Statistical assessment of shapes and magnetic field orientations in molecular clouds through polarization observations

Tassis, Konstantinos; Dowell, C. D.; Hildebrand, R. H.; Kirby, Larry; Vaillancourt, John E.

doi:10.1111/j.1365-2966.2009.15420.x

Cited by 49 publications

(54 citation statements)

References 34 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…FUTURE WORK Along with our work on interpreting the data from individual objects presented here (e.g., the last column of Table 1), we have begun to look for meaningful relationships in the Hertz database as a whole. For example, Tassis et al (2009) have tested models of magnetic cloud support by comparing the mean polarization position angles in each cloud with their observed shapes. Li et al (2009) have compared similar mean cloud position angles with those from optical polarimetry in an effort to investigate the relation between interstellar magnetic fields in dense clouds with those in the diffuse interstellar medium.…”

Section: Resultsmentioning

confidence: 99%

350 μm POLARIMETRY FROM THE CALTECH SUBMILLIMETER OBSERVATORY

Dotson¹,

Vaillancourt²,

Kirby³

et al. 2010

ApJS

106

156

View full text Add to dashboard Cite

We present a summary of data obtained with the 350 μm polarimeter, Hertz, at the Caltech Submillimeter Observatory. We give tabulated results and maps showing polarization vectors and intensity contours. The summary includes over 4300 individual measurements in 56 Galactic sources and two galaxies. Of these measurements, 2153 have P 3σ p statistical significance. The median polarization of the entire data set is 1.46%.

show abstract

Section: Resultsmentioning

confidence: 99%

350 μm POLARIMETRY FROM THE CALTECH SUBMILLIMETER OBSERVATORY

Dotson¹,

Vaillancourt²,

Kirby³

et al. 2010

ApJS

106

156

View full text Add to dashboard Cite

show abstract

“…Additionally, the gradient technique can sample multiple scales by increasing the size of the vicinity of pixels used for its calculation (derivative kernel; see Appendix B.1). Previous studies that assign an average orientation of the cloud (Tassis et al 2009;Li et al 2013) are equivalent to studying the relative orientation using a derivative kernel close to the cloud size.…”

Section: Histogram Of Relative Orientationsmentioning

confidence: 99%

“…On the other hand, if the plotted pseudo-vectors correspond to the polarization in a particular pixel, then the illustrated pattern is influenced by small-scale fluctuations that might not be significant in evaluating any trend in relative orientation. Tassis et al (2009) present a statistical study of relative orientation between structures in the intensity and the inferred magnetic field from polarization measured at 350 µm towards 32 Galactic clouds in maps of a few arcminutes in size. Comparing the mean direction of the field to the semi-major axis of each cloud, they find that the field is mostly perpendicular to that axis.…”

Section: Introductionmentioning

confidence: 99%

Planckintermediate results

Ade¹,

Aghanim²,

Alves³

et al. 2016

A&A

287

View full text Add to dashboard Cite

Within ten nearby (d < 450 pc) Gould belt molecular clouds we evaluate statistically the relative orientation between the magnetic field projected on the plane of sky, inferred from the polarized thermal emission of Galactic dust observed by Planck at 353 GHz, and the gas column density structures, quantified by the gradient of the column density, N H . The selected regions, covering several degrees in size, are analysed at an effective angular resolution of 10 FWHM, thus sampling physical scales from 0.4 to 40 pc in the nearest cloud. The column densities in the selected regions range from N H ≈ 10 21 to 10 23 cm −2 , and hence they correspond to the bulk of the molecular clouds. The relative orientation is evaluated pixel by pixel and analysed in bins of column density using the novel statistical tool called "histogram of relative orientations". Throughout this study, we assume that the polarized emission observed by Planck at 353 GHz is representative of the projected morphology of the magnetic field in each region, i.e., we assume a constant dust grain alignment efficiency, independent of the local environment. Within most clouds we find that the relative orientation changes progressively with increasing N H , from mostly parallel or having no preferred orientation to mostly perpendicular. In simulations of magnetohydrodynamic turbulence in molecular clouds this trend in relative orientation is a signature of Alfvénic or sub-Alfvénic turbulence, implying that the magnetic field is significant for the gas dynamics at the scales probed by Planck. We compare the deduced magnetic field strength with estimates we obtain from other methods and discuss the implications of the Planck observations for the general picture of molecular cloud formation and evolution.

show abstract

“…And indeed, observations of polarization in regions of star formation have shown that magnetic fields (B-fields) often are well-ordered on scales from ∼100 pc (Heiles 2000) down to ∼1 pc, which suggests that on large scales B-fields are dynamically important. At smaller scales ambipolar diffusion (e.g., Mestel & Spitzer 1956;Fiedler & Mouschovias 1993;Tassis et al 2009) or turbulent magnetic reconnection diffusion (Lazarian 2005;Leão et al 2013) are thought to allow 19 South Africa SKA Fellow. 20 Hubble Fellow.…”

Section: Introductionmentioning

confidence: 99%

TADPOL: A 1.3 mm SURVEY OF DUST POLARIZATION IN STAR-FORMING CORES AND REGIONS

Hull

Plambeck

Kwon

et al. 2014

ApJS

205

230

View full text Add to dashboard Cite

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.

show abstract

Statistical assessment of shapes and magnetic field orientations in molecular clouds through polarization observations

Cited by 49 publications

References 34 publications

350 μm POLARIMETRY FROM THE CALTECH SUBMILLIMETER OBSERVATORY

350 μm POLARIMETRY FROM THE CALTECH SUBMILLIMETER OBSERVATORY

Planckintermediate results

TADPOL: A 1.3 mm SURVEY OF DUST POLARIZATION IN STAR-FORMING CORES AND REGIONS

Contact Info

Product

Resources

About