Cosmological implications from the full shape of the large-scale power spectrum of the SDSS DR7 luminous red galaxies

We obtain cosmological constraints from a measurement of the spherically averaged power spectrum (PS) of the distribution of about 90000 luminous red galaxies (LRGs) across 7646 deg2 in the Northern Galactic Cap from the DR7 of the SDSS. The errors and mode correlations are estimated thanks to the 160 LasDamas mock catalogues, created in order to simulate the same galaxies and to have the same selection as the data. We apply a model, that can accurately describe the full shape of the PS with the use of a small number of free parameters. Using the LRG PS, in combination with the latest measurement of the temperature and polarisation anisotropy in the cosmic microwave background (CMB), the luminosity-distance relation from the largest available type 1a supernovae (SNIa) dataset and a precise determination of the local Hubble parameter, we obtain cosmological constraints for five different parameter spaces. When all the four experiments are combined, the flat LCDM model is characterised by Omega_M=0.259+-0.016, Omega_b=0.045+-0.001, n_s=0.963+-0.011, sigma_8=0.802+-0.021 and h=0.712+-0.014. When we consider curvature as a free parameter, we do not detect deviations from flatness: Omega_k=(1.6+-5.4)*10^{-3}, when only CMB and the LRG PS are used; the inclusion of the other two experiments do not improve this result. Considering the dark energy equation of state w_DE as time independent, we measure w_DE=-1.025+-0.065, for a flat geometry, w_DE=-0.981+-0.083 otherwise. When describing w_DE through a linear function of the scale factor, our results do not evidence any time evolution. In the next few years new experiments will allow to measure the clustering of galaxies with a precision much higher than achievable today. Models like the one used here will be a valuable tool in order to achieve the full potentials of the observations and obtain unbiased constraints on the cosmological parameters.Comment: 28 pages, 26 figures. Accepted for publication in MNRA

The clustering of galaxies at z~0.5 in the SDSS-III Data Release 9 BOSS-CMASS sample: a test for the LCDM cosmology

We present results on the clustering of 282,068 galaxies in the Baryon Oscillation Spectroscopic Survey (BOSS) sample of massive galaxies with redshifts 0.4<z<0.7 which is part of the Sloan Digital Sky Survey III project. Our results cover a large range of scales from ~0.5 to ~90 Mpc/h. We compare these estimates with the expectations of the flat LCDM cosmological model with parameters compatible with WMAP7 data. We use the MultiDark cosmological simulation together with a simple halo abundance matching technique, to estimate galaxy correlation functions, power spectra, abundance of subhaloes and galaxy biases. We find that the LCDM model gives a reasonable description to the observed correlation functions at z~0.5, which is a remarkably good agreement considering that the model, once matched to the observed abundance of BOSS galaxies, does not have any free parameters. However, we find a deviation (>~10%) in the correlation functions for scales less than ~1 Mpc/h and ~10-40 Mpc/h. A more realistic abundance matching model and better statistics from upcoming observations are needed to clarify the situation. We also estimate that about 12% of the "galaxies" in the abundance-matched sample are satellites inhabiting central haloes with mass M>~1e14 M_sun/h. Using the MultiDark simulation we also study the real space halo bias b(r) of the matched catalogue finding that b=2.00+/-0.07 at large scales, consistent with the one obtained using the measured BOSS projected correlation function. Furthermore, the linear large-scale bias depends on the number density n of the abundance-matched sample as b=-0.048-(0.594+/-0.02)*log(n/(h/Mpc)^3). Extrapolating these results to BAO scales we measure a scale-dependent damping of the acoustic signal produced by non-linear evolution that leads to ~2-4% dips at ~3 sigma level for wavenumbers k>~0.1 h/Mpc in the linear large-scale bias.Comment: Replaced to match published version. Typos corrected; 25 pages, 17 figures, 9 tables. To appear in MNRAS. Correlation functions (projected and redshift-space) and correlation matrices of CMASS presented in Appendix B. Correlation and covariance data for the combined CMASS sample can be downloaded from http://www.sdss3.org/science/boss_publications.ph

The clustering of galaxies in the SDSS-III Baryon Oscillation Spectroscopic Survey: mock galaxy catalogues for the low-redshift sample

We present one thousand mock galaxy catalogues for the analysis of the Low Redshift Sample (LOWZ, effective redshift z ~ 10.32) of the Baryon Oscillation Spectroscopic Survey Data Releases 10 and 11. These mocks have been created following the PTHalos method of Manera13 et al. (2013) revised to include new developments. The main improvement is the introduction of a redshift dependence in the Halo Occupation Distribution in order to account for the change of the galaxy number density with redshift. These mock catalogues are used in the analyses of the LOWZ galaxy clustering by the BOSS collaboration.Comment: 10 pages, 8 figure

Extragalactic Radio Continuum Surveys and the Transformation of Radio Astronomy

Next-generation radio surveys are about to transform radio astronomy by discovering and studying tens of millions of previously unknown radio sources. These surveys will provide new insights to understand the evolution of galaxies, measuring the evolution of the cosmic star formation rate, and rivalling traditional techniques in the measurement of fundamental cosmological parameters. By observing a new volume of observational parameter space, they are also likely to discover unexpected new phenomena. This review traces the evolution of extragalactic radio continuum surveys from the earliest days of radio astronomy to the present, and identifies the challenges that must be overcome to achieve this transformational change.Comment: To be published in Nature Astronomy 18 Sept 201

Towards a new full-sky list of radial velocity standard stars

The calibration of the Radial Velocity Spectrometer (RVS) onboard the ESA Gaia satellite (to be launched in 2012) requires a list of standard stars with a radial velocity (RV) known with an accuracy of at least 300 m/s. The IAU Commission 30 lists of RV standard stars are too bright and not dense enough. We describe the selection criteria due to the RVS constraints for building an adequate full-sky list of at least 1000 RV standards from catalogues already published in the literature. A preliminary list of 1420 candidate standard stars is built and its properties are shown. An important re-observation programme has been set up in order to ensure within it the selection of objects with a good stability until the end of the Gaia mission (around 2018). The present list of candidate standards is available at CDS and usable for many other projects.Comment: Astronomy & Astrophysics, in press, 8 pages, 8 figure

Discovery of optically faint obscured quasars with Virtual Observatory tools

We use Virtual Observatory (VO) tools to identify optically faint, obscured (i.e., type 2) active galactic nuclei (AGN) in the two Great Observatories Origins Deep Survey (GOODS) fields. By employing publicly available X-ray and optical data and catalogues we discover 68 type 2 AGN candidates. The X-ray powers of these sources are estimated by using a previously known correlation between X-ray luminosity and X-ray-to-optical flux ratio. Thirty-one of our candidates have high estimated powers (Lx > 10^44 erg/s) and therefore qualify as optically obscured quasars, the so-called ``QSO 2''. Based on the derived X-ray powers, our candidates are likely to be at relatively high redshifts, z ~ 3, with the QSO 2 at z ~ 4. By going ~ 3 magnitudes fainter than previously known type 2 AGN in the two GOODS fields we are sampling a region of redshift - power space which was previously unreachable with classical methods. Our method brings to 40 the number of QSO 2 in the GOODS fields, an improvement of a factor ~ 4 when compared to the only 9 such sources previously known. We derive a QSO 2 surface density down to 10^-15 erg/cm^2/s in the 0.5 - 8 keV band of >~ 330/deg^2, ~ 30% of which is made up of previously known sources. This is larger than current estimates and some predictions and suggests that the surface density of QSO 2 at faint flux limits has been underestimated. This work demonstrates that VO tools are mature enough to produce cutting-edge science results by exploiting astronomical data beyond ``classical'' identification limits (R <~ 25) with interoperable tools for statistical identification of sources using multiwavelength information.Comment: 16 pages, 6 figures, accepted for publication in Astronomy & Astrophysics. PDF file with higher resolution figures available at http://www.eso.org/~ppadovan/AVO-paper.pd

Radio-loud Narrow-Line Type 1 Quasars

We present the first systematic study of (non-radio-selected) radio-loud narrow-line Seyfert 1 (NLS1) galaxies. Cross-correlation of the `Catalogue of Quasars and Active Nuclei' with several radio and optical catalogues led to the identification of 11 radio-loud NLS1 candidates including 4 previously known ones. Most of the radio-loud NLS1s are compact, steep spectrum sources accreting close to, or above, the Eddington limit. The radio-loud NLS1s of our sample are remarkable in that they occupy a previously rarely populated regime in NLS1 multi-wavelength parameter space. While their [OIII]/H_beta and FeII/H_beta intensity ratios almost cover the whole range observed in NLS1 galaxies, their radio properties extend the range of radio-loud objects to those with small widths of the broad Balmer lines. Among the radio-detected NLS1 galaxies, the radio index R distributes quite smoothly up to the critical value of R ~ 10 and covers about 4 orders of magnitude in total. Statistics show that ~7% of the NLS1 galaxies are formally radio-loud while only 2.5% exceed a radio index R > 100. Several mechanisms are considered as explanations for the radio loudness of the NLS1 galaxies and for the lower frequency of radio-louds among NLS1s than quasars. While properties of most sources (with 2-3 exceptions) generally do not favor relativistic beaming, the combination of accretion mode and spin may explain the observations. (abbreviated)Comment: Astronomical Journal (first submitted in Dec. 2005); 45 pages incl. 1 colour figur