The RGB and AGB of Simple Stellar

Populations (SSP)Unusual views, perspectives, new applicationsby Michele Bellazzini (INAF – OA Bologna)

The Giant Branches Workshop – Leiden, The Netherlands, May 11-15, 2009

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

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

Both the bestobservational facilities ofthe future will

beoptimized for

thenear infrared

JWST will “see”also the I,i, and z) band

A dSph in the Virgo cluster.

Durrel et al. (2007) HST/ACS

AGBs and RGBsis what we will

seeof newly resolveddistant galaxies(old pop)

The Giant Branches Workshop – Leiden, The Netherlands, May 11-15, 2009

Understanding and calibrating the AGB/RGB [SSPs!] will be crucial for future stellar astronomy

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

The Giant Branches Workshop – Leiden, The Netherlands, May 11-15, 2009

Leo I CaT metallicities for 52 starsKoch et al. 2007ApJ, 657, 241 Bosler et al. 2007, MNRAS, 378, 318

Bellazzini et al. 2004, 2005CaT metallicities from Bellazzini et al. 2008

Sgr dSph

M54

SpecPhot

The RGB Tip: latest calibrations

The Giant Branches Workshop – Leiden, The Netherlands, May 11-15, 2009

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

RGB in the SDSS ugriz system. 1 perspectives

The Giant Branches Workshop – Leiden, The Netherlands, May 11-15, 2009

SDSS already cover part of the Northern Hem. LSST and Pan-STARRS will provide deepAnd accurate photometry of the whole sky:

1. Catalogues to work with

1. Photometric “standards” in each field

Optimization of the productivity of largetelescopes: get the best observations underthe best conditions and don’t care ofabsolute calibration, it comes for free

VV124 with LBC D=1.3 Mpc

RGB in the SDSS ugriz system. The RGB Tip: r, i, z

The Giant Branches Workshop – Leiden, The Netherlands, May 11-15, 2009

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].

Models of similar Z has similar YFor comparisons with other sets of models see Bellazzini (2008)

RGB in the SDSS ugriz system. Playing with real data

The Giant Branches Workshop – Leiden, The Netherlands, May 11-15, 2009

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)DAOPHOT photometry for all the clusters included in the SDSS, from SDSS original images: ugriz

An et al. (2008): all the catalogues are publicily available. We can start to play.

RGB in the SDSS ugriz system. The non-simple SPSSs - premise

The Giant Branches Workshop – Leiden, The Netherlands, May 11-15, 2009

Marino et al., 2008, A&A, 490, 625: M4See Yong et al. 2008, 2009; Lee et al 2009

NH CN CNCN

- CN-weak, Na-poor “primordial” stars

- CN-strong, Na-rich “second-generation” stars

See Carretta et al. 2008

RGB in the SDSS ugriz system. The non-simple SPSSs - results

The Giant Branches Workshop – Leiden, The Netherlands, May 11-15, 2009

Abundances from GIRAFFE spectra

Carretta et al. (2009)

Bimodality in (u-g) emerges from stars selected to lie very close to the RGB

rigde line in (g-r)

RGB in the SDSS ugriz system. The non-simple SPSSs - perspectives

The Giant Branches Workshop – Leiden, The Netherlands, May 11-15, 2009

We can search for Multiple Populations in distant clusters, where it is difficult

to obtain large samples of abundances

from HR spectra

We are looking into other clusters for which both abundances and SDSS

photometry is available: more can be observed

RGB in the SDSS ugriz system. The observed RGB bump

The Giant Branches Workshop – Leiden, The Netherlands, May 11-15, 2009

The luminosity of the bump depends on: 1. 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.

AMR from the bump - premise

The Giant Branches Workshop – Leiden, The Netherlands, May 11-15, 2009Richardson et al. (2008)

The bump can be used todisentangle different Populations:substructures

in M31

Sollima et al. (2008)

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.

AMR from the bump - a view of a special case

Sollima et al. (2009)

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

Vel and met for 2557 stars in the

outskirts of the cluster: 318 of which are bona fide members

The RGB and AGB of SSPConcluding 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!

The Giant Branches Workshop – Leiden, The Netherlands, May 11-15, 2009

A special thank to the organizers for having invited me to this very interesting meeting!