星形成ゼミ・報告 (SFN #307 N.21-30)資料
2018年8⽉3⽇

古屋玲(徳島⼤学・教養教育院)

21

Accepted
byfor
ApJof the disk,
example, the wavelength-dependent apocenter-to-pericenter ux ratio. Within the considered parameter
space, the impact of the material strength on the appearance of the disk is stronger than that of dynamical excitation
http://arxiv.org/pdf/1806.11127
of the system. Finally, we find that the impact of the collisional parameters on the net spectral energy distribution is
weak.

Impactof planetesimal eccentricities and material strength on the appearance of eccenAccepted by A&A
tric debris disks
https://arxiv.org/pdf/1806.02391
Minjae Kim1 , Sebastian Wolf1 , Torsten Löhne3 , Florian Kirchschlager1,2 and Alexander V. Krivov3
1

22

Institut für Theoretische Physik und Astrophysik, Christian-Albrechts-Universität zu Kiel, Leibnizstraße 15, 24118
2
From
Planetesimalto Planet
Turbulent
Disks. II.
Formationof GasGiant
Planets
Kiel,
Germany;
Departmentof Physicsin
andAstronomy, University
CollegeLondon, Gower
Street,London,WC1E
6BT,
UnitedKingdom;1 ,3Hidekazu
Astrophysikalisches
Hiroshi
Kobayashi
Tanaka2Institut und Universitäts-Sternwarte, Friedrich-Schiller-Universität Jena,
Schillergäßchen
2-3, 07745 Jena, Germany
1
Department of Physics, Nagoya University, Nagoya, Aichi 464-8602, Japan; 2 Astronomical Institute, Tohoku UniE-mailmkim
at astrophysik.uni-kiel.deversity,contact:
Aramaki,Aoba-ku,
Sendai 980-8578, Japan
Context.
Since circumstellar
in debris disks is short-lived, dust-replenishing requires the presence of a reservoir
E-mail contact:
hkobayas at dust
nagoya-u.jp
of planetesimals. These planetesimals in the parent belt of debris disks orbit their host star and continuously supply
In the core accretion scenario, gas giant planets are formed form solid cores with several Earth masses via gas
the disk with fine dust through their mutual collisions.
accretion. We investigate the formation of such cores via collisional growth from kilometer-sized planetesimals in
Aims. We aim to understand eﬀects of diﬀerent collisional parameters on the observational appearance of eccentric
turbulent disks. The stirring by forming cores induces collisional fragmentation and surrounding planetesimals aredebris disks. These parameters are the eccentricity of the planetesimal belt, dynamical excitation, and the material
ground down until radial drift. The core growth is therefore stalled by the depletion of surrounding planetesiamls due
strength.
to collisional fragmentation and radial drift. The collisional strength of planetesimals determines the planetesimaldepletion timescale, which is prolonged for large planetesiamls. The size of planetesiamls around growing cores isdetermined by the planetesimal size distribution at the20onset of runaway growth. Strong turbulence delays theonset of runaway growth, resulting in large planetesimals. Therefore, the core mass evolution depends on turbulent
parameter α; the formation of cores massive enough without significant depletion of surrounding planetesimals needs−3−3strong turbulence of α >10.
However,thestrongturbulence
with
α
>
10
leads to a significant delay of the∼∼onset of runaway growth and prevents the formation of massive cores within the disk lifetime. The formation of coresmassive enough within several millions years therefore requires the several times enhancement of the solid surface
densities, which is achieved in the inner disk <∼ 10 AU due to pile-up of drifting dust aggregates. In addition, the7−1collisional strength Q∗D even for kilometer-sized or smaller bodies aﬀects the growth of cores; Q∗D >
10
erg
g
for
∼
bodies <∼ 1 km is likely for this gas giant formation.

Accepted by ApJ
http://arxiv.org/pdf/1806.07354

23

The APOGEE-2 Survey of the Orion Star Forming Complex II: Six-dimensional structure

DR2 view of the Lupus V-VI clouds: the candidate diskless young stellar objects
30 Gaia
are mainly background contaminants
Carlo F. Manara1 , T. Prusti2 , F. Comeron1 , R. Mor3 , J.M. Alcalá4 , T. Antoja3 , S. Facchini5 , D. Fedele6 ,A. Frasca7 , T. Jerabkova1 , G. Rosotti8 , L. Spezzi9 and L. Spina10
1 動機
背景,
European Southern Observatory, Karl-Schwarzschild-Strasse 2, 85748 Garching bei München, Germany; 2 ScientificSupportOﬃce, Directorate of Science, European Space Research and Technology Centre(ESA/ESTEC), Keplerlaan 1,
1. ⼀般に,前主系列星の進化に伴い付随する円盤の質量は指数関数的に低減する(e.g.,
Haisch+01).
3
2201
AZ
Noordwijk,
The
Netherlands;
Institutde Ciéncies del Cosmos, Universitat de Barcelona (IEEC-UB), Martı́
Fig. 2. Proper motion of the Gaia targets in the fieldof view of the4
2. Spitzerによる探査では,
disk
fraction= 15%
towards
Lupus
V
and
VI.
これはLupus
I-IIIでのage= 16,
2–380131i Franqués
1, highlighting
E-08028 Barcelona,
Spain;
INAF-Osservatorio
Astronomico
diCapodimonte,
via MoiarielloManaraet al.:
Lupus
V-VI
with
Gaia
DR2
Lupus
V region,the candidate
young stellar
objects with
Napoli,
Max-Planck-Institut
Extraterrestrische
Physik, Giessenbachstrasse 1, 85748 Garching bei München,redcircles,Italy;
and the5 fiveconfirmed young starsfürwithcyan circles.
MyrsのYSOでの検出率50%に⽐べ有意に低い.
6
Germany; INAF-Osservatorio Astrofisico di Arcetri, L.go E. Fermi 5, 50125 Firenze, Italy; 7 INAF-Osservatorio
解析
Astrofisico di Catania, via S. Sofia, 78, 95123 Catania, Italy; 8 Institute of Astronomy, University of Cambridge,
et al.: Lupus
9 with Gaia
200
pc, are classified
as Class IIManara
bySpezziet UK;
al.V-VI(2011),
andDR2
thatOrganisation for the Exploitation of Meteorological Satellites
MadingleyRoad,
Cambridge
CB30HA,
European
1. Gaia固有運動データ(下図)から距離決定→
⾊等級図(CMD;
右図)で進化段階を推定
theremainingoneisclassified
as
Class
III.
This
classificationis10(Eumetsat), Eumetsat Allee 1, 64295 Darmstadt, Germany; Monash Centre for Astrophysics, School of Physics andconfirmed also by Dunham et al. (2015), and none of these five
Astronomy, Monash University, VIC 3800, Australia
targets are flagged as likely being AGB contaminants.
結果These fiveE-mailhave
contact:
cmanaraeso.orgof 6.662±0.013 mas, corobjects
a weighted
meanatparallax
responding to a mean distance of ⇠150 pc. If1.theGaiaデータ：Lupus
Lupus clouds
V andExtensive surveys of star-forming regions with Spitzer have revealed
populations of disk-bearing young stellar objects.
are at 150 pc (e.g., Comerón 2008), then three VIとされる天域内の星はof these targets
These
have
providedcrucialthe timescaleof dispersal of protoplanetary disks, obtained by carefullyarein thecloud,
while oneis in constraints,
front of it andsuch
one asbehindit.
combining infrared data with spectroscopic39+44=83天体
or X-ray data. While observations in various regions agree with the general
To further investigate whether the closer YSO candidates aretrend offrom
decreasing
disk fraction
with
the
Lupus
V and VI regions appeared to have been at odds, having andi↵erent
the backgroundobjects,
we age,
show
in
Fig.
2
the
2.CMDからYSOsは5天体のみextremely
lowfordisk
Here weinshow,
using V
thecloud.
recent Gaia data release 2 (DR2), that these extremely low disk
propermotionthefraction.
YSO candidates
the Lupus(残り78は⾚⾊巨星)
fractionsdue with
to a parallaxes
very high larger
contamination
Fourout ofaretheactually
five objects
than 5 masby background giants. Out of the 83 candidate young stellar
objects(YSOs)atinµ⇤↵theseGaia, andonlythefive have distances of ∼150 pc, similar to YSOs in the otherare
all clustered⇠ 9clouds
mas/yr,observedµ ⇠ 25bymas/yr,
3.分⼦雲の距離を150
pcとする
last
one clouds,
has µ⇤↵ ⇠and20have
mas/yr,µ ⇠ proper
34 mas/yr.
Theseverymembers in this star-forming complex. Of these five targets,
Lupus
similarmotions
toare
other
ならば,
3天体のみがLupusVdi↵erent
valuesfrom thosethe bulk
the candidate
YSOs,
four have
optically
thick of(ClassII) ofdisks.
On the one
hand, this result resolves the conundrum of the puzzling low⇤
which
are foundintothesehave µmas/yr,onµ the⇠VIに付随するYSOs.
2 mas/yr,
the it further clarifies the need to confirm the Spitzer selected↵ ⇠ 2while,
disk fraction
clouds,
other
hand,
same
parameter
space withas mostof tracers,
the Gaia especiallytargets in thefield at low galactic latitude like Lupus V and VI. The use of
diskless
populationotherin regions
注：この図ではofview,
which are ismainly
backgroundobjects.
Thedi↵erence
4.⾮常に低い星形成率.
Gaia
astrometry
now anindependentandreliableway to further assess the membership of candidate YSOs in these,星団の系統運動のin the proper motion space of these closer YSO candidates sugand potentially other, star-forming regions.
gests that they are a homogeneous group that is kinematically Fig. 3. Absolute magnitude vs color for the candidate YSOs in the Lu速度は引いていない.

Fig. 2. Proper motion of the Gaia targets in the field of view of thepus Vwith(top) and Lupus VI (bottom) regions with positive parallax anddistinctfrommore
objects.
This
that they
Accepted
bythe
Astronomy& Astrophysics
Letters
Lupus distantV region,
highlighting
theconfirms
candidate youngstellar objects
available Gaia magnitudes. Only the four confirmed young objects incircles,and population.
the five confirmed
youngstars with cyan
most likely belong red
to thecloud
Whencomparingthe circles.

Fig. 2. Propermotion of the Gaia targets in the field of view of thehttps://arxiv.org/pdf/1806.04943
propermotion values
for thefiveclose-bytargets with those of
Lupus V region, highlighting
the candidate
youngstellarobjects with
red circles,
and thefive confirmed
younginstars
cyan circles.
otherconfirmed
YSOs
thewithLupus
complex (López Martí, et al.

Lupus V with available Gaia magnitudes have color and magnitudes
compatible with age<10 Myr, according to the overplotted extinctionfree
200 pc, are classified as Class II by Spezzi et al. (2011),
andisochrones.
that

28

An ALMA Survey of faint disks in the Chamaeleon I star-forming region: Why aresome Class II disks so faint?
Feng Long1,2 , Gregory J. Herczeg1 , Ilaria Pascucci3 , Daniel Apai3,4 , Thomas Henning5 , Carlo F.
Manara6 , Gijs D. Mulders3 , László. Szűcs7 and Nathanial P. Hendler3
1

背景,Kavli
観測 Institute for Astronomy and Astrophysics, Peking University,3 Beijing 100871, China; ;2Department of
Astronomy, School of Physics, Peking University, Beijing 100871, China; Lunar and Planetary Laboratory, University
1. ALMA
850 micronでのClassII objects
円盤探査(Pascussi+16)から,ofCha
Iの2-3Myr-oldのclass
II天体5 Maxof Arizona,
Tucson, AZ 85721,
USA; 4 Steward
Observatory,
University
Arizona,Tucson, AZ 85721, USA;
Planck“dustInstituteformass”,
Astronomy,
Germany; 6 European Southern Observatory, Karl-Schwarzschild-Str. 2,
において,
disk
MdustHeidelberg,と星質量M*の相関が知られていた。本研究は、その発展。
D-85748 Garching bei München, Germany; 7 Max-Planck-Institut für extraterrestrische Physik, Giessenbachstrasse 1,
2. ALMA
at 850
micronGermany
連続波, ⾓度分解能~1”
D-85748
Garching,
E-mail contact: longfeng at pku.edu.cn
ALMA surveys of nearby star-forming regions have shown that the dust mass in the disk is correlated with the stellar
mass, but with a large scatter. This scatter could indicate either diﬀerent evolutionary paths of disks or diﬀerent
initial conditions within a single cluster. We present ALMA Cycle 3 follow-up observations for 14 Class II disks thatwere low S/N detections or non-detections in our Cycle 2 survey of the ∼ 2 Myr-old Chamaeleon I star-forming region.
With 5 times better sensitivity, we detect millimeter dust continuum emission from six more sources and increase thedetection rate to 94% (51/54) for Chamaeleon I disks around stars earlier than M3. The stellar-disk mass scaling
relation reported
Pascucciimages
et al. at(2016)
is forconfirmed
with these
updatedmeasurements.
outliersin the Fmm –Figure 1. inContinuum
887µm
Cycle 3 sample,
orderedby decreasing
millimeterFaint
flux withcolormap
00 ⇥ M⊕ andM∗ planescaled
includethree(CHXR71,
CHXR30A,
and T54)
with atdust
masscorner.
upperImages
limitsareof60.2by thepeaknon-detections
flux of each source.
Contour levels
for each panel
are labeled
the right
three very
(CHXR20,
ISO91,
and 00T51)
with
masses∼ 0.5
M⊕companions. By investigating
the SED
600faint
with disks
the typicalbeam sizeof 1.00 1⇥0.
7 shownin dustthe topleft panel.
Close
for CHXR79,
T27, morphology,
andaccretionT51
property
andwithstellarmultiplicity,suggestfor adopted
the threemillimeter
non-detections
that tidal interaction by
are marked
whitecrosses, withwe
positionanglesfrom
Daemgen etal. (2013).
解析
a close companion(<100 AU) and internal photoevaporation may play a role in hastening the overall disk evolution.
3
tainedofthe
the secondary
fitted parametersthat arebrighterthreethetimes
theuncertainty
5 and
1. 物理量へ:
⼲渉計visibilityデータをフィットし、位置,→M
The presenceof. aThe
diskuncertainties
around only
star inサイズ、フッラクス密度を推定
a binarysystemmaythanexplainobserved
diskへstellar SEDs
scaledthe squareroot of the reduced 2 ofand located near the expected source position are
low disk aremassesforby
somesystems.
Table
SourceProperties
the fit. The fitted fluxes
and2.phasecentero↵sets and Measured
considered Fluxes
detections. The median values of ↵Accepted by ApJ
are consistent within the uncertainties for both the= 0.00 34 and= 0.00 02 from the detections
https://arxiv.org/pdf/1806.04826
Gaussianand the point-source
areFconsistent
within Pascucci
2MASS ellipticalName
Multiplicity
SpTy log(Mmodels.
Fmm (P16)↵ the values reported
FWHM
log(Mdust )⇤)mm
Of the 14 observed sources in our Cycle 3 proet al. (2016) in the full sample. These o↵sets from(arcsec)
(M )
(mJy)
(mJy)
(arcsec)(arcsec)(arcsec)(M )gram, 11 are detected with a signal-to-noise ratio
the 2MASS coordinates are roughly consistentof >3. Table
2 summarizes
the measured
conwith(7)expectations(Lopez
(1)
(2)
(3)
(4)
(5)
(6)
(8) based on(9)proper motion
(10)
(11)
tinuum flux densities and associated uncertainMartı́ et al. 2013; Murphy et al. 2013).
J10533978-7712338
M2-0.41 in 4.60±0.79-0.47±0.02-0.04±0.01
ties (Fmm ), o↵sets from the phasecenterright 24 3.74±0.16
Three sources
remainundetected. For these0.24

8Long et al.

Figure 3. Left: Continuum flux densities as a function of stellar mass. The 14 sources re-observed in Cycle 3 areshown3.in orange,
while the othersflux
are shownin blue
fluxes adopted
from Cycle
2 observations(Pascucci re-observed
et al.
FigureLeft: Continuum
densities
aswitha functionof stellar
mass.
The 14 sourcesin Cycle 3 are2016). Open circles for detections and downward triangles for non-detections. The best fit relation (orange full line)howninorange, while the others are shown in blue with fluxes adopted from Cycle 2 observations (Pascucci et al.
using結果と議論
updated fluxes and upper limits are highly consistent with relation (almost overlapped thus not shown here) from
016).
Open
detections
and downwardfor
The best
fit relation(orange full line)
Pascucci
et al.circles(2016). for
Revisedrelation without
considerabletriangles
outliers (seetextnon-detections.
for how they are selected)
is shownin
1. 本研究の動機となったM
dust vs. M*相関
dottedline. The
medianerror
bars forlog(Marelog(Fmm) are shownwith
in therelation
left upper(almost
corner andoverlappedcorrespond tothus
0.1 not shown here) fromsing
updatedfluxesandupperlimitshighlyconsistent⇤ ) anddex(Fig.3)は⼤筋で確かめれたが,and 0.05 dex; Right: Distribution of o↵setsscatterは⼤きfrom data points to the fitted line. O↵sets in positive represent sources
Pascucci
et al. (2016). Revised relation without
considerable outliers (see text for how they are selected) is shown inwithくなった.
higher continuum
fluxes.
FittedparametersfortheGaussiandistribution are labeled in text. The non-detections
本論⽂では,
best-ﬁtからの残差の
otted
line.
The
median
error
bars
for
log(M
)
and
log(F
shown
inCyclethe left
upper corner⇤mm ) areandare shown in hatches to separate from the detections shownin full histogram,the three
3 non-detections
are and correspond to 0.1
要因(e.g.,中⼼星輻射による光
exshownand0.05
dex;潮汐相互作⽤,
Right: Distributionof o↵sets from data points to the fitted line. O↵sets in positive represent sourcesin orange.

Figure 7. millimeter flux densities as a function of projected binary separation. Single stars are shown in therighthatchedregionfor reference.
three Hot sam蒸発)をSED解析にもとづき議論.
withthese
higherFitted parameters
the Gaussian
distribution
are labeled
in text. The The
non-detections
faintcontinuum
disks to the fluxes.
entire Chamaeleon
I (略)sam- forFigure6)8 , indicatingthat any on-goingaccretionpleinThe
non-detections
arehighlighted
in orange downward
re ple,shown
in hatches
theitsdetections
fulluncertainties
histogram,inandthe threeareand thenattempt toto separate
place eachfrom
disk onown
isshown
weak.
accretion
rateCycle
are 3 non-detections
2. 連星間隔と850
evolutionary
track basedmicronフラックスの関係
on source properties.
typically⇠0.3 dex andare twomore verticaluncertain nearhown
in orange.
triangles.
The
gray dashed lines represent
9As
a parallel e↵ort to understand young stellar
the chromospheric boundary . The other two faint(Fig.7)で、30AU-300AUの範囲でフラックス
830CHXR20
AU
and300
AU, withas thatproposedin Harris
et al. (2012)
hese
faint
disks Manara
to the etentire
Chamaeleon
Figure, indicating
any on-goingaccretionsystemevolution,al. (2016,2017) mea- I samsources,and6)T51(markeda downがCha Iでは優位に低減しない(Taurusでは低
rates
for mosteachsourcesin ourward arrowin6), havecontradictoryaccre-inple,sured
andmass
thenaccretionattempt
to7 placedisk
on its own
is Figureweak.
The
uncertainties
accretion
are bar for
to grouptheTaurussample.
The
medianrate
error
減; Harris+12).
→ 周連星円盤の寿命を決め
ALMA
Cycle 2 Chamaeleon
disk survey (Pasmeasurements in the literature but are esvolutionary
track based onI source
properties. tion rate
typically⇠0.3 dex
dex andand shown
are more
uncertain
near corner.
log(F
)
is
0.05
in
the
left
lower
mm
cucci
et
al.
2016),
basedon
UV
continuum
extablishedby
X-Shooter
spectratobeaccreting(e.g.
る環境要因の違いの視点から精査必要.
9As
a orparallele↵ort whento understandthe2016,chromosphericboundarycess,line luminosity
signal-to-noiseyoung
ratio stellar
Manara et al.
2017). Meanwhile,
the vast. The other two faintCore Mass Function Across Galactic Environments.
26 TheClumpsII. Infrared Dark Cloud

Mengyao Liu1 , Jonathan C. Tan1,2 , Yu Cheng3 , Shuo Kong4
1

Dept. of Astronomy, University of Virginia, Charlottesville, Virginia 22904, USA; 2 Dept. of Space, Earth &Environment, Chalmers University of Technology, Gothenburg, Sweden; 3 Dept. of Astronomy, University of Florida,
Gainesville, Florida 32611, USA; 4 Dept. of Astronomy, Yale University, New Haven, CT 06511, USA
E-mail contact: ml7hc at virginia.edu
We study the core mass function (CMF) within 32 dense clumps in seven infrared dark clouds (IRDCs) with the
Atacama Large Millimeter/submillimeter Array (ALMA) via 1.3 mm continuum emission at a resolution of ∼ 1′′ .
We have identified 107 cores with the dendrogram algorithm, with a median radius of about 0.02 pc. Their masses
range from 0.261 to 178 M⊙ . After applying completeness corrections, we fit the combined IRDC CMF with a powerlaw of the form dN/d log M ∝ M −α and derive an index of α ≃ 0.86 ± 0.11 for M ≥ 0.79 M⊙ and α ≃ 0.70 ± 0.13
for M ≥ 1.26 M⊙ , which is a significantly more top-heavy distribution than the Salpeter stellar initial mass function(IMF) index of 1.35. We also make a direct comparison of these IRDC clump CMF results to those measured in
the more evolved protocluster G286 derived with similar methods, which have α ≃ 1.29 ± 0.19 and 1.08 ± 0.27 inthese mass ranges, respectively. These results provide a hint that, especially for the M ≥ 1.26 M⊙ range wherecompleteness corrections are modest, the CMF in high pressure, early-stage environments of IRDC clumps may be
top-heavy compared to that in the more evolved, global environment of the G286 protoclusters. However, larger
samples of cores probing these diﬀerent environments are needed to better establish the robustness of this potential
CMF variation.
Accepted by ApJ
http://arxiv.org/pdf/1806.02213

23↵ = 1.24 ± 0.17 for M 0.79 M , however, we have decided to focus on the lower resolution resolution results,
given that the IRDCs span a range of distances from 2.4
to 5.7 kpc, but with IRDC C at 5 kpc and IRDC D at
5.7 kpc contributing a large fraction of the sample sothat the average distance of the IRDC cores is 4.4 kpc.
Thus in the end the e↵ective linear resolutions are similar (within about 15%) for the average IRDC core andthat achieved in G286. Overall the mass sensitivities arealso quite similar between the two observations and thecompleteness correction factors are relatively modest, atleast for M 1.26 M .
4. DISCUSSION AND CONCLUSIONS

We have measured the CMF in a sample of about 30
IRDC clumps, including accounting for flux and number
recovery incompleteness factors. With simple fitting, wederived high-end power law indices of ↵ ' 0.86 ± 0.11
for M 0.79 M and ↵ ' 0.70 ± 0.13 for M 1.26 M .
An MLE analysis yielded similar values. These results
indicate a CMF that is top heavy compared the standard
Salpeter distribution with ↵ = 1.35.

which would also take a& Tan 2003). The fact
top-heavy CMF indica
the main factor resistin
in these environments,
some combination of in
netic field support is pr
Note that IRDC clum
tra thermal heating ofradiative feedback fromas proposed in the modis not expected to be
evolved stages as repr
calized heating of the
expected to be higher
environments, if power& Tan 2015). At therect indication if the lohigher in the IRDC cl
if localized IRDC core thigher than in G286, th
their masses. If this e29 The formation of high-mass binary star systems
Kristin Lund1 and Ian A. Bonnell1

School of Physics and Astronomy, University of St Andrews, North Haugh, St Andre
背景, 1動機
1. 熱的不安定性による分裂だけで⼤質量連星をつくることは難しい[連星形成には, 2つの分裂素⽚間の距離が2RJはE-mail contact: kblg at st-andrews.ac.uk
離れていないといけない. e.g., RJは=104AU for 10-19 g cm-3 gas at 10 K] .

We develop a semi-analytic model to investigate how accretion onto wide low-mass bin
2.連星系の質量と連星間隔は⽐例する(e.g.,
Bate
Bonnell 1997),
連星の諸元は星団内の最⼤質量の星の質量やhigh-mass binary system.
The
key& ingredientis toallow mass accretion while limiting th
星団の諸元と関わっているという予測(e.g.,
Larson1982, Elmegreen
2000,など)
We envision this process as
being
regulatedby an external
magnetic field during infall.
collapse spherically with material →eitheraccreting onto the stars or settling in a disk.
3.⼤質量星の近接連星系形成は研究が進んでいない
磁気制動による余剰⾓運動量の外部への移送を組み込んだ準解析的モデルinitial [⾮理想MHD効果は組み込んでいない.]
conditions are needed6 forthe resulting binary to be both massive and close. W
K. Lund & I. A. Bonnell
what happens to the binary separation as a result, depends on the relative size of it
2 K. Lund & I. A. Bonnell
⺟体の分⼦雲コアが⼀様密度
⺟体の分⼦雲コアが⾮⼀様密度
回転のみ compared to the specific angular momentum of the binary. When we add a magnetic fie
回転のみ
to the system which is capableandof✓ stripping
the molecular cloud of some of its angular◆ 1/2 ✓
◆ 1/2
5Rg T
4
RJ = binaries.
⇡⇢ Our, results suggest that(2)easing the formation of high-massclouds in excess of
2Gµ3
larger, can easily form binary systems
withmassesexcess Rof
25 M⊙ and separations
回転＋乱流＋磁場
where ⇢ is the gas
density,
T is the gasin
temperature,g is thegas constant, G is the gravitational constant, and µ is thefields of order 100 µG (mass-to-flux
ratios of order 5).
回転のみ
mean molecular weight. Typical values of the Jeans mass and
回転＋乱流＋磁場
Accepted by MNRAS

radius are ⇡ 1 M and ⇡ 104 au corresponding to densitiesof 10 19 g cm 3 and temperatures of 10 K. To form a binary
system, two fragments would have to be separated by twice
their Jeans radius, such that there is a direct relationshipbetween the mass and minimum separation of the fragments

回転＋乱流＋磁場

http://arxiv.org/pdf/1806.07394
M⇤,T

DR2 view of the Lupus V-VI clouds: the candidate diskles
30 Gaia
are mainly background contaminants
Rsep /

Figure 1. Accretion of material onto a wide low-mass binary with(bottom) and without (top) the presence of a magnetic field. The
1
masses of the binary stars will increase in either case, but the final
separation of the stars is more likely to decrease if a magnetic field
7
has stripped the system of some of its angular momentum.

(3)

Uniform
cloud density= ⇢0 )
such that(a)for
reasonablegas(⇢ temperatures,
fragmentation(b) Non-uniform cloud density (⇢ / R 2 )canonly form
close
systemsvery
low masses
Figure4. Changein binarymass binaryand separation
duringwith
accretion.
Di↵erent
coloured lines correspond to placing the binary system indi↵erent
environments.
For
the
red
line
the
initialmassofthebinaryis10M, in every other scenario it is 2 M . The black horizontal(Bonnell & Bate 1994). If fragmentation of molecular clouds
line marks
separation of 1 au, below which binary
likely to merge.
Mcloud = 500 M , Rcloud =0.5 pc,4⌦cloud = 3 ⇥ 10 14 rad s 1 and
2 a the1 stars are
3 systems,
were
only
way
to
form
high-massclose
binaryB0 = 100 µG.
1 then typical4 separations
8 would be expected9 to be in the
105range of 10 to 10 au.
collapse. The black horizontal line marks a separation of 1
an Mb /s ⇡ 4300. For these simulations we have restricted
Binary hardening in a stellar cluster is an alternative

Carlo F. Manara , T. Prusti , F. Comeron , R. Mor , J.M. Alcalá , T. Antoja
A. Frasca , T. Jerabkova , G. Rosotti , L. Spezzi and L. Spina

⼤質量星連星系の質量(a)

⼤質量星連星系の⾓運動量(b)

⼤質量星連星の間隔(c)Figure 3. Change in binary mass, angular momentum and separation as consecutive shells of a uniformly dense and turbulent molecular
cloud collapses. The di↵erent coloured lines correspond to placing the clouds in magnetic fields of di↵erent strengths. Mcloud = 500 M ,Rcloud = 0.5 pc and ⌦cloud = 3 ⇥ 10 14 rad s 1 .

結果と議論

in this particular scenario. In this calculation we are treatreach 5 M and the binary separation is almost 10 au. In
ing1.図3.
the molecular
cloud ass(t-ta uniformly
dense full sphere,
other words,
this is not a close high-mass system.
In contrast,
相似座標[x=r/c
進化に伴い磁場の効果は明らか(=中⼼部0)]なので横軸は時間と読み替えた場合,
neglecting the empty central region within the initial aca magnetic field of 100 µG or more results in a binary massの⾓運動量はほぼ⼀定だが, 磁場が強ければ質量は増し続け,
連星系間隔は⼩さくなっている.)
cretion radius, corresponding to ⇠0.1% of the total radius.
exceeding 19 M with a separation of less than 0.12 au.
Assuming a uniform spherical distribution the moment of
It is clear from Figure 3 that adding a magnetic field
2.連星系諸元の磁場強度依存性とは,
inertia,I, in the rotational energy equation,荷電粒⼦の磁場結合の度合いのこと。外側へ移送される余剰⾓運動量のcan be written
makes it easier to form binaries with higher mass and smaller
1979などから⼿であたえている。
as ⼤きさは結局、電離度が決めている。今、電離度はElmegreen
separation.
The e↵ect of the magnetic field increases withincreasing field strength, and in the case of the strongest field
2
2
I = Mcloud Rcloud,(28)
strength, 500 µG, most of the gas accreted from the cloud is
3.上記に加え,同時に形成される⼩質量星の影響 (例えば, ⼩質量星の分⼦流が駆動する乱流)や「現実的な環境
5
stripped entirely of angular momentum. Figure 3(b) shows
and theenergy ratio simplifies to要因」が考慮されていないけれども（考慮されていないから？）、100μGあればR=0.6 pc, 1100Msunの
how nearly no angular momentum is being added to the1
2
3
⺟体雲から間隔10R
sunで星質量10 -10 Msunの連星が形成可能.
binary during accretion of material starting at radii larger
Rcloud⌦2cloud
Erot
=
.
(29)
than ⇠ 0.2 pc.