Brown Dwarf Science with VLST

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Brown Dwarf Science with VLST

• Outline
• The Big Questions
• Where we are and how VLST would help...

John Gizis Physics and Astronomy
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Brown Dwarf Science with VLST
Formation Atmospheres
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Brown Dwarf Science with VLST
Formation IMF Binarity Disks Atmospheres
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Brown Dwarf Science with VLST
Formation IMF Binarity Disks Atmospheres Evolutio
n Beyond T dwarfs Activity
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Brown Dwarf Science with VLST

• Brown dwarfs below 0.074MM fail to achieve
  stable nuclear burning.
• Cool and fade steadily

Burrows et al. 1993, 1997
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Brown Dwarf Science with VLST

• Brown dwarfs below 0.074MM fail to achieve
  stable nuclear burning.
• Cool and fade steadily

Burrows et al. 1993, 1997
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Brown Dwarf Science with VLST

• Brown dwarfs below 0.074MM fail to achieve
  stable nuclear burning.
• Cool and fade steadily
• Planets vs. brown dwarfs

Burrows et al. 2003
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Brown Dwarf Science with VLST

• 2MASS and SDSS find objects
• Sequence to T8 or 800K.

Vrba et al. 2004
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• L dwarf sequence
• Disappearance of molecules as grains form.
• Cloud deck 1600K

Kirkpatrick et al. 1999
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• T dwarf sequence
• Classification in near-IR.
• Cloud deck 1600K below photosphere.

Burgasser et al. 2003
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• T dwarf sequence
• Classification in near-IR.

Burgasser et al. 2002
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• On beyond T with VLST?
• Not really...
• Want large sky area and mid-infrared.
• Spitzer, JWST
• WISE

Burrows et al. 2003
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• But followup will require large telescopes...
• We will have many cool, very-low-mass brown
  dwarfs by any VLST launch date

Burrows et al. 2003
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• But followup will require large telescopes...
• We will have many cool, very-low-mass brown
  dwarfs by any VLST launch date

Burrows et al. 2003
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Images

• 20 of L and T dwarfs are resolved by HST
• Separations 2-10AU
• P2 a3/MT
• Current periods are 30 years.
• We can expect that a VLST could find the binaries
  at 0.1 AU -- lt1 yr period.
• These could include very-low-mass companions.

Gizis et al. 2003
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• For 5 MJ field brown dwarfs, a separation of 5 AU
  will have a period gt100 years.
• Need a VLST both to get enough photons and to
  resolve them (at one micron).
• A VLST would get to separations of .1 AU and
  periods lt 1yr.
• Also need VLST to resolve open cluster and Taurus
  brown dwarfs.

Gizis et al. 2003
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• For 5 MJ field brown dwarfs, a separation of 5 AU
  will have a period gt100 years.
• Need a VLST both to get enough photons and to
  resolve them (at one micron).
• A VLST would get to separations of .1 AU and
  periods lt 1yr.
• Also need VLST to resolve open cluster and Taurus
  brown dwarfs.

Gizis et al. 2003
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• For 5 MJ field brown dwarfs, a separation of 5 AU
  will have a period gt100 years.
• Need a VLST both to get enough photons and to
  resolve them (at one micron).
• A VLST would get to separations of .1 AU and
  periods lt 1yr.
• Also need VLST to resolve open cluster and Taurus
  brown dwarfs.
• Resolution

Gizis et al. 2003
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• Open cluster T dwarfs
• Star-formking regions Probe to lowest masses.

Burrows et al. 1997
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• Open cluster T dwarfs
• Star-formking regions Probe to lowest masses.

UKIRT
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Low Metallicity/Halo

• Imaging at 1 micron should detect brown dwarfs
  in globular clusters.
• Need to reach T800K to be interesting.
• Resolution and field of view.

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Low Metallicity/Halo

• Field Halo Brown Dwarfs
• 2M05328346
• An L subdwarf

Burgasser et al. 2003
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Spectra

• Beyond T dwarfs

Liebert et al. 2002
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Activity

• Gizis et al. 2000 found that activity declines
  sharply after M6.
• But, flares are common.
• Burgasser et al. 2003 find some Ha at 10-18
  erg/sec/cm2

Liebert et al. 2002
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Activity

• Gizis et al. 2000 found that activity declines
  sharply after M6.
• But, flares are common.
• Burgasser et al. 2003 find some Ha at 10-18
  erg/sec/cm2

Liebert et al. 2002
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Activity

• HST/STIS can detect M8/M9 dwarfs
• Need VLST for Le/Te dwarfs.
• Also, for cluster late-M dwarfs.

Hawley Johns-Krull 2003
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Formation

• What about accreting brown dwarfs/planets
• Detection of emission lines in T dwarfs in
  star-forming regions.

Gizis 2002 r Oph BD from Luhman
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Resolution?

• Field brown dwarfs have v sin i 5-80 km/s
• Width of emission lines
• HDO 1 variations?
• Lithium in distant clusters

Gizis 2002 r Oph BD from Luhman
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• Weather?
• Variability at I band is few percent.
• Can we show that it is due to clouds? Hotspots?
  Sunspots?

Hurt
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Summary

• Very Large Space Telescope
• Needed for followup of expected discoveries.
• Needed for more distant L/T dwarfs

Hurt