Brown Dwarf Science with VLST

Brown Dwarf Science with VLST Outline: The Big

Questions Where we are

and how VLST would help...

John GizisPhysics and Astronomy

Brown Dwarf Science with VLSTFormation

Atmospheres

Brown Dwarf Science with VLSTFormationIMFBinarityDisks

Atmospheres

Brown Dwarf Science with VLSTFormationIMFBinarityDisks

AtmospheresEvolutionBeyond T dwarfsActivity

Brown Dwarf Science with VLST Brown

dwarfs below ~0.074Mfai

l to achieve stable nuclear burning.

Cool and fade steadily

Burrows et al. 1993, 1997

Brown Dwarf Science with VLST Brown

dwarfs below ~0.074Mfai

l to achieve stable nuclear burning.

Cool and fade steadily

Burrows et al. 1993, 1997

Brown Dwarf Science with VLST Brown

dwarfs below ~0.074Mfai

l to achieve stable nuclear burning.

Cool and fade steadily

Planets vs. brown dwarfs

Burrows et al. 2003

Brown Dwarf Science with VLST 2MASS and

SDSS find objects

Sequence to T8 or ~800K.

Vrba et al. 2004

L dwarf sequence Disappearance of

molecules as grains form.

Cloud deck ~1600K

Kirkpatrick et al. 1999

T dwarf sequence Classification in

near-IR. Cloud deck ~1600K

below photosphere.

Burgasser et al. 2003

T dwarf sequence Classification in

near-IR.

Burgasser et al. 2002

On beyond T with VLST?

Not really... Want large

sky area and mid-infrared.

Spitzer, JWST

WISE

Burrows et al. 2003

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

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 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

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

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

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.

ResolutionGizis et al. 2003

Open cluster T dwarfs

Star-formking regions: Probe to lowest masses.

Burrows et al. 1997

Open cluster T dwarfs

Star-formking regions: Probe to lowest masses.

UKIRT

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/Halo Field Halo Brown

Dwarfs 2M0532+8346 An L subdwarf

Burgasser et al. 2003

Spectra Beyond T dwarfs

Liebert et al. 2002

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

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

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 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? 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

Weather? Variability at

I band is few percent.

Can we show that it is due to clouds? Hotspots? Sunspots?

Hurt

Summary Very Large

Space Telescope

Needed for followup of expected discoveries.

Needed for more distant L/T dwarfsHurt