SPITZER IRS spectra of Virgo early-type galaxies: detection of stellar silicate emission Laura Silva (INAF-TS) Alessandro Bressan (INAF-PD), Pasquale Panuzzo (INAF-PD), Lucio Buson (INAF-PD), Marcel Clemens (INAF-PD) GianLuigi Granato (INAF-PD), Roberto Rampazzo (INAF-PD), Jose-Ramon Valdes (IANOE), Olga Vega (IANOE) AGB dusty envelopes as a tool to disentangle age and metallicity effects in the SEDs of E galaxies MIR observations: 10m feature and SF signatures Bressan, Granato, Silva 1998, A&A, 332, 135 Bressan et al. 2006, ApJL, accepted (astro-ph/0602014)
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SPITZER IRS spectra of Virgo early-type galaxies: detection of stellar silicate emission
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SPITZER IRS spectra of Virgo early-type galaxies: detection of stellar silicate
emission
Laura Silva (INAF-TS)
Alessandro Bressan (INAF-PD), Pasquale Panuzzo (INAF-PD), Lucio Buson (INAF-PD), Marcel Clemens (INAF-PD) GianLuigi Granato (INAF-PD), Roberto
Rampazzo (INAF-PD), Jose-Ramon Valdes (IANOE), Olga Vega (IANOE) AGB dusty envelopes as a tool to disentangle age and
metallicity effects in the SEDs of E galaxies
MIR observations: 10m feature and SF signatures
Bressan, Granato, Silva 1998, A&A, 332, 135Bressan et al. 2006, ApJL, accepted (astro-ph/0602014)Panuzzo et al. 2006, in preparation
The brightest stars in intermediate age (100 Myr to a few Gyrs) stellarpopulations are AGB stars
AGB stars are embedded within dusty envelopes originated by very strong stellar winds (10-7-10-4 Mo/yr)
We included the effect of AGB dusty envelopes in SSP:
Spherical symmetry and vexp independent of r =(M,R,L,Z).
Radiative transfer of the photospheric SED through the envelope computed with the Granato & Danese 94 code.
(Bressan, Granato, Silva 1998)
Modeling intermediate and old stellar populations: the effect of AGB dusty envelopes
SSP with AGBs
Age & Metallicity degeneracy hampers reconstructing the history of baryonassembly in the early universe, recorded in the fossil stellar populations (early typegalaxies)
Summarizing:• 17 E-type galaxies in Virgo observed with SL1 SL2 LL2
• Signature of AGB stars well detected by Spitzer IRS • In the majority (76%) of galaxies no other features• The bump is in very good agreement with model predictions• OPT and NIR follow-up is underway to break the age-Z degeneracy
• 2 galaxies show emission lines but no PAHsNGC4486 (M87) NGC 4636 (E/S0 Liner )
• 2 galaxies show PAHs (NGC 4550-SB0 Liner, NGC 4435-SB0 Liner HII)
• N4435 MIR SED remarkably similar to N7331 (Spiral) - Model suggests a post-starburst with residual SFR