Constraints on secular evolution in unbarred spiral galaxies: understanding bulge and disk formation

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1 Constraints on secular evolution in unbarred spiral galaxies: understanding bulge and disk formation July 10 th 2012 Marja Kristin Seidel Jesús Falcón - Barroso Instituto de Astrofísica de Canarias

2 Constraints on secular evolution in unbarred spiral galaxies: understanding bulge and disk formation disentangling disk heating agents July 10 th 2012 Marja Kristin Seidel Jesús Falcón - Barroso Instituto de Astrofísica de Canarias

3 Introduction: Disk heating More than half of the stellar mass in the local Universe is found in disk galaxies (e.g. Driver et al. 2007) but we are far from understanding them. Especially: What is driving the heating of the disk? Investigate 3D-distribution of stellar velocity dispersions ellipsoid with axes ratios: σz/σr (and σϕ/σr) σr σz Possible disk heating agents: encounters with giant molecular clouds (GMCs) scattering by dark halo objects or globular clusters perturbation by spiral structure perturbation by stellar bars dissolution of young stellar clusters disturbances by satellite galaxies or minor mergers (e.g. from Spitzer & hwarzschild, 1951 to ha et al. 2010)

4 Introduction: Disk heating Model predictions encounters with GMCs (Sellwood, 2008): 3D agent perturbation by spiral structure (Jenkins & Binney, 1990): σr Age radial migration (e.g. Roskar et al. 2008): σr increases with age Metallicity for an existing metallicity gradient (e.g. Sánchez-Blázquez, 2009)* : σz/σr increase with metallicity But: in the solar neighborhood little evidence for the age-metallicity-relation (e.g. Feltzing et al., 2001) *still present even with satellites!

5 Introduction: Our study Our study focuses on: 6 disk galaxies across the Hubble sequence obtaining the ages and metallicities in different regions of the galaxies via full-spectrum fitting techniques relating these stellar population parameters with earlier kinematic results, i.e. σz/σr and the individual values (Shapiro & Gerssen 2003 and 2012)

6 mple Disk-heating (Shapiro & Gerssen 2003 and 2012) credit: HST/WFPC2 image spectra with resolutions of ~ 30 km s -1 and ~ 23 km s -1 NTT KPNO NGC 2280 (d) NGC 3810 () NGC 4030 () NGC 1068 () NGC 2775 (/b) NGC 2460 () different regions from radial surface brightness profiles and disk scale lengths: center bulge [trans] disk Note: all our galaxies show central sigma drops!

7 Methods ppxf (Cappellari & Emsellem, 2004) ; Gandalf (rzi et al. 2006) STARLIGHT (Cid Fernandes, 2007) mseidel@iac.es NGC 3810 () DISK Starlight + Miles models (Sánchez-Blazquez et al.2006) V= ,!= 2.0 km/s 1.2 ppxf Gandalf +ELODIE (Prugniel et al. 2007) Intensity [arb.units] λ [Å] For all three regions in major and minor axes: mass & luminosity weighted Analyze the stellar populations! ages metallicities

8 How can stellar populations help us to understand secular evolution in spirals? disk heating processes?

9 Preliminary results: Ages and [Fe/H] Luminosity weighted Mass weighted age [Gyr] [Fe / H] repr. error b d center bulge disk center bulge Young populations dominate the luminosity weighted age (e.g. Serra & Trager, 2006) We mostly confirm inside-out growth scenario (e.g. Muños-Mateos, 2007) In our sample: late types show stronger [Fe/H] gradients than the early types (adding to MacArthur et al., 2009) disk

10 Preliminary results: Ages and [Fe/H] Luminosity weighted Mass weighted age [Gyr] [Fe / H] repr. error b d center bulge disk center bulge Young populations dominate the luminosity weighted age (e.g. Serra & Trager, 2006) We mostly confirm inside-out growth scenario (e.g. Muños-Mateos, 2007) In our sample: late types show stronger [Fe/H] gradients than the early types (adding to MacArthur et al., 2009) disk

11 Preliminary results: Disk heating With our stellar population results: is it possible to relate these two findings? Z B-V age [Gyr] Gerssen & Shapiro, 2012 Vazdekis et al., 2010

12 Preliminary results: σz/σr So far, only tentative correlations for both, [Fe/H] being stronger. 1.4 σz/σr [ km s -1 ] H0 = 80% H0 = 20% b d b d age [Gyr] [Fe/H]

13 Preliminary results: σr Best correlation obtained for σr with age: H0 = 30% b d σr [ km s -1 ]! R b d age [Gyr] Consistent with simulated predictions (Roskar et al. 2008a, 2008b): if radial migration of stars is present, one expects an increase of σr with age

14 Discussion: σr Best correlation obtained for σr with age: H0 = 30% b d σr [ km s -1 ]! R age [Gyr] b d Consistent with simulated predictions (Roskar et al. 2008a, 2008b): if radial migration of stars is present, one expects an increase of σr with age

15 Discussion: Spiral structure - σr Transcient spiral arms (Sellwood&Binney, 2002), no increase in σz, but increase in σr Comparison with arm-class (Gerssen & Shapiro, 2012): best for σr H0 = 30% b d σr [ km s -1 ]! R b d BUT: trend for σz with both age, metallicity and arm-class found however, not as strong as for σr age [Gyr]

16 Discussion: GMCs - σz GMCs (Sellwood, 2008), increase in σz and σr Comparison with H2 gas surface density (Young et al., 1995):σz H0 = 44% b d σz [ km s -1 ] b d Surprisingly not a very good correlation with σz age [Gyr]

17 Discussion: GMCs - σr GMCs (Sellwood, 2008), increase in σz and σr Comparison with H2 gas surface density (Young et al., 1995): best for σr H0 = 30% b d σr [ km s -1 ]! R b d Correlation with σr better! Adding to spiral structure? age [Gyr]

18 Summary and Outlook Potential relation between disk heating agents and stellar ages and Z. Strongest suspect: spiral structure in addition with GMCs: 1) best correlation for [Fe/H] with σz/σr 2) good correlation for age with σr However, it will be interesting to check: truly radial dependencies within the disk to even better compare with model predictions separate distinct populations in our SFHs to better understand the interplay of bulge, disk and individual components obtain a larger sample of galaxies in order to increase our statistics and the reliability of our results

19 Thank you for listening any questions? - apart from this one...! talk on:

20 Backup MORE SLIDES TO ILLUSTRATE IF WANTED

21 Backup (Jenkins & Binney, 1990)

22 Discussion: Disk heating Comparison with Roskar et al and Sánchez-Blázquez et al. 2009: Consistent with both simulations, but: which can be the disk heating agent? [Z/H] Age [Gyr] R [kpc]

23 Vertical vel. disp. vs. Metallicity [ km s -1 ] b d! z b d [Fe/H]

24 Ages and metallicities via line strengths sigma drop region bulge disk AGE Z

25 The idea Unravelling the nature of bars & bulges: observing secular evolution in action Use integral-field spectroscopic observations to study kinematics and stellar populations in two dimensions of (mainly) barred galaxies Reveal the mass distribution and star formation history of the chosen galaxies Link the 2D stellar dynamics and stellar populations to constrain scenarios for the secular evolution of galaxies under the influence of bars

26 Observations performed 2 successful observation proposals and observation at the WHT Data obtained and preliminarily reduced after the run: March 2012 for 3 out of 5 galaxies observed, binned to S/N = 40; SAURON mosaic on top of the photometric image from SDSS

27 Outlook Unravelling evolution processes by comparing with simulations From simulations: bars evolve and become stronger with time leaving an imprint in the LOSVD Growth as a consequence of angular momentum transfer between the different components of the galaxy: disk, bar, dark matter halo. Different stages in the time evolution of an early-type barred galaxy in one of our numerical simulations (Martinez-Valpuesta et al. 2006) :

28 Control sample and disk heating focus Disk-heating (Shapiro & Gerssen 2003 and 2012) NTT KPNO NGC 2280 (d) NGC 3810 () NGC 4030 () NGC 1068 () NGC 2775 (/b) NGC 2460 () ppxf (Cappellari & Emsellem, 2004) Gandalf (rzi et al. 2006) Mean ages and Z derived with Starlight (Roberto Cid Fernandes, 2007) age [Gyr] Z

29 Outline Introduction mple Methods Preliminary Results and Discussion Outlook

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