3,112 research outputs found

    Film Review: Narco Cultura – A Tale of Three Cities

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    This is a film review

    The Las Campanas Infra-red Survey. V. Keck Spectroscopy of a large sample of Extremely Red Objects

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    (Abridged) We present deep Keck spectroscopy, using the DEIMOS and LRIS spectrographs, of a large and representative sample of 67 ``Extremely Red Objects'' (EROs) to H=20.5, with I-H>3.0, in three of the Las Campanas Infrared Survey fields. Spectroscopic redshifts are determined for 44 sources, of which only two are contaminating low mass stars. When allowance is made for incompleteness, the spectroscopic redshift distribution closely matches that predicted earlier on the basis of photometric data. Our spectra are of sufficient quality that we can address the important question of the nature and homogeneity of the z>0.8 ERO population. A dominant old stellar population is inferred for 75% of our spectroscopic sample; a higher fraction than that seen in smaller, less-complete samples with broader photometric selection criteria (e.g. R-K). However, only 28% have spectra with no evidence of recent star formation activity, such as would be expected for a strictly passively-evolving population. More than ~30% of our absorption line spectra are of the `E+A' type with prominent Balmer absorption consistent, on average, with mass growth of 5-15% in the past Gyr. We use our spectroscopic redshifts to improve earlier estimates of the spatial clustering of this population as well as to understand the significant field-to-field variation. Our spectroscopy enables us to pinpoint a filamentary structure at z=1.22 in the Chandra Deep Field South. Overall, our study suggests that the bulk of the ERO population is an established population of clustered massive galaxies undergoing intermittent activity consistent with continued growth over the redshift interval 0.8<z<1.6.Comment: 27 pages, including 14 figures and appendix of spectra (at low resolution). Full resolution paper can be found at http://www.ast.cam.ac.uk/~md . To appear in MNRA

    Lyman Alpha Radiation From Collapsing Protogalaxies II: Observational Evidence for Gas Infall

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    We model the spectra and surface brightness distributions for the Lyman alpha (Lya) radiation expected from protogalaxies that are caught in the early stages of their assembly. We use the results of a companion paper to characterize the radiation emerging from spherically collapsing gas clouds. We then modify the intrinsic spectra to incorporate the effect of subsequent resonant scattering in the intergalactic medium (IGM). Using these models, we interpret a number of recent observations of extended Lya blobs (LABs) at high redshift. We suggest, based on the angular size, energetics, as well as the relatively shallow surface brightness profiles, and double-peaked spectra, that several of these LABs may be associated with collapsing protogalaxies. We suggest two follow-up observations to diagnose the presence of gas infall. High S/N spectra of LABs should reveal a preferential flattening of the surface brightness profile at the red side of the line. Complementary imaging of the blobs at redshifted Balmer alpha wavelengths should reveal the intrinsic Lya emissivity and allow its separation from radiative transfer effects. We show that Lya scattering by infalling gas can reproduce the observed spectrum of Steidel et al's LAB2 as accurately as a recently proposed outflow model. Finally, we find similar evidence for infall in the spectra of point-like Lyman alpha emitters. The presence of scattering by the infalling gas implies that the intrinsic Lya luminosities, and derived quantities, such as the star-formation rate, in these objects may have been underestimated by about an order of magnitude.Comment: Accepted for Publication in ApJ, 11 emulateapj pages with 6 figures, together with a companion pape

    Serendipitously Detected Galaxies in the Hubble Deep Field

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    We present a catalog of 74 galaxies detected serendipitously during a campaign of spectroscopic observations of the Hubble Deep Field North (HDF) and its environs. Among the identified objects are five candidate Ly-alpha emitters at z > 5, a galaxy cluster at z = 0.85, and a Chandra source with a heretofore undetermined redshift of z = 2.011. We report redshifts for 25 galaxies in the central HDF, 13 of which had no prior published spectroscopic redshift. Of the remaining 49 galaxies, 30 are located in the single-orbit HDF Flanking Fields. We discuss the redshift distribution of the serendipitous sample, which contains galaxies in the range 0.10 < z < 5.77 with a median redshift of z = 0.85, and we present strong evidence for redshift clustering. By comparing our spectroscopic redshifts to optical/IR photometric studies of the HDF, we find that photometric redshifts are in most cases capable of producing reasonable predictions of galaxy redshifts. Finally, we estimate the line-of-sight velocity dispersion and the corresponding mass and expected X-ray luminosity of the galaxy cluster, we present strong arguments for interpreting the Chandra source as an obscured AGN, and we discuss in detail the spectrum of one of the candidate z > 5 Ly-alpha emitters.Comment: 18 pages, 9 figures, accepted for publication in the Astronomical Journa

    Construction and measurements of a vacuum-swing-adsorption radon-mitigation system

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    Long-lived alpha and beta emitters in the 222^{222}Rn decay chain on (and near) detector surfaces may be the limiting background in many experiments attempting to detect dark matter or neutrinoless double-beta decay, and in screening detectors. In order to reduce backgrounds from radon-daughter plate-out onto the wires of the BetaCage during its assembly, an ultra-low-radon cleanroom is being commissioned at Syracuse University using a vacuum-swing-adsorption radon-mitigation system. The radon filter shows ~20×\times reduction at its output, from 7.47±\pm0.56 to 0.37±\pm0.12 Bq/m3^3, and the cleanroom radon activity meets project requirements, with a lowest achieved value consistent with that of the filter, and levels consistently < 2 Bq/m3^3.Comment: 5 pages, 3 figures, Proceedings of Low Radioactivity Techniques (LRT) 2013, Gran Sasso, Italy, April 10-12, 201

    The role of quenching time in the evolution of the mass-size relation of passive galaxies from the WISP survey

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    We analyze how passive galaxies at z \sim 1.5 populate the mass-size plane as a function of their stellar age, to understand if the observed size growth with time can be explained with the appearance of larger quenched galaxies at lower redshift. We use a sample of 32 passive galaxies extracted from the Wide Field Camera 3 Infrared Spectroscopic Parallel (WISP) survey with spectroscopic redshift 1.3 \lesssim z \lesssim 2.05, specific star-formation rates lower than 0.01 Gyr1^{-1}, and stellar masses above 4.5 ×\times 1010^{10} M_\odot. All galaxies have spectrally determined stellar ages from fitting of their rest-frame optical spectra and photometry with stellar population models. When dividing our sample into young (age \leq 2.1 Gyr) and old (age >> 2.1 Gyr) galaxies we do not find a significant trend in the distributions of the difference between the observed radius and the one predicted by the mass-size relation. This result indicates that the relation between the galaxy age and its distance from the mass-size relation, if it exists, is rather shallow, with a slope alpha \gtrsim -0.6. At face value, this finding suggests that multiple dry and/or wet minor mergers, rather than the appearance of newly quenched galaxies, are mainly responsible for the observed time evolution of the mass-size relation in passive galaxies.Comment: Accepted for publication in ApJ Letters; 6 pages, 3 figures, 1 tabl

    Archived time-series of Atlantic Ocean meteorological variables and surface fluxes

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    Includes ErrataTime-series of monthly averages of latent, sensible and radiational heat fluxes and momentum fluxes at the surfaces of the North and South Atlantic Oceans were calculated from ship weather observations. These fluxes, together with values of meteorological variables have been averaged over entire Marsden squares (10X10° squares) for all months from January 1948 through December 1972. The method of computing fluxes from ship weather observations, listing of variables averaged, addition of sea-ice coverage of sub-polar regions, correction of albedos for the presence of sea ice, correction of infrared radiational exchange for humidity conditions of the upper atmosphere, and format of the data on magnetic tapes are described. Statistics of the fluxes and variables have been computed. Standard data tapes containing these time series and statistics are available.Prepared for Climate Dynamics Research Program~ Division of Atmospheric Sciences, National Science Foundation under Grant ATM 77-01475 A01

    Woods Hole Oceanographic Institution collection of Climatology and Air/Sea Interaction (CASI) data

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    Scientists at Woods Hole routinely collect and analyze a considerable amount of data relating to the oceans of the world. Of the many different kinds of data, one particular subset concerns those events occurring at the sea surface. A large number of sea surface environmental observations have been collected at Woods Hole. These data, and the subsequent analyses generated from the Air/Sea Heat Flux and the Climatology study projects, have been collected and archived. This document describes the W.H.O.I./ Climatology and Air/Sea Interaction (WHOI/CASI) data collection and provides an initial index to its various components.Prepared for the Office of Naval Research under Contract N00014-74-C-0262; NR 083-004 and for the National Science Foundation (Climate Dynamics Program, Atmospheric Sciences Division) under Grant ATM 77-014?5

    Moving forward: Emerging themes in financial services technologies’ adoption

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    © 2015 by the Association for Information Systems. Financial services technologies (FST) are core to the continuous transformation of financial services organizations (FSO). To date, however, there has been a lack of empirical research into FST adoption against the backdrop of the recent financial crisis. In this paper, we re-examine how FSO are currently positioned to take advantage of emerging FST. Note that, in this paper, we look forward rather than provide a commentary on the state of the art in technology adoption research. We conducted this research by applying an exploratory qualitative study method: we analyzed interview transcripts from thirty recent interviews of FSO technology executives and CIOs by using a thematic network analysis tool. This analysis uncovered nineteen basic, eight organizing, and two global FST adoption research themes along with their links to FST adoption objectives, challenges, customer centricity, human resources, outsourcing, and overall IT strategy maintenance. This research has both practical and theoretical research implications and serves as a resource base for FSO and researchers to set future research priorities and directions. We intend for the emerging themes that we present in this paper to facilitate research directions by shedding light on the areas of greatest value and potential return in FST adoption
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