We describe the Sloan

The fourth generation of the Sloan

No abstract

This paper documents the seventeenth data release (DR17) from the Sloan Digital Sky Surveys; the fifth and final release from the fourth phase (SDSS-IV). DR17 contains the complete release of the Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) survey, which reached its goal of surveying over 10,000 nearby galaxies. The complete release of the MaNGA Stellar Library accompanies this data, providing observations of almost 30,000 stars through the MaNGA instrument during bright time. DR17 also contains the complete release of the Apache Point Observatory Galactic Evolution Experiment 2 survey that publicly releases infrared spectra of over 650,000 stars. The main sample from the Extended Baryon Oscillation Spectroscopic Survey (eBOSS), as well as the subsurvey Time Domain Spectroscopic Survey data were fully released in DR16. New single-fiber optical spectroscopy released in DR17 is from the SPectroscipic IDentification of ERosita Survey subsurvey and the eBOSS-RM program. Along with the primary data sets, DR17 includes 25 new or updated value-added catalogs. This paper concludes the release of SDSS-IV survey data. SDSS continues into its fifth phase with observations already underway for the Milky Way Mapper, Local Volume Mapper, and Black Hole Mapper surveys.

We present results of an age and metallicity gradient analysis inferred from both optical and near-infrared surface photometry. The analysis is based on a sample of 36 nearby early-type galaxies, obtained from the Early Data Release of the Sloan Digital Sky Survey and the Two Micron All Sky Survey. Surface brightness profiles were derived in each band, and used to study the color gradients of the galaxies. Using simple stellar population models with both optical and near infrared colors, we may interpret the color gradients in term of age and metallicity gradients of galaxies. Using g Z ≡ d log Z met /d log R and g A = d log Age/d log R to represent the metallicity and age gradients, we found a median value of g Z = −0.25 ± 0.03 for the metallicity gradient, with a dispersion σ g Z = 0.19 ± 0.02. The corresponding values for the age gradients were g A = 0.02 ± 0.04 and σ g A = 0.25 ± 0.03. These results are in good agreement with recent observational results, as well as with recent simulations that suggest both monolithic collapse and major mergers have played important roles in the formation of early-type galaxies. Our results demonstrate the potential of using multi-waveband colors obtained from current and future optical and infrared surveys in constraining the age and metallicity gradients of early-type galaxies.