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Sample records for 360nm galaxy counts

  1. GalaxyCount: Galaxy counts and variance calculator

    NASA Astrophysics Data System (ADS)

    Bland-Hawthorn, Joss; Ellis, Simon

    2013-12-01

    GalaxyCount calculates the number and standard deviation of galaxies in a magnitude limited observation of a given area. The methods to calculate both the number and standard deviation may be selected from different options. Variances may be computed for circular, elliptical and rectangular window functions.

  2. SUBMILLIMETER GALAXY NUMBER COUNTS AND MAGNIFICATION BY GALAXY CLUSTERS

    SciTech Connect

    Lima, Marcos; Jain, Bhuvnesh; Devlin, Mark; Aguirre, James

    2010-07-01

    We present an analytical model that reproduces measured galaxy number counts from surveys in the wavelength range of 500 {mu}m-2 mm. The model involves a single high-redshift galaxy population with a Schechter luminosity function that has been gravitationally lensed by galaxy clusters in the mass range 10{sup 13}-10{sup 15} M{sub sun}. This simple model reproduces both the low-flux and the high-flux end of the number counts reported by the BLAST, SCUBA, AzTEC, and South Pole Telescope (SPT) surveys. In particular, our model accounts for the most luminous galaxies detected by SPT as the result of high magnifications by galaxy clusters (magnification factors of 10-30). This interpretation implies that submillimeter (submm) and millimeter surveys of this population may prove to be a useful addition to ongoing cluster detection surveys. The model also implies that the bulk of submm galaxies detected at wavelengths larger than 500 {mu}m lie at redshifts greater than 2.

  3. Combining cluster number counts and galaxy clustering

    NASA Astrophysics Data System (ADS)

    Lacasa, Fabien; Rosenfeld, Rogerio

    2016-08-01

    The abundance of clusters and the clustering of galaxies are two of the important cosmological probes for current and future large scale surveys of galaxies, such as the Dark Energy Survey. In order to combine them one has to account for the fact that they are not independent quantities, since they probe the same density field. It is important to develop a good understanding of their correlation in order to extract parameter constraints. We present a detailed modelling of the joint covariance matrix between cluster number counts and the galaxy angular power spectrum. We employ the framework of the halo model complemented by a Halo Occupation Distribution model (HOD). We demonstrate the importance of accounting for non-Gaussianity to produce accurate covariance predictions. Indeed, we show that the non-Gaussian covariance becomes dominant at small scales, low redshifts or high cluster masses. We discuss in particular the case of the super-sample covariance (SSC), including the effects of galaxy shot-noise, halo second order bias and non-local bias. We demonstrate that the SSC obeys mathematical inequalities and positivity. Using the joint covariance matrix and a Fisher matrix methodology, we examine the prospects of combining these two probes to constrain cosmological and HOD parameters. We find that the combination indeed results in noticeably better constraints, with improvements of order 20% on cosmological parameters compared to the best single probe, and even greater improvement on HOD parameters, with reduction of error bars by a factor 1.4-4.8. This happens in particular because the cross-covariance introduces a synergy between the probes on small scales. We conclude that accounting for non-Gaussian effects is required for the joint analysis of these observables in galaxy surveys.

  4. A Comparison of Galaxy Counting Techniques in Spectroscopically Undersampled Regions

    NASA Astrophysics Data System (ADS)

    Specian, Mike A.; Szalay, Alex S.

    2016-11-01

    Accurate measures of galactic overdensities are invaluable for precision cosmology. Obtaining these measurements is complicated when members of one’s galaxy sample lack radial depths, most commonly derived via spectroscopic redshifts. In this paper, we utilize the Sloan Digital Sky Survey’s Main Galaxy Sample to compare seven methods of counting galaxies in cells when many of those galaxies lack redshifts. These methods fall into three categories: assigning galaxies discrete redshifts, scaling the numbers counted using regions’ spectroscopic completeness properties, and employing probabilistic techniques. We split spectroscopically undersampled regions into three types—those inside the spectroscopic footprint, those outside but adjacent to it, and those distant from it. Through Monte Carlo simulations, we demonstrate that the preferred counting techniques are a function of region type, cell size, and redshift. We conclude by reporting optimal counting strategies under a variety of conditions.

  5. Far-Ultraviolet Number Counts of Field Galaxies

    NASA Technical Reports Server (NTRS)

    Voyer, Elysse N.; Gardner, Jonathan P.; Teplitz, Harry I.; Siana, Brian D.; deMello, Duilia F.

    2010-01-01

    The Number counts of far-ultraviolet (FUV) galaxies as a function of magnitude provide a direct statistical measure of the density and evolution of star-forming galaxies. We report on the results of measurements of the rest-frame FUV number counts computed from data of several fields including the Hubble Ultra Deep Field, the Hubble Deep Field North, and the GOODS-North and -South fields. These data were obtained from the Hubble Space Telescope Solar Blind Channel of the Advance Camera for Surveys. The number counts cover an AB magnitude range from 20-29 magnitudes, covering a total area of 15.9 arcmin'. We show that the number counts are lower than those in previous studies using smaller areas. The differences in the counts are likely the result of cosmic variance; our new data cover more area and more lines of sight than the previous studies. The slope of our number counts connects well with local FUV counts and they show good agreement with recent semi-analytical models based on dark matter "merger trees".

  6. The local hole revealed by galaxy counts and redshifts

    NASA Astrophysics Data System (ADS)

    Whitbourn, J. R.; Shanks, T.

    2014-01-01

    The redshifts of ≈250 000 galaxies are used to study the local hole and its associated peculiar velocities. The sample, compiled from the 6dF Galaxy Redshift Survey and Sloan Digital Sky Survey, provides wide sky coverage to a depth of ≈300 h-1 Mpc. We have therefore examined K- and r-limited galaxy redshift distributions and number counts to map the local density field. Comparing observed galaxy n(z) distributions to homogeneous models in three large regions of the high-latitude sky, we find evidence for underdensities ranging from ≈4-40 per cent in these regions to depths of ≈150 h-1 Mpc with the deepest underdensity being over the southern Galactic cap. Using the Galaxy and Mass Assembly survey, we then establish the normalization of galaxy counts at fainter magnitudes and thus confirm that the underdensity over all three fields at K < 12.5 is ≈15 ± 3 per cent. Finally, we further use redshift catalogues to map sky-averaged peculiar velocities over the same areas using the average redshift-magnitude, overline{z}(m), technique of Soneira. After accounting for the direct effect of the large-scale structure on overline{z}(m), we can then search for peculiar velocities. Taking all three regions into consideration, the data reject at the ≈4σ level the idea that we have recovered the cosmic microwave background rest frame in the volume probed. We therefore conclude that there is some consistent evidence from both counts and Hubble diagrams for a `local hole' with an ≈150 h-1 Mpc underdensity that deeper counts and redshifts in the northern Galactic cap suggest may extend to ≈300 h-1 Mpc.

  7. Inferring Host Dark Matter Halo Masses of Individual Galaxies from Neighboring Galaxy Counts

    NASA Astrophysics Data System (ADS)

    Oguri, Masamune; Lin, Yen-Ting

    2015-03-01

    How well can we infer host dark matter halo masses of individual galaxies? Based on the halo occupation distribution framework, we analytically compute the number of neighboring galaxies within a cylinder of some redshift interval and radius in transverse comoving distance. The result is used to derive the conditional probability distribution function (PDF) of the host halo mass of a galaxy, given the neighboring galaxy counts. We compare our analytic results with those obtained using a realistic mock galaxy catalog, finding reasonable agreements. We find the optimal cylinder radius to be ∼ 0.5-1 {{h}-1} Mpc for the inference of halo masses. The PDF is generally broad, and sometimes has two peaks at low- and high-mass regimes because of the effect of chance projection along the line of sight. Potential applications and extensions of the new theoretical framework developed herein are also discussed.

  8. Galaxy Number Counts Applied to a Semi-Analytic Galaxy Model in the Millennium Run Simulation

    NASA Astrophysics Data System (ADS)

    Bucklein, Brian; Moody, J. W.; Hintz, E. G.

    2010-01-01

    The Millennium Run simulation used more than 10 billion particles to trace the evolution of the dark matter distribution in a ΛCDM cosmology in a cubic region of the Universe over 2 billion light-years on a side. This data was used by Croton et al. as the basis of a semi-analytic galaxy model, allowing the region to be populated with more than 9 million galaxies brighter than Mr = -17.4. We visually analyze this galaxy catalog searching for significant voids and then apply galaxy number count (GNC) analysis to the lines-of-sight to these voids. Using Wolf plots, we investigate whether GNC analysis would allow us to locate voids within the sample without the need to first find them visually.

  9. VizieR Online Data Catalog: K-Band Galaxy Counts (McLeod+ 1995)

    NASA Astrophysics Data System (ADS)

    McLeod, B. A.; Bernstein, G. M.; Rieke, M. J.; Tollestrup, E. V.; Fazio, G. G.

    1996-06-01

    We present new counts of field galaxies from more than 20 arcmin^2 to a limiting magnitude of K = 20 and from 2 arcmin^2 to K = 21.5. At the faintest magnitudes, the counts are slightly higher than those reported previously, though still consistent given the small numbers of galaxies in the two samples. (3 data files).

  10. Emission Features and Source Counts of Galaxies in Mid-Infrared

    NASA Technical Reports Server (NTRS)

    Xu, C.; Hacking, P. B.; Fang, F.; Shupe, D. L.; Lonsdale, C. J.; Lu, N. Y.; Helou, G.; Stacey, G. J.; Ashby, M. L. N.

    1998-01-01

    In this work we incorporate the newest ISO results on the mid-infrared spectral-energy-distributions (MIR SEDs) of galaxies into models for the number counts and redshift distributions of MIR surveys.

  11. A UNIFIED EMPIRICAL MODEL FOR INFRARED GALAXY COUNTS BASED ON THE OBSERVED PHYSICAL EVOLUTION OF DISTANT GALAXIES

    SciTech Connect

    Bethermin, Matthieu; Daddi, Emanuele; Sargent, Mark T.; Elbaz, David; Mullaney, James; Pannella, Maurilio; Hezaveh, Yashar; Le Borgne, Damien; Buat, Veronique; Charmandaris, Vassilis; Lagache, Guilaine; Scott, Douglas

    2012-10-01

    We reproduce the mid-infrared to radio galaxy counts with a new empirical model based on our current understanding of the evolution of main-sequence (MS) and starburst (SB) galaxies. We rely on a simple spectral energy distribution (SED) library based on Herschel observations: a single SED for the MS and another one for SB, getting warmer with redshift. Our model is able to reproduce recent measurements of galaxy counts performed with Herschel, including counts per redshift slice. This agreement demonstrates the power of our 2-Star-Formation Modes (2SFM) decomposition in describing the statistical properties of infrared sources and their evolution with cosmic time. We discuss the relative contribution of MS and SB galaxies to the number counts at various wavelengths and flux densities. We also show that MS galaxies are responsible for a bump in the 1.4 GHz radio counts around 50 {mu}Jy. Material of the model (predictions, SED library, mock catalogs, etc.) is available online.

  12. EFFECTS OF STRONG GRAVITATIONAL LENSING ON MILLIMETER-WAVE GALAXY NUMBER COUNTS

    SciTech Connect

    Hezaveh, Yashar D.; Holder, Gilbert P.

    2011-06-10

    We study the effects of strong lensing on the observed number counts of millimeter sources using a ray-tracing simulation and two number count models of unlensed sources. We employ a quantitative treatment of maximum attainable magnification factor depending on the physical size of the sources, also accounting for effects of lens halo ellipticity. We calculate predicted number counts and redshift distributions of millimeter galaxies including the effects of strong lensing and compare with the recent source count measurements of the South Pole Telescope (SPT). The predictions have large uncertainties, especially the details of the mass distribution in lens galaxies and the finite extent of sources, but the SPT observations are in good agreement with predictions. The sources detected by SPT are predicted to largely consist of strongly lensed galaxies at z > 2. The typical magnifications of these sources strongly depend on both the assumed unlensed source counts and the flux of the observed sources.

  13. QUASAR-GALAXY CLUSTERING THROUGH PROJECTED GALAXY COUNTS AT z = 0.6-1.2

    SciTech Connect

    Zhang Shaohua; Zhou Hongyan; Wang Tinggui; Wang Huiyuan E-mail: twang@ustc.edu.cn

    2013-08-20

    We investigate the spatial clustering of galaxies around quasars at z = 0.6-1.2 using photometric data from Sloan Digital Sky Survey Stripe 82. The quasar and galaxy cross-correlation functions are measured through the projected galaxy number density n(r{sub p} ) on scales of 0.05 < r{sub p} < 20 h {sup -1} Mpc around quasars for a sample of 2300 quasars from Schneider et al. We detect strong clustering signals at all redshifts and find that the clustering amplitude increases significantly with redshift. We examine the dependence of quasar-galaxy clustering on quasar and galaxy properties and find that the clustering amplitude is significantly larger for quasars with more massive black holes or with bluer colors, while there is no dependence on quasar luminosity. We also show that quasars have a stronger correlation amplitude with blue galaxies than with red galaxies. We finally discuss the implications of our findings.

  14. DEEP GALEX OBSERVATIONS OF THE COMA CLUSTER: SOURCE CATALOG AND GALAXY COUNTS

    SciTech Connect

    Hammer, D.; Hornschemeier, A. E.; Miller, N.; Jenkins, L.; Mobasher, B.; Smith, R.; Arnouts, S.; Milliard, B.

    2010-09-15

    the GALEX pipeline catalogs are confusion limited at NUV {approx} 23 and FUV {approx} 24. We have measured the UV field galaxy counts using our catalog and report a {approx}50% (30%) excess of counts across FUV = 22-23.5 (NUV = 21.5-23) relative to other GALEX studies. Our number counts are a better match to deeper UV galaxy counts measured with Hubble Space Telescope.

  15. Solar spectral irradiance observations between 200 and 360 NM made during the Atlas 1 mission: Comparisons between the SOLSPEC, SUSIM, and SSBUV measurements

    NASA Technical Reports Server (NTRS)

    Thuillier, G. O.; VanHoosier, M. E.; Cebula, R. P.

    1995-01-01

    The SOLSPEC, SSBUV, and SUSIM spectrometers observed the solar spectral irradiance simultaneously during the ATLAS-1 mission flown on board the Space Shuttle in March 1992. The three instruments use different methods and means of absolute calibration and were calibrated pre- and post-flight. The three data sets are reported from 200-360 nm at 1.1 nm resolution. The method of comparing the three independent data sets will be discussed. The importance of a common precise wavelength scale will be shown when comparing the data in the wavelength region of the strong Fraunhofer lines. The consistency of the three measurements is better than 5%. The fact that the calibrations of the three instruments were based on three independent national standards ensures that the absolute solar spectral irradiance in the range of 200-360 nm is now known with an accuracy of better than 5%. The data taken from this mission are compared with solar observations from other space based missions.

  16. Deep Galex Observations of the Coma Cluster: Source Catalog and Galaxy Counts

    NASA Technical Reports Server (NTRS)

    Hammer, D.; Hornschemeier, A. E.; Mobasher, B.; Miller, N.; Smith, R.; Arnouts, S.; Milliard, B.; Jenkins, L.

    2010-01-01

    We present a source catalog from deep 26 ks GALEX observations of the Coma cluster in the far-UV (FUV; 1530 Angstroms) and near-UV (NUV; 2310 Angstroms) wavebands. The observed field is centered 0.9 deg. (1.6 Mpc) south-west of the Coma core, and has full optical photometric coverage by SDSS and spectroscopic coverage to r-21. The catalog consists of 9700 galaxies with GALEX and SDSS photometry, including 242 spectroscopically-confirmed Coma member galaxies that range from giant spirals and elliptical galaxies to dwarf irregular and early-type galaxies. The full multi-wavelength catalog (cluster plus background galaxies) is 80% complete to NUV=23 and FUV=23.5, and has a limiting depth at NUV=24.5 and FUV=25.0 which corresponds to a star formation rate of 10(exp -3) solar mass yr(sup -1) at the distance of Coma. The GALEX images presented here are very deep and include detections of many resolved cluster members superposed on a dense field of unresolved background galaxies. This required a two-fold approach to generating a source catalog: we used a Bayesian deblending algorithm to measure faint and compact sources (using SDSS coordinates as a position prior), and used the GALEX pipeline catalog for bright and/or extended objects. We performed simulations to assess the importance of systematic effects (e.g. object blends, source confusion, Eddington Bias) that influence source detection and photometry when using both methods. The Bayesian deblending method roughly doubles the number of source detections and provides reliable photometry to a few magnitudes deeper than the GALEX pipeline catalog. This method is also free from source confusion over the UV magnitude range studied here: conversely, we estimate that the GALEX pipeline catalogs are confusion limited at NUV approximately 23 and FUV approximately 24. We have measured the total UV galaxy counts using our catalog and report a 50% excess of counts across FUV=22-23.5 and NUV=21.5-23 relative to previous GALEX

  17. Biases on cosmological parameter estimators from galaxy cluster number counts

    SciTech Connect

    Penna-Lima, M.; Wuensche, C.A.; Makler, M. E-mail: martin@cbpf.br

    2014-05-01

    Sunyaev-Zel'dovich (SZ) surveys are promising probes of cosmology — in particular for Dark Energy (DE) —, given their ability to find distant clusters and provide estimates for their mass. However, current SZ catalogs contain tens to hundreds of objects and maximum likelihood estimators may present biases for such sample sizes. In this work we study estimators from cluster abundance for some cosmological parameters, in particular the DE equation of state parameter w{sub 0}, the amplitude of density fluctuations σ{sub 8}, and the Dark Matter density parameter Ω{sub c}. We begin by deriving an unbinned likelihood for cluster number counts, showing that it is equivalent to the one commonly used in the literature. We use the Monte Carlo approach to determine the presence of bias using this likelihood and study its behavior with both the area and depth of the survey, and the number of cosmological parameters fitted. Our fiducial models are based on the South Pole Telescope (SPT) SZ survey. Assuming perfect knowledge of mass and redshift some estimators have non-negligible biases. For example, the bias of σ{sub 8} corresponds to about 40% of its statistical error bar when fitted together with Ω{sub c} and w{sub 0}. Including a SZ mass-observable relation decreases the relevance of the bias, for the typical sizes of current SZ surveys. Considering a joint likelihood for cluster abundance and the so-called ''distance priors'', we obtain that the biases are negligible compared to the statistical errors. However, we show that the biases from SZ estimators do not go away with increasing sample sizes and they may become the dominant source of error for an all sky survey at the SPT sensitivity. Finally, we compute the confidence regions for the cosmological parameters using Fisher matrix and profile likelihood approaches, showing that they are compatible with the Monte Carlo ones. The results of this work validate the use of the current maximum likelihood methods for

  18. The number counts and infrared backgrounds from infrared-bright galaxies

    NASA Technical Reports Server (NTRS)

    Hacking, P. B.; Soifer, B. T.

    1991-01-01

    Extragalactic number counts and diffuse backgrounds at 25, 60, and 100 microns are predicted using new luminosity functions and improved spectral-energy distribution density functions derived from IRAS observations of nearby galaxies. Galaxies at redshifts z less than 3 that are like those in the local universe should produce a minimum diffuse background of 0.0085, 0.038, and 0.13 MJy/sr at 25, 60, and 100 microns, respectively. Models with significant luminosity evolution predict backgrounds about a factor of 4 greater than this minimum.

  19. The number counts and infrared backgrounds from infrared-bright galaxies

    SciTech Connect

    Hacking, P.B.; Soifer, B.T. California Institute of Technology, Pasadena )

    1991-02-01

    Extragalactic number counts and diffuse backgrounds at 25, 60, and 100 microns are predicted using new luminosity functions and improved spectral-energy distribution density functions derived from IRAS observations of nearby galaxies. Galaxies at redshifts z less than 3 that are like those in the local universe should produce a minimum diffuse background of 0.0085, 0.038, and 0.13 MJy/sr at 25, 60, and 100 microns, respectively. Models with significant luminosity evolution predict backgrounds about a factor of 4 greater than this minimum. 22 refs.

  20. Deep galaxy counts in the K band with the Kech telescope

    NASA Technical Reports Server (NTRS)

    Djorgovski, S.; Soifer, B. T.; Pahre, M. A.; Larkin, J. E.; Smith, J. D.; Neugebauer, G.; Smail, I.; Matthews, K.; Hogg, D. W.; Blandford, R. D.

    1995-01-01

    We present deep galaxy counts in the K (lambda 2.2 micrometer) band, obtained at the W. M. Kech 10 m telescope. The data reach limiting magnitudes K approximately 24 mag, about 5 times deeper than the deepest published K-band images to date. The counts are performed in three small (approximately 1 min), widely separated high-latitude fields. Extensive Monte Carlo tests were used to derive the comleteness corrections and minimize photometric biases. The counts continue to rise, with no sign of a turnover, down to the limits of our data, with the logarithmic slope of d log N/dm = 0.315 +/- 0.02 between K = 20 and 24 mag. This implies a cumulative surface density of approximately 5 x 10(exp 5) galaxies/sq deg, or approximately 2 x 10(exp 10) over the entire sky, down to K = 24 mag. Our counts are in good agreement with, although slightly lower than, those from the Hawaii Deep Survey by Cowie and collaborators; the discrepancies may be due to the small differences in the aperture corrections. We compare our counts with some of the available theoretical predictions. The data do not require models with a high value of Omega(sub 0), but can be well fitted by models with no (or little) evolution, and cosmologies with a low value of Omega(sub 0). Given the uncertainties in the models, it may be premature to put useful constrains on the value of Omega(sub 0) from the counts alone. Optical-to-IR colors are computed, using CCD data obtaind previously at Palomar. We find a few red galaxies with (r-K) approximately greater than 5 mag, or (i-K) approximately greater than 5 mag; these may be ellipticals at z approximately 1. While the redshift distribution of galaxies in our counts is still unknown, the flux limits reached would allow us to detect unobscured L(sub *) galaxies out to substantial redshifts (z greater than 3?).

  1. Simulations of deep galaxy fields. 1: Monte Carlo simulations of optical and near-infrared counts

    NASA Technical Reports Server (NTRS)

    Chokshi, Arati; Lonsdale, Carol J.; Mazzei, Paola; De Zotti, Gianfranco

    1994-01-01

    Monte Carlo simulations of three-dimensional galaxy distributions are performed, following the 1988 prescription of Chokshi & Wright, to study the photometric properties of evolving galaxy populations in the optical and near-infrared bands to high redshifts. In this paper, the first of a series, we present our baseline model in which galaxy numbers are conserved, and in which no explicit 'starburst' population is included. We use the model in an attempt to simultaneously fit published blue and near-infrared photometric and spectroscopic observations of deep fields. We find that our baseline models, with a formation redshift, z(sub f), of 1000, and H(sub 0) = 50, are able to reproduce the blue counts to b(sub j) = 22, independent of the value of Omega(sub 0), and also to provide a satisfactory fit to the observed blue-band redshift distributions, but for no value of Omega(sub 0) do we achieve an acceptable fit to the fainter blue counts. In the K band, we fit the number counts to the limit of the present-day surveys only for an Omega(sub 0) = 0 cosmology. We investigate the effect on the model fits of varying the cosmological parameters H(sub 0), the formation red-shift z(sub f), and the local luminosity function. Changing H(sub 0) does not improve the fits to the observations. However, reducing the epoch of a galaxy formation used in our simulations has a substantial effect. In particular, a model with z(sub f) approximately equal to 5 in a low Omega(sub 0) universe improves the fit to the faintest photometric blue data without any need to invoke a new population of galaxies, substantial merging, or a significant starburst galaxy population. For an Omega(sub 0) = 1 universe, however, reducing z(sub f) is less successful at fitting the blue-band counts and has little effect at all at K. Varying the parameters of the local luminosity function can also have a significant effect. In particular the steep low end slope of the local luminosity function of Franceschini et

  2. PREDICTIONS FOR ULTRA-DEEP RADIO COUNTS OF STAR-FORMING GALAXIES

    SciTech Connect

    Mancuso, Claudia; Lapi, Andrea; De Zotti, Gianfranco; Bressan, Alessandro; Perrotta, Francesca; Danese, Luigi; Cai, Zhen-Yi; Negrello, Mattia; Bonato, Matteo

    2015-09-01

    We have worked outty predictions for the radio counts of star-forming galaxies down to nJy levels, along with redshift distributions down to the detection limits of the phase 1 Square Kilometer Array MID telescope (SKA1-MID) and of its precursors. Such predictions were obtained by coupling epoch-dependent star formation rate (SFR) functions with relations between SFR and radio (synchrotron and free–free) emission. The SFR functions were derived taking into account both the dust-obscured and the unobscured star formation, by combining far-infrared, ultraviolet, and Hα luminosity functions up to high redshifts. We have also revisited the South Pole Telescope counts of dusty galaxies at 95 GHz, performing a detailed analysis of the Spectral Energy Distributions. Our results show that the deepest SKA1-MID surveys will detect high-z galaxies with SFRs two orders of magnitude lower compared to Herschel surveys. The highest redshift tails of the distributions at the detection limits of planned SKA1-MID surveys comprise a substantial fraction of strongly lensed galaxies. We predict that a survey down to 0.25 μJy at 1.4 GHz will detect about 1200 strongly lensed galaxies per square degree, at redshifts of up to 10. For about 30% of them the SKA1-MID will detect at least 2 images. The SKA1-MID will thus provide a comprehensive view of the star formation history throughout the re-ionization epoch, unaffected by dust extinction. We have also provided specific predictions for the EMU/ASKAP and MIGHTEE/MeerKAT surveys.

  3. Herschel-ATLAS Galaxy Counts and High-redshift Luminosity Functions: The Formation of Massive Early-type Galaxies

    NASA Astrophysics Data System (ADS)

    Lapi, A.; González-Nuevo, J.; Fan, L.; Bressan, A.; De Zotti, G.; Danese, L.; Negrello, M.; Dunne, L.; Eales, S.; Maddox, S.; Auld, R.; Baes, M.; Bonfield, D. G.; Buttiglione, S.; Cava, A.; Clements, D. L.; Cooray, A.; Dariush, A.; Dye, S.; Fritz, J.; Herranz, D.; Hopwood, R.; Ibar, E.; Ivison, R.; Jarvis, M. J.; Kaviraj, S.; López-Caniego, M.; Massardi, M.; Michałowski, M. J.; Pascale, E.; Pohlen, M.; Rigby, E.; Rodighiero, G.; Serjeant, S.; Smith, D. J. B.; Temi, P.; Wardlow, J.; van der Werf, P.

    2011-11-01

    Exploiting the Herschel Astrophysical Terahertz Large Area Survey Science Demonstration Phase survey data, we have determined the luminosity functions (LFs) at rest-frame wavelengths of 100 and 250 μm and at several redshifts z >~ 1, for bright submillimeter galaxies with star formation rates (SFRs) >~ 100 M ⊙ yr-1. We find that the evolution of the comoving LF is strong up to z ≈ 2.5, and slows down at higher redshifts. From the LFs and the information on halo masses inferred from clustering analysis, we derived an average relation between SFR and halo mass (and its scatter). We also infer that the timescale of the main episode of dust-enshrouded star formation in massive halos (M H >~ 3 × 1012 M ⊙) amounts to ~7 × 108 yr. Given the SFRs, which are in the range of 102-103 M ⊙ yr-1, this timescale implies final stellar masses of the order of 1011-1012 M ⊙. The corresponding stellar mass function matches the observed mass function of passively evolving galaxies at z >~ 1. The comparison of the statistics for submillimeter and UV-selected galaxies suggests that the dust-free, UV bright phase is >~ 102 times shorter than the submillimeter bright phase, implying that the dust must form soon after the onset of star formation. Using a single reference spectral energy distribution (SED; the one of the z ≈ 2.3 galaxy SMM J2135-0102), our simple physical model is able to reproduce not only the LFs at different redshifts >1 but also the counts at wavelengths ranging from 250 μm to ≈1 mm. Owing to the steepness of the counts and their relatively broad frequency range, this result suggests that the dispersion of submillimeter SEDs of z > 1 galaxies around the reference one is rather small. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.

  4. Deep imaging of high redshift QSO fields below the Lyman limit. II - Number counts and colors of field galaxies

    NASA Technical Reports Server (NTRS)

    Steidel, Charles C.; Hamilton, Donald

    1993-01-01

    We present an analysis of the number counts and colors of faint galaxies to about 26.5 mag in the fields of two high Galactic latitude, very-high-redshift QSOs. We concentrate on the general properties of the field galaxies at faint magnitudes. In particular, we readdress the faint galaxy number counts and colors as a function of apparent magnitude and we reexamine the possible contribution of very-high-redshift galaxies to the faint samples. We find that the number counts to R = 26 are well fitted by the relation log N(m) = 0.31R + C. The G-band counts for the same galaxies are consistent with the same slope fainter than G about 23.5, but exhibit a much steeper slope at brighter magnitudes. At R = 25.5, the differential number counts have reached about 1.2 x 10 exp 5/sq deg; the same surface density of galaxies is reached at G = 26.5. We confirm the existence of a gradual 'blueing' trend of the field galaxies toward fainter apparent magnitude; however, the blueing trend appears to extend only as faint as G about 24, fainter than which both the (G-R) and (U sub n-G) colors appear to level off. The mean colors of faint galaxies are considerably redder than flat spectrum. There are essentially no objects to R = 26 which have spectral energy distributions which are bluer than flat spectrum. The potential contribution of very-high-redshift galaxies may have been underestimated in previous analyses; the current data are consistent with the same population of relatively luminous galaxies at z about 3 as exist at z about 0.7.

  5. Faint blue counts from formation of dwarf galaxies at z approximately equals 1

    NASA Technical Reports Server (NTRS)

    Babul, Arif; Rees, Martin J.

    1993-01-01

    The nature of faint blue objects (FBO's) has been a source of much speculation since their detection in deep CCD images of the sky. Their high surface density argues against them being progenitors of present-day bright galaxies and since they are only weakly clustered on small scales, they cannot be entities that merged together to form present-day galaxies. Babul & Rees (1992) have suggested that the observed faint blue counts may be due to dwarf elliptical galaxies undergoing their initial starburst at z is approximately equal to 1. In generic hierarchical clustering scenarios, however, dwarf galaxy halos (M is approximately 10(exp 9) solar mass) are expected to form at an earlier epoch; for example, typical 10(exp 9) solar mass halos will virialize at z is approximately equal to 2.3 if the power-spectrum for the density fluctuations is that of the standard b = 2 cold dark matter (CDM) model. Under 'ordinary conditions' the gas would rapidly cool, collect in the cores, and undergo star-formation. Conditions at high redshifts are far from 'ordinary'. The intense UV background will prevent the gas in the dwarf halos from cooling, the halos being released from their suspended state only when the UV flux has diminished sufficiently.

  6. Counts of galaxy clusters as cosmological probes: the impact of baryonic physics

    SciTech Connect

    Balaguera-Antolínez, Andrés; Porciani, Cristiano E-mail: porciani@astro.uni-bonn.de

    2013-04-01

    The halo mass function from N-body simulations of collisionless matter is generally used to retrieve cosmological parameters from observed counts of galaxy clusters. This neglects the observational fact that the baryonic mass fraction in clusters is a random variable that, on average, increases with the total mass (within an overdensity of 500). Considering a mock catalog that includes tens of thousands of galaxy clusters, as expected from the forthcoming generation of surveys, we show that the effect of a varying baryonic mass fraction will be observable with high statistical significance. The net effect is a change in the overall normalization of the cluster mass function and a milder modification of its shape. Our results indicate the necessity of taking into account baryonic corrections to the mass function if one wants to obtain unbiased estimates of the cosmological parameters from data of this quality. We introduce the formalism necessary to accomplish this goal. Our discussion is based on the conditional probability of finding a given value of the baryonic mass fraction for clusters of fixed total mass. Finally, we show that combining information from the cluster counts with measurements of the baryonic mass fraction in a small subsample of clusters (including only a few tens of objects) will nearly optimally constrain the cosmological parameters.

  7. Extragalactic gamma radiation: Use of galaxy counts as a galactic tracer

    NASA Technical Reports Server (NTRS)

    Thompson, D. J.; Fichtel, C. E.

    1982-01-01

    A derivation of the extragalactic diffuse gamma radiation with energies above 35 MeV was carried out using galaxy counts as a tracer of galactic matter. The extragalactic radiation has a differential photon number spectrum which may be expressed as a power law with index 2.35 (+0.4, -0.3) and an intensity above 35 MeV of (5.5 + or - 1.3) 0.00001 photons sq cm/s/ster, consistent with previous derivations. Use of a 1/sin of the absolute value of b expression of the galactic component produces a poorer fit, suggesting that the high-latitude galactic gamma-ray production may be dominated by cosmic ray interactions with matter rather than by Compton interactions of cosmic rays with photon fields.

  8. Far-infrared diffuse emission - Cosecant b law and galaxy counts

    SciTech Connect

    De bernardis, P.; Masi, S.; Melchiorri, F.; Moreno, G.; Vannoni, R.

    1988-03-01

    The IRAS diffuse emission data at 60 and 100 microns and the Lick Observatory galaxy counts are used here to study the large-scale distribution of interstellar dust at high Galactic latitudes, the isotropic component of diffuse emission, and the spectral behavior of the absorption coefficient in the far-IR. The results confirm the existence of the cosecant b law of Galactic far-IR emission. The isotropic component of diffuse emission is found to be comparable to the instrumental offset uncertainty at 100 microns. Therefore, the cosecant b law can provide an alternative local explanation for the extragalactic background claimed by Rowan-Robinson (1986). Assuming the IR absorption efficiency spectral index lying in the range one to two, a dust temperature in the range 22-25 K is found, in agreement with previous estimates. 20 references.

  9. Probing the cosmic-ray content of galaxy clusters by stacking Fermi-LAT count maps

    NASA Astrophysics Data System (ADS)

    Huber, B.; Tchernin, C.; Eckert, D.; Farnier, C.; Manalaysay, A.; Straumann, U.; Walter, R.

    2013-12-01

    Aims: Radio observations have shown that galaxy clusters are giant reservoirs of cosmic rays (CR). Although a gamma-ray signal from the cluster volume is expected to arise through interactions of CR protons with the ambient plasma, a confirming observation is still missing. Methods: We searched for a cumulative gamma-ray emission in the direction of galaxy clusters by analysing a collection of stacked Fermi-LAT count maps. Additionally, we investigated possible systematic differences in the emission between cool-core and non-cool-core cluster populations. Results: Making use of a sample of 53 clusters selected from the HIFLUGCS catalog, we do not detect a significant signal from the stacked sample. The upper limit on the average flux per cluster derived for the total stacked sample is at the level of a few 10-11 ph cm-2 s-1 at a 95% confidence level in the 1-300 GeV band, assuming power-law spectra with photon indices 2.0, 2.4, 2.8, and 3.2. Separate stacking of the cool-core and non-cool-core clusters in the sample lead to similar values of around 5 × 10-11 ph cm-2 s-1 and 2 × 10-11 ph cm-2 s-1, respectively. Conclusions: Under the assumption that decaying π0, produced in collisions between CRs and the ambient thermal gas, are responsible for gamma-ray emission, we set upper limits on the average CR content in galaxy clusters. For the entire cluster population, our upper limit on the gamma-ray flux translates into an upper limit on the average CR-to-thermal energy ratio of 4.6% for a photon index of 2.4, although it is possible for individual systems to exceed this limit. Our 95% upper limits are at the level expected from numerical simulations, which most likely suggests that the injection of CR at cosmological shocks is less efficient than previously assumed.

  10. High redshift galaxies in the ALHAMBRA survey . I. Selection method and number counts based on redshift PDFs

    NASA Astrophysics Data System (ADS)

    Viironen, K.; Marín-Franch, A.; López-Sanjuan, C.; Varela, J.; Chaves-Montero, J.; Cristóbal-Hornillos, D.; Molino, A.; Fernández-Soto, A.; Vilella-Rojo, G.; Ascaso, B.; Cenarro, A. J.; Cerviño, M.; Cepa, J.; Ederoclite, A.; Márquez, I.; Masegosa, J.; Moles, M.; Oteo, I.; Pović, M.; Aguerri, J. A. L.; Alfaro, E.; Aparicio-Villegas, T.; Benítez, N.; Broadhurst, T.; Cabrera-Caño, J.; Castander, J. F.; Del Olmo, A.; González Delgado, R. M.; Husillos, C.; Infante, L.; Martínez, V. J.; Perea, J.; Prada, F.; Quintana, J. M.

    2015-04-01

    Context. Most observational results on the high redshift restframe UV-bright galaxies are based on samples pinpointed using the so-called dropout technique or Ly-α selection. However, the availability of multifilter data now allows the dropout selections to be replaced by direct methods based on photometric redshifts. In this paper we present the methodology to select and study the population of high redshift galaxies in the ALHAMBRA survey data. Aims: Our aim is to develop a less biased methodology than the traditional dropout technique to study the high redshift galaxies in ALHAMBRA and other multifilter data. Thanks to the wide area ALHAMBRA covers, we especially aim at contributing to the study of the brightest, least frequent, high redshift galaxies. Methods: The methodology is based on redshift probability distribution functions (zPDFs). It is shown how a clean galaxy sample can be obtained by selecting the galaxies with high integrated probability of being within a given redshift interval. However, reaching both a complete and clean sample with this method is challenging. Hence, a method to derive statistical properties by summing the zPDFs of all the galaxies in the redshift bin of interest is introduced. Results: Using this methodology we derive the galaxy rest frame UV number counts in five redshift bins centred at z = 2.5,3.0,3.5,4.0, and 4.5, being complete up to the limiting magnitude at mUV(AB) = 24, where mUV refers to the first ALHAMBRA filter redwards of the Ly-α line. With the wide field ALHAMBRA data we especially contribute to the study of the brightest ends of these counts, accurately sampling the surface densities down to mUV(AB) = 21-22. Conclusions: We show that using the zPDFs it is easy to select a very clean sample of high redshift galaxies. We also show that it is better to do statistical analysis of the properties of galaxies using a probabilistic approach, which takes into account both the incompleteness and contamination issues in a

  11. Faint submillimeter galaxies revealed by multifield deep ALMA observations: number counts, spatial clustering, and a dark submillimeter line emitter

    SciTech Connect

    Ono, Yoshiaki; Ouchi, Masami; Momose, Rieko; Kurono, Yasutaka

    2014-11-01

    We present the statistics of faint submillimeter/millimeter galaxies (SMGs) and serendipitous detections of a submillimeter/millimeter line emitter (SLE) with no multi-wavelength continuum counterpart revealed by the deep ALMA observations. We identify faint SMGs with flux densities of 0.1-1.0 mJy in the deep Band-6 and Band-7 maps of 10 independent fields that reduce cosmic variance effects. The differential number counts at 1.2 mm are found to increase with decreasing flux density down to 0.1 mJy. Our number counts indicate that the faint (0.1-1.0 mJy, or SFR{sub IR} ∼ 30-300 M {sub ☉} yr{sup –1}) SMGs contribute nearly a half of the extragalactic background light (EBL), while the remaining half of the EBL is mostly contributed by very faint sources with flux densities of <0.1 mJy (SFR{sub IR} ≲ 30 M {sub ☉} yr{sup –1}). We conduct counts-in-cells analysis with multifield ALMA data for the faint SMGs, and obtain a coarse estimate of galaxy bias, b {sub g} < 4. The galaxy bias suggests that the dark halo masses of the faint SMGs are ≲ 7 × 10{sup 12} M {sub ☉}, which is smaller than those of bright (>1 mJy) SMGs, but consistent with abundant high-z star-forming populations, such as sBzKs, LBGs, and LAEs. Finally, we report the serendipitous detection of SLE-1, which has no continuum counterparts in our 1.2 mm-band or multi-wavelength images, including ultra deep HST/WFC3 and Spitzer data. The SLE has a significant line at 249.9 GHz with a signal-to-noise ratio of 7.1. If the SLE is not a spurious source made by the unknown systematic noise of ALMA, the strong upper limits of our multi-wavelength data suggest that the SLE would be a faint galaxy at z ≳ 6.

  12. A Quantitative Analysis of Star-Forming Galaxies at Intermediate Redshifts: Number Counts, Morphological Sequences, and Evolutionary Timescales

    NASA Astrophysics Data System (ADS)

    Voyer, Elysse

    2011-01-01

    We present a multiwavelength study of rest-frame far-ultraviolet (FUV) selected galaxies at intermediate redshifts (0.1 < z < 1) in the GOODS-N & -S fields. The HST data analyzed were taken with ACS, WFPC2, and WFC3 spanning from FUV to near-infrared bands. The galaxy sample is analyzed in bins of specified time to facilitate comparisons with predictions from theory and simulations of timescales for merger events and morphological transformation in secular evolution scenarios. Quantitative rest-frame i-band morphologies from GALFIT are compared with SED based spectral types revealing trends between morphology and star-formation at intermediate redshifts. Sizes of star-forming clumps are also measured in the rest-frame FUV data for different morphologies to test for size evolution which could be an indication of disk or bulge build-up. We compare morphologies of the star-forming sample to those of a large non-FUV selected galaxy sample in the GOODS-N & -S fields over the same redshift ranges to pinpoint significant morphological differences. We also compare with a local sample obtained from the Sloan Digital Sky Survey representing the local Hubble sequence. The FUV sample is used to measure faint end number counts and the resolved background contribution, covering a larger area (15.9 square arcmin.) than previously observed at these wavelengths (1614Å) and magnitudes (20.5-29.5). Our results are in good agreement with recent semi-analytical models based on dark matter "merger trees” (Somerville et al. 2008, Gilmore et al. 2009) and suggest that other HST studies using smaller detection areas have over-predicted the number counts.

  13. Primordial non-Gaussianity from the covariance of galaxy cluster counts

    SciTech Connect

    Cunha, Carlos; Huterer, Dragan; Dore, Olivier

    2010-07-15

    It has recently been proposed that the large-scale bias of dark matter halos depends sensitively on primordial non-Gaussianity of the local form. In this paper we point out that the strong scale dependence of the non-Gaussian halo bias imprints a distinct signature on the covariance of cluster counts. We find that using the full covariance of cluster counts results in improvements on constraints on the non-Gaussian parameter f{sub NL} of 3 (1) orders of magnitude relative to cluster counts (counts+clustering variance) constraints alone. We forecast f{sub NL} constraints for the upcoming Dark Energy Survey in the presence of uncertainties in the mass-observable relation, halo bias, and photometric redshifts. We find that the Dark Energy Survey can yield constraints on non-Gaussianity of {sigma}(f{sub NL}){approx}1-5 even for relatively conservative assumptions regarding systematics. Excess of correlations of cluster counts on scales of hundreds of megaparsecs would represent a smoking-gun signature of primordial non-Gaussianity of the local type.

  14. The 4 Ms CHANDRA Deep Field-South Number Counts Apportioned by Source Class: Pervasive Active Galactic Nuclei and the Ascent of Normal Galaxies

    NASA Technical Reports Server (NTRS)

    Lehmer, Bret D.; Xue, Y. Q.; Brandt, W. N.; Alexander, D. M.; Bauer, F. E.; Brusa, M.; Comastri, A.; Gilli, R.; Hornschemeier, A. E.; Luo, B.; Paolillo, M.; Ptak, A.; Shemmer, O.; Schneider, D. P.; Tozzi, P.; Vignali, C.

    2012-01-01

    We present 0.5-2 keV, 2-8 keV, 4-8 keV, and 0.5-8 keV (hereafter soft, hard, ultra-hard, and full bands, respectively) cumulative and differential number-count (log N-log S ) measurements for the recently completed approx. equal to 4 Ms Chandra Deep Field-South (CDF-S) survey, the deepest X-ray survey to date. We implement a new Bayesian approach, which allows reliable calculation of number counts down to flux limits that are factors of approx. equal to 1.9-4.3 times fainter than the previously deepest number-count investigations. In the soft band (SB), the most sensitive bandpass in our analysis, the approx. equal to 4 Ms CDF-S reaches a maximum source density of approx. equal to 27,800 deg(sup -2). By virtue of the exquisite X-ray and multiwavelength data available in the CDF-S, we are able to measure the number counts from a variety of source populations (active galactic nuclei (AGNs), normal galaxies, and Galactic stars) and subpopulations (as a function of redshift, AGN absorption, luminosity, and galaxy morphology) and test models that describe their evolution. We find that AGNs still dominate the X-ray number counts down to the faintest flux levels for all bands and reach a limiting SB source density of approx. equal to 14,900 deg(sup -2), the highest reliable AGN source density measured at any wavelength. We find that the normal-galaxy counts rise rapidly near the flux limits and, at the limiting SB flux, reach source densities of approx. equal to 12,700 deg(sup -2) and make up 46% plus or minus 5% of the total number counts. The rapid rise of the galaxy counts toward faint fluxes, as well as significant normal-galaxy contributions to the overall number counts, indicates that normal galaxies will overtake AGNs just below the approx. equal to 4 Ms SB flux limit and will provide a numerically significant new X-ray source population in future surveys that reach below the approx. equal to 4 Ms sensitivity limit. We show that a future approx. equal to 10 Ms CDF

  15. Galaxies

    SciTech Connect

    Not Available

    1981-01-01

    Normal galaxies, radio galaxies, and Seyfert galaxies are considered. The large magellanic cloud and the great galaxy in Andromedia are highlighted. Quasars and BL lacertae objects are also discussed and a review of the spectral observations of all of these galaxies and celestial objects is presented.

  16. Observed galaxy number counts on the lightcone up to second order: I. Main result

    SciTech Connect

    Bertacca, Daniele; Maartens, Roy; Clarkson, Chris E-mail: roy.maartens@gmail.com

    2014-09-01

    We present the galaxy number overdensity up to second order in redshift space on cosmological scales for a concordance model. The result contains all general relativistic effects up to second order that arise from observing on the past light cone, including all redshift effects, lensing distortions from convergence and shear, and contributions from velocities, Sachs-Wolfe, integrated SW and time-delay terms. This result will be important for accurate calculation of the bias on estimates of non-Gaussianity and on precision parameter estimates, introduced by nonlinear projection effects.

  17. Observed galaxy number counts on the lightcone up to second order: II. Derivation

    SciTech Connect

    Bertacca, Daniele; Maartens, Roy; Clarkson, Chris E-mail: roy.maartens@gmail.com

    2014-11-01

    We present a detailed derivation of the observed galaxy number over-density on cosmological scales up to second order in perturbation theory. We include all relativistic effects that arise from observing on the past lightcone. The derivation is in a general gauge, and applies to all dark energy models (including interacting dark energy) and to metric theories of modified gravity. The result will be important for accurate cosmological parameter estimation, including non-Gaussianity, since all projection effects need to be taken into account. It also offers the potential for new probes of General Relativity, dark energy and modified gravity. This paper accompanies Paper I which presents the key results for the concordance model in Poisson gauge.

  18. Measurements of Extragalactic Background Light from the Far UV to the Far IR from Deep Ground- and Space-based Galaxy Counts

    NASA Astrophysics Data System (ADS)

    Driver, Simon P.; Andrews, Stephen K.; Davies, Luke J.; Robotham, Aaron S. G.; Wright, Angus H.; Windhorst, Rogier A.; Cohen, Seth; Emig, Kim; Jansen, Rolf A.; Dunne, Loretta

    2016-08-01

    We combine wide and deep galaxy number-count data from the Galaxy And Mass Assembly, COSMOS/G10, Hubble Space Telescope (HST) Early Release Science, HST UVUDF, and various near-, mid-, and far-IR data sets from ESO, Spitzer, and Herschel. The combined data range from the far UV (0.15 μm) to far-IR (500 μm), and in all cases the contribution to the integrated galaxy light (IGL) of successively fainter galaxies converges. Using a simple spline fit, we derive the IGL and the extrapolated IGL in all bands. We argue that undetected low-surface-brightness galaxies and intracluster/group light are modest, and that our extrapolated-IGL measurements are an accurate representation of the extragalactic background light (EBL). Our data agree with most earlier IGL estimates and with direct measurements in the far IR, but disagree strongly with direct estimates in the optical. Close agreement between our results and recent very high-energy experiments (H.E.S.S. and MAGIC) suggests that there may be an additional foreground affecting the direct estimates. The most likely culprit could be the adopted model of zodiacal light. Finally we use a modified version of the two-component model to integrate the EBL and obtain measurements of the cosmic optical background (COB) and cosmic infrared background of {24}-4+4 nW m-2 sr-1 and {26}-5+5 nW m-2 sr-1 respectively (48%:52%). Over the next decade, upcoming space missions such as Euclid and the Wide Field Infrared Space Telescope will have the capacity to reduce the COB error to <1%, at which point comparisons to the very high-energy data could have the potential to provide a direct detection and measurement of the reionization field.

  19. Measurements of Extragalactic Background Light from the Far UV to the Far IR from Deep Ground- and Space-based Galaxy Counts

    NASA Astrophysics Data System (ADS)

    Driver, Simon P.; Andrews, Stephen K.; Davies, Luke J.; Robotham, Aaron S. G.; Wright, Angus H.; Windhorst, Rogier A.; Cohen, Seth; Emig, Kim; Jansen, Rolf A.; Dunne, Loretta

    2016-08-01

    We combine wide and deep galaxy number-count data from the Galaxy And Mass Assembly, COSMOS/G10, Hubble Space Telescope (HST) Early Release Science, HST UVUDF, and various near-, mid-, and far-IR data sets from ESO, Spitzer, and Herschel. The combined data range from the far UV (0.15 μm) to far-IR (500 μm), and in all cases the contribution to the integrated galaxy light (IGL) of successively fainter galaxies converges. Using a simple spline fit, we derive the IGL and the extrapolated IGL in all bands. We argue that undetected low-surface-brightness galaxies and intracluster/group light are modest, and that our extrapolated-IGL measurements are an accurate representation of the extragalactic background light (EBL). Our data agree with most earlier IGL estimates and with direct measurements in the far IR, but disagree strongly with direct estimates in the optical. Close agreement between our results and recent very high-energy experiments (H.E.S.S. and MAGIC) suggests that there may be an additional foreground affecting the direct estimates. The most likely culprit could be the adopted model of zodiacal light. Finally we use a modified version of the two-component model to integrate the EBL and obtain measurements of the cosmic optical background (COB) and cosmic infrared background of {24}-4+4 nW m‑2 sr‑1 and {26}-5+5 nW m‑2 sr‑1 respectively (48%:52%). Over the next decade, upcoming space missions such as Euclid and the Wide Field Infrared Space Telescope will have the capacity to reduce the COB error to <1%, at which point comparisons to the very high-energy data could have the potential to provide a direct detection and measurement of the reionization field.

  20. HerMES: a search for high-redshift dusty galaxies in the HerMES Large Mode Survey - catalogue, number counts and early results

    NASA Astrophysics Data System (ADS)

    Asboth, V.; Conley, A.; Sayers, J.; Béthermin, M.; Chapman, S. C.; Clements, D. L.; Cooray, A.; Dannerbauer, H.; Farrah, D.; Glenn, J.; Golwala, S. R.; Halpern, M.; Ibar, E.; Ivison, R. J.; Maloney, P. R.; Marques-Chaves, R.; Martinez-Navajas, P. I.; Oliver, S. J.; Pérez-Fournon, I.; Riechers, D. A.; Rowan-Robinson, M.; Scott, Douglas; Siegel, S. R.; Vieira, J. D.; Viero, M.; Wang, L.; Wardlow, J.; Wheeler, J.

    2016-10-01

    Selecting sources with rising flux densities towards longer wavelengths from Herschel/Spectral and Photometric Imaging Receiver (SPIRE) maps is an efficient way to produce a catalogue rich in high-redshift (z > 4) dusty star-forming galaxies. The effectiveness of this approach has already been confirmed by spectroscopic follow-up observations, but the previously available catalogues made this way are limited by small survey areas. Here we apply a map-based search method to 274 deg2 of the Herschel Multi-tiered Extragalactic Survey (HerMES) Large Mode Survey and create a catalogue of 477 objects with SPIRE flux densities S500 > S350 > S250 and a 5σ cut-off S500 > 52 mJy. From this catalogue we determine that the total number of these `red' sources is at least an order of magnitude higher than predicted by galaxy evolution models. These results are in agreement with previous findings in smaller HerMES fields; however, due to our significantly larger sample size we are also able to investigate the shape of the red source counts for the first time. We have obtained spectroscopic redshift measurements for two of our sources using the Atacama Large Millimeter/submillimeter Array. The redshifts z = 5.1 and 3.8 confirm that with our selection method we can indeed find high-redshift dusty star-forming galaxies.

  1. A galaxy model from two micron all sky survey star counts in the whole sky, including the plane

    SciTech Connect

    Polido, P.; Jablonski, F.; Lépine, J. R. D.

    2013-11-20

    We use the star count model of Ortiz and Lépine to perform an unprecedented exploration of the most important Galactic parameters comparing the predicted counts with the Two Micron All Sky Survey observed star counts in the J, H, and K{sub S} bands for a grid of positions covering the whole sky. The comparison is made using a grid of lines of sight given by the HEALPix pixelization scheme. The resulting best-fit values for the parameters are: 2120 ± 200 pc for the radial scale length and 205 ± 40 pc for the scale height of the thin disk, with a central hole of 2070{sub −800}{sup +2000} pc for the same disk, 3050 ± 500 pc for the radial scale length and 640 ± 70 pc for the scale height of the thick disk, 400 ± 100 pc for the central dimension of the spheroid, 0.0082 ± 0.0030 for the spheroid to disk density ratio, and 0.57 ± 0.05 for the oblate spheroid parameter.

  2. Constraints on Photoionization Feedback from Number Counts of Ultra-faint High-redshift Galaxies in the Frontier Fields

    NASA Astrophysics Data System (ADS)

    Castellano, M.; Yue, B.; Ferrara, A.; Merlin, E.; Fontana, A.; Amorín, R.; Grazian, A.; Mármol-Queralto, E.; Michałowski, M. J.; Mortlock, A.; Paris, D.; Parsa, S.; Pilo, S.; Santini, P.

    2016-06-01

    We exploit a sample of ultra-faint high-redshift galaxies (demagnified Hubble Space Telescope, HST, H 160 magnitude > 30) in the Frontier Fields clusters A2744 and M0416 to constrain a theoretical model for the UV luminosity function in the presence of photoionization feedback. The objects have been selected on the basis of accurate photometric redshifts computed from multi-band photometry including seven HST bands and deep K s and IRAC observations. Magnification is computed on an object-by-object basis from all available lensing models of the two clusters. We take into account source detection completeness as a function of luminosity and size, magnification effects, and systematics in the lens modeling of the clusters under investigation. We find that our sample of high-z galaxies constrain the cutoff halo circular velocity below which star formation is suppressed by photoionization feedback to {v}c{{cut}}\\lt 50 km s‑1. This circular velocity corresponds to a halo mass of ≈5.6 × 109 M ⊙ and ≈2.3 × 109 M ⊙ at z = 5 and 10, respectively: higher-mass halos can thus sustain continuous star formation activity without being quenched by external ionizing flux. More stringent constraints are prevented by the uncertainty in the modeling of the cluster lens, as embodied by systematic differences among the lens models available.

  3. Counting carbohydrates

    MedlinePlus

    Carb counting; Carbohydrate-controlled diet; Diabetic diet; Diabetes-counting carbohydrates ... Many foods contain carbohydrates (carbs), including: Fruit and fruit juice Cereal, bread, pasta, and rice Milk and milk products, soy milk Beans, legumes, ...

  4. Cell counting.

    PubMed

    Phelan, M C; Lawler, G

    2001-05-01

    This unit presents protocols for counting cells using either a hemacytometer or electronically using a Coulter counter. Cell counting with a hemacytometer permits effective discrimination of live from dead cells using trypan blue exclusion. In addition, the procedure is less subject to errors arising from cell clumping or size heterogeneity. Counting cells is more quickly and easily performed using an electronic counter, but live-dead discrimination is unreliable. Cell populations containing large numbers of dead cells and/or cell clumps are difficult to count accurately. In addition, electronic counting requires resetting of the instrument for cell populations of different sizes; heterogeneous populations can give rise to inaccurate counts, and resting and activated cells may require counting at separate settings. In general, electronic cell counting is best performed on fresh peripheral blood cells. PMID:18770655

  5. Multiplicity Counting

    SciTech Connect

    Geist, William H.

    2015-12-01

    This set of slides begins by giving background and a review of neutron counting; three attributes of a verification item are discussed: 240Pueff mass; α, the ratio of (α,n) neutrons to spontaneous fission neutrons; and leakage multiplication. It then takes up neutron detector systems – theory & concepts (coincidence counting, moderation, die-away time); detector systems – some important details (deadtime, corrections); introduction to multiplicity counting; multiplicity electronics and example distributions; singles, doubles, and triples from measured multiplicity distributions; and the point model: multiplicity mathematics.

  6. Reticulocyte count

    MedlinePlus

    ... radiation therapy, or infection) Cirrhosis of the liver Anemia caused by low iron levels, or low levels of vitamin B12 or folate Chronic kidney disease Reticulocyte count may be higher during pregnancy.

  7. Tower counts

    USGS Publications Warehouse

    Woody, Carol Ann; Johnson, D.H.; Shrier, Brianna M.; O'Neal, Jennifer S.; Knutzen, John A.; Augerot, Xanthippe; O'Neal, Thomas A.; Pearsons, Todd N.

    2007-01-01

    Counting towers provide an accurate, low-cost, low-maintenance, low-technology, and easily mobilized escapement estimation program compared to other methods (e.g., weirs, hydroacoustics, mark-recapture, and aerial surveys) (Thompson 1962; Siebel 1967; Cousens et al. 1982; Symons and Waldichuk 1984; Anderson 2000; Alaska Department of Fish and Game 2003). Counting tower data has been found to be consistent with that of digital video counts (Edwards 2005). Counting towers do not interfere with natural fish migration patterns, nor are fish handled or stressed; however, their use is generally limited to clear rivers that meet specific site selection criteria. The data provided by counting tower sampling allow fishery managers to determine reproductive population size, estimate total return (escapement + catch) and its uncertainty, evaluate population productivity and trends, set harvest rates, determine spawning escapement goals, and forecast future returns (Alaska Department of Fish and Game 1974-2000 and 1975-2004). The number of spawning fish is determined by subtracting subsistence, sport-caught fish, and prespawn mortality from the total estimated escapement. The methods outlined in this protocol for tower counts can be used to provide reasonable estimates ( plus or minus 6%-10%) of reproductive salmon population size and run timing in clear rivers. 

  8. Women Count

    NASA Astrophysics Data System (ADS)

    Hurley, Dana M.

    2014-11-01

    I am a counter by nature. I count things as an effective way to occupy my mind. How many people are in this room? How many are women? How many are wearing glasses? How many people are using a Mac versus a PC?

  9. Counting Populations

    ERIC Educational Resources Information Center

    Damonte, Kathleen

    2004-01-01

    Scientists use sampling to get an estimate of things they cannot easily count. A population is made up of all the organisms of one species living together in one place at the same time. All of the people living together in one town are considered a population. All of the grasshoppers living in a field are a population. Scientists keep track of the…

  10. Counting Penguins.

    ERIC Educational Resources Information Center

    Perry, Mike; Kader, Gary

    1998-01-01

    Presents an activity on the simplification of penguin counting by employing the basic ideas and principles of sampling to teach students to understand and recognize its role in statistical claims. Emphasizes estimation, data analysis and interpretation, and central limit theorem. Includes a list of items for classroom discussion. (ASK)

  11. Low surface brightness galaxies and tidally triggered star formation

    NASA Technical Reports Server (NTRS)

    Zaritsky, Dennis; Lorrimer, Stephen J.

    1993-01-01

    Counts of companions to low surface brightness (LSB) galaxies are presented and these are compared to counts of companions to normal galaxies obtained with the same techniques and criteria. Our results are consistent with LSB's having no clustered companions and support the hypothesis that LSB galaxies have low star-formation rates because they lack external tidal triggering.

  12. Luminosity function for galaxy clusters

    NASA Astrophysics Data System (ADS)

    Bajan, K.; Biernacka, M.; Flin, P.; Godłowski, W.; Panko, E.; Popiela, J.

    2016-10-01

    We constructed and studied the luminosity function of 6188 galaxyclusters. This was performed by counting brightness of galaxiesbelonging to clusters in the PF catalogue, taking galaxy data fromMRSS. Our result shows that the investigated structures arecharacterized by a luminosity function different from that ofoptical galaxies and radiogalaxies (Machalski & Godłowski2000). The implications of this result for theoriesof galaxy formation are briefly discussed.

  13. Reticulocyte Count Test

    MedlinePlus

    ... Reticulocyte Count Related tests: Red Blood Cell Count ; Hemoglobin ; Hematocrit ; Complete Blood Count ; Blood Smear ; Erythropoietin ; Vitamin ... on a complete blood count (CBC) , RBC count , hemoglobin or hematocrit , to help determine the cause To ...

  14. White Blood Cell Count

    MedlinePlus

    ... Home Visit Global Sites Search Help? White Blood Cell Count Share this page: Was this page helpful? Also ... Leukocyte Count; White Count Formal name: White Blood Cell Count Related tests: Complete Blood Count , Blood Smear , White ...

  15. Radio Galaxies.

    ERIC Educational Resources Information Center

    Downes, Ann

    1986-01-01

    Provides background information on radio galaxies. Topic areas addressed include: what produces the radio emission; radio telescopes; locating radio galaxies; how distances to radio galaxies are found; physics of radio galaxies; computer simulations of radio galaxies; and the evolution of radio galaxies with cosmic time. (JN)

  16. Eosinophil count - absolute

    MedlinePlus

    Eosinophils; Absolute eosinophil count ... the white blood cell count to give the absolute eosinophil count. ... than 500 cells per microliter (cells/mcL). Normal value ranges may vary slightly among different laboratories. Talk ...

  17. T-cell count

    MedlinePlus

    Thymus derived lymphocyte count; T-lymphocyte count; T cell count ... T cells are a type of lymphocyte. Lymphocytes are white blood cells. They make up part of the immune system. T cells help the body fight diseases or harmful ...

  18. The Environment of Barred Galaxies Revisited

    NASA Astrophysics Data System (ADS)

    Cervantes Sodi, B.; Li, C.; Park, C.; Wang, L.

    We present a study of the environment of barred galaxies using galaxies drawn from the SDSS. We use several different statistics to quantify the environment: the projected two-point cross-correlation function, the background-subtracted number counts of neighbor galaxies, the overdensity of the local environment, the membership of our galaxies to galaxy groups to segregate central and satellite systems, and, for central galaxies, the stellar to halo mass ratio (M∗/Mh). When we split our sample into early- and late-type galaxies, we see a weak but significant trend for early-type galaxies with a bar to be more strongly clustered on scales from a few 100 kpc to 1 Mpc when compared to unbarred early-type galaxies. This indicates that the presence of a bar in early-type galaxies depends on the location within their host dark matter halos. This is confirmed by the group catalog in the sense that for early-types, the fraction of central galaxies is smaller if they have a bar. For late-type galaxies, we find fewer neighbors within ˜ 50 kpc around the barred galaxies when compared to unbarred galaxies from the control sample, suggesting that tidal forces from close companions suppress the formation/growth of bars. For central late-type galaxies, bars are more common on galaxies with high M∗/Mh values, as expected from early theoretical works which showed that systems with massive dark matter halos are more stable against bar instabilities. Finally, we find no obvious correlation between overdensity and the bars in our sample, showing that galactic bars are not obviously linked to the large-scale structure of the universe.

  19. The Big Pumpkin Count.

    ERIC Educational Resources Information Center

    Coplestone-Loomis, Lenny

    1981-01-01

    Pumpkin seeds are counted after students convert pumpkins to jack-o-lanterns. Among the activities involved, pupils learn to count by 10s, make estimates, and to construct a visual representation of 1,000. (MP)

  20. Galaxy Clustering Around Nearby Luminous Quasars

    NASA Technical Reports Server (NTRS)

    Fisher, Karl B.; Bahcall, John N.; Kirhakos, Sofia; Schneider, Donald P.

    1996-01-01

    We examine the clustering of galaxies around a sample of 20 luminous low redshift (z approx. less than 0.30) quasars observed with the Wide Field Camera-2 on the Hubble Space Telescope (HST). The HST resolution makes possible galaxy identification brighter than V = 24.5 and as close as 1 min or 2 min to the quasar. We find a significant enhancement of galaxies within a projected separation of approx. less than 100 1/h kpc of the quasars. If we model the QSO/galaxy correlation function as a power law with a slope given by the galaxy/galaxy correlation function, we find that the ratio of the QSO/galaxy to galaxy/galaxy correlation functions is 3.8 +/- 0.8. The galaxy counts within r less than 15 1/h kpc of the quasars are too high for the density profile to have an appreciable core radius (approx. greater than 100 1/h kpc). Our results reinforce the idea that low redshift quasars are located preferentially in groups of 10-20 galaxies rather than in rich clusters. We see no significant difference in the clustering amplitudes derived from radio-loud and radio-quiet subsamples.

  1. Exploring galaxy environments on large and small scales

    NASA Astrophysics Data System (ADS)

    Berrier, Heather Danae

    I examine galaxy environments and galaxy interactions using LCDM N-body simulations, redshift surveys, and a sample of 77 galaxies in close pairs and groups. I show that some simulations and models for assigning luminosities to dark matter halos reproduce the observed counts-in-cylinders statistic distribution quite well, except for very isolated galaxies. I also find that the close-pair fraction from a LCDM simulation matches both the observed close- pair count at z=0 and the pair fraction evolution. Finally, I use U and V photometry of a sample of previously-studied galaxies to support results suggesting a relationship between galaxy separation and starburst strength, and confirm that U-B colors are a sensitive indicator of burst strength. This will be useful in studies of high redshift galaxies.

  2. Starbursts in blue compact dwarf galaxies

    NASA Technical Reports Server (NTRS)

    Thuan, Trinh Xuan

    1987-01-01

    All the arguments for a bursting mode of star formation in blue compact dwarf galaxies (BCD) are summarized. It is shown that spectral synthesis of far-ultraviolet spectra of BCDs constitutes a powerful way to study the star formation history in these galaxies. BCD luminosity functions show jumps and discontinuities. These jumps act like fossil records of the star-forming bursts, aiding in the counting and dating of the bursts.

  3. Les galaxies

    NASA Astrophysics Data System (ADS)

    Combes, Francoise

    2016-08-01

    Considerable progress has been made on galaxy formation and evolution in recent years, and new issues. The old Hubble classification according to the tuning fork of spirals, lenticulars and ellipticals, is still useful but has given place to the red sequence, the blue cloud and the green valley, showing a real bimodality of types between star forming galaxies (blue) and quenched ones (red). Large surveys have shown that stellar mass and environment density are the two main factors of the evolution from blue to red sequences. Evolution is followed directly with redshift through a look-back time of more than 12 billion years. The most distant galaxy at z=11. has already a stellar mass of a billion suns. In an apparent anti-hierarchical scenario, the most massive galaxies form stars early on, while essentially dwarf galaxies are actively star-formers now. This downsizing feature also applies to the growth of super-massive black holes at the heart of each bulgy galaxy. The feedback from active nuclei is essential to explain the distribution of mass in galaxies, and in particular to explain why the fraction of baryonic matter is so low, lower by more than a factor 5 than the baryonic fraction of the Universe. New instruments just entering in operation, like MUSE and ALMA, provide a new and rich data flow, which is developed in this series of articles.

  4. CSF cell count

    MedlinePlus

    The normal white blood cell count is between 0 and 5. The normal red blood cell count is 0. Note: Normal value ranges may vary slightly among different laboratories. Talk to your doctor about ... use different measurements or may test different specimens.

  5. Counting Sheep in Basque

    ERIC Educational Resources Information Center

    Araujo, Frank P.

    1975-01-01

    Demonstrates the interplay of a cognitive system, the Basque numerative system, and a behavioral one, counting sheep. The significant features of the Basque numerative system are analyzed; then it is shown how use of these features facilitates the counting of sheep on open ranges by Basque sheep farmers in California. (Author/RM)

  6. Counts-in-Cylinders in the Sloan Digital Sky Survey with Comparisons to N-Body

    SciTech Connect

    Berrier, Heather D.; Barton, Elizabeth J.; Berrier, Joel C.; Bullock, James S.; Zentner, Andrew R.; Wechsler, Risa H. /KIPAC, Menlo Park /SLAC

    2010-12-16

    Environmental statistics provide a necessary means of comparing the properties of galaxies in different environments and a vital test of models of galaxy formation within the prevailing, hierarchical cosmological model. We explore counts-in-cylinders, a common statistic defined as the number of companions of a particular galaxy found within a given projected radius and redshift interval. Galaxy distributions with the same two-point correlation functions do not necessarily have the same companion count distributions. We use this statistic to examine the environments of galaxies in the Sloan Digital Sky Survey, Data Release 4. We also make preliminary comparisons to four models for the spatial distributions of galaxies, based on N-body simulations, and data from SDSS DR4 to study the utility of the counts-in-cylinders statistic. There is a very large scatter between the number of companions a galaxy has and the mass of its parent dark matter halo and the halo occupation, limiting the utility of this statistic for certain kinds of environmental studies. We also show that prevalent, empirical models of galaxy clustering that match observed two- and three-point clustering statistics well fail to reproduce some aspects of the observed distribution of counts-in-cylinders on 1, 3 and 6-h{sup -1}Mpc scales. All models that we explore underpredict the fraction of galaxies with few or no companions in 3 and 6-h{sup -1} Mpc cylinders. Roughly 7% of galaxies in the real universe are significantly more isolated within a 6 h{sup -1} Mpc cylinder than the galaxies in any of the models we use. Simple, phenomenological models that map galaxies to dark matter halos fail to reproduce high-order clustering statistics in low-density environments.

  7. Galaxy cosmological mass function

    NASA Astrophysics Data System (ADS)

    Lopes, Amanda R.; Iribarrem, Alvaro; Ribeiro, Marcelo B.; Stoeger, William R.

    2014-12-01

    Aims: This paper studies the galaxy cosmological mass function (GCMF) in a semi-empirical relativistic approach that uses observational data provided by recent galaxy redshift surveys. Methods: Starting from a previously presented relation between the mass-to-light ratio, the selection function obtained from the luminosity function (LF) data and the luminosity density, the average luminosity L, and the average galactic mass ℳg were computed in terms of the redshift. ℳg was also alternatively estimated by means of a method that uses the galaxy stellar mass function (GSMF). Comparison of these two forms of deriving the average galactic mass allowed us to infer a possible bias introduced by the selection criteria of the survey. We used the FORS Deep Field galaxy survey sample of 5558 galaxies in the redshift range 0.5 counts, to finally calculate the GCMF, which can be fitted by a Schechter function, but whose fitted parameter values are different from the values found in the literature for the GSMF. Conclusions: This GCMF behavior follows the theoretical predictions from the cold dark matter models in which the less massive objects form first, followed later by more massive ones. In the range 0.5 galaxy mergers or as a strong evolution in the star formation history of these galaxies.

  8. AUTOMATIC COUNTING APPARATUS

    DOEpatents

    Howell, W.D.

    1957-08-20

    An apparatus for automatically recording the results of counting operations on trains of electrical pulses is described. The disadvantages of prior devices utilizing the two common methods of obtaining the count rate are overcome by this apparatus; in the case of time controlled operation, the disclosed system automatically records amy information stored by the scaler but not transferred to the printer at the end of the predetermined time controlled operations and, in the case of count controlled operation, provision is made to prevent a weak sample from occupying the apparatus for an excessively long period of time.

  9. Weak Lensing by Galaxy Troughs in DES Science Verification Data

    SciTech Connect

    Gruen, D.

    2015-09-29

    We measure the weak lensing shear around galaxy troughs, i.e. the radial alignment of background galaxies relative to underdensities in projections of the foreground galaxy field over a wide range of redshift in Science Verification data from the Dark Energy Survey. Our detection of the shear signal is highly significant (10σ–15σ for the smallest angular scales) for troughs with the redshift range z ϵ [0.2, 0.5] of the projected galaxy field and angular diameters of 10 arcmin…1°. These measurements probe the connection between the galaxy, matter density, and convergence fields. By assuming galaxies are biased tracers of the matter density with Poissonian noise, we find agreement of our measurements with predictions in a fiducial Λ cold dark matter model. Furthermore, the prediction for the lensing signal on large trough scales is virtually independent of the details of the underlying model for the connection of galaxies and matter. Our comparison of the shear around troughs with that around cylinders with large galaxy counts is consistent with a symmetry between galaxy and matter over- and underdensities. In addition, we measure the two-point angular correlation of troughs with galaxies which, in contrast to the lensing signal, is sensitive to galaxy bias on all scales. Finally, the lensing signal of troughs and their clustering with galaxies is therefore a promising probe of the statistical properties of matter underdensities and their connection to the galaxy field.

  10. Weak lensing by galaxy troughs in DES Science Verification data

    DOE PAGESBeta

    Gruen, D.; Friedrich, O.; Amara, A.; Bacon, D.; Bonnett, C.; Hartley, W.; Jain, B.; M. Jarvis; Kavprzak, T.; Krause, E.; et al

    2015-11-29

    In this study, we measure the weak lensing shear around galaxy troughs, i.e. the radial alignment of background galaxies relative to underdensities in projections of the foreground galaxy field over a wide range of redshift in Science Verification data from the Dark Energy Survey. Our detection of the shear signal is highly significant (10σ–15σ for the smallest angular scales) for troughs with the redshift range z ϵ [0.2, 0.5] of the projected galaxy field and angular diameters of 10 arcmin…1°. These measurements probe the connection between the galaxy, matter density, and convergence fields. By assuming galaxies are biased tracers ofmore » the matter density with Poissonian noise, we find agreement of our measurements with predictions in a fiducial Λ cold dark matter model. The prediction for the lensing signal on large trough scales is virtually independent of the details of the underlying model for the connection of galaxies and matter. Our comparison of the shear around troughs with that around cylinders with large galaxy counts is consistent with a symmetry between galaxy and matter over- and underdensities. In addition, we measure the two-point angular correlation of troughs with galaxies which, in contrast to the lensing signal, is sensitive to galaxy bias on all scales. The lensing signal of troughs and their clustering with galaxies is therefore a promising probe of the statistical properties of matter underdensities and their connection to the galaxy field.« less

  11. Weak lensing by galaxy troughs in DES Science Verification data

    SciTech Connect

    Gruen, D.; Friedrich, O.; Amara, A.; Bacon, D.; Bonnett, C.; Hartley, W.; Jain, B.; M. Jarvis; Kavprzak, T.; Krause, E.; Mana, A.; Rozo, E.; Rykoff, E. S.; Seitz, S.; Sheldon, E.; Troxel, M. A.; Vikram, V.; Abbott, T. M. C.; Abdalla, F. B.; Allam, S.; Armstrong, R.; Banerji, M.; Bauer, A. H.; Becker, M. R.; Benoit-Levy, A.; Bernstein, G. M.; Bernstein, R. A.; Bertin, E.; Bridle, S. L.; Brooks, D.; Buckley-Geer, E.; Burke, D. L.; Capozzi, D.; Rosell, A. Carnero; Carretero, J.; Crocce, M.; Cunha, C. E.; D'Andrea, C. B.; da Costa, L. N.; DePoy, D. L.; Desai, S.; Diehl, H. T.; Dietrich, J. P.; Doel, P.; Eifler, T. F.; Neto, A. Fausti; Fernandez, E.; Flaugher, B.; Fosalba, P.; Frieman, J.; Gerdes, D. W.; Gruendl, R. A.; Gutierrez, G.; Honscheid, K.; James, D. J.; Kuehn, K.; Kuropatkin, N.; Lahav, O.; Li, T. S.; Lima, M.; Maia, M. A. G.; March, M.; Martini, P.; Melchior, P.; Miller, C. J.; Miguel, R.; Mohr, J. J.; Nord, B.; Orgando, R.; Plazas, A. A.; Reil, K.; Romer, A. K.; Roodman, A.; Sako, M.; Sanchez, E.; Scarpine, V.; Schubnell, M.; Sevilla-Noarbe, I.; Smith, R. C.; Soares-Santos, M.; Sobreira, F.; Suchyta, E.; Swanson, M. E. C.; Tarle, G.; Thaler, J.; Thomas, D.; Walker, A. R.; Wechsler, R. H.; Weller, J.; Zhang, Y.; Zuntz, J.

    2015-11-29

    In this study, we measure the weak lensing shear around galaxy troughs, i.e. the radial alignment of background galaxies relative to underdensities in projections of the foreground galaxy field over a wide range of redshift in Science Verification data from the Dark Energy Survey. Our detection of the shear signal is highly significant (10σ–15σ for the smallest angular scales) for troughs with the redshift range z ϵ [0.2, 0.5] of the projected galaxy field and angular diameters of 10 arcmin…1°. These measurements probe the connection between the galaxy, matter density, and convergence fields. By assuming galaxies are biased tracers of the matter density with Poissonian noise, we find agreement of our measurements with predictions in a fiducial Λ cold dark matter model. The prediction for the lensing signal on large trough scales is virtually independent of the details of the underlying model for the connection of galaxies and matter. Our comparison of the shear around troughs with that around cylinders with large galaxy counts is consistent with a symmetry between galaxy and matter over- and underdensities. In addition, we measure the two-point angular correlation of troughs with galaxies which, in contrast to the lensing signal, is sensitive to galaxy bias on all scales. The lensing signal of troughs and their clustering with galaxies is therefore a promising probe of the statistical properties of matter underdensities and their connection to the galaxy field.

  12. Blood Count Tests

    MedlinePlus

    ... white blood cells (WBC), and platelets. Blood count tests measure the number and types of cells in ... helps doctors check on your overall health. The tests can also help to diagnose diseases and conditions ...

  13. Counting Knights and Knaves

    ERIC Educational Resources Information Center

    Levin,Oscar; Roberts, Gerri M.

    2013-01-01

    To understand better some of the classic knights and knaves puzzles, we count them. Doing so reveals a surprising connection between puzzles and solutions, and highlights some beautiful combinatorial identities.

  14. Galaxy Clusters

    NASA Astrophysics Data System (ADS)

    Miller, Christopher J. Miller

    2012-03-01

    There are many examples of clustering in astronomy. Stars in our own galaxy are often seen as being gravitationally bound into tight globular or open clusters. The Solar System's Trojan asteroids cluster at the gravitational Langrangian in front of Jupiter’s orbit. On the largest of scales, we find gravitationally bound clusters of galaxies, the Virgo cluster (in the constellation of Virgo at a distance of ˜50 million light years) being a prime nearby example. The Virgo cluster subtends an angle of nearly 8◦ on the sky and is known to contain over a thousand member galaxies. Galaxy clusters play an important role in our understanding of theUniverse. Clusters exist at peaks in the three-dimensional large-scale matter density field. Their sky (2D) locations are easy to detect in astronomical imaging data and their mean galaxy redshifts (redshift is related to the third spatial dimension: distance) are often better (spectroscopically) and cheaper (photometrically) when compared with the entire galaxy population in large sky surveys. Photometric redshift (z) [Photometric techniques use the broad band filter magnitudes of a galaxy to estimate the redshift. Spectroscopic techniques use the galaxy spectra and emission/absorption line features to measure the redshift] determinations of galaxies within clusters are accurate to better than delta_z = 0.05 [7] and when studied as a cluster population, the central galaxies form a line in color-magnitude space (called the the E/S0 ridgeline and visible in Figure 16.3) that contains galaxies with similar stellar populations [15]. The shape of this E/S0 ridgeline enables astronomers to measure the cluster redshift to within delta_z = 0.01 [23]. The most accurate cluster redshift determinations come from spectroscopy of the member galaxies, where only a fraction of the members need to be spectroscopically observed [25,42] to get an accurate redshift to the whole system. If light traces mass in the Universe, then the locations

  15. Fast counting electronics for neutron coincidence counting

    DOEpatents

    Swansen, James E.

    1987-01-01

    An amplifier-discriminator is tailored to output a very short pulse upon an above-threshold input from a detector which may be a .sup.3 He detector. The short pulse output is stretched and energizes a light emitting diode (LED) to provide a visual output of operation and pulse detection. The short pulse is further fed to a digital section for processing and possible ORing with other like generated pulses. Finally, the output (or ORed output ) is fed to a derandomizing buffer which converts the rapidly and randomly occurring pulses into synchronized and periodically spaced-apart pulses for the accurate counting thereof. Provision is also made for the internal and external disabling of each individual channel of amplifier-discriminators in an ORed plurality of same.

  16. Fast counting electronics for neutron coincidence counting

    DOEpatents

    Swansen, J.E.

    1985-03-05

    An amplifier-discriminator is tailored to output a very short pulse upon an above-threshold input from a detector which may be a /sup 3/He detector. The short pulse output is stretched and energizes a light emitting diode (LED) to provide a visual output of operation and pulse detection. The short pulse is further fed to a digital section for processing and possible ORing with other like generated pulses. Finally, the output (or ORed output) is fed to a derandomizing buffer which converts the rapidly and randomly occurring pulses into synchronized and periodically spaced-apart pulses for the accurate counting thereof. Provision is also made for the internal and external disabling of each individual channel of amplifier-discriminators in an ORed plurality of same.

  17. Whirlpool Galaxy

    NASA Technical Reports Server (NTRS)

    1999-01-01

    Scientists are seeing unprecedented detail of the spiral arms and dust clouds in the nearby Whirlpool galaxy, thanks to a new Hubble Space Telescope image, available at http://www.jpl.nasa.gov/pictures/wfpc/wfpc.html. The image uses data collected January 15 and 24, 1995, and July 21, 1999, by Hubble's Wide Field and Planetary Camera 2, designed and built by JPL. Using the image, a research group led by Dr. Nick Scoville of the California Institute of Technology, Pasadena, clearly defined the structure of the galaxy's cold dust clouds and hot hydrogen, and they linked star clusters within the galaxy to their parent dust clouds.

    The Whirlpool galaxy is one of the most photogenic galaxies. This celestial beauty is easily seen and photographed with smaller telescopes and studied extensively from large ground- and space-based observatories. The new composite image shows visible starlight and light from the emission of glowing hydrogen, which is associated with the most luminous young stars in the spiral arms.

    The galaxy is having a close encounter with a nearby companion galaxy, NGC 5195, just off the upper edge of the image. The companion's gravitational pull is triggering star formation in the main galaxy, lit up by numerous clusters of young and energetic stars in brilliant detail. Luminous clusters are highlighted in red by their associated emission from glowing hydrogen gas.

    This image was composed by the Hubble Heritage Team from Hubble archive data and was superimposed onto data taken by Dr. Travis Rector of the National Optical Astronomy Observatory at the .9-meter (35-inch) telescope at the National Science Foundation's Kitt Peak National Observatory, Tucson, Ariz. Scoville's team includes M. Polletta of the University of Geneva, Switzerland; S. Ewald and S. Stolovy of Caltech; and R. Thompson and M. Rieke of the University of Arizona, Tucson.

    The Space Telescope Science Institute, Baltimore, Md., manages space operations for the Hubble Space

  18. Photon counting digital holography

    NASA Astrophysics Data System (ADS)

    Demoli, Nazif; Skenderović, Hrvoje; Stipčević, Mario; Pavičić, Mladen

    2016-05-01

    Digital holography uses electronic sensors for hologram recording and numerical method for hologram reconstruction enabling thus the development of advanced holography applications. However, in some cases, the useful information is concealed in a very wide dynamic range of illumination intensities and successful recording requires an appropriate dynamic range of the sensor. An effective solution to this problem is the use of a photon-counting detector. Such detectors possess counting rates of the order of tens to hundreds of millions counts per second, but conditions of recording holograms have to be investigated in greater detail. Here, we summarize our main findings on this problem. First, conditions for optimum recording of digital holograms for detecting a signal significantly below detector's noise are analyzed in terms of the most important holographic measures. Second, for time-averaged digital holograms, optimum recordings were investigated for exposures shorter than the vibration cycle. In both cases, these conditions are studied by simulations and experiments.

  19. The high-redshift galaxy population in hierarchical galaxy formation models

    NASA Astrophysics Data System (ADS)

    Kitzbichler, M. G.; White, S. D. M.

    2007-03-01

    We compare observations of the high-redshift galaxy population to the predictions of the galaxy formation model of Croton et al. and De Lucia & Blaizot. This model, implemented on the Millennium Simulation of the concordance Lambda cold dark matter cosmogony, introduces `radio mode' feedback from the central galaxies of groups and clusters in order to obtain quantitative agreement with the luminosity, colour, morphology and clustering properties of the present-day galaxy population. Here we construct deep light cone surveys in order to compare model predictions to the observed counts and redshift distributions of distant galaxies, as well as to their inferred luminosity and mass functions out to redshift 5. With the exception of the mass functions, all these properties are sensitive to modelling of dust obscuration. A simple but plausible treatment agrees moderately well with most of the data. The predicted abundance of relatively massive (~M*) galaxies appears systematically high at high redshift, suggesting that such galaxies assemble earlier in this model than in the real Universe. An independent galaxy formation model implemented on the same simulation matches the observed mass functions slightly better, so the discrepancy probably reflects incomplete or inaccurate galaxy formation physics rather than problems with the underlying cosmogony.

  20. "Galaxy," Defined

    NASA Astrophysics Data System (ADS)

    Willman, B.; Strader, J.

    2012-09-01

    A growing number of low luminosity and low surface brightness astronomical objects challenge traditional notions of both galaxies and star clusters. To address this challenge, we propose a definition of galaxy that does not depend on a cold dark matter model of the universe: a galaxy is a gravitationally bound collection of stars whose properties cannot be explained by a combination of baryons and Newton's laws of gravity. After exploring several possible observational diagnostics of this definition, we critically examine the classification of ultra-faint dwarfs, globular clusters, ultra-compact dwarfs, and tidal dwarfs. While kinematic studies provide an effective diagnostic of the definition in many regimes, they can be less useful for compact or very faint systems. To explore the utility of using the [Fe/H] spread as a complementary diagnostic, we use published spectroscopic [Fe/H] measurements of 16 Milky Way dwarfs and 24 globular clusters to uniformly calculate their [Fe/H] spreads and associated uncertainties. Our principal results are (1) no known, old star cluster less luminous than MV = -10 has a significant (gsim0.1 dex) spread in its iron abundance; (2) known ultra-faint dwarf galaxies can be unambiguously classified with a combination of kinematic and [Fe/H] observations; (3) the observed [Fe/H] spreads in massive (gsim 106 M ⊙) globular clusters do not necessarily imply that they are the stripped nuclei of dwarfs, nor a need for dark matter; and (4) if ultra-compact dwarf galaxies reside in dark matter halos akin to those of ultra-faint dwarfs of the same half-light radii, then they will show no clear dynamical signature of dark matter. We suggest several measurements that may assist the future classification of massive globular clusters, ultra-compact dwarfs, and ultra-faint galaxies. Our galaxy definition is designed to be independent of the details of current observations and models, while our proposed diagnostics can be refined or replaced as

  1. Starburst Galaxy NGC 3310

    NASA Technical Reports Server (NTRS)

    1999-01-01

    Scientists using NASA's Hubble Space Telescope are studying the colors of star clusters to determine the age and history of starburst galaxies, a technique somewhat similar to the process of learning the age of a tree by counting its rings.

    This month's Hubble Heritage image showcases the galaxy NGC 3310. It is one of several starburst galaxies, which are hotbeds of star formation, being studied by Dr. Gerhardt Meurer and a team of scientists at Johns Hopkins University, Laurel, Md.

    The picture, taken by Hubble's Wide Field and Planetary Camera 2, is online at http://heritage.stsci.edu and http://oposite.stsci.edu/pubinfo/pr/2001/26 and http://www.jpl.nasa.gov/images/wfpc . The camera was designed and built by NASA's Jet Propulsion Laboratory, Pasadena, Calif.

    Most galaxies form new stars at a fairly slow rate, but starburst galaxies blaze with extremely active star formation. Measuring the clusters' colors yields information about stellar temperatures. Since young stars are blue and older stars redder, the colors relate to their ages.

    NGC 3310 is forming clusters of new stars at a prodigious rate. The new image shows several hundred star clusters, visible as the bright blue, diffuse objects that trace the galaxy's spiral arms. Each of these star clusters represents the formation of up to about a million stars, a process that takes less than 100,000 years. In addition, hundreds of individual young, luminous stars can be seen throughout the galaxy.

    The star clusters become redder with age as the most massive and bluest stars exhaust their fuel and burn out. Measurements in this image of the wide range of cluster colors show their ages range between about one million and more than one hundred million years. This suggests that the starburst 'turned on' more than 100 million years ago. It may have been triggered when NGC 3310 collided with a companion galaxy.

    These observations may change astronomers' view of starbursts. Starbursts were once

  2. What Counts as Evidence?

    ERIC Educational Resources Information Center

    Dougherty Stahl, Katherine A.

    2014-01-01

    Each disciplinary community has its own criteria for determining what counts as evidence of knowledge in their academic field. The criteria influence the ways that a community's knowledge is created, communicated, and evaluated. Situating reading, writing, and language instruction within the content areas enables teachers to explicitly…

  3. WY Kids Count.

    ERIC Educational Resources Information Center

    Wyoming Kids Count, Cheyenne.

    This WY Kids Count brochure uses the metaphor of children's building blocks to present information on the current well-being of Wyoming children and to advocate enhancing the lives of young children. Each block (i.e., each develop the brochure) presents concerns in a separate area: (1) poverty, highlighting the number of children living in…

  4. Counting Tech Prep Students.

    ERIC Educational Resources Information Center

    Barnett, Elizabeth

    2002-01-01

    Discusses the problems surrounding the counting of tech prep students. Suggests that one problem is the lack of a single definition for the term "tech prep." Suggests that if it is to be evaluated as a program, it needs more resources. (JOW)

  5. Accounting for What Counts

    ERIC Educational Resources Information Center

    Milner, Joseph O.; Ferran, Joan E.; Martin, Katharine Y.

    2003-01-01

    No Child Left Behind legislation makes it clear that outside evaluators determine what gets taught in the classroom. It is important to ensure they measure what truly counts in school. This fact is poignantly and sadly true for the under funded, poorly resourced, "low performing" schools that may be hammered by administration accountants in the…

  6. LOW ENERGY COUNTING CHAMBERS

    DOEpatents

    Hayes, P.M.

    1960-02-16

    A beta particle counter adapted to use an end window made of polyethylene terephthalate was designed. The extreme thinness of the film results in a correspondingly high transmission of incident low-energy beta particles by the window. As a consequence, the counting efficiency of the present counter is over 40% greater than counters using conventional mica end windows.

  7. Extragalatic zoo. I. [New galaxies

    SciTech Connect

    Schorn, R.A.

    1988-01-01

    The characteristics of various types of extragalactic objects are described. Consideration is given to cD galaxies, D galaxies, N galaxies, Markarian galaxies, liners, starburst galaxies, and megamasers. Emphasis is also placed on the isolated extragalatic H I region; the isolated extragalatic H II region; primeval galaxies or photogalaxies; peculiar galaxies; Arp galaxies; interacting galaxies; ring galaxies; and polar-ring galaxies. Diagrams of these objects are provided.

  8. Crashing galaxies, cosmic fireworks

    SciTech Connect

    Keel, W.C.

    1989-01-01

    The study of binary systems is reviewed. The history of the study of interacting galaxies, the behavior of gas in binary systems, studies to identify the processes that occur when galaxies interact, and the relationship of Seyfert galaxies and quasars to binary systems are discussed. The development of an atlas of peculiar galaxies (Arp, 1966) and methods for modeling galaxy interactions are examined.

  9. Hydrogen quantum yields in the 360 nm photolysis of Eu/2+/ solutions and their relationship to photochemical fuel formation

    NASA Technical Reports Server (NTRS)

    Ryason, P. R.

    1977-01-01

    Water decomposition by a cyclic photoredox process is discussed in general terms. Thermodynamics determines the wavelength of the charge-transfer band corresponding to electron transfer to or from water of hydration of a cation. These relationships indicate that it is unlikely that a photoreduction reaction resulting in water decomposition will occur in the sea-level solar range of wavelengths. Such is not the case for photooxidation, and an example is known: the photolysis of Eu(2+) in aqueous solution. Hydrogen quantum yields have been determined for this reaction. They are sufficiently high (about 0.3) as to offer encourangement for the further exploration of photoredox reactions as a means of solar energy conversion.

  10. Gamma-ray detected radio galaxies

    NASA Astrophysics Data System (ADS)

    Beckmann, Volker; Soldi, Simona; De Jong, Sandra; Kretschmer, Karsten; Savchenko, Volodymyr

    2016-07-01

    So far 15 radio galaxies have been detected in the gamma-ray domain by CGRO/EGRET and Fermi/LAT, with a few detections also in the VHE range. We search for distinguishing parameters and estimate the total number of gamma-ray emitting radio galaxies that are potentially detectable by Fermi/LAT. We use Fermi/LAT data in comparison with X-ray and hard X-ray data in order to constrain basic parameters such as the total power of the inverse Compton branch and the position of its peak. We search for possible correlations between the radio, UV, X-ray, and gamma-ray domain and derive the number counts distribution. We then compare their properties with those of the radio galaxies in the 3CRR and SMS4 catalogues. The data show no correlation between the peak of the inverse Compton emission and its luminosity. For the gamma-ray detected radio galaxies the luminosities in the various bands are correlated, except for the UV band, but there is no indication of a correlation of peak frequency or luminosity with the spectral slopes in the X-ray or gamma-ray band. The comparison with other bright radio galaxies shows that the gamma-ray detected objects are among those that have the largest X-ray but rather moderate radio fluxes. Their UV and X-ray luminosities are similar, but gamma-ray detected radio galaxies are predominantly of type FR-I, while the 3CRR sample contains mainly FR-II objects. The number counts of the so far gamma-ray detected radio galaxies shows a very shallow slope, indicating that potentially a fraction of radio galaxies has been missed so far or has not been identified as such, although the predicted number of 22 ± 7 is consistent with the observed 15 objects.

  11. Confronting dark energy models using galaxy cluster number counts

    SciTech Connect

    Basilakos, S.; Plionis, M.; Lima, J. A. S.

    2010-10-15

    The mass function of cluster-size halos and their redshift distribution are computed for 12 distinct accelerating cosmological scenarios and confronted to the predictions of the conventional flat {Lambda}CDM model. The comparison with {Lambda}CDM is performed by a two-step process. First, we determine the free parameters of all models through a joint analysis involving the latest cosmological data, using supernovae type Ia, the cosmic microwave background shift parameter, and baryon acoustic oscillations. Apart from a braneworld inspired cosmology, it is found that the derived Hubble relation of the remaining models reproduces the {Lambda}CDM results approximately with the same degree of statistical confidence. Second, in order to attempt to distinguish the different dark energy models from the expectations of {Lambda}CDM, we analyze the predicted cluster-size halo redshift distribution on the basis of two future cluster surveys: (i) an X-ray survey based on the eROSITA satellite, and (ii) a Sunayev-Zeldovich survey based on the South Pole Telescope. As a result, we find that the predictions of 8 out of 12 dark energy models can be clearly distinguished from the {Lambda}CDM cosmology, while the predictions of 4 models are statistically equivalent to those of the {Lambda}CDM model, as far as the expected cluster mass function and redshift distribution are concerned. The present analysis suggests that such a technique appears to be very competitive to independent tests probing the late time evolution of the Universe and the associated dark energy effects.

  12. COUNTS-IN-CYLINDERS IN THE SLOAN DIGITAL SKY SURVEY WITH COMPARISONS TO N-BODY SIMULATIONS

    SciTech Connect

    Berrier, Heather D.; Barton, Elizabeth J.; Bullock, James S.; Berrier, Joel C.; Zentner, Andrew R.; Wechsler, Risa H.

    2011-01-01

    Environmental statistics provide a necessary means of comparing the properties of galaxies in different environments, and a vital test of models of galaxy formation within the prevailing hierarchical cosmological model. We explore counts-in-cylinders, a common statistic defined as the number of companions of a particular galaxy found within a given projected radius and redshift interval. Galaxy distributions with the same two-point correlation functions do not necessarily have the same companion count distributions. We use this statistic to examine the environments of galaxies in the Sloan Digital Sky Survey Data Release 4 (SDSS DR4). We also make preliminary comparisons to four models for the spatial distributions of galaxies, based on N-body simulations and data from SDSS DR4, to study the utility of the counts-in-cylinders statistic. There is a very large scatter between the number of companions a galaxy has and the mass of its parent dark matter halo and the halo occupation, limiting the utility of this statistic for certain kinds of environmental studies. We also show that prevalent empirical models of galaxy clustering, that match observed two- and three-point clustering statistics well, fail to reproduce some aspects of the observed distribution of counts-in-cylinders on 1, 3, and 6 h{sup -1} Mpc scales. All models that we explore underpredict the fraction of galaxies with few or no companions in 3 and 6 h{sup -1} Mpc cylinders. Roughly 7% of galaxies in the real universe are significantly more isolated within a 6 h{sup -1} Mpc cylinder than the galaxies in any of the models we use. Simple phenomenological models that map galaxies to dark matter halos fail to reproduce high-order clustering statistics in low-density environments.

  13. Galaxy-galaxy(-galaxy) lensing as a sensitive probe of galaxy evolution

    NASA Astrophysics Data System (ADS)

    Saghiha, H.; Hilbert, S.; Schneider, P.; Simon, P.

    2012-11-01

    Context. The gravitational lensing effect provides various ways to study the mass environment of galaxies. Aims: We investigate how galaxy-galaxy(-galaxy) lensing can be used to test models of galaxy formation and evolution. Methods: We consider two semi-analytic galaxy formation models based on the Millennium Run N-body simulation: the Durham model by Bower et al. (2006, MNRAS, 370, 645) and the Garching model by Guo et al. (2011, MNRAS, 413, 101). We generate mock lensing observations for the two models, and then employ Fast Fourier Transform methods to compute second- and third-order aperture statistics in the simulated fields for various galaxy samples. Results: We find that both models predict qualitatively similar aperture signals, but there are large quantitative differences. The Durham model predicts larger amplitudes in general. In both models, red galaxies exhibit stronger aperture signals than blue galaxies. Using these aperture measurements and assuming a linear deterministic bias model, we measure relative bias ratios of red and blue galaxy samples. We find that a linear deterministic bias is insufficient to describe the relative clustering of model galaxies below ten arcmin angular scales. Dividing galaxies into luminosity bins, the aperture signals decrease with decreasing luminosity for brighter galaxies, but increase again for fainter galaxies. This increase is likely an artifact due to too many faint satellite galaxies in massive group and cluster halos predicted by the models. Conclusions: Our study shows that galaxy-galaxy(-galaxy) lensing is a sensitive probe of galaxy evolution.

  14. Galaxy formation.

    PubMed

    Peebles, P J

    1998-01-01

    It is argued that within the standard Big Bang cosmological model the bulk of the mass of the luminous parts of the large galaxies likely had been assembled by redshift z approximately 10. Galaxy assembly this early would be difficult to fit in the widely discussed adiabatic cold dark matter model for structure formation, but it could agree with an isocurvature version in which the cold dark matter is the remnant of a massive scalar field frozen (or squeezed) from quantum fluctuations during inflation. The squeezed field fluctuations would be Gaussian with zero mean, and the distribution of the field mass therefore would be the square of a random Gaussian process. This offers a possibly interesting new direction for the numerical exploration of models for cosmic structure formation.

  15. Galaxy formation

    PubMed Central

    Peebles, P. J. E.

    1998-01-01

    It is argued that within the standard Big Bang cosmological model the bulk of the mass of the luminous parts of the large galaxies likely had been assembled by redshift z ∼ 10. Galaxy assembly this early would be difficult to fit in the widely discussed adiabatic cold dark matter model for structure formation, but it could agree with an isocurvature version in which the cold dark matter is the remnant of a massive scalar field frozen (or squeezed) from quantum fluctuations during inflation. The squeezed field fluctuations would be Gaussian with zero mean, and the distribution of the field mass therefore would be the square of a random Gaussian process. This offers a possibly interesting new direction for the numerical exploration of models for cosmic structure formation. PMID:9419326

  16. Shaping galaxy evolution with galaxy structure

    NASA Astrophysics Data System (ADS)

    Cheung, Edmond

    A fundamental pursuit of astronomy is to understand galaxy evolution. The enormous scales and complex physics involved in this endeavor guarantees a never-ending journey that has enamored both astronomers and laymen alike. But despite the difficulty of this task, astronomers have still attempted to further this goal. Among of these astronomers is Edwin Hubble. His work, which includes the famous Hubble sequence, has immeasurably influenced our understanding of galaxy evolution. In this thesis, we present three works that continues Hubble's line of study by using galaxy structure to learn about galaxy evolution. First, we examine the dependence of galaxy quiescence on inner galactic structure with the AEGIS/ DEEP2 survey at 0.5In this thesis, we present three works that continues Hubble's line of study by using galaxy structure to learn about galaxy evolution. First, we examine the dependence of galaxy quiescence on inner galactic structure with the AEGIS/ DEEP2 survey at 0.5galaxies from quiescent galaxies. Our method indicates that the inner stellar mass is the most correlated parameter of quenching, implying that the process that quenches galaxies must also buildup their inner structure. Second, we explore the relationship between galactic bars and their host galaxies with Galaxy Zoo 2 at z˜0. The correlations of bar properties and galaxy properties are consistent with simulations of bar formation and evolution, indicating that bars affect their host galaxies. Finally, we investigate whether bars can drive supermassive black hole growth with data from Chandra and Galaxy Zoo: Hubble at 0.2galaxies to a matched sample of inactive, control galaxies shows that there is no statistically significant excess of bars in active hosts. Our result shows that bars are not the primary fueling mechanism of supermassive black hole

  17. Dwarf spheroidal galaxies: Keystones of galaxy evolution

    NASA Technical Reports Server (NTRS)

    Gallagher, John S., III; Wyse, Rosemary F. G.

    1994-01-01

    Dwarf spheroidal galaxies are the most insignificant extragalactic stellar systems in terms of their visibility, but potentially very significant in terms of their role in the formation and evolution of much more luminous galaxies. We discuss the present observational data and their implications for theories of the formation and evolution of both dwarf and giant galaxies. The putative dark-matter content of these low-surface-brightness systems is of particular interest, as is their chemical evolution. Surveys for new dwarf spheroidals hidden behind the stars of our Galaxy and those which are not bound to giant galaxies may give new clues as to the origins of this unique class of galaxy.

  18. Galaxies at High Redshift

    NASA Astrophysics Data System (ADS)

    Pérez-Fournon, I.; Balcells, M.; Moreno-Insertis, F.; Sánchez, F.

    2010-08-01

    Participants; Group photograph; Preface; Acknowledgements; 1. Galaxy formation and evolution: recent progress R. Ellis; 2. Galaxies at high redshift M. Dickinson; 3. High-redshift galaxies: the far-infrared and sub-millimeter view A. Franceschini; 4. Quasar absorption lines J. Bechtold; 5. Stellar population synthesis models at low and high redshift G. Bruzual A.; 6. Elliptical galaxies K. C. Freeman; 7. Disk galaxies K. C. Freeman; 8. Dark matter in disk galaxies K. C. Freeman.

  19. Galaxies Collide to Create Hot, Huge Galaxy

    NASA Technical Reports Server (NTRS)

    2009-01-01

    This image of a pair of colliding galaxies called NGC 6240 shows them in a rare, short-lived phase of their evolution just before they merge into a single, larger galaxy. The prolonged, violent collision has drastically altered the appearance of both galaxies and created huge amounts of heat turning NGC 6240 into an 'infrared luminous' active galaxy.

    A rich variety of active galaxies, with different shapes, luminosities and radiation profiles exist. These galaxies may be related astronomers have suspected that they may represent an evolutionary sequence. By catching different galaxies in different stages of merging, a story emerges as one type of active galaxy changes into another. NGC 6240 provides an important 'missing link' in this process.

    This image was created from combined data from the infrared array camera of NASA's Spitzer Space Telescope at 3.6 and 8.0 microns (red) and visible light from NASA's Hubble Space Telescope (green and blue).

  20. Galaxy NGC 55

    NASA Technical Reports Server (NTRS)

    2003-01-01

    This image of the nearby edge-on spiral galaxy NGC 55 was taken by Galaxy Evolution Explorer on September 14, 2003, during 2 orbits. This galaxy lies 5.4 million light years from our Milky Way galaxy and is a member of the 'local group' of galaxies that also includes the Andromeda galaxy (M31), the Magellanic clouds, and 40 other galaxies. The spiral disk of NGC 55 is inclined to our line of sight by approximately 80 degrees and so this galaxy looks cigar-shaped. This picture is a combination of Galaxy Evolution Explorer images taken with the far ultraviolet (colored blue) and near ultraviolet detectors, (colored red). The bright blue regions in this image are areas of active star formation detected in the ultraviolet by Galaxy Evolution Explorer. The red stars in this image are foreground stars in our own Milky Way galaxy.

  1. A unified multiwavelength model of galaxy formation

    NASA Astrophysics Data System (ADS)

    Lacey, Cedric G.; Baugh, Carlton M.; Frenk, Carlos S.; Benson, Andrew J.; Bower, Richard G.; Cole, Shaun; Gonzalez-Perez, Violeta; Helly, John C.; Lagos, Claudia D. P.; Mitchell, Peter D.

    2016-11-01

    We present a new version of the GALFORM semi-analytical model of galaxy formation. This brings together several previous developments of GALFORM into a single unified model, including a different initial mass function (IMF) in quiescent star formation and in starbursts, feedback from active galactic nuclei suppressing gas cooling in massive haloes, and a new empirical star formation law in galaxy discs based on their molecular gas content. In addition, we have updated the cosmology, introduced a more accurate treatment of dynamical friction acting on satellite galaxies, and updated the stellar population model. The new model is able to simultaneously explain both the observed evolution of the K-band luminosity function and stellar mass function, and the number counts and redshift distribution of sub-mm galaxies selected at 850 μm. This was not previously achieved by a single physical model within the Λcold dark matter framework, but requires having an IMF in starbursts that is somewhat top-heavy. The new model is tested against a wide variety of observational data covering wavelengths from the far-UV to sub-mm, and redshifts from z = 0 to 6, and is found to be generally successful. These observations include the optical and near-infrared (IR) luminosity functions, H I mass function, fraction of early type galaxies, Tully-Fisher, metallicity-luminosity and size-luminosity relations at z = 0, as well as far-IR number counts, and far-UV luminosity functions at z ˜ 3-6. Discrepancies are, however, found in galaxy sizes and metallicities at low luminosities, and in the abundance of low-mass galaxies at high-z, suggesting the need for a more sophisticated model of supernova feedback.

  2. Counting RG flows

    DOE PAGESBeta

    Gukov, Sergei

    2016-01-05

    Here, interpreting renormalization group flows as solitons interpolating between different fixed points, we ask various questions that are normally asked in soliton physics but not in renormalization theory. Can one count RG flows? Are there different "topological sectors" for RG flows? What is the moduli space of an RG flow, and how does it compare to familiar moduli spaces of (supersymmetric) dowain walls? Analyzing these questions in a wide variety of contexts -- from counting RG walls to AdS/CFT correspondence | will not only provide favorable answers, but will also lead us to a unified general framework that is powerfulmore » enough to account for peculiar RG flows and predict new physical phenomena. Namely, using Bott's version of Morse theory we relate the topology of conformal manifolds to certain properties of RG flows that can be used as precise diagnostics and "topological obstructions" for the strong form of the C-theorem in any dimension. Moreover, this framework suggests a precise mechanism for how the violation of the strong C-theorem happens and predicts "phase transitions" along the RG flow when the topological obstruction is non-trivial. Along the way, we also find new conformal manifolds in well-known 4d CFT's and point out connections with the superconformal index and classifying spaces of global symmetry groups.« less

  3. Galaxy groups

    SciTech Connect

    Brent Tully, R.

    2015-02-01

    Galaxy groups can be characterized by the radius of decoupling from cosmic expansion, the radius of the caustic of second turnaround, and the velocity dispersion of galaxies within this latter radius. These parameters can be a challenge to measure, especially for small groups with few members. In this study, results are gathered pertaining to particularly well-studied groups over four decades in group mass. Scaling relations anticipated from theory are demonstrated and coefficients of the relationships are specified. There is an update of the relationship between light and mass for groups, confirming that groups with mass of a few times 10{sup 12}M{sub ⊙} are the most lit up while groups with more and less mass are darker. It is demonstrated that there is an interesting one-to-one correlation between the number of dwarf satellites in a group and the group mass. There is the suggestion that small variations in the slope of the luminosity function in groups are caused by the degree of depletion of intermediate luminosity systems rather than variations in the number per unit mass of dwarfs. Finally, returning to the characteristic radii of groups, the ratio of first to second turnaround depends on the dark matter and dark energy content of the universe and a crude estimate can be made from the current observations of Ω{sub matter}∼0.15 in a flat topology, with a 68% probability of being less than 0.44.

  4. The origin of galaxies and clusters of galaxies.

    PubMed

    Peebles, P J

    1984-06-29

    Debate on how galaxies and clusters of galaxies formed has reached an interesting stage at which one can find arguments for quite different scenarios. The galaxy distribution has a complex "frothy" character that could be the fossil of a network of protoclusters or pancakes that produced galaxies. However, there are galaxies like our own that seem never to have been in a protocluster but are physically similar to the galaxies in dense clusters. Some clues to be assessed in resolving this dilemma are the possible existence of galaxy filaments, the relative ages of galaxies and clusters of galaxies, and the continuity between cluster and field galaxies and between galaxies and clusters of galaxies.

  5. The Herschel-ATLAS: Extragalatic Number Counts from 250 to 500 Microns

    NASA Technical Reports Server (NTRS)

    Clements, D. L.; Rigby, E.; Maddox, S.; Dunne, L.; Mortier, A.; Amblard, A.; Auld, R.; Bonfield, D.; Cooray, A.; Dariush, A.; Dye, S.; Eales, S.; Gardner, Jonathan P.; Ibar, E.; Ivison, R.; Leeuw, L.; Sibthorpe, B.; Smith, D. J. B.; Temi, P.; Pascale, E.; Pohlen, M.

    2010-01-01

    Aims.The Herschel-ATLAS survey (H-ATLAS) will be the largest area survey to be undertaken by the Herschel Space Observatory. It will cover 550 sq. deg. of extragalactic sky at wavelengths of 100, 160, 250, 350 and 500 microns when completed, reaching flux limits (50-) from 32 to 145mJy. We here present galaxy number counts obtained for SPIRE observations of the first -14 sq. deg. observed at 250, 350 and 500 m. Methods. Number counts are a fundamental tool in constraining models of galaxy evolution. We use source catalogs extracted from the H-ATLAS maps as the basis for such an analysis. Correction factors for completeness and flux boosting are derived by applying our extraction method to model catalogs and then applied to the raw observational counts. Results. We find a steep rise in the number counts at flux levels of 100-200mJy in all three SPIRE bands, consistent with results from BLAST. The counts are compared to a range of galaxy evolution models. None of the current models is an ideal fit to the data but all ascribe the steep rise to a population of luminous, rapidly evolving dusty galaxies at moderate to high redshift.

  6. Galaxy pairs in deep HST images: Evidence for evolution in the galaxy merger rate

    NASA Technical Reports Server (NTRS)

    Burkey, Jordan M.; Keel, William C.; Windhorst, Rogier A.; Franklin, Barbara E.

    1994-01-01

    We use four deep serendipitous fields observed with the Hubble Space Telescope (HST) Wide-Field Camera to constrain the rate of galaxy merging between the current epoch and z approximately equals 0.7. Since most mergers occur between members of bound pairs, the merger rate is given to a good approximation by (half) the rate of disappearance of galaxies in pairs. An objective criterion for pair membership shows that 34% +/- 9% of our HST galaxies with I = 18-22 belong to pairs, compared to 7% locally. This means that about 13% of the galaxy population has disappeared due to merging in the cosmic epoch corresponding to this magnitude interval (or 0.1 approximately less than z approximately less than 0.7). Our pair fraction is a lower limit: correction for pair members falling below our detection threshold might raise the fraction to approximately 50%. Since we address only two-galaxy merging, these values do not include physical systems of higher multiplicity. Incorporating I-band field-galaxy redshift distributions, the pair fraction grows with redshift as alpha(1 + z)(exp 3.5 +/- 0.5) and the merger rate as (1 + z)(exp 2.5 +/- 0.5). This may have significant implications for the interpretation of galaxy counts (disappearance of faint blue galaxies), the cosmological evolution of faint radio sources and quasars (which evolve approximately as (1 + z)(exp 3), the similarity in the power law is necessary but not sufficient evidence for a causal relation), statistics of QSO companions, the galaxy content in distant clusters, and the merging history of a 'typical' galaxy.

  7. Testing the MOND paradigm of modified dynamics with galaxy-galaxy gravitational lensing.

    PubMed

    Milgrom, Mordehai

    2013-07-26

    The MOND paradigm of modified dynamics predicts that the asymptotic gravitational potential of an isolated, bounded (baryonic) mass, M, is ϕ(r)=(MGa0)1/2ln(r). Relativistic MOND theories predict that the lensing effects of M are dictated by ϕ(r) as general-relativity lensing is dictated by the Newtonian potential. Thus MOND predicts that the asymptotic Newtonian potential deduced from galaxy-galaxy gravitational lensing will have (1) a logarithmic r dependence, and (2) a normalization (parametrized standardly as 2σ2) that depends only on M: σ=(MGa0/4)1/4. I compare these predictions with recent results of galaxy-galaxy lensing, and find agreement on all counts. For the “blue”-lenses subsample (“spiral” galaxies) MOND reproduces the observations well with an r′-band M/Lr′∼(1–3)(M/L)⊙, and for “red” lenses (“elliptical” galaxies) with M/Lr′∼(3–6)(M/L)⊙, both consistent with baryons only. In contradistinction, Newtonian analysis requires, typically, M/Lr′∼130(M/L)⊙, bespeaking a mass discrepancy of a factor ∼40. Compared with the staple, rotation-curve tests, MOND is here tested in a wider population of galaxies, through a different phenomenon, using relativistic test objects, and is probed to several-times-lower accelerations–as low as a few percent of a0. PMID:23931350

  8. The North Galactic Pole +30° Zone Galaxies. I. A Comparative Study of Galaxies with Different Nuclear Activity

    NASA Astrophysics Data System (ADS)

    Petrosian, Artashes; McLean, Brian; Allen, Ron; Kunth, Daniel; Leitherer, Claus

    2008-03-01

    A database containing 618 active and star-forming (A/SF) galaxies and 564 normal galaxies in a 120° × 6° wide strip crossing the north Galactic pole was constructed in order to compare the global properties of "active" galaxies against a control sample of "normal" galaxies. This database combines a literature and catalog search with new optical measurements from the Fpg (red) and Jpg (blue) band images of the STScI Digitized Sky Survey (DSS). We provide alternative names, accurate coordinates, morphological type, activity classes, red and blue apparent magnitudes, 2MASS near-infrared J-H and H-K colors, apparent diameters, axial ratios, position angles, and number counts of neighboring objects in a circle of radius 50 kpc. We also present an atlas of 103 interacting and merging systems among these galaxies. The integrated properties of A/SF and normal galaxies in this sample are compared using a multivariate factor analysis, which reveals that A/SF galaxies are objects with relatively late morphological types, and are more inclined and have bluer optical colors than normal galaxies. In this sample, all merging and interacting galaxies are A/SF objects. Star-forming galaxies are objects with relatively late morphological types, lower absolute luminosities and linear sizes, bluer colors, and higher inclination than sample X-ray or radio sources, as well as Seyfert galaxies. The near-infrared colors of the sample galaxies are independent parameters and do not correlate with activity level or any other parameter of the galaxies.

  9. Cinematique et dynamique des galaxies spirales barrees

    NASA Astrophysics Data System (ADS)

    Hernandez, Olivier

    The total mass (luminous and dark) of galaxies is derived from their circular velocities. Spectroscopic Fabry-Perot observations of the ionized gas component of spiral galaxies allow one to derive their kinematics. In the case of purely axisymmetric velocity fields--as in non-active and unbarred spirals galaxies-- the circular velocities can be derived directly. However, the velocity fields of barred galaxies (which constitute two thirds of the spirals) exhibit strong non-circular motions and need a careful analysis to retrieve the circular component. This thesis proposes the necessary steps to recover the axisymmetric component of barred spiral galaxies. The first step was to develop the best instrumentation possible for this work. [Special characters omitted.] , which is the most sensitive photon counting camera ever developed, was coupled to a Fabry-Perot interferometer. The observations of a sample of barred spiral galaxies--the BH a BAR sample--was assembled in order to obtain the most rigourous velocity fields. Then, the Tremaine-Weinberg method, which can determine the bar pattern speed and is usually used with the observations of stellar component, has been tested on the ionised gas and gave satisfactory results. Finally, all the above techniques have been applied to the BH a BAR sample in order to study the key parameters of the galaxies' evolution--bar pattern speeds, multiple stationary waves, resonances etc.--which will allow one to use N-body+SPH simulations to model properly the non-circular motions and determine the true total mass of barred spiral galaxies.

  10. Extracting Structural information from Galaxy Images

    NASA Astrophysics Data System (ADS)

    Hayes, Wayne B.; Davis, D.

    2010-05-01

    The amount of data from sky images is large and growing. About 1 million galaxies can be discerned in the Sloan Digital Sky Survey (SDSS). The Large Synoptic Survey Telescope (LSST) is being built and will scan the entire sky repeatedly, providing images of millions of galaxies and petabytes of data every night. The Joint Dark Energy Mission (JDEM) is a proposed orbiting satellite that will repeatedly map the entire sky from orbit, providing images of perhaps billions of galaxies. Unfortunately, given an image of a spiral galaxy, there does not exist an automated vision algorithm that can even tell us which direction the spiral arms wind, much less count them or provide any other quantitative information about them. To wit, the largest galaxy classification project is the Galaxy Zoo, in which thousands of human volunteers classify images by eye over the web. Although valuable, such human classifications will provide only limited objective quantitative measurements, and will soon be overwhelmed with more data than humans can handle. However, such information would prove an invaluable source for astronomers and cosmologists to test current theories of galaxy formation and cosmic evolution (which can now be simulated with high accuracy on large computers, producing copious predictions that cannot be tested due to a lack of objective, quantitative observational data). In this talk, I will report on preliminary results from dynamical grammars and other machine learning and vision techniques to "parse" images of galaxies, starting us on the road towards producing quantitative data that will be useful for astronomers to test theories.

  11. Information of Structures in Galaxy Distribution

    NASA Astrophysics Data System (ADS)

    Fang, Fan

    2006-06-01

    We introduce an information-theoretic measure, the Rényi information, to describe the galaxy distribution in space. We discuss properties of the information measure and demonstrate its relationship with the probability distribution function and multifractal descriptions. Using the First Look Survey galaxy samples observed by the Infrared Array Camera on board the Spitzer Space Telescope, we present measurements of the Rényi information, as well as the counts-in-cells distribution and multifractal properties of galaxies in mid-infrared wavelengths. Guided by a multiplicative cascade simulation based on a binomial model, we verify our measurements and discuss the spatial selection effects on measuring information of the spatial structures. We derive structure scan functions at scales where selection effects are small for the Spitzer samples. We discuss the results and the potential of applying the Rényi information to the measurement of other spatial structures.

  12. The Radio Luminosity Function and Galaxy Evolution of Abell 2256

    NASA Astrophysics Data System (ADS)

    Forootaninia, Zahra

    2015-05-01

    This thesis presents a study of the radio luminosity function and the evolution of galaxies in the Abell 2256 cluster (z=0.058, richness class 2). Using the NED database and VLA deep data with an rms sensitivity of 18 mu Jy.beam--1, we identified 257 optical galaxies as members of A2256, of which 83 are radio galaxies. Since A2256 is undergoing a cluster-cluster merger, it is a good candidate to study the radio activity of galaxies in the cluster. We calculated the Univariate and Bivariate radio luminosity functions for A2256, and compared the results to studies on other clusters. We also used the SDSS parameter fracDev to roughly classify galaxies as spirals and ellipticals, and investigated the distribution and structure of galaxies in the cluster. We found that most of the radio galaxies in A2256 are faint, and are distributed towards the outskirts of the cluster. On the other hand, almost all very bright radio galaxies are ellipticals which are located at the center of the cluster. We also found there is an excess in the number of radio spiral galaxies in A2256 compared to the number of radio ellipticals, counting down to a radio luminosity of log(luminosity)=20.135 W/Hz..

  13. Shape analysis of counts maps

    NASA Astrophysics Data System (ADS)

    Klatt, M. A.; Göring, D.; Stegmann, C.; Mecke, K.

    2012-12-01

    A novel approach for source detection via structural deviations from the typical features of a random background counts map is presented. Minkowski functionals, powerful tools from integral geometry, quantify the shape of level sets of a counts map. Compared to standard techniques, which use the total number of counts only, additional morphometric information is incorporated without the need for any prior knowledge about the source. Minkowski sky maps quantify local structural deviations; they localize and visualize potential sources.

  14. Making environmental DNA count.

    PubMed

    Kelly, Ryan P

    2016-01-01

    The arc of reception for a new technology or method--like the reception of new information itself--can pass through predictable stages, with audiences' responses evolving from 'I don't believe it', through 'well, maybe' to 'yes, everyone knows that' to, finally, 'old news'. The idea that one can sample a volume of water, sequence DNA out of it, and report what species are living nearby has experienced roughly this series of responses among biologists, beginning with the microbial biologists who developed genetic techniques to reveal the unseen microbiome. 'Macrobial' biologists and ecologists--those accustomed to dealing with species they can see and count--have been slower to adopt such molecular survey techniques, in part because of the uncertain relationship between the number of recovered DNA sequences and the abundance of whole organisms in the sampled environment. In this issue of Molecular Ecology Resources, Evans et al. (2015) quantify this relationship for a suite of nine vertebrate species consisting of eight fish and one amphibian. Having detected all of the species present with a molecular toolbox of six primer sets, they consistently find DNA abundances are associated with species' biomasses. The strength and slope of this association vary for each species and each primer set--further evidence that there is no universal parameter linking recovered DNA to species abundance--but Evans and colleagues take a significant step towards being able to answer the next question audiences tend to ask: 'Yes, but how many are there?' PMID:26768195

  15. Making environmental DNA count.

    PubMed

    Kelly, Ryan P

    2016-01-01

    The arc of reception for a new technology or method--like the reception of new information itself--can pass through predictable stages, with audiences' responses evolving from 'I don't believe it', through 'well, maybe' to 'yes, everyone knows that' to, finally, 'old news'. The idea that one can sample a volume of water, sequence DNA out of it, and report what species are living nearby has experienced roughly this series of responses among biologists, beginning with the microbial biologists who developed genetic techniques to reveal the unseen microbiome. 'Macrobial' biologists and ecologists--those accustomed to dealing with species they can see and count--have been slower to adopt such molecular survey techniques, in part because of the uncertain relationship between the number of recovered DNA sequences and the abundance of whole organisms in the sampled environment. In this issue of Molecular Ecology Resources, Evans et al. (2015) quantify this relationship for a suite of nine vertebrate species consisting of eight fish and one amphibian. Having detected all of the species present with a molecular toolbox of six primer sets, they consistently find DNA abundances are associated with species' biomasses. The strength and slope of this association vary for each species and each primer set--further evidence that there is no universal parameter linking recovered DNA to species abundance--but Evans and colleagues take a significant step towards being able to answer the next question audiences tend to ask: 'Yes, but how many are there?'

  16. Star Formation in Irregular Galaxies.

    ERIC Educational Resources Information Center

    Hunter, Deidre; Wolff, Sidney

    1985-01-01

    Examines mechanisms of how stars are formed in irregular galaxies. Formation in giant irregular galaxies, formation in dwarf irregular galaxies, and comparisons with larger star-forming regions found in spiral galaxies are considered separately. (JN)

  17. Compton suppression gamma-counting: The effect of count rate

    USGS Publications Warehouse

    Millard, H.T.

    1984-01-01

    Past research has shown that anti-coincidence shielded Ge(Li) spectrometers enhanced the signal-to-background ratios for gamma-photopeaks, which are situated on high Compton backgrounds. Ordinarily, an anti- or non-coincidence spectrum (A) and a coincidence spectrum (C) are collected simultaneously with these systems. To be useful in neutron activation analysis (NAA), the fractions of the photopeak counts routed to the two spectra must be constant from sample to sample to variations must be corrected quantitatively. Most Compton suppression counting has been done at low count rate, but in NAA applications, count rates may be much higher. To operate over the wider dynamic range, the effect of count rate on the ratio of the photopeak counts in the two spectra (A/C) was studied. It was found that as the count rate increases, A/C decreases for gammas not coincident with other gammas from the same decay. For gammas coincident with other gammas, A/C increases to a maximum and then decreases. These results suggest that calibration curves are required to correct photopeak areas so quantitative data can be obtained at higher count rates. ?? 1984.

  18. Combining Galaxy-Galaxy Lensing and Galaxy Clustering

    SciTech Connect

    Park, Youngsoo; Krause, Elisabeth; Dodelson, Scott; Jain, Bhuvnesh; Amara, Adam; Becker, Matt; Bridle, Sarah; Clampitt, Joseph; Crocce, Martin; Honscheid, Klaus; Gaztanaga, Enrique; Sanchez, Carles; Wechsler, Risa

    2015-01-01

    Combining galaxy-galaxy lensing and galaxy clustering is a promising method for inferring the growth rate of large scale structure, a quantity that will shed light on the mechanism driving the acceleration of the Universe. The Dark Energy Survey (DES) is a prime candidate for such an analysis, with its measurements of both the distribution of galaxies on the sky and the tangential shears of background galaxies induced by these foreground lenses. By constructing an end-to-end analysis that combines large-scale galaxy clustering and small-scale galaxy-galaxy lensing, we also forecast the potential of a combined probes analysis on DES datasets. In particular, we develop a practical approach to a DES combined probes analysis by jointly modeling the assumptions and systematics affecting the different components of the data vector, employing a shared halo model, HOD parametrization, photometric redshift errors, and shear measurement errors. Furthermore, we study the effect of external priors on different subsets of these parameters. We conclude that DES data will provide powerful constraints on the evolution of structure growth in the universe, conservatively/ optimistically constraining the growth function to 8%/4.9% with its first-year data covering 1000 square degrees, and to 4%/2.3% with its full five-year data covering 5000 square degrees.

  19. Galaxies as gravitational lenses.

    PubMed

    Barnothy, J; Barnothy, M F

    1968-10-18

    Of all the galaxies in the visible part of the universe, 500 million are seen through intervening galaxies. In some instances the foreground galaxy will act as a gravitational lens and produce distorted and (in brightness) greatly amplified images of the galaxy behind it; such images may simulate starlike superluminous objects such as quasars (quasi-stellar objects). The number of gravitational lenses is several times greater than the number of quasars yet observed. In other instances the superposition of the image upon a visible foreground galaxy may simulate morphological configurations resembling N-type, dumbbell, spiral, or barred-spiral galaxies. PMID:17836654

  20. THE GALAXY POPULATION OF LOW-REDSHIFT ABELL CLUSTERS

    SciTech Connect

    Barkhouse, Wayne A.; Yee, H. K. C.; Lopez-Cruz, Omar E-mail: hyee@astro.utoronto.c

    2009-10-01

    We present a study of the luminosity and color properties of galaxies selected from a sample of 57 low-redshift Abell clusters. We utilize the non-parametric dwarf-to-giant ratio (DGR) and the blue galaxy fraction (f{sub b} ) to investigate the clustercentric radial-dependent changes in the cluster galaxy population. Composite cluster samples are combined by scaling the counting radius by r {sub 200} to minimize radius selection bias. The separation of galaxies into a red and blue population was achieved by selecting galaxies relative to the cluster color-magnitude relation. The DGR of the red and blue galaxies is found to be independent of cluster richness (B {sub gc}), although the DGR is larger for the blue population at all measured radii. A decrease in the DGR for the red and red+blue galaxies is detected in the cluster core region, while the blue galaxy DGR is nearly independent of radius. The f{sub b} is found not to correlate with B {sub gc}; however, a steady decline toward the inner-cluster region is observed for the giant galaxies. The dwarf galaxy f{sub b} is approximately constant with clustercentric radius except for the inner-cluster core region where f{sub b} decreases. The clustercentric radial dependence of the DGR and the galaxy blue fraction indicates that it is unlikely that a simple scenario based on either pure disruption or pure fading/reddening can describe the evolution of infalling dwarf galaxies; both outcomes are produced by the cluster environment.

  1. A New Method for Calculating Counts in Cells

    NASA Astrophysics Data System (ADS)

    Szapudi, István

    1998-04-01

    In the near future, a new generation of CCD-based galaxy surveys will enable high-precision determination of the N-point correlation functions. The resulting information will help to resolve the ambiguities associated with two-point correlation functions, thus constraining theories of structure formation, biasing, and Gaussianity of initial conditions independently of the value of Ω. As one of the most successful methods of extracting the amplitude of higher order correlations is based on measuring the distribution of counts in cells, this work presents an advanced way of measuring it with unprecedented accuracy. Szapudi & Colombi identified the main sources of theoretical errors in extracting counts in cells from galaxy catalogs. One of these sources, termed as measurement error, stems from the fact that conventional methods use a finite number of sampling cells to estimate counts in cells. This effect can be circumvented by using an infinite number of cells. This paper presents an algorithm, which in practice achieves this goal; that is, it is equivalent to throwing an infinite number of sampling cells in finite time. The errors associated with sampling cells are completely eliminated by this procedure, which will be essential for the accurate analysis of future surveys.

  2. A Zoo of Galaxies

    NASA Astrophysics Data System (ADS)

    Masters, Karen L.

    2015-03-01

    We live in a universe filled with galaxies with an amazing variety of sizes and shapes. One of the biggest challenges for astronomers working in this field is to understand how all these types relate to each other in the background of an expanding universe. Modern astronomical surveys (like the Sloan Digital Sky Survey) have revolutionised this field of astronomy, by providing vast numbers of galaxies to study. The sheer size of the these databases made traditional visual classification of the types galaxies impossible and in 2007 inspired the Galaxy Zoo project (www.galaxyzoo.org); starting the largest ever scientific collaboration by asking members of the public to help classify galaxies by type and shape. Galaxy Zoo has since shown itself, in a series of now more than 30 scientific papers, to be a fantastic database for the study of galaxy evolution. In this Invited Discourse I spoke a little about the historical background of our understanding of what galaxies are, of galaxy classification, about our modern view of galaxies in the era of large surveys. I finish with showcasing some of the contributions galaxy classifications from the Galaxy Zoo project are making to our understanding of galaxy evolution.

  3. Neutral Hydrogen in Local Group Dwarf Galaxies

    NASA Astrophysics Data System (ADS)

    Grcevich, Jana

    The gas content of the faintest and lowest mass dwarf galaxies provide means to study the evolution of these unique objects. The evolutionary histories of low mass dwarf galaxies are interesting in their own right, but may also provide insight into fundamental cosmological problems. These include the nature of dark matter, the disagreement between the number of observed Local Group dwarf galaxies and that predicted by lambda cold dark matter models, and the discrepancy between the observed census of baryonic matter in the Milky Way's environment and theoretical predictions. This thesis explores these questions by studying the neutral hydrogen (HI) component of dwarf galaxies. First, limits on the HI mass of the ultra-faint dwarfs are presented, and the HI content of all Local Group dwarf galaxies is examined from an environmental standpoint. We find that those Local Group dwarfs within 270 kpc of a massive host galaxy are deficient in HI as compared to those at larger galactocentric distances. Ram-pressure arguments are invoked, which suggest halo densities greater than 2-3 x 10-4 cm-3 out to distances of at least 70 kpc, values which are consistent with theoretical models and suggest the halo may harbor a large fraction of the host galaxy's baryons. We also find that accounting for the incompleteness of the dwarf galaxy count, known dwarf galaxies whose gas has been removed could have provided at most 2.1 x 108 M⊙ of HI gas to the Milky Way. Second, we examine the possibility of discovering unknown gas-rich ultra-faint galaxies in the Local Group using HI. The GALFA-HI Survey catalog is searched for compact, isolated HI clouds which are most similar to the expected HI characteristics of low mass dwarf galaxies. Fifty-one Local Group dwarf galaxy candidates are identified through column density, brightness temperature, and kinematic selection criteria, and their properties are explored. Third, we present hydrodynamic simulations of dwarf galaxies experiencing a

  4. Young Children Counting at Home

    ERIC Educational Resources Information Center

    Griffiths, Rose

    2007-01-01

    Learning to count is something that most children start to do by the time they are about two, and parents know from first-hand experience that family members play a big part in helping with this complex process. In this article, the author describes a project involving families sharing effective counting activities. The project called "Getting…

  5. Hanford whole body counting manual

    SciTech Connect

    Palmer, H.E.; Brim, C.P.; Rieksts, G.A.; Rhoads, M.C.

    1987-05-01

    This document, a reprint of the Whole Body Counting Manual, was compiled to train personnel, document operation procedures, and outline quality assurance procedures. The current manual contains information on: the location, availability, and scope of services of Hanford's whole body counting facilities; the administrative aspect of the whole body counting operation; Hanford's whole body counting facilities; the step-by-step procedure involved in the different types of in vivo measurements; the detectors, preamplifiers and amplifiers, and spectroscopy equipment; the quality assurance aspect of equipment calibration and recordkeeping; data processing, record storage, results verification, report preparation, count summaries, and unit cost accounting; and the topics of minimum detectable amount and measurement accuracy and precision. 12 refs., 13 tabs.

  6. The Origins of Counting Algorithms

    PubMed Central

    Cantlon, Jessica F.; Piantadosi, Steven T.; Ferrigno, Stephen; Hughes, Kelly D.; Barnard, Allison M.

    2015-01-01

    Humans’ ability to ‘count’ by verbally labeling discrete quantities is unique in animal cognition. The evolutionary origins of counting algorithms are not understood. We report that non-human primates exhibit a cognitive ability that is algorithmically and logically similar to human counting. Monkeys were given the task of choosing between two food caches. Monkeys saw one cache baited with some number of food items, one item at a time. Then, a second cache was baited with food items, one at a time. At the point when the second set approximately outnumbered the first set, monkeys spontaneously moved to choose the second set even before it was completely baited. Using a novel Bayesian analysis, we show that monkeys used an approximate counting algorithm to increment and compare quantities in sequence. This algorithm is structurally similar to formal counting in humans and thus may have been an important evolutionary precursor to human counting. PMID:25953949

  7. Star Formation in Galaxies

    NASA Technical Reports Server (NTRS)

    1987-01-01

    Topics addressed include: star formation; galactic infrared emission; molecular clouds; OB star luminosity; dust grains; IRAS observations; galactic disks; stellar formation in Magellanic clouds; irregular galaxies; spiral galaxies; starbursts; morphology of galactic centers; and far-infrared observations.

  8. Galaxy NGC 300

    NASA Technical Reports Server (NTRS)

    2003-01-01

    This image of the nearby spiral galaxy NGC 300 was taken by Galaxy Evolution Explorer in a single orbit exposure of 27 minutes on October 10, 2003. NGC 300 lies 7 million light years from our Milky Way galaxy and is one of a group of galaxies in the constellation Sculptor. NGC 300 is often used as a prototype of a spiral galaxy because in optical images it displays flowing spiral arms and a bright central region of older (and thus redder) stars. The Galaxy Evolution Explorer image taken in ultraviolet light shows us that NGC 300 is an efficient star-forming galaxy. The bright blue regions in the Galaxy Evolution Explorer image reveal new stars forming all the way into the nucleus of NGC 300.

  9. Experimenting with galaxies

    NASA Technical Reports Server (NTRS)

    Miller, Richard H.

    1992-01-01

    A study to demonstrate how the dynamics of galaxies may be investigated through the creation of galaxies within a computer model is presented. The numerical technique for simulating galaxies is shown to be both highly efficient and highly robust. Consideration is given to the anatomy of a galaxy, the gravitational N-body problem, numerical approaches to the N-body problem, use of the Poisson equation, and the symplectic integrator.

  10. SUBMILLIMETER NUMBER COUNTS FROM STATISTICAL ANALYSIS OF BLAST MAPS

    SciTech Connect

    Patanchon, Guillaume; Ade, Peter A. R.; Griffin, Matthew; Hargrave, Peter C.; Mauskopf, Philip; Moncelsi, Lorenzo; Pascale, Enzo; Bock, James J.; Chapin, Edward L.; Halpern, Mark; Marsden, Gaelen; Scott, Douglas; Devlin, Mark J.; Dicker, Simon R.; Klein, Jeff; Rex, Marie; Gundersen, Joshua O.; Hughes, David H.; Netterfield, Calvin B.; Olmi, Luca

    2009-12-20

    We describe the application of a statistical method to estimate submillimeter galaxy number counts from confusion-limited observations by the Balloon-borne Large Aperture Submillimeter Telescope (BLAST). Our method is based on a maximum likelihood fit to the pixel histogram, sometimes called 'P(D)', an approach which has been used before to probe faint counts, the difference being that here we advocate its use even for sources with relatively high signal-to-noise ratios. This method has an advantage over standard techniques of source extraction in providing an unbiased estimate of the counts from the bright end down to flux densities well below the confusion limit. We specifically analyze BLAST observations of a roughly 10 deg{sup 2} map centered on the Great Observatories Origins Deep Survey South field. We provide estimates of number counts at the three BLAST wavelengths 250, 350, and 500 mum; instead of counting sources in flux bins we estimate the counts at several flux density nodes connected with power laws. We observe a generally very steep slope for the counts of about -3.7 at 250 mum, and -4.5 at 350 and 500 mum, over the range approx0.02-0.5 Jy, breaking to a shallower slope below about 0.015 Jy at all three wavelengths. We also describe how to estimate the uncertainties and correlations in this method so that the results can be used for model-fitting. This method should be well suited for analysis of data from the Herschel satellite.

  11. LENSING NOISE IN MILLIMETER-WAVE GALAXY CLUSTER SURVEYS

    SciTech Connect

    Hezaveh, Yashar; Vanderlinde, Keith; Holder, Gilbert; De Haan, Tijmen

    2013-08-01

    We study the effects of gravitational lensing by galaxy clusters of the background of dusty star-forming galaxies (DSFGs) and the cosmic microwave background (CMB), and examine the implications for Sunyaev-Zel'dovich-based (SZ) galaxy cluster surveys. At the locations of galaxy clusters, gravitational lensing modifies the probability distribution of the background flux of the DSFGs as well as the CMB. We find that, in the case of a single-frequency 150 GHz survey, lensing of DSFGs leads both to a slight increase ({approx}10%) in detected cluster number counts (due to a {approx}50% increase in the variance of the DSFG background, and hence an increased Eddington bias) and a rare (occurring in {approx}2% of clusters) 'filling-in' of SZ cluster signals by bright strongly lensed background sources. Lensing of the CMB leads to a {approx}55% reduction in CMB power at the location of massive galaxy clusters in a spatially matched single-frequency filter, leading to a net decrease in detected cluster number counts. We find that the increase in DSFG power and decrease in CMB power due to lensing at cluster locations largely cancel, such that the net effect on cluster number counts for current SZ surveys is subdominant to Poisson errors.

  12. FAINT END OF 1.3 mm NUMBER COUNTS REVEALED BY ALMA

    SciTech Connect

    Hatsukade, Bunyo; Ohta, Kouji; Seko, Akifumi; Yabe, Kiyoto; Akiyama, Masayuki

    2013-06-01

    We present the faint end of number counts at 1.3 mm (238 GHz) obtained with the Atacama Large Millimeter/submillimeter Array (ALMA). Band 6 observations were carried out targeting 20 star-forming galaxies at z ∼ 1.4 in the Subaru/XMM-Newton Deep Survey field. In the observations, we serendipitously detect 15 sources (≥3.8σ, S{sub 1.3} {sub mm} = 0.15-0.61 mJy) other than the targeted sources. We create number counts by using these ''sub-mJy sources'', which probe the faintest flux range among surveys at millimeter wavelengths. The number counts are consistent with (flux-scaled) number counts at 850 μm and 870 μm obtained with gravitational lensing clusters. The ALMA number counts agree well with model predictions, which suggest that these sub-mJy populations are more like ''normal'' star-forming galaxies than ''classical'' submillimeter galaxies with intense star-forming activity. In this flux range, ∼80% of the extragalactic background light at 1.3 mm is resolved into individual sources.

  13. Cosmology with velocity dispersion counts: an alternative to measuring cluster halo masses

    NASA Astrophysics Data System (ADS)

    Caldwell, C. E.; McCarthy, I. G.; Baldry, I. K.; Collins, C. A.; Schaye, J.; Bird, S.

    2016-11-01

    The evolution of galaxy cluster counts is a powerful probe of several fundamental cosmological parameters. A number of recent studies using this probe have claimed tension with the cosmology preferred by the analysis of the Planck primary cosmic microwave background (CMB) data, in the sense that there are fewer clusters observed than predicted based on the primary CMB cosmology. One possible resolution to this problem is systematic errors in the absolute halo mass calibration in cluster studies, which is required to convert the standard theoretical prediction (the halo mass function) into counts as a function of the observable (e.g. X-ray luminosity, Sunyaev-Zel'dovich flux, and optical richness). Here we propose an alternative strategy, which is to directly compare predicted and observed cluster counts as a function of the one-dimensional velocity dispersion of the cluster galaxies. We argue that the velocity dispersion of groups/clusters can be theoretically predicted as robustly as mass but, unlike mass, it can also be directly observed, thus circumventing the main systematic bias in traditional cluster counts studies. With the aid of the BAHAMAS suite of cosmological hydrodynamical simulations, we demonstrate the potential of the velocity dispersion counts for discriminating even similar Λ cold dark matter models. These predictions can be compared with the results from existing redshift surveys such as the highly complete Galaxy And Mass Assembly survey, and upcoming wide-field spectroscopic surveys such as the Wide Area Vista Extragalactic Survey and the Dark Energy Survey Instrument.

  14. The origins of counting algorithms.

    PubMed

    Cantlon, Jessica F; Piantadosi, Steven T; Ferrigno, Stephen; Hughes, Kelly D; Barnard, Allison M

    2015-06-01

    Humans' ability to count by verbally labeling discrete quantities is unique in animal cognition. The evolutionary origins of counting algorithms are not understood. We report that nonhuman primates exhibit a cognitive ability that is algorithmically and logically similar to human counting. Monkeys were given the task of choosing between two food caches. First, they saw one cache baited with some number of food items, one item at a time. Then, a second cache was baited with food items, one at a time. At the point when the second set was approximately equal to the first set, the monkeys spontaneously moved to choose the second set even before that cache was completely baited. Using a novel Bayesian analysis, we show that the monkeys used an approximate counting algorithm for comparing quantities in sequence that is incremental, iterative, and condition controlled. This proto-counting algorithm is structurally similar to formal counting in humans and thus may have been an important evolutionary precursor to human counting. PMID:25953949

  15. White blood cell counting system

    NASA Technical Reports Server (NTRS)

    1972-01-01

    The design, fabrication, and tests of a prototype white blood cell counting system for use in the Skylab IMSS are presented. The counting system consists of a sample collection subsystem, sample dilution and fluid containment subsystem, and a cell counter. Preliminary test results show the sample collection and the dilution subsystems are functional and fulfill design goals. Results for the fluid containment subsystem show the handling bags cause counting errors due to: (1) adsorption of cells to the walls of the container, and (2) inadequate cleaning of the plastic bag material before fabrication. It was recommended that another bag material be selected.

  16. Low surface brightness galaxies

    NASA Technical Reports Server (NTRS)

    Vanderhulst, J. M.; Deblok, W. J. G.; Mcgaugh, S. S.; Bothun, G. D.

    1993-01-01

    A program to investigate the properties of low surface brightness (LSB) galaxies involving surface photometry in U, B, V, R, I, and H-alpha, HI imaging with the Westerbork Synthesis Radio Telescope (WSRT) and the very large array (VLA) and spectrophotometry of H2 regions in LSB galaxies is underway. The goal is to verify the idea that LSB galaxies have low star formation rates because the local gas density falls below the critical density for star formation, and to study the stellar population and abundances in LSB galaxies. Such information should help understanding the evolutionary history of LSB galaxies. Some preliminary results are reported.

  17. Segregation properties of galaxies

    SciTech Connect

    Santiago, B.X.; Da Costa, L.N. )

    1990-10-01

    Using the recently completed Southern Sky Redshift Survey, in conjunction with measurements of the central surface brightness, the existence of segregation in the way galaxies of different morphology and surface brightness are distributed in space is investigated. Results indicate that there is some evidence that low surface brightness galaxies are more randomly distributed than brighter ones and that this effect is independent of the well-known tendency of early-type galaxies to cluster more strongly than spirals. Presuming that the observed clustering was established at the epoch of galaxy formation, it may provide circumstantial evidence for biased galaxy formation. 24 refs.

  18. Galaxies as gravitational lenses.

    PubMed

    Sadeh, D

    1967-12-01

    The probability that a galaxy gathers light from another remote galaxy, and deflects and focuses it toward an observer on Earth, is calculated according to various cosmologic models. I pose the question of whether an object called a quasar is a single, intrinsically luminous entity or the result of accidental alignment, along the line of sight, of two normal galaxies, the more distant of which has its light amplified by the gravitational-lens effect of the nearer galaxy. If galaxies are distributed at random in the universe, the former alternative is true. But, if we assume that most galaxies exist in pairs, we can find about 30 galaxies occurring exactly one behind the other in such a way as to enable amplification of the order of 50. This model explains also the variations in intensity in quasars, but fails to explain others of their observed properties. PMID:17734305

  19. How Do Galaxies Grow?

    NASA Astrophysics Data System (ADS)

    2008-08-01

    Astronomers have caught multiple massive galaxies in the act of merging about 4 billion years ago. This discovery, made possible by combining the power of the best ground- and space-based telescopes, uniquely supports the favoured theory of how galaxies form. ESO PR Photo 24/08 ESO PR Photo 24/08 Merging Galaxies in Groups How do galaxies form? The most widely accepted answer to this fundamental question is the model of 'hierarchical formation', a step-wise process in which small galaxies merge to build larger ones. One can think of the galaxies forming in a similar way to how streams merge to form rivers, and how these rivers, in turn, merge to form an even larger river. This theoretical model predicts that massive galaxies grow through many merging events in their lifetime. But when did their cosmological growth spurts finish? When did the most massive galaxies get most of their mass? To answer these questions, astronomers study massive galaxies in clusters, the cosmological equivalent of cities filled with galaxies. "Whether the brightest galaxies in clusters grew substantially in the last few billion years is intensely debated. Our observations show that in this time, these galaxies have increased their mass by 50%," says Kim-Vy Tran from the University of Zürich, Switzerland, who led the research. The astronomers made use of a large ensemble of telescopes and instruments, including ESO's Very Large Telescope (VLT) and the Hubble Space Telescope, to study in great detail galaxies located 4 billion light-years away. These galaxies lie in an extraordinary system made of four galaxy groups that will assemble into a cluster. In particular, the team took images with VIMOS and spectra with FORS2, both instruments on the VLT. From these and other observations, the astronomers could identify a total of 198 galaxies belonging to these four groups. The brightest galaxies in each group contain between 100 and 1000 billion of stars, a property that makes them comparable

  20. Counting Triangles to Sum Squares

    ERIC Educational Resources Information Center

    DeMaio, Joe

    2012-01-01

    Counting complete subgraphs of three vertices in complete graphs, yields combinatorial arguments for identities for sums of squares of integers, odd integers, even integers and sums of the triangular numbers.

  1. Complete Blood Count (For Parents)

    MedlinePlus

    ... KidsHealth in the Classroom What Other Parents Are Reading Upsetting News Reports? What to Say Vaccines: Which ... Metabolic Panel (BMP) Blood Test: Hemoglobin Basic Blood Chemistry Tests Word! Complete Blood Count (CBC) Medical Tests ...

  2. THE ORIENTATION OF GALAXIES IN GALAXY CLUSTERS

    SciTech Connect

    Godlowski, Wlodzimierz; Piwowarska, Paulina; Panko, Elena; Flin, Piotr E-mail: paoletta@interia.p E-mail: sfflin@cyf-kr.edu.p

    2010-11-10

    We present an analysis of the spatial orientations of galaxies in 247 optically selected rich Abell clusters which have at least 100 members in the considered area. We investigated the relation between angles that give information about galaxy angular momenta and the number of members in each structure. The position angles of the galaxies' major axes, as well as two angles describing the spatial orientation of the galaxy plane, were tested for isotropy by applying three different statistical tests. It is found that the values of the statistics increase with the amount of the galaxies' members, which is equivalent to the existence of a relation between anisotropy and the number of galaxies in a cluster. The search for connection between the galaxies' alignments and Bautz-Morgan (BM) morphological types of examined clusters showed a weak dependence. A statistically marginal relation between velocity dispersion and cluster richness was observed. In addition, it was found that the velocity dispersion decreases with BM type at almost 3{sigma} level. These results show the dependence of alignments with respect to clusters' richness, which can be regarded as an environmental effect.

  3. Using Galaxy Winds to Constrain Galaxy Evolution

    NASA Astrophysics Data System (ADS)

    Churchill, Christopher W.; Klypin, A.; Ceverino, D.; Kacprzak, G.; Klimek, E.

    2010-01-01

    Analysis of mock quasar spectra of metal absorption lines in the proximity of formed galaxies in cosmological simulation is a highly promising for understanding the role of galaxies in IGM physics, or IGM physics in the role of galaxy formation in context of the cosmic web. Such analysis using neutral hydrogen in the cosmic web has literally revolutionized our understanding of the Lyman alpha forest. We are undertaking a wholesale approach to use powerful Lambda-CDM simulations to interpret absorption line data from redshift 1-3 starbursting galaxies e.g. Lyman break galaxies, etc) The data with which direct quantitative comparison is made are from the DEEP survey (Weiner et al.) and the collective work of Steidel et al. and collaborators. The simulations are performed using the Eulerian Gasdynamics plus N-body Adaptive Refinement Tree (ART) code, which has gas cell resolutions of 20-50 pc. Physical processes implemented in the code include realistic radiative cooling, star formation, metal enrichment and thermal feedback due to type II and type Ia supernovae. We quantitatively compare the spatial and kinematic distribution of HI, MgII, CIV, and OVI of absorption lines over a range of impact parameters for various simulated galaxies as a function of redshift, and discuss key insights for interpreting the underlying temperature, density, and ionization structure of the halo/cosmic-web interface, and the influence of galaxies on its chemical enrichment.

  4. Counting on Using a Number Game

    ERIC Educational Resources Information Center

    Betts, Paul

    2015-01-01

    Counting all and counting on are distinct counting strategies that can be used to compute such quantities as the total number of objects in two sets (Wright, Martland, and Stafford 2010). Given five objects and three more objects, for example, children who use counting all to determine quantity will count both collections; that is, they count…

  5. Standardization of 241Am by digital coincidence counting, liquid scintillation counting and defined solid angle counting.

    PubMed

    Balpardo, C; Capoulat, M E; Rodrigues, D; Arenillas, P

    2010-01-01

    The nuclide (241)Am decays by alpha emission to (237)Np. Most of the decays (84.6%) populate the excited level of (237)Np with energy of 59.54 keV. Digital coincidence counting was applied to standardize a solution of (241)Am by alpha-gamma coincidence counting with efficiency extrapolation. Electronic discrimination was implemented with a pressurized proportional counter and the results were compared with two other independent techniques: Liquid scintillation counting using the logical sum of double coincidences in a TDCR array and defined solid angle counting taking into account activity inhomogeneity in the active deposit. The results show consistency between the three methods within a limit of a 0.3%. An ampoule of this solution will be sent to the International Reference System (SIR) during 2009. Uncertainties were analysed and compared in detail for the three applied methods. PMID:20031433

  6. Standardization of 241Am by digital coincidence counting, liquid scintillation counting and defined solid angle counting.

    PubMed

    Balpardo, C; Capoulat, M E; Rodrigues, D; Arenillas, P

    2010-01-01

    The nuclide (241)Am decays by alpha emission to (237)Np. Most of the decays (84.6%) populate the excited level of (237)Np with energy of 59.54 keV. Digital coincidence counting was applied to standardize a solution of (241)Am by alpha-gamma coincidence counting with efficiency extrapolation. Electronic discrimination was implemented with a pressurized proportional counter and the results were compared with two other independent techniques: Liquid scintillation counting using the logical sum of double coincidences in a TDCR array and defined solid angle counting taking into account activity inhomogeneity in the active deposit. The results show consistency between the three methods within a limit of a 0.3%. An ampoule of this solution will be sent to the International Reference System (SIR) during 2009. Uncertainties were analysed and compared in detail for the three applied methods.

  7. Galaxy NGC 247

    NASA Technical Reports Server (NTRS)

    2003-01-01

    This image of the dwarf spiral galaxy NGC 247 was taken by Galaxy Evolution Explorer on October 13, 2003, in a single orbit exposure of 1600 seconds. The region that looks like a 'hole' in the upper part of the galaxy is a location with a deficit of gas and therefore a lower star formation rate and ultraviolet brightness. Optical images of this galaxy show a bright star on the southern edge. This star is faint and red in the Galaxy Evolution Explorer ultraviolet image, revealing that it is a foreground star in our Milky Way galaxy. The string of background galaxies to the North-East (upper left) of NGC 247 is 355 million light years from our Milky Way galaxy whereas NGC 247 is a mere 9 million light years away. The faint blue light that can be seen in the Galaxy Evolution Explorer image of the upper two of these background galaxies may indicate that they are in the process of merging together.

  8. Galaxy redshift surveys with sparse sampling

    SciTech Connect

    Chiang, Chi-Ting; Wullstein, Philipp; Komatsu, Eiichiro; Jee, Inh; Jeong, Donghui; Blanc, Guillermo A.; Ciardullo, Robin; Gronwall, Caryl; Hagen, Alex; Schneider, Donald P.; Drory, Niv; Fabricius, Maximilian; Landriau, Martin; Finkelstein, Steven; Jogee, Shardha; Cooper, Erin Mentuch; Tuttle, Sarah; Gebhardt, Karl; Hill, Gary J.

    2013-12-01

    Survey observations of the three-dimensional locations of galaxies are a powerful approach to measure the distribution of matter in the universe, which can be used to learn about the nature of dark energy, physics of inflation, neutrino masses, etc. A competitive survey, however, requires a large volume (e.g., V{sub survey} ∼ 10Gpc{sup 3}) to be covered, and thus tends to be expensive. A ''sparse sampling'' method offers a more affordable solution to this problem: within a survey footprint covering a given survey volume, V{sub survey}, we observe only a fraction of the volume. The distribution of observed regions should be chosen such that their separation is smaller than the length scale corresponding to the wavenumber of interest. Then one can recover the power spectrum of galaxies with precision expected for a survey covering a volume of V{sub survey} (rather than the volume of the sum of observed regions) with the number density of galaxies given by the total number of observed galaxies divided by V{sub survey} (rather than the number density of galaxies within an observed region). We find that regularly-spaced sampling yields an unbiased power spectrum with no window function effect, and deviations from regularly-spaced sampling, which are unavoidable in realistic surveys, introduce calculable window function effects and increase the uncertainties of the recovered power spectrum. On the other hand, we show that the two-point correlation function (pair counting) is not affected by sparse sampling. While we discuss the sparse sampling method within the context of the forthcoming Hobby-Eberly Telescope Dark Energy Experiment, the method is general and can be applied to other galaxy surveys.

  9. STEALTH GALAXIES IN THE HALO OF THE MILKY WAY

    SciTech Connect

    Bullock, James S.; Stewart, Kyle R.; Kaplinghat, Manoj; Tollerud, Erik J.; Wolf, Joe

    2010-07-10

    We predict that there is a population of low-luminosity dwarf galaxies orbiting within the halo of the Milky Way (MW) that have surface brightnesses low enough to have escaped detection in star-count surveys. The overall count of stealth galaxies is sensitive to the presence (or lack) of a low-mass threshold in galaxy formation. These systems have luminosities and stellar velocity dispersions that are similar to those of known ultrafaint dwarf galaxies but they have more extended stellar distributions (half-light radii greater than about 100 pc) because they inhabit dark subhalos that are slightly less massive than their higher surface brightness counterparts. As a result, the typical peak surface brightness is fainter than 30 mag arcsec{sup -2}. One implication is that the inferred common mass scale for MW dwarfs may be an artifact of selection bias. If there is no sharp threshold in galaxy formation at low halo mass, then ultrafaint galaxies like Segue 1 represent the high-mass, early-forming tail of a much larger population of objects that could number in the hundreds and have typical peak circular velocities of about 8 km s{sup -1} and masses within 300 pc of about 5 million solar masses. Alternatively, if we impose a low-mass threshold in galaxy formation in order to explain the unexpectedly high densities of the ultrafaint dwarfs, then we expect only a handful of stealth galaxies in the halo of the MW. A complete census of these objects will require deeper sky surveys, 30 m class follow-up telescopes, and more refined methods to identify extended, self-bound groupings of stars in the halo.

  10. Stealth Galaxies in the Halo of the Milky Way

    NASA Astrophysics Data System (ADS)

    Bullock, James S.; Stewart, Kyle R.; Kaplinghat, Manoj; Tollerud, Erik J.; Wolf, Joe

    2010-07-01

    We predict that there is a population of low-luminosity dwarf galaxies orbiting within the halo of the Milky Way (MW) that have surface brightnesses low enough to have escaped detection in star-count surveys. The overall count of stealth galaxies is sensitive to the presence (or lack) of a low-mass threshold in galaxy formation. These systems have luminosities and stellar velocity dispersions that are similar to those of known ultrafaint dwarf galaxies but they have more extended stellar distributions (half-light radii greater than about 100 pc) because they inhabit dark subhalos that are slightly less massive than their higher surface brightness counterparts. As a result, the typical peak surface brightness is fainter than 30 mag arcsec-2. One implication is that the inferred common mass scale for MW dwarfs may be an artifact of selection bias. If there is no sharp threshold in galaxy formation at low halo mass, then ultrafaint galaxies like Segue 1 represent the high-mass, early-forming tail of a much larger population of objects that could number in the hundreds and have typical peak circular velocities of about 8 km s-1 and masses within 300 pc of about 5 million solar masses. Alternatively, if we impose a low-mass threshold in galaxy formation in order to explain the unexpectedly high densities of the ultrafaint dwarfs, then we expect only a handful of stealth galaxies in the halo of the MW. A complete census of these objects will require deeper sky surveys, 30 m class follow-up telescopes, and more refined methods to identify extended, self-bound groupings of stars in the halo.

  11. On the Morphology of the HST Faint Galaxies

    NASA Astrophysics Data System (ADS)

    Giavalisco, Mauro; Livio, Mario; Bohlin, Ralph C.; Macchetto, F. Duccio; Stecher, Theodore P.

    1996-08-01

    Deep imaging with the Hubble Space Telescope (HST) has revealed a population of rapidly evolving galaxies, which account for < 50% of the total counts at I <~ 22.5, are well distinct from the passively evolving normal ellipticals and spirals, and have morphologies that elude the traditional Hubble classification scheme. This classification has been derived from the morphological properties of local galaxies observed at optical wavelengths. Since galaxy morphology is a function of the wavelength and of the localization and intensity of the star-formation activity, the appearance of galaxies at large redshifts is subject to k- correction and evolutionary effects of the stellar populations, even if the underlying dynamics does not change significantly. In addition, the strong dependence of the surface brightness on redshift as σ ~(1 +z)^-4^ implies that the observed morphology of distant galaxies is also affected by the limiting surface brightness that can be reached. This paper shows how local galaxies observed at UV wavelengths with the Ultraviolet Imaging Telescope (UIT) would appear to HST if placed at cosmological distances, with the UV light redshifted to the optical wavelengths. The simulated distant galaxies have morphologies that are of later type or more irregular than their local (optical) counterparts, and some are in qualitative agreement with those revealed by the faint HST surveys, suggesting that dynamical evolution has played a minor role in the evolution of the majority of the galaxies over a large fraction of the Hubble time. However, the dependence of galaxy morphology on the star-formation activity and on the wavelength must be properly understood before any conclusion on the overall morphological evolution of galaxies can be derived.

  12. Magnification bias corrections to galaxy-lensing cross-correlations

    SciTech Connect

    Ziour, Riad; Hui, Lam

    2008-12-15

    Galaxy-galaxy or galaxy-quasar lensing can provide important information on the mass distribution in the Universe. It consists of correlating the lensing signal (either shear or magnification) of a background galaxy/quasar sample with the number density of a foreground galaxy sample. However, the foreground galaxy density is inevitably altered by the magnification bias due to the mass between the foreground and the observer, leading to a correction to the observed galaxy-lensing signal. The aim of this paper is to quantify this correction. The single most important determining factor is the foreground redshift z{sub f}: the correction is small if the foreground galaxies are at low redshifts but can become non-negligible for sufficiently high redshifts. For instance, we find that for the multipole l=1000, the correction is above 1%x(5s{sub f}-2)/b{sub f} for z{sub f} > or approx. 0.37, and above 5%x(5s{sub f}-2)/b{sub f} for z{sub f} > or approx. 0.67, where s{sub f} is the number count slope of the foreground sample and b{sub f} its galaxy bias. These considerations are particularly important for geometrical measures, such as the Jain and Taylor ratio or its generalization by Zhang et al. Assuming (5s{sub f}-2)/b{sub f}=1, we find that the foreground redshift should be limited to z{sub f} < or approx. 0.45 in order to avoid biasing the inferred dark energy equation of state w by more than 5%, and that even for a low foreground redshift (<0.45), the background samples must be well separated from the foreground to avoid incurring a bias of similar magnitude. Lastly, we briefly comment on the possibility of obtaining these geometrical measures without using galaxy shapes, using instead magnification bias itself.

  13. Reproducing the assembly of massive galaxies within the hierarchical cosmogony

    NASA Astrophysics Data System (ADS)

    Fontanot, Fabio; Monaco, Pierluigi; Silva, Laura; Grazian, Andrea

    2007-12-01

    In order to gain insight into the physical mechanisms leading to the formation of stars and their assembly in galaxies, we compare the predictions of the MOdel for the Rise of GAlaxies aNd Active nuclei (MORGANA) to the properties of K- and 850-μm-selected galaxies (such as number counts, redshift distributions and luminosity functions) by combining MORGANA with the spectrophotometric model GRASIL. We find that it is possible to reproduce the K- and 850-μm-band data sets at the same time and with a standard Salpeter initial mass function, and ascribe this success to our improved modelling of cooling in DM haloes. We then predict that massively star-forming discs are common at z ~ 2 and dominate the star formation rate, but most of them merge with other galaxies within ~100 Myr. Our preferred model produces an overabundance of bright galaxies at z < 1; this overabundance might be connected to the build-up of the diffuse stellar component in galaxy clusters, as suggested by Monaco et al., but a naive implementation of the mechanism suggested in that paper does not produce a sufficient slowdown of the evolution of these objects. Moreover, our model overpredicts the number of 1010-1011Msolar galaxies at z ~ 1; this is a common behaviour of theoretical models as shown by Fontana et al.. These findings show that, while the overall build-up of the stellar mass is correctly reproduced by galaxy formation models, the `downsizing' trend of galaxies is not fully reproduced yet. This hints to some missing feedback mechanism in order to reproduce at the same time the formation of both the massive and the small galaxies.

  14. Hanford whole body counting manual

    SciTech Connect

    Palmer, H.E.; Rieksts, G.A.; Lynch, T.P.

    1990-06-01

    This document describes the Hanford Whole Body Counting Program as it is administered by Pacific Northwest Laboratory (PNL) in support of the US Department of Energy--Richland Operations Office (DOE-RL) and its Hanford contractors. Program services include providing in vivo measurements of internally deposited radioactivity in Hanford employees (or visitors). Specific chapters of this manual deal with the following subjects: program operational charter, authority, administration, and practices, including interpreting applicable DOE Orders, regulations, and guidance into criteria for in vivo measurement frequency, etc., for the plant-wide whole body counting services; state-of-the-art facilities and equipment used to provide the best in vivo measurement results possible for the approximately 11,000 measurements made annually; procedures for performing the various in vivo measurements at the Whole Body Counter (WBC) and related facilities including whole body counts; operation and maintenance of counting equipment, quality assurance provisions of the program, WBC data processing functions, statistical aspects of in vivo measurements, and whole body counting records and associated guidance documents. 16 refs., 48 figs., 22 tabs.

  15. The Hawaii SCUBA-2 Lensing Cluster Survey: Number Counts and Submillimeter Flux Ratios

    NASA Astrophysics Data System (ADS)

    Hsu, Li-Yen; Cowie, Lennox L.; Chen, Chian-Chou; Barger, Amy J.; Wang, Wei-Hao

    2016-09-01

    We present deep number counts at 450 and 850 μm using the SCUBA-2 camera on the James Clerk Maxwell Telescope. We combine data for six lensing cluster fields and three blank fields to measure the counts over a wide flux range at each wavelength. Thanks to the lensing magnification, our measurements extend to fluxes fainter than 1 mJy and 0.2 mJy at 450 μm and 850 μm, respectively. Our combined data highly constrain the faint end of the number counts. Integrating our counts shows that the majority of the extragalactic background light (EBL) at each wavelength is contributed by faint sources with L IR < 1012 L ⊙, corresponding to luminous infrared galaxies (LIRGs) or normal galaxies. By comparing our result with the 500 μm stacking of K-selected sources from the literature, we conclude that the K-selected LIRGs and normal galaxies still cannot fully account for the EBL that originates from sources with L IR < 1012 L ⊙. This suggests that many faint submillimeter galaxies may not be included in the UV star formation history. We also explore the submillimeter flux ratio between the two bands for our 450 μm and 850 μm selected sources. At 850 μm, we find a clear relation between the flux ratio and the observed flux. This relation can be explained by a redshift evolution, where galaxies at higher redshifts have higher luminosities and star formation rates. In contrast, at 450 μm, we do not see a clear relation between the flux ratio and the observed flux.

  16. Galaxy NGC5474

    NASA Technical Reports Server (NTRS)

    2003-01-01

    NASA's Galaxy Evolution Explorer took this ultraviolet color image of the galaxy NGC5474 on June 7, 2003. NGC5474 is located 20 million light-years from Earth and is within a group of galaxies dominated by the Messier 101 galaxy. Star formation in this galaxy shows some evidence of a disturbed spiral pattern, which may have been induced by tidal interactions with Messier 101.

    The Galaxy Evolution Explorer mission is led by the California Institute of Technology, which is also responsible for the science operations and data analysis. NASA's Jet Propulsion Laboratory, Pasadena, Calif., a division of Caltech, manages the mission and built the science instrument. The mission was developed under NASA's Explorers Program, managed by the Goddard Space Flight Center, Greenbelt, Md. The mission's international partners include South Korea and France.

  17. Deep infrared galaxies

    NASA Technical Reports Server (NTRS)

    Ashby, Matthew; Houck, J. R.; Hacking, Perry B.

    1992-01-01

    High signal-to-noise ratio optical spectra of 17 infrared-bright emission-line galaxies near the north ecliptic pole are presented. Reddening-corrected line ratios forbidden O III 5007/H-beta, N II 6583/H-alpha, S II (6716 + 6731)/H-alpha, and O I 6300/H-alpha are used to discriminate between candidate energy generation mechanisms in each galaxy. These criteria have frequently been applied to optically selected samples of galaxies in the past, but this is the first time they have been applied to a set of faint flux-limited infrared-selected objects. The analysis indicates the sample contains seven starburst galaxies and three (AGN). However, seven galaxies in the present sample elude the classification scheme based on these line ratios. It is concluded that a two-component (starburst plus AGN) model for energy generation is inadequate for infrared galaxies.

  18. Classic Galaxy with Glamour

    NASA Technical Reports Server (NTRS)

    2005-01-01

    This color composite image of nearby NGC 300 combines the visible-light pictures from Carnegie Institution of Washington's 100-inch telescope at Las Campanas Observatory (colored red and yellow), with ultraviolet views from NASA's Galaxy Evolution Explorer. Galaxy Evolution Explorer detectors image far ultraviolet light (colored blue).

    This composite image traces star formation in progress. Young hot blue stars dominate the outer spiral arms of the galaxy, while the older stars congregate in the nuclear regions which appear yellow-green. Gases heated by hot young stars and shocks due to winds from massive stars and supernova explosions appear in pink, as revealed by the visible-light image of the galaxy.

    Located nearly 7 million light years away, NGC 300 is a member of a nearby group of galaxies known as the Sculptor Group. It is a spiral galaxy like our own Milky Way.

  19. Tidal Dwarf Galaxies

    NASA Astrophysics Data System (ADS)

    Duc, P.-A.; Mirabel, I. F.; Brinks, E.

    The life and evolution of galaxies are dramatically affected by environmental effects. Interactions with the intergalactic medium and collisions with companions cause major perturbations in the morphology and contents of galaxies: in particular stars and gas clouds may be gravitationally pulled out from their parent galaxies during tidal encounters, forming rings, tails and bridges. This debris of collisions lies at the origin of a new generation of small galaxies, the so-called "tidal dwarf galaxies" (TDGs). The authors have carried out multi-wavelength observations of some 20 TDGs. These systems are made of two stellar components: young stars, formed from the recent collapse of expelled H I clouds, and an older stellar population, tidally pulled out from the disks of their interacting parent galaxies. In the observed TDGs, the current star formation episode is fuelled by a large reservoir of H I gas and is younger than 10 Myr.

  20. Cosmological measurements with general relativistic galaxy correlations

    NASA Astrophysics Data System (ADS)

    Raccanelli, Alvise; Montanari, Francesco; Bertacca, Daniele; Doré, Olivier; Durrer, Ruth

    2016-05-01

    We investigate the cosmological dependence and the constraining power of large-scale galaxy correlations, including all redshift-distortions, wide-angle, lensing and gravitational potential effects on linear scales. We analyze the cosmological information present in the lensing convergence and in the gravitational potential terms describing the so-called ``relativistic effects'', and we find that, while smaller than the information contained in intrinsic galaxy clustering, it is not negligible. We investigate how neglecting them does bias cosmological measurements performed by future spectroscopic and photometric large-scale surveys such as SKA and Euclid. We perform a Fisher analysis using the CLASS code, modified to include scale-dependent galaxy bias and redshift-dependent magnification and evolution bias. Our results show that neglecting relativistic terms, especially lensing convergence, introduces an error in the forecasted precision in measuring cosmological parameters of the order of a few tens of percent, in particular when measuring the matter content of the Universe and primordial non-Gaussianity parameters. The analysis suggests a possible substantial systematic error in cosmological parameter constraints. Therefore, we argue that radial correlations and integrated relativistic terms need to be taken into account when forecasting the constraining power of future large-scale number counts of galaxy surveys.

  1. The onset of galactic winds in early-type galaxies

    NASA Technical Reports Server (NTRS)

    Forman, W.; Jones, C.; Tucker, W.; David, L. P.

    1990-01-01

    Researchers report on a program using Einstein x ray observations of the x ray spectra and surface brightness profiles (or extents) of a large sample of early-type (elliptical and SO) galaxies for which the goal is to determine the critical optical luminosity for which galactic winds are important. For galaxies in which the x ray emission is dominated by hydrostatic coronae, the x ray spectra will be relatively soft (characterized by a temperature of approx. 10 to the 7th power K), while for galaxies with a galactic wind, the emission will be dominated by the spectrally harder discrete sources (since the x ray emission from the wind is essentially negligible). In this new sample of 180 galaxies, there are 28 early type galaxies with sufficient counts to obtain a spectrum with the Einstein Image Proportional Counter (IPC). This sample more than doubles the total number of early-type galaxies in earlier compilations (Forman, Jones, and Tucker 1985; Canizares et al. 1987). The new spectral observations will help determine the critical optical luminosity for the onset of galactic winds which is important for understanding the chemical evolution of galaxies and of the intergalactic medium. The implications of galactic winds for the heavy element enrichment and energy content of the intracluster medium are discussed.

  2. The environment of barred galaxies in the low-redshift universe

    SciTech Connect

    Lin, Ye; Sodi, Bernardo Cervantes; Li, Cheng; Wang, Lixin; Wang, Enci E-mail: leech@shao.ac.cn

    2014-12-01

    We present a study of the environment of barred galaxies using a volume-limited sample of over 30,000 galaxies drawn from the Sloan Digital Sky Survey. We use four different statistics to quantify the environment: the projected two-point cross-correlation function, the background-subtracted number count of neighbor galaxies, the overdensity of the local environment, and the membership of our galaxies to galaxy groups to segregate central and satellite systems. For barred galaxies as a whole, we find a very weak difference in all the quantities compared to unbarred galaxies of the control sample. When we split our sample into early- and late-type galaxies, we see a weak but significant trend for early-type galaxies with a bar to be more strongly clustered on scales from a few 100 kpc to 1 Mpc when compared to unbarred early-type galaxies. This indicates that the presence of a bar in early-type galaxies depends on the location within their host dark matter halos. This is confirmed by the group catalog in the sense that for early-types, the fraction of central galaxies is smaller if they have a bar. For late-type galaxies, we find fewer neighbors within ∼50 kpc around the barred galaxies when compared to unbarred galaxies from the control sample, suggesting that tidal forces from close companions suppress the formation/growth of bars. Finally, we find no obvious correlation between overdensity and the bars in our sample, showing that galactic bars are not obviously linked to the large-scale structure of the universe.

  3. Finding the First Galaxies

    NASA Technical Reports Server (NTRS)

    Gardner, Jonathan P.

    2009-01-01

    Astronomers study distant galaxies by taking long exposures in deep survey fields. They choose fields that are empty of known sources, so that they are statistically representative of the Universe as a whole. Astronomers can compare the distribution of the detected galaxies in brightness, color, morphology and redshift to theoretical models, in order to puzzle out the processes of galaxy evolution. In 2004, the Hubble Space Telescope was pointed at a small, deep-survey field in the southern constellation Fornax for more than 500 hours of exposure time. The resulting Hubble Ultra-Deep Field could see the faintest and most distant galaxies that the telescope is capable of viewing. These galaxies emitted their light less than 1 billion years after the Big Bang. From the Ultra Deep Field and other galaxy surveys, astronomers have built up a history of star formation in the universe. the peak occurred about7 billion years ago, about half of the age of the current universe, then the number of stars that were forming was about 15 time the rate today. Going backward in time to when the very first starts and galaxies formed, the average star-formation rate should drop to zero. but when looking at the most distant galaxies in the Ultra Deep field, the star formation rate is still higher than it is today. The faintest galaxies seen by Hubble are not the first galaxies that formed in the early universe. To detect these galaxies NASA is planning the James Webb Space Telescope for launch in 2013. Webb will have a 6.5-meter diameter primary mirror, much bigger than Hubble's 2.4-meter primary, and will be optimized for infrared observations to see the highly redshifted galaxies.

  4. Amazing Andromeda Galaxy

    NASA Technical Reports Server (NTRS)

    2006-01-01

    The many 'personalities' of our great galactic neighbor, the Andromeda galaxy, are exposed in this new composite image from NASA's Galaxy Evolution Explorer and the Spitzer Space Telescope.

    The wide, ultraviolet eyes of Galaxy Evolution Explorer reveal Andromeda's 'fiery' nature -- hotter regions brimming with young and old stars. In contrast, Spitzer's super-sensitive infrared eyes show Andromeda's relatively 'cool' side, which includes embryonic stars hidden in their dusty cocoons.

    Galaxy Evolution Explorer detected young, hot, high-mass stars, which are represented in blue, while populations of relatively older stars are shown as green dots. The bright yellow spot at the galaxy's center depicts a particularly dense population of old stars.

    Swaths of red in the galaxy's disk indicate areas where Spitzer found cool, dusty regions where stars are forming. These stars are still shrouded by the cosmic clouds of dust and gas that collapsed to form them.

    Together, Galaxy Evolution Explorer and Spitzer complete the picture of Andromeda's swirling spiral arms. Hints of pinkish purple depict regions where the galaxy's populations of hot, high-mass stars and cooler, dust-enshrouded stars co-exist.

    Located 2.5 million light-years away, the Andromeda is our largest nearby galactic neighbor. The galaxy's entire disk spans about 260,000 light-years, which means that a light beam would take 260,000 years to travel from one end of the galaxy to the other. By comparison, our Milky Way galaxy's disk is about 100,000 light-years across.

    This image is a false color composite comprised of data from Galaxy Evolution Explorer's far-ultraviolet detector (blue), near-ultraviolet detector (green), and Spitzer's multiband imaging photometer at 24 microns (red).

  5. Galaxy evolution. Galactic paleontology.

    PubMed

    Tolstoy, Eline

    2011-07-01

    Individual low-mass stars have very long lives, comparable to the age of the universe, and can thus be used to probe ancient star formation. At present, such stars can be identified and studied only in the Milky Way and in the very closest of our neighboring galaxies, which are predominantly small dwarf galaxies. These nearby ancient stars are a fossil record that can provide detailed information about the physical processes that dominated the epoch of galaxy formation and subsequent evolution.

  6. LINEAR COUNT-RATE METER

    DOEpatents

    Henry, J.J.

    1961-09-01

    A linear count-rate meter is designed to provide a highly linear output while receiving counting rates from one cycle per second to 100,000 cycles per second. Input pulses enter a linear discriminator and then are fed to a trigger circuit which produces positive pulses of uniform width and amplitude. The trigger circuit is connected to a one-shot multivibrator. The multivibrator output pulses have a selected width. Feedback means are provided for preventing transistor saturation in the multivibrator which improves the rise and decay times of the output pulses. The multivibrator is connected to a diode-switched, constant current metering circuit. A selected constant current is switched to an averaging circuit for each pulse received, and for a time determined by the received pulse width. The average output meter current is proportional to the product of the counting rate, the constant current, and the multivibrator output pulse width.

  7. Photon Counting - One More Time

    NASA Astrophysics Data System (ADS)

    Stanton, Richard H.

    2012-05-01

    Photon counting has been around for more than 60 years, and has been available to amateurs for most of that time. In most cases single photons are detected using photomultiplier tubes, "old technology" that became available after the Second World War. But over the last couple of decades the perfection of CCD devices has given amateurs the ability to perform accurate photometry with modest telescopes. Is there any reason to still count photons? This paper discusses some of the strengths of current photon counting technology, particularly relating to the search for fast optical transients. Technology advances in counters and photomultiplier modules are briefly mentioned. Illustrative data are presented including FFT analysis of bright star photometry and a technique for finding optical pulses in a large file of noisy data. This latter technique is shown to enable the discovery of a possible optical flare on the polar variable AM Her.

  8. Opaque Matter in Spiral Galaxies. Cosmological Consequences

    NASA Astrophysics Data System (ADS)

    Faria, Peter Leroy

    1996-10-01

    The luminosity function plays a direct role in several points of cosmological interest, like the magnitud and redshift galaxy number counts, the determination of the mean luminosity density in a given volume and the determination of the spatial two point correlation function from the knowledge of the angular correlation function. In this work, we have related the optical thickness of the galactic disk with some cosmological observations. We assume that the absorbing material appears in a epoch z_d and obtain the absolute luminosity function corrected for the dust effects and study some cosmological consequences of this correction. Our main results are: 1.Luminosity function: As an effect of the opacity, an inclination i different from zero modifies the apparent luminosity of the galaxies and leads to a wrong estimation of the absolute luminosity. The corrections that must be applied depend on how the luminosities vary with inclination and therefore, in how to assign the corrected distribution function for the variable associated to the galaxy inclination. We have used a distribution function for the variable tau = |cos i|, assuming that the galaxies are uniformly distributed in a region of space, with the variable i (inclination) uniformly distributed. We have checked out that this hypothesis is reasonable for a pair of samples but further work must be done with larger and more complete samples in order to comfirm or to choose a more suitable distribution function to the variable mu and get more conclusions about the modifications in the luminosity function due to the opacity effects. We have found that the opacity modifies the luminosity function in the sense of increasing the number of more bright galaxies and keeping almost the same the number of faint galaxies. 2.Magnitude and redshift number counts: The modifications in the luminosity function affects directly the galaxy counts N(m) and N(z). We have found for N(m) in the B band (blue) that moderate opacities

  9. Reticulocyte counting using flow cytometry.

    PubMed

    Nobes, P R; Carter, A B

    1990-08-01

    A flow cytometric method for the quantitation of reticulocytes was refined for routine laboratory use. Blood (2 microliters) is added to 2 ml of 0.4 microM thiazole orange in phosphate buffered saline, incubated at room temperature for 90 minutes, and analysed on a Coulter EPICS Profile flow cytometer, with gating for red cells on the basis of forward and right angled light scatter. Blood (2 microliters) is also incubated with phosphate buffered saline alone as an unstained control. The adult reference range (mean +/- 2 SD), established from 30 laboratory personnel, is 19.4-59.2 x 10(9)/l (0.2-1.6%). Comparison of this technique was made on 39 selected patient samples with visual counting of cells stained with brilliant cresyl blue. The correlation between the two methods was 0.99 with slope 0.96 and intercept 0.02. The precision of the automated technique in three subjects with reticulocyte counts of 0.12%, 1.84%, and 14.3% was 33.3%, 7.3%, and 1.4%, respectively (coefficient of variations). In three patients studied serially after intensive chemotherapy, in whom the reticulocyte count quantitated by routine visual methods approached zero (0-0.1%) for eight to 18 days, the automated counts varied between 0 and 0.5%. Flow cytometric reticulocyte counting is thus a simple and highly reliable methodology for the quantitation of normal and raised reticulocyte counts but cannot be reliably used to quantitate a subnormal level.

  10. Galaxy UGC10445

    NASA Technical Reports Server (NTRS)

    2003-01-01

    This ultraviolet color image of the galaxy UGC10445 was taken by NASA's Galaxy Evolution Explorer on June 7 and June 14, 2003. UGC10445 is a spiral galaxy located 40 million light-years from Earth.

    The Galaxy Evolution Explorer mission is led by the California Institute of Technology, which is also responsible for the science operations and data analysis. NASA's Jet Propulsion Laboratory, Pasadena, Calif., a division of Caltech, manages the mission and built the science instrument. The mission was developed under NASA's Explorers Program, managed by the Goddard Space Flight Center, Greenbelt, Md. The mission's international partners include South Korea and France.

  11. Galaxy NGC5962

    NASA Technical Reports Server (NTRS)

    2003-01-01

    NASA's Galaxy Evolution Explorer took this ultraviolet color image of the galaxy NGC5962 on June 7, 2003. This spiral galaxy is located 90 million light-years from Earth.

    The Galaxy Evolution Explorer mission is led by the California Institute of Technology, which is also responsible for the science operations and data analysis. NASA's Jet Propulsion Laboratory, Pasadena, Calif., a division of Caltech, manages the mission and built the science instrument. The mission was developed under NASA's Explorers Program, managed by the Goddard Space Flight Center, Greenbelt, Md. The mission's international partners include South Korea and France.

  12. Multiple Core Galaxies

    NASA Technical Reports Server (NTRS)

    Miller, R.H.; Morrison, David (Technical Monitor)

    1994-01-01

    Nuclei of galaxies often show complicated density structures and perplexing kinematic signatures. In the past we have reported numerical experiments indicating a natural tendency for galaxies to show nuclei offset with respect to nearby isophotes and for the nucleus to have a radial velocity different from the galaxy's systemic velocity. Other experiments show normal mode oscillations in galaxies with large amplitudes. These oscillations do not damp appreciably over a Hubble time. The common thread running through all these is that galaxies often show evidence of ringing, bouncing, or sloshing around in unexpected ways, even though they have not been disturbed by any external event. Recent observational evidence shows yet another phenomenon indicating the dynamical complexity of central regions of galaxies: multiple cores (M31, Markarian 315 and 463 for example). These systems can hardly be static. We noted long-lived multiple core systems in galaxies in numerical experiments some years ago, and we have more recently followed up with a series of experiments on multiple core galaxies, starting with two cores. The relevant parameters are the energy in the orbiting clumps, their relative.masses, the (local) strength of the potential well representing the parent galaxy, and the number of cores. We have studied the dependence of the merger rates and the nature of the final merger product on these parameters. Individual cores survive much longer in stronger background potentials. Cores can survive for a substantial fraction of a Hubble time if they travel on reasonable orbits.

  13. Extremely Isolated Elliptical Galaxies

    NASA Astrophysics Data System (ADS)

    Fuse, Christopher R.; Marcum, P.; Fanelli, M.; Aars, C.

    2006-06-01

    Isolated galaxies provide a means of assessing the evolution of galactic systems. Extremely isolated galaxies define a zero-interaction baseline for comparative studies of galaxy evolution. We present results of a search for isolated elliptical galaxies (IEGs). We utilize the optical imaging data produced by the Sloan Digital Sky Survey (SDSS) to identify candidate galaxies from Release 1-4 of the SDSS. Candidate IEGs meet strict isolation criteria: Any IEG must be separated by at least 2.5 Mpc from any neighboring non-dwarf galaxy having a MV fainter than -16.5 mag. The candidate isolated systems have no non-dwarf neighbors within a distance such that we can insure that the IEGs have never interacted with another existing galaxy since formation.In order to increase the signal-to-noise ratio, we have used the SDSS images in the u,g,r filters to create combined sets of images for each IEG. The stacked images permit a more robust determination of the morphology of the candidate galaxies. Verification that these are spheroidal systems is achieved through a bulge/disk decomposition technique using standard surface photometry. Our preliminary sample of 51 isolated systems defines a complete volume-limited population of extremely isolated early-type galaxies within a distance of 72Mpc

  14. Gas in void galaxies

    NASA Astrophysics Data System (ADS)

    Kreckel, Kathryn Joyce

    Void galaxies, residing within the deepest underdensities of the Cosmic Web, present an ideal population for the study of galaxy formation and evolution in an environment undisturbed by the complex processes modifying galaxies in clusters and groups, and provide an observational test for theories of cosmological structure formation. We investigate the neutral hydrogen properties (i.e. content, morphology, kinematics) of void galaxies, both individually and systematically, using a combination of observations and simulations, to form a more complete understanding of the nature of these systems. We investigate in detail the H I morphology and kinematics of two void galaxies. One is an isolated polar disk galaxy in a diffuse cosmological wall situated between two voids. The considerable gas mass and apparent lack of stars in the polar disk, coupled with the general underdensity of the environment, supports recent theories of cold flow accretion as an alternate formation mechanism for polar disk galaxies. We also examine KK 246, the only confirmed galaxy located within the nearby Tully Void. It is a dwarf galaxy with an extremely extended H I disk and signs of an H I cloud with anomalous velocity. It also exhibits clear misalignment between the kinematical major and minor axes, and a general misalignment between the H I and optical major axes. The relative isolation and extreme underdense environment make these both very interesting cases for examining the role of gas accretion in galaxy evolution. To study void galaxies as a population, we have carefully selected a sample of 60 galaxies that reside in the deepest underdensities of geometrically identified voids within the SDSS. We have imaged this new Void Galaxy Survey in H I at the Westerbork Synthesis Radio Telescope with a typical resolution of 8 kpc, probing a volume of 1.2 Mpc and 12,000 km s^-1 surrounding each galaxy. We reach H I mass limits of 2 x 10^8 M_sun and column density sensitivities of 5 x 10^19 cm^-2

  15. Backwards Spiral Galaxy

    NASA Technical Reports Server (NTRS)

    1999-01-01

    Astronomers using NASA's Hubble Space Telescope have found a spiral galaxy that may rotate in the opposite direction from what was expected.

    A picture of the oddball galaxy is available at http://heritage.stsci.edu or http://oposite.stsci.edu/pubinfo/pr/2002/03 or http://www.jpl.nasa.gov/images/wfpc . It was taken in May 2001 by Hubble's Wide Field and Planetary Camera 2, designed and built by NASA's Jet Propulsion Laboratory, Pasadena, Calif.

    The picture showed which side of galaxy NGC 4622 is closer to Earth; that information helped astronomers determine that the galaxy may be spinning clockwise. The image shows NGC 4622 and its outer pair of winding arms full of new stars, shown in blue.

    Astronomers are puzzled by the clockwise rotation because of the direction the outer spiral arms are pointing. Most spiral galaxies have arms of gas and stars that trail behind as they turn. But this galaxy has two 'leading' outer arms that point toward the direction of the galaxy's clockwise rotation. NGC 4622 also has a 'trailing' inner arm that is wrapped around the galaxy in the opposite direction. Based on galaxy simulations, a team of astronomers had expected that the galaxy was turning counterclockwise.

    NGC 4622 is a rare example of a spiral galaxy with arms pointing in opposite directions. Astronomers suspect this oddity was caused by the interaction of NGC 4622 with another galaxy. Its two outer arms are lopsided, meaning that something disturbed it. The new Hubble image suggests that NGC 4622 consumed a smaller companion galaxy.

    Galaxies, which consist of stars, gas, and dust, rotate very slowly. Our Sun, one of many stars in our Milky Way galaxy, completes a circuit around the Milky Way every 250 million years. NGC 4622 lies 111 million light-years away in the direction of the constellation Centaurus.

    The science team, consisting of Drs. Ron Buta and Gene Byrd from the University of Alabama, Tuscaloosa, and Tarsh Freeman of Bevill State

  16. South Carolina Kids Count, 2001.

    ERIC Educational Resources Information Center

    Holmes, A. Baron

    This Kids Count report examines statewide trends in the well-being of South Carolina's children. The statistical portrait is based on 42 indicators in the areas of demographics, family, economic status, health, readiness and early school performance, scholastic achievement, and adolescent risk behaviors. The indicators are: (1) population; (2)…

  17. South Carolina Kids Count, 2000.

    ERIC Educational Resources Information Center

    Holmes, A. Baron

    This Kids Count report examines statewide trends in the well-being of South Carolina's children. The statistical portrait is based on 41 indicators in the areas of demographics, family, economic status, health, readiness and early school performance, scholastic achievement, and adolescent risk behaviors. The indicators are: (1) population; (2)…

  18. Kids Count Data Sheet, 2000.

    ERIC Educational Resources Information Center

    Annie E. Casey Foundation, Baltimore, MD.

    Data from the 50 United States are listed for 1997 from Kids Count in an effort to track state-by-state the status of children in the United States and to secure better futures for all children. Data include percent low birth weight babies; infant mortality rate; child death rate; rate of teen deaths by accident, homicide, and suicide; teen birth…

  19. Counting a Culture of Mealworms

    ERIC Educational Resources Information Center

    Ashbrook, Peggy

    2007-01-01

    Math is not the only topic that will be discussed when young children are asked to care for and count "mealworms," a type of insect larvae (just as caterpillars are the babies of butterflies, these larvae are babies of beetles). The following activity can take place over two months as the beetles undergo metamorphosis from larvae to adults. As the…

  20. Oklahoma Kids Count Factbook '96.

    ERIC Educational Resources Information Center

    Ingraham, Sandy

    This data book presents findings of the Kids Count Project on current conditions faced by Oklahoma children age birth through 18. This second annual factbook organizes state and county data over a period of time to enable conditions for children in each county to be compared and ranked. The benchmark indicators studied include low birthweight…

  1. Kids Count New Hampshire, 1996.

    ERIC Educational Resources Information Center

    Terry, Susan Palmer; Hall, Douglas E.

    This Kids Count report presents statewide trends in the well-being of New Hampshire's children. The statistical report is based on 14 indicators of child well being: (1) children in poverty; (2) fatherless families; (3) maternal education; (4) teen births; (5) births to unmarried mothers; (6) low birth weight births; (7) insurance coverage; (8)…

  2. Wiskids Count Data Book, 2003.

    ERIC Educational Resources Information Center

    Cranley, M. Martha; Bianchi, J. P.; Eleson, Charity; Hall, Linda; Jacobson, Bob; Jackson, Kristin; Peacock, Jon

    This WisKids Count data book provides a statistical portrait of the well-being of Wisconsin's children. In addition to demographic data indicating changing communities, the indicators and data are organized into five overarching goals: (1) Healthy Families and Children Thrive, including births to single women, infant deaths, and health care…

  3. KIDS COUNT Data Brief, 2009

    ERIC Educational Resources Information Center

    Annie E. Casey Foundation, 2009

    2009-01-01

    This 2009 KIDS COUNT Data Brief features highlights of the enhanced, mobile-friendly Data Center; data on the 10 key indicators of child well-being for all U.S. states, the District of Columbia, and many cities, counties, and school districts; and a summary of this year's essay, which calls for improvements to the nation's ability to design and…

  4. Shakespeare Live! and Character Counts.

    ERIC Educational Resources Information Center

    Brookshire, Cathy A.

    This paper discusses a live production of Shakespeare's "Macbeth" (in full costume but with no sets) for all public middle school and high school students in Harrisonburg and Rockingham, Virginia. The paper states that the "Character Counts" issues that are covered in the play are: decision making, responsibility and citizenship, trustworthiness,…

  5. Kids Count in Colorado! 2003.

    ERIC Educational Resources Information Center

    Boeke, Kaye

    This Kids Count report examines state, county, and regional trends in the well-being of Colorado's children. The first part of the report is presented in four chapters. Chapter 1 includes findings regarding the increasing diversity of the child population, linguistic isolation, the impact of parental unemployment, child poverty, and the affordable…

  6. On Counting the Rational Numbers

    ERIC Educational Resources Information Center

    Almada, Carlos

    2010-01-01

    In this study, we show how to construct a function from the set N of natural numbers that explicitly counts the set Q[superscript +] of all positive rational numbers using a very intuitive approach. The function has the appeal of Cantor's function and it has the advantage that any high school student can understand the main idea at a glance…

  7. Verbal Counting in Bilingual Contexts

    ERIC Educational Resources Information Center

    Donevska-Todorova, Ana

    2015-01-01

    Informal experiences in mathematics often include playful competitions among young children in counting numbers in as many as possible different languages. Can these enjoyable experiences result with excellence in the formal processes of education? This article discusses connections between mathematical achievements and natural languages within…

  8. Wyoming Kids Count Factbook, 1997.

    ERIC Educational Resources Information Center

    Wyoming Kids Count, Cheyenne.

    This Kids Count factbook details statewide trends in the well-being of Wyoming's children. The 1997 report has been expanded to include detailed information on the status of children by categories of welfare, health, and education. The first part of the factbook documents trends by county for 15 indicators: (1) poverty and population; (2)…

  9. KIDS COUNT New Hampshire, 2000.

    ERIC Educational Resources Information Center

    Shemitz, Elllen, Ed.

    This Kids Count report presents statewide trends in the well-being of New Hampshire's children. The statistical report is based on 22 indicators of child well-being in 5 interrelated areas: (1) children and families (including child population, births, children living with single parent, and children experiencing parental divorce); (2) economic…

  10. Meal Counting and Claiming Manual.

    ERIC Educational Resources Information Center

    Food and Nutrition Service (USDA), Washington, DC.

    This manual contains information about the selection and implementation of a meal counting and claiming system for the National School Lunch Program (NSLP) and the School Breakfast Program (BSP). Federal reimbursement is provided for each meal that meets program requirements and is served to an eligible student. Part 1 explains the six elements of…

  11. The RSA survey of dwarf galaxies, 1: Optical photometry

    NASA Technical Reports Server (NTRS)

    Vader, J. Patricia; Chaboyer, Brian

    1994-01-01

    merger candidates. Merger events may lead to anisotropic velocity distributions in systems of any luminosity, including dwarfs. The RSA sample of dwarf galaxies is more likely to contain mergers because, in contrast to earlier dwarf galaxy surveys that have focused on clusters and rich groups of galaxies, the RSA dwarfs are typically located in low density environments. The occurrence of mergers among dwarf galaxies is of interest in connection with the rapid evolution of faint blue galaxy counts at redshift z less than 1 which suggests that dwarf galaxies were about five times more numerous in the recent past. Finally, our sample contains several examples of late-type dwarfs and 'transition' types that are potential precursors of nucleated early-type dwarfs. All the above processes--mass loss, mergers, astration--are likely to have contributed to the formation of the current population of diffuse early-type dwarfs. A few new redshifts of dwarf galaxies are reported in this paper.

  12. Bars Triggered By Galaxy Flybys

    NASA Astrophysics Data System (ADS)

    Holley-Bockelmann, Kelly; Lang, Meagan; Sinha, Manodeep

    2015-05-01

    Galaxy mergers drive galaxy evolution and are a key mechanism by which galaxies grow and transform. Unlike galaxy mergers where two galaxies combine into one remnant, galaxy flybys occur when two independent galaxy halos interpenetrate but detach at a later time; these one-time events are surprisingly common and can even out-number galaxy mergers at low redshift for massive halos. Although these interactions are transient and occur far outside the galaxy disk, flybys can still drive a rapid and large pertubations within both the intruder and victim halos. We explored how flyby encounters can transform each galaxy using a suite of N-body simulations. We present results from three co-planar flybys between disk galaxies, demonstrating that flybys can both trigger strong bar formation and can spin-up dark matter halos.

  13. Luminous red galaxies in the Sloan digital sky survey

    NASA Astrophysics Data System (ADS)

    Loh, Yeong-Shang

    2004-04-01

    We determine the luminosity function and evolution of 22,562 Luminous Red Galaxies (LRG) with 0.08 < z < 0.44 from the Sloan Digital Sky Survey (SDSS). The universal field galaxy luminosity function with a steep exponential bright end cut-off expected from a Schechter form is confirmed to z ˜ 0.4. We do not discern any evolution in the comoving number density of these luminous early-type galaxies, once biases due to photometric errors are taken into account. Using 2099 deg2 of SDSS imaging data, we search for bright early-type galaxies within 1 h-1 Mpc of LRG with 0.12 < z < 0.38 to study the bright end of the luminosity distribution at this scale. The brightest galaxies (nearly always an LRG) in LRG fields are too bright if other members in the same field are drawn from an exponentially decaying luminosity function. The luminosity gap between the brightest and the second brightest galaxy is large (˜0.8 mag). When the LRG fields were split into group-like and cluster- like environments, the former gives a larger gap. The gap shows little evolution with redshifts, putting stringent constraints on the scenario of the growth of Brightest Cluster (or Group) Galaxies by recent cannibalism of cluster members. We calibrate the observed color-magnitude-redshift relation for early-type galaxies. We use LRGs as spectroscopic references and measure the color of imaging galaxies that clustered around each LRG. We bin these galaxies in redshift and perform an optimal background subtraction to recover the color-magnitude relation. The observed scatter around this color-magnitude relation is also measured. We study the environments of LRG by counting the number of early-type galaxies brighter than M* within 1 h-1 Mpc of the LRG. LRGs are binned in redshift and treated as a single population to infer the evolution trend of their environments. Both the rich optical clusters and moderately X-ray bright clusters host at least one LRG. However, LRG are most common in group

  14. Evolution of galaxy habitability

    NASA Astrophysics Data System (ADS)

    Gobat, R.; Hong, S. E.

    2016-08-01

    We combine a semi-analytic model of galaxy evolution with constraints on circumstellar habitable zones and the distribution of terrestrial planets in order to probe the suitability of galaxies of different mass and type to host habitable planets, and how it evolves with time. We find that the fraction of stars with terrestrial planets in their habitable zone (known as habitability) depends only weakly on galaxy mass, with a maximum around 4 × 1010M⊙. We estimate that 0.7% of all stars in Milky Way-type galaxies to host a terrestrial planet within their habitable zone, consistent with the value derived from Kepler observations. On the other hand, the habitability of passive galaxies is slightly but systematically higher, unless we assume an unrealistically high sensitivity of planets to supernovae. We find that the overall habitability of galaxies has not changed significantly in the last ~8 Gyr, with most of the habitable planets in local disk galaxies having formed ~1.5 Gyr before our own solar system. Finally, we expect that ~1.4 ×109 planets similar to present-day Earth have existed so far in our galaxy.

  15. Superluminous Spiral Galaxies

    NASA Astrophysics Data System (ADS)

    Ogle, Patrick M.; Lanz, Lauranne; Nader, Cyril; Helou, George

    2016-02-01

    We report the discovery of spiral galaxies that are as optically luminous as elliptical brightest cluster galaxies, with r-band monochromatic luminosity Lr = 8-14L* (4.3-7.5 × 1044 erg s-1). These super spiral galaxies are also giant and massive, with diameter D = 57-134 kpc and stellar mass Mstars = 0.3-3.4 × 1011M⊙. We find 53 super spirals out of a complete sample of 1616 SDSS galaxies with redshift z < 0.3 and Lr > 8L*. The closest example is found at z = 0.089. We use existing photometry to estimate their stellar masses and star formation rates (SFRs). The SDSS and Wide-field Infrared Survey Explorer colors are consistent with normal star-forming spirals on the blue sequence. However, the extreme masses and rapid SFRs of 5-65 M⊙ yr-1 place super spirals in a sparsely populated region of parameter space, above the star-forming main sequence of disk galaxies. Super spirals occupy a diverse range of environments, from isolation to cluster centers. We find four super spiral galaxy systems that are late-stage major mergers—a possible clue to their formation. We suggest that super spirals are a remnant population of unquenched, massive disk galaxies. They may eventually become massive lenticular galaxies after they are cut off from their gas supply and their disks fade.

  16. UPDATED NEARBY GALAXY CATALOG

    SciTech Connect

    Karachentsev, Igor D.; Makarov, Dmitry I.; Kaisina, Elena I.

    2013-04-15

    We present an all-sky catalog of 869 nearby galaxies having individual distance estimates within 11 Mpc or corrected radial velocities V{sub LG} < 600 km s{sup -1}. The catalog is a renewed and expanded version of the Catalog of Neighboring Galaxies by Karachentsev et al. It collects data on the following galaxy observables: angular diameters, apparent magnitudes in far-UV, B, and K{sub s} bands, H{alpha} and H I fluxes, morphological types, H I-line widths, radial velocities, and distance estimates. In this Local Volume (LV) sample, 108 dwarf galaxies still remain without measured radial velocities. The catalog yields also calculated global galaxy parameters: linear Holmberg diameter, absolute B magnitude, surface brightness, H I mass, stellar mass estimated via K-band luminosity, H I rotational velocity corrected for galaxy inclination, indicative mass within the Holmberg radius, and three kinds of ''tidal index,'' which quantify the local density environment. The catalog is supplemented with data based on the local galaxies, which presents their optical and available H{alpha} images, as well as other services. We briefly discuss the Hubble flow within the LV and different scaling relations that characterize galaxy structure and global star formation in them. We also trace the behavior of the mean stellar mass density, H I-mass density, and star formation rate density within the volume considered.

  17. Hubble's galaxy nomenclature

    NASA Astrophysics Data System (ADS)

    Baldry, Ivan K.

    2008-10-01

    It is widely written and believed that Edwin Hubble introduced the terms ``early'' and ``late types'' to suggest an evolutionary sequence for galaxies. This is incorrect. Hubble took these terms from spectral classification of stars to signify a sequence related to complexity of appearance, albeit based on images, not spectra. The temporal connotations had been abandoned before his 1926 paper on classification of galaxies.

  18. Brightest Cluster Galaxy Identification

    NASA Astrophysics Data System (ADS)

    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.

  19. GALAXIES: SNAPSHOTS IN TIME

    NASA Technical Reports Server (NTRS)

    2002-01-01

    This sequence of NASA Hubble Space Telescope (HST) images of remote galaxies offers tantalizing initial clues to the evolution of galaxies in the universe. [far left column] These are traditional spiral and elliptical-shaped galaxies that make up the two basic classes of island star cities that inhabit the universe we see in our current epoch (14 billion years after the birth of the universe in the Big Bang). Elliptical galaxies contain older stars, while spirals have vigorous ongoing star formation in their dusty, pancake-shaped disks. Our Milky Way galaxy is a typical spiral, or disk-shaped galaxy, on the periphery of the great Virgo cluster. Both galaxies in this column are a few tens of millions of light-years away, and therefore represent our current stage of the universe s evolution. [center left column] These galaxies existed in a rich cluster when the universe was approximately two-thirds its present age. Elliptical galaxies (top) appear fully evolved because they resemble today's descendants. By contrast, some spirals have a frothier appearance, with loosely shaped arms of young star formation. The spiral population appears more disrupted due to a variety of possible dynamical effects that result from dwelling in a dense cluster. [center right column] Distinctive spiral structure appears more vague and disrupted in galaxies that existed when the universe was nearly one-third its present age. These objects do not have the symmetry of current day spirals and contain irregular lumps of starburst activity. However, even this far back toward the beginning of time, the elliptical galaxy (top) is still clearly recognizable. However, the distinction between ellipticals and spirals grows less certain with increasing distance. [far right column] These extremely remote, primeval objects existed with the universe was nearly one-tenth its current age. The distinction between spiral and elliptical galaxies may well disappear at this early epoch. However, the object in

  20. The morphology of faint galaxies in Medium Deep Survey images using WFPC2

    NASA Technical Reports Server (NTRS)

    Griffiths, R. E.; Casertano, S.; Ratnatunga, K. U.; Neuschaefer, L. W.; Ellis, R. S.; Gilmore, G. F.; Glazebrook, K.; Santiago, B.; Huchra, J. P.; Windhorst, R. A.

    1994-01-01

    First results from Hubble Space Telescope (HST) Medium Deep Survey images taken with Wide Field/Planetary Camera-2 (WFPC2) demonstrate that galaxy classifications can be reliably performed to magnitudes I814 approximately less than 22.0 in the F815W band. Published spectroscopic surveys to this depth indicate a mean redshift of bar-z approximately 0.5. We have classified over 200 galaxies in nine WFPC2 fields according to a basic morphological scheme. The majority of these faint galaxies appear to be similar to regular Hubble-sequence examples observed at low redshift. To the precision of our classification scheme, the relative proportion of spheroidal and disk systems of normal appearance is as expected from nearby samples, indicating that the bulk of the local galaxy population was in place at half the Hubble time. However, the most intriguing result is the relatively high proportion (approximately 40%) of objects which are in some way anomalous, and which may be of relevance in understanding the origin of the familiar excess population of faint galaxies established by others. These diverse objects include apparently interacting pairs whose multiple structure is only revealed with HST's angular resolution, galaxies with superluminous star-forming regions, diffuse low surface brightness galaxies of various forms, and compact galaxies. These anomalous galaxies contribute a substantial fraction of the excess counts at our limiting magnitude, and may provide insights into the 'faint blue galaxy' problem.

  1. MULTIPLE GALAXY COLLISIONS

    NASA Technical Reports Server (NTRS)

    2002-01-01

    Here is a sampling of 15 ultraluminous infrared galaxies viewed by NASA's Hubble Space Telescope. Hubble's sharp vision reveals more complexity within these galaxies, which astronomers are interpreting as evidence of a multiple-galaxy pileup. These images, taken by the Wide Field and Planetary Camera 2, are part of a three-year study of 123 galaxies within 3 billion light-years of Earth. The study was conducted in 1996, 1997, and 1999. False colors were assigned to these photos to enhance fine details within these coalescing galaxies. Credits: NASA, Kirk Borne (Raytheon and NASA Goddard Space Flight Center, Greenbelt, Md.), Luis Colina (Instituto de Fisica de Cantabria, Spain), and Howard Bushouse and Ray Lucas (Space Telescope Science Institute, Baltimore, Md.)

  2. Colliding and merging galaxies.

    PubMed

    Schweizer, F

    1986-01-17

    Aided by advances in computer technology and observations from space, astronomers have begun to unravel the mysteries of galaxy formation and evolution. Galaxies evolve by interacting with their environment and especially with each other. During brief but often fierce galactic encounters, gravitational forces generate strong tides that survive as telltale signatures for billions of years. Because these so-called collisions dissipate orbital energy, galaxies on bound orbits may eventually merge. Collisions and mergers are responsible for a great variety of phenomena, including the triggering of widespread star formation in galaxies and the fueling of nuclear activity in quasars. Evidence is accumulating that not all galaxies formed shortly after the Big Bang. A sizable fraction of them may have formed later, and many are still experiencing significant dynamical evolution. PMID:17769643

  3. Galaxy Messier 83

    NASA Technical Reports Server (NTRS)

    2003-01-01

    This image of the spiral galaxy Messier 83 was taken by NASA's Galaxy Evolution Explorer on June 7, 2003. Located 15 million light years from Earth and known as the Southern Pinwheel Galaxy, Messier 83 displays significant amounts of ultraviolet emissions far from the optically bright portion of the galaxy. It is also known to have an extended hydrogen disc that appears to radiate a faint ultraviolet emission. The red stars in the foreground of the image are Milky Way stars.

    The Galaxy Evolution Explorer mission is led by the California Institute of Technology, which is also responsible for the science operations and data analysis. NASA's Jet Propulsion Laboratory, Pasadena, Calif., a division of Caltech, manages the mission and built the science instrument. The mission was developed under NASA's Explorers Program, managed by the Goddard Space Flight Center, Greenbelt, Md. The mission's international partners include South Korea and France.

  4. The Quest for Dusty Primeval Galaxies

    NASA Astrophysics Data System (ADS)

    Mancuso, C.; Lapi, A.; Danese, L.

    2016-06-01

    We exploit the continuity equation approach and the 'main sequence' star-formation timescales to show that the observed high abundance of galaxies with stellar masses ? a few >10^10 M_⊙ at redshift z >? 4 implies the existence of a galaxy population featuring large star formation rates (SFRs) ψ >? 10^2 M_⊙ yr^-1 in heavily dust-obscured conditions. These galaxies constitute the high-redshift counterparts of the dusty star-forming population already surveyed for z<3 in the far-IR band by the Herschel space observatory. We work out specific predictions for the evolution of the corresponding stellar mass and SFR functions out to z ˜ 10, elucidating that the number density at z 30 M_⊙ yr^-1 cannot be estimated relying on the UV luminosity function alone, even when standard corrections for dust extinction based on the UV slope are applied. We compute the number counts and redshift distributions (including galaxy-scale gravitational lensing) of this galaxy population, and show that current data from AzTEC-LABOCA, SCUBA-2 and ALMA-SPT surveys are already digging into it. We substantiate how an observational strategy based on a color preselection in the far-IR or (sub-)mm band with Herschel and SCUBA-2, supplemented by photometric data via on-source observations with ALMA, can allow to reconstruct the bright end of the SFR functions out to z ? 8. In parallel, such a challenging task can be managed by exploiting current UV surveys in combination with (sub-)mm observations by ALMA and NIKA2 and/or radio observations by SKA and its precursors.

  5. The galaxy ancestor problem

    NASA Astrophysics Data System (ADS)

    Disney, M. J.; Lang, R. H.

    2012-11-01

    The Hubble Space Telescope (HST) findsgalaxies whose Tolman dimming exceeds 10 mag. Could evolution alone explain these as our ancestor galaxies or could they be representatives of quite a different dynasty whose descendants are no longer prominent today? We explore the latter hypothesis and argue that surface brightness selection effects naturally bring into focus quite different dynasties from different redshifts. Thus, the HST z = 7 galaxies could be examples of galaxies whose descendants are both too small and too choked with dust to be recognizable in our neighbourhood easily today. Conversely, the ancestors of the Milky Way and its obvious neighbours would have completely sunk below the sky at z > 1.2, unless they were more luminous in the past, although their diffused light could account for the missing re-ionization flux. This Succeeding Prominent Dynasties Hypothesis (SPDH) fits the existing observations both naturally and well even without evolution, including the bizarre distributions of galaxy surface brightness found in deep fields, the angular size ˜(1 + z)-1 law, 'downsizing' which turns out to be an 'illusion' in the sense that it does not imply evolution, 'infant mortality', that is, the discrepancy between stars born and stars seen, the existence of 'red nuggets', and finally the recently discovered and unexpected excess of quasar absorption line damped Lyα systems at high redshift. If galaxies were not significantly brighter in the past and the SPDH were true, then a large proportion of galaxies could remain sunk from sight, possibly at all redshifts, and these sunken galaxies could supply the missing re-ionization flux. We show that fishing these sunken galaxies out of the sky by their optical emissions alone is practically impossible, even when they are nearby. More ingenious methods are needed to detect them. It follows that disentangling galaxy evolution through studying ever higher redshift galaxies may be a forlorn hope because one could

  6. The nature and evolution of infrared galaxies in clusters

    NASA Astrophysics Data System (ADS)

    Farahmandi, Alireza

    In chapter 1, I present a spectroscopic and photometric study of 105 Spitzer-MIPS 24 micron detected galaxies in the fields of candidate clusters from the SpARCS survey. I spectroscopically both confirm nine clusters of galaxies at 0.07 < z < 0.49 and investigate the nature of the cluster members and field galaxies to compare their optical and infrared star formation activities. Spectroscopic classifications reveal different populations of galaxies in clusters and in the field. Most 24 micron sources are star forming galaxies which are mostly dusty starbursts. I conclude that specific star formation rates of star forming galaxies in clusters are not dependent upon clustercentric radius, but, rather, dependent upon stellar mass. In chapter 2, I present the results of an infrared study of 250 galaxy clusters at 0.2 < z < 1 from the SpARCS survey. My sample spans a cluster mass range 14 < log M_sun < 15 with an average about 2x10. 14 M_sun overthe redshift. Assuming a star forming galaxy template, I statistically count the number of infrared luminous galaxies in clusters above a fixed inferred infrared luminosity of 6x10. 11 L_sun per unit cluster mass and find it increaseswith redshift. Fitting a simple power law, I measure an evolution of (1 + z ). (5.2+/-0.5) within R_200 and (1 + z ). (9.6+/-1.6) within R =2Mpc from the cluster center over the redshift range of this sample. By accounting for the evolution of infrared galaxies in the field, I show that this observed evolution in clusters is due to new infalling field galaxies. Also, I estimate the total star formation rate per unit cluster mass (SigmaSFR/M_cluster) and find a similar evolution of (1+z). (5.6+/-0.5) within R_(200) and(1+z). (8.6+/-1.5) within R = 2Mpc from the cluster center. The surfacedensity of the infrared luminous galaxies seems to decrease as the distance from cluster center increases. Finally, I show that the accretion rate of infalling infrared galaxies from the field into clusters increases

  7. Magnetic Fields in Galaxies

    NASA Astrophysics Data System (ADS)

    Beck, Rainer

    The origin and evolution of cosmic magnetic fields, their strength and structure in intergalactic space, their first occurrence in young galaxies, and their dynamical importance for galaxy evolution remain widely unknown. Radio synchrotron emission, its polarization and its Faraday rotation are powerful tools to study the strength and structure of magnetic fields in galaxies. Unpolarized radio synchrotron emission traces isotropic turbulent fields which are strongest in spiral arms and bars (20-30 μG) and in central starburst regions (50-100 μG). Such fields are dynamically important; they can affect gas flows and drive gas inflows in central regions. Polarized radio emission traces ordered fields which can be regular or anisotropic turbulent, generated from isotropic turbulent fields by compression or shear. The strongest ordered fields of 10-15 μG strength are generally found in interarm regions and follow the orientation of adjacent gas spiral arms. In galaxies with strong density waves, ordered (anisotropic turbulent) fields are also observed at the inner edges of the spiral arms. Ordered fields with spiral patterns exist in grand-design, barred and flocculent galaxies, and in central regions of starburst galaxies. Ordered fields in interacting galaxies have asymmetric distributions and are an excellent tracer of past interactions between galaxies or with the intergalactic medium. Irregular galaxies host isotropic turbulent fields often of similar strength as in spiral galaxies, but only weak ordered fields. Faraday rotation measures (RM) of the diffuse polarized radio emission from the disks of several galaxies reveal large-scale spiral patterns that can be described by the superposition of azimuthal modes; these are signatures of regular fields generated by a mean-field α -Ω dynamo. So far no indications were found in external galaxies of large-scale field reversals, like the one in the Milky Way. Ordered magnetic fields are also observed in radio halos

  8. Bayesian Kernel Mixtures for Counts

    PubMed Central

    Canale, Antonio; Dunson, David B.

    2011-01-01

    Although Bayesian nonparametric mixture models for continuous data are well developed, there is a limited literature on related approaches for count data. A common strategy is to use a mixture of Poissons, which unfortunately is quite restrictive in not accounting for distributions having variance less than the mean. Other approaches include mixing multinomials, which requires finite support, and using a Dirichlet process prior with a Poisson base measure, which does not allow smooth deviations from the Poisson. As a broad class of alternative models, we propose to use nonparametric mixtures of rounded continuous kernels. An efficient Gibbs sampler is developed for posterior computation, and a simulation study is performed to assess performance. Focusing on the rounded Gaussian case, we generalize the modeling framework to account for multivariate count data, joint modeling with continuous and categorical variables, and other complications. The methods are illustrated through applications to a developmental toxicity study and marketing data. This article has supplementary material online. PMID:22523437

  9. Bayesian Kernel Mixtures for Counts.

    PubMed

    Canale, Antonio; Dunson, David B

    2011-12-01

    Although Bayesian nonparametric mixture models for continuous data are well developed, there is a limited literature on related approaches for count data. A common strategy is to use a mixture of Poissons, which unfortunately is quite restrictive in not accounting for distributions having variance less than the mean. Other approaches include mixing multinomials, which requires finite support, and using a Dirichlet process prior with a Poisson base measure, which does not allow smooth deviations from the Poisson. As a broad class of alternative models, we propose to use nonparametric mixtures of rounded continuous kernels. An efficient Gibbs sampler is developed for posterior computation, and a simulation study is performed to assess performance. Focusing on the rounded Gaussian case, we generalize the modeling framework to account for multivariate count data, joint modeling with continuous and categorical variables, and other complications. The methods are illustrated through applications to a developmental toxicity study and marketing data. This article has supplementary material online. PMID:22523437

  10. Approximate Counting of Graphical Realizations

    PubMed Central

    2015-01-01

    In 1999 Kannan, Tetali and Vempala proposed a MCMC method to uniformly sample all possible realizations of a given graphical degree sequence and conjectured its rapidly mixing nature. Recently their conjecture was proved affirmative for regular graphs (by Cooper, Dyer and Greenhill, 2007), for regular directed graphs (by Greenhill, 2011) and for half-regular bipartite graphs (by Miklós, Erdős and Soukup, 2013). Several heuristics on counting the number of possible realizations exist (via sampling processes), and while they work well in practice, so far no approximation guarantees exist for such an approach. This paper is the first to develop a method for counting realizations with provable approximation guarantee. In fact, we solve a slightly more general problem; besides the graphical degree sequence a small set of forbidden edges is also given. We show that for the general problem (which contains the Greenhill problem and the Miklós, Erdős and Soukup problem as special cases) the derived MCMC process is rapidly mixing. Further, we show that this new problem is self-reducible therefore it provides a fully polynomial randomized approximation scheme (a.k.a. FPRAS) for counting of all realizations. PMID:26161994

  11. Galaxy 'Hunting' Made Easy

    NASA Astrophysics Data System (ADS)

    2007-09-01

    Galaxies found under the Glare of Cosmic Flashlights Astronomers using ESO's Very Large Telescope have discovered in a single pass about a dozen otherwise invisible galaxies halfway across the Universe. The discovery, based on a technique that exploits a first-class instrument, represents a major breakthrough in the field of galaxy 'hunting'. ESO PR Photo 40a/07 ESO PR Photo 40a/07 Newly Found Galaxies (SINFONI/VLT) The team of astronomers led by Nicolas Bouché have used quasars to find these galaxies. Quasars are very distant objects of extreme brilliance, which are used as cosmic beacons that reveal galaxies lying between the quasar and us. The galaxy's presence is revealed by a 'dip' in the spectrum of the quasar - caused by the absorption of light at a specific wavelength. The team used huge catalogues of quasars, the so-called SDSS and 2QZ catalogues, to select quasars with dips. The next step was then to observe the patches of the sky around these quasars in search for the foreground galaxies from the time the Universe was about 6 billion years old, almost half of its current age. "The difficulty in actually spotting and seeing these galaxies stems from the fact that the glare of the quasar is too strong compared to the dim light of the galaxy," says Bouché. This is where observations taken with SINFONI on ESO's VLT made the difference. SINFONI is an infrared 'integral field spectrometer' that simultaneously delivers very sharp images and highly resolved colour information (spectra) of an object on the sky. ESO PR Photo 32e/07 ESO PR Photo 40b/07 Chasing 'Hidden' Galaxies (Artist's Impression) With this special technique, which untangles the light of the galaxy from the quasar light, the team detected 14 galaxies out of the 20 pre-selected quasar patches of sky, a hefty 70% success rate. "This high detection rate alone is a very exciting result," says Bouché. "But, these are not just ordinary galaxies: they are most notable ones, actively forming a lot of

  12. JSPAM: Interacting galaxies modeller

    NASA Astrophysics Data System (ADS)

    Wallin, John F.; Holincheck, Anthony; Harvey, Allen

    2015-11-01

    JSPAM models galaxy collisions using a restricted n-body approach to speed up computation. Instead of using a softened point-mass potential, the software supports a modified version of the three component potential created by Hernquist (1994, ApJS 86, 389). Although spherically symmetric gravitationally potentials and a Gaussian model for the bulge are used to increase computational efficiency, the potential mimics that of a fully consistent n-body model of a galaxy. Dynamical friction has been implemented in the code to improve the accuracy of close approaches between galaxies. Simulations using this code using thousands of particles over the typical interaction times of a galaxy interaction take a few seconds on modern desktop workstations, making it ideal for rapidly prototyping the dynamics of colliding galaxies. Extensive testing of the code has shown that it produces nearly identical tidal features to those from hierarchical tree codes such as Gadget but using a fraction of the computational resources. This code was used in the Galaxy Zoo: Mergers project and is very well suited for automated fitting of galaxy mergers with automated pattern fitting approaches such as genetic algorithms. Java and Fortran versions of the code are available.

  13. HETDEX: Nearby Galaxies

    NASA Astrophysics Data System (ADS)

    Drory, Niv; Gebhardt, K.; Jogee, S.; Fabricius, M.; Greene, J.; HETDEX Collaboration

    2012-01-01

    The Hobby-Eberly Telescope Dark Energy Experiment (HETDEX) is a blind spectroscopic survey using the VIRUS instrument. VIRUS consists of 75 IFUs distributed across the 22-arcmin field of the upgraded 9.2-m HET. Each 50x50 arcsec IFU is made up of 448 1.5-arcsec fibers, and feeds a pair of spectrographs with a fixed bandpass of 350-550 nm and resolving power R 700. The IFUs have a fill-factor of 1/3 which will be filled-in by dithering. We cover 1/4.5 of our 300-square-degree main survey area with fibers. We reach m_AB 22.6 (21.5,20.7) at S/N 3 (5,10) per resolution element. With these limits, g 17 spiral galaxies will have S/N>3 per resolution element per fiber in the continuum to 2 effective radii, and emission line spectra to at least their optical radius. HETDEX will spatially resolve 4000 local galaxies to that limit without any pre-selection; an additional 9000 local galaxies will have spatially resolved spectroscopy beyond that limit. At g 19 we still obtain integrated galaxy spectra at S/N 10 per resolution element in the continuum. These spatially resolved absorption and emission spectra provide information on star formation, the state of the IGM, and stellar populations, as well as rotation curves for an unbiased galaxy sample unprecedented in size. Since a wealth of information about a galaxy's formation history is encoded in gradients across the galaxy, moving from single-fiber (SDSS-like) spectra to large samples of spatially resolved galaxy spectroscopy opens a new parameter space for future studies of galaxy formation.

  14. X-Ray Emission in Non-AGN Galaxies at z &8771 1

    NASA Astrophysics Data System (ADS)

    Chatterjee, Suchetana; Newman, Jeffrey A.; Jeltema, Tesla; Myers, Adam D.; Aird, James; Bundy, Kevin; Conselice, Christopher; Cooper, Michael; Laird, Elise; Nandra, Kirpal; Willmer, Christopher

    2015-06-01

    Using data from the DEEP2 galaxy redshift survey and the All Wavelength Extended Groth Strip International Survey we obtain stacked X-ray maps of galaxies at 0.7≤slant z≤slant 1.0 as a function of stellar mass. We compute the total X-ray counts of these galaxies and show that in the soft band (0.5-2 kev) there exists a significant correlation between galaxy X-ray counts and stellar mass at these redshifts. The best-fit relation between X-ray counts and stellar mass can be characterized by a power law with a slope of 0.58 ± 0.1. We do not find any correlation between stellar mass and X-ray luminosities in the hard (2-7 kev) and ultra-hard (4-7 kev) bands. The derived hardness ratios of our galaxies suggest that the X-ray emission is degenerate between two spectral models, namely point-like power-law emission and extended plasma emission in the interstellar medium. This is similar to what has been observed in low redshift galaxies. Using a simple spectral model where half of the emission comes from power-law sources and the other half from the extended hot halo we derive the X-ray luminosities of our galaxies. The soft X-ray luminosities of our galaxies lie in the range 1039-8× {{10}40} erg s-1. Dividing our galaxy sample by the criteria U-B\\gt 1, we find no evidence that our results for X-ray scaling relations depend on optical color.

  15. Spiral Galaxies Stripped Bare

    NASA Astrophysics Data System (ADS)

    2010-10-01

    Six spectacular spiral galaxies are seen in a clear new light in images from ESO's Very Large Telescope (VLT) at the Paranal Observatory in Chile. The pictures were taken in infrared light, using the impressive power of the HAWK-I camera, and will help astronomers understand how the remarkable spiral patterns in galaxies form and evolve. HAWK-I [1] is one of the newest and most powerful cameras on ESO's Very Large Telescope (VLT). It is sensitive to infrared light, which means that much of the obscuring dust in the galaxies' spiral arms becomes transparent to its detectors. Compared to the earlier, and still much-used, VLT infrared camera ISAAC, HAWK-I has sixteen times as many pixels to cover a much larger area of sky in one shot and, by using newer technology than ISAAC, it has a greater sensitivity to faint infrared radiation [2]. Because HAWK-I can study galaxies stripped bare of the confusing effects of dust and glowing gas it is ideal for studying the vast numbers of stars that make up spiral arms. The six galaxies are part of a study of spiral structure led by Preben Grosbøl at ESO. These data were acquired to help understand the complex and subtle ways in which the stars in these systems form into such perfect spiral patterns. The first image shows NGC 5247, a spiral galaxy dominated by two huge arms, located 60-70 million light-years away. The galaxy lies face-on towards Earth, thus providing an excellent view of its pinwheel structure. It lies in the zodiacal constellation of Virgo (the Maiden). The galaxy in the second image is Messier 100, also known as NGC 4321, which was discovered in the 18th century. It is a fine example of a "grand design" spiral galaxy - a class of galaxies with very prominent and well-defined spiral arms. About 55 million light-years from Earth, Messier 100 is part of the Virgo Cluster of galaxies and lies in the constellation of Coma Berenices (Berenice's Hair, named after the ancient Egyptian queen Berenice II). The third

  16. Growing Galaxies Gently

    NASA Astrophysics Data System (ADS)

    2010-10-01

    New observations from ESO's Very Large Telescope have, for the first time, provided direct evidence that young galaxies can grow by sucking in the cool gas around them and using it as fuel for the formation of many new stars. In the first few billion years after the Big Bang the mass of a typical galaxy increased dramatically and understanding why this happened is one of the hottest problems in modern astrophysics. The results appear in the 14 October issue of the journal Nature. The first galaxies formed well before the Universe was one billion years old and were much smaller than the giant systems - including the Milky Way - that we see today. So somehow the average galaxy size has increased as the Universe has evolved. Galaxies often collide and then merge to form larger systems and this process is certainly an important growth mechanism. However, an additional, gentler way has been proposed. A European team of astronomers has used ESO's Very Large Telescope to test this very different idea - that young galaxies can also grow by sucking in cool streams of the hydrogen and helium gas that filled the early Universe and forming new stars from this primitive material. Just as a commercial company can expand either by merging with other companies, or by hiring more staff, young galaxies could perhaps also grow in two different ways - by merging with other galaxies or by accreting material. The team leader, Giovanni Cresci (Osservatorio Astrofisico di Arcetri) says: "The new results from the VLT are the first direct evidence that the accretion of pristine gas really happened and was enough to fuel vigorous star formation and the growth of massive galaxies in the young Universe." The discovery will have a major impact on our understanding of the evolution of the Universe from the Big Bang to the present day. Theories of galaxy formation and evolution may have to be re-written. The group began by selecting three very distant galaxies to see if they could find evidence

  17. Turbulence and Star Formation in Dwarf Galaxies

    NASA Astrophysics Data System (ADS)

    Hollyday, Gigja; Hunter, Deidre Ann; Little Things Team

    2015-01-01

    We are interested in understanding the nature and role of turbulence in the interstellar medium of dwarf irregular galaxies. Turbulence, resulting from a variety of processes, is a potential source for cloud formation, and thus star formation. We have undertaken an indirect analysis of turbulence via the third (skewness) and fourth (kurtosis) moments of the distribution of atomic hydrogen gas densities using the LITTLE THINGS data for a 40-count sample of nearby (<10.3 Mpc) dwarf galaxies. We followed the formulism used by Burkhart et al. (2010) in a study of the SMC. We found that there is evidence of turbulence in dwarf galaxies at a level comparable to that found in the SMC, but we have found no correlation between integrated star formation rates and integrated kurtosis values nor a clear correlation between kurtosis as a function of radius with gas surface density and star formation profiles. We are grateful for a summer internship provided by the Research Experiences for Undergraduates program at Northern Arizona University, run by Dr. Kathy Eastwood and Dr. David Trilling and funded by the National Science Foundation through grant AST-1004107.

  18. Effects of simulated cosmological magnetic fields on the galaxy population

    NASA Astrophysics Data System (ADS)

    Marinacci, Federico; Vogelsberger, Mark

    2016-02-01

    We investigate the effects of varying the intensity of the primordial magnetic seed field on the global properties of the galaxy population in ideal magnetohydrodynamic cosmological simulations performed with the moving-mesh code AREPO. We vary the seed field in our calculations in a range of values still compatible with the current cosmological upper limits. We show that above a critical intensity of ≃10-9 G, the additional pressure arising from the field strongly affects the evolution of gaseous structures, leading to a suppression of the cosmic star formation history, which is stronger for larger seed fields. This directly reflects into a lower total galaxy count above a fixed stellar mass threshold at all redshifts, and a lower galaxy number density at fixed stellar mass and a less massive stellar component at fixed virial mass at all mass scales. These signatures may be used, in addition to the existing methods, to derive tighter constraints on primordial magnetic seed field intensities.

  19. The second byurakan survey galaxies. i. the optical database

    NASA Astrophysics Data System (ADS)

    Gyulzadyan, M.; McLean, B.; Adibekyan, V. Zh.; Allen, R. J.; Kunth, D.; Petrosian, A.; Stepanian, J. A.

    2011-03-01

    A database for the entire catalog of the Second Byurakan Survey (SBS) galaxies is presented. It contains new measurements of their optical parameters and additional information taken from the literature and other databases. The measurements were made using Ipg (near-infrared), Fpg (red), and Jpg (blue) band images from photographic sky survey plates obtained by the Palomar Schmidt telescope and extracted from the STScI Digital Sky Survey (DSS). The database provides accurate coordinates, morphological type, spectral and activity classes, apparent magnitudes and diameters, axial ratios and position angles, as well as number counts of neighboring objects in a circle of radius 50 kpc. The total number of individual SBS objects in the database is now 1676. The 188 Markarian galaxies that were re-discovered by SBS are not included in this database. We also include redshifts that are now available for 1576 SBS objects, as well as 2MASS infrared magnitudes for 1117 SBS galaxies.

  20. The Bolocam Lockman Hole millimeter-wave galaxy survey

    NASA Astrophysics Data System (ADS)

    Laurent, G. T.

    2006-06-01

    This work presents results of a new deep (s 1.1mm ~= 1.4 mJy beam -1 ) 1.1 mm submillimeter galaxy survey using Bolocam, a millimeter-wavelength bolometer array camera designed for mapping large fields at fast scan rates, without chopping. A map, galaxy candidate list, and derived number counts are presented. The data were reduced using a custom software pipeline to remove correlated sky and instrument noise via a principal component analysis. Extensive simulations and jackknife tests were performed to confirm the robustness of our source candidates and estimate the effects of false detections, bias, and completeness. In total, 17 source candidates were detected at a significance > 3.0 s, with six expected false detections. From both our observed number counts and a fluctuation analysis, we estimate the underlying differential number count distribution of submillimeter galaxies and find it to be in general agreement with previous surveys. This work also presents 350 mm photometry of all 17 galaxy candidates detected in the Lockman Hole survey. Nine of the Bolocam galaxy candidates were detected at 350 mm and two new candidates were serendipitously detected at 350 mm (bringing the total in the literature detected in this way to three). Five of the galaxies have published spectroscopic redshifts, enabling investigation of the implied temperature ranges and a comparison of photometric redshift techniques. Because l = 350 mm lies near the spectral energy distribution peak for z [approximate] 2.5 thermally emitting galaxies, luminosities can be measured without extrapolating to the peak from detection wavelengths of l >= 850 mm. Characteristically, the galaxy luminosities lie in the range 1.0--1.2 × 10 13 [Special characters omitted.] , with dust temperatures in the range of 40 K to 70 K, depending on the choice of spectral index and wavelength of unit optical depth. The implied dust masses are 3--5 × 10 8 [Special characters omitted.] . We find that the far

  1. The First Galaxies

    NASA Astrophysics Data System (ADS)

    Bromm, Volker

    2009-03-01

    An important open frontier in astrophysics is to understand how the first sources of light, the first stars and galaxies, ended the cosmic dark ages at redshifts z ≃ 15 - 20. Their formation signaled the transition from the simple initial state of the universe to one of ever increasing complexity. We here review recent progress in understanding the assembly process of the first galaxies with numerical simulations, starting with cosmological initial conditions and modelling the detailed physics of star formation. The key drivers in building up the primordial galaxies are the feedback effects from the first stars, due to their input of radiation and of heavy chemical elements in the wake of supernova explosions. In addition, the conditions inside the first galaxies are governed by the gravitationally-driven turbulence generated during the virialization of the dark matter host halo. Our theoretical predictions will be tested with upcoming near-infrared observatories, such as the James Webb Space Telecope, in the decade ahead.

  2. Galaxy Messier 51

    NASA Technical Reports Server (NTRS)

    2003-01-01

    NASA's Galaxy Evolution Explorer took this image of the spiral galaxy Messier 51 on June 19 and 20, 2003. Messier 51 is located 27 million light-years from Earth. Due to a lack of star formation, the companion galaxy in the top of the picture is barely visible as a near ultraviolet object.

    The Galaxy Evolution Explorer mission is led by the California Institute of Technology, which is also responsible for the science operations and data analysis. NASA's Jet Propulsion Laboratory, Pasadena, Calif., a division of Caltech, manages the mission and built the science instrument. The mission was developed under NASA's Explorers Program, managed by the Goddard Space Flight Center, Greenbelt, Md. The mission's international partners include South Korea and France.

  3. Percolation and galaxies.

    PubMed

    Schulman, L S; Seiden, P E

    1986-07-25

    A theory is presented in which much of the structure of spiral galaxies arises from a percolation phase transition that underlies the phenomenon of propagating star formation. According to this view, the appearance of spiral arms is a consequence of the differential rotation of the galaxy and the characteristic divergence of correlation lengths for continuous phase transitions. Other structural properties of spiral galaxies, such as the distribution of the gaseous components and the luminosity, arise directly from a feedback mechanism that pins the star formation rate close to the critical point of the phase transition. The approach taken in this article differs from traditional dynamical views. The argument is presented that, at least for some galaxies, morphological and other features are already fixed by general properties of phase transitions, irrespective of detailed dynamic or other considerations. PMID:17794566

  4. Galaxy NGC5398

    NASA Technical Reports Server (NTRS)

    2003-01-01

    This is an ultraviolet color image of the galaxy NGC5398 taken by NASA's Galaxy Evolution Explorer on June 7, 2003. NGC5398 is a barred spiral galaxy located 60 million light-years from Earth. The star formation is concentrated in the two bright regions of the image.

    The Galaxy Evolution Explorer mission is led by the California Institute of Technology, which is also responsible for the science operations and data analysis. NASA's Jet Propulsion Laboratory, Pasadena, Calif., a division of Caltech, manages the mission and built the science instrument. The mission was developed under NASA's Explorers Program, managed by the Goddard Space Flight Center, Greenbelt, Md. The mission's international partners include South Korea and France.

  5. Galaxy M101

    NASA Technical Reports Server (NTRS)

    2003-01-01

    This three-color image of galaxy M101 was taken by NASA's Galaxy Evolution Explorer on June 20, 2003. The far ultraviolet emissions are shown in blue, the near ultraviolet emissions are green, and the red emissions, which were taken from NASA's Digital Sky Survey, represent visible light. This image combines short, medium, and long 'exposure' pictures to best display the evolution of star formation in a spiral galaxy.

    The Galaxy Evolution Explorer mission is led by the California Institute of Technology, which is also responsible for the science operations and data analysis. NASA's Jet Propulsion Laboratory, Pasadena, Calif., a division of Caltech, manages the mission and built the science instrument. The mission was developed under NASA's Explorers Program, managed by the Goddard Space Flight Center, Greenbelt, Md. The mission's international partners include South Korea and France.

  6. Ripples in disk galaxies

    NASA Astrophysics Data System (ADS)

    Schweizer, Francois; Seitzer, Patrick

    1988-05-01

    The authors present evidence that ripples ("shells") occur not only in ellipticals, as hitherto believed, but also in disk galaxies of Hubble types S0, S0/Sa, and Sa, and probably even in the Sbc galaxy NGC 3310. This evidence includes the discovery of ripples in the northern disk galaxies NGC 3032, 3619, 4382, 5548 (a Seyfert), and 5739, and in the "diskless S0" NGC 7600. It is argued that these ripples cannot usually have resulted form transient spiral waves or other forced vibrations in the existing disks, but instead consist of extraneous sheet-like matter. The frequent presence of major disk-shaped companions suggests that ripple material may be acquired not only through wholesale mergers, but also through mass transfer from neighbor galaxies.

  7. White blood cell count - series (image)

    MedlinePlus

    ... measures two components: the total number of WBC's (leukocytes), and the differential count. The differential count measures the percentages of each type of leukocyte present. WBC's are composed of granulocytes (neutrophils, eosinophils, ...

  8. Low white blood cell count and cancer

    MedlinePlus

    Neutropenia and cancer; Absolute neutrophil count and cancer; ANC and cancer ... A person with cancer can get a low white blood cell count from the cancer or from treatment for the cancer. Cancer may ...

  9. Determination of the Cosmic Radio Background from the Radio-Infrared Relation in Galaxies

    NASA Technical Reports Server (NTRS)

    Dwek, Eli; Barker, Michael K.; Fisher, Richard R. (Technical Monitor)

    2001-01-01

    We use the radioactive flux correlation for star forming galaxies in the local universe to derive their contribution to the cosmic radio background (CRB). The CRB from these galaxies is therefore determined by the evolution of the comoving infrared luminosity density with redshift, which is constrained by galaxy number counts at various infrared wavelengths and by the cosmic infrared background. The research of ED was supported by NASA NRA 99-OSS-01 Astrophysics Theory Program. MB acknowledges the support of the "Research Opportunities for Undergraduates in the Laboratory for Astronomy and Solar Physics" for the summer student internship program at NASA/GSFC.

  10. Photometric and Morphological Properties of Galaxies at the North Galactic Pole

    NASA Astrophysics Data System (ADS)

    Odewahn, S. C.; Aldering, G.

    1994-12-01

    A two color survey of 9 fields of the first epoch Palomar Sky Survey, centered on the North Galactic Pole, has been performed with the Minnesota Automated Plate Scanner. Following photometric calibration using both direct comparison with galaxy surface photometry and a stellar PSF adjustment technique, an innovative automated classification method is used to establish catalogs of stars and galaxies to approximate magnitude limits of O=20.5 and E=20.0. Hubble type-dependent photometric properties such as mean integrated color, mean surface brightness, and concentration index are extracted from the O and E images of galaxies with an isophotal magnitude brighter than O = 20.5. The resultant photometric catalog of galaxies is used to study the large scale distribution of galaxies at the NGP with a variety of number count mapping methods. We primarily investigate the relationship between local galaxy number density and trends among type-dependent photometric properties in an effort to detect and quantify the well-known galaxy morphology-density relation. A multi-dimensional analysis of these quantities is performed using neural network pattern classifiers in an effort to perfect a viable galaxy morphology classifier for the APS POSS I material. We study the distribution of our automatically classified sample as a function of local galaxy number density.

  11. PEARS Emission Line Galaxies

    NASA Technical Reports Server (NTRS)

    Pirzkal, Nor; Rothberg, Barry; Ly, Chun; Rhoads, James E.; Malhotra, Sangeeta; Grogin, Norman A.; Dahlen, Tomas; Meurer, Gerhardt R.; Walsh, Jeremy; Hathi, Nimish P.; Cohen, Seth; Belini, Andrea; Holwerda, Benne W.; Straughn, Amber; Mechtley, Matthew

    2012-01-01

    We present a full analysis of the Probing Evolution And Reionization Spectroscopically (PEARS) slitless grism spectroscopic data obtained vl'ith the Advanced Camera for Surveys on HST. PEARS covers fields within both the Great Observatories Origins Deep Survey (GOODS) North and South fields, making it ideal as a random surveY of galaxies, as well as the availability of a wide variety of ancillary observations to support the spectroscopic results. Using the PEARS data we are able to identify star forming galaxies within the redshift volume 0 < z < 1.5. Star forming regions in the PEARS survey are pinpointed independently of the host galaxy. This method allOW8 us to detect the presence of multiple emission line regions (ELRs) within a single galaxy. 1162 [OII], [OIII] and/or H-alpha emission lines have been identified in the PEARS sample of approx 906 galaxies down to a limiting flux of approx 10 - 18 erg/s/sq cm . The ELRs have also been compared to the properties of the host galaxy, including morphology, luminosity, and mass. From this analysis we find three key results: 1) The computed line luminosities show evidence of a flattening in the luminosity function with increasing redshift; 2) The star forming systems show evidence of disturbed morphologies, with star formation occurring predominantly within one effective (half-light) radius. However, the morphologies show no correlation with host stellar mass; and 3) The number density of star forming galaxies with M(*) >= 10(exp 9) Solar M decreases by an order of magnitude at z<=0.5 relative to the number at 0.5 < z < 0.9 in support of the argument for galaxy downsizing.

  12. Abundance of field galaxies

    NASA Astrophysics Data System (ADS)

    Klypin, Anatoly; Karachentsev, Igor; Makarov, Dmitry; Nasonova, Olga

    2015-12-01

    We present new measurements of the abundance of galaxies with a given circular velocity in the Local Volume: a region centred on the Milky Way Galaxy and extending to distance ˜10 Mpc. The sample of ˜750 mostly dwarf galaxies provides a unique opportunity to study the abundance and properties of galaxies down to absolute magnitudes MB ≈ -10 and virial masses M_vir= 109{ M_{⊙}}. We find that the standard Λ cold dark matter (ΛCDM) model gives remarkably accurate estimates for the velocity function of galaxies with circular velocities V ≳ 70 kms-1 and corresponding virial masses M_vir≳ 5× 10^{10}{ M_{⊙}}, but it badly fails by overpredicting ˜5 times the abundance of large dwarfs with velocities V = 30-40 kms-1. The warm dark matter (WDM) models cannot explain the data either, regardless of mass of WDM particle. Just as in previous observational studies, we find a shallow asymptotic slope dN/dlog V ∝ Vα, α ≈ -1 of the velocity function, which is inconsistent with the standard ΛCDM model that predicts the slope α = -3. Though reminiscent to the known overabundance of satellite problem, the overabundance of field galaxies is a much more difficult problem. For the standard ΛCDM model to survive, in the 10 Mpc radius of the Milky Way there should be 1000 not yet detected galaxies with virial mass M_vir≈ 10^{10}{ M_{⊙}}, extremely low surface brightness and no detectable H I gas. So far none of this type of galaxies have been discovered.

  13. Chandra Galaxy Atlas

    NASA Astrophysics Data System (ADS)

    Kim, Dong-Woo; Anderson, Craig; Burke, Doug; Fabbiano, Giuseppina; Fruscione, Antonella; Lauer, Jennifer L.; McCollough, Michael L.; Morgan, Doug; Mossman, Amy; O'Sullivan, Ewan; Paggi, Alessandro; Trinchieri, Ginevra

    2016-01-01

    We present the new results from the Chandra Galaxy Atlas prpject. We have systematically analyzed the archival Chandra data of 50 early type galaxies to study their hot ISM. Taking full advantage of the Chandra capabilities, we produced spatially resolved data products with additional spectral information. We will make these products publicly available and use them for our focused science goals, e.g., gas morphology, scaling relation, X-ray based mass profile, circum-nuclear gas.

  14. Galaxy Formation and Evolution

    NASA Astrophysics Data System (ADS)

    Nagamine, Kentaro; Reddy, Naveen; Daddi, Emanuele; Sargent, Mark T.

    2016-07-01

    In this chapter, we discuss the current status of observational and computational studies on galaxy formation and evolution. In particular, a joint analysis of star-formation rates (SFRs), stellar masses, and metallicities of galaxies throughout cosmic time can shed light on the processes by which galaxies build up their stellar mass and enrich the environment with heavy elements. Comparison of such observations and the results of numerical simulations can give us insights on the physical importance of various feedback effects by supernovae and active galactic nuclei. In Sect. 1, we first discuss the primary methods used to deduce the SFRs, stellar masses, and (primarily) gas-phase metallicities in high-redshift galaxies. Then, we show how these quantities are related to each other and evolve with time. In Sect. 2, we further examine the distribution of SFRs in galaxies following the `Main Sequence' paradigm. We show how the so-called `starbursts' display higher specific SFRs and SF efficiencies by an order of magnitude. We use this to devise a simple description of the evolution of the star-forming galaxy population since z ˜3 that can successfully reproduce some of the observed statistics in the infrared (IR) wavelength. We also discuss the properties of molecular gas. In Sect. 3, we highlight some of the recent studies of high-redshift galaxy formation using cosmological hydrodynamic simulations. We discuss the physical properties of simulated galaxies such as luminosity function and escape fraction of ionizing photons, which are important statistics for reionization of the Universe. In particular the escape fraction of ionizing photons has large uncertainties, and studying gamma-ray bursts (which is the main topic of this conference) can also set observational constraints on this uncertain physical parameter as well as cosmic star formation rate density.

  15. Life in the Galaxy?

    NASA Astrophysics Data System (ADS)

    Shostak, G. S.

    The arguments for and against the SETI (Search for Extra Terrestrial Intelligence) program are discussed. Based on apparently reasonable assumptions regarding the number of civilizations likely to exist in the Galaxy, it seems that ten million years would be sufficient time for an ambitious group of aliens to colonize the Galaxy; since no concrete evidence of aliens has turned up, the assumptions have to be reconsidered. The views of Sagan, Hart, Drake and a number of other researchers are noted.

  16. Galaxies at High Redshift

    NASA Astrophysics Data System (ADS)

    Bauer, F. E.

    2014-10-01

    Recent years have seen tremendous progress in finding and charactering star-forming galaxies at high redshifts across the electromagnetic spectrum, giving us a more complete picture of how galaxies evolve, both in terms of their stellar and gas content, as well as the growth of their central supermassive black holes. A wealth of studies now demonstrate that star formation peaked at roughly half the age of the Universe and drops precariously as we look back to very early times, and that their central monsters apparently growth with them. At the highest-redshifts, we are pushing the boundaries via deep surveys at optical, X-ray, radio wavelengths, and more recently using gamma-ray bursts. I will review some of our accomplishments and failures. Telescope have enabled Lyman break galaxies to be robustly identified, but the UV luminosity function and star formation rate density of this population at z = 6 - 8 seems to be much lower than at z = 2 - 4. High escape fractions and a large contribution from faint galaxies below our current detection limits would be required for star-forming galaxies to reionize the Universe. We have also found that these galaxies have blue rest-frame UV colours, which might indicate lower dust extinction at z > 5. There has been some spectroscopic confirmation of these Lyman break galaxies through Lyman-α emission, but the fraction of galaxies where we see this line drops at z > 7, perhaps due to the onset of the Gunn-Peterson effect (where the IGM is opaque to Lyman-α).

  17. Count rate limitations in pulsed accelerator fields

    SciTech Connect

    Justus, Alan L

    2010-12-15

    This paper discusses various concepts involved in the counting losses of pulse-counting health physics instrumentation when used within the pulsed radiation environments of typical accelerator fields, in order to pre-establish appropriate limitations in use. Discussed are the 'narrow' pulse and the 'wide' pulse cases, the special effect of neutron moderating assemblies, and the effect of pulse microstructure on the counting losses of the pulse-counting instrumentation. Examples are provided which highlight the various concepts and limitations.

  18. CONFRONTING COLD DARK MATTER PREDICTIONS WITH OBSERVED GALAXY ROTATIONS

    SciTech Connect

    Obreschkow, Danail; Meyer, Martin; Power, Chris; Staveley-Smith, Lister; Ma, Xiangcheng; Zwaan, Martin; Drinkwater, Michael J.

    2013-04-01

    The rich statistics of galaxy rotations as captured by the velocity function (VF) provide invaluable constraints on galactic baryon physics and the nature of dark matter (DM). However, the comparison of observed galaxy rotations against cosmological models is prone to subtle caveats that can easily lead to misinterpretations. Our analysis reveals full statistical consistency between {approx}5000 galaxy rotations, observed in line-of-sight projection, and predictions based on the standard cosmological model ({Lambda}CDM) at the mass-resolution of the Millennium simulation (H I line-based circular velocities above {approx}50 km s{sup -1}). Explicitly, the H I linewidths in the H I Parkes All Sky Survey (HIPASS) are found to be consistent with those in S{sup 3}-SAX, a post-processed semi-analytic model for the Millennium simulation. Previously found anomalies in the VF can be plausibly attributed to (1) the mass-limit of the Millennium simulation, (2) confused sources in HIPASS, (3) inaccurate inclination measurements for optically faint sources, and (4) the non-detectability of gas-poor early-type galaxies. These issues can be bypassed by comparing observations and models using linewidth source counts rather than VFs. We investigate if and how well such source counts can constrain the temperature of DM.

  19. Morphological evolution of galaxies

    NASA Astrophysics Data System (ADS)

    Gardner, Jonathan P.; Heap, Sara R.; Malumuth, Eliot M.; Hill, Robert S.; Smith, Eric P.

    1997-05-01

    Recent studies of the Hubble Deep Field (Abraham et al. 1996) [1] and Medium Deep Survey (Driver, Windhorst & Griffiths 1995) [6] find that the frequency of irregular/peculiar/merger systems rises with increasing redshift. However, this finding must be carefully interpreted in light of UV images of low-redshift galaxies obtained by the Ultraviolet Imaging Telescope (Stecher et al. 1992) [9]. These UV images imply that K-correction effects may be at least partially responsible for the apparent increase in Irr galaxies with redshift. To assess the degree to which there is an overabundance of Irregular galaxies (relative to the present epoch), we must understand the degree to which the K-correction biases morphological studies. We demonstrate the importance of the morphological K-correction to the classification schemes used in the HDF. We find that high-redshift spiral galaxies are misclassified as Irr galaxies, while Elliptical/S0 galaxies, should not be affected substantially. We have been granted 40 orbits in Cycle 7 with STIS to place these conclusions on a statistical basis.

  20. SPERM COUNT DISTRIBUTIONS IN FERTILE MEN

    EPA Science Inventory

    Sperm concentration and count are often used as indicators of environmental impacts on male reproductive health. Existing clinical databases may be biased towards subfertile men with low sperm counts and less is known about expected sperm count distributions in cohorts of fertil...

  1. Count-doubling time safety circuit

    DOEpatents

    Rusch, Gordon K.; Keefe, Donald J.; McDowell, William P.

    1981-01-01

    There is provided a nuclear reactor count-factor-increase time monitoring circuit which includes a pulse-type neutron detector, and means for counting the number of detected pulses during specific time periods. Counts are compared and the comparison is utilized to develop a reactor scram signal, if necessary.

  2. DC KIDS COUNT e-Databook Indicators

    ERIC Educational Resources Information Center

    DC Action for Children, 2012

    2012-01-01

    This report presents indicators that are included in DC Action for Children's 2012 KIDS COUNT e-databook, their definitions and sources and the rationale for their selection. The indicators for DC KIDS COUNT represent a mix of traditional KIDS COUNT indicators of child well-being, such as the number of children living in poverty, and indicators of…

  3. Monte Carlo Simulation of Counting Experiments.

    ERIC Educational Resources Information Center

    Ogden, Philip M.

    A computer program to perform a Monte Carlo simulation of counting experiments was written. The program was based on a mathematical derivation which started with counts in a time interval. The time interval was subdivided to form a binomial distribution with no two counts in the same subinterval. Then the number of subintervals was extended to…

  4. A Calibration of NICMOS Camera 2 for Low Count Rates

    NASA Astrophysics Data System (ADS)

    Rubin, D.; Aldering, G.; Amanullah, R.; Barbary, K.; Dawson, K. S.; Deustua, S.; Faccioli, L.; Fadeyev, V.; Fakhouri, H. K.; Fruchter, A. S.; Gladders, M. D.; de Jong, R. S.; Koekemoer, A.; Krechmer, E.; Lidman, C.; Meyers, J.; Nordin, J.; Perlmutter, S.; Ripoche, P.; Schlegel, D. J.; Spadafora, A.; Suzuki, N.

    2015-05-01

    NICMOS 2 observations are crucial for constraining distances to most of the existing sample of z\\gt 1 SNe Ia. Unlike conventional calibration programs, these observations involve long exposure times and low count rates. Reciprocity failure is known to exist in HgCdTe devices and a correction for this effect has already been implemented for high and medium count rates. However, observations at faint count rates rely on extrapolations. Here instead, we provide a new zero-point calibration directly applicable to faint sources. This is obtained via inter-calibration of NIC2 F110W/F160W with the Wide Field Camera 3 (WFC3) in the low count-rate regime using z∼ 1 elliptical galaxies as tertiary calibrators. These objects have relatively simple near-IR spectral energy distributions, uniform colors, and their extended nature gives a superior signal-to-noise ratio at the same count rate than would stars. The use of extended objects also allows greater tolerances on point-spread function profiles. We find space telescope magnitude zero points (after the installation of the NICMOS cooling system, NCS) of 25.296\\+/- 0.022 for F110W and 25.803\\+/- 0.023 for F160W, both in agreement with the calibration extrapolated from count rates ≳1000 times larger (25.262 and 25.799). Before the installation of the NCS, we find 24.843\\+/- 0.025 for F110W and 25.498\\+/- 0.021 for F160W, also in agreement with the high-count-rate calibration (24.815 and 25.470). We also check the standard bandpasses of WFC3 and NICMOS 2 using a range of stars and galaxies at different colors and find mild tension for WFC3, limiting the accuracy of the zero points. To avoid human bias, our cross-calibration was “blinded” in that the fitted zero-point differences were hidden until the analysis was finalized. Based on observations with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by AURA, Inc., under NASA contract NAS 5-26555, under programs

  5. Extreme value statistics of weak lensing shear peak counts

    NASA Astrophysics Data System (ADS)

    Reischke, R.; Maturi, M.; Bartelmann, M.

    2016-02-01

    The statistics of peaks in weak gravitational lensing maps is a promising technique to constrain cosmological parameters in present and future surveys. Here we investigate its power when using general extreme value statistics which is very sensitive to the exponential tail of the halo mass function. To this end, we use an analytic method to quantify the number of weak lensing peaks caused by galaxy clusters, large-scale structures and observational noise. Doing so, we further improve the method in the regime of high signal-to-noise ratios dominated by non-linear structures by accounting for the embedding of those counts into the surrounding shear caused by large-scale structures. We derive the extreme value and order statistics for both overdensities (positive peaks) and underdensities (negative peaks) and provide an optimized criterion to split a wide field survey into subfields in order to sample the distribution of extreme values such that the expected objects causing the largest signals are mostly due to galaxy clusters. We find good agreement of our model predictions with a ray-tracing N-body simulation. For a Euclid-like survey, we find tight constraints on σ8 and Ωm with relative uncertainties of ˜10-3. In contrast, the equation of state parameter w0 can be constrained only with a 10 per cent level, and wa is out of reach even if we include redshift information.

  6. Airborne dust particle counting techniques.

    PubMed

    Sharma, S G; Prasad, B D

    2006-03-01

    The paper briefly describes an electro-optical system for counting of dust particles, which is based on the scattering phenomena. Utilizing the scattering of light by various size particles present in the environment, various particle counting techniques have been developed in order to measure the scattered intensity of light. Light scatters in all directions but much more in the so-called near forward direction 17( composite function) off axis, at 163( composite function) from the light source in the visible range. On the basis of two techniques, the right angle and forward angle scattering, opto-mechanical systems have been developed which measure scattered intensity and particulate matter. The forward scattering Nephelometer is more sensitive and therefore is more suitable for pollution monitoring than the right angle scattering Nephelometer. Whereas the right angle scattering Nephelometer has the utility in extremely low concentration in ppb level owing to the excellent light trap efficiency in comparison to forward scattering Nephelometer. In this paper measurement techniques and measurement results associated with design and development of a real time particle analyser are also discussed.

  7. Prevalence of galaxy-galaxy interactions in AGN hosts

    NASA Astrophysics Data System (ADS)

    Lim, Jeremy; Kuo, Cheng-Yu; Tang, Ya-Wen; Greene, Jenny; Ho, Paul T. P.

    2004-11-01

    Studies in optical starlight have failed to reach a consensus on the importance of either galaxy interactions, bars, or nuclear spirals in triggering luminous active galactic nuclei (AGNs). Here, we present the first systematic imaging study of Seyfert (disk) galaxies in the 21-cm line of neutral atomic hydrogen (HI) gas. HI is the most sensitive and enduring tracer of galaxy interactions, and can reveal tidal features not otherwise visible in optical starlight. Our sample comprises all twenty-eight galaxies in the Véron-Cetty & Véron (1998) catalog with nuclear magnitudes -19 ≥ MB > -23 (including Seyfert, LINER, and HII galaxies) at 0.015 ≤ z ≤ 0.017 in the northern hemisphere, and a matched control sample of twenty-seven inactive galaxies at z≈0.008. We have detected nearly all the galaxies observed, and find a much higher incidence of tidal interactions -- usually not seen in optical starlight -- among the Seyfert galaxies by comparison with the matched control sample. Those Seyferts with uncertain or no clear tidal features show disturbed HI morphologies and/or kinematics, as well as HI companion galaxies, more frequently than the control sample. Our study suggests that the undisturbed optical appearence of active galaxies may be deceptive, and imply that galaxy-galaxy interactions trigger a significant fraction luminous AGNs at low redshifts. The majority of the Seyfert galaxies in our sample appear to be at a relatively early stage of an encounter rather than late in a merger.

  8. H1 in RSA galaxies

    NASA Technical Reports Server (NTRS)

    Richter, OTTO-G.

    1993-01-01

    The original Revised Shapley-Ames (RSA) galaxy sample of almost 1300 galaxies has been augmented with further bright galaxies from the RSA appendix as well as newer galaxy catalogs. A complete and homogeneous, strictly magnitude-limited all-sky sample of 2345 galaxies brighter than 13.4 in apparent blue magnitude was formed. New 21 cm H1 line observations for more than 600 RSA galaxies have been combined with all previously available H1 data from the literature. This new extentise data act allows detailed tests of widely accepted 'standard' reduction and analysis techniques.

  9. The Las Campanas Infrared Survey: Early-Type Galaxy Progenitors beyond z=1

    NASA Astrophysics Data System (ADS)

    McCarthy, P. J.; Carlberg, R. G.; Chen, H.-W.; Marzke, R. O.; Firth, A. E.; Ellis, R. S.; Persson, S. E.; McMahon, R. G.; Lahav, O.; Wilson, J.; Martini, P.; Abraham, R. G.; Sabbey, C. N.; Oemler, A.; Murphy, D. C.; Somerville, R. S.; Beckett, M. G.; Lewis, J. R.; MacKay, C. D.

    2001-10-01

    We have identified a population of faint red galaxies from a 0.62 deg2 region of the Las Campanas Infrared Survey whose properties are consistent with their being the progenitors of early-type galaxies. The optical and IR colors, number-magnitude relation, and angular clustering together indicate modest evolution and increased star formation rates among the early-type field population at redshifts between 1 and 2. The counts of red galaxies with H magnitudes between 17 and 20 rise with a slope that is much steeper than that of the total H sample. The surface density of red galaxies drops from roughly 3000 deg-2 at H=20.5, I-H>3 to ~20 deg-2 at H=20, I-H>5. The V-I colors are approximately 1.5 mag bluer on average than a pure old population and span a range of more than 3 mag. The strength of the angular clustering of the red galaxies is an order of magnitude larger than that of the full galaxy sample. The colors, and photometric redshifts derived from them, indicate that the red galaxies have redshift distributions adequately described by Gaussians with σz~=0.2 centered near z=1, with the exception that galaxies having V-I<1.6 and I-H>3 are primarily in the 1.5<~z<~2 range. We invert the angular correlation functions using these n(z) and find comoving correlation lengths of r0~=9-10 h-1 Mpc at z~=1, comparable to, or larger than, those found for early-type galaxies at lower redshifts. A simple photometric evolution model reproduces the counts of the red galaxies, with only an ~30% decline in the underlying space density of early-type galaxies at z~1.2. The colors indicate characteristic star formation rates of ~1 Msolar yr-1 per 1010 Msolar. We suggest on the basis of the colors, counts, and clustering that these red galaxies are the bulk of the progenitors of present-day early-type galaxies.

  10. A HYBRID MODEL FOR THE EVOLUTION OF GALAXIES AND ACTIVE GALACTIC NUCLEI IN THE INFRARED

    SciTech Connect

    Cai Zhenyi; Lapi, Andrea; Xia Junqing; De Zotti, Gianfranco; Danese, Luigi; Negrello, Mattia; Gruppioni, Carlotta; Rigby, Emma; Castex, Guillaume; Delabrouille, Jacques

    2013-05-01

    We present a comprehensive investigation of the cosmological evolution of the luminosity function of galaxies and active galactic nuclei (AGNs) in the infrared (IR). Based on the observed dichotomy in the ages of stellar populations of early-type galaxies on one side and late-type galaxies on the other, the model interprets the epoch-dependent luminosity functions at z {>=} 1.5 using a physical approach for the evolution of proto-spheroidal galaxies and of the associated AGNs, while IR galaxies at z < 1.5 are interpreted as being mostly late-type ''cold'' (normal) and ''warm'' (starburst) galaxies. As for proto-spheroids, in addition to the epoch-dependent luminosity functions of stellar and AGN components separately, we have worked out, for the first time, the evolving luminosity functions of these objects as a whole (stellar plus AGN component), taking into account in a self-consistent way the variation with galactic age of the global spectral energy distribution. The model provides a physical explanation for the observed positive evolution of both galaxies and AGNs up to z {approx_equal} 2.5 and for the negative evolution at higher redshifts, for the sharp transition from Euclidean to extremely steep counts at (sub-)millimeter wavelengths, as well as the (sub-)millimeter counts of strongly lensed galaxies that are hard to account for by alternative, physical or phenomenological, approaches. The evolution of late-type galaxies and z < 1.5 AGNs is described using a parametric phenomenological approach. The modeled AGN contributions to the counts and to the cosmic infrared background (CIB) are always sub-dominant. They are maximal at mid-IR wavelengths: the contribution to the 15 and 24 {mu}m counts reaches 20% above 10 and 2 mJy, respectively, while the contributions to the CIB are of 8.6% and of 8.1% at 15 {mu}m and 24 {mu}m, respectively. The model provides a good fit to the multi-wavelength (from the mid-IR to millimeter waves) data on luminosity functions at

  11. Automatic cell counting with ImageJ.

    PubMed

    Grishagin, Ivan V

    2015-03-15

    Cell counting is an important routine procedure. However, to date there is no comprehensive, easy to use, and inexpensive solution for routine cell counting, and this procedure usually needs to be performed manually. Here, we report a complete solution for automatic cell counting in which a conventional light microscope is equipped with a web camera to obtain images of a suspension of mammalian cells in a hemocytometer assembly. Based on the ImageJ toolbox, we devised two algorithms to automatically count these cells. This approach is approximately 10 times faster and yields more reliable and consistent results compared with manual counting.

  12. Evidence for Evolution in the Galaxy Merger Rate

    NASA Astrophysics Data System (ADS)

    Franklin, Barbara E.; Windhorst, Rogier A.; Burkey, Jordan M.; Keel, William C.

    1993-12-01

    We use a set of four deep Cycle 1+2 fields with the HST Wide-Field Camera to constrain the rate of galaxy merging between the current epoch and approximately z=0.7. These fields were selected around weak radio sources not in rich or poor clusters so as to not bias these studies. Since most mergers occur between members of bound pairs, the merger rate is given by (half) the rate of disappearance of galaxy pairs. Using an objective criterion for pair membership, we find that more than 34% of galaxies in the magnitude range I=18-22 mag belong to pairs, while careful study of nearby comparison samples shows that only 7% of local galaxies belong to pairs. Hence, about 13% of the galaxy population has disappeared to merging in the cosmic epoch corresponding to this magnitude interval (or 0.1<= z<=0.7). This pair fraction is a lower limit, since correction for pairs in which one member falls below our detection threshold would raise the fraction of pair members with I=18---22 mag to about 50%. (we do not include physical system of higher multiplicity in these values). Hence, the number of galaxy pairs has dropped significantly between z ~ 0.7 and the current epoch. When using the best available I-band field galaxy redshift distributions, the HST pair-fraction grows with redshift as ~ (1+z)(3.0-3.5) , quite consistent with the expected evolution in the merger-rate from the decrease in comoving volume (~ (1+z)(3) ). This result has very significant implications for the interpretation of the ground-based galaxy counts (it explains the disappearance of faint blue galaxies), the cosmological evolution of faint radio sources and quasars (explains why these should indeed evolve as ~ (1+z)(3) ), the statistics of QSO companions, the galaxy content in distant clusters, and the merging history of a ``typical" galaxy. This work was supported by STScI grants GO-2405.*-87A and GO-3545.*-91A (to WCK and RAW) and in part through EPSCoR grant EHR-9108761 (to WCK).

  13. Bacterial counts associated with recycled newspaper bedding.

    PubMed

    Hogan, J S; Smith, K L; Todhunter, D A; Schoenberger, P S

    1990-07-01

    Bacterial counts associated with recycled newspaper, wood shavings, and pelleted corn cobs used as bedding for lactating dairy cows were compared. Chopped newspaper and pelleted corn cobs had similar gram-negative bacterial, coliform, and streptococcal bedding counts. Staphylococcal counts in pelleted corn cobs were greater than in chopped newspaper. Conversely, gram-negative bacterial, coliform, and staphylococcal counts in chopped newspaper were greater than in wood shavings. Coliform and streptococcal counts did not differ between chopped newspaper and wood shavings bedding materials. Teat swab counts from cows bedded on pelleted corn cobs were greater than those from cows bedded on chopped newspaper for gram-negative bacterial, coliform, Klebsiella species, and staphylococci. Streptococcal teat swab counts did not differ between cows bedded on chopped newspaper and pelleted corn cobs. Cows bedded on chopped newspaper and wood shavings had similar gram-negative bacterial, coliform, and Klebsiella species teat swab counts. Streptococcal and staphylococcal teat swab counts were greater from cows bedded on chopped newspaper than those from cows bedded on wood shavings. Teat swab and bedding counts were correlated. In general, bacterial counts in bedding suggest no advantage in using chopped newspaper over pelleted corn cobs or wood shavings in reducing exposure of teats to environmental mastitis pathogens. PMID:2229587

  14. Kids Count in Delaware, Families Count in Delaware: Fact Book, 2003.

    ERIC Educational Resources Information Center

    Delaware Univ., Newark. Kids Count in Delaware.

    This Kids Count Fact Book is combined with the Families Count Fact Book to provide information on statewide trends affecting children and families in Delaware. The Kids Count and Families Count indicators have been combined into four new categories: health and health behaviors, educational involvement and achievement, family environment and…

  15. Counting hypermaps by Egorychev's method

    NASA Astrophysics Data System (ADS)

    Mednykh, Alexander; Nedela, Roman

    2016-09-01

    The aim of this paper is to find explicit formulae for the number of rooted hypermaps with a given number of darts on an orientable surface of genus g≤ 3. Such formulae were obtained earlier for g=0 and g=1 by Walsh and Arquès respectively. We first employ the Egorychev's method of counting combinatorial sums to obtain a new version of the Arquès formula for genus g=1. Then we apply the same approach to get new results for genus g=2,3. We could do it due to recent results by Giorgetti, Walsh, and Kazarian, Zograf who derived two different, but equivalent, forms of the generating functions for the number of hypermaps of genus two and three.

  16. Counting solutions from finite samplings.

    PubMed

    Huang, Haiping; Zhou, Haijun

    2012-02-01

    We formulate the solution counting problem within the framework of the inverse Ising problem and use fast belief propagation equations to estimate the entropy whose value provides an estimate of the true one. We test this idea on both diluted models [random 2-SAT (2-satisfiability) and 3-SAT problems] and a fully connected model (binary perceptron), and show that when the constraint density is small, this estimate can be very close to the true value. The information stored by the salamander retina under the natural movie stimuli can also be estimated, and our result is consistent with that obtained by the Monte Carlo method. Of particular significance is that the sizes of other metastable states for this real neuronal network are predicted. PMID:22463290

  17. Counting solutions from finite samplings

    NASA Astrophysics Data System (ADS)

    Huang, Haiping; Zhou, Haijun

    2012-02-01

    We formulate the solution counting problem within the framework of the inverse Ising problem and use fast belief propagation equations to estimate the entropy whose value provides an estimate of the true one. We test this idea on both diluted models [random 2-SAT (2-satisfiability) and 3-SAT problems] and a fully connected model (binary perceptron), and show that when the constraint density is small, this estimate can be very close to the true value. The information stored by the salamander retina under the natural movie stimuli can also be estimated, and our result is consistent with that obtained by the Monte Carlo method. Of particular significance is that the sizes of other metastable states for this real neuronal network are predicted.

  18. Low Background Counting At SNOLAB

    SciTech Connect

    Lawson, Ian; Cleveland, Bruce

    2011-04-27

    It is a continuous and ongoing effort to maintain radioactivity in materials and in the environment surrounding most underground experiments at very low levels. These low levels are required so that experiments can achieve the required detection sensitivities for the detection of low-energy neutrinos, searches for dark matter and neutrinoless double-beta decay. SNOLAB has several facilities which are used to determine these low background levels in the materials and the underground environment. This proceedings will describe the SNOLAB High Purity Germanium Detector which has been in continuous use for the past five years and give results of many of the items that have been counted over that period. Brief descriptions of SNOLAB's alpha-beta and electrostatic counters will be given, and the radon levels at SNOLAB will be discussed.

  19. Well coincidence counting and analysis

    SciTech Connect

    Lu, Ming-Shih; Teichmann, T.; Ceo, R.N.; Collins, L.L.

    1994-03-01

    In several recent papers a physical/mathematical model was developed to describe the nuclear multiplicative processes in samples containing fissile material from a general statistical viewpoint, starting with the basic underlying physical phenomena. The results of this model agreed with the established picture used in ``standard`` HLNCC (High Level Neutron Coincidence Counter) measurements, but considerably extended them, and allowed a more detailed interpretation of the underlying physical mechanisms and of the higher moments of the neutron counts. The present paper examines some recent measurements made at Y-12 (Oak Ridge) using the AWCC, in the light of this model. The results show internal consistency under a variety of conditions, and give good agreement between experiment and theory.

  20. Photon counting compressive depth mapping.

    PubMed

    Howland, Gregory A; Lum, Daniel J; Ware, Matthew R; Howell, John C

    2013-10-01

    We demonstrate a compressed sensing, photon counting lidar system based on the single-pixel camera. Our technique recovers both depth and intensity maps from a single under-sampled set of incoherent, linear projections of a scene of interest at ultra-low light levels around 0.5 picowatts. Only two-dimensional reconstructions are required to image a three-dimensional scene. We demonstrate intensity imaging and depth mapping at 256 × 256 pixel transverse resolution with acquisition times as short as 3 seconds. We also show novelty filtering, reconstructing only the difference between two instances of a scene. Finally, we acquire 32 × 32 pixel real-time video for three-dimensional object tracking at 14 frames-per-second. PMID:24104293

  1. Counting paths with Schur transitions

    NASA Astrophysics Data System (ADS)

    Díaz, Pablo; Kemp, Garreth; Véliz-Osorio, Alvaro

    2016-10-01

    In this work we explore the structure of the branching graph of the unitary group using Schur transitions. We find that these transitions suggest a new combinatorial expression for counting paths in the branching graph. This formula, which is valid for any rank of the unitary group, reproduces known asymptotic results. We proceed to establish the general validity of this expression by a formal proof. The form of this equation strongly hints towards a quantum generalization. Thus, we introduce a notion of quantum relative dimension and subject it to the appropriate consistency tests. This new quantity finds its natural environment in the context of RCFTs and fractional statistics; where the already established notion of quantum dimension has proven to be of great physical importance.

  2. Probing the primordial power spectrum with cluster number counts

    SciTech Connect

    Chantavat, Teeraparb; Gordon, Christopher; Silk, Joseph

    2009-04-15

    We investigate how well galaxy cluster number counts can constrain the primordial power spectrum. Measurements of the primary anisotropies in the cosmic microwave background may be limited, by the presence of foregrounds from secondary sources, to probing the primordial power spectrum at wave numbers less than about 0.30h Mpc{sup -1}. We break up the primordial power spectrum into a number of nodes and interpolate linearly between each node. This allows us to show that cluster number counts could then extend the constraints on the form of the primordial power spectrum up to wave numbers of about 0.45h Mpc{sup -1}. We estimate combinations of constraints from PLANCK and SPT primary cosmic microwave background and their respective Sunyaev-Zeldovich surveys. We find that their constraining ability is limited by uncertainties in the mass-scaling relations. We also estimate the constraint from clusters detected from a SNAP-like gravitational lensing survey. As there is an unambiguous and simple relationship between the filtered shear of the lensing survey and the cluster mass, it may be possible to obtain much tighter constraints on the primordial power spectrum in this case.

  3. Counting Electrons on Liquid Helium

    NASA Astrophysics Data System (ADS)

    Glasson, Phillip

    2004-03-01

    Electrons on liquid helium, localised in an array of quantum dots, have been proposed as condensed matter qubits [M.I.Dykman et al. Phys.Rev. B 67, 155402 (2003)]. The ground and first excited Rydberg states in the vertical potential well on the helium surface would represent |0> and |1>. This requires (a) novel electronic devices on helium using microstructured substrates, (b) excitation of Rydberg states using millimetric microwaves and (c) detection of individual electrons and their quantum states. Progress in meeting these challenges will be presented. An AC-coupled Field Effect Transistor (FET) has been made on GaAs, using free electrons on suspended liquid helium microchannels, 16 micron wide and 1.6 microns deep [P.Glasson et al, Phys.Rev.Lett. 87 176802 (2001)]. The microwave absorption to the first excited Rydberg state near 200 GHz has been measured below 1 K [E.Collin et al. Phys.Rev.Lett. 89, 245301 (2002)], where the temperature-dependent contribution to the linewidth is small. High values of the ratio of the Rabi frequency to the linewidth are obtained. Electrons are trapped on a 5 micron diameter pool of superfluid helium, above a single-electron-transistor (SET) as a detector. The pool is charged from a surface electron reservoir and we count the electrons into and out of the trap. Individual electrons can be stored, detected and counted: the next stage is quantum state detection. The prospects for qubits and quantum information processing with electrons on helium will be assessed.

  4. Midsummer's Dream Galaxies

    NASA Astrophysics Data System (ADS)

    2005-08-01

    How does the Galaxy in which we live look like? It is almost certain that we will never be able to send a probe out of our Milky Way to take a snapshot, in the same way as the first satellites could do to give us striking images of planet Earth. But astronomers do not need this to imagine what our bigger home resembles. And they have a pretty good idea of it. The Milky Way with its several hundreds of billion stars is thought to be a relatively flat disc - 100,000 light-year across [1] - with a central bulge lying in the direction of the constellation Sagittarius (The Archer) and six spiral arms. The Milky Way has most probably also a central bar made of young, bright stars. If we can't take pictures of the Milky Way, we may photograph others galaxies which astronomers think look similar to it. The two galaxies presented here are just two magnificient examples of barred spiral galaxies. One - Messier 83 - is seen face-on, and the other - NGC 4565 - appears edge-on. Together, they give us a nice idea of how the Milky Way may appear from outer space. These images are based on data obtained with the twin FORS1 and FORS2 (FOcal Reducer and Spectrograph) instruments attached to two ESO's 8.2-m Unit Telescopes of the Very Large Telescope Array located on Cerro Paranal. The data were extracted from the ESO Science Archive Facility, which contains approximately 50 Terabytes [2] of scientific data and is, since April 1, 2005, open to the worldwide community. These invaluable data have already led to the publication of more than 1000 scientific papers. They also contains many nice examples of beautiful astronomical objects which could be the theme of as many midsummer's dreams. NGC 4565 The first galaxy pictured here is NGC 4565 [3], which for obvious reasons is also called the Needle Galaxy. First spotted in 1785 by Uranus' discoverer, Sir William Herschel (1738-1822), this is one of the most famous example of an edge-on spiral galaxy and is located some 30 million light

  5. Seeing Baby Dwarf Galaxies

    NASA Technical Reports Server (NTRS)

    2009-01-01

    [figure removed for brevity, see original site] [figure removed for brevity, see original site] [figure removed for brevity, see original site] Visible/DSS Click on image for larger version Ultraviolet/GALEX Click on image for larger version Poster Version Click on image for larger version

    The unique ultraviolet vision of NASA's Galaxy Evolution Explorer reveals, for the first time, dwarf galaxies forming out of nothing more than pristine gas likely leftover from the early universe. Dwarf galaxies are relatively small collections of stars that often orbit around larger galaxies like our Milky Way.

    The forming dwarf galaxies shine in the far ultraviolet spectrum, rendered as blue in the call-out on the right hand side of this image. Near ultraviolet light, also obtained by the Galaxy Evolution Explorer, is displayed in green, and visible light from the blue part of the spectrum here is represented by red. The clumps (in circles) are distinctively blue, indicating they are primarily detected in far ultraviolet light.

    The faint blue overlay traces the outline of the Leo Ring, a huge cloud of hydrogen and helium that orbits around two massive galaxies in the constellation Leo (left panel). The cloud is thought likely to be a primordial object, an ancient remnant of material that has remained relatively unchanged since the very earliest days of the universe. Identified about 25 years ago by radio waves, the ring cannot be seen in visible light.

    Only a portion of the Leo Ring has been imaged in the ultraviolet, but this section contains the telltale ultraviolet signature of recent massive star formation within this ring of pristine gas. Astronomers have previously only seen dwarf galaxies form out of gas that has already been cycled through a galaxy and enriched with metals elements heavier than helium produced as stars evolve.

    The visible data come from the Digitized Sky Survey of the Space Telescope Science Institute in Baltimore, Md. The

  6. A MINUET OF GALAXIES

    NASA Technical Reports Server (NTRS)

    2002-01-01

    This troupe of four galaxies, known as Hickson Compact Group 87 (HCG 87), is performing an intricate dance orchestrated by the mutual gravitational forces acting between them. The dance is a slow, graceful minuet, occurring over a time span of hundreds of millions of years. The Wide Field and Planetary Camera 2 on NASA's Hubble Space Telescope (HST) provides a striking improvement in resolution over previous ground-based imaging. In particular, this image reveals complex details in the dust lanes of the group's largest galaxy member (HCG 87a), which is actually disk-shaped, but tilted so that we see it nearly edge-on. Both 87a and its elliptically shaped nearest neighbor (87b) have active galactic nuclei which are believed to harbor black holes that are consuming gas. A third group member, the nearby spiral galaxy 87c, may be undergoing a burst of active star formation. Gas flows within galaxies can be intensified by the gravitational tidal forces between interacting galaxies. So interactions can provide fresh fuel for both active nuclei and starburst phenomena. These three galaxies are so close to each other that gravitational forces disrupt their structure and alter their evolution. From the analysis of its spectra, the small spiral near the center of the group could either be a fourth member or perhaps an unrelated background object. The HST image was made by combining images taken in four different color filters in order to create a three-color picture. Regions of active star formation are blue (hot stars) and also pinkish if hot hydrogen gas is present. The complex dark bands across the large edge-on disk galaxy are due to interstellar dust silhouetted against the galaxy's background starlight. A faint tidal bridge of stars can be seen between the edge-on and elliptical galaxies. HCG 87 was selected for Hubble imaging by members of the public who visited the Hubble Heritage website (http://heritage.stsci.edu) during the month of May and registered their votes

  7. Galaxies et trous noirs supermassifs

    NASA Astrophysics Data System (ADS)

    Collin-Zahn, Suzy

    2016-08-01

    A few percents of galaxies are classified as « active ». An active galaxy is a galaxy whose nucleus emits more energy than the whole galaxy in the form of electromagnetic radiation, relativistic particles, or mechanical energy. It is activated by a supermassive black hole fueled by matter falling on it, whose characteristics (Eddington luminosity, spin) are recalled. The class includes quasars and Seyfert galaxies. All massive "non active" galaxies contain a supermassive black hole, but there is not enough matter in its environment so as the nucleus becomes luminous. Different items are considered in the paper : how supermassive black holes are fueled, the accretion disc, the jets and the winds, the unified model of active galaxies, how are determined the masses of supermassive black holes, and what is the relation between the evolution of galaxies and supermassive black holes.

  8. Galaxy Centaurus A

    NASA Technical Reports Server (NTRS)

    2003-01-01

    This image of the active galaxy Centaurus A was taken by NASA's Galaxy Evolution Explorer on June 7, 2003. The galaxy is located 30 million light-years from Earth and is seen edge on, with a prominent dust lane across the major axis. In this image the near ultraviolet emission is represented as green, and the far ultraviolet emission as blue. The galaxy exhibits jets of high energy particles, which were traced by the X-ray emission and measured by NASA's Chandra X-ray Observatory. These X-ray emissions are seen as red in the image. Several regions of ultraviolet emission can be seen where the jets of high energy particles intersect with hydrogen clouds in the upper left corner of the image. The emission shown may be the result of recent star formation triggered by the compression of gas by the jet.

    The Galaxy Evolution Explorer mission is led by the California Institute of Technology, which is also responsible for the science operations and data analysis. NASA's Jet Propulsion Laboratory, Pasadena, Calif., a division of Caltech, manages the mission and built the science instrument. The mission was developed under NASA's Explorers Program, managed by the Goddard Space Flight Center, Greenbelt, Md. The mission's international partners include South Korea and France.

  9. Tidal alignment of galaxies

    NASA Astrophysics Data System (ADS)

    Blazek, Jonathan; Vlah, Zvonimir; Seljak, Uroš

    2015-08-01

    We develop an analytic model for galaxy intrinsic alignments (IA) based on the theory of tidal alignment. We calculate all relevant nonlinear corrections at one-loop order, including effects from nonlinear density evolution, galaxy biasing, and source density weighting. Contributions from density weighting are found to be particularly important and lead to bias dependence of the IA amplitude, even on large scales. This effect may be responsible for much of the luminosity dependence in IA observations. The increase in IA amplitude for more highly biased galaxies reflects their locations in regions with large tidal fields. We also consider the impact of smoothing the tidal field on halo scales. We compare the performance of this consistent nonlinear model in describing the observed alignment of luminous red galaxies with the linear model as well as the frequently used "nonlinear alignment model," finding a significant improvement on small and intermediate scales. We also show that the cross-correlation between density and IA (the "GI" term) can be effectively separated into source alignment and source clustering, and we accurately model the observed alignment down to the one-halo regime using the tidal field from the fully nonlinear halo-matter cross correlation. Inside the one-halo regime, the average alignment of galaxies with density tracers no longer follows the tidal alignment prediction, likely reflecting nonlinear processes that must be considered when modeling IA on these scales. Finally, we discuss tidal alignment in the context of cosmic shear measurements.

  10. Recent Galaxy Mergers and Residual Star Formation of Red Sequence Galaxies in Galaxy Clusters

    NASA Astrophysics Data System (ADS)

    Sheen, Yun-Kyeong; Yi, Sukyoung K.; Ree, Chang H.; Jaffé, Yara; Demarco, Ricardo; Treister, Ezequiel

    2016-08-01

    This study explored the Galaxy Evolution Explorer ultraviolet (UV) properties of optical red sequence galaxies in four rich Abell clusters at z≤slant 0.1. In particular, we tried to find a hint of merger-induced recent star formation (RSF) in red sequence galaxies. Using the NUV - r\\prime colors of the galaxies, RSF fractions were derived based on various criteria for post-merger galaxies and normal galaxies. Following k-correction, about 36% of the post-merger galaxies were classified as RSF galaxies with a conservative criterion (NUV - r\\prime ≤slant 5), and that number was doubled (˜72%) when using a generous criterion (NUV - r\\prime ≤slant 5.4). The trend was the same when we restricted the sample to galaxies within 0.5 × R 200. Post-merger galaxies with strong UV emission showed more violent, asymmetric features in the deep optical images. The RSF fractions did not show any trend along the clustocentric distance within R 200. We performed a Dressler–Shectman test to check whether the RSF galaxies had any correlation with the substructures in the galaxy clusters. Within R 200 of each cluster, the RSF galaxies did not appear to be preferentially related to the clusters’ substructures. Our results suggested that only 30% of RSF red sequence galaxies show morphological hints of recent galaxy mergers. This implies that internal processes (e.g., stellar mass loss or hot gas cooling) for the supply of cold gas to early-type galaxies may play a significant role in the residual star formation of early-type galaxies at a recent epoch.

  11. Recent Galaxy Mergers and Residual Star Formation of Red Sequence Galaxies in Galaxy Clusters

    NASA Astrophysics Data System (ADS)

    Sheen, Yun-Kyeong; Yi, Sukyoung K.; Ree, Chang H.; Jaffé, Yara; Demarco, Ricardo; Treister, Ezequiel

    2016-08-01

    This study explored the Galaxy Evolution Explorer ultraviolet (UV) properties of optical red sequence galaxies in four rich Abell clusters at z≤slant 0.1. In particular, we tried to find a hint of merger-induced recent star formation (RSF) in red sequence galaxies. Using the NUV - r\\prime colors of the galaxies, RSF fractions were derived based on various criteria for post-merger galaxies and normal galaxies. Following k-correction, about 36% of the post-merger galaxies were classified as RSF galaxies with a conservative criterion (NUV - r\\prime ≤slant 5), and that number was doubled (˜72%) when using a generous criterion (NUV - r\\prime ≤slant 5.4). The trend was the same when we restricted the sample to galaxies within 0.5 × R 200. Post-merger galaxies with strong UV emission showed more violent, asymmetric features in the deep optical images. The RSF fractions did not show any trend along the clustocentric distance within R 200. We performed a Dressler-Shectman test to check whether the RSF galaxies had any correlation with the substructures in the galaxy clusters. Within R 200 of each cluster, the RSF galaxies did not appear to be preferentially related to the clusters’ substructures. Our results suggested that only 30% of RSF red sequence galaxies show morphological hints of recent galaxy mergers. This implies that internal processes (e.g., stellar mass loss or hot gas cooling) for the supply of cold gas to early-type galaxies may play a significant role in the residual star formation of early-type galaxies at a recent epoch.

  12. Avian leucocyte counting using the hemocytometer

    USGS Publications Warehouse

    Dein, F.J.; Wilson, A.; Fischer, D.; Langenberg, P.

    1994-01-01

    Automated methods for counting leucocytes in avian blood are not available because of the presence of nucleated erythrocytes and thrombocytes. Therefore, total white blood cell counts are performed by hand using a hemocytometer. The Natt and Herrick and the Unopette methods are the most common stain and diluent preparations for this procedure. Replicate hemocytometer counts using these two methods were performed on blood from four birds of different species. Cells present in each square of the hemocytometer were counted. Counting cells in the corner, side, or center hemocytometer squares produced statistically equivalent results; counting four squares per chamber provided a result similar to that obtained by counting nine squares; and the Unopette method was more precise for hemocytometer counting than was the Natt and Herrick method. The Unopette method is easier to learn and perform but is an indirect process, utilizing the differential count from a stained smear. The Natt and Herrick method is a direct total count, but cell identification is more difficult.

  13. Peculiar galaxies and radio sources.

    PubMed

    Arp, H

    1966-03-11

    Pairs of radio sources which are separated by from 2 degrees to 6 degrees on the sky have been investigated. In a number of cases peculiar galaxies have been found approximately midway along a line joining the two radio sources. The central peculiar galaxies belong mainly to a certain class in the recently compiled Atlas of Peculiar Galaxies. Among the radio sources so far associated with the peculiar galaxies are at least five known quasars. These quasars are indicated to be not at cosmological distances (that is, red shifts not caused by expansion of the universe) because the central peculiar galaxies are only at distances of 10 to 100 megaparsecs. The absolute magnitudes of these quasars are indicated to be in the range of brightness of normal galaxies and downward. Some of the radio sources which have been found to be associated with peculiar galaxies are galaxies themselves. It is therefore implied that ejection of material took place within or near the parent peculiar galaxies with speeds between 10(2) and 10(4) kilometers per second. After traveling for times of the order of 10(7) to 10(9) years, the luminous matter (galaxies) and radio sources (plasma) have reached their observed separations from the central peculiar galaxy. The large red shifts measured for the quasars would seem to be either (i) gravitational, (ii) collapse velocities of clouds of material falling toward the center of these compact galaxies, or (iii) some as yet unknown cause.

  14. Kepler View of the Galaxy

    NASA Video Gallery

    Our Sun is just one out of over 200 billion stars in our galaxy, the Milky Way. The Sun is located in the Orion arm of our galaxy about 75,000 light years from the center of the Galaxy. Kepler will...

  15. Constraints on galaxy formation theories

    NASA Technical Reports Server (NTRS)

    Szalay, A. S.

    1986-01-01

    The present theories of galaxy formation are reviewed. The relation between peculiar velocities, temperature fluctuations of the microwave background and the correlation function of galaxies point to the possibility that galaxies do not form uniformly everywhere. The velocity data provide strong constraints on the theories even in the case when light does not follow mass of the universe.

  16. Microvariability in Seyfert galaxies

    USGS Publications Warehouse

    Carini, M.T.; Noble, J.C.; Miller, H.R.

    2003-01-01

    We present the results of a search for microvariability in a sample of eight Seyfert galaxies. Microvariability (i.e., variations occurring on timescales of tens of minutes to hours) has been conclusively demonstrated to exist in the class of active galactic nuclei (AGNs) known as blazars. Its existence in other classes of AGNs is far less certain. We present the results of a study of eight Seyfert 1 galaxies, which were intensively monitored in order to determine whether such variations exist in these objects. Only one object, Ark 120, displayed any evidence of microvariations. The implications of these results with respect to current models of the mechanisms responsible for the observed emission in Seyfert galaxies are discussed. We compare our results with those obtained from other studies of microvariability in different classes of AGNs.

  17. Local normal galaxies

    NASA Technical Reports Server (NTRS)

    Fichtel, Carl E.

    1990-01-01

    In the near future, high energy (E greater than 20 MeV) gamma ray astronomy offers the promise of a new means of examining the closest galaxies. Two and possibly three local galaxies, the Small and Large Magellanic Clouds and M31, should be visible to the high energy gamma ray telescope on the Gamma Ray Observatory, and the first should be seen by GAMMA-1. With the assumptions of adequate cosmic ray production and reasonable magnetic field strengths, both of which should likely be satisfied, specific predictions of the gamma ray emission can be made separating the concepts of the galactic and universal nature of cosmic rays. A study of the synchrotron radiation from the Large Magellanic Cloud (LMC) suggests that the cosmic ray density is similar to that in the local region of our galaxy, but not uniform. It is hoped the measurements will be able to verify this independent of assumptions about the magnetic fields in the LMC.

  18. High redshift radio galaxies

    NASA Technical Reports Server (NTRS)

    Mccarthy, Patrick J.

    1993-01-01

    High redshift galaxies that host powerful radio sources are examined. An overview is presented of the content of radio surveys: 3CR and 3CRR, 4C and 4C/USS, B2/1 Jy, MG, MRC/1Jy, Parkes/PSR, B3, and ESO Key-Project. Narrow-line radio galaxies in the visible and UV, the source of ionization and excitation of the emission lines, emission-line luminosities, morphology of the line-emitting gas, physical properties and energetics, kinematics of the line-emitting gas, and implications from the emission lines are discussed. The morphologies and environments of the host galaxies, the alignment effect, and spectral energy distributions and ages are also examined.

  19. Edge-on Galaxy

    NASA Technical Reports Server (NTRS)

    1999-01-01

    NASA's Hubble Space Telescope has imaged an unusual edge-on galaxy, revealing remarkable details of its warped dusty disc and showing how colliding galaxies trigger the birth of new stars.

    The image, taken by Hubble's Wide Field and Planetary Camera 2 (WFPC2), is online at http://heritage.stsci.edu and http://www.jpl.nasa.gov/images/wfpc. The camera was designed and built by NASA's Jet Propulsion Laboratory, Pasadena, Calif. During observations of the galaxy, the camera passed a milestone, taking its 100,000th image since shuttle astronauts installed it in Hubble in 1993.

    The dust and spiral arms of normal spiral galaxies, like our Milky Way, look flat when seen edge- on. The new image of the galaxy ESO 510-G13 shows an unusual twisted disc structure, first seen in ground-based photographs taken at the European Southern Observatory in Chile. ESO 510-G13 lies in the southern constellation Hydra, some 150 million light-years from Earth. Details of the galaxy's structure are visible because interstellar dust clouds that trace its disc are silhouetted from behind by light from the galaxy's bright, smooth central bulge.

    The strong warping of the disc indicates that ESO 510-G13 has recently collided with a nearby galaxy and is in the process of swallowing it. Gravitational forces distort galaxies as their stars, gas, and dust merge over millions of years. When the disturbances die out, ESO 510-G13 will be a single galaxy.

    The galaxy's outer regions, especially on the right side of the image, show dark dust and bright clouds of blue stars. This indicates that hot, young stars are forming in the twisted disc. Astronomers believe star formation may be triggered when galaxies collide and their interstellar clouds are compressed.

    The Hubble Heritage Team used WFPC2 to observe ESO 510-G13 in April 2001. Pictures obtained through blue, green, and red filters were combined to make this color-composite image, which emphasizes the contrast between the dusty

  20. Cloning Hubble Deep Fields. II. Models for Evolution by Bright Galaxy Image Transformation

    NASA Astrophysics Data System (ADS)

    Bouwens, Rychard; Broadhurst, Tom; Silk, Joseph

    1998-10-01

    In a companion paper, we outlined a methodology for generating parameter-free, model-independent ``no-evolution'' fields of faint galaxy images, demonstrating the need for significant evolution in the Hubble Deep Field (HDF) at faint magnitudes. Here we incorporate evolution into our procedure, by transforming the input bright galaxy images with redshift, for comparison with the HDF at faint magnitudes. Pure luminosity evolution is explored with the assumption that galaxy surface brightness evolves uniformly, at a rate chosen to reproduce the I-band counts. This form of evolution exacerbates the size discrepancy identified by our no-evolution simulations by increasing the area of a galaxy visible to a fixed isophote. Reasonable dwarf-augmented models are unable to generate the count excess invoking moderate rates of stellar evolution. A plausible fit to the counts and sizes is provided by ``mass-conserving'' density-evolution, consistent with small-scale hierarchical growth, in which the product of disk area and space density is conserved with redshift. Here the increased surface brightness generated by stellar evolution is accommodated by the reduced average galaxy size, for a wide range of geometries. These models are useful for calculating the rates of incompleteness and the degree of overcounting. Finally we demonstrate the potential for improvement in quantifying evolution at fainter magnitudes using the Hubble Space Telescope Advanced Camera, with its superior UV and optical performance.

  1. Ring Around a Galaxy

    NASA Technical Reports Server (NTRS)

    1999-01-01

    Space Telescope Science Institute astronomers are giving the public chances to decide where to aim NASA's Hubble Space Telescope. Guided by 8,000 Internet voters, Hubble has already been used to take a close-up, multi-color picture of the most popular object from a list of candidates, the extraordinary 'polar-ring' galaxy NGC 4650A. Located about 130 million light-years away, NGC 4650A is one of only 100 known polar-ring galaxies. Their unusual disk-ring structure is not yet understood fully. One possibility is that polar rings are the remnants of colossal collisions between two galaxies sometime in the distant past, probably at least 1 billion years ago. What is left of one galaxy has become the rotating inner disk of old red stars in the center. Meanwhile, another smaller galaxy which ventured too close was probably severely damaged or destroyed. The bright bluish clumps, which are especially prominent in the outer parts of the ring, are regions containing luminous young stars, examples of stellar rebirth from the remnants of an ancient galactic disaster. The polar ring appears to be highly distorted. No regular spiral pattern stands out in the main part of the ring, and the presence of young stars below the main ring on one side and above on the other shows that the ring is warped and does not lie in one plane. Determining the typical ages of the stars in the polar ring is an initial goal of our Polar Ring Science Team that can provide a clue to the evolution of this unusual galaxy. The HST exposures were acquired by the Hubble Heritage Team, consisting of Keith Noll, Howard Bond, Carol Christian, Jayanne English, Lisa Frattare, Forrest Hamilton, Anne Kinney and Zolt Levay, and guest collaborators Jay Gallagher (University of Wisconsin-Madison), Lynn Matthews (National Radio Astronomy Observatory-Charlottesville), and Linda Sparke (University of Wisconsin-Madison).

  2. Chandra Finds Surprising Black Hole Activity In Galaxy Cluster

    NASA Astrophysics Data System (ADS)

    2002-09-01

    bright active galaxies, often referred to as Active Galactic Nuclei, or AGN. Many astronomers think that all galaxies have central, supermassive black holes, yet only a small percent show activity. What is needed to power the AGN is fuel in the form of a nearby reservoir of gas and dust. Galaxy clusters contain hundreds to thousands of galaxies. They are the largest known structures in the universe and serve as a microcosm for the mechanics of the Universe at large. The galaxies in clusters are often old, reddish elliptically shaped galaxies, distinct from blue, spiral galaxies like our own. These old galaxies also do not have many young stars. The theory now in question is that as galaxies enter into clusters at high speeds, they are stripped of their interstellar gas, much as a strong wind strips leaves from a tree. Galaxies may also collide with one another and use up all of their gas in one huge burst of star formation triggered by this interaction. These processes remove most, if not all, of the gas that isn't locked up in stars. As they no longer have the raw material to form new stars, the stellar population slowly gets old and the Galaxy appears red. No gas is left to fuel an AGN. Previous surveys of galaxy clusters with optical telescopes have found that about only one percent of the galaxies in a cluster have AGN. This latest Chandra observation if typical, however, bumps the count up to about 5 percent. The team found six red galaxies with high X-ray activity during a nearly 14-hour Chandra observation of a galaxy cluster named Abell 2104, over 700 million light years from Earth. Based on previous optical surveys, only one was expected. "If we relied on optical data alone, we would have missed these hidden monsters," said co-author Dr. John Mulchaey. Only one of the six AGN, in fact, had the optical spectral properties typical of AGN activity. "The presence of these AGN indicate that supermassive black holes have somehow retained a fuel source, despite the

  3. THE MID-INFRARED ENVIRONMENTS OF HIGH-REDSHIFT RADIO GALAXIES

    SciTech Connect

    Galametz, Audrey; Stern, Daniel; De Breuck, Carlos; Vernet, Joeel; Hatch, Nina; Mayo, Jack; Miley, George; Rettura, Alessandro; Seymour, Nick; Adam Stanford, S.

    2012-04-20

    Taking advantage of the impressive sensitivity of Spitzer to detect massive galaxies at high redshift, we study the mid-infrared environments of powerful, high-redshift radio galaxies at 1.2 < z < 3. Galaxy cluster member candidates were isolated using a single Spitzer/IRAC mid-infrared color criterion, [3.6]-[4.5] > -0.1 (AB), in the fields of 48 radio galaxies at 1.2 < z < 3. Using a counts-in-cell analysis, we identify a field as overdense when 15 or more red IRAC sources are found within 1' (i.e., 0.5 Mpc at 1.2 < z < 3) of the radio galaxy to the 5{sigma} flux density limits of our IRAC data (f{sub 4.5} = 13.4 {mu}Jy). We find that radio galaxies lie preferentially in medium to dense regions, with 73% of the targeted fields denser than average. Our (shallow) 120 s data permit the rediscovery of previously known clusters and protoclusters associated with radio galaxies as well as the discovery of new promising galaxy cluster candidates at z > 1.2.

  4. Lightcone mock catalogues from semi-analytic models of galaxy formation - I. Construction and application to the BzK colour selection

    NASA Astrophysics Data System (ADS)

    Merson, Alexander I.; Baugh, Carlton M.; Helly, John C.; Gonzalez-Perez, Violeta; Cole, Shaun; Bielby, Richard; Norberg, Peder; Frenk, Carlos S.; Benson, Andrew J.; Bower, Richard G.; Lacey, Cedric G.; Lagos, Claudia del P.

    2013-02-01

    We introduce a method for constructing end-to-end mock galaxy catalogues using a semi-analytical model of galaxy formation, applied to the halo merger trees extracted from a cosmological N-body simulation. The mocks that we construct are lightcone catalogues, in which a galaxy is placed according to the epoch at which it first enters the past lightcone of the observer, and incorporate the evolution of galaxy properties with cosmic time. We determine the position between the snapshot outputs at which a galaxy enters the observer's lightcone by interpolation. As an application, we consider the effectiveness of the BzK colour selection technique, which was designed to isolate galaxies in the redshift interval 1.4 < z < 2.5. The mock catalogue is in reasonable agreement with the observed number counts of all BzK galaxies, as well as with the observed counts of the subsample of BzKs that are star-forming galaxies. We predict that over 75 per cent of the model galaxies with KAB ≤ 23, and 1.4 < z < 2.5, are selected by the BzK technique. Interloper galaxies, outside the intended redshift range, are predicted to dominate bright samples of BzK galaxies (i.e. with KAB ≤ 21). Fainter K-band cuts are necessary to reduce the predicted interloper fraction. We also show that shallow B-band photometry can lead to confusion in classifying BzK galaxies as being star forming or passively evolving. Overall, we conclude that the BzK colour selection technique is capable of providing a sample of galaxies that is representative of the 1.4 < z < 2.5 galaxy population.

  5. OPTOPUS spectroscopy of galaxies

    NASA Astrophysics Data System (ADS)

    Schnur, G. F. O.

    The spectra of selected H II regions in the center of the starburst galaxy NGC 1808 and of many faint galaxies surrounding the NGC 1808 were obtained simultaneously, using the Optopus fiber-optics spectrograph facility (described by Lund, 1986) at the ESO 3.6-m telescope. The preparation of Optopus plates (each of which employed more than 40 fibers), observations, and the procedures of data processing and Optopus calibration are described together with the problems caused by cosmic ray events. Preliminary results are included.

  6. Galaxy Alignments: An Overview

    NASA Astrophysics Data System (ADS)

    Joachimi, Benjamin; Cacciato, Marcello; Kitching, Thomas D.; Leonard, Adrienne; Mandelbaum, Rachel; Schäfer, Björn Malte; Sifón, Cristóbal; Hoekstra, Henk; Kiessling, Alina; Kirk, Donnacha; Rassat, Anais

    2015-11-01

    The alignments between galaxies, their underlying matter structures, and the cosmic web constitute vital ingredients for a comprehensive understanding of gravity, the nature of matter, and structure formation in the Universe. We provide an overview on the state of the art in the study of these alignment processes and their observational signatures, aimed at a non-specialist audience. The development of the field over the past one hundred years is briefly reviewed. We also discuss the impact of galaxy alignments on measurements of weak gravitational lensing, and discuss avenues for making theoretical and observational progress over the coming decade.

  7. Dwarf galaxy evolution within the environments of massive galaxies

    NASA Astrophysics Data System (ADS)

    Arraki, Kenza S.; Klypin, Anatoly A.; Ceverino, Daniel; Trujillo-Gomez, Sebastian; Primack, Joel R.

    2016-01-01

    Understanding galaxy evolution depends on connecting large-scale structure determined by the ΛCDM model with, at minimum, the small-scale physics of gas, star formation, and stellar feedback. Formation of galaxies within dark matter halos is sensitive to the physical phenomena occurring within and around the halo. This is especially true for dwarf galaxies, which have the smallest potential wells and are more susceptible to the effects of gas ionization and removal than larger galaxies. At dwarf galaxies scales comparisons of dark matter-only simulations with observations has unveiled various differences including the core-cusp, the missing satellites, and the too-big-to-fail problems. We have run a new suite of hydrodynamical simulations using the ART code to examine the evolution of dwarf galaxies in massive host environments. These are cosmological zoom-in simulations including deterministic star formation and stellar feedback in the form of supernovae feedback, stellar winds, radiation pressure, and photoionization pressure. We simulates galaxies with final halo masses on the order of 1012 M⊙ with high resolution, allowing us to examine the satellite dwarf galaxies and local isolated dwarf galaxies around each primary galaxy. We analyzed the abundance and structure of these dwarfs specifically the velocity function, their star formation rates, core creation and the circumgalactic medium. By reproducing observations of dwarf galaxies in simulations we show how including baryons in simulations relieves tensions seen in comparing dark matter only simulations with observations.

  8. Dwarf galaxies in the coma cluster: Star formation properties and evolution

    NASA Astrophysics Data System (ADS)

    Hammer, Derek M.

    The infall regions of galaxy clusters are unique laboratories for studying the impact of environment on galaxy evolution. This intermediate region links the low-density field environment and the dense core of the cluster, and is thought to host recently accreted galaxies whose star formation is being quenched by external processes associated with the cluster. In this dissertation, we measure the star formation properties of galaxies at the infall region of the nearby rich cluster of galaxies, Coma. We rely primarily on Ultraviolet (UV) data owing to its sensitivity to recent star formation and we place more emphasis on the properties of dwarf galaxies. Dwarf galaxies are good tracers of external processes in clusters but their evolution is poorly constrained as they are intrinsically faint and hence more challenging to detect. We make use of deep GALEX far-UV and near-UV observations at the infall region of the Coma cluster. This area of the cluster has supporting photometric coverage at optical and IR wavelengths in addition to optical spectroscopic data that includes deep redshift coverage of dwarf galaxies in Coma. Our GALEX observations were the deepest exposures taken for a local galaxy cluster. The depth of these images required alternative data analysis techniques to overcome systematic effects that limit the default GALEX pipeline analysis. Specifically, we used a deblending method that improved detection efficiency by a factor of ˜2 and allowed reliable photometry a few magnitudes deeper than the pipeline catalog. We performed deep measurements of the total UV galaxy counts in our field that were used to measure the source confusion limit for crowded GALEX fields. The star formation properties of Coma members were studied for galaxies that span from starbursts to passive galaxies. Star-forming galaxies in Coma tend to have lower specific star formation rates, on average, as compared to field galaxies. We show that the majority of these galaxies are likely

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

    NASA Astrophysics Data System (ADS)

    Holwerda, B. W.; Baldry, I. K.; Alpaslan, M.; Bauer, A.; Bland-Hawthorn, J.; Brough, S.; Brown, M. J. I.; Cluver, M. E.; Conselice, C.; Driver, S. P.; Hopkins, A. M.; Jones, D. H.; López-Sánchez, Á. R.; Loveday, J.; Meyer, M. J.; Moffett, A.

    2015-06-01

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

  10. Spatial density fluctuations and selection effects in galaxy redshift surveys

    SciTech Connect

    Labini, Francesco Sylos; Tekhanovich, Daniil; Baryshev, Yurij V. E-mail: d.tekhanovich@spbu.ru

    2014-07-01

    One of the main problems of observational cosmology is to determine the range in which a reliable measurement of galaxy correlations is possible. This corresponds to determining the shape of the correlation function, its possible evolution with redshift and the size and amplitude of large scale structures. Different selection effects, inevitably entering in any observation, introduce important constraints in the measurement of correlations. In the context of galaxy redshift surveys selection effects can be caused by observational techniques and strategies and by implicit assumptions used in the data analysis. Generally all these effects are taken into account by using pair-counting algorithms to measure two-point correlations. We review these methods stressing that they are based on the a-priori assumption that galaxy distribution is spatially homogeneous inside a given sample. We show that, when this assumption is not satisfied by the data, results of the correlation analysis are affected by finite size effects. In order to quantify these effects, we introduce a new method based on the computation of the gradient of galaxy counts along tiny cylinders. We show, by using artificial homogeneous and inhomogeneous point distributions, that this method identifies redshift dependent selection effects and disentangles them from the presence of large scale density fluctuations. We then apply this new method to several redshift catalogs and we find evidence that galaxy distribution, in those samples where selection effects are small enough, is characterized by power-law correlations with exponent γ=0.9 up to 20 Mpc/h followed by a change of slope that, in the range 20–100 Mpc/h, corresponds to a power-law exponent γ=0.25. Whether a crossover to spatial uniformity occurs at ∼ 100 Mpc/h or larger scales cannot be clarified by the present data.

  11. HUBBLE'S INFRARED GALAXY GALLERY

    NASA Technical Reports Server (NTRS)

    2002-01-01

    Astronomers have used the NASA Hubble Space Telescope to produce an infrared 'photo essay' of spiral galaxies. By penetrating the dust clouds swirling around the centers of these galaxies, the telescope's infrared vision is offering fresh views of star birth. These six images, taken with the Near Infrared Camera and Multi-Object Spectrometer, showcase different views of spiral galaxies, from a face-on image of an entire galaxy to a close-up of a core. The top row shows spirals at diverse angles, from face-on, (left); to slightly tilted, (center); to edge-on, (right). The bottom row shows close-ups of the hubs of three galaxies. In these images, red corresponds to glowing hydrogen, the raw material for star birth. The red knots outlining the curving spiral arms in NGC 5653 and NGC 3593, for example, pinpoint rich star-forming regions where the surrounding hydrogen gas is heated by intense ultraviolet radiation from young, massive stars. In visible light, many of these regions can be hidden from view by the clouds of gas and dust in which they were born. The glowing hydrogen found inside the cores of these galaxies, as in NGC 6946, may be due to star birth; radiation from active galactic nuclei (AGN), which are powered by massive black holes; or a combination of both. White is light from middle-age stars. Clusters of stars appear as white dots, as in NGC 2903. The galaxy cores are mostly white because of their dense concentration of stars. The dark material seen in these images is dust. These galaxies are part of a Hubble census of about 100 spiral galaxies. Astronomers at Space Telescope Science Institute took these images to fill gaps in the scheduling of a campaign using the NICMOS-3 camera. The data were non-proprietary, and were made available to the entire astronomical community. Filters: Three filters were used: red, blue, and green. Red represents emission at the Paschen Alpha line (light from glowing hydrogen) at a wavelength of 1.87 microns. Blue shows the

  12. Low Background Counting at LBNL

    DOE PAGESBeta

    Smith, A. R.; Thomas, K. J.; Norman, E. B.; Chan, Y. D.; Lesko, K. T.; Hurley, D. L.

    2015-03-24

    The Low Background Facility (LBF) at Lawrence Berkeley National Laboratory in Berkeley, California provides low background gamma spectroscopy services to a wide array of experiments and projects. The analysis of samples takes place within two unique facilities; locally within a carefully-constructed, low background cave and remotely at an underground location that historically has operated underground in Oroville, CA, but has recently been relocated to the Sanford Underground Research Facility (SURF) in Lead, SD. These facilities provide a variety of gamma spectroscopy services to low background experiments primarily in the form of passive material screening for primordial radioisotopes (U, Th, K)more » or common cosmogenic/anthropogenic products, as well as active screening via Neutron Activation Analysis for specific applications. The LBF also provides hosting services for general R&D testing in low background environments on the surface or underground for background testing of detector systems or similar prototyping. A general overview of the facilities, services, and sensitivities is presented. Recent activities and upgrades will also be presented, such as the completion of a 3π anticoincidence shield at the surface station and environmental monitoring of Fukushima fallout. The LBF is open to any users for counting services or collaboration on a wide variety of experiments and projects.« less

  13. Low Background Counting at LBNL

    SciTech Connect

    Smith, A. R.; Thomas, K. J.; Norman, E. B.; Chan, Y. D.; Lesko, K. T.; Hurley, D. L.

    2015-03-24

    The Low Background Facility (LBF) at Lawrence Berkeley National Laboratory in Berkeley, California provides low background gamma spectroscopy services to a wide array of experiments and projects. The analysis of samples takes place within two unique facilities; locally within a carefully-constructed, low background cave and remotely at an underground location that historically has operated underground in Oroville, CA, but has recently been relocated to the Sanford Underground Research Facility (SURF) in Lead, SD. These facilities provide a variety of gamma spectroscopy services to low background experiments primarily in the form of passive material screening for primordial radioisotopes (U, Th, K) or common cosmogenic/anthropogenic products, as well as active screening via Neutron Activation Analysis for specific applications. The LBF also provides hosting services for general R&D testing in low background environments on the surface or underground for background testing of detector systems or similar prototyping. A general overview of the facilities, services, and sensitivities is presented. Recent activities and upgrades will also be presented, such as the completion of a 3π anticoincidence shield at the surface station and environmental monitoring of Fukushima fallout. The LBF is open to any users for counting services or collaboration on a wide variety of experiments and projects.

  14. HUBBLE REVEALS 'BACKWARDS' SPIRAL GALAXY

    NASA Technical Reports Server (NTRS)

    2002-01-01

    Astronomers have found a spiral galaxy that may be spinning to the beat of a different cosmic drummer. To the surprise of astronomers, the galaxy, called NGC 4622, appears to be rotating in the opposite direction to what they expected. Pictures by NASA's Hubble Space Telescope helped astronomers determine that the galaxy may be spinning clockwise by showing which side of the galaxy is closer to Earth. A Hubble telescope photo of the oddball galaxy is this month's Hubble Heritage offering. The image shows NGC 4622 and its outer pair of winding arms full of new stars [shown in blue]. Astronomers are puzzled by the clockwise rotation because of the direction the outer spiral arms are pointing. Most spiral galaxies have arms of gas and stars that trail behind as they turn. But this galaxy has two 'leading' outer arms that point toward the direction of the galaxy's clockwise rotation. To add to the conundrum, NGC 4622 also has a 'trailing' inner arm that is wrapped around the galaxy in the opposite direction it is rotating. Based on galaxy simulations, a team of astronomers had expected that the galaxy was turning counterclockwise. NGC 4622 is a rare example of a spiral galaxy with arms pointing in opposite directions. What caused this galaxy to behave differently from most galaxies? Astronomers suspect that NGC 4622 interacted with another galaxy. Its two outer arms are lopsided, meaning that something disturbed it. The new Hubble image suggests that NGC 4622 consumed a small companion galaxy. The galaxy's core provides new evidence for a merger between NGC 4622 and a smaller galaxy. This information could be the key to understanding the unusual leading arms. Galaxies, which consist of stars, gas, and dust, rotate very slowly. Our Sun, one of many stars in our Milky Way Galaxy, completes a circuit around the Milky Way every 250 million years. NGC 4622 resides 111 million light-years away in the constellation Centaurus. The pictures were taken in May 2001 with Hubble

  15. Identification of CSF fistulas by radionuclide counting

    SciTech Connect

    Yamamoto, Y.; Kunishio, K.; Sunami, N.; Yamamoto, Y.; Satoh, T.; Suga, M.; Asari, S. )

    1990-07-01

    A radionuclide counting method, performed with the patient prone and the neck flexed, was used successfully to diagnose CSF rhinorrhea in two patients. A normal radionuclide ratio (radionuclide counts in pledget/radionuclide counts in 1-ml blood sample) was obtained in 11 normal control subjects. Significance was determined to be a ratio greater than 0.37. Use of radionuclide counting method of determining CSF rhinorrhea is recommended when other methods have failed to locate a site of leakage or when posttraumatic meningitis suggests subclinical CSF rhinorrhea.

  16. Chiral asymmetry in spiral galaxies?

    PubMed

    Kondepudi, D K; Durand, D J

    2001-07-01

    Spiral galaxies are chiral entities when coupled with the direction of their recession velocity. As viewed from the Earth, the S-shaped and Z-shaped spiral galaxies are two chiral forms. What is the nature of chiral symmetry in spiral galaxies? In the Carnegie Atlas of Galaxies that lists photographs of a total of 1,168 galaxies, we found 540 galaxies, classified as normal or barred spirals, that are clearly identifiable as S- or Z- type. The recession velocities for 538 of these galaxies could be obtained from this atlas and other sources. A statistical analysis of this sample reveals no overall asymmetry but there is a significant asymmetry in certain subclasses: dominance of S-type galaxies in the Sb class of normal spiral galaxies and a dominance of Z-type in the SBb class of barred spiral galaxies. Both S- and Z-type galaxies seem to have similar velocity distribution, indicating no spatial segregation of the two chiral forms.

  17. Stellar Populations of Shell Galaxies

    NASA Astrophysics Data System (ADS)

    Carlsten, Scott; Zenteno, Alfredo

    2016-01-01

    We present a study of the inner (out to ˜1 effective radius) stellar populations in a sample of 9 shell galaxies. We derive stellar population parameters from long slit spectra by both analyzing the Lick indices of the galaxies and by fitting high resolution SSP model spectra to the full galaxy spectra. The results from the two methods agree reasonably well. We find the presence of young stellar populations in several of the galaxies, implying recent star formation and allowing us to speculate on the age of the shells. Analyzing the metallicity gradients in our sample, we find an average metallicity gradient of -0.16±0.10 dex/decade in radius. Finally, we compare this with galaxy evolution models to try to constrain the merging history of shell galaxies. We argue that our galaxies likely have undergone major mergers in their past but it is unclear whether the shells formed from these events or from separate minor mergers.

  18. Life in the Galaxy

    ERIC Educational Resources Information Center

    Oliver, B. M.

    1973-01-01

    Discusses the origin of life on the basis of information about cosmic evolution, stellar alchemy, atmospheric histories, and rise and fall of civilizations. Indicates that man's contact with other civilizations in our galaxy may be made possible through studies of interstellar communication. (CC)

  19. Our wobbly galaxy

    NASA Astrophysics Data System (ADS)

    Moskvitch, Katia

    2014-04-01

    It is well known that the Milky Way rotates around a supermassive black hole, but researchers have found that our galaxy undulates up and down as well like a giant galactic merry-go-round. Katia Moskvitch reports on this surprising finding.

  20. The Hooked Galaxy

    NASA Astrophysics Data System (ADS)

    2006-06-01

    Life is not easy, even for galaxies. Some indeed get so close to their neighbours that they get rather distorted. But such encounters between galaxies have another effect: they spawn new generations of stars, some of which explode. ESO's VLT has obtained a unique vista of a pair of entangled galaxies, in which a star exploded. Because of the importance of exploding stars, and particularly of supernovae of Type Ia [1], for cosmological studies (e.g. relating to claims of an accelerated cosmic expansion and the existence of a new, unknown, constituent of the universe - the so called 'Dark Energy'), they are a preferred target of study for astronomers. Thus, on several occasions, they pointed ESO's Very Large Telescope (VLT) towards a region of the sky that portrays a trio of amazing galaxies. MCG-01-39-003 (bottom right) is a peculiar spiral galaxy, with a telephone number name, that presents a hook at one side, most probably due to the interaction with its neighbour, the spiral galaxy NGC 5917 (upper right). In fact, further enhancement of the image reveals that matter is pulled off MCG-01-39-003 by NGC 5917. Both these galaxies are located at similar distances, about 87 million light-years away, towards the constellation of Libra (The Balance). ESO PR Photo 22/06 ESO PR Photo 22/06 The Hooked Galaxy and its Companion NGC 5917 (also known as Arp 254 and MCG-01-39-002) is about 750 times fainter than can be seen by the unaided eye and is about 40,000 light-years across. It was discovered in 1835 by William Herschel, who strangely enough, seems to have missed its hooked companion, only 2.5 times fainter. As seen at the bottom left of this exceptional VLT image, a still fainter and nameless, but intricately beautiful, barred spiral galaxy looks from a distance the entangled pair, while many 'island universes' perform a cosmic dance in the background. But this is not the reason why astronomers look at this region. Last year, a star exploded in the vicinity of the hook

  1. CLEARING OUT A GALAXY

    SciTech Connect

    Zubovas, Kastytis; King, Andrew

    2012-02-15

    It is widely suspected that active galactic nucleus (AGN) activity ultimately sweeps galaxies clear of their gas. We work out the observable properties required to achieve this. Large-scale AGN-driven outflows should have kinetic luminosities {approx}{eta} L{sub Edd}/2 {approx} 0.05 L{sub Edd} and momentum rates {approx}20 L{sub Edd}/c, where L{sub Edd} is the Eddington luminosity of the central black hole and {eta} {approx} 0.1 its radiative accretion efficiency. This creates an expanding two-phase medium in which molecular species coexist with hot gas, which can persist after the central AGN has switched off. This picture predicts outflow velocities {approx}1000-1500 km s{sup -1} and mass outflow rates up to 4000 M{sub Sun} yr{sup -1} on kpc scales, fixed mainly by the host galaxy velocity dispersion (or equivalently black hole mass). All these features agree with those of outflows observed in galaxies such as Mrk231. This strongly suggests that AGN activity is what sweeps galaxies clear of their gas on a dynamical timescale and makes them red and dead. We suggest future observational tests of this picture.

  2. A GALAXY BLAZES WITH STAR FORMATION

    NASA Technical Reports Server (NTRS)

    2002-01-01

    Most galaxies form new stars at a fairly slow rate, but members of a rare class known as 'starburst' galaxies blaze with extremely active star formation. Scientists using NASA's Hubble Space Telescope are perfecting a technique to determine the history of starburst activity in galaxies by using the colors of star clusters. Measuring the clusters' colors yields information about stellar temperatures. Since young stars are blue, and older stars redder, the colors can be related to the ages, somewhat similar to counting the rings in a fallen tree trunk in order to determine the tree's age. The galaxy NGC 3310 is forming clusters of new stars at a prodigious rate. Astronomer Gerhardt Meurer of The Johns Hopkins University leads a team of collaborators who are studying several starburst galaxies, including NGC 3310, which is showcased in this month's Hubble Heritage image. There are several hundred star clusters in NGC 3310, visible in the Heritage image as the bright blue diffuse objects that trace the galaxy's spiral arms. Each of these star clusters represents the formation of up to about a million stars, a process that takes less than 100,000 years. In addition, hundreds of individual young, luminous stars can be seen throughout the galaxy. Once formed, the star clusters become redder with age as the most massive and bluest stars exhaust their fuel and burn out. Measurements in this image of the wide range of cluster colors show that they have ages ranging from about one million up to more than one hundred million years. This suggests that the starburst 'turned on' over 100 million years ago. It may have been triggered when a companion galaxy collided with NGC 3310. These observations may change astronomers' view of starbursts. Starbursts were once thought to be brief episodes, resulting from catastrophic events like a galactic collision. However, the wide range of cluster ages in NGC 3310 suggests that the starbursting can continue for an extended interval, once

  3. OPTIMAL CAPTURE OF NON-GAUSSIANITY IN WEAK-LENSING SURVEYS: POWER SPECTRUM, BISPECTRUM, AND HALO COUNTS

    SciTech Connect

    Berge, Joel; Refregier, Alexandre

    2010-04-01

    We compare the efficiency of weak-lensing-selected galaxy cluster counts and of the weak-lensing bispectrum at capturing non-Gaussian features in the dark matter distribution. We use the halo model to compute the weak-lensing power spectrum, the bispectrum, and the expected number of detected clusters, and derive constraints on cosmological parameters for a large, low systematic weak-lensing survey, by focusing on the OMEGA{sub m}-sigma{sub 8} plane and on the dark energy equation of state. We separate the power spectrum into the resolved and the unresolved parts of the data, the resolved part being defined as detected clusters, and the unresolved part as the rest of the field. We consider four kinds of clusters counts, taking into account different amount of information: signal-to-noise ratio peak counts, counts as a function of clusters' mass, counts as a function of clusters' redshift, and counts as a function of clusters' mass and redshift. We show that when combined with the power spectrum, those four kinds of counts provide similar constraints, thus allowing one to perform the most direct counts, signal-to-noise peak counts, and get percent level constraints on cosmological parameters. We show that the weak-lensing bispectrum gives constraints comparable to those given by the power spectrum and captures non-Gaussian features as well as cluster counts, its combination with the power spectrum giving errors on cosmological parameters that are similar to, if not marginally smaller than, those obtained when combining the power spectrum with cluster counts. We finally note that in order to reach its potential, the weak-lensing bispectrum must be computed using all triangle configurations, as equilateral triangles alone do not provide useful information. The appendices summarize the halo model, and the way the power spectrum and bispectrum are computed in this framework.

  4. Discovering Teenage Galaxies

    NASA Astrophysics Data System (ADS)

    2007-11-01

    Staring for the equivalent of every night for two weeks at the same little patch of sky with ESO's Very Large Telescope, an international team of astronomers has found the extremely faint light from teenage galaxies billions of light years away. These galaxies, which the research team believes are the building blocks of normal galaxies like our Milky Way, had eluded detection for three decades, despite intensive searches. ESO PR Photo 52/07 ESO PR Photo 52/07 A 92-hour long spectrum Two-dimensional spectrum obtained in 92 hours of exposure time, showing the line emitter candidates. The quasar absorption lines are visible close to the centre of the image. The team, led by Martin Haehnelt of the University of Cambridge, UK, Michael Rauch and George Becker of the Observatories of the Carnegie Institution, USA, and Andy Bunker of the Anglo-Australian Observatory, reports their results in the 1 March 2008 issue of the Astrophysical Journal. "This is the first time that the sky has been searched to this depth and the unrivalled sensitivity of the picture taken with the VLT was key to succeeding," says Haehnelt. Experts have long speculated that galaxies like ours were created by the amalgamation of proto-galaxies early in the history of the Universe, but the light from these fragments was so faint that astronomers had struggled to prove they were there at all. Astronomers thought that the teenage galaxies must be out there because they were blocking part of the light from objects even further away in space. "Previous attempts have usually been frustrated by the difficulty of detecting extremely faint objects: the amount of time required even with an 8-metre class telescope like the VLT considerably exceeds typical observing time awards. We have thus exploited the periods of less good weather with the FORS2 spectrograph at the VLT, taking advantage of the service observing mode," says Becker. In service mode, ESO staff astronomers at Paranal are responsible for carrying

  5. Redshifts for 115 galaxies near the equator

    SciTech Connect

    Shectman, S.A.; Stefanik, R.P.; Latham, D.W.

    1983-04-01

    We report new redshifts for 115 bright galaxies located near the celestial equator. The spectra were observed with a blue-sensitive photon-counting Reticon on the 100-in. DuPont telescope, and the redshifts were derived using the data-analysis system developed for the CfA Redshift Survey. Comparisons with other measured redshifts suggest that these data are similar in quality to the redshifts measured at Mt. Hopkins for the CfA Redshift Survey; the velocity zero point is good to 10 to 15 km s/sup -1/, with a typical error of 35 km s/sup -1/, with a typical error of 35 km s/sup -1/ for the individual measurements.

  6. The Densest Galaxy

    NASA Astrophysics Data System (ADS)

    Strader, Jay; Seth, Anil C.; Forbes, Duncan A.; Fabbiano, Giuseppina; Romanowsky, Aaron J.; Brodie, Jean P.; Conroy, Charlie; Caldwell, Nelson; Pota, Vincenzo; Usher, Christopher; Arnold, Jacob A.

    2013-09-01

    We report the discovery of a remarkable ultra-compact dwarf galaxy around the massive Virgo elliptical galaxy NGC 4649 (M60), which we call M60-UCD1. With a dynamical mass of 2.0 × 108 M ⊙ but a half-light radius of only ~24 pc, M60-UCD1 is more massive than any ultra-compact dwarfs of comparable size, and is arguably the densest galaxy known in the local universe. It has a two-component structure well fit by a sum of Sérsic functions, with an elliptical, compact (rh = 14 pc n ~ 3.3) inner component and a round, exponential, extended (rh = 49 pc) outer component. Chandra data reveal a variable central X-ray source with LX ~ 1038 erg s-1 that could be an active galactic nucleus associated with a massive black hole or a low-mass X-ray binary. Analysis of optical spectroscopy shows the object to be old (gsim 10 Gyr) and of solar metallicity, with elevated [Mg/Fe] and strongly enhanced [N/Fe] that indicates light-element self-enrichment; such self-enrichment may be generically present in dense stellar systems. The velocity dispersion (σ ~ 70 km s-1) and resulting dynamical mass-to-light ratio (M/LV = 4.9 ± 0.7) are consistent with—but slightly higher than—expectations for an old, metal-rich stellar population with a Kroupa initial mass function. The presence of a massive black hole or a mild increase in low-mass stars or stellar remnants is therefore also consistent with this M/LV . The stellar density of the galaxy is so high that no dynamical signature of dark matter is expected. However, the properties of M60-UCD1 suggest an origin in the tidal stripping of a nucleated galaxy with MB ~ -18 to -19.

  7. 2009 KidsCount in Colorado!

    ERIC Educational Resources Information Center

    Colorado Children's Campaign, 2009

    2009-01-01

    "KidsCount in Colorado!" is an annual publication of the Colorado Children's Campaign, which provides the best available state- and county-level data to measure and track the education, health and general well-being of the state's children. KidsCount in Colorado! informs policy debates and community discussions, serving as a valuable resource for…

  8. 2008 KidsCount in Colorado!

    ERIC Educational Resources Information Center

    Colorado Children's Campaign, 2008

    2008-01-01

    "KidsCount in Colorado!" is an annual publication of the Colorado Children's Campaign, which provides the best available state- and county-level data to measure and track the education, health and general well-being of the state's children. KidsCount in Colorado! informs policy debates and community discussions, serving as a valuable resource for…

  9. 2013 Kids Count in Colorado! Community Matters

    ERIC Educational Resources Information Center

    Colorado Children's Campaign, 2013

    2013-01-01

    "Kids Count in Colorado!" is an annual publication of the Children's Campaign, providing state and county level data on child well-being factors including child health, education, and economic status. Since its first release 20 years ago, "Kids Count in Colorado!" has become the most trusted source for data and information on…

  10. Accuracy of Carbohydrate Counting in Adults.

    PubMed

    Meade, Lisa T; Rushton, Wanda E

    2016-07-01

    In Brief This study investigates carbohydrate counting accuracy in patients using insulin through a multiple daily injection regimen or continuous subcutaneous insulin infusion. The average accuracy test score for all patients was 59%. The carbohydrate test in this study can be used to emphasize the importance of carbohydrate counting to patients and to provide ongoing education. PMID:27621531

  11. Early Concepts of Number and Counting

    ERIC Educational Resources Information Center

    Box, Katherine; Scott, Paul

    2004-01-01

    Before primitive man had grasped the concept of number, the written word or even speech, he was able to count. This was important for keeping track of food supplies, sending messages, trading between villages and even keeping track of how many animals were in their herd. Counting was done in various ways, but in all cases, the underlying principle…

  12. 7 CFR 1220.625 - Counting requests.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... AGREEMENTS AND ORDERS; MISCELLANEOUS COMMODITIES), DEPARTMENT OF AGRICULTURE SOYBEAN PROMOTION, RESEARCH, AND CONSUMER INFORMATION Procedures To Request a Referendum Definitions § 1220.625 Counting requests. (a) The... ineligibility determinations, the requests shall be counted no later than the 14th business day following...

  13. Is It Counting, or Is It Adding?

    ERIC Educational Resources Information Center

    Eisenhardt, Sara; Fisher, Molly H.; Thomas, Jonathan; Schack, Edna O.; Tassell, Janet; Yoder, Margaret

    2014-01-01

    The Common Core State Standards for Mathematics (CCSSI 2010) expect second grade students to "fluently add and subtract within 20 using mental strategies" (2.OA.B.2). Most children begin with number word sequences and counting approximations and then develop greater skill with counting. But do all teachers really understand how this…

  14. Triple Scoop from Galaxy Hunter

    NASA Technical Reports Server (NTRS)

    2006-01-01

    [figure removed for brevity, see original site] [figure removed for brevity, see original site] [figure removed for brevity, see original site] Figure 1Figure 2Figure 3

    Silver Dollar Galaxy: NGC 253 (figure 1) Located 10 million light-years away in the southern constellation Sculptor, the Silver Dollar galaxy, or NGC 253, is one of the brightest spiral galaxies in the night sky. In this edge-on view from NASA's Galaxy Evolution Explorer, the wisps of blue represent relatively dustless areas of the galaxy that are actively forming stars. Areas of the galaxy with a soft golden glow indicate regions where the far-ultraviolet is heavily obscured by dust particles.

    Gravitational Dance: NGC 1512 and NGC 1510 (figure 2) In this image, the wide ultraviolet eyes of NASA's Galaxy Evolution Explorer show spiral galaxy NGC 1512 sitting slightly northwest of elliptical galaxy NGC 1510. The two galaxies are currently separated by a mere 68,000 light-years, leading many astronomers to suspect that a close encounter is currently in progress.

    The overlapping of two tightly wound spiral arm segments makes up the light blue inner ring of NGC 1512. Meanwhile, the galaxy's outer spiral arm is being distorted by strong gravitational interactions with NGC 1510.

    Galaxy Trio: NGC 5566, NGC 5560, and NGC 5569 (figure 3) NASA's Galaxy Evolution Explorer shows a triplet of galaxies in the Virgo cluster: NGC 5560 (top galaxy), NGC 5566 (middle galaxy), and NGC 5569 (bottom galaxy).

    The inner ring in NGC 5566 is formed by two nearly overlapping bright arms, which themselves spring from the ends of a central bar. The bar is not visible in ultraviolet because it consists of older stars or low mass stars that do not emit energy at ultraviolet wavelengths. The outer disk of NGC 5566 appears warped, and the disk of NGC 5560 is clearly disturbed. Unlike its galactic neighbors, the disk of NGC 5569 does not appear to have been distorted by any passing

  15. Galaxy NGC 4013

    NASA Technical Reports Server (NTRS)

    1999-01-01

    An amazing 'edge-on' view of a spiral galaxy 55 million light years from Earth has been captured by the Hubble Space Telescope. The image, available at http://www.jpl.nasa.gov/pictures/wfpc , reveals in great detail huge clouds of dust and gas extending along and above the galaxy's main disk.

    The image was taken by Hubble's Wide Field and Planetary Camera 2, which was designed and built by NASA's Jet Propulsion Laboratory, Pasadena, Calif.

    The galaxy, called NGC 4013, lies in the direction of the constellation Ursa Major. If we could see it pole-on, it would look like a nearly circular pinwheel. In this Hubble image, NGC 4013 is seen edge-on, from our vantage point. Because the galaxy is larger than Hubble's field of view, the image shows only a little more than half the object, but with unprecedented detail.

    Dark clouds of interstellar dust stand out, since they absorb the light of background stars. Most of the clouds lie in the galaxy's plane and form the dark band, about 500 light years thick, that appears to cut the galaxy in two from upper right to lower left. Scientists believe that new stars form in dark interstellar clouds. NGC 4013 shows several examples of these stellar kindergartens near the center of the image, in front of the dark band along the galaxy's equator. One extremely bright star near the upper left corner is merely a nearby foreground star that lies in our Milky Way and happened to be in the line of sight.

    This new picture was constructed from Hubble images taken in January 2000 by Dr. J. Christopher Howk of Johns Hopkins University, Baltimore, Md., and Dr. Blair D. Savage of the University of Wisconsin-Madison. Images taken through three different filters have been combined into a color composite covering the region of the galaxy nucleus (behind the bright foreground star at the upper left) and extending along one edge of the galaxy to the lower right.

    The Space Telescope Science Institute, Baltimore, Md., manages space

  16. Kids Count in Delaware, Families Count in Delaware: Fact Book, 2002.

    ERIC Educational Resources Information Center

    Delaware Univ., Newark. Kids Count in Delaware.

    This Kids Count Fact Book is combined with the Families Count Fact Book to provide information on statewide trends affecting children and families in Delaware. The Kids Count statistical profile is based on 11 main indicators of child well-being: (1) births to teens 15-17 years; (2) births to teens 10 to 14 years; (3) low birth weight babies; (3)…

  17. Luminous Blue Compact Galaxies: Probes of galaxy assembly

    NASA Astrophysics Data System (ADS)

    Newton, Cassidy Louann

    The life cycles of galaxies over cosmic time is yet to be fully understood. How did galaxies evolve from their formative stages to the structures we observe today? This dissertation details the identification and analysis of a sample of Luminous Blue Compact Galaxies (LBCGs), a class of galaxy in the local (z < 0.05) universe exhibiting blue colors, high surface brightness, and high star formation rates. These systems appear to be very similar in their global properties to the early evolutionary phases of most galaxies, however their locality permits detailed investigation over a broad range of the electromagnetic spectrum in contrast to the smaller angular sizes and extreme faintness of distant galaxies. We use a combination of optical, ultraviolet, and infrared data to investigate a sample of LBCGs utilizing space and ground-based data.

  18. Galaxy Strategy for Ligo-Virgo Gravitational Wave Counterpart Searches

    NASA Technical Reports Server (NTRS)

    Gehrels, Neil; Cannizzo, John K.; Kanner, Jonah; Kasliwal, Mansi M.; Nissanke, Samaya; Singer, Leo P.

    2016-01-01

    In this work we continue a line of inquiry begun in Kanner et al. which detailed a strategy for utilizing telescopes with narrow fields of view, such as the Swift X-Ray Telescope (XRT), to localize gravity wave (GW) triggers from LIGO (Laser Interferometer Gravitational-Wave Observatory) / Virgo. If one considers the brightest galaxies that produce 50 percent of the light, then the number of galaxies inside typical GW error boxes will be several tens. We have found that this result applies both in the early years of Advanced LIGO when the range is small and the error boxes large, and in the later years when the error boxes will be small and the range large. This strategy has the beneficial property of reducing the number of telescope pointings by a factor 10 to 100 compared with tiling the entire error box. Additional galaxy count reduction will come from a GW rapid distance estimate which will restrict the radial slice in search volume. Combining the bright galaxy strategy with a convolution based on anticipated GW localizations, we find that the searches can be restricted to about 18 plus or minus 5 galaxies for 2015, about 23 plus or minus 4 for 2017, and about 11 plus or minus for 2020. This assumes a distance localization at the putative neutron star-neutron star (NS-NS) merger range mu for each target year, and these totals are integrated out to the range. Integrating out to the horizon would roughly double the totals. For localizations with r (rotation) greatly less than mu the totals would decrease. The galaxy strategy we present in this work will enable numerous sensitive optical and X-ray telescopes with small fields of view to participate meaningfully in searches wherein the prospects for rapidly fading afterglow place a premium on a fast response time.

  19. Galaxy Strategy for LIGO-Virgo Gravitational Wave Counterpart Searches

    NASA Astrophysics Data System (ADS)

    Gehrels, Neil; Cannizzo, John K.; Kanner, Jonah; Kasliwal, Mansi M.; Nissanke, Samaya; Singer, Leo P.

    2016-04-01

    In this work we continue a line of inquiry begun in Kanner et al. which detailed a strategy for utilizing telescopes with narrow fields of view, such as the Swift X-ray Telescope (XRT), to localize gravitational wave (GW) triggers from LIGO/Virgo. If one considers the brightest galaxies that produce ˜50% of the light, then the number of galaxies inside typical GW error boxes will be several tens. We have found that this result applies both in the early years of Advanced LIGO when the range was small and the error boxes were large, and will apply in the later years when the error boxes will be small and the range will be large. This strategy has the beneficial property of reducing the number of telescope pointings by a factor of 10-100 compared with tiling the entire error box. Additional galaxy count reduction will come from a GW rapid distance estimate which will restrict the radial slice in search volume. Combining the bright galaxy strategy with a convolution based on anticipated GW localizations, we find that the searches can be restricted to about 18 ± 5 galaxies for 2015, about 23 ± 4 for 2017, and about 11 ± 2 for 2020. This assumes a distance localization at the putative neutron star-neutron star merger range μ for each target year, and these totals are integrated out to the range. Integrating out to the horizon would roughly double the totals. For localizations with r\\ll μ the totals would decrease. The galaxy strategy we present in this work will enable numerous sensitive optical and XRTs with small fields of view to participate meaningfully in searches wherein the prospects for rapidly fading afterglow place a premium on a fast response time.

  20. A new model to predict weak-lensing peak counts. III. Filtering technique comparisons

    NASA Astrophysics Data System (ADS)

    Lin, Chieh-An; Kilbinger, Martin; Pires, Sandrine

    2016-09-01

    Context. This is the third in a series of papers that develop a new and flexible model to predict weak-lensing (WL) peak counts, which have been shown to be a very valuable non-Gaussian probe of cosmology. Aims: In this paper, we compare the cosmological information extracted from WL peak counts using different filtering techniques of the galaxy shear data, including linear filtering with a Gaussian and two compensated filters (the starlet wavelet and the aperture mass), and the nonlinear filtering method MRLens. We present improvements to our model that account for realistic survey conditions, which are masks, shear-to-convergence transformations, and non-constant noise. Methods: We create simulated peak counts from our stochastic model, from which we obtain constraints on the matter density Ωm, the power spectrum normalisation σ8, and the dark-energy parameter w0de. We use two methods for parameter inference, a copula likelihood, and approximate Bayesian computation (ABC). We measure the contour width in the Ωm-σ8 degeneracy direction and the figure of merit to compare parameter constraints from different filtering techniques. Results: We find that starlet filtering outperforms the Gaussian kernel, and that including peak counts from different smoothing scales helps to lift parameter degeneracies. Peak counts from different smoothing scales with a compensated filter show very little cross-correlation, and adding information from different scales can therefore strongly enhance the available information. Measuring peak counts separately from different scales yields tighter constraints than using a combined peak histogram from a single map that includes multiscale information. Conclusions: Our results suggest that a compensated filter function with counts included separately from different smoothing scales yields the tightest constraints on cosmological parameters from WL peaks.

  1. A pseudo-spectrum analysis of galaxy-galaxy lensing

    NASA Astrophysics Data System (ADS)

    Hikage, Chiaki; Oguri, Masamune

    2016-10-01

    We present the application of the pseudo-spectrum method to galaxy-galaxy lensing. We derive explicit expressions for the pseudo-spectrum analysis of the galaxy-shear cross-spectrum, which is the Fourier space counterpart of the stacked galaxy-galaxy lensing profile. The pseudo-spectrum method corrects observational issues such as the survey geometry, masks of bright stars and their spikes, and inhomogeneous noise, which distort the spectrum and also mix the E-mode and the B-mode signals. Using ray-tracing simulations in N-body simulations including realistic masks, we confirm that the pseudo-spectrum method successfully recovers the input galaxy-shear cross-spectrum. We also show that the galaxy-shear cross-spectrum has an excess covariance relative to the Gaussian covariance at small scales (k ≳ 1h Mpc-1) where the shot noise is dominated in the Gaussian approximation. We find that the excess is consistent with the expectation from the halo sample variance (HSV), which originates from the matter fluctuations at scales larger than the survey area. We apply the pseudo-spectrum method to the observational data of Canada-France-Hawaii Telescope Lensing survey shear catalogue and three different spectroscopic samples of Sloan Digital Sky Survey Luminous Red Galaxy, and Baryon Oscillation Spectroscopic Survey CMASS and LOWZ galaxies. The galaxy-shear cross-spectra are significantly detected at the level of 7-10σ using the analytic covariance with the HSV contribution included. We also confirm that the observed spectra are consistent with the halo model predictions with the halo occupation distribution parameters estimated from previous work. This work demonstrates the viability of galaxy-galaxy lensing analysis in the Fourier space.

  2. Radio Sources Toward Galaxy Clusters at 30 GHz

    NASA Technical Reports Server (NTRS)

    Coble, K.; Bonamente, M.; Carlstrom, J. E.; Dawson, K.; Hasler, N.; Holzapfel, W.; Joy, M.; LaRoque, S.; Marrone, D. P.; Reese, E. D.

    2007-01-01

    Extra-galactic radio sources are a significant contaminant in cosmic microwave background and Sunyaev-Zeldovich effect experiments. Deep interferometric observations with the BIMA and OVRO arrays are used to characterize the spatial, spectral, and flux distributions of radio sources toward massive galaxy clusters at 28.5 GHz. We compute counts of mJy source fluxes from 89 fields centered on known massive galaxy clusters and 8 non-cluster fields. We find that source counts in the inner regions of the cluster fields (within 0.5 arcmin of the cluster center) are a factor of 8.9 (+4.2 to -3.8) times higher than counts in the outer regions of the cluster fields (radius greater than 0.5 arcmin). Counts in the outer regions of the cluster fields are in turn a factor of 3.3 (+4.1 -1.8) greater than those in the noncluster fields. Counts in the non-cluster fields are consistent with extrapolations from the results of other surveys. We compute spectral indices of mJy sources in cluster fields between 1.4 and 28.5 GHz and find a mean spectral index of al[ja = 0.66 with an rms dispersion of 0.36, where flux S varies as upsilon(sup -alpha). The distribution is skewed, with a median spectral index of 0.72 and 25th and 75th percentiles of 0.51 and 0.92, respectively. This is steeper than the spectral indices of stronger field sources measured by other surveys.

  3. Radio Sources toward Galaxy Clusters at 30 GHz

    NASA Technical Reports Server (NTRS)

    Coble, K.; Bonamente, M.; Carlstrom, J. E.; Dawson, K.; Hasler, N.; Holzapfel, W.; Joy, M.; LaRoque, S.; Marrone, D. P.; Reese, E. D.

    2007-01-01

    Extragalactic radio sources are a significant contaminant in cosmic microwave background and Sunyaev-Zel'dovich effect experiments. Deep interferometric observations with the BIMA and OVRO arrays are used to characterize the spatial, spectral, and flux distributions of radio sources toward massive galaxy clusters at 28.5 GHz. We compute counts of millijansky source fluxes from 89 fields centered on known massive galaxy clusters and 8 noncluster fields. We find that source counts in the inner regions of the cluster fields (within 0.5' of the cluster center) are a factor of 8.9 (sup +4.3)(sub -2.8) times higher than counts in the outer regions of the cluster fields (radius greater than 0.5'). Counts in the outer regions of the cluster fields are, in turn, a factor of 3.3 (sup +4.1) (sub -1.8) greater than those in the noncluster fields. Counts in the noncluster fields are consistent with extrapolations from the results of other surveys. We compute the spectral indices of millijansky sources in the cluster fields between 1.4 and 28.5 GHz and find a mean spectral index of alpha = 0.66 with an rms dispersion of 0.36, where flux S proportional to nu(sup -alpha). The distribution is skewed, with a median spectral index of 0.72 and 25th and 75th percentiles of 0.51 and 0.92, respectively. This is steeper than the spectral indices of stronger field sources measured by other surveys.

  4. Discovery of an Ultra-diffuse Galaxy in the Pisces--Perseus Supercluster

    NASA Astrophysics Data System (ADS)

    Martínez-Delgado, David; Läsker, Ronald; Sharina, Margarita; Toloba, Elisa; Fliri, Jürgen; Beaton, Rachael; Valls-Gabaud, David; Karachentsev, Igor D.; Chonis, Taylor S.; Grebel, Eva K.; Forbes, Duncan A.; Romanowsky, Aaron J.; Gallego-Laborda, J.; Teuwen, Karel; Gómez-Flechoso, M. A.; Wang, Jie; Guhathakurta, Puragra; Kaisin, Serafim; Ho, Nhung

    2016-04-01

    We report the discovery of DGSAT I, an ultra-diffuse, quenched galaxy located 10.°4 in projection from the Andromeda galaxy (M31). This low-surface brightness galaxy (μV = 24.8 mag arcsec-2), found with a small amateur telescope, appears unresolved in sub-arcsecond archival Subaru/Suprime-Cam images, and hence has been missed by optical surveys relying on resolved star counts, in spite of its relatively large effective radius (Re(V) = 12″) and proximity (15‧) to the well-known dwarf spheroidal galaxy And II. Its red color (V - I = 1.0), shallow Sérsic index (nV = 0.68), and the absence of detectable Hα emission are typical properties of dwarf spheroidal galaxies and suggest that it is mainly composed of old stars. Initially interpreted as an interesting case of an isolated dwarf spheroidal galaxy in the local universe, our radial velocity measurement obtained with the BTA 6 m telescope (Vh = 5450 ± 40 km s-1) shows that this system is an M31-background galaxy associated with the filament of the Pisces-Perseus supercluster. At the distance of this cluster (˜78 Mpc), DGSAT I would have an Re ˜ 4.7 kpc and MV ˜ -16.3. Its properties resemble those of the ultra-diffuse galaxies (UDGs) recently discovered in the Coma cluster. DGSAT I is the first case of these rare UDGs found in this galaxy cluster. Unlike the UDGs associated with the Coma and Virgo clusters, DGSAT I is found in a much lower density environment, which provides a fresh constraint on the formation mechanisms for this intriguing class of galaxy.

  5. Radio Point Sources Toward Galaxy Clusters at 30 GHz

    NASA Technical Reports Server (NTRS)

    Coble, K.; Carlstrom, J. E.; Bonamente, M.; Dawson, K.; Holzapfel, W.; Joy, M.; LaRoque, S.; Reese, E. D.

    2006-01-01

    Extra-galactic point sources are a significant contaminant in cosmic microwave background and Sunyaev-Zel'dovich effect experiments. Deep interferometric observations with the BIMA and OVRO arrays are used to characterize the spatial, spectral, and flux distributions of radio point sources toward galaxy clusters at 28.5 GHz. We compute counts of mJy point source fluxes from 90 fields centered on known massive galaxy clusters and 8 non-cluster fields. Counts in the non-cluster fields are consistent with extrapolations from the results of other surveys. We also compute counts towards clusters as a function of luminosity in three redshift bins out to z = 1.0 and see no clear evidence for evolution with redshift. We compute spectral indices of mJy sources in cluster fields between 1.4 and 28.5 GHz. The distribution is skewed, with a median spectral index of 0.76 and 25th and 75th percentiles of 0.55 and 0.95, respectively. This is steeper than the spectral indices of brighter field point sources measured by other surveys.

  6. Island Universe or Big Galaxy?

    NASA Astrophysics Data System (ADS)

    Wolfschmidt, Gudrun

    In 1920, the "great debate" took place: Harlow Shapley defended his model of the "Big Galaxy", i.e. we live in a large galaxy and all nebulous objects belong to our galaxy. He got this result from the distribution of the globular nebulae. Heber D. Curtis on the other side analyzed novae and was then convinced that nebulae are far distant objects which are stellar systems themselves like our galaxy. The solution of the discussion was brought by Edwin P. Hubble who confirmed the interpretation of nebulae as extragalactic objects, i.e. galaxies, and introduced the red shift for getting the distance of galaxies. The resulting expansion of the universe led to a new cosmological world view.

  7. GALAXIES BEHIND THE GALACTIC PLANE: FIRST RESULTS AND PERSPECTIVES FROM THE VVV SURVEY

    SciTech Connect

    Amores, E. B.; Arsenijevic, V.; Sodre, L.; Minniti, D.; Padilla, N.; Alonso, M. V.; Gurovich, S.; Diaz Tello, J.; Tollerud, E. J.; Rodriguez-Ardila, A.

    2012-11-01

    VISTA Variables in the Via Lactea (VVV) is an ESO variability survey that is performing observations in near-infrared bands (ZY JHK{sub s}) toward the Galactic bulge and part of the disk with the completeness limits at least 3 mag deeper than Two Micron All Sky Survey. In the present work, we searched in the VVV survey data for background galaxies near the Galactic plane using ZY JHK{sub s} photometry that covers 1.636 deg{sup 2}. We identified 204 new galaxy candidates by analyzing colors, sizes, and visual inspection of multi-band (ZY JHK{sub s}) images. The galaxy candidate colors were also compared with the predicted ones by star count models considering a more realistic extinction model at the same completeness limits observed by VVV. A comparison of the galaxy candidates with the expected one by Millennium simulations is also presented. Our results increase the number density of known galaxies behind the Milky Way by more than one order of magnitude. A catalog with galaxy properties including ellipticity, Petrosian radii, and ZY JHK{sub s} magnitudes is provided, as well as comparisons of the results with other surveys of galaxies toward the Galactic plane.

  8. The Anatomy of Galaxies

    NASA Astrophysics Data System (ADS)

    D'Onofrio, Mauro; Rampazzo, Roberto; Zaggia, Simone; Longair, Malcolm S.; Ferrarese, Laura; Marziani, Paola; Sulentic, Jack W.; van der Kruit, Pieter C.; Laurikainen, Eija; Elmegreen, Debra M.; Combes, Françoise; Bertin, Giuseppe; Fabbiano, Giuseppina; Giovanelli, Riccardo; Calzetti, Daniela; Moss, David L.; Matteucci, Francesca; Djorgovski, Stanislav George; Fraix-Burnet, Didier; Graham, Alister W. McK.; Tully, Brent R.

    Just after WWII Astronomy started to live its "Golden Age", not differently to many other sciences and human activities, especially in the west side countries. The improved resolution of telescopes and the appearance of new efficient light detectors (e.g. CCDs in the middle eighty) greatly impacted the extragalactic researches. The first morphological analysis of galaxies were rapidly substituted by "anatomic" studies of their structural components, star and gas content, and in general by detailed investigations of their properties. As for the human anatomy, where the final goal was that of understanding the functionality of the organs that are essential for the life of the body, galaxies were dissected to discover their basic structural components and ultimately the mystery of their existence.

  9. Chandra Galaxy Atlas

    NASA Astrophysics Data System (ADS)

    Kim, Dong-Woo; Mossman, Amy; Fruscione, Antonella; Anderson, Craig; Morgan, Doug; Burke, Douglas J.; O'Sullivan, E. J; Fabbiano, Giuseppina; Lauer, Jennifer; McCollough, Mike

    2014-06-01

    The hot ISM in early type galaxies plays a crucial role for understanding their formation and evolution. Structural features of the hot ISM identified by Chandra (including jets, cavities, cold fronts, filaments and tails) point to key evolutionary mechanisms, e.g., AGN feedback, merging history, accretion/stripping and star formation and its quenching. In our new project, Chandra Galaxy Atlas, we will systematically analyze the archival Chandra data of 137 ETGs to study the hot ISM. Taking full advantage of the Chandra capabilities, we will derive uniform data products of spatially resolved dataset with additional spectral information. We will make these products publicly available and use them for our focused science goals.

  10. Collisionless galaxy simulations

    NASA Technical Reports Server (NTRS)

    Hohl, F.; Zang, T. A.; Miller, J. B.

    1979-01-01

    Three-dimensional fully self-consistent computer models were used to determine the evolution of galaxies consisting of 100 000 simulation stars. Comparison of two-dimensional simulations with three-dimensional simulations showed only a very slight stabilizing effect due to the additional degree of freedom. The addition of a fully self-consistent, nonrotating, exponential core/halo component resulted in considerable stabilization. A second series of computer experiments was performed to determine the collapse and relaxation of initially spherical, uniform density and uniform velocity dispersion stellar systems. The evolution of the system was followed for various amounts of angular momentum in solid body rotation. For initally low values of the angular momentum satisfying the Ostriker-Peebles stability criterion, the systems quickly relax to an axisymmetric shape and resemble elliptical galaxies in appearance. For larger values of the initial angular momentum bars develop and the systems undergo a much more drastic evolution.

  11. Organic dust in galaxies

    NASA Astrophysics Data System (ADS)

    Onaka, Takashi

    2016-07-01

    Recent space infrared telescopes, Infrared Space Observatory, Spitzer Space Telescope, and AKARI have made significant progress in our understanding of organic dust in the Universe. In this review, we discuss recent observations with these space telescopes of the unidentified infrared emission (UIE) features in the near to mid-infrared, which come from very small organic dust, and the absorption features from 3 to 7 µm, which characterize large organic dust. They provide us with a new view of organic dust in galaxies. We also briefly discuss latest AKARI observations of H2O and CO2 ices in 2.5-5 µm in the Large Magellanic Cloud in comparison with observations in our Galaxy, which suggests the importance of dust surface chemistry in the formation of organic matters in the Universe.

  12. Clusters of galaxies

    NASA Astrophysics Data System (ADS)

    Vikhlinin, A. A.; Kravtsov, A. V.; Markevich, M. L.; Sunyaev, R. A.; Churazov, E. M.

    2014-04-01

    Galaxy clusters are formed via nonlinear growth of primordial density fluctuations and are the most massive gravitationally bound objects in the present Universe. Their number density at different epochs and their properties depend strongly on the properties of dark matter and dark energy, making clusters a powerful tool for observational cosmology. Observations of the hot gas filling the gravitational potential well of a cluster allows studying gasdynamic and plasma effects and the effect of supermassive black holes on the heating and cooling of gas on cluster scales. The work of Yakov Borisovich Zeldovich has had a profound impact on virtually all cosmological and astrophysical studies of galaxy clusters, introducing concepts such as the Harrison-Zeldovich spectrum, the Zeldovich approximation, baryon acoustic peaks, and the Sunyaev-Zeldovich effect. Here, we review the most basic properties of clusters and their role in modern astrophysics and cosmology.

  13. Galaxy simulations: Kinematics and mock observations

    NASA Astrophysics Data System (ADS)

    Moody, Christopher E.

    2013-08-01

    There are six topics to my thesis, which are: (1) slow rotator production in varied simulation schemes and kinematically decoupled cores and twists in those simulations, (2) the change in number of clumps in radiation pressure and no-radiation pressure simulations, (3) Sunrise experiments and failures including UVJ color-color dust experiments and UVbeta slopes, (4) the Sunrise image pipeline and algorithms. Cosmological simulations of have typically produced too many stars at early times. We find that the additional radiation pressure (RP) feedback suppresses star formation globally by a factor of ~ 3. Despite this reduction, the simulation still overproduces stars by a factor of ~ 2 with respect to the predictions provided by abundance matching methods. In simulations with RP the number of clumps falls dramatically. However, only clumps with masses Mclump/Mdisk ≤ 8% are impacted by the inclusion of RP, and clump counts above this range are comparable. Above this mass, the difference between and RP and no-RP contrast ratios diminishes. If we restrict our selection to galaxies hosting at least a single clump above this mass range then clump numbers, contrast ratios, survival fractions and total clump masses show little discrepancy between RP and no-RP simulations. By creating mock Hubble Space Telescope observations we find that the number of clumps is slightly reduced in simulations with RP. We demonstrate that clumps found in any single gas, stellar, or mock observation image are not necessarily clumps found in another map, and that there are few clumps common to multiple maps. New kinematic observations from ATLAS3D have highlighted the need to understand the evolutionary mechanism leading to a spectrum of fast-rotator and slow-rotators in early-type galaxies. We address the formation of slow and fast rotators through a series of controlled, comprehensive hydrodynamic simulations sampling idealized galaxy merger formation scenarios constructed from model

  14. The history of the galaxies.

    PubMed

    Fukugita, M; Hogan, C J; Peebles, P J

    1996-06-01

    Astronomical observations now reach far enough back in time, in enough depth and detail, to reveal the history of galaxies since their formation. The early Universe contained a network of gas clouds that filled much of the space between the young galaxies, where stars were forming at a high rate. Since then, intergalactic space has been swept clean, and galaxies have continued to convert the dwindling supply of gas slow into stars.

  15. LENTICULAR GALAXIES AND THEIR ENVIRONMENTS

    SciTech Connect

    Van den Bergh, Sidney

    2009-09-10

    It is widely believed that lenticular (S0) galaxies were initially spirals from which the gas has been removed by interactions with hot cluster gas, or by ram pressure stripping of cool gas from spirals that are orbiting within rich clusters of galaxies. However, problems with this interpretation are that (1) some lenticulars, such as NGC 3115, are isolated field galaxies rather than cluster members. (2) The distribution of flattening values of S0 galaxies in clusters, in groups, and in the field are statistically indistinguishable. This is surprising because one might have expected most of the progenitors of field S0 galaxies to have been flattened late-type galaxies, whereas lenticulars in clusters are thought to have mostly been derived from bulge-dominated early-type galaxies. (3) It should be hardest for ram pressure to strip massive luminous galaxies with deep potential wells. However, no statistically significant differences are seen between the luminosity distributions of early-type Shapley-Ames galaxies in clusters, groups, and in the field. (4) Finally both ram pressure stripping and evaporation by hot intracluster gas would be most efficient in rich clusters. However, the small number of available data in the Shapley-Ames sample appears to show no statistically significant differences between the relative frequencies of dust-poor S0{sub 1} and dust-rich S0{sub 3} galaxies in clusters, groups, and in the field. It is tentatively concluded that ram pressure stripping and heating by intracluster gas, may not be the only evolutionary channels that lead to the formation of lenticular galaxies. It is speculated that gas starvation, or gas ejection by active nuclei, may have played a major role in the formation of a significant fraction of all S0 galaxies.

  16. Magnetic fields in ring galaxies

    NASA Astrophysics Data System (ADS)

    Moss, D.; Mikhailov, E.; Silchenko, O.; Sokoloff, D.; Horellou, C.; Beck, R.

    2016-07-01

    Context. Many galaxies contain magnetic fields supported by galactic dynamo action. The investigation of these magnetic fields can be helpful for understanding galactic evolution; however, nothing definitive is known about magnetic fields in ring galaxies. Aims: Here we investigate large-scale magnetic fields in a previously unexplored context, namely ring galaxies, and concentrate our efforts on the structures that appear most promising for galactic dynamo action, i.e. outer star-forming rings in visually unbarred galaxies. Methods: We use tested methods for modelling α-Ω galactic dynamos, taking into account the available observational information concerning ionized interstellar matter in ring galaxies. Results: Our main result is that dynamo drivers in ring galaxies are strong enough to excite large-scale magnetic fields in the ring galaxies studied. The variety of dynamo driven magnetic configurations in ring galaxies obtained in our modelling is much richer than that found in classical spiral galaxies. In particular, various long-lived transients are possible. An especially interesting case is that of NGC 4513, where the ring counter-rotates with respect to the disc. Strong shear in the region between the disc and the ring is associated with unusually strong dynamo drivers in such counter-rotators. The effect of the strong drivers is found to be unexpectedly moderate. With counter-rotation in the disc, a generic model shows that a steady mixed parity magnetic configuration that is unknown for classical spiral galaxies, may be excited, although we do not specifically model NGC 4513. Conclusions: We deduce that ring galaxies constitute a morphological class of galaxies in which identification of large-scale magnetic fields from observations of polarized radio emission, as well as dynamo modelling, may be possible. Such studies have the potential to throw additional light on the physical nature of rings, their lifetimes, and evolution.

  17. Bright Galaxies, Dark Matters

    NASA Astrophysics Data System (ADS)

    Rubin, Vera

    In 1965, Vera Rubin was the first woman permitted to observe at Palomar Observatory. In the intervening years, she has become one of the world's finest and most respected astronomers. This particular collection of essays is compiled from work written over the past 15 years and deals with a variety of subjects in astronomy and astrophysics, specifically galaxies and dark matter. The book also contains biographical sketches of astronomers who have been colleagues and friends, providing a stimulating view of a woman in science. About the Author Since 1965 Vera Rubin has been a staff member at the Department of Terrestrial Magnetism of the Carnegie Institution of Washington. Dr. Rubin has authored nearly 200 papers on the structure of our galaxy, motions within other galaxies, and large scale motions in the universe. She has been a distinguished visiting astronomer at the Cerro Tololo Inter American Observatory in Chile; a Chancellor's Distinguished Professor at the University of California, Berkeley; a President's Distinguished Visitor at Vassar College; and a Beatrice Tinsley visiting professor at the University of Texas, Austin.

  18. B Counting at BaBar

    SciTech Connect

    McGregor, Grant Duncan

    2008-12-16

    In this thesis we examine the method of counting B{bar B} events produced in the BABAR experiment. The original method was proposed in 2000, but improvements to track reconstruction and our understanding of the detector since that date make it appropriate to revisit the B Counting method. We propose a new set of cuts designed to minimize the sensitivity to time-varying backgrounds. We find the new method counts B{bar B} events with an associated systematic uncertainty of {+-} 0.6%.

  19. Bacterial colony counting by Convolutional Neural Networks.

    PubMed

    Ferrari, Alessandro; Lombardi, Stefano; Signoroni, Alberto

    2015-01-01

    Counting bacterial colonies on microbiological culture plates is a time-consuming, error-prone, nevertheless fundamental task in microbiology. Computer vision based approaches can increase the efficiency and the reliability of the process, but accurate counting is challenging, due to the high degree of variability of agglomerated colonies. In this paper, we propose a solution which adopts Convolutional Neural Networks (CNN) for counting the number of colonies contained in confluent agglomerates, that scored an overall accuracy of the 92.8% on a large challenging dataset. The proposed CNN-based technique for estimating the cardinality of colony aggregates outperforms traditional image processing approaches, becoming a promising approach to many related applications.

  20. The Carina dwarf spheroidal galaxy - How dark is it?

    NASA Technical Reports Server (NTRS)

    Mateo, Mario; Olszewski, Edward W.; Pryor, Carlton; Welch, Douglas L.; Fischer, Philippe

    1993-01-01

    Precise radial velocities obtained with a photon-counting echelle spectrograph for a sample of 17 red giants in the Carina dwarf spheroidal galaxy are presented. The calculation of the systemic velocity and central velocity dispersion of Carina is described, the existing data constraining the structural parameters of Carina are reviewed, and an estimate of the central surface brightness of the galaxy is derived. These data are used to estimate the central mass density of Carina, as well as central and global mass-to-light ratios. It is concluded that the inferred mass densities and mass-density limits for all acceptable models imply the presence of a significant DM component in Carina. DM properties of all well-studied dSph systems are summarized and compared.

  1. Reconstruction of SDSS Nearby Galaxies

    NASA Astrophysics Data System (ADS)

    Kushner, Laura K.; Obric, M.; West, A. A.; Dalcanton, J.

    2006-12-01

    We present The SDSS Multiple Offspring Recombination Engine (SMORE), a newly developed code that automatically and interactively recombines galaxies fragmented by the Sloan Digital Sky Survey (SDSS) Photo pipeline. The SDSS software was optimized for the faint-end of the brightness limit and tends to over-deblend galaxies with angular sizes over 2 arcmin, sometimes separating spiral arms and HII regions from their parent galaxies. This process can remove a large percentage of the flux from the galaxy and bias datasets due to incorrect photometry. SMORE automatically builds galaxies from the fragments ("children"). Decisions on which child to include are made on the basis of its g-r and r-i color (relative to the mean colors of the largest galaxy children), size, distance to the center of the galaxy, type (as assigned by SDSS Photo) and the position angle. If there are pieces for which a decision cannot be made and their relative flux is more than 5% of the total flux of the galaxy, the interactive SMORE gives a user option to manually choose which of those children should be included. Recombined galaxies are built on a clean background without foreground and background objects and new photometry is performed.

  2. Interacting galaxies resolved by IRAS

    NASA Technical Reports Server (NTRS)

    Mazzarella, Joseph M.; Surace, Jason A.

    1994-01-01

    We discuss procedures, limitations and results of high resolution processing of interacting galaxies observed by the Infrared Astronomical Satellite (IRAS). Among 56 potentially resolvable interacting groups selected from the IRAS Bright Galaxy Sample, 22 systems have been resolved yielding fluxes for a total of 51 galaxies. In about 2/3 of the resolved pairs, both galaxies were detected in the far-infrared. A set of isolated non-interacting galaxies was chosen from the Bright Galaxy Sample for comparison with the interacting galaxies. For the current sample, which naturally excludes close pairs and ultraluminous merging systems, the primary conclusions are: (1) It is not possible to distinguish individual interacting galaxies from isolated galaxies of similar luminosity on the basis of infrared properties alone. (2) No direct correlation was found between measures of interaction strength and indicators of enhanced star formation within the resolved systems. (3) Comparison of the interacting and isolated samples indicates statistically significant differences between their distributions of far-infrared color ratios, luminosities, and surface brightnesses. Even during the early stages of interaction spanned by these systems, in a statistical sense, tidal perturbations substantially boost far-infrared indicators of star formation compared to non-interacting systems. We also briefly discuss future prospects for pushing the IRAS data to its limits for additional interacting systems.

  3. The "Valencian-GALAXY-zoo"

    NASA Astrophysics Data System (ADS)

    Navarro-González, J.; Ricciardelli, E.; Quilis, V.; Vazdekis, A.

    2013-05-01

    We present a sample of the most massive galaxies (M^{*}>10^{11}{M}_{⊙}) found at z=0 in a fully cosmological simulation performed with MASCLET (Mesh Adaptative Scheme for CosmologicaL structurE evoluTion). te{quilis04} The Upper (lower) pannel shows the merger (quiet) galaxies depending on elipticity (ɛ) and velocity vs velocity-dispersion (v/σ). We use the ssp MILES models to make our galaxies bright and study some observables of our fully cosmological synthetic galaxies.

  4. Weak lensing by galaxy troughs

    NASA Astrophysics Data System (ADS)

    Gruen, Daniel

    2016-06-01

    Galaxy troughs, i.e. underdensities in the projected galaxy field, are a weak lensing probe of the low density Universe with high signal-to-noise ratio. I present measurements of the radial distortion of background galaxy images and the de-magnification of the CMB by troughs constructed from Dark Energy Survey and Sloan Digital Sky Survey galaxy catalogs. With high statistical significance and a relatively robust modeling, these probe gravity in regimes of density and scale difficult to access for conventional statistics.

  5. Dissipative processes in galaxy formation.

    PubMed Central

    Silk, J

    1993-01-01

    A galaxy commences its life in a diffuse gas cloud that evolves into a predominantly stellar aggregation. Considerable dissipation of gravitational binding energy occurs during this transition. I review here the dissipative processes that determine the critical scales of luminous galaxies and the generation of their morphology. The universal scaling relations for spirals and ellipticals are shown to be sensitive to the history of star formation. Semiphenomenological expressions are given for star-formation rates in protogalaxies and in starbursts. Implications are described for elliptical galaxy formation and for the evolution of disk galaxies. PMID:11607396

  6. Hot Gas Halos in Galaxies

    SciTech Connect

    Mulchaey, John S.; Jeltema, Tesla E.

    2010-06-08

    We use Chandra and XMM-Newton to study how the hot gas content in early-type galaxies varies with environment. We find that the L{sub X}-L{sub K} relationship is steeper for field galaxies than for comparable galaxies in groups and clusters. This suggests that internal processes such as supernovae driven winds or AGN feedback may expel hot gas from low mass field galaxies. Such mechanisms are less effective in groups and clusters where the presence of an intragroup or intracluster medium may confine outflowing material.

  7. Galaxy Alignments: Theory, Modelling & Simulations

    NASA Astrophysics Data System (ADS)

    Kiessling, Alina; Cacciato, Marcello; Joachimi, Benjamin; Kirk, Donnacha; Kitching, Thomas D.; Leonard, Adrienne; Mandelbaum, Rachel; Schäfer, Björn Malte; Sifón, Cristóbal; Brown, Michael L.; Rassat, Anais

    2015-11-01

    The shapes of galaxies are not randomly oriented on the sky. During the galaxy formation and evolution process, environment has a strong influence, as tidal gravitational fields in the large-scale structure tend to align nearby galaxies. Additionally, events such as galaxy mergers affect the relative alignments of both the shapes and angular momenta of galaxies throughout their history. These "intrinsic galaxy alignments" are known to exist, but are still poorly understood. This review will offer a pedagogical introduction to the current theories that describe intrinsic galaxy alignments, including the apparent difference in intrinsic alignment between early- and late-type galaxies and the latest efforts to model them analytically. It will then describe the ongoing efforts to simulate intrinsic alignments using both N-body and hydrodynamic simulations. Due to the relative youth of this field, there is still much to be done to understand intrinsic galaxy alignments and this review summarises the current state of the field, providing a solid basis for future work.

  8. Evolution of bulgeless low surface brightness galaxies

    NASA Astrophysics Data System (ADS)

    Shao, Xu; Hammer, Francois; Yang, Yanbin; Liang, Yanchun

    2015-08-01

    We study the environment, the morphology and stellar population of bulgeless low surface brightness (LSB) galaxies in a volume-limited sample. The differences of environments between LSB and high surface brightness (HSB) galaxies are not obvious, suggesting they may locate in similar environments. The stellar populations of LSB galaxies in low density region are similar with those of LSB galaxies in high density region. Irregular LSB galaxies have more young stars and are more metal-poor than the regular LSB galaxies.

  9. The intrinsic shape of galaxies in SDSS/Galaxy Zoo

    NASA Astrophysics Data System (ADS)

    Rodríguez, Silvio; Padilla, Nelson D.

    2013-09-01

    By modelling the axis ratio distribution of Sloan Digital Sky Survey (SDSS) Data Release 8 galaxies, we find the intrinsic 3D shapes of spirals and ellipticals. We use morphological information from the Galaxy Zoo project and assume a non-parametric distribution intrinsic of shapes, while taking into account dust extinction. We measure the dust extinction of the full sample of spiral galaxies and find a smaller value than previous estimations, with an edge-on extinction of E_0 = 0.284^{+0.015}_{-0.026} in the SDSS r band. We also find that the distribution of minor to major axis ratio has a mean value of 0.267 ± 0.009, slightly larger than previous estimates mainly due to the lower extinction used; the same affects the circularity of galactic discs, which are found to be less round in shape than in previous studies, with a mean ellipticity of 0.215 ± 0.013. For elliptical galaxies, we find that the minor to major axis ratio, with a mean value of 0.584 ± 0.006, is larger than previous estimations due to the removal of spiral interlopers present in samples with morphological information from photometric profiles. These interlopers are removed when selecting ellipticals using Galaxy Zoo data. We find that the intrinsic shapes of galaxies and their dust extinction vary with absolute magnitude, colour and physical size. We find that bright elliptical galaxies are more spherical than faint ones, a trend that is also present with galaxy size, and that there is no dependence of elliptical galaxy shape with colour. For spiral galaxies, we find that the reddest ones have higher dust extinction as expected, due to the fact that this reddening is mainly due to dust. We also find that the thickness of discs increases with luminosity and size, and that brighter, smaller and redder galaxies have less round discs.

  10. Intracluster Comptonization of the Cosmic Microwave Background: Mean Spectral Distortion and Cluster Number Counts

    NASA Astrophysics Data System (ADS)

    Colafrancesco, S.; Mazzotta, P.; Rephaeli, Y.; Vittorio, N.

    1997-04-01

    The mean sky-averaged Comptonization parameter, ȳ, describing the scattering of the cosmic microwave background (CMB) by hot gas in clusters of galaxies, is calculated in an array of flat and open cosmological and dark matter models. The models are globally normalized to fit cluster X-ray data, and intracluster gas is assumed to have evolved in a manner consistent with current observations. We predict values of ȳ lower than the COBE/FIRAS upper limit. The corresponding values of the overall optical thickness to Compton scattering are <~10-4 for relevant parameter values. Of more practical importance are number counts of clusters across which a net flux (with respect to the CMB) higher than some limiting value can be detected. Such number counts are specifically predicted for the COBRAS/SAMBA and BOOMERANG missions.

  11. UV TO FAR-IR CATALOG OF A GALAXY SAMPLE IN NEARBY CLUSTERS: SPECTRAL ENERGY DISTRIBUTIONS AND ENVIRONMENTAL TRENDS

    SciTech Connect

    Hernandez-Fernandez, Jonathan D.; Iglesias-Paramo, J.; Vilchez, J. M.

    2012-03-01

    In this paper, we present a sample of cluster galaxies devoted to study the environmental influence on the star formation activity. This sample of galaxies inhabits in clusters showing a rich variety in their characteristics and have been observed by the SDSS-DR6 down to M{sub B} {approx} -18, and by the Galaxy Evolution Explorer AIS throughout sky regions corresponding to several megaparsecs. We assign the broadband and emission-line fluxes from ultraviolet to far-infrared to each galaxy performing an accurate spectral energy distribution for spectral fitting analysis. The clusters follow the general X-ray luminosity versus velocity dispersion trend of L{sub X} {proportional_to} {sigma}{sup 4.4}{sub c}. The analysis of the distributions of galaxy density counting up to the 5th nearest neighbor {Sigma}{sub 5} shows: (1) the virial regions and the cluster outskirts share a common range in the high density part of the distribution. This can be attributed to the presence of massive galaxy structures in the surroundings of virial regions. (2) The virial regions of massive clusters ({sigma}{sub c} > 550 km s{sup -1}) present a {Sigma}{sub 5} distribution statistically distinguishable ({approx}96%) from the corresponding distribution of low-mass clusters ({sigma}{sub c} < 550 km s{sup -1}). Both massive and low-mass clusters follow a similar density-radius trend, but the low-mass clusters avoid the high density extreme. We illustrate, with ABELL 1185, the environmental trends of galaxy populations. Maps of sky projected galaxy density show how low-luminosity star-forming galaxies appear distributed along more spread structures than their giant counterparts, whereas low-luminosity passive galaxies avoid the low-density environment. Giant passive and star-forming galaxies share rather similar sky regions with passive galaxies exhibiting more concentrated distributions.

  12. Galaxy M82

    NASA Technical Reports Server (NTRS)

    1999-01-01

    A colorful image showing violent star formation triggered when two galaxies bumped into each other has been captured by NASA's Hubble Space Telescope.

    In the image, the starburst galaxy M82 has a disturbed appearance caused by violent activity after an ancient encounter with its large galactic neighbor, M81. The image, taken by Hubble's Wide Field and Planetary Camera 2, designed and built by NASA's Jet Propulsion Laboratory, Pasadena, Calif., is online at http://www.jpl.nasa.gov/pictures/wfpc .

    The huge lanes of dust that crisscross M82's disk are another telltale sign of the flurry of star formation. Below the center and to the right, a strong galactic wind is spewing knotty filaments of hydrogen and nitrogen gas. More than 100 super star clusters -- very bright, compact groupings of about 100,000 stars -- appear as white dots sprinkled throughout the galaxy's central area. The dark area just above center is a huge dust cloud.

    A collaboration of European and American scientists used these clusters to date the interaction between M82 and M81 to about 600 million years ago, when a region called M82 B (the bright area just below and to the left of the central dust cloud) exploded with new stars. Scientists have found that this ancient starburst was triggered by the encounter with M81. The results are published in the February 2001 issue of the Astronomical Journal.

    This discovery provides evidence linking the birth of super star clusters to violent interaction between galaxies. These clusters also provide insight into the rough-and-tumble universe of long ago, when galaxies bumped into each other more frequently.

    M82 is located 12 million light-years from Earth in the constellation Ursa Major. The picture was taken Sept. 15, 1997. The natural-color composite was constructed from three exposures taken with blue, green and red filters.

    The Space Telescope Science Institute, Baltimore, Md., manages space operations for the Hubble Space Telescope

  13. Where do galaxies end?

    SciTech Connect

    Shull, J. Michael

    2014-04-01

    Our current view of galaxies considers them as systems of stars and gas embedded in extended halos of dark matter, much of it formed by the infall of smaller systems at earlier times. The true extent of a galaxy remains poorly determined, with the 'virial radius' (R {sub vir}) providing a characteristic separation between collapsed structures in dynamical equilibrium and external infalling matter. Other physical estimates of the extent of gravitational influence include the gravitational radius, gas accretion radius, and 'galactopause' arising from outflows that stall at 100-200 kpc over a range of outflow parameters and confining gas pressures. Physical criteria are proposed to define bound structures, including a more realistic definition of R {sub vir}(M {sub *}, M{sub h} , z{sub a} ) for stellar mass M {sub *} and halo mass M{sub h} , half of which formed at 'assembly redshifts' ranging from z{sub a} ≈ 0.7-1.3. We estimate the extent of bound gas and dark matter around L* galaxies to be ∼200 kpc. The new virial radii, with mean (R {sub vir}) ≈ 200 kpc, are 40%-50% smaller than values estimated in recent Hubble Space Telescope/Cosmic Origins Spectrograph detections of H I and O VI absorbers around galaxies. In the new formalism, the Milky Way stellar mass, log M {sub *} = 10.7 ± 0.1, would correspond to R{sub vir}=153{sub −16}{sup +25} kpc for half-mass halo assembly at z{sub a} = 1.06 ± 0.03. The frequency per unit redshift of low-redshift O VI absorption lines in QSO spectra suggests absorber sizes ∼150 kpc when related to intervening 0.1L* galaxies. This formalism is intended to clarify semantic differences arising from observations of extended gas in galactic halos, circumgalactic medium (CGM), and filaments of the intergalactic medium (IGM). Astronomers should refer to bound gas in the galactic halo or CGM, and unbound gas at the CGM-IGM interface, on its way into the IGM.

  14. THE DENSEST GALAXY

    SciTech Connect

    Strader, Jay; Seth, Anil C.; Forbes, Duncan A.; Pota, Vincenzo; Usher, Christopher; Fabbiano, Giuseppina; Caldwell, Nelson; Romanowsky, Aaron J.; Brodie, Jean P.; Arnold, Jacob A.

    2013-09-20

    We report the discovery of a remarkable ultra-compact dwarf galaxy around the massive Virgo elliptical galaxy NGC 4649 (M60), which we call M60-UCD1. With a dynamical mass of 2.0 × 10{sup 8} M {sub ☉} but a half-light radius of only ∼24 pc, M60-UCD1 is more massive than any ultra-compact dwarfs of comparable size, and is arguably the densest galaxy known in the local universe. It has a two-component structure well fit by a sum of Sérsic functions, with an elliptical, compact (r{sub h} = 14 pc; n ∼ 3.3) inner component and a round, exponential, extended (r{sub h} = 49 pc) outer component. Chandra data reveal a variable central X-ray source with L{sub X} ∼ 10{sup 38} erg s{sup –1} that could be an active galactic nucleus associated with a massive black hole or a low-mass X-ray binary. Analysis of optical spectroscopy shows the object to be old (∼> 10 Gyr) and of solar metallicity, with elevated [Mg/Fe] and strongly enhanced [N/Fe] that indicates light-element self-enrichment; such self-enrichment may be generically present in dense stellar systems. The velocity dispersion (σ ∼ 70 km s{sup –1}) and resulting dynamical mass-to-light ratio (M/L{sub V} = 4.9 ± 0.7) are consistent with—but slightly higher than—expectations for an old, metal-rich stellar population with a Kroupa initial mass function. The presence of a massive black hole or a mild increase in low-mass stars or stellar remnants is therefore also consistent with this M/L{sub V} . The stellar density of the galaxy is so high that no dynamical signature of dark matter is expected. However, the properties of M60-UCD1 suggest an origin in the tidal stripping of a nucleated galaxy with M{sub B} ∼ –18 to –19.

  15. Calorie count - sodas and energy drinks

    MedlinePlus

    ... in each. Calorie count - sodas and energy drinks BEVERAGE SERVING SIZE CALORIES Soda 7 Up 12 oz. ... SN, PhD, Wolfson JA, Vine S, Wang YC. Diet-beverage consumption and caloric intake among US: adults, overall ...

  16. Pneumotachometer counts respiration rate of human subject

    NASA Technical Reports Server (NTRS)

    Graham, O.

    1964-01-01

    To monitor breaths per minute, two rate-to-analog converters are alternately used to read and count the respiratory rate from an impedance pneumograph sequentially displayed numerically on electroluminescent matrices.

  17. THE HUBBLE SPACE TELESCOPE WIDE FIELD CAMERA 3 EARLY RELEASE SCIENCE DATA: PANCHROMATIC FAINT OBJECT COUNTS FOR 0.2-2 {mu}m WAVELENGTH

    SciTech Connect

    Windhorst, Rogier A.; Cohen, Seth H.; Mechtley, Matt; Rutkowski, Michael J.; Hathi, Nimish P.; McCarthy, Patrick J.; Seibert, Mark; Ryan, Russell E. Jr; Yan Haojing; Baldry, Ivan K.; Driver, Simon P.; Hill, David T.; Kelvin, Lee S.; Robotham, Aaron S. G.; Frogel, Jay A.; Koekemoer, Anton M.; O'Connell, Robert W.; Straughn, Amber N.; Tuffs, Richard J.; Balick, Bruce

    2011-04-01

    We describe the Hubble Space Telescope (HST) Wide Field Camera 3 (WFC3) Early Release Science (ERS) observations in the Great Observatories Origins Deep Survey (GOODS) South field. The new WFC3 ERS data provide calibrated, drizzled mosaics in the UV filters F225W, F275W, and F336W, as well as in the near-IR filters F098M (Y{sub s} ), F125W (J), and F160W (H) with 1-2 HST orbits per filter. Together with the existing HST Advanced Camera for Surveys (ACS) GOODS-South mosaics in the BViz filters, these panchromatic 10-band ERS data cover 40-50 arcmin{sup 2} at 0.2-1.7 {mu}m in wavelength at 0.''07-0.''15 FWHM resolution and 0.''090 Multidrizzled pixels to depths of AB {approx_equal} 26.0-27.0 mag (5{sigma}) for point sources, and AB {approx_equal} 25.5-26.5 mag for compact galaxies. In this paper, we describe (1) the scientific rationale, and the data taking plus reduction procedures of the panchromatic 10-band ERS mosaics, (2) the procedure of generating object catalogs across the 10 different ERS filters, and the specific star-galaxy separation techniques used, and (3) the reliability and completeness of the object catalogs from the WFC3 ERS mosaics. The excellent 0.''07-0.''15 FWHM resolution of HST/WFC3 and ACS makes star-galaxy separation straightforward over a factor of 10 in wavelength to AB {approx_equal} 25-26 mag from the UV to the near-IR, respectively. Our main results are: (1) proper motion of faint ERS stars is detected over 6 years at 3.06 {+-} 0.66 mas year{sup -1} (4.6{sigma}), consistent with Galactic structure models; (2) both the Galactic star counts and the galaxy counts show mild but significant trends of decreasing count slopes from the mid-UV to the near-IR over a factor of 10 in wavelength; (3) combining the 10-band ERS counts with the panchromatic Galaxy and Mass Assembly survey counts at the bright end (10 mag {approx}< AB {approx}< 20 mag) and the Hubble Ultra Deep Field counts in the BVizY{sub s}JH filters at the faint end (24 mag {approx

  18. Galaxy and mass assembly (GAMA): projected galaxy clustering

    NASA Astrophysics Data System (ADS)

    Farrow, D. J.; Cole, Shaun; Norberg, Peder; Metcalfe, N.; Baldry, I.; Bland-Hawthorn, Joss; Brown, Michael J. I.; Hopkins, A. M.; Lacey, Cedric G.; Liske, J.; Loveday, Jon; Palamara, David P.; Robotham, A. S. G.; Sridhar, Srivatsan

    2015-12-01

    We measure the projected two-point correlation function of galaxies in the 180 deg2 equatorial regions of the GAMA II survey, for four different redshift slices between z = 0.0 and 0.5. To do this, we further develop the Cole method of producing suitable random catalogues for the calculation of correlation functions. We find that more r-band luminous, more massive and redder galaxies are more clustered. We also find that red galaxies have stronger clustering on scales less than ˜3 h-1 Mpc. We compare to two different versions of the GALFORM galaxy formation model, Lacey et al. (in preparation) and Gonzalez-Perez et al., and find that the models reproduce the trend of stronger clustering for more massive galaxies. However, the models underpredict the clustering of blue galaxies, can incorrectly predict the correlation function on small scales and underpredict the clustering in our sample of galaxies with {˜ } 3 Lr^*. We suggest possible avenues to explore to improve these clustering predictions. The measurements presented in this paper can be used to test other galaxy formation models, and we make the measurements available online to facilitate this.

  19. SIS Detectors for Terahertz Photon Counting System

    NASA Astrophysics Data System (ADS)

    Ezawa, Hajime; Matsuo, Hiroshi; Ukibe, Masahiro; Fujii, Go; Shiki, Shigetomo

    2016-07-01

    An Intensity interferometer with photon counting detector is a candidate to realize a THz interferometer for astronomical observations. We have demonstrated that synthesis imaging is possible even with intensity interferometers. An SIS junction (or STJ) with low leakage current of 1 pA is a suitable device for photon counting detectors. Readout circuit utilizing FETs with low gate leakage, low gate capacitance, and fast response is discussed.

  20. TVFMCATS. Time Variant Floating Mean Counting Algorithm

    SciTech Connect

    Huffman, R.K.

    1999-05-01

    This software was written to test a time variant floating mean counting algorithm. The algorithm was developed by Westinghouse Savannah River Company and a provisional patent has been filed on the algorithm. The test software was developed to work with the Val Tech model IVB prototype version II count rate meter hardware. The test software was used to verify the algorithm developed by WSRC could be correctly implemented with the vendor`s hardware.

  1. Time Variant Floating Mean Counting Algorithm

    SciTech Connect

    Huffman, Russell Kevin

    1999-06-03

    This software was written to test a time variant floating mean counting algorithm. The algorithm was developed by Westinghouse Savannah River Company and a provisional patent has been filed on the algorithm. The test software was developed to work with the Val Tech model IVB prototype version II count rate meter hardware. The test software was used to verify the algorithm developed by WSRC could be correctly implemented with the vendor''s hardware.

  2. Minimum Disclosure Counting for the Alternative Vote

    NASA Astrophysics Data System (ADS)

    Wen, Roland; Buckland, Richard

    Although there is a substantial body of work on preventing bribery and coercion of voters in cryptographic election schemes for plurality electoral systems, there are few attempts to construct such schemes for preferential electoral systems. The problem is preferential systems are prone to bribery and coercion via subtle signature attacks during the counting. We introduce a minimum disclosure counting scheme for the alternative vote preferential system. Minimum disclosure provides protection from signature attacks by revealing only the winning candidate.

  3. Measuring distance ratios with CMB-galaxy lensing cross-correlations

    NASA Astrophysics Data System (ADS)

    Das, Sudeep; Spergel, David N.

    2009-02-01

    We propose a method for cosmographic measurements by combining gravitational lensing of the cosmic microwave background (CMB) with cosmic shear surveys. We cross-correlate the galaxy counts in the lens plane with two different source planes: the CMB at z˜1100 and galaxies at an intermediate redshift. The ratio of the galaxy count/CMB lensing cross-correlation to the galaxy count/galaxy lensing cross-correlation is shown to be a purely geometric quantity, depending only on the distribution function of the source galaxies. By combining Planck, the Advanced Dark Energy Physics Telescope, and the Large Synoptic Survey Telescope, the ratio can be measured to ˜4% accuracy, whereas a future polarization-based experiment like CMBPOL can make a more precise (˜1%) measurement. For cosmological models where the curvature and the equation of state parameter are allowed to vary, the direction of degeneracy defined by the measurement of this ratio is different from that traced out by baryon acoustic oscillation measurements. Combining this method with the stacked cluster mass reconstruction cosmography technique as proposed by Hu, Holz, and Vale (2007), the uncertainty in the ratio can be further reduced, improving the constraints on cosmological parameters. We also study the implications of the lensing-ratio measurement for early dark energy models, in the context of the parametrization proposed by Doran and Robbers (2006). For models which are degenerate with respect to the CMB, we find both baryon acoustic oscillation and lensing-ratio measurements to be insensitive to the early component of the dark energy density.

  4. Measuring distance ratios with CMB-galaxy lensing cross-correlations

    SciTech Connect

    Das, Sudeep; Spergel, David N.

    2009-02-15

    We propose a method for cosmographic measurements by combining gravitational lensing of the cosmic microwave background (CMB) with cosmic shear surveys. We cross-correlate the galaxy counts in the lens plane with two different source planes: the CMB at z{approx}1100 and galaxies at an intermediate redshift. The ratio of the galaxy count/CMB lensing cross-correlation to the galaxy count/galaxy lensing cross-correlation is shown to be a purely geometric quantity, depending only on the distribution function of the source galaxies. By combining Planck, the Advanced Dark Energy Physics Telescope, and the Large Synoptic Survey Telescope, the ratio can be measured to {approx}4% accuracy, whereas a future polarization-based experiment like CMBPOL can make a more precise ({approx}1%) measurement. For cosmological models where the curvature and the equation of state parameter are allowed to vary, the direction of degeneracy defined by the measurement of this ratio is different from that traced out by baryon acoustic oscillation measurements. Combining this method with the stacked cluster mass reconstruction cosmography technique as proposed by Hu, Holz, and Vale (2007), the uncertainty in the ratio can be further reduced, improving the constraints on cosmological parameters. We also study the implications of the lensing-ratio measurement for early dark energy models, in the context of the parametrization proposed by Doran and Robbers (2006). For models which are degenerate with respect to the CMB, we find both baryon acoustic oscillation and lensing-ratio measurements to be insensitive to the early component of the dark energy density.

  5. Magnetic fields in spiral galaxies

    NASA Astrophysics Data System (ADS)

    Beck, Rainer

    2015-12-01

    Radio synchrotron emission, its polarization and Faraday rotation of the polarization angle are powerful tools to study the strength and structure of magnetic fields in galaxies. Unpolarized synchrotron emission traces isotropic turbulent fields which are strongest in spiral arms and bars (20-30 \\upmu G) and in central starburst regions (50-100 \\upmu G). Such fields are dynamically important; they affect gas flows and drive gas inflows in central regions. Polarized emission traces ordered fields, which can be regular or anisotropic turbulent, where the latter originates from isotropic turbulent fields by the action of compression or shear. The strongest ordered fields (10-15 \\upmu G) are generally found in interarm regions. In galaxies with strong density waves, ordered fields are also observed at the inner edges of spiral arms. Ordered fields with spiral patterns exist in grand-design, barred and flocculent galaxies and in central regions. Ordered fields in interacting galaxies have asymmetric distributions and are a tracer of past interactions between galaxies or with the intergalactic medium.—Faraday rotation measures of the diffuse polarized radio emission from galaxy disks reveal large-scale spiral patterns that can be described by the superposition of azimuthal modes; these are signatures of regular fields generated by mean-field dynamos. "Magnetic arms" between gaseous spiral arms may also be products of dynamo action, but need a stable spiral pattern to develop. Helically twisted field loops winding around spiral arms were found in two galaxies so far. Large-scale field reversals, like the one found in the Milky Way, could not yet be detected in external galaxies. In radio halos around edge-on galaxies, ordered magnetic fields with X-shaped patterns are observed. The origin and evolution of cosmic magnetic fields, in particular their first occurrence in young galaxies and their dynamical importance during galaxy evolution, will be studied with

  6. QUALITATIVE INTERPRETATION OF GALAXY SPECTRA

    SciTech Connect

    Sanchez Almeida, J.; Morales-Luis, A. B.; Terlevich, R.; Terlevich, E.; Cid Fernandes, R. E-mail: abml@iac.es E-mail: eterlevi@inaoep.mx

    2012-09-10

    We describe a simple step-by-step guide to qualitative interpretation of galaxy spectra. Rather than an alternative to existing automated tools, it is put forward as an instrument for quick-look analysis and for gaining physical insight when interpreting the outputs provided by automated tools. Though the recipe is for general application, it was developed for understanding the nature of the Automatic Spectroscopic K-means-based (ASK) template spectra. They resulted from the classification of all the galaxy spectra in the Sloan Digital Sky Survey data release 7, thus being a comprehensive representation of the galaxy spectra in the local universe. Using the recipe, we give a description of the properties of the gas and the stars that characterize the ASK classes, from those corresponding to passively evolving galaxies, to H II galaxies undergoing a galaxy-wide starburst. The qualitative analysis is found to be in excellent agreement with quantitative analyses of the same spectra. We compare the mean ages of the stellar populations with those inferred using the code STARLIGHT. We also examine the estimated gas-phase metallicity with the metallicities obtained using electron-temperature-based methods. A number of byproducts follow from the analysis. There is a tight correlation between the age of the stellar population and the metallicity of the gas, which is stronger than the correlations between galaxy mass and stellar age, and galaxy mass and gas metallicity. The galaxy spectra are known to follow a one-dimensional sequence, and we identify the luminosity-weighted mean stellar age as the affine parameter that describes the sequence. All ASK classes happen to have a significant fraction of old stars, although spectrum-wise they are outshined by the youngest populations. Old stars are metal-rich or metal-poor depending on whether they reside in passive galaxies or in star-forming galaxies.

  7. On the baryonic contents of low mass galaxies

    SciTech Connect

    Gnedin, Nickolay Y

    2012-07-16

    The baryonic Tully-Fisher relation is an important observational constraint on cosmological and galactic models. However, it is critical to keep in mind that in observations only stars, molecular, and atomic gas are counted, while the contribution of the ionized gas is almost universally missed. The ionized gas is, however, expected to be present in the gaseous disks of dwarf galaxies simply because they are exposed to the cosmic ionizing background and to the stellar radiation that manages to escape from the central regions of the galactic disks into their outer layers. Such an expectation is, indeed, born out both by cosmological numerical simulations and by simple analytical models.

  8. ON THE BARYONIC CONTENTS OF LOW-MASS GALAXIES

    SciTech Connect

    Gnedin, Nickolay Y.

    2012-08-01

    The baryonic Tully-Fisher relation is an important observational constraint on cosmological and galactic models. However, it is critical to keep in mind that in observations only stars and molecular and atomic gas are counted, while the contribution of the ionized gas is almost universally missed. The ionized gas is, however, expected to be present in the gaseous disks of dwarf galaxies simply because they are exposed to the cosmic ionizing background and to the stellar radiation that manages to escape from the central regions of the galactic disks into their outer layers. Such an expectation is, indeed, born out both by cosmological numerical simulations and by simple analytical models.

  9. Spectral evolution of galaxies. III - Cosmological predictions for the Space Telescope faint object camera

    NASA Astrophysics Data System (ADS)

    Bruzual A., G.

    1983-10-01

    The galactic spectral evolutionary models of Bruzual A. (1981) are employed to estimate parameters which will be observable by the wide-field camera and faint-object camera of the Space Telescope. The capabilities and bandpasses of the instruments are reviewed, and the results are presented in tables and graphs. Parameters calculated include the amplitude of the Lyman discontinuity at 912 A, stellar and galaxy rest-frame colors, color evolution, two-color diagrams as a function of redshift, luminosity evolution, surface brightness profiles, galaxy counts, and color and redshift distributions. In general, it is predicted that the space measurements will follow the trends noted in round-based observations.

  10. GALAXY Classroom: Television for Tomorrow.

    ERIC Educational Resources Information Center

    Graumann, Peter

    1994-01-01

    An interactive learning service for elementary grades, "GALAXY Classroom," offers enrichment opportunities to classrooms. Students communicate via fax in response to questions posed in satellite transmitted segments. The primary market for "GALAXY Classroom" is the at-risk student. Sidebars describe costs and current offerings. (SLW)

  11. The morphological evolution of galaxies.

    PubMed

    Abraham, R G; van Den Bergh, S

    2001-08-17

    Many galaxies have taken on their familiar appearance relatively recently. In the distant Universe, galaxy morphology deviates significantly (and systematically) from that of nearby galaxies at redshifts (z) as low as 0.3. This corresponds to a time approximately 3.5 x 10(9) years in the past, which is only approximately 25% of the present age of the Universe. Beyond z = 0.5 (5 x 10(9) years in the past), spiral arms are less well developed and more chaotic, and barred spiral galaxies may become rarer. At z = 1, around 30% of the galaxy population is sufficiently peculiar that classification on Hubble's traditional "tuning fork" system is meaningless. On the other hand, some characteristics of galaxies have not changed much over time. The space density of luminous disk galaxies has not changed significantly since z = 1, indicating that although the general appearance of these galaxies has continuously changed over time, their overall numbers have been conserved. PMID:11509719

  12. Computational astrophysics: Monstrous galaxies unmasked

    NASA Astrophysics Data System (ADS)

    Davé, Romeel

    2015-09-01

    The enigma of how the most luminous galaxies arise is closer to being solved. New simulations show that these are long-lived massive galaxies powered by prodigious gas infall and the recycling of supernova-driven outflows. See Letter p.496

  13. Cold Gas in Distant Galaxies

    NASA Astrophysics Data System (ADS)

    Carilli, Christopher; Walter, Fabian

    2015-08-01

    Over the past decade, observations of the cool interstellar medium (ISM) in distant galaxies via molecular and atomic fine structure line (FSL) emission have gone from a curious look into a few extreme, rare objects to a mainstream tool for studying galaxy formation out to the highest redshifts. Molecular gas has been observed in about 200 galaxies at z > 1 to z ~ 7, including AGN host-galaxies, highly star-forming submillimeter galaxies, and increasing samples of main-sequence color-selected star-forming galaxies. Studies have moved well beyond simple detections to dynamical imaging at kpc resolution and multiline, multispecies studies that determine the physical conditions in the ISM in early galaxies. Observations of the cool gas are the required complement to studies of the stellar density and star-formation history of the Universe as they reveal the phase of the ISM that immediately precedes star formation in galaxies.Current observations suggest that the order of magnitude increase in the cosmic star-formation rate density from z ~ 0 to 2 is commensurate with a similar increase in the gas-to-stellar mass ratio in star-forming disk galaxies. Progress has been made in determining the CO luminosity to H2 mass conversion factor at high z. The dichotomy between high versus low values for the conversion factor for main-sequence versus starburst galaxies, respectively, appears to persist with increasing redshift, with a likely dependence on metalicity and other local physical conditions. There may also be two sequences in the relationship between star-formation rate and gas mass: one for starbursts, in which the gas consumption timescale is short (~ few e7 years), and one for main sequence galaxies, with an order of magnitude longer gas consumption timescale.With the advent of ALMA, studies of atomic FSL emission are rapidly progressing, with ~ 50 galaxies detected in the exceptionally bright [CII] 158 um line to date, 50% in the last year or so. The [CII] line is

  14. Galaxies in extreme environments: Isolated galaxies versus compact groups

    NASA Astrophysics Data System (ADS)

    Durbala, Adriana

    2009-06-01

    This Dissertation comprises two distinct studies of galaxies in dramatically different environments: extreme isolation versus compact groups. We emphasize empirically how "nature" (i.e. internal, secular processes) plays the dominant role in defining the evolution of isolated galaxies and how "nurture" dictates the fate of galaxies in very crowded environments. Two chapters report on a detailed photometric study of a well-defined sample of N ~100 isolated Sb-Sc spiral galaxies. Data source is Sloan Digital Sky Survey. Using i-band images we perform three kinds of measures: (a) bulge/disk/bar decomposition, (b) CAS parametrization (Concentration, Asymmetry, Clumpiness), and (c) Fourier decomposition/analysis of spiral arms and bar properties including dynamical measures of the torque. Having quantified a large set of properties we look for: (i) the interplay between different components of the same galaxy, (ii) trends along the morphological sequence Sb-Sbc-Sc, and (iii) statistical differences between our "isolated" sample and samples of galaxies of similar morphology constructed without regard for isolation. We find that the majority of isolated late-type disk galaxies host pseudobulges rather than classical bulges. The pseudobulges probably form through internal secular processes and bars may play an important role. A clear separation is noted between Sb and Sbc/Sc in various measures, i.e. the former are redder, brighter, have larger disks and bars, more luminous bulges, are more concentrated, more symmetric and dumpier than the latter. Isolated galaxies host larger bars than galaxies in samples defined without isolation constraints. Longer bars are not necessarily stronger, but show a higher contrast in Fourier analysis. Another chapter is a multiwavelength study of Seyfert's Sextet, the highest density galaxy aggregate in the local Universe. Four of its five galaxies are interpreted as remnant bulges of accreted spirals and are now embedded in a luminous halo

  15. HII Galaxies in 3D

    NASA Astrophysics Data System (ADS)

    Telles, E.

    2016-06-01

    In this contribution I review some results of the integral field spectroscopy of HII galaxies. The two main topics are related to their internal kinematics and the distribution of physical conditions. HII galaxies present a L-σ relation similar to elliptical galaxies. However, the origin of supersonic motions of the ionized gas (σ) is still a matter of debate. We show that the core of the star forming region dominates the internal kinematics and probes the underlying turbulent motions. The show our latest calibration of the L-sigma relation of local HII galaxies. We also show that the physical conditions are very uniform throughout the whole extent of the star forming region, once you account for the levels of ionization. HII galaxies are excellent laboratories for constraining the ionization power of high mass stars at low metallicities.

  16. Disrupted Stars in Unusual Galaxies

    NASA Astrophysics Data System (ADS)

    Kohler, Susanna

    2016-03-01

    Tidal disruption events (TDEs) occur when a star passes a little too close to a supermassive black hole at the center of a galaxy. Tidal forces from the black hole cause the passing star to be torn apart, resulting in a brief flare of radiation as the stars material accretes onto the black hole. A recent study asks the following question: do TDEs occur most frequently in an unusual type of galaxy?A Trend in DisruptionsSo far, we have data from eight candidate TDEs that peaked in optical and ultraviolet wavelengths. The spectra from these observations have shown an intriguing trend: many of these TDEs host galaxies exhibit weak line emission (indicating little or no current star-formation activity), and yet they show strong Balmer absorption lines (indicating star formation activity occurred within the last Gyr). These quiescent, Balmer-strong galaxies likely underwent a period of intense star formation that recently ended.To determine if TDEs are overrepresented in such galaxies, a team of scientists led by Decker French (Steward Observatory, University of Arizona) has quantified the fraction of galaxies in the Sloan Digital Sky Survey (SDSS) that exhibit similar properties to those of TDE hosts.Quantifying OverrepresentationSpectral characteristics of SDSS galaxies (gray) and TDE candidate host galaxies (colored points): line emission vs. Balmer absorption. The lower right-hand box identifies thequiescent, Balmer-strong galaxies which contain most TDE events, yet are uncommon among the galaxy sample as a whole. Click for a better look! [French et al. 2016]French and collaborators compare the optical spectra of the TDE host galaxies to those of nearly 600,000 SDSS galaxies, using two different cutoffs for the Balmer absorption the indicator of past star formation. Their strictest cut, filtering for very high Balmer absorption, selected only 0.2% of the SDSS galaxies, yet 38% of the TDEs are hosted in such galaxies. Using a more relaxed cutoff selects 2.3% of

  17. Galaxy NGC 1850

    NASA Technical Reports Server (NTRS)

    1999-01-01

    By spying on a neighboring galaxy, NASA's Hubble Space Telescope has captured an image of a young, globular-like star cluster -- a type of object unknown in our Milky Way Galaxy.

    The image, taken by Hubble's Wide Field and Planetary Camera 2, is online at http://oposite.stsci.edu/pubinfo/pr/2001/25 and http://www.jpl.nasa.gov/images/wfpc. The camera was designed and built by NASA's Jet Propulsion Laboratory, Pasadena, Calif.

    The double cluster NGC 1850 lies in a neighboring satellite galaxy, the Large Magellanic Cloud. It has two relatively young components. The main, globular-like cluster is in the center. A smaller cluster is seen below and to the right, composed of extremely hot, blue stars and fainter red T-Tauri stars. The main cluster is about 50 million years old; the smaller one is 4 million years old.

    A filigree pattern of diffuse gas surrounds NGC 1850. Scientists believe the pattern formed millions of years ago when massive stars in the main cluster exploded as supernovas.

    Hubble can observe a range of star types in NGC 1850, including the faint, low-mass T-Tauri stars, which are difficult to distinguish with ground-based telescopes. Hubble's fine angular resolution can pick out these stars, even in other galaxies. Massive stars of the OB type emit large amounts of energetic ultraviolet radiation, which is absorbed by the Earth's atmosphere. From Hubble's position above the atmosphere, it can detect this ultraviolet light.

    NGC 1850, the brightest star cluster in the Large Magellanic Cloud, is in the southern constellation of Dorado, called the Goldfish or the Swordfish. This image was created from five archival exposures taken by the Wide Field Planetary Camera 2 between April 3, 1994 and February 6, 1996. More information about the Hubble Space Telescope is online at http://www.stsci.edu. More information about the Wide Field and Planetary Camera 2 is at http://wfpc2.jpl.nasa.gov.

    The Space Telescope Science Institute, Baltimore

  18. 7 CFR 51.564 - Requirements as to count.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... (INSPECTION, CERTIFICATION, AND STANDARDS) United States Standards for Celery Count § 51.564 Requirements as to count. (a) The number of stalks of celery in the container may be specified by numerical count...

  19. 7 CFR 51.564 - Requirements as to count.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... STANDARDS) United States Standards for Celery Count § 51.564 Requirements as to count. (a) The number of stalks of celery in the container may be specified by numerical count or in terms of dozens or...

  20. 7 CFR 51.564 - Requirements as to count.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... STANDARDS) United States Standards for Celery Count § 51.564 Requirements as to count. (a) The number of stalks of celery in the container may be specified by numerical count or in terms of dozens or...

  1. 7 CFR 51.564 - Requirements as to count.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... (INSPECTION, CERTIFICATION, AND STANDARDS) United States Standards for Celery Count § 51.564 Requirements as to count. (a) The number of stalks of celery in the container may be specified by numerical count...

  2. 7 CFR 51.564 - Requirements as to count.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... STANDARDS) United States Standards for Celery Count § 51.564 Requirements as to count. (a) The number of stalks of celery in the container may be specified by numerical count or in terms of dozens or...

  3. The clustering of warm and cool IRAS galaxies

    NASA Astrophysics Data System (ADS)

    Mann, R. G.; Saunders, W.; Taylor, A. N.

    1996-03-01

    We use a series of statistical techniques to compare the clustering of samples of IRAS galaxies selected on the basis of their far-infrared emission temperature, to see whether a temperature-dependent effect, such as might be produced by interaction-induced star formation, could be responsible for the increase in clustering strength with redshift in the QDOT redshift survey that has been reported by several authors. The temperature-luminosity relation for IRAS galaxies means that warm and cool samples drawn from a flux-limited sample like QDOT will sample quite different volumes of space. To overcome this problem, and to distinguish truly temperature-dependent results from those depending directly on the volume of space sampled, we consider a pair of samples of warmer and cooler galaxies with matched redshift distributions, as well as pairs of samples selected using a simple temperature cut. We find that the redshift-space autocorrelation function of warm QDOT galaxies is significantly stronger than that of cool galaxies on large scales, but that this difference disappears when we come to consider the warmer and cooler samples with matched redshift distributions. A counts- in-cells analysis reveals no significant difference between the clustering of the warm and cool QDOT samples, while the use of a new, symmetric estimator reveals that the cross-correlations of warm and cool IRAS galaxies with Abell clusters do not differ significantly. A higher signal-to-noise ratio test is provided by computing the projected cross- correlations of the matched samples with the parent two-dimensional catalogue from which QDOT is drawn, and this does yield a marginal detection of greater large-scale power for warmer galaxies. A direct comparison of the distributions of the warmer and cooler samples, using a new technique which tests the null hypothesis that they are drawn from the same population, reveals that the two classes of galaxy do cluster differently on small scales in

  4. Constraints on radio source clustering towards galaxy clusters: application for cm-wavelength simulations of blind sky surveys

    NASA Astrophysics Data System (ADS)

    Lew, Bartosz

    2016-10-01

    We derive constraints on radio source clustering towards Planck-selected galaxy clusters using the NVSS point source catalog. The constraint can be used for making a more realistic Sunyaev-Zeldovich effect (SZE) mocks, calculating predictions of detectable clusters count and for quantifying source confusion in radio surveys.

  5. Spectroscopic Observations of Merging Galaxies

    NASA Astrophysics Data System (ADS)

    Donzelli, C. J.; Pastoriza, M. G.

    2000-07-01

    In this paper we describe the spectroscopic and infrared properties of a sample of 25 merging galaxy pairs, selected from the catalog of Arp & Madore, and we compare them with those observed in a similar sample of interacting galaxies (Donzelli & Pastoriza). It is noted that mergers as well as interacting systems comprise a wide range of spectral types, going from those corresponding to well-evolved stellar populations (older than 200 Myr) to those that show clear signatures of H II regions with stellar populations younger than 8 Myr. However, merger galaxies show on average more excited spectra than interacting pairs, which could be attributed to lower gas metallicity. From the emission lines we also found that merging systems show on average higher (about a factor of 2) star formation rates than interacting galaxies. Classical diagnostic diagrams show that only three of 50 of the galaxies (6%) present some form of nuclear activity: two Seyfert galaxies and one LINER. However, through a detailed analysis of the pure emission-line spectra, we conclude that this fraction may raise up to 23% of the mergers if we consider that some galaxies host a low-luminosity active nucleus surrounded by strong star-forming regions. This latter assumption is also supported by the infrared colors of the galaxies. Regarding to the total infrared luminosities, the merging galaxies show on average an IR luminosity, log(Lir)=10.7, lower than that of interacting systems, log(Lir)=10.9. We find that only three mergers of the sample (12%) can be classified as luminous infrared galaxies, while this fraction increases to 24% in the interacting sample. Based on observations made at CASLEO. Complejo Astronómico El Leoncito is operated under agreement between the Consejo Nacional de Investigaciones Científicas y Técnicas de la República Argentina and the National Universities of La Plata, Córdoba and San Juan.

  6. Galaxy evolution and large-scale structure in the far-infrared. I - IRAS pointed observations

    NASA Technical Reports Server (NTRS)

    Lonsdale, Carol J.; Hacking, Perry B.

    1989-01-01

    Redshifts for 66 galaxies were obtained from a sample of 93 60-micron sources detected serendipitously in 22 IRAS deep pointed observations, covering a total area of 18.4 sq deg. The flux density limit of this survey is 150 mJy, 4 times fainter than the IRAS Point Source Catalog (PSC). The luminosity function is similar in shape with those previously published for samples selected from the PSC, with a median redshift of 0.048 for the fainter sample, but shifted to higher space densities. There is evidence that some of the excess number counts in the deeper sample can be explained in terms of a large-scale density enhancement beyond the Pavo-Indus supercluster. In addition, the faintest counts in the new sample confirm the result of Hacking et al. (1989) that faint IRAS 60-micron source counts lie significantly in excess of an extrapolation of the PSC counts assuming no luminosity or density evolution.

  7. Galaxy evolution and large-scale structure in the far-infrared. I - IRAS pointed observations

    NASA Astrophysics Data System (ADS)

    Lonsdale, Carol J.; Hacking, Perry B.

    1989-04-01

    Redshifts for 66 galaxies were obtained from a sample of 93 60-micron sources detected serendipitously in 22 IRAS deep pointed observations, covering a total area of 18.4 sq deg. The flux density limit of this survey is 150 mJy, 4 times fainter than the IRAS Point Source Catalog (PSC). The luminosity function is similar in shape with those previously published for samples selected from the PSC, with a median redshift of 0.048 for the fainter sample, but shifted to higher space densities. There is evidence that some of the excess number counts in the deeper sample can be explained in terms of a large-scale density enhancement beyond the Pavo-Indus supercluster. In addition, the faintest counts in the new sample confirm the result of Hacking et al. (1989) that faint IRAS 60-micron source counts lie significantly in excess of an extrapolation of the PSC counts assuming no luminosity or density evolution.

  8. The VIMOS Public Extragalactic Redshift Survey (VIPERS). On the recovery of the count-in-cell probability distribution function

    NASA Astrophysics Data System (ADS)

    Bel, J.; Branchini, E.; Di Porto, C.; Cucciati, O.; Granett, B. R.; Iovino, A.; de la Torre, S.; Marinoni, C.; Guzzo, L.; Moscardini, L.; Cappi, A.; Abbas, U.; Adami, C.; Arnouts, S.; Bolzonella, M.; Bottini, D.; Coupon, J.; Davidzon, I.; De Lucia, G.; Fritz, A.; Franzetti, P.; Fumana, M.; Garilli, B.; Ilbert, O.; Krywult, J.; Le Brun, V.; Le Fèvre, O.; Maccagni, D.; Małek, K.; Marulli, F.; McCracken, H. J.; Paioro, L.; Polletta, M.; Pollo, A.; Schlagenhaufer, H.; Scodeggio, M.; Tasca, L. A. M.; Tojeiro, R.; Vergani, D.; Zanichelli, A.; Burden, A.; Marchetti, A.; Mellier, Y.; Nichol, R. C.; Peacock, J. A.; Percival, W. J.; Phleps, S.; Wolk, M.

    2016-04-01

    We compare three methods to measure the count-in-cell probability density function of galaxies in a spectroscopic redshift survey. From this comparison we found that, when the sampling is low (the average number of object per cell is around unity), it is necessary to use a parametric method to model the galaxy distribution. We used a set of mock catalogues of VIPERS to verify if we were able to reconstruct the cell-count probability distribution once the observational strategy is applied. We find that, in the simulated catalogues, the probability distribution of galaxies is better represented by a Gamma expansion than a skewed log-normal distribution. Finally, we correct the cell-count probability distribution function from the angular selection effect of the VIMOS instrument and study the redshift and absolute magnitude dependency of the underlying galaxy density function in VIPERS from redshift 0.5 to 1.1. We found a very weak evolution of the probability density distribution function and that it is well approximated by a Gamma distribution, independently of the chosen tracers. Based on observations collected at the European Southern Observatory, Cerro Paranal, Chile, using the Very Large Telescope under programmes 182.A-0886 and partly 070.A-9007. Also based on observations obtained with MegaPrime/MegaCam, a joint project of CFHT and CEA/DAPNIA, at the Canada-France-Hawaii Telescope (CFHT), which is operated by the National Research Council (NRC) of Canada, the Institut National des Sciences de l'Univers of the Centre National de la Recherche Scientifique (CNRS) of France, and the University of Hawaii. This work is based in part on data products produced at TERAPIX and the Canadian Astronomy Data Centre as part of the Canada-France-Hawaii Telescope Legacy Survey, a collaborative project of NRC and CNRS. The VIPERS web site is http://www.vipers.inaf.it/

  9. ORIENTATION OF BRIGHTER GALAXIES IN NEARBY GALAXY CLUSTERS

    SciTech Connect

    Panko, E.; Juszczyk, T.; Flin, P. E-mail: sfflin@cyf-kr.edu.pl

    2009-12-15

    A sample of 6188 nearby galaxy structures, complete to r{sub F} = 18fm3 and containing at least 10 members each, was the observational basis for an investigation of the alignment of bright galaxies with the major axes for the parent clusters. The distribution of position angles for galaxies within the clusters, specifically the brightest, the second brightest, the third, and the tenth brightest galaxies was tested for isotropy. Galaxy position angles appear to be distributed isotropically, as are the distributions of underlying cluster structure position angles. The characterization of galaxy structures according to richness class also appears to be isotropic. Characterization according to BM types, which are known for 1056 clusters, is more interesting. Only in the case of clusters of BM type I is there an alignment of the brightest cluster member with the major axis of the parent cluster. The effect is observed at the 2 significance level. In other investigated cases the distributions are isotropic. The results confirm the special role of cD galaxies in the origin/evolution of large-scale structures.

  10. Testing galaxy formation models with galaxy stellar mass functions

    NASA Astrophysics Data System (ADS)

    Lim, S. H.; Mo, H. J.; Lan, Ting-Wen; Ménard, Brice

    2016-10-01

    We compare predictions of a number of empirical models and numerical simulations of galaxy formation to the conditional stellar mass functions (CSMF) of galaxies in groups of different masses obtained recently by Lan et al. to test how well different models accommodate the data. The observational data clearly prefer a model in which star formation in low-mass halos changes behavior at a characteristic redshift zc ˜ 2. There is also tentative evidence that this characteristic redshift depends on environment, becoming zc ˜ 4 in regions that eventually evolve into rich clusters of galaxies. The constrained model is used to understand how galaxies form and evolve in dark matter halos, and to make predictions for other statistical properties of the galaxy population, such as the stellar mass functions of galaxies at high z, the star formation and stellar mass assembly histories in dark matter halos. A comparison of our model predictions with those of other empirical models shows that different models can make vastly different predictions, even though all of them are tuned to match the observed stellar mass functions of galaxies.

  11. Heating and Turbulence Driving by Galaxy Motions in Galaxy Clusters

    NASA Astrophysics Data System (ADS)

    Kim, Woong-Tae

    2007-09-01

    Using three-dimensional hydrodynamic simulations, we investigate heating and turbulence driving in an intracluster medium (ICM) by orbital motions of galaxies in a galaxy cluster. We consider Ng member galaxies on isothermal and isotropic orbits through an ICM typical of rich clusters. An introduction of the galaxies immediately produces gravitational wakes, providing perturbations that can potentially grow via resonant interaction with the background gas. When N1/2gM11<~100, where M11 is each galaxy mass in units of 1011 Msolar, the perturbations are in the linear regime and the resonant excitation of gravity waves is efficient in generating kinetic energy in the ICM, resulting in the velocity dispersion σv~2.2N1/2gM11 km s-1. When N1/2gM11>~100, on the other hand, nonlinear fluctuations of the background ICM destroy galaxy wakes and thus render resonant excitation weak or absent. In this case, the kinetic energy saturates at the level corresponding to σv~220 km s-1. The angle-averaged velocity power spectra of turbulence driven in our models have slopes in the range of -3.7 to -4.3. With the nonlinear saturation of resonant excitation, none of the cooling models considered are able to halt the cooling catastrophe, suggesting that the galaxy motions alone are unlikely to solve the cooling flow problem.

  12. The dwarf galaxy population of nearby galaxy clusters

    NASA Astrophysics Data System (ADS)

    Lisker, Thorsten; Wittmann, Carolin; Pak, Mina; Janz, Joachim; Bialas, Daniel; Peletier, Reynier; Grebel, Eva; Falcon Barroso, Jesus; Toloba, Elisa; Smakced Collaboration, Focus Collaboration

    2015-01-01

    The Fornax, Virgo, Ursa Major and Perseus galaxy clusters all have very different characteristics, in terms of their density, mass, and large-scale environment. We can regard these clusters as laboratories for studying environmental influence on galaxy evolution, using the sensitive low-mass galaxies as probes for external mechanisms. Here we report on recent and ongoing observational studies of the said clusters with imaging and spectroscopy, as well as on the interpretation of present-day cluster galaxy populations with the aid of cosmological simulations.Multicolor imaging data allow us to identify residual star formation in otherwise red early-type dwarf galaxies, which hold clues to the strength of gas stripping processes. Major-axis spectra and 2D kinematical maps provide insight regarding the amount of rotational support and how much dynamical heating a dwarf galaxy may have experienced. To this end, dedicated N-body simulations that follow the evolution of galaxies since early epochs reveal their path through parameter space, and can be compared to observations in order to understand the time-integrated effect of environmental influence.

  13. A generalized method for measuring weak lensing magnification with weighted number counts

    NASA Astrophysics Data System (ADS)

    Gillis, Bryan R.; Taylor, Andy N.

    2016-03-01

    We present a derivation of a generalized optimally weighted estimator for the weak lensing magnification signal, including a calculation of errors. With this estimator, we present a local method for optimally estimating the local effects of magnification from weak gravitational lensing, using a comparison of number counts in an arbitrary region of space to the expected unmagnified number counts. We show that when equivalent lens and source samples are used, this estimator is simply related to the optimally weighted correlation function estimator used in past work and vice-versa, but this method has the benefits that it can calculate errors with significantly less computational time, that it can handle overlapping lens and source samples, and that it can easily be extended to mass-mapping. We present a proof-of-principle test of this method on data from the Canada-France-Hawaii Telescope Lensing Survey, showing that its calculated magnification signals agree with predictions from model fits to shear data. Finally, we investigate how magnification data can be used to supplement shear data in determining the best-fitting model mass profiles for galaxy dark matter haloes. We find that at redshifts greater than z ˜ 0.6, the inclusion of magnification can often significantly improve the constraints on the components of the mass profile which relate to galaxies' local environments relative to shear alone, and in high-redshift low- and medium-mass bins, it can have a higher signal-to-noise than the shear signal.

  14. Counting white blood cells using morphological granulometries

    NASA Astrophysics Data System (ADS)

    Theera-Umpon, Nipon; Gader, Paul D.

    2000-04-01

    We describe a modification of the mixture proportion estimation algorithm based on the granulometric mixing theorem. The modified algorithm is applied to the problem of counting different types of white blood cells in bone marrow images. In principle, the algorithm can be used to count the proportion of cells in each class without explicitly segmenting and classifying them. The direct application of the original algorithm does not converge well for more than two classes. The modified algorithm uses prior statistics to initially segment the mixed pattern spectrum and then applies the one-primitive estimation algorithm to each initial component. Applying the algorithm to one class at a time results in better convergence. The counts produced by the modified algorithm on six classes of cells--myeloblast, promyelocyte, myelocyte, metamyelocyte, band, and PolyMorphoNuclear--are very close to the human expert's numbers; the deviation of the algorithm counts is similar to the deviation of counts produced by human experts. The important technical contributions are that the modified algorithm uses prior statistics for each shape class in place or prior knowledge of the total number of objects in an image, and it allows for more than one primitive from each class.

  15. Stability of prepared iodine counting standards

    SciTech Connect

    McLain, M.E.; Yoon, S.C. )

    1987-05-01

    This paper reports that the uses for iodine-125 in the medical sciences are increasing. I-125 is often used to label organic molecules in the performance of radioimmunoassay (RIA) procedures, and it has recently been used in the form of 800-mCi sealed sources employed by bone mineral (density) analyzers in the diagnosis of osteoporosis. These applications of the 59.9-day half-life I-125 incur the need to perform contamination surveys. In the case of the use of I-125 labeled compounds, laboratory benches and floors must be regularly checked for the presence of contamination by counting smear or wipe samples. Where multimillicurie sealed I-125 sources are employed, leak tests must be performed, again by counting smear or wipe samples. The most sensitive method readily available for the measurement of I-125 on these smear samples is scintillation counting with a thin NaI(Tl) detector. The counting system used must be calibrated for I-125 counting efficiency.

  16. Galaxy and Mass Assembly (GAMA): merging galaxies and their properties

    NASA Astrophysics Data System (ADS)

    De Propris, Roberto; Baldry, Ivan K.; Bland-Hawthorn, Joss; Brough, Sarah; Driver, Simon P.; Hopkins, Andrew M.; Kelvin, Lee; Loveday, Jon; Phillipps, Steve; Robotham, Aaron S. G.

    2014-11-01

    We derive the close pair fractions and volume merger rates for galaxies in the Galaxy and Mass Assembly (GAMA) survey with -23 < Mr < -17 (ΩM = 0.27, ΩΛ = 0.73, H0 = 100 km s-1 Mpc-1) at 0.01 < z < 0.22 (look-back time of <2 Gyr). The merger fraction is approximately 1.5 per cent Gyr-1 at all luminosities (assuming 50 per cent of pairs merge) and the volume merger rate is ≈3.5 × 10-4 Mpc-3 Gyr-1. We examine how the merger rate varies by luminosity and morphology. Dry mergers (between red/spheroidal galaxies) are found to be uncommon and to decrease with decreasing luminosity. Fainter mergers are wet, between blue/discy galaxies. Damp mergers (one of each type) follow the average of dry and wet mergers. In the brighter luminosity bin (-23 < Mr < -20), the merger rate evolution is flat, irrespective of colour or morphology, out to z ˜ 0.2. The makeup of the merging population does not appear to change over this redshift range. Galaxy growth by major mergers appears comparatively unimportant and dry mergers are unlikely to be significant in the buildup of the red sequence over the past 2 Gyr. We compare the colour, morphology, environmental density and degree of activity (BPT class, Baldwin, Phillips & Terlevich) of galaxies in pairs to those of more isolated objects in the same volume. Galaxies in close pairs tend to be both redder and slightly more spheroid dominated than the comparison sample. We suggest that this may be due to `harassment' in multiple previous passes prior to the current close interaction. Galaxy pairs do not appear to prefer significantly denser environments. There is no evidence of an enhancement in the AGN fraction in pairs, compared to other galaxies in the same volume.

  17. Carbon monoxide emission from small galaxies

    NASA Technical Reports Server (NTRS)

    Thronson, Harley A., Jr.; Bally, John

    1987-01-01

    A search was conducted for J = 1 yields 0 CO emission from 22 galaxies, detecting half, as part of a survey to study star formation in small to medium size galaxies. Although substantial variation was found in the star formation efficiencies of the sample galaxies, there is no apparent systematic trend with galaxy size.

  18. Color and magnitude dependence of galaxy clustering

    NASA Astrophysics Data System (ADS)

    Müller, Volker

    2016-10-01

    A quantitative study of the clustering properties of galaxies in the cosmic web as a function of absolute magnitude and colour is presented using the SDSS Data Release 7 galaxy redshift survey. We compare our results with mock galaxy samples obtained with four different semi-analytical models of galaxy formation imposed on the merger trees of the Millenium simulation.

  19. Local Universe Dwarf Galaxies

    NASA Astrophysics Data System (ADS)

    Carignan, Claude

    2015-08-01

    One of the outstanding problems in cosmology is addressing the "small-scale crisis" and understanding structure formation at the smallest scales. Standard Lambda Cold Dark Matter cosmological simulations of Milky Way-size DM halos predict many more DM sub-halos than the number of dwarf galaxies observed. This is the so-called Missing Satellites Problem. The most popular interpretation of the Missing Satellites Problem is that the smallest dark matter halos in the universe are extremely inefficient at forming stars. The virialized extent of the Milky Way's halo should contain ~500 satellites, while only ˜100 satellites and dwarfs are observed in the whole Local Group. Despite the large amount of theoretical work and new optical observations, the discrepancy, even if reduced, still persists between observations and hierarchical models, regardless of the model parameters. It may be possible to find those isolated ultra-faint missing dwarf galaxies via their neutral gas component, which is one of the goals we are pursuing with the SKA precursor KAT-7 in South Africa, and soon with the SKA pathfinder MeerKAT.

  20. Extragalactic distance scale derived from ''sosie'' galaxies. I. Distances of 167 galaxies which are sosies of 14 nearby galaxies

    SciTech Connect

    Bottinelli; Gouguenheim, L.; Paturel, G.; de Vaucouleurs, G.

    1985-11-01

    The method of ''sosie'' galaxies is applied to a large sample of galaxies extracted from the BGP catalog of H I line data and the Second Reference Catalogue of Bright Galaxies. The ''sosies'' of 14 calibrating galaxies (primary calibrators and galaxies in the nearest groups) are defined as those having the same parameters, either (1) morphological type T, axis ratio R, and maximum rotation velocity V/sub M/ or (2) T, R, and luminosity index ..lambda../sub c/.

  1. Numerical simulation of galaxies in the M81 galaxy group.

    NASA Astrophysics Data System (ADS)

    Li, P. S.; Thronson, H. A., Jr.

    The M81 galaxy group is a typical nearby galaxy group which consists of 15 members, including M82 and NGC 3077. Recent observations of the M81 group using the VLA (Yun, Ho, Lo, 1994) show a large scale H I map of the whole system, with M81, M82 and NGC 3077 inter-connected by a large amount of H I gas. In addition, two gas concentrations are observed at the eastern side of M81. The authors simulate the system numerically to reproduce the morphology, the spatial distribution of these 3 galaxies, and the H I gas surrounding the system.

  2. Cosmological Parameter Estimation and Window Function in Counts-in-Cell Analysis

    NASA Astrophysics Data System (ADS)

    Murata, Y.; Matsubara, T.

    2006-11-01

    We estimate the cosmological parameter bounds expected from the counts-in-cells analysis of the galaxy distributions of SDSS samples, which are the Main Galaxies (MGs) and the Luminous Red Galaxies (LRGs). We use the m-weight Epanechnikov kernel as window function with expectation of improving the bounds of parameters. We apply the Fisher Information Matrix Analysis, which can estimate the minimum expected parameter bounds without any data. In this analysis, we derive the covariance matrix that includes the consideration of overlapping of cells. As a result, we found that the signal to noise of the LRG sample is bigger than that of the MG sample because the range of data using is only linear scale. Therefore, the LRG sample is more suitable for parameter estimation. For the LRG sample, about six hundred data points are sufficient to get maximum effect on parameter bounds. Large parameter set results in poor bounds because of degeneracy, the matter density, the baryon fraction, the neutrino density and σ2 8 including the amplitude of the power spectrum, the linear bias and the Kaiser effect seems to be an appropriate set.

  3. H I IN LOCAL GROUP DWARF GALAXIES AND STRIPPING BY THE GALACTIC HALO

    SciTech Connect

    Grcevich, Jana; Putman, Mary E E-mail: mputman@astro.columbia.edu

    2009-05-01

    We examine the H I content and environment of all of the Local Group dwarf galaxies (M {sub tot} < 10{sup 10} M {sub sun}), including the numerous newly discovered satellites of the Milky Way and M31. All of the new dwarfs, with the exception of Leo T, have no detected H I. The majority of dwarf galaxies within {approx}270 kpc of the Milky Way or Andromeda are undetected in H I (<10{sup 4} M {sub sun} for Milky Way dwarfs), while those further than {approx}270 kpc are predominantly detected with masses {approx}10{sup 5} to 10{sup 8} M {sub sun}. Analytical ram-pressure arguments combined with velocities obtained via proper motion studies allow for an estimate of the halo density of the Milky Way at several distances. This halo density is constrained to be greater than 2x 10{sup -4}-3 x 10{sup -4} cm{sup -3} out to distances of at least 70 kpc. This is broadly consistent with theoretical models of the diffuse gas in a Milky Way-like halo and is consistent with this component hosting a large fraction of a galaxy's baryons. Accounting for completeness in the dwarf galaxy count, gasless dwarf galaxies could have provided at most 2.1 x 10{sup 8} M {sub sun} of H I gas to the Milky Way, which suggests that most of our Galaxy's star formation fuel does not come from accreted small satellites in the current era.

  4. Observing Evolution in Star-Forming Galaxies in X-Rays

    NASA Technical Reports Server (NTRS)

    Ptak, Andrew

    2011-01-01

    The Chandra Deep Fields (CDFs) have reached flux limits where normal/starburst galaxies are significant contributors to the X-ray number counts (approximately 40% at F _{0.5-2.0} = 1 x 10(^)-17). Based on these results and current theoretical models of X-ray binary evolution we will discuss expectations for observing galaxy evolution in X-rays in IXO deep surveys. With the high sensitivity of IXO (particularly approximately 5" resolution constant across the WFI FOV and high effective area) IXO surveys should detect large numbers of galaxies which will allow evolution to be studied in multiple redshift bins. High spatial resolution will also drive the need to minimize source confusion below F _{0.5-2.0 keV} = 10^{-17} ergs/s/cm^2. In addition to detecting starburst galaxies individually, stacking will be used to constrain their properties on average, particularly Lyman-break galaxies at z greater than 2. We will also discuss challenges in segregating galaxies from obscured AGN in IXO deep fields and expectations proposed survey X-ray missions.

  5. [A simple method for counting Rickettsia cells].

    PubMed

    Emel'ianov, V V

    1990-01-01

    A simple modification of the method for counting Rickettsiae is described. The Escherichia coli cells (ECC) which served as reference particles were stained in suspension with methylene blue mixed with Rickettsia prowazekii (RP) and quickly sprayed over the glass slide. After fixation the samples were stained according to the technique of Gimenez and examined in the light microscope under oil immersion. Through a grid in the eye-piece it was not so difficult to count red-coloured RP and dark-blue ECC against a background formed by impurities. To calculate RP concentration, the reference particles' concentration was multiplied by the dilution factor of RP suspension by the ratio of RP to ECC enumerated. The statistical approach has shown that the wash of the slides during staining procedure does not change this ratio. Differential staining of Rickettsiae with fuchsin is the main clue of this new method to count them even in the crude preparations of infected yolk sacs. PMID:1693751

  6. Efficient statistical mapping of avian count data

    USGS Publications Warehouse

    Royle, J. Andrew; Wikle, C.K.

    2005-01-01

    We develop a spatial modeling framework for count data that is efficient to implement in high-dimensional prediction problems. We consider spectral parameterizations for the spatially varying mean of a Poisson model. The spectral parameterization of the spatial process is very computationally efficient, enabling effective estimation and prediction in large problems using Markov chain Monte Carlo techniques. We apply this model to creating avian relative abundance maps from North American Breeding Bird Survey (BBS) data. Variation in the ability of observers to count birds is modeled as spatially independent noise, resulting in over-dispersion relative to the Poisson assumption. This approach represents an improvement over existing approaches used for spatial modeling of BBS data which are either inefficient for continental scale modeling and prediction or fail to accommodate important distributional features of count data thus leading to inaccurate accounting of prediction uncertainty.

  7. Vortex Counting and Lagrangian 3-Manifolds

    NASA Astrophysics Data System (ADS)

    Dimofte, Tudor; Gukov, Sergei; Hollands, Lotte

    2011-12-01

    To every 3-manifold M one can associate a two-dimensional {mathcal{N}=(2, 2)} supersymmetric field theory by compactifying five-dimensional {mathcal{N}=2} super-Yang-Mills theory on M. This system naturally appears in the study of half-BPS surface operators in four-dimensional {mathcal{N}=2} gauge theories on one hand, and in the geometric approach to knot homologies, on the other. We study the relation between vortex counting in such two-dimensional {mathcal{N}=(2, 2)} supersymmetric field theories and the refined BPS invariants of the dual geometries. In certain cases, this counting can also be mapped to the computation of degenerate conformal blocks in two-dimensional CFT's. Degenerate limits of vertex operators in CFT receive a simple interpretation via geometric transitions in BPS counting.

  8. Analysis of reticulocyte counts using various methods.

    PubMed

    McKenzie, S B; Gauger, C A

    1991-01-01

    The precision and accuracy of manual reticulocyte counts using the Miller disc reticle, other ruled reticle and no reticle are compared with the reticulocyte results from the automated Hematrak 590 instrument. Two slides of each of 50 patient blood specimens were sent to the hematology laboratories of each of six participating hospitals. In addition to between-method comparison (precision), the manual method results using the three different counting techniques were each compared with the Hematrak results to determine if there were significant differences in reported results (accuracy). Statistical analysis revealed that the Miller disc method was the most precise and accurate manual method as compared with the Hematrak. Methods without a Miller disc reported significantly higher reticulocyte counts. Imprecision was also higher among non-Miller manual methods. By using the Miller disc, the accuracy and precision of manual methods may be increased to that of the automated Hematrak method. PMID:10149411

  9. [A simple method for counting Rickettsia cells].

    PubMed

    Emel'ianov, V V

    1990-01-01

    A simple modification of the method for counting Rickettsiae is described. The Escherichia coli cells (ECC) which served as reference particles were stained in suspension with methylene blue mixed with Rickettsia prowazekii (RP) and quickly sprayed over the glass slide. After fixation the samples were stained according to the technique of Gimenez and examined in the light microscope under oil immersion. Through a grid in the eye-piece it was not so difficult to count red-coloured RP and dark-blue ECC against a background formed by impurities. To calculate RP concentration, the reference particles' concentration was multiplied by the dilution factor of RP suspension by the ratio of RP to ECC enumerated. The statistical approach has shown that the wash of the slides during staining procedure does not change this ratio. Differential staining of Rickettsiae with fuchsin is the main clue of this new method to count them even in the crude preparations of infected yolk sacs.

  10. Dark count rates in the STIS MAMA

    NASA Astrophysics Data System (ADS)

    Cox, Colin

    2013-06-01

    The dark count rates in the STIS MAMA detectors have been monitored. This report covers the period since the Servicing Mission 4 of May 2009. We find both long-term and short-term variations which for the NUV side we express as a function of date and temperature. The NUV dark rate has declined significantly from its surprisingly high initial rate of 0.014 counts/pixel/s that was seen immediately after SM4. By October, 2012 it had dropped to an average value of about 0.002 counts/pixel/sec The behavior and characteristics of the FUV dark rate remain very similar to that seen in 2004, prior to the STIS side-2 failure and subsequent repair.

  11. DISTANT CLUSTER OF GALAXIES [left

    NASA Technical Reports Server (NTRS)

    2002-01-01

    One of the deepest images to date of the universe, taken with NASA's Hubble Space Telescope (HST), reveals thousands of faint galaxies at the detection limit of present day telescopes. Peering across a large volume of the observable cosmos, Hubble resolves thousands of galaxies from five to twelve billion light-years away. The light from these remote objects has taken billions of years to cross the expanding universe, making these distant galaxies fossil evidence' of events that happened when the universe was one-third its present age. A fraction of the galaxies in this image belong to a cluster located nine billion light-years away. Though the field of view (at the cluster's distance) is only two million light-years across, it contains a multitude of fragmentary objects. (By comparison, the two million light-years between our Milky Way galaxy and its nearest large companion galaxy, in the constellation Andromeda, is essentially empty space!) Very few of the cluster's members are recognizable as normal spiral galaxies (like our Milky Way), although some elongated members might be edge-on disks. Among this zoo of odd galaxies are ``tadpole-like'' objects, disturbed and apparently merging systems dubbed 'train-wrecks,' and a multitude of faint, tiny shards and fragments, dwarf galaxies or possibly an unknown population of objects. However, the cluster also contains red galaxies that resemble mature examples of today's elliptical galaxies. Their red color comes from older stars that must have formed shortly after the Big Bang. The image is the full field view of the Wide Field and Planetary Camera-2. The picture was taken in intervals between May 11 and June 15, 1994 and required an 18-hour long exposure, over 32 orbits of HST, to reveal objects down to 29th magnitude. [bottom right] A close up view of the peculiar radio galaxy 3C324 used to locate the cluster. The galaxy is nine billion light-years away as measured by its spectral redshift (z=1.2), and located in the

  12. Revisiting the NVSS number count dipole

    NASA Astrophysics Data System (ADS)

    Tiwari, Prabhakar; Nusser, Adi

    2016-03-01

    We present a realistic modeling of the dipole component of the projected sky distribution of NVSS radio galaxies. The modeling relies on mock catalogs generated within the context of ΛCDM cosmology, in the linear regime of structure formation. After removing the contribution from the solar motion, the mocks show that the remaining observed signal is mostly (70%) due to structures within z lesssim 0.1. The amplitude of the model signal depends on the bias factor b of the NVSS mock galaxies. For sources with flux density, S > 15 mJy, the bias recipe inferred from higher order moments is consistent with the observed dipole signal at 2.12σ. Flux thresholds above 20 mJy yield a disagreement close to the 3σ level. A constant high bias, b = 3 is needed to mitigate the tension to the ~ 2.3σ level.

  13. Modelling nova populations in galaxies

    NASA Astrophysics Data System (ADS)

    Chen, Hai-Liang; Woods, T. E.; Yungelson, L. R.; Gilfanov, M.; Han, Zhanwen

    2016-05-01

    Theoretical modelling of the evolution of classical and recurrent novae plays an important role in studies of binary evolution, nucleosynthesis and accretion physics. However, from a theoretical perspective the observed statistical properties of novae remain poorly understood. In this paper, we have produced model populations of novae using a hybrid binary population synthesis approach for differing star formation histories (SFHs): a starburst case (elliptical-like galaxies), a constant star formation rate case (spiral-like galaxies) and a composite case (in line with the inferred SFH for M31). We found that the nova rate at 10 Gyr in an elliptical-like galaxy is ˜10-20 times smaller than a spiral-like galaxy with the same mass. The majority of novae in elliptical-like galaxies at the present epoch are characterized by low-mass white dwarfs (WDs), long decay times, relatively faint absolute magnitudes and long recurrence periods. In contrast, the majority of novae in spiral-like galaxies at 10 Gyr have massive WDs, short decay times, are relatively bright and have short recurrence periods. The mass-loss time distribution for novae in our M31-like galaxy is in agreement with observational data for Andromeda. However, it is possible that we underestimate the number of bright novae in our model. This may arise in part due to the present uncertainties in the appropriate bolometric correction for novae.

  14. FIR statistics of paired galaxies

    NASA Technical Reports Server (NTRS)

    Sulentic, Jack W.

    1990-01-01

    Much progress has been made in understanding the effects of interaction on galaxies (see reviews in this volume by Heckman and Kennicutt). Evidence for enhanced emission from galaxies in pairs first emerged in the radio (Sulentic 1976) and optical (Larson and Tinsley 1978) domains. Results in the far infrared (FIR) lagged behind until the advent of the Infrared Astronomy Satellite (IRAS). The last five years have seen numerous FIR studies of optical and IR selected samples of interacting galaxies (e.g., Cutri and McAlary 1985; Joseph and Wright 1985; Kennicutt et al. 1987; Haynes and Herter 1988). Despite all of this work, there are still contradictory ideas about the level and, even, the reality of an FIR enhancement in interacting galaxies. Much of the confusion originates in differences between the galaxy samples that were studied (i.e., optical morphology and redshift coverage). Here, the authors report on a study of the FIR detection properties for a large sample of interacting galaxies and a matching control sample. They focus on the distance independent detection fraction (DF) statistics of the sample. The results prove useful in interpreting the previously published work. A clarification of the phenomenology provides valuable clues about the physics of the FIR enhancement in galaxies.

  15. Uncovering Blue Diffuse Dwarf Galaxies

    NASA Astrophysics Data System (ADS)

    James, Bethan; Koposov, Sergey; Stark, Daniel; Belokurov, Vasily; Pettini, Max; Olszewski, Edward W.

    2015-01-01

    Extremely metal-poor galaxies (XMPs) and the star-formation within their chemically pristine environments are fundamental to our understanding of the galaxy formation process at early times. However, traditional emission-line surveys detect only the brightest metal-poor galaxies where star-formation occurs in compact, starbursting environments, and thereby give us only a partial view of the dwarf galaxy population. To avoid such biases, we have developed a new search algorithm based on the morphological, rather then spectral, properties of XMPs and have applied to the Sloan Digital Sky Survey database of images. Using this novel approach, we have discovered ~100 previously undetected, faint blue galaxies, each with isolated HII regions embedded in a diffuse continuum. In this talk I will present the first results from follow-up optical spectroscopy of this sample, which reveals these blue diffuse dwarfs (BDDs) to be young, very metal-poor and actively forming stars despite their intrinsically low luminosities. I will present evidence showing that BDDs appear to bridge the gap between quiescent dwarf irregular (dIrr) galaxies and blue compact galaxies (BCDs) and as such offer an ideal opportunity to assess how star-formation occurs in more `normal' metal-poor systems.

  16. High Count Rate Electron Probe Microanalysis

    PubMed Central

    Geller, Joseph D.; Herrington, Charles

    2002-01-01

    Reducing the measurement uncertainty of quantitative analyses made using electron probe microanalyzers (EPMA) requires a careful study of the individual uncertainties from each definable step of the measurement. Those steps include measuring the incident electron beam current and voltage, knowing the angle between the electron beam and the sample (takeoff angle), collecting the emitted x rays from the sample, comparing the emitted x-ray flux to known standards (to determine the k-ratio) and transformation of the k-ratio to concentration using algorithms which includes, as a minimum, the atomic number, absorption, and fluorescence corrections. This paper discusses the collection and counting of the emitted x rays, which are diffracted into the gas flow or sealed proportional x-ray detectors. The representation of the uncertainty in the number of collected x rays collected reduces as the number of counts increase. The uncertainty of the collected signal is fully described by Poisson statistics. Increasing the number of x rays collected involves either counting longer or at a higher counting rate. Counting longer means the analysis time increases and may become excessive to get to the desired uncertainty. Instrument drift also becomes an issue. Counting at higher rates has its limitations, which are a function of the detector physics and the detecting electronics. Since the beginning of EPMA analysis, analog electronics have been used to amplify and discriminate the x-ray induced ionizations within the proportional counter. This paper will discuss the use of digital electronics for this purpose. These electronics are similar to that used for energy dispersive analysis of x rays with either Si(Li) or Ge(Li) detectors except that the shaping time constants are much smaller. PMID:27446749

  17. Count rate performance of a silicon-strip detector for photon-counting spectral CT

    NASA Astrophysics Data System (ADS)

    Liu, X.; Grönberg, F.; Sjölin, M.; Karlsson, S.; Danielsson, M.

    2016-08-01

    A silicon-strip detector is developed for spectral computed tomography. The detector operates in photon-counting mode and allows pulse-height discrimination with 8 adjustable energy bins. In this work, we evaluate the count-rate performance of the detector in a clinical CT environment. The output counts of the detector are measured for x-ray tube currents up to 500 mA at 120 kV tube voltage, which produces a maximum photon flux of 485 Mphotons/s/mm2 for the unattenuated beam. The corresponding maximum count-rate loss of the detector is around 30% and there are no saturation effects. A near linear relationship between the input and output count rates can be observed up to 90 Mcps/mm2, at which point only 3% of the input counts are lost. This means that the loss in the diagnostically relevant count-rate region is negligible. A semi-nonparalyzable dead-time model is used to describe the count-rate performance of the detector, which shows a good agreement with the measured data. The nonparalyzable dead time τn for 150 evaluated detector elements is estimated to be 20.2±5.2 ns.

  18. Nutsedge Counts Predict Meloidogyne incognita Juvenile Counts in an Integrated Management System.

    PubMed

    Ou, Zhining; Murray, Leigh; Thomas, Stephen H; Schroeder, Jill; Libbin, James

    2008-06-01

    The southern root-knot nematode (Meloidogyne incognita), yellow nutsedge (Cyperus esculentus) and purple nutsedge (Cyperus rotundus) are important pests in crops grown in the southern US. Management of the individual pests rather than the pest complex is often unsuccessful due to mutually beneficial pest interactions. In an integrated pest management scheme using alfalfa to suppress nutsedges and M. incognita, we evaluated quadratic polynomial regression models for prediction of the number of M. incognita J2 in soil samples as a function of yellow and purple nutsedge plant counts, squares of nutsedge counts and the cross-product between nutsedge counts . In May 2005, purple nutsedge plant count was a significant predictor of M. incognita count. In July and September 2005, counts of both nutsedges and the cross-product were significant predictors. In 2006, the second year of the alfalfa rotation, counts of all three species were reduced. As a likely consequence, the predictive relationship between nutsedges and M. incognita was not significant for May and July. In September 2006, purple nutsedge was a significant predictor of M. incognita. These results lead us to conclude that nutsedge plant counts in a field infested with the M. incognita-nutsedge pest complex can be used as a visual predictor of M. incognita J2 populations, unless the numbers of nutsedge plants and M. incognita are all very low. PMID:19259526

  19. Measures of Child Well-Being in Utah, 2002: Counting the Kids Who Count on Us. Utah KIDS COUNT.

    ERIC Educational Resources Information Center

    Haven, Terry, Ed.

    This Kids Count report details statewide trends in the well-being of Utah's children. The statistical portrait is based on 29 indicators of children's well-being in five areas: (1) child health and safety (prenatal care, low birthweight, infant mortality, child injury deaths, injury-related hospital discharges, child abuse, childhood…

  20. Optical planar waveguide for cell counting

    NASA Astrophysics Data System (ADS)

    LeBlanc, John; Mueller, Andrew J.; Prinz, Adrian; Butte, Manish J.

    2012-01-01

    Low cost counting of cells has medical applications in screening, military medicine, disaster medicine, and rural healthcare. In this report, we present a shallow, buried, planar waveguide fabricated by potassium ion exchange in glass that enables low-cost and rapid counting of metal-tagged objects that lie in the evanescent field of the waveguide. Laser light transmitted through the waveguide was attenuated proportionately to the presence of metal-coated microstructures fabricated from photoresist. This technology enables the low-cost enumeration of cells from blood, urine, or other biofluids.

  1. The Assembly of Galaxy Clusters

    SciTech Connect

    Berrier, Joel C.; Stewart, Kyle R.; Bullock, James S.; Purcell, Chris W.; Barton, Elizabeth J.; Wechsler, Risa H.

    2008-05-16

    We study the formation of fifty-three galaxy cluster-size dark matter halos (M = 10{sup 14.0-14.76} M{sub {circle_dot}}) formed within a pair of cosmological {Lambda}CDM N-body simulations, and track the accretion histories of cluster subhalos with masses large enough to host {approx} 0.1L{sub *} galaxies. By associating subhalos with cluster galaxies, we find the majority of galaxies in clusters experience no 'pre-processing' in the group environment prior to their accretion into the cluster. On average, {approx} 70% of cluster galaxies fall into the cluster potential directly from the field, with no luminous companions in their host halos at the time of accretion; and less than {approx} 12% are accreted as members of groups with five or more galaxies. Moreover, we find that cluster galaxies are significantly less likely to have experienced a merger in the recent past ({approx}< 6 Gyr) than a field halo of the same mass. These results suggest that local, cluster processes like ram-pressure stripping, galaxy harassment, or strangulation play the dominant role in explaining the difference between cluster and field populations at a fixed stellar mass; and that pre-evolution or past merging in the group environment is of secondary importance for setting cluster galaxy properties for most clusters. The accretion times for z = 0 cluster members are quite extended, with {approx} 20% incorporated into the cluster halo more than 7 Gyr ago and {approx} 20% within the last 2 Gyr. By comparing the observed morphological fractions in cluster and field populations, we estimate an approximate time-scale for late-type to early-type transformation within the cluster environment to be {approx} 6 Gyr.

  2. The mass of spiral galaxy halos

    NASA Technical Reports Server (NTRS)

    Zaritsky, Dennis

    1992-01-01

    A discussion is presented of previous and current work on the determination of the mass distribution of spiral galaxy halos. The two most common tools utilized to determine the mass of spiral galaxies, i.e., companion galaxies and rotation curves are discussed. The most recent research of companion galaxies, which probes the potential to larger distances and utilizes more accurate dynamic modeling, demonstrates that isolated late-type galaxies do have very large dark-matter halos.

  3. Morphological Galaxy Classification with Shapelets

    NASA Astrophysics Data System (ADS)

    Andrae, René; Melchior, Peter

    2008-12-01

    We present an unsupervised classification algorithm, that identifies natural classes of galaxy morphologies. Working on SDSS G-band imaging data, we encode the morphologies by shapelet decomposition. The algorithm employs a model-based soft clustering analysis to find groupings of similar data points. We demonstrate that the algorithm is able to clearly identify and distinguish groups of elliptical, face-on and edge-on spiral galaxies in a training data set. Based on the soft clustering results, we set up a soft classifier for a data set containing 1602 SDSS galaxies.

  4. Triangulum galaxy viewed by Planck

    NASA Astrophysics Data System (ADS)

    De Paolis, F.; Gurzadyan, V. G.; Nucita, A. A.; Chemin, L.; Qadir, A.; Kashin, A. L.; Khachatryan, H. G.; Sargsyan, S.; Yegorian, G.; Ingrosso, G.; Jetzer, Ph.; Vetrugno, D.

    2016-09-01

    We used Planck data to study the M 33 galaxy and find a substantial temperature asymmetry with respect to its minor axis projected onto the sky plane. This temperature asymmetry correlates well with the HI velocity field at 21 cm, at least within a galactocentric distance of 0.5°, and it is found to extend up to about 3° from the galaxy center. We conclude that the revealed effect, that is, the temperature asymmetry and its extension, implies that we detected the differential rotation of the M 33 galaxy and of its extended baryonic halo.

  5. Dark matter in elliptical galaxies

    NASA Technical Reports Server (NTRS)

    Carollo, C. M.; Zeeuw, P. T. DE; Marel, R. P. Van Der; Danziger, I. J.; Qian, E. E.

    1995-01-01

    We present measurements of the shape of the stellar line-of-sight velocity distribution out to two effective radii along the major axes of the four elliptical galaxies NGC 2434, 2663, 3706, and 5018. The velocity dispersion profiles are flat or decline gently with radius. We compare the data to the predictions of f = f(E, L(sub z)) axisymmetric models with and without dark matter. Strong tangential anisotropy is ruled out at large radii. We conclude from our measurements that massive dark halos must be present in three of the four galaxies, while for the fourth galaxy (NGC 2663) the case is inconclusive.

  6. "Dead quasars" in nearby galaxies?

    PubMed

    Rees, M J

    1990-02-16

    The nuclei of some galaxies undergo violent activity, quasars being the most extreme instances of this phenomenon. Such activity is probably short-lived compared to galactic lifetimes, and was most prevalent when the universe was only about one-fifth of its present age. A massive black hole seems the inevitable end point of such activity, and dead quasars should greatly outnumber active ones. In recent years, studies of stellar motions in the cores of several nearby galaxies indicate the presence of central dark masses which could be black holes. This article discusses how such evidence might be corroborated, and the potential implications for our understanding of active galaxies and black holes.

  7. Asymmetric Galaxies: Nature or Nurture?

    NASA Astrophysics Data System (ADS)

    Wilcots, E. M.

    2010-10-01

    Asymmetry is a common characteristic of many disk galaxies, but we have little understanding of its causes. In this contribution we look at the H I properties of a sample of Magellanic spirals, some of the most lopsided galaxies in the local Universe, and a sample of isolated spirals. In neither case do we see evidence of a link between the presence of a companion and asymmetry; indeed, asymmetry persists even in the absence of a companion or evidence of a recent interaction. These results suggest that once it arises, asymmetry may be a very long-lived characteristic of disk galaxies.

  8. Galaxy and Mass Assembly (GAMA): galaxy pairwise velocity dispersion

    NASA Astrophysics Data System (ADS)

    Loveday, Jon; Christodoulou, Leonidas

    2016-10-01

    We describe preliminary measurements of the pairwise velocity dispersion (PVD) of galaxies in the Galaxy and Mass Assembly (GAMA) survey as a function of projected separation and galaxy luminosity. Due to the faint magnitude limit (r < 19.8) and highly-complete spectroscopic sampling of the GAMA survey, we are able to measure the PVD to smaller scales and for lower-luminosity galaxies than previous SDSS-based work. We see no strong scale-dependence at most luminosities in the quasi-linear regime. We observe an apparent drop in PVD towards very small scales (below ~ 0.1h -1 Mpc), but this could in part be due to a restriction of the streaming model employed. At intermediate scales, the PVD is highest (~ 500 km/s) at intermediate luminosities, dropping at both fainter and brighter luminosities.

  9. Galaxy NGC 1512

    NASA Technical Reports Server (NTRS)

    1999-01-01

    A rainbow of colors is captured in the center of a magnificent barred spiral galaxy, as witnessed by the three cameras of NASA's Hubble Space Telescope.

    The color-composite image of the galaxy NGC 1512 was created from seven images taken with the JPL-designed and built Wide Field and Planetary Camera 2 (WFPC-2), along with the Faint Object Camera and the Near Infrared Camera and Multi-Object Spectrometer. Hubble's unique vantage point high above the atmosphere allows astronomers to see objects over a broad range of wavelengths from the ultraviolet to the infrared and to detect differences in the regions around newly born stars.

    The new image is online at http://oposite.stsci.edu/pubinfo/pr/2001/16 and http://www.jpl.nasa.gov/images/wfpc .

    The image reveals a stunning 2,400 light-year-wide circle of infant star clusters in the center of NGC 1512. Located 30 million light-years away in the southern constellation of Horologium, NGC 1512 is a neighbor of our Milky Way galaxy.

    With the Hubble data, a team of Israeli and American astronomers performed one of the broadest, most detailed studies ever of such star-forming regions. Results will appear in the June issue of the Astronomical Journal. The team includes Dr. Dan Maoz, Tel-Aviv University, Israel and Columbia University, New York, N.Y.; Dr. Aaron J. Barth, Harvard-Smithsonian Center for Astrophysics, Cambridge, Mass.; Dr. Luis C. Ho, The Observatories of the Carnegie Institution of Washington; Dr. Amiel Sternberg, Tel-Aviv University, Israel; and Dr. Alexei V. Filippenko, University of California, Berkeley.

    The Space Telescope Science Institute, Baltimore, Md., manages space operations for the Hubble Space Telescope for NASA's Office of Space Science, Washington, D.C. The Institute is operated by the Association of Universities for Research in Astronomy Inc., for NASA under contract with NASA's Goddard Space Flight Center, Greenbelt, Md. The Hubble Space Telescope is a project of international

  10. Galaxy NGC 3079

    NASA Technical Reports Server (NTRS)

    1999-01-01

    A lumpy bubble of hot gas rises from a cauldron of glowing matter in a distant galaxy, as seen by NASA's Hubble Space Telescope.

    The new images, taken by Hubble's Wide Field and Planetary Camera 2, are online at http://oposite.stsci.edu/pubinfo/pr/2001/28 and http://www.jpl.nasa.gov/images/wfpc. The camera was designed and built by NASA's Jet Propulsion Laboratory, Pasadena, Calif.

    Galaxy NGC 3079, located 50 million light-years from Earth in the constellation Ursa Major, has a huge bubble in the center of its disc, as seen in the image on the left. The smaller photo at right shows a close-up of the bubble. The two white dots are stars.

    Astronomers suspect the bubble is being blown by 'winds,' or high-speed streams of particles, released during a burst of star formation. The bubble's lumpy surface has four columns of gaseous filaments towering above the galaxy's disc. The filaments whirl around in a vortex and are expelled into space. Eventually, this gas will rain down on the disc and may collide with gas clouds, compress them and form a new generation of stars.

    Theoretical models indicate the bubble formed when winds from hot stars mixed with small bubbles of hot gas from supernova explosions. Radio telescope observations indicate those processes are still active. Eventually, the hot stars will die, and the bubble's energy source will fade away.

    The images, taken in 1998, show glowing gas as red and starlight as blue/green. Results appear in the July 1, 2001 issue of the Astrophysical Journal. More information about the Hubble Space Telescope is at http://www.stsci.edu. More information about the Wide Field and Planetary Camera 2 is at http://wfpc2.jpl.nasa.gov.

    The Space Telescope Science Institute, Baltimore, Md., manages space operations for Hubble for NASA's Office of Space Science, Washington, D.C. The institute is operated by the Association of Universities for Research in Astronomy, Inc., for NASA, under contract with the Goddard

  11. Fantastic Four Galaxies with Planet (Artist Concept)

    NASA Technical Reports Server (NTRS)

    2007-01-01

    This artist's concept shows what the night sky might look like from a hypothetical planet around a star tossed out of an ongoing four-way collision between big galaxies (yellow blobs). NASA's Spitzer Space Telescope spotted this 'quadruple merger' of galaxies within a larger cluster of galaxies located nearly 5 billion light-years away.

    Though the galaxies appear intact, gravitational disturbances have caused them to stretch and twist, flinging billions of stars into space -- nearly three times as many stars as are in our Milky Way galaxy. The tossed stars are visible in the large plume emanating from the central, largest galaxy. If any of these stars have planets, their night skies would be filled with the monstrous merger, along with other galaxies in the cluster (smaller, bluish blobs).

    This cosmic smash-up is the largest known merger between galaxies of a similar size. While three of the galaxies are about the size of our Milky Way galaxy, the fourth (center of image) is three times as big. All four of the galaxies, as well as most other galaxies in the huge cluster, are blob-shaped ellipticals instead of spirals like the Milky Way.

    Ultimately, in about one hundred million years or so, the four galaxies E will unite into one. About half of the stars kicked out during the merger will fall back and join the new galaxy, making it one of the biggest galaxies in the universe.

  12. Empirical measurements of massive galaxy and active galaxy evolution

    NASA Astrophysics Data System (ADS)

    Cool, Richard Jacob

    Using new wide-area galaxy redshift surveys, we explore the evolution of the most massive galaxies and the most luminous quasars in the universe over much of cosmic history. Quasars and massive red galaxies both are extremes; the most luminous high redshift quasars likely play a key role in shaping their nearby environment and the universe as a whole. The most massive galaxies represent the end points of galaxy evolution and contain a fossil record of the galaxy evolution process. Using the AGES redshift survey completed with the MMT and the Hectospec multi- object spectrograph as well as new z -band observations of the NOAO Deep Wide- Field Survey Bootes field, we report the discovery of three new quasars at z > 5. We explore new mid-infrared selection in light of these three new quasars and place constraints on the slope of the high-redshift quasar luminosity function. At lower redshift (0.1< z <0.4) we measure the scatter in red galaxy colors around the optical red-sequence using imaging and spectroscopy from the Sloan Digital Sky Survey. With our sample of nearly 20,000 massive early-type galaxies ( L [Special characters omitted.] 2.2 L *), we find that the scatter around the color-magnitude relation is quite small in colors studied. Each of three model star formation histories can reproduce the scatter we measure, none of the models produce color distributions matching those observed. We measure the evolution of the LRG luminosity function in the redshift range 0.1< z <0.9. We find that the LRG population has evolved little beyond the passive fading of its stellar populations since z ~ 0.9. The most massive (L > 3 L *) red galaxies have grown by less than 50% (at 99% confidence) since z = 0.9 in stark contrast to the factor of 2 to 4 growth observed in the L * red galaxy population over the same epoch. Finally, we introduce the PRIsm MUlti-object Survey (PRIMUS), a new redshift survey aimed at collecting ~300,000 galaxy spectra over 10 deg 2 to z ~ 1. We

  13. Secular Evolution in Disk Galaxies

    NASA Astrophysics Data System (ADS)

    Kormendy, John

    2013-10-01

    Self-gravitating systems evolve toward the most tightly bound configuration that is reachable via the evolution processes that are available to them. They do this by spreading -- the inner parts shrink while the outer parts expand -- provided that some physical process efficiently transports energy or angular momentum outward. The reason is that self-gravitating systems have negative specific heats. As a result, the evolution of stars, star clusters, protostellar and protoplanetary disks, black hole accretion disks and galaxy disks are fundamentally similar. How evolution proceeds then depends on the evolution processes that are available to each kind of self-gravitating system. These processes and their consequences for galaxy disks are the subjects of my lectures and of this Canary Islands Winter School. I begin with a review of the formation, growth and death of bars. Then I review the slow (`secular') rearrangement of energy, angular momentum, and mass that results from interactions between stars or gas clouds and collective phenomena such as bars, oval disks, spiral structure and triaxial dark haloes. The `existence-proof' phase of this work is largely over: we have a good heuristic understanding of how nonaxisymmetric structures rearrange disk gas into outer rings, inner rings and stuff dumped onto the centre. The results of simulations correspond closely to the morphology of barred and oval galaxies. Gas that is transported to small radii reaches high densities. Observations confirm that many barred and oval galaxies have dense central concentrations of gas and star formation. The result is to grow, on timescales of a few Gyr, dense central components that are frequently mistaken for classical (elliptical-galaxy-like) bulges but that were grown slowly out of the disk (not made rapidly by major mergers). The resulting picture of secular galaxy evolution accounts for the richness observed in galaxy structure. We can distinguish between classical and pseudo

  14. Statistical association of QSO's with foreground galaxy clusters

    NASA Technical Reports Server (NTRS)

    Rodrigues-Williams, Liliya L.; Hogan, Craig J.

    1994-01-01

    We report a statistically significant overdensity of high redshift quasi-stellar objects (QSO's) in the directions of foreground galaxy clusters. QSO's are taken from the Large Bright QSO Survey (LBQS) between 1.4 less than or equal z less than or equal 2.2 with a limiting magnitude of m(sub B) = 18.5. Foreground clusters are regions within 6 Zwicky radii of small Zwicky clusters at a characteristic redshift of about z approximately = 0.2, covering about 40% of the total area surveyed (304 sq. deg). The overdensity, defined as the ratio of the number density of QSO's in the directions of clusters ('association QSO's) to that in the remainder of the fields ('background QSO's), is equal to 1.7, and formally differs from unity at 4.7 sigma significance. The observed overdensity probably is not due to statistical variation in QSO density, intrinsic QSO-QSO and/or cluster-cluster autocorrelations, or patchy Galactic obscuration. We thus interpret this observation as being due to statistical gravitational lensing of background QSO's by galaxy clusters. However, this amplitude of overdensity behind clusters cannot be accounted for in any cluster lensing model if the background QSO number-magnitude counts are similar to the intrinsic (unlensed) counts, and is implausible in any conventional model of cosmic mass distribution.

  15. Very deep IRAS survey - constraints on the evolution of starburst galaxies

    SciTech Connect

    Hacking, P.; Houck, J.R.; Condon, J.J.

    1987-05-01

    Counts of sources (primarily starburst galaxies) from a deep 60 microns IRAS survey published by Hacking and Houck (1987) are compared with four evolutionary models. The counts below 100 mJy are higher than expected if no evolution has taken place out to a redshift of approximately 0.2. Redshift measurements of the survey sources should be able to distinguish between luminosity-evolution and density-evolution models and detect as little as a 20 percent brightening or increase in density of infrared sources per billion years ago (H/0/ = 100 km/s per Mpc). Starburst galaxies cannot account for the reported 100 microns background without extreme evolution at high redshifts. 21 references.

  16. A very deep IRAS survey - Constraints on the evolution of starburst galaxies

    NASA Astrophysics Data System (ADS)

    Hacking, Perry; Condon, J. J.; Houck, J. R.

    1987-05-01

    Counts of sources (primarily starburst galaxies) from a deep 60 microns IRAS survey published by Hacking and Houck (1987) are compared with four evolutionary models. The counts below 100 mJy are higher than expected if no evolution has taken place out to a redshift of approximately 0.2. Redshift measurements of the survey sources should be able to distinguish between luminosity-evolution and density-evolution models and detect as little as a 20 percent brightening or increase in density of infrared sources per billion years ago (H/0/ = 100 km/s per Mpc). Starburst galaxies cannot account for the reported 100 microns background without extreme evolution at high redshifts.

  17. Sub-mm galaxies as progenitors of compact quiescent galaxies

    NASA Astrophysics Data System (ADS)

    Toft, Sune

    2015-08-01

    Three billion years after the big bang (at redshift z=2), half of the most massive galaxies were already old, quiescent systems with little to no residual star formation and extremely compact with stellar mass densities at least an order of magnitude larger than in low redshift ellipticals, their descendants. Little is known about how they formed, but their evolved, dense stellar populations suggest formation within intense, compact starbursts 1-2 Gyr earlier (at 3 < z < 6). Simulations show that gas-rich major mergers can give rise to such starbursts which produce dense remnants. Sub-millimetre selected galaxies (SMGs) are prime examples of intense, gas-rich, starbursts. With a new, mass-complete spectroscopic sample of compact quiescent galaxies at z=2 and a statistically well-understood sample of SMGs, we show that z = 3 -6 SMGs are consistent with being the progenitors of z = 2 quiescent galaxies, matching their formation redshifts and their distributions of sizes, stellar masses and internal velocities. Assuming an evolutionary connection, their space densities also match if the mean duty cycle of SMG starbursts is 42 (+40/-29) Myr (consistent with independent estimates), indicating that the bulk of stars in these massive galaxies were formed in a major, early surge of star-formation. These results suggests a coherent picture of the formation history of the most massive galaxies in the universe, from their initial burst of violent star-formation through their appearance as high stellardensity galaxy cores and to their ultimate fate as giant ellipticals.If time permits i will show novel, spatially resolved spectroscopic observations of the inner regions (rgalaxies at z>2, allowing for strong new constraints on their formation and evolutionary path

  18. SMA observations on faint submillimeter galaxies with S {sub 850} < 2 mJy: Ultra dusty low-luminosity galaxies at high redshift

    SciTech Connect

    Chen, Chian-Chou; Cowie, Lennox L.; Barger, Amy J.; Williams, Jonathan P.; Wang, Wei-Hao

    2014-07-01

    We obtained Submillimeter Array (SMA) observations of eight faint (intrinsic 850 μm fluxes < 2 mJy) submillimeter galaxies (SMGs) discovered in SCUBA images of the massive lensing cluster fields A370, A2390, and A1689 and detected five. In total, we obtain five SMA detections, all of which have de-lensed fluxes <1 mJy with estimated total infrared luminosities 10{sup 10}-10{sup 12} L {sub ☉}, comparable to luminous infrared galaxies and normal star-forming galaxies. Based on the latest number counts, these galaxies contribute ∼70% of the 850 μm extragalactic background light and represent the dominant star-forming galaxy population in the dusty universe. However, only 40{sub −16}{sup +30}% of our faint SMGs would be detected in deep optical or near-infrared surveys, which suggests many of these sources are at high redshifts (z ≳ 3) or extremely dusty, and they are not included in current star formation history estimates.

  19. Joint Analysis of Galaxy-Galaxy Lensing and Galaxy Clustering: Methodology and Forecasts for DES

    SciTech Connect

    Park, Y.

    2015-07-19

    The joint analysis of galaxy-galaxy lensing and galaxy clustering is a promising method for inferring the growth function of large scale structure. Our analysis will be carried out on data from the Dark Energy Survey (DES), with its measurements of both the distribution of galaxies and the tangential shears of background galaxies induced by these foreground lenses. We develop a practical approach to modeling the assumptions and systematic effects affecting small scale lensing, which provides halo masses, and large scale galaxy clustering. Introducing parameters that characterize the halo occupation distribution (HOD), photometric redshift uncertainties, and shear measurement errors, we study how external priors on different subsets of these parameters affect our growth constraints. Degeneracies within the HOD model, as well as between the HOD and the growth function, are identified as the dominant source of complication, with other systematic effects sub-dominant. The impact of HOD parameters and their degeneracies necessitate the detailed joint modeling of the galaxy sample that we employ. Finally, we conclude that DES data will provide powerful constraints on the evolution of structure growth in the universe, conservatively/optimistically constraining the growth function to 7.9%/4.8% with its first-year data that covered over 1000 square degrees, and to 3.9%/2.3% with its full five-year data that will survey 5000 square degrees, including both statistical and systematic uncertainties.

  20. Population of the Galaxy

    SciTech Connect

    Troitskii, V.

    1981-09-01

    A new theory of the population of the Galaxy, based on the hypothesis of explosive: simultaneous and one-time-origination of life in the universe at a certain moment of its evolutionary development, is discussed in the report. According to the proposed theory, civilizations began to arise around the present moment of the history of the universe. Their possible number is limited even when their lifetime is unlimited. The age and number of simultaneously existing civilizations when their lifetime is unlimited is determined by the duration and dispersion of the time of evolution of life on different planets from the cell level to civilization. The proposed theory explains better than Drake's theory the negative results of the search for evidence of the existence of superpowerful extraterrestrial civilizations and the noncolonization of the earth.

  1. Infrared Star Counts Do Not Indicate Distances to Galactic Molecular Clouds

    NASA Astrophysics Data System (ADS)

    Finn, Susanna C.; Jackson, J. M.

    2008-05-01

    Molecular clouds are important objects for studying Galactic structure. Star formation occurs in molecular clouds and through observations of other galaxies, we know that they are largely confined to spiral arms. Therefore, with precise distance measurements toward molecular clouds in our Galaxy, the spiral structure of the Milky Way can in principle be deduced. However, current distance measurements to molecular clouds are fraught with errors. Kinematic distance measurements rely on the measured radial velocity of a cloud as well as the rotation of the Milky Way, both of which are uncertain. Therefore, it is important to find new methods independent of velocity for finding distances to molecular clouds. One potential method is the use of star counts. Because molecular clouds extinct stars, stars behind the cloud appear dimmer or completely disappear. Accordingly, one would expect to find fewer stars toward a molecular cloud than in a region without clouds. A cloud nearer to the observer would have a smaller overall stellar areal density. Conversely, a more distant cloud would have more stars in front of it. Because of the large extinctions, this method will work best in the infrared. This method was tested using the Galactic Legacy Infrared Mid-Plane Survey Extraordinaire (GLIMPSE). Star count maps were made for all four GLIMPSE bands (3.6, 4.5, 5.8, and 8.0 microns). Results show that a lack of star counts in a field does not correlate with distance to the cloud, contrary to expectation. One reason for this failure is that bright emission from many star-forming clouds artificially lowers the number of detected stars due to the difficulty of extracting point sources from regions of extended bright emission. Another reason is the superposition of multiple clouds along the same line of sight. Funding for this research was provided by NSF grant AST-0507657.

  2. Reading Authentic Texts: What Counts as Cognate?

    ERIC Educational Resources Information Center

    Balling, Laura Winther

    2013-01-01

    Most research on cognates has focused on words presented in isolation that are easily defined as cognate between L1 and L2. In contrast, this study investigates what counts as cognate in authentic texts and how such cognates are read. Participants with L1 Danish read news articles in their highly proficient L2, English, while their eye-movements…

  3. Weighted power counting and perturbative unitarity

    SciTech Connect

    Albrecht, Dylan

    2011-02-15

    We consider the relationship between renormalizability and unitarity at a Lifshitz point in d dimensions. We test tree unitarity for theories containing only scalars and fermions, and for pure gauge theory. In both cases, we find the requirement of weighted power-counting renormalizability is equivalent to that of tree unitarity.

  4. KidsCount in Colorado! 2001.

    ERIC Educational Resources Information Center

    Boeke, Kaye

    This Kids Count report examines statewide and county trends in the well-being of Colorado's children. Indicators are presented in the general areas of demographics, abuse and neglect, child health, family issues, and teen issues. The statistical portrait is based on 16 indicators of well-being: (1) confirmed incidents of child abuse and neglect;…

  5. KidsCount in Colorado! 1999.

    ERIC Educational Resources Information Center

    Staberg, Christine

    This Kids Count report examines statewide and county trends in the well-being of Colorado's children. The statistical portrait is based on 12 indicators of well-being: (1) infant mortality; (2) low birth weight births; (3) immunizations; (4) child poverty; (5) early prenatal care; (6) child abuse deaths; (7) health insurance; (8) paternity…

  6. Kids Count in Nebraska: 1997 Report.

    ERIC Educational Resources Information Center

    Bentz, Cara Anderson

    This Kids Count report is the fifth to examine statewide trends and county data on the well-being of Nebraska's children. The bulk of this statistical report presents findings on 32 indicators of well-being in 8 areas: (1) juvenile justice, including juvenile arrests, and numbers committed to youth rehabilitation and treatment centers; (2)…

  7. KidsCount in Colorado! 2000.

    ERIC Educational Resources Information Center

    Vasquez, Jenifer

    This Kids Count report examines statewide and county trends in the well-being of Colorado's children. The statistical portrait is based on 24 indicators of well-being: (1) children receiving AFDC (Aid to Families with Dependent children); (2) children receiving TANF; (3) children qualifying for free lunch; (4) children in out-of-home placements;…

  8. Maine KIDS COUNT 2002 Data Book.

    ERIC Educational Resources Information Center

    Maine Children's Alliance, Augusta.

    This KIDS COUNT data book details statewide trends in the well-being of Maine's children. Following a brief overview of the data book and a summary of indicators, state trend data are presented in the areas of: (1) poverty; (2) child and adolescent suicide; (3) public high school dropouts; (4) teen pregnancy; (5) public high school graduates…

  9. Maine Kids Count 1998 Data Book.

    ERIC Educational Resources Information Center

    Maine Children's Alliance, Augusta.

    This Kids Count report details statewide trends in the well-being of Maine's children. The statistical portrait is based on indicators of children's well-being in four areas: (1) physical and mental health; (2) community and family environment; (3) social and economic opportunity; and (4) education and learning. The report's introduction describes…

  10. Kids Count in Nebraska: 1998 Report.

    ERIC Educational Resources Information Center

    Cassatt, Susan

    This Kids Count report is the sixth to examine statewide trends and county data on the well-being of Nebraska's children. The bulk of this statistical report presents findings on 32 indicators of well-being in 8 areas: (1) child abuse and neglect/domestic violence, including abuse fatalities and serious injuries; (2) early childhood care and…

  11. KidsCount in Colorado! 1998.

    ERIC Educational Resources Information Center

    Staberg, Christine

    This Kids Count report examines statewide and county trends in the well-being of Colorado's children. The statistical portrait is based on 12 indicators of well-being: (1) infant mortality; (2) low birth weight births; (3) immunizations; (4) child poverty; (5) early prenatal care; (6) child abuse deaths; (7) health insurance; (8) paternity…

  12. KidsCount in Colorado! 1994.

    ERIC Educational Resources Information Center

    Buck, Beverly R.

    This 1994 Kids Count report focuses on risk-taking behaviors among Colorado adolescents and discusses how prevention and early intervention strategies can impact the lives of the state's children. Statistics and descriptions are given for: (1) alcohol, tobacco, and drug use; (2) teen sexuality, including sexual activity and teen pregnancy and…

  13. Maine Kids Count 2003 Data Book.

    ERIC Educational Resources Information Center

    Jelcich, Susan, Ed.

    This Kids Count data book details statewide trends in the well-being of Maine's children. The statistical portrait is based on indicators in the areas of physical and mental health, including insurance enrollment, adolescent health and safety, and child welfare; social and economic status, including poverty, unemployment, and teen pregnancies; and…

  14. Nevada Kids Count Data Book, 1997.

    ERIC Educational Resources Information Center

    We Can, Inc., Las Vegas, NV.

    This Kids Count data book is the first to examine statewide indicators of the well being of Nevada's children. The statistical portrait is based on 15 indicators of child well being: (1) percent low birth-weight babies; (2) infant mortality rate; (3) percent of children in poverty; (4) percent of children in single-parent families; (5) percent of…

  15. KidsCount in Colorado! 1997.

    ERIC Educational Resources Information Center

    Shulman, Shanna

    This 1997 Kids Count report examines challenges to Colorado children and youth and how prevention and early intervention can enhance their well-being. The report includes a summary of recent research on brain development and the importance of early experience and stimulation in early intervention programs. The levels of state funding for various…

  16. Kids Count in Nebraska: 1999 Report.

    ERIC Educational Resources Information Center

    Johnston, Janet M.

    This Kids Count report is the seventh to examine statewide trends and county data on the well-being of Nebraska's children. The bulk of this statistical report presents findings on indicators of well-being in eight areas: (1) child abuse and neglect/domestic violence (investigated and substantiated cases, who reports, types of abuse, domestic…

  17. Uncertainty in particle counting and sizing procedures.

    PubMed

    Leith, D; First, M W

    1976-02-01

    A method is described for calculating confidence intervals for particle or fiber concentration, and for dust collector penetration. The span of the interval depends upon the value of fiber concentration or collector penetration reported and upon the number of particles or fibres counted.

  18. People Count: Analyzing a Country's Future

    ERIC Educational Resources Information Center

    Kranendonk, Henry A.

    2004-01-01

    Counting can be done using a linear, exponential method or by using a technique incorporating a recursive process which gives a visual analysis of population data. Population estimates are based on assumptions about change brought about by immigration, emigration, deaths and births.

  19. KIDS COUNT in Virginia, 2001 [Data Book].

    ERIC Educational Resources Information Center

    Action Alliance for Virginia's Children and Youth, Richmond.

    This Kids Count data book details statewide trends in the well-being of Virginia's children. The statistical portrait is based on the following four areas of children's well-being: health and safety; education; family; and economy. Key indicators examined are: (1) prenatal care; (2) low birth weight babies; (3) infant mortality; (4) child abuse or…

  20. Quality assurance and high count rate

    SciTech Connect

    Lindstrom, R.M.

    1994-12-31

    A high count rate can distort the expected linear relation between the charge spectrum generated in a semiconductor gamma-ray detector and that recorded in the pulse-height analyzer. The busy time of the analog-to-digital converter (ADC) is accurately compensated for in commercial analyzers by extending the live counting time. As fast successive-approximation ADCs have become more generally used (note that 10{mu}s fixed digitizing time for 8192 channels is equivalent to an 800-MHz Wilkinson ADC), the resolution times of the other components in the counting system have become relatively more important limitations of the throughput of the total system and also more important sources of nonlinearity, which lead to biased measurements. A loss-free counting technique (LFC) has been developed which gives an undistorted spectrum and zero dead time so that decay equations can be solved. Tests of an LFC system have shown that, with systematic calibration, the system can give stable values in practice for a reference spectrum up to at least 100 kHz. To obtain higher quality data with confidence, quality control test are needed.

  1. Chimpanzee counting and rhesus monkey ordinality judgments

    NASA Technical Reports Server (NTRS)

    Rumbaugh, Duane M.; Washburn, David A.; Hopkins, William D.; Savage-Rumbaugh, E. S.

    1991-01-01

    An investigation is conducted to address the questions of whether chimpanzees can count and whether rhesus monkeys can differentiate written numbers. One investigation demonstrates the capacity of a chimpanzee to produce a quantity of responses appropriate to a given Arabic numeral. Rhesus monkeys are shown to have the capability for making fine differentiations between quantities of pellets and Arabic numerals.

  2. Higher Education Counts: Achieving Results. 2006 Report

    ERIC Educational Resources Information Center

    Connecticut Department of Higher Education (NJ1), 2006

    2006-01-01

    "Higher Education Counts" is the annual accountability report on Connecticut's state system of higher education, as required under Connecticut General Statutes Section 10a-6a. The report contains accountability measures developed through the Performance Measures Task Force and approved by the Board of Governors for Higher Education. The measures…

  3. Higher Education Counts: Achieving Results. 2008 Report

    ERIC Educational Resources Information Center

    Connecticut Department of Higher Education (NJ1), 2008

    2008-01-01

    "Higher Education Counts" is the annual accountability report on Connecticut's state system of higher education, as required under Connecticut General Statutes Section 10a-6a. The report contains accountability measures developed through the Performance Measures Task Force and approved by the Board of Governors for Higher Education. The measures…

  4. Higher Education Counts: Achieving Results. 2007 Report

    ERIC Educational Resources Information Center

    Connecticut Department of Higher Education (NJ1), 2007

    2007-01-01

    "Higher Education Counts" is the annual accountability report on Connecticut's state system of higher education, as required under Connecticut General Statutes Section 10a-6a. The report contains accountability measures developed through the Performance Measures Task Force and approved by the Board of Governors for Higher Education. The measures…

  5. Higher Education Counts: Achieving Results. 2009 Report

    ERIC Educational Resources Information Center

    Connecticut Department of Higher Education (NJ1), 2009

    2009-01-01

    "Higher Education Counts" is the annual accountability report on Connecticut's state system of higher education, as required under Connecticut General Statutes Section 10a-6a. The report contains accountability measures developed through the Performance Measures Task Force and approved by the Board of Governors for Higher Education. The measures…

  6. Alabama Kids Count 2002 Data Book.

    ERIC Educational Resources Information Center

    Curtis, Apreill; Bogie, Don

    This Kids Count data book examines statewide trends in well-being of Alabamas children. The statistical portrait is based on 18 indicators in the areas of child health, education, safety, and security: (1) infant mortality rate; (2) low weight births; (3) child health index; (4) births to unmarried teens; (5) first grade retention; (6) school…

  7. Kansas KIDS COUNT Data Book, 2001.

    ERIC Educational Resources Information Center

    Kansas Action for Children, Inc., Topeka.

    This Kids Count Data Book provides state and county trends in the well-being of Kansas' children. The statistical portrait is based on 21 indicators of well-being: (1) births to single teens; (2) children in poverty; (3) children approved for free school meals; (4) childhood deaths; (5) infant mortality; (6) births with early prenatal care; (7)…

  8. KIDS COUNT in Missouri 1999 Data Book.

    ERIC Educational Resources Information Center

    Citizens for Missouri's Children, St. Louis.

    This Kids Count Data Book examines statewide trends in the well-being of Missouri's children. The statistical portrait is based on the following indicators of general areas of children's well being: (1) students enrolled in free/reduced price lunch program; (2) births to mothers without a high school diploma; (3) low birth weight; (4) infant…

  9. Restricted Schur polynomials and finite N counting

    SciTech Connect

    Collins, Storm

    2009-01-15

    Restricted Schur polynomials have been posited as orthonormal operators for the change of basis from N=4 SYM to type IIB string theory. In this paper we briefly expound the relationship between the restricted Schur polynomials and the operators forwarded by Brown, Heslop, and Ramgoolam. We then briefly examine the finite N counting of the restricted Schur polynomials.

  10. Health Advocacy--Counting the Costs

    ERIC Educational Resources Information Center

    Dyall, Lorna; Marama, Maria

    2010-01-01

    Access to, and delivery of, safe and culturally appropriate health services is increasingly important in New Zealand. This paper will focus on counting the costs of health advocacy through the experience of a small non government charitable organisation, the Health Advocates Trust, (HAT) which aimed to provide advocacy services for a wide range of…

  11. KidsCount in Colorado! 2002.

    ERIC Educational Resources Information Center

    Boeke, Kaye

    This Kids Count report examines statewide, countywide, and citywide trends in the well-being of Colorado's children. Following a brief foreword, the report presents state data and city data for 15 major cities in the form of a report card. The report cards relay: demographic data related to number of children by age and race; indicators of child…

  12. Kansas Kids Count Data Book, 1996.

    ERIC Educational Resources Information Center

    Kansas Action for Children, Inc., Topeka.

    This 1996 Kids Count data book presents data on 20 indicators of child well-being in Kansas, grouped into 6 areas: economic well-being, physical health and safety, educational achievement, early childhood care and education, emotional well-being, and social behavior and social control. The data are grouped by county for each indicator, by…

  13. Going Online to Make Learning Count

    ERIC Educational Resources Information Center

    Brigham, Cathy; Klein-Collins, Rebecca

    2011-01-01

    Adult students often come to higher education with college-level learning that they have acquired outside of the classroom--from the workplace, military service, self-study, or hobbies. For decades, many forward-thinking colleges and universities have been offering services to evaluate that learning and award it college credit that counts towards…

  14. KidsCount in Colorado! 1995.

    ERIC Educational Resources Information Center

    Shulman, Shanna

    This 1995 KidsCount in Colorado report examines challenges and offers examples of how prevention and early intervention strategies can make a difference in the lives of Colorado children. The report looks at the state of child well-being in Colorado in terms of health, early care and education, and primary education. Statistics and descriptions…

  15. Georgia Kids Count Factbook, 1998-99.

    ERIC Educational Resources Information Center

    Georgians for Children, Atlanta, GA.

    This Kids Count factbook presents statistical data and examines trends for 10 indicators of children's well-being in Georgia. The indicators are: (1) low birthweight babies; (2) infant mortality; (3) child deaths; (4) teen deaths by accident, homicide, and suicide; (5) juvenile arrests; (6) reading and math scores on the Iowa Test of Basic Skills;…

  16. Spontaneous Non-verbal Counting in Toddlers

    ERIC Educational Resources Information Center

    Sella, Francesco; Berteletti, Ilaria; Lucangeli, Daniela; Zorzi, Marco

    2016-01-01

    A wealth of studies have investigated numerical abilities in infants and in children aged 3 or above, but research on pre-counting toddlers is sparse. Here we devised a novel version of an imitation task that was previously used to assess spontaneous focusing on numerosity (i.e. the predisposition to grasp numerical properties of the environment)…

  17. Maine KIDS COUNT 2000 Data Book.

    ERIC Educational Resources Information Center

    Maine Children's Alliance, Augusta.

    This KIDS COUNT Report details statewide trends in the well-being of Maine's children. The statistical portrait is based on a variety of indicators in the areas of: (1) physical and mental health; (2) social and economic opportunity; (3) education and learning; and (4) child health care access. The report contains a special section on Maine…

  18. Kids Count in Nebraska 1996 Report.

    ERIC Educational Resources Information Center

    Voices for Children in Nebraska, Omaha.

    This Kids Count report examines statewide trends in the well-being of Nebraska's children. The statistical portrait is based on seven general areas of children's well-being: (1) early care and education; (2) physical and behavioral health; (3) child abuse, neglect, and domestic violence; (4) out of home care; (5) education; (6) economic…

  19. Wilmington Kids Count Fact Book, 2001.

    ERIC Educational Resources Information Center

    Delaware Univ., Newark. Kids Count in Delaware.

    This Kids Count fact book provides a statistical portrait of the well-being of children in Wilmington, Delaware, and is designed as a resource for policymakers and citizens to use in shaping local action to improve the status of children and families in Wilmington. In addition to demographic information, 11 featured indicators are used to describe…

  20. Georgia Kids Count Factbook, 2000-2001.

    ERIC Educational Resources Information Center

    Dopkins, Laurie B.; Carter, John; Beavers, Barbara

    This Kids Count factbook examines statewide and county trends in the well-being of Georgia's children. The statistical portrait is based on indicators in five domains: family and community, economic well-being, health, education, and safety and security. The 21 indicators of well-being are: (1) child population; (2) public school enrollment; (3)…

  1. Montana Kids Count 1996 Data Book.

    ERIC Educational Resources Information Center

    Healthy Mothers, Healthy Babies--The Montana Coalition, Helena.

    This 1996 KIDS COUNT data book presents comparative data on child well-being for each county in Montana and for the state as a whole. Data in the county profiles, which comprise the bulk of the report, are grouped into: background facts (demographic, mental health, education, security, and income support information); charts showing changes in…

  2. All Our Children: Massachusetts Kids Count 1994.

    ERIC Educational Resources Information Center

    Diamond, Franna, Ed.

    This Kids Count report examines statewide trends from 1990 to 1994 in the well-being of Massachusetts' children. The statistical portrait is based on indicators of well-being in five areas: (1) economic well-being of children and their families, including child poverty rate, family income, job loss, earnings of male high school dropouts and…

  3. 7 CFR 1221.228 - Counting ballots.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 7 Agriculture 10 2013-01-01 2013-01-01 false Counting ballots. 1221.228 Section 1221.228 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (MARKETING AGREEMENTS AND ORDERS; MISCELLANEOUS COMMODITIES), DEPARTMENT OF AGRICULTURE SORGHUM PROMOTION, RESEARCH,...

  4. 7 CFR 1221.228 - Counting ballots.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 7 Agriculture 10 2014-01-01 2014-01-01 false Counting ballots. 1221.228 Section 1221.228 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (MARKETING AGREEMENTS AND ORDERS; MISCELLANEOUS COMMODITIES), DEPARTMENT OF AGRICULTURE SORGHUM PROMOTION, RESEARCH,...

  5. 7 CFR 1221.228 - Counting ballots.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 7 Agriculture 10 2011-01-01 2011-01-01 false Counting ballots. 1221.228 Section 1221.228 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (MARKETING AGREEMENTS AND ORDERS; MISCELLANEOUS COMMODITIES), DEPARTMENT OF AGRICULTURE SORGHUM PROMOTION, RESEARCH,...

  6. 7 CFR 1221.228 - Counting ballots.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 7 Agriculture 10 2012-01-01 2012-01-01 false Counting ballots. 1221.228 Section 1221.228 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (MARKETING AGREEMENTS AND ORDERS; MISCELLANEOUS COMMODITIES), DEPARTMENT OF AGRICULTURE SORGHUM PROMOTION, RESEARCH,...

  7. WisKids Count Data Book, 2000.

    ERIC Educational Resources Information Center

    Jacobson, Bob; Grigsby, Tamara; Roberts, Brandon; Wehrly, Mark

    This WisKids Count data book examines statewide trends in the well-being of Wisconsin's children, revisiting indicators that have been followed since 1991. The statistical portrait is based on ten general areas: (1) county demographics; (2) county labor market; (3) housing; (4) maternal and child health; (5) early childhood program participation;…

  8. KIDS COUNT in Missouri 2000 Data Book.

    ERIC Educational Resources Information Center

    Citizens for Missouri's Children, St. Louis.

    This KIDS COUNT data book details statewide trends in the well-being of Missouri's children in the areas of economic security, school success, child health, child safety, and adolescent success. The statistical portrait is based on the following indicators: (1) students enrolled in free/reduced price lunch programs; (2) births to mothers without a…

  9. Rhode Island Kids Count Factbook, 2003.

    ERIC Educational Resources Information Center

    Rhode Island KIDS COUNT, Providence.

    This KIDS COUNT databook is the eighth annual profile examining statewide trends in the well-being of Rhode Island's children. The statistical portrait is based on 53 indicators (3 new indicators in this databook) in 5 areas: (1) family and community (including child population, children in single parent families, and racial and ethnic diversity);…

  10. South Carolina Kids Count Report, 1996.

    ERIC Educational Resources Information Center

    South Carolina Kids Count, Columbia.

    This KIDS COUNT report examines trends in the status of South Carolina children on a state-wide and county basis. The statistical portrait is based on 32 indicators of well-being, grouped into 6 categories: (1) family (family characteristics, child neglect/abuse); (2) economic status (poverty, mean family income); (3) health (prenatal care,…

  11. Differential white cell count by centrifugal microfluidics.

    SciTech Connect

    Sommer, Gregory Jon; Tentori, Augusto M.; Schaff, Ulrich Y.

    2010-07-01

    We present a method for counting white blood cells that is uniquely compatible with centrifugation based microfluidics. Blood is deposited on top of one or more layers of density media within a microfluidic disk. Spinning the disk causes the cell populations within whole blood to settle through the media, reaching an equilibrium based on the density of each cell type. Separation and fluorescence measurement of cell types stained with a DNA dye is demonstrated using this technique. The integrated signal from bands of fluorescent microspheres is shown to be proportional to their initial concentration in suspension. Among the current generation of medical diagnostics are devices based on the principle of centrifuging a CD sized disk functionalized with microfluidics. These portable 'lab on a disk' devices are capable of conducting multiple assays directly from a blood sample, embodied by platforms developed by Gyros, Samsung, and Abaxis. [1,2] However, no centrifugal platform to date includes a differential white blood cell count, which is an important metric complimentary to diagnostic assays. Measuring the differential white blood cell count (the relative fraction of granulocytes, lymphocytes, and monocytes) is a standard medical diagnostic technique useful for identifying sepsis, leukemia, AIDS, radiation exposure, and a host of other conditions that affect the immune system. Several methods exist for measuring the relative white blood cell count including flow cytometry, electrical impedance, and visual identification from a stained drop of blood under a microscope. However, none of these methods is easily incorporated into a centrifugal microfluidic diagnostic platform.

  12. An Optical Bit-Counting Algorithm

    NASA Technical Reports Server (NTRS)

    Mack, Marilyn; Lapir, Gennadi M.; Berkovich, Simon

    2000-01-01

    This paper addresses the omnipresent problem of counting bits - an operation discussed since the very early stages of the establishing of computer science. The need for a quick bit-counting method acquires a special significance with the proliferation of search engines on the Internet. It arises in several other computer applications. This is especially true in information retrieval in which an array of binary vectors is used to represent a characteristic function (CF) of a set of qualified documents. The number of "I"s in the CF equals the cardinality of the set. The process of repeated evaluations of this cardinality is a pivotal point in choosing a rational strategy for deciding whether to constrain or broaden the search criteria to ensure selection of the desired items. Another need for bit-counting occurs when trying to determine the differences between given files, (images or text), in terms of the Hamming distance. An Exclusive OR operation applied to a pair of files results in a binary vector array of mismatches that must be counted.

  13. Nevada Kids Count Data Book, 1998.

    ERIC Educational Resources Information Center

    Ford, Paula R.

    This Kids Count report provides information on statewide trends affecting children and families in Nevada. The report is comprised of eight sections: an overview; Nevada's demographic profile; key facts regarding children in the state; Nevada's comparison to the rest of the United States; trends in the state; indicators of child well-being;…

  14. Radionuclide Counting Technique Measures Wind Velocity

    NASA Technical Reports Server (NTRS)

    Singh, J. J.; Khandelwal, G. S.; Mall, G. H.

    1983-01-01

    Proposed technique for measuring wind velocity based on inverse-squarelaw variation of radioactive counting rates. In proposal, radioative source is deposited on bottom of light, hollow sphere and suspended by flexible wire over radiation counter, Anemometer based on this concept is self-contained, portable, yet not too fragile. Used for extended periods of time, even at remote, inhospitable and inaccessible sites.

  15. Rhode Island KIDS COUNT Issue Brief, 1996.

    ERIC Educational Resources Information Center

    Bryant, Elizabeth Burke, Ed.; Walsh, Catherine Boisvert, Ed.

    1996-01-01

    These two Kids Count brief reports discuss issues related to the well-being of Rhode Island children. The first report identifies ways to measure the impact of state and federal welfare reform proposals on children who receive benefits through Aid to Families with Dependent Children (AFDC). Potential measures of success for welfare reform include…

  16. Illinois Kids Count 2001: Envisioning the Future.

    ERIC Educational Resources Information Center

    Baker, Brenda; Familia, Yahaira; Gifford, Amy; Knowlton, Gretchen; Matakis, Brian; Olson, Melissa; Owens, Tracy; Zasadny, Julie

    This Kids Count report examines statewide trends in the well-being of Illinois' children. The statistical portrait is based on indicators in the areas of family, education and child care, arts and recreation, safety, health, and economic security. The indicators are: (1) percent of children living in poverty; (2) number of children enrolled in…

  17. Kids Count in Nebraska: 2001 Report.

    ERIC Educational Resources Information Center

    Johnston, Janet M.

    This Kids Count report examines statewide trends and county data on the well-being of Nebraska's children. Section 1 contains a commentary on promoting quality early childhood care and education services. Section 2, the bulk of this statistical report, presents finding on indicators of well-being in eight areas: (1) child abuse and…

  18. Kids Count in Nebraska: 2000 Report.

    ERIC Educational Resources Information Center

    Johnston, Janet M.

    This Kids Count report examines statewide trends and county data on the well-being of Nebraska's children. Section 1 contains a commentary on juvenile justice in Nebraska. Section 2, the bulk of this statistical report, presents findings on indicators of well-being in eight areas: (1) child abuse and neglect/domestic violence (investigated and…

  19. Multidimensional time-correlated single photon counting

    NASA Astrophysics Data System (ADS)

    Becker, Wolfgang; Bergmann, Axel

    2006-10-01

    Time-correlated single photon counting (TCSPC) is based on the detection of single photons of a periodic light signal, measurement of the detection time of the photons, and the build-up of the photon distribution versus the time in the signal period. TCSPC achieves a near ideal counting efficiency and transit-time-spread-limited time resolution for a given detector. The drawback of traditional TCSPC is the low count rate, long acquisition time, and the fact that the technique is one-dimensional, i.e. limited to the recording of the pulse shape of light signals. We present an advanced TCSPC technique featuring multi-dimensional photon acquisition and a count rate close to the capability of currently available detectors. The technique is able to acquire photon distributions versus wavelength, spatial coordinates, and the time on the ps scale, and to record fast changes in the fluorescence lifetime and fluorescence intensity of a sample. Biomedical applications of advanced TCSPC techniques are time-domain optical tomography, recording of transient phenomena in biological systems, spectrally resolved fluorescence lifetime imaging, FRET experiments in living cells, and the investigation of dye-protein complexes by fluorescence correlation spectroscopy. We demonstrate the potential of the technique for selected applications.

  20. An Introduction to Adults Count Too.

    ERIC Educational Resources Information Center

    Benn, Roseanne

    This paper provides an overview of a book entitled "Adults Count Too: Mathematics for Empowerment". The introduction to the book details why the author spent three years writing about adults learning mathematics, and outlines the shape and structure of the book. A chapter from the book, entitled "A Matrix of Factors," is presented as an example of…