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L. Clark Seelye Professor of Astronomy
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Clark Science Center
Ph.D., M.A, University of Hawaii
B.A., Dartmouth College
Edwards studies stars that are forming deep within molecular clouds in the galaxy. The gravitational collapse of rotating, denser-than-average "cores" within a molecular cloud results in the creation of a central protostar surrounded by a flattened spinning disk of gaseous material, with dimensions comparable to the solar system. At first the circumstellar disk is in a phase called an accretion disk, where mass is transported inward toward the star and angular momentum is transported outward. Planet formation likely occurs primarily during the accretion era.
Edwards’ work has focused on studying star formation in the accretion disk phase, particularly for low-mass protostars that are progenitors of sun-like stars. The accretion phase is intriguing because it is always accompanied by the simultaneous presence of a high-velocity ejection of material into collimated, bipolar jets that emerge perpendicular to the plane of the disk. Although we know that accretion disks and jets of expelled material are always seen together, exactly how this pairing happens is a mystery.
She uses spectroscopic techniques to explore the dynamical processes that occur in the disk itself as well as in the region where the disk meets the star with the goal of understanding how material is launched into winds that leave the system, carrying away mass and angular momentum. The evidence indicates there are multiple modes of launching these winds, characterized by different velocities. Magnetic fields of the star and the disk are implicated in the high velocity ejection that arises close to the star while high energy radiation from the star is the more likely cause of the lower velocity winds that arise in the out part of the disk. In addition to evidence for winds, some of the lines that she studies also show kinematic signatures of mass falling towards the stellar surface, leaving from the truncated inner edge of the disk and lifted up along magnetic funnel flows to fall ballistically toward the star. We also see spectroscopic evidence for accretion shocks where the funnel flow meets the stellar surface. All of these phenomena occur at the same time planets are forming in the disk, and they are important in determining the environment in which planet formation occurs. This work is being carried out in collaboration with Smith students and scientists from other institutions.
"Tracing Slow Winds from T Tauri Stars via Low Velocity Forbidden Line Emission," Simon, M., Pascucci, I., Edwards, S., Feng, W., Gorti, U., Hollenbach, D., Rigliaco, E., 2016, Astrophysical Journal, in press
"Probing Stellar Accretion with Mid-Infrared Hydrogen Lines," Rigliaco, E., Pascucci, I., Duchene, G., Edwards, S., Ardila, D. and 10 additional authors, 2014, Astrophysical Journal, 2015, 801, 31
"Interpreting Near Infrared Hydrogen Line Ratios in T Tauri Stars," Edwards, S., Kwan, J., Fischer, W., Hillenbrand, L., Finn, K. , Fedorenko, K.. Feng, W., 2013, Astrophysical Journal, 778, 148.
"Understanding the origin of the [OI] low-velocity component from T Tauri stars," Rigliaco,E., Pascucci, I., Gorti, U., Edwards, S., and Hollenbach D., 2013, Astrophysical Journal, 2013, 772, 60.
"Hot Gas Lines in T Tauri Stars," Ardila, D. et al., 2013, Astrophysical Journal Supplement, 207, 1A
"Characterizing the IYJ Excess Continuum Emission in T Tauri Stars,'' Fischer, W, Edwards, S., Hillenbrand, L, and Kwan, J. 2011, Astrophysical Journal 730, 73
"Winds and Accretion in Young Stars," Edwards, S. 2009, Proceedings of the 15th Workshop of Cool Stars, Stellar Systems, and the Sun, AIP Conference Proceedings, Volume 1094, pp. 29-38
"Redshifted Absorption at He I 10830 as a Probe of the Accretion Geometry of T Tauri Stars," Fischer, W., Kwan, J., Edwards, S. and Hillenbrand, L. 2008,Astrophysical Journal 687,1117.
"Spectroscopic Diagnostics of T Tauri Inner Winds," Edwards, S. 2007, Star–Disk Interaction in Young Stars, Proceedings of the International Astronomical Union, IAU Symposium, Volume 243, ed. J. Bouvier and I. Appenzeller (Cambridge University Press) pp. 171–182.
"Stellar Jets: Clues to the Process of Star and Planet Formation," Edwards, S. 2007,Jets from Young Stars II, Clues to High Angular Resolution Observations, Lecture Notes in Physics, ed. E. Whelan (Springer-Verlag) pp. 3–13.
"Modeling T Tauri Winds from He I 10830 Profiles," Kwan, J., Edwards, S. Fischer, W., 2007 Astrophysical Journal, 567, 897.
"Probing T Tauri Accretion and Outflow with 1 Micron Spectroscopy," Edwards, S. Fischer, W., Hillenbrand, L. Kwan, J. 2006, Astrophysical Journal.
"Going Slitless: Images of Forbidden Line Emission Regions of Classical T Tauri Stars Observed with the Hubble Space Telescope," Hartigan, P., Edwards, S. and Pierson, R. 2004, Astrophysical Journal 609, 261.
"Helium I 10830 as a Probe of Winds in Accreting Young Stars," Edwards, S., Fischer, W., Kwan, J., Hillenbrand, L. and Dupree A.K. 2003, Astrophysical Journal Letters, 599, L41.
"Observations of the Star–Disk Interface: A Search for Wind Origins," Edwards, S. 2004, Jets in Young Stellar Objects: Theory and Observations, ed. A. Fernandez, P. Garcia, J. Lima (Kluwer).
"Helium Emission from Classical T Tauri Stars: Dual Origin in Magnetospheric Infall and Hot Wind," Beristain, G., Edwards, S. and Kwan, J. 2001, Astrophysical Journal, 551, 1037.
"Spectroscopic Probes of Inner Accretion Disks and the Star–Disk Interface," Najita, J., Edwards, S., Basri, G. and Carr, J. 2000, Protostars and Planets IV, University of Arizona Press, editors V. Mannings and A. Boss, 457.
"Near–Infrared Classification Spectroscopy: H–band Spectra of Fundamental MK Standards," Meyer, M., Edwards, S., Hinkle, K. and Strom, S.E. 1998, The Astrophysical Journal, 508, 397.
"Permitted Iron Emission Lines in the Classical T Tauri Star DR Tauri," Beristain, G., Edwards, S. and Kwan, J. 1998, The Astrophysical Journal, 488, 828.