Transcript Studio nel vicino infrarosso di Jet in sorgenti stellari

Near infrared, IFU
spectroscopy of HH99
Teresa Giannini
[email protected]
INAF-Osservatorio Astronomico di Roma
The star forming process
gravitational
Accretion
and ejection of material
molecular cores
contraction
from the protostar
Bipolar Outflow
Infalling Gas
Young Star
t = 104 – 105 yr
accretion
disc
planetary
system
t > 107 yr
T Tauri star
Main sequence star
t = 106 – 107 yr
Protostellar Jets: observations
HH111
infrared
visual
HH34
Bow wing
Properties:
Size: 0.1 - 10 pc
Velocity: 50 - 500 km s-1
Density: 102 - 106 cm-3
Temperature: 102 - 104 K
Mass loss: 10-5 - 10-8 M/yr
Ionization fraction: 0.02 – 0.5
Bow
head
Jet Vjet
Mach disc
(reverse shock)
Bow shape
forward shock
Vs
Why is important to study bow-shocks?
C-shock
H2
emission
H2
J-shock
ionic
emission
ionic emission
• direct interaction with the ISM:
compression, heating, medium
acceleration
• irreversible chemical changes of
gas composition (molecular
dissociation, sublimation of ices,
endothermic reactions, disruption of
dust grains)
• accumulated thermal energy
irradiated through line emission
Near-Infrared lines
H2 ro-vibrational
[FeII] fine structure
From line intensity ratios
and profiles:
V=7
Ground
electronic
state
•
•
•
•
•
•
Extinction
Temperature
Electron density
Ionization fraction
Velocity
Bow geometry
First 2-D analysis of a bow-shock:
observing HH99 with SINFONI
2-D structure of the shock surface
 IFU spectroscopy well suited
SINFONI spectrograph
• Spatial resolution ~250 mas; FoV=8x8 arcsec2
• IFU spectroscopy in J, H, K
• Spectral resolution: 2000 (J), 3000 (H), 4000 (K)
SINFONI data-cube
Davis et al.,1999
HH99: well known prototype of
bow shock !
D~130 pc (RCra star forming region)
1.7447
1.7449
1.7451
1.7472
1.7476
1.7478
1.7484
1.7492
1.7466
1.7457
1.7462
1.7480
1.7482
µm
1.7488
1.7453
1.7464
1.7470
1.7474
1.7486
1.7490
1.7455
1.7468 µm
• More than 170 observed lines (normally few lines are observed)
H2 ro-vibrational transitions
• Different morphology for low
(E  30000 K) and high (E  30000 K )
excitation lines.
Atomic transitions
• Mainly [FeII] transitions (46 lines)
• H, He recombination lines (8 and 2) and
[PII], [CoII], [TiII] transitions
• The atomic lines are emitted at the bow
apex region
C: [FeII] 1.64 µm
D: [FeII] 1.75 µm
A: H2 1-0 S(1) 2.12 µm B: H2 2-1 S(17) 1.76 µm
The intensity maps show a clear
bow-shape morphology
E: H Paß 1.28 µm
F: [PII] 1.18 µm
Giannini, Calzoletti et al. 2008
H2 diagnostics: temperature map  modelling the molecular emission
H2 critical density values are very low (102-103 cm-3)
ncr
A

  (T )
ij
i j
j i
ij
In the shocked gas the H2 ro-vibrational
transitions are thermalized at the
(kinetical) temperature T (LTE).
N v,J
g , J
ln(N / g )v, J  Ev, J / kT  ln Ntot / Q

e
 E v,J /kT
Q
N tot
with:
gv,J = (2I +1) (2J+1)
N: Column density
Q: Partition function
• Temperature gradient from
~2000 K up to ~ 6000 K
• H2 emission ‘survives’ beyond
the maximum temperature
predicted by C-shocks (~3000 K)
• N(H2) strongly decreases
toward the head (H2 dissociation)
103 K units
Fast non-dissociative C-type shock for the molecular emission (also at the bow-head)
H2 breakdown velocity
Le Bourlot et al., 2002
vdis important parameter that regulates :
• shock models
• efficiency of the H2 collisional dissociation
• fractional abundance H/H2 and chemical
reactions in the post-shock gas.
• vdis is a function of the
pre-shock density
• model predictions : vdis up
to:
25 km s-1 (Kwan 1972) ;
50 km s-1 (Smith, 1996) ;
80 km s-1 (Le Bourlot, 2002)
The 1.644 m peak is shifted with respect to the
intensity peak: geometrical effect due to the
inclination of the paraboloid :  ~ 40-60
From the line profile  vb~ 115 km s-1
• Rdis: cap radius beyond which H2
emission disappears : this happens at a
certain point along the bow where vshock
exceeds vdis, at which H2 dissociates.
• D’ : projected distance between the
intensity peak and the velocity peak
 From Rdis and D’ we measure
Vdis = 70-90 km
s-1
[FeII] at 1.644 µm
Our result agrees with the maximum value of Le Bourlot model  Models to be revised?
Gas-phase iron abundance  modelling the atomic emission
Iron is normally locked onto dust grains: the observation of iron lines is a measure of
the shock efficiency in disrupting dust grains and releasing metals in the gas phase.
Comparison of the observed ratio:
Iron fractional abundance map
[ FeII]1.26
[ PII]1.18
refractory element
non-refractory element
with the solar abundance ratio
• P and Fe are assumed all single ionized
• P and Fe lines lie nearby in wavelength,
have similar excitation energy, critical
density and first ionization potential
[FeII]1.257µm
line contours
• up to 70% of iron is in gas-phase (at
the bow-head) .
According to models this implies:
• partial disruption of the dust grains
• vshock > 100 km s-1
• T  104 K
Dissociative J-type shock for the atomic emission at the bow head
Conclusions
•
First detailed analysis of the interaction region between a protostellar jet and the ISM
•
First multiline analysis  detailed map parameters  stringent observative constraints
to shock models
•
The classical “C-shock” (wings) plus “J-shock” (head) scenario is just a first order
approximation :
- “hot” H2 also at the bow head (C-shock to be revised)
- FeII also in the wings
 new input for bi-dimensional shock models
•
From kinematics  new method to evaluate geometry and inclination angle
•
First measurement of the H2 breakdown velocity  new input for astrochemical models
Thanks!!
One-dimensional shock models: shock types
J-shock
TMAX ~ 105 K
J-shock with 200 yr
magnetic precursor
J(Jump)-type shock: discontinuity in the physical
properties on a planar surface
1
 nn kT  2

Vs  Vn  
 n 
• The ISM is permeated by magnetic field
• Into the ISM ions and neutral are decoupled
V Ai
J-shock with 900 yr
magnetic precursor
B

4i
 V  Vi 

Vims  
2
2 
 1  VAi Vn 
2
Ai
2
1
2
If Vs > Vn and Vs < Vims
J-shock with Magnetic Precursor
C-shock
As the Magnetic Precursor grows, the J
discontinuity becomes fainter, up to disappear
TMAX ~ 3-4·103 K
C(Continuous)-type shock
McCoey,2004
First of all: the extinction maps !
Intensity of an optically thin transition i
I ij 
h ij
4
Aij  ni ds
Observed intensity:
I
obs
ij
 A / 2.5
 Iij 10
H2
j:
I1obs I1 ( A1  A2
 10
obs
I2
I2
) / 2.5
If the transitions are originated from the same upper level, the line
ratio is independent from the local physical conditions, being a
function only of atomic parameters (Aij and νij) and extinction.
[FeII]
In the observed field of view variations of Av up to 4 mag are recognized
[FeII] diagnostics: electron density map
ne from line ratios between lines with:
• different critical density
• similar excitation energy
Te~18000 K
Te<10000 K
103 cm-3 units
Nisini et al, 2002
T = 2000K
T = 15000K
ne is typically 2-4 103 cm-3 with a peak
up to 6 103 cm-3 at the bow head
• Highly excited [FeII] lines observed for the first time: electron temperature
estimate at the bow head.
Fast J-type shock for the atomic emission
Bow kinematics and geometry
Line profile compared with the
instrumental profile
From the line profiles  vshock~ 115 km s-1
The 1.644 m peak is shifted with respect to
the intensity peak: geometrical effect due to
the inclination of the paraboloid :  ~ 40-60
H2 at 2.122µm
• Rdis: cap radius beyond which H2 emission
disappears : this happens at a certain
point along the bow where vshock exceeds
vdis, at which H2 dissociates.
• D’ : projected distance between the
intensity peak and the velocity peak
 From Rdis and D’ we measure
Vdis = 70-90 km s-1
[FeII] at 1.644 µm
Diagnostics with [FeII] lines
Most of prominent observed transitions are originate from
the 4D term and have similar excitation energies (~104 K)
They
are
NOT
suitable to diagnose
the gas temperature
A measure of the FWZI of
a high resolution [FeII] line
profile provides a direct
estimate of the shock
velocity (Hartigan,1987)
FWZI
They have different critical
density (104105 cm-3)
ncr = 7.2 104 cm-3
The ratio with lines
originated from the
4P term probes the
electron temperature
The
ratio
of
these lines is
sensitive to gas
density variation
Nisini,2002
Diagnostics with H2 lines
In the shocked gas the H2 ro-vibrational levels are
thermalized at the (kinetical) temperature T (LTE)
N v,J
Electronic
ground
state
g , J

e
 E v,J /kT
Q
N tot
with:
gv,J = (2I +1) (2J+1)
N: Column density
Q: Partition function
ln(N / g )v, J  E / kT  ln Ntot / Q
Constraining shock models with Boltzmann diagrams
J-shock
• A pure C-shock predicts temperature up to 3000 K
• A pure J-shock predicts temperature up to 500 K
A J-type component is responsible for the emissions
from higher excitation levels (Flower,1999)
C-shock
Temperature stratification
Departure from LTE (NLTE component):
• Increase in Vs and n decreases the departure
• Increase in B enhances the departure
NLTE
Problema dei coefficienti di Einstein (A) delle transizioni [FeII]
Esistono 3 determinazioni teoriche (due di Quinet et al. 1996 e una di Nussbaumer &
Storey 1988) che differiscono più del 30%, il che comporta:
~ 3 mag di differenza nel calcolo di AV, di conseguenza
un fattore ~ 3 nella stima delle intensità di righe a 1 µm,
un fattore ~ 34 nella stima delle intensità di righe a 0.5 µm !!!!
Per stimare i coefficienti di Einstein tramite osservazioni è necessaria una
determinazione indipendente dell’estinzione, i.e. effettuata con rapporti di righe
diverse dal [FeII]
Dalle righe di ricombinazione dell’idrogeno:
AV=1.8+/-1.9 mag
Tale indeterminazione non permette una
misura accurata dei coefficienti A
Le determinazioni teoriche di A non
riproducono i dati sperimentali
Tale metodo dovrebbe essere applicato
ad una sorgente di estinzione nota
One-dimensional Shock Models
Shock = discontinuity in the physical properties of a fluid
Shock  Vs > cs
in the InterStellar Medium (ISM): cs ~ 10 km/s
Rankine-Hugoniot Jump (J) Conditions for a strong (Vs >> cs), non-radiating (adiabatic)
shock in a monatomic gas.
Effects of magnetic field on a J-type shock
 ps  4  i
Vps  (1/4)Vs
Alfvén velocity
Pps  (3/4) i V 2 s
Pps
 ps
Into the ISM ions and
neutrals are decoupled
B
VA 
4
 (3 / 16)V 2 s
2
Vs


Tps  1.410 
K
-1 
100
km
s


12
V Ai

    VA
 i 
 n kT 
vn   n 
 n 
5
1
2
 V  Vi 

vims  
2
2 
1

V
V
Ai
n 

2
Ai
2
1
2
If B=0 and vs > vn
If B≠0 and vs > vn,ims
Discontinuous Shock (J-type shock)
If B ≠ 0 and vs < vims and vs > vn
Magnetic Precursor
If B < Bcrit
J-shock with Magnetic Precursor ((C+J)-type shock)
If B > Bcrit
C-type shock
(Draine, 1980)
We measure vdis between 70 and 90 km s-1
 H2 dissociation inefficient process
Le Bourlot et al., 2002
Our result (vdis =80-90 km s-1)
marginally agrees with the maximum
value of Le Bourlot model, but would
imply a very low pre-shock density
 Models to be revised?