Measuring the Physical Properties of the Coldest Brown Dwarfs with 测量最冷褐矮星的理性质.pptVIP

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Measuring the Physical Properties of the Coldest Brown Dwarfs with 测量最冷褐矮星的理性质.ppt

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Measuring the Physical Properties of the Coldest Brown Dwarfs with 测量最冷褐矮星的理性质

Measuring the Physical Properties of the Coldest Brown Dwarfs with SpeX Adam J. Burgasser (MIT) Adam Burrows (U. Arizona) J. Davy Kirpatrick (IPAC/Caltech) T dwarfs are the coldest, lowest luminosity brown dwarfs currently known. With effective temperatures Teff 1200 K (as low as 700 K), these objects are distinguished by the presence of H2O and CH4 absorption bands in their near infrared spectra, and blue J-K colors arising from strong collision-induced H2 absorption. They have spectral properties similar to hot extrasolar planets.Modeling of T dwarf spectra is hampered by deep and overlapping molecular bands, a hinderance in the determination of the physical properties for these sources, including, mass, age and composition. Such parameters are crucial for understanding the origins and evolution of brown dwarfs. Determination of Teff and log g yields masses, radii and ages for individual field brown dwarfs, paving the way for direct measurements of the field substellar luminosity and mass functions, the age distribution of brown dwarfs, identification of coeval low mass moving groups, and correlations between metallicity and age. These are all key ingredients in our understanding of the formation and evolution of the Galaxy and the local Solar environment. Our procedure can be generalized to other spectral types. Furthermore, by basing our technique on low resolution near infrared spectra, it can be applied to statistically large samples of intrinsically faint sources as will soon be uncovered by UKIDSS and PanStarrs. “A Method for Determining the Physical Properties of the Coldest Known Brown Dwarfs” Burgasser, Burrows Kirkpatrick 2006, ApJ, 639, 1095 We searched for gravity and metallicity features in low resolution near infrared T dwarf spectra obtained with SpeX. In this set of T6-T6.5 dwarfs (Teff ≈ 1000 K), we see that the 1.05 and 2.1μm peaks clearly vary in peak strength while most other features are identical. We see similar variations in t