The RGB and AGB of Simple Stellar Populations (SSP)

1. The RGB and AGB of Simple Stellar Populations (SSP) Francesco has already discussed the use of GCs as calibrators for RGB/AGB properties; RGB in NIR etc. Carme will review RGB/AGB in resolved galaxies Let me have a look to less frequented corners Unusual views, perspectives, new applications by Michele Bellazzini (INAF – OA Bologna) Some of the results shown here are have been obtained with: F. Ferraro, R. Ibata, L. Monaco, E. Pancino, A. Sollima, G. Beccari, E. Carretta, A. Bragaglia and many other friends and collaborators The Giant Branches Workshop – Leiden, The Netherlands, May 11-15, 2009

2. Understanding and calibrating the AGB/RGB [SSPs!] will be crucial for future stellar astronomy A dSph in the Virgo cluster. Durrel et al. (2007) HST/ACS AGBs and RGBs is what we will see of newly resolved distant galaxies (old pop) Both the best observational facilities of the future will be optimized for the near infrared JWST will “see” also the I,i, and z) band The Giant Branches Workshop – Leiden, The Netherlands, May 11-15, 2009

3. RGB as metallicity indicators: do they work well? Photometric MDs from interpolation on grids of GC RGB templates compares very well with their spectroscopic counterparts Leo I CaT metallicities for 52 stars Koch et al. 2007ApJ, 657, 241 Bosler et al. 2007, MNRAS, 378, 318 M54 Sgr dSph Spec Phot CaT metallicities from Bellazzini et al. 2008 Bellazzini et al. 2004, 2005 The Giant Branches Workshop – Leiden, The Netherlands, May 11-15, 2009

4. The RGB Tip: latest calibrations The RGB Tip is a mature and widely used technique. It can be used to build-up a comprehensive cosmological distance ladder independent of Cepheids [Tamman et al. 2008; Mould et al. 2009] Classical empirical calibrators are GCs See: Madore et al. (2009); Bellazzini et al. (2008); Rizzi et al. (2007) for recent developments and reviews The Giant Branches Workshop – Leiden, The Netherlands, May 11-15, 2009

5. RGB in the SDSS ugriz system. 1 perspectives VV124 with LBC D=1.3 Mpc SDSS already cover part of the Northern Hem. LSST and Pan-STARRS will provide deep And accurate photometry of the whole sky: Catalogues to work with Photometric “standards” in each field Optimization of the productivity of large telescopes: get the best observations under the best conditions and don’t care of absolute calibration, it comes for free The Giant Branches Workshop – Leiden, The Netherlands, May 11-15, 2009

6. RGB in the SDSS ugriz system. The RGB Tip: r, i, z Models of similar Z has similar Y For comparisons with other sets of models see Bellazzini (2008) i and z are the most interesting SDSS bands for the TRGB, but r seems also very good for [M/H]<-1 Basti and Girardi et al. 2004 isochrones differ widely for very red models in i and z (Teff - color transformations to be blamed, as usual for low Teff?). To be checked with observations. Also with SDSS passbands, calibrations as a function of color strongly mitigate the age dependency [this is true for any set of models and any color I’ve looked at]. The Giant Branches Workshop – Leiden, The Netherlands, May 11-15, 2009

7. RGB in the SDSS ugriz system. Playing with real data An et al. (2008) DAOPHOT photometry for all the clusters included in the SDSS, from SDSS original images: ugriz Clem et al. (2008) u’g’r’i’z’ of 5 clusters from CFHT deep images; only ridge lines are pubicily available An et al. (2008): all the catalogues are publicily available. We can start to play. The Giant Branches Workshop – Leiden, The Netherlands, May 11-15, 2009

8. RGB in the SDSS ugriz system. The non-simple SPSSs - premise NH CN CN CN Marino et al., 2008, A&A, 490, 625: M4 See Yong et al. 2008, 2009; Lee et al 2009 • CN-weak, Na-poor “primordial” stars • CN-strong, Na-rich “second-generation” stars • See Carretta et al. 2008 The Giant Branches Workshop – Leiden, The Netherlands, May 11-15, 2009

9. RGB in the SDSS ugriz system. The non-simple SPSSs - results Bimodality in (u-g) emerges from stars selected to lie very close to the RGB rigde line in (g-r) Abundances from GIRAFFE spectra Carretta et al. (2009) The Giant Branches Workshop – Leiden, The Netherlands, May 11-15, 2009

10. RGB in the SDSS ugriz system. The non-simple SPSSs - perspectives We are looking into other clusters for which both abundances and SDSS photometry is available: more can be observed We can search for Multiple Populations in distant clusters, where it is difficult to obtain large samples of abundances from HR spectra The Giant Branches Workshop – Leiden, The Netherlands, May 11-15, 2009

11. RGB in the SDSS ugriz system. The observed RGB bump • The luminosity of the bump depends on: • metallicity, 2. age, and 3. He content • Is a good observable (easy to spot and to measure accurately) as it is a PEAK in the Luminosity Function. The Giant Branches Workshop – Leiden, The Netherlands, May 11-15, 2009

12. AMR from the bump - premise The bump can be used to disentangle different Populations: substructures in M31 Coupled with independent info on the metallicity it can be used to Constrain the (average) Age, the and the Age-Metallicity Relation. We have done this in Sgr, Leo II, ω Cen, etc. Sollima et al. (2008) Richardson et al. (2008) The Giant Branches Workshop – Leiden, The Netherlands, May 11-15, 2009

13. AMR from the bump - a view of a special case Sollima et al. (2009) Vel and met for 2557 stars in the outskirts of the cluster: 318 of which are bona fide members Individual metallicities of individual stars from Giraffe HR spectroscopy (elemental abundance analisys ongoing). The run of the bump mag with [Fe/H]: Constraints on the SFH/AMR at the earliest stages of chemical evolution of ω Cen

14. The RGB and AGB of SSP Concluding remarks… An era is approaching in which our ability to extract information about stellar systems from their AGB/RGB will become more and more important It’s time to look at old problems with new eyes: new photometric systems, new techniques etc… Thank you very much! A special thank to the organizers for having invited me to this very interesting meeting! The Giant Branches Workshop – Leiden, The Netherlands, May 11-15, 2009