near-ir spectral properties of young brown dwarfs
DESCRIPTION
Near-IR Spectral Properties of Young Brown Dwarfs. Katelyn Allers, IfA-Hawaii. Mike Liu Mark Pitts Jonathan Leong Joan Najita Alan Tokunaga. Kelle Cruz Davy Kirkpatrick Adam Burgasser Greg Doppmann Dan Jaffe Kevin Luhman. Why should we search for young brown dwarfs?. - PowerPoint PPT PresentationTRANSCRIPT
Mike LiuMark Pitts
Jonathan LeongJoan Najita
Alan Tokunaga
Near-IR Spectral Properties of Young
Brown Dwarfs
Kelle CruzDavy KirkpatrickAdam BurgasserGreg Doppmann
Dan JaffeKevin Luhman
Katelyn Allers, IfA-Hawaii
Why should we search for young brown dwarfs?
• Exploring the low mass end of the IMF
• Formation Mechanism: Ejection vs. Isolated Collapse
• Disks around the lowest-mass objects
Image Credits: NASA/HST; NASA/JPL-Caltech/T. Pyle
Not So Fast!
Mass (A)MJup
Mass (B)MJup
65±30 35±20
14±1 7±0.5
17.5±2.5 15.5±2.5
55±10 19±10/5
Oph1622-2405 A & B
ObservedSpectrum
Teff
SpT
ModelSpectrum
Photometry L*AVdist BC
Just the M8’s
Determining Gravity
The 1.14 micron Na doublet is gravity sensitive, and through the late-M and early-L types is only weakly dependent on SpT.
Is there an age (gravity) spread?
Na(1.14)
K(1.169)
K(1.177)
K(1.253)
TWA 3.87 0.75
1.73 0.50 2.47 0.32
1.60 0.26
Young 2.96 0.54 0.98 0.21 1.78 0.22 1.15 0.36
Line EW’s
Determining SpT
Even though the overall shapes of the H-band differ, the slope of the blue end of the H-band is SpT sensitive, yet gravity insensitive.
A Custom Filter for Determining SpT
• Central wavelength: 1.45 microns• Filter width = 6%• Estimated Sensitivity:• H=19.9 mag (10 in 1 hour)• W~18.0 mag (10 in 1 hour)• Designed for 1.0 subtype uncertainty in
SpT determination for 5% photometric accuracy W-band detections.
• Designed for use in 1-5mm of pwv (Mauna Kea)
J W H
Conclusions•We need more young cluster and young
field objects in analysis! (Please?)
•Na and K lines are better gravity indicators than the shape of the H-band continuum
•We don’t see an age spread indicated in the alkali line EW’s.
•The 1.45 micron steam absorption feature is very sensitive to SpT.