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Image Decomposition of Barred Galaxies and AGN Hosts Dimitri Gadotti

Image Decomposition of Barred Galaxies and AGN Hosts Dimitri Gadotti Max Planck Institute for Astrophysics. Outline. Tests and exercises on the reliability of image decomposition brief introduction and results for a very nearby sample (z ~ 0.005) the effects of not including bars

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Image Decomposition of Barred Galaxies and AGN Hosts Dimitri Gadotti

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  1. Image Decomposition of Barred Galaxies and AGN Hosts Dimitri Gadotti Max Planck Institute for Astrophysics

  2. Outline • Tests and exercises on the reliability of image decomposition • brief introduction and results for a very nearby sample (z ~ 0.005) • the effects of not including bars • the effects of not accounting for bright, type 1 AGN • artificially redshifted images • the effects of low physical spatial resolution • some consequences • the stellar mass budget in the local universe Dimitri Gadotti (MPA) – Image Decomposition of Barred Galaxies and AGN Hosts

  3. The BUDDA Code (de Souza, Gadotti & dos Anjos 2004) • BUlge/Disk Decomposition Analysis v2.1 (Gadotti 2008) • (http://www.mpa-garching.mpg.de/~dimitri/budda.html) • 2D (Image Fitting) • Bulge (Sérsic 1968) • Disk (Freeman 1970) Dimitri Gadotti (MPA) – Image Decomposition of Barred Galaxies and AGN Hosts

  4. The BUDDA Code (de Souza, Gadotti & dos Anjos 2004) • BUlge/Disk Decomposition Analysis v2.1 (Gadotti 2008) • (http://www.mpa-garching.mpg.de/~dimitri/budda.html) • 2D (Image Fitting) • Bar • Sérsic profile • n=1: late-type bars • n<1: early-type bars Dimitri Gadotti (MPA) – Image Decomposition of Barred Galaxies and AGN Hosts

  5. The BUDDA Code (de Souza, Gadotti & dos Anjos 2004) • BUlge/Disk Decomposition Analysis v2.1 (Gadotti 2008) • (http://www.mpa-garching.mpg.de/~dimitri/budda.html) • 2D (Image Fitting) • Central Source • Moffat (1969) Dimitri Gadotti (MPA) – Image Decomposition of Barred Galaxies and AGN Hosts

  6. BUDDA on Very Nearby Galaxies 17 galaxies (mostly barred and some AGN) @ V & R broadbands resolution ~ 150 pc Gadotti & de Souza (2006)

  7. Athanassoula (1992a, b)

  8. Athanassoula (1992a, b)

  9. BUDDA on Very Nearby Galaxies Kormendy (1977) relation for bulges scaling relation for disks Dimitri Gadotti (MPA) – Image Decomposition of Barred Galaxies and AGN Hosts

  10. BUDDA on Very Nearby Galaxies • bar ellipticity from image fitting 1 – b/a • effect is on average 20%, but a factor of 3 is also seen ellipticity peak in ellipse fitting bars might be more eccentric! Dimitri Gadotti (MPA) – Image Decomposition of Barred Galaxies and AGN Hosts

  11. BUDDA on Very Nearby Galaxies What if you don’t include bars? Dimitri Gadotti (MPA) – Image Decomposition of Barred Galaxies and AGN Hosts

  12. BUDDA on Very Nearby Galaxies What if you don’t include bars? D/T increase by 10% (average) 30% maximum B/T increase by 50% (average) 100% maximum See also Laurikainen, Salo & Buta (2005)

  13. BUDDA on Very Nearby Galaxies What if you don’t include AGN? Dimitri Gadotti (MPA) – Image Decomposition of Barred Galaxies and AGN Hosts

  14. BUDDA on Artificially Redshifted Galaxies resolution ~ 1.5 kpc

  15. BUDDA on Artificially Redshifted Galaxies What if you go for farther galaxies? original images resolution = 1.5 kpc 1.5” @ z = 0.05 (my SDSS sample) 0.75” @ z = 0.1 (MGC – Allen et al. 2006) HST, VLT (w/ AO) @ z ≈ 1-2 artificially redshifted images Dimitri Gadotti (MPA) – Image Decomposition of Barred Galaxies and AGN Hosts

  16. general good agreement • disk parameters are the most robust • B/T overestimated on average by 5% (re ~ seeing radius…)

  17. BUDDA on Artificially Redshifted Galaxies What if you go for farther galaxies? • bar effect still present (even worse for re) • AGN light is diluted Dimitri Gadotti (MPA) – Image Decomposition of Barred Galaxies and AGN Hosts

  18. The Stellar Mass Budget at z ~ 0 • Driver et al. (2007): • 26+/-4% (bulges) • 58+/-6% (disks) • Correcting for: • 5% overestimation of B/T due to poor resolution • average overestimation of (models without bars): • B/T (50%) • D/T (10%) • bar fraction of 70% • Results in: • 13.5% (bulges), 58.5% (disks), 12% (bars) Dimitri Gadotti (MPA) – Image Decomposition of Barred Galaxies and AGN Hosts

  19. The Stellar Mass Budget at z ~ 0 • Bars as important as spheroids in the stellar mass budget at z ~ 0 (Gadotti 2008) • ~ 1/2 in disks • ~ 15% in bars • ~ 15% in elliptical galaxies • ~ 15% in bulges Dimitri Gadotti (MPA) – Image Decomposition of Barred Galaxies and AGN Hosts

  20. Summary • Structural analysis of high spatial resolution images must take into account bars and type 1 AGN (otherwise B/T is overestimated  wrong comparison to models) • At lower spatial resolution AGN light is diluted but bars remain important • Image decomposition works fine for SDSS at z ~ 0.05, but B/T is overestimated by 5% on average if re≤ seeing • True axial ratio of bars can only be obtained through image decomposition (ellipse fits result in rounder bars if axisymmetric component is strong) • Bars as important as spheroids in the stellar mass budget at z ~ 0 Dimitri Gadotti (MPA) – Image Decomposition of Barred Galaxies and AGN Hosts

  21. The BUDDA Code (de Souza, Gadotti & dos Anjos 2004) generalized ellipses (e.g., Athanassoula et al. 1990) Pure c = 2 Boxy c > 2 Disky c < 2 Dimitri Gadotti (MPA) – Image Decomposition of Barred Galaxies and AGN Hosts

  22. BUDDA on Very Nearby Galaxies bar semi-major axis from image fitting bar semi-major axis from ellipse fitting scale-length of disk (see also Erwin 2005) Dimitri Gadotti (MPA) – Image Decomposition of Barred Galaxies and AGN Hosts

  23. BUDDA on Very Nearby Galaxies comparison with Laurikainen et al. (2004) and Laurikainen, Salo & Buta (2005) Dimitri Gadotti (MPA) – Image Decomposition of Barred Galaxies and AGN Hosts

  24. BUDDA on Very Nearby Galaxies Two special cases Gadotti & de Souza (2003): where is the disk? (fits without bar) Rearrangement (capture) of disk stars by evolving bar (Athanassoula & Misiriotis 2002; Athanassoula 2003) Dimitri Gadotti (MPA) – Image Decomposition of Barred Galaxies and AGN Hosts

  25. BUDDA on Very Nearby Galaxies Two special cases But best fit is achieved with Freeman (1970) type II disk Gadotti (2008): bar growth is ~ 70%, through capture of ≈ 13% of disk stars (one and only observational constraint to date) Dimitri Gadotti (MPA) – Image Decomposition of Barred Galaxies and AGN Hosts

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