The JCMT BISTRO Survey: the magnetized evolution of star-forming cores in the Ophiuchus molecular cloud interpreted using histograms of relative orientation

ABSTRACT The relationship between B-field orientation and density structure in molecular clouds is often assessed using the histogram of relative orientations (HRO). We perform a plane-of-the-sky geometrical analysis of projected B-fields, by interpreting HROs in dense, spheroidal, pre-stellar, and protostellar cores. We use James Clerk Maxwell Telescope POL-2 850 $\mu$m polarization maps and Herschel column density maps to study dense cores in the Ophiuchus molecular cloud complex. We construct two-dimensional core models, assuming Plummer column density profiles and modelling both linear and hourglass B-fields. We find that high-aspect ratio ellipsoidal cores produce strong HRO signals, as measured using the shape parameter $\xi$. Cores with linear fields oriented $<\!\! 45 ^{\circ }$ from their minor axis produce constant HROs with $-1 \lt \xi \lt 0$, indicating that fields are preferentially parallel to column density gradients. Fields parallel to the core minor axis produce the most negative value of $\xi$. For low-aspect ratio cores, $\xi \approx 0$ for linear fields. Hourglass fields produce a minimum in $\xi$ at intermediate densities in all cases, converging to the minor-axis-parallel linear field value at high and low column densities. We create HROs for six dense cores in Ophiuchus. $\rho$ Oph A and IRAS 16293 have high aspect ratios and preferentially negative HROs, consistent with moderately strong field behaviour. $\rho$ Oph C, L1689A, and L1689B have low aspect ratios, and $\xi \approx 0$. $\rho$ Oph B is too complex to be modelled using a simple spheroidal field geometry. We see no signature of hourglass fields, agreeing with previous findings that dense cores generally exhibit linear fields on these size scales.

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Journal
Monthly Notices of the Royal Astronomical Society
Published
2024-11-28
DOI
https://doi.org/10.1093/mnras/stae2659
Primary Topic
Astro and Planetary Science
Type
article
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0.00

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article

The JCMT BISTRO Survey: the magnetized evolution of star-forming cores in the Ophiuchus molecular cloud interpreted using histograms of relative orientation

Eun Jung Chung, Jihye Hwang, S. Lai, Simon Coudé et al.
Monthly Notices of the Royal Astronomical Society
Astro and Planetary Science
article

The JCMT BISTRO Survey: the magnetized evolution of star-forming cores in the Ophiuchus molecular cloud interpreted using histograms of relative orientation

Eun Jung Chung, Jihye Hwang, S. Lai, Simon Coudé, Jungmi Kwon, Lapo Fanciullo, Tyler L. Bourke, Yasuo Doi, Chang Won Lee, Woojin Kwon, Kate Pattle, Doug Johnstone, Sarah Sadavoy, G. Savini, Valentin J. M. Le Gouellec, Motohide Tamura, Ekta Sharma, Nagayoshi Ohashi, Zacariyya A. Khan, J. Perry
article en

Abstract

ABSTRACT The relationship between B-field orientation and density structure in molecular clouds is often assessed using the histogram of relative orientations (HRO). We perform a plane-of-the-sky geometrical analysis of projected B-fields, by interpreting HROs in dense, spheroidal, pre-stellar, and protostellar cores. We use James Clerk Maxwell Telescope POL-2 850 $\mu$m polarization maps and Herschel column density maps to study dense cores in the Ophiuchus molecular cloud complex. We construct two-dimensional core models, assuming Plummer column density profiles and modelling both linear and hourglass B-fields. We find that high-aspect ratio ellipsoidal cores produce strong HRO signals, as measured using the shape parameter $\xi$. Cores with linear fields oriented $<\!\! 45 ^{\circ }$ from their minor axis produce constant HROs with $-1 \lt \xi \lt 0$, indicating that fields are preferentially parallel to column density gradients. Fields parallel to the core minor axis produce the most negative value of $\xi$. For low-aspect ratio cores, $\xi \approx 0$ for linear fields. Hourglass fields produce a minimum in $\xi$ at intermediate densities in all cases, converging to the minor-axis-parallel linear field value at high and low column densities. We create HROs for six dense cores in Ophiuchus. $\rho$ Oph A and IRAS 16293 have high aspect ratios and preferentially negative HROs, consistent with moderately strong field behaviour. $\rho$ Oph C, L1689A, and L1689B have low aspect ratios, and $\xi \approx 0$. $\rho$ Oph B is too complex to be modelled using a simple spheroidal field geometry. We see no signature of hourglass fields, agreeing with previous findings that dense cores generally exhibit linear fields on these size scales.

Monthly Notices of the Royal Astronomical SocietyVol. 536(2)
Herzberg Institute of Astrophysics (CA), Ames Research Center (US), Institute of Astronomy and Astrophysics, Academia Sinica (TW), Seoul National University (KR), Seoul National University of Education (KR), National Chung Hsing University (TW), Chungnam National University (KR), Chinese Academy of Sciences (CN), National Institutes of Natural Sciences (JP), Queen's University (CA), University of Victoria (CA), National Tsing Hua University (TW), Korea Astronomy and Space Science Institute (KR), Worcester State University (US), University of Manchester (GB), SKA Observatory (GB), Astrobiology Center (JP), Center for Astrophysics Harvard & Smithsonian (US), National Astronomical Observatory of Japan (JP), National Astronomical Observatories (CN), University College London (GB), The University of Tokyo (JP), Korea University of Science and Technology (KR)
National Aeronautics and Space Administration, Neurosciences Research Foundation, Canada Foundation for Innovation, Royal Society, National Research Foundation, Korea Astronomy and Space Science Institute, National Research Foundation of Korea, Ministry of Education, Science and Technology, National Astronomical Observatory of Japan, Ministry of Science and ICT, South Korea, National Science and Technology Council, Natural Sciences and Engineering Research Council of Canada, Science and Technology Facilities Council, National Key Research and Development Program of China
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