Docstoc

massive

Document Sample
massive Powered By Docstoc
					     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.html
                                       beuther@mpia.de, fendt@mpia.de
                                         Importance of
                                         massive stars
                    Optisch
                                      Great impact on ISM and
                                      star clusters, LM3

                                      - Outflows and Jets

                                      - UV-radiation
Problem: With the typical accretion
                                      - Supernovae
rates known from low-mass star
formation, the radiation pressure     - The majority of all stars
of the forming massive stars would      form in clusters, massive
revert any infall for protostars        stars exclusively.
>10Msun.
                                      - They produce all heavy
                                        elements
                    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




                Pudritz & Banerjee
                2005
Coalescence and competitive accretion scenario:
Bonnell et al. 1998, 2004, 2004
Stahler et al. 2000
Bally & Zinnecker 2005

                                                                        Bally & Zinnecker 2005

          How to differentiate between both scenario?
          - Molecular outflows and accretion disks
          - Fragmentation and global collapse
          -…
            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)
                       F||
             F_|_




If F_|_ decreases --> gas pressure gradient lifts plasma
                      from disk surface
If F|| increases --> radial centrifugal acceleration of plasma
                      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
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'')
               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/vout~20 and a ratio of outflow rate to
  the accretion rate of ~0.3, one can estimate accretion rates:
                      --> Mean accretion rate 10-4 Msun/year
                        high enough to overcome radiation pressure   Beuther et al. 2002
         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)
Outflow rate   Mechanical L
                              Outflow properties
                               Flashlight effect




- With outflow cavities the average gas         Black: gravity
  temperatures are cooler.                      Red: no cavity
- Gravitational force stronger in eq. plane.    Green, blue, purple: 5, 10, 15o opening angle
- Radiation escapes through outflow cavities.
  --> Reduction of radiation pressure and                        Krumholz et al. 2005
      angular momentum problem.                                  (also Yorke & Sonnhalter 2002)
The pre-UCHII region IRAS05358+3543

        IRAM 30m data
        Grey: 1.2mm
        Contours:CO(2-1)




Lbol ~ 6.3x103 Lsun; no cm emission --> pre-UCHII region
                                                           Beuther et al. 2002
             The Outflows in IRAS 19410+2336
                                   PdBI + 30m, CO(1-0), Beam 3.9'' x 3.6''
  IRAM 30m, CO(2-1),
      Beam 11''             blue wing               red wing             both




Lbol ~ 6.3x103 Lsun; very weak cm emission --> HCHII region, pre-UCHII region
                                                                     Beuther et al. 2003
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
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
  A young UCHII region: G192


                               Lbol ~ 3x103 Lsun

                               Small UCHII at
                               center

                               Collimation con-
                               sistent with wind-
                               blown bubble

Color contours: CO(1-0)
Inlay: mm continuum
                               Shepherd et al.
                               1998, 1999
                               Devine et al. 1999




                                  [SII]
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
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
       Position velocity diagrams
19217+1651                      23033+5951




  20126+4104                    20293+3952




                  IRAS20126+4104,
                  Lebron et al. 2006
                                         Beuther et al. 2004
  Approximate Timescales for massive outflows

      W75 N
      G192.16

ZAMS
No real jet with UCHIIs



       IRAS 20126
       IRAS 05358


Pre-ZAMS & Pre-UCHII
Jet-like outflows




                          (Yorke 2004)
                                         Adapted from Shepherd 2004
An evolutionary scenario




                           Beuther & Shepherd 2005
                        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.
     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.html
                                       beuther@mpia.de, fendt@mpia.de

				
DOCUMENT INFO
Shared By:
Categories:
Tags:
Stats:
views:12
posted:8/5/2011
language:English
pages:22