Galaxy And Mass Assembly (GAMA) blended spectra catalogue: strong galaxy-galaxy lens and occulting galaxy pair candidates

We present the catalogue of blended galaxy spectra from the Galaxy And Mass Assembly (GAMA) survey. These are cases where light from two galaxies are significantly detected in a single GAMA fibre. Galaxy pairs identified from their blended spectrum fall into two principal classes: they are either strong lenses, a passive galaxy lensing an emission-line galaxy; or occulting galaxies, serendipitous overlaps of two galaxies, of any type. Blended spectra can thus be used to reliably identify strong lenses for follow-up observations (high-resolution imaging) and occulting pairs, especially those that are a late-type partly obscuring an early-type galaxy which are of interest for the study of dust content of spiral and irregular galaxies. The GAMA survey setup and its AUTOZ automated redshift determination were used to identify candidate blended galaxy spectra from the cross-correlation peaks. We identify 280 blended spectra with a minimum velocity separation of 600 km s−1, of which 104 are lens pair candidates, 71 emission-line-passive pairs, 78 are pairs of emission-line galaxies and 27 are pairs of galaxies with passive spectra. We have visually inspected the candidates in the Sloan Digital Sky Survey (SDSS) and Kilo Degree Survey (KiDS) images. Many blended objects are ellipticals with blue fuzz (Ef in our classification). These latter ‘Ef’ classifications are candidates for possible strong lenses, massive ellipticals with an emission-line galaxy in one or more lensed images. The GAMA lens and occulting galaxy candidate samples are similar in size to those identified in the entire SDSS. This blended spectrum sample stands as a testament of the power of this highly complete, second-largest spectroscopic survey in existence and offers the possibility to expand e.g. strong gravitational lens surveys

Causes and Consequences of Collective Turnover: A Meta-Analytic Review

Given growing interest in collective turnover (i.e., employee turnover at unit and organizational levels), the authors propose an organizing framework for its antecedents and consequences and test it using meta-analysis. Based on analysis of 694 effect sizes drawn from 82 studies, results generally support expected relationships across the 6 categories of collective turnover antecedents, with somewhat stronger and more consistent results for 2 categories: human resource management inducements/investments and job embeddedness signals. Turnover was negatively related to numerous performance outcomes, more strongly so for proximal rather than distal outcomes. Several theoretically grounded moderators help to explain average effect-size heterogeneity for both antecedents and consequences of turnover. Relationships generally did not vary according to turnover type (e.g., total or voluntary), although the relative absence of collective-level involuntary turnover studies is noted and remains an important avenue for future research

Quantified Morphology of HI Disks in the Universe

he upcoming new perspective of the high redshift Universe in the 21 cm line of atomic hydrogen opens possibilities to explore topics of spiral disk evolution, hitherto reserved for the optical regime. The growth of spiral gas disks over Cosmic time can be explored with the new generation of radio telescopes, notably the SKA, and its precursors, as accurately as with the Hubble Space Telescope for stellar disks. Since the atomic hydrogen gas is the building block of these disks, it should trace their formation accurately. Morphology of HI disks can now equally be quantified over Cosmic time. In studies of HST deep fields, the optical or UV morphology of high-redshift galaxy disks have been characterized using a few quantities: concentration (C), asymmetry (A), smoothness (S), second-order-moment (M20), the GINI coefficient (G), and Ellipticity (E). We have applied these parameters across wavelengths and compared them to the HI morphology over the THINGS sample. NGC 3184, an unperturbed disk, and NGC 5194, the canonical 3:1 interaction, serve as examples for quantified morphology. We find that morphology parameters determined in HI are as good or better a tracer of interaction compared to those in any other wavelength, notably in Asymmetry, Gini and M20. This opens the possibility of using them in the parameterization pipeline for SKA precursor catalogues to select interacting or harassed galaxies from their HI morphology. Asymmetry, Gini and M20 may be redefined for use on data-cubes rather than HI column density image.Comment: 6 pages, 3 figures, proceeding of the conference "Panoramic Radio Astronomy: Wide-field 1-2 GHz research on galaxy evolution", June 02 - 05 2009, Groningen, update after small edit

All NIRspec needs is HST/WFC3 pre-imaging? The use of Milky Way Stars in WFC3 Imaging to Register NIRspec MSA Observations

The James Webb Space Telescope (JWST) will be an exquisite new near-infrared observatory with imaging and multi-object spectroscopy through ESA's NIRspec instrument with its unique Micro-Shutter Array (MSA), allowing for slits to be positioned on astronomical targets by opening specific 0.002"-wide micro shutter doors. To ensure proper target acquisition, the on-sky position of the MSA needs to be verified before spectroscopic observations start. An onboard centroiding program registers the position of pre-identified guide stars in a Target Acquisition (TA) image, a short pre-spectroscopy exposure without dispersion (image mode) through the MSA with all shutters open. The outstanding issue is the availability of Galactic stars in the right luminosity range for TA relative to typical high redshift targets. We explore this here using the stars and $z\sim8$ candidate galaxies identified in the source extractor catalogs of Brightest of Reionizing Galaxies survey (BoRG[z8]), a pure-parallel program with Hubble Space Telescope Wide-Field Camera 3. We find that (a) a single WFC3 field contains enough Galactic stars to satisfy the NIRspec astrometry requirement (20 milli-arcseconds), provided its and the NIRspec TA's are $m_{lim}>24.5$ AB in WFC3 F125W, (b) a single WFC3 image can therefore serve as the pre-image if need be, (c) a WFC3 mosaic and accompanying TA image satisfy the astrometry requirement at $\sim23$ AB mag in WFC3 F125W, (d) no specific Galactic latitude requires deeper TA imaging due to a lack of Galactic stars, and (e) a depth of $\sim24$ AB mag in WFC3 F125W is needed if a guide star in the same MSA quadrant as a target is required. We take the example of a BoRG identified $z\sim8$ candidate galaxy and require a Galactic star within 20" of it. In this case, a depth of 25.5 AB in F125W is required (with $\sim$97% confidence).Comment: 17 pages, 15 figures, to appear in the Journal of Astronomical Instrumentatio

Kinetics of the reduction of metalloproteins by chromous ion

The reduction of Cu(330) in Rhus vernicifera laccase by chromous ion is 30% faster than reduction of Cu(614) at room temperature [pH 4.8, µ = 0.1 (NaCl)], and two parallel first-order paths, attributed to heterogeneity of the protein, are observed at both wavelengths. The reactions of stellacyanin, spinach and French-bean plastocyanins, and cytochrome c with chromous ion under similar conditions are faster than that with laccase by factors of 102 to 104, and are first order in protein concentration. Comparison of rates and activation parameters for the reduction of "blue" copper in laccase, stellacyanin, and the two plastocyanins indicates that reduction of the Cu(614) site in laccase may occur by intramolecular electron transfer from one of the Cu(330) sites. Our value of ΔH (17.4 kcal/mol) for the chromous ion reduction of cytochrome c is consistent with a mechanism in which major conformational changes in the protein must accompany electron transfer

Total Opacity of Local Group Galaxies and Large Scale Structure behind the Galactic Bulge

Recently, we have developed and calibrated the Synthetic Field Method to derive total extinction through disk galaxies. The method is based on the number counts and colors of distant background field galaxies that can be seen through the foreground object. Here, we investigate how large (10-m) and very large (20 to 30-m), diffraction-limited, optical and infrared telescopes in space would improve the detection of background galaxies behind Local Group objects, including the Galactic bulge. We find that, besides and perhaps more important than telescope size, a well-behaved, well-characterized PSF would facilitate in general the detection of faint objects in crowded fields, and greatly benefit several other important research areas, like the search for extrasolar planets, the study of quasar hosts and, most relevant for this meeting, the surveying of nearby large scale structure in the Zone of Avoidance, in particular behind the Galactic bulge.Comment: 9 pages, 4 figures, 1 table, uses asp2004.sty. To appear in ``Nearby Large-Scale Structures and the Zone of Avoidance,'' eds. A.P. Fairall, P. Woudt, ASP Conf. Series, in press, San Francisco: Astronomical Society of the Pacifi

Quantified HI Morphology III: Merger Visibility Times from HI in Galaxy Simulations

Major mergers of disk galaxies are thought to be a substantial driver in galaxy evolution. To trace the fraction and the rate galaxies are in mergers over cosmic times, several observational techniques, including morphological selection criteria, have been developed over the last decade. We apply this morphological selection of mergers to 21 cm radio emission line (HI) column density images of spiral galaxies in nearby surveys. In this paper, we investigate how long a 1:1 merger is visible in HI from N-body simulations. We evaluate the merger visibility times for selection criteria based on four parameters: Concentration, Asymmetry, M20, and the Gini parameter of second order moment of the flux distribution (GM). Of three selection criteria used in the literature, one based on Concentration and M20 works well for the HI perspective with a merger time scale of 0.4 Gyr. Of the three selection criteria defined in our previous paper, the GM performs well and cleanly selects mergers for 0.69 Gyr. The other two criteria (A-M20 and C-M20), select isolated disks as well, but perform best for face-on, gas-rich disks (T(merger) ~ 1 Gyr). The different visibility scales can be combined with the selected fractions of galaxies in any large HI survey to obtain merger rates in the nearby Universe. All-sky surveys such as WALLABY with ASKAP and the Medium Deep Survey with the APETIF instrument on Westerbork are set to revolutionize our perspective on neutral hydrogen and will provide an accurate measure of the merger fraction and rate of the present epoch.Comment: 12 pages, 6 figures, 4 tables, accepted by MNRAS, appendix not include

The Opacity of Spiral Galaxy Disks IV: Radial Extinction Profiles from Counts of Distant Galaxies seen through Foreground Disks

Dust extinction can be determined from the number of distant field galaxies seen through a spiral disk. To calibrate this number for the crowding and confusion introduced by the foreground image, Gonzalez et al.(1998) and Holwerda et al. (2005) developed the ``Synthetic Field Method'' (SFM), which analyses synthetic fields constructed by adding various deep exposures of unobstructed background fields to the candidate foreground galaxy field. The advantage of the SFM is that it gives the average opacity for area of galaxy disk without assumptions about either the distribution of absorbers or of the disk starlight. However it is limited by low statistics of the surviving field galaxies, hence the need to combine a larger sample of fields. This paper presents the first results for a sample of 32 deep HST/WFPC2 archival fields of 29 spirals. The radial profiles of average dust extinction in spiral galaxies based on calibrated counts of distant field galaxies is presented here, both for individual galaxies as well as for composites from our sample. The effects of inclination, spiral arms and Hubble type on the radial extinction profile are discussed. (Abbreviated)Comment: 43 pages, 16 figures, 3 tables, accepted for publication in the Astronomical Journal, (typos, table update, updates abstract

When Does Employee Turnover Matter? Dynamic Member Configurations, Productive Capacity, and Collective Performance

In theory, employee turnover has important consequences for groups, work units, and organizations. However, past research has not revealed consistent empirical support for a relationship between aggregate levels of turnover and performance outcomes. In this paper, we present a novel conceptualization of turnover to explain when, why, and how it affects important outcomes. We suggest that greater attention to five characteristics—leaver proficiencies, time dispersion, positional distribution, remaining member proficiencies, and newcomer proficiencies—will reveal dynamic member configurations that predictably influence productive capacity and collective performance. We describe and illustrate the five properties, explain how particular member configurations exacerbate or diminish turnover’s effects, and present a new measurement approach that captures these characteristics in a collective context and over time