3d spectrography iii - the sauron survey

Padova 033D Spectrography

3D spectrography3D spectrography

III - The SAURON SurveyIII - The SAURON Survey


IntroductionIntroduction

Dynamical evolution ?– Impossible to really disentangle the chemical and

dynamical evolution in a galaxy…



Cosmological context:– Hierarchical building of the structures

Lacey 1992



Cosmological context:Numerical simulations Density fluctuations:

/ << 1

P(δ) = (2π)-1/2 /σ(M) exp[ -δ2/2σ2(M)] Press & Schechter (1974)


IntroductionIntroduction Cosmological context:

– Inhomogeneous distribution– Evolution with redshift



Cosmological context:– Interactions, harassment, mergers


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


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


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


SAURONSAURON

Spectroscopic

Areal

Unit

for Research

on Optical

Nebulae

• Bacon et al. 2001, MNRAS 326, 23

• de Zeeuw et al. 2002, MNRAS 329, 513


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


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)


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


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)


The Sample The Sample

Status :

Survey completed in April 2002

7 observing runs 71/72 galaxies observed + 10 “specials” > 160 000 independent spectra!


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


Science VerificationScience Verification


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


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


Science VerificationScience Verification Line strength

– NGC 3384– Long slit, Fisher et al

(H) = 0.1 A (Mgb) = 0.1A (Fe5270) = 0.1A


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


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%


Stellar KinematicsStellar Kinematics


SAURON I,V,SAURON I,V, Maps Maps


'Axisymmetric' objects ?'Axisymmetric' objects ?

Kinematics axis aligned with photometric axis 'Normal' rotator ? (but see later in the talk…)


‘‘Non-axisymmetric' objectsNon-axisymmetric' objects

Misalignement of photometric and kinematical axis


Complex DynamicsComplex Dynamics


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


Stellar populationsStellar populations


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?


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


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)


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)


Model comparisonModel comparison


Absorption line subtractionAbsorption line subtraction


Emission Lines - NGC 5813

comparison withCaon et al. (2000)


Line Strengths in NGC 5813


A few examplesA few examples


NGC 7742 (Sb/field)NGC 7742 (Sb/field)


NGC 4314 (S/cluster)NGC 4314 (S/cluster)


POSS, 7' x 7'

SAURON, Intensity

NGC 3623 NGC 3623 (S/cluster)(S/cluster)


NGC 3377 (E!!/cluster)NGC 3377 (E!!/cluster)


NGC 5866 (special)NGC 5866 (special)


NGC 4698 (S/cluster)NGC 4698 (S/cluster)


Kinematically Decoupled Cores Kinematically Decoupled Cores (KDC)(KDC)


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?


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


NGC 4365 – Age, [M/H]NGC 4365 – Age, [M/H]

The KDC is old and in line with main body


NGC 4150 (S0/cluster)NGC 4150 (S0/cluster)

Only ±10 km/s


NGC 4150 (S0) : post-starburstNGC 4150 (S0) : post-starburst


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


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


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, …)


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/

3d spectrography iii - the sauron survey

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