3D spectrography III - The SAURON Survey
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Transcript of 3D spectrography III - The SAURON Survey
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Padova 033D Spectrography
3D spectrography3D spectrography
III - The SAURON SurveyIII - The SAURON Survey
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Padova 033D Spectrography
IntroductionIntroduction
Dynamical evolution ?– Impossible to really disentangle the chemical and
dynamical evolution in a galaxy…
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Padova 033D Spectrography
IntroductionIntroduction
Cosmological context:– Hierarchical building of the structures
Lacey 1992
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Padova 033D Spectrography
IntroductionIntroduction
Cosmological context:Numerical simulations Density fluctuations:
/ << 1
P(δ) = (2π)-1/2 /σ(M) exp[ -δ2/2σ2(M)] Press & Schechter (1974)
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Padova 033D Spectrography
IntroductionIntroduction Cosmological context:
– Inhomogeneous distribution– Evolution with redshift
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Padova 033D Spectrography
IntroductionIntroduction
Cosmological context:– Interactions, harassment, mergers
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Padova 033D Spectrography
GalaxyGalaxyFormationFormation
When and how do E/S0/Sa galaxies form?– What is the orbital make-up of E/S0s?– What is the average age?– What is the average metal content?– Origin of substructures; e.g. faint disks in Es,
decoupled cores, etc.– E S0 Sa transformations ? – What is the relationship between global properties
and supermassive black holes ?
SAURON
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Padova 033D Spectrography
Aims of the SAURON SurveyAims of the SAURON Survey
For a representative sample of nearby E/S0/Sa: Measure intrinsic shapes Determine velocity distribution (stars+gas)
orbital make-up Schwarzschild modelling Determine metallicity and age distribution Determine frequency of kinematically decoupled
structures and black holes Unravel the stellar population – kinematics
connection
Ideal tool: integral field spectrographs
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Padova 033D Spectrography
IngredientsIngredients A team
with relevant expertise in Integral field spectroscopy Data reduction Modelling Dynamics and population of early-type galaxies
Funds Total 600 k€ From NL, F and UK
A unique instrumentan IFU with
Large field of view High throughput (20%, everything included) Efficient data reduction pipeline
Telescope time ~54 nights of 4.2m WHT over 3 years
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Padova 033D Spectrography
SAURONSAURON
Spectroscopic
Areal
Unit
for Research
on Optical
Nebulae
• Bacon et al. 2001, MNRAS 326, 23
• de Zeeuw et al. 2002, MNRAS 329, 513
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Padova 033D Spectrography
SAURON versus OASISSAURON versus OASIS
Larger field of view– Sampling ~1" f/1.8
camera (oasis f/3) Simultaneous sky
– 1.9' from object Spectrum length
– 580 pixels (OASIS 360) spectra more densely
packed Number of spectra
– 1577 including 146 for the sky
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Padova 033D Spectrography
SpecificationsSpecifications
Telescope William Hershell (4.2 m)
Sampling 0.94 x 0.94 arcsec (LR)
0.27 x 0.27 arcsec (HR)
Field of view 33 x 41 arcsec (LR)
9 x 11 arcsec (HR)
Lenslets 1577 (146 sky)
Wavelength range 4810-5350 Å
Spectral features H, [OIII], Mgb, Fe5270
Instrumental resolution ~ 110 km/s
Total Efficiency 14.7 % > 20% (VPH)
Commissioned February 1999 (at WHT)
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Padova 033D Spectrography
Data ReductionData Reduction
Goal is to produce uniform and high quality reduced data
Inherit from the experience gained with TIGER and OASIS
Specific developments :– To take into account the denser packing of the SAURON
spectra– To mosaic and merge exposures– To efficiently reduce a large amount of data– 2D binning– Pipeline and database– More analysis tools
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Padova 033D Spectrography
The Sample The Sample
Representative sample of 72 nearby E/S0/Sa galaxies
cz < 3000 km/s DEC: -6° < d < +64° and |b|
15°
MB -18 mag (factor of 50 in luminosity)
24 E, 24 S0, 24 Sa (12 cluster, 12 field)
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Padova 033D Spectrography
The Sample The Sample
Status :
Survey completed in April 2002
7 observing runs 71/72 galaxies observed + 10 “specials” > 160 000 independent spectra!
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Padova 033D Spectrography
Complementary DataComplementary Data
The nucleus– Imaging
HST WFPC2
– A large fraction available in archive
– Spectrography OASIS/CFHT observations
– Completed in April 2002 (20 nights) A few STIS observations
The extended halo– Ground-based imaging– Long slit observations
Up to 2 re
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Padova 033D Spectrography
Science VerificationScience Verification
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Padova 033D Spectrography
Science Verification Science Verification Photometry
– Is photometry preserved in the reconstructed images ?
– Comparison with HST photometry µv = 0.016 = 0.012 PA = 1°
NGC 4365
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Padova 033D Spectrography
Science Verification Science Verification Stellar kinematics
– NGC 3384 SAURON 2h Fisher 97, 2" slit v=7 km.s-1 =6 km.s-1 h3=0.015 h4=0.015
Major Minor
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Padova 033D Spectrography
Science VerificationScience Verification Line strength
– NGC 3384– Long slit, Fisher et al
(H) = 0.1 A (Mgb) = 0.1A (Fe5270) = 0.1A
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Padova 033D Spectrography
Science VerificationScience Verification Emission Lines
– NGC 5813, SAURON 2 x 1h mosaic– Long slit Caon et al
v([OIII]) ~15 km.s-1
– Continuum subtraction is critical
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Padova 033D Spectrography
Science Verification Science Verification
Conclusion
– SAURON achieve equivalent or better data quality
Absorption lines studies– Stellar kinematics, up to h4
• Precision : 6-7 km.s-1 (1/17 of resolution)– Line index
• Precision : 0.1 A
Emission line studies– Morphology and flux– Kinematics
– But SAURON is 2D !!
Photometric accuracy better than 2%
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Padova 033D Spectrography
Stellar KinematicsStellar Kinematics
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Padova 033D Spectrography
SAURON I,V,SAURON I,V, Maps Maps
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Padova 033D Spectrography
'Axisymmetric' objects ?'Axisymmetric' objects ?
Kinematics axis aligned with photometric axis 'Normal' rotator ? (but see later in the talk…)
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Padova 033D Spectrography
‘‘Non-axisymmetric' objectsNon-axisymmetric' objects
Misalignement of photometric and kinematical axis
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Padova 033D Spectrography
Complex DynamicsComplex Dynamics
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Padova 033D Spectrography
Is photometry the good Is photometry the good indicator ?indicator ?
Stellar kinematical maps are richer than light distribution
Bacon et al. 2001, de Zeeuw et al. 2002, Emsellem et al. 2003
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Padova 033D Spectrography
Stellar populationsStellar populations
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Padova 033D Spectrography
What would we like to know?What would we like to know?
As a function of luminosity,
Hubble type and environment.
How common are (young?) disks in ellipticals?
How were galaxies assembled? What are the ages & metallicities of their stellar populations?
What is the connection between the kinematics and stellar populations of the galaxies?
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Padova 033D Spectrography
SAURON – SAURON – Stellar Population GoalsStellar Population Goals
• Probe the star-formation history
• Age of stars (luminosity weighted)
• Metallicity of stars (luminosity weighted)
• Abundance ratios (e.g. [Mg/Fe]),
• i.e. probe star-formation time-scales
• Unravel the stellar population – kinematics connection (coloured orbits)
• SAURON:
• Delivers unprecedented quality, uniformity
• 2-D distribution
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Padova 033D Spectrography
SAURON - IndicesSAURON - Indices
• H – age sensitive
• Fe5015 – metallicity and age sensitive
• Mgb – metallicity and age sensitive
• Fe5270 -- good Fe indicator
Needed for [Mg/Fe]
• [OIII] (emission feature)
Probing the ionized gas (also H)
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Padova 033D Spectrography
The Vazdekis (1999) modelsThe Vazdekis (1999) models
Spectral resolution 1.8 A (FWHM) (Lick 9A)
"latest” isochrones, photometric libraries
Predict full spectra, rather than indices
• 3856-4476 A and 4795-5465 A (all we need)
• Ability to define new indices (Sauron Fe5270, H+)
• Spectral fitting of two populations (difficult!)
Problems with the Lick system:• Resolution low, so few features can be analysed• Not flux calibrated• Corrections for velocity broadening difficult• Measurements of Lick stars based on a non-linear detector
Vazdekis (1999) stellar library of Jones (1997)
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Padova 033D Spectrography
Model comparisonModel comparison
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Padova 033D Spectrography
Absorption line subtractionAbsorption line subtraction
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Padova 033D Spectrography
Emission Lines - NGC 5813
comparison withCaon et al. (2000)
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Padova 033D Spectrography
Line Strengths in NGC 5813
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Padova 033D Spectrography
A few examplesA few examples
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Padova 033D Spectrography
NGC 7742 (Sb/field)NGC 7742 (Sb/field)
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Padova 033D Spectrography
NGC 4314 (S/cluster)NGC 4314 (S/cluster)
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Padova 033D Spectrography
POSS, 7' x 7'
SAURON, Intensity
NGC 3623 NGC 3623 (S/cluster)(S/cluster)
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Padova 033D Spectrography
NGC 3377 (E!!/cluster)NGC 3377 (E!!/cluster)
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Padova 033D Spectrography
NGC 5866 (special)NGC 5866 (special)
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Padova 033D Spectrography
NGC 4698 (S/cluster)NGC 4698 (S/cluster)
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Padova 033D Spectrography
Kinematically Decoupled Cores Kinematically Decoupled Cores (KDC)(KDC)
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Padova 033D Spectrography
KDC – ‘morphology’KDC – ‘morphology’
Central location Varying rotation speeds (60-100 km/s) Misalignments of
- KDC with phot axis
- Zero velocity curve
with phot axis
When did the KDCs form?
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Padova 033D Spectrography
NGC 4365 (E3) – Line-strengthNGC 4365 (E3) – Line-strength
No sign of KDC!Metal enrichment?
Davies, Kuntschner, Emsellem, et al., 2001, ApJL, 548, L33
Clear KDC
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Padova 033D Spectrography
NGC 4365 – Age, [M/H]NGC 4365 – Age, [M/H]
The KDC is old and in line with main body
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Padova 033D Spectrography
NGC 4150 (S0/cluster)NGC 4150 (S0/cluster)
Only ±10 km/s
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Padova 033D Spectrography
NGC 4150 (S0) : post-starburstNGC 4150 (S0) : post-starburst
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Padova 033D Spectrography
The stellar kinematics of early-type galaxies exhibit a rich variety of structures
Axisymmetry is the exception rather than the rule
The view we have from galaxy photometry is misleading
The view we have from major and minor axis kinematics is too restricted
Have we found the tracer of the complex history of galaxy formation and evolution ?
SummarySummary
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Padova 033D Spectrography
SummarySummary
KDC
KDC Frequency 15% … awaiting full sample
Misalignments of kinematic and photometric axis for KDC and main body triaxial structure?
3/4 KDC show old stellar populations, perhaps increased metallicity & abundance ratios
Kinematic arrangement stable over a long time for old KDCs
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Padova 033D Spectrography
ConclusionsConclusions
SAURON+OASIS+HST+gd-based Imaging =
a unique atlas to probe the formation and evolution processes of early-type galaxies
Adapted tools for the analysis
(MGE, 2D binning, kinemetry, Schwarzschild, “coloured N-body”, new stellar libraries, …)
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Padova 033D Spectrography
Further readingsFurther readings
SAURON papers:– Bacon et al. 2001, MNRAS 326, 23– Davies, Kuntschner, Emsellem, et al., 2001, ApJL, 548, L33– de Zeeuw, Bureau, Emselle, et al. 2002, MNRAS 329, 513– Verolme et al. 2002 & 2003, McDermid, et al., …– Emsellem et al. 2003, to be submitted soon
http://www.strw.leidenuniv.nl/sauron/