on the nature of the planetary mass companion candidate in ... fileon the nature of the planetary...
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On the nature of the planetary mass companion candidate in the FW Tau system
Claudio CáceresUniversidad de Valparaíso
Astrobio 2015 European Southern Observatory October 1 st, 2015
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What do I mean with planetary mass companion?
Marois et al. (2010)
~68 au
HD 8799
(at 40 pc)
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What do I mean with planetary mass companion at large separations (PMC)?
~6-10 Mjup
at 140 au
~13 Mjup
at 250 au
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A small population of PMCs at large separations
Roughly 20 to date, with a > 100 au
All are giant planets
Large fraction are very young (<10Myr)
Kraus et al. (2014)
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PMC formation scenarios
Gravitational disk instability
Core accretion
Disk fragmentation
Predicts giant-planets at intermediate separations <100 au
Predicts giant-planets at small separations <50 au (but very slow)
If acting at class 0/I, predicts planetary mass objects at large separations > 100 au (Kratter et al. 2011)
Mayer et al. (2002)
Cooling time needs to be shorter than thermodynamical scale
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The FW Tau system
FW Tau
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The FW Tau system
Binary system at 145 pc in the Taurus molecular cloud
Two twin M5 dwarfs:
- Ages of ~2 Myr (consistent with mean age of Taurus)
- Separation of 11 au (projected)
- An unresolved 4-sigma detection at 850 microns (Andrews & Williams 2005)
- Unresolved mid-IR and far-IR emission from WISE, Spitzer and HerschelFW Tau
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The third component in the FW Tau system
Kraus et al. (2014)
Projected separation of ~300 au
It looks like its position lies in the orbital plane of the binary.
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Kraus et al. (2014)
The third component in the FW Tau system
Bowler et al. (2014)
Accreting nature
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An ALMA dust detection
Kraus et al. (2015)
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An ALMA gas detection
CO(2-1) + 1.3 mm continuum
Caceres et al. (2015)
Cycle 1 observations in Band 6
Sensitivity:- 0.1 mJy in 7.5 GHz bandwidth (continuum)-20 mJy in 0.6 km/s bandwidth (gas)
Results:- Detected dust at 1.3mm
- Detected CO(2-1) line
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SED modeling: a circumplanetary disk around FW Tau b?
Brown-dwarf in edge-on disk and giant planet in face-on disk can explain the SED
Only 2-3 Mearth
are require to explain the dust detection.
Disk size and composition are unconstrained
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Planet or brown-dwarf?
Caceres et al. (2015)
… and line detection as well...
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Planet or brown-dwarf?
Single-peaked CO line origin:
- Cloud contamination (filtering)
Velocity distribution in Taurus
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Planet or brown-dwarf?
Single-peaked CO line origin:
- Cloud contamination (filtering)
- Inclination/Mass effect
- Low SNR?
Also to consider: faint emission.
- Small gas-to-dust mass ratio (photodissociation?)
- Cloud effects
- Very small disk
< 30 MJup
< 15 deg
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Limits to the possible brown-dwarf
Caceres et al. (2015)
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Take home message
FW Tau b or C... still unknown.
- Evidence for both a face-on disk (planetary nature) and edge-on disk (brown-dwarf nature).
- A confirmation of the circumplanetary nature of the disk is required!
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Thank you!