We empirically test the relation between the SFR ( L _ { IR } ) derived from the infrared luminosity , L _ { IR } , and the SFR ( H \alpha ) derived from the H \alpha emission line luminosity using simple conversion relations .
We use a sample of 474 galaxies at z = 0.06 - 0.46 with both H \alpha detection ( from 20k zCOSMOS survey ) and new far-IR Herschel data ( 100 and 160 \mu m ) .
We derive SFR ( H \alpha ) from the H { \alpha } extinction corrected emission line luminosity .
We find a very clear trend between E ( B - V ) and L _ { IR } that allows to estimate extinction values for each galaxy even if the H \beta emission line measurement is not reliable .
We calculate the L _ { IR } by integrating from 8 up to 1000 \mu m the SED that is best fitting our data .
We compare the SFR ( H \alpha ) with the SFR ( L _ { IR } ) .
We find a very good agreement between the two SFR estimates , with a slope of m = 1.01 \pm 0.03 in the log SFR ( L _ { IR } ) vs log SFR ( H { \alpha } ) diagram , a normalization constant of a = -0.08 \pm 0.03 and a dispersion of \sigma = 0.28 dex .
We study the effect of some intrinsic properties of the galaxies in the SFR ( L _ { IR } ) -SFR ( H \alpha ) relation , such as the redshift , the mass , the SSFR or the metallicity .
The metallicity is the parameter that affects most the SFR comparison .
The mean ratio of the two SFR estimators log [ SFR ( L _ { IR } ) /SFR ( H \alpha ) ] varies by \sim 0.6 dex from metal-poor to metal-rich galaxies ( 8.1 < log ( O / H ) +12 < 9.2 ) .
This effect is consistent with the prediction of a theoretical model for the dust evolution in spiral galaxies .
Considering different morphological types , we find a very good agreement between the two SFR indicators for the Sa , Sb and Sc morphologically classified galaxies , both in slope and normalization .
For the Sd , irregular sample ( Sd/Irr ) , the formal best-fit slope becomes much steeper ( m = 1.62 \pm 0.43 ) , but it is still consistent with 1 at the 1.5 \sigma level , because of the reduced statistics of this sub-sample .