We present a study of the circumstellar environment of IRAS~04158+2805 based on multi-wavelength observations and models .
Images in the optical and near-infrared , a polarisation map in the optical , and mid-infrared spectra were obtained with VLT-FORS1 , CFHT-IR , and Spitzer -IRS .
Additionally we used an X-ray spectrum observed with Chandra .
We interpret the observations in terms of a central star surrounded by an axisymmetric circumstellar disc , but without an envelope , to test the validity of this simple geometry .
We estimate the structural properties of the disc and its gas and dust content .
We modelled the dust disc with a 3D continuum radiative transfer code , MCFOST , based on a Monte-Carlo method that provides synthetic scattered light images and polarisation maps , as well as spectral energy distributions .
We find that the disc images and spectral energy distribution narrowly constrain many of the disc model parameters , such as a total dust mass of 1.0 - 1.75 \cdot 10 ^ { -4 } M _ { \odot } and an inclination of 62 \degr - 63 \degr .
The maximum grain size required to fit all available data is of the order of 1.6 - 2.8 \mu m although the upper end of this range is loosely constrained .
The observed optical polarisation map is reproduced well by the same disc model , suggesting that the geometry we find is adequate and the optical properties are representative of the visible dust content .
We compare the inferred dust column density to the gas column density derived from the X-ray spectrum and find a gas-to-dust ratio along the line of sight that is consistent with the ISM value .
To our knowledge , this measurement is the first to directly compare dust and gas column densities in a protoplanetary disc .