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present composite spectra constructed from a sample of 242 150 Lyman a (Lyα) forest absorbers at redshifts 2.4 < z < 3.1 identified in quasar spectra from the Baryon Oscillation Spectroscopic Survey (BOSS) as part of Data Release 9 of the Sloan Digital Sky Survey III. We select forest absorbers by their flux in bins 138 km s-1 wide (approximately the size of the BOSS resolution element). We split these absorbers into five samples spanning the range of flux -0.05 ≤ F < 0.45. Tests on a smaller set of high-resolution spectra show that our three strongest absorption samples would probe circumgalactic regions (projected separation

We report discoveries of 165 new quasar Ca  ii absorbers from the Sloan Digital Sky Survey (SDSS) Data Releases 7 and 12. Our c a  ii rest-frame equivalent width distribution supports the weak and strong subpopulations, split at |${W}^{\lambda 3934}_{0}=0.7$| Å. Comparison of both populations' dust depletion shows clear consistency for weak absorber association with halo-type gas in the Milky Way (MW), while strong absorbers have environments consistent with halo and disc-type gas. We probed our high-redshift Ca  ii absorbers for 2175 Å dust bumps, discovering 12 2175 Å dust absorbers (2DAs). This clearly shows that some Ca  ii absorbers follow the Large Magellanic Cloud (LMC) extinction law rather than the Small Magellanic Cloud extinction law. About 33 per cent of our strong Ca  ii absorbers exhibit the 2175 Å dust bump, while only 6 per cent of weak Ca  ii absorbers show this bump. 2DA detection further supports the theory that strong Ca  ii absorbers are associated with disc components and are dustier than the weak population. Comparing average Ca  ii absorber dust depletion patterns to that of Damped Ly α absorbers (DLAs), Mg  ii absorbers, and 2DAs shows that Ca  ii absorbers generally have environments with more dust than DLAs and Mg  ii absorbers, but less dust than 2DAs. Comparing 2175 Å dust bump strengths from different samples and also the MW and LMC, the bump strength appears to grow stronger as the redshift decreases, indicating dust growth and the global chemical enrichment of galaxies in the Universe over time. [ABSTRACT FROM AUTHOR]

TOU is an extremely high resolution optical spectrograph (R  = 100 000, 380–900 nm), which is designed to detect low-mass exoplanets using the radial velocity technique. We describe an IDL-based radial velocity (RV) data reduction pipeline for the TOU spectrograph and its performance with stable stars. This pipeline uses a least-squares fitting algorithm to match observed stellar spectra to a high-signal-to-noise template created for each star. By carefully controlling all of the error contributions to RV measurements in both the hardware and data pipeline, we have achieved ∼0.9 m s−1 long-term RV precision with one of the most RV-stable stars, Tau Ceti, similar to what has been achieved with HARPS. This paper presents steps and details in our data pipeline on how to reach the sub-m s−1 RV precision and also all major error sources that contribute to the final RV measurement uncertainties. The lessons learned in this pipeline development can be applied to other environmentally controlled, very high resolution optical spectrographs to improve RV precision. [ABSTRACT FROM AUTHOR]

We present the results of time-resolved high-resolution spectroscopic observations of the very active RS Canum Venaticorum (RS CVn) star SZ Piscium (SZ Psc), obtained during two consecutive observing nights on 2011 October 24 and 25. Several optical chromospheric activity indicators are analysed using the spectral subtraction technique, which show the remarkably different behaviour between two nights. Gradually blue-shifted and strengthened excess absorption features presented in the series of the subtracted spectra (especially for the Hα, |$\rm{He\,{\small I}}$| D3, and Hβ lines), as a result of active stellar prominence that is rising its height along the line of our sight, was detected in the observations on October 24. This prominence activation event was probably associated with the subsequently occurred optical flare, and part of that flare decay phase was hunted in the observations on October 25. The flare was characterized by the prominent |$\rm{He\,{\small I}}$| D3 line emission, as well as stronger chromospheric emission in the Hα, Hβ, and other active lines. The gradual decay of flare was accompanied by an obviously developmental absorption feature in the blue wing of the Hα and other active lines, which could be explained as cool post-flare loops which projected against the bright flare background. Therefore, a series of possibly associated magnetic activity phenomena, including flare-related prominence activation, optical flare, and post-flare loops, were detected during our observations. [ABSTRACT FROM AUTHOR]

We present the effective temperatures (Teff), metallicities, and colours in Sloan Digital Sky Survey (SDSS), Two Micron All Sky Survey, andWide-field Infrared Survey Explorer filters, of a sample of 3834 late-K and early-M dwarfs selected from the SDSS Apache Point Observatory Galactic Evolution Experiment (APOGEE) spectroscopic survey ASPCAP (APOGEE Stellar Parameters and Chemical Abundances Pipeline) catalogue. We confirm that ASPCAP Teff values between 3550 < Teff < 4200 K are accurate to ~100 K compared to interferometric Teff values. In that same Teff range, ASPCAP metallicities are accurate to 0.18 dex between -1.0 <[M/H]<0.2. For these cool dwarfs, nearly every colour is sensitive to both Teff and metallicity. Notably, we find that g - r is not a good indicator of metallicity for near-solar metallicity early-M dwarfs. We confirm that J - KS colour is strongly dependent on metallicity, and find that W1 - W2 colour is a promising metallicity indicator. Comparison of the late-K and early-M dwarf colours, metallicities, and Teff to those from three different model grids shows reasonable agreement in r - z and J - KS colours, but poor agreement in u - g, g - r, and W1 - W2. Comparison of the metallicities of the KM dwarf sample to those from previous colour-metallicity relations reveals a lack of consensus in photometric metallicity indicators for late-K and early-M dwarfs. We also present empirical relations for Teff as a function of r - z colour combined with either [M/H] or W1 - W2 colour, and for [M/H] as a function of r - z and W1 - W2 colour. These relations yield Teff to ~100 K and [M/H] to ~0.18 dex precision with colours alone, for Teff in the range of 3550-4200 K and [M/H] in the range of -0.5-0.2. [ABSTRACT FROM AUTHOR]

The baryon acoustic oscillation (BAO) feature in the power spectrum of galaxies provides a standard ruler to probe the accelerated expansion of the Universe. The current surveys covering a comoving volume sufficient to unveil the BAO scale are limited to redshift z ≲ 0.7. In this paper, we study several galaxy selection schemes aiming at building an emission-line galaxy (ELG) sample in the redshift range 0.6 < z < 1.7 that would be suitable for future BAO studies using the Baryonic Oscillation Spectroscopic Survey (BOSS) spectrograph on the Sloan Digital Sky Survey (SDSS) telescope. We explore two different colour selections using both the SDSS and the Canada–France–Hawaii Telescope Legacy Survey (CFHT-LS) photometry in the u, g, r and i bands and evaluate their performance selecting luminous ELGs. From about 2000 ELGs, we identified a selection scheme that has a 75 per cent redshift measurement efficiency. This result confirms the feasibility of massive ELG surveys using the BOSS spectrograph on the SDSS telescope for a BAO detection at z ∼ 1, in particular the proposed eBOSS experiment, which plans to use the SDSS telescope to combine the use of the BAO ruler with redshift space distortions using ELGs and quasars in the redshift range 0.6 < z < 2.2. [ABSTRACT FROM PUBLISHER]