ALMA reveals a hub of ﬁlamentary molecular
clouds in Sgr B2(N)Aya Higuchi (RIKEN)
Atsushi Nishimura (Nagoya University)
Tetsuo Hasegawa, Patricio Sanhueza, Kazuya Saigo (NAOJ)
James Chibueze (University of Nigeria)

11Molinari et al. (2011)•How massive star form?
Massive dense clumps (> 103-4Msun in 1 pc) are need for massive starformaSon regardless the formaSon scenarios.
• Triggering mechanism can be necessary.
•2

SgrB2•Giant molecular cloud in the GC•

D=7.8kpc (Reid et al. 2009)•T=50-100K; n=106-7cm-3; M=107Msun•

Chemically rich complex••

Line survey (Belloche et al. 2013)

Star forming acSviSes in SgrB2(N)••Site of massive star formaSon triggered by cloud-cloud collision• Massive dense cores formed at the dense interface of colliding clouds(Hasegawa et al. 1994)
SgrB2(N) -K2: massive stars at the earliest stage of formaSon• ParScularly rich in complex organic molecules (Belloche et al. 2014)• Massive system of rotaSng torus + bipolar ouclows (Higuchi et al. 2015b)
33

SgrB2(N): ALMA4

Higuchi et al. 2015(b)SO2 Moment-1

0.2pc

5

SgrB2(N): C18O ﬁlamentary structure➕ 44GHz mathanol maser■ 6.7GHz mathanol maser

➕

■

➕
➕➕

➕ ➕
➕

■6■

SgrB2(N): ﬁlamentary structure•

Perego et al.

C18O(1-0)•X-shape ﬁlaments with
diﬀerent velociSes•

Mass supply to cores
through ﬁlaments has
been suggested forother regions (e.g.,
N2H+ line by Perego etal. 2013)

•+ K2
0.5pc

Early stage of cluster
formaSon including
high-mass stars
7

Does the core form from the ﬁlaments?
Physical condiIon of the ﬁlaments•

Filament width = 0.1pc, dv=1-2km/s•

Line mass= 102Msun/pc : opScally thin,
LTE at T=100K, X(C18O)=10-7••

50-60% of ﬂux in the 16” beam ofNobeyama 45-m telescope isreproduced•

Total ﬁlament mass (103Msun) issmaller compared with that of thecore (104Msun)

0.5pc

+ K2

No rapid mass ﬂow along the ﬁlaments
discerned (within the limited velocity
resoluSon of 1.2 km/s of theobservaSons)

88

IdenIﬁcaIon of the ﬁlaments: by A. Nishimura
DisPerSE v0.9.24 (3D data)
idenSﬁed small number ofﬁlaments with aspect raSo > 3

0.1pc

0.2pc

0.3pc

0.4pc

ﬁlament width [pc]99IdenIﬁcaIon of the ﬁlaments
Origin of the ﬁlaments•

SE-NW ﬁlament•••

results of interacSon withthe bipolar ouclow(Higuchi et al. 2015b)
0.5pc

alignment with theouclow+ K2

The other ﬁlaments•

formed in a sheet with alarge velocity sheer of -30
km/s/pc at the cloud
collision interface
1010

Summary
Physical condiIon of the ﬁlaments•C18O(1-0) 1.9”×1.4” (0.07×0.05 pc) resoluSon image (ALMA archival data without ACA)••

A hub of 10 ﬁlaments centered at the massive-star forming hot core at K2•••50-60% of ﬂux in the 16” beam of Nobeyama 45-m telescope is reproduced
Filaments have the typical 0.1 pc diameter, but with relaSvely large line mass of 102
Msun/pc•

SE - NW ﬁlaments - may be a result of interacSon with the massive bipolar ouclow•

The other ﬁlaments - may have formed in a sheet with large velocity sheer at thecloud collision interface

The total ﬁlament mass (103 Msun) is small compared with that of the core (>104 Msun)

Not a posiSve evidence for the core forming from the ﬁlaments

11

MagneIc ﬁeld in SgrB2 region
Molinari et al. (2011)

Crutcher et al. (2003): - 0.5 mG

Sato et al. (2000)(VLA HI observaSon)

12