3,494 research outputs found

    Current Star Formation in Post-Starburst Galaxies?

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    Radio continuum observations are a probe of star formation in galaxies, and are unaffected by dust extinction. Observations of the distant rich cluster Cl 0939+4713 have detected radio galaxies classified as post-starburst (``k+a'') on the basis of their optical spectra, and presumably this situation arises from heavily dust-obscured star formation (Smail et al. 1999). We present the results of a radio continuum survey of post-starburst galaxies identified from the Las Campanas Redshift Survey by Zabludoff et al. (1996). This sample was selected using very stringent criteria, and therefore provides an estimate on the incidence of potential star formation in galaxies whose optical spectra exhibit the strongest post-starburst features. We detected two of fifteen such galaxies at radio luminosities consistent with moderate levels of star formation. This result underscores the potential importance of dust extinction when investigating star formation in galaxies.Comment: Replaced with corrected version of Table

    The Radio Galaxy Populations of Nearby Northern Abell Clusters

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    We report on the use of the NRAO VLA Sky Survey (NVSS) to identify radio galaxie s in eighteen nearby Abell clusters. The listings extend from the cores of the clusters out to radii of 3 Mpc, which corresponds to 1.5 Abell radii and approximately four orders of magnitude in galaxy density. To create a truly useful catalog, we have collected optical spectra for nearly all of the galaxies lacking public velocity measurements. Consequently, we are able to discriminate between those radio galaxies seen in projection on the cluster and those which are in actuality cluster members. The resulting catalog consists of 329 cluster radio galaxies plus 138 galaxies deemed foreground/background objects, and new velocity measurements are reported for 273 of these radio galaxies. The motivation for the catalog is the study of galaxy evolution in the cluster environment. The radio luminosity function (RLF) is a powerful tool in the identification of active galaxies, as it is dominated by star-forming galaxies at intermediate luminosities and active galactic nuclei (AGN) at higher luminosities. The flux limit of the NVSS allows us to identify AGN and star- forming galaxies down to star formation rates (SFR) less than 1 solar mass per year. This sensitivity, coupled with the all-sky nature of the NVSS, allows us to produce a catalog of considerable depth and breadth. In addition to these data, we report detected infrared fluxes and upper limits obtained from IRAS data. It is hoped that this database will prove useful in a number of potential studies of the effect of environment on galaxy evolution.Comment: 53 pages (AASTeX v5.0), plus 3 figures. To appear in the Astrophysical Journal Supplement Serie

    Star Formation and AGN in the Core of the Shapley Supercluster: A VLA Survey of A3556, A3558, SC1327-312, SC1329-313, and A3562

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    The core of the Shapley supercluster (A3556, A3558, SC1327-312, SC1329-313, and A3562) is an ideal region in which to study the effects of cluster mergers on the activity of individual galaxies. This paper presents the most comprehensive radio continuum investigation of the region, relying on a 63-pointing mosaic obtained with the Very Large Array yielding an areal coverage of nearly 7 square degrees. The mosaic provides a typical sensitivity of about 80 uJy at a resolution of 16", enabling detection of galaxies with star formation rates as low as 1 solar mass per year. The radio data are complemented by optical imaging in B and R, producing a catalog of 210 radio-detected galaxies with m_R <= 17.36 (M_R <= -19). At least 104 of these radio-detected galaxies are members of the supercluster on the basis of public velocity measurements. Across the entire core of the supercluster, there appears to be a significant deficit of radio galaxies at intermediate optical magnitudes (M_R between -21 and -22). This deficit is offset somewhat by an increase in the frequency with which brighter galaxies (M_R less than -22) host radio sources. More dramatic is the highly significant increase in the probability for fainter galaxies (M_R between -20 and -21) in the vicinity of A3562 and SC1329-313 to be associated with radio emission. The radio and optical data for these sources strongly suggest that these active galaxies are powered by star formation. In conjunction with recent X-ray analysis, this is interpreted as young starbursts related to the recent merger of SC1329-313 with A3562 and the rest of the supercluster.Comment: Accepted by AJ; 50 pages, including 16 figures (for full resolution PDF, see http://mywebpages.comcast.net/nealamiller2/Shapley_pp.pdf

    Abell 2111: An Optical and Radio Study of the Richest Butcher-Oemler Cluster

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    We present an in-depth analysis of the Butcher-Oemler cluster A2111, including new optical spectroscopy plus a deep Very Large Array (VLA) radio continuum observation. These are combined with optical imaging from the Sloan Digital Sky Survey (SDSS) to assess the activity and properties of member galaxies. Prior X-ray studies have suggested A2111 is a head-on cluster merger, a dynamical state which might be connected to the high level of activity inferred from its blue fraction. We are able to directly assess this claim, using our spectroscopic data to identify 95 cluster members among 196 total galaxy spectra. These galaxy velocities do not themselves provide significant evidence for the merger interpretation, however they are consistent with it provided the system is viewed near the time of core passage and at a viewing angle >~30 degrees different from the merger axis. The SDSS data allow us to confirm the high blue fraction for A2111, f_b = 0.15 +/- 0.03 based on photometry alone and f_b = 0.23 +/- 0.03 using spectroscopic data to remove background galaxies. We are able to detect 175 optical sources from the SDSS in our VLA radio data, of which 35 have redshift information. We use the SDSS photometry to determine photometric redshifts for the remaining 140 radio-optical sources. In total we identify up to 26 cluster radio galaxies, 14 of which have spectroscopic redshifts. The optical spectroscopy and radio data reveal a substantial population of dusty starbursts within the cluster. The high blue fraction and prevalence of star formation is consistent with the hypothesis that dynamically-active clusters are associated with more active member galaxies than relaxed clusters.Comment: To appear in AJ; 53 pages including 10 figures and several long table

    Experimental Evaluation of High Performance Integrated Heat Pump

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    Integrated heat pump (IHP) technology provides significant potential for energy savings and comfort improvement for residential buildings. In this study, we evaluate the performance of a high performance IHP that provides space heating, cooling, and water heating services. Experiments were conducted according to the ASHRAE Standard 206-2013 where 24 test conditions were identified in order to evaluate the IHP performance indices. An 8-in by 8-in Air Monitor Fan Evaluator is used to measure the volumetric flowrate of air discharged from the air handler unit (AHU) in order to evaluate the airside performance. Empirical curve fits of the unit’s compressor maps are used in conjunction with saturated condensing and evaporating refrigerant conditions to deduce the refrigerant mass flowrate, which, in turn is used to evaluate the refrigerant-side performance. Heat pump (compressor, fans, and controls) and water pump power were measured separately per requirements of Standard 206. The system was charged per the system manufacturer’s specifications. System test results are presented for each operating mode along with overall IHP performance metrics according to ASHRAE standard 206-2013. The paper ends with discussion on system operation and impact on typical energy consumption in residential buildings

    The Dynamics of Abell 2125

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    We present 371 galaxy velocities in the field of the very rich cluster Abell 2125 (z~0.25). These were determined using optical spectroscopy collected over several years from both the WIYN 3.5m telescope and NOAO Mayall 4m telescope. Prior studies at a variety of wavelengths (radio, optical, and X-ray) have indicated that A2125 is a likely cluster-cluster merger, a scenario which we are able to test using our large velocity database. We identified 224 cluster galaxies, which were subjected to a broad range of statistical tests using both positional and velocity information to evaluate the cluster dynamics and substructure. The tests confirmed the presence of substructures within the Abell 2125 system at high significance, demonstrating that A2125 is a complex dynamical system. Comparison of the test results with existing simulations strengthens the merger hypothesis, and provides clues about the merger geometry and stage. The merger model for the system can reconcile A2125's low X-ray temperature and luminosity with its apparently high richness, and might also explain A2125's high fraction of active galaxies identified in prior radio and optical studies.Comment: 34 pages, including tables and 3 color figures; to appear in Ap

    Using the XMM Optical Monitor to Study Cluster Galaxy Evolution

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    We explore the application of XMM-Newton Optical Monitor (XMM-OM) ultraviolet (UV) data to study galaxy evolution. Our sample is constructed as the intersection of all Abell clusters with z < 0.05 and having archival XMM-OM data in either the UVM2 or UVW1 filters, plus optical and UV photometry from the Sloan Digital Sky Survey and GALEX, respectively. The eleven resulting clusters include 726 galaxies with measured redshifts, 520 of which have redshifts placing them within their parent Abell clusters. We develop procedures for manipulating the XMM-OM images and measuring galaxy photometry from them, and confirm our results via comparison with published catalogs. Color magnitude diagrams (CMDs) constructed using the XMM-OM data along with SDSS optical data show promise for evolutionary studies, with good separation between red and blue sequences and real variation in the width of the red sequence that is likely indicative of differences in star formation history. This is particularly true for UVW1 data, as the relative abundance of data collected using this filter and its depth make it an attractive choice. Available tools that use stellar synthesis libraries to fit the UV and optical photometric data may also be used, thereby better describing star formation history within the past Gyr and providing estimates of total stellar mass that include contributions from young stars. Finally, color-color diagrams that include XMM-OM UV data appear useful to the photometric identification of both extragalactic and stellar sources.Comment: 44 pages with 14 figures, to appear in PAS

    Public Purpose Recreation Marketing: A Focus on the Relationships Between the Public and Public Lands

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    Marketing has long had a place in the planning and management of public sector recreation. In particular, the use of market segmentation has allowed leisure providers to better understand their clients’ needs and to tailor their services to the diversity of those needs. However, the use of marketing approaches is not without controversy and is sometimes perceived to be at odds with the public service or stewardship mandates often associated with recreation management. We suggest that wholesale adoption of basic marketing principles (such as the notion of giving people exactly what they want at a great price) may be inappropriate. An alternative form, relational marketing, may be better suited to public purpose organizations. Relational marketing focuses on the development or fostering of a relationship between the public and the public agency. Thus, relational marketing focuses on building confidence in the agency’s ability to guard the short- and long-term interests of the public. For example, for land management agencies, these objectives are embedded in legislative and policy mandates to provide outstanding opportunities for recreation, while at the same time protecting and enhancing the environment. Relational marketing seems better suited to these objectives compared with transactional marketing, which is more dominant in private sector businesses. Whereas transactional marketing focuses on fostering current and continuing purchases of goods and services, relational marketing extends beyond the direct economic exchange. In the public recreation settings, the public is considered more than a current or potential customer, they are also considered an owner or shareholder of the agency. Thus, repeat purchases or customer satisfaction are not sufficient measures of success for organizations with a public service mandate. Instead, relational marketing considers the perceptions that the many different groups of the public (e.g. participants and non-participants, supporters and non-supporters) have of the agency and its actions. The research reported here conceptualizes the relationship between the public and the agency into three dimensions: social trust (the degree to which individuals perceive the agency to share their views, goals, and values); commitment (the investment, attachment, and longevity of the relationship to the agency); and social responsibility (which includes attitudes towards the goals or public purposes of the agency). A market segmentation based on these dimensions yielded distinct subpopulations of the general public. The challenge for public agencies, such as the Forest Service, is to be responsive to the different relationships the public has with the agency. Collaborative planning efforts must acknowledge and incorporate knowledge of these differences in social trust, commitment, and social responsibility. Any public action or policy change should consider how it potentially affects the varying public’s relationship with the agency and the services it provides. Managers must demonstrate stewardship, care, responsiveness, and continuing service to today’s public and future generations. Any interaction with the public (e.g., marketing) should focus on the intended public purpose which guides the agency
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