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Radiation Feedback on Star and Planet Formation
With special thanks to
James Owen, CathieTaurus
Clarke
(IoA);
– Spitzer Space Telescope
Al Glassgold (Berkeley);
Jeremy Drake, John Raymond (CfA);
Richard Alexander (Leiden)
Barbara Ercolano
(Institute of Astronomy, Cambridge; University College London)
How do stars form?
Molecular Cloud Complex
Star Forming Globule
Galaxy
Planetary System + Debris Disk
Circumstellar Disk
Radiative Transfer : Why?
How is the medium affected by the radiation?
How is radiation reprocessed by the medium?
NGC 346 - SMC
Orion
Monte Carlo Radiative Transfer: The Basics
The 3D grid
The primary
radiation source(s)
MOnte CArlo SimulationS of Ionised Nebulae
(Version 3.03.00, Ercolano et al., 2003, 2005,2008)
…can treat…
Arbitrary geometries
Multiple grids of arbitrary resolution
Density &/or chemical inhomogeneities
Multiple/diffuse/non central ionising sources
3D photoionisation &/or dust radiative transfer
 X-ray ionisation and heating
…can provide…
Emission line intensity tables
Spectral energy distributions
3D (gas &/or dust) temperature distributions
3D ionisation structures
Emission line(s), continuum images
Some Recent Applications
• Metallicity of HII regions & Star Forming Galaxies
(Ercolano, Bastian & Stasinska 2007, Ercolano, 2009, Ercolano, Wesson & Bastian, 2009, in prep)
• Dust in the early Universe from Type II SNe (SEEDs)
(Barlow et al. 2005, Sugerman et al. 2006, Ercolano et al. 2007, Barlow et al., 2009, in
prep; Wesson et al., 2009, in prep)
• X-ray fluorescence studies
(Drake, Ercolano & Swarz, 2007; Drake & Ercolano 2008a; Drake & Ercolano 2008b,
Ercolano et al., 2008b, Testa et al., 2008)
• Radiation pressure & the formation of massive stars
(Ercolano and Clarke, in prep)
• X-ray irradiation of protoplanetary disks
(Ercolano et al. 2008c, Ercolano, Drake & Clarke, 2009a,b, Drake et al., 2009,
Glassgold , Ercolano & Drake, 2009, sub; Schisano, Ercolano & Guedel, 2009, sub,
Ercolano & Clarke, 2009, in prep; Owen, Ercolano & Clarke in prep)
• Photoionisation feedback in Star Forming Regions
(Dale, Ercolano & Clarke, 2007)
Feedback on Low Mass Star & Planet Formation
In what environments is the formation of
Taurus – Spitzer Space Telescope
terrestrial and giant planets favoured?
What is the effect of irradiation on
planetary atmospheres?
Guedel et al., 2007
What drives the dispersal of circumstellar
disks? On what timescales?
Photoevaporation
MRI
Lx ~ 1029-1032erg/s
Dead Zone
Proto-Earth
Proto-Jupiter
Viscous evolution predicts the following
time
high mass
high accretion rate
low mass
low accretion rate
Observations instead show the following
t~106yrs
Rare transition disk
t~107yrs
Disk Dispersal – The observations
•Two-timescale phenomenon
- Global disk lifetime: few 106 yrs
- Dispersal phase:
few 105 yrs
•Accretion rates ~ 10-11 – 10-7 Msun/yr
Modelling photoevaporating disks: HOW?
1) Radiative Transfer (MOCASSIN)
a) 2D (at least)
b) gas (photoionisation) + dust
2) Hydrodynamics (ZEUS)
3) Viscous Evolution
Previous studies (Glassgold et al., 1997, 2004, 2008,
Meijerink et al., 2008, Alexander et al., 2004, Gorti &
Hollenbach 2008a,b)
all missed some of the above.
Log Height [AU]
The Density Distribution
MOCASSIN:
Tgas, Tdust
Ionisation structure
D’Alessio et al. 2001
M = 0.7 Msun, Teff = 4000K
Hydrostatic Eqlbm:
Density structure
Log Radius [AU]
Log Height [AU]
The Density Distribution
Ercolano et al. 2009
Log Radius [AU]
Log Height [AU]
The Density Distribution
D’Alessio et al. 2001
M = 0.7 Msun, Teff = 4000K
Log Radius [AU]
Log Height [AU]
The Density Distribution
Total photoevaporation rate
of ~2e-9 Msun/yr
Ercolano et al. 2009
Log Radius [AU]
Owen, Ercolano & Clarke, 2009, in prep
Cumulative mass loss rate (Msun/yr)
Owen, Ercolano & Clarke 2009, in prep
1.5 x 10-8 Msun/yr
Radius (AU)
Disk Dispersal Conclusions:
X-rays from the central pre-main sequence star drive a
photoevaporative wind able to disperse the disk within
the timescales observed
Further Questions
•How does it all fit in with planet formation? Can we
apply these methods to planetary atmospheres?
•How does dispersal proceed in different environments
(metallicity, stellar mass, X-ray flux)
•What observational diagnostics can we use?
Ionizing radiation feedback:
High Mass Star and Cluster Formation
1) Gas is removed from the centre of the potential
(Negative feedback)
2) Gas is compressed behind the
ionisation front – collect &
collapse – (Positive feedback)
L*
What is the effect of ionisation feedback
(e.gthe
Dale
et al. 2007,of
from massive stars on
formation
Gritschneder et al. 2008)
successive generations of stars?
Gritschneder et al 2009
Dale , Ercolano & Clarke 2007
Summary
The interplay of gas dynamics and radiation is at the
basis of many fundamental astrophysical questions.
Some examples in star formation include:
1) Low Mass Star/Planet Formation – Protoplanetary
disk evolution and dispersal
2) High mass star formation – Radiation Pressure on
dust grains
3) High mass star formation – Ionisation Feedback &
Triggered star formation
Future
Questions can only be answered if a solid theoretical
framework can be built to match the observational
constraints available.
1) Efficient, multidimensional and frequency resolved
radiative transfer coupled to hydrodynamic needed
2) Codes must be able to simulate the observed light –
ionisation as well as molecular chemistry is needed
(Herschel/JWST)
3) Our efforts to answer some of the fundamental star
formation questions are likely to results in techniques
which will have broader applicability
Thank You for your attention
Molecular Cloud Complex
Star Forming Globule
Galaxy
Planetary System + Debris Disk
Circumstellar Disk
Thank You
X-ray + EUV Photoevaporation Rates
Total photoevaporation rate
of ~2e-9 Msun/yr
Ercolano et al. 2009
X-ray
wouldon
work
like a EUV switch
modelevolution
Alexander,
based
a description
of viscous
Clarke et al. (2001); Matsuyama et al. (2003); Ruden (2004)
Viscous evolution
Photoevaporation rate
Viscous + photoevaporation
Disk Dispersal: the observations I
Haisch, Lada & Lada, 2005
Primordial disks disperse
after a few Myr
The transition phase is fast (105yrs)
Only 10% of disks have inner holes
(but see Sicilia-Aguilar et al., 2008- but
also see Ercolano & Clarke, 2009)
Owen, Ercolano & Clarke, 2009, in prep
Common
Underestimates
radiationSF: Some
Feedback
on High Mass
OpenAssumptions:
Questions
pressure at the first strike
- frequency-independent (grey) grains
(e.g. Krumholz
et al.on
2009)
How does radiation
pressure
dust affect
the formation
Dust Destruction
Radius
p = L* / c
of massive stars by accretion?
- 1D treatment of radiative transfer
Radiative transfer
multi 2003)
(e.g. must
Edgarbe
& Clarke
dimensional and frequency resolved
sdswe
L*
Cannot treat non-spherical
(e.g. disk) geometries
What is the effect of ionisation feedback
from massive stars on the formation of
successive generations of stars?
Ionizing radiation feedback:
High Mass SF: Some Open Questions
1) Gas is removed from the centre of the potential
(Negativepressure
feedback)on dust affect
How does radiation
the formation of massive stars by accretion?
2) Gas is compressed behind the
ionisation
– collect &
Radiative transfer
mustfront
be multi
collapse
– (Positive
feedback)
dimensional and
frequency
resolved
L*
(e.g Dale et al. 2007,
Gritschneder et al. 2008,
Pawlik& Joop 2008, Altay
et al 2008)
What is the effect of ionisation feedback
from massive stars on the formation of
successive generations of stars?
Ionizing radiation feedback:
High Mass SF: Some Open Questions
1) Gas is removed from the centre of the potential
(Negativepressure
feedback)on dust affect
How does radiation
the formation of massive stars by accretion?
2) Gas is compressed behind the
ionisation
– collect &
Radiative transfer
mustfront
be multi
collapse
– (Positive
feedback)
dimensional and
frequency
resolved
L*
(e.g Dale et al. 2007,
Gritschneder et al. 2008,
Pawlik& Joop 2008, Altay
et al 2008)
What is the effect of ionisation feedback
from massive stars on the formation of
successive generations of stars?