disentangling luminosity, morphology, stellar age, star formation, and environment in galaxy...
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Kant : Systems of Fixed Stars, Arrangements of Worlds, Worlds of Worlds, Milky Ways of Worlds. Island Universes. Disentangling Luminosity, Morphology, Stellar Age, Star Formation, and Environment in Galaxy Evolution. Daniel Christlein Andes Fellow Yale University & Universidad de Chile & - PowerPoint PPT PresentationTRANSCRIPT
Disentangling Luminosity, Morphology, Stellar Age, Star Formation, and Environment in Galaxy Evolution
Daniel Christlein Andes Fellow
Yale University & Universidad de Chile &
Ann Zabludoff (U Arizona)
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Kant: Systems of Fixed Stars, Arrangements of Worlds, Worlds of Worlds, Milky Ways of Worlds
Island Universes
We know some basic statistics about galaxies:
- Luminosity Function
- Morphology-Environment Relation
- Star Formation-Environment Relation
but understanding incomplete:
-environmental dependence of LF?
-origin of morphological sequence?
-Nature or Nurture?
< Binggeli, Sandage & Tamman 1988
The Data- 6 nearby (z<0.07), rich clusters
- R-band photometry
- spectroscopy for ~3000 galaxies:
star formation indices, stellar age indices
- 2MASS J-, K-photometry -> stellar mass
- quantitative morphology with GIM2D (Simard 2002)
- new ML algorithmAbell 1060
Christlein & Zabludoff (2003)Is Luminosity Function Dependent on Environment?
● field and cluster overall GLFs same
● no difference for star-forming galaxies
● GLFs for quiescent galaxies steeper in clusters
X
● steepening of quiescent LF ●difference between field and groups, not groups and clusters
Which Environments Shape the GLF?
Which Environments Shape the GLF?
GLFs are pretty uniform in clusters (>60%, >40% for NEL)
all galaxies quiescent galaxies
- the high-mass end
● quiescent GLF● dwarf/giant ratio● uniformity of GLF in clusters● 2dF & SDSS: break in SFR● cD < 400 km s-1
● gE in subclumps ● early type fraction ● HI deficiency in groups
many saturation points:
=> Groups are where it's at! Gomez et al.
Lewis et al.
Are Groups the Most Important Environments?
x
● quantify morphology by bulge fraction (B/T; GIM2D)
● dense environments => higher bulge fraction
● two types of transformation mechanisms:
● disk fading (e.g., ram-pressure stripping, strangulation)● increasing bulge luminosity (e.g., tidal interactions, mergers)
Christlein & Zabludoff 2004How to Make an Early-Type Galaxy
The Discrete Maximum Likelihood Method
- ansatz for parent distribution:
- pipe it through maximum likelihood optimizer
- natural treatment of multivariate distributions- correct relative normalization- easy to code- retains advantage of ML method
Christlein, McIntosh & Zabludoff, 2004
X
How to Make an Early-Type Galaxy
B/T
0 0.2late-type spirals
How to Make an Early-Type Galaxy
B/T
0.2 0.3early-type spirals
How to Make an Early-Type Galaxy
B/T
0.3 0.4early-type spirals & S0s
How to Make an Early-Type Galaxy
B/T
0.4 0.5S0
How to Make an Early-Type Galaxy
B/T
0.5 0.7S0s & Es
How to Make an Early-Type Galaxy
B/T
0.7 1.0E
How to Make an Early-Type Galaxy
B/T
0.7 1.0E
disk-dominated
bulges are brighter, but disks not fainter, in bulge-dominated systems
=> bulge-dominated systems (e.g., "S0s") cannot be producedby disk-fading alone
The Star Formation Gradient
Gomez et al.
Lewis et al.
Christlein & Zabludoff 2004bMorDen
Star Formation
Morphology
Stellar Mass
Stellar Age
Star formation gradient and morphology-environment relation the same?
Star formation gradient due to initial conditions?
Partial Correlation Coefficients
rStar Formation,Environment . Morphology,Stellar Mass, Mean Stellar Age
Star Formation EW([OII])
Environment R
Morphology B/T
Stellar Mass from 2MASS J, K & D4000
Mean Stellar Age D4000
hold constantresidual correlation
Removing Morphology, Stellar Mass, Stellar Age...
total SF gradient residual SF gradient
r = 0.295 (Z=10.9) r = 0.221 (Z=8.0)
=> SF gradient not explained by Morphology, Stellar Mass, Stellar Age gradients
Conclusions
LF vs. environment - little change in LF from field -> cluster or cluster -> cluster
- significant steepening of quiescent LF field -> groups
- little variation of quiescent LF groups -> clusters or cluster -> cluster
=> strong impact of environment on SF properties, little on luminosity
=> lower-density envs. decisive
Bulge/Disk LFs vs. Morph. & Env.
-Early Types are Early Types because
Bulges are brighter, not because Disks are
fainter
=> Bulge-enhancing processes (e.g., tidal interactions, mergers) necessary -> low-density envs
Conclusions(2)
Residual SF gradient remains after accounting for Morphology, Stellar Mass, Stellar Age
- smoking gun for late-epoch environmental transformations
- net effect of evolutionary/formation mechanisms on star formation & morph. dependent on environment
Conclusions (3)
The End
Morphology-Environment Relation
SF gradientThe End
- Which Environment?
Radius or Local Density?
Morph. Evolution (bulge enhancement) probably driven by LD
but residual SF impact could have different dependence
- define environmental indices sensitive to mechanisms?
uncorrected
corrected
Corrected vs. uncorrected Spearman Coefficients
The End
Corrected vs. uncorrected Spearman Coefficients
<r>=0
uncorrected rcorrected r
The End