The Luminosity Function The Luminosity Function of Ultracool Dwarfsof Ultracool Dwarfs

Kelle Cruz

UPenn American Museum of Natural History (NYC)

Cool Stars 13

July 8, 2004

Colloborators:Neill Reid (STScI)Jim Liebert (UArizona)Davy Kirkpatrick (IPAC)

Cool Stars 13 2/16Kelle Cruz

Project SummaryProject Summary

• Measure the luminosity function of low-mass stars and BDs using a large sample of nearby objects

– Sample well understood so biases and selection effects can be accounted for

– Large volume with distance limit of 20 pc

– Aimed to be complete for objects between M7 and L8

– Cover 40% of the sky

Cool Stars 13 3/16Kelle Cruz

Luminosity FunctionLuminosity Function

Courtesy of Neill Reid

Cool Stars 13 4/16Kelle Cruz

Present-Day Mass FunctionPresent-Day Mass Function

Reid, Gizis, Hawley, 2002, AJ, 124, 2721

(M) = M--1

Salpeter

~1~0.5-1?

Cool Stars 13 5/16Kelle Cruz

2MASS Second Release2MASS Second Release

• Covers 47% of the sky in JHKS• Contains over 162 million point sources

Cool Stars 13 6/16Kelle Cruz

Selection CriteriaSelection Criteria

cool stars

ultracool dwarfs

T dwarfs

Cool Stars 13 7/16Kelle Cruz

Selection Criteria (cont.)Selection Criteria (cont.)

cool stars

ultracool dwarfs

L dwarfs

T dwarfs

giants

Cool Stars 13 8/16Kelle Cruz

The 2MU2 SampleThe 2MU2 Sample

• 1700 hits!

• Bright objects (J<9) analyzed separately

• 500 require follow-up observations

Cool Stars 13 9/16Kelle Cruz

Follow-up StatusFollow-up Status

• 98% complete. Only 15 left!

far-red

near-infrared

none

Cool Stars 13 10/16Kelle Cruz

Spectral Type DistributionSpectral Type Distribution

Optical Spectral Type

Cool Stars 13 11/16Kelle Cruz

MMJJ/ST Relation/ST Relation

Tinney, Burgasser, Kirkpatrick, 2003, AJ, 126,975

Optical Sp. Type NIR Sp. Type

Cool Stars 13 12/16Kelle Cruz

Ultracool Dwarf LFUltracool Dwarf LF

Cool Stars 13 13/16Kelle Cruz

Solar Neighborhood LFSolar Neighborhood LF

Courtesy of Neill Reid

Cool Stars 13 14/16Kelle Cruz

Constraining the MF with the LFConstraining the MF with the LF

Courtesy of Peter Allen

M

L

TY?

Cool Stars 13 15/16Kelle Cruz

Future WorkFuture Work

• Find more:

– Faintest 2MU2 objects with NIR and Gemini follow-up

– 2MASS All-Sky Release 2MUF, Paper X

• Study Near-infrared features (IRTF)

• Measure Multiplicity (HST and AO)

• Study Mid-Infrared Properties (Spitzer)

Cool Stars 13 16/16Kelle Cruz

• Created robust sample to measure fundamental properties of M7–L8 dwarfs

• Completing the census of the Solar Neighborhood

• First measurement of LF of objects that span the stellar/brown dwarf boundary

• Need more T dwarf data to put strong constraints on the mass function

• Papers:

– Cruz et al. 2003 (Paper V)

– Cruz et al. in prep (Paper IX)

SummarySummary

The Luminosity Function The Luminosity Function of Ultracool Dwarfsof Ultracool Dwarfs

Kelle Cruz

UPenn American Museum of Natural History (NYC)

Cool Stars 13

July 8, 2004

Colloborators:Neill Reid (STScI)Jim Liebert (UArizona)Davy Kirkpatrick (IPAC)