First Detection of a Bipolar Molecular Outflow from a Young BonaFide Brown Dwarf Ngoc PhanBao Academ

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First Detection of a Bipolar Molecular Outflow
from a Young Bona-Fide Brown DwarfNgoc
Phan-BaoAcademia Sinica IAA
NTHU, Oct. 17 2008
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Outline of Talk

• Physical Properties of Brown Dwarfs
• Most Important Issues of the Brown Dwarf Science
• Brown Dwarf Formation Scenarios
• Millimeter observations of a Young Brown Dwarf
• Implications for Rocky Planet Formation around
  Brown Dwarfs

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Very Low Mass Stars and Brown Dwarfs
Main sequence stars O B A F G K M
L T Y(?)
Sun (G2)
M0 M1 M2 M3 M4M9
(Oh Be A Fine Girl Kiss My Lips Tonight Yahoo!)

• Very low mass stars M lt 0.35M? (later than
  M3-M4) ? fully convective.
• Brown dwarfs M lt 0.075M? (later than M9), below
  the Hydrogen-burning limit.

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M dwarf part
Brown Dwarfs
Credit ESA (Hipparcos)
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(No Transcript)
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Credit Gemini Observatory/Artwork by Jon Lomberg
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Fundamental Parameters(solar metallicity and a
few gigayear old)

• MASS
• Very low mass stars below 0.35 M? (spectral
  type M3-M4) ? fully convective stars (Chabrier
  Baraffe 1997).
• Brown dwarfs 13 MJupiter 75 MJupiter, massive
  enough for deuterium-burning but below the
  hydrogen-burning limit.

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Brown Dwarf Structure
p p ? d e ?e Tcrit ? 3 ? 106 K, Mmin ?
0.075 M? p d ? 3He ? Tcrit ? 5 ? 105 K,
Mmin ? 0.013 M? 7Li p ? 4He 4He Tcrit ? 2.5
x 106 K, Mmin ? 0.065 M?
Burrow et al. 1997
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• 2) TEMPERATURE
• Very low mass stars below 3500 K (Chabrier
  Baraffe 1997).
• Brown dwarfs 750 2200 K (Burrow et al. 2001).
• 3) RADIUS
• 0.1-0.3 R? for VLM stars.
• 0.1 R? or 1 RJupiter for all brown dwarfs.

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M9, 75 MJupiter
L, 65 MJ
T, 35 MJ
Jupiter
Artwork Credit Dr. Robert Hurt (IPAC/Caltech)
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Where Do VLM Stars and BDs Locate?

• In the field, freely floating objects identified
  by color-color diagrams, high-proper motion
  surveys, spectroscopic observations.

An M9 at 8 pc
1984.915
1996.937
Phan-Bao et al. 2006a
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• In star-forming region (young sub-stellar objects)

Zapatero Osorio et al. 2000
Sigma Orionis, 350 pc, 2-4 Myr
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• Around nearby stars

G2, 18 pc
Potter et al. 2002
Phan-Bao et al. 2006b
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Most Important Issues of the Brown Dwarf Science

• Does the new spectral type Y exist?
• How are their magnetic field activity and the
  topology?
• How do they form?
• What are the properties of planets around brown
  dwarfs?

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How do brown dwarfs form?

• Primary difficulty in making a BD Balance
  between requirement of very low mass core
  formation but prevention of subsequent accretion
  of gas
• Four alternative scenarios
• Turbulent fragmentation (Padoan Nordlund 2002)
• Disc fragmentation (Boss 2001 Bate et al. 2002)
• Ejection (Reipurth Clarke 2001, Bate et al.
  2004)
• Photo-erosion (Whitworth Zinnecker 2004)
• Key Issue All of these mechanisms might be
  happening but it is not clear which one dominates!

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Same way as stars

• Large number of BDs with accretion
• disks (Halpha) reported, five showing optical
  jets.
• Non-detection of molecular outflows from BDs.
• Our Goal Search for molecular outflows in young
  BDs
• Why?
• Study physical properties ? place strong
  constraints on the theory

Whelan et al. 2007, ESO
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Mm-Observation of ? Oph 102

• 125 parsecs in Ophiuchus, 60 MJ (0.06 M?)
• Evidence for disk accretion of 10-9 M?/yr (Natta
  et al. 2002)
• Blue shifted component of a jet detected (Whelan
  et al. 2005)

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176
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Oph 102
NRAO
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Results
CO J2?1 MAP (230 GHz)

• Outflow mass
• 1.6 ? 10-4 M?
• Mass loss
• 1.4 ? 10-9 M?
• over 100 times smaller than the typical values
  for T Tauri stars!

Brown dwarfs formed in a scaled-down version of
stars
Phan-Bao et al. 2008)
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Jet-Driven Bow Show Structure
Lee et al. 2000
Position-Velocity Diagram
A brown dwarf of 0.08 L? versus A more massive
object of 17 L?
If the structure is confirmed, ? Oph 102 will be
the first test of the star formation theory in
the sub-stellar domain!
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Disk Parameters
Spectral Energy Distribution

• Disk Mass
• 8 ? 10-3 M?
• Outer disk radius
• 80 AU
• Inclination
• 63o
• ? Projected disk of 36 AU ? hiding the
  red-shifted jet component (16 AU) from our view.

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Detection of Strong Crystallization
Enstatite (MgSiO3)
Forsterite (Mg2SiO4)
Flux(11.3 ?m)/Flux(9.8 ?m) 1.1
Apai et al. 2005
Strong grain growth and dust settling in Oph 102?
reaching the final mass
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Summary

• Detection of Molecular Outflow supports the idea
  that BDs form like stars (a scaled-down version),
  providing the first insight on the outflow
  morphology.
• Oph 102 is the first test for the theoretical
  models.
• The coexistence of molecular outflow and
  crystallization favors the rocky planet formation
  around brown dwarfs.