COSMOGRAIL: Measuring Time Delays of Gravitationally Lensed Quasars to Constrain Cosmology

COSMOGRAIL is a long-term programme for the photometric monitoring of gravitationally lensed quasars. It makes use of several medium-size telescopes to derive long and well-sampled light curves of lensed quasars, in order to measure the time delays between the quasar images. These delays directly relate to the Hubble constant H0, without any need for secondary distance calibrations. COSMOGRAIL was initiated in 2004, and has now secured almost a decade of data, resulting in cosmological constraints that are very complementary to other cosmological probes

The Stellar Abundances and Galactic Evolution Survey (SAGES). I. General Description and the First Data Release (DR1)

The Stellar Abundances and Galactic Evolution Survey (SAGES) of the northern sky is a specifically designed multiband photometric survey aiming to provide reliable stellar parameters with accuracy comparable to those from low-resolution optical spectra. It was carried out with the 2.3 m Bok telescope of Steward Observatory and three other telescopes. The observations in the u _s and v _s passband produced over 36,092 frames of images in total, covering a sky area of ∼9960 deg ^2 . The median survey completenesses of all observing fields for the two bands are u _s = 20.4 mag and v _s = 20.3 mag, respectively, while the limiting magnitudes with signal-to-noise ratio of 100 are u _s ∼ 17 mag and v _s ∼ 18 mag, correspondingly. We combined our catalog with the data release 1 (DR1) of the first Panoramic Survey Telescope And Rapid Response System (Pan-STARRS, PS1) catalog, and obtained a total of 48,553,987 sources that have at least one photometric measurement in each of the SAGES u _s and v _s and PS1 grizy passbands. This is the DR1 of SAGES, released in this paper. We compared our gri point-source photometry with those of PS1 and found an rms scatter of ∼2% difference between PS1 and SAGES for the same band. We estimated an internal photometric precision of SAGES to be of the order of ∼1%. Astrometric precision is better than 0.″2 based on comparison with DR1 of the Gaia mission. In this paper, we also describe the final end-user database, and provide some science applications