1. Distances & Stellar population properties using SBF Michele Cantiello INAF Oss. Astronomico di Teramo Stellar POpulations Tools - SPoT - group –Gabriella Raimondo –Michele Cantiello –Enzo Brocato –Ilaria Biscardi (Univ. “Tor Vergata”) »with: John P. Blakeslee - Herzberg Institute of Astronomy (Canada) Massimo Capaccioli - Università degli Studi di Napoli (Italy) Simona Mei - Observatoire de Paris Meudon (France)

2. SBF method (1) Tonry & Schneider (1988): Distance indicator for ellipticals up to 20 Mpc Today: D.I. for unresolved and resolved stellar systems with regular brightness profiles, ellipticals+bulges of spirals+dwarfs+cDs+globular clusters … distances’ range: few kpc up to hundred of Mpc –where “regular” means (nearly) dust free and smooth profiles > Nearby  mottled/granulous > Far  smooth The “mottling” correlates with the distance!

3. SBF method (2) Measure the Amplitude of the spatial fluctuations (SBF) + Calibration of the absolute SBF magnitude = ________________________ Distances m SBF – M SBF = DM Stellar population properties’ analysis MeasuredCalibrated

4. TEramo-SPoT group : SBF measurement 1)Mask the dust patches, saturated stars and other bright objects (if any) 2)Model the galaxy profile (that’s why the “smooth profile”) 3) Mask the globular clusters, bkgrnd galaxies, foreground stars, etc. 4)Get the power spectrum of the residual frame & match/fit it with the PSF power spectrum  SBF amplitudes We developed a SBF measurement procedure specifically optimized to detect/analyse SBF gradients 5) Once you get m SBF (usually: ), you need M SBF  

5. TEramo-SPoT group : SBF calibration Empirical methods Galaxies with known distance moduli (DM) then: M SBF =m SBF -DM Tonry & collaborators: M SBF is not constant. It is more or less correlated to the integrated color, i.e. the stellar population content of the galaxy, depending on the wavelength interval used Example calibration: M SBF,I =-1.58+4.5 x [(V-I)-1.15] from Tonry et al. (2001) + Jensen et al. (2003) Stellar population synthesis SPoT models (Raimondo et al. 2005) In the Figure: Ages in the range 3-14 Gyr Metallicity range: [Fe/H]=-1.8 to 0.3 dex Example calibration derived: M SBF,I =-1.6+4.5[(V-I)-1.15] Problems  Need DMs from other distance indicators. Reliable?  One single filter! Good  No DM needed  All filters you can/want do in one single shot! Problems  Models suffer for uncertainties as well!

6. TEramo-SPoT group : SBF Distances SBF-based distances have been derived from few-kpc up to ~ 150 Mpc SPoT (1): SBF for young & old stellar clusters in the Magellanic Clouds at ~ 50 kpc (Raimondo et al. 2005) SPoT (2): Using high resolution data (ACS@HST), & the theoretical calibrations from the SPoT models, we derived the first distances of 4 ellipticals @ 55-110 Mpc With such distances we got H 0 ~75 (see Biscardi et al. Poster’s - #1) m SBF – M SBF  DM as usual MeasuredCalibrated Nearly 5 orders of magnitude with one single distance indicator! Quite uncommon…

7. SBF and Stellar population properties Absolute SBF mags. If the DM is known – from another D.I. – then: M SBF =m SBF - DM  e.g. Age and t comparing data with models SBF colors No DM is required. Some examples Cool…but you need the right color choice. Best results with B-K or I-H, i.e. optical to near-IR colors (last slide) SBF gradients Gradients allow a relative comparison between galaxies, e.g. C05: Models&data tell us that most of the observed grads are driven by metallicity changes, except for NGC1344 that is probably an “age- gradient” dominated

8. Summary Teramo SPoT group distances & stellar population properties with SBF -Refined SSP models (also) for the specific purpose of SBF analysis -SBF measurements -a) Multi-annuli SBF data and/or -b) Multi color SBF measurements -c) SBF measurements for very distant galaxies  H0 Future works  multi-color SBF to help remove the t-Z degeneracy