John J. Tobin, Leslie W. Looney , Zhi-Yun Li , Sarah I. Sadavoy , Michael M. Dunham , Dominique Segura-Cox4 , Kaitlin Kratter8 , Claire J. Chandler9 , Carl Melis10 , Robert J. Harris4 , andLaura Perez11
1Current address: National Radio Astronomy Observatory, 520 Edgemont Rd., Charlottesville, VA 22903, USA; 2Homer L. Dodge Department of Physics and Astronomy, University of Oklahoma, 440 W. Brooks Street, Norman,
OK 73019, USA; 3 Leiden Observatory, Leiden University, P.O. Box 9513, 2300-RA Leiden, The Netherlands; 4 Department of Astronomy, University of Illinois, Urbana, IL 61801; 5 Department of Astronomy, University of Virginia,Charlottesville, VA 22903; 6 Harvard-Smithsonian Center for Astrophysics, 60 Garden St, MS 78, Cambridge, MA02138; 7 Department of Physics, State University of New York Fredonia, Fredonia, New York 14063, USA; 8 University of Arizona, Steward Observatory, Tucson, AZ 85721; 9 National Radio Astronomy Observatory, P.O. Box O,Socorro, NM 87801; 10 Center for Astrophysics and Space Sciences, University of California, San Diego, CA 92093; 11Departamento de Astronomı́a, Universidad de Chile, Camino El Observatorio 1515, Las Condes, Santiago, Chile

星形成ゼミ・報告 (SFN #310 N.55-58)資料
2018年12⽉7⽇

E-mail contact: jjtobin at gmail.com

古屋玲

We present Atacama Large Millimeter/submillimeter Array (ALMA) observations of multiple protostar systems in
the Perseus molecular cloud previously detected by the Karl G. Jansky Very Large Array (VLA). We observed 17close (<600 AU separation) multiple systems at 1.3 mm in continuum and five molecular lines (i.e., 12 CO, C18 O,(徳島⼤学・教養教育院)
13CO, H2 CO, SO) to characterize the circum-multiple
environments in which these systems are forming. We detect atleast one component in the continuum for the 17 multiple systems. In three systems, one companion is not detected,and for two systems the companions are unresolved at our observed resolution. We also detect circum-multiple dust
emission toward 8 out of 9 Class 0 multiples. Circum-multiple dust emission is not detected toward any of the 8 ClassI multiples. Twelve systems are detected in the dense gas tracers toward their disks/inner envelopes. For these 12systems, we use the dense gas observations to characterize their formation mechanism. The velocity gradients in thecircum-multiple gas are clearly orthogonal to the outflow directions in 8 out of the 12 systems, consistent with diskfragmentation. Moreover, only two systems with separations <200 AU are inconsistent with disk fragmentation, inaddition to the two widest systems (>500 AU). Our results suggest that disk fragmentation via gravitational instability
is an important formation mechanism for close multiple systems, but further statistics are needed to better determine
the relative fraction formed via this method.

紹介しない論⽂
http://arxiv.org/pdf/1809.06434
Accepted by ApJ

55

EPIC 203868608: A low-mass quadruple star system in the Upper Scorpius OB associationJi Wang1,2 , Trevor J. David1,3 , Lynne Hillenbrand1 , Dimitri Mawet1 , Simon Albrecht4 , and Zibo Liu5
1

Department of Astronomy, California Institute of Technology, MC 249-17, 1200 E. California Blv, Pasadena, CA

ALMA reveals a collision between protostellar outflows in BHR 71

Alma reveals
collision
betweenprotostellar outflowsin BHR 71 , Guido
5 Garay , Satoko Takahashi ,58
Luis A. aZapata, ManuelFernández-López, Luis F. Rodrıǵuez
12134Chin-Fei Lee5 , and Antonio Hernández-Gómez1,61

Instituto de Radioastronomı́a y Astrofı́sica, Universidad Nacional Autónomade México, P.O. Box 3-72, 58090,
要旨
Morelia, Michoacán, México; 2 Instituto Argentino de Radioastronomı́a (CCT-La Plata, CONICET; CICPBA), C.C.
No. 5, 1894, Villa Elisa, Buenos Aires, Argentina; 3 Departamento de Astronomı́a,Universidad de Chile, Camino el
1. 分⼦流と分⼦流が相互作⽤する系(345Observatorio 1515, Santiago, Chile; Joint ALMA Observatory, Alonso de Cordova
3108,Vitacura,Santiago,Chile;
例⽬)をALMAでは初めて⾒つけた.
Academia Sinica Institute of Astronomy and Astrophysics, P.O. Box 23-141, Taipei 106, Taiwan; 6 IRAP, Universitéde Toulouse, CNRS, UPS, CNES, Toulouse, France
2.【中⼼星のひとつ；BHR71 IRS1】
E-mail contact: lzapata@irya.unam.mx• Lbol13.5+/-(the1.0separationLsun
For a binary protostellar outflow system in which its members are located closeto =eachotherbeingsmaller than the addition of the widths of the flows) and with large opening •angles,
collision seems unavoidable
Mdustythe
envelope = 0.215 +/- 0.003
regardless of the orientation of the outflows. This is in contrast to the current observational evidence of just a few
Msun(ALMA),
19M
sun(ハーシェル衛regions with indications of colliding outflows, which could also suggests that the average
distance
betweenprotostars is星) Large Millimeter/Submillimeter
larger than the width of the flows. Here, using sensitive observations of the Atacama
Array (ALMA), we report resolved images of carbon monoxide (CO) towards the binary flows associated with the• 分⼦流の⼒学年齢の下限値は,BHR 71 protostellar system. These images reveal for the first time solid evidence that their flows are partially colliding,
GREG> say '200*30*au|(25e5)|yr'
increasing the brightness of the CO, the dispersion of the velocities in the interaction
zone, and changing part of the1.1384E+03年くらい, second collapse後orientation in one of the flows. Additionally, this impact opened the possibility ofknowing the 3D geometry of the
それほど時間は経っていないか？
system, revealing that one of its components (IRS 2) should be closer to us.
Accepted by The Astronomical Journal
https://arxiv.org/pdf/1804.00625

On the origin of magnetic fields in stars

57

On the origin of magnetic field

James Wurster1 , Matthew R Bate1 and Daniel J Price2

School of Physics and Astronomy, University of Exeter, Stocker Rd, Exeter EX4 4QL, UK; 2 Monash Centre for
106 Astrophysics and School of Physics and Astronomy, Monash University, Vic 3800, AustraliaIdeal MHD-10
4Ideal MHD: Central = Maximum
ρmax=10105 E-mail contact: j.wurster at exeter.ac.uk-910
ρmax=10Non-ideal MHD: Central-8
4 Are the kG-strength magnetic fields observed in young stars a fossil field left over from
3 their formation or are theyρ
=10max10
10 generated
Non-ideal
MHD: Maximum-4-3
by a dynamo?
We use radiation non-ideal magnetohydrodynamics simulations of the gravitational collapseρmax=10 g cm ;dts
103 of a rotating, magnetized molecular cloud core over 17 orders of magnitude in density, 2past the first hydrostatic core10
to the formation of the second, stellar core, to examine the fossil field hypothesis. Whereas in previous work we found
210 that magnetic fields in excess of 10 kG can be implanted in stars at birth, this assumed ideal magnetohydrodynamics
1calculations which include
101 (MHD), i.e. that the gas is coupled to the magnetic field. Here we present non-ideal MHD
10
Ohmic resistivity, ambipolar diﬀusion and the Hall eﬀect. For realistic cosmic ray ionization rates, we find thata 0strong fossil field. While these
100 magnetic field strengths of <∼ kG are implanted in the stellar core at birth, ruling out 10results remain sensitive to resolution, they cautiously provide evidence against a fossil field origin for stellar magnetic
10-1 fields, suggesting instead that magnetic fields in stars originate in a dynamo process. -1
1010-2

10-3 http://adsabs.harvard.edu/pdf/2018MNRAS.481.2450W

10-4

Accepted by MNRAS-17 -1

Non-ideal MHD: ζcr=10410s

http://arxiv.org/pdf/1809.01234

10-18

10-16

10-14

10-12-10-81010ρmax [g cm-3]

10-6

10-4

10-2

103

100Figure 1. Evolution of the magnetic field strength against maximum density, which is a proxy for time. The vertical grey line indicates the formation
density of the stellar core, and the black circles are placed 6 months after
the formation of the stellar core for each model (i.e. dtsc = 0.541yr). For
both models, the maximum density is coincident with the centre of the system (i.e. ρmax = ρcen ). In the ideal MHD model, the maximum and central
magnetic field strength are the same for the entire simulation. In the nonideal MHD model, the central and maximum magnetic field strengths are
no longer coincident near the end of the first core phase, and at stellar coreformation, are a few orders of magnitude lower than the values in the ideal
MHD model.

2µ(r)B [G]µ(r)110110010-110-410-310-210-110010r [au]110原始星
誕⽣直後

0x [AU]

5-5100-1-5105
10410103
B [G]102-1Ideal MHD: Central = Maximum
時 Central
Non-ideal 始MHD:
開Non-idealseMHD: Maximum
plaolc2
第初期100.01
AU~2Rsun(原始星半径；図4から)10110010100stio µ(r)also decreases in this region. Outside of this central re-1
10gion, µ(r) > 5 since the cloud
collapses faster along the mag-17 -1
Non-ideal
MHD:perpendicularζcr=10 s
netic10fieldlines
thanto them, increasing the mass
4
as a greater rate than the flux. During this phase in the non-ideal
MHD
3model, µnon-ideal (r) > µideal (r), indicating that the non-ideal
10
processes are diffusing the magnetic field, with significant diffu--2

10-4 -18
10
10-16 10-14 10-12 10-10 10-8
ρmax [g cm-3]

210

10-6

10-4

10-2

100210M/ΦB

μ = (M/Φ )µ(r)3x [AU]1010-3103t = 0 slices throughFigure 2. Density(top) and magnetic field strength (bottom)
Ideal MHD
-10-3
4
ρmax
=10 gaxis
cm for the ideal (left)
10 hydrostatic core perpendicular to thethe firstrotation-9-3
max=10 g cm
and non-ideal (right) MHD models once theρmaximum
density
has reached
-8-3
ρmax
=10 phase).
g cm The initial magρmax10≈3 10−8 g cm−3 (near the end of the firstcore-4-3ρmax=10cm critical; dtsc=0 mass-to-flux ranetic field strength in both models is fivetimesg thedt
sc=0.5yr2tio. The
10 density slices are qualitatively similar. The magnetic field strength
follows the density profile in the ideal MHD model, while the maximum
magnetic
1 field strength in the non-ideal MHD model is in a structured torus
10at 1-3 au from the centre of the core.

-17 -1-1
Non-ideal10MHD:
ζcr=104

5

On theoriginof magnetic
fieldsin 5stars-505-50106

00x [AU]µ(r)

1=M(r)
πr 2 B(r)≃Figure 1. Evolution of the magnetic field strength against maximum den1
10sity, which is a proxy for time. The vertical grey line indicates the formationc1
5B critdensity of the stellar core,時and the black circles are placed 6 months after
0
始
10G
3π
開
the formation of the stellar
core for each model (i.e. dtsc = 0.5 yr). Forepsboth models, the maximum
density is coincident with the centre of the sys-1
lal
10 say ‘Msun|(pi*(0.013*pc)**2*163e-6)|((.53|(3*pi)*sqrt(5|G)))’oGREG>
初期ctem (i.e. ρmax =2 ρcen ). In the ideal MHD model, the maximum and central-3-2-101234.987 10-410101010101010
第magnetic field strength are the same for the entire simulation. In the nonr [au]ideal MHD model, the central and maximum magnetic field strengths are
no longer coincident near the end of the first core phase, and at stellar core
Figure 3. The mass-to-flux ratio in units of the critical value as a function
formation, are a few orders of magnitude lower than the values in the idealof radius at six different epochs for the ideal (top) and non-ideal (bottom)
MHD model.
MHD models. The horizontal grey line represents the initial mass-to-flux

110010-1

10-410-3

10-2

5-1

10010 Ideal MHD 10=10 g cm
r [au]
max-8]µ(r)-12-5x [AU]

10M/ΦBµ(r) ≡,(M/ΦB )crit

51

21010Non-ideal MHD

310-3-9nsity [g/cm3]µ(r)210-5log |B| [G]310log dy [A10y [AU]4-11t=0-10-3
ρmax=10 g cm-9-3ρmax=10 g cm-8-3
ρmax=10 g cm-4-3
ρmax=10 g cm ; dtsc=0
dtsc=0.5yr

Ideal MHD

-100ratio, µ0 = 5. At t = 0, µ(r) = µ0 = 5 at r = Rc . The non-ideal MHD
processes diffuse the magnetic field even by ρmax ≈ 10−10 g cm−3 , yielding µnon-ideal (r) > µideal (r). There is significant diffusion of the magnetic
field for r ! 10 au in the non-ideal MHD model.

y [AU]

56

Hall eﬀect-driven formation of gravitationally unstable discs in magnetized molecular
cloud coresJames Wurster1 , Matthew R Bate1 and Daniel J Price2
1School of Physics and Astronomy, University of Exeter, Stocker Rd, Exeter EX4 4QL, UK; 2 Monash Centre forAstrophysics and School of Physics and Astronomy, Monash University, Vic 3800, Australia
E-mail contact: j.wurster at exeter.ac.uk
We demonstrate the formation of gravitationally unstable discs in magnetized molecular cloud cores with initial massto-flux ratios of five times the critical value, eﬀectively solving the magnetic braking catastrophe. We model thegravitational collapse through to the formation of the stellar core, using Ohmic resistivity, ambipolar diﬀusion andthe Hall eﬀect, and using the canonical cosmic ray ionization rate of ζCR = 10−17 s−1 . When the magnetic field androtation axis are initially aligned, a <∼ 1 au disc forms after the first core phase, whereas when they are anti-aligned,a gravitationally unstable 25 au disc forms during the first core phase. The aligned model launches a 3 km s−1 first−1
core outflow, while the anti-aligned model launches only a weak <∼ 0.3 km s first core outflow. Qualitatively, we findthat models with ζCR = 10−17 s−1 are similar to purely hydrodynamical models if the rotation axis and magnetic field
are initially anti-aligned, whereas they are qualitatively similar to ideal magnetohydrodynamical models if initiallyaligned.
Accepted by Monthly Notices of the Royal Astronomical Society
http://adsabs.harvard.edu/pdf/2018MNRAS.480.4434W
http://arxiv.org/pdf/1808.04376

57

On the origin of magnetic fields in stars
James Wurster1 , Matthew R Bate1 and Daniel J Price2
1

School of Physics and Astronomy, University of Exeter, Stocker Rd, Exeter EX4 4QL, UK; 2 Monash Centre forAstrophysics and School of Physics and Astronomy, Monash University, Vic 3800, Australia
E-mail contact: j.wurster at exeter.ac.uk
Are the kG-strength magnetic fields observed in young stars a fossil field left over from their formation or are theygenerated by a dynamo? We use radiation non-ideal magnetohydrodynamics simulations of the gravitational collapseof a rotating, magnetized molecular cloud core over 17 orders of magnitude in density, past the first hydrostatic coreto the formation of the second, stellar core, to examine the fossil field hypothesis. Whereas in previous work we foundthat magnetic fields in excess of 10 kG can be implanted in stars at birth, this assumed ideal magnetohydrodynamics(MHD), i.e. that the gas is coupled to the magnetic field. Here we present non-ideal MHD calculations which include
Ohmic resistivity, ambipolar diﬀusion and the Hall eﬀect. For realistic cosmic ray ionization rates, we find thatmagnetic field strengths of <∼ kG are implanted in the stellar core at birth, ruling out a strong fossil field. While theseWurster, Bate & Price'([AU%8,-./0(&1

3 4,&5(&'() *+A678&A9836:

4*/0(&01 &0;