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Brown Dwarf Science with VLST. John Gizis Physics and Astronomy. Outline: The Big Questions Where we are and how VLST would help. Brown Dwarf Science with VLST. Formation Atmospheres. Brown Dwarf Science with VLST. Formation IMF Binarity Disks Atmospheres.

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brown dwarf science with vlst
Brown Dwarf Science with VLST

John Gizis

Physics and Astronomy

  • Outline:
  • The Big Questions
  • Where we are and how VLST would help...
brown dwarf science with vlst1
Brown Dwarf Science with VLST

Formation

Atmospheres

brown dwarf science with vlst2
Brown Dwarf Science with VLST

Formation

IMF

Binarity

Disks

Atmospheres

brown dwarf science with vlst3
Brown Dwarf Science with VLST

Formation

IMF

Binarity

Disks

Atmospheres

Evolution

Beyond T dwarfs

Activity

brown dwarf science with vlst4
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

brown dwarf science with vlst5
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

brown dwarf science with vlst6
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

brown dwarf science with vlst7
Brown Dwarf Science with VLST
  • 2MASS and SDSS find objects
  • Sequence to T8 or ~800K.

Vrba et al. 2004

slide9
L dwarf sequence
  • Disappearance of molecules as grains form.
  • Cloud deck ~1600K

Kirkpatrick et al. 1999

slide10
T dwarf sequence
  • Classification in near-IR.
  • Cloud deck ~1600K below photosphere.

Burgasser et al. 2003

slide11
T dwarf sequence
  • Classification in near-IR.

Burgasser et al. 2002

slide12
On beyond T with VLST?
  • Not really...
  • Want large sky area and mid-infrared.
  • Spitzer, JWST
  • WISE

Burrows et al. 2003

slide13
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

slide14
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

images
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 -- <1 yr period.
  • These could include very-low-mass companions.

Gizis et al. 2003

slide16
For 5 MJ field brown dwarfs, a separation of 5 AU will have a period >100 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 < 1yr.
  • Also need VLST to resolve open cluster and Taurus brown dwarfs.

Gizis et al. 2003

slide17
For 5 MJ field brown dwarfs, a separation of 5 AU will have a period >100 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 < 1yr.
  • Also need VLST to resolve open cluster and Taurus brown dwarfs.

Gizis et al. 2003

slide18
For 5 MJ field brown dwarfs, a separation of 5 AU will have a period >100 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 < 1yr.
  • Also need VLST to resolve open cluster and Taurus brown dwarfs.
  • Resolution

Gizis et al. 2003

slide19
Open cluster T dwarfs
  • Star-formking regions: Probe to lowest masses.

Burrows et al. 1997

slide20
Open cluster T dwarfs
  • Star-formking regions: Probe to lowest masses.

UKIRT

low metallicity halo
Low Metallicity/Halo
  • Imaging at ~1 micron should detect brown dwarfs in globular clusters.
  • Need to reach T~800K to be interesting.
  • Resolution and field of view.
low metallicity halo1
Low Metallicity/Halo
  • Field Halo Brown Dwarfs
  • 2M0532+8346
  • An L subdwarf

Burgasser et al. 2003

spectra
Spectra
  • Beyond T dwarfs

Liebert et al. 2002

activity
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

activity1
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

activity2
Activity
  • HST/STIS can detect M8/M9 dwarfs
  • Need VLST for Le/Te dwarfs.
  • Also, for cluster late-M dwarfs.

Hawley & Johns-Krull 2003

formation
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

resolution
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

slide29
Weather?
  • Variability at I band is few percent.
  • Can we show that it is due to clouds? Hotspots? Sunspots?

Hurt

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

Hurt