water chemistry: from collapsing cores to...
TRANSCRIPT
Water chemistry: from collapsing
cores to disks
RCW120
Herschel
A. Zavagno
Ewine F. van Dishoeck
Leiden Observatory/MPE
www.strw.leidenuniv.nl/WISH
Water In Star-forming regions with Herschel
The WISH team
70+ scientists from 30 institutions (PI: EvD)
36 papers total, see WISH website
Summary in van Dishoeck et al. 2011, PASP; Bergin & van Dishoeck 2012
Leiden, December 2011 Toledo, June 2011
GT-KP, 425 hr program approved in 2007
HDO addition ~25 hr in 2011
Ringberg January 2013
Water questions
Where is water formed in space and by which processes? Gas vs grains
Which physical components does water trace? Quiescent envelope, hot core, outflows, disks, …
From low to high mass
Cooling budget
What is the water ‘trail’ from clouds to planets? Origin of water on Earth
H2O lines: HIFI and PACS
Observe mix of low- and high-excitation lines to probe
cold and hot environments; Include 12CO 10-9, 13CO 10-9, C18O 9-8
Also: OH+, H2O+, H3O
+, CH+, …. as radiation diagnostics
~1-10 ~100-1000 ~104-105 LSun
0
~2 Myr
~0.4 Myr
+outflow
Velocity (km s-1)
TM
B (K
)
12CO 10-9 987 GHz
LM
IM
HM HM
IM
LM
Lbol
(Lsun
)
LC
O (K
km
s-1 p
c2) Luminosity
Dis
tan
ce
an
d S
ize
Low-mass
Inter.-mass
High-mass
Linking low- and high-mass protostars using CO and H2O
San José-Garcia et al. 2013
Yildiz et al. 2013
Note similar but complex line profiles
(even for H218O)
H2O chemistry: three routes
O OH+
H2O+
H3O+
OH
O:gr H2O:gr
H2O
H
H2
H2
H2
H2
e
H3+
Low T High T
Ice
Hot water and CO:
Physics
Nisini, Liseau, Tafalla,
Vasta, Santangelo + WISH team
3’
Water traces ‘hot spots’ where jet/wind interacts with cloud
L1157-mm outflow
D = 440 pc, Lbol = 11 Lo
Early highlight
Hot H2O, OH and CO in low-mass protostars
CO H2O
OH
Herczeg et al. 2012
- All lines assigned to 4 species, from levels up to several thousand K
NGC1333
IRAS4B
PACS
Spectral
scan
Outflow,
not disk
The CO ladder as a
physical probe
0
1 2 3
6 5
7
49
48
100
30
2000
4000
6000
E(K)
Not to scale
Herczeg et al. 2012
Goicoechea et al. 2012
Karska et al. 2013
Green et al. 2013 DIGIT
Dionatos et al.
Lee et al.
Serpens SMM1 PACS + SPIRE full scan
Goicoechea
et al. 2012
Serpens SMM1 Trot
Goicoechea et al. 2012
Herczeg et al. 2012
Physical interpretation
of these CO components?
(UV heating + shocks)
H2O excitation implies
high T (>400 K) and high n(>105 cm-3)
H2O/CO~0.4
Visser et al.
2012
Water in outflows
- H2O and H2 go together, not low-J CO
- H2O abundance as low as 10-7
Tafalla et al. 2013
Nisini et al. 2013
Santangelo, Vasta
et al. 2012, in prep
=H2
Conclusion 1
CO reveals universal cold, warm and hot components
Water associated with warm and hot components
Kinematic information crucial!
Emission dominated by shocks
Non dissociative shocks: CO, H2O, some OH
Dissociative shocks: OH, [O I]
Water does not reach maximum abundance of 3x10-4 →
UV irradiated shocks?
Processes similar from low- to high-mass YSOs
WISH =
Water IS Hot M. Tafalla
Cold water:
chemistry
Pre-stellar cores: where is
water formed?
H2O gas ring
n=2.104 – 5.106 cm-3, T=10 K
Layer of water gas where ice is photodesorbed
Alves et al. 2001
Bergin et al. 2002
B68
Ice H2O gas=
Ice formation
Photodesorption
Andersson&vD2008
Öberg et al. 2009
Lab + Theory
How to make water ice A success story lab-observations
Detailed laboratory experiments reveal multiple routes at 10 K
Ioppolo et al. 08,10
Cuppen et al. 10
Miyauchi et al. 10
Watanabe+
Dulieu et al. 10
Romanzin et al. 10
Tielens & Hagen82
Detected in 2011 and 2012
Bergman, Parise et al.
Detection of cold water reservoir
in pre-stellar cores
Caselli et al. 2012
ESA Sci-Tech
Note
- Simple ice chemistry works
- High density required for emission
Using water to measure infall rates
and test chemistry
Mottram
et al. In prep.
Inverse
P-Cygni
profiles
J. Tobin cartoon
Infall modeling Jump H2O abundance profile
Such an abundance profile cannot reproduce
the observations
T ≥ 100K
Physical-chemical model
Similar model as for pre-stellar cores works
Infall must continue to R<1000 AU
T ≥ 100K PDL
Mottram et al. in prep.
Follow the water trail
Visser et al. 2009
Herbst & vD 2009
Cold quiescent
water
Warm
water
Most of detected water gas is associated with outflows, lost to space
But we want to know amount of quiescent water going into disks
Zooming in with interferometers: Hot water in the deeply embedded phase
NGC 1333 IRAS4B
Plateau de Bure
H218O 313-220 203 GHz
Jørgensen & vD 2010a
Persson et al. 2012, 2013
Compact warm
water abundance
Hot water near protostars
ALMA 692 GHz
SMA 203 GHz
IRAS 16293 -2422 CSV data
Persson et al.
2013
Warm HDO/H2O~10-3
The chemistry of water in disks
Evaporation in
inner disk (<3 AU)
Freeze out in outer
disk (> 3 AU)
Equilibrium between
photodesorption and -
dissociation in outer disk
(Dominik et al. 2005):
H2Ogas ~fraction×H2Oice
Detection of cold water reservoir in disks
p-H2O 111-000
1113 GHz
o-H2O 110-101
557 GHz
- Emission comes from ~100 AU radius
- Points to 6000 oceans of water ice
- Signal weaker than expected →Most icy grains must be settled
TW Hya
Hogerheijde et al.
2011, Science
Water in disks survey
-Firm detections TW Hya, HD 100546
- In both cases, o/p<1
- No detections in DM Tau, AA Tau, LkCa 15, MWC 480,
HD 163296 in spite of very deep observations
- up to 25 hr/line
(Would have seen TW Hya signal at 140 pc)
- Shallower limits for another dozen sources
Hogerheijde et al., in prep.
Absence of cold water emission is common feature
Conclusions 2
Water is formed mostly on grains in cold
clouds
Photodesorption controls gas-phase water
abundance in cold cores and disks
Cold water emission from disks is weak→
settling of icy grains common?
Where detected, o/p ratio <1