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319 — 17 July 2019 Editor: Bo Reipurth (Reipurth@Ifa.Hawaii.Edu) List of Contents THE STAR FORMATION NEWSLETTER An electronic publication dedicated to early stellar/planetary evolution and molecular clouds No. 319 — 17 July 2019 Editor: Bo Reipurth ([email protected]) List of Contents The Star Formation Newsletter Interview ...................................... 3 Perspective .................................... 5 Editor: Bo Reipurth [email protected] Abstracts of Newly Accepted Papers .......... 10 Associate Editor: Anna McLeod Dissertation Abstracts ........................ 35 [email protected] New Jobs ..................................... 37 Technical Editor: Hsi-Wei Yen Meetings ..................................... 38 [email protected] Summary of Upcoming Meetings ............. 41 Editorial Board Short Announcements ........................ 42 Joao Alves Alan Boss Jerome Bouvier Lee Hartmann Cover Picture Thomas Henning Paul Ho IC 2944 and IC 2948 form a large HII region in Cen- Jes Jorgensen taurus, energized by a group of OB stars dominated Charles J. Lada by the O7 III star HD 101205. Projected towards Thijs Kouwenhoven the OB stars is a group of compact dark globules, Michael R. Meyer discovered by A.D. Thackeray in 1955. The glob- Ralph Pudritz ules are splintered and have convulsed shapes, as Luis Felipe Rodr´ıguez well illustrated in this image taken with the ESO Ewine van Dishoeck VLT. The globule complex is likely in the process Hans Zinnecker of being destroyed by the powerful UV radiation. The Star Formation Newsletter is a vehicle for Image courtesy ESO. 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 journals), Abstracts of recently accepted major re- Submitting your abstracts views (not standard conference contributions), Dis- sertation Abstracts (presenting abstracts of new Latex macros for submitting abstracts Ph.D dissertations), Meetings (announcing meet- and dissertation abstracts (by e-mail to ings broadly of interest to the star and planet for- [email protected]) are appended to mation and early solar system community), New each Call for Abstracts. You can also Jobs (advertising jobs specifically aimed towards submit via the Newsletter web inter- persons within the areas of the Newsletter), and face at http://www2.ifa.hawaii.edu/star- Short Announcements (where you can inform or re- formation/index.cfm 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 ject of your 1971 Annual Reviews article. What were the issues back then? Carl Heiles A: My thesis work covered an area about 160 square de- in conversation with Bo Reipurth grees, which happened to contain some dust clouds with sizes of a degree or so. We had the idea that the dust/gas ratio was roughly constant, which meant that these clouds should have contained enormous amounts of interstellar gas. But the 21-cm line showed no excess intensity to- wards these clouds; if anything, it tended to be weaker! This planted the idea that the gas in the clouds might be molecular. When I got to Berkeley immediately after re- ceiving my PhD, I was in the amazingly fortunate position that Berkeley’s Hat Creek telescope was tuned to the OH line. So it was easy pickings to see if OH resided in those clouds. And it did! Using the dust content as a surrogate for the gas provided an estimate for the strength of self- gravity. And self-gravity turned out to be important! So these were likely areas of star formation. Connecting all those dots was an exciting prospect for an Annual Reviews Q: Your PhD thesis from 1966 dealt with observations of article. History repeats itself: these days, the presence of the spatial structure of interstellar hydrogen. What moti- ‘dark gas’—large-density regions with no CO emission—is vated you to choose that topic? inferred in the same way. A: As a kid I was interested in technical things and became Q: Your discovery of H I shells and supershells at high a ‘ham’ radio operator. This began my interest in elec- Galactic latitudes appeared in 1979, with a follow-up in tronics and sparked my desire to be an electrical engineer, 1984, and these papers have been very widely cited. Please which was my original major at Cornell University in 1958. tell how this discovery came about. Cornell had a program of public lectures on various science A: It was totally obvious that supershells would be de- topics. In my third year it focused on astronomy and had tectable in the Galactic plane! Harm Habing and I had four amazing lecturers: Tommy Gold, Fred Hoyle, Her- recently finished the Hat Creek 85-foot telescope survey of mann Bondi, and Geoffrey Burbidge. They talked about high-latitude 21-cm line emission—half a million H i line the great astronomical questions, ranging from Solar mag- profiles! We pioneered using grayscale and color imaging netohydrodynamics (MHD) to cosmology. I was hooked: I to look at them. What jumped out of those first images changed my major to Engineering Physics and took every were the Orion-Eridanus superbubble and the Sco-Oph su- course related to those areas that I could. Marshall Cohen pershell. They were tens of degrees in diameter and were taught Plasma physics; he went on to CalTech and special- nearby. Given the Copernican Principle, the Galaxy had ized in VLBI. I took two courses on stellar structure: the to be peppered with such objects. At 1 Kpc distance, the conventional version with the differential equations, beau- angular diameter would be about 6 degrees. So I looked tifully taught by John Cox; in contrast, Ed Salpeter es- at Harold Weaver’s Hat Creek H i survey of the Galactic chewed the equations and emphasized phenomenology and plane—and there they were. order-of-magnitude estimates. Those two courses opened Q: A few years later you calculated the rate at which clus- my eyes: you achieve deeper understanding by looking at tered Type II supernovae produce bubbles that break through problems from multiple viewpoints. the dense, thin layer of disk gas. How is the correspon- All this, plus being a grad student at Princeton under dence with current observations? George Field and Lyman Spitzer, made the interstellar A: That’s an excellent question because such events are re- medium a hugely attractive research area. When the time sponsible for transferring mass from the disk to the halo. came for my thesis work, the 300-foot telescope had just This was explicitly shown by Colin Norman and Satoru been finished and was superbly equipped for 21-cm line Ikeuchi, who in 1989 wrote my favorite paper on this work with a 100-channel 1-bit digital correlator. There I subject and invented the compelling moniker ‘interstellar was, a lowly graduate student, empowered with the best chimneys’. Also, infalling pristine intergalactic gas clouds telescope/electronics in the world for this project. Who have to transit through the ambient halo gas. These days wouldn’t jump in that direction? there’s a lot of activity pursuing these issues at high red- Q: Shortly after your PhD you became interested in the shift, because they directly affect galactic evolution, but physical conditions inside dust clouds, which was the sub- 3 it’s my impression that more work on synthesizing multi- A: The agglomeration was an update of the original one ple data sets for local galaxies would reveal lots of impor- by Mathewson and Ford; their spectacular result was the tant details. amazingly coherent pattern of linear polarization aligned Q: You were early on interested in magnetic fields in clouds, with Radio Loop I (the North Polar Spur). The new ag- i and summarized what was known in an Annual Reviews glomeration, together with the then-new all-sky H maps, article in 1976. You have maintained this interest all your showed that the morphological similarity was essentially life, so you must have a unique perspective on how the sub- universal and applied to structure on all scales. These ject has developed over the years. days, Susan Clark has used polarized dust emission from Planck together with the GALFA H i survey data to find A: My interest in magnetic fields stems from those public highly elongated H i ‘fibers’ that are aligned with the neigh- lectures at Cornell, where they were reinforced by a spec- boring magnetic field. This is proving to be a rich subject! tacular display of aurorae—rare at Cornell’s magnetic lat- itude. In many astronomical systems, magnetic pressure Q: In the early 2000s you embarked, together with Thomas is comparable to other pressures, so the field has to be Troland, on the Millennium Arecibo 21 cm Absorption- important. But specifying the influence of the magnetic Line Survey. What were the goals and achievements? field as a single number misses the fundamental point that A: Tom was the only grad student crazy enough to work the magnetic forces are anisotropic, meaning that not only with me on interstellar magnetic fields, specifically mea- pressure but also magnetic tension plays a role, particu- suring Zeeman splitting of the 21-cm line seen in emission. larly because of the coupling of cosmic rays to the field and Why ‘crazy’? The detected signatures were weak, requir- its frozen-in gas. It’s these aspects that produce unique ing huge integration times, and the instrumental effects and important dynamics, such as sunspots and angular (especially polarized beam response) comparable to the momentum transport. actual splitting. Fortunately, Tom is very methodical and Regarding my ‘unique perspective’, there’s the scientific careful, compensating for my deficiencies in those areas.
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