ALBERT

Description: We report the discovery of 13 confirmed two-image quasar lenses from a systematic search for gravitationally lensed quasars in the SDSS-III Baryon Oscillation Spectroscopic Survey (BOSS). We adopted a methodology similar to that used in the SDSS Quasar Lens Search (SQLS). In addition to the confirmed lenses, we report 11 quasar pairs with small angular separations ( 2 arcsec) confirmed from our spectroscopy, which are either projected pairs, physical binaries, or possibly quasar lens systems whose lens galaxies have not yet been detected. The newly discovered quasar lens system, SDSS J1452+4224 at z s 4.8 is one of the highest redshift multiply imaged quasars found to date. Furthermore, we have over 50 good lens candidates yet to be followed up. Owing to the heterogeneous selection of BOSS quasars, the lens sample presented here does not have a well-defined selection function.

Description: Using the Low Dispersion Survey Spectrograph 3 at the Magellan II Clay Telescope, we target candidate absorption host galaxies detected in deep optical imaging (reaching limiting apparent magnitudes of 23.0–26.5 in g , r , i , and z filters) in the fields of three QSOs, each of which shows the presence of high metallicity, high $N_{\rm H\,\small {i}}$ absorption systems in their spectra (Q0826-2230: z abs = 0.9110, Q1323-0021: z abs = 0.7160, Q1436-0051: z abs = 0.7377, 0.9281). We confirm three host galaxies at redshifts 0.7387, 0.7401, and 0.9286 for two of the Lyman α absorption systems (one with two galaxies interacting). For these systems, we are able to determine the star formation rates (SFRs); impact parameters (from previous imaging detections); the velocity shift between the absorption and emission redshifts; and, for one system, also the emission metallicity. Based on previous photometry, we find these galaxies have L 〉 L *. The [O ii ] SFRs for these galaxies are in the range 11–25 M  yr –1 (uncorrected for dust), while the impact parameters lie in the range 35–54 kpc. Despite the fact that we have confirmed galaxies at 50 kpc from the QSO, no gradient in metallicity is indicated between the absorption metallicity along the QSO line of sight and the emission line metallicity in the galaxies. We confirm the anticorrelation between impact parameter and $N_{\rm H\,\small {i}}$ from the literature. We also report the emission redshift of five other galaxies: three at z em 〉 z QSO , and two ( L 〈 L *) at z em 〈 z QSO not corresponding to any known absorption systems.

Description: We exploit stellar population models of absorption line indices in the ultraviolet (from 2000 to 3200 Å) to study the spectra of massive galaxies. Our central aim is to investigate the occurrence at high redshift of the UV upturn, i.e. the increased UV emission due to old stars observed in massive galaxies and spiral bulges in the local Universe. We use a large (~275 000) sample of z  ~ 0.6 massive ( M */M  〉 11.5) galaxies using both individual spectra and stacks and employ a suite of models including a UV contribution from old populations, spanning various effective temperatures, fuel consumptions and metallicities. We find that a subset of our indices; Mg i , Fe i , and BL3096, are able to differentiate between old and young UV ages. We find evidence for old stars contributing to the UV in massive galaxies, rather than star formation. The data favour models with low/medium upturn temperatures (10 000–25 000 K) consistent with local galaxies, depending on the assumed metallicity, and with a larger fuel ( $f \sim 6.5\times 10^{-2}\, \rm {M}_{{\odot }}$ ). Models with one typical temperature are favoured over models with a temperature range, which would be typical of an extended horizontal branch. Old UV-bright populations are found in the whole galaxy sample (92 per cent), with a mass fraction peaking around 20–30 per cent. Upturn galaxies are massive and have redder colours, in agreement with findings in the local Universe. We find that the upturn phenomenon appears at z  ~ 1 and its frequency increases towards lower redshift, as expected by stellar evolution of low-mass stars. Our findings will help constrain stellar evolution in the exotic UV upturn phase.

Description: We present photometric and spectroscopic measurements of 53 QSO–galaxy pairs from the Sloan Digital Sky Survey (SDSS), where nebular emission lines from a 0 〈 z 〈 0.84 foreground galaxy are detected in the fibre spectra of a background QSO, bringing the overall sample to 103 QSO–galaxy pairs detected in the SDSS. We here study the nature of these systems. Detected foreground galaxies appear at impact parameters between 0.37 and 12.68 kpc. The presence of oxygen and Balmer emission lines allows us to determine the emission line metallicities for our sample, which are on average supersolar in value. Star formation rates for our sample are in the range 0.01–12 M  yr –1 . We utilize photometric redshift fitting techniques to estimate the M * values of our galaxies (log M * = 7.34–11.54), and extrapolate this relationship to those galaxies with no imaging detections. Where available, we measure the absorption features present in the QSO spectrum due to the foreground galaxy and the relationships between their rest equivalent widths. We report an anticorrelation between impact parameter and E ( B  –  V ) ( g  –  i ) , as well as a correlation between galaxy colour ( u  –  r ) and E ( B  –  V ) ( g  –  i ) . We find that our sample is one of late-type, star-forming galaxies comparable to field galaxies in a similar redshift range, providing important clues to better understand absorption systems. These galaxies represent a sample of typical galaxies in the local Universe for which abundances, extinction, morphology, and absorption properties may be measured using background QSOs with great potential for follow-up observations.

Description: We present a tentative detection of the large-scale structure of Ly α emission in the Universe at redshifts z = 2–3.5 by measuring the cross-correlation of Ly α surface brightness with quasars in Sloan Digital Sky Survey/Baryon Oscillation Spectroscopic Survey. We use a million spectra targeting luminous red galaxies at z 〈 0.8, after subtracting a best-fitting model galaxy spectrum from each one, as an estimate of the high-redshift Ly α surface brightness. The quasar–Ly α emission cross-correlation is detected on scales 1 ~ 15 h –1 Mpc, with shape consistent with a CDM model with $\Omega _{\rm m} =0.30^{+0.10}_{-0.07}$ . The predicted amplitude of this cross-correlation is proportional to the product of the mean Ly α surface brightness, 〈μ α 〉, the amplitude of mass fluctuations and the quasar and Ly α emission bias factors. We infer 〈μ α 〉 ( b α /3) = (3.9 ± 0.9) x 10 –21 erg s –1  cm –2 Å –1  arcsec –2 , where b α is the Ly α emission bias. If star-forming galaxies dominate this emission, we find SFR = (0.28 ± 0.07)(3/ b α ) yr –1  Mpc –3 . For b α = 3, this value is ~30 times larger than previous estimates from individually detected Ly α emitters, but consistent with the total SFR derived from dust-corrected, continuum UV galaxy surveys, if most of the Ly α photons from these galaxies avoid dust absorption and are reemitted after diffusing in large gas haloes. Heating of intergalactic gas by He ii photoionization from quasar radiation or jets may alternatively explain the detected correlation, and cooling radiation from gas in galactic haloes may also contribute. We also detect redshift space anisotropy of the quasar–Ly α emission cross-correlation, finding evidence at the 3.0 level that it is radially elongated, which may be explained by radiative-transfer effects. Our measurements represent the first application of the intensity mapping technique to optical observations.

Description: The use of background quasars provides a powerful tool to probe the cool gas in the circumgalactic medium of foreground galaxies. Here, we present new observations with SINFONI and X-Shooter of absorbing-galaxy candidates at z = 0.7–1. We report the detection with both instruments of the Hα emission line of one sub-damped Lyman α (sub-DLA) at z abs = 0.941 87 with $\log N({\rm H}\,{\small {I}})$ = 19.38 $^{+0.10}_{-0.15}$ towards SDSS J002133.27+004300.9. We estimate the star formation rate: SFR = 3.6 ± 2.2 M  yr –1 in that system. A detailed kinematic study indicates a dynamical mass M dyn = 10 9.9±0.4 M and a halo mass M halo = 10 11.9±0.5 M . In addition, we report the [O ii ] detection with X-Shooter of another DLA at z abs = 0.7402 with $\log N({\rm H}\,{\small {I}})$ = 20.4 ± 0.1 towards Q0052+0041 and an estimated SFR of 5.3 ± 0.7 M  yr –1 . Three other objects are detected in the continuum with X-Shooter but the nature and redshift of two of these objects are unconstrained due to the absence of emission lines, while the third object might be at the redshift of the quasar. We use the objects detected in our whole $N({\rm H}\,{\small {I}})$ -selected SINFONI survey to compute the metallicity difference between the galaxy and the absorbing gas, $\delta _{\rm H\,\small {I}}(X)$ , where a positive (negative) value indicates infall (outflow). We compare this quantity with the quasar line-of-sight alignment with the galaxy's major (minor) axis, another tracer of infall (outflow). We find that these quantities do not correlate as expected from simple assumptions. Additional observations are necessary to relate these two independent probes of gas flows around galaxies.

Description: We present a measurement of the cross-correlation of Mg ii absorption and massive galaxies, using the Data Release (DR)11 main galaxy sample of the Baryon Oscillation Spectroscopic Survey (BOSS) of Sloan Digital Sky Survey III (SDSS-III; CMASS galaxies), and the DR7 quasar spectra of SDSS-II. The cross-correlation is measured by stacking quasar absorption spectra shifted to the redshift of galaxies that are within a certain impact parameter bin of the quasar, after dividing by a quasar continuum model. This results in an average Mg ii equivalent width as a function of impact parameter from a galaxy, ranging from 50 kpc to more than 10 Mpc in proper units, which includes all Mg ii absorbers. We show that special care needs to be taken to use an unbiased quasar continuum estimator, to avoid systematic errors in the measurement of the mean stacked Mg ii equivalent width. The measured cross-correlation follows the expected shape of the galaxy correlation function, although measurement errors are large. We use the cross-correlation amplitude to derive the bias factor of Mg ii absorbers, finding $b_{\mathrm{Mg\,\small {II}}}=2.33\pm 0.19$ , where the error accounts only for the statistical uncertainty in measuring the mean equivalent width. This bias factor is larger than that obtained in previous studies and may be affected by modelling uncertainties that we discuss, but if correct it suggests that Mg ii absorbers at redshift z ~= 0.5 are spatially distributed on large scales similarly to the CMASS galaxies in BOSS.

Description: We present new Multi Unit Spectroscopic Explorer observations of quasar field Q2131–1207 with a log $N\mathrm{(H\,\small {I})}$ = 19.50 ± 0.15 sub-damped Lyman α at z abs = 0.42980. We detect four galaxies at a redshift consistent with that of the absorber where only one was known before this study. Two of these are star-forming galaxies, while the ones further away from the quasar (〉140 kpc) are passive galaxies. We report the metallicities of the H  ii regions of the closest objects (12 + log(O/H) = 8.98 ± 0.02 and 8.32 ± 0.16) to be higher or equivalent within the errors to the metallicity measured in absorption in the neutral phase of the gas (8.15 ± 0.20). For the closest object, a detailed morphokinematic analysis indicates that it is an inclined large rotating disc with V max = 200 ± 3 km s –1 . We measure the masses to be M dyn = 7.4 ± 0.4  x  10 10  M and M halo = 2.9 ± 0.2  x  10 12  M . Some of the gas seen in absorption is likely to be corotating with the halo of that object, possibly due to a warped disc. The azimuthal angle between the quasar line-of-sight and the projected major axis of the galaxy on the sky is 12 $^\circ$ ± 1 $^\circ$ which indicates that some other fraction of the absorbing gas might be associated with accreting gas. This is further supported by the galaxy to gas metallicity difference. Based on the same arguments, we exclude outflows as a possibility to explain the gas in absorption. The four galaxies form a large structure (at least 200 kpc wide) consistent with a filament or a galaxy group so that a fraction of the absorption could be related to intragroup gas.