Aims

• Gamma ray detection unbiased
• Estimate column density distribution (CDD) of GRBs from their X-ray afterglows
• GRB environment central CDD (upper limit)
• GRB host galaxies central CDD (upper limit)
• Low-luminosity AGN host galaxies
• Obscured fraction from galaxy-scale gas
• Compton-thick fraction from galaxy-scale gas
• Is Galaxy-scale obscuration important?