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Hull C.L.H.,University of California at Berkeley | Plambeck R.L.,University of California at Berkeley | Kwon W.,SRON Netherlands Institute for Space Research | Bower G.C.,University of California at Berkeley | And 24 more authors.
Astrophysical Journal, Supplement Series | Year: 2014

We present λ 1.3 mm Combined Array for Research in Millimeter-wave Astronomy observations of dust polarization toward 30 star-forming cores and eight star-forming regions from the TADPOL survey. We show maps of all sources, and compare the 2.″5 resolution TADPOL maps with 20″ resolution polarization maps from single-dish submillimeter telescopes. Here we do not attempt to interpret the detailed B-field morphology of each object. Rather, we use average B-field orientations to derive conclusions in a statistical sense from the ensemble of sources, bearing in mind that these average orientations can be quite uncertain. We discuss three main findings. (1) A subset of the sources have consistent magnetic field (B-field) orientations between large (20″) and small (2.″5) scales. Those same sources also tend to have higher fractional polarizations than the sources with inconsistent large-to-small-scale fields. We interpret this to mean that in at least some cases B-fields play a role in regulating the infall of material all the way down to the 1000 AU scales of protostellar envelopes. (2) Outflows appear to be randomly aligned with B-fields; although, in sources with low polarization fractions there is a hint that outflows are preferentially perpendicular to small-scale B-fields, which suggests that in these sources the fields have been wrapped up by envelope rotation. (3) Finally, even at 2.″5 resolution we see the so-called polarization hole effect, where the fractional polarization drops significantly near the total intensity peak. All data are publicly available in the electronic edition of this article. © 2014. The American Astronomical Society. All rights reserved.


Hull C.L.H.,University of California at Berkeley | Plambeck R.L.,University of California at Berkeley | Bolatto A.D.,University of Maryland University College | Bower G.C.,University of California at Berkeley | And 26 more authors.
Astrophysical Journal | Year: 2013

We present results of λ1.3 mm dust-polarization observations toward 16 nearby, low-mass protostars, mapped with ∼2.″5 resolution at CARMA. The results show that magnetic fields in protostellar cores on scales of ∼1000 AU are not tightly aligned with outflows from the protostars. Rather, the data are consistent with scenarios where outflows and magnetic fields are preferentially misaligned (perpendicular), or where they are randomly aligned. If one assumes that outflows emerge along the rotation axes of circumstellar disks, and that the outflows have not disrupted the fields in the surrounding material, then our results imply that the disks are not aligned with the fields in the cores from which they formed. © 2013. The American Astronomical Society. All rights reserved.


Chandra P.,Royal Military College of Canada | Frail D.A.,U.S. National Radio Astronomy Observatory | Fox D.,University Park | Kulkarni S.R.,California Institute of Technology | And 5 more authors.
AIP Conference Proceedings | Year: 2011

At a redshift of 8.3 GRB 090423 marks the highest known redshift object in the Universe. By combining our radio measurements with existing X-ray and infrared observations, we estimated the kinetic energy of the afterglow, the geometry of the outflow and the density of the circumburst medium. Our best fit model is a quasi-spherical, high-energy explosion in a low, constant-density medium. We compare the properties of GRB 090423 with a sample of GRBs at moderate redshifts. We find that the high energy and afterglow properties of GRB 090423 are not sufficiently different from other GRBs to suggest a different kind of progenitor, such as a Population III star. However, we argue that it is not clear that the afterglow properties alone can provide convincing identification of Population III progenitors. We suggest that the millimeter and centimeter radio detections of GRB 090423 at early times contained emission from a reverse shock component. This has important implications for the detection of high redshift GRBs by the next generation of radio facilities. © 2011 American Institute of Physics.


Cenko S.B.,University of California at Berkeley | Frail D.A.,U.S. National Radio Astronomy Observatory | Harrison F.A.,California Institute of Technology | Kulkarni S.R.,California Institute of Technology | And 24 more authors.
Astrophysical Journal | Year: 2010

Long-duration gamma-ray bursts (GRBs) are widely believed to be highly collimated explosions (bipolar conical outflows with half-opening angle θ ≈ 1°-10°). As a result of this beaming factor, the true energy release from a GRB is usually several orders of magnitude smaller than the observed isotropic value. Measuring this opening angle, typically inferred from an achromatic steepening in the afterglow light curve (a "jet" break), has proven exceedingly difficult in the Swift era. Here, we undertake a study of five of the brightest (in terms of the isotropic prompt γ-ray energy release, E γ,iso) GRBs in the Swift era to search for jet breaks and hence constrain the collimation-corrected energy release. We present multi-wavelength (radio through X-ray) observations of GRBs050820A, 060418, and 080319B, and construct afterglow models to extract the opening angle and beaming-corrected energy release for all three events. Together with results from previous analyses of GRBs050904 and 070125, we find evidence for an achromatic jet break in all five events, strongly supporting the canonical picture of GRBs as collimated explosions. The most natural explanation for the lack of observed jet breaks from most Swift GRBs is therefore selection effects. However, the opening angles for the events in our sample are larger than would be expected if all GRBs had a canonical energy release of ∼ s10 51erg. The total energy release we measure for the "hyper-energetic" (E tot ≳ 1052erg) events in our sample is large enough to start challenging models with a magnetar as the compact central remnant. © 2010 The American Astronomical Society.


Perez L.M.,California Institute of Technology | Lamb J.W.,California Institute of Technology | Woody D.P.,California Institute of Technology | Carpenter J.M.,California Institute of Technology | And 16 more authors.
Astrophysical Journal | Year: 2010

We present 0′′15 resolution observations of the 227 GHz continuum emission from the circumstellar disk around the FU Orionis star PP 13S*. The data were obtained with the Combined Array for Research in Millimeter-wave Astronomy (CARMA) Paired Antenna Calibration System (C-PACS), which measures and corrects the atmospheric delay fluctuations on the longest baselines of the array in order to improve the sensitivity and angular resolution of the observations. A description of the C-PACS technique and the data reduction procedures are presented. C-PACS was applied to CARMA observations of PP 13S*, which led to a factor of 1.6 increase in the observed peak flux of the source, a 36% reduction in the noise of the image, and a 52% decrease in the measured size of the source major axis. The calibrated complex visibilities were fitted with a theoretical disk model to constrain the disk surface density. The total disk mass from the best-fit model corresponds to 0.06 M⊙, which is larger than the median mass of a disk around a classical T Tauri star. The disk is optically thick at a wavelength of 1.3 mm for orbital radii less than 48 AU. At larger radii, the inferred surface density of the PP 13S* disk is an order of magnitude lower than that needed to develop a gravitational instability.


Enoch M.L.,University of California at Berkeley | Corder S.,NRAO ALMA JAO | Duchene G.,University of California at Berkeley | Duchene G.,CNRS Grenoble Institute for Particle Astrophysics and Cosmology Laboratory | And 15 more authors.
Astrophysical Journal, Supplement Series | Year: 2011

We present high-resolution CARMA 230GHz continuum imaging of nine deeply embedded protostars in the Serpens Molecular Cloud, including six of the nine known Class 0 protostars in Serpens. This work is part of a program to characterize disk and envelope properties for a complete sample of Class 0 protostars in nearby low-mass star-forming regions. Here, we present CARMA maps and visibility amplitudes as a function of uv-distance for the Serpens sample. Observations are made in the B, C, D, and E antenna configurations, with B configuration observations utilizing the CARMA Paired Antenna Calibration System. Combining data from multiple configurations provides excellent uv-coverage (4-500kλ), allowing us to trace spatial scales from 10 2 to 104AU. We find evidence for compact disk components in all of the observed Class 0 protostars, suggesting that disks form at very early times (t < 0.2Myr) in Serpens. We make a first estimate of disk masses using the flux at 50kλ, where the contribution from the envelope should be negligible, assuming an unresolved disk. The resulting disk masses range from 0.04 M⊙ to 1.7 M⊙, with a mean of approximately 0.2 M⊙. Our high-resolution maps are also sensitive to binary or multiple sources with separations ≳ 250AU, but significant evidence of multiplicity on scales <2000AU is seen in only one source. © 2011. The American Astronomical Society. All rights reserved.


Chandra P.,Royal Military College of Canada | Frail D.A.,U.S. National Radio Astronomy Observatory | Fox D.,Pennsylvania State University | Kulkarni S.,California Institute of Technology | And 5 more authors.
Astrophysical Journal Letters | Year: 2010

We report on the discovery of radio afterglow emission from the gamma-ray burst GRB090423, which exploded at a redshift of 8.3, making it the object with the highest known redshift in the universe. By combining our radio measurements with existing X-ray and infrared observations, we estimate the kinetic energy of the afterglow, the geometry of the outflow, and the density of the circumburst medium. Our best-fit model suggests a quasi-spherical, high-energy explosion in a low, constant-density medium. GRB 090423 had a similar energy release to the other well-studied high redshift GRB 050904 (z = 6.26), but their circumburst densities differ by 2 orders of magnitude. We compare the properties of GRB 090423 with a sample of gamma-ray bursts (GRBs) at moderate redshifts. We find that the high energy and afterglow properties of GRB 090423 are not sufficiently different from other GRBs to suggest a different kind of progenitor, such as a Population III (Pop III) star. However, we argue that it is not clear that the afterglow properties alone can provide convincing identification of Pop III progenitors. We suggest that the millimeter and centimeter radio detections of GRB 090423 at early times contained emission from the reverse shock. If true, this may have important implications for the detection of high-redshift GRBs by the next generation of radio facilities. © 2010. The American Astronomical Society. All rights reserved.

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