Star Formation NewsletterNov 14, 2014
Shin Koyamatsu

1. Kompaneets model fitting of the Orion-Eridanus superbubble
Andy Pon, Doug Johnstone, John Bally and Carl Heiles	

概要• OB Associationからの風や超新星によりISMにSuperbubbleと呼ばれる大きな穴が空く• 最も近い大質量星形成領域であるオリオン分子雲には20°×45°の大きく偏平したSuperbubbleがある• Orion-Eridanus superbubbleをKompaneetsモデルでフィット• SuperbubbleのEridanus側が太陽から遠い方向にあるモデルの方が合うBisnovatyi-Kogan, Blinnikov & Silich 1989; Mac Low et al.
1989;
Tenorio-Tagle, Rozyczka & Bodenheimer
1990;
2.2 Orion–Eridanus Superbubble
Tomisaka 1992, 1998; Stil et al. 2009), Kompaneets models
In this paper, all references to north or souhave been shown to provide an excellent first-order solution
1本目つづきcreasing or decreasing declination and referen
for the shape of a bubble expanding in an exponential
KompaneetsModelwest refer to increasing or decreasing right asc
atmosphere (e.g.
Mac Low et al. 1989). Kompaneets modotherwise specified. References to above or b
are the current, de facto
choice for analytic models of• els
純粋なexponential
atmosphereへのショック波の伝播のsemi-analytic解
will refer to directions along the major axis
superbubbles. For this paper, we will use the continuous• injection
天の川銀河の円盤中のsuperbubbleの進化に適用できる(W4superbubble,
Eridanus superbubble
either towards the lowe
variant described in detail by Basu et al. (1999)
tion of the exponential atmosphere or the hOphiuchus
andwill refer superbubble,
to such a modellocal
simplybubble)
as a Kompaneets
portion, respectively. Thus, the top of the b• model.
exponential atmosphere内を膨張するbubbleの形状のよい1次近似解
the portion of the bubble farthest from the sThe three key assumptions of the Kompaneets model• arekey(1)assumptionrounded by lower density regions of the expo
the pressure within the bubble is spatially uniform,
sphere, and the bottom of the bubble will be(2)1.thebubble expands in the direction of the surface normal
bubble内の圧力は空間的に一定
the bubble closest to the source and surroun
at all locations, and (3) the expansion speed of the bubble is
2. bubbleはすべての場所で表面に垂直な方向に拡がる
density portions of the exponential atmosphgiven
by Hugoniot jump conditions for a strong shock, wherewe will use upper and lower to refer to direct
the3.exteriorpressure is negligible compared to the interior
膨張のはやさは強いショックに対するHugoniot
jump条件
major axis of the bubble. While ‘above’ or ‘topressure. The Kompaneets model predicts that the location
will generally refer to larger absolute magnitudof the wall of the superbubble is given by!
"#$latitude, we emphasize that we intend these1 z/2Hy2−z/Hto directions along the major axis of the supr(z, y) = 2H arccos e
1−+e,(1)24H 2
not a direction along a line of constant Gala
since the Orion–Eridanus superbubble’s majo
where r is the perpendicular distance from the central axis
to make an angle of approximately 30◦ to theof the superbubble to the bubble wall, z is the distance along
Galactic plane in the plane of the sky.
the central axis from the driving source, H is the scaleheight
The Orion star-forming region is the neaof the exponential atmosphere, and y is a parameter withforming region to the Sun that is actively
dimensions of length which varies from 0 to 2H and essenand is located 400 pc away in the constella
tially specifies the evolutionary stage of the bubble, with(Hirota et al. 2007; Menten et al. 2007; Sa
more evolved bubbles having a larger value of y.
2007). It is approximately 130 pc distant fromAt early times in the evolution of a Kompaneets model,plane and contains both young subgroups ofthe superbubble remains relatively spherical and the y pamolecular clouds in which stars are actively
rameter is roughly equal to the radius of the superbubble. After a bubble expands to a radial size approximately
Bally 2008).

6A. Pon et al.

Kompaneets Fitting of Ori–Eri Superbubble

Figure 4. Schematic diagram of models T and A. Model T isshown in the top panel and model A is shown in the bottom panel.
In each of these schematic diagrams, the superbubble major axis
is inclined roughly 30◦ into the page, in order to match the oﬀset
between the superbubble axis and the normal to the Galactic
plane apparent in Fig. 1. Thus, the major axis of the bubble inmodel A is still 35◦ inclined from the normal to the Galactic
plane.

Table 1. Kompaneets model properties

3

eter, rathe
bubble, asparameters
bubble in t
the inclina
sky, and thcation is coand the faa distanceThe bthe bottom
model A (fgiven in thof this modA slig
reasonable
Because thend and nmuch widebubble orie
fits, howev
In model A
the closest
300 pc dist
bubble is 2
T. For a dfrom this m

4DISCU

Model T dogy of theArcs A andmajor axis
the bubble
driving sou2. Mid-J CO observations of Perseus B1-East 5: evidence for turbulent
dissipation via low-velocity shocks
Andy	  Pon,	  Doug	  Johnstone,	  Michael	  J.	  Kaufman,	  Paola	  Caselli,	  and	  Ren	  é 	  Plume	  	  概要• 巨大分子雲は超音速乱流を含んでいるが、MHDシミュレーションによるとすぐに消失する• 乱流の散逸は分子雲内に温かいガスを作る可能性がある• Perseus B1-East 5領域のCO (J=5–4, 6–5)をHerschelで観測• 過去の低回転遷移の測定量も合わせてPDRモデルをフィット• B1-E5では6–5の積分強度が異常に強い → 温かいガス成分• 体積フィリングファクタ0.15%の低速度ショック領域での乱流散逸によるショック加熱• 乱流エネルギーの散逸率は3.5×1032 erg s-1

2本目つづきMid-J CO Observations of Perseus B1-E57

3. A Spitzer View of The Giant Molecular Cloud Mon OB1 East/NGC 2264
Rapson,	  Valerie	  A.,	  Pipher,	  Judith	  L.,	  Gutermuth,	  Robert	  A.,	  Megeath,	  S.	  Thomas,	  Allen,	  Thomas	  S.,	  	  Myers,	  Philip	  C.,	  Allen,	  Lori	  E.	  	  

概要• 巨大分子雲Mon OB1 Eastの3.6, 4.5, 5.8, 8.0, 24μm画像をSpitzerで観測• 星周円盤 and/or 星周エンベロープをもつYSOを赤外超過により同定・分類、また分子雲の物質に対する分布を調査• YSOの局所面密度とダスト減光から見積もられる分子ガスの柱密度とのあいだにべきの相関関係を発見• 内部の星形成領域NGC 2264の内と外で異なるべき、円盤の割合• Mon OB1 cloudでは非一様な同時でない星形成が起きている30:00.0
9:00:00.0

9:00:00.0

30:00.0

10:00:00.0

Declination

10:00:00.0
30:00.0

Declination

30:00.0

11:00:00.0

11:00:00.0

3本目つづき42:00.0

6:40:00.0

42:00.0

Right ascension

01632480 64

16 80

6:40:00.0

Right ascension

32 95

48 11164 12780 14395 159111127143159

3本目つづき– 26 –Fig. 9.— YSO mass surface density vs. molecular gas mass column density of all Spitzer identified Class0/I (red triangles), Class II (green squares) and transition disk sources (blue diamonds) for NGC 2264 (topleft), Mon OB1 cloud (top right), and all of Mon OB1 East (bottom). Overplotted are polygons marking thefit to, and estimated spread in, data of the Mon R2 molecular cloud (black; N=2.67 ± 0.02), and Ophiuchus
molecular cloud (gray; N=1.87 ± 0.03) from Gutermuth et al. (2011). Hatched regions show where AV < 1and the gas column density cannot be reliably determined from the near-IR extinction.

– 27 –