The study of the gaseous component of disks is still in its infancy. The past few decades have seen marked improvement in our ability to actually probe the gaseous component through the development of multiple spectral line diagnostics of the gas in disks. These diagnostics now span a wide range in wavelength (from UV through radio) and together probe disks from the inner disk edge, at a few stellar radii, out to the distant reaches of the disk, beyond the Kuiper Belt region. Complementing these in situ diagnostics is the more indirect method of using stellar accretion rates to probe the gaseous component. As I have described, this possibly under-utilized tool already seems to suggest that dynamically significant reservoirs of gas can survive over the timescales needed to influence the outcome of terrestrial planet formation. Determining exactly how much gas survives and how frequently this occurs requires the calibration of stellar accretion rates using the in situ diagnostics.

While the modest rate of progress in this field might initially be seen as discouraging (a sentiment expressed to me by more than one person at the symposium!), there is great reason for optimism that more rapid progress is on the horizon. Many of the spectral line probes that have been developed require high sensitivity and high spectral resolution in order to be effective and widely applicable. Facilities meeting these criteria (TEXES on Gemini; ALMA; and ground-based 30-m telescopes located at high, dry sites) will become available over the next 1-10 years. In parallel with these advancements in observing sensitivity, we will also need to develop and test the detailed thermal-chemical models of gaseous disks that will be needed in order to interpret future observations.

Once the required observational sensitivity and thermal-chemical models are available, it will be possible to use them to measure the gas dissipation timescale in disks over a range of radii. These will place constraints on important planet formation issues, such as the dominant modes of giant planet formation, the extent of giant planet migration, and the outcome of terrestrial planet formation. These tools can further be used in combination with other observations to explore the evolutionary status of various classes of T Tauri stars. Studies of the transitional T Tauri stars may be able to place constraints on the timescale for forming planetary cores, accreting gaseous envelopes, or photoevap-orating disks. Studies of weak T Tauri stars can address whether these are systems in which planet formation has failed, been successful, or is ongoing. It is hoped that observations such as these will place useful constraints on the processes and outcomes of planet formation.

I would like to thank my colleagues Steve Strom, John Carr, and Al Glassgold, with whom I have discussed many of the issues reviewed in this contribution.


Aikawa, Y., van Zadelhoff, G. J., van Dishoeck, E. F., & Herbst, E. 2002 AA 386, 622.

Alenoar, S. H. P. & Basri, G. 2000 ApJ 119, 1881.

Andrews, S. M. & Williams, J. P. 2005 ApJ 631, 1134.

Bary, J. S., Weintraub, D. A., & Kastner, J. H. 2003 ApJ 586, 1138.

Beckwith, S. V. W., Sargent, A. I., Chini, R. S., & Guesten, R. 1990 AJ 99, 924.

Blake, G. A. & Boogert, A. C. A. 2004 ApJ 606, L73.

Bodenheimer, P. & Lin, D. N. C. 2002 Annual Review of Earth and Planetary Sciences 30, 113.

Brandeker, A., Liseau, R., Olofsson, G., & Fridlund, M. 2004 AA 413, 681. Brittain, S. D., Rettig, T. W., Simon, T., Kulesa, C., DiSanti, M. A., & Dello RusSO, N. 2003 ApJ 588, 535. Calvet, N., D'Alessio, P., Hartmann, L, Wilner, D., Walsh, A., & Sitko, M. 2002 ApJ

568, 1008. Calvet, N., et al. 2005 AJ 129, 935. Calvet, N., et al. 2005 ApJ 630, L185.

Chen, C. H., Van Cleve, J. E., Watson, D. M., Houck, J. R., Werner, M. W., Sta-PELFELDT, K. R., Fazio, G. G., & Rieke, G. H. 2004 American Astronomical Society Meeting Abstracts 204, 204. Clarke, C. J., Gendrin, A., & Sotomayor, M. 2001 MNRAS 328, 485. D'Alessio, P., Canto, J., Calvet, N., & Lizano, S. 1998 ApJ 500, 411. D'Alessio, P., et al. 2005 ApJ 621, 461.

DENT, W. R. F., GREAVES, J. S., & COULSON, I. M. 2005 MNRAS 359, 663.

Dutrey, A., Guilloteau, S., Duvert, G., Prato, L., Simon, M., Schuster, K., &

menard, F. 1996 AA 309, 493. Duvert, G., Guilloteau, S., MEnard, F., Simon, M. & Dutrey, A. 2000 AA 355, 165. Glassgold, A. E., Najita, J., & Igea, J. 2004 ApJ 615, 972. Gorti, U. & Hollenbach, D. 2004 ApJ 613, 424. Greaves, J. S. 2004 MNRAS 351, L99.

Gullbring, E., Hartmann, L., BriceNo, C., & Calvet, N. 1998 ApJ 492, 323. Haisch, K. E., Lada, E. A., & Lada, C. J. 2001 ApJ 553, L153. Hartigan, P., Edwards, S., & Ghandour, L. 1995 ApJ 452, 736. Hartmann, L., Calvet, N., Gullbring, E., & D'Alessio, P. 1998 ApJ 495, 385. Herbig, G. H. & Bell, K. R. 1988 Lick Obs. Publ. 1111.

Herczeg, G. J., Linsky, J. L., Valenti, J. A., Johns-Krull, C. M., & Wood, B. E. 2004 ApJ 572, 310.

Hollenbach, D. J., Yorke, H. W., & Johnstone, D. 2000 In Protostars and Planets IV

(eds. V. Mannings, A. P. Boss, & S. S. Russell). p. 401. Univ. Arizona Press. Hollenbach, D., et al. 2005 ApJ 631, 1180. Kenyon, S. J. & Bromley, B. C. 2004 ApJ 602, L133. Kenyon, S. J. & Hartmann, L. 1995 ApJS 101, 117. Koerner, D. W. 1995 Ph.D. Thesis, California Institute of Technology. Kominami, J. & IDA, S. 2002 Icarus 157, 43.

LAWSON, W. A., LYO, A. R., & MUZEROLLE, J. 2004 MNRAS 351, L39.

Mamajek, E. E., Meyer, M. R., Hinz, P. M., Hoffmann, W. F., Cohen, M., & Hora,

J. L. 2005 ApJ 612, 496. Marsh, K. A. & Mahoney, M. J. 1992 ApJ 395, L115.

Massarotti, A., Latham, D. W., Torres, G., Brown, R. A., & Oppenheimer, B. D. 2005 AJ 129, 2294.

Mayer, L., Quinn, T., Wadsley, J., & Stadel, J. 2002 Science 298, 1756. McCabe, C., Ghex, A. M., Prato, L., DuchEne, G., Fisher, S., & Telesco, C. 2006 ApJ 636, 932.

MuzEROLLE, J., Calvet, N., Briceño, C., Hartmann, L., & Hillenbrand, L. 2000 ApJ 535, L47.

MuzEROLLE, J., Hartmann, L., & Calvet, N. 1998 AJ 116, 2965.

Najita, J. 2004 In Star Formation in the Interstellar Medium: In Honor of David Hollenbach, Chris McKee and Frank Shu (eds. D. Johnstone, F. C. Adams, D. N. C. Lin, D. A. Neufeld, & E. C. Ostriker). ASP Conf. Proc. 323, p. 271. ASP.

Najita, J., Carr, J. S., & Mathieu, R. D. 2003 ApJ 589, 931.

Najita, J., Edwards, S., Basri, G., & Carr, J. 2000 In Protostars and Planets IV (eds. V. Mannings, A. P. Boss, & S. S. Russell). p. 457. Univ. Arizona Press.

Osterloh, M. & Beckwith, S. V. W. 1995 ApJ 439, 288.

Rettig, T. W., Haywood, J., Simon, T., Brittain, S. D., & Gibb, E. 2004 ApJ 616, L163.

Rice, W. K. M., Wood, K., Armitage, P. J., Whitney, B. A., & Bjorkman, J. E. 2003 MNRAS 342, 79.

Richter, M. J., Jaffe, D. T., Blake, G. A., & Lacy, J. H. 2002 ApJ 572, L161.

Sargent, A. I. & Beckwith, S. V. W. 1991 ApJ 382, L31.

SHERET, I., RAMSAY HOWAT, S. K., & DENT, W. R. F. 2003 MNRAS 343, L65.

Shu, F. H., Johnstone, D., & Hollenbach, D. 1993 Icarus 106, 92.

Sicilia-Aguilar, A., Hartmann, L. W., Hernández, J., Briceño, C., & Calvet, N. 2005 AJ 130, 188.

Siess, L., Forestini, M., & Bertout, C. 1999 AA 342, 480.

Simon, M., Dutrey, A., & Guilloteau, S. 2000 ApJ 545, 1034.

Skrutskie, M. F., Dutkevitch, D., Strom, S. E., Edwards, S., Strom, K. M., & Shure, M. A. 1990 AJ 99, 1187.

Takeuchi, T. & Lin, D. N. C. 2005 ApJ 623, 482.

Thi, W. F., van Dishoeck, E. F., Blake, G. A., van Zadelhoff, G. J., Horn, J., Becklin, E. E., Mannings, V., Sargent, A. I., van den Ancker, M. E., Natta, A., & Kessler, J. 1995 ApJ 561, 1074.

White, R. J. & Hillenbrand, L. A. 2005 ApJ 621, L65.

Zuckerman, B., Forveille, T., & Kastner, J. H. 1995 Nature 373, 494.

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