Type 1 AGN at low z. I. Emission properties

We analyze the emission properties of a new sample of 3 596 type 1 AGN, selected from the SDSS DR7 based on the detection of broad Hα emission. The sample extends over a broad Hα luminosity L_bHα of 10⁴⁰-10⁴⁴ erg s^-1 and a broad Hα FWHM of 1 000-25 000 km s^-1, which covers the range of black hole mass 10⁶ < M_BH/Mȯ < 10^9.5 and luminosity in Eddington units 10^-3 < L/L_Edd < 1. We combine ROSAT, GALEX and 2MASS observations to form the SED from 2.2 μm to 2 keV. We find the following: 1. The distribution of the Hα FWHM values is independent of luminosity. 2. The observed mean optical-UV SED is well matched by a fixed shape SED of luminous quasars, which scales linearly with L _bHα, and a host galaxy contribution. 3. The host galaxy r-band (fibre) luminosity function follows well the luminosity function of inactive non-emission line galaxies (NEG), consistent with a fixed fraction of ∼ 3% of NEG hosting an AGN, regardless of the host luminosity. 4. The optical-UV SED of the more luminous AGN shows a small dispersion, consistent with dust reddening of a blue SED, as expected for thermal thin accretion disc emission. 5. There is a rather tight relation of νL_ν(2 keV) and L _bHα, which provides a useful probe for unobscured (true) type 2 AGN.