AKARI-SDSS-GALEX: Spectral energy distributions

of nearby galaxiesStar formation rates and dust attenuation

propertiesV. Buat1 , T. T. Takeuchi2 , F.-T. Yuan2,

E. Giovannoli1 , S. Heinis1

1 Laboratoire d’Astrophysique de Marseille2 Nagoya University•Takeuchi et al. A&A, 2010, 514, A4

•Buat et al. A&A, 2011, 529, A22•Yuan et al. PASJ, 2011, 63, 1207

Jeju, 27-29 Feb 2012, The legacy of Akari: a panoramic view of the dusty universe

Outline

• Samples definition • SED fitting on multi-λ data• Dust attenuation recipes• Green valley galaxies • SFR calibrations

Sample selections

AKARI FIS all sky survey FIS Bright Source Catalogue Xmatched with IRAS PSCz + SDSS/DR7 and GALEX/GR4-5 surveys

2MASS data also addedPrimary sample: 776 galaxies selected at 90 µm:

(Takeuchi et al. 2010)

363 galaxies all detected 153 galaxies Xmatched at 140 µm with AKARI/IRC PSC

(Buat et al. 2011) (Yuan et al. 2011) and poster 2-21 for details

SED fitting with CIGALE

Reliability of SED fitting results checked on artificial galaxies:

Buat et al. 2011

Parameter estimationStar formation history

Dust attenuation

Dust emission

Dust attenuation

Takeuchi et al. 2010, Buat et al. 2011

Meurer et al. 95, 99, Calzetti et al. 00

f(1200-2500Å), : a proxy for dust attenuation in local starburst galaxies observed by IUE and IRAS

The slope of the UV continuum: a measure dust attenuation?

Dale et al. 07See also Boissier et al. 07Munoz-Mateos et al. 09

SINGS

see also Howell et al 2010, Goldader et al. 2002, Buat et al. 2005, Seibert et al. 05 Munoz-Mateos et al. 09, Overzier et al. 10 etc…

Buat et al. 2011AKARI-SDSS-GALEX data + SED fitting Very dispersed relations

A FUV

(fro

m L

ir/L U

V) m

ag

o LIRGs__ Meurer et al 99 Seibert et al. 05- - Salim et al 07

Takeuchi et al. 10

FUV-NUV a proxy for ß

AKARI-SDSS-GALEX: a very large dispersion

FUV-NUV

FUV-r

colour

AFUV = 2.39 (FUV-NUV)+0.89 (σ = 0.83) σ(FUV-NUV) = 0.2 mag σ(AFUV) = 0.5 magAFUV = 0.65 (FUV-r)+0.04 (σ = 0.76) σ(FUV-r) = 0.2 mag σ(AFUV) = 0.1 mag

UV-optical colours are only crude estimators of dust attenuation

See also Johnson et al. 2007

Green valley: star formation and dust attenuationTakeuchi et al. 2010, Heinis et al. in prep

Blue cloud star forming galaxies NUV-r < 3.5Red cloud, quiescent galaxiesNUV-r > 4.7Green valley3.5<NUV-r<4.7

Galaxies in the green valley:

Distributions of D4000 and SSFR close to those of the blue cloud galaxies but with a tail towards quiescent galaxies.The galaxies in the green valley have larger attenuations than blue galaxies

On going work

SFR calibrations

Buat et al. 2011: Combining IR and UV dataYuan et al. 2011: Calibration of MIR fluxes

Adding UV and IR measurements to estimate the SFRsBuat et al. 11

SFR(Msun yr-1) = (1-) SFR(IR)+SFR(UVobs)

SFR(IR) and SFR(UV) from recipes (e.g. Kennicutt 98)

corresponds to the fraction of L(IR) due to the heating by old starsHirashita et al. 03, Iglesias-Paramo et al. 04,06, Bell 03 = 0.3-0.4 (star forming galaxies)

η= 0.17 +/- 0.10

logSFR9 = 0.99 log(L9)-9.02 (σ=0.18 dex) logSFR18 = 0.90 log(L18)-8.03 (σ=0.20 dex)

MIR luminosities calibrated in SFRsYuan et al. 2011

Comparison with calibrations from Spitzer

AKARI

Log(SFR8/SFR9) = -0.14 +/- 0.18 (Wu et al)Log(SFR8/SFR9) = -0.25 +/- 0.16 (Zhu et al)

Fluxes at 8 and 24 µm from the best model (Dale and Helou 02 templates)

Log(SFR24/SFR18) = -0.01 +/- 0.12 (Wu et al)Log(SFR24/SFR18) = -0.05 +/- 0.11 (Zhu et al)Log(SFR24/SFR18) = -0.04 +/- 0.17 (Rieke et al)

Conclusions• Reference samples based on a FIR selection and with

large wavelength coverage.• Reliable SFR and dust attenuation retrieved from SED

fitting, calibrations investigated. • Green valley galaxies easily identified: combination of

dusty « blue cloud » galaxies and more quiescent objects

• Samples which can be used for comparison in high z studies:

Elbaz et al., Wang et al. (similar samples) Symeonidis et al (in prep)