S2T01 Bergin Star and Planet Formation
25
Future Challenges Related to Star and Planet Formation Edwin Bergin University of Michigan
Transcript of S2T01 Bergin Star and Planet Formation
Future Challenges Related to Star and Planet Formation
Edwin Bergin University of Michigan
Molecules and Star/Planet Formation
• We - as a field - need to connect to exoplanets as the largest growth area in astrophysics.
• Two ways to accomplish this
➡Composition of giant planet atmospheres
➡Bulk/surface composition of terrestrial planets
• All relate to formation…..
• New capabilities: Space based submm/far-IR, expand VLA, enhance ALMA
!"#$%&'$()*+%#",-*).
Caveat: assuming some O in silicates but does not include organics (C-rich + O) and additional unidentified oxygen component
water snow line
CO2 snow line
CO snow line
Oberg, Murray-Clay, & Bergin 2011
Beyond our solar system: C/O Ratio
!"#$%&'$()*+%#",-*).
Inside water snow-line: volatiles in gas. C/O = (C/O)⊙ ~ 0.5
CO, CO2 in gas, water in ice Gas: C/O ~ 2/3
Ice: C/O << (C/O)⊙
C/O Ratio CO in gas, water, CO2 in ice Gas: C/O ~ 1
Ice: C/O < (C/O)⊙
water, CO, CO2 in ice Ice: C/O = (C/O)⊙
Oberg, Murray-Clay, & Bergin 2011
Need to isolate snow-lines of major condensibles:
water, ammonia, carbon monoxide, carbon dioxide, molecular nitrogen
Carbon
10-4
10-3
10-2
10-1
100
101
(N/S
i) A
tom
ic R
atio
810-5
2
4
Venu
s (B
S)
(Low
er L
imit)
ISM
Gas
Ear
th S
urfa
ce R
eser
voir
ISM
Dus
t(lo
wer
lim
it)
Terrestrial Planet/Asteroid Forming Zone
Comet Forming Zone ISM
10-5
10-4
10-3
10-2
10-1
100
101
(C/S
i) A
tom
ic R
atio
ISM
Gas
ISM
Dus
t(lo
wer
lim
it)
Ear
th
(BSE
)
Sun
enst
atit
e ch
ond
rite
s
ordinary chondrites
carb
ona
ceo
us
cho
ndri
tes
comets
sun-grazing
Halley
dus
t
dus
t+g
as ISM
dus
t
gas
carb
ona
ceo
us
cho
ndri
tes
ord
inar
y ch
ond
rite
s
enst
atit
e ch
ond
rite
s
Ear
th
(BSE
)
Sun
comets
sun-grazing
Halley
dus
t
dus
t+g
as ISMd
ust
gas
10-4
10-3
10-2
10-1
100
101
(N/S
i) A
tom
ic R
atio
810-5
2
4
Venu
s (B
S)
(Low
er L
imit)
ISM
Gas
Ear
th S
urfa
ce R
eser
voir
ISM
Dus
t(lo
wer
lim
it)
Terrestrial Planet/Asteroid Forming Zone
Comet Forming Zone ISM
10-5
10-4
10-3
10-2
10-1
100
101
(C/S
i) A
tom
ic R
atio
ISM
Gas
ISM
Dus
t(lo
wer
lim
it)
Ear
th
(BSE
)
Sun
enst
atit
e ch
ond
rite
s
ordinary chondrites
carb
ona
ceo
us
cho
ndri
tes
comets
sun-grazing
Halley
dus
t
dus
t+g
as ISM
dus
t
gas
carb
ona
ceo
us
cho
ndri
tes
ord
inar
y ch
ond
rite
s
enst
atit
e ch
ond
rite
s
Ear
th
(BSE
)
Sun
comets
sun-grazing
Halley
dus
t
dus
t+g
as ISM
dus
t
gas
Ber
gin
et a
l. 20
15
Carbon
10-4
10-3
10-2
10-1
100
101
(N/S
i) A
tom
ic R
atio
810-5
2
4
Venu
s (B
S)
(Low
er L
imit)
ISM
Gas
Ear
th S
urfa
ce R
eser
voir
ISM
Dus
t(lo
wer
lim
it)
Terrestrial Planet/Asteroid Forming Zone
Comet Forming Zone ISM
10-5
10-4
10-3
10-2
10-1
100
101
(C/S
i) A
tom
ic R
atio
ISM
Gas
ISM
Dus
t(lo
wer
lim
it)
Ear
th
(BSE
)
Sun
enst
atit
e ch
ond
rite
s
ordinary chondrites
carb
ona
ceo
us
cho
ndri
tes
comets
sun-grazing
Halley
dus
t
dus
t+g
as ISM
dus
t
gas
carb
ona
ceo
us
cho
ndri
tes
ord
inar
y ch
ond
rite
s
enst
atit
e ch
ond
rite
s
Ear
th
(BSE
)
Sun
comets
sun-grazing
Halley
dus
t
dus
t+g
as ISMd
ust
gas
10-4
10-3
10-2
10-1
100
101
(N/S
i) A
tom
ic R
atio
810-5
2
4
Venu
s (B
S)
(Low
er L
imit)
ISM
Gas
Ear
th S
urfa
ce R
eser
voir
ISM
Dus
t(lo
wer
lim
it)
Terrestrial Planet/Asteroid Forming Zone
Comet Forming Zone ISM
10-5
10-4
10-3
10-2
10-1
100
101
(C/S
i) A
tom
ic R
atio
ISM
Gas
ISM
Dus
t(lo
wer
lim
it)
Ear
th
(BSE
)
Sun
enst
atit
e ch
ond
rite
s
ordinary chondrites
carb
ona
ceo
us
cho
ndri
tes
comets
sun-grazing
Halley
dus
t
dus
t+g
as ISM
dus
t
gas
carb
ona
ceo
us
cho
ndri
tes
ord
inar
y ch
ond
rite
s
enst
atit
e ch
ond
rite
s
Ear
th
(BSE
)
Sun
comets
sun-grazing
Halley
dus
t
dus
t+g
as ISM
dus
t
gas
something happensto interstellar
carbonaceous grains
something happensduring planet formation
Ber
gin
et a
l. 20
15
Nitrogen
10-4
10-3
10-2
10-1
100
101
(N/S
i) A
tom
ic R
atio
810-5
2
4Ve
nus
(BS
)(L
ower
Lim
it)
ISM
Gas
Ear
th S
urfa
ce R
eser
voir
ISM
Dus
t(lo
wer
lim
it)
Terrestrial Planet/Asteroid Forming Zone
Comet Forming Zone ISM
10-5
10-4
10-3
10-2
10-1
100
101
(C/S
i) A
tom
ic R
atio
ISM
Gas
ISM
Dus
t(lo
wer
lim
it)
Ear
th
(BSE
)
Sun
enst
atit
e ch
ond
rite
s
ordinary chondrites
carb
ona
ceo
us
cho
ndri
tes
comets
sun-grazing
Halley
dus
t
dus
t+g
as ISM
dus
t
gas
carb
ona
ceo
us
cho
ndri
tes
ord
inar
y ch
ond
rite
s
enst
atit
e ch
ond
rite
s
Ear
th
(BSE
)
Sun
comets
sun-grazing
Halley
dus
t
dus
t+g
as ISM
dus
t
gas
On the way to making the Earth there is a tale of successive depletion
of major elements - need to track origins and abundances of major carriers
Ber
gin
et a
l. 20
15
Locating Snow-Lines• Methods:
➡ Infer temperature profile and assume ice/vapor transition at sublimation temperature
HL Tau
➡ Indirect inference from unresolved data spanning a range of molecular excitation states
Spitzer (hot water) + Herschel (cold water)
➡Direct imaging
SMA, NOEMA, ALMA
Water and CO Snow-line
• H2O snow-line (Tdust ~150 - 200 K)
➡ close to the star (~1-3 AU)
➡ strongest transitions need space-based observation (e.g. Spitzer/Herschel)
➡ see Zhang+ 2013; Du+ 2015; Blevins+ 2015, in. prep.)
Oxygen in TW HyaDebes et al. 2013
Zhang et al. 2013
hot water
warm water
Zhang et al. 2013Hogerheijde et al. 2011
cold water
Water and CO Snow-line• H2O snow-line (Tdust ~150 - 200 K)
➡ close to the star (~1-3 AU)
➡ JWST cannot do this alone!! need access to cold transitions from space
➡OR!!!! could add dishes to ALMA to increase sensitivity —- ALMA 2.0 — resolve the most important chemical transition!
Water and CO Snow-line
• CO snow-line (Tdust ~ 20 - 40 K)
➡greater distances from star (tens of AU)
➡ can be resolved with ground-based telescopes
➡ numerous stable C and O isotopes to reduce optical depth (12C16O, 13C16O, 12C18O, 12C17O, 13C18O, 13C17O)
TW Hya CO Snow-line
-2-1012
-2
-1
0
1
2
Δα (″)
Δδ
(″)
N2H+ J = 4-3
-2-1012-2
-1
0
1
2
Δα (″)
Δδ
(″)
C18O J =3-2
N2H+ + CO ⇒ N2 + HCO+
50 AU
Qi+ 2013Schwarz+ 2015, in prep.
TW Hya CO Snow-line
-2-1012-2
-1
0
1
2
Δα (″)
Δδ
(″)
C18O J =3-2
13CO 6-5, 3-2, C18O 6-5, 3-2 & abundance analysis CO surface snow-line = 25 - 30 AU; midplane ~20 -25 AU
Schwarz+ 2015, in prep.
Protoplanetary Disk Gas Mass
• Linchpin for determination of chemical abundances
• Cannot trace H2 directly - need to use proxies
➡ thermal emission from dust grains at mm/sub-mm
➡ thermo-chemical modeling of CO gas emission
important question: If we measure abundance in emissive layers (excluding freeze out zone) - is it low gas mass or low abundance?
• Low CO/dust & CI/dust
(Chapillon+ 2008; Dutrey+ 2003; Tsukagoshi+2015; Kama+ 2015)
• Cold water emission survey - no detections beyond TW Hya and HD100546 (Hogerheijde+ 2011; Du et al., in prep.)
• C+ detected in 27% of 47 T Tauri stars (Dent et al. 2013)
• O I less emissive compared to continuum in 21 disks (Keane et al. 2014)
Missing C,O or H2?
Herschel Detection of HD towards TW Hya
➡HD is a million times more emissive than H2 at T ~ 20 K.
➡Atomic D/H ratio inside the local bubble is well characterized (~1.5 x 10-5)
➡More direct measurement of disk gas mass (~0.05 M⨀)
➡Caveat: strong T dependency
3.8
3.7
3.6
3.5
Flux
(Jy)
114113112Wavelength (µm)
HD J = 1-0
CO J = 23-22
4.2
4.0
3.8
3.6
3.4
Flux
(Jy)
57.056.556.0Wavelength (µm)
HD J = 2-1
OH 2Π1/2 9/2-7/2
Bergin et al. 2013
Surface CO Snow-line
freeze-out
snowline
warm mol. layer
TW Hya
13CO 6-5
13CO 3-2average
Schwarz et al. 2015, in prep.
Mass DistributionMenu small grainsMenu large grainsCleevesAndrews pCAndrews sC13CO 6-5 profile
0 10 20 30 40 50 60R (AU)
0
5
10
15
20
Σ w
arm
gas
(g c
m-2
)
Schwarz et al. 2015, in prep.
HD and C18O in TW Hya• Favre et al. 2013
➡Emission ratio FJ=2-1(C18O)/FJ=1-0(HD) is proportional to the CO abundance
➡ Excitation
-HD will not emit if Tgas < 20 K
-CO freezes onto grains if Tgr < 20 K
➡ CO Abundance < 10-5 (+ confirmed by ALMA observations - Schwarz et al. 2015, in prep.)
➡ Same result for water (Du et al. 2015).
Where is the O and C
0 100 200 300
50
100
150
Z(A
U)
a)
−24.0
−21.0
−18.0
−15.0
−12.0
ρ gas[g
cm−3]
0 100 200 300
50
100
150
b)
−24.0
−21.5
−19.0
−16.5
−14.0
ρ dust[g
cm−3]
0 100 200 300
50
100
150
c)
0.8
1.1
1.4
1.7
2.0
Tdust[K
]
0 100 200 300
R(AU)
50
100
150
Z(A
U)
d)
0.8
1.1
1.4
1.7
2.0
Tga
s[K
]
0 100 200 300
R(AU)
50
100
150
e)
101.0
102.5
104.0
105.5
107.0
FXR[phot/s/cm
2]
0 100 200 300
R(AU)
50
100
150
f)
103.0
105.0
107.0
109.0
1011.0
FUV(con
t)[phot/s/cm
2]
evaporation
(thermal/photo)
0 100 200 300
50
100
150
Z(A
U)
a)
−24.0
−21.0
−18.0
−15.0
−12.0
ρ gas[g
cm−3]
0 100 200 300
50
100
150
b)
−24.0
−21.5
−19.0
−16.5
−14.0ρ d
ust[g
cm−3]
0 100 200 300
50
100
150
c)
0.8
1.1
1.4
1.7
2.0
Tdust[K
]
0 100 200 300
R(AU)
50
100
150
Z(A
U)
d)
0.8
1.1
1.4
1.7
2.0
Tga
s[K
]
0 100 200 300
R(AU)
50
100
150
e)
101.0
102.5
104.0
105.5
107.0
FXR[phot/s/cm
2]
0 100 200 300
R(AU)
50
100
150
f)
103.0
105.0
107.0
109.0
1011.0
FUV(con
t)[phot/s/cm
2]
Possible Mechanism• radial + vertical
pressure gradients
• dust settling + growth + radial drift
• sequesters volatiles in midplane (more water than CO)
• particles must be large enough to frustrate feedback Du+ 2015; but see Chapillon+ 2008
Evidence for Radial DriftCO 3-2
Andrews 2015Consequences:
1.Dust mass and surface density concentrated vertically and radially
2. Ices must follow 3. What about larger grains - expanded VLA!
We are tracking the implantation of ices that seed terrestrial worlds!
What about Nitrogen?
• Trace N2 via N2H+ - cannot measure inside CO snow-line!
•Cannot get NH3 - we will NOT know what is going on with N
• emission is very weak — need expanded VLA
Salinas et al. 2015, in prep.
Summary• Far-IR/Space:
➡ Survey of HD emission in disks using a sensitive Far-IR telescope is central to science case for a future instrument
➡ Could survey hundreds of systems and obtain real statistics.
• Expanded VLA:
➡ ONLY way to set any constraints on nitrogen - the 5th most abundant element, a key biogenic element, major constituent of our atmosphere
➡ needed to probe dust evolution
• ALMA 2.0
➡ Could resolve water snowline - most important chemical/physical transition in the disk
