Transcript banff04

Outflows from High Mass
Protostars
Debra Shepherd
National Radio Astronomy Observatory
Cores, Disks, Jets & Outflows in Low &
High Mass Star Forming Environments
Observations, Theory & Simulations
Banff, Alberta, Canada - July 12-16, 2004
Contents
• Motivation – why study outflows from Young Stellar
Objects
• Review of Outflow Energetics
• Observational summary:
•
•
Outflows from Mid- to Early-B (Proto)stars
Outflows from young O Stars
• Impact of Luminosity on Outflows
• Impact of Mass-loading and Disk Turbulence on
Outflows
• Summary
Motivation
• Outflow & infall dynamics affect:
– Energy input & turbulent support of molecular clouds
– Dissipation of molecular clouds
– Final mass of the central star
– Disk (and planet) evolution
• Outflows provide a fossil record of mass-loss history of a
protostar (or protostellar cluster).
• Outflow orientation establishes that a velocity gradient in
circumstellar material (e.g. masers, dense gase) is due to a disk.
• Why massive protostellar outflows may differ from lower-mass
flows:
– OB stars usually form in clusters  expect dynamical interactions
– Expect massive YSO to evolve to ZAMS more rapidly:
O stars: tevolve ~ few x 104 yrs, G star: tevolve ~ few x 107 yrs
– OB stars reach ZAMS while still embedded  increased radiation
pressure may affect outflow dynamics
Massive vs Low-Mass Protostars
Kelvin-Helmholtz
time scale (time to
reach ZAMS):
t
KH
= GM 2/RL
Accretion time scale:
.
tacc = M /Macc
*
Ae
For M ~ 8 M .
*
t
acc
= tKH
And for M > 8 M .
*
the star reaches the
ZAMS while still
accreting – ionizing
radiation affects
outflow & infall
(Yorke 2003)
Formation Mechanisms
Disk accretion: Sufficiently large, non-spherical accretion rates can overcome
radiation pressure (Behrend & Maeder 2001, Yorke & Sonnhalter 2002, Tan &
McKee 2002). Isolated and cluster formation possible.
.
Disk  linked accretion &
outflow may be similar to
low mass protostars, e.g.,
x-winds (Shu et al. 2000)
..
& disk winds (Konigl &
Pudritz 2000).
-4.0
.
Log Mcrit (M . yr -1)
Critical Macc at which all stellar UV
photons are absorbed by in-falling
matter plotted against spectral type
(Walmsley 1995, Churchwell 2002):
B0 O9 O8 O7 O6 O5
-4.2
-4.4
-4.6
-4.8
-5.0
-5.2
30
35
40
Teff (1000 K)
45
50
Formation Mechanisms
.
Coalescence: coalescence of stars/protostars with masses below
the critical value of 8 M (Bonnell & Bate 2002). Radiation
pressure no longer a problem. Requires cluster formation only.
Mergers destroy accretion
disks around lower mass
components and disrupt their
outflows. Resulting massive
star will likely have rotating
circumstellar material but
accretion is not a necessary
criteria for formation.
Outflow Energetics
.
Pf
.
Mf
Lacc
.
Ef
LZAMS
.
Independent studies establish correlations like M ~ Lbol0.6 for:
• The bipolar molecular outflow rate
• The mass accretion rate
• The ionized mass outflow rate
For Lbol = 0.3 to 105 Lsun  strong link between accretion & outflow for most Lbol
e.g. Cabrit & Bertout 1992, Shepherd & Churchwell 1996, Henning et al. 2000
Outflow Energetics
More recently Beuther et al. (2002) added new massive outflows to correlations:
.
Pf
.
Mf
Mcore
Lbol
Mout
Lacc
Mcore
Lbol
LZAMS
.
Mechanical force, Pf vs Lbol correlation holds
.
Mf vs Lbol correlation may be an upper limit
May be a function of the entrainment efficiency?
Mout ~ 0.1 Mcore0.8 (derived from 1.2 mm dust emission)
Dust emission increases with protostar age.
(see also Sarceno et al. 1996, Chandler & Richer 2000,
Richer et al. 2000)
Outflow Energetics
CO Outflows from low and high mass stars show a mass-velocity (MV) relation in the
form of a power law dM(v)/dv ~ vg with g ranging from -1 to -8; g steepens with age and
energy in the flow (e.g. Rodriguez et al. 1982; Lada & Fich 1996; Shepherd et al. 1998;
Richer et al. 2000; Beuther et al. 2002).
A similar relation of H2 Flux-velocity also exists with g between -1.8 and -2.6 for low and
high mass outflows (Salas & Cruz-Gonzalez 2002):
Vbreak differs but overlap where
g(H2 ) ~ g(CO)  association
between CO & H2 in molecular
outflows.
H2 Vbreak versus outflow length, l,
correlation: g steepens and Vbreak
increases for older flows - similar
to molecular flows.
Vbreak ~ l 0.4
g ~ l 0.08
Ionized Jet Energetics
Jet Knot Spacing:
T Tauri stars: Knot spacing = 500-1000 AU, vjet ~ 300 km/s  timescale = 10-20 yrs
HH 80-81: Knot spacing = 2000-3000 AU, vjet ~ 500-1400 km/s  timescale = 10-30 yrs
Cautionary note: HH 30 knots are ejected every few years and knots appear to merge
after a few years. (Stapelfeld et al. in prep). Thus, knot spacing at large distances from
the central source may be more a function of the evolution of the jet structure and
excitation rather than an intrinsic property of the star/disk system.
Ionized wind mass loss rates:
Determined from optical lines [SII] & [OI] for T Tauri stars and radio emission for
massive protostars up to early B spectral type.
.
.
T Tauri jets
Mwind
(Msun/yr)
Massive YSO
Jet/wind
Mwind (Msun/yr)
HH 34
2 x 10-7
Ceph A HW2
8 x 10-7
HH 47
4 x 10-7
HH 80-81
6 x 10-6
HH 111
3 x 10-7
G192.16
1 x 10-6
Cabrit (2002), Rodriguez et al. (1994), Marti et al. (1995), Shepherd & Kurtz (1999)
Ionized Jet Energetics
Ionization fraction in jets:
Collimated jets from low-mass sources appear to be mostly neutral (e.g. Bacciotti &
Eisloffel 1999; Bacciotti, Eisloffel, & Ray 1999; Lavalley-Fouquet, Cabrit, & Dougados
2000). Ionization fraction xe ~ 0.01 to 0.1 within 50 AU from source.
Molecular jets from low-mass Class 0 sources have sufficient momentum to drive
molecular flows (e.g. Richer et al. 1989; Bachiller et al. 1991; and discussion in Cabrit
2002)
The SiO jet from one early B protostar, IRAS 20126, may also have adequate momentum
to power the larger-scale CO flow but uncertainties in assumed SiO abundance makes this
difficult to prove (Cesaroni et al. 1999; Shepherd et al. 2000):
SiO:
CO:
.
Pwind ~ 2 x 10 -1 2 x 10 -9 Msun km/s/yr
[SiO/H2]
.
Pwind ~ 6 x 10 -3 Msun km/s/yr
Young Early B Stars
IRAS 18162-2048,
GGD 27, HH 80-81
CO red & blue-shifted emission
6 cm continuum
HH 80 North
Yamashita et al. (1989)
Aspin et al. (1991)
Marti, Rodriguez, Reipurth
(1993, 1995)
Gomez et al. (1995, 2003)
Stecklum et al. (1997)
Benedettini et al. (2004)
B star cluster with
Lbol ~ 2 x 10 4Lsun
Tdyn ~ 10 6 yrs
Mf ~ 570 Msun
.
Mf ~ 6 x 10 -4 Msun yr -1
GGD 27 ILL powers jet &
illuminates reflection
nebula, Sp. type < B1
CO opening angle > 40o
Collimated, ionized jet, no
apparent UC HII region
 Later than B3?
K band reflection nebula
HH 81
HH 80
POSTER J7: Gomez et al.
GGD 27 ILL
K band & 8.5 mm
K band & 6 cm
IR nebula
GGD 27 ILL
B2 star
Young Early B Stars
7 mm
continuum
& model
CO(1-0)
K-band
G192.16-3.82
YSO
Indebetouw et al. (2003)
Devine et al. (1999)
Shepherd et al. (1998,1999,2001)
Lbol ~ 3 x 10 3Lsun
Tdyn ~ 2 x 10 5 yrs
M2.6mm ~ 10 Msun
Mf ~ 95 Msun
.
Mf ~ 6 x 10 -4 Msun yr -1
.
Pf ~ 4 x 10 -3 Msun km s -1 yr -1
B2 ZAMS star with UC HII region
50o-90o-45o opening angle outflow
Collimation consistent with wind-blown bubble
Evidence for 100AU accretion disk, 1000AU rotating torus
NH3 core not
graviatationally
bound – near end of
accretion phase
[SII]
Young Early B Stars
6 cm
2 cm
H2O masers
jet
VLBA H2O maser
proper motions
 Wide-angle flow
W75 N B Star Cluster
Torrelles et al. (2004)
Shepherd et al. (2003, 2004)
Combined outflows:
Lbol ~ 4 x 10 4Lsun (combined)
Tdyn ~ 2 x 10 5 yrs
M2.6mm ~ 340 Msun
Mf ~ 165 Msun
.
Mf ~ 10 -3 Msun yr -1
.
Pf ~ 2 x 10 -2 Msun km s -1 yr -1
B0.5 – B2 ZAMS stars
Jet seen in ionized gas & water
masers from YSO (unknown
spectral type)
Wide-angle outflow from B2
ZAMS star with UC HII
region
Early B Protostars
IRAS 20126+4104
Ha & CO(1-0)
Lebron et al. (in prep)
Cesaroni et al. (1999,2004, in prep)
Hofner et al (1999,2001, in prep)
Moscadelli et al. (2000, in prep)
Shepherd et al. (2000)
Zhang et al. (1998, 1999)
B0.5 Protostar (not ZAMS
but cm continuum detected)
Precessing jet may create
wider angle CO outflow
Lbol ~ 10 4Lsun
Tdyn ~ 2x10 4 yrs
M2.6mm ~ 50 Msun
.
Mf ~ 50-60 Msun
.
Mf ~ 8 x 10 -4 Msun yr -1
.
Pf ~ 6 x 10 -3 Msun km s -1 yr -1
Evidence for 2000 AU
rotating torus & 10,000 AU
rotating NH3 core
Estimated jet full
opening angle q ~ 40o
(based on SiO
emission) – wider
than typically
observed in low-mass
systems (q ~ 1-2o)
CO(2-1) & 1mm cont
POSTER J16: Lebron et al
POSTER J38: Rosen –
rotating molecular jets
Early B Protostars
IRAS 05358+3543 B Star Cluster
Beuther et al. (2002, 2004)
Sridharan et al. (2002)
Combined outflows:
Lbol ~ 6 x 10 3Lsun (combined)
Tdyn ~ 3-4 x 10 4 yrs
M1.2mm ~ 75 - 100 Msun
(near each protostar)
Mf ~ 20 Msun (combined)
.
Mf ~ 6 x 10 -4 Msun yr -1
Collimated flows are
produced by early B
protostars.
3 or 4 early B protostars (not on Main Sequence yet)
CO & SiO outflows are well collimated
No cm continuum emission detected – perhaps accretion is so
large that UC HII region is quenched? Thus, effects of stellar
UV radiation field absent or minimized.
Early B to Late O Protostars
M 17 new massive YSO
2.2 mm image, 13CO contours trace
disk.
Chini et al. (2004)
Lbol ~ 6 x 10 4Lsun
(B0 – O9 star, 20 Msun)
Mdisk > 110 Msun
Rdisk ~ 20,000 AU (largest known)
Mf ~ unknown
Outflow
Disk seen
in
silhouette
Outflow opening angle > 120o based
on reflection nebula (molecular
outflow not mapped).
Spectra of central source (Ha, Ca II,
and He I)  ongoing accretion.
Massive accretion disks
(Mdisk/M > 5) exist around
*
stars as early as late O type 
turbulent disks, linked
accretion/outflow.
POSTER C22: Nuernberger on the M17 disk
POSTER D15: Yamashita et al. on the M17 disk
See also POSTER D2: Beltran et al. on massive disks
Early B to Late O Protostars
IRAS 16547-4247
Brooks et al. (2003)
Garay et al. (2003)
Lbol ~ 6 x 10 sun (B0 – O9 star
assuming single central star)
Mcore ~ 900 Msun
Mf ~ unknown
Centimeter continuum consistent
with a thermal jet. Synchrotron
emission farther out in jet 
strong B field collimating
ionized gas.
4L
HH 80-81 like jets may be possible in more massive stars
(up to late O spectral type)
2.12 mm image
1.2 mm continuum contours
8.4 GHz contours
Spectra show HV molecular gas
(v ~ 20 km/s) but outflow not
mapped yet.
Assuming v = 1000 km/s, inner
synchrotron knots were ejected ~
140 years ago.
See also POSTER J5: Davis et al. - jets from massive YSOs (IRAS 18151-1208)
and Poster J27: Wolf-Chase et al. - search for jets near HM YSOs
Outflows from Early B (proto)stars
Location of early B stars
with outflow in M vs t plot:
POSTER C9: Forster – Infall/Outflow in massive cores
Poster C16: Klein et al. – Protostar Cores in outer Galaxy
W75 N
G192.16
HH 80-81
ZAMS stars
No jet with UC HII
regions (W75N, G192)
Ae
Jet (HH 80-81)
IRAS 20126
IRAS 05358
Not on ZAMS – little or no
ionizing radiation from
protostar, jet-like
molecular outflows
(Yorke 2003)
Young O Stars
3.6 cm HII region expansion
O6 (proto)star
C34S outflow detected along axis of
UC HII region expansion – outflow
affecting the ionized gas?
No accretion disk. Star located in a
10,000 AU dust-free cavity
C34S(J=3-2)
Red-shifted
G5.89-0.39
Cesaroni et al. (1991)
Acord et al. (1997, 1998)
Faison et al. (1998)
Feldt et al. (1999)
Lbol ~ 3 x 10 5Lsun
Tdyn ~ 3 x 10 3 yrs (very young)
Mf ~ 80 Msun
.
Mf ~ 3 x 10 -2 Msun yr -1
Blue-shifted
Young O Stars
POSTER J12:
Klaassen et al.
Feldt et al. (2003): ~ O5 star
G5.89-0.39 New Results
detected, no disk-like structure
Sollins et al. (2004): SiO(5-4)
but small excess 3.5 mm emission
outflow opening angle ~ 90o.
 circumstellar material.
Outflow axis does not match
axis found in C34S or
CO/HCO+. Dust continuum
POSTER C51:
extension along SiO outflow
Sollins on G5.89
axis.
H, K, & L’ NIR image
Watson et al. (2002):
CO outflow larger
than SiO. Outflow
roughly ^ to UC HII
region expansion.
Lbol ~ 3 x 10 5Lsun
Tdyn = 7.5 x 10 3 yrs
Mf > 77 Msun
.
Mf > 10 -3 Msun yr -1
Multiple flows?
O Protostars
POSTER C2:
Beuther – submm lines &
continuum in
Orion
Orion
H2 ‘fingers’ 
Explosive event forming fragmented stellar
wind bubble (McCaughrean & Mac Low
1997)
Or a precessing flow (Rodriguez-Franco et
al. 1999)
Subaru J, H, K Images
O Protostars
POSTER J21: Satoko
– SiO in Orion
H2 and HV blue-shifted CO
Orion
?
Snell et al. (1984)
Plambeck, Wright, Carlstrom (1990)
Dougados et al. (1993)
Menten & Reid (1995)
Chernin & Wright (1996)
Greenhill et al. (1998, in prep)
Doeleman et al. (2004)
And many others
Lbol >10 4Lsun
Tdyn ~ 1.5 x 10 3 yrs (very young)
Mf ~ 8 Msun
.
Mf ~ 5 x 10 -3 Msun yr -1
Assuming a single source powers the outflow:
Outflow opening angle ~ 90o – 120o. Low collimation even at
highest CO velocities.
Elongated emission seen in 7mm continuum within 25 AU of
protostar (source I)  disk or outflow?
SiO masers trace outflow opening angle and slow equitorial flow.
SiO masers
O Protostars
DR21
Roelfsema et al. (1989)
Garden et al. (1991)
Davis & Smith (1996)
Smith et al. (2004, in prep)
Lbol ~ 3 x 10 5Lsun
Tdyn > 5 x 10 4 yrs
Mf ~ 3000 Msun
.
Mf < 6 x 10 -2 Msun yr -1
Blue: 3.6mm
green: 4.5mm
orange: 5.8mm
red: 8mm
POSTER S8: Smith et al.
– Spitzer images of DR21
DR21 outflow powered by mid-IR cluster of OB stars,
most have no circumstellar material.
A newly discovered O star DR21:IRAC-4 appears to
have a hot, accreting envelope: Lacc > L
*
A few recent significant contributions
Characteristics of OB outflows (and accretion disks).
A few references not already mentioned (there are MANY more):
• Billmeier, Jayawardhana, Marengo, Mardones, Alves (POSTER D3) – Mid-IR imaging of Massive
Young Stars
• Forster (POSTER C9) – Infall & Outflow in Massive Cores
• Kim, Churchwell, Friedel, Sewilo (POSTER J11) – Molecular Outflows from Massive Stars
• Varricatt, Davis, Ramsay-Howat, Todd (POSTER J23) – A Near Infrared Imaging Survey of High
Mass Young Stellar Candidates
•
•
•
•
•
•
•
•
Beuther, Schilke, Sridharan, Menten, Walmsley, Wyrowski (2002) – Massive Molecular Outflows
Beuther, Schilke, Gueth (2004) – Massive Molecular Outflows at High Spatial Resolution
Henning, Schreyer, Launhardt, Burkert (2000) – Massive YSOs with Molecular Outflows
Molinari, Testi, Rodriguez, Zhang (2002) – The Formation of Massive Stars. I. High-Resolution
Millimeter and Radio Studies of High-Mass Protostellar Candidates.
Ridge et al. (2002) – Massive Molecular Outflows
Shepherd, Testi, Stark (2003) – Clustered Star Formation in W75N
Su, Zhang, Lim (2004) – Bipolar Molecular Outflows from High-Mass Protostars
Zhang, Hunter, Brand, Sriharan, Molinari, Kramer, Cesaroni (2001) – Search for CO Outflows
toward a Sample of 69 High-Mass Protostellar Candidates: Frequency of Occurrence
Impact of Luminosity on Outflow Structure
Expect high luminosity of massive protostars to play an important role in
• Dynamical Evolution
• Outflow (& disk) thermal structure and morphology
Review by Konigl (1999) summarizes the issues:
• Enhanced field-matter coupling near disk surface due to UV radiation may cause
higher accretion rates and mass outflow rates (e.g. Pudritz 1985).
• Disk photo-evaporation could create a low-velocity disk outflow (e.g. Hollenbach
et al. 1994; Yorke & Welz 1996).
• Radiation pressure higher for dusty gas (e.g. Wolfire & Cassinelli 1987), may
contribute to flow acceleration and also lead to the ‘opening up’ of the outflow
streamlines (e.g. Konigl & Kartje 1994).
• Expect a strong, radiatively driven stellar wind (although momentum factor of 10100 too low to power observed molecular outflow).
Consider an example of how radiatively-driven stellar winds could potentially affect
outflow dynamics (Yorke & Sonnhalter 2002):
Frequency-dependent opacity calculations – 30Msun and 60Msun molecular cores which
collapse to produce a protostar (M* ~ 30Msun & 34Msun, respectively) with disk and
radiatively-induced outflow.
Radiatively-Induced Outflows
F30: M* = 31 Msun in 2.4x104 yrs
104 yrs
17 Msun
2.1x104 yrs
31 Msun
F60: M* = 34 Msun in 4.5x104 yrs
Density: gray
scale & white
contours
104 yrs
13 Msun
3x104 yrs
34 Msun
2x104 yrs
28 Msun
3.5x104 yrs
34 Msun
2.5x104 yrs
33 Msun
4.5x104 yrs
34 Msun
Velocity:
arrows
1.5x104 yrs
24 Msun
1.9x104 yrs
29 Msun
2.2x104 yrs
31 Msun
2.4x104 yrs
31 Msun
Carbon grain
temperature:
solid black
contours
Silicate grain
temperature:
dotted contours
Numbers: age
& M*
Stellar radiation softens at outflowRadiatively-induced outflow encased
shock boundry  cloud collapses
by shock fronts, relatively poorly
along flow axis to produce wellcollimated flow.
collimated jet.
Yorke & Sonnhalter 2002
Mass loading impact on outflows
X-winds:
T Tauri star
FU Ori
Outburst
Bstar (G)
380
380
380
1500
R* (Rsun)
2.5
2.5
4
4
M* (Msun)
0.5
0.5
2.5
2.5
Macc (Msun yr-1)
10-8
10-5
8x10-5
8x10-5
Rx/R*
5
0.7
0.45
1
.
B9 Protostar
B9 protostar
(Low B field) (High B field)
Shu et al. (1994) – ‘X-point’ (outflow launching point) ~ 5 R in a typical T Tauri star.
*
Hartmann & Kenyon (1996) – FU Ori stars in outburst have no hot UV continuum:
magnetospheric accretion columns have been crushed onto stellar surface.
Even late B stars have high enough accretion rate to crush accretion columns.
 Massive star outflows can not be due to X-winds from truncated disks.
X-wind from rapidly rotating protostar (Shu et al. 1998) or pure disk-wind
(Konigl & Pudritz 2001).
Mass loading impact on outflows
.
Ouyed & Pudritz (1999) – Magnetized Disk-Wind Simulations: For Mw ~ 10-8 Msun yr -1,
disturbances
appear to grow producing instabilities & shocks – outflows become episodic.
.
As Mw increase 3 orders of magnitude, jet behavior goes from episodic to steady ejection.
Ideal MHD assumed: all solutions re-collimate.
Anderson, Li, Krasnopolsky & Blandford (POSTER
mass loading from the
. D17) – How
disk affects structure and dynamics of the wind. Mw = 3 x 10 -5 to 3 x 10 -10 Msun yr -1
Degree of collimation increases with mass loading up to ~10 -5 Msun yr -1.
Re-collimation of the wind expected for ideal MHD where trecomb >> tdynamical and plasma
and B fields are frozen-in. But, ideal MHD assumptions break down as:
• Plasma T and r increase
Expected for outflows & disks
• Turbulence in the disk or wind increases
associated with luminous YSOs.
• B field decreases
Not clear what the implications are, will this affect outflow?
Disk turbulence - impact on outflows
Gravitational instabilities induce spiral density waves; expected to be prevalent if
Mdisk > 0.3 M*, (Laughlin & Bodenheimer 1994). Toomre Q stability parameter (Yorke,
Bodenheimer & Laughlin 1995):
Q = cs W / p GS = 56 (M*/Msun)1/2 (Rd /AU) -3/2 (Td /100K)1/2 (S /103 g cm -3)
Where cs = local sound speed, W = epicycle frequency of disk, S = disk surface density, Rd
= disk radius & Td = disk temperature.
For Q < 1 disk susceptible to local gravitational instability and axisymmertric
fragmentation.
. . Q = 1-2 disk susceptible to gravito-turbulence (Gammie 2001): Could be a
significant angular momentum transport.
TALK: Matzner – Low-mass star formation: initial conditions and disk instabilities.
Irradiation quenches fragmentation due to local instability because disk temperature is
raised above parent cloud temperature.
POSTER D18: Bodo et al. – Spiral density wave generation by vortices in accretion disks
Early B (proto)stars appear to have Md /M* > 0.3 and can be as high as 1-10.
Example: Md ~ 3 Msun , M* ~ 8 Msun Assume Td = 100 K & Rd = 70 AU, then Q ~ 0.5
 disk locally unstable, higher angular momentum transport through disk?
Will the outflow be less efficient for a given Macc ?
Disk turbulence - impact on outflows
POSTER:
Observations (Richer et al. 2000):
Outflow Force
Fco
vw
------------------ = ------------= f ---.
Accretion Force
Macc vkep
vkep
vw
f ----- ~ 0.3 (1/1)
vkep
.
Mw
where f = -----.
Macc
for X-winds
2
Lbol = Lacc
~ 0.03 (10/1) for Disk winds
Lbol = ZAMS
1
.
.
Coffey et al – low
mass jet can
carry away
adequate angular
momemtum.
vw
Log f --vkep
Decrease in Mw / Macc
between Lbol = 1 and 104 Lsun ?
Errors are too large now to say.
0
-1
-2
-1
0
1 2 3 4
Log Lbol (Lsun )
5
6
Deflected Infall?
Moutflow ~ few x M* for T Tauri stars
Moutflow >> M* for OB protostars.
Churchwell (1999) points out that entrainment & swept-up mass do
not appear to be able to account for large observed outflow masses.
Circulation models: Moutflow > M*
easy (Richer et al. 2000). Most
infalling material diverted
magnetically at large radii into slowmoving outflow along the polar
direction, infall proceeds along the
equitorial plane (Fiege & Henriksen
1996: Lery, Henriksen, Fiege 1999;
Aburihan et al 2001).
Summary
• Mid- to early-B protostars and late O protostars have
accretion disks & outflows that can be well-collimated.
• Once UCHII region forms, associated ionized outflows have
strong wide-angle winds. Jet component not detected?
Must be verified.
- This would be unlike low-mass flows where there is
evidence for a 2-component wind (jet+wide-angle) in
older sources (e.g. Arce & Goodman 2002; Solf 2000).
• Mid to early O stars: Outflows appear to be poorly collimated.
Explosive events  coalescence a possibility in some cases.
• Expect changes in outflow dynamics due to increased:
- Luminosity (accretion & stellar)
- Mass-loading onto the wind
- Disk turbulence
Massive Star Formation & Outflow Reviews
1.
2.
3.
4.
5.
6.
7.
8.
Cesaroni 2004, in press “Outflow, Infall, and Rotation in High-Mass
Star Forming Regions”
Churchwell 1998, in The Origin of Stars & Planetary Systems, NATO
Science Series 540, p 515 “Massive Star Formation”
Churchwell 2002, ASP conf series, 267, 3 “The Formation and Early
Evolution of Massive Stars”
Garay & Lizano, 1999, PASP, 111, 1049 “Massive Stars: Their
Environment & Formation”
Konigl, 1999, New Astronomy Reviews, 43, 67 “Theory of Bipolar
Outflows from High-Mass Young Stellar Objects”
Lizano, 2002, Nature, 416, 29L “Astronomy: How Big Stars are Made”
Richer, Shepherd, Cabrit, Bachiller, Churchwell, 2000, in Protostars &
Planets IV, p 867 “Molecular Outflows from Young Stellar Objects”
Shepherd, 2003, ASP conf series, 287, 333 “The Energetics of Outflow
and Infall from Low to High Mass YSOs”