We examine the properties of the host galaxies of 22 623 narrow‐line active galactic nuclei (AGN) with 0.02 < z < 0.3 selected from a complete sample of 122 808 galaxies from the Sloan Digital Sky Survey. We focus on the luminosity of the [O iii]λ5007 emission line as a tracer of the strength of activity in the nucleus. We study how AGN host properties compare with those of normal galaxies and how they depend on L[O iii]. We find that AGN of all luminosities reside almost exclusively in massive galaxies and have distributions of sizes, stellar surface mass densities and concentrations that are similar to those of ordinary early‐type galaxies in our sample. The host galaxies of low‐luminosity AGN have stellar populations similar to normal early types. The hosts of high‐luminosity AGN have much younger mean stellar ages. The young stars are not preferentially located near the nucleus of the galaxy, but are spread out over scales of at least several kiloparsecs. A significant fraction of high‐luminosity AGN have strong Hδ absorption‐line equivalent widths, indicating that they experienced a burst of star formation in the recent past. We have also examined the stellar populations of the host galaxies of a sample of broad‐line AGN. We conclude that there is no significant difference in stellar content between type 2 Seyfert hosts and quasars (QSOs) with the same [O iii] luminosity and redshift. This establishes that a young stellar population is a general property of AGN with high [O iii] luminosities.

The Sloan Digital Sky Survey (SDSS) will provide the data to support detailed investigations of the distribution of luminous and non- luminous matter in the Universe: a photometrically and astrometrically calibrated digital imaging survey of pi steradians above about Galactic latitude 30 degrees in five broad optical bands to a depth of g' about 23 magnitudes, and a spectroscopic survey of the approximately one million brightest galaxies and 10^5 brightest quasars found in the photometric object catalog produced by the imaging survey. This paper summarizes the observational parameters and data products of the SDSS, and serves as an introduction to extensive technical on-line documentation.Comment: 9 pages, 7 figures, AAS Latex. To appear in AJ, Sept 200

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We refine a technique to measure the absorption corrected ultraviolet (UV) luminosity of starburst galaxies using rest frame UV quantities alone, and apply it to Lyman-limit U -dropouts at z ≈ 3 found in the Hubble Deep field (HDF). The method is based on an observed correlation between the ratio of far infrared (FIR) to UV fluxes with spectral slope β (a UV color). A simple fit to this relation allows the UV flux absorbed by dust and reprocessed to the FIR to be calculated, and hence the dust-free UV luminosity to be determined. International Ultraviolet Explorer spectra and InfraRed Astronomical Satellite fluxes of local starbursts are used to calibrate the F FIR /F 1600 versus β relation in terms of A 1600 (the dust absorption at 1600Å), and the transformation from broad band photometric color to β. Both calibrations are almost completely independent of theoretical stellar population models. We show that the recent marginal and non-detections of HDF U -dropouts at radio and sub-mm wavelengths are consistent with their assumed starburst nature, and our calculated A 1600 . This is also true of recent observations of the ratio of optical emission line flux to UV flux density in the brightest U -dropouts. This latter ratio turns out not to be a good indicator of dust extinction. In U -dropouts, absolute magnitude M 1600,0 correlates with β: brighter galaxies are redder, as is observed to be the case for local starburst galaxies. This suggests that a mass-metallicity relationship is already in place at z ≈ 3. The absorption-corrected UV luminosity function of U -dropouts extends up to M 1600,0 ≈ −24 ABmag corresponding to a star formation rate ∼ 200 M ⊙ yr −1 (H 0 = 50 km s −1 Mpc −1 , q 0 = 0.5 assumed throughout). The absorption-corrected UV luminosity density at z ≈ 3 is ρ 1600,0 ≥ 1.4 × 10 27 erg s −1 Hz −1 Mpc −3 . It is still a lower limit since completeness corrections have not been done and because only galaxies with A 1600 ∼ < 3.6 mag are blue enough in the UV to be selected as U -dropouts. The luminosity weighted mean dust absorption factor of our sample is 5.4 ± 0.9 at 1600Å.

The Sloan Digital Sky Survey (SDSS) is an imaging and spectroscopic survey that will eventually cover approximately one-quarter of the celestial sphere and collect spectra of %10 6 galaxies, 100,000 quasars, 30,000 stars, and 30,000 serendipity targets. In 2001 June, the SDSS released to the general astronomical community its early data release, roughly 462 deg 2 of imaging data including almost 14 million detected objects and 54,008 follow-up spectra. The imaging data were collected in drift-scan mode in five bandpasses (u, g, r, i, and z); our 95% completeness limits for stars are 22.0, 22.2, 22.2, 21.3, and 20.5, respectively. The photometric calibration is reproducible to 5%, 3%, 3%, 3%, and 5%, respectively. The spectra are flux-and wavelength-calibrated, with 4096 pixels from 3800 to 9200 Å at R % 1800. We present the means by which these data are distributed to the astronomical community, descriptions of the hardware used to obtain the data, the software used for processing the data, the measured quantities for each observed object, and an overview of the properties of this data set.