Joe Filippazzo edited untitled.tex  almost 10 years ago

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Figure 1. shows $L_{bol}$ versus selected absolute magnitudes $M_J$, $M_{Ks}$ and $M_{W2}$ for the 59 field age, 27 low-g, and 11 young moving group member L dwarfs of our sample. The flux of low-g L dwarfs appears to be redistributed from the NIR into the MIR, primarily from J to W2, as compared to field age Ls of the same luminosity (Faherty et al. 2012/2013, Liu et al. 2013, Zapaterio Osario et al. 2014, Gizis et al. submitted). Indeed we find low gravity Ls are 0.5-1 magnitudes dimmer in $M_J$ and 0.3-0.6 magnitudes brighter in $M_{W2}$ (Filippazzo et al. in prep). This is probably due to the scattering of light to longer wavelengths by diffuse, unsettled dust in the atmospheres of young objects (BurgTK, TK refs). Additionally, $M_{Ks}$ magnitudes appear to be largely unaffected by surface gravity making it an ideal band from which to determine age-independent bolometric corrections for L dwarfs.  Bolometric luminosities are one of the few direct measurements we can make for brown dwarfs for identification of substellar touchstones, however, effective temperatures can also be tightly constrained while minimizing our assumptions about the source. Qualitatively, low-g L dwarfs have larger radii than their field age counterparts of the same $L_{bol}$ so they must have cooler photospheres according to the Stefan-Boltzmann Law. We use the DUSTY evolutionary models of Baraffe et al. (2002) and assume the full range of posible radii for field age (0.5-10 Gyr) dwarfs of 1.0 +/- 0.21 $R_{Jup}$. For young moving group members, we interpolated between isochrones to retrieve the uncertainty in radius at a given $L_{bol}$. And for low-g objects, we... Preliminary results suggest that confirmed young objects are 100-400 K cooler than field age L dwarfs of the same spectral type implying that surface gravity must be taken into account when using spectral type as a proxy for $T_{eff}$.