Dmitry Bizyaev

Quasar-Lyman α forest cross-correlation from BOSS DR11: Baryon Acoustic Oscillations

Author(s): Font-Ribera, A; Kirkby, D; Busca, N; Miralda-Escude, J; Ross, NP; Slosar, A; Rich, J; Aubourg, E; Bailey, S; Bhardwaj, V; Bautista, J; Beutler, F; Bizyaev, D; Blomqvist, M; Brewington, H; Brinkmann, J; Brownstein, JR; Carithers, B; Dawson, KS; Delubac, T; Ebelke, G; Eisenstein, DJ; Ge, J; Kinemuchi, K; Lee, KG; Malanushenko, V; Malanushenko, E; Marchante, M; Margala, D; Muna, D; Myers, AD; Noterdaeme, P; Oravetz, D; Palanque-Delabrouille, N; Pâris, I; Petitjean, P; Pieri, MM; Rossi, G; Schneider, DP; Simmons, A; Viel, M; Yeche, C; York, DG | Abstract: We measure the large-scale cross-correlation of quasars with the Lyα forest absorption, using over 164,000 quasars from Data Release 11 of the SDSS-III Baryon Oscillation Spectroscopic Survey. We extend the previous study of roughly 60,000 quasars from Data Release 9 to larger separations, allowing a measurement of the Baryonic Acoustic Oscillation (BAO) scale along the line of sight c/(H(z = 2.36)rs) = 9.0±0.3 and across the line of sight DA (z = 2.36)/rs = 10.8±0.4, consistent with CMB and other BAO data. Using the best fit value of the sound horizon from Planck data (rs = 147.49 Mpc), we can translate these results to a measurement of the Hubble parameter of H(z = 2.36) = 226±8 km s -1 Mpc-1 and of the angular diameter distance of D A (z = 2.36) = 1590±60 Mpc. The measured cross-correlation function and an update of the code to fit the BAO scale (baofit) are made publicly available.©2014 IOP Publishing Ltd and Sissa Medialab srl.

The progenitors of present-day massive red galaxies up to z ≈ 0.7 - finding passive galaxies using SDSS-I/II and SDSS-III

We present a comprehensive study of 250 000 galaxies targeted by the Baryon Oscillation Spectroscopic Survey (BOSS) up to z≈ 0.7 with the specific goal of identifying and characterizing a population of galaxies that has evolved without significant merging. We compute a likelihood that each BOSS galaxy is a progenitor of the luminous red galaxies (LRGs) sample, targeted by SDSS-I/II up z≈ 0.5, by using the fossil record of LRGs and their inferred star formation histories, metallicity histories and dust content. We determine merger rates, luminosity growth rates and the evolution of the large-scale clustering between the two surveys, and we investigate the effect of using different stellar population synthesis models in our conclusions. We demonstrate that our sample is slowly evolving (of the order of 2 ± 1.5 per cent Gyr−1 by merging) by computing the change in weighted luminosity-per-galaxy between the two samples, and that this result is robust to our choice of stellar population models. Our conclusions refer to the bright and massive end of the galaxy population, with Mi0.55≲−22 and M*≳ 1011.2 M⊙, corresponding roughly to 95 and 40 per cent of the LRGs and BOSS galaxy populations, respectively. Our analysis further shows that any possible excess of flux in BOSS galaxies, when compared to LRGs, from potentially unresolved targets at z≈ 0.55 must be less than 1 per cent in the r0.55 band (approximately equivalent to the g band in the rest frame of galaxies at z= 0.55). When weighting the BOSS galaxies based on the predicted properties of the LRGs, and restricting the analysis to the reddest BOSS galaxies, we find an evolution of the large-scale clustering that is consistent with dynamical passive evolution, assuming a standard cosmology. We conclude that our likelihoods give a weighted sample that is as clean and as close to passive evolution (in dynamical terms, i.e. no or negligible merging) as possible, and that is optimal for cosmological studies

High-Resolution H-Band Spectroscopy Of Be Stars With SDSS-III/Apogee. I. New Be Stars, Line Identifications, And Line Profiles

APOGEE has amassed the largest ever collection of multi-epoch, high-resolution (R~22,500), H-band spectra for B-type emission line (Be) stars. The 128/238 APOGEE Be stars for which emission had never previously been reported serve to increase the total number of known Be stars by ~6%. We focus on identification of the H-band lines and analysis of the emission peak velocity separations (v_p) and emission peak intensity ratios (V/R) of the usually double-peaked H I and non-hydrogen emission lines. H I Br11 emission is found to preferentially form in the circumstellar disks at an average distance of ~2.2 stellar radii. Increasing v_p toward the weaker Br12--Br20 lines suggests these lines are formed interior to Br11. By contrast, the observed IR Fe II emission lines present evidence of having significantly larger formation radii; distinctive phase lags between IR Fe II and H I Brackett emission lines further supports that these species arise from different radii in Be disks. Several emission lines have been identified for the first time including ~16895, a prominent feature in the spectra for almost a fifth of the sample and, as inferred from relatively large v_p compared to the Br11-Br20, a tracer of the inner regions of Be disks. Unlike the typical metallic lines observed for Be stars in the optical, the H-band metallic lines, such as Fe II 16878, never exhibit any evidence of shell absorption, even when the H I lines are clearly shell-dominated. The first known example of a quasi-triple-peaked Br11 line profile is reported for HD 253659, one of several stars exhibiting intra- and/or extra-species V/R and radial velocity variation within individual spectra. Br11 profiles are presented for all discussed stars, as are full APOGEE spectra for a portion of the sample.