Reservoirs of Water
in Protoplanetary Disks:
a multi-wavelength view
Davide FEDELE (INAF - Osservatorio Astrofisico di Arcetri)
S. Bruderer, E. F. van Dishoeck, DIGIT team
Outline
•
Introduction
•
H2O in Disks: from Spitzer to Herschel
•
H2O abundance in HD 100546 & HD 163296
•
Conclusions
Water in protoplanetary disks
T < 150 K
T > 150 K
H2O phase transition gas —> solid
• Local enhancement of solid surface density
• Affects physical and chemical evolution
Water on Earth
•
“Wet” formation (e.g., Drake ’05)
By adsorption of H2O-vapor on dust
grains. Accretion of hydrated silicates
•
“Dry” formation (e.g.Morbidelli et al. ’00)
Water delivered from asteroids and
comets after the planet has formed
Where is H2O in protoplanetary disks ?
Motivation
•
What is the H2O abundance in planet forming
disks?
•
How is H2O distributed ?
•
Are all disks the same ?
H2O in disks:
a multi-wavelength view
Early results
e.g.
Carr & Najita 2004, 2008
Salyk+ 2008
Mandell+ 2008
Pontoppidan+ 2010
Fedele+ 2011
e.g.
Glassgold+ 2009
Woitke+ 2009
Meijerink+ 2009
Bethell & Bergin 2010
Najita+ 2011
Adamkovics+ 2014
Antonellini+ 2015a,b
Abundant (~ 1017 cm-2) H2O in disks around Solar-like stars
The Astrophysical Journal Letters, 759:L10 (6pp), 2012 November 1
H2O - ice
60 micron
λFλ [10-15 W/m2]
3 micron
Wavelength (μm)
Terada et al. 2007, ApJ, 667, 303
Terada 2007
Malfait 1999
Honda
2009
McClure
2012
Figure
1. SED (orange lines and symbols) for GQ Lup.
Photometry
are from Covino et al. (1992), 2MASS, WISE, AKARI, IR
from the Spitzer Heritage Archive and this work. The best-fitting non-ice model is shown, along with two ice models. One fi
solid gray) and the other fits everything except 120–140 µm (15 µm grains, solid black). The remaining model parameters are g
the optical data because we do not include emission from the accretion shock itself.
(A color version of this figure is available in the online journal.)
PACS, we obtained 55–145 µm spectra of GQ Lup. To characterize simultaneously the distribution of silicates and water
3. ANA
Normalized flux + offset
clouds to planets will be discussed. The focus is on lowmass protostars (<100 L⊙ ) and pre-main sequence stars
(spectral type A or later). Unless stated otherwise, frac3 micron
micron
tional abundances are
quoted with respect to50/200
H2 and are
557 micron
(T ~ 1000Often
K) the denominator,
(T ~ i.e.,
100 K)
simply called ‘abundances’.
(T ~ 10 K)
H 2O
OHthe nu- H2O
OH
the
(column)
density
of
H
,
is
more
uncertain
than
2
the crucial
Herschel/PACS
VLT/CRIRES
merator.
netary sysThe bulk of the water in space is formed on the surfaces
, combined
T Tauri
T Tauri
of dust grains in dense molecular
clouds. Although a small
various waamount of water is produced in the gas in diffuse molecmapped out.
ular clouds through ion-molecule chemistry, its abundance
of ∼ 10−8 found by Herschel-HIFI (Flagey et al., 2013) is
ut of which
disk’. 3 negligible compared with that produced in the solid state.
Ae3 µm water ice band toIn contrast, observationsHerbig
of the
Herbig Ae
ward numerous infrared sources behind molecular clouds,
ons
2.930
65 ice for- 66
from the ground and
from2.932
space,2.934
show that water
67
her out and
mation starts at a threshold extinction
of A(micron)
Fig. 3.— Herschel-HIFI spectra of the H2 O 110 –101 line at
V ≈ 3 mag
Wavelength
et al., 2013). These clouds have densities of at least 557 GHz in aHogerheijde
pre-stellar core2011
(top), protostellar envelope
ce layers (Whittet
of
e.g.,
e.g.,
1000 cm−3 , but are not yet collapsing to form stars. The (middle) and two protoplanetary disks (bottom) (spectra
r- and midFig.Carr
6.— &Near-IR
(left)
far-IRFedele
(right) 2012,
spectra2013
of a T Tau
2008 and−5
ice abundance
is s-HNajita
, indicating that
a shifted vertically for clarity). The red dashed line indicates
2 O/H2 ≈ 5 × 10
sing wealth and Pontopiddan
a Herbig
Aeavailable
disk,
OHbeen
lines
in both
2O
2010showing
significant fraction
of the
oxygen has
transthebut
rest H
velocity
of the source. Note the different scales:
m water formed
at primarily
in2011
disks
T Tau stars.
by D.emission is strong toward protostars, but very
Fedele
to water
ice
even
at around
this earlycooler
stage (Whittet
et al., Figure
water vapor
2008), and
1988; Murakawa
et al.,on
2000;
Boogert
et al.,
2011).
Such weak in cold cores and disks. The feature at -15 km s−1 in
Fedele, based
Fedele
et al.
(2011,
2013).
ous in disks
high ice abundances are too large to result from freeze-out the TW Hya spectrum is due to NH3 . Figure by L. Krisof gas-phase water produced by ion-molecule reactions.
tensen, adapted from Caselli et al. (2012), Kristensen et al.
al., 2010a;
cold coresthe
justpattern
prior toof
collapse
(2012) and Hogerheijde et al. (2011, and in prep.).
In principle,
waterhave
linessuch
with wavelength
with a disk The densest
high extinctions
that direct
ice observations
are gaseous
not pos- water-rich to
should allow
the IR
transition
from the
r excitation
λ = 5-50 µm
λ = 50-500 µm
sible. In contrast, the water reservoir (gas plus ice) can
the water-poor (theλsnow
probed. As shown by
ved ground=
1-5line)
µm toofbe
be inferred from Herschel-HIFI
observations
such cores. ice, but where they are no longer effective in photodissociatLTE excitation
diskof models,
largest sensitivity
the vapor. In the central
ing thetowater
shielded
3 µm show
Fig. 3 presents
the detection
the H2 O 1the
λ > 500
µm part of the core,
10 –101 557 GHz
−9
cosmic
ray
induced
UV
photons
keep
a
small,
∼
10
,
location
of
the
snow
line
is
provided
by
lines
in
the
40–60
h a disk and
line toward L1544 (Caselli et al., 2012). The line shows
but measurable
µm region,
is exactly
the wavelength
without fraction of water in the gas (Caselli et al.,
blue-shifted
emissionwhich
and red-shifted
absorption,
indicative range
t al., 2012).
2012). Quantitatively, the models indicate that the bulk of
of inward
motions in the
core. Because
high critiobservational
facilities
except offortheSOFIA
(Meijerink
et al.,
he observathe
available
oxygen has been transformed into water ice in
cal density
of water,
the
emission
indicates
that water
vapor
2009).
For
one
disk,
that
around
TW
Hya,
the
available
−4
, in the case
must be present in the dense central part. The infalling red- the core, with an ice abundance of ∼ 10 with respect to
shorter and longer wavelength water data have been used
he IR lines
shifted gas originates on the near-side. Because the differ- H2 .
to ofput
a probe
waterdifferent
abundance
profile
across the entire
sk until the
ent parts
thetogether
line profile
parts of
the core,
Herschel/PACS detection rate
Detection rate [%]
100
80
60
40
20
0
[OI]
OH
H2O
CO
Water reservoirs in disks
0.5
200
150
0K
K
e the gaps of a small sample of transition
r1 2013).
ppidan et al., 2010a; Zhang et al.,
(hot)
log (H O)
> 20 AU; surface layers
andgas-phase
outer disk
0.4
se disk layers the dust temperature is unisublimation temperature of water. Fure high densities (n > 106 cm−3
0.3
r2) atoms
eze out on dust grains on short
timescales
gas-phase
se circumstances, in the absence of nonon mechanisms, models predict strong
0.2
0K
150
he majority of available oxygen present
2
r3
er ice. Much of this may be primordial
grain-surface
0.1
10.7
d by the natal cloud (Visser
et al., 2011,
photodesorption
1
of rotationally cold water vapor emission
ice 3
0.0
of TW Hya demonstrates that a tenu10
100
1
er vapor is present and that some nonR [AU]
All reservoirs
are etdetected
on process
is active (Hogerheijde
al.,
ng candidate is photodesorption of water Fig. 8.—
Abundance 2009;
of gaseous
waterWalsh
relative
to total
e.g.,Glassgold
Woitke 2009;
2011
l., 2005; Öberg et al., 2009), as discussed hydrogenBruderer
as a function
of radial distance, R, and rela2012
ularly given the high UV luminosities of tive height above the midplane, z/R, for a disk around
ng et al., 2012a). This UV excess is gen- an A-type star (T∗ =8600 K). Three regions with high H2 O
10.7
200
K
z/R
2
H2O abundance distribution in
HD 100546 and HD 163296
A&A proofs: manuscript no. water
Table 1. H2 O line fluxes
Integrated line flux [W m-2]
observed with Herschel/PACS
2013) and GASPS (Dent et al.
spectra used here are from the
ations are presented in Fedele
window of Herschel/PACS (50nal H2 O transitions ranging in
14 K, (212 101 at 179.52 µm)
2.93 µm). A deep PACS obsered as part of a calibration pronsition 321 212 at 75.38 µm in
also include the CO J = 35 34
spectrum
mission is detected toward HD
deep PACS integration on the
n a non detection. In the case
-J H2 O lines are detected with
l. (2012); Meeus et al. (2012).
have been detected with Herogerheijde et al. in preparation)
fluxes and upper limits are retransitions used for the anlysis
paper is based on the DALI
ks (Bruderer et al. 2012; Brudive transfer to measure the dust
parametrized density structure.
Transition
110
111
212
321
707
818
101
000
101
212
616
707
[µm]
538.29
269.28
179.54
75.38
71.95
63.32
Eup [K]
53
61
114
305
843
1070
Int. flux [10 18 W m 2 ]
HD 100546 HD 163296
1.3 ± 0.1
< 0.15
2.9 ± 0.2
< 0.30
< 58.3
< 16.5
< 7.5
< 77.0
< 33.0
22.0 ± 5.0
< 33.0
20.0 ± 6.0
Notes.
Table 2. DALI model parameters
M?
T e↵
Lbol
[M ]
[K]
[L ]
Rsubl
Rgap
Rcav
[au]
[au]
[au]
gas/dust
Mdisk
[M ]
Rc
[au]
[radians]
c
H2Ohtransition
LX
[erg s 1 ]
flarge
x1
[x(H2 )]
HD 100546
0.25
0.1
1
13
HD 163296
2
10,000
20
0.05
0.1
1,10,100,10000
10 4 , 10 3 , 10 2 , 10 1
1
75
0.1
H2O transition
29
10
Fedele in prep
0.2, 1.0
0.5, 0.85, 0.999
3 ⇥ 10 4
DALI - thermo-chemical code
Physical-chemical modeling
Density structure
Stellar spectrum
1 Continuum RT
Tdust <Jcontinuum>
4 Excitation
Atomic/molecular
level population
Spectra
Image cubes
5 Raytracing
Ab
ce
n
a
und
2 Chemical
network
Tgas
3 Thermal
Balance
How do different physical / chemical mechanism work together?
What is their relative importance?
Bruderer 2012, 20013
What are trends with input parameters?
Parametrised Tgas
and x(H2O)
H2O vs physical structure
•
Gas mass
•
Gas-to-Dust mass ratio
•
Scale height
•
Flaring angle
•
…
Gas temperature constrained
by CO rotational ladder
Fedele+ 2016
Tune H2O abundance
K
200
0K
150
log (H2O)
0.4
0.3
0.2
0K
150
0.1
2
200
K
z/R
10.7
10.7
e the gaps of a small sample of transition
r1 2013).
ppidan et al., 2010a; Zhang et al.,
> 100
Av >disk
2 mag
> 20 AU; surface T
layers
andK,outer
se disk layers the dust temperature is unisublimation temperature of water. Fure high densities (n > 106 cm−3 ) atoms
eze out on dust grains on short timescales
r2 of nonse circumstances, in the absence
T > 250predict
K, Av >
0.5 mag
on mechanisms, models
strong
he majority of available oxygen present
er ice. Much of this may be primordial
d by the natal cloud (Visser et al., 2011,
0.5
1
of rotationally cold water vaporr3emission
ice 3
0.0
of TW Hya demonstrates
that
10
100
1
T < 100 K,
Ava>tenu0.5 mag
er vapor is present and that some nonR [AU]
on process is active (Hogerheijde et al.,
ng candidate is photodesorption of water Fig. 8.— Abundance of gaseous water relative to total
l., 2005; Öberg et al., 2009), as discussed hydrogen as a function of radial distance, R, and relaularly given the high UV luminosities of tive height above the midplane, z/R, for a disk around
ng et al., 2012a). This UV excess is gen- an A-type star (T∗ =8600 K). Three regions with high H2 O
x(H2O) in HD 100546
•
• x2 < 10
• x3 = 10
x1 < 10-8
-8
-8
H2O mainly in outer disk (r > 20 au)
Photodissociation in inner disk
Photodesorption in outer disk
x3
10-6
10-7
10-8
10-9
x(H2O) in HD 163296
•
• x2 = 10
• x3 = 10
x1 = 10-5
-6
-9
H2O mainly in inner disk (r < 20 au)
UV-shielded inner disk
No photodesorption in outer disk
x3
10-7
10-8
10-9
Conclusions
•
All H2O reservoirs in disks are detected
•
Multiple-J analysis to map H2O abundance structure
•
x(H2O) varies from disk to disk
•
50-600 micron H2O data on a few disks only
•
Need for a new FIR cold telescope for warm/cold H2O
and ice
SPICA
The water trail: tracing the snow line