B-fields In STar-forming Region Observations (BISTRO): Dual-Wavelength Constraints on Size-Dependent Grain Alignment in Star-Forming Regions

@misc{furuya2026bfields,
  title = {{B-fields In STar-forming Region Observations (BISTRO): Dual-Wavelength Constraints on Size-Dependent Grain Alignment in Star-Forming Regions}},
  author = {Ray S. Furuya and David Berry and Pierre Bastien and Tetsuo Hasegawa and Masafumi Matsumura and Thiem Hoang and Lapo Fanciullo and Kazunari Iwasaki and Simon Coudé and Takashi Onaka and Pham Ngoc Diep and Sarah Sadavoy and Hua-bai Li and Koji Kawabata and Doris Arzoumanian and Yasuo Doi and Jia-Wei Wang and Tao-Chung Ching and Janik Karoly and Jihye Hwang and Glenn J. White and A-Ran Lyo and Kohji Tomisaka and Le Ngoc Tram and Frédérick Poidevin and Valentin J. M. Le Gouellec and Hiroko Shinnaga and Masato I. N. Kobayashi and Junhao Liu and Mehrnoosh Tahani and Nguyen Bich Ngoc and Jennifer Hatchell and Archana Soam and Hsi-Wei Yen and Chakali Eswaraiah and Vera Könyves and Jintai Wu and Jeong-Eun Lee and Yusuke Tsukamoto and Ekta Sharma and Tie Liu and Qilao Gu and Hiroyuki Nakanishi and Tsuyoshi Inoue and Fumitaka Nakamura and Rachel Friesen and Jean-François Robitaille and Yoshiaki Misugi and Raiga Kashiwagi and Per Friberg and Sarah Graves and Mark Rawlings and Harriet Parsons and David Eden and Huei-Ru Vivien Chen and Najimudeen Bijas and Motohide Tamura and Tyler L. Bourke and Nagayoshi Ohashi and Woojin Kwon},
  howpublished = {arXiv},
  year = {2026},
  month = oct,
  doi = {10.48550/arxiv.2610.29285},
  eprint = {2610.29285},
  archivePrefix = {arXiv},
  url = {https://arxiv.org/abs/2610.29285},
}

TY  - UNPB
TI  - B-fields In STar-forming Region Observations (BISTRO): Dual-Wavelength Constraints on Size-Dependent Grain Alignment in Star-Forming Regions
AU  - Ray S. Furuya
AU  - David Berry
AU  - Pierre Bastien
AU  - Tetsuo Hasegawa
AU  - Masafumi Matsumura
AU  - Thiem Hoang
AU  - Lapo Fanciullo
AU  - Kazunari Iwasaki
AU  - Simon Coudé
AU  - Takashi Onaka
AU  - Pham Ngoc Diep
AU  - Sarah Sadavoy
AU  - Hua-bai Li
AU  - Koji Kawabata
AU  - Doris Arzoumanian
AU  - Yasuo Doi
AU  - Jia-Wei Wang
AU  - Tao-Chung Ching
AU  - Janik Karoly
AU  - Jihye Hwang
AU  - Glenn J. White
AU  - A-Ran Lyo
AU  - Kohji Tomisaka
AU  - Le Ngoc Tram
AU  - Frédérick Poidevin
AU  - Valentin J. M. Le Gouellec
AU  - Hiroko Shinnaga
AU  - Masato I. N. Kobayashi
AU  - Junhao Liu
AU  - Mehrnoosh Tahani
AU  - Nguyen Bich Ngoc
AU  - Jennifer Hatchell
AU  - Archana Soam
AU  - Hsi-Wei Yen
AU  - Chakali Eswaraiah
AU  - Vera Könyves
AU  - Jintai Wu
AU  - Jeong-Eun Lee
AU  - Yusuke Tsukamoto
AU  - Ekta Sharma
AU  - Tie Liu
AU  - Qilao Gu
AU  - Hiroyuki Nakanishi
AU  - Tsuyoshi Inoue
AU  - Fumitaka Nakamura
AU  - Rachel Friesen
AU  - Jean-François Robitaille
AU  - Yoshiaki Misugi
AU  - Raiga Kashiwagi
AU  - Per Friberg
AU  - Sarah Graves
AU  - Mark Rawlings
AU  - Harriet Parsons
AU  - David Eden
AU  - Huei-Ru Vivien Chen
AU  - Najimudeen Bijas
AU  - Motohide Tamura
AU  - Tyler L. Bourke
AU  - Nagayoshi Ohashi
AU  - Woojin Kwon
PY  - 2026
DA  - 2026/10/21
PB  - arXiv
DO  - 10.48550/arxiv.2610.29285
UR  - https://arxiv.org/abs/2610.29285
AB  - We compared 450 and 850 μm POL-2 observations from the James Clerk Maxwell Telescope at 12.6'' resolution. The median absolute difference in polarization angle between bands is 6.7^∘ across 21 regions. For total intensity I∝ν^α and polarized intensity PI∝ν^γ, 24-27 of 35 regions have γ<α, allowing for 3σ limits on weak polarized intensities. The median γ−α is −0.51, ranging from −0.57 to −0.45 under these limits. The ratio of polarization fractions is P_450/P_850=0.69±0.02_sys±0.03_stat, with no detected dependence on the angle difference. We suggest that the dependence of alignment on grain size offers the simplest explanation of these findings. For optically thin components sharing a polarization angle and opacity law, temperature mixing reproduces the median −0.51 only if the warm dust is polarized less efficiently than the cold dust. If the cold dust is at 10 K or warmer and the warm dust at 40 K or cooler, the median requires a ratio of warm to cold effective polarization efficiencies r≲0.18. We tested mixtures with opacity index β=2 in four fields against Herschel dust temperatures and Green Bank Ammonia Survey kinetic temperatures. We assumed equal gas and dust temperatures, ammonia tracing cold gas, and model ranges of 3-20 K for cold dust and 25-40 K for warm dust carrying at most half the mass. Mixtures matching both temperatures cannot reproduce γ−α within 1σ in three fields, including OMC 2 tentatively, even for r=0. Allowing warm dust at 10-100 K and up to 95% of the mass permits solutions only for r≤0.041. To explain these three fields by temperature mixing, we need wider model ranges and a very strong contrast in polarization efficiency. The origin of this contrast remains undetermined.
ER  -