Deep imaging of Q2112+059: A bright host galaxy but no DLA absorber

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Abstract
In a ongoing programme aimed at studying galaxy counterparts of Damped Ly-alpha Absorbers (DLAs) we have obtained high resolution deep I-band imaging data of the field around the z_em = 0.457 BAL QSO Q2112+059. In the literature this QSO is listed to have a candidate DLA at z_abs = 0.2039 along the line of sight. After subtraction of the QSO Point Spread Function (PSF) we detect a galaxy centred on the position of Q2112+059. To help answer whether this galaxy is the DLA or the QSO host galaxy we retrieved a GHRS spectrum of Q2112+059 from the HST-archive. This spectrum shows that there is no Ly-alpha absorption line at z_abs = 0.2039. This fact in combination with the perfect alignment on the sky of the galaxy and Q2112+059 lead us to the conclusion that the galaxy must be the host galaxy of Q2112+059. The host galaxy of Q2112+059 is bright (M_I^obs = -23.6), and has a radial profile well fitted by a {\it modified Hubble + de Vaucouleurs} profile with R_c = 0.5 kpc and R_e = 3.6 kpc. Our results are well in line with the conclusion of earlier work done at lower redshifts, that bright low redshift QSOs preferentially reside in luminous, elliptical galaxies. The host of Q2112+059 is however, despite it's brightness, very compact when compared to early type galaxies at lower redshifts.

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