Distortion of Magnetic Fields in Barnard 335. (arXiv:2001.08542v1 [astro-ph.GA])
<a href="http://arxiv.org/find/astro-ph/1/au:+Kandori_R/0/1/0/all/0/1">Ryo Kandori</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Saito_M/0/1/0/all/0/1">Masao Saito</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Tamura_M/0/1/0/all/0/1">Motohide Tamura</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Tomisaka_K/0/1/0/all/0/1">Kohji Tomisaka</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Matsumoto_T/0/1/0/all/0/1">Tomoaki Matsumoto</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Tazaki_R/0/1/0/all/0/1">Ryo Tazaki</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Nagata_T/0/1/0/all/0/1">Tetsuya Nagata</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kusakabe_N/0/1/0/all/0/1">Nobuhiko Kusakabe</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Nakajima_Y/0/1/0/all/0/1">Yasushi Nakajima</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kwon_J/0/1/0/all/0/1">Jungmi Kwon</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Nagayama_T/0/1/0/all/0/1">Takahiro Nagayama</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Tatematsu_K/0/1/0/all/0/1">Ken'ichi Tatematsu</a>
In this study, the detailed magnetic field structure of the dense
protostellar core Barnard 335 (B335) was revealed based on near-infrared
polarimetric observations of background stars to measure dichroically polarized
light produced by magnetically aligned dust grains in the core. Magnetic fields
pervading B335 were mapped using 24 stars after subtracting unrelated ambient
polarization components, for the first time revealing that they have an
axisymmetrically distorted hourglass-shaped structure toward the protostellar
core. On the basis of simple two- and three-dimensional magnetic field
modeling, magnetic inclination angles in the plane-of-sky and line-of-sight
directions were determined to be $90^{circ} pm 7^{circ}$ and $50^{circ} pm
10^{circ}$, respectively. The total magnetic field strength of B335 was
determined to be $30.2 pm 17.7$ $mu {rm G}$. The critical mass of B335,
evaluated using both magnetic and thermal/turbulent support against collapse,
was determined to be $M_{rm cr} = 3.37 pm 0.94$ ${rm M}_{odot}$, which is
identical to the observed core mass of $M_{rm core}=3.67$ M$_{odot}$. We thus
concluded that B335 started its contraction from a condition near equilibrium.
We found a linear relationship in the polarization versus extinction diagram,
up to $A_V sim 15$ mag toward the stars with the greatest obscuration, which
verified that our observations and analysis provide an accurate depiction of
the core.
In this study, the detailed magnetic field structure of the dense
protostellar core Barnard 335 (B335) was revealed based on near-infrared
polarimetric observations of background stars to measure dichroically polarized
light produced by magnetically aligned dust grains in the core. Magnetic fields
pervading B335 were mapped using 24 stars after subtracting unrelated ambient
polarization components, for the first time revealing that they have an
axisymmetrically distorted hourglass-shaped structure toward the protostellar
core. On the basis of simple two- and three-dimensional magnetic field
modeling, magnetic inclination angles in the plane-of-sky and line-of-sight
directions were determined to be $90^{circ} pm 7^{circ}$ and $50^{circ} pm
10^{circ}$, respectively. The total magnetic field strength of B335 was
determined to be $30.2 pm 17.7$ $mu {rm G}$. The critical mass of B335,
evaluated using both magnetic and thermal/turbulent support against collapse,
was determined to be $M_{rm cr} = 3.37 pm 0.94$ ${rm M}_{odot}$, which is
identical to the observed core mass of $M_{rm core}=3.67$ M$_{odot}$. We thus
concluded that B335 started its contraction from a condition near equilibrium.
We found a linear relationship in the polarization versus extinction diagram,
up to $A_V sim 15$ mag toward the stars with the greatest obscuration, which
verified that our observations and analysis provide an accurate depiction of
the core.
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