2021

Astronomers Discover Mysterious 500-Light-Year-Wide Void in Space (Newsweek)

Astronomers Discover Mysterious 500-Light-Year-Wide Void in Space (Newsweek)

September 22, 2021

Robert Lea of Newsweek covers the bubble-shaped void in the Milky Way located between the star-forming clusters of gas, or molecular clouds, in the Perseus and Taurus constellations. The 3D molecular cloud maps were created using data visualization software called "Glue," founded by CfA astronomer Alyssa Goodman who is a co-author on both studies....

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Astronomers Have Discovered a Gigantic Sphere-Shaped Cavity in Space (SciTech Daily)

Astronomers Have Discovered a Gigantic Sphere-Shaped Cavity in Space (SciTech Daily)

September 22, 2021

SciTech Daily covers the discovery of a giant, spherical cavity within the Milky Way galaxy and how Alyssa Goodman's work with astronomy visualizations in augmented reality marks a new role in published work. Scientists and the public may interact with the visualization of the cavity and its surrounding molecular clouds by simply scanning a QR code in the paper with their smartphone....

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Catherine Zucker, Alyssa A. Goodman, João Alves, Shmuel Bialy, Eric W. Koch, Joshua S. Speagle, Michael M. Foley, Douglas Finkbeiner, Reimar Leike, Torsten Enßlin, Joshua E.G. Peek, and Gordian Edenhofer. 9/22/2021. “On the Three-dimensional Structure of Local Molecular Clouds.” The Astrophysical Journal, 919, 1, Pp. 35. Publisher's VersionAbstract
We leverage the 1 pc spatial resolution of the Leike et al. three-dimensional (3D)dust map to characterize the 3D structure of nearby molecular clouds (d  400 pc). We start by “skeletonizing” the clouds in 3D volume density space to determine their “spines,” which we project on the sky to constrain cloud distances with ≈ 1% uncertainty. For each cloud, we determine an average radial volume density profile around its 3D spine and fit the profiles using Gaussian and Plummer functions. The radial volume density profiles are well described by a two-component Gaussian function, consistent with clouds having broad, lower-density outer envelopes and narrow, higher-density inner layers. The ratio of the outer to inner envelope widths is ≈ 3:1. We hypothesize that these two components may be tracing a transition between atomic and diffuse molecular gas or between the unstable and cold neutral medium. Plummer-like models can also provide a good fit, with molecular clouds exhibiting shallow power-law wings with density, n, falling off like n− 2 at large radii. Using Bayesian model selection, we find that parameterizing the clouds’ profiles using a single Gaussian is disfavored. We compare our results with two- dimensional dust extinction maps, finding that the 3D dust recovers the total cloud mass from integrated approaches with fidelity, deviating only at higher levels of extinction (AV  2–3 mag). The 3D cloud structure described here will enable comparisons with synthetic clouds generated in simulations, offering unprecedented insight into the origins and fates of molecular clouds in the interstellar medium.
Shmuel Bialy, Catherine Zucker, Alyssa A. Goodman, Michael M. Foley, João Alves, Vadim A. Semenov, Robert Benjamin, Reimar Leike, and Torsten Enßlin. 9/22/2021. “The Per-Tau Shell: A Giant Star-forming Spherical Shell Revealed by 3D Dust Observations.” The Astrophysical Journal Letters, 919, 1, Pp. L5. Publisher's VersionAbstract
A major question in the field of star formation is how molecular clouds form out of the diffuse interstellar medium (ISM). Recent advances in 3D dust mapping are revolutionizing our view of the structure of the ISM. Using the highest-resolution 3D dust map to date, we explore the structure of a nearby star-forming region, which includes the well-known Perseus and Taurus molecular clouds. We reveal an extended near-spherical shell, 156 pc in diameter (hereafter called the “Per-Tau Shell” ), in which the Perseus and Taurus clouds are embedded. We also find a large ring structure at the location of Taurus (hereafter called the “Tau Ring” ). We discuss a formation scenario for the Per-Tau Shell, in which previous stellar and supernova feedback events formed a large expanding shell, where the swept-up ISM has condensed to form both the shell and the Perseus and Taurus molecular clouds within it. We present auxiliary observations of H I,Hα, 26 Al, and X-rays that further support this scenario, and estimate the Per-Tau Shell’s age to be ≈ 6–22 Myrs. The Per-Tau shell offers the first 3D observational view of a phenomenon long-hypothesized theoretically, molecular cloud formation and star formation triggered by previous stellar and supernova feedback.
Your PRISE Universe, 2021, at Harvard University, Tuesday, August 3, 2021:

 A discussion of visualization, glue, glupyter, the Path to Newton, and the Prediction Project, with the Harvard PRISE (Program for Research in Science and Engineering) students, summer 2021 (AKA "Distinguished Speaker Lecture")

Chilloquium, at (Online only), Tuesday, May 4, 2021:
A discussion with Harvard's Society of Physics Students (unscripted). The small number of slides that were used to guide the discussion are posted here to make the links  embedded in them available. 
Male student standing in Harvard Yard, trying to navigate using limited instructions

Students Navigate Harvard Yard to Understand the History of Prediction - and Uncertainty

April 1, 2021

Harvard Yard becomes an outdoor classroom for Professor Alyssa Goodman's Spring 2021 GenEd Prediction  class, as 14 pairs of students try to navigate to a designated location using limited information and their own tuition - then make predictions about their own success by reporting their "estimated uncertainty". 

How did they do?    ...

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Shuo Kong, Volker Ossenkopf-Okada, Héctor G. Arce, John Bally, Álvaro Sánchez-Monge, Peregrine McGehee, Sümeyye Suri, Ralf S. Klessen, John M. Carpenter, Dariusz C. Lis, Fumitaka Nakamura, Peter Schilke, Rowan J. Smith, Steve Mairs, Alyssa Goodman, and María José Maureira. 2021. “The CARMA-NRO Orion Survey: Filament Formation via Collision-induced Magnetic Reconnectionthe Stick in Orion A.” The Astrophysical Journal, 906, Pp. 80. Publisher's VersionAbstract
A unique filament is identified in the Herschel maps of the Orion A giant molecular cloud. The filament, which we name the Stick, is ruler-straight and at an early evolutionary stage. Transverse position–velocity diagrams show two velocity components closing in on the Stick. The filament shows consecutive rings/forks in C18O (1−0) channel maps, which is reminiscent of structures generated by magnetic reconnection. We propose that the Stick formed via collision-induced magnetic reconnection (CMR). We use the magnetohydrodynamics code Athena++ to simulate the collision between two diffuse molecular clumps, each carrying an antiparallel magnetic field. The clump collision produces a narrow, straight, dense filament with a factor of >200 increase in density. The production of the dense gas is seven times faster than freefall collapse. The dense filament shows ring/fork-like structures in radiative transfer maps. Cores in the filament are confined by surface magnetic pressure. CMR can be an important dense-gas-producing mechanism in the Galaxy and beyond.
Anika Schmiedeke, Jaime E. Pineda, Paola Caselli, Héctor G. Arce, Gary A Fuller, Alyssa A. Goodman, María José Maureira, Stella S. R. Offner, Dominique Segura-Cox, and Daniel Seifried. 2021. “Dissecting the super-critical filaments embedded in the 0.5 pc subsonic region of Barnard 5.” arXiv, 2101, 00248. Publisher's VersionAbstract
We characterize in detail the two ~0.3 pc long filamentary structures found within the subsonic region of Barnard 5. We use combined GBT and VLA observations of the molecular lines NH3(1,1) and (2,2) at a resolution of 1800 au, as well as JCMT continuum observations at 850 and 450 μm at a resolution of 4400 au and 3000 au, respectively. We find that both filaments are highly super-critical with a mean mass per unit length, M/L, of ~80 M⊙ pc−1, after background subtraction, with local increases reaching values of ~150 M⊙ pc−1. This would require a magnetic field strength of ~500 μG to be stable against radial collapse.
We extract equidistant cuts perpendicular to the spine of the filament and fit a modified Plummer profile as well as a Gaussian to each of the cuts. The filament widths (deconvolved FWHM) range between 6500-7000 au (~0.03 pc) along the filaments. This equals ~2.0 times the radius of the flat inner region. We find an anti-correlation between the central density and this flattening radius, suggestive of contraction. Further, we also find a strong correlation between the power-law exponent at large radii and the flattening radius. We note that the measurements of these three parameters fall in a plane and derive their empirical relation. Our high-resolution observations provide direct constraints of the distribution of the dense gas within super-critical filaments showing pre- and protostellar activity.
Cameren Swiggum, Elena D’Onghia, João Alves, Josefa Großschedl, Michael Foley, Catherine Zucker, Stefan Meingast, Boquan Chen, and Alyssa Goodman. 2021. “Evidence for Radial Expansion at the Core of the Orion Complex with Gaia EDR3.” arXiv, 2101, 10380.Abstract
We present a phase-space study of two stellar groups located at the core of the Orion complex: Briceño-1 and Orion Belt Population-near (OBP-near). We identify the groups with the unsupervised clustering algorithm, Shared Nearest Neighbor (SNN), which previously identified twelve new stellar substructures in the Orion complex. For each of the two groups, we derive the 3D space motions of individual stars using Gaia EDR3 proper motions supplemented by radial velocities from Gaia DR2, APOGEE-2, and GALAH DR3. We present evidence for radial expansion of the two groups from a common center. Unlike previous work, our study suggests that evidence of stellar group expansion is confined only to OBP-near and Briceño-1 whereas the rest of the groups in the complex show more complicated motions. Interestingly, the stars in the two groups lie at the center of a dust shell, as revealed via an extant 3D dust map. The exact mechanism that produces such coherent motions remains unclear, while the observed radial expansion and dust shell suggest that massive stellar feedback could have influenced the star formation history of these groups.

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