Date

Speaker

Title

Aug 30

Neal Evans

University of Texas at Austin

Organizational meeting.

Sep 6

Joel Green

University of Texas at Austin

"Episodic Accretion in Young Stars"

abstract

Sep 13

Charles "Chat" Hull

University of California, Berkeley

"From Clouds to Cores to Envelopes to Disks: A Multi-scale View of Magnetized Star Formation" (host: Joel Green)

Magnetic fields are thought to play an important role in the formation of stars. However, that importance has been called into question by previous observations showing misalignment between protostellar outflows and magnetic fields, as well as inconsistency in field morphology from 10,000 -- 1,000 AU scales. To investigate these inconsistencies, we used the 1.3 mm full-Stokes polarimeter at CARMA to map dust polarization with ~2.5" resolution toward 29 star-forming cores and 8 high-mass star-forming regions as part of the TADPOL survey. We find that a subset of the sources have consistent magnetic field orientations between the large (~20") scales measured by single-dish submillimeter bolometers and the small scales measured by CARMA. Those same sources also tend to have higher fractional polarizations (measured by CARMA) than the sources with inconsistent large- to small-scale fields, presumably because there is less field twisting to reduce the polarization fraction. This suggests that at least in some sources, magnetic fields dominate turbulence over many orders of magnitude, from ~100 pc molecular cloud scales down to ~1000 AU protostellar envelope scales. However, even in the sources with consistent large-to-small-scale field orientations, the magnetic fields in the cores are misaligned with the disks and outflows in the central protostars -- a key result of the TADPOL survey. We also find that all sources exhibit the so-called "polarization hole" effect, where the polarization drops significantly near the total intensity peak. When this effect was seen in low-resolution single-dish maps, it was attributed to the averaging of unresolved structure in the plane of the sky. However, the higher resolution maps we present here resolve these twisted polarization morphologies, and yet the drop in fractional polarization persists, suggesting that fields are twisted along the line of sight, or that grain alignment is poor in dense regions with high extinction and high collision rates.

close

Sep 20

Mike Pavel

University of Texas at Austin

"Polarimetric Tomography of the Galactic Magnetic Field"

Sep 27

Adam Kraus, Joel Green, Michael Gully-Santiago, Neal Evans

University of Texas at Austin

"Highlights from the Protostars & Planets VI Conference (Heidelberg, Germany: 15-20 July 2013)"

Oct 4

Vanessa Bailey

University of Arizona

(host: Neal Evans) "Hole-y Debris Disks, Batman! (Giant planets sculpting disks and the technology we need to image them)"

abstract

Oct 11

No talk scheduled, to avoid conflict with the Bashfest 2013 Symposium (on 7-8 October).

Oct 18

Megan Reiter

University of Arizona

"Jets from Intermediate-mass Protostars as a Fossil Record of Accretion"

abstract

Oct 18

Johanna Teske

University of Arizona

"Diamonds in the Rough: A Cautionary Tale of C/O Ratios in Exoplanet Host Stars"

abstract

Oct 25

Yao-Lun Yang

University of Texas at Austin

"Molecular Hydrogen in the Diffuse Medium of the Large Magellanic Cloud"

Nov 1

"NRAO Community Day: NRAO Data Analysis Workshop (8 AM - 6 PM: POB 2.302 Avaya Auditorium)

Nov 8

Jeong-Eun Lee

Kyung Hee University, South Korea

"Detailed Analysis of DIGIT Embedded Protostars"

abstract

Nov 15

Presentations by Manuel Merello and Emma Yu have been rescheduled to next week (22 November).

Nov 22

Manuel Merello

University of Texas at Austin

"Physical Characterization of Galactic Star-forming Clumps using (Sub)millimeter Continuum Surveys"

Nov 22

Emma Yu

University of Texas at Austin

"Probing the Protoplanetary Disks with ALMA - a CO Perspective"

Nov 29

Day after Thanksgiving Day: Staff Holiday. University Closed: No classes or seminars held today.

Dec 6

Harriet Dinerstein

University of Texas at Austin

"Kappa Distributions: A Possible Solution to the Nebular Abundance Problem"

Dec 6

Amanda Turbyfill

University of Texas at Austin

"Application of Kappa Distributions to Planetary Nebulae Spectra"