reaction
Gas-phase reaction
UV, CR, X-ray
Mantle
Grain
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30.01.2004 Friday-seminar talk at AIU Jena 20
Disk positional angle
Positional angle of the disk oo 3080 = 40o = 80o = 120o
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HCO+(1-0) [29’’]
Line wings disk, central peak envelope
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Temperature of the envelope
Envelope temperature (r 800 AU) 35Kkinmb TT
T = 15K T = 25K T = 35K
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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)
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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
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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