The observed ultraviolet continuum ( UVC ) slope is potentially a powerful diagnostic of dust obscuration in star forming galaxies .
However , the intrinsic slope is also sensitive to the form of the stellar initial mass function ( IMF ) and to the recent star formation and metal enrichment histories of a galaxy .
Using the galform semi-analytical model of galaxy formation , we investigate the intrinsic distribution of UVC slopes .
For star-forming galaxies , we find that the intrinsic distribution of UVC slopes at z = 0 , parameterised by the power law index \beta , has a standard deviation of \sigma _ { \beta } \simeq 0.30 .
This suggests an uncertainty on the inferred UV attenuation of A _ { fuv } \simeq 0.7 ( assuming a Calzetti attenuation curve ) for an individual object , even with perfect photometry .
Furthermore , we find that the intrinsic UVC slope correlates with star formation rate , intrinsic UV luminosity , stellar mass and redshift .
These correlations have implications for the interpretation of trends in the observed UVC slope with these quantities irrespective of the sample size or quality of the photometry .
Our results suggest that in some cases the attenuation by dust has been incorrectly estimated .