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.