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3D spectrography III - The SAURON Survey

3D spectrography III - The SAURON Survey. Introduction. Dynamical evolution ? Impossible to really disentangle the chemical and dynamical evolution in a galaxy…. Introduction. Cosmological context: Hierarchical building of the structures. Lacey 1992. Introduction. Cosmological context:

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3D spectrography III - The SAURON Survey

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  1. 3D spectrographyIII - The SAURON Survey

  2. Introduction • Dynamical evolution ? • Impossible to really disentangle the chemical and dynamical evolution in a galaxy…

  3. Introduction • Cosmological context: • Hierarchical building of the structures Lacey 1992

  4. Introduction • Cosmological context: Numerical simulations Density fluctuations: / = d << 1 P(δ) = (2π)-1/2 /σ(M) exp[ -δ2/2σ2(M)] Press & Schechter (1974)

  5. Introduction • Cosmological context: • Inhomogeneous distribution • Evolution with redshift

  6. Introduction • Cosmological context: • Interactions, harassment, mergers

  7. SAURON GalaxyFormation • 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 ?

  8. Aims 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

  9. Ingredients • 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 instrument an 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

  10. SAURON Spectroscopic Areal Unit for Research on Optical Nebulae • Bacon et al. 2001, MNRAS 326, 23 • de Zeeuw et al. 2002, MNRAS 329, 513

  11. 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 SAURON versus OASIS

  12. Specifications

  13. Data Reduction • Goal is to produce uniform and high quality reduced data • Inherit from the experience gained with TIGERandOASIS • 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

  14. 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

  15. The Sample Status : Survey completed in April 2002 • 7 observing runs • 71/72 galaxies observed + 10 “specials” • > 160 000 independent spectra!

  16. Complementary 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

  17. Science Verification

  18. Photometry Is photometry preserved in the reconstructed images ? Comparison with HST photometry Dµv = 0.016 De = 0.012 DPA = 1° NGC 4365 Science Verification

  19. Stellar kinematics NGC 3384 SAURON 2h Fisher 97, 2" slit Dv=7 km.s-1 Ds=6 km.s-1 Dh3=0.015 Dh4=0.015 Major Minor Science Verification

  20. Line strength NGC 3384 Long slit, Fisher et al D(Hb) = 0.1 A D(Mgb) = 0.1A D(Fe5270) = 0.1A Science Verification

  21. Emission Lines NGC 5813, SAURON 2 x 1h mosaic Long slit Caon et al Dv([OIII]) ~15 km.s-1 Continuum subtraction is critical Science Verification

  22. 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%

  23. Stellar Kinematics

  24. SAURON I,V,s Maps

  25. 'Axisymmetric' objects ? • Kinematics axis aligned with photometric axis • 'Normal' rotator ? (but see later in the talk…)

  26. ‘Non-axisymmetric' objects • Misalignement of photometric and kinematical axis

  27. Complex Dynamics

  28. Is photometry the good indicator ? • Stellar kinematical maps are richer than light distribution Bacon et al. 2001, de Zeeuw et al. 2002, Emsellem et al. 2003

  29. Stellar populations

  30. 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?

  31. SAURON – Stellar 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

  32. SAURON - Indices • Hb– 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 Hb!)

  33. The 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, Hb+) • 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 ofJones (1997)

  34. Model comparison

  35. Absorption line subtraction

  36. Emission Lines - NGC 5813 comparison with Caon et al. (2000)

  37. Line Strengths in NGC 5813

  38. A few examples

  39. NGC 7742 (Sb/field)

  40. NGC 4314 (S/cluster)

  41. POSS, 7' x 7' SAURON, Intensity NGC 3623 (S/cluster)

  42. NGC 3377 (E!!/cluster)

  43. NGC 5866 (special)

  44. NGC 4698 (S/cluster)

  45. Kinematically Decoupled Cores (KDC)

  46. 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?

  47. NGC 4365 (E3) – Line-strength Clear KDC Metal enrichment? No sign of KDC! Davies, Kuntschner, Emsellem, et al., 2001, ApJL, 548, L33

  48. NGC 4365 – Age, [M/H] The KDC is old and in line with main body

  49. Only ±10 km/s NGC 4150 (S0/cluster)

  50. NGC 4150 (S0) : post-starburst

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