Brown Dwarf Science with VLST " Outline: " The Big Questions " Where we are and how VLST would help... John Gizis Physics and Astronomy

Brown Dwarf Science with VLST Formation Atmospheres

Brown Dwarf Science with VLST Formation IMF Binarity Disks Atmospheres

Brown Dwarf Science with VLST Formation IMF Binarity Disks Atmospheres Evolution Beyond T dwarfs Activity

Brown Dwarf Science with VLST  Brown dwarfs below ~0.074M M fail to achieve stable nuclear burning. " Cool and fade steadily Burrows et al. 1993, 1997

Brown Dwarf Science with VLST  Brown dwarfs below ~0.074M M fail to achieve stable nuclear burning. " Cool and fade steadily Burrows et al. 1993, 1997

Brown Dwarf Science with VLST  Brown dwarfs below ~0.074M M fail 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 " P 2 = a 3 /M T " 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 M J 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 M J 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 M J 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

" 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 " 2M " An L subdwarf Burgasser et al. 2003

Spectra " Beyond T dwarfs Liebert et al. 2002

Activity " Gizis et al found that activity declines sharply after M6. " But, flares are common.  Burgasser et al find some H  at erg/sec/cm2 Liebert et al. 2002

Activity " Gizis et al found that activity declines sharply after M6. " But, flares are common.  Burgasser et al find some H  at erg/sec/cm 2 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;  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;  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 dwarfs Hurt