Outflows and Jets: Theory and Observations

1
Outflows and Jets Theory and Observations
Winter term 2006/2007 Henrik Beuther Christian
Fendt
20.10 Introduction Overview (H.B.
C.F.) 27.10   Definitions, parameters, basic
observations (H.B) 03.11   Basic theoretical
concepts models I (C.F.) 10.11   Basic
theoretical concepts models II (C.F.) 17.11  
Observational properties of accretion disks
(H.B.) 24.11   Accretion disk theory and jet
launching (C.F.) 01.12   Outflow-disk connection,
outflow entrainment (H.B.) 08.12   Outflow-ISM
interaction, outflow chemistry (H.B.) 15.12  
Theory of outflow interactions Instabilities
Shocks (C.F.) 22.12, 29.12 and 05.01     
Christmas and New Years break 12.01   Outflows
from massive star-forming regions
(H.B.) 19.01   Radiation processes (H.B.
C.F.) 26.01   Observations of AGN jets (Guest
speaker Klaus Meisenheimer) 02.02   AGN jet
theory (C.F.) 09.02   Summary, Outlook,
Questions (H.B. C.F.)
More Information and the current lecture files
http//www.mpia.de/homes/beuther/lecture_ws0607.ht
ml beuther_at_mpia.de, fendt_at_mpia.de
2
Importance of massive stars
Optisch

• Great impact on ISM and
• star clusters, LµM3
• Outflows and Jets
• UV-radiation
• Supernovae
• The majority of all stars
• form in clusters, massive
• stars exclusively.
• They produce all heavy
• elements

Problem With the typical accretion rates known
from low-mass star formation, the radiation
pressure of the forming massive stars
would revert any infall for protostars gt10Msun.
3
Massive Star Formation
Modified classical scenario Wolfire Cassinelli
1987 Jijina Adams 1996 Yorke Sonnhalter
2002 Norberg Maeder 2002 Keto 2002,
2003 Krumholz et al. 2005, 2006 Banerjee
Pudritz 2005
Coalescence and competitive accretion
scenario Bonnell et al. 1998, 2004, 2004 Stahler
et al. 2000 Bally Zinnecker 2005

• How to differentiate between both scenario?
• Molecular outflows and accretion disks
• Fragmentation and global collapse

4
Jet launching and early collimation
magnetic accretion-ejection structures
(Ferreira et al 1995-1997) 1) disk material
diffuses across magnetic field lines 2) is
lifted upwards by MHD forces, then 3)
couples to the field and 4) becomes
accelerated magnetocentrifugally and 5)
collimated






Banerjee Pudritz 2006
Magnetic field lines (thick) and streamlines
(dashed)

• If F__ decreases --gt gas pressure gradient
  lifts plasma
• from disk surface
  
• If F increases --gt radial centrifugal
  acceleration of plasma

5
Outflow entrainment

• Various outflow-entrainment models
  jet-entrainment and wide-angle winds
• are likely the two most reasonable mechanisms.
• Observational tools like pv-diagrams,
  mv-diagrams and various different
• jet/outflow tracers allow to constrain the
  models.

Arce et al. 2007
6
Results of early massive outflow research
Seem to be ubiquitous phenomena Very massive
and energetic Seemingly less collimated than
low-mass flows Different entrainment scenarios
proposed (deflection, winds...)
However, these results were based on small
samples and poor angular resolution (between
21'' and 60'')
7
Massive molecular outflow maps
Grey 1.2mm continuum, contours CO(2-1) wing
emission
IRAM 30m, Beam 11''

• - Assuming momentum conservation pout Moutvout
  Mjetvjet dMjet/dt vjett pjet
• - With a jet/outflow velocity ratio vjet/vout20
  and a ratio of outflow rate to
• the accretion rate of 0.3, one can estimate
  accretion rates
• --gt Mean accretion
  rate 10-4 Msun/year
• high enough to
  overcome radiation pressure

Beuther et al. 2002
8
Outflow masses versus core masses
.
.
.
Accretion rate Macc facc Mcore/tff
deflection efficiency fr Mjet/Macc
Multiply both equations and assume momentum
conservation frfacc Mjet/Mcore vout/vjet x
Mout/Mcore constant
.
Macc is approximately a linear function of
Mcore (and the mass of the jet is proportional to
the core mass)
9
Outflow properties
Mechanical Force Mass
Outflow rate Mechanical
L
10
Flashlight effect

• With outflow cavities the average gas
• temperatures are cooler.
• Gravitational force stronger in eq. plane.
• Radiation escapes through outflow cavities.
• --gt Reduction of radiation pressure and
• angular momentum problem.

Black gravity Red no cavity Green, blue,
purple 5, 10, 15o opening angle
Krumholz et al. 2005 (also Yorke Sonnhalter
2002)
11
The pre-UCHII region IRAS053583543
Lbol 6.3x103 Lsun no cm emission --gt pre-UCHII
region
Beuther et al. 2002
12
The Outflows in IRAS 194102336
IRAM 30m, CO(2-1), Beam 11''
Lbol 6.3x103 Lsun very weak cm emission --gt
HCHII region, pre-UCHII region
13
Shocked H2 emission in IRAS 18151-1208

• Lbol 2x104 Lsun
• no cm emission
• pre-UCHII region
• Spectroscopy of the H2
• features reveals similar
• characteristics to low-
• mass outflows

Davis et al. 2004
14
A centimeter continuum jet in IRAS 16547-4247
K-band 1.2mm
8.4 GHz
Lbol 6x104 Lsun Collimated thermal
non-thermal jet Brooks et al. 2003 Graray et
al. 2003
15
A young UCHII region G192
Lbol 3x103 Lsun Small UCHII at center Collimat
ion con- sistent with wind- blown bubble
Color contours CO(1-0) Inlay mm continuum
Shepherd et al. 1998, 1999 Devine et al. 1999
SII
16
The UCHII region W75
Cluster of B0.5 to B2 stars associated with
UCHIIs Lbol 4x104 Lsun Wide-angle
large-scale outflow, is that associated with the
small-scale maser outflows?
Shepherd et al. 2003, 2004
Torrelles et al. 2003
17
The luminous UCHII region G5.89
Lbol 3x105 Lsun Harbours O5 star Multiple
outflows
Sollins et al. 2004 Watson et al. 2002 Feldt et
al. 2003 Puga et al. 2006
18
Position velocity diagrams
192171651
230335951
201264104
202933952
Beuther et al. 2004
19
Approximate Timescales for massive outflows
W75 N G192.16
ZAMS No real jet with UCHIIs
Pre-ZAMS Pre-UCHII Jet-like outflows
Adapted from Shepherd 2004
20
An evolutionary scenario
Beuther Shepherd 2005
21
Summary
Massive molecular outflows are ubiquitous
phenomena. Jet-like outflows exists at least
up to early-B and late-O-type stars. Like in
low-mass star formation, some outflows are likely
driven by jet-entrainment whereas others are
consistent with wide-angle winds.
Estimated accretion rates are high enough to
overcome radiation pressure. Flashlight
effect additional helps reducing radiation
pressure in equatorial plane. Hence the
observations support the classical scenario that
massive star formation proceeds similarly to
low-mass star formation. The observations
suggests tentatively an evolutionary scenario.
22
Outflows and Jets Theory and Observations
Winter term 2006/2007 Henrik Beuther Christian
Fendt
20.10 Today Introduction Overview (H.B.
C.F.) 27.10   Definitions, parameters, basic
observations (H.B) 03.11   Basic theoretical
concepts models I (C.F.) 10.11   Basic
theoretical concepts models II (C.F.) 17.11  
Observational properties of accretion disks
(H.B.) 24.11   Accretion disk theory and jet
launching (C.F.) 01.12   Outflow-disk connection,
outflow entrainment (H.B.) 08.12   Outflow-ISM
interaction, outflow chemistry (H.B.) 15.12  
Theory of outflow interactions Instabilities,
Shocks (C.F.) 22.12, 29.12 and 05.01     
Christmas and New Years break 12.01   Outflows
from massive star-forming regions
(H.B.) 19.01   Radiation processes (H.B.
C.F.) 26.01   Observations of AGN jets (Guest
speaker K. Meisenheimer) 02.02   AGN jet theory
(C.F.) 09.02   Summary, Outlook, Questions (H.B.
C.F.)
More Information and the current lecture files
http//www.mpia.de/homes/beuther/lecture_ws0607.ht
ml beuther_at_mpia.de, fendt_at_mpia.de