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Register a new userThe Century Survey: A Deeper Slice of the Universe
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The ``Century Survey (CS hereafter) is a complete redshift survey of a 1$^circ$-wide strip. It covers 0.03 steradians to a limiting m$_R$ = 16.13. The survey is 98.4% complete and contains 1762 galaxies. Large-scale features in the survey are qualitatively similar to those in other surveys: there are large voids surrounded or nearly surrounded by thin dense regions which are sections of structures like (and including) the Great Wall. The survey crosses the classical Corona Borealis supercluster. The galaxy density enhancement associated with this system extends for $simgreat 100 h^{-1}$ Mpc (the Hubble constant is H$_0 = 100h$ km s$^{-1}$Mpc$^{-1}$). The Schechter (1976) luminosity function parameters for the CS are: $M^*_{CS} = -20.73 ^{+0.17}_{-0.18}$, $alpha_{CS} = -1.17 ^{+0.19}_{-0.19}$, and $phi^*_{CS} = 0.0250pm0.0061$ Mpc$^{-3}$mag$^{-1}$. In concert with the ESO Key Program (cite{vet97}; cite{zuc97}) and the AUTOFIB (cite{ell96}) surveys, the CS indicates that the absolute normalization of the luminosity function exceeds estimates based on shallower and/or sparser surveys.
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We present the Deeper Wider Faster (DWF) program that coordinates more than 30 multi-wavelength and multi-messenger facilities worldwide and in space to detect and study fast transients (millisecond-to-hours duration). DWF has four main components, (1) simultaneous observations, where about 10 major facilities, from radio to gamma-ray, are coordinated to perform deep, wide-field, fast-cadenced observations of the same field at the same time. Radio telescopes search for fast radio bursts while optical imagers and high-energy instruments search for seconds-to-hours timescale transient events, (2) real-time (seconds to minutes) supercomputer data processing and candidate identification, along with real-time (minutes) human inspection of candidates using sophisticated visualisation technology, (3) rapid-response (minutes) follow-up spectroscopy and imaging and conventional ToO observations, and (4) long-term follow up with a global network of 1-4m-class telescopes. The principal goals of DWF are to discover and study counterparts to fast radio bursts and gravitational wave events, along with millisecond-to-hour duration transients at all wavelengths.
A large fraction of the baryons and most of the metals in the Universe are unaccounted for. They likely lie in extended galaxy halos, galaxy groups, and the cosmic web, and measuring their nature is essential to understanding galaxy formation. These environments have virial temperatures >10^5.5 K, so the gas should be visible in X-rays. Here we show the breakthrough capabilities of grating spectrometers to 1) detect these reservoirs of hidden metals and mass, and 2) quantify hot gas flows, turbulence, and rotation around the Milky Way and external galaxies. Grating spectrometers are essential instruments for future X-ray missions, and existing technologies provide 50-1500-fold higher throughput compared to current orbiting instruments.
We present deep 15.7-GHz observations made with the Arcminute Microkelvin Imager Large Array in two fields previously observed as part of the Tenth Cambridge (10C) survey. These observations allow the source counts to be calculated down to 0.1 mJy, a factor of five deeper than achieved by the 10C survey. The new source counts are consistent with the extrapolated fit to the 10C source count, and display no evidence for either steepening or flattening of the counts. There is thus no evidence for the emergence of a significant new population of sources (e.g. starforming) at 15.7 GHz flux densities above 0.1 mJy, the flux density level at which we expect starforming galaxies to begin to contribute. Comparisons with the de Zotti et al. model and the SKADS Simulated Sky show that they both underestimate the observed number of sources by a factor of two at this flux density level. We suggest that this is due to the flat-spectrum cores of radio galaxies contributing more significantly to the counts than predicted by the models.
The Century Survey Galactic Halo Project is a photometric and spectroscopic survey from which we select relatively blue stars (V-R<0.30 mag) as probes of the Milky Way halo. The Survey strip spans the range of Galactic latitude 35<b<88 deg, allowing us to study the nature of populations of stars and their systematic motions as a function of Galactic latitude. One of our primary goals is to use blue horizontal-branch stars to trace potential star streams in the halo, and to test the hierarchical model for the formation of the Galaxy. In this paper we discuss spectroscopy and multi-passband photometry for a sample of 764 blue stars in the Century Survey region. Our sample consists predominantly of A- and F-type stars. We describe our techniques for determination of radial velocities, effective temperatures, metallicities, and surface gravities. Based on these measurements, we derive distance estimates by comparison with a set of calibrated isochrones. We devote special attention to the classification of blue horizontal-branch stars, and compare the results obtained from the application of the techniques of Kinman et al., Wilhelm et al., and Clewley et al. We identify 55 blue horizontal-branch stars. Our large sample of stars also uncovers a number of unusual objects, including three carbon-enhanced stars, a late B-type star located 0.8 kpc above the Galactic plane, and a DZ white dwarf.
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