Fitting the full SED (from UV to far-IR) of galaxies to put constraints ondust attenuation and star formation

determinations, from z=0 to z=2The CIGALE code and its application to Herschel

surveys

SED2011-Preston- sept-2011

Véronique Buat, Elodie Giovannoli, Médéric Boquien, Sébastien Heinis, Denis Burgarella & the Herschel Reference Survey and GOODS-Herschel teams

Outline

• Description of the CIGALE code• Applications:-z=0 [Herschel Reference Survey]: integrated and

spatially resolved SEDs-1<z<2: [GOODS-Herschel]: evidence for a UV

bump in the attenuation curves of IR detected galaxies

CIGALE : Code Investigating GALaxy Emission P.I. D. Burgarella (Noll et al. 2009) http://www.oamp.fr/cigale/

INPUT PARAMETERS: •Photometric data +errors•Star Formation Histories•Dust attenuation curves•IR libraries OUTPUT PARAMETERS :All based on a Bayesian analysis• input parameters• Stellar Mass•Dust luminosity•Amount of obscuration•D4000 break, slope of the UV continuum….

A physically-motivated code:CIGALE combines a UV-optical SED & a dust IR emitting component:

Energetic balance fully conserved between stellar and dust emission.

STELLAR COMPONENT

•« Old » stellar population: SFR exponentially decreasing, age, e-folding rates are free parameters•« Young » stellar population: SFR exponentially decreasing or constant, age, e-folding rates are free parameters•Composite population: mass fraction due to the young stellar population as free parameter

Populations synthesis models from:•Maraston 2005•PEGASE (Fioc & Rocca-Volmerange)

CIGALE: optimized to study dust attenuation curves

different amount of dust attenuation (and same attenuation curve) for the young and the old stellar population

5500 Å slope

Calzetti et al. (2000) UV bump power law

AmplitudeCentral wavelength Width

Various mid and far-IR libraries of star forming and starburst galaxies

Dale & Helou (2002)

64 templates

Chary & Elbaz (2001)

105 templates

Siebenmorgen & Krügel (2007)

~7000 SEDs -Library of modified Black bodies

Now : β=1.5, Tdust varies

several β and Tdust: collaboration with the Herschel Reference Survey Team, nearby universe

-Draine & Li (2007) library, work in progress

AGN librariesGiovannoli, 2011, PhD thesis

To go deeper in the AGN analysis32 AGNs from Fritz et al. 2006

Current Baseline: 9 SED templates of AGNs2 AGNs Siebenmorgen & Krugel (04)Mean AGN from Mullaney et al. (10)6 AGNs from Fritz et al. (06)

We build mock catalogues to check the robustness of parameter estimates:•Run CIGALE a first time and take the best model for each galaxy •Create an artificial dataset with the best models integrated in the photometric bands and add noise•Run again CIGALE on the mock catalogue and compare « true » and estimated parameters

(Giovannoli et al. 2011, Buat et al. 2011)

SED fitting in the Herschel Reference Survey

HRS (PI S. Eales): Volume limited, K-selected survey of 323 galaxies observed at 250, 350, 500 µm 15 < D < 25 Mpc, b > 55°, AB < 0.2K < 8.7 for E, S0, S0a and K < 12 for Sa-Im-BCD

9

all

Early-types

Late-types

Boselli et al. 2010

Full integrated IR SEDs (cf L. Ciesla poster)

Draine & Li 2007M99

Dale & Helou 2002Mean SEDs

Chary & Elbaz 2001Mean SEDs

HRS SEDs by morphological type

•Individual SEDs: Dale & Helou (02) give good fits, Draine & Li (07) better reproduce the data•Mean SEDs per morphological type: Dale & Helou (02), Chary & Elbaz (01), Elbaz et al. (11) well reproduce mean SEDs of late types.

All the data are convolved and regridded to the same reference frame (at 350 microns) and a pixel-to-pixel analysis of the emission is performed by fitting the SED of each pixel with CIGALE

FUV 350 µm

HRS102-M99

FUV NUV u

g r i

70 µm 250 µm 350 µm

z H

Spatially resolved SEDs on large galaxies(M. Boquien et al. In prep.)

Subset of ~30 late-type galaxies and pixel to pixel analysis at the resolution of the 350 microns frame

A(FUV) LIR

Dust attenuation curve in external galaxies:Evidence for a UV bump in galaxies detected in IR at 1<z<2

Buat et al. 2011, A&A, in press

Calzetti et al. 94, 00: from spectroscopic datano bump in local starburt galaxies, moderate rise in UV

Wild et al.

In local galaxies: GALEX UV bands and u(SDSS) well suited to test the presence of the bump

FUV NUV u

Calzetti 01 Wild et al. 11

Similar conclusion by Wild et al 11 but see also Wijesinghe et al. 2010, Johnson et al. 2007

At low z: some evidence for a bump in local star forming galaxies from broad band analyses

Burgarella et al. 05- SED-fitting IRAS-GALEX data

Conroy et al. 2010, broad band colours and model (SDSS)

MW

LMC

NUV-u

FUV-

NU

V0.4 0.6 0.8 1.0 1.2 1.4

Ilbert et al. 2009- Cosmos field-30 photometric bands from UV to NIR:« A broad absorption excess at 2175 A seems necessary to explain the UV flux of some starburst galaxies »

At high z:Composite spectrum

1.5<z<2.5: evidence for a bump for 30% of the

sourcesNoll et al. 2009

But no evidence for a bump in Lyman Break Galaxies at z≈2 (Vijh et al. 03, Reddy et al. 08)

•We work at high z to redshift the UV range in the visible•We combine optical (UV rest-frame) and far-IR data: strong constraint on SFR and dust attenuation•We use intermediate band filters in optical to tightly sample the UV rest frame

Working in the CDFS combining Herschel/PACS (GOODS-Herschel project, PI: D Elbaz) andSubaru/MUSYC broad and intermediate band filters (Cardamone et al. 2010)+IRAC & MIPS data (Dickinson et al. 2003)30 sources (28 with spec-z) in the GOODS-S field with 1<z<2 and high SNR in 30 photometric bands: SNR > 5 in optical, NIR, mid-IR and at 100 µm, SNR > 3 at 160 µm:

GOODS-H-CDFS field at 24-100-160 µm

Subaru Intermediate band filters

Selection of the sources with 1<z<2 to sample the region of the UV bump

•Evidence for a UV bump on the observed SEDs•Intermediate band photometry very powerful for SED analyses•Very good fits for the whole sample: a bump is always found.

General shape of the average attenuation curve consistent with that of Charlot & Fall and (marginally) with that of Calzetti et al. on top of which there is a bump at 2175 A whose amplitude is 35% (76%) that of the MW (LMC2) one .Width of the feature: 356 Å (437 Å for the MW)

Charlot & Fall 00, cst SFR over3 108 yrs

Calzetti et al. 00

BUMP

Conclusions

•We have developped a physically-motivated code of SED fitting, well suited for the analysis of dust attenuation and star formation •The code has been applied both at low and high redshift, in the framework of Herschel surveys

•HRS: analysis of both integrated and spatially resolved SEDs•GOODS-Herschel: dust attenuation curve derived for galaxies at 1<z<2 and with a UV bump whose amplitude is 35% that of the MW•PEP/HerMES/COSMOS : work in progress