Scott Wolk - Academia.edu (original) (raw)

Papers by Scott Wolk

The Encyclopedia of Astronomy and Astrophysics

The virtual meeting was a success. Several people told us that this was “the best virtual meeting... more The virtual meeting was a success. Several people told us that this was “the best virtual meeting they had seen so far”, which, a year into the pandemic and without a commercial provider in the back, is a great success. The biggest point of criticism was the timing: We had programming from UTC 17:00-22:00 (evening and night in central Europe, afternoon on the US East Coast, during the day in South America and on the US West coast, but in the middle of the night for Asia and Australia). There is no good solution, but at least some variation in session time might go a long way to make it easier for all to attend at least some sessions. Feedback also indicates that the schedule was too compressed. Poster sessions and social contacts with the tool Gathertown worked out really well for all that used it. Our way of combining several services (Zoom for plenary and break-out rooms, Zenodo for uploading and viewing posters and proceedings, Google forms for registration and abstract submissio...

Theσ Orionis cluster is the group of stars surrounding the high ma ssσ Ori stellar system. It is ... more Theσ Orionis cluster is the group of stars surrounding the high ma ssσ Ori stellar system. It is kinematically distinct from the Orion OB1a and OB1b associations, against which it is projected. The cluster could contain up t o ∼700 stars and substellar mass objects, with a total mass of about 225 M ⊙ within a radius of about 30 arcmin. The age is 2–3 million years. The distance, from main sequenc e fitting corrected for the sub-solar metallicity, is 420 ±30 pc. The mass function is similar to the field star mass function, and has been traced well into the planetary mass re gime. The disk fraction is normal for its age. The cluster appears to be an older and less ma ive analog of the Orion Nebula Cluster.

Symposium - International Astronomical Union, 2003

We have photometrically identified eleven candidate brown dwarfs in 0.2 deg2 of the Orion OB1b as... more We have photometrically identified eleven candidate brown dwarfs in 0.2 deg2 of the Orion OB1b association. This is consistent with a rising mass function down to ~0.06M⊙. Assuming the IMF of Kroupa (2002) this suggests a population of 40–200 brown dwarfs per deg2…

Proceedings of the National Academy of Sciences of the United States of America, Oct 25, 2016

Earth sustains its magnetic field by a dynamo process driven by convection in the liquid outer co... more Earth sustains its magnetic field by a dynamo process driven by convection in the liquid outer core. Geodynamo simulations have been successful in reproducing many observed properties of the geomagnetic field. However, although theoretical considerations suggest that flow in the core is governed by a balance between Lorentz force, rotational force, and buoyancy (called MAC balance for Magnetic, Archimedean, Coriolis) with only minute roles for viscous and inertial forces, dynamo simulations must use viscosity values that are many orders of magnitude larger than in the core, due to computational constraints. In typical geodynamo models, viscous and inertial forces are not much smaller than the Coriolis force, and the Lorentz force plays a subdominant role; this has led to conclusions that these simulations are viscously controlled and do not represent the physics of the geodynamo. Here we show, by a direct analysis of the relevant forces, that a MAC balance can be achieved when the v...

Symposium - International Astronomical Union, 2003

VRI images within the belt of Orion and the Ori OB1a association reveal a pre-main sequence locus... more VRI images within the belt of Orion and the Ori OB1a association reveal a pre-main sequence locus extending to below our completeness limit of about V=21. We report here on followup JHK imaging and optical and near–IR spectroscopy of the faintest and reddest of the PMS candidates. We find that they are unreddened mid-to-late M “stars” which fall on a few million year isochrone. Masses are largely substellar, reaching as low as about 0.02 M⊙ (20 Jovian masses). The space density of the substellar objects is high.

Symposium - International Astronomical Union, 2004

In this short paper, I summarize Chandra observations of various objects in the Solar System. In ... more In this short paper, I summarize Chandra observations of various objects in the Solar System. In addition to the Moon and several comets, Chandra has observed all the planets between Venus and Uranus. With one exception, all have been clearly detected.

Springer eBooks, 1996

ABSTRACT

Springer Proceedings in Physics, 1997

The HII region RCW 38 is one of the nearest (1.7 kpc) embedded (A V ~ 10) cluster forming regions... more The HII region RCW 38 is one of the nearest (1.7 kpc) embedded (A V ~ 10) cluster forming regions containing an O star (O5.5 — IRS2; [1] [2] [3]). However the region has received only scant attention, no doubt due to its southern location. At 10 µm [1] [2] the brightest feature lies to the NW of IRS2, called IRS1, and the dust in the region interior to IRS1, centred on IRS2, is depleted by a factor of 100 w.r.t. to the interstellar value [2] [4]. Low resolution 1-mm continuum observations [5] suggest A V up to 800, implying that the cluster lies near the front surface of a dense molecular cloud, and so represents an embedded blister HII region. Previous near-infrared (NIR) observations have revealed the embedded cluster associated with this region [6] [7] but none had the spatial resolution or sensitivity required to obtain a complete picture.