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THE STAR FORMATION NEWSLETTER An electronic publication dedicated to early stellar/planetary evolution and molecular clouds No. 269 — 12 May 2015 Editor: Bo Reipurth ([email protected]) List of Contents The Star Formation Newsletter Interview ...................................... 3 My Favorite Object ............................ 8 Editor: Bo Reipurth [email protected] Perspective ................................... 12 Technical Editor: Eli Bressert Abstracts of Newly Accepted Papers .......... 17 [email protected] New Jobs ..................................... 42 Technical Assistant: Hsi-Wei Yen Meetings ..................................... 44 [email protected] Summary of Upcoming Meetings ............. 46 Editorial Board Short Announcements ........................ 48 Joao Alves Alan Boss Jerome Bouvier Lee Hartmann Cover Picture Thomas Henning Paul Ho The HII region on the cover is known as Sharp- Jes Jorgensen less 171, or W1, or NGC 7822. The young cluster Charles J. Lada Berkeley 59, seen in the upper left corner, contains Thijs Kouwenhoven a group of OB-stars at a distance of∼845 pc. The Michael R. Meyer cluster is sculpting the neutral gas into cometary Ralph Pudritz clouds and elephant trunks. North is left and east Luis Felipe Rodr´ıguez is down in this image. Ewine van Dishoeck Hans Zinnecker Image courtesy Neil Fleming http://flemingastrophotography.com The Star Formation Newsletter is a vehicle for fast distribution of information of interest for as- tronomers working on star and planet formation and molecular clouds. You can submit material for the following sections: Abstracts of recently accepted papers (only for papers sent to refereed Submitting your abstracts journals), Abstracts of recently accepted major re- views (not standard conference contributions), Dis- Latex macros for submitting abstracts sertation Abstracts (presenting abstracts of new and dissertation abstracts (by e-mail to Ph.D dissertations), Meetings (announcing meet- [email protected]) are appended to ings broadly of interest to the star and planet for- each Call for Abstracts. You can also mation and early solar system community), New submit via the Newsletter web inter- Jobs (advertising jobs specifically aimed towards face at http://www2.ifa.hawaii.edu/star- persons within the areas of the Newsletter), and formation/index.cfm Short Announcements (where you can inform or re- quest information from the community). Addition- ally, the Newsletter brings short overview articles on objects of special interest, physical processes or theoretical results, the early solar system, as well as occasional interviews. Newsletter Archive www.ifa.hawaii.edu/users/reipurth/newsletter.htm tential of a small-amplitude density perturbation, in stars or gas, in a flattened axisymmetric galaxy. The perturba- Frank Shu tions were oscillatory in time and had a m-fold sinusoidal in conversation with Bo Reipurth variation in azimuthal angle, with the radial variation to be determined self-consistently from the joint equations of dynamics for the stars and gas plus Newton’s theory of gravity. These calculations, supervised by Lin’s sure vision that the actual phenomenon had to be quasi-stationary and not transitory, grew to become the foundations of modern spiral density-wave theory. It was pure dumb luck that brought me there for the beginning, but density-wave the- ory holds a special place in my heart. It is a topic to which I have returned many times in my career, as the ideas turned out to have important applications not only in disk galaxies (e.g., the study of flocculence resulting from the chaos induced by overlapping subharmonic resonances with Greg Laughlin and Sukanya Chakrabarti, and ”feath- ering” as a parasitic instability behind self-gravitating, Q: The Lin-Shu density wave theory for the spiral struc- magnetohydrodynamic spiral shocks with Wing Kit Lee), ture of disk galaxies was published in 1964. What was the but also in planetary rings (resonantly driven, linear and genesis of this enormously influential concept? nonlinear, density waves with Jack Lissauer, Luke Dones, A: The project started when C. C. Lin of MIT spent a sab- Jeff Cuzzi, and Chi Yuan), and in heavy protoplanetary batical year in 1961 at the Institute for Advanced Study disks (e.g., m =1 SLING instability for binary and giant in Princeton, to work with C. N. Yang on the theory of planet formation with Scott Tremaine, Fred Adams, and superfluids. Lin attended a symposium on the spiral struc- Steve Ruden). ture of disk galaxies organized by Bengt Str¨omgren, who Q: From the linear theory of density wave theory of the was then the Professor of Astrophysics at the IAS. At this stars you began to study the nonlinear theory of the re- meeting, Jan Oort gave the plenary lecture on the wind- sponse of the interstellar medium and its implications for ing dilemma of material spiral arms. Per Olof Lindblad, star formation. What influenced you to change your fo- the son of Bertil Lindblad (for whom Lindblad resonances cus, given that there were major unresolved issues with the are named), presented some early numerical N-body sim- stellar theory? ulations of a system of self-gravitating stars in a flattened geometry. The idealized system exhibited transient spi- A: After getting my PhD from Harvard in 1968, I spent ral patterns that sporadically formed and dissolved. From five years on the faculty at Stony Brook, which was just those two lectures, Lin got the seminal idea that the spiral getting started with a newly formed astronomy group headed patterns were really a wave phenomena, and not material by Steve Strom. From Steve, I learned a lot about stars arms. as points of light and not just as points of mass. I had become interested in the problem of OB star formation When Lin returned to MIT, he started to organize a team behind the two-armed shockwave patterns in spiral galax- of young theorists to help him develop this idea. The ies and was collaborating with Chi Yuan and Bill Roberts group grew eventually to include Alar Toomre, Chris Hunter,for a better astrophysical understanding of the triggering Chi Yuan, Bill Roberts, James Mark, Y. Y. Lau, and mechanism. It soon became clear that we had to have Guiseppe Bertin. I was then a MIT physics undergraduate a much better model for the interstellar medium than major, uncertain about how to have a career in science. the adopted default of a single-phase isothermal gas, so Lin hired me as a summer research assistant to help him I went to Berkeley on a one-semester sabbatical to learn perform some numerical calculations on the problem of about the elegant two-phase model that had been devel- wind-driven ocean circulation, another scientific problem oped by George Field, Don Goldsmith, and Harm Habing. that interested him at the time. After spending a sum- Together with Vinny Milione, Don Goldsmith (whom I mer crunching numbers on an old mechanical calculator, helped later to recruit to Stony Brook), Chi Yuan, Bill I managed to finish the assigned calculations well enough Gebel, and Bill Roberts, we wrote a paper that dealt with that Lin agreed to be my adviser for the senior thesis that the problems of phase transformations and star formation all MIT physics students had to write before graduation. in a two-phase ISM periodically exposed to shockwaves in This thesis was on density wave theory, and my primary a spiral galaxy. job was to calculate asymptotically the gravitational po- 3 This work drew the interest of Ron Allen, who then headed papers on the subject of mass transfer in semi-detached a radio group at Groningen building 21cm-line receivers binaries that are still considered benchmarks in the field. for the newly commissioned Westerbork Radio Synthesis From semi-detached binaries to contact binaries was a Telescope. Ron wanted to learn how WRST might be used small step seemingly. But in semi-detached binaries, all to test density wave theory in the context of the response the action is at the surface or outside the stars and can of the interstellar medium, and he came to MIT (where be observed. In contact binaries, all the important ac- I was visiting) to question C. C. Lin and me about this tion is inside the stars, or within a common envelope, and problem. Ron later asked me to go for an extended visit cannot be observed (or so we thought). A naive idea for at Groningen, an invitation that I accepted in the summer the structure of contact binaries is simply to jam two sin- of 1973. It was the first time that my wife Helen and I gle stars together. This idea leads to the conclusion that had spent appreciable time living in Europe, a wonderful two main-sequence stars cannot form a co-rotating con- experience that we both still cherish. It was also a valu- tact binary because their mass-radius relationships on the able learning opportunity for me, as a theorist, to interact main-sequence are inappropriate for them both to fill their closely with radio astronomers of the caliber of Ron Allen, Roche lobes except in the single case of equal-mass compo- Ron Ekers, Miller Goss, and Renzo Sancisi, who were all nents. Observationally, W Ursa Majoris stars constitute at Groningen at the time. They taught me up close the the most common form of close binary systems; the two value of checking beautiful theoretical ideas with the hard components are undoubtedly both on the main-sequence; empirical facts from observations. they are co-rotating; yet no W UMa system is known that Q From density wave theory of the interstellar medium, has equal mass components! Clearly, the naive theory is you then began to study the internal structure of contact inadequate, and some drastic new ingredient needs to be binaries. What initiated such a major change of research added.

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