Computer Science
Scientific paper
Jun 2005
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2005sptz.prop20803m&link_type=abstract
Spitzer Proposal ID #20803
Computer Science
Scientific paper
We propose to investigate the evolution of brown dwarf disks beyond the initial disk-accretion phase, using Spitzer IRS and MIPS. Our sample comprises 29 young brown dwarfs in nearby star-forming regions and young clusters (rho Oph, Taurus, IC348, Cha I, R CrA, sig Ori and Upper Sco), spanning ages of <1 ? 5 Myr, and ranging in mass from the hydrogen-burning limit (80 MJup) down to nearly the planetary-mass domain (12 MJup). Extensive optical spectroscopy has revealed that most of the sources are either past, or nearing the end of, their main disk-accretion stage; nevertheless, they are still girdled by remaining disk material, as evinced by their observed infrared excesses. Stellar disks in such a transitional phase strongly manifest various evolutionary signatures, such as significant grain growth, gradual settling of dust to the disk midplane, annealing of amorphous silicates into crystalline ones, and the clearing of large inner holes by incipient planetesimal formation. Our goal is to explore whether similar processes occur in the sub-stellar domain as well. To this end, we will obtain: (1) low-resolution 5.2?14.5um spectra with Spitzer IRS, and (2) 24um photometry with MIPS. Combined with IRAC 3.6?8?m photometry already being acquired for our sample within large-scale GTO/GO surveys, our observations will allow us to determine the disk spectral energy distribution (SED) down to photospheric levels out to 24um, and precisely map out the shape of the 10um silicate emission feature. By comparing the SED and silicate feature to detailed disk radiative-transfer models and synthetic grain emission spectra, we will examine grain growth and composition, dust settling, and (possibly planetesimal-induced) gap formation in our brown dwarf disks, as a function of age and mass.
Apai Daniel
Bouwman Jeroen
Luhman Kevin
Mohanty Subhanjoy
Natta Antonella
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