The Star Cluster Population of M51 · O b s e r v a tio n s Arches Stolte et al. 2008. N e e d f o...
Transcript of The Star Cluster Population of M51 · O b s e r v a tio n s Arches Stolte et al. 2008. N e e d f o...
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Testing the Universality of the Stellar IMF with the E-ELT
Nate Bast ian ( IoA)
Michael Meyer (ETH Zurich)Kev in Covey (Cornell)
Selma De Mink (Utrecht)
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Quotes“Resorting to altering the initial mass function
is a sign of moral weakness” Mike Edmunds
“All problems in extragalactic astrophyics can be solved by a suitable choice of the IMF” Romeel Dave
IMF is one of the best hopes to constrain the process of star-formation
Nearly all stellar properties of galaxies and populations are controlled by the IMF at some level.
“... the last refuge for scoundrels” Mike Edmunds
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IMF: Resolved Star Approach
ONC - VLT/ISAAC
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IMF: Resolved Star Approach
ONC - VLT/ISAAC
Muench et al. 2002
Mtot ~ 103 Msun
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IMF: Resolved Star Approach
high mass clusters rare -> far away -> can’t get their low mass stars
due to stochasticity, need IMF in many clusters over the full mass range
ONC - VLT/ISAAC
Muench et al. 2002
Mtot ~ 103 Msun
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IMF: Resolved Star Approach
high mass clusters rare -> far away -> can’t get their low mass stars
due to stochasticity, need IMF in many clusters over the full mass range
ONC - VLT/ISAAC
Muench et al. 2002
E-ELT same sensitivity as has been done for the ONC out to ~4kpc - 10-20 MJupiter
Mtot ~ 103 Msun
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Need for ever deeper Observations
Arches
Stolte et al. 2008
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Need for ever deeper Observations
Arches
Stolte et al. 2008
Kim et al. 2006
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cluster distance (kpc) Mass (Msun) lower mass limit
Cygnus OB2 1.7 ~104 < 20 MJupiter
Trumpler 14 2.8 ~ 104 < 20 MJupiter
NGC 3603 6.5 few * 104 < 0.02 Msun
Westerlund 1 5.5 >105 < 0.02 Msun
Arches 8 few * 104 < 0.02 Msun
E-ELT: reaching into the substellar mass regime for all known Galactic young massive clusters
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cluster distance (kpc) Mass (Msun) lower mass limit
Cygnus OB2 1.7 ~104 < 20 MJupiter
Trumpler 14 2.8 ~ 104 < 20 MJupiter
NGC 3603 6.5 few * 104 < 0.02 Msun
Westerlund 1 5.5 >105 < 0.02 Msun
Arches 8 few * 104 < 0.02 Msun
E-ELT: reaching into the substellar mass regime for all known Galactic young massive clusters
While crowding will be an issue in the centers of the clusters, limits still possible outside the cluster cores
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de Marchi, Paresce, & Portegies Zwart 2009, in prep.
MC
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de Marchi, Paresce, & Portegies Zwart 2009, in prep.
MC
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de Marchi, Paresce, & Portegies Zwart 2009, in prep.
MC
-The form of the (low mass) IMF doesn’t depend on formation epoch
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Wyse et al. 2002
Ursa Minor dSph
M92
-The form of the (low mass) IMF doesn’t depend on densityor dark matter content.
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Wyse et al. 2002
Ursa Minor dSph
M92
-The form of the (low mass) IMF doesn’t depend on densityor dark matter content.
It has been claimed that the IMF may be dependent on the SFR density, hence it should vary with redshift.
Local stellar clusters (ONC, Arches, NGC 3603) have SFR densities orders of magnitudes larger than high-z galaxies.
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IMF variations in Extreme Environments
Smith et al. 2006
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IMF variations in Extreme Environments
Direct detection of low mass starsPoint sources: I=20-23, K=20.5-23.5
Smith et al. 2006
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IMF variations in Extreme Environments
Direct detection of low mass starsPoint sources: I=20-23, K=20.5-23.5
need S/N > 100
Meyer & Greissl 2005
Smith et al. 2006
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High Redshift Universe
Pettini et al. 2000
UV spectral features (CIV)
sensitive to the shape of the high mass end of the IMF
can compare with UV surveys of local star-forming regions
(e.g. Pellerin 2007)
Quider et al. 2009
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Many Indirect Studies Report IMF Variations
Larson 2005
Baugh et al. 2005
Weidner, Kroupa, Pflamm-Altenburg et al. 2006, 2007, 2009
Wang et al. 2006
Fardal et al. 2007
Maness et al. 2007
Mieske & Kroupa 2008
Wilkins et al. 2008a,b
Dave 2008
Hoversten & Glazebrook 2008
van Dokkum 2008
Meurer et al. 2009
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Many Indirect Studies Report IMF Variations
Larson 2005
Baugh et al. 2005
Weidner, Kroupa, Pflamm-Altenburg et al. 2006, 2007, 2009
Wang et al. 2006
Fardal et al. 2007
Maness et al. 2007
Mieske & Kroupa 2008
Wilkins et al. 2008a,b
Dave 2008
Hoversten & Glazebrook 2008
van Dokkum 2008
Meurer et al. 2009
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Conclusions
❖ Many lines of evidence point to the universality of the stellar IMF.
❖ But absence of evidence is not evidence of absence.
❖ The E-ELT will be able to refine the tests carried out so far, and search for variations in the sub-stellar regime.
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Intermediate age clusters in the LMC
Mackey & Brobie Neilson 2007
~1.5 Gyr
V-I
mv
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Intermediate age clusters in the LMC
Mackey & Brobie Neilson 2007
~1.5 Gyr
V-I
mv
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Intermediate age clusters in the LMC
Mackey & Brobie Neilson 2007
~1.5 Gyr
300 Myr age difference
V-I
mv
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V-I
MV
Bastian & de Mink 2009
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1.25 Gyr isochrone
1.5 Gyr isochrone
1.2 Msun
V-I
MV
Bastian & de Mink 2009
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1.25 Gyr isochrone
1.5 Gyr isochrone
1.2 Msun
V-I
MV
Bastian & de Mink 2009
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1.25 Gyr isochrone
1.5 Gyr isochrone
1.2 Msun
V-I
MV
Bastian & de Mink 2009
fast rotators
slow rotators
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Outline
❖ Stellar IMF in starbursts and the early universe
❖ Multiple populations within clusters?
❖ Resolved star approach
❖ Universality of the IMF?
Stellar IMF in the Galaxy
Extreme environments