Arlin P. S. Crotts, Professor in the Astronomy Department at Columbia University, died on 19 November 2015 after a long battle with cancer. Born on 6 October 1958, Crotts received his bachelors degree in Physics from Princeton University in 1980 and his Ph.D. in Physics from the University of Chicago in 1986. His Ph.D. thesis, “The Halo and Disk Populations of M31,” was completed under the supervision of Richard G. Kron, and was published in the Astronomical Journal 92 (August 1986): 292-301. He was a McDonald Postdoctoral Fellow at the University of Texas at Austin from 1985-1988, then a National Research Council Associate at NASA Goddard Space Flight Center from 1988-1990. He joined the Astronomy Department at Columbia University in 1991, and advanced to Associate Professor in 1996 and Full Professor in 2004. Crotts received a Packard Fellowship for Science and Engineering in 1991 and the AAS's Newton Lacy Pierce Prize for outstanding achievement in observational astronomy in 1993.
One component of Crotts’s research program addressed how matter on cosmological and galactic scales has rearranged itself over the life of the Universe. His 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 he and his collaborators showed to be much larger in diameter than previously suspected. He initiated follow-up studies to better determine how these objects evolve in size, what their shape is, and how they fit into large scale structure at different stages of the Universe.
Crotts also studied the microlensing properties of objects that compose the dark matter in the halo of M31 to better establish the spatial distribution of these objects, and perhaps their component mass distribution. In addition, he and his colleagues mapped the three-dimensional structure of the 30 Doradus star-forming region in the Large Magellanic Cloud by observing “light echos” from Supernova 1987A. Crotts also was active in the development of astronomical instrumentation, including MDM 8K, a 67 million pixel CCD imager at MDM Observatory on Kitt Peak. His book, The New Moon: Water, Exploration, and Future Habitation, was published by Cambridge University Press in 2004.
A memorial essay from the Columbia Astronomy Department notes that:
[Arlin] made contributions in an unusually wide range of areas, addressing each topic with his characteristic daring and flare—from supernova light echoes in the Magellanic Clouds and nearby galaxies, to pixel-scale microlensing in Andromeda, to absorption lines in pairs and groups of quasars, to building giant liquid mirrors for telescopes, to finding water on the moon. The review in Nature of his 2014 book, The New Moon, noted that, “Arlin Crotts mines lunar research and its implications for human colonization in staggering, often deeply engaging, detail.”
As someone who valued intellectual discourse, Arlin was a fixture at our bi-weekly coffee hours where he delighted in discussing the latest scientific discoveries with professors and students alike. Occasionally the conversation would also turn to human space exploration and the development of rockets, the history of science, his latest movie project, or the state of the world. His strong presence in the department, his sharp mind, and his quirky laugh and sense of humor will be sorely missed.
Photo: Columbia University