SBF with HST Previous ACS

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SBF with HSTPrevious ACS Future WFC3
measurementsMichele Cantiello

• INAF Osservatorio Astronomico di Teramo
• Gabriella Raimondo
• Enzo Brocato
• Ilaria Biscardi
• with
• John P. Blakeslee - Herzberg Institute of
  Astronomy (Canada)
• Massimo Capaccioli - Università degli Studi di
  Napoli (Italy)
• Simona Mei - Observatoire de Paris (France)

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Surface Brightness Fluctuations (SBF) 101
Tonry Schneider (1988, TS88) distance
indicator for ellipticals up to 20 Mpc
20 years later
SBF distance indicator for a much larger family
of objects (Galactic and MC star clusters,
dwarfs, bulges of spirals, cDs ) distances
reached up to now from few Kpc up to 130 Mpc
SBF also a Tracer of Stellar Population
Properties Integrated colors classical mags
first moment of the LF SBF mags also 2 LF
moment, more sensitive to the bright stellar
component
Basic idea nearby ? mottled/granulous Far ?
smooth The mottling correlates with distance!
TS88 quantify SBF Spatial fluctuations of
the Surface Brightness / average Brightness
Credits J. Jensen
NGC 7768 (100 Mpc)
M 32 (0.77 Mpc)
SBF Sinifi2/Snifi Ratio of the 2 to the 1
moment of the stellar LF
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• Our Results (1)
• Theoretical modeling since 1997 (Brocato et al.,
  1997)
• 2003-2005 SPoT models (Raimondo et al., 2005)
• (available at www.oa-teramo.inaf.it/spot)
• Applications to stellar pops, as an example SBF
  gradients?

8 ellipticals (6 bright Es NGC1344 1 local
dwarf) from the ACS archive (Cantiello et
al., 2005)
Images for SBF analysis High S/N High
resolution Large FoV
ACS!
Z0.01
Z0.02 t5-15 Gyr
Z0.04

• STELLAR POPULATION ANALYSIS
• 6 bright Es SBF vs color gradient mainly due
  to Fe/H variations
• NGC1344 Fe/Hage?
• Local dwarf (NGC404) no gradients

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Our Results (2)
First B-band SBF at Dgt10 Mpc B-I SBF color nice,
but
Standard SSP
t 5,7,9,11,13,14 Gyr
Composite SP
Why?
SSP including extra hot stars (Cantiello et al.
2003, Cantiello et al. 2007a)
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Our Results (3)
SBF from archival ACS data 14 very different
galaxies (dwarfs, shells, giants) Very different
physical properties (Cantiello et al., 2007b)
SBF color vs integrated color
Absolute SBF vs color Mm-DM (!)
t 5,7,9,11,13,14 Gyr
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Possible applications with WFC3
STELLAR POPULATIONS Stellar population studies
based on SBF require wide wavelength coverage.
Optical to near-IR colors will be
perfect! WFC3/UVISIR large FoVs high
resolution high efficiency SBF color
gradients?

• DISTANCES
• We have done SBF distances for ellipticals, not
  discussed here
• Biscardi et al. (2008) D100 Mpc
• Raimondo et al. (2005) D50 Kpc
• Using also SBF gradients ? high accuracy
  (Cantiello et al., 2005)
• Farthest SBF distance up to now 130 Mpc with
  NICMOS (Jensen et al. 2001) WFC3/IR channel
  distances farther than 130 Mpc? If so then
• SBF more then 104 range of distances!

see Raimondo et al. Poster at this conference