Panchromatic population synthesis studies of galaxies

Laura Silva (INAF-Trieste, It)

Sandro Bressan (INAF-Padova, It), Gian Luigi Granato (INAF-Padova, It), Pasquale Panuzzo (INAF -

Padova, It), Olga Vega (INAOE -Puebla, Mx)

Outline:

* Modelling UV to radio SED of galaxies with GRASIL (short summary)

* Detailed analysis of galaxy SEDs with GRASIL to retrieve physical information:

(1) Early-type galaxies in the Virgo cluster: NGC4435 (with SF activity ) (2) Attenuation in spiral galaxies(3) SED analysis of ULIRGs including radio

(Very brief) Description of GRA(phite)SIL(icate)(Silva et al 98, Silva 99, Granato et al 00, Bressan et al 02, Silva et al

03, Panuzzo et al 03, Vega et al 05)

3 dusty environments: dense phase ISM (star forming Molecular Clouds), diffuse phase (cirrus) clumping of stars and dust, dusty envelopes of AGB stars

Stars are born within MCs and gradually escape as a function of their age age-dependent extinction

Stars and dust are distributed in a bulge (King profile) + disk (double exponential profile) geometry Radiative transfer exactly solved

in MCs, with approximation in the cirrus (reasonable computing time)

Dust includes big grains, very small grains and PAHs. The emission is appropriately computed for each component

UV-to radio SEDs (continuum & nebular lines)

- - - emission from star forming MCs….. emission from cirrus (diffuse ISM).-.-.-extincted stars___ non extincted stars

Input SF (and metallicity) history(“classical” chemical evolution codeor galaxy formation model)

(1) Early-type galaxies in Virgo: SED analysis of NGC4435

Systematic spectroscopic study with Spitzer IRS of 17 Early type galaxies along the Color-Magnitude relation in Virgo Cluster (cycle 1)

Aim: *Optical+MIR SED as a tool to disentangle age and metallicity in passive E where the MIR is dominated by AGB dusty envelopes.

*MIR to detect also possible signs of nuclear SF

Result:

* 13 galaxies with the 10m bump expected from AGB dusty envelopes

* 4 galaxies with MIR signs of SF activity

Modelling intermediate age stellar populations in the IR: accounting for AGB dusty envelopes in SSPs

(Bressan, Granato, Silva 1998)

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 et al code.

SEDs for Single Stellar Populations

Age & Metallicity degeneracy hampers reconstructing the history of baryon assembly in the early universe, recorded in the fossil stellar populations (early type galaxies)

Old & Metal Poor = Young & Metal Rich

NO Dusty AGBs Lot of Dusty AGBs

OPT:

MIR:

Age & m

etallicity

Age

Metallicity

Bressan, Granato, Silva 1998

Old Stellar PopulationsMIR emission from dusty (silicates) AGB Stars

(Bressan, Granato & Silva 98)

Degeneracy in the Optical

Degeneracy in the MIR

MIR +

Optical NIRRemoves degeneracy

13 galaxies (76%)with a broad and spatially extended 10m emission feature

10Gyr SSP models withZ=0.008, 0.02, 0.05

SSP with 5Gyr Z=0.008

Dashed: mean outflowAGB starDotted: C-rich star U Cam

Bressan et al 2006

NGC4435

4 galaxies with MIR signs of SF activity: SED analysis of NGC4435

N4435: Circumnuclear disk (4”) source of IR emission - Interacting with NGC4438 - Opt classified LINER/HII (Ho et al 97) - MBH < 7.5e6 Msun 1/10 average MBH-L relation (Coccato et al 06)

(5”)

NGC4435: Direct information from MIR (5”)

PAH revealed by Spitzer: 10.7m, complex at 17m (16.9 & 17.4 m), 19.07 m

Known PAHs: 6.2, 7.7, 8.2, 8.6, 11.2, 11.9, 12.7, 13.5, 14.5, 15.9, 16.4 m

Only low inization emission lines - [NeIII]15.5/[NeII]12.8=0.38 comparing to CLOUDY models AGN < 2%

NGC4435: full SED fit (5”)Spitzer/IRS

MCs

CIRRUS

SF component

Old component

No dust SF comp

•Central 5” SED (Galex, JHK, IRAC, MIPS, IRAS, radio)

•Starburst + old component

•Grid of models with GRASIL:* exp SFR (e-folding , age )* 2 phase ISM (opt depth of MCs 1, escape time scale of young stars from MCs tesc , Mmol/Mgas, disk geometry for stars and dust i=45°, dust/gas metallicity)

Derived quantities:

•Nuclear disk in a post-starburst phase: e-fold=55 Myr, age=186 Myr, SFRc= 0.089 Mo/yr, <SFR>=0.75 Mo/yr Consistent with interaction with NGC4438 (Vollmer et al 05: direct ISM-ISM interaction 100Myr ago, tidal interaction older)

•M*SB=1.4% stellar mass 5” ( 0.3% total aperture stellar mass ) LSB=32% Lbol 5” ( 8% total aperture Lbol )

•No need of AGN to fit the SED consistent with MIR lines

•Solar metallicity from fit of broad band SED + ionizing flux -> good agreement with observed MIR lines ([NeII], [NeIII], [ArII], [SIII])

NGC4435: attenuation law

Attenuation curve resulting from age-dependent extinction and spatial distributions of stars and dust

Average Galactic extinction curve (adopted for dust intrinsic properties)

(2) Attenuation in spiral galaxies Panuzzo et al astro-ph/0612087

b=SFR/<SFR>Analysis of a sample of GALEX NUV-selected late type galaxies (Buat et al 2005, Iglesias-Paramo et al 2006)

Meurer e

t al 1

999

UV-bright s

b

GRASIL models: geometrical age- dependent effects and intrinsic dust properties effects

b=0.25

b=1.25

1520 A- 2310 A

•No age-dependent extinction: only diffuse dust, stars smoothly distributed independently from age•Sequence of models with increasing dust content (1m polar opt depth =0.05-6.4)•MW and SMC dust composition•2175A bump within NUV

MW

SMC

•Age-dependent extinction due to MCs only, no cirrus• Sequence of models with increasing escape time scale from MCs, 0.5-64Myr•Reddest data require tesc>30Myr

•Age-dependent extinction due to cirrus only•Stars younger than tthin with smaller disk scale height than older, dust in between•Sequence of models with increasing dust content and tthin=25-200 Myr

•Age-dependent extinction due to MCs and cirrus•Sequence of models with increasing dust content in the cirrus and tthin=25-200 Myr

Attenuation curves

Only cirrus age- dependent extinctionMCs+cirrus age- dependent extinction Granato et al 2000

GALFORM+GRASIL simulated galaxy catalogues

MW extinction curve

Calzetti et al attenuation curve

(3) SED analysis of LIRGs and ULIRGsSample of 24 LIRGs and ULIRGs (from Condon et al 1991) observed at 22 GHz + full SED

22 GHz data to better constrain the thermal radio emission and radio slope:•Thermal radio direct measure of SFR•Deviations from the FIR/Radio correlations and radio slope linked to the evolutionary status of a starburst (Bressan, Silva, Granato 2002)

Large grid of GRASIL + AGN tori model SEDs (Granato et al 94,97)

Parameters grid for SF histories

Parameters grid for GRASIL

Parameters grid for AGN tori

q (FIR/Radio) vs Radio slope

Effect of free-free absorption:

= Radio Slope 1.4 - 8.4 GHz

1.2

e2

ff

1.35-

T 0.082

GHz

ln pce

Models evolve from left to rightas NTh-emission from SN overcomes Th-emission from HII

Does not affect higher

q 1.4GHz

q 8.4GHz

Bressan,Silva,Granato 2002

Radio observations

allow finer age tuning

M82ARP220

Bressan,Silva,Granato 2002

13/24 galaxies do not require AGN

MCs

cirrusNTh

Th

11/24 require AGN

MCs

cirrus NTh

Th

AGN

* Esb=(Starburst age / e-folding starburst time scale) of the best fit to quantify the phase of the starburst (Vega et al 2005)* No apparent correlation between sb phase and presence of AGN

Early phaseEsb < 0.2

Peak starburst phaseEsb=0.2-217 galaxies

Old starburst phaseEsb=2-46 galaxies

Post starburst phaseEsb>41 galaxy

= only SB = SB+AGN

8-1000m LIR

SB+AGNOnly SB

Fit for SB only:LIR/Mdense=183 Lo/Mo

<Mdense/L_HCN>=5.25average value for objects in common with G&S04 sample

Fit SB+AGN

Gao&Solomon 2004LIR/Mdense=90 Lo/Mo

Mdense/L_HCN=10 Mo/(Kkms-1pc2)^-1

Molecular mass associated with SF

AGN fraction:• ~50% have an AGN, only ~10% have LAGN/Lbol>10%•No significant differences in the sb parameter values for pure sb and sb+agn

GALSYNTH: a friendly WEB interface to run GRASIL

http://web.pd.astro.it/galsynth• Anyone can register and be a

user• Users have their workspaces• Interactive editing of parameters,

with explanations and bound checking, including iterations

• Sets of parameters can be saved, modified, reused.

• Batch jobs are executed on a pool of our computers

• When job completed, user is notified and downloads models

Derived AGN fractions in different bands

Best fit starburst parameters Age sb/ e-fold sb

Best fit AGN parameters

Some derived quantities