1. The Luminosity Function of 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)

2. Kelle Cruz Cool Stars 13 2/16 Project 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

3. Kelle Cruz Cool Stars 13 3/16 Luminosity Function Courtesy of Neill Reid

4. Kelle Cruz Cool Stars 13 4/16 Present-Day Mass Function Reid, Gizis, Hawley, 2002, AJ, 124, 2721  (M) = M -  -1 Salpeter  ~1  ~0.5-1?

5. Kelle Cruz Cool Stars 13 5/16 2MASS Second Release Covers 47% of the sky in JHK S Contains over 162 million point sources

6. Kelle Cruz Cool Stars 13 6/16 Selection Criteria cool stars ultracool dwarfs T dwarfs

7. Kelle Cruz Cool Stars 13 7/16 Selection Criteria (cont.) cool stars ultracool dwarfs L dwarfs T dwarfs giants

8. Kelle Cruz Cool Stars 13 8/16 The 2MU2 Sample 1700 hits! Bright objects (J<9) analyzed separately 500 require follow-up observations

9. Kelle Cruz Cool Stars 13 9/16 Follow-up Status 98% complete. Only 15 left! far-red near- infrared none

10. Kelle Cruz Cool Stars 13 10/16 Spectral Type Distribution Optical Spectral Type

11. Kelle Cruz Cool Stars 13 11/16 M J /ST Relation Tinney, Burgasser, Kirkpatrick, 2003, AJ, 126,975 Optical Sp. TypeNIR Sp. Type

12. Kelle Cruz Cool Stars 13 12/16 Ultracool Dwarf LF

13. Kelle Cruz Cool Stars 13 13/16 Solar Neighborhood LF Courtesy of Neill Reid

14. Kelle Cruz Cool Stars 13 14/16 Constraining the MF with the LF Courtesy of Peter Allen M L T Y?

15. Kelle Cruz Cool Stars 13 15/16 Future 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)

16. Kelle Cruz Cool Stars 13 16/16 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) Summary

17. The Luminosity Function of 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)