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Sample records for acs fornax cluster

  1. The ACS Fornax Cluster Survey. VI. The Nuclei of Early-Type Galaxies in the Fornax Cluster

    Turner, Monica L; Ferrarese, Laura; Jordan, Andres; Blakeslee, John P; Mei, Simona; Peng, Eric W; West, Michael J

    2012-01-01

    The Advanced Camera for Surveys (ACS) Fornax Cluster Survey is a Hubble Space Telescope program to image 43 early-type galaxies in the Fornax cluster, using the F475W and F850LP bandpasses of the ACS. We employ both 1D and 2D techniques to characterize the properties of the stellar nuclei in these galaxies, defined as the central "luminosity excesses" relative to a Sersic model fitted to the underlying host. We find 72+/-13% of our sample (31 galaxies) to be nucleated, with only three of the nuclei offset by more than 0.5" from their galaxy photocenter, and with the majority of nuclei having colors bluer than their hosts. The nuclei are observed to be larger, and brighter, than typical Fornax globular clusters, and to follow different structural scaling relations. A comparison of our results to those from the ACS Virgo Cluster Survey reveals striking similarities in the properties of the nuclei belonging to these different environments. We briefly review a variety of proposed formation models and conclude tha...

  2. The ACS Fornax Cluster Survey. XII. Diffuse Star Clusters in Early-type Galaxies

    Liu, Yiqing; Lim, Sungsoon; Jordán, Andrés; Blakeslee, John; Côté, Patrick; Ferrarese, Laura; Pattarakijwanich, Petchara

    2016-01-01

    Diffuse star clusters (DSCs) are old and dynamically hot stellar systems that have lower surface brightness and more extended morphology than globular clusters (GCs). Using the images from HST/ACS Fornax Cluster Survey, we find that 12 out of 43 early-type galaxies (ETGs) in the Fornax cluster host significant numbers of DSCs. Together with literature data from the HST/ACS Virgo Cluster Survey, where 18 out of 100 ETGs were found to host DSCs, we systematically study the relationship of DSCs with GCs, and their host galaxy environment. Two DSC hosts are post-merger galaxies, with most of the other hosts either having low mass or showing clear disk components. We find that while the number ratio of DSCs to GCs is nearly constant in massive galaxies, the DSC-to-GC ratio becomes systematically higher in lower mass hosts. This suggests that DSCs may be more efficient at forming (or surviving) in low density environments. DSC hosts are not special either in their position in the cluster, or in the galactic color-m...

  3. Hubble flow around Fornax cluster of galaxies

    Nasonova, Olga G; Karachentsev, Igor D

    2011-01-01

    Aims. This work aims to provide a new mass estimate for the Fornax cluster and the Fornax-Eridanus complex, avoiding methods like the virial or fits of X-ray emission profile, which assume that the system is in equilibrium, probably not the case of Fornax, still in process of formation. Methods. Our mass estimate is based on the determination of the zero-velocity surface which, in the context of the spherical infall model permits an evaluation of the total mass inside such a surface. The zero-velocity surface radius R0 was estimated either by a running median procedure or by fitting the data to the velocity field expected from the spherical model, including effects of the cosmological constant. The velocity field in a region within 20 Mpc of the Fornax center was mapped using a list of 109 galaxies whose distances have an average accuracy of 0.31 mag in their distance modulus. Results. Our analysis indicates that the mass of the Fornax cluster itself inside a radius of [2.62-5.18] Mpc is [0.40-3.32] \\times 10...

  4. A Deep Look at the Fornax Cluster

    Kohler, Susanna

    2016-04-01

    Traditionally, dense cluster centers are cannibalistic environments, with larger galaxies stripping stars from smaller interlopers in minor mergers and dynamical harassment. A recent survey of the Fornax cluster, one example of such an environment, reveals how this cluster may have been built.Clues in HalosContext for the southern constellation Fornax (the furnace). The Fornax cluster is marked with a red circle. [ESO, IAU and Sky Telescope]Deep surveys of dense cluster environments are necessary because the imprint of mass assembly is hidden in galactic halos, the faint outer regions of galaxies. Deep observations can reveal answers to questions about how the galaxies in these extreme environments formed and evolved for instance, did the majority of the galaxies stars form in situ, or were they accreted from interactions with other galaxies?The Fornax Deep Survey (FDS) is just such a campaign. FDS uses the European Southern Observatorys VLT Survey Telescope to obtain deep photometry of the entire 26 square degrees of the Fornax cluster, a spectacular galaxy cluster located 65 million light-years away.Central ObservationsThe FDS team plans to release the full results from the survey soon. For now, in an initial study led by Enrichetta Iodice (INAFs Astronomical Observatory of Capodimonte, Italy), the team presents their first findings from the two square degrees around NGC 1399, a supergiant elliptical galaxy in the cluster center.The two main results from this study are:The discovery of a faint stellar bridge between NGC 1399 and a nearby galaxy, NGC 1387.The characterization of NGC 1399s light profile, which shows that the galaxy consists of two main components separated by a strong break. The bright central galaxy is likely composed of stars that formed in situ, whereas the exponential outer component is a stellar halo composed of stars likely captured from accretion events.What do these points tell us about the history of the center of the Fornax cluster? These

  5. Substructure and dynamics of the Fornax Cluster

    Drinkwater, M J; Colless, M

    2001-01-01

    We present the first dynamical analysis of a galaxy cluster to include a large fraction of dwarf galaxies. Our sample of 108 Fornax Cluster members measured with the UK Schmidt Telescope FLAIR-II spectrograph contains 55 dwarf galaxies (15.5>bj>18.0 or -16>Mb>-13.5). Halpha emission shows that 36+/-8 per cent of the dwarfs are star-forming, twice the fraction implied by morphological classifications. The total sample has a mean velocity of 1493+/-36 km/s and a velocity dispersion of 374+/-26 km/s. The dwarf galaxies form a distinct population: their velocity dispersion (429+/-41 km/s) is larger than that of the giants (308+/-30 km/s) at the 98 per cent confidence level. This suggests that the dwarf population is dominated by infalling objects whereas the giants are virialized. The Fornax system has two components; the main Fornax Cluster centered on NGC 1399 with mean velocity 1478 km/s and velocity dispersion 370 km/s, and a subcluster centered 3 degrees to the south-west including NGC 1316 with mean velocit...

  6. The complex star cluster system of NGC 1316 (Fornax A)

    Sesto, Leandro A; Forte, Juan C

    2016-01-01

    This paper presents Gemini-$gri'$ high quality photometry for cluster candidates in the field of NGC 1316 (Fornax A) as part of a study that also includes GMOS spectroscopy. A preliminary discussion of the photometric data indicates the presence of four stellar cluster populations with distinctive features in terms of age, chemical abundance and spatial distribution. Two of them seem to be the usually old (metal poor and metal rich) populations typically found in elliptical galaxies. In turn, an intermediate-age (5 Gyr) globular cluster population is the dominant component of the sample (as reported by previous papers). We also find a younger cluster population with a tentative age of $\\approx$ 1 Gyr.

  7. Compact stellar systems in the Fornax cluster: a UV perspective

    Mieske, Steffen; Bomans, Dominik J; Rey, Soo-Chang; Kim, Suk; Yoon, Suk-Jin; Chung, Chul

    2008-01-01

    In recent years, increasing evidence for chemical complexity and multiple stellar populations in massive globular clusters (GCs) has emerged, including extreme horizontal branches (EHBs) and UV excess. Our goal is to improve our understanding of UV excess in the regime of both massive GCs and ultra-compact dwarf galaxies (UCDs). To this end, we use deep archival GALEX data of the central Fornax cluster to measure NUV and FUV magnitudes of UCDs and massive GCs. We obtain NUV photometry for a sample of 35 compact objects with -13.5Fornax GCs exhibit a NUV excess with respect to expectations from stellar population models, even for models with enhanced Helium abundance. This suggests that not only He-enrichment has contributed to forming the EHB population of these GCs. The GCs extend to stronger UV excess than GCs in M31 and m...

  8. The distance of the Fornax Cluster based on Globular Cluster Luminosity Functions

    Kohle, Sven; Kissler-Patig, Markus; Hilker, Michael; Richtler, Tom; Infante, L.; Quintana, H.

    1996-01-01

    We present Globular Cluster Luminosity Functions for four ellipticals and one S0-Galaxy in the Fornax cluster of galaxies, derived from CCD photometry in V and I. The averaged turnover magnitudes are $V_{TO} = 23.80 \\pm 0.06$ and $I_{TO} =22.39 \\pm 0.05$, respectively. We derive a relative distance modulus $(m-M)_{Fornax} - (m-M)_{M87} = 0.08 \\pm 0.09$ mag using the turnover of M87 based on HST data.

  9. Peculiar compact stellar systems in the Fornax cluster

    Wittmann, Carolin; Pasquali, Anna; Hilker, Michael; Grebel, Eva K

    2016-01-01

    We search for hints to the origin and nature of compact stellar systems in the magnitude range of ultracompact dwarf galaxies in deep wide-field imaging data of the Fornax cluster core. We visually investigate a large sample of 355 spectroscopically confirmed cluster members with V-band equivalent magnitudes brighter than -10 mag for faint extended structures. Our data reveal peculiar compact stellar systems, which appear asymmetric or elongated from their outer light distribution. We characterize the structure of our objects by quantifying their core concentration, as well as their outer asymmetry and ellipticity. For the brighter objects of our sample we also investigate their spatial and phase-space distribution within the cluster. We argue that the distorted outer structure alone that is seen for some of our objects, is not sufficient to decide whether these systems have a star cluster or a galaxy origin. However, we find that objects with low core concentration and high asymmetry (or high ellipticity) ar...

  10. The Extended Spatial Distribution of Globular Clusters in the Core of the Fornax Cluster

    D'Abrusco, R.; Cantiello, M.; Paolillo, M.; Pota, V.; Napolitano, N. R.; Limatola, L.; Spavone, M.; Grado, A.; Iodice, E.; Capaccioli, M.; Peletier, R.; Longo, G.; Hilker, M.; Mieske, S.; Grebel, E. K.; Lisker, T.; Wittmann, C.; van de Ven, G.; Schipani, P.; Fabbiano, G.

    2016-03-01

    We report the discovery of a complex extended density enhancement in the Globular Clusters (GCs) in the central ˜ 0.5{(^\\circ )}2 (˜ 0.06 Mpc2) of the Fornax cluster, corresponding to ˜ 50% of the area within 1 core radius. This overdensity connects the GC system of NGC 1399 to most of those of neighboring galaxies within ˜ 0\\_\\_AMP\\_\\_fdg;6 (˜ 210 kpc) along the W-E direction. The asymmetric density structure suggests that the galaxies in the core of the Fornax cluster experienced a lively history of interactions that have left a clear imprint on the spatial distribution of GCs. The extended central dominant structure is more prominent in the distribution of blue GCs, while red GCs show density enhancements that are more centrally concentrated on the host galaxies. We propose that the relatively small-scale density structures in the red GCs are caused by galaxy-galaxy interactions, while the extensive spatial distribution of blue GCs is due to stripping of GCs from the halos of core massive galaxies by the Fornax gravitational potential. Our investigations are based on density maps of candidate GCs extracted from the multi-band VLT Survey Telescope (VST) survey of Fornax (FDS), identified in a three-dimensional color space and further selected based on their g-band magnitude and morphology.

  11. The mass distribution of the Fornax dSph: constraints from its globular cluster distribution

    Cole, David R.; Dehnen, Walter; Read, Justin I.; Wilkinson, Mark I.

    2012-10-01

    Uniquely among the dwarf spheroidal (dSph) satellite galaxies of the Milky Way, Fornax hosts globular clusters. It remains a puzzle as to why dynamical friction has not yet dragged any of Fornax's five globular clusters to the centre, and also why there is no evidence that any similar star cluster has been in the past (for Fornax or any other tidally undisrupted dSph). We set up a suite of 2800 N-body simulations that sample the full range of globular cluster orbits and mass models consistent with all existing observational constraints for Fornax. In agreement with previous work, we find that if Fornax has a large dark matter core, then its globular clusters remain close to their currently observed locations for long times. Furthermore, we find previously unreported behaviour for clusters that start inside the core region. These are pushed out of the core and gain orbital energy, a process we call 'dynamical buoyancy'. Thus, a cored mass distribution in Fornax will naturally lead to a shell-like globular cluster distribution near the core radius, independent of the initial conditions. By contrast, cold dark matter-type cusped mass distributions lead to the rapid infall of at least one cluster within Δt = 1-2 Gyr, except when picking unlikely initial conditions for the cluster orbits (˜2 per cent probability), and almost all clusters within Δt = 10 Gyr. Alternatively, if Fornax has only a weakly cusped mass distribution, then dynamical friction is much reduced. While over Δt = 10 Gyr this still leads to the infall of one to four clusters from their present orbits, the infall of any cluster within Δt = 1-2 Gyr is much less likely (with probability 0-70 per cent, depending on Δt and the strength of the cusp). Such a solution to the timing problem requires (in addition to a shallow dark matter cusp) that in the past the globular clusters were somewhat further from Fornax than today; they most likely did not form within Fornax, but were accreted.

  12. Four and one more: The formation history and total mass of globular clusters in the Fornax dSph

    de Boer, T. J. L.; Fraser, M.

    2016-05-01

    We have determined the detailed star formation history and total mass of the globular clusters in the Fornax dwarf spheroidal using archival HST WFPC2 data. Colour-magnitude diagrams were constructed in the F555W and F814W bands and corrected for the effect of Fornax field star contamination, after which we used the routine Talos to derive the quantitative star formation history as a function of age and metallicity. The star formation history of the Fornax globular clusters shows that Fornax 1, 2, 3, and 5 are all dominated by ancient (>10 Gyr) populations. Clusters Fornax 1, 2, and 3 display metallicities as low as [Fe/H] = -2.5, while Fornax 5 is slightly more metal-rich at [Fe/H] = -1.8, consistent with resolved and unresolved metallicity tracers. Conversely, Fornax 4 is dominated by a more metal-rich ([Fe/H] = -1.2) and younger population at 10 Gyr, inconsistent with the other clusters. A lack of stellar populations overlapping with the main body of Fornax argues against the nucleus cluster scenario for Fornax 4. The combined stellar mass in globular clusters as derived from the SFH is (9.57 ± 0.93) × 105 M⊙, which corresponds to 2.5 ± 0.2 percent of the total stellar mass in Fornax. The mass of the four most metal-poor clusters can also be compared to the metal-poor Fornax field to yield a mass fraction of 19.6 ± 3.1 percent. Therefore, the SFH results provide separate supporting evidence for the unusually high mass fraction of the globular clusters compared to the Fornax field population.

  13. Nitrogen abundances and multiple stellar populations in the globular clusters of the Fornax dSph

    Larsen, Søren S. [Department of Astrophysics/IMAPP, Radboud University, P.O. Box 9010, 6500 GL Nijmegen (Netherlands); Brodie, Jean P. [UCO/Lick Observatory, University of California, Santa Cruz, CA 95064 (United States); Grundahl, Frank [Stellar Astrophysics Centre, Department of Physics and Astronomy, Aarhus University, Ny Munkegade 120, DK-8000 Aarhus C (Denmark); Strader, Jay, E-mail: s.larsen@astro.ru.nl [Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48824 (United States)

    2014-12-10

    We use measurements of nitrogen abundances in red giants to search for multiple stellar populations in the four most metal-poor globular clusters (GCs) in the Fornax dwarf spheroidal galaxy (Fornax 1, 2, 3, and 5). New imaging in the F343N filter, obtained with the Wide Field Camera 3 on the Hubble Space Telescope, is combined with archival F555W and F814W observations to determine the strength of the NH band near 3370 Å. After accounting for observational errors, the spread in the F343N-F555W colors of red giants in the Fornax GCs is similar to that in M15 and corresponds to an abundance range of Δ[N/Fe] ∼ 2 dex, as observed also in several Galactic GCs. The spread in F555W-F814W is, instead, fully accounted for by observational errors. The stars with the reddest F343N-F555W colors (indicative of N-enhanced composition) have more centrally concentrated radial distributions in all four clusters, although the difference is not highly statistically significant within any individual cluster. From double-Gaussian fits to the color distributions, we find roughly equal numbers of 'N-normal' and 'N-enhanced' stars (formally ∼40% N-normal stars in Fornax 1, 3, and 5 and ∼60% in Fornax 2). We conclude that GC formation, in particular, regarding the processes responsible for the origin of multiple stellar populations, appears to have operated similarly in the Milky Way and in the Fornax dSph. Combined with the high ratio of metal-poor GCs to field stars in the Fornax dSph, this places an important constraint on scenarios for the origin of multiple stellar populations in GCs.

  14. Cannibal Stars Cause Giant Explosions in Fornax Cluster Galaxy

    2000-07-01

    been necessary to detect a few distant novae [3]. VLT observations of NGC 1316 in the Fornax Cluster ESO PR Photo 18a/00 ESO PR Photo 18a/00 [Preview - JPEG: 400 x 448 pix - 28k] [Normal - JPEG: 800 x 895 pix - 136k] [Full-Res - JPEG: 1941 x 2172 pix - 904k] Caption : Colour composite photo of the central area of NGC 1316 , a giant elliptical galaxy in the Fornax cluster of galaxies. Many dark dust clouds and lanes are visible. Some of the star-like objects in the field are globular clusters of stars that belong to the galaxy. It is based on CCD exposures, obtained with the 8.2-m VLT/ANTU telescope and the FORS-1 multi-mode instrument through B (blue), V (green-yellow) and I (here rendered as red) filters, respectively. The "pyramids" above and below the bright centre of the galaxy and the vertical lines at some of the brighter stars are caused by overexposure ("CCD bleeding"). The field measures 6.8 x 6.8 arcmin 2 , with 0.2 arcsec/pixel. The image quality of this composite is about 0.9 arcsec. North is up and East is left. NGC 1316 is a giant "dusty" galaxy ( PR Photo 18a/00 ), located in the Fornax cluster seen in the southern constellation of that name ("The Oven"). This galaxy is of special interest in connection with current attempts to establish an accurate distance scale in the Universe. In 1980 and 1981, NGC 1316 was the host of two supernovae of type Ia , a class of object that is widely used as a "cosmological standard candle" to determine the distance to very distant galaxies, cf. ESO PR 21/98. A precise measurement of the distance to NGC 1316 may therefore provide an independent calibration of the intrinsic brightness of these supernovae. The new observations were performed during 8 nights distributed over the period from January 9 to 19, 2000. They were made in service mode at the 8.2-m VLT/ANTU telescope with the FORS-1 multi-mode instrument, using a 2k x 2k CCD camera with 0.2 arcsec pixels and a field of 6.8 x 6.8 arcmin 2. The exposures lasted 20 min

  15. The Extended Spatial Distribution of Globular Clusters in the Core of the Fornax Cluster

    D'Abrusco, R; Paolillo, M; Pota, V; Napolitano, N R; Limatola, L; Spavone, M; Grado, A; Iodice, E; Capaccioli, M; Peletier, R; Longo, G; Hilker, M; Mieske, S; Grebel, E K; Lisker, T; Wittmann, C; van de Ven, G; Fabbiano, G

    2016-01-01

    We report the discovery of a complex extended density enhancement in the Globular Clusters (GCs) in the central $\\sim 0.5(^{\\circ})^2$ ($\\sim 0.06$ Mpc$^2$) of the Fornax cluster, corresponding to $\\sim 50\\%$ of the area within 1 core radius. This overdensity connects the GC system of NGC1399 to most of those of neighboring galaxies within $\\sim 0.6^{\\circ}$ ($\\sim 210$ kpc) along the W-E direction. The asymmetric density structure suggests that the galaxies in the core of the Fornax cluster experienced a lively history of interactions that have left a clear imprint on the spatial distribution of GCs. The extended central dominant structure is more prominent in the distribution of blue GCs, while red GCs show density enhancements that are more centrally concentrated on the host galaxies. We propose that the relatively small-scale density structures in the red GCs are caused by galaxy-galaxy interactions, while the extensive spatial distribution of blue GCs is due to stripping of GCs from the halos of core mas...

  16. Four and one more: The formation history and total mass of globular clusters in the Fornax dSph

    de Boer, T J L

    2015-01-01

    We have determined the detailed star formation history and total mass of the globular clusters in the Fornax dwarf spheroidal using archival HST WFPC2 data. Colour magnitude diagrams are constructed in the F555W and F814W bands and corrected for the effect of Fornax field star contamination, after which we use the routine Talos to derive the quantitative star formation history as a function of age and metallicity. The star formation history of the Fornax globular clusters shows that Fornax 1, 2, 3 and 5 are all dominated by ancient~(>10 Gyr) populations. Cluster Fornax 1 and 3 display metallicities as low as [Fe/H]=-2.5 while Fornax 2 and 5 are slightly more metal-rich at [Fe/H]=-2.0, consistent with resolved and unresolved metallicity tracers. Conversely, Fornax 4 displays a more extended star formation history dominated by metal-rich~([Fe/H]=-1.4 dex) stars, with an age of ~10 Gyr, inconsistent with the other clusters. Its central location and complex population mix favours the proposed model that it might ...

  17. Globular clusters as tracers of the host galaxy mass distribution: the Fornax dSph test case

    Arca-Sedda, Manuel; Capuzzo-Dolcetta, Roberto

    2016-01-01

    The Fornax dwarf spheroidal galaxy is the most massive satellites of the Milky Way, claimed to be embedded in a huge dark matter halo, and the only among the Milky Way satellites hosting five globular clusters. Interestingly, their estimated masses, ages and positions seem hardly compatible with the presence of a significant dark matter component, as expected in the $\\Lambda$ CDM scheme. Indeed, if Fornax would have a CDM halo with a standard density profile, all its globular clusters should ...

  18. Optical identifications of IRAS point sources: the Fornax, Hydra I and Coma clusters

    We present optical identifications for 66 IRAS point sources in the region of the Fornax cluster of galaxies, 106 IRAS point sources in the region of the Hydra I cluster of galaxies (Abell 1060) and 59 IRAS point sources in the region of the Coma cluster of galaxies (Abell 1656). Eight other sources in Hydra I do not have optical counterparts and are very probably due to infrared cirrus. Twenty-three (35 per cent) of the Fornax sources are associated with stars and 43 (65 per cent) with galaxies; 48 (42 per cent) of the Hydra I sources are associated with stars and 58 (51 per cent) with galaxies; 18 (31 per cent) of the Coma sources are associated with stars and 41 (69 per cent) with galaxies. The stellar and infrared cirrus surface density is consistent with the galactic latitude of each field. (author)

  19. Optical identifications of IRAS point sources: the Fornax, Hydra I and Coma clusters

    Wang, G.; Leggett, S.K. (Edinburgh Univ. (UK). Dept. of Astronomy); Clowes, R.G.; MacGillivray, H.T. (Royal Observatory, Edinburgh (UK)); Savage, A. (Anglo-Australian Observatory, Coonabarabran, NSW (Australia). UK Schmidt Telescope)

    1991-01-01

    We present optical identifications for 66 IRAS point sources in the region of the Fornax cluster of galaxies, 106 IRAS point sources in the region of the Hydra I cluster of galaxies (Abell 1060) and 59 IRAS point sources in the region of the Coma cluster of galaxies (Abell 1656). Eight other sources in Hydra I do not have optical counterparts and are very probably due to infrared cirrus. Twenty-three (35 per cent) of the Fornax sources are associated with stars and 43 (65 per cent) with galaxies; 48 (42 per cent) of the Hydra I sources are associated with stars and 58 (51 per cent) with galaxies; 18 (31 per cent) of the Coma sources are associated with stars and 41 (69 per cent) with galaxies. The stellar and infrared cirrus surface density is consistent with the galactic latitude of each field. (author).

  20. Globular clusters as tracers of the host galaxy mass distribution: the Fornax dSph test case

    Arca-Sedda, Manuel

    2016-01-01

    The Fornax dwarf spheroidal galaxy is the most massive satellites of the Milky Way, claimed to be embedded in a huge dark matter halo, and the only among the Milky Way satellites hosting five globular clusters. Interestingly, their estimated masses, ages and positions seem hardly compatible with the presence of a significant dark matter component, as expected in the $\\Lambda$ CDM scheme. Indeed, if Fornax would have a CDM halo with a standard density profile, all its globular clusters should have sunk to the galactic centre many Gyr ago due to dynamical friction. Due to this, some authors proposed that the most massive clusters may have formed out of Fornax and later tidally captured. In this paper we investigate the past evolution of the Fornax GC system by using both a recently developed, semi-analytical treatment of dynamical friction and direct $N$-body simulations of the orbital evolution of the globular clusters within Fornax and of Fornax galaxy around the Milky Way. Our results suggest that an "in-sit...

  1. Resolving the timing problem of the globular clusters orbiting the Fornax dwarf galaxy

    Angus, Garry W

    2009-01-01

    We re-investigate the old problem of the survival of the five globular clusters orbiting the Fornax dwarf galaxy in both standard and modified Newtonian dynamics. For the first time in the history of the topic, we use accurate mass models for the Fornax dwarf, obtained through Jeans modelling of the recently published line of sight velocity dispersion data, and we are also not resigned to circular orbits for the globular clusters. Previously conceived problems stem from fixing the starting distances of the globulars to be less than half the tidal radius. We relax this constraint since there is absolutely no evidence for it and show that the dark matter paradigm, with either cusped or cored dark matter profiles, has no trouble sustaining the orbits of the two least massive globular clusters for a Hubble time almost regardless of their initial distance from Fornax. The three most massive globulars can remain in orbit as long as their starting distances are marginally outside the tidal radius. The outlook for mo...

  2. Fermi-LAT constraints on dark matter annihilation cross section from observations of the Fornax cluster

    We analyze 2.8-yr data of 1–100 GeV photons for clusters of galaxies, collected with the Large Area Telescope onboard the Fermi satellite. By analyzing 49 nearby massive clusters located at high Galactic latitudes, we find no excess gamma-ray emission towards directions of the galaxy clusters. Using flux upper limits, we show that the Fornax cluster provides the most stringent constraints on the dark matter annihilation cross section. Stacking a large sample of nearby clusters does not help improve the limit for most dark matter models. This suggests that a detailed modeling of the Fornax cluster is important for setting robust limits on the dark matter annihilation cross section based on clusters. We therefore perform the detailed mass modeling and predict the expected dark matter annihilation signals from the Fornax cluster, by taking into account effects of dark matter contraction and substructures. By modeling the mass distribution of baryons (stars and gas) around a central bright elliptical galaxy, NGC 1399, and using a modified contraction model motivated by numerical simulations, we show that the dark matter contraction boosts the annihilation signatures by a factor of 4. For dark matter masses around 10 GeV, the upper limit obtained on the annihilation cross section times relative velocity is (σν)∼−25 cm3 s−1, which is within a factor of 10 from the value required to explain the dark matter relic density. This effect is more robust than the annihilation boost due to substructure, and it is more important unless the mass of the smallest subhalos is much smaller than that of the Sun

  3. Searching for star-forming galaxies in the Fornax and Hydra clusters

    Vaduvescu, O; Vilchez, J M; Unda-Sanzana, E; 10.1051/0004-6361/201116651

    2011-01-01

    The formation and evolution of dwarf galaxies is relatively difficult to understand because of their faint emission in all regimes that require large aperture telescopes. We intend to study the evolution of star forming dwarf galaxies in clusters. We selected Fornax and Hydra clusters to complement our previous study of Virgo. On the basis of available literature data, we selected ten star-forming candidates in Fornax and another ten objects in Hydra. We used Gemini South with GMOS to acquire H-alpha images necessary to detect star-forming regions in the two galaxy samples. We then performed long-slit spectroscopy for the brightest six candidates, to derive their chemical properties. Finally, we employed the VLT with HAWK-I to observe all galaxies in the K' band to derive their main physical properties. We studied the morphology of our two samples, finding five objects in Fornax and six in Hydra with structures consistent with those of star-forming dwarfs, i.e., dwarf irregulars (dIs) or blue compact dwarfs (...

  4. Bright galaxies in the Fornax cluster. Automated galaxy surface photometry: Pt. 7

    We have determined surface-brightness profiles for all galaxies down to magnitude B = 16 in the central region of the Fornax cluster. Using existing redshift data, we have determined the distributions of surface brightness for both the whole sample and for cluster disc galaxies only. Although both distributions peak at extrapolated central surface brightness ∼ 21.7B mag/arcsec2 (the canonical result), it is shown that they are, in fact, consistent with very broad distributions of disc central surface brightness once selection effects and the effects of bulge contamination of the profile are taken into account. (author)

  5. WIDE-FIELD MULTIBAND PHOTOMETRY OF GLOBULAR CLUSTER SYSTEMS IN THE FORNAX GALAXY CLUSTER

    We present wide-field multiband photometry of globular cluster (GC) systems in NGC 1399, NGC 1404, and NGC 1387 located in the central region of the Fornax galaxy cluster. Observation was carried out through U, B, V, and I bands, which marks one of the widest and deepest U-band studies on extragalactic GC systems. The present U-band photometry enables us to significantly reduce the contamination by a factor of two for faint sources (V 0 ∼ 23.5). The main results based on some 2000 GC candidates around NGC 1399, NGC 1404, and NGC 1387 are as follows: (1) the GC system in each galaxy exhibits bimodal color distributions in all colors examined, but the shape of color histograms varies systematically depending on colors; (2) NGC 1399 shows that the mean colors of both blue and red GCs become bluer with increasing galactocentric radius; (3) NGC 1399 shows overabundance of GCs in the directions of NGC 1404 and NGC 1387, indicating their ongoing interactions; and (4) NGC 1399 also exhibits a ∼0.'5 offset between the center of the inner GC distribution and the galaxy's optical center, suggesting that NGC 1399 is not yet dynamically relaxed and may be undergoing merger events.

  6. The chemical composition of Ultracompact Dwarf Galaxies in the Virgo and Fornax Clusters

    Francis, K J; Chilingarian, Igor V; Bolt, A M; Firth, P

    2012-01-01

    We present spectroscopic observations of ultra compact dwarf (UCD) galaxies in the Fornax and Virgo Clusters made to measure and compare their stellar populations. The spectra were obtained on the Gemini-North (Virgo) and Gemini-South (Fornax) Telescopes using the respective Gemini Multi-Object Spectrographs. We estimated the ages, metallicities and abundances of the objects from mea- surements of Lick line-strength indices in the spectra; we also estimated the ages and metallicities independently using a direct spectral fitting technique. Both methods re- vealed that the UCDs are old (mean age 10.8 \\pm 0.7 Gyr) and (generally) metal-rich (mean [Fe/H] = -0.8 \\pm 0.1). The alpha-element abundances of the objects measured from the Lick indices are super-Solar. We used these measurements to test the hypothesis that UCDs are formed by the tidal disruption of present-day nucleated dwarf elliptical galaxies. The data are not consistent with this hypothesis because both the ages and abundances are significantly high...

  7. Low surface brightness galaxies in the Fornax Cluster: automated galaxy surface photometry

    A sample is presented of low surface brightness galaxies (with extrapolated central surface brightness fainter than 22.0 Bμ) in the Fornax Cluster region which has been measured by the APM machine. Photometric parameters, namely profile shape, scale length, central brightness and total magnitude, are derived for the sample galaxies and correlations between the parameters of low surface brightness dwarf galaxies are discussed, with particular reference to the selection limits. Contrary to previous authors we find no evidence for a luminosity-surface brightness correlation in the sense of lower surface brightness galaxies having lower luminosities and scale sizes. In fact, the present data suggest that it is the galaxies with the largest scale lengths which are more likely to be of very low surface brightness. In addition, the larger scale length galaxies occur preferentially towards the centre of the Cluster. (author)

  8. The central region of the Fornax cluster; 3, Dwarf galaxies, globular clusters, and cD halo are there interrelations?

    Hilker, M; Richtler, T

    1999-01-01

    In this paper we briefly review the properties of the dwarf galaxy population at the core of the Fornax cluster, as well as the properties of the extraordinary rich globular cluster system and the cD halo around the central galaxy NGC 1399. In turn, the question whether a scenario in which dwarf galaxies have been accreted and dissolved in the cluster center can explain the observed properties is addressed. The possibility of accretion of a certain number of dwarf galaxies, the stripping of their globular clusters and gas, and the formation of new globular clusters from stripped infalling gas are discussed. An increase in the specific frequency of the central globular cluster system is only possible, if the infalling gas from stripped dwarfs formed globulars very efficiently and/or accreted and stripped dwarf galaxies possessed a rich globular cluster system themselves. In conclusion, we argue that although the dwarf galaxy infall is a very attractive scenario to explain a number of properties in the system t...

  9. Suzaku observation of the metallicity distribution in the intracluster medium of the Fornax cluster

    Matsushita, K; Hughes, J P; Kitaguchi, T; Makishima, K; Nakazawa, K; Ohashi, T; Ota, N; Tamura, T; Tozuka, M; Tsuru, T G; Urata, Y; Yamasaki, N Y; Matsushita, Kyoko; Fukazawa, Yasushi; Hughes, John P.; Kitaguchi, Takao; Makishima, Kazuo; Nakazawa, Kazuhiro; Ohashi, Takaya; Ota, Naomi; Tamura, Takayuki; Tozuka, Miyako; Tsuru, Takeshi Go; Urata, Yuji; Yamasaki, Noriko Y.

    2006-01-01

    The metallicity distribution in the Fornax cluster was studied with the XIS instrument onboard the Suzaku satellite. K-shell lines of O and Mg were resolved clearly, and the abundances of O, Mg, Si, S and Fe were measured with good accuracy. The region within a 4' radius of NGC 1399 shows approximately solar abundances of Fe, Si and S, while the O/Fe and Mg/Fe abundance ratios are about 0.4--0.5 and 0.7 in solar units. In the outer region spanning radii between 6' and 23', the Fe and Si abundances drop to 0.4--0.5 solar and show no significant gradient within this region. The abundance ratios, O/Fe and Mg/Fe, are consistent with those in the central region. We also measured the Fe abundance around NGC 1404 to be approximately solar, and the O, Ne and Mg abundances to be 0.5--0.7 times the Fe level. The significant relative enhancement of Fe within 130 kpc of NGC 1399 and in NGC 1404 indicates an origin in SN Ia, in contrast to the species O, Ne, and Mg which reflect the stellar metallicity. The mass-to-light ...

  10. The Stellar Populations of Nuclei, Globular Clusters, and Stars in dE Galaxies in Virgo and Fornax

    Whitfield Miller, Bryan; Hyazinth Puzia, Thomas; Hilker, Michael; Sanchez-Janssen, Ruben; Kissler-Patig, Markus

    2015-08-01

    We present ages and metallicities for globular clusters, nuclei, and underlying stars in nucleated dwarf elliptical galaxies (dE,N) in the Virgo and Fornax Cluster based on Lick/IDS index measurements and SSP models. Gemini/GMOS spectroscopy shows that the globular clusters are mostly old and metal-poor, very similar to the globular clusters in the Milky Way halo. The nuclei and underlying stars tend to be more metal-rich than the globular clusters and have a wide range of ages. The [α/Fe] ratios for both the globular clusters and nuclei range between 0.0 and 0.3. Formation scenarios for globular clusters and nuclei will be discussed.

  11. Evidence for a chemical enrichment coupling of globular clusters and field stars in the Fornax dSph

    Hendricks, Benjamin; Johnson, Christian I; Frank, Matthias J; Koch, Andreas; Mateo, Mario; Bailey, John I

    2016-01-01

    The globular cluster H4, located in the center of the Fornax dwarf spheroidal galaxy, is crucial for understanding the formation and chemical evolution of star clusters in low-mass galactic environments. H4 is peculiar because the cluster is significantly more metal-rich than the galaxy's other clusters, is located near the galaxy center, and may also be the youngest cluster in the galaxy. In this study, we present detailed chemical abundances derived from high-resolution (R~28000) spectroscopy of an isolated H4 member star for comparison with a sample of 22 nearby Fornax field stars. We find the H4 member to be depleted in the alpha-elements Si, Ca, and Ti with [Si/Fe]=-0.35+-0.34, [Ca/Fe]=+0.05+-0.08, and [Ti/Fe]=-0.27+-0.23, resulting in an average [alpha/Fe]=-0.19+-0.14. If this result is representative of the average cluster properties, H4 is the only known system with a low [alpha/Fe] ratio and a moderately low metallicity embedded in an intact birth environment. For the field stars we find a clear sequ...

  12. The central region of the Fornax cluster; 2, Spectroscopy and radial velocities of member and background galaxies

    Hilker, M; Vieria, G; Kissler-Patig, M; Richtler, T

    1998-01-01

    Radial velocities of 94 galaxies brighter than about V_tot = 20 mag in the direction of the central Fornax cluster have been measured. Except for 8 Fornax members, all galaxies lie in the background. Among the 8 members, there are 5 nucleated dwarf ellipticals that are already listed in the FCC (Ferguson 1989, AJ 98, 367). Two of the 3 ``new'' members are very compact and have surface brightnesses comparable to globular clusters, however their luminosities are in the range of dwarf elliptical nuclei. The measured line indices (especially Mg2, H beta, and iron) of the brighter of the compact objects suggest a solar metallicity, whereas the fainter compact object as well as the dE,Ns have line indices that are similar to those of old metal-poor globular clusters (GCs). However, with these data it is not possible to clearly classify the compact objects either as very bright globular clusters, isolated nuclei of dE,Ns, or even compact ellipticals. A background galaxy cluster at z = 0.11 has been found just behind...

  13. VizieR Online Data Catalog: Galaxies in Fornax Cluster and five nearby groups (Ferguson+ 1990)

    Ferguson, H. C.

    1997-07-01

    This catalog represents the combination of results published in two papers: Ferguson, H.C. 1989 A.J. 98, 367 (Paper II) and Ferguson, H.C. and Sandage, A. 1990 A.J. 100, 1 (Paper III). See the Historical Notes section below. Please note that the data from Paper II were previously archived as catalog VII/160. This catalog supersedes that earlier dataset. The following paragraphs describe the data included from the two papers. (Paper II) This paper presents a catalog of 2678 galaxies within an area of nearly 40 deg2 centered on the Fornax Cluster at α=3h35m and δ=-35.7deg. The data have been obtained from visual inspection of 26 deep large-scale (10.9arcsec/mm) plates taken with the du Pont 2.5m reflector at the Las Campanas Observatory, and from digital photometry of an ESO/SRC blue survey plate covering roughly the same area of the sky. The catalog is essentially diameter limited, with a limiting diameter of 17arcsec at an isophoto of BT =26.5. Within this survey region, the catalog includes 340 likely cluster members and 2338 likely background galaxies. For cluster members, this listing should be complete to BT=18 (corresponding to MBT=13.0, assuming a distance modulus of m-M=31.9) and contains likely members down to BT=20. Cluster membership is for the most part based on galaxy morphology. By virtue of their low surface brightness, dwarf galaxies in the cluster can be distinguished with a high degree of certainty from background galaxies. Radial velocities are included for 89 galaxies in the survey, providing a reliable indicator of membership in these cases. As additional support for our rejection of background galaxies, we model the spatial distribution of various types of galaxies as the sum of a King model cluster component superimposed on a uniform background. Using maximum-likelyhood fits to these spatial distributions, we find a core radius of 0.7deg. for a King model fit to the cluster, and show that there are few, if any, cluster members contained in

  14. Evidence for a chemical enrichment coupling of globular clusters and field stars in the Fornax dSph

    Hendricks, Benjamin; Boeche, Corrado; Johnson, Christian I.; Frank, Matthias J.; Koch, Andreas; Mateo, Mario; Bailey, John I.

    2016-01-01

    The globular cluster H4, located in the center of the Fornax dwarf spheroidal galaxy, is crucial for understanding the formation and chemical evolution of star clusters in low-mass galactic environments. H4 is peculiar because the cluster is significantly more metal-rich than the galaxy's other clusters, is located near the galaxy center, and may also be the youngest cluster in the galaxy. In this study, we present detailed chemical abundances derived from high-resolution (R ~ 28 000) spectroscopy of an isolated H4 member star for comparison with a sample of 22 nearby Fornax field stars. We find the H4 member to be depleted in the alpha-elements Si, Ca, and Ti with [Si/Fe] = -0.35 ± 0.34, [Ca/Fe] = + 0.05 ± 0.08, and [Ti/Fe] = -0.27 ± 0.23, resulting in an average [α/Fe] = -0.19 ± 0.14. If this result is representative of the average cluster properties, H4 is the only known system with a low [α/Fe] ratio and a moderately low metallicity embedded in an intact birth environment. For the field stars we find a clear sequence, seen as an early depletion in [α/Fe] at low metallicities, in good agreement with previous measurements. H4 falls on top of the observed field star [α/Fe] sequence and clearly disagrees with the properties of Milky Way halo stars. We therefore conclude that within a galaxy, the chemical enrichment of globular clusters may be closely linked to the enrichment pattern of the field star population. The low [α/Fe] ratios of H4 and similar metallicity field stars in Fornax give evidence that slow chemical enrichment environments, such as dwarf galaxies, may be the original hosts of alpha-depleted clusters in the halos of the Milky Way and M31. This article includes data gathered with the 6.5 m Magellan Telescopes located at Las Campanas Observatory, Chile.

  15. The central region of the Fornax cluster; 2, A catalog and photometric properties of galaxies in selected CCD fields

    Hilker, M; Richtler, T; Infante, L; Quintana, H

    1998-01-01

    We present a photometric catalog (based on V and I photometry) of galaxies in the central regions of the Fornax galaxy cluster. Our 11 CCD fields cover 0.17 degrees in total. The limiting surface brightness is around 24 mag arsec^-2, similar to that of Ferguson's (1989, AJ 98, 367) catalog, whereas our limiting total magnitude is around V = 22 mag, about two magnitudes fainter. It is the surface brightness limit, however, that prevents us from detecting the counterparts of the faintest Local Group dwarf spheroidals. The photometric properties of all objects are presented as a catalog. The properties and fit parameters of the surface brightness profiles for a sub-sample are presented as a second catalog (both catalogs are available in electronic form at the CDS). We can only add 4 new dwarf galaxies to Ferguson's catalog. However, we confirm that the dwarf galaxies in Fornax follow a similar surface brightness-magnitude relation as the Local Group dwarfs. They also follow the color (metallicity) - relation see...

  16. B and R CCD surface photometry of selected low surface brightness galaxies in the region of the Fornax cluster

    The recent discoveries of large numbers of low surface brightness (LSB) galaxies in clusters and of the extreme LSB giant galaxy Malin 1 are changing our view of the galactic contents of the Universe. In this paper we describe B and R band CCD photometry of a sample of LSB galaxies previously identified from photographic plates of the Fornax cluster. This sample contains some of the lowest surface brightness galaxies known, one having the same central surface brightness as Main 1. The objects in this sample have a wide range of morphologies, and galaxies of similar appearance may have very different (B-R) colours. The range of (B-R) colours for this sample (almost all of which would have been described as dE from their B band morphology alone) is as large as that of the entire Hubble sequence. (author)

  17. Search for Dark Matter Annihilation Signals from the Fornax Galaxy Cluster with H.E.S.S

    Abramowski, A; Aharonian, F; Akhperjanian, A G; Anton, G; Balzer, A; Barnacka, A; de Almeida, U Barres; Becherini, Y; Becker, J; Behera, B; Bernlöhr, K; Birsin, E; Biteau, J; Bochow, A; Boisson, C; Bolmont, J; Bordas, P; Brucker, J; Brun, F; Brun, P; Bulik, T; Büsching, I; Carrigan, S; Casanova, S; Cerruti, M; Chadwick, P M; Charbonnier, A; Chaves, R C G; Cheesebrough, A; Clapson, A C; Coignet, G; Cologna, G; Conrad, J; Dalton, M; Daniel, M K; Davids, I D; Degrange, B; Deil, C; Dickinson, H J; Djannati-Ataï, A; Domainko, W; Drury, L O'C; Dubus, G; Dutson, K; Dyks, J; Dyrda, M; Egberts, K; Eger, P; Espigat, P; Fallon, L; Farnier, C; Fegan, S; Feinstein, F; Fernandes, M V; Fiasson, A; Fontaine, G; Förster, A; Füßling, M; Gallant, Y A; Gast, H; Gérard, L; Gerbig, D; Giebels, B; Glicenstein, J F; Glück, B; Goret, P; Göring, D; Häffner, S; Hague, J D; Hampf, D; Hauser, M; Heinz, S; Heinzelmann, G; Henri, G; Hermann, G; Hinton, J A; Hoffmann, A; Hofmann, W; Hofverberg, P; Holler, M; Horns, D; Jacholkowska, A; de Jager, O C; Jahn, C; Jamrozy, M; Jung, I; Kastendieck, M A; Katarzyński, K; Katz, U; Kaufmann, S; Keogh, D; Khangulyan, D; Khélifi, B; Klochkov, D; Kluźniak, W; Kneiske, T; Komin, Nu; Kosack, K; Kossakowski, R; Laffon, H; Lamanna, G; Lennarz, D; Lohse, T; Lopatin, A; Lu, C -C; Marandon, V; Marcowith, A; Masbou, J; Maurin, D; Maxted, N; Mayer, M; McComb, T J L; Medina, M C; Méhault, J; Moderski, R; Moulin, E; Naumann, C L; Naumann-Godo, M; de Naurois, M; Nedbal, D; Nekrassov, D; Nguyen, N; Nicholas, B; Niemiec, J; Nolan, S J; Ohm, S; Wilhelmi, E de Oña; Opitz, B; Ostrowski, M; Oya, I; Panter, M; Arribas, M Paz; Pedaletti1, G; Pelletier, G; Petrucci, P -O; Pita, S; Pühlhofer, G; Punch, M; Quirrenbach, A; Raue, M; Rayner, S M; Reimer, A; Reimer, O; Renaud, M; Reyes, R de los; Rieger, F; Ripken, J; Rob, L; Rosier-Lees, S; Rowell, G; Rudak, B; Rulten, C B; Ruppel, J; Sahakian, V; Sanchez, D A; Santangelo, A; Schlickeiser, R; Schöck, F M; Schulz, A; Schwanke, U; Schwarzburg, S; Schwemmer, S; Sheidaei, F; Skilton, J L; Sol, H; Spengler, G; Stawarz, Ł; Steenkamp, R; Stegmann, C; Stinzing, F; Stycz, K; Sushch, I; Szostek, A; Tavernet, J -P; Terrier, R; Tluczykont, M; Valerius, K; van Eldik, C; Vasileiadis, G; Venter, C; Vialle, J P; Viana, A; Vincent, P; Völk, H J; Volpe, F; Vorobiov, S; Vorster, M; Wagner, S J; Ward, M; White, R; Wierzcholska, A; Zacharias, M; Zajczyk, A; Zdziarski, A A; Zech, A; Zechlin, H -S

    2012-01-01

    The Fornax galaxy cluster was observed with the High Energy Stereoscopic System (H.E.S.S.) for a total live time of 14.5 hours, searching for very-high-energy (VHE, E>100 GeV) gamma-rays from dark matter (DM) annihilation. No significant signal was found in searches for point-like and extended emissions. Using several models of the DM density distribution, upper limits on the DM velocity-weighted annihilation cross-section as a function of the DM particle mass are derived. Constraints are derived for different DM particle models, such as those arising from Kaluza-Klein and supersymmetric models. Various annihilation final states are considered. Possible enhancements of the DM annihilation gamma-ray flux, due to DM substructures of the DM host halo, or from the Sommerfeld effect, are studied. Additional gamma-ray contributions from internal bremsstrahlung and inverse Compton radiation are also discussed. For a DM particle mass of 1 TeV, the exclusion limits at 95% of confidence level reach values of ~ 10^-23...

  18. Searches for dark matter self-annihilation signals from dwarf spheroidal galaxies and the Fornax galaxy cluster with imaging air Cherenkov telescopes

    Many astronomical observations indicate that dark matter pervades the universe and dominates the formation and dynamics of cosmic structures. Weakly interacting massive particles (WIMPs) with masses in the GeV to TeV range form a popular class of dark matter candidates. WIMP self-annihilation may lead to the production of γ-rays in the very high energy regime above 100 GeV, which is observable with imaging air Cherenkov telescopes (IACTs). For this thesis, observations of dwarf spheroidal galaxies (dSph) and the Fornax galaxy cluster with the Cherenkov telescope systems H.E.S.S., MAGIC and VERITAS were used to search for γ-ray signals of dark matter annihilations. The work consists of two parts: First, a likelihood-based statistical technique was introduced to combine published results of dSph observations with the different IACTs. The technique also accounts for uncertainties on the ''J factors'', which quantify the dark matter content of the dwarf galaxies. Secondly, H.E.S.S. observations of the Fornax cluster were analyzed. In this case, a collection of dark matter halo models was used for the J factor computation. In addition, possible signal enhancements from halo substructures were considered. None of the searches yielded a significant γ-ray signal. Therefore, the results were used to place upper limits on the thermally averaged dark matter self-annihilation cross-section left angle σν right angle. Different models for the final state of the annihilation process were considered. The cross-section limits range from left angle σν right angle UL∝10-19 cm3s-1 to left angle σν right angle UL∝10-25 cm3s-1 for dark matter particles masses between 100 GeV and 100 TeV. Some of the diverse model uncertainties causing this wide range of left angle σν right angle UL values were analyzed.

  19. Distances of the Virgo, Fornax and Hydra clusters of galaxies and the local value of the Hubble ratio

    Distances of these three nearby clusters of galaxies as derived from recent observations of the brightest globular clusters in the brightest galaxies are found to be in good agreement with other distance indications and suggest a local value of the Hubble constant H = 86 +- 9 km s-1 Mpc-1. (author)

  20. Ultra-Compact Dwarfs in the Coma Cluster

    Chiboucas, Kristin; Tully, R. Brent; Marzke, ; Ronald O.; Phillipps, Steve; Price, James; Peng, Eric; Trentham, Neil; Carter, David; Hammer, Derek

    2011-01-01

    We have undertaken a spectroscopic search for ultra compact dwarf galaxies (UCDs) in the dense core of the dynamically evolved, massive Coma cluster as part of the HST/ACS Coma Cluster Treasury Survey. UCD candidates were initially chosen based on color, magnitude, degree of resolution within the ACS images, and the known properties of Fornax and Virgo UCDs. Follow-up spectroscopy with Keck/LRIS confirmed 27 candidates as members of the Coma Cluster, a success rate > 60% for targeted objects ...

  1. CCD photometry of apparent dwarf galaxies in Fornax

    Blue and red CCD surface photometry of two apparent dwarf galaxies in the Fornax cluster region is presented. Luminosity profiles are derived and their form discussed. The fainter galaxy resembles an archetypal diffuse dwarf elliptical but the brighter of the pair is either an unusual red dwarf or a background galaxy in chance juxtaposition. (author)

  2. Global properties of the Sculptor and Fornax dwarf elliptical galaxies

    The global properties of the Sculptor and Fornax dwarf elliptical galaxies are examined. These are determined from star counts from Schmidt plates. Luminosity functions (LFs) are constructed. Giants and horizontal-branch star counts imply Y = 0.23 ± 0.05 for Sculptor. Comparisons of globular cluster and theoretical LFs with Sculptor's indicate a range in the turn-off mass, or the RGB mass loss rate. The LF of Fornax shows a larger ratio of bright to faint giants than is seen in clusters, or in two-burst model functions. This indicates that a two-burst model for Fornax is inadequate. Radial profiles are compared with King (1966) models and exponential laws. Fits confirm the assertion that the profiles of the halo dwarfs are as well fit by exponentials as are many irregulars. Results for the King model fits imply a mass for the Galaxy of 1.2 ± 0.6 x 1011 solar masses. Two-dimensional structure in both systems is investigated using residual maps of the raw star counts minus symmetric fits. These maps clearly show internal structure

  3. Unveiling a Rich System of Faint Dwarf Galaxies in the Next Generation Fornax Survey

    Munoz, Roberto P; Puzia, Thomas H; Taylor, Matthew A; Ordenes-Briceno, Yasna; Alamo-Martinez, Karla; Ribbeck, Karen X; Angel, Simon; Capaccioli, Massimo; Cote, Patrick; Ferrarese, Laura; Galaz, Gaspar; Hempel, Maren; Hilker, Michael; Jordan, Andres; Lancon, Ariane; Mieske, Steffen; Paolillo, Maurizio; Richtler, Tom; Sanchez-Janssen, Ruben; Zhang, Hongxin

    2015-01-01

    We report the discovery of 158 previously undetected dwarf galaxies in the Fornax cluster central regions using a deep coadded $u, g$ and $i$-band image obtained with the DECam wide-field camera mounted on the 4-meter Blanco telescope at the Cerro Tololo Interamerican Observatory as part of the {\\it Next Generation Fornax Survey} (NGFS). The new dwarf galaxies have quasi-exponential light profiles, effective radii $0.1\\!\\!75\\%$ at luminosities brighter than $M_i\\!\\simeq\\!-15.0$ mag to $0\\%$ at luminosities fainter than $M_i\\!\\simeq\\!-10.0$ mag. The two-point correlation function analysis of the NGFS dwarf sample shows an excess on length scales below $\\sim\\!100$ kpc, pointing to the clustering of dwarf galaxies in the Fornax cluster core.

  4. The HST/ACS Coma Cluster Survey IV. Intergalactic Globular Clusters and the Massive Globular Cluster System at the Core of the Coma Galaxy Cluster

    Peng, Eric W.; Ferguson, Henry C.; Goudfrooij, Paul; Hammer, Derek; Lucey, John R.; Marzke, ; Ronald O.; Puzia, Thomas H.; Carter, David; Balcells, Marc; Bridges, Terry; Chiboucas, Kristin; del Burgo, Carlos; Graham, Alister W.; Guzman, Rafael; Hudson, Michael J.

    2011-01-01

    Intracluster stellar populations are a natural result of tidal interactions in galaxy clusters. Measuring these populations is difficult, but important for understanding the assembly of the most massive galaxies. The Coma cluster is one of the nearest truly massive galaxy clusters, and is host to a correspondingly large system of globular clusters (GCs). We use imaging from the HST/ACS Coma Cluster Survey to present the first definitive detection of a large population of intracluster GCs (IGC...

  5. The ACS Survey of Galactic Globular Clusters. I. Overview and Clusters Without Previous HST Photometry

    Sarajedini, A; Chaboyer, B; Dotter, A; Siegel, M; Anderson, J; Aparicio, A; King, I; Majewski, S; Marin-Franch, A; Piotto, G; Reid, I N; Rosenberg, A L; Sarajedini, Ata

    2006-01-01

    We present the first results of a large ACS Survey of Galactic globular clusters. This Hubble Space Telescope (HST) Treasury project is designed to obtain photometry with S/N > ~10 for main sequence stars with masses > ~0.2Msun in a sample of globulars using the Advanced Camera for Surveys (ACS) Wide Field Channel. Here we focus on clusters without previous HST imaging data. These include NGC 5466, 6779, 5053, 6144, Palomar 2, E 3, Lynga 7, Palomar 1, and NGC 6366. Our CMDs extend reliably from the horizontal branch to as much as seven magnitudes fainter than the main sequence turnoff and represent the deepest CMDs published to-date for these clusters. Using fiducial sequences for three standard clusters (M92, NGC 6752, and 47 Tuc) with well-known metallicities and distances, we perform main sequence fitting on the target clusters in order to obtain estimates of their distances and reddenings. These comparisons along with fitting the cluster main sequences to theoretical isochrones yield ages for the target c...

  6. A Large Dark Matter Core in the Fornax Dwarf Spheroidal Galaxy?

    Strigari, L E; Kaplinghat, M; Kravtsov, A V; Gnedin, O Y; Abazajian, Kevork N; Klypin, A A; Strigari, Louis E.; Bullock, James S.; Kaplinghat, Manoj; Kravtsov, Andrey V.; Gnedin, Oleg Y.; Abazajian, Kevork; Klypin, Anatoly A.

    2006-01-01

    We use measurements of the stellar velocity dispersion profile of the Fornax dwarf spheroidal galaxy to derive constraints on its dark matter distribution. Though the data are unable to distinguish between models with small cores and those with cusps, we show that a large > 1 kpc dark matter core in Fornax is highly implausible. Irrespective of the origin of the core, reasonable dynamical limits on the mass of the Fornax halo constrain its core radius to be no larger than 700 pc. We derive an upper limit core radius of 300 pc by demanding that the central phase space density of Fornax not exceed that directly inferred from the rotation curves of low-mass spiral galaxies. Further, if the halo is composed of warm dark matter then phase-space constraints force the core to be quite small in order to avoid conservative limits from the Ly alpha forest power spectrum, implying a core radius < 85 pc. We discuss our results in the context of the idea that the extended globular cluster distribution in Fornax can be ...

  7. The Chemical Enrichment History of the Fornax Dwarf Spheroidal Galaxy from the Infrared Calcium Triplet

    Pont, F; Gallart, C; Hardy, E; Winnick, R A; Pont, Frederic; Zinn, Robert; Gallart, Carme; Hardy, Eduardo; Winnick, Rebeccah

    2004-01-01

    Near infrared spectra were obtained for 117 red giants in the Fornax dwarf spheroidal galaxy with the FORS1 spectrograph on the VLT, in order to study the metallicity distribution of the stars and to lift the age-metallicity degeneracy of the red giant branch (RGB) in the color-magnitude diagram (CMD). Metallicities are derived from the equivalent widths of the infrared Calcium triplet lines at 8498, 8542, and 8662 A, calibrated with data from globular clusters, the open cluster M67 and the LMC. For a substantial portion of the sample, the strength of the Calcium triplet is unexpectedly high, clearly indicating that the main stellar population of Fornax is significantly more metal-rich than could be inferred from the position of its RGB in the CMD. We show that the relative narrowness of the RGB in Fornax is caused by the superposition of stars of very different ages and metallicities. The metallicity distribution in Fornax is centered at [Fe/H]= -0.9, with a metal-poor tail extending to [Fe/H] ~= -2. While t...

  8. Ac hopping conduction at extreme disorder takes place on the percolating cluster

    Schrøder, Thomas; Dyre, J. C.

    2008-01-01

    Simulations of the random barrier model show that ac currents at extreme disorder are carried almost entirely by the percolating cluster slightly above threshold; thus contributions from isolated low activation-energy clusters are negligible. The effective medium approximation in conjunction with...

  9. Fornax compact object survey FCOS: On the nature of Ultra Compact Dwarf galaxies

    Mieske, S; Infante, L

    2004-01-01

    The results of the Fornax Compact Object Survey (FCOS) are presented. The FCOS aims at investigating the nature of the Ultra Compact Dwarf galaxies (UCDs) recently discovered in the center of the Fornax cluster (Drinkwater et al. 2000). 280 unresolved objects in the magnitude space covering UCDs and bright globular clusters (1820 mag) at 96% confidence. The mean velocity of the bright compact objects is consistent with that of the dwarf galaxy population in Fornax, but inconsistent with that of NGC 1399's globular cluster system at 93.5% confidence. The compact objects follow a colour magnitude relation with a slope very similar to that of normal dEs, but shifted about 0.2 mag redwards. The magnitude distribution of compact objects shows a fluent transition between UCDs and GCs with an overpopulation of 8 +/- 4 objects for V<20 mag with respect to the extrapolation of NGC 1399's GC luminosity function. The spatial distribution of bright compact objects is in comparison to the faint ones more extended at 88...

  10. HST/ACS colour-magnitude diagrams of M31 globular clusters

    Perina, Sibilla; Bellazzini, Michele; Cacciari, Carla; Pecci, Flavio Fusi; Galleti, Silvia

    2009-01-01

    With the aim of increasing the sample of M31 clusters for which a colour magnitude diagram is available, we searched the HST archive for ACS images containing objects included in the Revised Bologna Catalogue of M31 globular clusters. Sixty-three such objects were found. We used the ACS images to confirm or revise their classification and we obtained useful CMDs for 11 old globular clusters and 6 luminous young clusters. We obtained simultaneous estimates of the distance, reddening, and metallicity of old clusters by comparing their observed field-decontaminated CMDs with a grid of template clusters of the Milky Way. We estimated the age of the young clusters by fitting with theoretical isochrones. For the old clusters, we found metallicities in the range -0.410 Gyr. All six candidate young clusters are found to have ages <1Gyr. With the present work the total number of M31 GCs with reliable optical CMD increases from 35 to 44 for the old clusters, and from 7 to 11 for the young ones. The old clusters show...

  11. An XMM-Newton search for X-ray sources in the Fornax dwarf galaxy

    Nucita, A A; De Paolis, F; Vetrugno, D; Ingrosso, G

    2013-01-01

    We report the results of a deep archive XMM-Newton observation of the Fornax spheroidal galaxy that we analyzed with the aim of fully characterizing the X-ray source population (in most of the cases likely to be background active galactic nuclei) detected towards the target. A cross correlation with the available databases allowed us to find a source that may be associated with a variable star belonging to the galaxy. We also searched for X-ray sources in the vicinity of the Fornax globular clusters GC 3 and GC 4 and found two sources probably associated with the respective clusters. The deep X-ray observation was also suitable for the search of the intermediate-mass black hole (of mass $\\simeq 10^{4}$ M$_{\\odot}$) expected to be hosted in the center of the galaxy. In the case of Fornax, this search is extremely difficult since the galaxy centroid of gravity is poorly constrained because of the large asymmetry observed in the optical surface brightness. Since we cannot firmly establish the existence of an X-r...

  12. The HST/ACS Coma Cluster Survey: I - Survey Objectives and Design

    Carter, David; Mobasher, Bahram; Ferguson, Henry C; Puzia, Thomas H; Aguerri, Alfonso L; Balcells, Marc; Batcheldor, Dan; Bridges, Terry J; Davies, Jonathan I; Erwin, Peter; Graham, Alister W; Guzmán, Rafael; Hammer, Derek; Hornschemeier, Ann; Hoyos, Carlos; Hudson, Michael J; Huxor, Avon; Jogee, Shardha; Komiyama, Yutaka; Lotz, Jennifer; Lucey, John R; Marzke, Ronald O; Merritt, David; Miller, Bryan W; Miller, Neal A; Mouhcine, Mustapha; Okamura, Sadanori; Peletier, Reynier F; Phillipps, Steven; Poggianti, Bianca M; Sharples, Ray M; Smith, Russell J; Trentham, Neil; Tully, R Brent; Valentijn, Edwin; Kleijn, Gijs Verdoes

    2008-01-01

    We describe the HST ACS Coma cluster Treasury survey, a deep two-passband imaging survey of one of the nearest rich clusters of galaxies, the Coma cluster (Abell 1656). The survey was designed to cover an area of 740 square arcmin in regions of different density of both galaxies and intergalactic medium within the cluster. The ACS failure of January 27th 2007 leaves the survey 28% complete, with 21 ACS pointings (230 square arcmin) complete, and partial data for a further 4 pointings (44 square arcmin). Predicted survey depth for 10 sigma detections for optimal photometry of point sources is g' = 27.6 in the F475W filter, and IC=26.8 mag in F814 (AB magnitudes). Initial simulations with artificially injected point sources show 90% recovered at magnitude limits of g' = 27.55 and IC = 26.65. For extended sources, the predicted 10 sigma limits for a 1 square arcsecond region are g' = 25.8 mag/sq. arcsec and IC = 25.0 mag/sq. arcsec. We highlight several motivating science goals of the survey, including study of ...

  13. THE HST/ACS COMA CLUSTER SURVEY. IV. INTERGALACTIC GLOBULAR CLUSTERS AND THE MASSIVE GLOBULAR CLUSTER SYSTEM AT THE CORE OF THE COMA GALAXY CLUSTER

    Intracluster stellar populations are a natural result of tidal interactions in galaxy clusters. Measuring these populations is difficult, but important for understanding the assembly of the most massive galaxies. The Coma cluster of galaxies is one of the nearest truly massive galaxy clusters and is host to a correspondingly large system of globular clusters (GCs). We use imaging from the HST/ACS Coma Cluster Survey to present the first definitive detection of a large population of intracluster GCs (IGCs) that fills the Coma cluster core and is not associated with individual galaxies. The GC surface density profile around the central massive elliptical galaxy, NGC 4874, is dominated at large radii by a population of IGCs that extend to the limit of our data (R +4000-5000 (systematic) IGCs out to this radius, and that they make up ∼70% of the central GC system, making this the largest GC system in the nearby universe. Even including the GC systems of other cluster galaxies, the IGCs still make up ∼30%-45% of the GCs in the cluster core. Observational limits from previous studies of the intracluster light (ICL) suggest that the IGC population has a high specific frequency. If the IGC population has a specific frequency similar to high-SN dwarf galaxies, then the ICL has a mean surface brightness of μV ∼ 27 mag arcsec-2 and a total stellar mass of roughly 1012 Msun within the cluster core. The ICL makes up approximately half of the stellar luminosity and one-third of the stellar mass of the central (NGC 4874+ICL) system. The color distribution of the IGC population is bimodal, with blue, metal-poor GCs outnumbering red, metal-rich GCs by a ratio of 4:1. The inner GCs associated with NGC 4874 also have a bimodal distribution in color, but with a redder metal-poor population. The fraction of red IGCs (20%), and the red color of those GCs, implies that IGCs can originate from the halos of relatively massive, L* galaxies, and not solely from the disruption of dwarf

  14. Rotating stellar populations in the Fornax dSph galaxy

    del Pino, Andrés; Hidalgo, Sebastian L; Lokas, Ewa L

    2016-01-01

    We present a novel analysis of the internal kinematics of the Fornax dwarf spheroidal galaxy. Our results are based on the largest sample of spectroscopic data for Fornax stars presently available ($> 2500$ stars), for which we have chemical and kinematic information. We introduce new software, Beacon, designed to detect chemo-kinematic patterns among stars of different stellar populations using their metallicity and velocity along the line of sight. Applying Beacon to Fornax we have detected non-negligible rotation signals around main optical axes of the galaxy, characteristic for a triaxial system partially supported by rotation. The dominant rotation pattern is relatively strong ($\\sim 12$ km s$^{-1}$), but the galaxy also shows additional weaker albeit complex rotation patterns. Using the information available from the star formation history of Fornax we have also derived the average age of the different chemo-kinematic components found by Beacon, which has allowed us to obtain its kinematic history. Our ...

  15. The shell game: a panoramic view of Fornax

    Bate, N F; Lewis, G F; Irwin, M J; Gonzalez-Solares, E; Shanks, T; Metcalfe, N

    2015-01-01

    We present a panoramic study of the Fornax dwarf spheroidal galaxy, using data obtained as part of the VLT Survey Telescope (VST) ATLAS Survey. The data presented here -- a subset of the full survey -- uniformly cover a region of 25 square degrees centred on the galaxy, in $g$, $r$ and $i$-bands. This large area coverage reveals two key differences to previous studies of Fornax. First, data extending beyond the nominal tidal radius of the dwarf highlight the presence of a second distinct red giant branch population. This bluer red giant branch appears to be coeval with the horizontal branch population. Second, a shell structure located approximately 1.4 degrees from the centre of Fornax is shown to be a mis-identified background overdensity of galaxies. This last result casts further doubt on the hypothesis that Fornax underwent a gas-rich merger in its relatively recent past.

  16. The ACS survey of globular clusters. XIII. Photometric calibration in comparison with Stetson standards

    Hempel, Maren; Anderson, Jay; Aparicio, Antonio; Bedin, Luigi R; Chaboyer, Brian; Majewski, Steven R; Marín-Franch, Antonio; Milone, Antonino; Paust, Nathaniel E Q; Piotto, Giampaolo; Reid, I Neill; Rosenberg, Alfred; Siegel, Michael

    2013-01-01

    In this study we compare the photometric data of 34 Milky Way globular clusters, observed within the ACS Treasury Program (PI: Ata Sarajedini) with the corresponding ground-based data, provided by the Photometric Standard Field Catalogs of Stetson (2000, 2005). We focus on the transformation between the HST/ACS F606W to V-band and F814W to I-band only. The goal is to assess the validity of the filter transformation equations by Sirianni et al.(2005) with respect to their dependence on metallicity, Horizontal Branch morphology, mass and integrated (V-I) colour of the various globular clusters. Such a dependence is expected due to the fact that the transformation equations are based on the observations of only one globular cluster, i.e., NGC 2419. Surprisingly, the correlation between offset and metallicity is found to be weak, with a low level significance. The correlation between offset and Horizontal Branch structure, as well as total cluster mass is still weaker. Based on the available data we do not find t...

  17. THE ACS SURVEY OF GLOBULAR CLUSTERS. XIII. PHOTOMETRIC CALIBRATION IN COMPARISON WITH STETSON STANDARDS

    Hempel, Maren [Instituto de Astrofísica, Facultad de Fisica, Pontificia Universidad Católica de Chile, Vicuña Mackenna 4860, 7820436 Macul, Santiago (Chile); Sarajedini, Ata [Department of Astronomy, University of Florida, 211 Bryant Space Science Center, Gainesville, FL 32611 (United States); Anderson, Jay; Reid, I. Neill, E-mail: mhempel@astro.puc.cl, E-mail: ata@astro.ufl.edu, E-mail: jayander@stsci.edu, E-mail: inr@stsci.edu [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); and others

    2014-03-01

    In this study we compare the photometric data of 34 Milky Way globular clusters, observed within the Advanced Camera for Surveys (ACS) Treasury Program (PI: A. Sarajedini) with the corresponding ground-based data, provided by the Photometric Standard Field Catalogs of Stetson. We focus on the transformation between the Hubble Space Telescope/ACS F606W to V-band and F814W to I-band only. The goal is to assess the validity of the filter transformation equations by Sirianni et al. with respect to their dependence on metallicity, horizontal branch morphology, mass, and integrated (V – I) color of the various globular clusters. The transformation equations as recommended by Sirianni et al. are based on synthetic photometry, were mostly tested on NGC 2419, and may introduce additional uncertainties when applied to different stellar populations. Such a dependence is expected due to the fact that the transformation equations are based on the observations of only one globular cluster, i.e., NGC 2419. Surprisingly, the correlation between offset and metallicity is found to be weak, with a low level significance. The correlation between offset and horizontal branch structure, as well as total cluster mass is still weaker. Based on the available data we do not find the photometric offset to be linked to multiple stellar populations, e.g., as found in NGC 0288, NGC 1851, and NGC 5139. The results of this study show that there are small systematic offsets between the transformed ACS- and observed ground-based photometry, and that these are only weakly correlated, if at all, with various cluster parameters and their underlying stellar populations. As a result, investigators wishing to transform globular cluster photometry from the Sirianni et al. ground-based V, I system onto the Stetson system simply need to add –0.040 (±0.012) to the V magnitudes and –0.047 (±0.011) to the I magnitudes. This in turn means that the transformed ACS V – I colors match the ground

  18. The sluggs survey: HST/ACS mosaic imaging of the NGC 3115 globular cluster system

    Jennings, Zachary G.; Romanowsky, Aaron J.; Brodie, Jean P.; Arnold, Jacob A. [University of California Observatories, Santa Cruz, CA 95064 (United States); Strader, Jay [Department of Physics and Astronomy, Michigan State University, East Lansing, Michigan, MI 48824 (United States); Lin, Dacheng; Irwin, Jimmy A.; Wong, Ka-Wah [Department of Physics and Astronomy, University of Alabama, Box 870324, Tuscaloosa, AL 35487 (United States); Sivakoff, Gregory R., E-mail: zgjennin@ucsc.edu [Department of Physics, University of Alberta, Edmonton, Alberta T6G 2E1 (Canada)

    2014-08-01

    We present Hubble Space Telescope/Advanced Camera for Surveys (HST/ACS) g and z photometry and half-light radii R {sub h} measurements of 360 globular cluster (GC) candidates around the nearby S0 galaxy NGC 3115. We also include Subaru/Suprime-Cam g, r, and i photometry of 421 additional candidates. The well-established color bimodality of the GC system is obvious in the HST/ACS photometry. We find evidence for a 'blue tilt' in the blue GC subpopulation, wherein the GCs in the blue subpopulation get redder as luminosity increases, indicative of a mass-metallicity relationship. We find a color gradient in both the red and blue subpopulations, with each group of clusters becoming bluer at larger distances from NGC 3115. The gradient is of similar strength in both subpopulations, but is monotonic and more significant for the blue clusters. On average, the blue clusters have ∼10% larger R {sub h} than the red clusters. This average difference is less than is typically observed for early-type galaxies but does match that measured in the literature for the Sombrero Galaxy (M104), suggesting that morphology and inclination may affect the measured size difference between the red and blue clusters. However, the scatter on the R {sub h} measurements is large. We also identify 31 clusters more extended than typical GCs, which we term ultra-compact dwarf (UCD) candidates. Many of these objects are actually considerably fainter than typical UCDs. While it is likely that a significant number will be background contaminants, six of these UCD candidates are spectroscopically confirmed as NGC 3115 members. To explore the prevalence of low-mass X-ray binaries in the GC system, we match our ACS and Suprime-Cam detections to corresponding Chandra X-ray sources. We identify 45 X-ray-GC matches: 16 among the blue subpopulation and 29 among the red subpopulation. These X-ray/GC coincidence fractions are larger than is typical for most GC systems, probably due to the increased

  19. The HST/ACS Coma Cluster Survey. II. Data Description and Source Catalogs

    Hammer, Derek; Hoyos, Carlos; Brok, Mark den; Balcells, Marc; Ferguson, Henry C; Goudfrooij, Paul; Carter, David; Guzman, Rafael; Peletier, Reynier F; Smith, Russell J; Graham, Alister W; Trentham, Neil; Peng, Eric; Puzia, Thomas H; Lucey, John R; Jogee, Shardha; Aguerri, Alfonso L; Batcheldor, Dan; Bridges, Terry J; Davies, Jonathan I; del Burgo, Carlos; Erwin, Peter; Hornschemeier, Ann; Hudson, Michael J; Huxor, Avon; Jenkins, Leigh; Karick, Arna; Khosroshahi, Habib; Kourkchi, Ehsan; Komiyama, Yutaka; Lotz, Jennifer; Marzke, Ronald O; Marinova, Irina; Matkovic, Ana; Merritt, David; Miller, Bryan W; Miller, Neal A; Mobasher, Bahram; Mouhcine, Mustapha; Okamura, Sadanori; Percival, Sue; Phillipps, Steven; Poggianti, Bianca M; Price, James; Sharples, Ray M; Tully, R Brent; Valentijn, Edwin

    2010-01-01

    The Coma cluster, Abell 1656, was the target of a HST-ACS Treasury program designed for deep imaging in the F475W and F814W passbands. Although our survey was interrupted by the ACS instrument failure in early 2007, the partially-completed survey still covers ~50% of the core high-density region in Coma. Observations were performed for twenty-five fields with a total coverage area of 274 arcmin^2, and extend over a wide range of cluster-centric radii (~1.75 Mpc or 1 deg). The majority of the fields are located near the core region of Coma (19/25 pointings) with six additional fields in the south-west region of the cluster. In this paper we present SExtractor source catalogs generated from the processed images, including a detailed description of the methodology used for object detection and photometry, the subtraction of bright galaxies to measure faint underlying objects, and the use of simulations to assess the photometric accuracy and completeness of our catalogs. We also use simulations to perform apertur...

  20. Extended Star Clusters in NGC 1023 from HST/ACS Mosaic Imaging

    Forbes, Duncan; Spitler, Lee; Pota, Vincenzo

    2014-01-01

    Faint fuzzies are a relatively new class of star cluster, first found in the nearby S0 galaxy NGC 1023 by Larsen & Brodie using WFPC2 images from the Hubble Space Telescope (HST). Here we investigate the star cluster system of NGC 1023 using an eight pointing mosaic of ACS images from HST. We identify blue and red normal globular clusters (two of which are particularly luminous and dense) and two ultra compact dwarf objects (with effective radius ~10 pc). With our more complete spatial coverage, we also find 81 red and 27 blue faint fuzzies (FFs). We confirm the association of the red FFs with the disk of NGC 1023, consistent with them being long-lived open clusters. Half of the blue FFs appear to be associated with the dwarf satellite galaxy NGC 1023A (which was largely absent from the original HST/WFPC2 coverage), while the remainder are spatially coincident with the densest HI gas that surrounds NGC 1023. The blue FFs have colours that are consistent with young (few 100 Myr old) star clusters that form...

  1. THE HST/ACS COMA CLUSTER SURVEY. II. DATA DESCRIPTION AND SOURCE CATALOGS

    The Coma cluster, Abell 1656, was the target of an HST-ACS Treasury program designed for deep imaging in the F475W and F814W passbands. Although our survey was interrupted by the ACS instrument failure in early 2007, the partially completed survey still covers ∼50% of the core high-density region in Coma. Observations were performed for 25 fields that extend over a wide range of cluster-centric radii (∼1.75 Mpc or 10) with a total coverage area of 274 arcmin2. The majority of the fields are located near the core region of Coma (19/25 pointings) with six additional fields in the southwest region of the cluster. In this paper, we present reprocessed images and SEXTRACTOR source catalogs for our survey fields, including a detailed description of the methodology used for object detection and photometry, the subtraction of bright galaxies to measure faint underlying objects, and the use of simulations to assess the photometric accuracy and completeness of our catalogs. We also use simulations to perform aperture corrections for the SEXTRACTOR Kron magnitudes based only on the measured source flux and its half-light radius. We have performed photometry for ∼73,000 unique objects; approximately one-half of our detections are brighter than the 10σ point-source detection limit at F814W = 25.8 mag (AB). The slight majority of objects (60%) are unresolved or only marginally resolved by ACS. We estimate that Coma members are 5%-10% of all source detections, which consist of a large population of unresolved compact sources (primarily globular clusters but also ultra-compact dwarf galaxies) and a wide variety of extended galaxies from a cD galaxy to dwarf low surface brightness galaxies. The red sequence of Coma member galaxies has a color-magnitude relation with a constant slope and dispersion over 9 mag (-21 F814W < -13). The initial data release for the HST-ACS Coma Treasury program was made available to the public in 2008 August. The images and catalogs described in

  2. THE HST/ACS COMA CLUSTER SURVEY. VIII. BARRED DISK GALAXIES IN THE CORE OF THE COMA CLUSTER

    Marinova, Irina; Jogee, Shardha; Weinzirl, Tim [Department of Astronomy, University of Texas at Austin, Austin, TX (United States); Erwin, Peter [Max-Planck-Insitut fuer extraterrestrische Physik, Giessenbachstrasse, 85748 Garching (Germany); Trentham, Neil [Institute of Astronomy, Madingley Road, Cambridge, CB3 0HA (United Kingdom); Ferguson, Henry C.; Goudfrooij, Paul [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Hammer, Derek [Department of Physics and Astronomy, Johns Hopkins, Baltimore, MD 21218 (United States); Den Brok, Mark; Peletier, Reynier F.; Kleijn, Gijs V. [Kapteyn Astronomical Institute, University of Groningen, Groningen (Netherlands); Graham, Alister W. [Centre for Astrophysics and Supercomputing, Swinburne University, Hawthorn (Australia); Carter, David; Mouhcine, Mustapha [Astrophysics Research Institute, Liverpool John Moores University, Birkenhead (United Kingdom); Balcells, Marc [Instituto de Astrofisica de Canarias, 38200 La Laguna, Tenerife (Spain); Guzman, Rafael; Hoyos, Carlos [Department of Astronomy, University of Florida, Gainesville, FL 32611 (United States); Mobasher, Bahram [Department of Physics and Astronomy, University of California, Riverside, CA 92521 (United States); Peng, Eric W., E-mail: marinova@astro.as.utexas.edu, E-mail: sj@astro.as.utexas.edu [Department of Astronomy, Peking University, Beijing 100871 (China)

    2012-02-20

    We use high-resolution ({approx}0.''1) F814W Advanced Camera for Surveys (ACS) images from the Hubble Space Telescope ACS Treasury survey of the Coma cluster at z {approx} 0.02 to study bars in massive disk galaxies (S0s), as well as low-mass dwarf galaxies in the core of the Coma cluster, the densest environment in the nearby universe. Our study helps to constrain the evolution of bars and disks in dense environments and provides a comparison point for studies in lower density environments and at higher redshifts. Our results are: (1) we characterize the fraction and properties of bars in a sample of 32 bright (M{sub V} {approx}< -18, M{sub *} > 10{sup 9.5} M{sub Sun }) S0 galaxies, which dominate the population of massive disk galaxies in the Coma core. We find that the measurement of a bar fraction among S0 galaxies must be handled with special care due to the difficulty in separating unbarred S0s from ellipticals, and the potential dilution of the bar signature by light from a relatively large, bright bulge. The results depend sensitively on the method used: the bar fraction for bright S0s in the Coma core is 50% {+-} 11%, 65% {+-} 11%, and 60% {+-} 11% based on three methods of bar detection, namely, strict ellipse fit criteria, relaxed ellipse fit criteria, and visual classification. (2) We compare the S0 bar fraction across different environments (the Coma core, A901/902, and Virgo) adopting the critical step of using matched samples and matched methods in order to ensure robust comparisons. We find that the bar fraction among bright S0 galaxies does not show a statistically significant variation (within the error bars of {+-}11%) across environments which span two orders of magnitude in galaxy number density (n {approx} 300-10,000 galaxies Mpc{sup -3}) and include rich and poor clusters, such as the core of Coma, the A901/902 cluster, and Virgo. We speculate that the bar fraction among S0s is not significantly enhanced in rich clusters compared to

  3. THE HST/ACS COMA CLUSTER SURVEY. VIII. BARRED DISK GALAXIES IN THE CORE OF THE COMA CLUSTER

    We use high-resolution (∼0.''1) F814W Advanced Camera for Surveys (ACS) images from the Hubble Space Telescope ACS Treasury survey of the Coma cluster at z ∼ 0.02 to study bars in massive disk galaxies (S0s), as well as low-mass dwarf galaxies in the core of the Coma cluster, the densest environment in the nearby universe. Our study helps to constrain the evolution of bars and disks in dense environments and provides a comparison point for studies in lower density environments and at higher redshifts. Our results are: (1) we characterize the fraction and properties of bars in a sample of 32 bright (MV ∼* > 109.5 M☉) S0 galaxies, which dominate the population of massive disk galaxies in the Coma core. We find that the measurement of a bar fraction among S0 galaxies must be handled with special care due to the difficulty in separating unbarred S0s from ellipticals, and the potential dilution of the bar signature by light from a relatively large, bright bulge. The results depend sensitively on the method used: the bar fraction for bright S0s in the Coma core is 50% ± 11%, 65% ± 11%, and 60% ± 11% based on three methods of bar detection, namely, strict ellipse fit criteria, relaxed ellipse fit criteria, and visual classification. (2) We compare the S0 bar fraction across different environments (the Coma core, A901/902, and Virgo) adopting the critical step of using matched samples and matched methods in order to ensure robust comparisons. We find that the bar fraction among bright S0 galaxies does not show a statistically significant variation (within the error bars of ±11%) across environments which span two orders of magnitude in galaxy number density (n ∼ 300-10,000 galaxies Mpc–3) and include rich and poor clusters, such as the core of Coma, the A901/902 cluster, and Virgo. We speculate that the bar fraction among S0s is not significantly enhanced in rich clusters compared to low-density environments for two reasons. First, S0s in rich clusters are

  4. The HST/ACS Coma Cluster Survey. VIII. Barred Disk Galaxies in the Core of the Coma Cluster

    Marinova, Irina; Weinzirl, Tim; Erwin, Peter; Trentham, Neil; Ferguson, Henry C; Hammer, Derek; Brok, Mark den; Graham, Alister W; Carter, David; Balcells, Marc; Goudfrooij, Paul; Guzman, Rafael; Hoyos, Carlos; Mobasher, Bahram; Mouhcine, Mustapha; Peletier, Reynier F; Peng, Eric; Kleijn, Gijs Verdoes

    2012-01-01

    (ABRIDGED) We use high resolution (~0.1") F814W ACS images from the HST ACS Treasury survey of the Coma cluster at z~0.02 to study bars in massive disk galaxies (S0s), and in dwarf galaxies in the Coma core. Our study helps constrain the evolution of bars and disks in dense environments and provides a comparison point for studies in lower density environments and at higher redshifts. (1) We characterize the fraction and properties of bars in a sample of 32 bright (M_V 10^9.5 M_sun) S0 galaxies, which dominate the population of massive disk galaxies in the Coma core. Measuring the S0 bar fraction must be handled carefully, as the results depend on the method used: the bar fraction for bright S0s in the Coma core is 50%+/-11%, 65%+/-11%, and 60%+/-11% for three methods of bar detection: strict ellipse fit criteria, relaxed ellipse fit criteria, and visual classification. (2) We compare the S0 bar fraction across different environments (Coma core, A901/902, Virgo). We find that the bar fraction among bright S0 ...

  5. The structure and dynamics of the AC114 galaxy cluster revisited

    Proust, Dominique; Saviane, Ivo; Ivanov, Valentin D; Bresolin, Fabio; Salzer, John J; Capelato, Hugo V

    2015-01-01

    We present a dynamical analysis of the galaxy cluster AC114 based on a catalogue of 524 velocities. Of these, 169 (32%) are newly obtained at ESO (Chile) with the VLT and the VIMOS spectrograph. Data on individual galaxies are presented and the accuracy of the measured velocities is discussed. Dynamical properties of the cluster are derived. We obtain an improved mean redshift value z= 0.31665 +/- 0.0008 and velocity dispersion \\sigma= 1893+73-82 \\kms. A large velocity dispersion within the core radius and the shape of the infall pattern suggests that this part of the cluster is in a radial phase of relaxation with a very elongated radial filament spanning 12000 \\kms. A radial foreground structure is detected within the central 0.5/h Mpc radius, recognizable as a redshift group at the same central redshift value. We analyze the color distribution for this archetype Butcher-Oemler galaxy cluster and identify the separate red and blue galaxy sequences. The latter subset contains 44% of confirmed members of the ...

  6. ULTRA-COMPACT DWARFS IN THE COMA CLUSTER

    We have undertaken a spectroscopic search for ultra-compact dwarf galaxies (UCDs) in the dense core of the dynamically evolved, massive Coma cluster as part of the Hubble Space Telescope/Advanced Camera for Surveys (HST/ACS) Coma Cluster Treasury Survey. UCD candidates were initially chosen based on color, magnitude, degree of resolution within the ACS images, and the known properties of Fornax and Virgo UCDs. Follow-up spectroscopy with Keck/Low-Resolution Imaging Spectrometer confirmed 27 candidates as members of the Coma cluster, a success rate >60% for targeted objects brighter than MR = -12. Another 14 candidates may also prove to be Coma members, but low signal-to-noise spectra prevent definitive conclusions. An investigation of the properties and distribution of the Coma UCDs finds these objects to be very similar to UCDs discovered in other environments. The Coma UCDs tend to be clustered around giant galaxies in the cluster core and have colors/metallicity that correlate with the host galaxy. With properties and a distribution similar to that of the Coma cluster globular cluster population, we find strong support for a star cluster origin for the majority of the Coma UCDs. However, a few UCDs appear to have stellar population or structural properties which differentiate them from the old star cluster populations found in the Coma cluster, perhaps indicating that UCDs may form through multiple formation channels.

  7. THE ACS VIRGO CLUSTER SURVEY. XVII. THE SPATIAL ALIGNMENT OF GLOBULAR CLUSTER SYSTEMS WITH EARLY-TYPE HOST GALAXIES

    Wang Qiushi; Peng, Eric W. [Department of Astronomy, Peking University, Beijing 100871 (China); Blakeslee, John P.; Cote, Patrick; Ferrarese, Laura [Herzberg Institute of Astrophysics, National Research Council of Canada, 5071 West Saanich Road, Victoria, BC V9E 2E7 (Canada); Jordan, Andres [Departamento de Astronomia y Astrofisica, Pontificia Universidad Catolica de Chile, Casilla 306, Santiago 22 (Chile); Mei, Simona [University of Paris 7 Denis Diderot, F-75205 Paris Cedex 13 (France); West, Michael J., E-mail: peng@pku.edu.cn [Maria Mitchell Observatory, 4 Vestal Street, Nantucket, MA 02554 (United States)

    2013-06-01

    We study the azimuthal distribution of globular clusters (GCs) in early-type galaxies and compare them to their host galaxies using data from the ACS Virgo Cluster Survey. We find that in host galaxies with visible elongation ({epsilon} > 0.2) and intermediate to high luminosities (M{sub z} < -19), the GCs are preferentially aligned along the major axis of the stellar light. The red (metal-rich) GC subpopulations show strong alignment with the major axis of the host galaxy, which supports the notion that these GCs are associated with metal-rich field stars. The metal-rich GCs in lenticular galaxies show signs of being more strongly associated with disks rather than bulges. Surprisingly, we also find that the blue (metal-poor) GCs can also show the same correlation. If the metal-poor GCs are part of the early formation of the halo and built up through mergers, then our results support a picture where halo formation and merging occur anisotropically, and that the present-day major axis is an indicator of the preferred merging axis.

  8. The distance to NGC1316 (Fornax A): yet another curious case

    Cantiello, Michele; Blakeslee, John P; Di Rico, Gianluca; Limatola, Luca; Brocato, Enzo; Della Valle, Massimo; Gilmozzi, Roberto

    2013-01-01

    The distance of NGC1316, the brightest galaxy in Fornax, is an interesting test for the cosmological distance scale. First, because Fornax is the 2nd largest cluster of galaxies at <~25 Mpc after Virgo and, in contrast to Virgo, has a small line-of-sight depth; and second, because NGC1316 is the galaxy with the largest number of detected SNeIa, giving the opportunity to test the consistency of SNeIa distances internally and against other indicators. We measure SBF mags in NGC1316 from ground and space-based imaging data, providing a homogeneous set of measurements over a wide wavelength interval. The SBF, coupled with empirical and theoretical calibrations, are used to estimate the distance to the galaxy. We present the first B-band SBF measurements of NGC1316 and use them together with the optical and near-IR SBF data to analyze the properties of field stars. Our distance modulus m-M=31.59 +-0.05(stat) +-0.14(sys), when placed in a consistent Cepheid distance scale, agrees with the results from other indi...

  9. Dust in the Radio Galaxy and Merger Remnant NGC 1316 (Fornax A)

    Asabere, Bernard Duah; Winkler, Hartmut; Jarrett, Thomas; Leeuw, Lerothodi

    2014-01-01

    We present dust maps of NGC 1316 (Fornax A), a well-studied early-type galaxy located in the outskirts of the Fornax cluster. We used the Large APEX BOlometer CAmera (LABOCA), operating at 870 micron with an angular resolution of 19.5 arcseconds on the Atacama Pathfinder EXperiment (APEX) 12m submillimeter telescope in Chile and the Wide-field Infrared Survey Explorer (WISE). WISE observes in four mid-infrared bands centered at 3.4, 4.6, 12 and 22 micron with angular resolutions ranging from 6 to 12 arcseconds. The WISE and LABOCA maps reveal emission from dust in the central 2 arcminutes of NGC 1316. The disturbed optical morphology with many shells and loops, the complex distribution of molecular gas and our dust maps are evidences of past merger activity or gas accretion in the galaxy. Combining the LABOCA flux measurement with existing mid- and far-infrared measurements, we estimate the temperature of the cold (~20 K) and warm (~55 K) dust components in the galaxy. This study will be extended to other sou...

  10. The surface brightness of 1550 galaxies in Fornax: automated galaxy surface photometry: Pt. 2

    A survey of a complete sample of galaxies in the region of the Fornax cluster is presented. Measurements with the Automatic Plate Measuring machine are used to derive the observed distribution of galaxy surface brightness for 1550 objects. Corrections for surface brightness dependent selection effects are then made in order to estimate the true distribution. It is found that the sample (with 16.6 ≤ Msub(APM) ≤ 19.1) is divided into two distinct populations. The 'normal' galaxies with extrapolated central surface brightness Ssub(x) ≤ 22.5 Bμ form a uniformly distributed background of field galaxies. Low surface brightness galaxies (Ssub(x) ≥ 22.5 Bμ), on the other hand, are strongly clumped about the cluster centre. There appear to be few low surface brightness field galaxies. (author)

  11. The HST/ACS Coma Cluster Survey. II. Data Description and Source Catalogs

    Hammer, Derek; Kleijn, Gijs Verdoes; Hoyos, Carlos; Den Brok, Mark; Balcells, Marc; Ferguson, Henry C.; Goudfrooij, Paul; Carter, David; Guzman, Rafael; Peletier, Reynier F.; Smith, Russell J.; Graham, Alister W.; Trentham, Neil; Peng, Eric; Puzia, Thomas H.; Lucey, John R.; Jogee, Shardha; Aguerri, Alfonso L.; Batcheldor, Dan; Bridges, Terry J.; Davies, Jonathan I.; Del Burgo, Carlos; Erwin, Peter; Hornschemeier, Ann; Hudson, Michael J.

    2010-01-01

    The Coma cluster, Abell 1656, was the target of a HST-ACS Treasury program designed for deep imaging in the F475W and F814W passbands. Although our survey was interrupted by the ACS instrument failure in early 2007, the partially-completed survey still covers approximately 50% of the core high density region in Coma. Observations were performed for twenty-five fields with a total coverage area of 274 aremin(sup 2), and extend over a wide range of cluster-centric radii (approximately 1.75 Mpe or 1 deg). The majority of the fields are located near the core region of Coma (19/25 pointings) with six additional fields in the south-west region of the cluster. In this paper we present SEXTRACTOR source catalogs generated from the processed images, including a detailed description of the methodology used for object detection and photometry, the subtraction of bright galaxies to measure faint underlying objects, and the use of simulations to assess the photometric accuracy and completeness of our catalogs. We also use simulations to perform aperture corrections for the SEXTRACTOR Kron magnitudes based only on the measured source flux and its half-light radius. We have performed photometry for 76,000 objects that consist of roughly equal numbers of extended galaxies and unresolved objects. Approximately two-thirds of all detections are brighter than F814W=26.5 mag (AB), which corresponds to the 10sigma, point-source detection limit. We estimate that Coma members are 5-10% of the source detections, including a large population of compact objects (primarily GCs, but also cEs and UCDs), and a wide variety of extended galaxies from cD galaxies to dwarf low surface brightness galaxies. The initial data release for the HST-ACS Coma Treasury program was made available to the public in August 2008. The images and catalogs described in this study relate to our second data release.

  12. The Fornax Deep Survey with VST. I. The Extended and Diffuse Stellar Halo of NGC 1399 out to 192 kpc

    Iodice, E.; Capaccioli, M.; Grado, A.; Limatola, L.; Spavone, M.; Napolitano, N. R.; Paolillo, M.; Peletier, R. F.; Cantiello, M.; Lisker, T.; Wittmann, C.; Venhola, A.; Hilker, M.; D'Abrusco, R.; Pota, V.; Schipani, P.

    2016-03-01

    We have started a new, deep multi-imaging survey of the Fornax cluster, dubbed the Fornax Deep Survey (FDS), at the VLT Survey Telescope (VST). In this paper we present the deep photometry inside two square degrees around the bright galaxy NGC 1399 in the core of the cluster. We found that the core of the Fornax cluster is characterized by a very extended and diffuse envelope surrounding the luminous galaxy NGC 1399: we map the surface brightness out to 33 arcmin (˜192 kpc) from the galaxy center and down to μg ˜ 31 mag arcsec-2 in the g band. The deep photometry allows us to detect a faint stellar bridge in the intracluster region on the west side of NGC 1399 and toward NGC 1387. By analyzing the integrated colors of this feature, we argue that it could be due to the ongoing interaction between the two galaxies, where the outer envelope of NGC 1387 on its east side is stripped away. By fitting the light profile, we found that there exists a physical break radius in the total light distribution at R = 10 arcmin (˜58 kpc) that sets the transition region between the bright central galaxy and the outer exponential halo, and that the stellar halo contributes 60% of the total light of the galaxy (Section 3.5). We discuss the main implications of this work on the build-up of the stellar halo at the center of the Fornax cluster. By comparing with the numerical simulations of the stellar halo formation for the most massive bright cluster galaxies (i.e., 13\\lt {log}{M}200/{M}⊙ \\lt 14), we find that the observed stellar halo mass fraction is consistent with a halo formed through the multiple accretion of progenitors with stellar mass in the range 108-1011 M⊙. This might suggest that the halo of NGC 1399 has also gone through a major merging event. The absence of a significant number of luminous stellar streams and tidal tails out to 192 kpc suggests that the epoch of this strong interaction goes back to an early formation epoch. Therefore, different from the Virgo

  13. Ultra-Compact Dwarfs in the Coma Cluster

    Chiboucas, Kristin; Marzke, Ronald O; Phillipps, Steve; Price, James; Peng, Eric; Trentham, Neil; Carter, David; Hammer, Derek

    2011-01-01

    We have undertaken a spectroscopic search for ultra compact dwarf galaxies (UCDs) in the dense core of the dynamically evolved, massive Coma cluster as part of the HST/ACS Coma Cluster Treasury Survey. UCD candidates were initially chosen based on color, magnitude, degree of resolution within the ACS images, and the known properties of Fornax and Virgo UCDs. Follow-up spectroscopy with Keck/LRIS confirmed 27 candidates as members of the Coma Cluster, a success rate > 60% for targeted objects brighter than M_R = -12. Another 14 candidates may also prove to be Coma members, but low signal-to-noise spectra prevent definitive conclusions. An investigation of the properties and distribution of the Coma UCDs finds these objects to be very similar to UCDs discovered in other environments. The Coma UCDs tend to be clustered around giant galaxies in the cluster core and have colors/metallicity that correlate with the host galaxy. With properties and a distribution similar to that of the Coma cluster globular cluster p...

  14. A low global star formation rate in the rich galaxy cluster AC114 at z=0.32

    Couch, W J; Bower, R G; Smail, I; Taylor, K G M; Couch, Warrick J.; Balogh, Michael L.; Bower, Richard G.; Smail, Ian; Taylor, Karl Glazebrook & Melinda

    2001-01-01

    We present the results of a wide-field survey for H-alpha emitting galaxies in the cluster AC114 at z=0.32. Spectra centred on H-alpha at the cluster redshift have been obtained for 586 galaxies to I~22 out to a radius around 2Mpc. At most, only ~10% of these were found to be H-alpha-emitting cluster members. These objects are predominantly blue and of late-type spiral morphology, consistent with them hosting star formation. However, ~65% of the cluster members classified morphologically as spirals (with HST), have no detectable H-alpha emission; star-formation and morphological evolution in cluster galaxies appear to be largely decoupled. Changes in the H-alpha detection rate and the strength of H-alpha emission with environment are found to be weak within the region studied. Star formation within the cluster members is also found to be strongly and uniformly suppressed, with the rates inferred from the H-alpha emission not exceeding 4Mo/yr, and AC114's H-alpha luminosity function being an order of magnitude...

  15. Dark Matter Cores in the Fornax and Sculptor Dwarf Galaxies

    C. Amorisco, Nicola; Zavala Franco, Jesus; J. L. de Boer, Thomas

    2014-01-01

    We combine the detailed Star Formation Histories of the Fornax and Sculptor dwarf Spheroidals with the mass assembly history of their dark matter halo progenitors to estimate if the energy deposited by Supernova type II (SNeII) is sufficient to create a substantial dark matter core. Assuming...... the efficiency of energy injection of the SNeII into dark matter particles is \\epsilon=0.05, we find that a single early episode, z...

  16. The Hubble Constant from the Fornax Cluster Distance

    Richtler, Tom; Drenkhahn, Georg; Gomez, Matias; Seggewiss, Wilhelm

    1999-01-01

    Type Ia supernovae are the best cosmological standard candles available. The intrinsic scatter of their decline-rate- and colour-corrected peak brightnesses in the Hubble diagram is within observational error limits, corresponding to an uncertainty of only 3km/s/Mpc of the Hubble constant. Any additional uncertainty, resulting from peak-brightness calibration, must be kept small by measuring distances to nearby host galaxies most precisely. A number of different distance determinations of the...

  17. A Chemical Evolution Model for the Fornax Dwarf Spheroidal Galaxy

    Yuan Zhen

    2016-01-01

    Full Text Available Fornax is the brightest Milky Way (MW dwarf spheroidal galaxy and its star formation history (SFH has been derived from observations. We estimate the time evolution of its gas mass and net inflow and outflow rates from the SFH usinga simple star formation law that relates the star formation rate to the gas mass. We present a chemical evolution model on a 2D mass grid with supernovae (SNe as sources of metal enrichment. We find that a key parameter controlling the enrichment is the mass Mx of the gas to mix with the ejecta from each SN. The choice of Mx depends on the evolution of SN remnants and on the global gas dynamics. It differs between the two types of SNe involved and between the periods before and after Fornax became an MW satellite at time t = tsat. Our results indicate that due to the global gas outflow at t > tsat, part of the ejecta from each SN may directly escape from Fornax. Sample results from our model are presented and compared with data.

  18. A Chemical Evolution Model for the Fornax Dwarf Spheroidal Galaxy

    Yuan, Zhen; Jing, Y P

    2015-01-01

    Fornax is the brightest Milky Way (MW) dwarf spheroidal galaxy and its star formation history (SFH) has been derived from observations. We estimate the time evolution of its gas mass and net inflow and outflow rates from the SFH using a simple star formation law that relates the star formation rate to the gas mass. We present a chemical evolution model on a 2D mass grid with supernovae (SNe) as sources of metal enrichment. We find that a key parameter controlling the enrichment is the mass M_x of the gas to mix with the ejecta from each SN. The choice of M_x depends on the evolution of SN remnants and on the global gas dynamics. It differs between the two types of SNe involved and between the periods before and after Fornax became an MW satellite at time t = t_sat . Our results indicate that due to the global gas outflow at t > t_sat , part of the ejecta from each SN may directly escape from Fornax. Sample results from our model are presented and compared with data.

  19. The effect of tides on the Fornax dwarf spheroidal galaxy

    Battaglia, Giuseppina; Nipoti, Carlo

    2015-01-01

    Estimates of the mass distribution and dark-matter (DM) content of dwarf spheroidal galaxies (dSphs) are usually derived under the assumption that the effect of the tidal field of the host galaxy is negligible over the radial extent probed by kinematic data-sets. We assess the implications of this assumption in the specific case of the Fornax dSph by means of N-body simulations of a satellite orbiting around the Milky Way. We consider observationally-motivated orbits and we tailor the initial distributions of the satellite's stars and DM to match, at the end of the simulations, the observed structure and kinematics of Fornax. In all our simulations the present-day observable properties of Fornax are not significantly influenced by tidal effects. The DM component is altered by the interaction with the Galactic field (up to 20% of the DM mass within 1.6 kpc is lost), but the structure and kinematics of the stellar component are only mildly affected even in the more eccentric orbit (more than 99% of the stellar ...

  20. The HST/ACS Coma Cluster Survey. X. Nuclear star clusters in low-mass early-type galaxies: scaling relations

    Brok, Mark den; Seth, Anil; Balcells, Marc; Dominguez, Lilian; Graham, Alister W; Carter, David; Erwin, Peter; Ferguson, Henry C; Goudfrooij, Paul; Guzman, Rafael; Hoyos, Carlos; Jogee, Shardha; Lucey, John; Phillipps, Steven; Puzia, Thomas; Valentijn, Edwin; Kleijn, Gijs Verdoes; Weinzirl, Tim

    2014-01-01

    We present scaling relations between structural properties of nuclear star clusters and their host galaxies for a sample of early-type dwarf galaxies observed as part of the Hubble Space Telescope (HST) Advanced Camera for Surveys (ACS) Coma Cluster Survey. We have analysed the light profiles of 200 early-type dwarf galaxies in the magnitude range $16.0 < m_{F814W} < 22.6 $ mag, corresponding to $-19.0 < M_{F814W} < -12.4 $ mag. Nuclear star clusters are detected in 80% of the galaxies, thus doubling the sample of HST-observed early-type dwarf galaxies with nuclear star clusters. \\changed{We confirm that the} nuclear star cluster detection fraction decreases strongly toward faint magnitudes. The luminosities of nuclear star clusters do not scale linearly with host galaxy luminosity. A linear fit yields L$_{nuc} \\sim $L$_{gal}^{0.57\\pm0.05}$. The nuclear star cluster-host galaxy luminosity scaling relation for low-mass early-type dwarf galaxies is consistent with formation by globular cluster accre...

  1. The HST/ACS Coma Cluster Survey: VII - Colour Gradients in Giant and Dwarf Early-Type Galaxies

    Brok, M den; Valentyn, E A; Balcells, M; Carter, D; Erwin, P; Ferguson, H C; Goudfrooij, P; Graham, A W; Hammer, D; Lucey, J R; Trentham, N; Guzman, R; Hoyos, C; Kleijn, G Verdoes; Jogee, S; Karick, A M; Marinova, I; Mouhcine, M; Weinzirl, T

    2011-01-01

    Using deep, high-spatial resolution imaging from the HST ACS Coma Cluster Treasury Survey, we determine colour profiles of early-type galaxies in the Coma cluster. From 176 galaxies brighter than $M_\\mathrm{F814W(AB)} = -15$ mag that are either spectroscopically confirmed members of Coma or identified by eye as likely members from their low surface brightness, data are provided for 142 early-type galaxies. Typically, colour profiles are linear against $\\log(R)$, sometimes with a nuclear region of distinct, often bluer colour associated with nuclear clusters. Colour gradients are determined for the regions outside the nuclear components. We find that almost all colour gradients are negative, both for elliptical and lenticular galaxies. Most likely, earlier studies that report positive colour gradients in dwarf galaxies are affected by the bluer colours of the nuclear clusters, underlining that high resolution data are essential to disentangle the colour properties of the different morphological components in g...

  2. The Large Scale Distribution of Neutral Hydrogen in the Fornax Region

    Waugh, M; Webster, R L; Staveley-Smith, L; Kilborn, V A; Barnes, D G; Bhathal, R; De Blok, W J G; Boyce, P J; Disney, M J; Ekers, R D; Freeman, K C; Gibson, B K; Henning, P A; Jerjen, H; Knezek, P M; Koribalski, B S; Marquarding, M; Minchin, R F; Price, R M; Putman, M E; Ryder, S D; Sadler, E M; Stootman, F; Zwaan, M A; Waugh, Meryl

    2002-01-01

    Using HIPASS data, we have searched for HI in a ~25x25 sq.deg. region centred on the Fornax cluster. Within a velocity search range of 300 - 3700 km/s and a lower flux limit of ~40 mJy, 110 galaxies with HI emission were detected, one of which is previously uncatalogued. None of the detections has early-type morphology. Previously unknown velocities for 14 galaxies have been determined, with a further 4 velocity measurements being significantly dissimilar to published values. Identification of an optical counterpart is relatively unambiguous for more than ~90% of our HI galaxies. The galaxies appear to be embedded in a sheet at the cluster velocity which extends for more than 30 deg across the search area. At the nominal cluster distance of ~20 Mpc, this corresponds to an elongated structure more than 10 Mpc in extent. A velocity gradient across the structure is detected, with radial velocities increasing by \\~500 km/s from SE to NW. The clustering of galaxies evident in optical surveys is only weakly suggest...

  3. The Fornax Deep Survey with VST. I. The extended and diffuse stellar halo of NGC~1399 out to 192 kpc

    Iodice, E; Grado, A; Limatola, L; Spavone, M; Napolitano, N R; Paolillo, M; Peletier, R F; Cantiello, M; Lisker, T; Wittmann, C; Venhola, A; Hilker, M; D'Abrusco, R; Pota, V; Schipani, P

    2016-01-01

    [Abrigded] We have started a new deep, multi-imaging survey of the Fornax cluster, dubbed Fornax Deep Survey (FDS), at the VLT Survey Telescope. In this paper we present the deep photometry inside two square degrees around the bright galaxy NGC1399 in the core of the cluster. We found a very extended and diffuse envelope surrounding the luminous galaxy NGC1399: we map the surface brightness out to 33 arcmin (~ 192 kpc) from the galaxy center and down to about 31 mag/arcsec^2 in the g band. The deep photometry allows us to detect a faint stellar bridge in the intracluster region between NGC1399 and NGC1387. By analyzing the integrated colors of this feature, we argue that it could be due to the ongoing interaction between the two galaxies, where the outer envelope of NGC1387 on its east side is stripped away. By fitting the light profile, we found that it exists a physical break radius in the total light distribution at R=10 arcmin (~58 kpc) that sets the transition region between the bright central galaxy and...

  4. Multi-wavelength observations of a rich galaxy cluster at z ~ 1: the HST/ACS colour-magnitude diagram

    Santos, Joana S; Gobat, Raphael; Lidman, Chris; Dawson, Kyle; Perlmutter, Saul; Boehringer, Hans; Balestra, Italo; Mullis, Chris R; Fassbender, Rene; Kohnert, Jan; Lamer, Georg; Rettura, Alessandro; Rite, Charles; Schwope, Axel

    2009-01-01

    XMMU J1229+0151 is a rich galaxy cluster with redshift z=0.975, that was serendipitously detected in X-rays within the scope of the XMM-Newton Distant Cluster Project. HST/ACS observations in the i775 and z850 passbands, as well as VLT/FORS2 spectroscopy were further obtained, in addition to follow-up Near-Infrared (NIR) imaging in J- and Ks-bands with NTT/SOFI. We investigate the photometric, structural and spectral properties of the early-type galaxies in the high-redshift cluster XMMU J1229+0151. Source detection and aperture photometry are performed in the optical and NIR imaging. Galaxy morphology is inspected visually and by means of Sersic profile fitting to the 21 spectroscopically confirmed cluster members in the ACS field of view. The i775-z850 colour-magnitude relation (CMR) is derived with a method based on galaxy magnitudes obtained by fitting the surface brightness of the galaxies with Sersic models. The i775-z850 CMR of the spectroscopic members shows a very tight red-sequence with a zero point...

  5. The Star Formation & Chemical Evolution History of the Fornax Dwarf Spheroidal Galaxy

    de Boer, T J L; Hill, V; Saha, A; Olszewski, E W; Mateo, M; Starkenburg, E; Battaglia, G; Walker, M G

    2012-01-01

    We present deep photometry in the B,V and I filters from CTIO/MOSAIC for about 270.000 stars in the Fornax dwarf Spheroidal galaxy, out to a radius of r_ell\\sim0.8 degrees. By combining the accurately calibrated photometry with the spectroscopic metallicity distributions of individual Red Giant Branch stars we obtain the detailed star formation and chemical evolution history of Fornax. Fornax is dominated by intermediate age (1-10 Gyr) stellar populations, but also includes ancient (10-14 Gyr), and young (-1.5 dex, with a clear trend in age.

  6. Mass assembly history and infall time of the Fornax dwarf spheroidal galaxy.

    Wang, M.-Y.; Strigari, L. E.; Lovell, M R; Frenk, C. S.; Zentner, A. R.

    2016-01-01

    We use cosmological simulations to identify dark matter subhalo host candidates of the Fornax dwarf spheroidal galaxy using the stellar kinematic properties of Fornax. We consider cold dark matter (CDM), warm dark matter (WDM), and decaying dark matter (DDM) simulations for our models of structure formation. The subhalo candidates in CDM typically have smaller mass and higher concentrations at z = 0 than the corresponding candidates in WDM and DDM. We examine the formation histories of the ∼1...

  7. Mass assembly history and infall time of the Fornax Dwarf Spheroidal Galaxy

    Wang, Mei-Yu; Lovell, Mark R; Frenk, Carlos S; Zentner, Andrew R

    2015-01-01

    We use cosmological simulations to identify dark matter subhalo host candidates of the Fornax dwarf spheroidal galaxy using the stellar kinematic properties of Fornax. We consider cold dark matter (CDM), warm dark matter (WDM), and decaying dark matter (DDM) simulations for our models of structure formation. The subhalo candidates in CDM typically have smaller mass and higher concentrations at z = 0 than the corresponding candidates in WDM and DDM. We examine the formation histories of the ~ 100 Fornax candidate subhalos identified in CDM simulations and, using approximate luminosity-mass relationships for subhalos, we find two of these subhalos that are consistent with both the Fornax luminosity and kinematics. These two subhalos have a peak mass over ten times larger than their z = 0 mass. We suggest that in CDM the dark matter halo hosting Fornax must have been severely stripped of mass and that it had an infall time into the Milky Way of ~ 9 Gyr ago. In WDM, we find that candidate subhalos consistent with...

  8. HOMOGENEOUS UGRIZ PHOTOMETRY FOR ACS VIRGO CLUSTER SURVEY GALAXIES: A NON-PARAMETRIC ANALYSIS FROM SDSS IMAGING

    We present photometric and structural parameters for 100 ACS Virgo Cluster Survey (ACSVCS) galaxies based on homogeneous, multi-wavelength (ugriz), wide-field SDSS (DR5) imaging. These early-type galaxies, which trace out the red sequence in the Virgo Cluster, span a factor of nearly ∼103 in g-band luminosity. We describe an automated pipeline that generates background-subtracted mosaic images, masks field sources and measures mean shapes, total magnitudes, effective radii, and effective surface brightnesses using a model-independent approach. A parametric analysis of the surface brightness profiles is also carried out to obtain Sersic-based structural parameters and mean galaxy colors. We compare the galaxy parameters to those in the literature, including those from the ACSVCS, finding good agreement in most cases, although the sizes of the brightest, and most extended, galaxies are found to be most uncertain and model dependent. Our photometry provides an external measurement of the random errors on total magnitudes from the widely used Virgo Cluster Catalog, which we estimate to be σ(BT )∼ 0.13 mag for the brightest galaxies, rising to ∼ 0.3 mag for galaxies at the faint end of our sample (BT ∼ 16). The distribution of axial ratios of low-mass (dwarf) galaxies bears a strong resemblance to the one observed for the higher-mass (giant) galaxies. The global structural parameters for the full galaxy sample-profile shape, effective radius, and mean surface brightness-are found to vary smoothly and systematically as a function of luminosity, with unmistakable evidence for changes in structural homology along the red sequence. As noted in previous studies, the ugriz galaxy colors show a nonlinear but smooth variation over a ∼7 mag range in absolute magnitude, with an enhanced scatter for the faintest systems that is likely the signature of their more diverse star formation histories.

  9. Wide-Field Hubble Space Telescope Observations of the Globular Cluster System in NGC1399

    Puzia, Thomas H; Goudfrooij, Paul; Maccarone, Thomas J; Fabbiano, Giuseppina; Angelini, Lorella

    2014-01-01

    We present a comprehensive high spatial-resolution imaging study of globular clusters (GCs) in NGC1399, the central giant elliptical cD galaxy in the Fornax galaxy cluster, conducted with HST/ACS. Using a novel technique to construct drizzled PSF libraries for HST/ACS data, we accurately determine the fidelity of GC structural parameter measurements from detailed artificial star cluster experiments. The measurement of rh for the major fraction of the NGC1399 GC system reveals a trend of increasing rh versus galactocentric distance, Rgal, out to about 10 kpc and a flat relation beyond. This trend is very similar for blue and red GCs which are found to have a mean size ratio of rh(red)/rh(blue)=0.82+/-0.11 at all galactocentric radii from the core regions of the galaxy out to ~40 kpc. This suggests that the size difference between blue and red GCs is due to internal mechanisms related to the evolution of their constituent stellar populations. Modeling the mass density profile of NGC1399 shows that additional ex...

  10. Atomic and molecular gas in the merger galaxy NGC 1316 (Fornax A) and its environment

    Horellou, C; Black, JH; van Gorkom, JH; Combes, F; van der Hulst, JM; Charmandaris, [No Value

    2001-01-01

    We present and interpret observations of atomic and molecular gas toward the southern elliptical galaxy NGC 1316 (Fornax A), a strong double-lobe radio source with a disturbed optical morphology that includes numerous shells and loops. The (CO)-C-12(1-0), (CO)-C-12(2-1), and Hi observations were mad

  11. An Empirical Model for Halo Evolution and Global Gas Dynamics of the Fornax Dwarf Spheroidal Galaxy

    Yuan, Zhen; Jing, Y P

    2015-01-01

    We present an empirical model for the halo evolution and global gas dynamics of Fornax, the brightest Milky Way (MW) dwarf spheroidal galaxy (dSph). Assuming a global star formation rate psi(t)=lambda_*[M_g(t)/M_sun]^alpha consistent with observations of star formation in nearby galaxies and using the data on Fornax's psi(t), we derive the evolution of the total mass M_g(t) for cold gas in Fornax's star-forming disk and the rate Delta F(t) of net gas flow to or from the disk. We identify the onset of the transition in Delta F(t) from a net inflow to a net outflow as the time t_sat at which the Fornax halo became an MW satellite and estimate the evolution of its total mass M_h(t) at t

  12. Merger traces in the spatial distribution of stellar populations in the Fornax dSph galaxy

    del Pino, Andrés; Hidalgo, Sebastial L

    2015-01-01

    We present a comprehensive and detailed study of the stellar populations of the Fornax dwarf spheroidal galaxy. We analyse their spatial distributions along the main body of the galaxy, obtaining their surface density maps, together with their radial density profiles. Results are based on the largest and most complete catalogue of stars in Fornax, with more than $3.5\\times10^{5}$ stars covering the main body of the galaxy up to $\\rm V \\sim 24$. We find a differentiated structure in Fornax depending on the stellar ages. Old stars ($\\gtrsim 10$ Gyr) follow an elliptical distribution well fitted by King profiles with relatively large core radius ($r_c = 760\\pm60$ pc). On another hand, young populations ($\\lesssim 3$ Gyr) concentrate in the central region of the galaxy ($r_c = 210\\pm10$ pc), and are better fitted by Sersic profiles with $0.8 < n < 1.2$, indicating some disky shape. These stars show strong asymmetries and substructures not aligned with the main optical axes of Fornax. This together with the ...

  13. The DART imaging and CaT survey of the Fornax Dwarf Spheroidal Galaxy

    Battaglia, G; Helmi, A; Irwin, M J; Letarte, B; Jablonka, P; Hill, V; Venn, K A; Shetrone, M D; Arimoto, N; Primas, F; Kaufer, A; François, P; Szeifert, T; Abel, T; Sadakane, K

    2006-01-01

    As part of the DART project we have used the ESO/2.2m Wide Field Imager in conjunction with the VLT/FLAMES GIRAFFE spectrograph to study the detailed properties of the resolved stellar population of the Fornax dwarf spheroidal galaxy out to and beyond its tidal radius. We re-derived the structural parameters of the Fornax dwarf spheroidal using our wide field imaging covering the galaxy out to its tidal radius, and analysed the spatial distribution of the Fornax stars of different ages as selected from Colour-Magnitude Diagram analysis. We have obtained accurate velocities and metallicities from spectra in the CaII triplet wavelength region for 562 Red Giant Branch stars which have velocities consistent with membership in Fornax dwarf spheroidal. We have found evidence for the presence of at least three distinct stellar components: a young population (few 100 Myr old) concentrated in the centre of the galaxy, visible as a Main Sequence in the Colour-Magnitude Diagram; an intermediate age population (2-8 Gyr o...

  14. HST/Acs Weak-Lensing and Chandra X-Ray Studies of the High-Redshift Cluster MS 1054-0321

    Jee, M J; Ford, H C; Blakeslee, J P; Illingworth, G D; Coe, D A; Tran, K V H

    2005-01-01

    We present Hubble Space Telescope/Advanced Camera for Surveys (ACS) weak-lensing and Chandra X-ray analyses of MS 1054-0321 at z=0.83, the most distant and X-ray luminous cluster in the Einstein Extended Medium-Sensitivity Survey (EMSS). The high-resolution mass reconstruction through ACS weak-lensing reveals the complicated dark matter substructure in unprecedented detail, characterized by the three dominant mass clumps with the four or more minor satellite groups within the current ACS field. The direct comparison of the mass map with the Chandra X-ray image shows that the eastern weak-lensing substructure is not present in the X-ray image and, more interestingly, the two X-ray peaks are displaced away from the hypothesized merging direction with respect to the corresponding central and western mass clumps, possibly because of ram pressure. In addition, as observed in our previous weak-lensing study of another high-redshift cluster CL 0152-1357 at z=0.84, the two dark matter clumps of MS 1054-0321 seem to b...

  15. The DART Imaging And CaT Survey of the Fornax Dwarf Spheroidal Galaxy

    Battaglia, Giuseppina; Tolstoy, E.; Helmi, A.; /Kapteyn Astron. Inst., Groningen; Irwin, M.J.; /Cambridge U., Inst. of Astron.; Letarte, B.; /Kapteyn Astron. Inst.,; Jablonka, P.; /LASTRO Observ.; Hill, V.; /Meudon Observ.; Venn, K.A.; /Victoria U.; Shetrone, M.D.; /Texas U., McDonald Observ.; Arimoto, N.; /Tokyo, Astron. Observ.; Primas,; /European Southern Observ.; Kaufer, A.; /European Southern Obs., Chile; Francois, P.; /Meudon Observ.; Szeifert, T.; /European Southern Obs., Chile; Abel, T.; /KIPAC, Menlo Park; Sadakane, K.; /Osaka Kyoiku U.

    2006-08-28

    As part of the DART project we have used the ESO/2.2m Wide Field Imager in conjunction with the VLT/FLAMES* GIRAFFE spectrograph to study the detailed properties of the resolved stellar population of the Fornax dwarf spheroidal galaxy out to and beyond its tidal radius. Fornax dSph has had a complicated evolution and contains significant numbers of young, intermediate age and old stars. We investigate the relation between these different components by studying their photometric, kinematic and abundance distributions. We re-derived the structural parameters of the Fornax dwarf spheroidal using our wide field imaging covering the galaxy out to its tidal radius, and analyzed the spatial distribution of the Fornax stars of different ages as selected from Colour-Magnitude Diagram analysis. We have obtained accurate velocities and metallicities from spectra in the Ca II triplet wavelength region for 562 Red Giant Branch stars which have velocities consistent with membership in Fornax dwarf spheroidal. We have found evidence for the presence of at least three distinct stellar components: a young population (few 100 Myr old) concentrated in the center of the galaxy, visible as a Main Sequence in the Colour-Magnitude Diagram; an intermediate age population (2-8 Gyr old); and an ancient population (> 10Gyr), which are distinguishable from each other kinematically, from the metallicity distribution and in the spatial distribution of stars found in the Colour-Magnitude Diagram. From our spectroscopic analysis we find that the ''metal rich'' stars ([Fe/H] > -1.3) show a less extended and more concentrated spatial distribution, and display a colder kinematics than the ''metal poor'' stars ([Fe/H] < -1.3). There is tentative evidence that the ancient stellar population in the center of Fornax does not exhibit equilibrium kinematics. This could be a sign of a relatively recent accretion of external material, such as the merger of another

  16. The star formation and chemical evolution history of the Fornax dwarf spheroidal galaxy

    de Boer, T. J. L.; Tolstoy, E.; Hill, V.; Saha, A.; Olszewski, E. W.; Mateo, M.; Starkenburg, E.; Battaglia, G.; Walker, M. G.

    2012-08-01

    We present deep photometry in the B, V and I filters from CTIO/MOSAIC for about 270 000 stars in the Fornax dwarf spheroidal galaxy, out to a radius of rell ≈ 0.8 degrees. By combining the accurately calibrated photometry with the spectroscopic metallicity distributions of individual red giant branch stars we obtain the detailed star formation and chemical evolution history of Fornax. Fornax is dominated by intermediate age (1-10 Gyr) stellar populations, but also includes ancient (10-14 Gyr), and young (≤1 Gyr) stars. We show that Fornax displays a radial age gradient, with younger, more metal-rich populations dominating the central region. This confirms results from previous works. Within an elliptical radius of 0.8 degrees, or 1.9 kpc from the centre, a total mass in stars of 4.3 × 107 M⊙ was formed, from the earliest times until 250 Myr ago. Using the detailed star formation history, age estimates are determined for individual stars on the upper RGB, for which spectroscopic abundances are available, giving an age-metallicity relation of the Fornax dSph from individual stars. This shows that the average metallicity of Fornax went up rapidly from [Fe/H] ≤ -2.5 dex to [Fe/H] = -1.5 dex between 8-12 Gyr ago, after which a more gradual enrichment resulted in a narrow, well-defined sequence which reaches [Fe/H] ≈ -0.8 dex, ≈3 Gyr ago. These ages also allow us to measure the build-up of chemical elements as a function of time, and thus determine detailed timescales for the evolution of individual chemical elements. A rapid decrease in [Mg/Fe] is seen for the stars with [Fe/H] ≥ -1.5 dex, with a clear trend in age. Table 1 is only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/544/A73

  17. Detection of Extended Emission from Fornax A and Measurement of the Extragalactic Background Light

    Magill, Jeffrey; McConville, William; Georganopoulos, Markos; Meyer, Eileen; Perkins, Jeremy; Stawarz, Lukasz; Fermi-LAT Collaboration

    2015-04-01

    Prior to the launch of Fermi in 2008, the radio galaxy Fornax A was identified as one of the few extragalactic objects that might be detected as spatially extended above 100 MeV. However, even though it was detected with high confidence in the first 2 years of the mission, it was not determined to be an extended source. Recently, the Fermi-LAT collaboration developed a new event-level analysis called Pass 8 which yields a larger acceptance, a better angular and energy resolution, as well as smaller systematic uncertainties. The improvements provided with Pass 8 combined with a longer exposure means that the spatial extension of Fornax A is significantly detected, making it only the second extragalactic gamma-ray source so far to show extent. Details of this measurement will be presented along with modeling of the emission above 100 MeV.

  18. INVESTIGATION OF THE PUZZLING ABUNDANCE PATTERN IN THE STARS OF THE FORNAX DWARF SPHEROIDAL GALAXY

    Many works have found unusual characteristics of elemental abundances in nearby dwarf galaxies. This implies that there is a key factor of galactic evolution that is different from that of the Milky Way (MW). The chemical abundances of the stars in the Fornax dwarf spheroidal galaxy (Fornax dSph) provide excellent information for setting constraints on the models of galactic chemical evolution. In this work, adopting the five-component approach, we fit the abundances of the Fornax dSph stars, including α elements, iron group elements, and neutron-capture elements. For most sample stars, the relative contributions from the various processes to the elemental abundances are not usually in the MW proportions. We find that the contributions from massive stars to the primary α elements and iron group elements increase monotonically with increasing [Fe/H]. This means that the effect of the galactic wind is not strong enough to halt star formation and the contributions from the massive stars to α elements did not halt for [Fe/H] ∼< –0.5. The average contribution ratios of various processes between the dSph stars and the MW stars monotonically decrease with increasing progenitor mass. This is important evidence of a bottom-heavy initial mass function (IMF) for the Fornax dSph, compared to the MW. Considering a bottom-heavy IMF for the dSph, the observed relations of [α/Fe] versus [Fe/H], [iron group/Fe] versus [Fe/H], and [neutron-capture/Fe] versus [Fe/H] for the dSph stars can be explained

  19. Spitzer Space Telescope spectral observations of AGB stars in the Fornax dwarf spheroidal galaxy

    Matsuura, M; Bernard-Salas, J; Menzies, J W; Sloan, G C; Whitelock, P A; Wood, P R; Cioni, M -R L; Feast, M W; Lagadec, E; van Loon, J Th; Groenewegen, M A T; Harris, G J

    2007-01-01

    We have observed five carbon-rich AGB stars in the Fornax dwarf spheroidal (dSph) galaxy, using the Infrared Spectrometer on board the Spitzer Space Telescope. The stars were selected from a near-infrared survey of Fornax and include the three reddest stars, with presumably the highest mass-loss rates, in that galaxy. Such carbon stars probably belong to the intermediate-age population (2-8 Gyr old and metallicity of [Fe/H] -1) of Fornax. The primary aim of this paper is to investigate mass-loss rate, as a function of luminosity and metallicity, by comparing AGB stars in several galaxies with different metallicities. The spectra of three stars are fitted with a radiative transfer model. We find that mass-loss rates of these three stars are 4-7x10^-6 Msun yr-1. The other two stars have mass-loss rates below 1.3x10^-6 Msun yr-1. We find no evidence that these rates depend on metallicity, although we do suggest that the gas-to-dust ratio could be higher than at solar metallicity, in the range 240 to 800. The C2H...

  20. Investigation of the Puzzling Abundance Pattern in the Stars of the Fornax Dwarf Spheroidal Galaxy

    Li, Hongjie; Zhang, Bo

    2013-01-01

    Many works have found unusual characteristics of elemental abundances in nearby dwarf galaxies. This implies that there is a key factor of galactic evolution that is different from that of the Milky Way (MW). The chemical abundances of the stars in the Fornax dwarf spheroidal galaxy (Fornax dSph) provide excellent information for setting constraints on the models of the galactic chemical evolution. In this work, adopting the five-component approach, we fit the abundances of the Fornax dSph stars, including $\\alpha$ elements, iron group elements and neutron-capture elements. For most sample stars, the relative contributions from the various processes to the elemental abundances are not usually in the MW proportions. We find that the contributions from massive stars to the primary $\\alpha$ elements and iron group elements increase monotonously with increasing [Fe/H]. This means that the effect of the galactic wind is not strong enough to halt star formation and the contributions from massive stars to $\\alpha$ e...

  1. Low surface brightness galaxies in the cluster A1367

    We have obtained deep CCD frames of apparently blank regions of sky in the hope of detecting very low surface brightness (LSB) objects in the cluster A1367. We discuss our data reduction, and image detection and selection techniques. If the galaxies detected are actually cluster members then they are dwarfs and the conclusions of a previous paper on the Fornax cluster are essentially confirmed. One area of variance is that the lowest surface brightness galaxies do not appear to be preferentially concentrated towards the cluster centre. This can be explained by there being a much larger density of dwarf galaxies over this bright galaxy-rich region of the universe. We find over our small area approximately four times as many LSB galaxies as would be expected from our Fornax data. We speculate on the possible origin and likely intensity of intergalactic light within clusters. (author)

  2. THE ACS NEARBY GALAXY SURVEY TREASURY. X. QUANTIFYING THE STAR CLUSTER FORMATION EFFICIENCY OF NEARBY DWARF GALAXIES

    We study the relationship between the field star formation and cluster formation properties in a large sample of nearby dwarf galaxies. We use optical data from the Hubble Space Telescope and from ground-based telescopes to derive the ages and masses of the young (tage ∼< 100 Myr) cluster sample. Our data provide the first constraints on two proposed relationships between the star formation rate (SFR) of galaxies and the properties of their cluster systems in the low SFR regime. The data show broad agreement with these relationships, but significant galaxy-to-galaxy scatter exists. In part, this scatter can be accounted for by simulating the small number of clusters detected from stochastically sampling the cluster mass function. However, this stochasticity does not fully account for the observed scatter in our data, suggesting that there may be true variations in the fraction of stars formed in clusters in dwarf galaxies. Comparison of the cluster formation and the brightest cluster in our sample galaxies also provide constraints on cluster destruction models.

  3. VLT and ACS observations of RDCS J1252.9-2927: dynamical structure and galaxy populations in a massive cluster at z=1.237

    Demarco, R; Lidman, C; Girardi, M; Nonino, M; Rettura, A; Strazzullo, V; Van der Wel, A; Ford, H C; Mainieri, V; Holden, B P; Stanford, S A; Blakeslee, J P; Gobat, R; Postman, M; Tozzi, P; Overzier, R A; Zirm, A W; Benítez, N; Homeier, N L; Illingworth, G D; Infante, L; Jee, M J; Mei, S; Menanteau, F; Motta, V; Zheng, W; Clampin, M; Hartig, G

    2007-01-01

    (Abridged) We present results from an extensive spectroscopic survey, carried out with FORS on the ESO VLT, and from an extensive multi-wavelength imaging data set from the ACS and ground based facilities of the cluster of galaxies RDCS J1252.9-2927. We have spectroscopically confirmed 38 cluster members in the redshift range 1.22 1, kinematic structure. The velocity distribution, which is not Gaussian at the 95% confidence level, is consistent with two groups that are also responsible for the projected elongation of the cluster in the East-West direction. The groups are composed of 26 and 12 galaxies with velocity dispersions of 486^{+47}_{-85} km s^-1 and 426^{+57}_{-105} km s^-1, respectively. The elongation is also seen in the intracluster gas and the dark matter distribution. This leads us to conclude that RDCS J1252.9-2927 has not yet reached a final virial state. We extend the analysis of the color-magnitude diagram of spectroscopic members to more than 1 Mpc from the cluster center. The scatter and s...

  4. Two Populations of Old Star Clusters in the Spiral Galaxy M101 Based on HST/ACS Observations

    Simanton, Lesley A; Whitmore, Bradley C

    2015-01-01

    We present a new photometric catalog of 326 candidate globular clusters (GCs) in the nearby spiral galaxy M101, selected from B, V, and I Hubble Space Telescope Advanced Camera for Surveys images. The luminosity function (LF) of these clusters has an unusually large number of faint sources compared with GCLFs in many other spiral galaxies. Accordingly, we separate and compare the properties of "bright" (M_V -6.5; one magnitude fainter than the expected GC peak) clusters within our sample. The LF of the bright clusters is well fit by a peaked distribution similar to those observed in the Milky Way (MW) and other galaxies. These bright clusters also have similar size (r_{eff}) and spatial distributions as MW GCs. The LF of the faint clusters, on the other hand, is well described by a power law, dN(L_V)/dL_V proportional to L_V^alpha with alpha = -2.6 plus or minus 0.3, similar to those observed for young and intermediate-age cluster systems in star forming galaxies. We find that the faint clusters have larger ...

  5. THE CLUSTER LENSING AND SUPERNOVA SURVEY WITH HUBBLE (CLASH): STRONG-LENSING ANALYSIS OF A383 FROM 16-BAND HST/WFC3/ACS IMAGING

    Zitrin, A. [School of Physics and Astronomy, Tel Aviv University, Tel Aviv (Israel); Broadhurst, T. [Department of Theoretical Physics, University of Basque Country, Bilbao (Spain); Coe, D.; Postman, M.; Bradley, L.; Koekemoer, A. [Space Telescope Science Institute, Baltimore, MD (United States); Umetsu, K. [Institute of Astronomy and Astrophysics, Academia Sinica, Taipei, Taiwan (China); Benitez, N.; Molino, A. [Instituto de Astrofisica de Andalucia (CSIC), Granada (Spain); Meneghetti, M. [INAF, Osservatorio Astronomico di Bologna (Italy); INFN, Sezione di Bologna, Bologna (Italy); Medezinski, E.; Zheng, W.; Ford, H.; Lemze, D. [Department of Physics and Astronomy, The Johns Hopkins University, Baltimore, MD (United States); Jouvel, S.; Lahav, O. [Department of Physics and Astronomy, University College London, London (United Kingdom); Merten, J. [Institut fuer Theoretische Astrophysik, ZAH, Heidelberg (Germany); Kelson, D. [Observatories of the Carnegie Institution of Washington, Pasadena, CA (United States); Nonino, M. [INAF-Osservatorio Astronomico di Trieste, Trieste (Italy); Donahue, M., E-mail: adiz@wise.tau.ac.il [Department of Physics and Astronomy, Michigan State University, East Lansing, MI (United States); and others

    2011-12-01

    We examine the inner mass distribution of the relaxed galaxy cluster A383 (z = 0.189), in deep 16 band Hubble Space Telescope/ACS+WFC3 imaging taken as part of the Cluster Lensing And Supernova survey with Hubble (CLASH) multi-cycle treasury program. Our program is designed to study the dark matter distribution in 25 massive clusters, and balances depth with a wide wavelength coverage, 2000-16000 A, to better identify lensed systems and generate precise photometric redshifts. This photometric information together with the predictive strength of our strong-lensing analysis method identifies 13 new multiply lensed images and candidates, so that a total of 27 multiple images of nine systems are used to tightly constrain the inner mass profile gradient, dlog {Sigma}/dlog r {approx_equal} -0.6 {+-} 0.1 (r < 160 kpc). We find consistency with the standard distance-redshift relation for the full range spanned by the lensed images, 1.01 < z < 6.03, with the higher-redshift sources deflected through larger angles as expected. The inner mass profile derived here is consistent with the results of our independent weak-lensing analysis of wide-field Subaru images, with good agreement in the region of overlap ({approx}0.7-1 arcmin). Combining weak and strong lensing, the overall mass profile is well fitted by a Navarro-Frenk-White profile with M{sub vir} = (5.37{sup +0.70}{sub -0.63} {+-} 0.26) Multiplication-Sign 10{sup 14} M{sub Sun} h{sup -1} and a relatively high concentration, c{sub vir} = 8.77{sup +0.44}{sub -0.42} {+-} 0.23, which lies above the standard c-M relation similar to other well-studied clusters. The critical radius of A383 is modest by the standards of other lensing clusters, r{sub E} {approx_equal} 16 {+-} 2'' (for z{sub s} = 2.55), so the relatively large number of lensed images uncovered here with precise photometric redshifts validates our imaging strategy for the CLASH survey. In total we aim to provide similarly high-quality lensing data for 25

  6. The metal-poor knee in the Fornax dwarf spheroidal galaxy

    Hendricks, Benjamin; Koch, Andreas [Zentrum für Astronomie der Universität Heidelberg, Landessternwarte, Königstuhl 12, D-69117, Heidelberg (Germany); Lanfranchi, Gustavo A. [Núcleo de Astrofísica Teórica, Universidade Cruzeiro do Sul, R. Galvão Bueno 868, Liberdade, 01506-000, São Paulo, SP (Brazil); Boeche, Corrado [Zentrum für Astronomie der Universität Heidelberg, Astronomisches Rechen-Institut, Mönchhofstr. 12-14, D-69120, Heidelberg (Germany); Walker, Matthew [McWilliams Center for Cosmology, Carnegie Mellon University, 5000 Forbes Ave., Pittsburgh, PA 15213 (United States); Johnson, Christian I. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, MS-15, Cambridge, MA 02138 (United States); Peñarrubia, Jorge [Institute for Astronomy, University of Edinburgh, Royal Observatory, Blackford Hill, Edinburgh EH9 3HJ (United Kingdom); Gilmore, Gerard, E-mail: ben.hendricks@lsw.uni-heidelberg.de [Institute of Astronomy, Cambridge University, Madingley Rd, Cambridge CB3 OHA (United Kingdom)

    2014-04-20

    We present α-element abundances of Mg, Si, and Ti for a large sample of field stars in two outer fields of the Fornax dwarf spheroidal (dSph) galaxy, obtained with Very Large Telescope/GIRAFFE (R ∼ 16, 000). Due to the large fraction of metal-poor (MP) stars in our sample, we are able to follow the α-element evolution from [Fe/H] ≈ –2.5 continuously to [Fe/H] ≈ –0.7. For the first time we are able to resolve the turnover from the Type II supernovae (SNe) dominated, α-enhanced plateau down to subsolar [α/Fe] values, due to the onset of SNe Ia, and thus to trace the chemical enrichment efficiency of the galaxy. Our data support the general concept of an α-enhanced plateau at early epochs, followed by a well-defined 'knee' caused by the onset of SNe Ia, and finally a second plateau with sub-solar [α/Fe] values. We find the position of this knee to be at [Fe/H] ≈ –1.9 and therefore significantly more MP than expected from comparison with other dSphs and standard evolutionary models. Surprisingly, this value is rather comparable to the knee in Sculptor, a dSph ∼10 times less luminous than Fornax. Using chemical evolution models, we find that the position of the knee and the subsequent plateau at the sub-solar level can hardly be explained unless the galaxy experienced several discrete star formation (SF) events with a drastic variation in SF efficiency, while a uniform SF can be ruled out. One possible evolutionary scenario is that Fornax experienced one or several major accretion events from gas-rich systems in the past, so that its current stellar mass is not indicative of the chemical evolution environment at ancient times. If Fornax is the product of several smaller buildings blocks, this may also have implications for the understanding of the formation process of dSphs in general.

  7. The metal-poor knee in the Fornax dwarf spheroidal galaxy

    We present α-element abundances of Mg, Si, and Ti for a large sample of field stars in two outer fields of the Fornax dwarf spheroidal (dSph) galaxy, obtained with Very Large Telescope/GIRAFFE (R ∼ 16, 000). Due to the large fraction of metal-poor (MP) stars in our sample, we are able to follow the α-element evolution from [Fe/H] ≈ –2.5 continuously to [Fe/H] ≈ –0.7. For the first time we are able to resolve the turnover from the Type II supernovae (SNe) dominated, α-enhanced plateau down to subsolar [α/Fe] values, due to the onset of SNe Ia, and thus to trace the chemical enrichment efficiency of the galaxy. Our data support the general concept of an α-enhanced plateau at early epochs, followed by a well-defined 'knee' caused by the onset of SNe Ia, and finally a second plateau with sub-solar [α/Fe] values. We find the position of this knee to be at [Fe/H] ≈ –1.9 and therefore significantly more MP than expected from comparison with other dSphs and standard evolutionary models. Surprisingly, this value is rather comparable to the knee in Sculptor, a dSph ∼10 times less luminous than Fornax. Using chemical evolution models, we find that the position of the knee and the subsequent plateau at the sub-solar level can hardly be explained unless the galaxy experienced several discrete star formation (SF) events with a drastic variation in SF efficiency, while a uniform SF can be ruled out. One possible evolutionary scenario is that Fornax experienced one or several major accretion events from gas-rich systems in the past, so that its current stellar mass is not indicative of the chemical evolution environment at ancient times. If Fornax is the product of several smaller buildings blocks, this may also have implications for the understanding of the formation process of dSphs in general.

  8. Clustering

    Jinfei Liu

    2013-04-01

    Full Text Available DBSCAN is a well-known density-based clustering algorithm which offers advantages for finding clusters of arbitrary shapes compared to partitioning and hierarchical clustering methods. However, there are few papers studying the DBSCAN algorithm under the privacy preserving distributed data mining model, in which the data is distributed between two or more parties, and the parties cooperate to obtain the clustering results without revealing the data at the individual parties. In this paper, we address the problem of two-party privacy preserving DBSCAN clustering. We first propose two protocols for privacy preserving DBSCAN clustering over horizontally and vertically partitioned data respectively and then extend them to arbitrarily partitioned data. We also provide performance analysis and privacy proof of our solution..

  9. The HST/ACS Coma Cluster Survey - VII. Structure and Assembly of Massive Galaxies in the Center of the Coma Cluster

    Weinzirl, Tim; Neistein, Eyal; Khochfar, Sadegh; Kormendy, John; Marinova, Irina; Hoyos, Carlos; Balcells, Marc; Brok, Mark den; Hammer, Derek; Peletier, Reynier F; Kleijn, Gijs Verdoes; Carter, David; Goudfrooij, Paul; Mobasher, Bahram; Trentham, Neil; Erwin, Peter; Puzia, Thomas

    2013-01-01

    We constrain the assembly history of galaxies in the central 0.6 Mpc of the rich Coma cluster at z~0.02 based on the structure of 69 massive (M*>1e9 M_sun) galaxies using images from the HST Treasury Survey of Coma. Our findings are: (1) We make no a priori assumptions on the shape of the profile for outer and central structures, which can include disk-dominated components, bars, and classical bulges/ellipticals. After excluding the 2 cDs, we find that most (56%) of the galactic stellar mass resides in classical bulges/Es while (44%) resides in cold disk-dominated structures. This suggests that most of the stellar mass in Coma galaxies may have been assembled and shaped through the redistribution of stars during major mergers, and possibly minor mergers, but that gas-rich dissipative processes that build disk-dominated structures remain important even in the center of a rich cluster like Coma. (2) We see strong evidence of a morphology-density relation. In the central 0.6 Mpc of the Coma cluster, there are 2 ...

  10. The optical gravitational lensing experiment variable stars in globular clusters; 1, fields 5139A-C in Omega Centauri

    Kaluzny, J; Szymanski, M H; Udalski, A; Krzeminski, W; Mateo, M

    1996-01-01

    Three fields covering the central part of the globular cluster Omega Cen were surveyed in a search for variable stars. We present V-band light curves for 22 periodic variables: 9 SX~Phe stars, 7 contact binaries, 5 detached or semi-detached binaries, and one spotted variable (FK Com or RS CVn type star). Only 2 of these variables were previously known. All SX Phe stars and all contact binaries from our sample belong to blue stragglers. Observed properties of these stars are consistent with their cluster membership. Of particular interest is detection of two well detached binaries with periods P=1.50 day and P=2.47 day. Further study of these two binaries can provide direct information about properties of turnoff stars in Omega Cen. An uncomplete light curve of a Mira variable known as V2 was obtained. We present V vs. V-I color-magnitude diagrams for the monitored part of the cluster.

  11. The HST/ACS Coma Cluster Survey III. Structural Parameters of Galaxies using single-S\\'ersic Fits

    Hoyos, Carlos; Kleijn, Gijs Verdoes; Carter, David; Balcells, Marc; Guzman, Rafael; Peletier, Reynier; Ferguson, Henry C; Goudfrooij, Paul; Graham, Alister W; Hammer, Derek; Karick, Arna M; Lucey, John R; Matkovic, Ana; Merritt, David; Mouhcine, Mustapha; Valentijn, Edwin

    2010-01-01

    We present a catalogue of structural parameters for 8814 galaxies in the 25 fields of the HST/ACS Coma Treasury Survey. Parameters from S\\'ersic fits to the two-dimensional surface brightness distributions are given for all galaxies from our published Coma photometric catalogue with mean effective surface brightness brighter than 26.0 mag/sq. arcsec and brighter than 24.5 mag (equivalent to absolute magnitude - 10.5), as given by the fits, all in F814W(AB). The sample comprises a mixture of Coma members and background objects; 424 galaxies have redshifts and of these 163 are confirmed members. The fits were carried out using both the Gim2D and Galfit codes. We provide the following parameters: Galaxy ID, RA, DEC, the total corrected automatic magnitude from the photometric catalogue, the total magnitude of the model (F814W_AB), the geometric mean effective radius Re, the mean surface brightness within the effective radius _e, the S\\'ersic index n, the ellipticity and the source position angle. The selection l...

  12. Dwarf galaxies in the Antlia Cluster: First results

    Castelli, A V S; Cellone, S A; Richtler, T; Dirsch, B; Infante, L; Aruta, C; Gómez, M

    2006-01-01

    We present the first results of a project aimed to study the galaxy population of the Antlia cluster, the third nearest galaxy cluster after Virgo and Fornax. The observations for the Antlia project consist of Washington wide-field images taken with the MOSAIC camera mounted at the prime focus of the CTIO 4-m Blanco telescope. Our preliminary results correspond to the identification and classification of dwarf galaxies in the central cluster region, extending the list of Ferguson & Sandage (1990). The final aim of our project is to study the luminosity function, morphology and structural parameters of dwarf galaxies in the Antlia cluster with a more complete sample.

  13. The Star-forming Region NGC 346 in the Small Magellanic Cloud with Hubble Space Telescope ACS Observations. II. Photometric Study of the Intermediate-Age Star Cluster BS 90

    Rochau, Boyke; Gouliermis, Dimitrios A.; Brandner, Wolfgang; Dolphin, Andrew E.; Henning, Thomas

    2007-01-01

    We present the results of our investigation of the intermediate-age star cluster BS 90, located in the vicinity of the HII region N 66 in the SMC, observed with HST/ACS. The high-resolution data provide a unique opportunity for a very detailed photometric study performed on one of the rare intermediate-age rich SMC clusters. The complete set of observations is centered on the association NGC 346 and contains almost 100,000 stars down to V ~28 mag. In this study we focus on the northern part o...

  14. Prospects of detecting gamma-ray emission from galaxy clusters: cosmic rays and dark matter annihilations

    Pinzke, Anders; Bergstrom, Lars

    2011-01-01

    We study the possibility for detecting gamma-ray emission in galaxy clusters. We consider 1) cosmic ray (CR) induced pion decay which is thought to dominate the astrophysical signal from clusters, 2) different representative benchmark models of supersymmetric dark matter (DM), and 3) leptophilic models of DM annihilation that include a Sommerfeld enhancement (SFE). To model DM annihilation, we consider hadronization of annihilating neutralinos, internal bremsstrahlung, and inverse Compton emission from the cosmic microwave background as well as from a realistic spatial and spectral distribution of dust and stellar light. We predict the Virgo and Fornax clusters to be the brightest DM sources and find a particularly low CR induced background for Fornax. For a minimum substructure mass given by the DM free-streaming scale, we find a substructure boost factor of more than 1000. Since the annihilation flux of substructures is mostly contributed by the regions around the virial radius, the resulting surface bright...

  15. High-quality Spectrophotometry of the Planetary Nebula in the Fornax dSph

    Kniazev, A Yu; Pustilnik, S A; Pramsky, A G

    2007-01-01

    We present results of NTT spectroscopy of the one known planetary nebula (PN) in the dwarf spheroidal galaxy Fornax, a gas-deficient Local Group galaxy that stopped its star formation activity a few hundred million years ago. We detected the [OIII] 4363 line with a signal-to-noise ratio of ~22. For the first time we detected the weak [SII] 6717,6731 lines (I(6717+6731) ~0.01 I(Hbeta)), determined the electron number density (Ne(SII) = 750 cm^-3), and calculated O, N, Ne, Ar, S, Cl, Fe, He and C abundances. The abundance analysis presented here is based on the direct calculation of the electron temperature Te and yields an oxygen abundance of 12+log(O/H) = 8.28+/-0.02. The analysis of the O, Ne, Ar and S abundances shows that the original ISM oxygen abundance was 0.27+/-0.10 dex lower and that third-dredge-up self-pollution in oxygen took place. The blue spectrum shows weak Wolf-Rayet features, and the progenitor star is classified as a weak emission-line star. Four of the five PNe in dwarf spheroidal galaxies...

  16. Hard X-Ray Spectrum from West Lobe of Radio Galaxy Fornax A Observed with Suzaku

    Tashiro, Makoto S; Seta, Hiromi; Matsuta, Keiko; Yaji, Yuichi

    2009-01-01

    An observation of the West lobe of radio galaxy Fornax A (NGC 1316) with Suzaku is reported. Since Feigelson et al. (1995) and Kaneda et al. (1995) discovered the cosmic microwave background boosted inverse-Comptonized (IC) X-rays from the radio lobe, the magnetic field and electron energy density in the lobes have been estimated under the assumption that a single component of the relativistic electrons generates both the IC X-rays and the synchrotron radio emission. However, electrons generating the observed IC X-rays in the 1 -- 10 keV band do not possess sufficient energy to radiate the observed synchrotron radio emission under the estimated magnetic field of a few micro-G. On the basis of observations made with Suzaku, we show in the present paper that a 0.7 -- 20 keV spectrum is well described by a single power-law model with an energy index of 0.68 and a flux density of 0.12+/-0.01 nJy at 1 keV from the West lobe. The derived multiwavelength spectrum strongly suggests that a single electron energy distr...

  17. The metal-poor Knee in the Fornax Dwarf Spheroidal Galaxy

    Hendricks, Benjamin; Lanfranchi, Gustavo A; Boeche, Corrado; Walker, Matthew; Johnson, Christian I; Penarrubia, Jorge; Gilmore, Gerard

    2014-01-01

    We present alpha-element abundances of Mg, Si, and Ti for a large sample of field stars in two outer fields of the Fornax dwarf spheroidal galaxy (dSph), obtained with VLT/GIRAFFE (R~16,000). Due to the large fraction of metal-poor stars in our sample, we are able to follow the alpha-element evolution from [Fe/H]=-2.5 continuously to [Fe/H]=-0.7 dex. For the first time we are able to resolve the turnover from the Type II supernovae (SNe) dominated, alpha-enhanced plateau down to subsolar [alpha/Fe] values due to the onset of SNe Ia, and thus to trace the chemical enrichment efficiency of the galaxy. Our data support the general concept of an alpha-enhanced plateau at early epochs, followed by a well-defined "knee", caused by the onset of SNe Ia, and finally a second plateau with sub-solar [alpha/Fe] values. We find the position of this knee to be at [Fe/H]=-1.9 and therefore significantly more metal-poor than expected from comparison with other dSphs and standard evolutionary models. Surprisingly, this value ...

  18. Globular clusters as tracers of the halo assembly of nearby central cluster galaxies

    Hilker, Michael

    2015-01-01

    The properties of globular cluster systems (GCSs) in the core of the nearby galaxy clusters Fornax and Hydra I are presented. In the Fornax cluster we have gathered the largest radial velocity sample of a GCS system so far, which enables us to identify photometric and kinematic sub-populations around the central galaxy NGC 1399. Moreover, ages, metallicities and [alpha/Fe] abundances of a sub-sample of 60 bright globular clusters (GCs) with high S/N spectroscopy show a multi-modal distribution in the correlation space of these three parameters, confirming heterogeneous stellar populations in the halo of NGC 1399. In the Hydra I cluster very blue GCs were identified. They are not uniformly distributed around the central galaxies. 3-color photometry including the U-band reveals that some of them are of intermediate age. Their location coincides with a group of dwarf galaxies under disruption. This is evidence of a structurally young stellar halo 'still in formation', which is also supported by kinematic measure...

  19. DARK MATTER CORES IN THE FORNAX AND SCULPTOR DWARF GALAXIES: JOINING HALO ASSEMBLY AND DETAILED STAR FORMATION HISTORIES

    We combine the detailed star formation histories of the Fornax and Sculptor dwarf spheroidals with the mass assembly history of their dark matter (DM) halo progenitors to estimate if the energy deposited by Type II supernovae (SNe II) is sufficient to create a substantial DM core. Assuming the efficiency of energy injection of the SNe II into DM particles is εgc = 0.05, we find that a single early episode, z ≳ z infall, that combines the energy of all SNe II due to explode over 0.5 Gyr is sufficient to create a core of several hundred parsecs in both Sculptor and Fornax. Therefore, our results suggest that it is energetically plausible to form cores in cold dark matter (CDM) halos via early episodic gas outflows triggered by SNe II. Furthermore, based on CDM merger rates and phase-space density considerations, we argue that the probability of a subsequent complete regeneration of the cusp is small for a substantial fraction of dwarf-size halos

  20. Insights from the Outskirts: Chemical and Dynamical Properties in the outer Parts of the Fornax Dwarf Spheroidal Galaxy

    Hendricks, Benjamin; Walker, Matthew; Johnson, Christian I; Penarrubia, Jorge; Gilmore, Gerard

    2014-01-01

    We present radial velocities and [Fe/H] abundances for 340 stars in the Fornax dwarf spheroidal from R~16,000 spectra. The targets have been obtained in the outer parts of the galaxy, a region which has been poorly studied before. Our sample shows a wide range in [Fe/H], between -0.5 and -3.0 dex, in which we detect three subgroups. Removal of stars belonging to the most metal-rich population produces a truncated metallicity distribution function that is identical to Sculptor, indicating that these systems have shared a similar early evolution, only that Fornax experienced a late, intense period of star formation (SF). The derived age-metallicity relation shows a fast increase in [Fe/H] at early ages, after which the enrichment flattens significantly for stars younger than ~8 Gyr. Additionally, the data indicate a strong population of stars around 4 Gyr, followed by a second rapid enrichment in [Fe/H]. A leaky-box chemical enrichment model generally matches the observed relation but does not predict a signifi...

  1. VLT AND ACS OBSERVATIONS OF RDCS J1252.9-2927: DYNAMICAL STRUCTURE AND GALAXY POPULATIONS IN A MASSIVE CLUSTER AT Z=1.237*

    Demarco, R; Rosati, P; Lidman, C; Girardi, M; Nonino, M; Rettura, A; Strazzullo, V; der Wel, A v; Ford, H C; Mainieri, V; Holden, B P; Stanford, S A; Blakeslee, J P; Gobat, R; Postman, M; Tozzi, P; Overzier, R A; Zirm, A W; Benitez, N; Homeier, N L; Illingworth, G D; Infante, L; Jee, M J; Mei, S; Menanteau, F; Motta, V; Zheng, W; Clampin, M; Hartig, G

    2007-03-23

    We present results from an extensive spectroscopic survey, carried out with FORS on the ESO Very Large Telescope, and from an extensive multi-wavelength imaging data set from the Advanced Camera for Surveys and ground based facilities of the cluster of galaxies RDCS J1252.9-2927. We have spectroscopically confirmed 38 cluster members in the redshift range 1.22 < z < 1.25. The distribution in velocity of these spectroscopic members yields a cluster median redshift of z = 1.237 and a rest-frame velocity dispersion of 747{sub -84}{sup +74} km s{sup -1}. Star-forming members are observed to mainly populate the outskirts of the cluster while passive galaxies dominate the central cluster region. Using the 38 confirmed redshifts, we were able to resolve, for the first time at z > 1, kinematic structure. The velocity distribution, which is not Gaussian at the 95% confidence level, is consistent with two groups that are also responsible for the projected elongation of the cluster in the East-West direction. The groups are composed of 26 and 12 galaxies and have velocity dispersions of 486{sub -85}{sup +47} km s{sup -1} and 426{sub -105}{sup +57} km s{sup -1}, respectively. The elongation is also seen in the intracluster gas (from X-ray observations) and the dark matter distribution (from a weak lensing analysis). This leads us to conclude that RDCS J1252.9-2927 has not yet reached a final virial state. We extend the analysis of the color-magnitude diagram of spectroscopic members to more than 1 Mpc from the cluster center. The scatter and slope of non-[OII]-emitting cluster members in the near-IR red sequence is similar to that seen in clusters at lower redshift. Furthermore, none of the galaxies with luminosities greater than {approx} K*{sub s} + 1.5 show any [OII] emission feature, indicating that these more luminous, redder galaxies have stopped forming stars earlier than the fainter, bluer galaxies. Our observations provide detailed dynamical and spectrophotometric

  2. The Star-forming Region NGC 346 in the Small Magellanic Cloud with Hubble Space Telescope ACS Observations. II. Photometric Study of the Intermediate-Age Star Cluster BS 90

    Rochau, Boyke; Brandner, Wolfgang; Dolphin, Andrew E; Henning, Thomas

    2007-01-01

    We present the results of our investigation of the intermediate-age star cluster BS 90, located in the vicinity of the HII region N 66 in the SMC, observed with HST/ACS. The high-resolution data provide a unique opportunity for a very detailed photometric study performed on one of the rare intermediate-age rich SMC clusters. The complete set of observations is centered on the association NGC 346 and contains almost 100,000 stars down to V ~28 mag. In this study we focus on the northern part of the region, which covers almost the whole stellar content of BS 90. We construct its stellar surface density profile and derive structural parameters. Isochrone fits on the CMD of the cluster results in an age of about 4.5 Gyr. The luminosity function is constructed and the present-day mass function of BS 90 has been obtained using the mass-luminosity relation, derived from the isochrone models. We found a slope between -1.30 and -0.95, comparable or somewhat shallower than a typical Salpeter IMF. Examination of the rad...

  3. Wide-field Hubble space telescope observations of the globular cluster system in NGC 1399

    We present a comprehensive high spatial resolution imaging study of globular clusters (GCs) in NGC 1399, the central giant elliptical cD galaxy in the Fornax galaxy cluster, conducted with the Advanced Camera for Surveys (ACS) aboard the Hubble Space Telescope (HST). Using a novel technique to construct drizzled point-spread function libraries for HST/ACS data, we accurately determine the fidelity of GC structural parameter measurements from detailed artificial star cluster experiments and show the superior robustness of the GC half-light radius, rh , compared with other GC structural parameters, such as King core and tidal radius. The measurement of rh for the major fraction of the NGC 1399 GC system reveals a trend of increasing rh versus galactocentric distance, R gal, out to about 10 kpc and a flat relation beyond. This trend is very similar for blue and red GCs, which are found to have a mean size ratio of r h, red/r h, blue = 0.82 ± 0.11 at all galactocentric radii from the core regions of the galaxy out to ∼40 kpc. This suggests that the size difference between blue and red GCs is due to internal mechanisms related to the evolution of their constituent stellar populations. Modeling the mass density profile of NGC 1399 shows that additional external dynamical mechanisms are required to limit the GC size in the galaxy halo regions to rh ≈ 2 pc. We suggest that this may be realized by an exotic GC orbit distribution function, an extended dark matter halo, and/or tidal stress induced by the increased stochasticity in the dwarf halo substructure at larger galactocentric distances. We compare our results with the GC rh distribution functions in various galaxies and find that the fraction of extended GCs with rh ≥ 5 pc is systematically larger in late-type galaxies compared with GC systems in early-type galaxies. This is likely due to the dynamically more violent evolution of early-type galaxies. We match our GC rh measurements with radial velocity data from

  4. The Globular Cluster System of the Coma cD Galaxy NGC 4874 from Hubble Space Telescope ACS and WFC3/IR Imaging

    Cho, Hyejeon; Blakeslee, John P.; Chies-Santos, Ana L.; Jee, M. James; Jensen, Joseph B.; Peng, Eric W.; Lee, Young-Wook

    2016-05-01

    We present new Hubble Space Telescope (HST) optical and near-infrared (NIR) photometry of the rich globular cluster (GC) system NGC 4874, the cD galaxy in the core of the Coma cluster (Abell 1656). NGC 4874 was observed with the HST Advanced Camera for Surveys in the F475W (g 475) and F814W (I 814) passbands and with the Wide Field Camera 3 IR Channel in F160W (H 160). The GCs in this field exhibit a bimodal optical color distribution with more than half of the GCs falling on the red side at g 475‑I 814 > 1. Bimodality is also present, though less conspicuously, in the optical-NIR I 814‑H 160 color. Consistent with past work, we find evidence for nonlinearity in the g 475‑I 814 versus I 814‑H 160 color–color relation. Our results thus underscore the need for understanding the detailed form of the color–metallicity relations in interpreting observational data on GC bimodality. We also find a very strong color–magnitude trend, or “blue tilt,” for the blue component of the optical color distribution of the NGC 4874 GC system. A similarly strong trend is present for the overall mean I 814‑H 160 color as a function of magnitude; for M 814 < ‑10 mag, these trends imply a steep mass–metallicity scaling with Z\\propto {M}{{GC}}1.4+/- 0.4, but the scaling is not a simple power law and becomes much weaker at lower masses. As in other similar systems, the spatial distribution of the blue GCs is more extended than that of the red GCs, partly because of blue GCs associated with surrounding cluster galaxies. In addition, the center of the GC system is displaced by 4 ± 1 kpc toward the southwest from the luminosity center of NGC 4874, in the direction of NGC 4872. Finally, we remark on a dwarf elliptical galaxy with a noticeably asymmetrical GC distribution. Interestingly, this dwarf has a velocity of nearly ‑3000 km s‑1 with respect to NGC 4874; we suggest it is on its first infall into the cluster core and is undergoing stripping of its GC system by

  5. The Globular Cluster System of the Coma cD Galaxy NGC 4874 from Hubble Space Telescope ACS and WFC3/IR Imaging

    Cho, Hyejeon; Chies-Santos, Ana L; Jee, M James; Jensen, Joseph B; Peng, Eric W; Lee, Young-Wook

    2016-01-01

    We present new HST optical and near-infrared (NIR) photometry of the rich globular cluster (GC) system of NGC 4874, the cD galaxy in the core of the Coma cluster (Abell 1656). NGC 4874 was observed with the HST Advanced Camera for Surveys in the F475W (g) and F814W (I) passbands and the Wide Field Camera 3 IR Channel in F160W (H). The GCs in this field exhibit a bimodal optical color distribution with more than half of the GCs falling on the red side at g-I > 1. Bimodality is also present, though less conspicuously, in the optical-NIR I-H color. Consistent with past work, we find evidence for nonlinearity in the g-I versus I-H color-color relation. Our results thus underscore the need for understanding the detailed form of the color-metallicity relations in interpreting observational data on GC bimodality. We also find a very strong color-magnitude trend, or "blue tilt," for the blue component of the optical color distribution of the NGC 4874 GC system. A similarly strong trend is present for the overall mean...

  6. Fermi Large Area Telescope Detection of Extended Gamma-Ray Emission from the Radio Galaxy Fornax A

    ,

    2016-01-01

    We report the Fermi Large Area Telescope detection of extended gamma-ray emission from the lobes of the radio galaxy Fornax A using 6.1 years of Pass 8 data. After Centaurus A, this is now the second example of an extended gamma-ray source attributed to a radio galaxy. Both an extended flat disk morphology and a morphology following the extended radio lobes were preferred over a point-source description, and the core contribution was constrained to be 100 MeV gamma-ray emission established, we model the source broadband emission considering currently available total lobe radio and millimeter flux measurements, as well as X-ray detections attributed to inverse Compton (IC) emission off the cosmic microwave background (CMB). Unlike the Centaurus A case, we find that a leptonic model involving IC scattering of CMB and extragalactic background light (EBL) photons underpredicts the gamma-ray fluxes by factors of about ~ 2 - 3, depending on the EBL model adopted. An additional gamma-ray spectral component is thus ...

  7. Mid-infrared dust in two nearby radio galaxies, NGC 1316 (Fornax A) and NGC 612 (PKS 0131-36)

    Asabere, B Duah; Jarrett, T; Winkler, H

    2016-01-01

    Most radio galaxies are hosted by giant gas-poor ellipticals, but some contain significant amounts of dust, which is likely to be of external origin. In order to characterize the mid-IR properties of two of the most nearby and brightest merger-remnant radio galaxies of the Southern hemisphere, NGC 1316 (Fornax A) and NGC 612 (PKS 0131-36), we used observations with the Wide-field Infrared Survey Explorer (WISE) at wavelengths of 3.4, 4.6, 12 and 22 micron and Spitzer mid-infrared spectra. By applying a resolution-enhancement technique, new WISE images were produced at angular resolutions ranging from 2.6" to 5.5". Global measurements were performed in the four WISE bands, and stellar masses and star-formation rates were estimated using published scaling relations. Two methods were used to uncover the distribution of dust, one relying on two-dimensional fits to the 3.4 micron images to model the starlight, and the other one using a simple scaling and subtraction of the 3.4 micron images to estimate the stellar...

  8. Wide-Field Hubble Space Telescope Observations of the Globular Cluster System in NGC 1399*

    Puzia, Thomas H.; Paolillo, Maurizio; Goudfrooij, Paul; Maccarone, Thomas J.; Fabbiano, Giuseppina; Angelini, Lorella

    2014-01-01

    We present a comprehensive high spatial resolution imaging study of globular clusters (GCs) in NGC 1399, thecentral giant elliptical cD galaxy in the Fornax galaxy cluster, conducted with the Advanced Camera for Surveys(ACS) aboard theHubble Space Telescope(HST).Using a novel technique to construct drizzled point-spreadfunction libraries for HSTACS data, we accurately determine the fidelity of GC structural parameter measurementsfrom detailed artificial star cluster experiments and show the superior robustness of the GC half-light radius,rh,compared with other GC structural parameters, such as King core and tidal radius. The measurement ofrhfor themajor fraction of the NGC 1399 GC system reveals a trend of increasingrhversus galactocentric distance,Rgal,out to about 10 kpc and a flat relation beyond. This trend is very similar for blue and red GCs, which are found tohave a mean size ratio ofrh,redrh,blue0.820.11 at all galactocentric radii from the core regions of the galaxyout to40 kpc. This suggests that the size difference between blue and red GCs is due to internal mechanismsrelated to the evolution of their constituent stellar populations. Modeling the mass density profile of NGC 1399shows that additional external dynamical mechanisms are required to limit the GC size in the galaxy halo regionstorh2 pc. We suggest that this may be realized by an exotic GC orbit distribution function, an extended darkmatter halo, andor tidal stress induced by the increased stochasticity in the dwarf halo substructure at largergalactocentric distances. We compare our results with the GCrhdistribution functions in various galaxies and findthat the fraction of extended GCs withrh5 pc is systematically larger in late-type galaxies compared with GCsystems in early-type galaxies. This is likely due to the dynamically more violent evolution of early-type galaxies.We match our GCrhmeasurements with radial velocity data from the literature and split the resulting sample at

  9. The Dynamical Origin of Early-Type Dwarfs in Galaxy Clusters: A Theoretical Investigation

    Vijayaraghavan, Rukmani; Ricker, Paul M

    2014-01-01

    Observations of early-type dwarf galaxies in clusters often show that cluster dwarf members have significantly higher velocities and less symmetric distributions than cluster giant ellipticals, suggesting that these dwarfs are recently accreted galaxies, possibly from an infalling group. We use a series of $N$-body simulations, exploring a parameter space of groups falling into clusters, to study the observed velocity distributions of the infall components along various lines of sight. We show that, as viewed along a line of sight parallel to the group's infall direction, there is a significant peculiar velocity boost during the pericentric passage of the group, and an increase in velocity dispersion that persists for many Gyr after the merger. The remnants of the infalling group, however, do not form a spatially distinct system -- consistent with recent observations of dwarf galaxies in the Virgo and Fornax clusters. This velocity signature is completely absent when viewed along a direction perpendicular to ...

  10. Caracterização sazonal de acúmulos isolados de própolis em colônias de Plebeia emerina (Hymenoptera, Apidae no sul do Brasil Seasonal characterization of isolated propolis clusters in Plebeia emerina (Hymenoptera, Apidae colonies in the south of Brazil

    Camila G. dos Santos

    2009-06-01

    Full Text Available Em colônias de abelhas sem ferrão a aplicação da própolis é ampla, sendo utilizada como matéria-prima nas construções e defesa contra inimigos. Há registros de armazenamento de própolis viscosa, sob forma de acúmulos isolados. Neste trabalho propõe-se a caracterização sazonal da área, do número e da distribuição espacial dos acúmulos isolados de própolis em colônias de Plebeia emerina (Friese, 1900. Colônias foram avaliadas entre outubro/2003 e setembro/2004, medindo-se mensalmente os acúmulos isolados de própolis e registrando-se a posição relativa dos mesmos nas colméias. Entre outubro e março, a área dos acúmulos de própolis nas colônias variou entre 0,50 e 4,92 cm² e o número de acúmulos foi de 3 a 16. No período de abril a setembro, a área foi de 4,54 a 18,48 cm² e o número de acúmulos de 9 a 36. Sugere-se que o aumento da própolis acumulada possa estar relacionado à preparação das colônias para o outonoinverno quando a coleta do produto é reduzida. A análise sazonal da distribuição dos depósitos isolados de própolis corrobora com os registros da área total, indicando preferência da posição anterior da colônia para acumular a própolis. Esta constatação fortalece a hipótese do uso da própolis viscosa dos depósitos isolados na defesa, principalmente junto à entrada das colônias.In colonies of stingless bees, propolis is used for many applications, such as in raw material for constructions and for their defense against enemies. There are records of viscous propolis storage, in form of isolated clusters. In this work, the seasonal characterization of area, number and spatial distribution of isolated propolis clusters in Plebeia emerina (Friese, 1900 colonies is proposed. Colonies were evaluated between October/2003 and September/2004, by measuring in a monthly basis the isolated propolis clusters and recording the relative position of these clusters within the beehives. Between

  11. The binuclear nickel center in the A-cluster of acetyl-CoA synthase (ACS) and two biomimetic dinickel complexes studied by X-ray absorption and emission spectroscopy

    Schrapers, P.; Mebs, S.; Ilina, Y.; Warner, D. S.; Wörmann, C.; Schuth, N.; Kositzki, R.; Dau, H.; Limberg, C.; Dobbek, H.; Haumann, M.

    2016-05-01

    Acetyl-CoA synthase (ACS) is involved in the bacterial carbon oxide conversion pathway. The binuclear nickel sites in ACS enzyme and two biomimetic synthetic compounds containing a Ni(II)Ni(II) unit (1 and 2) were compared using XAS/XES. EXAFS analysis of ACS proteins revealed similar Ni-N/O/S bond lengths and Ni-Ni/Fe distances as in the crystal structure in oxidized ACS, but elongated Ni-ligand bonds in reduced ACS, suggesting more reduced nickel species. The XANES spectra of ACS and the dinickel complexes showed overall similar shapes, but less resolved pre-edge and edge features in ACS, attributed to more distorted square-planar nickel sites in particular in reduced ACS. DFT calculation of pre-edge absorption and Kβ2,5 emission features reproduced the experimental spectra of the synthetic complexes, was sensitive even to the small geometry differences in 1 and 2, and indicated low-spin Ni(II) sites. Comparison of nickel sites in proteins and biomimetic compounds is valuable for deducing structural and electronic differences in response to ligation and redox changes.

  12. K2: A NEW METHOD FOR THE DETECTION OF GALAXY CLUSTERS BASED ON CANADA-FRANCE-HAWAII TELESCOPE LEGACY SURVEY MULTICOLOR IMAGES

    We have developed a new method, K2, optimized for the detection of galaxy clusters in multicolor images. Based on the Red Sequence approach, K2 detects clusters using simultaneous enhancements in both colors and position. The detection significance is robustly determined through extensive Monte Carlo simulations and through comparison with available cluster catalogs based on two different optical methods, and also on X-ray data. K2 also provides quantitative estimates of the candidate clusters' richness and photometric redshifts. Initially, K2 was applied to the two color (gri) 161 deg2 images of the Canada-France-Hawaii Telescope Legacy Survey Wide (CFHTLS-W) data. Our simulations show that the false detection rate for these data, at our selected threshold, is only ∼1%, and that the cluster catalogs are ∼80% complete up to a redshift of z = 0.6 for Fornax-like and richer clusters and to z ∼ 0.3 for poorer clusters. Based on the g-, r-, and i-band photometric catalogs of the Terapix T05 release, 35 clusters/deg2 are detected, with 1-2 Fornax-like or richer clusters every 2 deg2. Catalogs containing data for 6144 galaxy clusters have been prepared, of which 239 are rich clusters. These clusters, especially the latter, are being searched for gravitational lenses-one of our chief motivations for cluster detection in CFHTLS. The K2 method can be easily extended to use additional color information and thus improve overall cluster detection to higher redshifts. The complete set of K2 cluster catalogs, along with the supplementary catalogs for the member galaxies, are available on request from the authors.

  13. Constraining ultracompact dwarf galaxy formation with galaxy clusters in the local universe

    Pfeffer, J.; Hilker, M.; Baumgardt, H.; Griffen, B. F.

    2016-05-01

    We compare the predictions of a semi-analytic model for ultracompact dwarf galaxy (UCD) formation by tidal stripping to the observed properties of globular clusters (GCs) and UCDs in the Fornax and Virgo clusters. For Fornax we find the predicted number of stripped nuclei agrees very well with the excess number of GCs+UCDs above the GC luminosity function. GCs+UCDs with masses >107.3 M⊙ are consistent with being entirely formed by tidal stripping. Stripped nuclei can also account for Virgo UCDs with masses >107.3 M⊙ where numbers are complete by mass. For both Fornax and Virgo, the predicted velocity dispersions and radial distributions of stripped nuclei are consistent with that of UCDs within ˜50-100 kpc but disagree at larger distances where dispersions are too high and radial distributions too extended. Stripped nuclei are predicted to have radially biased anisotropies at all radii, agreeing with Virgo UCDs at clustercentric distances larger than 50 kpc. However, ongoing disruption is not included in our model which would cause orbits to become tangentially biased at small radii. We find the predicted metallicities and central black hole masses of stripped nuclei agree well with the metallicities and implied black hole masses of UCDs for masses >106.5 M⊙. The predicted black hole masses also agree well with that of M60-UCD1, the first UCD with a confirmed central black hole. These results suggest that observed GC+UCD populations are a combination of genuine GCs and stripped nuclei, with the contribution of stripped nuclei increasing towards the high-mass end.

  14. Massive Star Clusters in Dwarf Galaxies

    Larsen, Soeren S

    2015-01-01

    Dwarf galaxies can have very high globular cluster specific frequencies, and the GCs are in general significantly more metal-poor than the bulk of the field stars. In some dwarfs, such as Fornax, WLM, and IKN, the fraction of metal-poor stars that belong to GCs can be as high as 20%-25%, an order of magnitude higher than the 1%-2% typical of GCs in halos of larger galaxies. Given that chemical abundance anomalies appear to be present also in GCs in dwarf galaxies, this implies severe difficulties for self-enrichment scenarios that require GCs to have lost a large fraction of their initial masses. More generally, the number of metal-poor field stars in these galaxies is today less than what would originally have been present in the form of low-mass clusters if the initial cluster mass function was a power-law extending down to low masses. This may imply that the initial GC mass function in these dwarf galaxies was significantly more top-heavy than typically observed in present-day star forming environments.

  15. ACAC Converters for UPS

    Rusalin Lucian R. Păun

    2008-05-01

    Full Text Available This paper propose a new control technique forsingle – phase ACAC converters used for a on-line UPSwith a good dynamic response, a reduced-partscomponents, a good output characteristic, a good powerfactorcorrection(PFC. This converter no needs anisolation transformer. A power factor correction rectifierand an inverter with the proposed control scheme has beendesigned and simulated using Caspoc2007, validating theconcept.

  16. Binary populations in Milky Way satellite galaxies: Constraints from multi-epoch data in the Carina, Fornax, Sculptor, and Sextans dwarf spheroidal galaxies

    We introduce a likelihood analysis of multi-epoch stellar line-of-sight velocities to constrain the binary fractions and binary period distributions of dwarf spheroidal galaxies. This method is applied to multi-epoch data from the Magellan/MMFS survey of the Carina, Fornax, Sculptor, and Sextans dSph galaxies, after applying a model for the measurement errors that accounts for binary orbital motion. We find that the Fornax, Sculptor, and Sextans dSphs are consistent with having binary populations similar to that of Milky Way field binaries to within 68% confidence limits, whereas the Carina dSph is remarkably deficient in binaries with periods less than ∼10 yr. If Carina is assumed to have a period distribution identical to that of the Milky Way field, its best-fit binary fraction is 0.14−0.05+0.28, and is constrained to be less than 0.5 at the 90% confidence level; thus it is unlikely to host a binary population identical to that of the Milky Way field. By contrast, the best-fit binary fraction of the combined sample of all four galaxies is 0.46−0.09+0.13, consistent with that of Milky Way field binaries. More generally, we infer probability distributions in binary fraction, mean orbital period, and dispersion of periods for each galaxy in the sample. Looking ahead to future surveys, we show that the allowed parameter space of binary fraction and period distribution parameters in dSphs will be narrowed significantly by a large multi-epoch survey. However, there is a degeneracy between the parameters that is unlikely to be broken unless the measurement error is of order ∼0.1 km s–1 or smaller, presently attainable only by a high-resolution spectrograph.

  17. Mid-infrared dust in two nearby radio galaxies, NGC 1316 (Fornax A) and NGC 612 (PKS 0131-36)

    Duah Asabere, B.; Horellou, C.; Jarrett, T. H.; Winkler, H.

    2016-07-01

    Context. Most radio galaxies are hosted by giant gas-poor ellipticals, but some contain significant amounts of dust, which is likely to be of external origin. Aims: In order to characterize the mid-IR properties of two of the most nearby and brightest merger-remnant radio galaxies of the Southern hemisphere, NGC 1316 (Fornax A) and NGC 612 (PKS 0131-36), we used observations with the Wide-field Infrared Survey Explorer (WISE) at wavelengths of 3.4, 4.6, 12 and 22 μm and Spitzer mid-infrared spectra. Methods: By applying a resolution-enhancement technique, new WISE images were produced at angular resolutions ranging from 2.̋6 to 5.̋5. Global measurements were performed in the four WISE bands, and stellar masses and star-formation rates were estimated using published scaling relations. Two methods were used to uncover the distribution of dust, one relying on two-dimensional fits to the 3.4 μm images to model the starlight, and the other one using a simple scaling and subtraction of the 3.4 μm images to estimate the stellar continuum contribution to the emission in the 12 and 22 μm bands. Results: The two galaxies differ markedly in their mid-IR properties. The 3.4 μm brightness distribution can be well represented by the superposition of two Sérsic models in NGC 1316 and by a Sérsic model and an exponential disk in NGC 612. The WISE colors of NGC 1316 are typical of those of early-type galaxies; those of NGC 612 are in the range found for star-forming galaxies. From the 22 μm luminosity, we infer a star-formation rate of ~0.7 M⊙ yr-1 in NGC 1316 and ~7 M⊙ yr-1 in NGC 612. Spitzer spectroscopy shows that the 7.7-to-11.3 μm PAH line ratio is significantly lower in NGC 1316 than in NGC 612. The WISE images reveal resolved emission from dust in the central 1'-2' of the galaxies. In NGC 1316, the extra-nuclear emission coincides with two dusty regions NW and SE of the nucleus seen in extinction in optical images and where molecular gas is known to reside

  18. AC power supply systems

    An ac power supply system includes a rectifier fed by a normal ac supply, and an inverter connected to the rectifier by a dc link, the inverter being effective to invert the dc output of the receiver at a required frequency to provide an ac output. A dc backup power supply of lower voltage than the normal dc output of the rectifier is connected across the dc link such that the ac output of the rectifier is derived from the backup supply if the voltage of the output of the inverter falls below that of the backup supply. The dc backup power may be derived from a backup ac supply. Use in pumping coolant in nuclear reactor is envisaged. (author)

  19. AcEST: DK950971 [AcEST

    Full Text Available optera acutorost... 37 0.66 tr|B1ACS6|B1ACS6_BALBN DMP1 (Fragment) OS=Balaenoptera ...bonaerens... 37 0.66 tr|B1ACS5|B1ACS5_BALED DMP1 (Fragment) OS=Balaenoptera edeni... GN=... 37 0.66 tr|B1ACS4|B1ACS4_BALBO DMP1 (Fragment) OS=Balaenoptera borealis ... 37 0.66 tr|B1ACS3|B1ACS3..._BALMU DMP1 (Fragment) OS=Balaenoptera musculus ... 37 0.86 tr|B1ACS1|B1ACS1_MEGNO DMP1 (Fragment) OS=Megapt...1ACS2_BALPH DMP1 (Fragment) OS=Balaenoptera physalus ... 37 1.1 tr|B1ACT6|B1ACT6_MESPE DMP1 (Fragment) OS=Me

  20. Scaling and universality of ac conduction in disordered solids

    Schrøder, Thomas; Dyre, Jeppe

    2000-01-01

    Recent scaling results for the ac conductivity of ionic glasses by Roling et al. [Phys. Rev. Lett. 78, 2160 (1997)] and Sidebottom [Phys. Rev. Lett. 82, 3653 (1999)] are discussed. We prove that Sidebottom's version of scaling is completely general. A new approximation to the universal ac conduct...... conductivity arising in the extreme disorder limit of the symmetric hopping model, the "diffusion cluster approximation," is presented and compared to computer simulations and experiments....

  1. AC1 Wing

    Adrian DOBRE

    2010-03-01

    Full Text Available The AC1 wing replaces the old wing of the wind tunnel model AEROTAXI, which has been made at scale 1:9. The new wing is part of CESAR program and improves the aerodynamic characteristics of the old one. The geometry of the whole wing was given by FOI Sweden and position of AC1 wing must coincide with the structure of the AEROTAXI model.

  2. AC1 Wing

    Adrian DOBRE

    2010-01-01

    The AC1 wing replaces the old wing of the wind tunnel model AEROTAXI, which has been made at scale 1:9. The new wing is part of CESAR program and improves the aerodynamic characteristics of the old one. The geometry of the whole wing was given by FOI Sweden and position of AC1 wing must coincide with the structure of the AEROTAXI model.

  3. ac bidirectional motor controller

    Schreiner, K.

    1988-01-01

    Test data are presented and the design of a high-efficiency motor/generator controller at NASA-Lewis for use with the Space Station power system testbed is described. The bidirectional motor driver is a 20 kHz to variable frequency three-phase ac converter that operates from the high-frequency ac bus being designed for the Space Station. A zero-voltage-switching pulse-density-modulation technique is used in the converter to shape the low-frequency output waveform.

  4. Dwarf Galaxies in the Coma Cluster; 2, Photometry and Analysis

    Secker, J; Plummer, J D; Secker, Jeff; Harris, William E.; Plummer, Julia D.

    1997-01-01

    We study the dwarf galaxy population in the central ~700 arcmin^2 of the Coma cluster, the majority of which are early-type dwarf elliptical (dE) galaxies. Analysis of the statistically-decontaminated dE galaxy sequence in the color-magnitude diagram reveals a highly significant trend of color with magnitude (\\Delta (B-R)/\\Delta R = -0.056\\pm0.002 mag), in the sense that fainter dEs are bluer and thus presumably more metal-poor. The mean color of the faintest dEs in our sample is (B-R)~1.15 mag, consistent with a color measurement of the diffuse intracluster light in the Coma core. This intracluster light could then have originated from the tidal disruption of faint dEs in the cluster core. The total galaxy luminosity function (LF) is well modeled as the sum of a log-normal distribution for the giant galaxies, and a Schechter function for the dE galaxies with a faint-end slope \\alpha = -1.41\\pm0.05. This value of \\alpha is consistent with those measured for the Virgo and Fornax clusters. The spatial distribut...

  5. Featured Image: A Galaxy Plunges Into a Cluster Core

    Kohler, Susanna

    2015-10-01

    The galaxy that takes up most of the frame in this stunning image (click for the full view!) is NGC 1427A. This is a dwarf irregular galaxy (unlike the fortuitously-located background spiral galaxy in the lower right corner of the image), and its currently in the process of plunging into the center of the Fornax galaxy cluster. Marcelo Mora (Pontifical Catholic University of Chile) and collaborators have analyzed observations of this galaxy made by both the Very Large Telescope in Chile and the Hubble Advanced Camera for Surveys, which produced the image shown here as a color composite in three channels. The team worked to characterize the clusters of star formation within NGC 1427A identifiable in the image as bright knots within the galaxy and determine how the interactions of this galaxy with its cluster environment affect the star formation within it. For more information and the original image, see the paper below.Citation:Marcelo D. Mora et al 2015 AJ 150 93. doi:10.1088/0004-6256/150/3/93

  6. Cluster Automorphisms

    Assem, Ibrahim; Schiffler, Ralf; Shramchenko, Vasilisa

    2010-01-01

    In this article, we introduce the notion of cluster automorphism of a given cluster algebra as a $\\ZZ$-automorphism of the cluster algebra that sends a cluster to another and commutes with mutations. We study the group of cluster automorphisms in detail for acyclic cluster algebras and cluster algebras from surfaces, and we compute this group explicitly for the Dynkin types and the Euclidean types.

  7. AC/RF Superconductivity

    Ciovati, Gianluigi [JLAB

    2015-02-01

    This contribution provides a brief introduction to AC/RF superconductivity, with an emphasis on application to accelerators. The topics covered include the surface impedance of normal conductors and superconductors, the residual resistance, the field dependence of the surface resistance, and the superheating field.

  8. AC/RF Superconductivity

    Ciovati, G.

    2015-01-01

    This contribution provides a brief introduction to AC/RF superconductivity, with an emphasis on application to accelerators. The topics covered include the surface impedance of normal conductors and superconductors, the residual resistance, the field dependence of the surface resistance, and the superheating field.

  9. Increased Ac excision (iae): Arabidopsis thaliana mutations affecting Ac transposition

    The maize transposable element Ac is highly active in the heterologous hosts tobacco and tomato, but shows very much reduced levels of activity in Arabidopsis. A mutagenesis experiment was undertaken with the aim of identifying Arabidopsis host factors responsible for the observed low levels of Ac activity. Seed from a line carrying a single copy of the Ac element inserted into the streptomycin phosphotransferase (SPT) reporter fusion, and which displayed typically low levels of Ac activity, were mutagenized using gamma rays. Nineteen mutants displaying high levels of somatic Ac activity, as judged by their highly variegated phenotypes, were isolated after screening the M2 generation on streptomycin-containing medium. The mutations fall into two complementation groups, iae1 and iae2, are unlinked to the SPT::Ac locus and segregate in a Mendelian fashion. The iae1 mutation is recessive and the iae2 mutation is semi-dominant. The iae1 and iae2 mutants show 550- and 70-fold increases, respectively, in the average number of Ac excision sectors per cotyledon. The IAE1 locus maps to chromosome 2, whereas the SPT::Ac reporter maps to chromosome 3. A molecular study of Ac activity in the iae1 mutant confirmed the very high levels of Ac excision predicted using the phenotypic assay, but revealed only low levels of Ac re-insertion. Analyses of germinal transposition in the iae1 mutant demonstrated an average germinal excision frequency of 3% and a frequency of independent Ac re-insertions following germinal excision of 22%. The iae mutants represents a possible means of improving the efficiency of Ac/Ds transposon tagging systems in Arabidopsis, and will enable the dissection of host involvement in Ac transposition and the mechanisms employed for controlling transposable element activity

  10. Hybrid AC-DC offshore wind power plant topology: optimal design

    Prada Gil, Mikel de; Igualada González, Lucía; Corchero García, Cristina; Gomis Bellmunt, Oriol; Sumper, Andreas

    2015-01-01

    The aim of this paper is to present a hybrid AC-DC offshore wind power plant (OWPP) topology and to optimize its design in order to minimize the OWPP's total cost. This hybrid concept is based on clustering wind turbines and connecting each group to an AC/DC power converter installed on a collector platform which is located between the AC wind turbine array and the HVDC offshore platform. Thereby, individual power converters of each wind turbine are not required, since such AC/DC converters c...

  11. Hermetisk AC-Krets

    Hirsch, Carl; Smirnoff, Alexander

    2007-01-01

    Under sex månader våren 2007 har ett samarbete mellan Volvo Lastvagnar och två studenter från KTH, inriktning Integrerad produktutveckling vid institutionen för maskinkonstruktion, pågått i form av ett examensarbete på 20 poäng. Dagens AC-system i Volvos lastbilar avger 20-40 g/år av köldmediet R134a som är en kraftfull växthusgas. Detta sker främst genom diffusion via slangar och tätningsmaterial. Syftet med detta examensarbete är att ta fram förslag på tekniska lösningar på ett nytt AC-syst...

  12. UCDs in the Coma Cluster

    Chiboucas, Kristin; Marzke, Ronald O; Phillipps, Steven; Price, James; Peng, Eric W; Trentham, Neil; Carter, David; Hammer, Derek

    2010-01-01

    As part of the HST/ACS Coma Cluster Treasury Survey, we have undertaken a Keck/LRIS spectroscopic campaign to determine membership for faint dwarf galaxies. In the process, we discovered a population of Ultra Compact Dwarf galaxies (UCDs) in the core region of the Coma cluster. At the distance of Coma, UCDs are expected to have angular sizes 0.01 < R_e < 0.2 arcsec. With ACS imaging, we can resolve all but the smallest ones with careful fitting. Candidate UCDs were chosen based on magnitude, color, and degree of resolution. We spectroscopically confirm 27 objects as bona fide UCD members of the Coma cluster, a 60% success rate for objects targeted with M_R < -12. We attribute the high success rate in part to the high resolution of HST data and to an apparent large population of UCDs in Coma. We find that the UCDs tend to be strongly clustered around giant galaxies, at least in the core region of the cluster, and have a distribution and colors that are similar to globular clusters. These findings sugg...

  13. Dwarf galaxy populations in present-day galaxy clusters: I. Abundances and red fractions

    Weinmann, Simone M; Guo, Qi; Meyer, Hagen T; Janz, Joachim

    2011-01-01

    We compare the galaxy population in the Virgo, Fornax, Coma and Perseus cluster to a state-of-the-art semi-analytic model, focusing on the regime of dwarf galaxies with luminosities from approximately 10^8 L_sun to 10^9 L_sun. We find that the number density profiles of dwarfs in observed clusters are reproduced reasonably well, and that the red fractions of model clusters provide a good match to Coma and Perseus. On the other hand, the red fraction among dwarf galaxies in Virgo is clearly lower than in model clusters. We argue that this is mainly caused by the treatment of environmental effects in the model. This explanation is supported by our finding that the colours of central ("field") dwarf galaxies are reproduced well, in contrast to previous claims. Finally, we report on several differences in the properties of galaxies in observed and simulated clusters that may indicate an underestimate of tidal disruption in the model: The dwarf-to-giant ratio is too high in the model; there is an unexplained flatt...

  14. The early-type dwarf galaxy population of the Hydra I cluster

    Misgeld, I; Hilker, M

    2008-01-01

    We analyse the properties of the early-type dwarf galaxy population in the Hydra I cluster. We investigate the galaxy luminosity function (LF), the colour-magnitude relation (CMR), and the magnitude-surface brightness relation down to M_V -10 mag. Another goal of this study is to find candidates for ultra-compact dwarf galaxies (UCDs). Two spectroscopic surveys performed with Magellan I/LDSS2 and VLT/VIMOS, as well as deep VLT/FORS1 images in V and I bands were examined. We identify cluster members by radial velocity measurements and select other cluster galaxy candidates by their morphology. One possible UCD candidate with M_V=-13.26 mag is found. Our sample of 100 morphologically selected dwarf galaxies defines a CMR that extends the CMR of the giant cluster galaxies to the magnitude limit of our survey (M_V -10 mag). It matches the relations found for the Local Group and the Fornax cluster dwarfs almost perfectly. The Hydra I dwarfs also follow a magnitude-surface brightness relation similar to that of the...

  15. Constraining Extended Gamma-ray Emission from Galaxy Clusters

    Han, Jiaxin; Eke, Vincent R; Gao, Liang; White, Simon D M; Boyarsky, Alexey; Malyshev, Denys; Ruchayskiy, Oleg

    2012-01-01

    Cold dark matter models predict the existence of a large number of substructures within dark matter halos. If the cold dark matter consists of weakly interacting massive particles, their annihilation within these substructures could lead to diffuse GeV emission that would dominate over the annihilation signal of the host halo. In this work we search for GeV emission from three nearby galaxy clusters: Coma, Virgo and Fornax. We first remove known extragalactic and galactic diffuse gamma-ray backgrounds and point sources from the Fermi 2-year catalog and find a significant residual diffuse emission in all three clusters. We then investigate whether this emission is due to (i) unresolved point sources; (ii) dark matter annihilation; or (iii) cosmic rays (CR). Using 45 months of Fermi-LAT data we detect several new point sources (not present in the Fermi 2-year point source catalogue) which contaminate the signal previously analyzed by Han et al.(arxiv:1201.1003). Including these and accounting for the effects of...

  16. Globular cluster clustering and tidal features around ultra compact dwarf galaxies in the halo of NGC1399

    Voggel, Karina; Richtler, Tom

    2015-01-01

    We present a novel approach to constrain the formation channels of Ultra-Compact Dwarf Galaxies (UCDs). This inhomogeneous class of objects of remnants of tidally stripped dwarf elliptical galaxies and high mass globular clusters. We use three methods to unravel their nature: 1) we analysed their surface brightness profiles, 2) we carried out a direct search for tidal features around UCDs and 3) we compared the spatial distribution of GCs and UCDs in the halo of their host galaxy. Based on FORS2 observations, we have studied the detailed structural composition of a large sample of 97 UCDs in the halo of NGC1399, the central galaxy of the Fornax cluster, by analysing theirsurface brightness profiles. We derived the structural parameters of 13 extended UCDs modelling them with a single Sersic function and decomposing them into composite King and Sersic profiles. We find evidence for faint stellar envelopes at mu=~26 mag\\arcsec^-2 surrounding the UCDs up to an extension of 90pc in radius. We also show new eviden...

  17. Weighted Clustering

    Ackerman, Margareta; Ben-David, Shai; Branzei, Simina;

    2012-01-01

    We investigate a natural generalization of the classical clustering problem, considering clustering tasks in which different instances may have different weights.We conduct the first extensive theoretical analysis on the influence of weighted data on standard clustering algorithms in both the...... partitional and hierarchical settings, characterizing the conditions under which algorithms react to weights. Extending a recent framework for clustering algorithm selection, we propose intuitive properties that would allow users to choose between clustering algorithms in the weighted setting and classify...

  18. Cluster Headache

    Frederick G Freitag

    1985-01-01

    Learning Objectives: Review the current understanding of the pathophysiology of cluster headache Be able to recognize the clinical features of cluster headache Be able to develop a strategy for treatment of cluster headache Cluster headache is divided into multiple subtypes under the IHC classification criteria. The vast majority of patients present with episodic cluster headache (3.1.1). This will be the focus of the presentation. The syndrome is characterized by repeated at...

  19. High performance AC drives

    Ahmad, Mukhtar

    2010-01-01

    This book presents a comprehensive view of high performance ac drives. It may be considered as both a text book for graduate students and as an up-to-date monograph. It may also be used by R & D professionals involved in the improvement of performance of drives in the industries. The book will also be beneficial to the researchers pursuing work on multiphase drives as well as sensorless and direct torque control of electric drives since up-to date references in these topics are provided. It will also provide few examples of modeling, analysis and control of electric drives using MATLAB/SIMULIN

  20. Superconducting ac cable

    The components of a superconducting 110 kV ac cable for power ratings >= 2000 MVA have been developed. The cable design especially considered was of the semiflexible type, with a rigid cryogenic envelope and flexible hollow coaxial cable cores pulled into the former. The cable core consists of spirally wound Nb-Al composite wires and a HDPE-tape wrapped electrical insulation. A 35 m long single phase test cable with full load terminations for 110 kV and 10 kA was constructed and successfully tested. The results obtained prove the technical feasibility and capability of our cable design. (orig.)

  1. Cluster headache

    Histamine headache; Headache - histamine; Migrainous neuralgia; Headache - cluster; Horton's headache ... Doctors do not know exactly what causes cluster headaches. They ... (chemical in the body released during an allergic response) or ...

  2. Isotopic clusters

    Spectra of isotopically mixed clusters (dimers of SF6) are calculated as well as transition frequencies. The result leads to speculations about the suitability of the laser-cluster fragmentation process for isotope separation. (Auth.)

  3. Searching for star-forming dwarf galaxies in the Antlia cluster

    Vaduvescu, O; Bassino, L P; Castelli, A V Smith; Calderon, J P

    2014-01-01

    The formation and evolution of dwarf galaxies in clusters need to be understood, and this requires large aperture telescopes. In this sense, we selected the Antlia cluster to continue our previous work in the Virgo, Fornax, and Hydra clusters and in the Local Volume (LV). Because of the scarce available literature data, we selected a small sample of five blue compact dwarf (BCD) candidates in Antlia for observation. Using the Gemini South and GMOS camera, we acquired the Halpha imaging needed to detect star-forming regions in this sample. With the long-slit spectroscopic data of the brightest seven knots detected in three BCD candidates, we derived their basic chemical properties. Using archival VISTA VHS survey images, we derived K_S magnitudes and surface brightness profile fits for the whole sample to assess basic physical properties. FS90-98, FS90-106, and FS90-147 are confirmed as BCDs and cluster members, based on their morphology, K_S surface photometry, oxygen abundance, and velocity redshift. FS90-15...

  4. Weighted Clustering

    Ackerman, Margareta; Ben-David, Shai; Branzei, Simina; Loker, David

    2012-01-01

    We investigate a natural generalization of the classical clusteringproblem, considering clustering tasks in which differentinstances may have different weights.We conduct the firstextensive theoretical analysis on the influence of weighteddata on standard clustering algorithms in both the partitionaland hierarchical settings, characterizing the conditions underwhich algorithms react to weights. Extending a recent frameworkfor clustering algorithm selection, we propose intuitiveproperties that...

  5. Meaningful Clusters

    Sanfilippo, Antonio P.; Calapristi, Augustin J.; Crow, Vernon L.; Hetzler, Elizabeth G.; Turner, Alan E.

    2004-05-26

    We present an approach to the disambiguation of cluster labels that capitalizes on the notion of semantic similarity to assign WordNet senses to cluster labels. The approach provides interesting insights on how document clustering can provide the basis for developing a novel approach to word sense disambiguation.

  6. Ac Hybrid Charge Controller

    Shalini S. Durgam

    2015-03-01

    Full Text Available One of the primary needs for socio-economic development in any nation in the world is the provision of reliable electricity supply systems with lower carbon footprint levels. The purpose of this work is the development of a hybrid Power system that harnesses the renewable energy in sun and electricity to generate electricity. The working model can able to run on dual mode- solar and electricity. It can also be driven independently either by solar or electricity. The battery can be charge from solar panel (40W or by power supply. The household single phase A.C. power supply of 230V is converted into 12V D.C. using step down transformer and rectifying circuit. The working model can achieve energy saving, low carbon emission, environmental protection for the upcoming future of human life.

  7. Cluster Lenses

    Kneib, Jean-Paul; 10.1007/s00159-011-0047-3

    2012-01-01

    Clusters of galaxies are the most recently assembled, massive, bound structures in the Universe. As predicted by General Relativity, given their masses, clusters strongly deform space-time in their vicinity. Clusters act as some of the most powerful gravitational lenses in the Universe. Light rays traversing through clusters from distant sources are hence deflected, and the resulting images of these distant objects therefore appear distorted and magnified. Lensing by clusters occurs in two regimes, each with unique observational signatures. The strong lensing regime is characterized by effects readily seen by eye, namely, the production of giant arcs, multiple-images, and arclets. The weak lensing regime is characterized by small deformations in the shapes of background galaxies only detectable statistically. Cluster lenses have been exploited successfully to address several important current questions in cosmology: (i) the study of the lens(es) - understanding cluster mass distributions and issues pertaining...

  8. AcEST: BP920072 [AcEST

    Full Text Available YMU001_000132_F11 525 Adiantum capillus-veneris mRNA. clone: YMU001_000132_F11. BP920072 - Show ... YGMYGEGEKALETFADMEKSGIVPDSVVFIAII 617 Query: 139 NACSR SCLFHECHSYFEAMSTHHGIVPCLEHHSCVV 32 ACS S L E + FE M ... KLMTRDVVSWNTLIAGYAQVGQNEGLFCTFSDMLGQRVKPDLITFVIVLNACSR ... 125 VF+ + +D VSWN++I+GY Q G F M+ + D IT++++++ +R S ... YGVHGYGKKAIQIFEEMLANGASP 384 Query: 166 DLITFVIVLNACSR SCLFHECHSYFEAMSTHHGIVPCLEHHSCVV 32 +TFV VL ACS L E ... KLMTRDVVSWNTLIAGYAQVGQNEGLFCTFSDMLGQRVKPDLITFVIVLNACSR S 122 +VFDK R + WN L G E + + M V+ D T+ VL AC S Sbjc ...

  9. Stellar Populations of Bulges in 14 Cluster Disc Galaxies

    Morelli, L; Pizzella, A; Méndez-Abreu, J; Corsini, E M; Coccato, L; Saglia, R P; Sarzi, M; Bertola, F

    2008-01-01

    Photometry and long-slit spectroscopy are presented for 14 S0 and spiral galaxies of the Fornax, Eridanus and Pegasus cluster, and NGC 7582 group. The structural parameters of the galaxies are derived from the R-band images by performing a two-dimensional photometric decomposition of the surface-brightness distribution. This is assumed to be the sum of the contribution of a bulge and disc component characterized by elliptical and concentric isophotes with constant (but possibly different) ellipticity and position angles. The rotation curves and velocity dispersion profiles are measured from the spectra obtained along the major axis of galaxies. The radial profiles of the Hb, Mg, and Fe line-strength indices are presented too. Correlations between the central values of Mgd, , Hb, and sigma are found. The age, metallicity and alpha/Fe enhancement of the stellar population in the center and at the radius where bulge and disc give the same contribution to the total surface brightness are obtained using stellar po...

  10. Data Clustering

    Wagstaff, Kiri L.

    2012-03-01

    On obtaining a new data set, the researcher is immediately faced with the challenge of obtaining a high-level understanding from the observations. What does a typical item look like? What are the dominant trends? How many distinct groups are included in the data set, and how is each one characterized? Which observable values are common, and which rarely occur? Which items stand out as anomalies or outliers from the rest of the data? This challenge is exacerbated by the steady growth in data set size [11] as new instruments push into new frontiers of parameter space, via improvements in temporal, spatial, and spectral resolution, or by the desire to "fuse" observations from different modalities and instruments into a larger-picture understanding of the same underlying phenomenon. Data clustering algorithms provide a variety of solutions for this task. They can generate summaries, locate outliers, compress data, identify dense or sparse regions of feature space, and build data models. It is useful to note up front that "clusters" in this context refer to groups of items within some descriptive feature space, not (necessarily) to "galaxy clusters" which are dense regions in physical space. The goal of this chapter is to survey a variety of data clustering methods, with an eye toward their applicability to astronomical data analysis. In addition to improving the individual researcher’s understanding of a given data set, clustering has led directly to scientific advances, such as the discovery of new subclasses of stars [14] and gamma-ray bursts (GRBs) [38]. All clustering algorithms seek to identify groups within a data set that reflect some observed, quantifiable structure. Clustering is traditionally an unsupervised approach to data analysis, in the sense that it operates without any direct guidance about which items should be assigned to which clusters. There has been a recent trend in the clustering literature toward supporting semisupervised or constrained

  11. Induction Motor Control through AC/DC/AC Converters

    Elfadili, Abderrahim; Giri, Fouad; Ouadi, Hamid; El Magri, Abdelmounime; Dugard, Luc; Abouloifa, Abdelmajid

    2010-01-01

    We consider the problem of controlling inductions motors driven through AC/DC rectifiers and DC/AC inverters. The control objectives are threefold: (i) forcing the motor speed to track a reference signal, (ii) regulating the DC Link voltage, (iii) assuring a satisfactory power factor correction (PFC) with respect to the power supply net. First, a nonlinear model of the whole controlled system is developed in the Park-coordinates. Then, a nonlinear multi-loop controller is synthesized using th...

  12. AcEST: BP920905 [AcEST

    Full Text Available EM + + D ++S L AC Sbjct: 374 NSAYKLFERMPKKNVVAWNAIISGYSQHGHPHEALALFIEMQAQGIKPDSFAIVSVLPAC 433 Query: 71 SHSSTLNDGKLIHFYILMNNFE...EM++ ++ + V + S L +C Sbjct: 255 SSERIFEKIAKKNAVSWTAMISSYNRGEFSEKALRSFSEMIKSGIEPNLVTLYSVLSSCG 314 Query: 68 HSSTLNDGKLIHFYILMNNFE...VVVMSCLKACS 69 ++ +F RRD VTW A+I GYA HG E A+ LF+ M+ EN+ + V +S L+AC+ Sbjct: 656 DSRLMFEKSLRRDFVTWNAMICGYAHHGKGEEAIQLFERMILEN...ELEKMHNKRLQEMCVSWNSIISGYVMKEQSEDAQMLFTRMME 596 Query: 122 ENVDTDGVVVMSCLKACSHSSTLNDGKLIHFYILMNNFE ...FCEADT-NVITWNAMIASYVHCEQSEKAIALFDRMVSENFKPSSITLVTLLMAC 543 Query: 71 SHSSTLNDGKLIHFYILMNNFEL 3 ++ +L G++

  13. AcEST: DK950147 [AcEST

    Full Text Available TST38A01NGRL0007_O05 706 Adiantum capillus-veneris mRNA. clone: TST38A01NGRL0007_O05. 5' end seq ... _MEDTR Peptidase, trypsin-like serine and cysteine proteases ... OS=Medicago truncatula GN=MtrDRAFT_AC149576g3v2 PE ... _MEDTR Peptidase, trypsin-like serine and cysteine proteases ... (Fragment) OS=Medicago truncatula GN=MtrDRAFT_AC14 ...

  14. AcEST: DK959344 [AcEST

    Full Text Available TST39A01NGRL0004_G23 714 Adiantum capillus-veneris mRNA. clone: TST39A01NGRL0004_G23. 5' end seq ... _MEDTR Peptidase, trypsin-like serine and cysteine proteases ... OS=Medicago truncatula GN=MtrDRAFT_AC149576g3v2 PE ... _MEDTR Peptidase, trypsin-like serine and cysteine proteases ... (Fragment) OS=Medicago truncatula GN=MtrDRAFT_AC14 ...

  15. AcEST: DK949716 [AcEST

    Full Text Available TST38A01NGRL0006_L20 613 Adiantum capillus-veneris mRNA. clone: TST38A01NGRL0006_L20. 5' end seq ... _MEDTR Peptidase, trypsin-like serine and cysteine proteases ... OS=Medicago truncatula GN=MtrDRAFT_AC149576g3v2 PE ... _MEDTR Peptidase, trypsin-like serine and cysteine proteases ... (Fragment) OS=Medicago truncatula GN=MtrDRAFT_AC14 ...

  16. AC drives for industrial plants. Plant kudoyo AC drive sochi

    Miyazaki, M.; Shibata, M.; Yamada, S. (Toshiba Corp., Tokyo (Japan))

    1992-08-01

    Features and product series of AC drives for industrial plants were outlined. Configurations and features of various types of AC drives were briefly discussed which are put into market to meet various requirements for industrial plants and wide ranges of output voltage and capacity. The following product series were outlined; the power bipolar transistor inverter for 3.5-600 kVA in output capacity, IGBT inverter for AC 400 V in output voltage and 1,000 kVA or less, GTO inverter for AC 600 V and 700-2,000 kVA, and cycloconverter for AC 1,000-3,000 V and 1,000 kW-20 MW. The following subjects were outlined as current technical trends of AC drives for industrial plants; increasing in capacity of voltage-source PWM inverters, downsizing of converters through highly efficient cooling and highly dense mounting, spreading of sensorless vector controls, and development of high-voltage large-capacity PWM inverters. 6 figs., 2 tabs.

  17. Cluster Chemistry

    2011-01-01

    @@ Cansisting of eight scientists from the State Key Laboratory of Physical Chemistry of Solid Surfaces and Xiamen University, this creative research group is devoted to the research of cluster chemistry and creation of nanomaterials.After three-year hard work, the group scored a series of encouraging progresses in synthesis of clusters with special structures, including novel fullerenes, fullerene-like metal cluster compounds as well as other related nanomaterials, and their properties study.

  18. Carbon in Red Giants in Globular Clusters and Dwarf Spheroidal Galaxies

    Kirby, Evan N; Zhang, Andrew J; Deng, Michelle; Cohen, Judith G; Guhathakurta, Puragra; Shetrone, Matthew D; Lee, Young Sun; Rizzi, Luca

    2015-01-01

    We present carbon abundances of red giants in Milky Way globular clusters and dwarf spheroidal galaxies (dSphs). Our sample includes measurements of carbon abundances for 154 giants in the clusters NGC 2419, M68, and M15 and 398 giants in the dSphs Sculptor, Fornax, Ursa Minor, and Draco. This sample doubles the number of dSph stars with measurements of [C/Fe]. The [C/Fe] ratio in the clusters decreases with increasing luminosity above log(L/L_sun) ~= 1.6, which can be explained by deep mixing in evolved giants. The same decrease is observed in dSphs, but the initial [C/Fe] of the dSph giants is not uniform. Stars in dSphs at lower metallicities have larger [C/Fe] ratios. We hypothesize that [C/Fe] (corrected to the initial carbon abundance) declines with increasing [Fe/H] due to the metallicity dependence of the carbon yield of asymptotic giant branch stars and due to the increasing importance of Type Ia supernovae at higher metallicities. We also identified 11 very carbon-rich giants (8 previously known) in...

  19. Cancer Clusters

    ... of cancer. Cancer clusters can help scientists identify cancer-causing substances in the environment. For example, in the early 1970s, a cluster ... the area and time period over which the cancers were diagnosed. They also ask about specific environmental hazards or concerns in the affected area. If ...

  20. Estimating the abundance of clustered animal population by using adaptive cluster sampling and negative binomial distribution

    Bo, Yizhou; Shifa, Naima

    2013-09-01

    An estimator for finding the abundance of a rare, clustered and mobile population has been introduced. This model is based on adaptive cluster sampling (ACS) to identify the location of the population and negative binomial distribution to estimate the total in each site. To identify the location of the population we consider both sampling with replacement (WR) and sampling without replacement (WOR). Some mathematical properties of the model are also developed.

  1. Clustering processes

    Ryabko, Daniil

    2010-01-01

    The problem of clustering is considered, for the case when each data point is a sample generated by a stationary ergodic process. We propose a very natural asymptotic notion of consistency, and show that simple consistent algorithms exist, under most general non-parametric assumptions. The notion of consistency is as follows: two samples should be put into the same cluster if and only if they were generated by the same distribution. With this notion of consistency, clustering generalizes such classical statistical problems as homogeneity testing and process classification. We show that, for the case of a known number of clusters, consistency can be achieved under the only assumption that the joint distribution of the data is stationary ergodic (no parametric or Markovian assumptions, no assumptions of independence, neither between nor within the samples). If the number of clusters is unknown, consistency can be achieved under appropriate assumptions on the mixing rates of the processes. (again, no parametric ...

  2. Spectroscopy of globular clusters in the low-luminosity spiral galaxy NGC 45

    Mora, M.D.; Larsen, S.S.; Kissler-Patig, M.

    2008-01-01

    Context. Extragalactic globular clusters have been studied in elliptical galaxies and in a few luminous spiral galaxies, but little is known about globular clusters in low-luminosity spirals. Aims. Past observations with the ACS have shown that NGC 45 hosts a large population of globular clusters (1

  3. Molecular cluster theory of chemical bonding in actinide oxide

    The electronic structure of actinide monoxides AcO and dioxides AcO2, where Ac = Th, U, Np, Pu, Am, Cm and Bk has been studied by molecular cluster methods based on the first-principles one-electron local density theory. Molecular orbitals for nearest neighbor clusters AcO10-6 and AcO12-8 representative of monoxide and dioxide lattices were obtained using non-relativistic spin-restricted and spin-polarized Hartree-Fock-Slater models for the entire series. Fully relativistic Dirac-Slater calculations were performed for ThO, UO and NpO in order to explore magnitude of spin-orbit splittings and level shifts in valence structure. Self-consistent iterations were carried out for NpO, in which the NpO6 cluster was embedded in the molecular field of the solid. Finally, a ''moment polarized'' model which combines both spin-polarization and relativistic effects in a consistent fashion was applied to the NpO system. Covalent mixing of oxygen 2p and Ac 5f orbitals was found to increase rapidly across the actinide series; metal s,p,d covalency was found to be nearly constant. Mulliken atomic population analysis of cluster eigenvectors shows that free-ion crystal field models are unreliable, except for the light actinides. X-ray photoelectron line shapes have been calculated and are found to compare rather well with experimental data on the dioxides

  4. Population studies in groups and clusters of galaxies. IV. Comparison of the luminosity functions and morphological-type distributions in seven nearby groups

    Published observational data on the Leo, Dorado, NGC 1400, NGC 5044, Antlia, Fornax, and Virgo groups of galaxies are analyzed in terms of the luminosity functions and morphological types of their members. The data sets employed are characterized, and the results are presented in extensive tables and graphs and discussed in detail. While the fractions of early and late galaxies in the groups are similar, the ratio of dwarfs to giants (D/G) in the early galaxies varies monotonically with the richness of the cluster, leading to artificial flattening at the faint end of the total luminosity function in environments with low D/G. The luminosity function for dwarfs in all environments is found to have a slope of about -1.3. 54 refs

  5. Deriving physical parameters of unresolved star clusters III. Application to M31 PHAT clusters

    de Meulenaer, Philippe; Mineikis, Tadas; Vansevičius, Vladas

    2015-01-01

    This study is the third of a series that investigates the degeneracy and stochasticity problems present in the determination of physical parameters such as age, mass, extinction, and metallicity of partially resolved or unresolved star cluster populations situated in external galaxies when using broad-band photometry. This work tests the derivation of parameters of artificial star clusters using models with fixed and free metallicity for the WFC3+ACS photometric system. Then the method is applied to derive parameters of a sample of 203 star clusters in the Andromeda galaxy observed with the HST. Following Papers I \\& II, the star cluster parameters are derived using a large grid of stochastic models that are compared to the observed cluster broad-band integrated WFC3+ACS magnitudes. We derive the age, mass, and extinction of the sample of M31 star clusters with one fixed metallicity in agreement with previous studies. Using artificial tests we demonstrate the ability of the WFC3+ACS photometric system to ...

  6. Distribution of star formation rates during the rapid assembly of NGC 1399 as deduced from its globular cluster system

    Schulz, C; Kroupa, P; Pflamm-Altenburg, J

    2016-01-01

    Ultra-compact dwarf galaxies (UCDs) share many properties with globular clusters (GCs) and are found in similar environments. A large sample of UCDs and GCs around NGC 1399, the central giant elliptical of the Fornax galaxy cluster, is used to infer their formation history and also that of NGC 1399. We assumed that all GCs and UCDs in our sample are star clusters (SCs) and used them as tracers of past star formation activities. After correcting our GC/UCD sample for mass loss, we interpreted their overall mass function to be a superposition of SC populations that formed coevally during different times. The SC masses of each population were distributed according to the embedded cluster mass function (ECMF), a pure power law with the slope $-\\beta$ and a stellar upper mass limit, $M_{\\mathrm{max}}$, which depended on the star formation rate (SFR). We decomposed the observed GC/UCD mass function into individual SC populations and converted $M_{\\mathrm{max}}$ of each SC population to an SFR. The overall distribut...

  7. Clustering analysis

    Cluster analysis is the name of group of multivariate techniques whose principal purpose is to distinguish similar entities from the characteristics they process.To study this analysis, there are several algorithms that can be used. Therefore, this topic focuses to discuss the algorithms, such as, similarity measures, and hierarchical clustering which includes single linkage, complete linkage and average linkage method. also, non-hierarchical clustering method, which is popular name K-mean method' will be discussed. Finally, this paper will be described the advantages and disadvantages of every methods

  8. Cluster editing

    Böcker, S.; Baumbach, Jan

    2013-01-01

    The Cluster Editing problem asks to transform a graph into a disjoint union of cliques using a minimum number of edge modifications. Although the problem has been proven NP-complete several times, it has nevertheless attracted much research both from the theoretical and the applied side. The...... algorithms for biological problems. © 2013 Springer-Verlag....... problem has been the inspiration for numerous algorithms in bioinformatics, aiming at clustering entities such as genes, proteins, phenotypes, or patients. In this paper, we review exact and heuristic methods that have been proposed for the Cluster Editing problem, and also applications of these...

  9. Cluster analysis

    Everitt, Brian S; Leese, Morven; Stahl, Daniel

    2011-01-01

    Cluster analysis comprises a range of methods for classifying multivariate data into subgroups. By organizing multivariate data into such subgroups, clustering can help reveal the characteristics of any structure or patterns present. These techniques have proven useful in a wide range of areas such as medicine, psychology, market research and bioinformatics.This fifth edition of the highly successful Cluster Analysis includes coverage of the latest developments in the field and a new chapter dealing with finite mixture models for structured data.Real life examples are used throughout to demons

  10. AcEST: DK955197 [AcEST

    Full Text Available TST39A01NGRL0022_H07 532 Adiantum capillus-veneris mRNA. clone: TST39A01NGRL0022_H07. 5' end seq ... KDEVTALPLLK 192 Query: 194 RFAFGIACELLMSRYEKEEQEMLEEPF TTMMKGILQLPIKLPGTRFSKAIVAANMLRARF 373 R+ F +AC+L S ... KDEVMALPLLK 192 Query: 194 RFAFGIACELLMSRYEKEEQEMLEEPF TTMMKGILQLPIKLPGTRFSKAIVAANMLRARF 373 R+ F +AC+L S ... KDEVKVLP 189 Query: 185 LMKRFAFGIACELLMSRYEKEEQEMLEEPF TTMMKGILQLPIKLPGTRFSKAIVAANMLR 364 L++ F IA L + +Q+ ... KDEATVLP 177 Query: 185 LMKRFAFGIACELLMSRYEKEEQEMLEEPF TTMMKGILQLPIKLPGTRFSKAIVAANMLR 364 L+K F +A L E+ QE ...

  11. AcEST: BP915640 [AcEST

    Full Text Available YMU001_000074_A01 462 Adiantum capillus-veneris mRNA. clone: YMU001_000074_A01. BP915640 CL3685C ... y: 462 GPLILRACLVYMQGAPVGSLAEDGIVSAATGKDMEQSTVGFRLMLAKI IHRLIAAFKEVG 283 G IL+AC YM+G +GSL +D V ++VGF+LMLAK ... : 1032 GYYILKACDAYMKGYLIGSLTKDASVIDERSS-ANSTSVGFKLMLAKI APKLFSALSEVG 1090 Query: 282 AYCDAYE 262 A C+ ++ Sb ... uery: 453 ILRACLVYMQGAPVGSLAEDGIVSAATGKDMEQSTVGFRLMLAKI IHRLIAAFKEVGAYC 274 +L AC YM+G PVGS A G ST GF++ML+K ... ame = -1 Query: 423 GAPVGSLAEDGIVSAATGKDMEQSTVGFRLMLAKI I----HRLIAAFKEVGAYCD 271 G P+ L D +S GK + S RL + L+ ...

  12. Spitzer Clusters

    Krick, Kessica

    This proposal is a specific response to the strategic goal of NASA's research program to "discover how the universe works and explore how the universe evolved into its present form." Towards this goal, we propose to mine the Spitzer archive for all observations of galaxy groups and clusters for the purpose of studying galaxy evolution in clusters, contamination rates for Sunyaev Zeldovich cluster surveys, and to provide a database of Spitzer observed clusters to the broader community. Funding from this proposal will go towards two years of support for a Postdoc to do this work. After searching the Spitzer Heritage Archive, we have found 194 unique galaxy groups and clusters that have data from both the Infrared array camera (IRAC; Fazio et al. 2004) at 3.6 - 8 microns and the multiband imaging photometer for Spitzer (MIPS; Rieke et al. 2004) at 24microns. This large sample will add value beyond the individual datasets because it will be a larger sample of IR clusters than ever before and will have sufficient diversity in mass, redshift, and dynamical state to allow us to differentiate amongst the effects of these cluster properties. An infrared sample is important because it is unaffected by dust extinction while at the same time is an excellent measure of both stellar mass (IRAC wavelengths) and star formation rate (MIPS wavelengths). Additionally, IRAC can be used to differentiate star forming galaxies (SFG) from active galactic nuclei (AGN), due to their different spectral shapes in this wavelength regime. Specifically, we intend to identify SFG and AGN in galaxy groups and clusters. Groups and clusters differ from the field because the galaxy densities are higher, there is a large potential well due mainly to the mass of the dark matter, and there is hot X-ray gas (the intracluster medium; ICM). We will examine the impact of these differences in environment on galaxy formation by comparing cluster properties of AGN and SFG to those in the field. Also, we will

  13. Speed Control of DC Motor using AC/AC/DC Converter Based on Intelligent Techniques

    Rakan Kh Antar

    2013-05-01

    Full Text Available    This paper describes the application of ac/ac/dc and ac/dc converters to control the speed of a separately excited DC motor. Artificial neural network and PI controller are trained to select the desired values of firing angles for triggering thyristors of the ac/ac/dc and ac/dc bridge converters in order to control the speed of the dc motor at a desired value with constant and different load torques in order to obtain the best speed response. Simulation results show that the rising time for ac/dc and ac/ac/dc converters at 250rpm are reduced about 79% and 89% respectively, while delay time it reduced about 69% and 64% respectively. Therefore, speed response of the dc motor is more efficient for closed loop system compared with open loop also the response of ac/ac/dc converter is better than ac/dc converter.

  14. Cluster Bulleticity

    Massey, Richard; Kitching, Thomas D.; Nagai, Daisuke

    2010-01-01

    The unique properties of dark matter are revealed during collisions between clusters of galaxies, like the bullet cluster (1E 0657-56) and baby bullet (MACSJ0025-12). These systems provide evidence for an additional, invisible mass in the separation between the distribution of their total mass, measured via gravitational lensing, and their ordinary 'baryonic' matter, measured via its X-ray emission. Unfortunately, the information available from these systems is limited by th...

  15. Cluster Bulleticity

    Massey, R; Kitching, T.; Nagai, D.

    2010-01-01

    The unique properties of dark matter are revealed during collisions between clusters of galaxies, such as the bullet cluster (1E 0657−56) and baby bullet (MACS J0025−12). These systems provide evidence for an additional, invisible mass in the separation between the distributions of their total mass, measured via gravitational lensing, and their ordinary ‘baryonic’ matter, measured via its X-ray emission. Unfortunately, the information available from these systems is limited by their rarity. C...

  16. Cluster generator

    Donchev, Todor I.; Petrov, Ivan G.

    2011-05-31

    Described herein is an apparatus and a method for producing atom clusters based on a gas discharge within a hollow cathode. The hollow cathode includes one or more walls. The one or more walls define a sputtering chamber within the hollow cathode and include a material to be sputtered. A hollow anode is positioned at an end of the sputtering chamber, and atom clusters are formed when a gas discharge is generated between the hollow anode and the hollow cathode.

  17. Nuclear structure of $^{231}$Ac

    Boutami, R; Mach, H; Kurcewicz, W; Fraile, L M; Gulda, K; Aas, A J; García-Raffi, L M; Løvhøiden, G; Martínez, T; Rubio, B; Taín, J L; Tengblad, O

    2008-01-01

    The low-energy structure of 231Ac has been investigated by means of gamma ray spectroscopy following the beta-decay of 231Ra. Multipolarities of 28 transitions have been established by measuring conversion electrons with a mini-orange electron spectrometer. The decay scheme of 231Ra --> 231Ac has been constructed for the first time. The Advanced Time Delayed beta-gamma-gamma(t) method has been used to measure the half-lives of five levels. The moderately fast B(E1) transition rates derived suggest that the octupole effects, albeit weak, are still present in this exotic nucleus.

  18. AcEST: BP920800 [AcEST

    Full Text Available DLNLALQVHSRMVRFGFNAEVEACGALINMYGKCGKVLYAQRVFDDT 298 Query: 206 RQQDVISWNDIISACAQRGHGTEALENFSQMLHEGIVPNSMTFTSVMQA---CNSIEGG...G L +A S F ++ +D+ISW +I +Q EA+ F Sbjct: 217 SEKNEATSNCLINGYMGLGNLEQAESLFNQMPVKDIISWTTMIKGYSQNKRYREAIAVFY 276 Query: 119 QMLHEG...EKAWRIFDGVSCKNLPSWNAIITGCVQGGLLEEAIDLYRHMK 281 Query: 110 HEGIVPNSMTFTSVMQAC---NSIEGGR 36 + + PN +T +V+ AC +...N IIS AQ G +EA+E ++ M Sbjct: 383 DITIGNAVVVMYAKLGLVDSARAVFNWLPNTDVISWNTIISGYAQNGFASEAIEMYNIME 442 Query: 110 HEG...EIDLGEQIHSLSVKTGFESDMYVSGVLIDMYSKYGWLEKARRVLEML 406 Query: 206 RQQDVISWNDIISACAQRGHGTEALENFSQMLHEGIVPNSMTFTSVMQACNSIEGG

  19. AcEST: DK945549 [AcEST

    Full Text Available AGGCGATTTCATCTTTTCTGAGAACCCTGATTTTGTGATTGTGTAATTACA ACTGTGGAACAGAAGGATGAGAAGTCTACTGACACAACAAGATATCTCTGGAGAGGAGA...A AATTGAGAAGGTTTGAGTTCTCAACAATGGGCTATGAGGCAATAATGGGAAGGCACCGAT TGTGGGCTTGTATAGGTTTTGAC...LCTG 239 L++R+LRR + + ++ G AC+ DP +P PLC+G Sbjct: 108 LQQRELRRKLLADSGALNTNSVNGPRNWKACVQQDPSSRPGTPLCSG 154 >sp|A6UUY8|RNZ_META3...49 Tissue type young leaves Developmental stage sporophyte Contig ID CL454Contig1 Sequence GATGAGCGA...CCACCTGTGCAACCGTCAGCGCCTTTGTGCACTGGTG CAATGTCCTGTGGTTACCTTGTTTGGAATCTTAATTGTTCTCATGTAT

  20. AcEST: BP917632 [AcEST

    Full Text Available YMU001_000103_D10 554 Adiantum capillus-veneris mRNA. clone: YMU001_000103_D10. BP917632 - Show ... YSKCKIHQKALELLVLML 154 Query: 466 KDSLEPDEVTYLNVLKACARE EDLKV 543 +D++ P+ TY +VL++C D+++ Sbjct: 155 RDNVRPN ... 185 Query: 415 GHSDSS--KEALKLLTQMRKDSLEPDEVTYLNVLKACARE EDLK 540 + EA KL +M+ ++ PDE+ N++ AC R +++ Sbjct: 18 ...

  1. AcEST: DK961189 [AcEST

    Full Text Available OS=A... 127 7e-29 sp|Q94B08|GCP1_ARATH Germination-specific cysteine protease 1 OS... 125 2e-28 sp|P00785|AC...IRNSWGLNWGDSGYVKLQRNIDDPFGKCGIAMMPSYP 347 >sp|Q94B08|GCP1_ARATH Germination-specific cysteine protease 1 OS=

  2. AcEST: DK946687 [AcEST

    Full Text Available YMU02A01NGRL0013_G11 544 Adiantum capillus-veneris mRNA. clone: YMU02A01NGRL0013_G11. 5' end seq ... + G P+ TY+ + AC+ E Sbjct: 97 YSFNYMIRGLTNTWN-------DHEA ---ALSLYRRMKFSGLKPDKFTYNFVFIACAKLE 146 Query: 214 A ... Sbjct: 71 LIPKAVELGDFNYSSFLFSVTEEPNHYSFNYMIRGLTNTWNDHEA ALSLYRRMKFSGLKP 130 Query: 469 DGATFSCVLRACGNVGALDV ...

  3. AcEST: DK949372 [AcEST

    Full Text Available TST38A01NGRL0005_N02 627 Adiantum capillus-veneris mRNA. clone: TST38A01NGRL0005_N02. 5' end seq ... 363 DQLREKTC-GVDKFDDIVMACXXXXXXXXXXXXXXXXXXKARVHAYGVCD DPEYFYDYVQ 539 Q++EK G+ FDDIV+AC KA+VHA+ VCD DP+YFYD ... 264 QQVQEKKVPGITFFDDIVVACGSGGSIAGLSLGSYLSNLKAKVHAFAVCD DPDYFYDYTQ 323 Query: 540 GLLDGMNANIASRDIVNVIDAKGLG ...

  4. Globular clusters kinematics and dynamical models of the massive early-type galaxy NGC 1399

    Samurović, S.

    2016-06-01

    We analyze the dynamical models of the massive early-type galaxy NGC 1399, the central galaxy of the Fornax cluster. We use the sample of 790 globular clusters as tracers of gravitational potential and we first extract the kinematics, which is then dynamically modeled. We find that the velocity dispersion remains high and approximately constant throughout the whole galaxy and that the departures from the Gaussian distribution of the orbits are not large. We use the spherical Jeans equation in both Newtonian and MOND approaches, assuming three cases of orbital anisotropies: we study isotropic, tangentially and radially anisotropic models in order to establish the best-fitting values of the mass-to-light ratios. We found that in the Newtonian approximation a significant amount of dark matter is needed and that Navarro-Frenk-White (NFW) model with a dark halo provides a satisfactory description of the kinematics of NGC 1399. We tested three MOND models (standard, simple and toy) and found that none of them can provide a fit of the velocity dispersion profile without the inclusion of dark matter. Finally, using our findings, we placed the galaxy NGC 1399 within the context of other observed early-type galaxies and discuss its location among them.

  5. The complex nature of the nuclear star cluster in FCC 277

    Lyubenova, Mariya; Cote, Patrick; Kuntschner, Harald; van de Ven, Glenn; Ferrarese, Laura; Jordan, Andres; Infante, Leopoldo

    2013-01-01

    Recent observations have shown that compact nuclear star clusters (NSCs) are present in up to 80% of galaxies. However, detailed studies of their dynamical and chemical properties are confined mainly to spiral galaxy hosts, where they are more easily observed. In this paper we present our study of the NSC in FCC 277, a nucleated elliptical galaxy in the Fornax cluster. We use a combination of adaptive optics assisted near-infrared integral field spectroscopy, Hubble Space Telescope imaging, and literature long slit data. We show that while the NSC does not appear to rotate within our detection limit of ~6 km/s, rotation is detected at larger radii, where the isophotes appear to be disky, suggesting the presence of a nuclear disk. We also observe a distinct central velocity dispersion drop that is indicative of a dynamically cold rotating sub-system. Following the results of orbit-based dynamical modelling, co-rotating as well as counter-rotating stellar orbits are simultaneously needed to reproduce the observ...

  6. Denominators of cluster variables

    Buan, Aslak Bakke; Marsh, Robert J.; Reiten, Idun

    2007-01-01

    Associated to any acyclic cluster algebra is a corresponding triangulated category known as the cluster category. It is known that there is a one-to-one correspondence between cluster variables in the cluster algebra and exceptional indecomposable objects in the cluster category inducing a correspondence between clusters and cluster-tilting objects. Fix a cluster-tilting object T and a corresponding initial cluster. By the Laurent phenomenon, every cluster variable can be written as a Laurent...

  7. Energy saving in ac generators

    Nola, F. J.

    1980-01-01

    Circuit cuts no-load losses, without sacrificing full-load power. Phase-contro circuit includes gate-controlled semiconductor switch that cuts off applied voltage for most of ac cycle if generator idling. Switch "on" time increases when generator is in operation.

  8. Apuntes de Acústica

    Martín Domingo, Agustín

    2014-01-01

    Esta publicacion contiene unos apuntes para la parte de Acústica de las asignaturas de la ETSAM, junto con cierta cantidad de material adicional que excede el ámbito del curso. Aunque está lejos de ser completa y de estar libre de errores, el autor espera sea útil.

  9. SSTI Clark ACS Technology Demonstrations

    Freesland, Douglas

    1997-01-01

    SSTI Clark, one of two spacecraft built under NASA's Small Satellite Technology Initiative, includes seven ACS technology demonstrations. The technologies redefine the performance cost envelope, providing improved sensor and actuator performance at reduced costs. Six sensing technologies are being flown consisting of both hardware and algorithmic demonstrations: autonomous star tracker, hemispherical resonating gyro, GPS attitude determination, miniature horizon sensors, low cost course sun s...

  10. Cluster Bulleticity

    Massey, Richard; Nagai, Daisuke

    2010-01-01

    The unique properties of dark matter are revealed during collisions between clusters of galaxies, like the bullet cluster (1E 0657-56) and baby bullet (MACSJ0025-12). These systems provide evidence for an additional, invisible mass in the separation between the distribution of their total mass, measured via gravitational lensing, and their ordinary 'baryonic' matter, measured via its X-ray emission. Unfortunately, the information available from these systems is limited by their rarity. Constraints on the properties of dark matter, such as its interaction cross-section, are therefore restricted by uncertainties in the individual systems' impact velocity, impact parameter and orientation with respect to the line of sight. Here we develop a complementary, statistical measurement in which every piece of substructure falling into every massive cluster is treated as a bullet. We define 'bulleticity' as the mean separation between dark matter and ordinary matter, and we measure a positive signal in hydrodynamical si...

  11. AcEST: DK950895 [AcEST

    Full Text Available |A7SFA3|A7SFA3_NEMVE Predicted protein OS=Nematostella vectens... 210 5e-53 tr|Q0CVA9|Q0CVA9_ASPTN ATP-citrate synthase subunit...stX Result : Swiss-Prot sp_hit_id Q54YA0 Definition sp|Q54YA0|ACLY_DICDI Probable ATP-citrate synthase OS=Dictyos...PIDYSWAQELGLIRKPAAFISTI 404 >sp|Q8X097|ACL1_NEUCR Probable ATP-citrate synthase subunit 1 OS=Neurospora cras...IRKPASFMTSI 844 >sp|Q9P7W3|ACL1_SCHPO Probable ATP-citrate synthase subunit 1 OS=Schizosaccharomyces pombe G....done Score E Sequences producing significant alignments: (bits) Value sp|Q54YA0|ACLY_DICDI Probable ATP-citrate synthase OS=Dictyos

  12. A New Coordinated Voltage Control Scheme for Offshore AC Grid of HVDC Connected Offshore Wind Power Plants

    Sakamuri, Jayachandra N.; Nicolaos Antonio CUTULULIS; Rather, Zakir Hussain; Rimez, Johan

    2015-01-01

    This paper proposes a coordinated voltage control scheme (CVCS) which enhances the voltage ride through (VRT) capability of an offshore AC grid comprised of a cluster of offshore wind power plants (WPP) connected through AC cables to the offshore voltage source converter based high voltage DC (VSC-HVDC) converter station. Due to limited short circuit power contribution from power electronic interfaced variable speed wind generators and with the onshore main grid decoupled by the HVDC link, th...

  13. AcEST: BP914304 [AcEST

    Full Text Available IDEHTFVFTLRAC 4 V+ NA++ Y G+ E A++ + +M+ E++ + TF+ LRAC Sbjct: 670 VTWNAMICGYAHHGKGEEAIQLFERMILENIKPNHVTFISI...KSLRRDFVTWNAMICGYAHHGKGEEAIQLFERMILENIKPN 703 Query: 339 NLTYVSLFKACGNVLDFGQG-RTIHGEARANGFSSDRFICTTLI...TFVFTLRAC 4 +F + + V+ N ++ +YV A +++M + D TL+AC Sbjct: 484 QIFERMCDRDNVTWNTIIGSYVQDENESEAFDLFKRMNLCGIVSDGACL...K + A+Q+ + R + +W++MI++ +A + ++ M Sbjct: 93 LGNSLINFYSKFEDVASAEQVFRRMTLRDVVTWSSMIAAYAGNNHPAKAFDTFERMTDAN 152... + R + +W++MI++ +A + ++ M Sbjct: 93 LGNSLINFYSKFEDVASAEQVFRRMTLRDVVTWSSMIAAYAGNNHPAKAFDTFERM

  14. AcEST: BP911793 [AcEST

    Full Text Available + +VSWN +++ Y QHG + ++L+ M+AE T N + + A Sbjct: 58 EAKFVFERIQNKDVVSWNCIINGYSQHGPSGSSHVMELFQRMRAENTAPNAHTFAGVF... N + + A Sbjct: 58 EAKFVFERIQNKDVVSWNCIINGYSQHGPSGSSHVMELFQRMRAENTAPNAHTFAGVFTA 117 Query: 359 CIQTGNLELCKQM...D VT S+LSACSH G + +G YF Sbjct: 602 IIGGSAQHGRGQDALQLFERMKMEGVKPDIVTFVSLLSACSHAGLLEEGRRYF 654 Score = 115 bit...53 QTGNLELCKQMHFNIVSAGNELNPSLASSLIRTYGNCGSMLDAHAVFDSLPLPDIVSWNV 174 Q +E+ K++ F+++ N S +++I Y CG + +A +FD +P D VSW Sbjct: 324 QGERME... L+ M +E + I+LV +L AC+ TG+LE + +H Sbjct: 498 VITWNAMIASYVHCEQSEKAIALFDRMVSENFKPSSITLVTLLMACVNTGSLER

  15. AcEST: BP921649 [AcEST

    Full Text Available 40 + ++LV YAK L + ++ +P R W+ +I+ + + ++E AL+ + M+ G Sbjct: 144 VASSLVGMYAKFNLFENSLQVFDEMPERDVASWNTVISCFYQSGEAEKALELFGRME...LDCYKEM 52 ++L +GNALVD YAKCG L A ++ +R+ R V W+ +I Y + E A D +K M Sbjct: 461 KNLFVGNALVDMYAKCGALEDARQIFERMCDRDNVTWNTIIGSYVQDEN...RD+ WNA+I Sbjct: 237 LEQGKQIHCYAIRSG-IESDVLVVNGLVNMYAKCGNVNTAHKLFERMPIRDVASWNAIIG 295 Query: 411 GYVNHGRAEVALDCFGKME...SNDVV-GNALVNMYAKCGNVNSAYKLFERMPKKNVVAWNAIIS 396 Query: 411 GYVNHGRAEVALDCFGKME... HGR + AL F +M+ EG PD +TF +L AC G + + + + Sbjct: 603 IGGSAQHGRGQDALQLFERMKMEGVKPDIVTFVSLLSACSHAGLLEEGRRYFCSM

  16. AcEST: BP919669 [AcEST

    Full Text Available D + RDV SW ++S + + G+ ++F M G +P+ Sbjct: 148 LVGMYAKFNLFENSLQVFDEMPERDVASWNTVISCFYQSGEAEKALELFGRMESSGFEPN 20...+ +++AC L + +G+E+H + K+G EL V Sbjct: 190 EKALELFGRMESSGFEPNSVSLTVAISACSRLLWLERGKE...F Sbjct: 468 IY---VVNSLIDSYGKCSHVEDAERIFEECTIGDLVSFTSMITAYAQYGQGEEALKLFLE 524 Query: 226 MVGEGTKPDSISLLVVLRA-YNF...+ IR DV W +LMSGY+K D ++F ++ Sbjct: 44 SLINVYFTCKDHCSARHVFENFDIRSDVYIWNSLMSGYSKNSMFHDTLEVFKRLLNCSIC 103 Query: 208 KPDSISLLVVLRAYNF...KPD Sbjct: 261 VDMYAKCGCIETAVEVFEKLTRRNVFSWAALIGGYAAYGYAKKATTCLDRIEREDGIKPD 320 Query: 199 SISLLVVLRAYNFLGFP

  17. AcEST: DK957916 [AcEST

    Full Text Available PQKQPVPAVSHSPQKSSTPPTPAATKPKEEPSVPKEVPKLQQGKLEKT 967 Query: 577 --TTEASQGIPVEEG...G E+ P+ P Sbjct: 1974 QEQGRAPSQDQEAPSPEALPSPGQEPAAGASPRRGELRRGSSAESALPRAGP 2025 >sp|Q05175|BASP_RAT Brain ac... +P AP P Sbjct: 388 ERETAASAGPQG----AFPEPRPAQPSAGPEPRPAQPSAGPEPRPAQPSAAPEPRP---- 439 Query: 571 GQTTE... L ++ +A+ +E AP Sbjct: 406 IVTTPEPEGSGEEDVPKPDEIPEKEVTEEELIKVSTAAPAKASPEEEVVKATTLAPSEED 465 Query: 550 VSPYIASGQTTE... Query: 424 KGQAYEAIPDPHVDPAAGVHERLAQLQLGDEPEATKPKEAPG-VSPYI--ASGQTTEASQ 594 K A E P + + G E + E EA P A G +P

  18. AcEST: DK956923 [AcEST

    Full Text Available CCATAGTCTCAA CAGCGATAAGCAGGAAATGCATGCAGTGACCATGGGTAAGAAAAGGGTCATGGTGGGCGC CATTAACACGATACTTATCCTA...CTCCTCTTGCAGTTTATGAAGCAATGTTCTTCCTCTTC TAGTCATGATGATGATGGCGATGCCTTTGCGGATGACACTCTAAGCAGACGCAACGAT...AC GGTCGAGTCTGCTCCTCGACATTGGCCAAGGCGAATGCTGGGCAGCCAAGAACCTGCCTC CAACAAGACTTCATATGGTATTCCTGAT...H At1g73965 (CLE13 / CLAVATA3/ESR-Related 13) (CLE13) OS=Arabidopsis thaliana Align length 25 Sco...icant alignments: (bits) Value tr|Q6NMF0|Q6NMF0_ARATH At1g73965 (CLE13 / CLAVATA3/ESR-Related 1... 49 3e-04

  19. AcEST: BP921492 [AcEST

    Full Text Available + AL +G+ +H Sbjct: 286 DVASWNAIIGGYSLNSQHHEALAFFNRMQVRGIKPNSITMVSVLPACAHLFAL... ++ L +GK +H Sbjct: 178 NLVSWTAMVSGYAQGGFADEALRMFYEMQGEDVKANYVTVASVLPACAQLSDLQQGKEIH 237 Query: 153 AC...FDRMPEK 171 Query: 333 DVVSWSAMIAMYGQQGCGKEAFQLFQEMACEGGMPNRVTYVSILDACASVAALPEGKLVH 154 +V+W+++++ + Q G EA Q+F +M G P+ T+VS+L ACA...333 DVVSWSAMIAMYGQQGCGKEAFQLFQEMACE-GGMPNRVTYVSILDACASVAALPEGKLV 157 +V +W+AMI+ YG G G++A +LF +M + G +PN VT+V++L ACA...SKL 85 Query: 288 GCGKEAFQLFQEMACEGGMPNRVTYVSILDACASVAALPEGKLVHACFMESELELDVVVG 109 ++ M P+ T+ S++ +CA ++AL G

  20. Globular Cluster Systems in Brightest Cluster Galaxies. II: NGC 6166

    Harris, William E; Whitmore, Bradley C; Gnedin, Oleg Y; Geisler, Douglas; Rothberg, Barry

    2015-01-01

    We present new deep photometry of the globular cluster system (GCS) around NGC 6166, the central supergiant galaxy in Abell 2199. HST data from the ACS and WFC3 cameras in F475W, F814W are used to determine the spatial distribution of the GCS, its metallicity distribution function (MDF), and the dependence of the MDF on galactocentric radius and on GC luminosity. The MDF is extremely broad, with the classic red and blue subpopulations heavily overlapped, but a double-Gaussian model can still formally match the MDF closely. The spatial distribution follows a Sersic-like profile detectably to a projected radius of at least $R_{gc} = 250$ kpc. To that radius, the total number of clusters in the system is N_{GC} = 39000 +- 2000, the global specific frequency is S_N = 11.2 +- 0.6, and 57\\% of the total are blue, metal-poor clusters. The GCS may fade smoothly into the Intra-Cluster Medium of A2199; we see no clear transition from the core of the galaxy to the cD halo or the ICM. The radial distribution, projected e...

  1. Bayesian Analysis of Two Stellar Populations in Galactic Globular Clusters III: Analysis of 30 Clusters

    Wagner-Kaiser, R; Sarajedini, A; von Hippel, T; van Dyk, D A; Robinson, E; Stein, N; Jefferys, W H

    2016-01-01

    We use Cycle 21 Hubble Space Telescope (HST) observations and HST archival ACS Treasury observations of 30 Galactic Globular Clusters to characterize two distinct stellar populations. A sophisticated Bayesian technique is employed to simultaneously sample the joint posterior distribution of age, distance, and extinction for each cluster, as well as unique helium values for two populations within each cluster and the relative proportion of those populations. We find the helium differences among the two populations in the clusters fall in the range of ~0.04 to 0.11. Because adequate models varying in CNO are not presently available, we view these spreads as upper limits and present them with statistical rather than observational uncertainties. Evidence supports previous studies suggesting an increase in helium content concurrent with increasing mass of the cluster and also find that the proportion of the first population of stars increases with mass as well. Our results are examined in the context of proposed g...

  2. Cluster radioactivities — past, present and future

    The half-lives of cluster emitters predicted by the analytical superasymmetric fission model have been experimentally confirmed. Potential energy surfaces of cluster emitters are showing deep valleys due to the strong shell effect of the doubly magic daughter 208Pb. Cluster radioactivities allow us to study transitions from a deformed parent nucleus, with a complex structure resulted from mixing of several single-particle states, to a spherical daughter possessing a pure well known state. Recently, preliminary data concerning the 14C radioactivity of 223Ac were reported. The following modes have been experimentally confirmed: 14C, 20O, 24,25Ne, 28,30Mg, and 32,34Si; lower limits for 18O, 23F and 26Ne are available. We give a list of some other experiments which have a good chance to be performed in the future. Applications for true ternary fission, 2α-accompanied fission, and atomic clusters are outlined. (author)

  3. Fuzzy Clustering

    Berks, G.; Keyserlingk, Diedrich Graf von; Jantzen, Jan;

    2000-01-01

    and clustering are the basic concerns in medicine. Classification depends on definitions of the classes and their required degree of participant of the elements in the cases' symptoms. In medicine imprecise conditions are the rule and therefore fuzzy methods are much more suitable than crisp ones...

  4. Quotients of cluster categories

    Jorgensen, Peter

    2007-01-01

    Higher cluster categories were recently introduced as a generalization of cluster categories. This paper shows that in Dynkin types A and D, half of all higher cluster categories are actually just quotients of cluster categories. The other half can be obtained as quotients of 2-cluster categories, the "lowest" type of higher cluster categories. Hence, in Dynkin types A and D, all higher cluster phenomena are implicit in cluster categories and 2-cluster categories. In contrast, the same is not...

  5. Performance of AC/graphite capacitors at high weight ratios of AC/graphite

    Wang, Hongyu [IM and T Ltd., Advanced Research Center, Saga University, 1341 Yoga-machi, Saga 840-0047 (Japan); Yoshio, Masaki [Advanced Research Center, Department of Applied Chemistry, Saga University, 1341 Yoga-machi, Saga 840-0047 (Japan)

    2008-03-01

    The effect of negative to positive electrode materials' weight ratio on the electrochemical performance of both activated carbon (AC)/AC and AC/graphite capacitors has been investigated, especially in the terms of capacity and cycle-ability. The limited capacity charge mode has been proposed to improve the cycle performance of AC/graphite capacitors at high weight ratios of AC/graphite. (author)

  6. Simultaneous distribution of AC and DC power

    Polese, Luigi Gentile

    2015-09-15

    A system and method for the transport and distribution of both AC (alternating current) power and DC (direct current) power over wiring infrastructure normally used for distributing AC power only, for example, residential and/or commercial buildings' electrical wires is disclosed and taught. The system and method permits the combining of AC and DC power sources and the simultaneous distribution of the resulting power over the same wiring. At the utilization site a complementary device permits the separation of the DC power from the AC power and their reconstruction, for use in conventional AC-only and DC-only devices.

  7. Regional Innovation Clusters

    Small Business Administration — The Regional Innovation Clusters serve a diverse group of sectors and geographies. Three of the initial pilot clusters, termed Advanced Defense Technology clusters,...

  8. A Triple Main Sequence in the Globular Cluster NGC 2808

    Piotto, G; Anderson, J; King, I R; Cassisi, S; Milone, A P; Villanova, S; Pietrinferni, A; Renzini, A

    2007-01-01

    Accurate photometry with HST/ACS shows that the main sequence of the globular cluster NGC 2808 splits into three separate branches. The three MS branches may be associated with complexities of the cluster's horizontal branch and of its abundance distribution. We attribute the MS branches to successive rounds of star formation, with different helium abundances; we discuss possible sources of helium enrichment. Some other massive globulars also appear to have complex populations; we compare them with NGC 2808.

  9. Clustering experiments

    Wang, Zhengwei; Tan, Ken; Di, Zengru; Roehner, Bertrand M

    2011-01-01

    It is well known that bees cluster together in cold weather, in the process of swarming (when the ``old'' queen leaves with part of the colony) or absconding (when the queen leaves with all the colony) and in defense against intruders such as wasps or hornets. In this paper we describe a fairly different clustering process which occurs at any temperature and independently of any special stimulus or circumstance. As a matter of fact, this process is about four times faster at 28 degree Celsius than at 15 degrees. Because of its simplicity and low level of ``noise'' we think that this phenomenon can provide a means for exploring the strength of inter-individual attraction between bees or other living organisms. For instance, and at first sight fairly surprisingly, our observations showed that this attraction does also exist between bees belonging to different colonies. As this study is aimed at providing a comparative perspective, we also describe a similar clustering experiment for red fire ants.

  10. AcEST: DK948526 [AcEST

    Full Text Available TST38A01NGRL0003_I19 675 Adiantum capillus-veneris mRNA. clone: TST38A01NGRL0003_I19. 5' end seq ... IAMVRTTTPVYV 214 Query: 542 ALALFNQARVSSLPIIDDNGSLIDIY ARSDITALARDDTY 661 AL +F Q RVS+LP++D+ G ++DIY ++ D+ ... LA + TY Sbjct: 215 ALGIFVQHRVSALPVVDEKGRVVDIY SKFDVINLAAEKTY 254 >sp|Q09138|AAKG1_PIG 5'-AMP-acti ... IAMVRTTTPVYV 215 Query: 542 ALALFNQARVSSLPIIDDNGSLIDIY ARSDITALARDDTY 661 AL +F Q RVS+LP++D+ G ++DIY ++ D+ ... LA + TY Sbjct: 216 ALGIFVQHRVSALPVVDEKGRVVDIY SKFDVINLAAEKTY 255 >sp|O54950|AAKG1_MOUSE 5'-AMP-ac ...

  11. AcEST: DK962916 [AcEST

    Full Text Available TST39A01NGRL0015_C06 596 Adiantum capillus-veneris mRNA. clone: TST39A01NGRL0015_C06. 5' end seq ... NA. clone: TST39A01NGRL0015_C06. 5' end sequence. Acce ssion DK962916 Tissue type prothallia with plantlet ... 2 Query: 317 MPKSKEPCSQEACDIQTCLVKNNFITERCFPVIEALQACCE K 442 MP+ K+PC ++AC+IQ CL NN++ +C VI+ L+ CC + Sbjct ... me = +2 Query: 335 PCSQEACDIQTCLVKNNFITERCFPVIEALQACCE K 442 PC +EAC IQ CL+ + + +C VI+ L CC K Sbjct: 4 PCQ ... = +2 Query: 326 SKEPCSQEACDIQTCLVKNNFITERCFPVIEALQACCE KCNSK 454 + E C+ CD +TC +K F +C AL CCE KC K Sbjct: 4 ...

  12. AcEST: DK955705 [AcEST

    Full Text Available TST39A01NGRL0023_N02 635 Adiantum capillus-veneris mRNA. clone: TST39A01NGRL0023_N02. 5' end seq ... NA. clone: TST39A01NGRL0023_N02. 5' end sequence. Acce ssion DK955705 Tissue type prothallia with plantlet ... 2 Query: 296 MPKSKEPCSQEACDIQTCLVKNNFITERCFPVIEALQACCE K 421 MP+ K+PC ++AC+IQ CL NN++ +C VI+ L+ CC + Sbjct ... me = +2 Query: 314 PCSQEACDIQTCLVKNNFITERCFPVIEALQACCE K 421 PC +EAC IQ CL+ + + +C VI+ L CC K Sbjct: 4 PCQ ... = +2 Query: 305 SKEPCSQEACDIQTCLVKNNFITERCFPVIEALQACCE KCNSK 433 + E C+ CD +TC +K F +C AL CCE KC K Sbjct: 4 ...

  13. AcEST: DK961330 [AcEST

    Full Text Available FWVPCMHTPIKQEKHTHA 405 +AR P W +++PI+ ++C++ P + AK+ PL DVTH+F+V + +QE Sbjct: 61 VARRTRP-SWHEDNPINYVQCDISDPDD...+IL +D PGGPWKVYG Sbjct: 4 WWAGAIGAAKKKLEEDDAPPKHS---SVALIVGVTGIIGNSLAEILPLADTPGGP...AWHEDNPINYIQCDISDPDDSLAKLSPLTDVTHVFYVTCANR--STEPENCE 117 Query: 406 MATHMFENIIGVLLTHAPNLQHVCMQTSDKHY-... : Swiss-Prot sp_hit_id Q7MXT7 Definition sp|Q7MXT7|LPXD_PORGI UDP-3-O-[3-hydroxymyristoyl] glucosamine N-ac...lue sp|Q7MXT7|LPXD_PORGI UDP-3-O-[3-hydroxymyristoyl] glucosamine N-... 34 0.62 sp|P60369|KR103_HUMAN Kerati

  14. AcEST: BP913772 [AcEST

    Full Text Available N VT V L C+ G G+ H Sbjct: 350 NVVTWSAVIAGYAQRGLGFEALDVFRQMRLCGSEPNVVTLVSLLSGCALAGTLLHGKETH 409 Query: 376 IEIER--RGLLEVDP-...VFNKLSVQDIVSW 236 + + A ++G+++H I RRGL + PV+ + LV MY R G L Q VF+++ +D+VSW Sbjct: 296 ASLAALEQGKLIHGYILRRGLDSILPVI-S... TF M+ +PN+VT V VL+AC+ + Q + Sbjct: 250 SWSAMIACYAKNGKAFEALRTFREMMRETKDSSPNSVTMVSVLQACASLA...MIEGGVAPNAVTFVVVLRACSQTGSYSQSQTFFEAMSKNF 50 + G A G + F+ M + GV PNAVTFV VLR CS G + Q F++M F Sbjct: 312 ALNGLAMNGFGEKCLELFSL...L YA G + + +F++ D+ +TA + + Sbjct: 48 IHAAILRHNLLLHPRYPVLNLKLHRAYASHGKIRHSLALFHQTIDP

  15. AcEST: DK952954 [AcEST

    Full Text Available TST38A01NGRL0015_H21 616 Adiantum capillus-veneris mRNA. clone: TST38A01NGRL0015_H21. 5' end seq ... LIHAHIVCSCNDVDNFVRSTLVNLYSKCGSIEDAHNVFAKLATRRSVDWSMMIS ... 541 ++ Q K +HA I + D + V + L+++Y+KCGSI DA F +++T+ ... LIHAHIVCSCNDVDNFVRSTLVNLYSKCGSIEDAHNVFAKLATRRSVDWSMMIS GS 547 + + IHA S D ++ LV LYS+CG IE+++ F + ++ W+ ++S ... LIHAHIVCSCNDVDNFVRSTLVNLYSKCGSIEDAHNVFAKLATRRSVDWSMMIS ... 541 DL + IH+ I+ + ++ +V S L+++Y+K G ++ A ++ + A + ... EA+ LF +M G+ P + + L AC Sbjct: 243 RVFDGLRLKDHSSWVAMIS GLSKNECEAEAIRLFCDMYVLGIMPTPYAFSSVLSACKKIE 302 Query ...

  16. AcEST: BP912540 [AcEST

    Full Text Available YMU001_000020_B03 501 Adiantum capillus-veneris mRNA. clone: YMU001_000020_B03. BP912540 - Show ... 2 EELTVHHTASVGDVEALKALLAEGADKDEKDSEGRTALHFACGYGEVMCAE VLLEAGVAV 181 EE VH TAS+GDVE LKA LA G +KDE+DSEGRTAL ... ry: 14 VHHTASVGDVEALKALLAEGADKDEKDSEGRTALHFACGYGEVMCAE VLLEAGVAVDAVD 193 +H A V ++ LL GAD KD G LH AC YG AE ... uery: 26 ASVGDVEALKALLAEGADKDEKDSEGR--TALHFACGYGEVMCAE VLLEAGVAVDAVDKN 199 + GD+E +K L + + + +D EGR T LHFA ... ry: 14 VHHTASVGDVEALKALLAEGADKDEKDSEGRTALHFACGYGEVMCAE VLLEAGVAVDAVD 193 +H A ++E + LL GAD + +D G LH A YG ...

  17. Dark Matter Searches with Cherenkov Telescopes: Nearby Dwarf Galaxies or Local Galaxy Clusters?

    In this paper, we compare dwarf galaxies and galaxy clusters in order to elucidate which object class is the best target for gamma-ray DM searches with imaging atmospheric Cherenkov telescopes (IACTs). We have built a mixed dwarfs+clusters sample containing some of the most promising nearby dwarf galaxies (Draco, Ursa Minor, Wilman 1 and Segue 1) and local galaxy clusters (Perseus, Coma, Ophiuchus, Virgo, Fornax, NGC 5813 and NGC 5846), and then compute their DM annihilation flux profiles by making use of the latest modeling of their DM density profiles. We also include in our calculations the effect of DM substructure. Willman 1 appears as the best candidate in the sample. However, its mass modeling is still rather uncertain, so probably other candidates with less uncertainties and quite similar fluxes, namely Ursa Minor and Segue 1, might be better options. As for galaxy clusters, Virgo represents the one with the highest flux. However, its large spatial extension can be a serious handicap for IACT observations and posterior data analysis. Yet, other local galaxy cluster candidates with more moderate emission regions, such as Perseus, may represent good alternatives. After comparing dwarfs and clusters, we found that the former exhibit annihilation flux profiles that, at the center, are roughly one order of magnitude higher than those of clusters, although galaxy clusters can yield similar, or even higher, integrated fluxes for the whole object once substructure is taken into account. Even when any of these objects are strictly point-like according to the properties of their annihilation signals, we conclude that dwarf galaxies are best suited for observational strategies based on the search of point-like sources, while galaxy clusters represent best targets for analyses that can deal with rather extended emissions. Finally, we study the detection prospects for present and future IACTs in the framework of the constrained minimal supersymmetric standard model. We

  18. Dark matter searches with Cherenkov telescopes: nearby dwarf galaxies or local galaxy clusters?

    In this paper, we compare dwarf galaxies and galaxy clusters in order to elucidate which object class is the best target for gamma-ray DM searches with imaging atmospheric Cherenkov telescopes (IACTs). We have built a mixed dwarfs+clusters sample containing some of the most promising nearby dwarf galaxies (Draco, Ursa Minor, Wilman 1 and Segue 1) and local galaxy clusters (Perseus, Coma, Ophiuchus, Virgo, Fornax, NGC 5813 and NGC 5846), and then compute their DM annihilation flux profiles by making use of the latest modeling of their DM density profiles. We also include in our calculations the effect of DM substructure. Willman 1 appears as the best candidate in the sample. However, its mass modeling is still rather uncertain, so probably other candidates with less uncertainties and quite similar fluxes, namely Ursa Minor and Segue 1, might be better options. As for galaxy clusters, Virgo represents the one with the highest flux. However, its large spatial extension can be a serious handicap for IACT observations and posterior data analysis. Yet, other local galaxy cluster candidates with more moderate emission regions, such as Perseus, may represent good alternatives. After comparing dwarfs and clusters, we found that the former exhibit annihilation flux profiles that, at the center, are roughly one order of magnitude higher than those of clusters, although galaxy clusters can yield similar, or even higher, integrated fluxes for the whole object once substructure is taken into account. Even when any of these objects are strictly point-like according to the properties of their annihilation signals, we conclude that dwarf galaxies are best suited for observational strategies based on the search of point-like sources, while galaxy clusters represent best targets for analyses that can deal with rather extended emissions. Finally, we study the detection prospects for present and future IACTs in the framework of the constrained minimal supersymmetric standard model. We

  19. Dark Matter Searches with Cherenkov Telescopes: Nearby Dwarf Galaxies or Local Galaxy Clusters?

    Sanchez-Conde, Miguel A.; /KIPAC, Menlo Park /SLAC /IAC, La Laguna /Laguna U., Tenerife; Cannoni, Mirco; /Huelva U.; Zandanel, Fabio; /IAA, Granada; Gomez, Mario E.; /Huelva U.; Prada, Francisco; /IAA, Granada

    2012-06-06

    In this paper, we compare dwarf galaxies and galaxy clusters in order to elucidate which object class is the best target for gamma-ray DM searches with imaging atmospheric Cherenkov telescopes (IACTs). We have built a mixed dwarfs+clusters sample containing some of the most promising nearby dwarf galaxies (Draco, Ursa Minor, Wilman 1 and Segue 1) and local galaxy clusters (Perseus, Coma, Ophiuchus, Virgo, Fornax, NGC 5813 and NGC 5846), and then compute their DM annihilation flux profiles by making use of the latest modeling of their DM density profiles. We also include in our calculations the effect of DM substructure. Willman 1 appears as the best candidate in the sample. However, its mass modeling is still rather uncertain, so probably other candidates with less uncertainties and quite similar fluxes, namely Ursa Minor and Segue 1, might be better options. As for galaxy clusters, Virgo represents the one with the highest flux. However, its large spatial extension can be a serious handicap for IACT observations and posterior data analysis. Yet, other local galaxy cluster candidates with more moderate emission regions, such as Perseus, may represent good alternatives. After comparing dwarfs and clusters, we found that the former exhibit annihilation flux profiles that, at the center, are roughly one order of magnitude higher than those of clusters, although galaxy clusters can yield similar, or even higher, integrated fluxes for the whole object once substructure is taken into account. Even when any of these objects are strictly point-like according to the properties of their annihilation signals, we conclude that dwarf galaxies are best suited for observational strategies based on the search of point-like sources, while galaxy clusters represent best targets for analyses that can deal with rather extended emissions. Finally, we study the detection prospects for present and future IACTs in the framework of the constrained minimal supersymmetric standard model. We

  20. Factor PD-Clustering

    Gettler Summa, Mireille; Palumbo, Francesco; Tortora, Cristina

    2012-01-01

    Factorial clustering methods have been developed in recent years thanks to the improving of computational power. These methods perform a linear transformation of data and a clustering on transformed data optimizing a common criterion. Factorial PD-clustering is based on Probabilistic Distance clustering (PD-clustering). PD-clustering is an iterative, distribution free, probabilistic, clustering method. Factor PD-clustering make a linear transformation of original variables into a reduced numb...

  1. Speed Control of DC Motor using AC/AC/DC Converter Based on Intelligent Techniques

    Rakan Kh Antar

    2013-01-01

       This paper describes the application of ac/ac/dc and ac/dc converters to control the speed of a separately excited DC motor. Artificial neural network and PI controller are trained to select the desired values of firing angles for triggering thyristors of the ac/ac/dc and ac/dc bridge converters in order to control the speed of the dc motor at a desired value with constant and different load torques in order to obtain the best speed response. Simulation results show that the rising time fo...

  2. Chemical composition and constraints on mass loss for globular clusters in dwarf galaxies: WLM and IKN

    Larsen, S S; Forbes, D A; Strader, J

    2014-01-01

    We determine the metallicities for globular clusters (GCs) in the WLM and IKN dwarf galaxies, using VLT/UVES and Keck/ESI spectroscopy. For the WLM GC we also measure detailed abundance ratios for a number of light, alpha, Fe-peak and n-capture elements. We find low metallicities of [Fe/H]=-2.0 and -2.1 for the WLM GC and the GC IKN-5, respectively. We estimate that 17%-31% of the metal-poor stars in WLM belong to the GC, and IKN-5 may even contain a similar number of metal-poor stars as the whole of the IKN dwarf itself. These high ratios of metal-poor GCs to field stars are in tension with GC formation scenarios that require GCs to have lost a very large fraction of their initial mass. The GCs in the WLM and IKN dwarf galaxies resemble those in the Fornax dSph by being significantly more metal-poor than a typical halo GC in the Milky Way and other large galaxies. They are also substantially more metal-poor than the bulk of the field stars in their parent galaxies. The overall abundance patterns in the WLM G...

  3. Spectroelectrochemical and cyclic voltamperometry of trigonal cluster of ruthenium acetate with pirazine in aqueous solution

    The electrochemical and spectroelectrochemical behavior of the trinuclear μ - oxo - cluster [Ru3O (Ac)6 (pirazine)3] in aqueous solution is reported. The reductive potential of the clusters and energy from transfer of charge metal-ligand are analysed. (M.J.C.)

  4. Universality of ac conduction in disordered solids

    Dyre, Jeppe; Schrøder, Thomas

    2000-01-01

    non-power-law universalities. It is argued that ac universality reflects an underlying percolation determining dc as well as ac conductivity in the extreme disorder limit. Three analytical approximations to the universal ac conductivities are presented and compared to computer simulations. Finally......The striking similarity of ac conduction in quite different disordered solids is discussed in terms of experimental results, modeling, and computer simulations. After giving an overview of experiment, a macroscopic and a microscopic model are reviewed. For both models the normalized ac conductivity...... as a function of a suitably scaled frequency becomes independent of details of the disorder in the extreme disorder limit, i.e., when the local randomly varying mobilities cover many orders of magnitude. The two universal ac conductivities are similar, but not identical; both are examples of unusual...

  5. Cluster automorphisms and compatibility of cluster variables

    Assem, Ibrahim; Schiffler, Ralf; Shramchenko, Vasilisa

    2013-01-01

    In this paper, we introduce a notion of unistructural cluster algebras, for which the set of cluster variables uniquely determines the clusters. We prove that cluster algebras of Dynkin type and cluster algebras of rank 2 are unistructural, then prove that if $\\mathcal{A}$ is unistructural or of Euclidean type, then $f: \\mathcal{A}\\to \\mathcal{A}$ is a cluster automorphism if and only if $f$ is an automorphism of the ambient field which restricts to a permutation of the cluster variables. In ...

  6. Globular Cluster Formation in the Virgo Cluster

    Moran, C Corbett; Lake, G

    2014-01-01

    Metal poor globular clusters (MPGCs) are a unique probe of the early universe, in particular the reionization era. Systems of globular clusters in galaxy clusters are particularly interesting as it is in the progenitors of galaxy clusters that the earliest reionizing sources first formed. Although the exact physical origin of globular clusters is still debated, it is generally admitted that globular clusters form in early, rare dark matter peaks (Moore et al. 2006; Boley et al. 2009). We provide a fully numerical analysis of the Virgo cluster globular cluster system by identifying the present day globular cluster system with exactly such early, rare dark matter peaks. A popular hypothesis is that that the observed truncation of blue metal poor globular cluster formation is due to reionization (Spitler et al. 2012; Boley et al. 2009; Brodie & Strader 2006); adopting this view, constraining the formation epoch of MPGCs provides a complementary constraint on the epoch of reionization. By analyzing both the l...

  7. Short term dynamic aperture with AC dipoles

    Mönig, Saskia; Persson, Tobias Hakan Bjorn; Coello De Portugal, Jaime; Langner, Andy; Tomas, Rogelio; CERN. Geneva. ATS Department

    2015-01-01

    The dynamic aperture of an accelerator is determined by its non-linear components and errors. Control of the dynamic aperture is important for a good understanding and operation of the accelerator. The AC dipole, installed in the LHC for the diagnostic of linear and non-linear optics, could serve as a tool for the determination of the dynamic aperture. However, since the AC dipole itself modifies the non-linear dynamics, the dynamic aperture with and without AC dipole are expected to differ. The effect of the AC dipole on the dynamic aperture is studied within this note.

  8. ac electroosmosis in rectangular microchannels.

    Campisi, Michele; Accoto, Dino; Dario, Paolo

    2005-11-22

    Motivated by the growing interest in ac electroosmosis as a reliable no moving parts strategy to control fluid motion in microfluidic devices for biomedical applications, such as lab-on-a-chip, we study transient and steady-state electrokinetic phenomena (electroosmosis and streaming currents) in infinitely extended rectangular charged microchannels. With the aid of Fourier series and Laplace transforms we provide a general formal solution of the problem, which is used to study the time-dependent response to sudden ac applied voltage differences in case of finite electric double layer. The Debye-Huckel approximation has been adopted to allow for an algebraic solution of the Poisson-Boltzmann problem in Fourier space. We obtain the expressions of flow velocity profiles, flow rates, streaming currents, as well as expressions of the complex hydraulic and electrokinetic conductances. We analyze in detail the dependence of the electrokinetic conductance on the extension of linear dimensions relative to the Debye length, with an eye on finite electric double layer effects. PMID:16351310

  9. DESARROLLO RURAL A.C.

    Alfredo Aguilar Valdés

    2015-01-01

    Full Text Available El objetivo de este trabajo fue analizar el diagnostico situacional de una Empresa de Servicios Profesionales en el caso de: Instituto de Promoción Para el Desarrollo Rural A.C., a través de la Metodología “UALAE” así como la oportunidad que como empresa presenta. Este estudio se realizó en el municipio de Saltillo, Coahuila, México. Adoptó esta Metodología UALAE y se difundió su opinión. El Instituto de Promoción Para el Desarrollo Rural A.C., está formado por profesionistas y productores cuya finalidad es la de contribuir al desarrollo del medio rural con proyectos de viabilidad técnica, económica y social, sobre la base de necesidades reales y al aprovechamiento sustentable del potencial de los recursos naturales. Su buen funcionamiento es indispensable e importante para el desarrollo de los productores agropecuarios principalmente, debido a que se ven muy beneficiados con todos los servicios que se les brinda, se han logrado buenos proyectos, buenas capacitaciones y un gran crecimiento de sus productos. Mediante el proceso de asistencia técnica a organizaciones de productores, se induce la formulación adecuada de proyectos viables desde el punto visto del mercado, la rentabilidad económica, las tecnologías disponibles y de la organización social.

  10. Adaptive Evolutionary Clustering

    Xu, Kevin S.; Kliger, Mark; Hero III, Alfred O.

    2011-01-01

    In many practical applications of clustering, the objects to be clustered evolve over time, and a clustering result is desired at each time step. In such applications, evolutionary clustering typically outperforms traditional static clustering by producing clustering results that reflect long-term trends while being robust to short-term variations. Several evolutionary clustering algorithms have recently been proposed, often by adding a temporal smoothness penalty to the cost function of a st...

  11. Relational visual cluster validity

    Ding, Y.; Harrison, R F

    2007-01-01

    The assessment of cluster validity plays a very important role in cluster analysis. Most commonly used cluster validity methods are based on statistical hypothesis testing or finding the best clustering scheme by computing a number of different cluster validity indices. A number of visual methods of cluster validity have been produced to display directly the validity of clusters by mapping data into two- or three-dimensional space. However, these methods may lose too much information to corre...

  12. AcEST: BP920845 [AcEST

    Full Text Available 45|Adiantum capillus-veneris mRNA, clone: YMU001_000142_D08. (514 letters) Database: uniprot_sprot.fasta 412,525 seq...P7 OS=Magnapor... 33 1.0 sp|Q7VF68|SYH_HELHP Histidyl-tRNA synthetase OS=Helicobacter hep... 31 3.8 sp|P1305...90 FTGFLVLHSEPRQQPQVDL 1608 >sp|A4QX49|DBP7_MAGGR ATP-dependent RNA helicase DBP7 OS=Magnaporthe grise...T PT VT+H + T+ AC+ A+TT+ H H Sbjct: 481 PPKETKPTK------PVTNHTESTVGKACYITSAANTTITLHKLH 519 >sp|Q7VF68|SYH_HELHP His...rot_trembl.fasta 7,341,751 sequences; 2,391,615,440 total letters Searching.................................

  13. AcEST: DK960083 [AcEST

    Full Text Available ome P450 71D7 OS=Solanum chacoense ... 96 1e-19 sp|Q9SAB6|C71AI_ARATH Cytochrome ...... 96 2e-19 sp|P93530|C71D6_SOLCH Cytochrome P450 71D6 OS=Solanum chacoense ... 94 5e-19 sp|Q9T0K2|C71AK_AR... paten... 176 1e-42 tr|Q9AXP9|Q9AXP9_POPJC Cinnamate 4-hydroxylase OS=Populus jackii... 176 2e-42 tr|Q40907|Q40907_POPKI Cinnamic ac...8 KVVQQSRGAWEDEALRVIQDLKA 160 >tr|Q9AXP9|Q9AXP9_POPJC Cinnamate 4-hydroxylase OS=Populus jackii GN=C4H PE=2 ...e-42 tr|A9PBZ7|A9PBZ7_POPTR Putative uncharacterized protein OS=Popul... 176 2e-4

  14. AcEST: DK955376 [AcEST

    Full Text Available TST39A01NGRL0022_O23 611 Adiantum capillus-veneris mRNA. clone: TST39A01NGRL0022_O23. 5' end seq ... LMDETRAAGIKL 210 Query: 602 AIC 610 A+C Sbjct: 211 AVC ... 213 >tr|A9SM81|A9SM81_PHYPA Predicted protein OS=P ... C 610 VLELMD A+ KGLKVA+C Sbjct: 196 VLELMDAAREKGLKVAVC ... 213 >tr|Q8L7U1|Q8L7U1_ARATH AT4g39970/T5J17_140 OS ... LKVAIC 610 LMDEA+A G K+A+C Sbjct: 182 RLMDEAKAAGKKLAVC ... 197 >tr|Q680K2|Q680K2_ARATH MRNA, complete cds, cl ... LKVAIC 610 LMDEA+A G K+A+C Sbjct: 182 RLMDEAKAAGKKLAVC ... 197 >tr|Q8LAS1|Q8LAS1_ARATH Putative uncharacteriz ...

  15. AcEST: BP913416 [AcEST

    Full Text Available GCATGTAGTTTGGA CAGAGATG ■■Homology search results ■■ - Swiss-Prot (release 56.9) Link to BlastX Result : Swi...AC_BACFN Uronate isomerase OS=Bacteroides fragilis (... 30 4.5 sp|Q3ITT7|SYA_NATPD Alanyl-tRNA synthetase OS=Natronomonas phar...C++ N IP+ M C Sbjct: 417 LSYPRHEYFRRTLCNLLGCDVENGEIPLSEMERVC 451 >sp|Q3ITT7|SYA_NATPD Alanyl-tRNA synthetase OS=Natronomonas phar...ng, Webb Miller, and David J. Lipman (1997), Gapped BLAST and PSI-BLAST: a new generation of protein database searc...148,809,765 total letters Searching..................................................done Score E Sequences

  16. AcEST: DK947388 [AcEST

    Full Text Available Lipman (1997), Gapped BLAST and PSI-BLAST: a new generation of protein database search programs, Nucleic Ac...ids Res. 25:3389-3402. Query= DK947388|Adiantum capillus-veneris mRNA, clone: YMU02A01NGRL0015_L18, 5' (587 letters) Databa... generation of protein database search programs, Nucleic Acids Res. 25:3389-3402. Query= DK947388|Adiantum c...apillus-veneris mRNA, clone: YMU02A01NGRL0015_L18, 5' (587 letters) Database: uniprot_trembl.fasta...-ribosylation factor 1 OS=Salix bakko GN... 268 1e-71 sp|P49076|ARF_MAIZE ADP-ribosylation factor OS=Zea may

  17. AcEST: BP916217 [AcEST

    Full Text Available inase kinase 7-interacting protein 3 OS=Mus musculus Align length 119 Score (bit) 35.0 E-value 0.16 Report B...visiae GN... 30 6.8 >sp|Q571K4|TAB3_MOUSE Mitogen-activated protein kinase kinase kinase 7-interacting protein 3 OS=Mus musculus...protein kinase kinase kinase 7 interacting protein 3 OS=Mus musculus GN=Map3k7ip3 PE=2 SV=1 Length = 716 Sco...(3)malignant brain tumor-like 2 prot... 31 2.3 sp|P33234|ADIY_ECOLI HTH-type transcriptional regulator adiY ...ZZC3_PSEU2 Membrane protein, putative OS=Pseudomonas... 35 2.5 tr|Q5U7D5|Q5U7D5_9BACI OpuAC OS=Halobacillus trueperi GN=opu

  18. AcEST: DK953324 [AcEST

    Full Text Available |LSRR_PHOLL Transcriptional regulator lsrR OS=Photorhab... 30 6.1 sp|A0JY64|ATPB_ARTS2 ATP synthase subunit beta OS=Arthroba...cter s... 30 6.1 sp|A1R7V3|ATPB_ARTAT ATP synthase subunit beta OS=Arthroba...ATP synthase subunit beta OS=Arthrobacter sp. (strain FB24) GN=atpD PE=3 SV=1 Len...KD 372 Query: 311 HLHFTHRGKQRL 346 H + R KQ L Sbjct: 373 HYNTAVRVKQIL 384 >sp|A1R7V3|ATPB_ARTAT ATP synthase subunit beta OS=Arthroba...T and PSI-BLAST: a new generation of protein database search programs, Nucleic Ac

  19. AcEST: DK945049 [AcEST

    Full Text Available R 148 >sp|Q9X5X3|ATCU_SINMW Copper-transporting P-type ATPase OS=Sinorhizobium medicae (strain WSM419) GN=ac...|Q4EPP8|Q4EPP8_LISMO Heavy metal-binding protein OS=Listeria m... 34 3.2 tr|A6AST1|A6AST1_VIBHA Copper-trans..... 31 2.7 sp|Q4X0S7|DPH1_ASPFU Diphthamide biosynthesis protein 1 OS=Asper... 30 4.5 sp|A2VDJ0|T131L_HUMAN Transmembran...P58342|ATCU2_RHIME Copper-transporting ATPase 2 OS=Rhizobium meliloti Align length 75 Score (bit) 34.7 E-val...sophila ... 30 7.8 >sp|P58342|ATCU2_RHIME Copper-transporting ATPase 2 OS=Rhizobium me

  20. Applying Machine Learning to Star Cluster Classification

    Fedorenko, Kristina; Grasha, Kathryn; Calzetti, Daniela; Mahadevan, Sridhar

    2016-01-01

    Catalogs describing populations of star clusters are essential in investigating a range of important issues, from star formation to galaxy evolution. Star cluster catalogs are typically created in a two-step process: in the first step, a catalog of sources is automatically produced; in the second step, each of the extracted sources is visually inspected by 3-to-5 human classifiers and assigned a category. Classification by humans is labor-intensive and time consuming, thus it creates a bottleneck, and substantially slows down progress in star cluster research.We seek to automate the process of labeling star clusters (the second step) through applying supervised machine learning techniques. This will provide a fast, objective, and reproducible classification. Our data is HST (WFC3 and ACS) images of galaxies in the distance range of 3.5-12 Mpc, with a few thousand star clusters already classified by humans as a part of the LEGUS (Legacy ExtraGalactic UV Survey) project. The classification is based on 4 labels (Class 1 - symmetric, compact cluster; Class 2 - concentrated object with some degree of asymmetry; Class 3 - multiple peak system, diffuse; and Class 4 - spurious detection). We start by looking at basic machine learning methods such as decision trees. We then proceed to evaluate performance of more advanced techniques, focusing on convolutional neural networks and other Deep Learning methods. We analyze the results, and suggest several directions for further improvement.

  1. Star Clusters in Pseudo-Bulges of Spiral Galaxies

    Di Nino, Daiana; Stiavelli, Massimo; Carollo, C Marcella; Scarlata, Claudia; Wyse, Rosemary F G

    2009-01-01

    We present a study of the properties of the star-cluster systems around pseudo-bulges of late-type spiral galaxies using a sample of 11 galaxies with distances from 17 to 37 Mpc. Star clusters are identified from multiband HST ACS and WFPC2 imaging data by combining detections in 3 bands (F435W and F814W with ACS and F606W with WFPC2). The photometric data are then compared to population synthesis models to infer the masses and ages of the star clusters. Photometric errors and completeness are estimated by means of artificial source Monte Carlo simulations. Dust extinction is estimated by considering F160W NICMOS observations of the central regions of the galaxies, augmenting our wavelength coverage. In all galaxies we identify star clusters with a wide range of ages, from young (age 100-250 Myr), more massive, red clusters. Some of the latter might likely evolve into objects similar to the Milky Way's globular clusters. We compute the specific frequencies for the older clusters with respect to the galaxy an...

  2. Partitional clustering algorithms

    2015-01-01

    This book summarizes the state-of-the-art in partitional clustering. Clustering, the unsupervised classification of patterns into groups, is one of the most important tasks in exploratory data analysis. Primary goals of clustering include gaining insight into, classifying, and compressing data. Clustering has a long and rich history that spans a variety of scientific disciplines including anthropology, biology, medicine, psychology, statistics, mathematics, engineering, and computer science. As a result, numerous clustering algorithms have been proposed since the early 1950s. Among these algorithms, partitional (nonhierarchical) ones have found many applications, especially in engineering and computer science. This book provides coverage of consensus clustering, constrained clustering, large scale and/or high dimensional clustering, cluster validity, cluster visualization, and applications of clustering. Examines clustering as it applies to large and/or high-dimensional data sets commonly encountered in reali...

  3. Cluster Evaluation of Density Based Subspace Clustering

    Sembiring, Rahmat Widia; Zain, Jasni Mohamad

    2010-01-01

    Clustering real world data often faced with curse of dimensionality, where real world data often consist of many dimensions. Multidimensional data clustering evaluation can be done through a density-based approach. Density approaches based on the paradigm introduced by DBSCAN clustering. In this approach, density of each object neighbours with MinPoints will be calculated. Cluster change will occur in accordance with changes in density of each object neighbours. The neighbours of each object ...

  4. Clustering with Spectral Methods

    Gaertler, Marco

    2002-01-01

    Grouping and sorting are problems with a great tradition in the history of mankind. Clustering and cluster analysis is a small aspect in the wide spectrum. But these topics have applications in most scientific disciplines. Graph clustering is again a little fragment in the clustering area. Nevertheless it has the potential for new pioneering and innovative methods. One such method is the Markov Clustering presented by van Dongen in 'Graph Clustering by Flow Simulation'. We investigated the qu...

  5. Sparse Convex Clustering

    Wang, Binhuan; Zhang, Yilong; Sun, Wei; Fang, Yixin

    2016-01-01

    Convex clustering, a convex relaxation of k-means clustering and hierarchical clustering, has drawn recent attentions since it nicely addresses the instability issue of traditional nonconvex clustering methods. Although its computational and statistical properties have been recently studied, the performance of convex clustering has not yet been investigated in the high-dimensional clustering scenario, where the data contains a large number of features and many of them carry no information abo...

  6. SINGLE PHASE HIGH FREQUENCY AC CONVERTER FOR INDUCTION HEATING APPLICATION

    M.A INAYATHULLAAH,; Dr. R. Anita

    2010-01-01

    The proposed topology reduces the total harmonic distortion (THD) of a high frequency AC/AC Converter well below the acceptable limit. This paper deals with a novel single phase AC/DC/AC soft switching utility frequency AC to high frequency AC converter. In this paper a single phase full bridge inverter with Vienna rectifier as front end is used instead of conventional diode bridge rectifier to provide continuous sinusoidal input current with nearly unity power factor at the source side with ...

  7. Memory Convergence and Optimization with Fuzzy PSO and ACS

    Subhash C. Pandey

    2008-01-01

    Full Text Available Associative neural memories are models of biological phenomena that allow for the storage of pattern associations and the retrieval of the desired output pattern upon presentation of a possibly noisy or incomplete version of an input pattern. In this study, we introduce fuzzy swarm particle optimization technique for convergence of associative neural memories based on fuzzy set theory. A Fuzzy Particle Swarm Optimization (FPSO consists of clustering of swarm's particle by applying fuzzy c-mean algorithm to attain the neighborhood best. We present a singular value decomposition method for the selection of efficient rule from a given rule base required to attain the global best. Finally, we illustrate the proposed method by virtue of some examples. Further, ant colony system ACS algorithm is used to study the Symmetric Traveling Salesman Problem TSP. The optimum parameters for this algorithm have to found by trial and error. The ACS parameters working in a designed subset of TSP instances has also been optimized by virtue of Particle Swarm Optimization PSO.

  8. Characterization of AcMNPV with a deletion of ac69 gene

    Jianhao Ke

    2011-07-01

    Full Text Available ORF69 (Ac69 of Autographa californica multiple nucleopolyhedrovirus (AcMNPV is conserved in some baculovirus genomes. Although it has been shown that Ac69 has cap 0-dependent methyltransferase activity and is not required for budded virus production in Spodoptera frugiperda Sf-9 cells, its role in occlusion-derived virus synthesis and virus oral infectivity is not known. This paper describes generation of an ac69 knockout AcMNPV bacmid mutant and analyses of the influence of ac69 deletion on the viral infectivity in Sf-9 cells and Trichoplusia ni larvae so as to investigate the role of ac69 in the viral life cycle. Results indicated that ac69 deletion has little effect on the production rates and morphogenesis of budded virus and occlusion-derived virus in Sf-9 cells. In addition, animal experiment revealed that the deletion mutant did not affect AcMNPV infectivity for Trichoplusia ni larvae in LD50 and LT50 bioassay when administered orally. These results suggest that ac69 may be dispensable for viral infectivity both in vitro and in vivo.

  9. Cluster categories and cluster-tilted algebras

    Torkildsen, Hermund Andre

    2006-01-01

    We have given an introduction to the theory of cluster categories and cluster-tilted algebras, and this was one of our main objectives in this thesis. We have seen that cluster-tilted algebras are relation-extension algebras, and this gave us a way of constructing the quiver of a cluster-tilted algebra from a tilted algebra. A cluster-tilted algebra of finite representation type is determined by its quiver, and this raised questions about the generality of this result. We defined a new class...

  10. Noise reduction in AC-coupled amplifiers

    Serrano Finetti, Roberto Ernesto; Pallàs Areny, Ramon

    2014-01-01

    AC-coupled amplifiers are noisier than dc-coupled amplifiers because of the thermal noise of the resistor(s) in the ac-coupling network and the increased contribution of the amplifier input noise current i(n). Both contributions, however, diminish if the corner frequency f(c) of the high-pass filter observed by the signal is lowered, the cost being a longer transient response. At the same time, the presence of large resistors in the ac-coupling network suggests that the use of FET-input ampli...

  11. Barred Galaxies in the Coma Cluster

    Marinova, Irina; Trentham, Neil; Ferguson, Henry C; Weinzirl, Tim; Balcells, Marc; Carter, David; Brok, Mark den; Erwin, Peter; Graham, Alister W; Goudfrooij, Paul; Guzman, Rafael; Hammer, Derek; Hoyos, Carlos; Peletier, Reynier F; Huxor, Avon P; Peng, Erik; Kleijn, Gijs Verdoes

    2010-01-01

    We use ACS data from the HST Treasury survey of the Coma cluster (z~0.02) to study the properties of barred galaxies in the Coma core, the densest environment in the nearby Universe. This study provides a complementary data point for studies of barred galaxies as a function of redshift and environment. From ~470 cluster members brighter than M_I = -11 mag, we select a sample of 46 disk galaxies (S0--Im) based on visual classification. The sample is dominated by S0s for which we find an optical bar fraction of 47+/-11% through ellipse fitting and visual inspection. Among the bars in the core of the Coma cluster, we do not find any very large (a_bar > 2 kpc) bars. Comparison to other studies reveals that while the optical bar fraction for S0s shows only a modest variation across low-to-intermediate density environments (field to intermediate-density clusters), it can be higher by up to a factor of ~2 in the very high-density environment of the rich Coma cluster core.

  12. Learning predictive clustering rules

    Ženko, Bernard; Džeroski, Sašo; Struyf, Jan

    2005-01-01

    The two most commonly addressed data mining tasks are predictive modelling and clustering. Here we address the task of predictive clustering, which contains elements of both and generalizes them to some extent. We propose a novel approach to predictive clustering called predictive clustering rules, present an initial implementation and its preliminary experimental evaluation.

  13. Clustering of correlated networks

    Dorogovtsev, S. N.

    2003-01-01

    We obtain the clustering coefficient, the degree-dependent local clustering, and the mean clustering of networks with arbitrary correlations between the degrees of the nearest-neighbor vertices. The resulting formulas allow one to determine the nature of the clustering of a network.

  14. Structures of Mn clusters

    Tina M Briere; Marcel H F Sluiter; Vijay Kumar; Yoshiyuki Kawazoe

    2003-01-01

    The geometries of several Mn clusters in the size range Mn13–Mn23 are studied via the generalized gradient approximation to density functional theory. For the 13- and 19-atom clusters, the icosahedral structures are found to be most stable, while for the 15-atom cluster, the bcc structure is more favoured. The clusters show ferrimagnetic spin configurations.

  15. Foodservice Occupations Cluster Guide.

    Oregon State Dept. of Education, Salem.

    Intended to assist vocational teachers in developing and implementing a cluster program in food service occupations, this guide contains sections on cluster organization and implementation and instructional emphasis areas. The cluster organization and implementation section covers goal-based planning and includes a proposed cluster curriculum, a…

  16. The Effect of the Feedback Controller on Superconducting Tokamak AC Losses + AC-CRPP user manual

    Superconducting coils in a Tokamak are subject to AC losses when the field transverse to the coil current varies. A simple model to evaluate the AC losses has been derived and benchmarked against a complete model used in the ITER design procedure. The influence of the feedback control strategy on the AC losses is examined using this model. An improved controller is proposed, based on this study. (author)

  17. Guiding Principles in Selecting AC To DC Converters For Power Factor Corrections in AC Transmission System

    Ibekwe B.E

    2014-10-01

    Full Text Available The ac to dc converters’ power factors correction in ac transmission system were investigated. The studies include: phase-controlled converter; pulse width modulated (PWM converter and ac input current shaped converter. Using Fourier series, power factors of these converters were calculated and simulated using MATLAB. The resulting curves are displayed in the hard copies for practical guides in the choice of converters; and comparatively, current shaped type is the best.

  18. Relevant Subspace Clustering

    Müller, Emmanuel; Assent, Ira; Günnemann, Stephan; Krieger, Ralph; Seidl, Thomas

    Subspace clustering aims at detecting clusters in any subspace projection of a high dimensional space. As the number of possible subspace projections is exponential in the number of dimensions, the result is often tremendously large. Recent approaches fail to reduce results to relevant subspace...... clusters. Their results are typically highly redundant, i.e. many clusters are detected multiple times in several projections. In this work, we propose a novel model for relevant subspace clustering (RESCU). We present a global optimization which detects the most interesting non-redundant subspace clusters...... achieves top clustering quality while competing approaches show greatly varying performance....

  19. Tilting theory and cluster algebras

    Reiten, Idun

    2010-01-01

    We give an introduction to the theory of cluster categories and cluster tilted algebras. We include some background on the theory of cluster algebras, and discuss the interplay with cluster categories and cluster tilted algebras.

  20. A Simple Load Power Estimator For Quasi-Direct AC-AC Converter System

    Marian GAICEANU; Emil ROSU

    2003-01-01

    In this paper a simple load power estimator for the three-phase quasi-direct acac converter system is reported. Since the ac-ac converter control by means of pulsewidth modulation (PWM) is based on the power balance concept, its load power should be known. Two control boards, based on the dSMC (digital Smart Motion Controller) 30 MIPS 32-bit fixed-point digital signal processor (DSP), were involved in the ac-ac system driving. By using the power balance control, the DC link voltage variation ...

  1. Transport AC losses in YBCO coated conductors

    Majoros, M [Ohio State University, Columbus, OH 43210 (United States); Ye, L [IRC in Superconductivity, University of Cambridge, Madingley Road, Cambridge CB3 0HE (United Kingdom); Velichko, A V [IRC in Superconductivity, University of Cambridge, Madingley Road, Cambridge CB3 0HE (United Kingdom); Coombs, T A [IRC in Superconductivity, University of Cambridge, Madingley Road, Cambridge CB3 0HE (United Kingdom); Sumption, M D [Ohio State University, Columbus, OH 43210 (United States); Collings, E W [Ohio State University, Columbus, OH 43210 (United States)

    2007-09-15

    Transport AC loss measurements have been made on YBCO-coated conductors prepared on two different substrate templates-RABiTS (rolling-assisted biaxially textured substrate) and IBAD (ion-beam-assisted deposition). RABiTS samples show higher losses compared with the theoretical values obtained from the critical state model, with constant critical current density, at currents lower than the critical current. An origin of this extra AC loss was demonstrated experimentally by comparison of the AC loss of two samples with different I-V curves. Despite a difference in I-V curves and in the critical currents, their measured losses, as well as the normalized losses, were practically the same. However, the functional dependence of the losses was affected by the ferromagnetic substrate. An influence of the presence of a ferromagnetic substrate on transport AC losses in YBCO film was calculated numerically by the finite element method. The presence of a ferromagnetic substrate increases transport AC losses in YBCO films depending on its relative magnetic permeability. The two loss contributions-transport AC loss in YBCO films and ferromagnetic loss in the substrate-cannot be considered as mutually independent.

  2. Parallel Local Graph Clustering

    Shun, Julian; Roosta-Khorasani, Farbod; Fountoulakis, Kimon; Mahoney, Michael W.

    2016-01-01

    Graph clustering has many important applications in computing, but due to growing sizes of graph, even traditionally fast clustering methods such as spectral partitioning can be computationally expensive for real-world graphs of interest. Motivated partly by this, so-called local algorithms for graph clustering have received significant interest due to the fact that they can find good clusters in a graph with work proportional to the size of the cluster rather than that of the entire graph. T...

  3. Clustering and classification

    Arabie, Phipps

    1996-01-01

    At a moderately advanced level, this book seeks to cover the areas of clustering and related methods of data analysis where major advances are being made. Topics include: hierarchical clustering, variable selection and weighting, additive trees and other network models, relevance of neural network models to clustering, the role of computational complexity in cluster analysis, latent class approaches to cluster analysis, theory and method with applications of a hierarchical classes model in psychology and psychopathology, combinatorial data analysis, clusterwise aggregation of relations, review

  4. Cluster ion beam facilities

    A brief state-of-the-art review in the field of cluster-surface interactions is presented. Ionised cluster beams could become a powerful and versatile tool for the modification and processing of surfaces as an alternative to ion implantation and ion assisted deposition. The main effects of cluster-surface collisions and possible applications of cluster ion beams are discussed. The outlooks of the Cluster Implantation and Deposition Apparatus (CIDA) being developed in Guteborg University are shown

  5. Graded cluster algebras

    Grabowski, Jan

    2015-01-01

    In the cluster algebra literature, the notion of a graded cluster algebra has been implicit since the origin of the subject. In this work, we wish to bring this aspect of cluster algebra theory to the foreground and promote its study. We transfer a definition of Gekhtman, Shapiro and Vainshtein to the algebraic setting, yielding the notion of a multi-graded cluster algebra. We then study gradings for finite type cluster algebras without coefficients, giving a full classification. Translating ...

  6. Cluster Evaluation of Density Based Subspace Clustering

    Sembiring, Rahmat Widia

    2010-01-01

    Clustering real world data often faced with curse of dimensionality, where real world data often consist of many dimensions. Multidimensional data clustering evaluation can be done through a density-based approach. Density approaches based on the paradigm introduced by DBSCAN clustering. In this approach, density of each object neighbours with MinPoints will be calculated. Cluster change will occur in accordance with changes in density of each object neighbours. The neighbours of each object typically determined using a distance function, for example the Euclidean distance. In this paper SUBCLU, FIRES and INSCY methods will be applied to clustering 6x1595 dimension synthetic datasets. IO Entropy, F1 Measure, coverage, accurate and time consumption used as evaluation performance parameters. Evaluation results showed SUBCLU method requires considerable time to process subspace clustering; however, its value coverage is better. Meanwhile INSCY method is better for accuracy comparing with two other methods, altho...

  7. AcEST: BP917188 [AcEST

    Full Text Available RLLFTKLDESESYGCIVNAQVRN 415 >tr|B8KW59|B8KW59_9GAMM Iron-sulfur cluster binding protein, putative OS=gamma proteobacte...id... 30 6.7 sp|A1S7L7|FADI_SHEAM 3-ketoacyl-CoA thiolase OS=Shewanella amazo... 30 6.7 sp|Q92JD4|Y133_RICCN Uncharacterized prote... Hemicentin 2 OS=Mus musculus GN=Hmcn2 PE=... 34 3.8 tr|A3ZSD0|A3ZSD0_9PLAN Putative uncharacterized protein OS=Bla...A0B2Y2_BURCH Transcriptional regulator, DeoR family OS... 33 8.3 tr|A7T3H3|A7T3H3_NEMVE Predicted protein OS=Nematostella vecte...CSNAAGTSSQEQS 2283 >tr|A3ZSD0|A3ZSD0_9PLAN Putative uncharacterized protein OS=Blastopirellula marina DSM 36

  8. Media Clusters and Media Cluster Policies

    Karlsson, Charlie; Picard, Robert

    2011-01-01

    Large media clusters have emerged in a limited number of large cities, characterizing the geographical concentration of the global media industry. This paper explores the reasons behind the localization patterns of media industries, the effect of the rapid advancement of Information and Communication Technologies (ICT) on media clusters and the role of media cluster policies. One might draw the conclusion that with the developments of the ICT sector and the fact that there are no raw material...

  9. Cluster selection in divisive clustering algorithms

    Savaresi, Sergio,; Boley, Daniel L.; Bittanti, Sergio; Gazzaniga, Giovanna

    2002-01-01

    This paper deals with the problem of clustering a data-set. In particular, the bisecting divisive approach is here considered. This approach can be naturally divided into two sub-problems: the problem of choosing which cluster must be divided, and the problem of splitting the selected cluster. The focus here is on the first problem. The contribution of this work is to propose a new technique for the selection of the cluster to split. This technique is based upon the shape of...

  10. Ac magnetic susceptibility measurements in nanoparticulate powders of iron-doped ZnO

    Low temperature (T) ac magnetic susceptibility (χac) measurements were performed in powder samples of the Zn1−xFexO (x=0–0.078) prepared by a combustion reaction method. The amplitude of the ac magnetic field was kept constant (1 mT) while its frequency (f) varied in the range 10–104 Hz for 5≤T≤300 K. The diluted samples presented cusps with maxima distributed around Tf=17.5±0.5 K while no such feature was observed for the pure sample (x=0). The cusp was found to become more pronounced with the increasing Fe content. Also it decreased and shifted to higher values of T by increasing f. The shift in Tf was found to follow a Vogel–Fulcher law with Ea/kB=317.6 K, T0=4.65 K and τ0=10−14 s, for the activation energy, critical temperature and characteristic time-constant, respectively. The energy gap of the sample was measured and they were found to vary in the range 3.75–3.80 eV. The overall χac-data resembles those obtained for cluster spin-glass state. - Highlights: ► Low temperature (T) ac magnetic susceptibility (χac) measurements. ► Zn1−xFexO prepared by a combustion reaction method. ► Spin-glass phase. ► High energy gap semiconductors.

  11. Young massive star clusters

    Zwart, Simon Portegies; Gieles, Mark

    2010-01-01

    Young massive clusters are dense aggregates of young stars that form the fundamental building blocks of galaxies. Several examples exist in the Milky Way Galaxy and the Local Group, but they are particularly abundant in starburst and interacting galaxies. The few young massive clusters that are close enough to resolve are of prime interest for studying the stellar mass function and the ecological interplay between stellar evolution and stellar dynamics. The distant unresolved clusters may be effectively used to study the star-cluster mass function, and they provide excellent constraints on the formation mechanisms of young cluster populations. Young massive clusters are expected to be the nurseries for many unusual objects, including a wide range of exotic stars and binaries. So far only a few such objects have been found in young massive clusters, although their older cousins, the globular clusters, are unusually rich in stellar exotica. In this review we focus on star clusters younger than $\\sim100$\\,Myr, m...

  12. Cluster automorphism groups of cluster algebras with coefficients

    Chang, Wen; Zhu, Bin

    2015-01-01

    We study the cluster automorphism group of a skew-symmetric cluster algebra with geometric coefficients. For this, we introduce the notion of gluing free cluster algebra, and show that under a weak condition the cluster automorphism group of a gluing free cluster algebra is a subgroup of the cluster automorphism group of its principal part cluster algebra (i.e. the corresponding cluster algebra without coefficients). We show that several classes of cluster algebras with coefficients are gluin...

  13. The Sloan Lens ACS Survey. V. The full ACS strong-lens sample

    Bolton, Adam S.; Burles, Scott; Koopmans, Leon V. E.; Treu, Tommaso; Gavazzi, Raphael; Moustakas, Leonidas A.; Wayth, Randall; Schlegel, David J.

    2008-01-01

    We present the definitive data for the full sample of 131 strong gravitational lens candidates observed with the Advanced Camera for Surveys (ACS) aboard the Hubble Space Telescope by the Sloan Lens ACS (SLACS) Survey. All targets were selected for higher redshift emission lines and lower redshift c

  14. What Makes Clusters Decline?

    Østergaard, Christian Richter; Park, Eun Kyung

    2015-01-01

    Most studies on regional clusters focus on identifying factors and processes that make clusters grow. However, sometimes technologies and market conditions suddenly shift, and clusters decline. This paper analyses the process of decline of the wireless communication cluster in Denmark. The...... longitudinal study on the high-tech cluster reveals that technological lock-in and exit of key firms have contributed to decline. Entrepreneurship has a positive effect on the cluster’s adaptive capabilities, while multinational companies have contradicting effects by bringing in new resources to the cluster...

  15. Identifying Contaminated K-band Globular Cluster RR Lyrae Photometry

    Majaess, Daniel J; Gieren, Wolfgang P

    2012-01-01

    Acquiring near-infrared K-band (2.2 um) photometry for RR Lyrae variables in globular clusters and nearby galaxies is advantageous since the resulting distances are less impacted by reddening and metallicity. However, K-band photometry for RR Lyrae variables in M5, Reticulum, M92, omega Cen, and M15 display clustercentric trends. HST ACS data imply that multiple stars in close proximity to RR Lyrae variables located near the cluster core, where the stellar density increases markedly, are generally unresolved in ground-based images. RR Lyrae variables near the cluster cores appear to suffer from photometric contamination, thereby yielding underestimated cluster distances and biased ages. The impact is particularly pernicious since the contamination propagates a systematic uncertainty into the distance scale, and hinders the quest for precision cosmology. The clustercentric trends are probably unassociated with variations in chemical composition since an empirical K-band period-magnitude relation inferred from ...

  16. AC losses in filamentary YBCO/hastelloy

    Full text: The AC hysteresis loss of a long YBCO thin-film superconducting strip in a perpendicular AC magnetic field can be reduced by subdividing the film into narrow parallel strips (filaments). The hysteresis loss depends on the film critical current density Jc, the film thickness d, the filament width 2a and the lateral spacing L between filaments as well as on the AC magnetic field amplitude Hm. In addition, if the film is deposited onto a YSZ/hastelloy substrate to form a flexible tape, eddy current loss occurs in the hastelloy metal. The eddy current loss depends on the resistivity p of the hastelloy, the width 2w and thickness dm of the hastelloy substrate as well as on the frequency f and amplitude Hm. We have calculated the hysteresis and eddy current losses as a function of Jc, d, 2a, L, p, w, dm, f, and Hm to find optimal design parameters for a YBCO/hastelloy tape. As the AC loss is related to the loss component X'' of the AC susceptibility, we have measured X'' at different frequencies f and amplitudes Hm for several filamentary designs of YBCO/hastelloy tapes and compared our experimental results with our model calculations

  17. Analysis of Various Clustering Algorithms

    Asst Prof. Sunila Godara,; Ms. Amita Verma,

    2013-01-01

    Data clustering is a process of putting similar data into groups. A clustering algorithm partitions a data set into several groups such that the similarity within a group is larger than among groups. This paper reviews four types of clustering techniques- k-Means Clustering, Farther first clustering, Density Based Clustering, Filtered clusterer. These clustering techniques are implemented and analyzed using a clustering tool WEKA. Performance of the 4 techniques are presented and compared.

  18. Where is the matter in the Merging Cluster Abell 2218?

    Elíasdóttir, Árdís; Limousin, Marceau; Richard, Johan,; Hjorth, Jens,; Kneib, Jean-Paul,; Natarajan, Priya; Pedersen, Kristian; Jullo, Eric; Paraficz, Danuta

    2007-01-01

    We present a parametric strong lensing model of the cluster Abell 2218 based on HST ACS data. We constrain the lens model using 8 previously known multiply imaged systems, of which 7 have spectroscopically confirmed redshifts. In addition, we propose five candidate multiply imaged systems and estimate their redshifts using our mass model. The model parameters are optimized in the source plane by a bayesian Monte Carlo Markov Chain as implemented in the the publicly available software Lenstool...

  19. Kinematic and Structural Evolution of Field and Cluster Spiral Galaxies

    Ziegler, Bodo L.; Kutdemir, Elif; Da Rocha, Cristiano; Böhm, Asmus; Peletier, Reynier F; Verdugo, Miguel

    2009-01-01

    To understand the processes that build up galaxies we investigate the stellar structure and gas kinematics of spiral and irregular galaxies out to redshift 1. We target 92 galaxies in four cluster (z = 0.3 & 0.5) fields to study the environmental influence. Their stellar masses derived from multiband VLT/FORS photometry are distributed around but mostly below the characteristic Schechter-fit mass. From HST/ACS images we determine morphologies and structural parameters like disk length, positi...

  20. The galaxy cluster outskirts via stacking

    Morandi, Andrea; Forman, William; Jones, Christine

    2015-01-01

    We studied the physical properties of the intracluster medium in the virialization region of a sample of 320 clusters ($0.056 3$ keV) in the Chandra archive. We stacked the emission measure profiles of the clusters to detect a signal out to and beyond $R_{200}$. We then measured the average emission measure, gas density and gas fraction. We observe a steepening of the density profiles beyond $R_{500}$ with $\\beta \\sim 0.68$ at $R_{500}$ and $\\beta \\sim 1$ at $R_{200}$ and beyond. By tracking the direction of the cosmic filaments where the clusters are embedded, we report that galaxy clusters deviate from spherical symmetry, with only small differences between relaxed and disturbed systems. We also did not find evolution of the gas density with redshift, confirming the self-similar evolution of the gas density. The value of the baryon fraction reaches the cosmic value at $R_{200}$: however, systematics due to non-thermal pressure support and clumpiness might enhance the measured gas fraction, leading to an ac...

  1. Clustering high dimensional data

    Assent, Ira

    2012-01-01

    for clustering are required. Consequently, recent research has focused on developing techniques and clustering algorithms specifically for high-dimensional data. Still, open research issues remain. Clustering is a data mining task devoted to the automatic grouping of data based on mutual similarity. Each cluster......High-dimensional data, i.e., data described by a large number of attributes, pose specific challenges to clustering. The so-called ‘curse of dimensionality’, coined originally to describe the general increase in complexity of various computational problems as dimensionality increases, is known...... groups objects that are similar to one another, whereas dissimilar objects are assigned to different clusters, possibly separating out noise. In this manner, clusters describe the data structure in an unsupervised manner, i.e., without the need for class labels. A number of clustering paradigms exist...

  2. Star clusters and associations

    All 33 papers presented at the symposium were inputted to INIS. They dealt with open clusters, globular clusters, stellar associations and moving groups, and local kinematics and galactic structures. (E.S.)

  3. AC loss performance of CS insert coil

    The ITER Central Solenoid (CS) model coil and the CS insert coil were fabricated, and the test was carried out. The AC loss measurement of the coil is one of the most important tests to determine coil performance. The AC loss of a short sample conductor for the CS insert coil was measured by using the calorimetric method, and the coupling time constants of the conductor were estimated to be 30 ms and 20 ms for pulse and discharge tests, respectively. The AC loss of the CS insert coil was measured by using the calorimetric method for pulse and discharge tests. The coupling time constant estimated from the result of the pulse tests was 34 ms and almost equal to that of the short sample. The coupling time constant for the discharge test was estimated to be 140 ms and about 4 times that of the pulse test. (author)

  4. ac propulsion system for an electric vehicle

    Geppert, S.

    1980-01-01

    It is pointed out that dc drives will be the logical choice for current production electric vehicles (EV). However, by the mid-80's, there is a good chance that the price and reliability of suitable high-power semiconductors will allow for a competitive ac system. The driving force behind the ac approach is the induction motor, which has specific advantages relative to a dc shunt or series traction motor. These advantages would be an important factor in the case of a vehicle for which low maintenance characteristics are of primary importance. A description of an EV ac propulsion system is provided, taking into account the logic controller, the inverter, the motor, and a two-speed transmission-differential-axle assembly. The main barrier to the employment of the considered propulsion system in EV is not any technical problem, but inverter transistor cost.

  5. Controlled clustering of carboxylated SPIONs through polyethylenimine

    Clusters of magnetite nanoparticles (MNPs) were synthesized using poly(acrylic acid-co-maleic acid) coated MNPs (PAM@MNP) and branched polyethylenimine (PEI). Materials were characterized by potentiometric titration, zeta potential and dynamic light scattering (DLS) measurements. PEI and PAM@MNP are oppositely charged as characterized by zeta potential measurements (+8, −34 mV respectively) and titration (10.30 mmol −NH3+/g PEI; 0.175 mmol −COO−/g PAM@MNP) at pH 6.5±0.2; therefore magnetic clusters are formed by electrostatic adhesion. Two different preparation methods and the effect of PEI and electrolyte (NaCl) concentration on the cluster formation was studied. Choosing an optimal concentration of PEI (charge ratio of PEI to PAM@MNP: 0.17) and electrolyte (10 mM), a concentrated (10 g MNP/L) product containing PEI–PAM@MNP nanoclusters with size of 165±10 nm was prepared. Its specific absorption rate (SAR) measured in AC magnetic field (110 kHz, 25 mT) is 12 W/g Fe. The clustered product is expected to have enhanced contrast efficiency in MRI. - Highlights: • SPION clusters of controlled size were prepared by means of electrostatic adhesion. • Nanocluster formation optimum was at 0.17 charge ratio of PEI to PAM@MNP. • Huge aggregates form at higher PEI to PAM@MNP charge ratio. • Higher ionic strength promotes the formation of clusters at lower PEI concentrations

  6. Melting of clusters

    Haberland, H. [Freiburg Univ., Facultat fur Physik (Germany)

    2001-07-01

    An experiment is described which allows to measure the caloric curve of size selected sodium cluster ions. This allows to determine rather easily the melting temperatures, and latent heats in the size range between 55 and 340 atoms per cluster. A more detailed analysis is necessary to show that the cluster Na{sub 147}{sup +} has a negative microcanonical heat capacity, and how to determine the entropy of the cluster from the data. (authors)

  7. Cluster beam sources. Part 1. Methods of cluster beams generation

    A.Ju. Karpenko

    2012-10-01

    Full Text Available The short review on cluster beams generation is proposed. The basic types of cluster sources are considered and the processes leading to cluster formation are analyzed. The parameters, that affects the work of cluster sources are presented.

  8. Cluster beam sources. Part 1. Methods of cluster beams generation

    A.Ju. Karpenko; V.A. Baturin

    2012-01-01

    The short review on cluster beams generation is proposed. The basic types of cluster sources are considered and the processes leading to cluster formation are analyzed. The parameters, that affects the work of cluster sources are presented.

  9. Multireference Coupled Cluster Ansatz

    Jeziorski, Bogumil

    2010-01-01

    Abstract The origin of the multireference coupled cluster Ansatz for the wave function and the wave operator, discovered in Quantum Theory Project in 1981, is presented from the historical perspective. Various methods of obtaining the cluster amplitudes - both state universal and state selective are critically reviewed and further prospects of using the multireference coupled cluster Ansatz in electronic structure theory are briefly discussed.

  10. Quantum Annealing for Clustering

    Kurihara, Kenichi; Tanaka, Shu; Miyashita, Seiji

    2014-01-01

    This paper studies quantum annealing (QA) for clustering, which can be seen as an extension of simulated annealing (SA). We derive a QA algorithm for clustering and propose an annealing schedule, which is crucial in practice. Experiments show the proposed QA algorithm finds better clustering assignments than SA. Furthermore, QA is as easy as SA to implement.

  11. The Durban Auto Cluster

    Lorentzen, Jochen; Robbins, Glen; Barnes, Justin

    2004-01-01

    The paper describes the formation of the Durban Auto Cluster in the context of trade liberalization. It argues that the improvement of operational competitiveness of firms in the cluster is prominently due to joint action. It tests this proposition by comparing the gains from cluster activities i...

  12. Relational aspects of clusters

    Gjerding, Allan Næs

    The present paper is the first preliminary account of a project being planned for 2013, focussing on the development of the biomedico cluster in North Denmark. The project focusses on the relational capabilities of the cluster in terms of a number of organizational roles which are argued to be...... necessary for the development and growth of the upcoming cluster in question....

  13. Minimalist's linux cluster

    Using barebone PC components and NIC's, we construct a linux cluster which has 2-dimensional mesh structure. This cluster has smaller footprint, is less expensive, and use less power compared to conventional linux cluster. Here, we report our experience in building such a machine and discuss our current lattice project on the machine

  14. Electric properties of carbon nano-onion/polyaniline composites: a combined electric modulus and ac conductivity study

    Papathanassiou, Anthony N.; Mykhailiv, Olena; Echegoyen, Luis; Sakellis, Ilias; Plonska-Brzezinska, Marta E.

    2016-07-01

    The complex electric modulus and the ac conductivity of carbon nano-onion/polyaniline composites were studied from 1 mHz to 1 MHz at isothermal conditions ranging from 15 K to room temperature. The temperature dependence of the electric modulus and the dc conductivity analyses indicate a couple of hopping mechanisms. The distinction between thermally activated processes and the determination of cross-over temperature were achieved by exploring the temperature dependence of the fractional exponent of the dispersive ac conductivity and the bifurcation of the scaled ac conductivity isotherms. The results are analyzed by combining the granular metal model (inter-grain charge tunneling of extended electron states located within mesoscopic highly conducting polyaniline grains) and a 3D Mott variable range hopping model (phonon assisted tunneling within the carbon nano-onions and clusters).

  15. AC loss in superconducting tapes and cables

    Oomen, Marijn Pieter

    High-temperature superconductors are developed for use in power-transmission cables, transformers and motors. The alternating magnetic field in these devices causes AC loss, which is a critical factor in the design. The study focuses on multi-filament Bi-2223/Ag tapes exposed to a 50-Hz magnetic field at 77 K. The AC loss is measured with magnetic, electric and calorimetric methods. The results are compared to theoretical predictions based mainly on the Critical-State Model. The loss in high- temperature superconductors is affected by their characteristic properties: increased flux creep, high aspect ratio and inhomogeneties. Filament intergrowths and a low matrix resistivity cause a high coupling-current loss especially when the filaments are fully coupled. When the wide side of the tape is parallel to the external magnetic field, the filaments are decoupled by twisting. In a perpendicular field the filaments can be decoupled only by combining a short twist pitch with a transverse resistivity much higher than that of silver. The arrangement of the inner filaments determines the transverse resistivity. Ceramic barriers around the filaments cause partial decoupling in perpendicular magnetic fields at power frequencies. The resultant decrease in AC loss is greater than the accompanying decrease in critical current. With direct transport current in alternating magnetic field, the transport-current loss is well described with a new model for the dynamic resistance. The Critical- State Model describes well the magnetisation and total AC loss in parallel magnetic fields, at transport currents up to 0.7 times the critical current. When tapes are stacked face-to-face in a winding, the AC-loss density in perpendicular fields is greatly decreased due to the mutual shielding of the tapes. Coupling currents between the tapes in a cable cause an extra AC loss, which is reduced by a careful cable design. The total AC loss in complex devices with many tapes is generally well

  16. ACS air bearing test-bed design

    Glitt, Sascha

    2010-01-01

    This thesis is about the construction and design of a new air bearing test-bed to verify the programmed ACS attitude control algorithm and to validate the ACS MATLAB/SimuLink¬ model of NPSAT1, the second small satellite currently under development at the Naval Postgraduate School Space Systems Academic Group. The software was already verified and validated using a comparable air bearing test-bed. But due to changes in hardware from commercial magnetic torque rods to custom, NPS-built, magneti...

  17. The Effective AC Response of Nonlinear Composites

    WEI En-Bo; GU Guo-Qing

    2001-01-01

    A perturbative approach is used to study the AC response of nonlinear composite media, which obey a current-field relation of the form J = σ E + χ|E|2 E with components having nonlinear response at finite frequencies. For a sinusoidal applied field, we extend the local potential in terms of sinusoidal components at fundamental frequency and high-order harmonic frequencies to treat the nonlinear composites. For nonlinear composite media vith a low concentrations of spherical inclusions, we give the formulae of the nonlinear effective AC susceptibility χ*3ω at the third harmonic frequency.

  18. Cluster Physics with Merging Galaxy Clusters

    Sandor M. Molnar

    2016-02-01

    Full Text Available Collisions between galaxy clusters provide a unique opportunity to study matter in a parameter space which cannot be explored in our laboratories on Earth. In the standard LCDM model, where the total density is dominated by the cosmological constant ($Lambda$ and the matter density by cold dark matter (CDM, structure formation is hierarchical, and clusters grow mostly by merging.Mergers of two massive clusters are the most energetic events in the universe after the Big Bang,hence they provide a unique laboratory to study cluster physics.The two main mass components in clusters behave differently during collisions:the dark matter is nearly collisionless, responding only to gravity, while the gas is subject to pressure forces and dissipation, and shocks and turbulenceare developed during collisions. In the present contribution we review the different methods used to derive the physical properties of merging clusters. Different physical processes leave their signatures on different wavelengths, thusour review is based on a multifrequency analysis. In principle, the best way to analyze multifrequency observations of merging clustersis to model them using N-body/HYDRO numerical simulations. We discuss the results of such detailed analyses.New high spatial and spectral resolution ground and space based telescopeswill come online in the near future. Motivated by these new opportunities,we briefly discuss methods which will be feasible in the near future in studying merging clusters.

  19. Clustering high dimensional data using subspace and projected clustering algorithms

    Rahmat Widia Sembiring; Jasni Mohamad Zain; Abdullah Embong

    2010-01-01

    Problem statement: Clustering has a number of techniques that have been developed in statistics, pattern recognition, data mining, and other fields. Subspace clustering enumerates clusters of objects in all subspaces of a dataset. It tends to produce many over lapping clusters. Approach: Subspace clustering and projected clustering are research areas for clustering in high dimensional spaces. In this research we experiment three clustering oriented algorithms, PROCLUS, P3C and STATPC. Results...

  20. YBCO thin films in ac and dc films

    Shahzada, S

    2001-01-01

    We report studies on the dc magnetization of YBCO thin films in simultaneously applied dc and ac fields. The effect of the ac fields is to decrease the irreversible magnetization drastically leading to complete collapse of the hysteresis loops for relatively small ac fields (250e). The magnitude of the decrease depends on the component of the ac field parallel to the c-axis. The decrease is non-linear with ac amplitude and is explained in the framework of the critical state response of ultra thin films in perpendicular geometry. The ac fields increase the relaxation rapidly at short times while the long time response appears unaffected. (author)

  1. SINGLE PHASE HIGH FREQUENCY AC CONVERTER FOR INDUCTION HEATING APPLICATION

    M.A INAYATHULLAAH,

    2010-12-01

    Full Text Available The proposed topology reduces the total harmonic distortion (THD of a high frequency AC/AC Converter well below the acceptable limit. This paper deals with a novel single phase AC/DC/AC soft switching utility frequency AC to high frequency AC converter. In this paper a single phase full bridge inverter with Vienna rectifier as front end is used instead of conventional diode bridge rectifier to provide continuous sinusoidal input current with nearly unity power factor at the source side with extremely low distortion.. This power converter is more suitable and acceptable for cost effective high frequency (HF consumer induction heating applications.

  2. HST/ACS Imaging of Omega Centauri: Optical Counterparts of Chandra X-Ray Sources

    Cool, Adrienne M; Arias, Tersi; Brochmann, Michelle; Dorfman, Jason; Gafford, April; White, Vivian; Anderson, Jay

    2012-01-01

    We present results of a search for optical counterparts of X-ray sources in and toward the globular cluster Omega Centauri (NGC 5139) using the Advanced Camera for Surveys (ACS) on the Hubble Space Telescope. The ACS data consist of a mosaic of Wide Field Channel (WFC) images obtained using F625W, F435W, and F658N filters; with 9 pointings we cover the central ~10'x10' of the cluster and encompass 109 known Chandra sources. We find promising optical counterparts for 59 of the sources, ~40 of which are likely to be associated with the cluster. These include 27 candidate cataclysmic variables (CVs), 24 of which are reported here for the first time. Fourteen of the CV candidates are very faint, with absolute magnitudes in the range M_625 = 10.4 - 12.6, making them comparable in brightness to field CVs near the period minimum discovered in the SDSS (Gansicke et al. 2009). Additional optical counterparts include three BY Dra candidates, a possible blue straggler, and a previously-reported quiescent low-mass X-ray ...

  3. AcsA-AcsB: The core of the cellulose synthase complex from Gluconacetobacter hansenii ATCC23769.

    McManus, John B; Deng, Ying; Nagachar, Nivedita; Kao, Teh-hui; Tien, Ming

    2016-01-01

    The gram-negative bacterium, Gluconacetobacter hansenii, produces cellulose of exceptionally high crystallinity in comparison to the cellulose of higher plants. This bacterial cellulose is synthesized and extruded into the extracellular medium by the cellulose synthase complex (CSC). The catalytic component of this complex is encoded by the gene AcsAB. However, several other genes are known to encode proteins critical to cellulose synthesis and are likely components of the bacterial CSC. We have purified an active heterodimer AcsA-AcsB from G. hansenii ATCC23769 to homogeneity by two different methods. With the purified protein, we have determined how it is post-translationally processed, forming the active heterodimer AcsA-AcsB. Additionally, we have performed steady-state kinetic studies on the AcsA-AcsB complex. Finally through mutagenesis studies, we have explored the roles of the postulated CSC proteins AcsC, AcsD, and CcpAx. PMID:26672449

  4. Polynuclear technetium halide clusters

    Development of chemistry of polynuclear technetium halide clusters in works devoted to synthesis, structure and investigation of their chemical and physical properties is considered. The role of academician V.I. Spitsyn as an initiator of investigation of polynuclear technetium halide clusters in the Institute of Physical Chemistry of Academy of Science of USSR is noted. Reactions and stability of cluster halides, their molecular and electronic structures are analyzed. Prospects of development of polynuclear technetium halide clusters chemistry as a direction being on the junction of cluster chemistry and theory of metal-metal multiple bonds are appreciated

  5. Cluster analysis for applications

    Anderberg, Michael R

    1973-01-01

    Cluster Analysis for Applications deals with methods and various applications of cluster analysis. Topics covered range from variables and scales to measures of association among variables and among data units. Conceptual problems in cluster analysis are discussed, along with hierarchical and non-hierarchical clustering methods. The necessary elements of data analysis, statistics, cluster analysis, and computer implementation are integrated vertically to cover the complete path from raw data to a finished analysis.Comprised of 10 chapters, this book begins with an introduction to the subject o

  6. Survey on Text Document Clustering

    M.Thangamani; Dr.P.Thangaraj

    2010-01-01

    Document clustering is also referred as text clustering, and its concept is merely equal to data clustering. It is hardly difficult to find the selective information from an ‘N’number of series information, so that document clustering came into picture. Basically cluster means a group of similar data, document clustering means segregating the data into different groups of similar data. Clustering can be of mathematical, statistical or numerical domain. Clustering is a fundamental data analysi...

  7. Unconventional methods for clustering

    Kotyrba, Martin

    2016-06-01

    Cluster analysis or clustering is a task of grouping a set of objects in such a way that objects in the same group (called a cluster) are more similar (in some sense or another) to each other than to those in other groups (clusters). It is the main task of exploratory data mining and a common technique for statistical data analysis used in many fields, including machine learning, pattern recognition, image analysis, information retrieval, and bioinformatics. The topic of this paper is one of the modern methods of clustering namely SOM (Self Organising Map). The paper describes the theory needed to understand the principle of clustering and descriptions of algorithm used with clustering in our experiments.

  8. Clusters in nuclei

    Beck, Christian

    Following the pioneering discovery of alpha clustering and of molecular resonances, the field of nuclear clustering is today one of those domains of heavy-ion nuclear physics that faces the greatest challenges, yet also contains the greatest opportunities. After many summer schools and workshops, in particular over the last decade, the community of nuclear molecular physicists has decided to collaborate in producing a comprehensive collection of lectures and tutorial reviews covering the field. This third volume follows the successful Lect. Notes Phys. 818 (Vol. 1) and 848 (Vol. 2), and comprises six extensive lectures covering the following topics:  - Gamma Rays and Molecular Structure - Faddeev Equation Approach for Three Cluster Nuclear Reactions - Tomography of the Cluster Structure of Light Nuclei Via Relativistic Dissociation - Clustering Effects Within the Dinuclear Model : From Light to Hyper-heavy Molecules in Dynamical Mean-field Approach - Clusterization in Ternary Fission - Clusters in Light N...

  9. Spatial cluster modelling

    Lawson, Andrew B

    2002-01-01

    Research has generated a number of advances in methods for spatial cluster modelling in recent years, particularly in the area of Bayesian cluster modelling. Along with these advances has come an explosion of interest in the potential applications of this work, especially in epidemiology and genome research. In one integrated volume, this book reviews the state-of-the-art in spatial clustering and spatial cluster modelling, bringing together research and applications previously scattered throughout the literature. It begins with an overview of the field, then presents a series of chapters that illuminate the nature and purpose of cluster modelling within different application areas, including astrophysics, epidemiology, ecology, and imaging. The focus then shifts to methods, with discussions on point and object process modelling, perfect sampling of cluster processes, partitioning in space and space-time, spatial and spatio-temporal process modelling, nonparametric methods for clustering, and spatio-temporal ...

  10. AC power generation from microbial fuel cells

    Lobo, Fernanda Leite; Wang, Heming; Forrestal, Casey; Ren, Zhiyong Jason

    2015-11-01

    Microbial fuel cells (MFCs) directly convert biodegradable substrates to electricity and carry good potential for energy-positive wastewater treatment. However, the low and direct current (DC) output from MFC is not usable for general electronics except small sensors, yet commercial DC-AC converters or inverters used in solar systems cannot be directly applied to MFCs. This study presents a new DC-AC converter system for MFCs that can generate alternating voltage in any desired frequency. Results show that AC power can be easily achieved in three different frequencies tested (1, 10, 60 Hz), and no energy storage layer such as capacitors was needed. The DC-AC converter efficiency was higher than 95% when powered by either individual MFCs or simple MFC stacks. Total harmonic distortion (THD) was used to investigate the quality of the energy, and it showed that the energy could be directly usable for linear electronic loads. This study shows that through electrical conversion MFCs can be potentially used in household electronics for decentralized off-grid communities.

  11. Performance of Halbach magnetized brushless AC motors

    Zhu, Z.Q.; Xia, Z.P.; Shi, Y.F.; Howe, D.; Pride, A.; X. J. Chen

    2003-01-01

    The steady-state performance of Halbach magnetized brushless ac machines when operated in constant torque and flux-weakening modes is investigated both theoretically and experimentally, with particular emphasis on the influence of cross-coupling magnetic saturation on the torque capability.

  12. Ac-dc converter firing error detection

    Each of the twelve Booster Main Magnet Power Supply modules consist of two three-phase, full-wave rectifier bridges in series to provide a 560 VDC maximum output. The harmonic contents of the twelve-pulse ac-dc converter output are multiples of the 60 Hz ac power input, with a predominant 720 Hz signal greater than 14 dB in magnitude above the closest harmonic components at maximum output. The 720 Hz harmonic is typically greater than 20 dB below the 500 VDC output signal under normal operation. Extracting specific harmonics from the rectifier output signal of a 6, 12, or 24 pulse ac-dc converter allows the detection of SCR firing angle errors or complete misfires. A bandpass filter provides the input signal to a frequency-to-voltage converter. Comparing the output of the frequency-to-voltage converter to a reference voltage level provides an indication of the magnitude of the harmonics in the ac-dc converter output signal

  13. AC loss in superconducting tapes and cables

    Oomen, Marijn Pieter

    2000-01-01

    The present study discusses the AC loss in high-temperature superconductors. Superconducting materials with a relatively high critical temperature were discovered in 1986. They are presently developed for use in large-scale power-engineering devices such as power-transmission cables, transformers an

  14. Agricultural Clusters in the Netherlands

    Schouten, M.A.; Heijman, W.J.M.

    2012-01-01

    Michael Porter was the first to use the term cluster in an economic context. He introduced the term in The Competitive Advantage of Nations (1990). The term cluster is also known as business cluster, industry cluster, competitive cluster or Porterian cluster. This article aims at determining and mea

  15. Digital model for harmonic interactions in AC/DC/AC systems

    Guarini, A.P.; Rangel, R.D.; Pilotto, L.A.S.; Pinto, R.J.; Passos Junior, R. [Centro de Pesquisas de Energia Eletrica (CEPEL), Rio de Janeiro, RJ (Brazil)

    1994-12-31

    The main purpose of this paper is to present a model for calculation of HVdc converter harmonics taking into account the influence of the harmonic interactions between the ac systems in dc link transmissions. The ideas and methodologies used in the model development take into account the dc current ripple and ac voltage distortion in the ac systems. The theory of switching functions is applied to contemplate for the frequency conversions between the ac and dc sides, in an iterative process. It is possible then to obtain, even in balanced situations, non-characteristic harmonics that are produced by frequencies originated in the other terminal, which can be significant in a strongly coupled system, such as back-to-back configuration. (author) 9 refs., 3 figs.

  16. A Comparison Between Two Average Modelling Techniques of AC-AC Power Converters

    Pawel Szczesniak

    2015-03-01

    Full Text Available In this paper, a comparative evaluation of two modelling tools for switching AC-AC power converters is presented. Both of them are based on average modelling techniques. The first approach is based on the circuit averaging technique and consists in the topological manipulations, applied to a converters states. The second approach makes use of state-space averaged model of the converter and is based on analytical manipulations using the different state representations of a converter. The two modelling techniques are applied to a same AC-AC converter called matrix-reactance frequency converter based on buck-boost topology. These techniques are compared on the basis of their rapidity, quantity of calculations and transformations and its limitations.

  17. High voltage AC/AC electrochemical capacitor operating at low temperature in salt aqueous electrolyte

    Abbas, Qamar; Béguin, François

    2016-06-01

    We demonstrate that an activated carbon (AC)-based electrochemical capacitor implementing aqueous lithium sulfate electrolyte in 7:3 vol:vol water/methanol mixture can operate down to -40 °C with good electrochemical performance. Three-electrode cell investigations show that the faradaic contributions related with hydrogen chemisorption in the negative AC electrode are thermodynamically unfavored at -40 °C, enabling the system to work as a typical electrical double-layer (EDL) capacitor. After prolonged floating of the AC/AC capacitor at 1.6 V and -40°C, the capacitance, equivalent series resistance and efficiency remain constant, demonstrating the absence of ageing related with side redox reactions at this temperature. Interestingly, when temperature is increased back to 24 °C, the redox behavior due to hydrogen storage reappears and the system behaves as a freshly prepared one.

  18. Rapid cycling synchrotron magnet with separate ac and dc circuit

    In present rapid cycling synchrotron magnets ac and dc currents flow in the same coil to give the desired field. The circuit reactance is made zero at dc and the operating frequency by running the magnet in series with an external parallel resonant LC current. We propose to return the ac flux in a gap next to the synchrotron. The dc coil encloses the ac magnetic circuit and thus links no ac flux. A shorted turn between the dc coil and ac flux enhances the separation of the two circuits. Several interesting developments are possible. The dc coil could be a stable superconductor to save power. The ac flux return gap could be identical with the synchrotron gap and contain a second synchrotron. This would double the output of the system. If the return flux gap were used for a booster, the ac coil power could be greatly reduced or radiation hardening of the ac coil could be simplified

  19. Quantum tunnelling of magnetization in Mn12-ac studied by 55Mn NMR

    Morello, A.; Bakharev, O. N.; Brom, H. B.; de Jongh, L.J.

    2002-01-01

    We present an ultra-low temperature study (down to T = 20 mK) of the nuclear spin-lattice relaxation (SLR) in the 55Mn nuclei of the molecular magnet Mn12-ac. The nuclear spins act as local probes for the electronic spin fluctuations, due to thermal excitations and to tunnelling events. In the quantum regime (below T = 0.75 K), the nuclear SLR becomes temperature-independent and is driven by fluctuations of the cluster's electronic spin due to the quantum tunnelling of magnetization in the gr...

  20. Design of Three Phase Matrix Converter AC-AC Utility Power Supply using SPWM Technique

    Sagar.S.Pawar; Prakash.T.Patil

    2015-01-01

    This paper describes the control analysis and design of an three phase matrix AC-AC utility power supply .The SPWM modulation techniques is used to control the desired output voltage and gives the control output voltage and reduced input harmonic distortions .In this Matrix converter Input is directly connected to output no DC link components is required. Simulation had been done using mat lab simulink and Simulated results are observed

  1. Design of Three Phase Matrix Converter AC-AC Utility Power Supply using SPWM Technique

    Sagar. S. Pawar

    2015-04-01

    Full Text Available This paper describes the control analysis and design of an three phase matrix AC-AC utility power supply .The SPWM modulation techniques is used to control the desired output voltage and gives the control output voltage and reduced input harmonic distortions .In this Matrix converter Input is directly connected to output no DC link components is required. Simulation had been done using mat lab simulink and Simulated results are observed

  2. A Comparison Between Two Average Modelling Techniques of AC-AC Power Converters

    Pawel Szczesniak

    2015-01-01

    In this paper, a comparative evaluation of two modelling tools for switching AC-AC power converters is presented. Both of them are based on average modelling techniques. The first approach is based on the circuit averaging technique and consists in the topological manipulations, applied to a converters states. The second approach makes use of state-space averaged model of the converter and is based on analytical manipulations using the different state representations of a converter. The two m...

  3. Approaches to building single-stage AC/AC conversion switch-mode audio power amplifiers

    Ljusev, P.; Andersen, Michael A.E.

    2005-07-01

    This paper discusses the possible topologies and promising approaches towards direct single-phase AC-AC conversion of the mains voltage for audio applications. When compared to standard Class-D switching audio power amplifiers with a separate power supply, it is expected that direct conversion will provide better efficiency and higher level of integration, leading to lower component count, volume and cost, but at the expense of a minor performance deterioration. (au)

  4. Implementation of Low Frequency Ac to High Frequency Ac with Single Stage Zvs-Pwm Inverter

    S. Arumugam S. Ramareddy M. Sridhar

    2011-01-01

    This paper presents a novel soft-switching pulse width modulation (PWM) utility frequency AC to high frequency (HF) AC power conversion circuit incorporating boost-active clamp single stage inverter topology. This power converter is more suitable and acceptable for cost effective HF consumer induction heating applications. Its operating principle is presented. The operating performances of this high frequency inverter using the latest insulated gate bipolar transistors are illustrated, which ...

  5. Adaptive Nonlinear Control of Induction Motors through AC/DC/AC Converters

    Elfadili, Abderrahim; Giri, Fouad; El Magri, Abdelmounime; Dugard, Luc; Chaoui, Fatima Zara

    2012-01-01

    The problem of controlling induction motors, together with associated AC/DC rectifiers and DC/AC inverters, is addressed. The control objectives are threefold: (i) the motor speed should track any reference signal despite mechanical parameter uncertainties and variations; (ii) the DC Link voltage must be tightly regulated; (iii) the power factor correction (PFC) w.r.t. the power supply net must be performed in a satisfactory way. First, a nonlinear model of the whole controlled system is deve...

  6. Robust control of synchronous motors through AC/DC/AC converters

    El Magri, Abdelmounime; Giri, Fouad; Abouloifa, Abdelmajid; Chaoui, Fatima Zara

    2010-01-01

    The problem of controlling synchronous motors, driven through AC/DC rectifiers and DC/AC inverters is addressed. The control objectives are three fold: (i) forcing the motor speed to track a varying reference signal in presence of motor parameter uncertainties;(ii) regulating the DC Link voltage; (iii )assuring a satisfactory power factor correction (PFC) with respect to the power supply net .First, a nonlinear model of the whole controlled system is developed in the Park-coordinates. Then, a...

  7. A new class of hybrid AC/AC direct power converters

    Klumpner, Christian; Wijekoon, Thiwanka; Wheeler, Patrick

    2005-01-01

    Variable voltage and variable frequency conversion of electrical energy from an AC source to an AC load is done in traditional power converters via a DC-link where an energy storage element (electrolytic capacitors) is situated. Despite its well-known benefits, it has the disadvantage of being bulky and to limit the converter lifetime. On the other hand, Direct Power Conversion (DPC) is an attractive concept, which doesn’t need an energy storage buffer, but has two main disadvantages: reduced...

  8. Approaches to building single-stage AC/AC conversion switch-mode audio power amplifiers

    Ljusev, Petar; Andersen, Michael Andreas E.

    2004-01-01

    This paper discusses the possible topologies and promising approaches towards direct single-phase AC-AC conversion of the mains voltage for audio applications. When compared to standard Class-D switching audio power amplifiers with a separate power supply, it is expected that direct conversion...... will provide better efficiency and higher level of integration, leading to lower component count, volume and cost, but at the expense of a minor performance deterioration....

  9. AC losses in a HTS coil carrying DC current in AC external magnetic field

    We electrically measured AC losses in a Bi2223/Ag-sheathed pancake coil excited by a DC current in AC external magnetic field. Losses in the coil contain two kinds of loss components that are the magnetization losses and dynamic resistance losses. In the measurement, current leads to supply a current to the coil were specially arranged to suppress electromagnetic coupling between the coil current and the AC external magnetic field. A double pick-up coils method was used to suppress a large inductive voltage component contained in voltage signal for measuring the magnetization losses. It was observed that the magnetization losses were dependent on the coil current and that a peak of a curve of the loss factor vs. amplitude of the AC external magnetic field shifted to lower amplitude of the AC magnetic field as the coil current increased. This result suggests the full penetration magnetic field of the coil tape decreases as the coil current increases. The dynamic resistance losses were measured by measuring a DC voltage appearing between the coil terminals. It was observed that the DC voltage appearing in the coil subject to the AC external magnetic field was much larger than that in the coil subject to DC magnetic field

  10. 21 CFR 880.5500 - AC-powered patient lift.

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false AC-powered patient lift. 880.5500 Section 880.5500... Devices § 880.5500 AC-powered patient lift. (a) Identification. An AC-powered lift is an electrically powered device either fixed or mobile, used to lift and transport patients in the horizontal or...

  11. Spatial Scan Statistic: Selecting clusters and generating elliptic clusters

    Christiansen, Lasse Engbo; Andersen, Jens Strodl

    2004-01-01

    The spatial scan statistic is widely used to search for clusters. This paper shows that the usually applied elimination of overlapping clusters to find secondary clusters is sensitive to smooth changes in the shape of the clusters. We present an algorithm for generation of set of confocal elliptic...... clusters. In addition, we propose a new way to present the information in a given set of clusters based on the significance of the clusters....

  12. Cluster brand as a competitive advantage. Case: Airport cluster Finland

    Väinölä, Lotta-Elviira

    2015-01-01

    Objective of the Study: The objective of this study is to explore the phenomenon of cluster branding. This study investigates cluster brand as a competitive advantage that impacts the success or decline of the cluster. The research questions examine three aspects: (1) cluster branding as a process, (2) the concrete tools that can be used in cluster branding and (3) the perceived benefits of cluster brand. The study aims to produce a generic model for cluster branding, which can be used as...

  13. Integrating cluster formation and cluster evaluation in interactive visual analysis

    Turkay, C.; Parulek, J.; Reuter, N.; Hauser, H.

    2011-01-01

    Cluster analysis is a popular method for data investigation where data items are structured into groups called clusters. This analysis involves two sequential steps, namely cluster formation and cluster evaluation. In this paper, we propose the tight integration of cluster formation and cluster evaluation in interactive visual analysis in order to overcome the challenges that relate to the black-box nature of clustering algorithms. We present our conceptual framework in the form of an interac...

  14. Clustering Categorical Data:A Cluster Ensemble Approach

    He Zengyou(何增友); Xu Xiaofei; Deng Shengchun

    2003-01-01

    Clustering categorical data, an integral part of data mining,has attracted much attention recently. In this paper, the authors formally define the categorical data clustering problem as an optimization problem from the viewpoint of cluster ensemble, and apply cluster ensemble approach for clustering categorical data. Experimental results on real datasets show that better clustering accuracy can be obtained by comparing with existing categorical data clustering algorithms.

  15. AC LED的研究现状与发展%Current research and development of AC LED

    满瑞; 李秋俊

    2012-01-01

    介绍了AC LED的特征及其工作原理,分析了AC LED相比于DC LED的优缺点,概述了AC LED在国内外的研究进展及其应用现状,讨论了AC LED技术发展过程中面临的挑战,并展望了其发展趋势.%The characteristics and operation principles of AC LED were presented.The advantages and disadvantages of AC LED compared with the DC LED were analyzed.The development and the latest application of AC LED were described.The challenges of the competition with the traditional light source were discussed,as well as the development trend of AC LED.

  16. Carbon in Red Giants in Globular Clusters and Dwarf Spheroidal Galaxies

    Kirby, Evan N.; Guo, Michelle; Zhang, Andrew J.; Deng, Michelle; Cohen, Judith G.; Guhathakurta, Puragra; Shetrone, Matthew D.; Lee, Young Sun; Rizzi, Luca

    2015-03-01

    We present carbon abundances of red giants in Milky Way (MW) globular clusters and dwarf spheroidal galaxies (dSphs). Our sample includes measurements of carbon abundances for 154 giants in the clusters NGC 2419, M68, and M15 and 398 giants in the dSphs Sculptor, Fornax, Ursa Minor, and Draco. This sample doubles the number of dSph stars with measurements of [C/Fe]. The [C/Fe] ratio in the clusters decreases with increasing luminosity above log (L/{{L}})≃ 1.6, which can be explained by deep mixing in evolved giants. The same decrease is observed in dSphs, but the initial [C/Fe] of the dSph giants is not uniform. Stars in dSphs at lower metallicities have larger [C/Fe] ratios. We hypothesize that [C/Fe] (corrected to the initial carbon abundance) declines with increasing [Fe/H] due to the metallicity dependence of the carbon yield of asymptotic giant branch stars and due to the increasing importance of SNe Ia at higher metallicities. We also identified 11 very carbon-rich giants (eight previously known) in three dSphs. However, our selection biases preclude a detailed comparison to the carbon-enhanced fraction of the MW stellar halo. Nonetheless, the stars with [C/Fe]\\lt +1 in dSphs follow a different [C/Fe] track with [Fe/H] than the halo stars. Specifically, [C/Fe] in dSphs begins to decline at lower [Fe/H] than in the halo. The difference in the metallicity of the [C/Fe] “knee” adds to the evidence from [α/Fe] distributions that the progenitors of the halo had a shorter timescale for chemical enrichment than the surviving dSphs. The data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation.

  17. Disentangling Porterian Clusters

    Jagtfelt, Tue

    This dissertation investigates the contemporary phenomenon of industrial clusters based on the work of Michael E. Porter, the central progenitor and promoter of the cluster notion. The dissertation pursues two central questions: 1) What is a cluster? and 2) How could Porter’s seemingly fuzzy......, contested theory become so widely disseminated and applied as a normative and prescriptive strategy for economic development? The dissertation traces the introduction of the cluster notion into the EU’s Lisbon Strategy and demonstrates how its inclusion originates from Porter’s colleagues: Professor Örjan...... Sölvell, Dr. Christian Ketels and Dr. Göran Lindqvist. Taking departure in Porter’s works and the cluster literature, the dissertations shows a considerable paradigmatic shift has occurred from the first edition of Nations to the present state of cluster cooperation. To elaborate on this change and the...

  18. From collisions to clusters

    Loukonen, Ville; Bork, Nicolai; Vehkamaki, Hanna

    2014-01-01

    overcome the possible initial non-optimal collision orientations. No post-collisional cluster break up is observed. The reasons for the efficient clustering are (i) the proton transfer reaction which takes place in each of the collision simulations and (ii) the subsequent competition over the proton......The clustering of sulphuric acid with base molecules is one of the main pathways of new-particle formation in the Earth's atmosphere. First step in the clustering process is likely the formation of a (sulphuric acid)1(base)1(water)n cluster. Here, we present results from direct first......-principles molecular dynamics collision simulations of (sulphuric acid)1(water)0, 1 + (dimethylamine) → (sulphuric acid)1(dimethylamine)1(water)0, 1 cluster formation processes. The simulations indicate that the sticking factor in the collisions is unity: the interaction between the molecules is strong enough to...

  19. Cosmology with cluster surveys

    Subhabrata Majumdar

    2004-10-01

    Surveys of clusters of galaxies provide us with a powerful probe of the density and nature of the dark energy. The red-shift distribution of detected clusters is highly sensitive to the dark energy equation of state parameter . Upcoming Sunyaev–Zel'dovich (SZ) surveys would provide us large yields of clusters to very high red-shifts. Self-calibration of cluster scaling relations, possible for such a huge sample, would be able to constrain systematic biases on mass estimators. Combining cluster red-shift abundance with limited mass follow-up and cluster mass power spectrum can then give constraints on , as well as on 8 and to a few per cents.

  20. Cluster Management Institutionalization

    Normann, Leo; Agger Nielsen, Jeppe

    2015-01-01

    This article explores a new management form – cluster management – in Danish public sector day care. Although cluster management has been widely adopted in Danish day care at the municipality level, it has attracted only sparse research attention. We use theoretical insights from Scandinavian...... institutionalism together with a longitudinal case-based inquiry into how cluster management has entered and penetrated the management practices of day care in Denmark. We demonstrate how cluster management became widely adopted in the day care field not only because of its intrinsic properties but also because...... of how it was legitimized as a “ready-to-use” management model. Further, our account reveals how cluster management translated into considerably different local variants as it travelled into specific organizations. However, these processes have not occurred sequentially with cluster management first...

  1. Dicty_cDB: FCL-AC08 [Dicty_cDB

    Full Text Available FCL (Link to library) FCL-AC08 (Link to dictyBase) - - - Contig-U15080-1 FCL-AC08P ...(Link to Original site) FCL-AC08F 616 FCL-AC08Z 291 FCL-AC08P 907 - - Show FCL-AC08 Library FCL (Link to library) Clone ID FCL-...-1 Original site URL http://dictycdb.biol.tsukuba.ac.jp/CSM/FCL/FCL-AC/FCL-AC08Q....Seq.d/ Representative seq. ID FCL-AC08P (Link to Original site) Representative DNA sequence >FCL-AC08 (FCL-AC08Q) /CSM/FCL/FCL-...ignificant alignments: (bits) Value FCL-AC08 (FCL-AC08Q) /CSM/FCL/FCL-AC/FCL-AC08Q.Seq.d/ 1322 0.0 SFA226 (S

  2. Clustering Techniques in Bioinformatics

    Muhammad Ali Masood

    2015-01-01

    Full Text Available Dealing with data means to group information into a set of categories either in order to learn new artifacts or understand new domains. For this purpose researchers have always looked for the hidden patterns in data that can be defined and compared with other known notions based on the similarity or dissimilarity of their attributes according to well-defined rules. Data mining, having the tools of data classification and data clustering, is one of the most powerful techniques to deal with data in such a manner that it can help researchers identify the required information. As a step forward to address this challenge, experts have utilized clustering techniques as a mean of exploring hidden structure and patterns in underlying data. Improved stability, robustness and accuracy of unsupervised data classification in many fields including pattern recognition, machine learning, information retrieval, image analysis and bioinformatics, clustering has proven itself as a reliable tool. To identify the clusters in datasets algorithm are utilized to partition data set into several groups based on the similarity within a group. There is no specific clustering algorithm, but various algorithms are utilized based on domain of data that constitutes a cluster and the level of efficiency required. Clustering techniques are categorized based upon different approaches. This paper is a survey of few clustering techniques out of many in data mining. For the purpose five of the most common clustering techniques out of many have been discussed. The clustering techniques which have been surveyed are: K-medoids, K-means, Fuzzy C-means, Density-Based Spatial Clustering of Applications with Noise (DBSCAN and Self-Organizing Map (SOM clustering.

  3. Cluster Symmetries and Dynamics

    Freer Martin

    2016-01-01

    Full Text Available Many light nuclei display behaviour that indicates that rather than behaving as an A-body systems, the protons and neutrons condense into clusters. The α-particle is the most obvious example of such clustering. This contribution examines the role of such α-clustering on the structure, symmetries and dynamics of the nuclei 8Be, 12C and 16O, recent experimental measurements and future perspectives.

  4. Agricultural Clusters in China

    Kiminami, Lily; Kiminami, Akira

    2009-01-01

    The purpose of this study is to assess the potential of clustering in the development of agriculture and rural communities in China. We shall examine in detail the food industry, which is the link in the food chain that propels the industrialization of agriculture, and identify instances of industrial agglomeration and business collaboration. Next, we shall analyze the externalities (i.e. spillovers) of clusters, demand conditions in cluster formation, and the effectiveness of business collab...

  5. The Durban Auto Cluster

    Lorentzen, Jochen; Robbins, Glen; Barnes, Justin

    2004-01-01

    The paper describes the formation of the Durban Auto Cluster in the context of trade liberalization. It argues that the improvement of operational competitiveness of firms in the cluster is prominently due to joint action. It tests this proposition by comparing the gains from cluster activities in the areas of supplier development, human resource development, logistics, and benchmarking, and by contrasting the impact of joint action against a host of other variables, notably international com...

  6. Securing personal network clusters

    Jehangir, Assed; Heemstra de Groot, Sonia M.

    2007-01-01

    A Personal Network is a self-organizing, secure and private network of a user’s devices notwithstanding their geographic location. It aims to utilize pervasive computing to provide users with new and improved services. In this paper we propose a model for securing Personal Network clusters. Clusters are ad-hoc networks of co-located personal devices. The ad-hoc makeup of clusters, coupled with the resource constrained nature of many constituent devices, makes enforcing security a challenging ...

  7. Cluster headache with aura

    Martínez-Fernández, Eva; Alberca, Roman; Mir, Pablo; Franco, Emilio; Montes, Enrique; Lozano, Pilar

    2002-01-01

    The objective of our study is to report the frequency and characteristics of cluster headache with aura among the population of patients with cluster headache treated in our outpatient neurology clinic. 254 patients were submitted to semi-structured interviews to identify the presence of symptoms similar to the migraine aura. 5 patients who suffered from a cluster headache with aura filled a diary with the characteristics of the pain attacks and the aura. All the patients with either episodic...

  8. Measuring the Mass-to-Light Ratio of Cluster Galaxies

    Natarajan, P.

    1996-12-01

    dispersion. The results of the application of these techniques to the mosaic-ed HST data of the cluster AC114, and the stacked HST-archive clusters are presented.

  9. 15th Cluster workshop

    Laakso, Harri; Escoubet, C. Philippe; The Cluster Active Archive : Studying the Earth’s Space Plasma Environment

    2010-01-01

    Since the year 2000 the ESA Cluster mission has been investigating the small-scale structures and processes of the Earth's plasma environment, such as those involved in the interaction between the solar wind and the magnetospheric plasma, in global magnetotail dynamics, in cross-tail currents, and in the formation and dynamics of the neutral line and of plasmoids. This book contains presentations made at the 15th Cluster workshop held in March 2008. It also presents several articles about the Cluster Active Archive and its datasets, a few overview papers on the Cluster mission, and articles reporting on scientific findings on the solar wind, the magnetosheath, the magnetopause and the magnetotail.

  10. Management of cluster headache.

    Tfelt-Hansen, Peer C; Jensen, Rigmor H

    2012-07-01

    The prevalence of cluster headache is 0.1% and cluster headache is often not diagnosed or misdiagnosed as migraine or sinusitis. In cluster headache there is often a considerable diagnostic delay - an average of 7 years in a population-based survey. Cluster headache is characterized by very severe or severe orbital or periorbital pain with a duration of 15-180 minutes. The cluster headache attacks are accompanied by characteristic associated unilateral symptoms such as tearing, nasal congestion and/or rhinorrhoea, eyelid oedema, miosis and/or ptosis. In addition, there is a sense of restlessness and agitation. Patients may have up to eight attacks per day. Episodic cluster headache (ECH) occurs in clusters of weeks to months duration, whereas chronic cluster headache (CCH) attacks occur for more than 1 year without remissions. Management of cluster headache is divided into acute attack treatment and prophylactic treatment. In ECH and CCH the attacks can be treated with oxygen (12 L/min) or subcutaneous sumatriptan 6 mg. For both oxygen and sumatriptan there are two randomized, placebo-controlled trials demonstrating efficacy. In both ECH and CCH, verapamil is the prophylactic drug of choice. Verapamil 360 mg/day was found to be superior to placebo in one clinical trial. In clinical practice, daily doses of 480-720 mg are mostly used. Thus, the dose of verapamil used in cluster headache treatment may be double the dose used in cardiology, and with the higher doses the PR interval should be checked with an ECG. At the start of a cluster, transitional preventive treatment such as corticosteroids or greater occipital nerve blockade can be given. In CCH and in long-standing clusters of ECH, lithium, methysergide, topiramate, valproic acid and ergotamine tartrate can be used as add-on prophylactic treatment. In drug-resistant CCH, neuromodulation with either occipital nerve stimulation or deep brain stimulation of the hypothalamus is an alternative treatment strategy

  11. Fast Density Based Clustering Algorithm

    Priyanka Trikha; Singh Vijendra

    2013-01-01

    Clustering problem is an unsupervised learning problem. It is a procedure that partition data objects into matching clusters. The data objects in the same cluster are quite similar to each other and dissimilar in the other clusters. The traditional algorithms do not meet the latest multiple requirements simultaneously for objects. Density-based clustering algorithms find clusters based on density of data points in a region. DBSCAN algorithm is one of the density-based clustering algorithms. I...

  12. Statistical Properties of Convex Clustering

    Tan, Kean Ming; Witten, Daniela

    2015-01-01

    In this manuscript, we study the statistical properties of convex clustering. We establish that convex clustering is closely related to single linkage hierarchical clustering and $k$-means clustering. In addition, we derive the range of tuning parameter for convex clustering that yields a non-trivial solution. We also provide an unbiased estimate of the degrees of freedom, and provide a finite sample bound for the prediction error for convex clustering. We compare convex clustering to some tr...

  13. A Uniqueness Theorem for Clustering

    Zadeh, Reza Bosagh; Ben-David, Shai

    2012-01-01

    Despite the widespread use of Clustering, there is distressingly little general theory of clustering available. Questions like "What distinguishes a clustering of data from other data partitioning?", "Are there any principles governing all clustering paradigms?", "How should a user choose an appropriate clustering algorithm for a particular task?", etc. are almost completely unanswered by the existing body of clustering literature. We consider an axiomatic approach to the theory of Clustering...

  14. Statistical properties of convex clustering

    Tan, Kean Ming; Witten, Daniela

    2015-01-01

    In this manuscript, we study the statistical properties of convex clustering. We establish that convex clustering is closely related to single linkage hierarchical clustering and $k$-means clustering. In addition, we derive the range of the tuning parameter for convex clustering that yields a non-trivial solution. We also provide an unbiased estimator of the degrees of freedom, and provide a finite sample bound for the prediction error for convex clustering. We compare convex clustering to so...

  15. Hierarchically Clustered Star Formation in the Magellanic Clouds

    Gouliermis, Dimitrios A; Ossenkopf, Volker; Klessen, Ralf S; Dolphin, Andrew E

    2012-01-01

    We present a cluster analysis of the bright main-sequence and faint pre--main-sequence stellar populations of a field ~ 90 x 90 pc centered on the HII region NGC 346/N66 in the Small Magellanic Cloud, from imaging with HST/ACS. We extend our earlier analysis on the stellar cluster population in the region to characterize the structuring behavior of young stars in the region as a whole with the use of stellar density maps interpreted through techniques designed for the study of the ISM structuring. In particular, we demonstrate with Cartwrigth & Whitworth's Q parameter, dendrograms, and the Delta-variance wavelet transform technique that the young stellar populations in the region NGC 346/N66 are hierarchically clustered, in agreement with other regions in the Magellanic Clouds observed with HST. The origin of this hierarchy is currently under investigation.

  16. Document Clustering Based on Semi-Supervised Term Clustering

    Hamid Mahmoodi

    2012-05-01

    Full Text Available The study is conducted to propose a multi-step feature (term selection process and in semi-supervised fashion, provide initial centers for term clusters. Then utilize the fuzzy c-means (FCM clustering algorithm for clustering terms. Finally assign each of documents to closest associated term clusters. While most text clustering algorithms directly use documents for clustering, we propose to first group the terms using FCM algorithm and then cluster documents based on terms clusters. We evaluate effectiveness of our technique on several standard text collections and compare our results with the some classical text clustering algorithms.

  17. Lifting to cluster-tilting objects in higher cluster categories

    Liu, Pin

    2008-01-01

    In this note, we consider the $d$-cluster-tilted algebras, the endomorphism algebras of $d$-cluster-tilting objects in $d$-cluster categories. We show that a tilting module over such an algebra lifts to a $d$-cluster-tilting object in this $d$-cluster category.

  18. Fractional ac Josephson effect in unconventional superconductors

    For certain orientations of Josephson junctions between two px-wave or two d-wave superconductors, the subgap Andreev bound states produce a 4π-periodic relation between the Josephson current I and the phase difference ψ: I propor to sin(ψ/2) . Consequently, the ac Josephson current has the fractional frequency eV/h where V is the dc voltage. In the tunneling limit, the Josephson current is proportional to the first power (not square) of the electron tunneling amplitude. Thus, the Josephson current between unconventional superconductors is carried by single electrons, rather than by Cooper pairs. The fractional ac Josephson effect can be observed experimentally by measuring frequency spectrum of microwave radiation from the junction

  19. AC motor drive system for electric cars

    Morohoshi, Yukinobu; Yoshinori, Naoto; Naito, Hironobu (Fuji Electric Co., Ltd., Tokyo, (Japan))

    1989-08-10

    Various main circuit equipment with large capacity GTO thyristors are outlined for AC and DC electric cars. The configuration of a PWM converter system is presented for the AC main motor drive system of the Shinkansen trains, and its following features are described: the high power factor control capable of keeping a power factor 100% constantly, energy saving by power regenerative braking, the small triple structure with large capacity reverse-conducting GTO thyristors of 4,500V/3,000A, and the reduction of equivalent interfering current and harmonic current by three phase-triple phase difference operation. Furthermore, a control logic equipment with 16 bit MPU and a main transformer are outlined, and the verification test results of the control logic equipment by an analog model simulation and the combinational test results of the commercial equipment are reported. Prototype VVVF inverter system for DC electric cars is also presented. 6 refs., 13 figs., 3 tabs.

  20. β-delayed fission from 230Ac

    ThO2 is irradiated with 60 MeV/u 18O beams. 230Ra is produced via the multi-nucleon transfer and dissipative fragmentation reactions of the target. 230Ra is radio-chemical separated from ThO2 and the other reaction products. The thin Ra sources are prepared. The mica fission track detectors are exposed to the Ra sources. γ-rays of Ra decay in the sources are measured by a HPGe detector. The mica foil is etched in HF solution. The etched mica foil is scanned with an optical microscope. The fission tracks that should come from β-delayed fission of 230Ac are observed. The β-delayed fission probability of 230Ac is determined to be (1.19 +- 0.85) x 10-8

  1. Fuzzy Clustering: Determining the Number of Clusters

    Řezanková, H.; Húsek, Dušan

    Piscataway : IEEE, 2012, s. 277-282. ISBN 978-1-4673-4793-8. [CASoN 2012. International Conference on Computational Aspects of Social Networks /4./. Sao Carlos (BR), 21.11.2012-23.11.2012] R&D Projects: GA ČR GAP202/10/0262 Grant ostatní: GA MŠk(CZ) ED1.1.00/02.0070 Institutional support: RVO:67985807 Keywords : fuzzy cluster analysis * determining number of clusters * Dunn’s coefficient * average silhouette width Subject RIV: BB - Applied Statistics, Operational Research

  2. AC Dielectrophoresis Using Elliptic Electrode Geometry

    S. M. Rezaul Hasan; Aanan Khurma

    2011-01-01

    This paper presents negative AC dielectrophoretic investigations using elliptic electrode geometry. Simulations of the electric field gradient variation using various ratios of the semimajor and the semiminor axis were carried out to determine the optimum elliptic geometry for the dielectrophoretic electrokinetics of specimen in an assay with laminar (low Reynolds number) fluid flow. Experimental setup of the elliptic electrode assembly using PCB fabrication and electrokinetic accumulation of...

  3. Lazy AC-Pattern Matching for Rewriting

    Belkhir, Walid; 10.4204/EPTCS.82.3

    2012-01-01

    We define a lazy pattern-matching mechanism modulo associativity and commutativity. The solutions of a pattern-matching problem are stored in a lazy list composed of a first substitution at the head and a non-evaluated object that encodes the remaining computations. We integrate the lazy AC-matching in a strategy language: rewriting rule and strategy application produce a lazy list of terms.

  4. Entropy production in ac-calorimetry

    Garden, Jean-Luc; Richard, Jacques

    2007-01-01

    In calorimetry and particularly in heat capacity measurements, different characteristic relaxation time constants may perturb the experiment which cannot be considered at thermodynamic equilibrium. In this case, thermodynamics of irreversible processes has to be taken into account and the calorimetric measurements must be considered as dynamic. In a temperature modulated experiment, such as ac-calorimetry, these non-equilibrium experiments give rise to the notion of frequency dependent comple...

  5. The Cluster Substructure - Alignment Connection

    Plionis, M

    2002-01-01

    Using the APM cluster data we investigate whether the dynamical status of clusters is related to the large-scale structure of the Universe. We find that cluster substructure is strongly correlated with the tendency of clusters to be aligned with their nearest neighbour and in general with the nearby clusters that belong to the same supercluster. Furthermore, dynamically young clusters are more clustered than the overall cluster population. These are strong indications that cluster develop in a hierarchical fashion by anisotropy merging along the large-scale filamentary superclusters within which they are embedded.

  6. Development of a hardware-based AC microgrid for AC stability assessment

    Swanson, Robert R.

    As more power electronic-based devices enable the development of high-bandwidth AC microgrids, the topic of microgrid power distribution stability has become of increased interest. Recently, researchers have proposed a relatively straightforward method to assess the stability of AC systems based upon the time-constants of sources, the net bus capacitance, and the rate limits of sources. In this research, a focus has been to develop a hardware test system to evaluate AC system stability. As a first step, a time domain model of a two converter microgrid was established in which a three phase inverter acts as a power source and an active rectifier serves as an adjustable constant power AC load. The constant power load can be utilized to create rapid power flow transients to the generating system. As a second step, the inverter and active rectifier were designed using a Smart Power Module IGBT for switching and an embedded microcontroller as a processor for algorithm implementation. The inverter and active rectifier were designed to operate simultaneously using a synchronization signal to ensure each respective local controller operates in a common reference frame. Finally, the physical system was created and initial testing performed to validate the hardware functionality as a variable amplitude and variable frequency AC system.

  7. Mixed-Initiative Clustering

    Huang, Yifen

    2010-01-01

    Mixed-initiative clustering is a task where a user and a machine work collaboratively to analyze a large set of documents. We hypothesize that a user and a machine can both learn better clustering models through enriched communication and interactive learning from each other. The first contribution or this thesis is providing a framework of…

  8. Density Adaptive Parallel Clustering

    La Rocca, Marcello

    2014-01-01

    In this paper we are going to introduce a new nearest neighbours based approach to clustering, and compare it with previous solutions; the resulting algorithm, which takes inspiration from both DBscan and minimum spanning tree approaches, is deterministic but proves simpler, faster and doesnt require to set in advance a value for k, the number of clusters.

  9. Star Formation in Clusters

    Larsen, S S

    2004-01-01

    HST is very well tailored for observations of extragalactic star clusters. One obvious reason is HST's high spatial resolution, but equally important is the wavelength range offered by the instruments on board HST, in particular the blue and near-UV coverage which is essential for age-dating young clusters. HST observations have helped establish the ubiquity of young massive clusters (YMCs) in a wide variety of star-forming environments, from dwarf galaxies and spiral disks to nuclear starbursts and mergers. These YMCs have masses and sizes similar to those of old globular clusters (GCs), and the two may be closely related. A large fraction of all stars seem to be born in clusters, but most clusters disrupt rapidly and the stars disperse to become part of the field population. In most cases studied to date the luminosity functions of young cluster systems are well fit by power-laws dN(L)/dL ~ L^-2, and the luminosity of the brightest cluster can (with few exceptions) be predicted from simple sampling statisti...

  10. Coma cluster of galaxies

    1999-01-01

    Atlas Image mosaic, covering 34' x 34' on the sky, of the Coma cluster, aka Abell 1656. This is a particularly rich cluster of individual galaxies (over 1000 members), most prominently the two giant ellipticals, NGC 4874 (right) and NGC 4889 (left). The remaining members are mostly smaller ellipticals, but spiral galaxies are also evident in the 2MASS image. The cluster is seen toward the constellation Coma Berenices, but is actually at a distance of about 100 Mpc (330 million light years, or a redshift of 0.023) from us. At this distance, the cluster is in what is known as the 'Hubble flow,' or the overall expansion of the Universe. As such, astronomers can measure the Hubble Constant, or the universal expansion rate, based on the distance to this cluster. Large, rich clusters, such as Coma, allow astronomers to measure the 'missing mass,' i.e., the matter in the cluster that we cannot see, since it gravitationally influences the motions of the member galaxies within the cluster. The near-infrared maps the overall luminous mass content of the member galaxies, since the light at these wavelengths is dominated by the more numerous older stellar populations. Galaxies, as seen by 2MASS, look fairly smooth and homogeneous, as can be seen from the Hubble 'tuning fork' diagram of near-infrared galaxy morphology. Image mosaic by S. Van Dyk (IPAC).

  11. Computing upper cluster algebras

    Matherne, Jacob; Muller, Greg

    2013-01-01

    This paper develops techniques for producing presentations of upper cluster algebras. These techniques are suited to computer implementation, and will always succeed when the upper cluster algebra is totally coprime and finitely generated. We include several examples of presentations produced by these methods.

  12. Cluster growth kinetics

    Processes of some traffic blocking coming into existence are considered as probabilistic ones. We study analytic solutions for models for the dynamics of both cluster growth and cluster growth with fragmentation in the systems of finite number of objects. Assuming rates constancy of both coalescence and fragmentation, the models under consideration are linear on the probability functions

  13. Clustering Text Data Streams

    Yu-Bao Liu; Jia-Rong Cai; Jian Yin; Ada Wai-Chee Fu

    2008-01-01

    Clustering text data streams is an important issue in data mining community and has a number of applications such as news group filtering, text crawling, document organization and topic detection and tracing etc. However, most methods are similarity-based approaches and only use the TF*IDF scheme to represent the semantics of text data and often lead to poor clustering quality. Recently, researchers argue that semantic smoothing model is more efficient than the existing TF.IDF scheme for improving text clustering quality. However, the existing semantic smoothing model is not suitable for dynamic text data context. In this paper, we extend the semantic smoothing model into text data streams context firstly. Based on the extended model, we then present two online clustering algorithms OCTS and OCTSM for the clustering of massive text data streams. In both algorithms, we also present a new cluster statistics structure named cluster profile which can capture the semantics of text data streams dynamically and at the same time speed up the clustering process. Some efficient implementations for our algorithms are also given. Finally, we present a series of experimental results illustrating the effectiveness of our technique.

  14. Phases of cluster states

    The question of phases and phase transitions of cluster states is reviewed. First some features of the vibron model are recalled, then its extensions are investigated. Preliminary results are also presented from a study on the cluster-shell competition. (authors)

  15. Illinois' Career Cluster Model

    Jankowski, Natasha A.; Kirby, Catherine L.; Bragg, Debra D.; Taylor, Jason L.; Oertle, Kathleen M.

    2009-01-01

    This booklet provides information to multiple stakeholders on the implementation of career clusters in Illinois. The booklet is an extension of the previous edition titled "An Introduction to Illinois CTE Programs of Study" (2008), and provides a resource for partners to understand Illinois' Career Cluster Model as its own adaptation of the…

  16. Calixarene-supported clusters

    Taylor, Stephanie M.; McIntosh, Ruaraidh D.; Piligkos, Stergios; Dalgarno, Scott J.; Brechin, Euan K.

    2012-01-01

    A combination of complementary cluster ligands results in the formation of a new calixarene-supported ferromagnetic [Mn(5)] cage that displays the characteristic bonding modes of each support.......A combination of complementary cluster ligands results in the formation of a new calixarene-supported ferromagnetic [Mn(5)] cage that displays the characteristic bonding modes of each support....

  17. Brightest Cluster Galaxy Identification

    Leisman, Luke; Haarsma, D. B.; Sebald, D. A.; ACCEPT Team

    2011-01-01

    Brightest cluster galaxies (BCGs) play an important role in several fields of astronomical research. The literature includes many different methods and criteria for identifying the BCG in the cluster, such as choosing the brightest galaxy, the galaxy nearest the X-ray peak, or the galaxy with the most extended profile. Here we examine a sample of 75 clusters from the Archive of Chandra Cluster Entropy Profile Tables (ACCEPT) and the Sloan Digital Sky Survey (SDSS), measuring masked magnitudes and profiles for BCG candidates in each cluster. We first identified galaxies by hand; in 15% of clusters at least one team member selected a different galaxy than the others.We also applied 6 other identification methods to the ACCEPT sample; in 30% of clusters at least one of these methods selected a different galaxy than the other methods. We then developed an algorithm that weighs brightness, profile, and proximity to the X-ray peak and centroid. This algorithm incorporates the advantages of by-hand identification (weighing multiple properties) and automated selection (repeatable and consistent). The BCG population chosen by the algorithm is more uniform in its properties than populations selected by other methods, particularly in the relation between absolute magnitude (a proxy for galaxy mass) and average gas temperature (a proxy for cluster mass). This work supported by a Barry M. Goldwater Scholarship and a Sid Jansma Summer Research Fellowship.

  18. Management of cluster headache

    Tfelt-Hansen, Peer C; Jensen, Rigmor H

    2012-01-01

    should be checked with an ECG. At the start of a cluster, transitional preventive treatment such as corticosteroids or greater occipital nerve blockade can be given. In CCH and in long-standing clusters of ECH, lithium, methysergide, topiramate, valproic acid and ergotamine tartrate can be used as add...

  19. Blue emitting undecaplatinum clusters

    Chakraborty, Indranath; Bhuin, Radha Gobinda; Bhat, Shridevi; Pradeep, T.

    2014-07-01

    A blue luminescent 11-atom platinum cluster showing step-like optical features and the absence of plasmon absorption was synthesized. The cluster was purified using high performance liquid chromatography (HPLC). Electrospray ionization (ESI) and matrix assisted laser desorption ionization (MALDI) mass spectrometry (MS) suggest a composition, Pt11(BBS)8, which was confirmed by a range of other experimental tools. The cluster is highly stable and compatible with many organic solvents.A blue luminescent 11-atom platinum cluster showing step-like optical features and the absence of plasmon absorption was synthesized. The cluster was purified using high performance liquid chromatography (HPLC). Electrospray ionization (ESI) and matrix assisted laser desorption ionization (MALDI) mass spectrometry (MS) suggest a composition, Pt11(BBS)8, which was confirmed by a range of other experimental tools. The cluster is highly stable and compatible with many organic solvents. Electronic supplementary information (ESI) available: Details of experimental procedures, instrumentation, chromatogram of the crude cluster; SEM/EDAX, DLS, PXRD, TEM, FT-IR, and XPS of the isolated Pt11 cluster; UV/Vis, MALDI MS and SEM/EDAX of isolated 2 and 3; and 195Pt NMR of the K2PtCl6 standard. See DOI: 10.1039/c4nr02778g

  20. Melting of graphene clusters

    Singh, Sandeep Kumar; Neek-Amal, M.; Peeters, F. M.

    2013-01-01

    Density-functional tight-binding and classical molecular dynamics simulations are used to investigate the structural deformations and melting of planar carbon nano-clusters $C_{N}$ with N=2-55. The minimum energy configurations for different clusters are used as starting configuration for the study of the temperature effects on the bond breaking/rotation in carbon lines (N$

  1. Cold cluster ferromagnetism

    Bertsch, G.F. [Washington Univ., Seattle, WA (United States). Inst. for Nuclear Theory; Yabana, K. [Niigata Univ. (Japan). Dept. of Physics

    1993-12-31

    We examine the magnetic moment distribution of ferromagnetic clusters under conditions where the magnetic moment is aligned with the internal cluster axis. Analytic expressions are obtained for the moment distribution and the adiabatic average moment induced in low fields. The result differs from the low-field Langevin function by a factor 2/3.

  2. Investigation of Cluster and Cluster Queuing System

    Halifu, Saerda

    2008-01-01

    Cluster became main platform as parallel and distributed computing structure for high performance computing. Following the development of high performance computer architecture more and more different branches of natural science benefit fromhuge and efficient computational power. For instance bio-informatics, climate science, computational physics, computational chemistry, marine science, etc. Efficient and reliable computing powermay not only expending demand of existing high performance com...

  3. Job Oriented Monitoring Clusters

    Vijayalaxmi Cigala,

    2011-03-01

    Full Text Available There has been a lot of development in the field of clusters and grids. Recently, the use of clusters has been on rise in every possible field. This paper proposes a system that monitors jobs onlarge computational clusters. Monitoring jobs is essential to understand how jobs are being executed. This helps us in understanding the complete life cycle of the jobs being executed on large clusters. Also, this paper describes how the information obtained by monitoring the jobs would help in increasing the overall throughput of clusters. Heuristics help in efficient job distribution among the computational nodes, thereby accomplishing fair job distribution policy. The proposed system would be capable of loadbalancing among the computational nodes, detecting failures, taking corrective actions after failure detection, job monitoring, system resource monitoring, etc.

  4. Cool Cluster Correctly Correlated

    Sergey Aleksandrovich Varganov

    2005-12-17

    Atomic clusters are unique objects, which occupy an intermediate position between atoms and condensed matter systems. For a long time it was thought that physical and chemical properties of atomic dusters monotonically change with increasing size of the cluster from a single atom to a condensed matter system. However, recently it has become clear that many properties of atomic clusters can change drastically with the size of the clusters. Because physical and chemical properties of clusters can be adjusted simply by changing the cluster's size, different applications of atomic clusters were proposed. One example is the catalytic activity of clusters of specific sizes in different chemical reactions. Another example is a potential application of atomic clusters in microelectronics, where their band gaps can be adjusted by simply changing cluster sizes. In recent years significant advances in experimental techniques allow one to synthesize and study atomic clusters of specified sizes. However, the interpretation of the results is often difficult. The theoretical methods are frequently used to help in interpretation of complex experimental data. Most of the theoretical approaches have been based on empirical or semiempirical methods. These methods allow one to study large and small dusters using the same approximations. However, since empirical and semiempirical methods rely on simple models with many parameters, it is often difficult to estimate the quantitative and even qualitative accuracy of the results. On the other hand, because of significant advances in quantum chemical methods and computer capabilities, it is now possible to do high quality ab-initio calculations not only on systems of few atoms but on clusters of practical interest as well. In addition to accurate results for specific clusters, such methods can be used for benchmarking of different empirical and semiempirical approaches. The atomic clusters studied in this work contain from a few atoms

  5. Pulsars in Globular Clusters

    Camilo, F; Camilo, Fernando; Rasio, Frederic A.

    2005-01-01

    More than 100 radio pulsars have been detected in 24 globular clusters. The largest observed samples are in Terzan 5 and 47 Tucanae, which together contain 45 pulsars. Accurate timing solutions, including positions in the cluster, are known for many of these pulsars. Here we provide an observational overview of some properties of pulsars in globular clusters, as well as properties of the globular clusters with detected pulsars. The many recent detections also provide a new opportunity to re-examine theoretically the formation and evolution of recycled pulsars in globular clusters. Our brief review considers the most important dynamical interaction and binary evolution processes: collisions, exchange interactions, mass transfer, and common-envelope phases.

  6. Cluster ion beam evaporation

    Cluster ions can be made by the supercooling due to adiabatic expansion of substances to be vaporized which are ejected from a nozzle. This paper is described on the recent progress of studies concerning the cluster beam. The technique of cluster ion beam has been applied for the studies of thermonuclear plasma, the fabrication of thin films, crystal growth and electronic devices. The density of cluster ion beam is larger than that of atomic ion beam, and the formation of thin films can be easily done in high vacuum. This method is also useful for epitaxial growth. Metallic vapour cluster beam was made by the help of jetting rare gas beam. Various beam sources were developed. The characteristics of these sources were measured and analyzed. (Kato, T.)

  7. On TPC cluster reconstruction

    Dydak, F; Nefedov, Y; Wotschack, J; Zhemchugov, A

    2004-01-01

    For a bias-free momentum measurement of TPC tracks, the correct determination of cluster positions is mandatory. We argue in particular that (i) the reconstruction of the entire longitudinal signal shape in view of longitudinal diffusion, electronic pulse shaping, and track inclination is important both for the polar angle reconstruction and for optimum r phi resolution; and that (ii) self-crosstalk of pad signals calls for special measures for the reconstruction of the z coordinate. The problem of 'shadow clusters' is resolved. Algorithms are presented for accepting clusters as 'good' clusters, and for the reconstruction of the r phi and z cluster coordinates, including provisions for 'bad' pads and pads next to sector boundaries, respectively.

  8. Mathematical classification and clustering

    Mirkin, Boris

    1996-01-01

    I am very happy to have this opportunity to present the work of Boris Mirkin, a distinguished Russian scholar in the areas of data analysis and decision making methodologies. The monograph is devoted entirely to clustering, a discipline dispersed through many theoretical and application areas, from mathematical statistics and combina­ torial optimization to biology, sociology and organizational structures. It compiles an immense amount of research done to date, including many original Russian de­ velopments never presented to the international community before (for instance, cluster-by-cluster versions of the K-Means method in Chapter 4 or uniform par­ titioning in Chapter 5). The author's approach, approximation clustering, allows him both to systematize a great part of the discipline and to develop many in­ novative methods in the framework of optimization problems. The optimization methods considered are proved to be meaningful in the contexts of data analysis and clustering. The material presented in ...

  9. Improved Suffix Tree Clustering for Efficient Document Clustering

    Sonia Bansal; Niranjan Kumar

    2010-01-01

    Document clustering is a technology that puts pages into groups and is useful for categorizing, organizing, and refining search results. When clustering using only documents, Suffix Tree Clustering (STC) outperforms other clustering algorithms by making use of phrases and allowing clusters to overlap. STC is a linear time clustering which is based on identifying phrases that are common to groups of documents. STC treats a document as a string, making use of proximity information between words...

  10. The Antennae Galaxies (NGC 4038/4039) Revisited: ACS and NICMOS Observations of a Prototypical Merger

    Whitmore, Bradley C; Schweizer, Francois; Rothberg, Barry; Leitherer, Claus; Rieke, Marcia; Rieke, George; Blair, W P; Mengel, S; Alonso-Herrero, A

    2010-01-01

    The ACS and NICMOS have been used to obtain new HST images of NGC 4038/4039 ("The Antennae"). These new observations allow us to better differentiate compact star clusters from individual stars, based on both size and color. We use this ability to extend the cluster luminosity function by approximately two magnitudes over our previous WFPC2 results, and find that it continues as a single power law, dN/dL propto L^alpha with alpha=-2.13+/-0.07, down to the observational limit of Mv~-7. Similarly, the mass function is a single power law dN/dM propto M^beta with beta=-2.10+/-0.20 for clusters with ages t<3x10^8 yr, corresponding to lower mass limits that range from 10^4 to 10^5 Msun, depending on the age range of the subsample. Hence the power law indices for the luminosity and mass functions are essentially the same. The luminosity function for intermediate-age clusters (i.e., ~100-300 Myr old objects found in the loops, tails, and outer areas) shows no bend or turnover down to Mv~-6, consistent with relaxat...

  11. The Burst Cluster: Dark Matter in a Cluster Merger Associated with the Short Gamma Ray Burst, GRB 050509B

    Dahle, Hakon; Lopez, Laura A; Kouveliotou, Chryssa; Patel, Sandeep K; Rol, Evert; van der Horst, Alexander J; Fynbo, Johan P; Wijers, Ralph A M J; Burrows, David N; Gehrels, Neil; Grupe, Dirk; Ramirez-Ruiz, Enrico; Michalowski, Michal J

    2013-01-01

    We have identified a merging galaxy cluster with evidence of two distinct sub-clusters. The X-ray and optical data suggest that the subclusters are moving away from each other after closest approach. This cluster merger was discovered from observations of the well localized short-duration gamma-ray burst (GRB), GRB 050509B. The Swift/Burst Alert Telescope (BAT) source position is coincident with a cluster of galaxies ZwCl 1234.0+02916. The subsequent Swift/X-Ray Telescope (XRT) localization of the X-ray afterglow found the GRB coincident with 2MASX J12361286+2858580, a giant red elliptical galaxy in the cluster. Deep multi-epoch optical images were obtained to constrain the evolution of the GRB afterglow, including a 27480s exposure in the F814W band with Hubble Space Telescope Advanced Camera for Surveys (ACS), among the deepest imaging ever obtained towards a known galaxy cluster in a single passband. We perform a weak gravitational lensing analysis, including mapping the total mass distribution of the merg...

  12. Document clustering methods, document cluster label disambiguation methods, document clustering apparatuses, and articles of manufacture

    Sanfilippo, Antonio; Calapristi, Augustin J.; Crow, Vernon L.; Hetzler, Elizabeth G.; Turner, Alan E.

    2009-12-22

    Document clustering methods, document cluster label disambiguation methods, document clustering apparatuses, and articles of manufacture are described. In one aspect, a document clustering method includes providing a document set comprising a plurality of documents, providing a cluster comprising a subset of the documents of the document set, using a plurality of terms of the documents, providing a cluster label indicative of subject matter content of the documents of the cluster, wherein the cluster label comprises a plurality of word senses, and selecting one of the word senses of the cluster label.

  13. Textile Industrial Clusters in China

    2010-01-01

    "National Textile Industry Cluster Development Seminar" convened, held by China National Textile and Apparel Council, 23 cities and towns were awarded as China’s Textile Industry Cluster Pilot District. By far, China’s textile industrial clusters have grown

  14. Spanning Tree Based Attribute Clustering

    Zeng, Yifeng; Jorge, Cordero Hernandez

    2009-01-01

    inconsistent edges from a maximum spanning tree by starting appropriate initial modes, therefore generating stable clusters. It discovers sound clusters through simple graph operations and achieves significant computational savings. We compare the Star Discovery algorithm against earlier attribute clustering...

  15. Implementation of Low Frequency Ac to High Frequency Ac with Single Stage Zvs-Pwm Inverter

    S. Arumugam S. Ramareddy M. Sridhar

    2011-12-01

    Full Text Available This paper presents a novel soft-switching pulse width modulation (PWM utility frequency AC to high frequency (HF AC power conversion circuit incorporating boost-active clamp single stage inverter topology. This power converter is more suitable and acceptable for cost effective HF consumer induction heating applications. Its operating principle is presented. The operating performances of this high frequency inverter using the latest insulated gate bipolar transistors are illustrated, which includes HFAC power regulation ranges and actual efficiency characteristics based on zero voltage soft switching operation ranges.. The simulation circuits are models are developed and they are simulated using ORCAD.

  16. Implementation and Control of an AC/DC/AC Converter for Double Wound Flywheel Application

    Oliveira, J. G.; Schettino, H.; Gama, V; Carvalho, R.; H. Bernhoff

    2012-01-01

    An all-electric driveline based on a double wound flywheel, connected in series between main energy storage and a wheel motor, is presented. The flywheel works as a power buffer, allowing the battery to deliver optimized power. It also separates electrically the system in two sides, with the battery connected to the low voltage side and the wheel motor connected to the high voltage side. This paper presents the implementation and control of the AC/DC/AC converter, used to connect the flywheel...

  17. GRID-CONNECTECD DOUBLE-STAGE AC-AC POWER CONVERTER FOR CSP RENEWABLE ENERGY SYSTEMS

    Sorrentino, Vincenzo

    2015-01-01

    In the last years the renewable energy sources have known a state of their advanced diffusion considering their advantages compared to the traditional energy sources like fossil fuels. For this reason the combined heat and power (CHP) plant fueled by renewable sources are widely used. The purpose of this Ph.D. thesis is the design of a new Grid-connected Double-Stage AC-DC/DC-AC Power Converter (DSACPC) for a Concentrating Solar plant for Combined generation of Heat and Power (CS-CHP), th...

  18. AcEST Contig - AcEST | LSDB Archive [Life Science Database Archive metadata

    Full Text Available [ Credit s ] BLAST Search Image Search Home About Archive Update History Contact us AcEST AcEST C ... c.jp/togodb/view/archive_acestcontig#en Data acquisit ion method - Data analysis method - Number of data ... entries 4,298 entries Data it em Description Contig ID ID of contig sequence of A ... ris Number of clones The number of EST clones constit uting the contig sequence of Adiantum capillus-vene ... ris Definit ion Definit ion Link to clone list In the TogoDB edi ...

  19. Realization of a Direct Soft Switching AC/AC Converter for Wireless Power Transfer Applications

    Vuorsalo, Simo

    2015-01-01

    This thesis describes the design, realization and testing of a three-phase to one-phase direct AC/AC converter, also known as the matrix converter. The switching is using the soft-switching strategy which is also known in the literature as the Zero Current Switching strategy. To achieve ZCS, the circuit needs resonant behavior which is achieved by the transmitter primary side that is an LC circuit. This circuit acts as a tank circuit and the switching frequency is the resonant frequency of th...

  20. Three-Level AC-DC-AC Z-Source Converter Using Reduced Passive Component Count

    Loh, Poh Chiang; Gao, Feng; Tan, Pee-Chin;

    2007-01-01

    This paper presents a three-level ac-dc-ac Z-source converter with output voltage buck-boost capability. The converter is implemented by connecting a low cost front-end diode rectifier to a neutral-point-clamped inverter through a single X-shaped LC impedance network. The inverter is controlled to...... low cost alternative to sensitive applications that need to ride-through frequent input voltage sags. For confirming the converter performance, experimental testing using a constructed laboratory prototype is performed with its captured results presented in a later section of the paper....

  1. Three-Level AC-DC-AC Z-Source Converter Using Reduced Passive Component Count

    Loh, Poh Chiang; Gao, Feng; Tan, Pee-Chin;

    2009-01-01

    This paper presents a three-level ac-dc-ac Z-source converter with output voltage buck-boost capability. The converter is implemented by connecting a low-cost front-end diode rectifier to a neutral-point-clamped inverter through a single X-shaped LC impedance network. The inverter is controlled to...... semiconductor commutations, and hence, no increase in switching losses. The proposed converter therefore offers a low-cost alternative to applications that need to ride through frequent input voltage sags. For confirming the converter performance, experimental testing using a constructed laboratory prototype is...

  2. Software-Defined Cluster

    聂华; 杨晓君; 刘淘英

    2015-01-01

    The cluster architecture has played an important role in high-end computing for the past 20 years. With the advent of Internet services, big data, and cloud computing, traditional clusters face three challenges: 1) providing flexible system balance among computing, memory, and I/O capabilities;2) reducing resource pooling overheads;and 3) addressing low performance-power efficiency. This position paper proposes a software-defined cluster (SDC) architecture to deal with these challenges. The SDC architecture inherits two features of traditional cluster: its architecture is multicomputer and it has loosely-coupled interconnect. SDC provides two new mechanisms: global I/O space (GIO) and hardware-supported native access (HNA) to remote devices. Application software can define a virtual cluster best suited to its needs from resources pools provided by a physical cluster, and traditional cluster ecosystems need no modification. We also discuss a prototype design and implementation of a 32-processor cloud server utilizing the SDC architecture.

  3. Cluster knockout reactions

    Arun K Jain; B N Joshi

    2014-04-01

    Cluster knockout reactions are expected to reveal the amount of clustering (such as that of , d and even of heavier clusters such as 12C, 16O etc.) in the target nucleus. In simple terms, incident medium high-energy nuclear projectile interacts strongly with the cluster (present in the target nucleus) as if it were existing as a free entity. Theoretically, the relatively softer interactions of the two outgoing particles with the residual nucleus lead to optical distortions and are treated in terms of distorted wave (DW) formalism. The long-range projectile–cluster interaction is accounted for, in terms of the finite range (FR) direct reaction formalism, as against the more commonly adopted zero-range (ZR) distorted wave impulse approximation (DWIA) formalism. Comparison of the DWIA calculations with the observed data provide information about the momentum distribution and the clustering spectroscopic factor of the target nucleus. Interesting results and some recent advancements in the area of (, 2) reactions and heavy cluster knockout reactions are discussed. Importance of the finite-range vertex and the final-state interactions are brought out.

  4. Spectroscopy of globular clusters in the low-luminosity spiral galaxy NGC 45

    Mora, Marcelo D; Kissler-Patig, Markus

    2008-01-01

    CONTEXT: Extragalactic globular clusters have been studied in elliptical galaxies and in a few luminous spiral galaxies, but little is known about globular clusters in low-luminosity spirals. AIMS: Past observations with the ACS have shown that NGC 45 hosts a large population of globular clusters (19), as well as several young star clusters. In this work we aim to confirm the bona fide globular cluster status for 8 of 19 globular cluster candidates and to derive metallicities, ages, and velocities. METHODS: VLT/FORS2 multislit spectroscopy in combination with the Lick/IDS system was used to derive velocities and to constrain metallicities and [alpha/Fe] element ratio of the globular clusters. RESULTS: We confirm the 8 globular clusters as bona fide globular clusters. Their velocities indicate halo or bulge-like kinematics, with little or no overall rotation. From absorption indices such as H_beta, H_gamma, and H_delta and the combined [MgFe]' index, we found that the globular clusters are metal-poor [Z/H]<...

  5. Introduction to cluster dynamics

    Reinhard, Paul-Gerhard

    2008-01-01

    Clusters as mesoscopic particles represent an intermediate state of matter between single atoms and solid material. The tendency to miniaturise technical objects requires knowledge about systems which contain a ""small"" number of atoms or molecules only. This is all the more true for dynamical aspects, particularly in relation to the qick development of laser technology and femtosecond spectroscopy. Here, for the first time is a highly qualitative introduction to cluster physics. With its emphasis on cluster dynamics, this will be vital to everyone involved in this interdisciplinary subje

  6. Raspberry Pi super cluster

    Dennis, Andrew K

    2013-01-01

    This book follows a step-by-step, tutorial-based approach which will teach you how to develop your own super cluster using Raspberry Pi computers quickly and efficiently.Raspberry Pi Super Cluster is an introductory guide for those interested in experimenting with parallel computing at home. Aimed at Raspberry Pi enthusiasts, this book is a primer for getting your first cluster up and running.Basic knowledge of C or Java would be helpful but no prior knowledge of parallel computing is necessary.

  7. Partially supervised speaker clustering.

    Tang, Hao; Chu, Stephen Mingyu; Hasegawa-Johnson, Mark; Huang, Thomas S

    2012-05-01

    Content-based multimedia indexing, retrieval, and processing as well as multimedia databases demand the structuring of the media content (image, audio, video, text, etc.), one significant goal being to associate the identity of the content to the individual segments of the signals. In this paper, we specifically address the problem of speaker clustering, the task of assigning every speech utterance in an audio stream to its speaker. We offer a complete treatment to the idea of partially supervised speaker clustering, which refers to the use of our prior knowledge of speakers in general to assist the unsupervised speaker clustering process. By means of an independent training data set, we encode the prior knowledge at the various stages of the speaker clustering pipeline via 1) learning a speaker-discriminative acoustic feature transformation, 2) learning a universal speaker prior model, and 3) learning a discriminative speaker subspace, or equivalently, a speaker-discriminative distance metric. We study the directional scattering property of the Gaussian mixture model (GMM) mean supervector representation of utterances in the high-dimensional space, and advocate exploiting this property by using the cosine distance metric instead of the euclidean distance metric for speaker clustering in the GMM mean supervector space. We propose to perform discriminant analysis based on the cosine distance metric, which leads to a novel distance metric learning algorithm—linear spherical discriminant analysis (LSDA). We show that the proposed LSDA formulation can be systematically solved within the elegant graph embedding general dimensionality reduction framework. Our speaker clustering experiments on the GALE database clearly indicate that 1) our speaker clustering methods based on the GMM mean supervector representation and vector-based distance metrics outperform traditional speaker clustering methods based on the “bag of acoustic features” representation and statistical

  8. Dwarfs in Coma Cluster

    2007-01-01

    [figure removed for brevity, see original site] Click on image for larger poster version This false-color mosaic of the central region of the Coma cluster combines infrared and visible-light images to reveal thousands of faint objects (green). Follow-up observations showed that many of these objects, which appear here as faint green smudges, are dwarf galaxies belonging to the cluster. Two large elliptical galaxies, NGC 4889 and NGC 4874, dominate the cluster's center. The mosaic combines visible-light data from the Sloan Digital Sky Survey (color coded blue) with long- and short-wavelength infrared views (red and green, respectively) from NASA's Spitzer Space Telescope.

  9. Clustering in nuclear environment

    The properties of few-body clusters (mass number A ≤ 4) are modified if they are immersed in a nuclear medium. In particular, Pauli blocking that reflects the antisymmetrization of the many-body wave function is responsible for the medium modification of light clusters and the dissolution with increasing density. A more consistent description is given with takes also the contribution of correlations in the continuum into account. The relation between cluster formation in warm dense matter and in nuclear structure is discussed

  10. Dicty_cDB: FCL-AC03 [Dicty_cDB

    Full Text Available FCL (Link to library) FCL-AC03 (Link to dictyBase) - - - Contig-U16477-1 FCL-AC03P ...(Link to Original site) FCL-AC03F 538 FCL-AC03Z 570 FCL-AC03P 1108 - - Show FCL-AC03 Library FCL (Link to library) Clone ID FCL-...7-1 Original site URL http://dictycdb.biol.tsukuba.ac.jp/CSM/FCL/FCL-AC/FCL-AC03Q....Seq.d/ Representative seq. ID FCL-AC03P (Link to Original site) Representative DNA sequence >FCL-AC03 (FCL-AC03Q) /CSM/FCL/FCL-...AC/FCL-AC03Q.Seq.d/ AATTTTTAAAAAAAAAAGAAAATAAAAAAAAAAATAATATTTTATTAGTCATTATAAAAT TGTGAAT

  11. Dicty_cDB: FCL-AC20 [Dicty_cDB

    Full Text Available FCL (Link to library) FCL-AC20 (Link to dictyBase) - - - Contig-U15117-1 FCL-AC20Z ...(Link to Original site) - - FCL-AC20Z 600 - - - - Show FCL-AC20 Library FCL (Link to library) Clone ID FCL-A... http://dictycdb.biol.tsukuba.ac.jp/CSM/FCL/FCL-AC/FCL-AC20Q.Seq.d/ Representative seq. ID FCL-...AC20Z (Link to Original site) Representative DNA sequence >FCL-AC20 (FCL-AC20Q) /CSM/FCL/FCL-AC/FCL-...Homology vs CSM-cDNA Score E Sequences producing significant alignments: (bits) Value FCL-AC20 (FCL-AC20Q) /CSM/FCL/FCL-AC/FCL-

  12. Levantamiento del campo acústico de una fuente sonora subacuática en el tanque hidroacústico del Instituto de Acústica

    Ranz Guerra, Carlos; Cobo, Pedro

    2000-01-01

    6 pp.-- PACS nrs.: 43.30.Jx, 43.30.Sf.-- Comunicación presentada en los siguientes congresos: Acústica 2000, II Congreso Iberoamericano de Acústica. XXXI Congreso Nacional de Acústica: TecniAcústica 2000. II Congreso Ibérico de Acústica. II Jornadas Iberoamericanas de Acústica. EAA Symposium on Architectural Acoustics.

  13. DC injection into low voltage AC networks

    NONE

    2005-07-01

    This report summarises the results of a study investigating the impact of levels of injected DC current injections on a low voltage AC distribution network systems in order to recommend acceptable limits of DC from microgeneration. Relevant literature is reviewed, and the impact of DC levels in distribution transformers, transformer modelling, and instrumental transformers are discussed. The impact of DC in residual current devices (RCD) and in domestic electricity watt hour meters is examined along with DC enhanced corrosion, corrosion failure, and the measurement of DC current injection. Sources of DC injection outlined include DC from computer power supplies, network faults, geomagnetic phenomena, lighting circuits/dimmers, and embedded generators.

  14. Mapa acústico parcial de Benetusser

    MORILLA CASTELLANOS, EMILIO

    2012-01-01

    Se establece el mapa de ruido del municipio de Benetússer para evaluar y conocer su exposición al ruido ambiental y así poder dar cumplimiento a la Directiva Europea sobre Gestión y Evaluación de Ruido Ambiental (2002/49/CE) y a la Ley nacional 37/2003 del Ruido. Los mapas estratégicos de ruido nos aportan la información fundamental para diagnosticar la situación acústica y para la gestión del ruido ambiental.

  15. An ac biased superconducting flux transformer

    The coupled motion of the vortex lattice of two electrically insulated, superimposed, superconducting thin films (primary and secondary) in a perpendicular magnetic field, is predicted to exhibit a Josephson-like behavior. For a dc applied current flowing in the primary film, the voltage difference between the time-averaged primary and secondary flux flow voltages obeys the equations of a resistively shunted junction model. If an ac current is superimposed on the dc current. Shapiro-type steps are predicted in the current-voltage characteristic. In contrast to the conventional Josephson effect, the voltage positions of these steps can be tuned by the applied magnetic field. (orig.)

  16. Flexible AC transmission systems modelling and control

    Zhang, Xiao-Ping; Pal, Bikash

    2012-01-01

    The extended and revised second edition of this successful monograph presents advanced modeling, analysis and control techniques of Flexible AC Transmission Systems (FACTS). The book covers comprehensively a range of power-system control problems: from steady-state voltage and power flow control, to voltage and reactive power control, to voltage stability control, to small signal stability control using FACTS controllers. In the six years since the first edition of the book has been published research on the FACTS has continued to flourish while renewable energy has developed into a mature and

  17. Comparison three methods of clustering: k-means, spectral clustering and hierarchical clustering

    Kowsari, Kamran

    2013-01-01

    Comparison of three kind of the clustering and find cost function and loss function and calculate them. Error rate of the clustering methods and how to calculate the error percentage always be one on the important factor for evaluating the clustering methods, so this paper introduce one way to calculate the error rate of clustering methods. Clustering algorithms can be divided into several categories including partitioning clustering algorithms, hierarchical algorithms and density based algor...

  18. Spatial connectivity of urban clusters and regional climate effects

    Jia, G.; Hu, Y.; Xu, R.

    2015-12-01

    Rapid urbanization in East Asia in past three decades is considered as a remarkable process that featured with expansion of urban clusters and tightened linkages within and among clusters. Such process could lead to much larger scale climate effects, and could even contribute to sub-regional and regional climate change. In large area of urban clusters with significant expansion of built-up in relatively short period, local urban heat islands could contribute to sub-regional climate forcing. Here we use visible/near infrared and thermal infrared satellite data to estimate multiple scale structure of urban clusters, and to assess effects of urban heat islands at local and regional scales in East Asia. Our estimates of urban extent were greater than previously reported in most global datasets. Strong spatial connection and internal expansion were found in major urban clusters in past 30 years, and was accelerated in past 10 years. Many city clusters were merging into each other, with gradual blurring boundaries and disappearing of gaps among member cities. Cities and towns were more connected with roads and commercial corridors, while wildland and urban greens became more isolated as patches among built-up areas. We would argue that in many cases in this region, urban clusters are no longer "islands", they are now "seas" in term of climate related urban canopy. Urban greens such as parks and plantation were long recognized for their cooling effects that buffer the urban heat island effect, however, such cooling effects tend to be weakened as their patches became smaller and isolated, and over dominated by urban surfaces. There were significant positive relations between urban fraction and urban heat island effects as demonstrated by VNIR and TIR data from multiple satellites. Those new estimates are expected to effectively improve climate simulation for better understanding the impacts of inter-connected urban clusters on air temperature, precipitation, wind speed

  19. A Uniqueness Theorem for Clustering

    Zadeh, Reza Bosagh

    2012-01-01

    Despite the widespread use of Clustering, there is distressingly little general theory of clustering available. Questions like "What distinguishes a clustering of data from other data partitioning?", "Are there any principles governing all clustering paradigms?", "How should a user choose an appropriate clustering algorithm for a particular task?", etc. are almost completely unanswered by the existing body of clustering literature. We consider an axiomatic approach to the theory of Clustering. We adopt the framework of Kleinberg, [Kle03]. By relaxing one of Kleinberg's clustering axioms, we sidestep his impossibility result and arrive at a consistent set of axioms. We suggest to extend these axioms, aiming to provide an axiomatic taxonomy of clustering paradigms. Such a taxonomy should provide users some guidance concerning the choice of the appropriate clustering paradigm for a given task. The main result of this paper is a set of abstract properties that characterize the Single-Linkage clustering function. ...

  20. Modes of clustered star formation

    Pfalzner, S; Olczak, C

    2012-01-01

    The realization that most stars form in clusters, raises the question of whether star/planet formation are influenced by the cluster environment. The stellar density in the most prevalent clusters is the key factor here. Whether dominant modes of clustered star formation exist is a fundamental question. Using near-neighbour searches in young clusters Bressert et al. (2010) claim this not to be the case and conclude that star formation is continuous from isolated to densely clustered. We investigate under which conditions near-neighbour searches can distinguish between different modes of clustered star formation. Near-neighbour searches are performed for model star clusters investigating the influence of the combination of different cluster modes, observational biases, and types of diagnostic and find that the cluster density profile, the relative sample sizes, limitations in observations and the choice of diagnostic method decides whether modelled modes of clustered star formation are detected. For centrally ...

  1. Clustering of Emerging Flux

    Ruzmaikin, A.

    1997-01-01

    Observations show that newly emerging flux tends to appear on the Solar surface at sites where there is flux already. This results in clustering of solar activity. Standard dynamo theories do not predict this effect.

  2. Dynamic Bayesian clustering.

    Fowler, Anna; Menon, Vilas; Heard, Nicholas A

    2013-10-01

    Clusters of time series data may change location and memberships over time; in gene expression data, this occurs as groups of genes or samples respond differently to stimuli or experimental conditions at different times. In order to uncover this underlying temporal structure, we consider dynamic clusters with time-dependent parameters which split and merge over time, enabling cluster memberships to change. These interesting time-dependent structures are useful in understanding the development of organisms or complex organs, and could not be identified using traditional clustering methods. In cell cycle data, these time-dependent structure may provide links between genes and stages of the cell cycle, whilst in developmental data sets they may highlight key developmental transitions. PMID:24131050

  3. Internal Cluster Structure

    Bartelmann, Matthias; Meneghetti, Massimo; Schmidt, Robert

    2013-01-01

    The core structure of galaxy clusters is fundamentally important. Even though self-gravitating systems have no stable equilibrium state due to their negative heat capacity, numerical simulations find density profiles which are universal in the sense that they are fairly flat within a scale radius and gradually steepen farther outward, asymptotically approaching a logarithmic slope of $\\approx-3$ near the virial radius. We argue that the reason for the formation of this profile is not satisfactorily understood. The ratio between the virial radius and the scale radius, the so-called concentration, is found in simulations to be closely related to the mass and the redshift and low for cluster-sized haloes, but observed to be substantially higher at least in a subset of observed clusters. Haloes formed from cold dark matter should furthermore be richly substructured. We review theoretical and observational aspects of cluster cores here, discuss modifications by baryonic physics and observables that can provide bet...

  4. Evolution of clustered storage

    CERN. Geneva; Van de Vyvre, Pierre

    2007-01-01

    The session actually featured two presentations: * Evolution of clustered storage by Lance Hukill, Quantum Corporation * ALICE DAQ - Usage of a Cluster-File System: Quantum StorNext by Pierre Vande Vyvre, CERN-PH the second one prepared at short notice by Pierre (thanks!) to present how the Quantum technologies are being used in the ALICE experiment. The abstract to Mr Hukill's follows. Clustered Storage is a technology that is driven by business and mission applications. The evolution of Clustered Storage solutions starts first at the alignment between End-users needs and Industry trends: * Push-and-Pull between managing for today versus planning for tomorrow * Breaking down the real business problems to the core applications * Commoditization of clients, servers, and target devices * Interchangeability, Interoperability, Remote Access, Centralized control * Oh, and yes, there is a budget and the "real world" to deal with This presentation will talk through these needs and trends, and then ask the question, ...

  5. Modeling the Formation of Globular Cluster Systems in the Virgo Cluster

    Li, Hui

    2014-01-01

    Globular cluster (GC) systems are some of the oldest and most unique building blocks of galaxies. The mass and chemical composition of GCs preserve the fossil record of the early stages of formation of their host galaxies. The observed distribution of GC colors within massive early-type galaxies in the ACS Virgo Cluster Survey (ACSVCS) reveals a multi-modal shape, which likely corresponds to a multi-modal metallicity distribution. In this paper, we present a simple model for the formation and dynamical disruption of globular clusters that aims to match the ACSVCS data. We test the hypothesis that GCs are formed during major mergers of gas-rich galaxies and inherit the metallicity of their hosts. To trace merger events, we use halo merger trees extracted from a large cosmological N-body simulation. We select 20 halos in the mass range 2*10^{12}-7*10^{13} M_sun and match them to 18 Virgo galaxies with K-band luminosity between 3*10^{10} and 3*10^{11}L_sun. To set the Iron abundances, we use an empirical galaxy ...

  6. Cauchy cluster process

    Ghorbani, Mohammad

    2013-01-01

    In this paper we introduce an instance of the well-know Neyman–Scott cluster process model with clusters having a long tail behaviour. In our model the offspring points are distributed around the parent points according to a circular Cauchy distribution. Using a modified Cramér-von Misses test...... statistic and the simulated pointwise envelopes it is shown that this model fits better than the Thomas process to the frequently analyzed long-leaf pine data-set....

  7. Bayesian Nonparametric Graph Clustering

    Banerjee, Sayantan; Akbani, Rehan; Baladandayuthapani, Veerabhadran

    2015-01-01

    We present clustering methods for multivariate data exploiting the underlying geometry of the graphical structure between variables. As opposed to standard approaches that assume known graph structures, we first estimate the edge structure of the unknown graph using Bayesian neighborhood selection approaches, wherein we account for the uncertainty of graphical structure learning through model-averaged estimates of the suitable parameters. Subsequently, we develop a nonparametric graph cluster...

  8. Finnish Mobile Gaming Cluster

    Masira, Elijah; Chowdhury, Nafis Ahmed

    2014-01-01

    Abstract The Finnish mobile gaming cluster is one of the most promising industries that have been growing significantly in the past few years to become a substantial cultural export product / service of Finland. The main objective of this research was to gain a persuasive understanding about the emergence of the mobile gaming cluster in Finland and explore the factors behind its success. The literature review centers on M. E Porter’s publications on competitiveness and other publication...

  9. Industry clusters and SMEs

    Arnoud Muizer; Gert Jan Hospers

    1999-01-01

    Studie naar de rol van clusters van bedrijven in de economie. Clusters van bedrijven krijgen een groeiende aandacht op alle bestuurlijke niveaus. De achterliggende gedachte is dat samenwerking tussen bedrijven op technologisch gebied leidt tot de creatie van extra toegevoegde waarde, niet alleen voor de samenwerkingspartners zelf, maar ook voor de lokale, regionale en nationale economie. In de studie wordt een clusterdefinitie gepresenteerd en een raamwerk dat als basis kan dienen voor nader ...

  10. Clustering with topological constraints

    GRBEC, DEJAN

    2012-01-01

    In data analysis we often have to deal with object located somewhere in space. Data can be bound to cities, countries or other space object that have known spatial coordinates. This object can be clustered by selected attributes considering their adjacency. The object of diploma thesis was to develop procedures that consider objects neighboring relation. To determine the adjacency of object in space, we used the Voronoi diagram where the clusters of data should preset related parts of diagra...

  11. Hipax Cluster PACS Server

    Ramin Payrovi

    2007-01-01

    Best Performace: With our Hipax Cluster PACS Server solution we are introducing the parallel computing concept as an extremely fast software system to the PACS world. In contrast to the common PACS servers, the Hipax Cluster PACS software is not only restricted to one or two computers, but can be used on a couple of servers controlling each other."nThus, the same services can be run simultaneously on different computers. The scalable system can also be expanded subsequently without lost ...

  12. Clustering audiology data

    Anwar, Naveed; Oakes, Michael; Wermter, Stefan; Heinrich, Stefan

    2010-01-01

    In this paper we describe new results of statistical and neural data mining of audiology patient records, with the ultimate aim of looking for factors influencing which patients would most benefit from being fitted with a hearing aid. We describe how a combination of neural and statistical techniques can usefully subdivide a set of patients into clusters, based on their hearing thresholds at six different frequencies, and then label the clusters with meaningful text labels. In our first exper...

  13. Determination of atomic cluster structure with cluster fusion algorithm

    Obolensky, Oleg I.; Solov'yov, Ilia; Solov'yov, Andrey V.; Greiner, Walter

    We report an efficient scheme of global optimization, called cluster fusion algorithm, which has proved its reliability and high efficiency in determination of the structure of various atomic clusters.......We report an efficient scheme of global optimization, called cluster fusion algorithm, which has proved its reliability and high efficiency in determination of the structure of various atomic clusters....

  14. Cluster fusion algorithm: application to Lennard-Jones clusters

    Solov'yov, Ilia; Solov'yov, Andrey V.; Greiner, Walter

    2008-01-01

    We present a new general theoretical framework for modelling the cluster structure and apply it to description of the Lennard-Jones clusters. Starting from the initial tetrahedral cluster configuration, adding new atoms to the system and absorbing its energy at each step, we find cluster growing ...

  15. Cluster fusion algorithm: application to Lennard-Jones clusters

    Solov'yov, Ilia; Solov'yov, Andrey V.; Greiner, Walter

    2006-01-01

    We present a new general theoretical framework for modelling the cluster structure and apply it to description of the Lennard-Jones clusters. Starting from the initial tetrahedral cluster configuration, adding new atoms to the system and absorbing its energy at each step, we find cluster growing ...

  16. Cluster bomb ocular injuries

    Ahmad M Mansour

    2012-01-01

    Full Text Available Purpose: To present the visual outcomes and ocular sequelae of victims of cluster bombs. Materials and Methods: This retrospective, multicenter case series of ocular injury due to cluster bombs was conducted for 3 years after the war in South Lebanon (July 2006. Data were gathered from the reports to the Information Management System for Mine Action. Results: There were 308 victims of clusters bombs; 36 individuals were killed, of which 2 received ocular lacerations and; 272 individuals were injured with 18 receiving ocular injury. These 18 surviving individuals were assessed by the authors. Ocular injury occurred in 6.5% (20/308 of cluster bomb victims. Trauma to multiple organs occurred in 12 of 18 cases (67% with ocular injury. Ocular findings included corneal or scleral lacerations (16 eyes, corneal foreign bodies (9 eyes, corneal decompensation (2 eyes, ruptured cataract (6 eyes, and intravitreal foreign bodies (10 eyes. The corneas of one patient had extreme attenuation of the endothelium. Conclusions: Ocular injury occurred in 6.5% of cluster bomb victims and 67% of the patients with ocular injury sustained trauma to multiple organs. Visual morbidity in civilians is an additional reason for a global ban on the use of cluster bombs.

  17. Centroid Based Text Clustering

    Priti Maheshwari

    2010-09-01

    Full Text Available Web mining is a burgeoning new field that attempts to glean meaningful information from natural language text. Web mining refers generally to the process of extracting interesting information and knowledge from unstructured text. Text clustering is one of the important Web mining functionalities. Text clustering is the task in which texts are classified into groups of similar objects based on their contents. Current research in the area of Web mining is tacklesproblems of text data representation, classification, clustering, information extraction or the search for and modeling of hidden patterns. In this paper we propose for mining large document collections it is necessary to pre-process the web documents and store the information in a data structure, which is more appropriate for further processing than a plain web file. In this paper we developed a php-mySql based utility to convert unstructured web documents into structured tabular representation by preprocessing, indexing .We apply centroid based web clustering method on preprocessed data. We apply three methods for clustering. Finally we proposed a method that can increase accuracy based on clustering ofdocuments.

  18. Galaxy cluster's rotation

    Manolopoulou, Maria

    2016-01-01

    We study the possible rotation of cluster galaxies, developing, testing and applying a novel algorithm which identifies rotation, if such does exits, as well as its rotational centre, its axis orientation, rotational velocity amplitude and, finally, the clockwise or counterclockwise direction of rotation on the plane of the sky. To validate our algorithms we construct realistic Monte-Carlo mock rotating clusters and confirm that our method provides robust indications of rotation. We then apply our methodology on a sample of Abell clusters with z<~0.1 with member galaxies selected from the SDSS DR10 spectroscopic database. We find that ~35% of our clusters are rotating when using a set of strict criteria, while loosening the criteria we find this fraction increasing to ~48%. We correlate our rotation indicators with the cluster dynamical state, provided either by their Bautz-Morgan type or by their X-ray isophotal shape and find for those clusters showing rotation that the significance and strength of their...

  19. Estudio acústico del Conservatorio de Piles

    VILLA MORANT, SARA

    2014-01-01

    El objetivo de este proyecto es realizar un estudio acústico general de la "Casa de la Cultura" de Piles, sobre todo de los recintos que más lo requieren, como la sala principal de música. El edificio, al tratarse de una construcción antigua, no reúne las especificaciones acústicas establecidas en el Código Técnico vigente en la actualidad. En primer lugar, se realiza el estudio del acondicionamiento acústico de la sala principal, entendiéndose como acondicionamiento acústico la definición de...

  20. AC Own Motion Percentage of Randomly Sampled Cases

    Social Security Administration — Longitudinal report detailing the numbers and percentages of Appeals Council (AC) own motion review actions taken on un-appealed favorable hearing level decisions...

  1. AC electric motors control advanced design techniques and applications

    Giri, Fouad

    2013-01-01

    The complexity of AC motor control lies in the multivariable and nonlinear nature of AC machine dynamics. Recent advancements in control theory now make it possible to deal with long-standing problems in AC motors control. This text expertly draws on these developments to apply a wide range of model-based control designmethods to a variety of AC motors. Contributions from over thirty top researchers explain how modern control design methods can be used to achieve tight speed regulation, optimal energetic efficiency, and operation reliability and safety, by considering online state var

  2. Study of AC electrical conduction mechanisms in an epoxy polymer

    Jilani, Wissal; Mzabi, Nissaf; Gallot-Lavallée, Olivier; Fourati, Najla; Zerrouki, Chouki; Zerrouki, Rachida; Guermazi, Hajer

    2015-11-01

    The AC conductivity of an epoxy resin was investigated in the frequency range 10^{-1} - 106 Hz at temperatures ranging from -100 to 120 °C. The frequency dependence of σ_{ac} was described by the law: σ_{ac}=ω \\varepsilon0\\varepsilon^''_{HN}+Aωs. The study of temperature variation of the exponent (s) reveals two conduction models: the AC conduction dependence upon temperature is governed by the small polaron tunneling mechanism (SPTM) at low temperature (-100 -60 °C) and the correlated barrier hopping (CHB) model at high temperature (80-120 °C).

  3. Djungle power. A more remote AC bus

    Boehnke, Heinz W. [Technosol, Jork (Germany)

    2010-07-01

    The Dzanga-Sangha Reserve in the Central African Republic is probably one of the world's most remote protected rainforest areas, much to the benefit of the rare species of lowland gorilla, forest elephant and local pygmy population Ba'Aka. The park is co-managed by the ''WWF-World Wide Fund for Nature'' with sponsoring from the German Regenwald-Stiftung. In 2008 wwf decided to switch from the old, failing generator supply to a solar hybrid mini-grid, along with stringent measures of energy conservation and management. After a careful energy audit Technosol designed an AC-bus system with a 22 kWp PV generator which should overcome the dependency on the old generators and their fuel demands. For 15 buildings, an entirely new distribution network was installed, state of the art energy saving devices introduced and an energy metering system deviced. The installation is operating since August 2009. In such remote locations, the reliability of the AC-bus over other generator-based solutions will be demonstrated and with the support of international organisations like the wwf the practical application of solar hybrid supply becomes a landmark of sustainable energy concepts. (orig.)

  4. An improved AC-amplifier for electrophysiology

    Jorgovanović Nikola

    2009-01-01

    Full Text Available We present the design, simulation and test results of a new AC amplifier for electrophysiological measurements based on a three op-amp instrumentation amplifier (IA. The design target was to increase the common mode rejection ratio (CMRR, thereby improving the quality of the recorded physiological signals in a noisy environment. The new amplifier actively suppresses the DC component of the differential signal and actively reduces the common mode signal in the first stage of the IA. These functions increase the dynamic range of the amplifier's first stage of the differential signal. The next step was the realization of the amplifier in a single chip technology. The design and tests of the new AC amplifier with a differential gain of 79.2 dB, a CMRR of 130 dB at 50 Hz, a high-pass cutoff frequency at 0.01 Hz and common mode reduction in the first stage of the 49.8 dB are presented in this paper.

  5. The clustered nature of star formation. Pre--main-sequence clusters in the star-forming region NGC 602/N90 in the Small Magellanic Cloud

    Gouliermis, Dimitrios A; Dolphin, Andrew E; Gennaro, Mario; Tognelli, Emanuele; Moroni, Pier Giorgio Prada

    2012-01-01

    Located at the tip of the wing of the Small Magellanic Cloud (SMC), the star-forming region NGC602/N90 is characterized by the HII nebular ring N90 and the young cluster of pre--main-sequence (PMS) and early-type main sequence stars NGC602. We present a thorough cluster analysis of the stellar sample identified with HST/ACS camera in the region. We show that apart from the central cluster, low-mass PMS stars are congregated in thirteen additional small compact sub-clusters at the periphery of NGC602. We find that the spatial distribution of the PMS stars is bimodal, with an unusually large fraction (~60%) of the total population being clustered, while the remaining is diffusely distributed in the inter-cluster area. From the corresponding color-magnitude diagrams we disentangle an age-difference of ~2.5Myr between NGC602 and the compact sub-clusters which appear younger. The diffuse PMS population appears to host stars as old as those in NGC602. Almost all detected PMS sub-clusters appear to be centrally conc...

  6. Dicty_cDB: FCL-AC29 [Dicty_cDB

    Full Text Available FCL (Link to library) FCL-AC29 (Link to dictyBase) - - - Contig-U15392-1 FCL-AC29P ...(Link to Original site) FCL-AC29F 104 FCL-AC29Z 591 FCL-AC29P 695 - - Show FCL-AC29 Library FCL (Link to library) Clone ID FCL-...-1 Original site URL http://dictycdb.biol.tsukuba.ac.jp/CSM/FCL/FCL-AC/FCL-AC29Q....Seq.d/ Representative seq. ID FCL-AC29P (Link to Original site) Representative DNA sequence >FCL-AC29 (FCL-AC29Q) /CSM/FCL/FCL-...roducing significant alignments: (bits) Value VSC293 (VSC293Q) /CSM/VS/VSC2-D/VSC293Q.Seq.d/ 1063 0.0 FCL-AC29 (FCL-

  7. A Non-linear Controller for Single-Phase AC-AC Power Converter to meet UPS Performance Index

    Abdelhafid Ait Elmahjoub

    2012-07-01

    Full Text Available This article focuses on AC-AC power converter that can be used for uninterruptible power supply (UPS. The converter is built on two stages: a AC-DC input stage and a DC-AC output stage. The two blocks are connected by an intermediate DC bus. The aim of control is threefold: i power factor correction ii regulation of DC bus iii generating a sinusoidal voltage at the output. The synthesis of controllers has been achieved through the technique of nonlinear backstepping control. A detailed analysis of the stability control system is presented. The performances of regulators have been validated by numerical simulation in MATLAB / SIMULINK.

  8. The rotation of Galaxy Clusters

    Tovmassian, Hrant M.

    2015-01-01

    The method for detection of the galaxy cluster rotation based on the study of distribution of member galaxies with velocities lower and higher of the cluster mean velocity over the cluster image is proposed. The search for rotation is made for flat clusters with $a/b>1.8$ and BMI type clusters which are expected to be rotating. For comparison there were studied also round clusters and clusters of NBMI type, the second by brightness galaxy in which does not differ significantly from the cluste...

  9. Cluster Implantation and Deposition Apparatus

    Hanif, Muhammad; Popok, Vladimir

    In the current report, a design and capabilities of a cluster implantation and deposition apparatus (CIDA) involving two different cluster sources are described. The clusters produced from gas precursors (Ar, N etc.) by PuCluS-2 can be used to study cluster ion implantation in order to develop...... contributions to the theory of cluster stopping in matter as well as for practical applications requiring ultra-shallow implantation and modification of surfaces on the nanoscale. Metal clusters from the magnetron cluster source are of interest for the production of optical sensors to detect specific biological...

  10. Spectroscopy of nuclei 215Fr and 219 Ac: a contribution to the study of the nuclear structure of light actinides

    Using α-particle and γ-ray spectroscopy, it has been possible to establish the high spin pattern in 215Fr and propose a decay scheme up to Iπ = (47/2+) containing six isomeric states. These results are interpreted using the recent version of the deformed Woods-Saxon model and the Strutinsky normalisation technique. A similar study in 219 Ac has revealed the existence of two quasi-bands each formed of states of alternating parity and connected by strong E1 transitions. This data for 219Ac fits better with the stable octupole deformation model, mainly because of the high-spin parity doublets observed for the first time, than with the α-cluster model

  11. Stellar populations in star clusters

    Li, Chengyuan; Deng, Licai

    2016-01-01

    Stellar populations contain the most important information about star clus- ter formation and evolution. Until several decades ago, star clusters were believed to be ideal laboratories for studies of simple stellar populations (SSPs). However, discoveries of multiple stellar populations in Galactic globular clusters have expanded our view on stellar populations in star clusters. They have simultaneously generated a number of controversies, particularly as to whether young star clusters may have the same origin as old globular clusters. In addition, extensive studies have revealed that the SSP scenario does not seem to hold for some intermediate-age and young star clusters either, thus making the origin of multiple stellar populations in star clusters even more complicated. Stellar population anomalies in numerous star clusters are well-documented, implying that the notion of star clusters as true SSPs faces serious challenges. In this review, we focus on stellar populations in massive clusters with different ...

  12. Bayesian Analysis of Two Stellar Populations in Galactic Globular Clusters II: NGC 5024, NGC 5272, and NGC 6352

    Wagner-Kaiser, R; Robinson, E; von Hippel, T; Sarajedini, A; van Dyk, D A; Stein, N; Jefferys, W H

    2016-01-01

    We use Cycle 21 Hubble Space Telescope (HST) observations and HST archival ACS Treasury observations of Galactic Globular Clusters to find and characterize two stellar populations in NGC 5024 (M53), NGC 5272 (M3), and NGC 6352. For these three clusters, both single and double-population analyses are used to determine a best fit isochrone(s). We employ a sophisticated Bayesian analysis technique to simultaneously fit the cluster parameters (age, distance, absorption, and metallicity) that characterize each cluster. For the two-population analysis, unique population level helium values are also fit to each distinct population of the cluster and the relative proportions of the populations are determined. We find differences in helium ranging from $\\sim$0.05 to 0.11 for these three clusters. Model grids with solar $\\alpha$-element abundances ([$\\alpha$/Fe] =0.0) and enhanced $\\alpha$-elements ([$\\alpha$/Fe]=0.4) are adopted.

  13. Structure of Dark Matter and Baryons in AMIBA SZE Galaxy Clusters (II)

    Ho, Paul

    2010-01-01

    We propose deep BR_cz' imaging with Suprime-Cam of several hot X-ray (> 8 keV) clusters of galaxies for which Sunyaev-Zel'dovich effect (SZE) observations are underway at 3mm with the Array for Microwave Background Anisotropy (AMiBA) and superb resolution HST/ACS strong lensing (SL) data are readily available. Joint weak lensing (WL), SL, multicolor imaging, and SZE observations, combined with archival X-ray data, will probe in a model-independent manner the structure of dark matter, member galaxies, and the hot cluster gas in rich cluster environments. Our targets are composed of a class of the most massive clusters at moderate redshifts (0.2 <~ z <~ 0.7), allowing us to derive reliable WL shape measurements and thus accurate mass profiles out to the cluster virial radius. Our proposal aims to (1) map out the mass distribution in clusters via WL techniques, and compare with the distributions of hot and cold baryonic components, (2) make an accurate determination of the cluster mass profile from a joint WL+SL analysis, (3) derive cluster gas-mass fraction profiles free from the hydrostatic equilibrium assumption, and (4) examine directly the cluster mass vs. SZE observable relation, which will provide an important basis for cosmological tests with upcoming blind SZE surveys.

  14. [Intestinal occlusion and abdominal compartment syndrome (ACS)].

    Stagnitti, Franco

    2009-01-01

    Intestinal occlusion is defined as an independent predictive factor of intra-abdominal hypertension (IAH) which represents an independent predictor of mortality. Baggot in 1951 classified patients operated with intestinal occlusion as being at risk for IAH ("abdominal blow-out"), recommending them for open abdomen surgery proposed by Ogilvie. Abdominal surgery provokes IAH in 44.7% of cases with mortality which, in emergency, triples with respect to elective surgery (21.9% vs 6.8%). In particular, IAH is present in 61.2% of ileus and bowel distension and is responsible for 52% of mortality (54.8% in cases with intra-abdominal infection). These patients present with an increasing intra-abdominal pressure (IAP) which, over 20-25 mmHg, triggers an Abdominal Compartment Syndrome (ACS) with altered functions in some organs arriving at Multiple Organ Dysfunction Syndrome (MODS). The intestine normally covers 58% of abdominal volume but when there is ileus distension, intestinal pneumatosis develops (third space) which can occupy up to 90% of the entire cavity. At this moment, Gastro Intestinal Failure (GIF) can appear, which is a specific independent risk factor of mortality, motor of "Organ Failure". The pathophysiological evolution has many factors in 45% of cases: intestinal pneumatosis is associated with mucosal and serous edema, capillary leakage with an increase in extra-cellular volume and peritoneal fluid collections (fourth space). The successive loss of the mucous barrier permits a bacterial translocation which includes bacteria, toxins, pro-inflammatory factors and oxygen free radicals facilitating the passage from an intra-abdominal to inter-systemic vicious cyrcle. IAH provokes the raising of the diaphragm, and vascular and visceral compressions which induce hypertension in the various spaces with compartmental characteristics. These trigger hypertension in the renal, hepatic, pelvic, thoracic, cardiac, intracranial, orbital and lower extremity areas, giving

  15. Clustering is Easy When ....What?

    Ben-David, Shai

    2015-01-01

    It is well known that most of the common clustering objectives are NP-hard to optimize. In practice, however, clustering is being routinely carried out. One approach for providing theoretical understanding of this seeming discrepancy is to come up with notions of clusterability that distinguish realistically interesting input data from worst-case data sets. The hope is that there will be clustering algorithms that are provably efficient on such "clusterable" instances. This paper addresses th...

  16. Splitting Methods for Convex Clustering

    Chi, Eric C.; Lange, Kenneth

    2013-01-01

    Clustering is a fundamental problem in many scientific applications. Standard methods such as $k$-means, Gaussian mixture models, and hierarchical clustering, however, are beset by local minima, which are sometimes drastically suboptimal. Recently introduced convex relaxations of $k$-means and hierarchical clustering shrink cluster centroids toward one another and ensure a unique global minimizer. In this work we present two splitting methods for solving the convex clustering problem. The fir...

  17. Crossings in Clustered Level Graphs

    Forster, Michael

    2005-01-01

    Clustered graphs are an enhanced graph model with a recursive clustering of the vertices according to a given nesting relation. This prime technique for expressing coherence of certain parts of the graph is used in many applications, such as biochemical pathways and UML class diagrams. For directed clustered graphs usually level drawings are used, leading to clustered level graphs. In this thesis we analyze the interrelation of clusters and levels and their influence on edge crossings and clu...

  18. Bootstrap clustering for graph partitioning

    Gambette, Philippe; Guénoche, Alain

    2011-01-01

    Given a simple undirected weighted or unweighted graph, we try to cluster the vertex set into communities and also to quantify the robustness of these clusters. For that task, we propose a new method, called bootstrap clustering which consists in (i) defining a new clustering algorithm for graphs, (ii) building a set of graphs similar to the initial one, (iii) applying the clustering method to each of them, making a profile (set) of partitions, (iv) computing a consensus partition for this pr...

  19. Signature of cluster disruption within magnetic fluid samples: The key information provided by low frequency alternating current susceptibility measurements

    Du, Zhongzhou; Liu, Wenzhong; Zhong, Jing; Zhou, Ming; Zhang, Pu; Cesar Morais, Paulo

    2014-05-01

    This paper is focused on the signature of thermal-assisted cluster disruption while analyzing the inverse alternating current (AC) susceptibility (1/χ) versus temperature (T) curves recorded at lower AC frequencies (f), below 300 Hz. A commercial oil-based magnetic fluid (MF) sample was used in the experiments to investigate the critical temperature (T*) that characterizes the thermal disruption of aggregates suspended within the MF sample. T* was found to reduce as f increased within the frequency range of our investigation (63-263 Hz). Furthermore, T* was found to scale with the square of the applied AC frequency. Both theoretical and experimental evidences support that the excitation field frequency (f) dependence of the critical temperature (T*) is well described by T*(f)=T*(0)-Af/21+Bf2. The model is based on energy absorption of magnetic nanoparticles in an AC magnetic field.

  20. Clustering by Pattern Similarity

    Hai-xun Wang; Jian Pei

    2008-01-01

    The task of clustering is to identify classes of similar objects among a set of objects. The definition of similarity varies from one clustering model to another. However, in most of these models the concept of similarity is often based on such metrics as Manhattan distance, Euclidean distance or other Lp distances. In other words, similar objects must have close values in at least a set of dimensions. In this paper, we explore a more general type of similarity. Under the pCluster model we proposed, two objects are similar if they exhibit a coherent pattern on a subset of dimensions. The new similarity concept models a wide range of applications. For instance, in DNA microarray analysis, the expression levels of two genes may rise and fall synchronously in response to a set of environmental stimuli. Although the magnitude of their expression levels may not be close, the patterns they exhibit can be very much alike. Discovery of such clusters of genes is essential in revealing significant connections in gene regulatory networks. E-commerce applications, such as collaborative filtering, can also benefit from the new model, because it is able to capture not only the closeness of values of certain leading indicators but also the closeness of (purchasing, browsing, etc.) patterns exhibited by the customers. In addition to the novel similarity model, this paper also introduces an effective and efficient algorithm to detect such clusters, and we perform tests on several real and synthetic data sets to show its performance.

  1. Mesoscopic turbulence and local order in Janus particles self-propelling under an ac electric field

    Nishiguchi, Daiki; Sano, Masaki

    2015-11-01

    To elucidate mechanisms of mesoscopic turbulence exhibited by active particles, we experimentally study turbulent states of nonliving self-propelled particles. We realize an experimental system with dense suspensions of asymmetrical colloidal particles (Janus particles) self-propelling on a two-dimensional surface under an ac electric field. Velocity fields of the Janus particles in the crowded situation can be regarded as a sort of turbulence because it contains many vortices and their velocities change abruptly. Correlation functions of their velocity field reveal the coexistence of polar alignment and antiparallel alignment interactions, which is considered to trigger mesoscopic turbulence. Probability distributions of local order parameters for polar and nematic orders indicate the formation of local clusters with particles moving in the same direction. A broad peak in the energy spectrum of the velocity field appears at the spatial scales where the polar alignment and the cluster formation are observed. Energy is injected at the particle scale and conserved quantities such as energy could be cascading toward the larger clusters.

  2. Cooperative Frequency Control for Autonomous AC Microgrids

    Shafiee, Qobad; Quintero, Juan Carlos Vasquez; Guerrero, Josep M.; Nasirian, Vahidreza; Davoudi, Ali

    2015-01-01

    Distributed secondary control strategies have been recently studied for frequency regulation in droop-based AC Microgrids. Unlike centralized secondary control, the distributed one might fail to provide frequency synchronization and proportional active power sharing simultaneously, due to having...... different control parameters. This paper introduces a cooperative algorithm that regulates the system frequency while maintaining the power sharing properties of droop control. Dynamic consensus protocol is used to estimate the average of normalized active powers in the entire MG. This estimation is then...... added to primary control, compensating the frequency drop caused by the droop mechanism. The proposed controller is fully distributed, meaning that each source exchange information with only its direct neighbors through a sparse communication network. This controller has a unique feature that it does...

  3. Mapa Acústico del Gran Madrid

    Santiago Páez, José Salvador; Perera, P

    2006-01-01

    El desarrollo urbanístico de Madrid desde los años 1980 a finales de la década de los 90 hizo que su Ayuntamiento, que ya había promovido la realización entre 1985 y 1991 de un Mapa Acústico parcial de la ciudad, pensase en extender el ámbito de éste a todo el término municipal. Siguiendo el mismo criterio anterior, se superpuso una cuadrícula sobre el plano de Madrid, y se llevaron a cabo registros sonoros de 5 minutos en cada vértice de la misma, en los puntos de medición fuera del área ant...

  4. Josephson arrays for dc and ac metrology

    Large series arrays of underdamped SIS tunnel junctions are the basic element of the primary dc voltage standards used at present. The development of versatile quantum voltmeters for dc and ac metrology requires the preparation of large and perfect series arrays of overdamped Josephson junctions. Overdamped junctions can be realized by externally shunted SIS junctions or by internally shunted SNS or SINIS junctions. Arrays of up to 8000 SINIS junctions or 30000 SNS junctions were successfully operated at the 1 V dc level. In addition to being used in large arrays for voltage metrology and oscillators, the described junction types may become very useful for the preparation of highly integrated single-flux-quantum digital devices. (author)

  5. An ac bridge readout for bolometric detectors

    Rieke, F. M.; Lange, A. E.; Beeman, J. W.; Haller, E. E.

    1989-01-01

    The authors have developed a bolometer readout circuit which greatly improves the low-frequency stability of bolometric detectors. The circuit uses an ac bias voltage and two matched bolometers and allows stable dc bolometer operation for integration times greater than 10 s. In astronomical applications the readout allows for qualitatively different observation modes (e.g. staring or slow-drift scanning) which are particularly well suited for space observations and for the use of arrays. In many applications the readout can increase sensitivity. The authors present noise spectra for 4He temperature bolometers with no excess noise at frequencies greater than 0.1 Hz. The measured optical responsivity of a bolometer operated with the present readout is the same as that of a bolometer operated with a conventional readout.

  6. Composite Based EHV AC Overhead Transmission Lines

    Sørensen, Thomas Kjærsgaard

    Overhead lines at transmission level are the backbone of any national power grid today. New overhead line projects however are at the same time subject to ever greater public resistance due to the lines environmental impact. As full undergrounding of transmission lines at extra high voltage (EHV......) levels are still not seen as possibility, the future expansion of transmission grids are dependent on new solutions with lessened environment impact, especially with regard to the visual impact. In the present Thesis, composite materials and composite based overhead line components are presented and...... analysed with regard to the possibilities, limitations and risks widespread application of composite materials on EHV AC overhead transmission lines may present. To form the basis for evaluation of the useability of composite materials, dierent overhead line projects aimed at reducing the environmental...

  7. Effective ac response in weakly nonlinear composites

    Wei Enbo [Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071 (China); Yang Zidong [College of Power Engineering, University of Shanghai Science and Technology, Shanghai 200093 (China); Gu Guoqing [Information College of Science and Technology, East China Normal University, Shanghai 200062 (China)

    2004-01-07

    The perturbation method is developed to deal with the problem of determining the effective nonlinear conductivity of Kerr-like nonlinear media under an external ac electric field. As an example, we have considered the cylindrical inclusion embedded in a host under the sinusoidal external field E{sub 1} sin (<{omega}t) + E{sub 3} sin (3<{omega}t) with frequencies{omega} and 3{omega}. The potentials of composites at higher harmonics are derived in both local inclusion particle and host regions. The effective responses of bulk nonlinear composites at basic frequency and harmonics are given for cylindrical composites in the dilute limit. Moreover, the relationships between the nonlinear effective responses at the basic frequency and the third harmonics are derived.

  8. Modeling of long High Voltage AC Underground

    Gudmundsdottir, Unnur Stella; Bak, Claus Leth; Wiechowski, W. T.

    2010-01-01

    This paper presents the work and findings of a PhD project focused on accurate high frequency modelling of long High Voltage AC Underground cables. The project is cooperation between Aalborg University and Energinet.dk. The objective of the project is to investigate the accuracy of most up to date...... cable models, perform highly accurate field measurements for validating the model and identifying possible disadvantages of the cable model. Furthermore the project suggests and implements improvements and validates them against several field measurements. It is shown in this paper how a new method for...... calculating the frequency dependent cables impedance greatly improves the modeling procedure and gives a highly accurate result for high frequency simulations....

  9. Nonlinear ac conductivity of interacting 1d electron systems

    Rosenow, Bernd; Nattermann, Thomas

    2004-01-01

    We consider low energy charge transport in one-dimensional (1d) electron systems with short range interactions under the influence of a random potential. Combining RG and instanton methods, we calculate the nonlinear ac conductivity and discuss the crossover between the nonanalytic field dependence of the electric current at zero frequency and the linear ac conductivity at small electric fields and finite frequency.

  10. Flexible AC transmission systems: the state of the art

    Edris, Abdel-Aty [Electric Power Research Inst., Palo Alto, CA (United States). Electric Systems Division

    1994-12-31

    Flexible AC transmission systems (FACTS) is a concept promoting the use of power electronic controllers to enhance the controllability and usable capacity of AC transmission. This paper presents the state of the art of FACTS and the status of the current projects for the application of the FACTS controllers in transmission systems. (author) 8 refs., 8 figs.

  11. 78 FR 39345 - ACS Wireless, Inc.; Notice of Application

    2013-07-01

    ... will transfer to AWN all remaining tangible and intangible assets owned, leased or held by ACS Wireless.... \\6\\ ACS Group will cause certain of its other subsidiaries to transfer wireless spectrum licenses and...'' as the power to exercise a controlling influence over the management or policies of a company,...

  12. Operation of AC Adapters Visualized Using Light-Emitting Diodes

    Regester, Jeffrey

    2016-01-01

    A bridge rectifier is a diamond-shaped configuration of diodes that serves to convert alternating current(AC) into direct current (DC). In our world of AC outlets and DC electronics, they are ubiquitous. Of course, most bridge rectifiers are built with regular diodes, not the light-emitting variety, because LEDs have a number of disadvantages. For…

  13. Search for β-delayed fission of 228Ac

    Radium was radiochemically separated from natural thorium. Thin 228Ra→β-228Ac sources were prepared and exposed to mica fission track detectors, and measured by an HPGe γ-ray detector. The β-delayed fission events of 228Ac were observed and its β-delayed fission probability was found to be (5±2)x10-12

  14. Improved Design Methods for Robust Single- and Three-Phase ac-dc-ac Power Converters

    Qin, Zian

    proposed new active power decoupling method, the ripple power in the converter can be compensated in a more efficient and more compact way. Then, Chapter 5 changes the scope of the thesis to three-phase converters, and the nine-switch converter, as a reduced switch version of two three-phase full......-bridges connected back-to-back, is studied. Application criteria of the nine-switch converter are investigated for reducing the relatively high stress introduced by the less number of switches. In Chapter 6 a rotating speed controller design method is proposed for improving the thermal loading of the three...... to users. Their performances including cost, efficiency, reliability, and so on, therefore are more important concerns than they were. The objective of this thesis is to study and propose advanced design methods for robust ac-dc-ac converters, which are widely used interfaces in energy conversion...

  15. Globular cluster winds

    Current evolutionary theory indicates that the evolving stars in globular clusters arrive on the horizontal branch with approx. 30% less mass than they had on the main sequence. If, as seems likely, this mass loss results from the outflow of unprocessed material at the stellar surface during the giant stage, and if the ejected mass were retained within the cluster during the giant stage, and if the ejected mass were retained within the cluster between successive sweeps through the galactic plane (about 108 yr), sufficient hydrogen (100-2000Msub(o)) should accumulate for detection. Radio searches have failed to find evidence for either neutral or ionized gas. The search was therefore extended into the optical region and the time independant gas flow models were calculated to resolve this anomaly. (R.L.)

  16. Ants for Document Clustering

    Priya Vaijayanthi

    2012-03-01

    Full Text Available The usage of computers for mass storage has become mandatory nowadays due to World Wide Web (WWW. This has placed many challenges to the Information Retrieval (IR system. Clustering of documents available improves the efficiency of IR system. The problem of clustering has become a combinatorial optimization problem in IR system due to the exponential growth in information over WWW. In this paper, a hybrid algorithm that combines the basic Ant Colony Optimization with Tabu search has been proposed. The feasibility of the proposed algorithm is tested over a few standard benchmark datasets. The experimental results reveal that the proposed algorithm yields promising quality clusters compared to other ones produced by K-means algorithm.

  17. Clustering Game Behavior Data

    Bauckhage, C.; Drachen, Anders; Sifa, Rafet

    2015-01-01

    data scientists and present a review and tutorial focusing on the application of clustering techniques to mine behavioral game data. Several algorithms are reviewed and examples of their application shown. Key topics such as feature normalization are discussed and open problems in the context of game......Recent years have seen a deluge of behavioral data from players hitting the game industry. Reasons for this data surge are many and include the introduction of new business models, technical innovations, the popularity of online games, and the increasing persistence of games. Irrespective of the...... causes, the proliferation of behavioral data poses the problem of how to derive insights therefrom. Behavioral data sets can be large, time-dependent and high-dimensional. Clustering offers a way to explore such data and to discover patterns that can reduce the overall complexity of the data. Clustering...

  18. Spanish clitic clusters

    María Cristina Cuervo

    2013-11-01

    Full Text Available This paper deals with a small set of data from clusters of three clitics in Spanish that questions the empirical adequacy and scope of previous analyses of clitic clusters in Romance. It is shown that the output of the Spurious se Rule is not identical to genuine se, at some level that is relevant for linearization of clitics within a cluster. A proposal is presented to capture the neglected data, and this is done in a way that illuminates the debate on the division of labour in clitic phenomena between phonology, morphology and syntax. Central questions in morphology, such as ordering of operations, syncretisms, linearization principles and consequences of lexical insertion are addressed and re-examined.

  19. 40 CFR 86.162-00 - Approval of alternative air conditioning test simulations and descriptions of AC1 and AC2.

    2010-07-01

    ... Procedures § 86.162-00 Approval of alternative air conditioning test simulations and descriptions of AC1 and AC2. The alternative air conditioning test procedures AC1 and AC2 are approved by the Administrator... requirements of paragraph (a) of this section and meet the requirements of § 86.163-00. Air conditioning...

  20. Determination for β-delayed fission probability of 230Ac

    袁双贵; 杨维凡; 徐岩冰; 肖永厚; 罗亦孝

    2002-01-01

    The 230Ra has been produced via 232Th-2p reaction induced by 60 MeV/u 18O ion irradia-tion of natural thorium. The radium was radiochemically separated from the mixture of thorium andreaction products. Thin Ra sources in which 230Ac was got through 230Ra β- → 230Ac were pre-pared for observing fission fragments from β-delayed fission of 230Ac. The sources were exposedto the mica fission track detectors and measured by the HPGe γ detector. The precursor 230Ac wasidentified by means of observed two fission events as well as γ spectra, and the β-delayed fissionprobability of 230Ac was obtained to be (1.19±0.85) × 10-8.