Columbia Astrophysics Laboratory Arlin Crotts e-mail: arlinastro.columbia.edu Telephone: (212) 854-7899

Teaching, Autumn 2009 Course: C1403 "Earth, Moon & Planets"

Research Interests:

- The nature of quasar absorption lines and the intergalactic medium
- Galaxy formation, galactic haloes: gravitational microlensing in M31
- Star formation, the interstellar medium in the Large Magellanic Cloud: light echoes from SN 1987A
- Understanding lunar outgassing and optical transients

I am interested in how matter on cosmological and galactic scales has rearranged itself over the life of the Universe. Our studies of Lyman alpha forest absorbers in the spectra of quasars, for example, showed that at early times a large fraction of the baryonic matter in the Universe was tied up in these clouds, which we showed to be much larger in diameter than previously suspected. We have embarked on a number of projects to determine better how these objects evolve in size, what their shape is, and how they fit into large scale structure at different stages of the Universe. We are also studying whether the objects that compose the dark matter in M31 fall within the mass range (slightly less massive than the Sun) seen by gravitational microlensing studies of our Galaxy's halo. A study of M31's halo microlensing promises to better establish the spatial distribution of these objects, and perhaps their component mass distribution, while being sensitive to halo masses as small as 10^-8M. We have also taken the unique opportunity of the explosion of Supernova 1987A in the vicinity of the 30 Doradus star-forming region in the nearby galaxy, the Large Magellanic Cloud, to follow the reflection of the supernova light (or "light echo") from surrounding material in the manner of a radar pulse, using it to map the structure in three dimensions of the interstellar medium affected by star formation processes, as well as the supernova's circumstellar material, which was affected by the late stages of evolution of the star that exploded. Soon this structure will brighten once more as Supernova Remnant 1987A, as the debris from the explosion strikes the surrounding material that we have mapped.

In addition to my research into astronomical and cosmological systems, I also build astronomical instrumentation, most recently the MDM 8K, a 67 million pixel CCD imager which has become one of the most popular instruments at MDM Observatory. I am also building and designing instrumentation connected with large aperture, liquid mirror telescopes, most notably the LZT, ALPACA and LLAMA projects.

Background:

Selected Publications:

• "Evidence of Halo Microlensing in M31" R.R. Uglesich, A.P.S. Crotts, E.A. Baltz, J. de Jong, R.P. Bioyle and C. Corbally, Ap.J., 612, 877 (2004)
• "First microlensing candidates from the MEGA survey of M31" J.T.A. de Jong, K. Kuijken, A.P.S. Crotts, P.D. Sackett, W.J. Sutherland, R.R. Uglesich, E.A. Baltz, P. Cseresnjes, G. Gyuk, and L.M. Widrow (The MEGA collaboration), A.&A., 417, 461 (2004)
• "Event Rates and Timescale Distributions from Realistic Microlensing Models of M31" E.A. Baltz, G. Gyuk and A.P.S. Crotts, Ap.J., 582, 30 (2003)
• "Multiple Light Echoes from SN 1993J" B.E.K. Sugerman and A.P.S. Crotts, Ap.J.Let., 581, L97 (2002)
• "Evolution and Geometry of Hot Spots in Supernova Remnant 1987A" B.E.K. Sugerman, S.S. Lawrence, A.P.S. Crotts, P. Bouchet and S.R. Heathcote, Ap.J., 572, 209 (2002)
• "On the Emergence and Discovery of Hot Spots in SNR 1987A" S.S. Lawrence, B.E.K. Sugerman, P. Bouchet, A.P.S. Crotts, R.R. Uglesich and S.R. Heathcote, Ap.J.Let., 537, L123 (2000)
• "SN 1987A's Circumstellar Envelope. II. Kinematics of the Three Rings and the Diffuse Nebula" A.P.S. Crotts and S.R. Heathcote, Ap.J., 528, 426 (2000)
• "Structure and Kinematics of the Interstellar Medium in Front of SN 1987A" J.Xu and A.P.S. Crotts, Ap.J., 511, 262 (1999)
• "Reobservation of Close QSO Groups: The Size Evolution and Shape of Lyman Alpha Clouds," A.P.S. Crotts and Y. Fang, Ap.J., 502, 16 (1998)
• "Results from a Survey of Gravitational Microlensing toward M31," A.P.S. Crotts and A.B. Tomaney, Ap.J., 473, 87 (1997)
• "The Circumstellar Envelope of SN 1987A, I: The Shape of the Double-lobed Nebula and Its Rings, and the Distance to the LMC," A.P.S. Crotts, W.E. Kunkel and S.R. Heathcote, Ap.J. 438, 724 (1995)
• "Spectroscopy of the Double Quasars 1343+266AB: The Relationship between Galaxies and QSO CIV Absorption Lines," A.P.S. Crotts, J. Bechtold, Y. Fang and R. C. Duncan, Ap.J.Let., 437, L79 (1994)
• "Spectroscopy of the Double Quasars 1343+266AB: A New Determination of the Size of Ly-alpha Forest Absorbers," A.P.S. Crotts, J. Bechtold, R. C. Duncan and Y. Fang, Ap.J.Let., 437, L83. (1994)
• "M31: A Unique Laboratory for Gravitational Microlensing," A.P.S. Crotts, Ap.J.Let., 399, L43. (1992)
• "The Dynamics of the Nebula Around SN1987A: Ring Structure and Progenitor Mass Loss," A.P.S. Crotts and S. R. Heathcote, Nature, 350, 683. (1991)
• "Discovery of the Optical Echoes from Supernova 1987A: New Probes of the Large Magellanic Cloud," A.P.S. Crotts, Ap.J.Let., 333, L51. (1988)
• "The Halo and Disk Populations of M31," A.P.S. Crotts, A.J., 292, 92. (1986)

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