2004MNRAS.352L...6Z

We analyse the detailed structure of a highly-inclined (i≳ 80°) disc galaxy that lies within the Hubble Ultra Deep Field (UDF). The unprecedented depth of the UDF data allow disc and extraplanar emission to be traced reliably to surface brightness levels of µ_V,i,z_∼ 29-30 mag/arcsec2 (corresponding to rest-frame equivalents of µ_g,r,i_∼ 28-29 mag/arcsec2) in this redshift z= 0.32 system. We detect excess emission above the disc, which is characterized by a moderately flattened (b/a∼ 0.6) power law (I∝R^–2.6). The structure and colour of this component are very similar to the stellar halo detected in an SDSS stacking analysis of local disc galaxies and lend support to the idea that we have detected a stellar halo in this distant system. Although the peculiar colours of the halo are difficult to understand in terms of normal stellar populations, the consistency found between the UDF and SDSS analyses suggests that they cannot be easily discounted.