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Sample records for 360nm galaxy counts

  1. Vector perturbations of galaxy number counts

    NASA Astrophysics Data System (ADS)

    Durrer, Ruth; Tansella, Vittorio

    2016-07-01

    We derive the contribution to relativistic galaxy number count fluctuations from vector and tensor perturbations within linear perturbation theory. Our result is consistent with the the relativistic corrections to number counts due to scalar perturbation, where the Bardeen potentials are replaced with line-of-sight projection of vector and tensor quantities. Since vector and tensor perturbations do not lead to density fluctuations the standard density term in the number counts is absent. We apply our results to vector perturbations which are induced from scalar perturbations at second order and give numerical estimates of their contributions to the power spectrum of relativistic galaxy number counts.

  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. 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".

  5. Passive Evolution: Are the Faint Blue Galaxy Counts Produced by a Population of Eternally Young Galaxies?

    NASA Astrophysics Data System (ADS)

    Bouwens, Rychard J.; Silk, Joseph

    1996-11-01

    A constant-age population of blue galaxies, postulated in the model of Gronwall & Koo, seems to provide an attractive explanation of the excess of very blue galaxies in the deep galaxy counts. Such a population may be generated by a set of galaxies with cycling star formation rates or, at the other extreme, be maintained by the continual formation of new galaxies that fade after they reach the age specified in the Gronwall & Koo model. For both of these hypotheses, we have calculated the luminosity functions, including the respective selection criteria, the redshift distributions, and the number counts in the BJ and K bands. We find a substantial excess in the number of galaxies at low redshift (0 < z < 0.05) over that observed in the Canada-France-Hawaii redshift survey (Lilly et al.) and at the faint end of the Las Campanas luminosity function (Lin et al.). Passive or mild evolution fails to account for the deep galaxy counts because of the implications for low-redshift determinations of the I-selected redshift distribution and the r-selected luminosity function in samples where the faded counterparts of the star-forming galaxies would be detectable.

  6. The opacity of spiral disks from counts of distant galaxies.

    NASA Astrophysics Data System (ADS)

    Holwerda, B. W.; Gonzalez, R. A.; Allen, R. J.; van der Kruit, P. C.

    2004-12-01

    The numbers of distant galaxies seen in an HST image of a spiral galaxy is an indication of the average extinction by dust in the disk. This number of distant galaxies has to be calibrated for crowding effects and for this the ``Synthetic Field Method'' (SFM, Gonzalez et al. 1998) was developed. Synthetic fields are the science field with a dimmed Hubble Deep Field added. From the relation between the dimming and the number of synthetic galaxies, the average extinction in the science field can be derived. 32 HST/WFPC2 fields were analysed and from the numbers of distant galaxies an average radial extinction profile for spiral disks was constructed, for the whole sample, arm and disk regions and different Hubble types. When the average radial extinction profile is compared to the HI surface density profile, an estimate of the average gas-to-dust ratio as a function of radius can be obtained. The effects of the phase of the hydrogen and metallicity gradient in disks are discussed. The average radial extinction profile is compared to the light distribution of spiral disks. The relation between typical radii of light and dust and the relation between surface brightness and extinction is also explored. Combining the detailed images of dust emission from the Spitzer space telescope with the extinction measurements from counts in HST images could offer insight into the relative prominence of cold dust and possibly the dust geometry in the disk. Future work on dust extinction using the wealth of new imaging in the HST archive is briefly discussed. This research was supported by funding from STSCI, the Director's Discretionary Research Fund and the Kapteyn Institute.

  7. GALAXY COUNTS ON THE COSMIC MICROWAVE BACKGROUND COLD SPOT

    SciTech Connect

    Granett, Benjamin R.; Szapudi, Istvan; Neyrinck, Mark C.

    2010-05-01

    The cold spot on the cosmic microwave background (CMB) could arise due to a supervoid at low redshift through the integrated Sachs-Wolfe effect. We imaged the region with MegaCam on the Canada-France-Hawaii Telescope and present galaxy counts in photometric redshift bins. We rule out the existence of a 100 Mpc radius spherical supervoid with underdensity {delta} = -0.3 at 0.5 < z < 0.9 at high significance. The data are consistent with an underdensity at low redshift, but the fluctuations are within the range of cosmic variance and the low-density areas are not contiguous on the sky. Thus, we find no strong evidence for a supervoid. We cannot resolve voids smaller than a 50 Mpc radius; however, these can only make a minor contribution to the CMB temperature decrement.

  8. The Galaxy Counts-in-cells Distribution from the Sloan Digital Sky Survey

    NASA Astrophysics Data System (ADS)

    Yang, Abel; Saslaw, William C.

    2011-03-01

    We determine the galaxy counts-in-cells distribution from the Sloan Digital Sky Survey (SDSS) for three-dimensional spherical cells in redshift space as well as for two-dimensional projected cells. We find that cosmic variance in the SDSS causes the counts-in-cells distributions in different quadrants to differ from each other by up to 20%. We also find that within this cosmic variance, the overall galaxy counts-in-cells distribution agrees with both the gravitational quasi-equilibrium distribution and the negative binomial distribution. We also find that brighter galaxies are more strongly clustered than if they were randomly selected from a larger complete sample that includes galaxies of all luminosities. The results suggest that bright galaxies could be in dark matter halos separated by less than ~10 h -1 Mpc.

  9. 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.

  10. 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.

  11. Measuring the Cosmic Equation of State with Counts of Galaxies.

    PubMed

    Newman; Davis

    2000-05-01

    The classical dN/dz test allows one to determine fundamental cosmological parameters from the evolution of the cosmic volume element. This test is applied by measuring the redshift distribution of a tracer whose evolution in number density is known. In the past, ordinary galaxies have been used for this; however, in the absence of a complete theory of galaxy formation, that method is fraught with difficulties. In this Letter, we propose studying instead the evolution of the apparent numbers of dark matter halos as a function of their circular velocity, observable via the line widths or rotation speeds of visible galaxies. Upcoming redshift surveys will allow the line width distribution of galaxies to be determined at both z approximately 1 and the present day. In the course of studying this test, we have devised a rapid, improved semianalytic method for calculating the circular velocity distribution of dark halos based on the analytic mass function of Sheth, Mo, & Tormen and the formation time distribution of Lacey & Cole. We find that if selection effects are well controlled and minimal external constraints are applied, the planned DEEP Redshift Survey could allow us to measure the cosmic equation-of-state parameter w to +/-10% (as little as 3% if Omegam has been well determined from other observations). This type of test also has the potential to provide a constraint on any evolution of w, such as that predicted by "tracker" models. PMID:10790059

  12. A Bridge from Optical to Infrared Galaxies: Explaining Local Properties, Predicting Galaxy Counts and the Cosmic Background Radiation

    NASA Astrophysics Data System (ADS)

    Totani, T.; Takeuchi, T. T.

    2001-12-01

    A new model of infrared galaxy counts and the cosmic background radiation (CBR) is developed by extending a model for optical/near-infrared galaxies. Important new characteristics of this model are that mass scale dependence of dust extinction is introduced based on the size-luminosity relation of optical galaxies, and that the big grain dust temperature T dust is calculated based on a physical consideration for energy balance, rather than using the empirical relation between T dust and total infrared luminosity L IR found in local galaxies, which has been employed in most of previous works. Consequently, the local properties of infrared galaxies, i.e., optical/infrared luminosity ratios, L IR-T dust correlation, and infrared luminosity function are outputs predicted by the model, while these have been inputs in a number of previous models. Our model indeed reproduces these local properties reasonably well. Then we make predictions for faint infrared counts (in 15, 60, 90, 170, 450, and 850 μ m) and CBR by this model. We found considerably different results from most of previous works based on the empirical L IR-T dust relation; especially, it is shown that the dust temperature of starbursting primordial elliptical galaxies is expected to be very high (40--80K). This indicates that intense starbursts of forming elliptical galaxies should have occurred at z ~ 2--3, in contrast to the previous results that significant starbursts beyond z ~ 1 tend to overproduce the far-infrared (FIR) CBR detected by COBE/FIRAS. On the other hand, our model predicts that the mid-infrared (MIR) flux from warm/nonequilibrium dust is relatively weak in such galaxies making FIR CBR, and this effect reconciles the prima facie conflict between the upper limit on MIR CBR from TeV gamma-ray observations and the COBE\\ detections of FIR CBR. The authors thank the financial support by the Japan Society for Promotion of Science.

  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. A Bridge from Optical to Infrared Galaxies: Explaining Local Properties and Predicting Galaxy Counts and the Cosmic Background Radiation

    NASA Astrophysics Data System (ADS)

    Totani, Tomonori; Takeuchi, Tsutomu T.

    2002-05-01

    We give an explanation for the origin of various properties observed in local infrared galaxies and make predictions for galaxy counts and cosmic background radiation (CBR) using a new model extended from that for optical/near-infrared galaxies. Important new characteristics of this study are that (1) mass scale dependence of dust extinction is introduced based on the size-luminosity relation of optical galaxies and that (2) the large-grain dust temperature Tdust is calculated based on a physical consideration for energy balance rather than by using the empirical relation between Tdust and total infrared luminosity LIR found in local galaxies, which has been employed in most previous works. Consequently, the local properties of infrared galaxies, i.e., optical/infrared luminosity ratios, LIR-Tdust correlation, and infrared luminosity function are outputs predicted by the model, while these have been inputs in a number of previous models. Our model indeed reproduces these local properties reasonably well. Then we make predictions for faint infrared counts (in 15, 60, 90, 170, 450, and 850 μm) and CBR using this model. We found results considerably different from those of most previous works based on the empirical LIR-Tdust relation; especially, it is shown that the dust temperature of starbursting primordial elliptical galaxies is expected to be very high (40-80 K), as often seen in starburst galaxies or ultraluminous infrared galaxies in the local and high-z universe. This indicates that intense starbursts of forming elliptical galaxies should have occurred at z~2-3, in contrast to the previous results that significant starbursts beyond z~1 tend to overproduce the far-infrared (FIR) CBR detected by COBE/FIRAS. On the other hand, our model predicts that the mid-infrared (MIR) flux from warm/nonequilibrium dust is relatively weak in such galaxies making FIR CBR, and this effect reconciles the prima facie conflict between the upper limit on MIR CBR from TeV gamma

  15. FAINT SUBMILLIMETER GALAXY COUNTS AT 450 {mu}m

    SciTech Connect

    Chen, Chian-Chou; Cowie, Lennox L.; Barger, Amy J.; Casey, Caitlin M.; Lee, Nicholas; Sanders, David B.; Williams, Jonathan P.; Wang, Wei-Hao

    2013-01-10

    We present the results of SCUBA-2 observations at 450 {mu}m and 850 {mu}m of the field lensed by the massive cluster A370. With a total survey area >100 arcmin{sup 2} and 1{sigma} sensitivities of 3.92 and 0.82 mJy beam{sup -1} at 450 and 850 {mu}m, respectively, we find a secure sample of 20 sources at 450 {mu}m and 26 sources at 850 {mu}m with a signal-to-noise ratio (S/N) > 4. Using the latest lensing model of A370 and Monte Carlo simulations, we derive the number counts at both wavelengths. The 450 {mu}m number counts probe a factor of four deeper than the counts recently obtained from the Herschel Space Telescope at similar wavelengths, and we estimate that {approx}47%-61% of the 450 {mu}m extragalactic background light resolved into individual sources with 450 {mu}m fluxes greater than 4.5 mJy. The faint 450 {mu}m sources in the 4{sigma} sample have positional accuracies of 3 arcsec, while brighter sources (S/N >6{sigma}) are good to 1.4 arcsec. Using a deep radio map (1{sigma} {approx} 6 {mu}Jy) we find that the percentage of submillimeter sources having secure radio counterparts is 85% for 450 {mu}m sources with intrinsic fluxes >6 mJy and 67% for 850 {mu}m sources with intrinsic fluxes >4 mJy. We also find that 67% of the >4{sigma} 450 {mu}m sources are detected at 850 {mu}m, while the recovery rate at 450 {mu}m of >4{sigma} 850 {mu}m sources is 54%. Combined with the source redshifts estimated using millimetric flux ratios, the recovered rate is consistent with the scenario where both 450 {mu}m and 20 cm emission preferentially select lower redshift dusty sources, while 850 {mu}m emission traces a higher fraction of dusty sources at higher redshifts. We identify potential counterparts in various wavelengths from X-ray to mid-infrared and measure the multiwavelength photometry, which we then use to analyze the characteristics of the sources. We find three X-ray counterparts to our robust submillimeter sample (S/N > 5), giving an active galactic nucleus

  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. Deep galaxy count predictions in the radio, infrared, and X-ray spectral bands

    NASA Technical Reports Server (NTRS)

    Treyer, Marie-Agnes; Silk, Joseph

    1993-01-01

    The existence of a dominant population of strongly evolving starburst sources at moderate redshift is a plausible explanation for the excess number of faint blue galaxies detected in deep sky surveys. Multiwavelength observations at faint magnitudes would allow the existence of such a population to be confirmed. We use observed luminosity correlations and physical properties of known starburst galaxies to predict their contribution to the deep radio, infrared, and X-ray counts, as well as to the diffuse extragalactic background radiation in these various spectral bands.

  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. Hubble Space Telescope Counts of Elliptical Galaxies: Constraints on Cosmological Models?

    NASA Astrophysics Data System (ADS)

    Driver, Simon P.; Windhorst, Rogier A.; Phillipps, Steven; Bristow, Paul D.

    1996-04-01

    The interpretation of galaxy number counts in terms of cosmological models is fraught with difficulty because of uncertainties in the overall galaxy population (mix of morphological types, luminosity functions, etc.) and in the observations (loss of low surface brightness images, image blending, etc.). Many of these can be overcome if we use deep high- resolution imaging of a single class of high surface brightness galaxies, whose evolution is thought to be fairly well understood. This is now possible by selecting elliptical and S0 galaxies using Hubble Space Telescope images from the Medium Deep Survey and other ultradeep Wide Field and Planetary Camera 2 images. In the present paper, we examine whether such data can be used to discriminate between open and closed universes, or between conventional cosmological models and those dominated by a cosmological constant. We find, based on the currently available data, that unless elliptical galaxies undergo very strong merging since z ~ 1 (and/or very large errors exist in the morphological classifications), then flat models dominated by a cosmological constant are ruled out. However, both an Einstein-de Sitter ({OMEGA}_0_ = 1) model with standard passive stellar evolution and an open ({OMEGA}_0_ = 0.05) model with no net evolution (i.e., canceling stellar and dynamical evolution) predict virtually identical elliptical and S0 galaxy counts. Based on these findings and the recent reportings of H_0_ ~ 80 km s^- 1^ Mpc^-1^, we find that the maximum acceptable age of the universe is 13.3 Gyr, and a value of <= 9 Gyr is favored. A flat ({LAMBDA} not equal to 0) universe is therefore not a viable solution to the H_0_/globular cluster age problem.

  3. 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.

  4. Comparative study of the lethal effects of near-UV light (360 nm) and 8-methoxypsoralen plus near-UV on plasmid DNA

    SciTech Connect

    Paramio, J.M.; Bauluz, C.; de Vidania, R. )

    1991-01-01

    The authors have studied the lethality produced on pBR322 by near-UV radiation and by 8-Methoxypsoralen plus near-UV (PUV treatment). Samples of pBR322 DNA were irradiated with increasing fluences of 360 nm-light either in the absence or presence of 400 molecules of 8-Methoxypsoralen (8-MOP) per plasmid molecule. They have estimated to what extent the global lethality of PUVA treatment is due to the presence of psoralen adducts in DNA or to radiation itself. In order to analyse the involvement of DNA repair mechanisms in the removal of plasmid lesions, several strains of E. coli (differing in their repair capacities) they are used as recipients of the treated plasmids. Results showed that excision and recombination participate in the repair of near-UV-induced plasmid lesions. Repair of PUV-induced lesions showed an even greater requirement of the excision pathway. Besides, a slight increase on plasmid mutation frequencies was observed after near-UV or PUV treatment in wild type and uvrA cells. Estimation of the contribution of 8-MOP to the global lethality of PUV treatment showed that only the excision pathway was involved in removing psoralen adducts from plasmid DNA, suggesting the involvement of the recombinational pathway in the repair of near-UV-derived lesions.

  5. The universe at faint magnitudes. I - Models for the galaxy and the predicted star counts

    NASA Astrophysics Data System (ADS)

    Bahcall, J. N.; Soneira, R. M.

    1980-09-01

    A detailed model is constructed for the disk and spheroid components of the Galaxy from which the distribution of visible stars and mass in the Galaxy is calculated. The application of star counts to the determination of galactic structure parameters is demonstrated. The possibility of detecting a halo component with the aid of star counts is also investigated quantitatively. The stellar luminosity functions and scale heights are determined from observations in the solar neighborhood. The global distribution of matter is assumed, based on studies of other galaxies, to be an exponential disk plus a de Vaucouleurs spheroid. The spheroid luminosity function is found to have the same shape as the disk luminosity function over the range of absolute magnitudes (+4 to + 12) that contributes significantly to the star counts for mV ≤ 30. The density of spheroid stars in the solar neighborhood is 1/800 of the value for the disk. The star counts calculated using the density variation of a de Vaucouleurs spheroid are consistent with the available data; the counts predicted with the aid of a Hubble law are inconsistent with observations at more than the two-sigma level of significance. The variations of the calculated star densities with apparent magnitude, latitude, and longitude agree well with the available star count data for the observationally well studied range of 4 ≲ mV ≲ 22. The calculated (B - V) color distributions are also in good agreement with existing data. The color data also indicate that QSOs comprise only a few percent of the total number of stellar objects to mV = 22 (mB = 22.5). The spheroid component is found to be approximately spherical. The scale lengths of the Galaxy model and computed total luminosity and M/L ratios for the disk and spheroid are in agreement with observations of other Sbc galaxies. Illustrative Fig. and a table of interesting characteristics (such as the mass and luminosity contained within various radii and the escape velocity

  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. Digitized POSS-II: Galaxy Number Counts in Two Colors Over a Multi-Plate Region

    NASA Astrophysics Data System (ADS)

    Weir, N.; Djorgovski, S.; Fayyad, U.

    1993-05-01

    We have developed a software system for the reduction and analysis of the Palomar-STScI Digital Sky Survey (cf. B.A.A.S. 23, p. 1434, and B.A.A.S. 24, pp. 741, 750, and 1139). This system, named SKICAT, uses a number of image processing and machine-learning based modules, and conducts pipeline processing of the plate scans, from raw pixel measurement, object classification, photometric matching of multiple plate images, to high-level catalog database manipulation using an X-windows based GUI. We are now in the process of implementing a variety of tools for the scientific and multivariate statistical analysis of the object catalogs. We will present our initial results on galaxy and star counts in two colors (photographic J and F, calibrated to Gunn g and r bands), for a multi-plate region near the north Galactic pole, covering up to 5 Survey fields ( ~ 125 square degrees), and up to 11 Survey fields ( ~ 275 square degrees) in a single color. The data have been uniformly calibrated using CCD sequences and plate overlaps over the range 16 < r < 20, within which we are over 90% complete. We also performed extensive tests to assure the accuracy of automatic galaxy classifications over this magnitude range. Previous results from the southern APM Survey implied dramatic evolution of galaxies at low redshift. We will present our new galaxy counts as function of magnitudes colors in the context of these measurements and galaxy evolution models. Acknowledgements: The POSS-II is partially funded by grants to Caltech from the Eastman Kodak Co., the National Geographic Society, the Samuel Oschin Foundation, the NSF grants AST 84-08225 and AST 87-19465, and the NASA grants NGL 05002140 and NAGW 1710. NW was supported in part by a NSF graduate fellowship and by IPAC. SD acknowledges a partial support from the NASA contract NAS5-31348, the NSF PYI award AST-9157412, the Caltech President's fund, and JPL. Work at JPL is performed under a contract with the NASA.

  8. Near-Infrared Faint Galaxies in the Subaru Deep Field: Comparing the Theory with Observations for Galaxy Counts, Colors, and Size Distributions to K ~ 24.5

    NASA Astrophysics Data System (ADS)

    Totani, Tomonori; Yoshii, Yuzuru; Maihara, Toshinori; Iwamuro, Fumihide; Motohara, Kentaro

    2001-10-01

    Galaxy counts in the K band, (J-K) colors, and apparent size distributions of faint galaxies in the Subaru Deep Field (SDF) down to K~24.5 were studied in detail. Special attention has been paid to take into account various selection effects, including the cosmological dimming of surface brightness, to avoid any systematic bias that may be the origin of controversy in previously published results. We also tried to be very careful about systematic model uncertainties; we present a comprehensive survey of these systematic uncertainties and dependence on various parameters, and we have shown that the dominant factors to determine galaxy counts in this band are cosmology and number evolution. We found that the pure luminosity evolution (PLE) model is very consistent with all the SDF data down to K~22.5, without any evidence for number or size evolution in a low-density, Λ-dominated flat universe, which is now favored by various cosmological observations. On the other hand, a number evolution of galaxies with η~2, when invoked as the luminosity conserving mergers as φ*~(1+z)η and L*~(1+z)-η for all types of galaxies, is necessary to explain the data in the Einstein-de Sitter universe. If the popular Λ-dominated universe is taken for granted, our result then gives a strong constraint on the number evolution of giant elliptical or early-type galaxies to z~1-2 that must be met by any models in the hierarchically clustering universe, since such galaxies are the dominant population in this magnitude range (K<~22.5). A number evolution with η~1 is already difficult to reconcile with the data in this universe. On the other hand, number evolution of late-type galaxies and/or dwarf galaxies, which has been suggested by previous studies of optical galaxies, is allowed from the data. In the fainter magnitude range of K>~22.5, we found a slight excess of observed counts over the prediction of the PLE model when elliptical galaxies are treated as a single population. We

  9. Near-Infrared Galaxy Counts and Evolution from the Wide-Field ALHAMBRA Survey

    NASA Astrophysics Data System (ADS)

    Cristóbal-Hornillos, D.; Aguerri, J. A. L.; Moles, M.; Perea, J.; Castander, F. J.; Broadhurst, T.; Alfaro, E. J.; Benítez, N.; Cabrera-Caño, J.; Cepa, J.; Cerviño, M.; Fernández-Soto, A.; González Delgado, R. M.; Husillos, C.; Infante, L.; Márquez, I.; Martínez, V. J.; Masegosa, J.; del Olmo, A.; Prada, F.; Quintana, J. M.; Sánchez, S. F.

    2009-05-01

    The ALHAMBRA survey aims to cover 4 deg2 using a system of 20 contiguous, equal width, medium-band filters spanning the range 3500 Å-9700 Å plus the standard JHKs filters. Here we analyze deep near-IR number counts of one of our fields (ALH08) for which we have a relatively large area (0.5 deg2) and faint photometry (J = 22.4, H = 21.3, and K = 20.0 at the 50% of recovery efficiency for point-like sources). We find that the logarithmic gradient of the galaxy counts undergoes a distinct change to a flatter slope in each band: from 0.44 at [17.0, 18.5] to 0.34 at [19.5, 22.0] for the J band; for the H band 0.46 at [15.5, 18.0] to 0.36 at [19.0, 21.0], and in Ks the change is from 0.53 in the range [15.0, 17.0] to 0.33 in the interval [18.0, 20.0]. These observations together with faint optical counts are used to constrain models that include density and luminosity evolution of the local type-dependent luminosity functions. Our models imply a decline in the space density of evolved early-type galaxies with increasing redshift, such that only 30%-50% of the bulk of the present day red ellipticals was already in place at z ~ 1. Based on observations collected at the German-Spanish Astronomical Center, Calar Alto, jointly operated by the Max-Planck-Institut für Astronomie Heidelberg and the Instituto de Astrofísica de Andalucía (CSIC).

  10. Constraining the Luminous Red Galaxy Halo Occupation Distribution Using Counts-In-Cylinders

    NASA Astrophysics Data System (ADS)

    Reid, Beth A.; Spergel, David N.

    2009-06-01

    The low number density of the Sloan Digital Sky Survey (SDSS) luminous red galaxies (LRGs) suggests that LRGs occupying the same dark matter halo can be separated from pairs occupying distinct dark matter halos with high fidelity. We present a new technique, Counts-in-Cylinders (CiC), to constrain the parameters of the satellite contribution to the LRG halo occupation distribution once the parameters of the central galaxy contribution have been fixed. For a fiber-collision-corrected SDSS spectroscopic LRG subsample at 0.16 < z < 0.36, we find that the CiC multiplicity function is fitted by a halo model where the average number of satellites in a halo of mass M is = ((M - M cut)/M 1)α with M cut = 5.0+1.5 -1.3(+2.9 -2.6) × 1013 M sun, M 1 = 4.95+0.37 -0.26(+0.79 -0.53) × 1014 M sun, and α = 1.035+0.10 -0.17(+0.24 -0.31) at the 68% and 95% confidence levels using a WMAP3 cosmology and z = 0.2 halo catalog. Our method tightly constrains the fraction of LRGs that are satellite galaxies, 6.36+0.38 -0.39%, and the combination M cut/1014 M sun + α = 1.53+0.08 -0.09 at the 95% confidence level, though these constraints may be relaxed when cosmological parameters and the central galaxy parameters are allowed to vary simultaneously. We also find that mocks based on a halo catalog produced by a spherical overdensity finder reproduce both the measured CiC multiplicity function and the projected correlation function, while mocks based on a Friends-of-Friends halo catalog has a deficit of close pairs at ~1 h -1 Mpc separations. Because the CiC method relies on higher order statistics of close pairs, it is robust to the choice of halo finder, and yields mock catalogs reproducing Finger-of-God (FOG) features in the observations probed by the CiC group multiplicity function. In a companion paper, we will apply this technique to optimize FOG compression to eliminate the one-halo contribution to the LRG power spectrum.

  11. GALAXYCOUNT: a JAVA calculator of galaxy counts and variances in multiband wide-field surveys to 28 AB mag

    NASA Astrophysics Data System (ADS)

    Ellis, S. C.; Bland-Hawthorn, J.

    2007-05-01

    We provide a consistent framework for estimating galaxy counts and variances in wide-field images for a range of photometric bands. The variances include both Poissonian noise and variations due to large-scale structure. We demonstrate that our statistical theory is consistent with the counts in the deepest multiband surveys available. The statistical estimates depend on several observational parameters (e.g. seeing, signal-to-noise ratio), and include a sophisticated treatment of detection completeness. The JAVA calculator is freely available1 and offers the user the option to adopt our consistent framework or a different scheme. We also provide a summary table of statistical measures in the different bands for a range of different fields of view. Reliable estimation of the background counts has profound consequences in many areas of observational astronomy. We provide two such examples. One is from a recent study of the Sculptor galaxy NGC300 where stellar photometry has been used to demonstrate that the outer disc extends to 10 effective radii, far beyond what was thought possible for a normal low-luminosity spiral. We confirm this finding by a re-analysis of the background counts. Secondly, we determine the luminosity function of the galaxy cluster Abell 2734, both through spectroscopically determined cluster membership, and through statistical subtraction of the background galaxies using the calculator and offset fields. We demonstrate very good agreement, suggesting that expensive spectroscopic follow-up, or off-source observations, may often be bypassed via determination of the galaxy background with GALAXYCOUNT.

  12. 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

  13. Counts and Sizes of Galaxies in the Hubble Deep Field South: Implications for the Next Generation Space Telescope

    NASA Astrophysics Data System (ADS)

    Gardner, Jonathan P.; Satyapal, Shobita

    2000-06-01

    Science objectives for the Next Generation Space Telescope (NGST) include a large component of galaxy surveys, both imaging and spectroscopy. The Hubble Deep Field data sets include the deepest observations ever made in the ultraviolet, optical, and near-infrared, reaching depths comparable to that expected for NGST spectroscopy. We present the source counts, galaxy sizes, and isophotal filling factors of the Hubble Deep Field South (HDF-S) images. The observed integrated galaxy counts reach over 500 galaxies per square arcminute at magnitudes AB < 30. We extend these counts to fainter levels and further into the infrared using galaxy-count models. It was determined from the HDF (North) and other deep Wide Field Planetary Camera 2 imaging that fainter galaxies are smaller. This trend continues to AB=29 in the high-resolution HDF-S Space Telescope Imaging Spectrograph (STIS) image, where galaxies have a typical half-light radius of 0.1". We have run extensive Monte Carlo simulations of the galaxy detection in the HDF-S, and we show that the small measured sizes are not due to selection effects until AB > 29. We compare observed sizes in the optical and near-infrared using the HDF-S Near Infrared Camera and Multi-Object Spectrometer image, showing that after taking into account the different point-spread functions and pixel sizes of the images, galaxies are smaller in the near-infrared than they are in the optical. We analyze the isophotal filling factor of the HDF-S STIS image and show that this image is mostly empty sky even at the limits of galaxy detection, a conclusion we expect to hold true for NGST spectroscopy. At the surface brightness limits expected for NGST imaging, however, about a quarter of the sky is occupied by the outer isophotes of AB < 30 galaxies, requiring deblending to detect the faintest objects. We discuss the implications of these data on several design concepts for the NGST near-infrared spectrography. We compare the effects of resolution

  14. AzTEC/ASTE 1.1 mm Deep Surveys: Number Counts and Clustering of Millimeter-bright Galaxies

    NASA Astrophysics Data System (ADS)

    Hatsukade, B.; Kohno, K.; Aretxaga, I.; Austermann, J. E.; Ezawa, H.; Hughes, D. H.; Ikarashi, S.; Iono, D.; Kawabe, R.; Matsuo, H.; Matsuura, S.; Nakanishi, K.; Oshima, T.; Perera, T.; Scott, K. S.; Shirahata, M.; Takeuchi, T. T.; Tamura, Y.; Tanaka, K.; Tosaki, T.; Wilson, G. W.; Yun, M. S.

    2010-10-01

    We present number counts and clustering properties of millimeter-bright galaxies uncovered by the AzTEC camera mounted on the Atacama Submillimeter Telescope Experiment (ASTE). We surveyed the AKARI Deep Field South (ADF-S), the Subaru/XMM Newton Deep Field (SXDF), and the SSA22 fields with an area of ~0.25 deg2 each with an rms noise level of ~0.4-1.0 mJy. We constructed differential and cumulative number counts, which provide currently the tightest constraints on the faint end. The integration of the best-fit number counts in the ADF-S find that the contribution of 1.1 mm sources with fluxes >=1 mJy to the cosmic infrared background (CIB) at 1.1 mm is 12-16%, suggesting that the large fraction of the CIB originates from faint sources of which the number counts are not yet constrained. We estimate the cosmic star-formation rate density contributed by 1.1 mm sources with >=1 mJy using the best-fit number counts in the ADF-S and find that it is lower by about a factor of 5-10 compared to those derived from UV/optically-selected galaxies at z~2-3. The average mass of dark halos hosting bright 1.1 mm sources was calculated to be 1013-1014 Msolar. Comparison of correlation lengths of 1.1 mm sources with other populations and with a bias evolution model suggests that dark halos hosting bright 1.1 mm sources evolve into systems of clusters at present universe and the 1.1 mm sources residing the dark halos evolve into massive elliptical galaxies located in the center of clusters.

  15. Galaxy formation in Lambda greater than 0 Friedmann models: Consequences for the number counts versus redshift test

    NASA Technical Reports Server (NTRS)

    Martel, Hugo

    1994-01-01

    We study the effect of the cosmological constant Lambda on galaxy formation using a simple spherical top-hat overdensity model. We consider models with Omega(sub 0) = 0.2, lambda(sub 0) = 0, and Omega(sub 0) = 0.2, lambda(sub 0) = 0.8 (where Omega(sub 0) is the density parameter, and lambda(sub 0) identically equal Lambda/3 H(sub 0 exp 2) where H(sub 0) is the Hubble constant). We adjust the initial power spectrum amplitude so that both models reproduce the same large-scale structures. The galaxy formation era in the lambda(sub 0) = 0 model occurs early (z approximately 6) and is very short, whereas in the lambda(sub 0) = 0.8 model the galaxy formation era starts later (z approximately 4), and last much longer, possibly all the way to the present. Consequently, galaxies at low redshift (z less than 1) are significantly more evolved in the lambda(sub 0) = 0 model than in the lambda(sub 0) = 0.8 model. This result implies that previous attempts to determine Lambda using the number counts versus redshift test are probably unreliable.

  16. Chemical and luminosity evolution, and counts of galaxies in a merger model

    NASA Technical Reports Server (NTRS)

    Colin, P.; Schramm, D. N.

    1993-01-01

    A merger model is applied to the chemical and luminosity evolution of galaxies. Two aspects are focused on. The first is the problem of abundance ratios as a function of metallicity. The second is related to the luminosity evolution of galaxies. In relation to the former, we calculate the evolution of several chemical elements exploring a broad space of possible star formation rates, including those derived using phenomenological arguments from a multiple merger galaxy formation scenario. We are able to reproduce the observed plateau in the ratio of the abundances of oxygen to iron versus metallicity as a direct consequence of one of the merging SFR used; we have utilized a standard Type II supernovae nucleosynthesis scenario coupled with a reasonable binary model for Type Ia supernovae and its consequent nucleosynthetic yields. Following the consequent luminosity effects in a straightforward way enables the estimation of the evolution of bolometric luminosity. We have used our recently developed code for photometric evolution of galaxies to make a preliminary computation of the number-magnitude relationship, assuming a standard picture of galaxy evolution, in the B and K bands.

  17. 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.

  18. 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

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. Starburst galaxies

    NASA Technical Reports Server (NTRS)

    Weedman, Daniel W.

    1987-01-01

    The infrared properties of star-forming galaxies, primarily as determined by the Infrared Astronomy Satellite (IRAS), are compared to X-ray, optical, and radio properties. Luminosity functions are reviewed and combined with those derived from optically discovered samples using 487 Markarian galaxies with redshifts and published IRAS 60 micron fluxes, and 1074 such galaxies in the Center for Astrophysics redshift survey. It is found that the majority of infrared galaxies which could be detected are low luminosity sources already known from the optical samples, but non-infrared surveys have found only a very small fraction of the highest luminosity sources. Distributions of infrared to optical fluxes and available spectra indicate that the majority of IRAS-selected galaxies are starburst galaxies. Having a census of starburst galaxies and associated dust allow severl important global calculations. The source counts are predicted as a function of flux limits for both infrared and radio fluxes. These galaxies are found to be important radio sources at faint flux limits. Taking the integrated flux to z = 3 indicates that such galaxies are a significant component of the diffuse X-ray background, and could be the the dominant component depending on the nature of the X-ray spectra and source evolution.

  6. 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

  7. 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.

  8. 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)

  9. RBC count

    MedlinePlus

    ... Drugs that can increase the RBC count include: Gentamicin Methyldopa Lower-than-normal numbers of RBCs may be due to: Anemia Bleeding Bone marrow failure (for example, from radiation, toxins, or tumor) Deficiency of a hormone called erythropoietin (caused by ...

  10. 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…

  11. 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 ...

  12. 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 ...

  13. 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)

  14. MOIRCS Deep Survey. I: DRG Number Counts

    NASA Astrophysics Data System (ADS)

    Kajisawa, Masaru; Konishi, Masahiro; Suzuki, Ryuji; Tokoku, Chihiro; Uchimoto, Yuka; Katsuno; Yoshikawa, Tomohiro; Akiyama, Masayuki; Ichikawa, Takashi; Ouchi, Masami; Omata, Koji; Tanaka, Ichi; Nishimura, Tetsuo; Yamada, Toru

    2006-12-01

    We used very deep near-infrared imaging data taken with the Multi-Object InfraRed Camera and Spectrograph (MOIRCS) on the Subaru Telescope to investigate the number counts of Distant Red Galaxies (DRGs). We observed a 4' × 7' field in the Great Observatories Origins Deep Survey-North (GOODS-N), and our data reached J=24.6 and K=23.2 (5σ, Vega magnitude). The surface density of DRGs selected by J - K > 2.3 is 2.35 ± 0.31 arcmin-2 at K < 22 and 3.54 ± 0.38 arcmin-2 at K < 23, respectively. These values are consistent with those in the GOODS-South and FIRES. Our deep and wide data suggest that the number counts of DRGs turn over at K ˜ 22, and the surface density of the faint DRGs with K > 22 is smaller than that expected from the number counts at the brighter magnitude. The result indicates that while there are many bright galaxies at 2 < z < 4 with the relatively old stellar population and/or heavy dust extinction, the number of faint galaxies with a similar red color is relatively small. Different behavior patterns of the number counts of the DRGs and bluer galaxies with 2 < zphot < 4 at K > 22 suggest that the mass-dependent color distribution, where most of the low-mass galaxies are blue, while more massive galaxies tend to have redder colors, had already been established at that epoch.

  15. 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 ...

  16. Faint Blue Galaxies and the Epoch of Dwarf Galaxy Formation

    NASA Astrophysics Data System (ADS)

    Babul, Arif; Ferguson, Henry C.

    1996-02-01

    Several independent lines of reasoning, both theoretical and observational, suggest that the very faint (B ≳ 24) galaxies seen in deep images of the sky are small low-mass galaxies that experienced a short starburst at redshifts 0.5 ≲ z ≲ 1 and have since faded into low-luminosity, low surface brightness (LSB) objects. We examine this hypothesis in detail in order to determine whether a model incorporating such dwarfs can account for the observed wavelength-dependent number counts, as well as redshift, color, and size distributions. Low-mass galaxies generically arise in large numbers in hierarchical clustering scenarios with realistic initial conditions. Generally, these galaxies are expected to form at high redshifts. Babul & Rees have argued that the formation epoch of these galaxies is, in fact, delayed until z ≲ 1 due to the photoionization of the gas by the metagalactic UV radiation at high redshifts. We combine these two elements, along with simple heuristic assumptions regarding star formation histories and efficiency, to construct our bursting dwarf model. The slope and the normalization of the mass function of the dwarf galaxies are derived from the initial conditions and are not adjusted to fit the data. We further augment the model with a phenomenological prescription for the formation and evolution of the locally observed population of galaxies (E, S0, Sab, Sbc, and Sdm types). We use spectral synthesis and Monte Carlo methods to generate realistic model galaxy catalogs for comparison with observations. We find that for reasonable choices of the star formation histories for the dwarf galaxies, the model results are in very good agreement with the results of the deep galaxy surveys. Such a dwarf-dominated model is also qualitatively supported by recent studies of faint galaxy gravitational lensing and clustering, by galaxy size distributions measured with the Hubble Space Telescope, and by the evidence for very modest evolution in regular galaxy

  17. 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)

  18. Tidally triggered galaxy formation. I - Evolution of the galaxy luminosity function

    NASA Astrophysics Data System (ADS)

    Lacey, Cedric; Silk, Joseph

    1991-11-01

    Motivated by accumulating evidence that large-scale galactic star formation is initiated and sustained by tidal interactions, a phenomenological model is developed for the galaxy luminosity function, commencing from a galaxy mass function that is predicted by a hierarchical model of structure formation such as the cold dark matter dominated cosmology. The epoch of luminous galaxy formation and the galactic star-formation rate are determined by the environment. Gas cooling and star-formation feedback are incorporated; the present epoch luminosity function of bright galaxies and the distribution of galaxy colors are well reproduced. Biasing, via the preferential formation of luminous galaxies in denser regions associated with groups of clusters, is a natural outcome of this tidally triggered star-formation model. A large frequency is inferred of 'failed' galaxies, prematurely stripped by supernova-driven winds, that populate groups and clusters in the form of low surface brightness gas-poor dwarfs, and of 'retarded' galaxies, below the threshold for effective star formation, in the field, detectable as gas-rich, extremely low surface brightness objects. Predictions are presented for the evolution with redshift of the distribution of characteristic star formation timescales, galaxy ages, and colors. Estimates are also made of galaxy number counts, and it is suggested that dwarf galaxies undergoing bursts of star formation at z of about 1 may dominate the counts at the faintest magnitudes.

  19. The faint galaxy contribution to the diffuse extragalactic background light

    NASA Technical Reports Server (NTRS)

    Cole, Shaun; Treyer, Marie-Agnes; Silk, Joseph

    1992-01-01

    Models of the faint galaxy contribution to the diffuse extragalactic background light are presented, which are consistent with current data on faint galaxy number counts and redshifts. The autocorrelation function of surface brightness fluctuations in the extragalactic diffuse light is predicted, and the way in which these predictions depend on the cosmological model and assumptions of biasing is determined. It is confirmed that the recent deep infrared number counts are most compatible with a high density universe (Omega-0 is approximately equal to 1) and that the steep blue counts then require an extra population of rapidly evolving blue galaxies. The faintest presently detectable galaxies produce an interesting contribution to the extragalactic diffuse light, and still fainter galaxies may also produce a significant contribution. These faint galaxies still only produce a small fraction of the total optical diffuse background light, but on scales of a few arcminutes to a few degrees, they produce a substantial fraction of the fluctuations in the diffuse light.

  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. Galaxy masses

    NASA Astrophysics Data System (ADS)

    Courteau, Stéphane; Cappellari, Michele; de Jong, Roelof S.; Dutton, Aaron A.; Emsellem, Eric; Hoekstra, Henk; Koopmans, L. V. E.; Mamon, Gary A.; Maraston, Claudia; Treu, Tommaso; Widrow, Lawrence M.

    2014-01-01

    Galaxy masses play a fundamental role in our understanding of structure formation models. This review addresses the variety and reliability of mass estimators that pertain to stars, gas, and dark matter. The different sections on masses from stellar populations, dynamical masses of gas-rich and gas-poor galaxies, with some attention paid to our Milky Way, and masses from weak and strong lensing methods all provide review material on galaxy masses in a self-consistent manner.

  2. Andromeda Galaxy

    NASA Technical Reports Server (NTRS)

    2003-01-01

    [figure removed for brevity, see original site]

    This image is a Galaxy Evolution Explorer observation of the large galaxy in Andromeda, Messier 31. The Andromeda galaxy is the most massive in the local group of galaxies that includes our Milky Way. Andromeda is the nearest large galaxy to our own. The image is a mosaic of 10 separate Galaxy Evolution Explorer images taken in September, 2003. The color image (with near ultraviolet shown by red and far ultraviolet shown by blue) shows blue regions of young, hot, high mass stars tracing out the spiral arms where star formation is occurring, and the central orange-white 'bulge' of old, cooler stars formed long ago. The star forming arms of Messier 31 are unusual in being quite circular rather than the usual spiral shape. Several companion galaxies can also be seen. These include Messier 32, a dwarf elliptical galaxy directly below the central bulge and just outside the spiral arms, and Messier 110 (M110), which is above and to the right of the center. M110 has an unusual far ultraviolet bright core in an otherwise 'red,' old star halo. Many other regions of star formation can be seen far outside the main body of the galaxy.

  3. 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)

  4. The Makah Counting Workbook.

    ERIC Educational Resources Information Center

    Flinn, Arlington A., Jr.

    The first edition of the counting workbook centers around the numbers from 1 to 100 and focuses on number and set concepts. The workbook introduces the Makah spelling of each number and reinforces the spelling with exercises such as matching words to numbers, writing the words, counting symbols, and circling the correct number. Spaced throughout…

  5. Complexities of Counting.

    ERIC Educational Resources Information Center

    Stake, Bernadine Evans

    This document focuses on one child's skip counting methods. The pupil, a second grade student at Steuben School, in Kankakee, Illinois, was interviewed as she made several attempts at counting twenty-five poker chips on a circular piece of paper. The interview was part of a larger study of "Children's Conceptions of Number and Numeral," funded by…

  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. Sublattice counting and orbifolds

    NASA Astrophysics Data System (ADS)

    Hanany, Amihay; Orlando, Domenico; Reffert, Susanne

    2010-06-01

    Abelian orbifolds of mathbb{C}3 are known to be encoded by hexagonal brane tilings. To date it is not known how to count all such orbifolds. We fill this gap by employing number theoretic techniques from crystallography, and by making use of Polya's Enumeration Theorem. The results turn out to be beautifully encoded in terms of partition functions and Dirichlet series. The same methods apply to counting orbifolds of any toric non-compact Calabi-Yau singularity. As additional examples, we count the orbifolds of the conifold, of the L aba theories, and of mathbb{C}4.

  8. Imprint of inflation on galaxy shape correlations

    NASA Astrophysics Data System (ADS)

    Schmidt, Fabian; Chisari, Nora Elisa; Dvorkin, Cora

    2015-10-01

    We show that intrinsic (not lensing-induced) correlations between galaxy shapes offer a new probe of primordial non-Gaussianity and inflationary physics which is complementary to galaxy number counts. Specifically, intrinsic alignment correlations are sensitive to an anisotropic squeezed limit bispectrum of the primordial perturbations. Such a feature arises in solid inflation, as well as more broadly in the presence of light higher spin fields during inflation (as pointed out recently by Arkani-Hamed and Maldacena). We present a derivation of the all-sky two-point correlations of intrinsic shapes and number counts in the presence of non-Gaussianity with general angular dependence, and show that a quadrupolar (spin-2) anisotropy leads to the analog in galaxy shapes of the well-known scale-dependent bias induced in number counts by isotropic (spin-0) non-Gaussianity. Moreover, in the presence of non-zero anisotropic non-Gaussianity, the quadrupole of galaxy shapes becomes sensitive to far superhorizon modes. These effects come about because long-wavelength modes induce a local anisotropy in the initial power spectrum, with which galaxies will correlate. We forecast that future imaging surveys could provide constraints on the amplitude of anisotropic non-Gaussianity that are comparable to those from the Cosmic Microwave Background (CMB). These are complementary as they probe different physical scales. The constraints, however, depend on the sensitivity of galaxy shapes to the initial conditions which we only roughly estimate from observed tidal alignments.

  9. 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.

  10. 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.

  11. Inventory count strategies.

    PubMed

    Springer, W H

    1996-02-01

    An important principle of accounting is that asset inventory needs to be correctly valued to ensure that the financial statements of the institution are accurate. Errors is recording the value of ending inventory in one fiscal year result in errors to published financial statements for that year as well as the subsequent fiscal year. Therefore, it is important that accurate physical counts be periodically taken. It is equally important that any system being used to generate inventory valuation, reordering or management reports be based on consistently accurate on-hand balances. At the foundation of conducting an accurate physical count of an inventory is a comprehensive understanding of the process coupled with a written plan. This article presents a guideline of the physical count processes involved in a traditional double-count approach. PMID:10165241

  12. Calorie count - Alcoholic beverages

    MedlinePlus

    ... want to watch how much you drink. Cocktails mixed with soda, cream, or ice cream can have especially high calorie counts. If you find you are having trouble cutting back on alcohol , talk with your doctor. Here is a list ...

  13. Blood Count Tests

    MedlinePlus

    Your blood contains red blood cells (RBC), white blood cells (WBC), and platelets. Blood count tests measure the number and types of cells in your blood. This helps doctors check on your overall health. ...

  14. 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 ...

  15. 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.

  16. Andromeda Galaxy

    NASA Astrophysics Data System (ADS)

    Walterbos, R.; Murdin, P.

    2000-11-01

    The Andromeda galaxy is the closest SPIRAL GALAXY to the MILKY WAY, just visible to the naked eye on a dark night as a faint smudge of light in the constellation Andromeda. The earliest records of the Andromeda nebula, as it is still often referred to, date back to AD 964, to the `Book of the Fixed Stars' published by the Persian astronomer AL-SÛFI. The first European to officially note the Andro...

  17. Ring Galaxies

    NASA Astrophysics Data System (ADS)

    Dennefeld, M.; Materne, J.

    1980-09-01

    Among the 338 exotic, intriguing and/or fascinating objects contained in Arp's catalogue of peculiar galaxies, two, Arp 146 and 147, are calling special attention as a presumably separate class of objects displaying closed rings with almost empty interior. It is difficult to find out when, historically speaking, attention was called first to this type of object as a peculiar class, but certainly ga1axies with rings were widely found and recognized in the early sixties, ul}der others by Vorontsov-Velyaminov (1960), Sandage (1961) in the Hubble Atlas or de Vaucouleurs (1964) in the first reference catalogue of ga1axies. The most recent estimates by Arp and Madore (1977) from a search on about 200 Schmidt plates covering 7,000 square degrees give 3.6 per cent of ring galaxies among 2,784 peculiar galaxies found. However, despite the mythological perfection associated with a circle, some ordering is necessary before trying to understand the nature of such objects. This is particularly true because a large fraction of those galaxies with rings are probably normal spiral galaxies of type RS or S(r) as defined by de Vaucouleurs, where the spiral arms are simply "closing the circle". A good example of such "ordinary" galaxy is NGC 3081 in the Hubble Atlas .

  18. 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

  19. 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.

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

    NASA Astrophysics Data System (ADS)

    Gruen, D.; Friedrich, O.; Amara, A.; Bacon, D.; Bonnett, C.; Hartley, W.; Jain, B.; Jarvis, M.; Kacprzak, 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-Lévy, A.; Bernstein, G. M.; Bernstein, R. A.; Bertin, E.; Bridle, S. L.; Brooks, D.; Buckley-Geer, E.; Burke, D. L.; Capozzi, D.; Carnero Rosell, A.; Carrasco Kind, M.; 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.; Miquel, R.; Mohr, J. J.; Nord, B.; Ogando, 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.

    2016-01-01

    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 ∈ [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.

  1. 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.

  2. 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.

  3. 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.

  4. Whose interests count?

    PubMed

    Brudney, Daniel; Lantos, John D

    2014-10-01

    Whose interests should count and how should various interests be balanced at the pediatric patient's bedside? The interests of the child patient clearly count. Recently, however, many authors have argued that the family's interests also count. But how should we think about the interests of others? What does it mean to talk about "the family" in this context? Does it really just mean the interests of each individual family member? Or is the family itself a moral entity that has interests of its own independent of the interests of each of its members? Are such interests important only as they affect the patient's interest or also for their own sake? In this special supplement to Pediatrics, a group of pediatricians, philosophers, and lawyers grapple with these questions. They examine these issues from different angles and reach different conclusions. Jointly, they demonstrate the ethical importance and, above all, the ethical complexity of the family's role at the bedside. PMID:25274878

  5. 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.

  6. 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

  7. 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…

  8. Making Research Count

    ERIC Educational Resources Information Center

    Appleby, Yvon; Kerwin, Marie; McCulloch, Sue

    2008-01-01

    Making research count in the education sector is often difficult to achieve as people, quite properly, question its relevance, purpose and impact. One of the significant barriers to research supporting practice in the lifelong learning sector is that funded research carried out in higher education institutions is frequently privileged above…

  9. 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.

  10. Counting digital filters

    NASA Technical Reports Server (NTRS)

    Zohar, S. (Inventor)

    1973-01-01

    Several embodiments of a counting digital filter of the non-recursive type are disclosed. In each embodiment two registers, at least one of which is a shift register, are included. The shift register received j sub x-bit data input words bit by bit. The kth data word is represented by the integer.

  11. 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…

  12. Galaxy formation

    SciTech Connect

    Silk, J.

    1984-11-01

    Implications of the isotropy of the cosmic microwave background on large and small angular scales for galaxy formation are reviewed. In primeval adiabatic fluctuations, a universe dominated by cold, weakly interacting nonbaryonic matter, e.g., the massive photino is postulated. A possible signature of photino annihilation in our galactic halo involves production of cosmic ray antiprotons. If the density is near its closure value, it is necessary to invoke a biasing mechanism for suppressing galaxy formation throughout most of the universe in order to reconcile the dark matter density with the lower astronomical determinations of the mean cosmological density. A mechanism utilizing the onset of primordial massive star formation to strip gaseous protogalaxies is described. Only the densest, early collapsing systems form luminous galaxies. (ESA)

  13. 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

  14. 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

  15. Evolutionary phenomena in galaxies; Summer School, Puerto de la Cruz, Spain, July 4-15, 1988, Contributed Papers

    NASA Astrophysics Data System (ADS)

    Beckman, John E.; Pagel, Bernard E.

    1989-07-01

    Topics discussed in this symposium are on the Galaxy, the Magellanic Clouds, elliptical galaxies, the structure of spirals and galaxy interactions, and the gas and star formation in galaxies. Papers are presented on the Galactic evolution and the star counts in the Galaxy, the physical parameters of reflection nebulae in the Galaxy, chemical abundances in the LMC and SMC planetary nebulae, and the initial mass functions of Magellanic Cloud star clusters, the morphological properties of radio elliptical galaxies, and the synthetic integrated fluxes and colors for elliptical galaxies. Attention is also given to the magnetic fields in M31, NGC 7331, NGC 2841, NGC 6946, and our Galaxy, two high-velocity encounters of elliptical galaxies, evidence for high-velocity gas in giant H II regions, molecules in external galaxies, a photometric study of the double-ring structure of NGC 4736, and the chemical and dynamical evolution of galactic discs.

  16. 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.

  17. Counting every quantum

    PubMed Central

    Sakitt, B.

    1972-01-01

    1. Human subjects were asked to rate both blanks and very dim flashes of light under conditions of complete dark adaptation at 7° in the periphery. The ratings used were 0, 1, 2, 3, 4, 5, and 6. 2. For one subject (B.S.) the distributions of ratings were approximately Poisson distributions. The data were consistent with each rating being the actual number of effective quantal absorptions plus the number of noise events. This subject was presumably able to count every rod signal (effective absorptions plus noise). 3. For two other subjects, the data were consistent with the ratings being one less (L.F.) and two less (K.D.) than the number of effective absorptions plus noise. They were able to count every rod signal beginning with 2 and 3 respectively. A fourth subject's erratic data could not be fitted. 4. The fraction of quanta incident at the cornea that resulted in a rod signal was estimated to be about 0·03 which is consistent with physical estimates of effective absorption for that retinal region. 5. A simulated forced choice experiment leads to an absolute threshold about 0·40 log units below the normal yes-no absolute threshold. This and other results indicate that subjects can use the sensory information they receive even when only 1, 2 or 3 quanta are effectively absorbed, depending on the individual. Humans may be able to count every action potential or every discrete burst of action potentials in some critical neurone. PMID:5046137

  18. 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.

  19. 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.

  20. 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.

  1. Counting supersymmetric branes

    NASA Astrophysics Data System (ADS)

    Kleinschmidt, Axel

    2011-10-01

    Maximal supergravity solutions are revisited and classified, with particular emphasis on objects of co-dimension at most two. This class of solutions includes branes whose tension scales with xxxx. We present a group theory derivation of the counting of these objects based on the corresponding tensor hierarchies derived from E 11 and discrete T- and U-duality transformations. This provides a rationale for the wrapping rules that were recently discussed for σ ≤ 3 in the literature and extends them. Explicit supergravity solutions that give rise to co-dimension two branes are constructed and analysed.

  2. 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

  3. Submillimeter Galaxies

    NASA Astrophysics Data System (ADS)

    Blain, A. W.

    2009-12-01

    The Universe was a more exciting place at moderate to high redshifts z˜3, after reionization took place, but before the present day galaxy properties were firmly established. From a wide variety of directions, we are gaining insight into the Universe at these epochs. Less gas was sequestered into stars and had been ejected into the interstellar medium as weakly emitting, slowly cooling debris, because a significant amount of star formation and supermassive blackhole growth in active galactic nuclei (AGNs) was still to occur. Furthermore, the processes that shape today’s galaxies were at work, and can be seen in real time with the appropriate tools. The most active regions of galaxies at these redshifts are deeply obscured at ultraviolet and optical wavelengths by an opaque interstellar medium (ISM) that absorbs most of their radiation, and then re-emits at far-infrared (IR) wavelengths. This emission provides us with a very powerful probe of the regions within galaxies where the most intense activity takes place; both their total energy output, and from spectroscopy, about the physics and chemistry of the atomic and molecular gas that fuels, hides and surrounds these regions. This information is unique, but not complete: radio, mid- and near-IR, optical and X-ray observations each provide unique complementary views. Nevertheless, probing the obscured Universe, with the Atacama Large (Sub-)Millimeter Array (ALMA), James Webb Space Telescope (JWST), Herschel Space Observatory, Wide Field Infrared Survey Explorer (WISE), and missions and telescopes that are not yet in construction, like an actively cooled sub-10-m class IR space telescope and a 25-m class ground-based submillimeter/THz telescope (CCAT) will provide a more complete picture of in which neighborhoods, by what means and how quickly the most vigorous bursts of activity take place.

  4. 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.

  5. High background photon counting lidar

    NASA Technical Reports Server (NTRS)

    Lentz, W. J.

    1992-01-01

    Photon counting with lidar returns is usually limited to low light levels, while wide dynamic range is achieved by counting for long times. The broad emission spectrum of inexpensive high-power semiconductor lasers makes receiver filters pass too much background light for traditional photon counting in daylight. Very high speed photon counting is possible, however, at more than 500 MHz which allows the construction of eyesafe lidar operating in the presence of bright clouds. Detector improvements are possible to count to 20 GHz producing a single shot dynamic range of ten decades.

  6. 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).

  7. 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.

  8. 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.

  9. 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.

  10. Galaxy Groups

    NASA Astrophysics Data System (ADS)

    Tully, R. Brent

    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}12}{{M}⊙ } 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}matter}˜ 0.15 in a flat topology, with a 68% probability of being less than 0.44.

  11. 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.

  12. 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

  13. Thousand Papers and Counting

    NASA Astrophysics Data System (ADS)

    2005-04-01

    , adaptive optics instruments for small-field high spatial-resolution imaging, high-resolution spectroscopy and multi-object spectroscopy. The VLT was also designed from the beginning with the use of interferometry as a major goal. The VLT Interferometer (VLTI) combines starlight captured by two or three UTs or ATs, dramatically increasing the spatial resolution and showing fine details of a large variety of celestial objects. The impressive battery of top-ranking instruments, coupled with the enormous light-collecting power of the VLT and what is certainly the best overall efficiency for an observatory of this size, has provided a real research bonanza of outstanding scientific results, some of which have been true breakthroughs. They include the amazing new knowledge about the Black Hole at the Galactic Centre, the first image of an exoplanet, the discovery of the most distant group of galaxies, the detection of spatially resolved emission from an Active Galactic Nucleus, the study of resolved stellar populations in nearby galaxies, etc. Other important discoveries deal with accurate cosmochronological dating by means of Uranium and Thorium spectral lines, high-redshift galaxy rotation curves, micro-quasars, properties of the optical counterparts of gamma-ray bursts, high-redshift supernovae and trans-neptunian objects. These and other results are among the 1,000 scientific papers published in the six years of operation. The large impact of VLT-based results is demonstrated by their citation rates, which are among the best of ground-based observatories. Some refereed papers based on VLT data have a citation mark close to 250 only three or four years after publication. Jason Spyromilio, Director of the La Silla Paranal Observatory, believes this is only the beginning: "With second generation instruments to be installed and the start of operations of the Auxiliary Telescopes, providing the Very Large Telescope Interferometer a further boost, I have no doubt that the VLT will

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

    USGS Publications Warehouse

    Millard, H.T., Jr.

    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.

  16. Large-scale inhomogeneities and galaxy statistics

    NASA Technical Reports Server (NTRS)

    Schaeffer, R.; Silk, J.

    1984-01-01

    The density fluctuations associated with the formation of large-scale cosmic pancake-like and filamentary structures are evaluated using the Zel'dovich approximation for the evolution of nonlinear inhomogeneities in the expanding universe. It is shown that the large-scale nonlinear density fluctuations in the galaxy distribution due to pancakes modify the standard scale-invariant correlation function xi(r) at scales comparable to the coherence length of adiabatic fluctuations. The typical contribution of pancakes and filaments to the J3 integral, and more generally to the moments of galaxy counts in a volume of approximately (15-40 per h Mpc)exp 3, provides a statistical test for the existence of large scale inhomogeneities. An application to several recent three dimensional data sets shows that despite large observational uncertainties over the relevant scales characteristic features may be present that can be attributed to pancakes in most, but not all, of the various galaxy samples.

  17. 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.

  18. 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.

  19. The luminosity function of galaxies in compact groups

    NASA Technical Reports Server (NTRS)

    Ribeiro, A. L. B.; De Carvalho, R. R.; Zepf, S. E.

    1994-01-01

    We use counts of faint galaxies in the regions of compact groups to extend the study of the luminosity function of galaxies in compact groups to absolute magnitudes as faint as M(sub B) = -14.5 + 5 log h. We find a slope of the faint end of the luminosity function of approximately alpha = -0.8, with a formal uncertainty of 0.15. This slope is not significantly different from that found for galaxies in other environments. Our results do not support previous suggestions of a dramatic underabundance of intrinsically faint galaxies in compact groups, which were based on extrapolations from fits at brighter magnitudes. The normal faint-end slope of the luminosity function in compact groups is in agreement with previous evidence that most galaxies in compact groups have not been dramatically affected by recent merging.

  20. 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..

  1. 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…

  2. Preschooler's Counting in Peer Interaction.

    ERIC Educational Resources Information Center

    Curtis, Reagan P.

    For this experiment, part of a larger study on preschoolers' counting competence, 3-, 4-, and 5-year-olds played a counting game with their peers after becoming familiar with the game during structured interviews with an adult. It was expected that the symmetrical nature of peer interaction would allow children to display quantitative knowledge in…

  3. Star counts as an indicator of galactic structure and quasar evolution

    NASA Technical Reports Server (NTRS)

    Bahcall, J. N.; Soneira, R. M.

    1980-01-01

    A detailed model of the stellar content of the Galaxy is described briefly. Illustrative applications of the model are made, using existing data, to indicate how star counts can be used to determine some parameters of galactic structure, to detect a massive (stellar) halo, and to constrain models of quasar evolution.

  4. 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)

  5. 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.

  6. 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.

  7. Uncertainty in measurements by counting

    NASA Astrophysics Data System (ADS)

    Bich, Walter; Pennecchi, Francesca

    2012-02-01

    Counting is at the base of many high-level measurements, such as, for example, frequency measurements. In some instances the measurand itself is a number of events, such as spontaneous decays in activity measurements, or objects, such as colonies of bacteria in microbiology. Countings also play a fundamental role in everyday life. In any case, a counting is a measurement. A measurement result, according to its present definition, as given in the 'International Vocabulary of Metrology—Basic and general concepts and associated terms (VIM)', must include a specification concerning the estimated uncertainty. As concerns measurements by counting, this specification is not easy to encompass in the well-known framework of the 'Guide to the Expression of Uncertainty in Measurement', known as GUM, in which there is no guidance on the topic. Furthermore, the issue of uncertainty in countings has received little or no attention in the literature, so that it is commonly accepted that this category of measurements constitutes an exception in which the concept of uncertainty is not applicable, or, alternatively, that results of measurements by counting have essentially no uncertainty. In this paper we propose a general model for measurements by counting which allows an uncertainty evaluation compliant with the general framework of the GUM.

  8. 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

  9. Mice can count and optimize count-based decisions.

    PubMed

    Çavdaroğlu, Bilgehan; Balcı, Fuat

    2016-06-01

    Previous studies showed that rats and pigeons can count their responses, and the resultant count-based judgments exhibit the scalar property (also known as Weber's Law), a psychophysical property that also characterizes interval-timing behavior. Animals were found to take a nearly normative account of these well-established endogenous uncertainty characteristics in their time-based decision-making. On the other hand, no study has yet tested the implications of scalar property of numerosity representations for reward-rate maximization in count-based decision-making. The current study tested mice on a task that required them to press one lever for a minimum number of times before pressing the second lever to collect the armed reward (fixed consecutive number schedule, FCN). Fewer than necessary number of responses reset the response count without reinforcement, whereas emitting responses at least for the minimum number of times reset the response counter with reinforcement. Each mouse was tested with three different FCN schedules (FCN10, FCN20, FCN40). The number of responses emitted on the first lever before pressing the second lever constituted the main unit of analysis. Our findings for the first time showed that mice count their responses with scalar property. We then defined the reward-rate maximizing numerical decision strategies in this task based on the subject-based estimates of the endogenous counting uncertainty. Our results showed that mice learn to maximize the reward-rate by incorporating the uncertainty in their numerosity judgments into their count-based decisions. Our findings extend the scope of optimal temporal risk-assessment to the domain of count-based decision-making. PMID:26463617

  10. 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.

  11. 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.

  12. 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.

  13. A Galaxy Blazes With Star Formation

    NASA Technical Reports Server (NTRS)

    2001-01-01

    Scientists using NASA's Hubble Space Telescope (HST) 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. One such galaxy, Galaxy NGC 3310, a hotbed of star formation showcased in this HST photograph, is forming clusters of stars at a prodigious rate. The image shows several hundred star clusters, visible as the bright blue diffuse objects tracing 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 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 that one hundred million years. This suggests the starburst 'turned on' more than 100 million years ago.

  14. 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.

  15. 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.

  16. 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 ...

  17. 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.

  18. 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…

  19. 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.

  20. A Bayesian Approach to Constraining Dwarf Galaxy Evolution

    NASA Astrophysics Data System (ADS)

    Lotz, J. M.; Ferguson, H. C.

    2001-12-01

    We use a Bayesian - maximum likelihood analysis of the Hubble Deep Field to constrain the epoch of dwarf galaxy formation. Late formation of dwarf galaxies arises as a natural consequence of proposed solutions to the "over-cooling" problem in hierarchical structure formation. Although dwarf-sized halos are among the first objects to collapse out of a cold dark matter dominated universe, photo-ionization from the inter-galactic UV background and stellar feedback at early epochs may suppress or delay significant star formation in dwarf galaxies until redshifts ~ 1. Such late-forming dwarf galaxies may make up a portion of the population of the faint blue galaxies observed at intermediate redshifts. Previous attempts to understand the nature of the faint blue galaxy population have fit the binned number counts, luminosity functions, color and size distributions and compared the results to a handful of possible scenarios. Our approach sums the likelihood of observing each object in the HDF catalog given a dwarf galaxy formation scenario and computes the total likelihood of the given dwarf formation scenario. The parameters of the input model are then varied, and the model with the maximum total likelihood is determined. This technique does not bin the data in any way, tests a wide range of input model parameters, and allows us to quantify the goodness-of-fit and constraints on dwarf galaxy evolution.

  1. DEMOGRAPHICS OF BULGE TYPES WITHIN 11 Mpc AND IMPLICATIONS FOR GALAXY EVOLUTION

    SciTech Connect

    Fisher, David B.; Drory, Niv

    2011-06-01

    We present an inventory of galaxy bulge types (elliptical galaxy, classical bulge, pseudobulge, and bulgeless galaxy) in a volume-limited sample within the local 11 Mpc sphere using Spitzer 3.6 {mu}m and Hubble Space Telescope data. We find that whether counting by number, star formation rate, or stellar mass, the dominant galaxy type in the local universe has pure disk characteristics (either hosting a pseudobulge or being bulgeless). Galaxies that contain either a pseudobulge or no bulge combine to account for over 80% of the number of galaxies above a stellar mass of 10{sup 9} M{sub sun}. Classical bulges and elliptical galaxies account for {approx}1/4, and disks for {approx}3/4 of the stellar mass in the local 11 Mpc. About 2/3 of all star formation in the local volume takes place in galaxies with pseudobulges. Looking at the fraction of galaxies with different bulge types as a function of stellar mass, we find that the frequency of classical bulges strongly increases with stellar mass, and comes to dominate above 10{sup 10.5} M{sub sun}. Galaxies with pseudobulges dominate at 10{sup 9.5}-10{sup 10.5} M{sub sun}. Yet lower-mass galaxies are most likely to be bulgeless. If pseudobulges are not a product of mergers, then the frequency of pseudobulges in the local universe poses a challenge for galaxy evolution models.

  2. 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.

  3. Questions on Pure Luminosity Evolution for Elliptical Galaxies

    NASA Astrophysics Data System (ADS)

    He, Ping; Zhang, Yuan-Zhong

    1999-02-01

    The explanation for the existence of an excess population of faint blue galaxies (FBGs) has been a mystery for nearly two decades and remains one of the grand astronomical issues to date. Existing models cannot explain all of the observational data, such as galaxy number counts in the optical and infrared passbands and the redshift distributions of galaxies. Here, by modeling the morphological number counts derived from the Hubble Space Telescope, as well as the number counts in optical and infrared passbands and the redshift and color distributions of galaxies obtained from ground-based observations, we show that the ``FBG problem'' cannot be resolved if elliptical galaxies are assumed to have formed in an instantaneous burst of star formation at high redshift with no subsequent star formation events, which is the conventional scenario for formation and evolution of ellipticals. There exist great discrepancies between the observed B-K color distribution and the predicted distribution for ellipticals by such a pure luminosity evolution (PLE) model in the context of the conventional scenario. Neither can the mild evolution (i.e., the star formation events have lasted for a longer time than those of the instantaneous burst and passive evolution since the formation of galaxies) for ellipticals be accepted in the context of PLE assumption. The introduction of dust extinction also cannot save the PLE models. This conclusion holds for each of the three cosmological models under consideration: flat, open, and Λ-dominated. Hence, our investigation suggests that PLE assumption for elliptical galaxies is questionable, and number evolution may be essential for ellipticals.

  4. 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

  5. An approach to measuring the density of the environment of galaxies: results and comparisons with other measurements

    NASA Astrophysics Data System (ADS)

    Ortega-Minakata, R. A.; Torres-Papaqui, J. P.; Andernach, H.

    2014-10-01

    With the aim of obtaining a homogeneous and reliable measurement of the density of the environment of a large sample of galaxies, we developed a code that counts the number of neighboring galaxies around a target galaxy. As targets, we selected a large sample of 666,387 galaxies from the spectroscopic catalogue of the SDSS-DR7 with redshifts between 0.03 and 0.30 and more luminous than absolute magnitude of -19 in the SDSS r band. The photometric catalogue of the SDSS-DR7 was used to extract and count the neighboring galaxies from, including about 24M objects, also more luminous than an r-band absolute magnitude of -19, for which a photometric redshift was available to serve as a distance estimate. The code counts all galaxies within an absolute distance of 1.5 Mpc around the target (translated to an apparent radius and a redshift range around that of the target). We avoid galaxies close to the survey edges, leaving 527,074 target galaxies for which we have a measurement of environmental density. We present our results and compare them to other measurements of the density of the environment of galaxies, such as those in the MaxBCG catalogue of brightest cluster galaxies. As a control of our method, we apply it to a sample of galaxies from the 2MIG catalogue of isolated galaxies, and also to a sample of galaxies from a compilation of members of Abell clusters. We aim to use our results to test the morphology-local density relation and to study the relationship between the different types of emission-line activity of galaxies and their ambient density.

  6. 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.

  7. The redshift evolution of the mass function of cold gas in hierarchical galaxy formation models

    NASA Astrophysics Data System (ADS)

    Power, C.; Baugh, C. M.; Lacey, C. G.

    2010-07-01

    Accurately predicting how the cosmic abundance of neutral hydrogen evolves with redshift is a challenging problem facing modellers of galaxy formation. We investigate the predictions of four currently favoured semi-analytical galaxy formation models applied to the Millennium simulation for the mass function of cold neutral gas (atomic and molecular) in galaxies as a function of redshift, and we use these predictions to construct number counts for the next generation of all-sky neutral atomic hydrogen (HI) surveys. Despite the different implementations of the physical ingredients of galaxy formation, we find that the model predictions are broadly consistent with one another; the key differences reflect how the models treat active galactic nuclei feedback and how the time-scale for star formation evolves with redshift. The models produce mass functions of cold gas in galaxies that are generally in good agreement with HI surveys at . Interestingly, we find that these mass functions do not evolve significantly with redshift. Adopting a simple conversion factor for cold gas mass to HI mass that we apply to all galaxies at all redshifts, we derive mass functions of HI in galaxies from the predicted mass functions of cold gas, which we use to predict the number counts of sources likely to be detected by HI surveys on next generation radio telescopes such as the Square Kilometre Array and its pathfinders. We find the number counts peak at galaxies deg at for a year long HI hemispheric survey on a 1/10/100 per cent SKA with a 30 deg field of view, corresponding to an integration time of 12 h. On a full SKA with a 200 deg field of view (equivalent to an integration time of 80 h) the number counts peak at galaxies deg at . We show also how adopting a conversion factor for cold gas mass to HI mass that varies from galaxy to galaxy impacts on number counts. In addition, we examine how the typical angular sizes of galaxies vary with redshift. These decline strongly with

  8. 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.

  9. 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.

  10. Kentucky Kids Count 2001 County Data Book: Families Count.

    ERIC Educational Resources Information Center

    Salley, Valerie

    This Kids Count county data book is the eleventh in a series to measure the well-being of Kentucky's children and focuses on the vital role that families play in ensuring their children's success. Included at the beginning of this document is an executive summary of the databook providing an overview of the statewide data for six child and family…

  11. Two-fluid simulations of galaxy formation

    NASA Technical Reports Server (NTRS)

    Evrard, August E.; Summers, F. J.; Davis, Marc

    1994-01-01

    We investigate the formation of galaxies and larger structure with a simulation modeling two gravitationally coupled fluids representing dark matter and baryons. The baryon gas dynamics are calculated with a smoothed particle hydrodynamics (SPH) method, and the physics modeled includes thermal pressure, shock heating, and radiative cooling. We simulate a 16 Mpc periodic cube with 64(exp 3) particles in each fluid and 10% baryon mass fraction. We confirm, for the first time experimentally, disk formation as a natural consequence of hierarchical clustering in a large-scale cosmological environment. The majority of isolated galaxies exhibit centrifugally supported disks. A power-law relation between cold baryonic mass and maximum rotation velocity is found, M varies as nu(sub rot)(exp alpha) with alpha = 2.5 after correcting for differential numerical resolution. Both the spatial and velocity distributions of the simulated galaxies are biased with respect to the dark matter. A counts-in-cells analysis indicates that an unphysical degree of merging in the central cluster is likely responsible for the antibias signal in the correlation function. A robust, scale-dependent velocity bias is measured. The ratio of galaxy to dark matter pairwise velocity dispersions on a scale of 1 Mpc is 0.7. The amplitude is only mildly dependent on redshift or mass cutoff and scales with separation as r(exp 0.2). The degree to which these results depend on numerical parameters is discussed. Mass resolution plays a key role in controlling the resulting fraction of cold, dense baryons. The mass fraction associated with galaxies decreases by a factor of approximately greater than 3 when the mass per particle is increased by a factor 8. Photoionization and energy input from supernova will have to be included to determine more carefully the fraction of highly dissipated material and the characteristics of the stellar component of galaxies.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. Isolated galaxies, pairs, and groups of galaxies

    NASA Technical Reports Server (NTRS)

    Kuneva, I.; Kalinkov, M.

    1990-01-01

    The authors searched for isolated galaxies, pairs and groups of galaxies in the CfA survey (Huchra et al. 1983). It was assumed that the distances to galaxies are given by R = V/H sub o, where H sub o = 100 km s(exp -1) Mpc(exp -1) and R greater than 6 Mpc. The searching procedure is close to those, applied to find superclusters of galaxies (Kalinkov and Kuneva 1985, 1986). A sphere with fixed radius r (asterisk) is described around each galaxy. The mean spatial density in the sphere is m. Let G (sup 1) be any galaxy and G (sup 2) be its nearest neighbor at a distance R sub 2. If R sub 2 exceeds the 95 percent quintile in the distribution of the distances of the second neighbors, then G (sup 1) is an isolated galaxy. Let the midpoint of G (sup 1) and G (sup 2) be O sub 2 and r sub 2=R sub 2/2. For the volume V sub 2, defined with the radius r sub 2, the density D sub 2 less than k mu, the galaxy G (sup 2) is a single one and the procedure for searching for pairs and groups, beginning with this object is over and we have to pass to another object. Here the authors present the groups - isolated and nonisolated - with n greater than 3, found in the CfA survey in the Northern galactic hemisphere. The parameters used are k = 10 and r (asterisk) = 5 Mpc. Table 1 contains: (1) the group number, (2) the galaxy, nearest to the multiplet center, (3) multiplicity n, (4) the brightest galaxy if it is not listed in (2); (5) and (6) are R.A. and Dec. (1950), (7) - mean distance D in Mpc. Further there are the mean density rho (8) of the multiplet (galaxies Mpc (exp -3), (9) the density rho (asterisk) for r (asterisk) = 5 Mpc and (10) the density rho sub g for the group with its nearest neighbor. The parenthesized digits for densities in the last three columns are powers of ten.

  17. 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.

  18. 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.

  19. 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,…

  20. 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…

  1. What Really Counts in Schools.

    ERIC Educational Resources Information Center

    Eisner, Elliot W.

    1991-01-01

    Brains are biological, but minds are cultural achievements. What really counts in schools is teaching children the excitement of exploring ideas, helping youngsters formulate their own problems and resolution strategies, developing multiple literacy forms, imparting the importance of wonder, creating a sense of community, and recognizing each…

  2. 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)…

  3. Oklahoma Kids Count Factbook, 2002.

    ERIC Educational Resources Information Center

    Ingraham, Sandy

    This Kids Count Factbook details county and statewide trends in the well-being of children in Oklahoma. The statistical portrait is based on seven indicators or benchmarks of child well-being: (1) low birthweight infants; (2) infant mortality; (3) births to young teens; (4) child abuse and neglect; (5) child and teen death; (6) high school…

  4. 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…

  5. 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…

  6. Automatic Crater Counts on Mars

    NASA Astrophysics Data System (ADS)

    Plesko, C.; Brumby, S.; Asphaug, E.; Chamberlain, D.; Engel, T.

    2004-03-01

    We present results of an automated crater counting technique for THEMIS data. Algorithms were developed using GENIE machine learning software. The technique detects craters, generalizes well to new data, and is used to rapidly produce R-plots and statistical data.

  7. Carbon fiber counting. [aircraft structures

    NASA Technical Reports Server (NTRS)

    Pride, R. A.

    1980-01-01

    A method was developed for characterizing the number and lengths of carbon fibers accidentally released by the burning of composite portions of civil aircraft structure in a jet fuel fire after an accident. Representative samplings of carbon fibers collected on transparent sticky film were counted from photographic enlargements with a computer aided technique which also provided fiber lengths.

  8. 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…

  9. 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)…

  10. 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…

  11. 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…

  12. 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…

  13. 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…

  14. 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…

  15. 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…

  16. 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.

  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. Infrared Polarimetry of Galaxies

    NASA Astrophysics Data System (ADS)

    Jones, T. J.

    2005-12-01

    Imaging polarimetry at near infrared wavelengths can probe the magnetic field geometry in external galaxies in regions of high extinction inaccessible to optical techniques. Polarization of starlight from deep into dustlanes, blowouts, and dust enshrouded nuclei can be measured. A total of twelve galaxies showing only interstellar polarization have been observed to date. Normal galaxies such as NGC 4565 show a magnetic field geometry lying in the plane of the disk and a polarization strength very similar to what is observed in the Milky Way. Ultraluminous galaxies and galaxies with starburst nuclei show a polar magnetic field geometry in the nucleus, causing a crossed polaroid effect and reduced polarization. Interestingly, galaxies with active disks, but otherwise normal, such as NGC 891 show the effects of blowouts in the polarization maps.

  20. 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.

  1. ROSAT PSPC observations of two starburst galaxies

    NASA Astrophysics Data System (ADS)

    Junkes, N.; Pietsch, W.; Hensler, G.

    1993-12-01

    We present results from ROSAT observations of NGC 1808 and NGC 2903. Exposures of 10 ksec each with the Position-Sensitive Proportional Counter (PSPC) detector show X-ray sources at the central positions of both galaxies which are classified as nuclear starburst galaxies. Both targets, NGC 1808 and NGC 2903 appear slightly extended in X-ray maps in the energy band 0.1-2.4 keV. The X-ray spectrum of NGC 1808 shows almost complete absorption below 0.5 keV, indicating an extremely high hydrogen column density towards that source (NH approx. = 8 x 1021/sq cm resulting from model fits on the PSPC spectrum). In the case of NGC 2903, the number of counts in the ROSAT band is significantly lower than expected from a previous EINSTEIN (HEAO 2) investigation of the source.

  2. 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.

  3. 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).

  4. The first source counts at 18 μm from the AKARI NEP Survey

    NASA Astrophysics Data System (ADS)

    Pearson, Chris P.; Serjeant, S.; Oyabu, S.; Matsuhara, H.; Wada, T.; Goto, T.; Takagi, T.; Lee, H. M.; Im, M.; Ohyama, Y.; Kim, S. J.; Murata, K.

    2014-10-01

    We present the first galaxy counts at 18 μm using the Japanese AKARI satellite's survey at the North Ecliptic Pole (NEP), produced from the images from the NEP-Deep and NEP-Wide surveys covering 0.6 and 5.8 deg2, respectively. We describe a procedure using a point source filtering algorithm to remove background structure and a minimum variance method for our source extraction and photometry that delivers the optimum signal to noise for our extracted sources, confirming this by comparison with standard photometry methods. The final source counts are complete and reliable over three orders of magnitude in flux density, resulting in sensitivities (80 per cent completeness) of 0.15 and 0.3 mJy for the NEP-Deep and NEP-Wide surveys, respectively, a factor of 1.3 deeper than previous catalogues constructed from this field. The differential source counts exhibit a characteristic upturn from Euclidean expectations at around a milliJansky and a corresponding evolutionary bump between 0.2-0.4 mJy consistent with previous mid-infrared surveys with ISO and Spitzer at 15 and 24 μm. We compare our results with galaxy evolution models confirming the striking divergence from the non-evolving scenario. The models and observations are in broad agreement implying that the source counts are consistent with a strongly evolving population of luminous infrared galaxies at redshifts higher than unity. Integrating our source counts down to the limit of the NEP survey at the 150 μJy level we calculate that AKARI has resolved approximately 55 per cent of the 18 μm cosmic infrared background relative to the predictions of contemporary source count models.

  5. Cluster evolution and microwave source counts

    NASA Technical Reports Server (NTRS)

    Markevitch, M.; Blumenthal, G. R.; Forman, W.; Jones, C.; Sunyaev, R. A.

    1994-01-01

    We present the modeled counts for the expected Sunyaev-Zel'dovich microwave sources associated with clusters of galaxies, predicted for experiments with arcminute-scale spatial resolution, assuming self-similar cluster evolution, for different spectra of the primordial density fluctuations and values of the cosmological density parameter Omega. Our simulations show that the source counts should be a powerful test of the evolution of very high redshift clusters. Experiments with 1 - 2 min spatial resolution, with moderate sensitivity but covering a large area of the sky, would be most effective for studying the SZ source population. Recent arcminute-scale radio experiments, the Owens Valley Radio Observatory (OVRO) RING experiment and VLA deep imaging, achieved sensitivity and sky coverage close to that needed for the detection of negative sources associated with very distant clusters. From the absence of cluster detections in these experiments, we rule out, with 90% confidence, models with Omega less than 0.3 and n = +1 as predicting too many bright sources; or there is no hot gas in clusters more distant than z(sub max) = 5 in such models. If the single negative source detected in the RING experiment is a distant cluster, the Omega = 1, n = -2 model also may be ruled out as it predicts too few sources. The new generation of telescopes, including the new SUZIE and Ryle instruments, will soon be able to detect distant clusters. The cluster population in the past has been modeled by scaling the observed present-day sample of X-ray clusters back to high redshifts, an approach which makes the best use of the observed cluster gas parameters, and makes the simulations robust to the assumed evolution at very early epochs. Although the pure self-similar model may be incompatible with the variety of observed evolutionary effects, we show that reasonable modifications to the intracluster gas history in that model, proposed to reconcile the self-similar evolution of cluster

  6. Photometry of compact galaxies.

    NASA Technical Reports Server (NTRS)

    Shen, B. S. P.; Usher, P. D.; Barrett, J. W.

    1972-01-01

    Photometric histories of the N galaxies 3C 390.3 and PKS 0521-36. Four other compact galaxies, Markarian 9, I Zw 92, 2 Zw 136, and III Zw 77 showed no evidence of variability. The photometric histories were obtained from an exhaustive study of those plates of the Harvard collection taken with large aperture cameras. The images of all galaxies reported were indistinguishable from stars due to the camera f-ratios and low surface brightness of the outlying nebulosities of the galaxies. Standard techniques for the study of variable stars are therefore applicable.

  7. 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.

  8. Ripples in disk galaxies

    SciTech Connect

    Schweizer, F.; Seitzer, P.

    1988-05-01

    Evidence is presented that ripples occur not only in ellipticals but also in disk galaxies of Hubble types S0, S0/Sa, and Sa, and probably even in the Sbc galaxy NGC 3310. It is argued that the ripples cannot usually have resulted from transient spiral waves or other forced vibrations in existing disks, but instead consist of extraneous sheetlike 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. The implications of ripples in early-type disk galaxies are addressed. 40 references.

  9. Starbursts in colliding galaxies.

    NASA Astrophysics Data System (ADS)

    Mirabel, I. F.; Duc, P. A.

    Global starbursts are a consequence of rapid changes in the dynamics of the interstellar gas. The most violent starbursts take place in the nuclear regions of galaxies, when galaxy-galaxy encounters cause a sudden reduction of angular momentum, with the subsequent infall to the central regions of a large fraction of the overall interstellar gas. Although starbursts are also observed in the central regions of isolated barred spiral galaxies, most of the starbursts with bolometric luminosities above 1012Lsun occur in mergers. Super-starbursts in galactic nuclei seem to require high infall rates of interstellar gas that can only be produced during mergers. The authors discuss the phenomenon of extranuclear starbursts in relation to the formation of dwarf galaxies during galaxy-galaxy collisions. As a consequence of tidal interactions a fraction of the less gravitationally bound atomic hydrogen that populates the outskirts of disk galaxies may escape into the intergalactic medium. It is found that the ejected gas may assemble again and collapse, leading to the formation of intergalactic starbursts, namely, tidal dwarf galaxies.

  10. From tidal dwarf galaxies to satellite galaxies

    NASA Astrophysics Data System (ADS)

    Bournaud, F.; Duc, P.-A.

    2006-09-01

    The current popular cosmological models have granted the population of dwarf satellite galaxies a key role: their number, location, and masses constrain both the distribution of dark matter and the physical evolution of their hosts. In the past years, there has been increasing observational evidence that objects with masses of dwarf galaxies can form in the tidal tails of colliding galaxies, as well as speculations that they could become satellite-like galaxies orbiting around their progenitors and thus be cosmologically important. Yet, whether the so-called "Tidal Dwarf Galaxy" (TDG) candidates are really long-lived objects and not transient features only present in young interacting systems is still largely an open question to which numerical simulations may give precise answers. We present here a set of 96 N-body simulations of colliding galaxies with various mass ratios and encounter geometries, including gas dynamics and star formation. We study the formation and long-term evolution of their TDG candidates. Among the 593 substructures initially identified in tidal tails, about 75% fall back onto their progenitor or are disrupted in a few 108 years. The remaining 25% become long-lived bound objects that typically survive more than 2 Gyr with masses above 108 M⊙. These long-lived, satellite-like objects, are found to form in massive gaseous accumulations originally located in the outermost regions of the tidal tails. Studying the statistical properties of the simulated TDGs, we infer several basic properties that dwarf galaxies should meet to have a possible tidal origin and apply these criteria to the Local Group dwarfs. We further found that the presence of TDGs would foster the anisotropy observed in the distribution of classical satellite galaxies around their host. Identifying the conditions fulfilled by interacting systems that were able to form long-lived tidal dwarfs - a spiral merging with a galaxy between 1/4 and 8 times its mass, on a prograde orbit

  11. 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

  12. Two Galaxies for a Unique Event

    NASA Astrophysics Data System (ADS)

    2009-04-01

    of the image is clearly demonstrated by the remarkable number of background galaxies seen, as well as the huge numbers of individual stars that can be counted within NGC 55. The second image shows another galaxy belonging to the Sculptor group. This is NGC 7793, which has a chaotic spiral structure, unlike the class of grand-design spiral galaxies to which our Milky Way belongs. The image shows how difficult it is to identify any particular spiral arm in these chaotic structures, although it is possible to guess at a general rotating pattern. NGC 7793 is located slightly further away than NGC 55, about 12.5 million light-years from us, and is about half the size of NGC 55. NGC 7793 was observed with one of the workhorses of the ESO Paranal Observatory, the FORS instrument, attached to the Very Large Telescope.

  13. A photon-counting multichannel spectrometer. [for astronomical optical spectroscopy

    NASA Technical Reports Server (NTRS)

    Shectman, S. A.; Hiltner, W. A.

    1977-01-01

    A multichannel detector system is described in which the positions of individual photon events in a high-gain image intensifier are decoded in the output of a video detector. The high-gain intensifier consists of a pair of three-stage electrostatic image-tube assemblies each containing three fiber-optically-coupled tubes potted in a rugged package with an internal high-voltage supply. Operation of the electrooptical system is discussed along with the pulse-detection process and the operation of the spectrograph in which the image-tube assembly is mounted. It is noted that the spectrometer detects 1.0 count/sec per A for an object of magnitude 13.0 at the peak of its response in the visual band when no light is lost on the slit, that a 10% coincidence correction is reached at an overall count rate of 860 per sec, and that the response follows an exponential law up to count rates of about 4000 per sec. The measured spectrum of the Seyfert galaxy NGC 5548 is provided as an example of the raw data produced by the instrument on a 1.5 meter telescope.

  14. 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.

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

    NASA Astrophysics Data System (ADS)

    Vader, J. Patricia; Chaboyer, Brian

    1994-10-01

    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. galaxies are reported in this paper.

  16. 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

  17. Imaging by terahertz photon counting

    NASA Astrophysics Data System (ADS)

    Ikushima, Kenji; Komiyama, Susumu

    2010-08-01

    Photon counting method is indispensable in visible/near-infrared optical measurements for detecting extremely weak radiation. The method, however, has been inaccessible in terahertz region, where the photon energies are more than 100 times smaller and catching individual photons is difficult. Here we review photon counting measurements of terahertz waves, by incorporating a semiconductor quantum-dot terahertz-photon detector into a scanning terahertz microscope. By using a quantum Hall effect detector as well, measurements cover the intensity dynamic range more than six orders of magnitude. Applying the measurement system to the study of semiconductor quantum Hall effect devices, we image extremely weak cyclotron radiation emitted by nonequilibrium electrons. Owing to the unprecedented sensitivity, a variety of new features of electron kinetics are unveiled. Besides semiconductor electric devices studied here, the experimental method will find application in diverse areas of molecular dynamics, microthermography, and cell activities.

  18. 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

  19. 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

  20. 1/Nc Countings in Baryons

    SciTech Connect

    Jose Goity

    2004-05-01

    The 1/N{sub c} power countings for baryon decays and configuration mixings are determined by means of a non-relativistic quark picture. Such countings are expected to be robust as the quark masses are decreased towards the chiral limit. It is shown that excited baryons have natural widths of {Omicron}(N{sub c}{sup 0}). These dominant widths are due to the decays that proceed directly to the ground state baryons, with cascade decays being suppressed to {Omicron}(1/N{sub c}). Configuration mixings, defined as mixings between states belonging to different O(3) x SU(2N{sub f}) multiplets, are shown to be sub-leading in an expansion in 1/{radical}N{sub c}, except for certain mixings between excited multiplets belonging to the mixed-symmetric spin-flavor representation and different O(3) representations, where the mixings are of zeroth order in 1/N{sub c}.

  1. 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

  2. Stability of fringe counting interferometers

    NASA Technical Reports Server (NTRS)

    Edgerton, J. W.; Andrew, K. L.

    1974-01-01

    Two configurations of an automatic bidirectional, fringe-counting corner-cube interferometer are compared. They differ only in the method of quadrature phase introduction. The one using polarization coding has good phase stability at optical path differences as large as 955 mm, the one using adjacent beams has such poor phase stability as to render it useless at path differences greater than 700 mm. A useful well-defined alignment procedure is given for the corner-cube interferometer.

  3. 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

  4. Approximate Counting of Graphical Realizations.

    PubMed

    Erdős, Péter L; Kiss, Sándor Z; Miklós, István; Soukup, Lajos

    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

  5. 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.

  6. Simulating Galaxies and Active Galactic Nuclei in the LSST Image Simulation Effort

    NASA Astrophysics Data System (ADS)

    Pizagno, James; Ahmad, Z.; Bankert, J.; Bard, D.; Connolly, A.; Chang, C.; Gibson, R. R.; Gilmore, K.; Grace, E.; Hannel, M.; Jernigan, J. G.; Jones, L.; Kahn, S. M.; Krughoff, S. K.; Lorenz, S.; Marshall, S.; Shmakova, S. M.; Sylvestri, N.; Todd, N.; Young, M.

    2011-01-01

    We present an extragalactic source catalog, which includes galaxies and Active Galactic Nuclei, that is used for the Large Survey Synoptic Telescope Imaging Simulation effort. The galaxies are taken from the De Lucia et. al. (2006) semi-analytic modeling (SAM) of the Millennium Simulation. The LSST Image Simulation effort requires full SED information and galaxy morphological information, which is added to the catalog by fitting Bruzual & Charlot (2003) stellar population models, with Cardelli, Clayton, Mathis (1989) dust models, to the BVRIK colors provided by the De Lucia et. al. (2006) SAM. Galaxy morphology is modeled as a double Sersic profile for the disk and bulge. Galaxy morphological information and number counts are matched to existing observations. The catalog contains galaxies with a limiting r-band magnitude of mr=28, which results in roughly 1E6 galaxies per square degree. An existing AGN catalog (MacLeod et. al. 2010) is matched to galaxy hosts in the galaxy catalog using SDSS observations. AGN are morphologically modeled as variable point sources located at the center of the host galaxy. We demonstrate how this extragalactic source catalog allows LSST to plan for extended object extraction, variable extragalactic source detection, sensitivity level determination after image stacking, and perform various other cosmological tests.

  7. 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.

  8. 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.

  9. 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.

  10. 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

  11. 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.

  12. 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.)

  13. 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.

  14. What I Need to Know about Carbohydrate Counting and Diabetes

    MedlinePlus

    ... URL Español What I need to know about Carbohydrate Counting and Diabetes Page Content On this page: ... counting? Points to Remember Clinical Trials What is carbohydrate counting? Carbohydrate * counting, also called carb counting, is ...

  15. Insights on galaxy formation

    NASA Astrophysics Data System (ADS)

    Bullock, James Steven

    1999-12-01

    Recent advances in theoretical modeling coupled with a wealth of new observational data, provide a unique opportunity for gaining insight into process of galaxy formation. I present results which test and develop current theories. The analysis utilizes state of the art theoretical modeling and makes predictions aimed at comparisons with some of the latest and upcoming observational data sets. In part I, I discuss an analysis of the structure and properties of dark matter halos (believed to govern the dynamical evolution of galaxies). The results make use of very high-resolution N-body simulations, and are derived from a new hierarchical halo finder, designed especially for these projects and to complement advancements in simulation technology. I present information on the dark matter halo substructure, density profiles, angular momentum structure, and collision rates. In part II, I discuss some aspects of galaxy formation theory in light of new observational data. The discussion includes an investigation of the nature of high-redshift galaxies, the local velocity function of galaxies, and the use of gamma ray telescopes to probe the extra-galactic background light-the latter analysis is done in the context of semi-analytic modeling of galaxy formation. The most important conclusions of this thesis are as follows. (1)Dark matter halos at high redshift are much less concentrated than previously believed. implying that quiescently star-forming galaxies at high redshift are larger and dimmer than expected. (2)The observed bright. abundant. and highly clustered high- redshift (Lyman-break) galaxies are likely starbursts driven by collisions between relatively small galaxies at z ~ 3. And (3)there is a real possibility of using the growing advances in γ-ray astronomy to probe many poorly constrained processes of galaxy formation, including the stellar initial mass function and the star formation history of the universe.

  16. 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

  17. Markarian Galaxies. I. The Optical Database and Atlas

    NASA Astrophysics Data System (ADS)

    Petrosian, Artashes; McLean, Brian; Allen, Ronald J.; MacKenty, John W.

    2007-05-01

    A database for the entire Markarian catalog is presented that combines extensive new measurements of their optical parameters with a literature and database search. The measurements were made using images extracted from the STScI Digitized Sky Survey (DSS) of Fpg(red) and Jpg(blue) band photographic sky survey plates obtained by the Palomar and UK Schmidt telescopes. We provide accurate coordinates, morphological type, spectral and activity classes, red and blue apparent magnitudes, apparent diameters, axial ratios, and position angles, as well as number counts of neighboring objects in a circle of radius 50 kpc. Special attention was paid to the individual descriptions of the galaxies in the original Markarian lists, which clarified many cases of misidentifications of the objects, particularly among interacting systems, larger galaxies with knots of star formation, possible stars, and cases of stars projected on galaxies. The total number of individual Markarian objects in the database is now 1544. We also include redshifts that are now available for 1524 objects with UV-excess radiation, as well as galactic color excess E(B-V) values and their 2MASS or DENIS infrared magnitudes. The database also includes extensive notes that summarize information about the membership of Markarian galaxies in different systems of galaxies and about new and revised activity classes and redshifts. An atlas of several interesting subclasses of Markarian galaxies is also presented.

  18. 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 ...

  19. Are spiral galaxies heavy smokers

    SciTech Connect

    Davies, J.; Disney, M.; Phillipps, S )

    1990-07-01

    The dustiness of spiral galaxies is discussed. Starburst galaxies and the shortage of truly bright spiral galaxies is cited as evidence that spiral galaxies are far dustier than has been thought. The possibility is considered that the dust may be hiding missing mass.

  20. 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

  1. Rebuilding Spiral Galaxies

    NASA Astrophysics Data System (ADS)

    2005-01-01

    Major Observing Programme Leads to New Theory of Galaxy Formation Summary Most present-day large galaxies are spirals, presenting a disc surrounding a central bulge. Famous examples are our own Milky Way or the Andromeda Galaxy. When and how did these spiral galaxies form? Why do a great majority of them present a massive central bulge? An international team of astronomers [1] presents new convincing answers to these fundamental questions. For this, they rely on an extensive dataset of observations of galaxies taken with several space- and ground-based telescopes. In particular, they used over a two-year period, several instruments on ESO's Very Large Telescope. Among others, their observations reveal that roughly half of the present-day stars were formed in the period between 8,000 million and 4,000 million years ago, mostly in episodic burst of intense star formation occurring in Luminous Infrared Galaxies. From this and other evidence, the astronomers devised an innovative scenario, dubbed the "spiral rebuilding". They claim that most present-day spiral galaxies are the results of one or several merger events. If confirmed, this new scenario could revolutionise the way astronomers think galaxies formed. PR Photo 02a/05: Luminosity - Oxygen Abundance Relation for Galaxies (VLT) PR Photo 02b/05: The Spiral Rebuilding Scenario A fleet of instruments How and when did galaxies form? How and when did stars form in these island universes? These questions are still posing a considerable challenge to present-day astronomers. Front-line observational results obtained with a fleet of ground- and space-based telescopes by an international team of astronomers [1] provide new insights into these fundamental issues. For this, they embarked on an ambitious long-term study at various wavelengths of 195 galaxies with a redshift [2] greater than 0.4, i.e. located more than 4000 million light-years away. These galaxies were studied using ESO's Very Large Telescope, as well as the

  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. 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.

  4. 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...

  5. 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.

  6. Featured Image: Spitzer Galaxies

    NASA Astrophysics Data System (ADS)

    Kohler, Susanna

    2015-11-01

    These three galaxies (click for a full view!) were imaged as a part of the Spitzer Survey of Stellar Structure in Galaxies (S4G), a recent survey of 2352 nearby galaxies with deep imaging at 3.6 and 4.5 m. The bottom panels show false-color near-UV and far-UV images previously obtained with GALEX. The top panels show the new images obtained with Spitzer as part of S4G. The three galaxies shown here represent three types of galaxies that have a high concentration of mass in their centers, yet still have a high specific star-formation rate (the star formation rate per unit stellar mass):Barred galaxies with a prominent ring around their nucleus, like NGC 7552Interacting systems, like NGC 2782Galaxies with compact bulges and smooth extended disks, like NGC 3642To learn why this is the case, and to see more results from S4G, see the original paper below.CitationJuan Carlos Muoz-Mateos et al 2015 ApJS 219 3. doi:10.1088/0067-0049/219/1/3

  7. Cluster galaxies die hard

    NASA Astrophysics Data System (ADS)

    Weinmann, Simone M.; Kauffmann, Guinevere; von der Linden, Anja; De Lucia, Gabriella

    2010-08-01

    We investigate how the specific star formation rates of galaxies of different masses depend on cluster-centric radius and on the central/satellite dichotomy in both field and cluster environments. Recent data from a variety of sources, including the cluster catalogue of von der Linden et al., are compared to the semi-analytic models of De Lucia & Blaizot. We find that these models predict too many passive satellite galaxies in clusters, too few passive central galaxies with low stellar masses and too many passive central galaxies with high masses. We then outline a series of modifications to the model necessary to solve these problems: (a) instead of instantaneous stripping of the external gas reservoir after a galaxy becomes a satellite, the gas supply is assumed to decrease at the same rate that the surrounding halo loses mass due to tidal stripping and (b) the active galactic nuclei (AGN) feedback efficiency is lowered to bring the fraction of massive passive centrals in better agreement with the data. We also allow for radio mode AGN feedback in satellite galaxies. (c) We assume that satellite galaxies residing in host haloes with masses below 1012h-1Msolar do not undergo any stripping. We highlight the fact that in low-mass galaxies, the external reservoir is composed primarily of gas that has been expelled from the galactic disc by supernovae-driven winds. This gas must remain available as a future reservoir for star formation, even in satellite galaxies. Finally, we present a simple recipe for the stripping of gas and dark matter in satellites that can be used in models where subhalo evolution is not followed in detail.

  8. 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

  9. 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. PMID:21737732

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. Clues to (Radio) Galaxy Formation from Deep HST Images

    NASA Astrophysics Data System (ADS)

    Windhorst, Rogier A.

    We review recent clues from deep HST images on the formation and evolution of galaxies, and of μJy and mJy radio sources in particular. Constraints from the radio source counts over 7 dex in flux and 1 dex in frequency are discussed. We review recent results from deep HST primary and parallel surveys relevant to (radio) galaxy formation. The WFPC2 galaxy counts as a function of morphological type for B < ~ 27 mag show that E/S0's and Sabc's are only marginally above the non-evolving predictions. The faint blue galaxy counts are dominated by Sd/Irr's, and are explained by a combination of a moderately steep local luminosity function undergoing strong luminosity evolution plus low-luminosity lower-redshift dwarf galaxies. Deep WFPC2 images in the medium-band filter F410M yielded 18 faint, compact Lyα emitting candidates at z ≃ 2.4 surrounding the radio galaxy 53W002 at z𢐲.390, as well as 18 more z ≃ 2.4 candidates in three random parallel fields. These objects appear to be star-forming spheroids smaller (rhl ≍ 0''.1 or 0.5-1 kpc) and fainter (MV (z=0)=-17--> -21) than the bulges of typical galaxies seen today. They may the building blocks from which many of the luminous nearby galaxies were formed through repeated hierarchical mergers. HST/PC images in BV I - as well as in redshifted Lyα - of 53W002 show several morphological components: (1) a blue AGN with < ~ 20-25% of the total continuum light; (2) an r1/4-like light distribution with colors indicating a stellar population age ~0.4 Gyr; and (3) two small blue clouds roughly aligned with the radio axis and the main stellar population. We show that both reflected AGN light and jet-induced starformation likely play a role in explaining its "alignment effect". We discuss a possible formation and evolution scenario of 53W002 in context of its surrounding sub-galactic objects, and argue that it will end up like a giant elliptical today.

  15. Galaxy clustering in the Two Micron All Sky Redshift Survey

    NASA Astrophysics Data System (ADS)

    Westover, Michael

    To make cosmological measurements using the galaxy distribution we must first understand galaxy biasing the way in which the galaxy distribution differs from the underlying matter distribution. Here I present studies of galaxy biasing using the Two Micron All Sky Redshift Survey, a near-infrared selected survey not subject to many of the selection effects that limit other samples. The relationship between galaxy bias and luminosity is steeper for our near- infrared selected sample than it is for optical samples, with b/b [low *] 0.73 + 0.24 L/L [low *] . I found no dependence upon luminosity in the relative bias between early and late morphologically typed galaxies once the mean dependence of bias upon luminosity was removed. I tested the relative biasing between early- and late-type galaxies using joint counts in cells. I found that a power law biasing model with b PL = 0.86-0.91 was a better fit than linear models. I did not see a significant increase in the quality of the fit when stochasticity was added to the model, in contrast with results from color- and spectral type-selected samples. I tested the hierarchical scaling hypothesis and confirmed that the scale factors S 3 , S 4 , and S 5 are independent of scale, as expected for a matter distribution evolved from Gaussian initial perturbations. There was no increase in the scale factors at large cell sizes as seen in some earlier surveys. I also measured the generalized dimensions D q using a multifractal analysis and found smaller values than have been seen in optically-selected surveys and simulations, indicating that galaxies in the near-infrared selected sample may be more likely to reside in filamentary rather than sheet-like structures.

  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. 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

  18. Tidal Dwarf Galaxies In Gas-rich Interacting Galaxy Groups

    NASA Astrophysics Data System (ADS)

    Eigenthaler, Paul

    2014-01-01

    Galaxy-galaxy interactions in gas-rich galaxy groups or pairs can form tidal bridges and tails. These tidal arms can contain kinematically decoupled structures with active star formation in the same mass range as dwarf galaxies, so-called tidal dwarf galaxies (TDGs). They differ from ordinary dwarf galaxies by their lack of dark matter and higher metallicity content. Compact groups of galaxies are an ideal environment to study the origin and evolution of TDGs since the high spatial volume density of member galaxies allows for frequent and efficient interactions between galaxies forming tidal tails. Hunsberger et al. (1996) identified 47 TDG candidates in Hickson compact groups (HCGs) and estimated that more than 50% of all dwarf galaxies in compact groups are former TDGs. Statistical considerations based on observations of interacting galaxies illustrate that a significant fraction of today's dwarf galaxies could have had a tidal origin. In their early evolution, TDGs can easily be distinguished from classical dwarf galaxies as they are still embedded in large tidal structures and show ongoing star formation, identified via strong Hα emission in these aggregates. Simulations of interacting galaxies, and of TDGs in particular, have shown that TDGs can survive their first starburst event and turn into long-lived dwarf sized objects. Preliminary results from deep Hα imaging with the SOAR telescope to detect new TDGs in a sample of 10 Hickson compact groups will be presented.

  19. 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…

  20. Somatic Cell Counts in Bovine Milk

    PubMed Central

    Dohoo, I. R.; Meek, A. H.

    1982-01-01

    Factors which influence somatic cell counts in bovine milk are reviewed and guidelines for their interpretation are presented. It is suggested that the thresholds of 300 000 and 250 000 cells/mL be used to identify infected quarters and cows respectively. However, it is stressed that somatic cell counts are general indicators of udder health which are subject to the influence of many factors. Therefore the evaluation of several successive counts is preferable to the interpretation of an individual count. Relationships between somatic cell counts and both milk production and milk composition are discussed. Subclinical mastitis reduces milk quality and decreases yield although the relationship between production loss and somatic cell count requires clarification. Finally the availability of somatic cell counting programs in Canada is presented. PMID:17422127

  1. 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.

  2. Differential Density Statistics of the Galaxy Distribution and the Luminosity Function

    NASA Astrophysics Data System (ADS)

    Albani, V. V. L.; Iribarrem, A. S.; Ribeiro, M. B.; Stoeger, W. R.

    2007-03-01

    This paper uses data obtained from the galaxy luminosity function (LF) to calculate two types of radial number density statistics of the galaxy distribution as discussed in Ribeiro, namely, the differential density γ and the integral differential density γ*. By applying the theory advanced by Ribeiro & Stoeger, which connects the relativistic cosmology number counts with the astronomically derived LF, the differential number counts dN/dz are extracted from the LF and used to calculate both γ and γ* with various cosmological distance definitions, namely, area distance, luminosity distance, galaxy area distance, and redshift distance. LF data are taken from the CNOC2 galaxy redshift survey, and γ and γ* are calculated for two cosmological models: Einstein-de Sitter and an Ωm0=0.3, ΩΛ0=0.7 standard cosmology. The results confirm the strong dependency of both statistics on the distance definition, as predicted in Ribeiro, as well as showing that plots of γ and γ* against the luminosity and redshift distances indicate that the CNOC2 galaxy distribution follows a power-law pattern for redshifts higher than 0.1. These findings support Ribeiro's theoretical proposition that using different cosmological distance measures in statistical analyses of galaxy surveys can lead to significant ambiguity in drawing conclusions about the behavior of the observed large-scale distribution of galaxies.

  3. 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.

  4. Supernovae in paired galaxies

    NASA Astrophysics Data System (ADS)

    Nazaryan, T. A.; Petrosian, A. R.; Hakobyan, A. A.; Adibekyan, V. Zh.; Kunth, D.; Mamon, G. A.; Turatto, M.; Aramyan, L. S.

    2014-07-01

    We investigate the influence of close neighbor galaxies on the properties of supernovae (SNe) and their host galaxies using 56 SNe located in pairs of galaxies with different levels of star formation (SF) and nuclear activity. The mean distance of type II SNe from nuclei of hosts is greater by about a factor of 2 than that of type Ibc SNe. The distributions and mean distances of SNe are consistent with previous results compiled with the larger sample. For the first time it is shown that SNe Ibc are located in pairs with significantly smaller difference of radial velocities between components than pairs containing SNe Ia and II. We consider this as a result of higher star formation rate (SFR) of these closer systems of galaxies.

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. 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

  11. 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.

  12. 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

  13. 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.

  14. Automated Quantification of Arbitrary Arm-Segment Structure in Spiral Galaxies

    NASA Astrophysics Data System (ADS)

    Davis, Darren Robert

    This thesis describes a system that, given approximately-centered images of spiral galaxies, produces quantitative descriptions of spiral galaxy structure without the need for per-image human input. This structure information consists of a list of spiral arm segments, each associated with a fitted logarithmic spiral arc and a pixel region. This list-of-arcs representation allows description of arbitrary spiral galaxy structure: the arms do not need to be symmetric, may have forks or bends, and, more generally, may be arranged in any manner with a consistent spiral-pattern center (non-merging galaxies have a sufficiently well-defined center). Such flexibility is important in order to accommodate the myriad structure variations observed in spiral galaxies. From the arcs produced from our method it is possible to calculate measures of spiral galaxy structure such as winding direction, winding tightness, arm counts, asymmetry, or other values of interest (including user-defined measures). In addition to providing information about the spiral arm "skeleton" of each galaxy, our method can enable analyses of brightness within individual spiral arms, since we provide the pixel regions associated with each spiral arm segment. For winding direction, arm tightness, and arm count, comparable information is available (to various extents) from previous efforts; to the extent that such information is available, we find strong correspondence with our output. We also characterize the changes to (and invariances in) our output as a function of modifications to important algorithm parameters. By enabling generation of extensive data about spiral galaxy structure from large-scale sky surveys, our method will enable new discoveries and tests regarding the nature of galaxies and the universe, and will facilitate subsequent work to automatically fit detailed brightness models of spiral galaxies.

  15. Coma cluster of galaxies

    NASA Technical Reports Server (NTRS)

    1999-01-01

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

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. 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).

  1. Probing Cosmology with Weak Lensing Peak Counts and Minkowski Functionals

    NASA Astrophysics Data System (ADS)

    Kratochvil, Jan Michael; Wang, S.; Lim, E. A.; Haiman, Z.; May, M.

    2010-05-01

    The new method of counting peaks in weak lensing (WL) maps, as a function of their height, to probe models of dark energy and to constrain cosmological parameters offers advantages over similar, more traditional statistics like cluster counts: Because peaks can be identified in two-dimensional WL maps directly, they can provide constraints which are free from potential selection effects and biases involved in identifying and determining the masses of galaxy clusters. Our pilot study (Kratochvil, Haiman, May 2009), where we investigated three cosmological models with different constant values of the dark energy equation of state parameter w=-0.8, w=-1, w=-1.2 and with a fixed normalization of the primordial power spectrum, revealed a parameter sensitivity of w which warrants a numerically very costly in-depth study when marginalization over other uncertain cosmological parameters is included. Towards that goal, we present recent results from a new, extensive simulation suite of ninety 5123-particle N-body simulations, run on New York Blue at BNL, allowing us to vary several cosmological parameters individually and yielding vastly improved statistics. Studies have shown that weak lensing maps likely contain as much information in the nonlinear regime as in the linear one. While being a powerful probe of the nonlinear regime, weak lensing peak counts capture by definition only a subset of the total available information in the convergence maps. In particular, we found that relatively low-amplitude peaks account for most of the parameter sensitivity detected, hinting to a more complicated structure. Therefore, we extend our work by probing the morphology of the maps with Minkowski functionals, in our quest to extract the most possible information from the nonlinear aspects of large-scale structure formation.

  2. 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

  3. Measuring Galaxy Properties in the Cluster Abell 160

    NASA Astrophysics Data System (ADS)

    Koontz, Craig; Pinkney, Jason

    2007-10-01

    We develop a procedure for building a large catalog of cluster galaxies and their photometric properties, as measured with CCDs. Our first case, Abell 160, is relatively nearby and we have already obtained spectroscopic redshifts for its brightest galaxies. We have mosaiced this cluster in R and V filters using a CCD imager on the 1.3-meter McGraw-Hill telescope. We fit a world coordinate system to the images using the software ``WCStools.'' We use ``SExtractor'' to extract sources from the images. We create software for merging catalogs in such a way as to avoid double counting, to reject cosmic rays, and to combine redundant measurements. The measured properties include magnitude, ellipticity, position angle, size, and color (V-R). We investigate the efficacy of our separation of galaxies and stars and find that it begins breaking down around R=19.0. We attempt to separate cluster members from foreground and background galaxies using the color-magnitude relation. In future work, we will investigate substructure (clumping) within clusters and its correlation with galaxy properties (especially color, size and morphology).

  4. Galaxy Properties and Substructure in the Cluster Abell 160

    NASA Astrophysics Data System (ADS)

    Koontz, Craig; Pinkney, Jason

    2009-04-01

    We have developed a procedure for building a large catalog of cluster galaxies and their photometric properties as measured with CCDs. Our first case, Abell 160, is relatively nearby and redshifts exist for its brightest galaxies. We have mosaiced this cluster in R and V filters using a CCD imager on the 1.3-meter McGraw-Hill telescope. We fitted a world coordinate system to the images using the software ``WCStools,'' then used ``Source Extractor'' to extract sources from the images. We have created software for merging catalogs in such a way as to avoid double counting, to reject cosmic rays, and to combine redundant measurements. The software also corrects magnitude differences by comparing the mean difference and adding this to each individual catalog before merging it to a master catalog. The measured properties included in this study were magnitude, ellipticity, position angle, size, and color (V-R). We investigate the efficacy of our separation of galaxies and stars and find that it begins breaking down around R=19.0. We divide our master catalog into several subsamples for substructure analysis. For one subsample, we attempt to separate cluster members from foreground and background galaxies using the color-magnitude relation. We compare the results of substructure diagnostics for the subsamples. In future work, we will examine correlation of substructure with galaxy properties (especially color, size and morphology).

  5. Statistical aspects of point count sampling

    USGS Publications Warehouse

    Barker, R.J.; Sauer, J.R.

    1995-01-01

    The dominant feature of point counts is that they do not census birds, but instead provide incomplete counts of individuals present within a survey plot. Considering a simple model for point count sampling, we demon-strate that use of these incomplete counts can bias estimators and testing procedures, leading to inappropriate conclusions. A large portion of the variability in point counts is caused by the incomplete counting, and this within-count variation can be confounded with ecologically meaningful varia-tion. We recommend caution in the analysis of estimates obtained from point counts. Using; our model, we also consider optimal allocation of sampling effort. The critical step in the optimization process is in determining the goals of the study and methods that will be used to meet these goals. By explicitly defining the constraints on sampling and by estimating the relationship between precision and bias of estimators and time spent counting, we can predict the optimal time at a point for each of several monitoring goals. In general, time spent at a point will differ depending on the goals of the study.

  6. 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.

  7. Effect of counting errors on immunoassay precision

    SciTech Connect

    Klee, G.G.; Post, G. )

    1989-07-01

    Using mathematical analysis and computer simulation, we studied the effect of gamma scintillation counting error on two radioimmunoassays (RIAs) and an immunoradiometric assay (IRMA). To analyze the propagation of the counting errors into the estimation of analyte concentration, we empirically derived parameters for logit-log data-reduction models for assays of digoxin and triiodothyronine (RIAs) and ferritin (IRMA). The component of the analytical error attributable to counting variability, when expressed as a CV of the analyte concentration, decreased approximately linearly with the inverse of the square root of the maximum counts bound. Larger counting-error CVs were found at lower concentrations for both RIAs and the IRMA. Substantially smaller CVs for overall assay were found when the maximum counts bound progressively increased from 500 to 10,000 counts, but further increases in maximum bound counts resulted in little decrease in overall assay CV except when very low concentrations of analyte were being measured. Therefore, RIA and IRMA systems based in duplicate determinations having at least 10,000 maximum counts bound should have adequate precision, except possibly at very low concentrations.

  8. 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

  9. 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

  10. 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

  11. 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

  12. 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.

  13. Photon counting with an EMCCD

    NASA Astrophysics Data System (ADS)

    Daigle, Olivier; Blais-Ouellette, Sébastien

    2010-01-01

    In order to make faint flux imaging efficient with an EMCCD, the Clock Induced Charges (CIC) must be reduced to a minimum. Some techniques were proposed to reduce the CIC but until now, neither commercially available CCD controller nor commercial cameras were able to implement them and get satisfying results. CCCP, the CCD Controller for Counting Photons, has been designed with the aim of reducing the CIC generated when an EMCCD is read out. It is optimized for driving EMCCDs at high speed (>= 10MHz), but may be used also for driving conventional CCDs (or the conventional output of an EMCCD) at high, moderate, or low speed. This new controller provides an arbitrary clock generator, yielding a timing resolution of ~20 ps and a voltage resolution of ~2mV of the overlap of the clocks used to drive the EMCCD. The frequency components of the clocks can be precisely controlled, and the inter-clock capacitance effect of the CCD can be nulled to avoid overshoots and undershoots. Using this controller, CIC levels as low as 0.001 - 0.002 e per pixel per frame were measured on a 512×512 CCD97 operating in inverted mode, at an EM gain of ~2000. This is 5 to 10 times less than what is usually seen in commercial EMCCD cameras using the same EMCCD chip.

  14. Low Background Counting at LBNL

    NASA Astrophysics Data System (ADS)

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

    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.

  15. 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.

  16. Nuclear sources in galaxies

    NASA Astrophysics Data System (ADS)

    Elvis, M.

    In the local Universe most massive black holes at the centers of galaxies are not luminous quasars. Is this because (1) they are starved of gas, (2) they accrete without emitting radiation, (3) they refuse to eat, ejecting the incoming material, or (4) they are storing up matter in an accretion disk to feast later?With Chandra ACIS we have imaged a pilot sample of 6 nearby (D 30 Mpc) elliptical galaxies chosen to be especially quiescent based on the careful optical spectroscopy of Ho, measured black hole masses (Mbh > 10(7)Msol), and with existing X-ray upper limits (Lx 10(40)erg/s) implying far sub-Eddington accretion. In these galaxies we can measure, or limit, the diffuse hot interstellar medium, and so constrain the Bondi accretion rate.Faint X-ray emission is detected at or around the nucleus in each galaxy. The morphology of these weak X-ray sources is complex. The X-ray colors of the sources can be determined, and a moderate quality spectrum for one was obtained. We discuss these results against the possible explanations of black hole quiescence.On the other hand, a few percent of all galaxies shows evidence for nuclear activity and a brief review of the high energy emission from Active Galactic Nuclei is given.

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. Star formation in distant galaxies.

    NASA Astrophysics Data System (ADS)

    Rocca-Volmerange, B.

    Scenarios of galactic evolution, essentially based on our knowledge of nearby galaxies have been proposed. Star formation laws, initial mass function, metallicity are the main parameters. The author shortly reviews the present status of these parameters in distant galaxies and gives some deductive conclusions from a comparison with the most distant (z ≥ 3) galaxies.

  3. 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.

  4. 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...

  5. Theories of galaxy formation

    SciTech Connect

    Jones, B.J.T.

    1980-01-01

    The current status of some theories of galaxy formation that are consistent with the hot big bang origin of the universe is reviewed. In the cosmic turbulence theory, an attempt is made to explain not only the characteristic masses and angular momenta of galaxies, but to describe in detail the spectrum of galaxy clustering problems with regard to the observed abundances of the light elements, a Kolmogorov spectrum of turbulence and the fireball are discussed. Attention is given to a primordial chaotic magnetic field, the comparison between baryon-symmetric cosmologies, the origin of galactic spin and theories starting from isothermal perturbations. Also considered are the dilemma of the initial conditions with respect to the era after 10 to the -4th s, and the pancake theory, in which the planar structures that arise provide a natural explanation for filamentary structures.

  6. 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.

  7. Dynamics of Galaxy Interactions

    NASA Astrophysics Data System (ADS)

    Barnes, Joshua E.

    Preface Theory of Interacting Galaxies The Role of Gravity Holmberg's Work on Tidal Interactions "Galactic Bridges and Tails" Dark Matter Numerical Stellar Dynamics Collisionless Stellar Systems Simulating the Stars Force Calculation Time Integration Errors and Relaxation Effects Initial Conditions Numerical Gas Dynamics A Sketch of the Interstellar Medium Simulating the ISM Gas in B/D/H Models Tidal Interactions Test-Particle Studies: Bridges and Tails Self-Consistent Studies Bars and Spirals Tidal Dwarf Galaxies Self-Consistent "Lookalikes" Getting the Feel of the Antennae Sneaking Up on the Mice What Happened to the Whirlpool? Unresolved Issues Mechanics of Merging Tidal Drag Orbit Decay Violent Relaxation Final Encounters Remnant Structure Phase Mixing Characteristics Scales Radial Profiles Shapes and Kinematics Orbit Structure Gas Dynamics in Mergers Inflows in Perturbed Disks Merging Encounters Remnant Structure Dissipation and Stellar Backlash Galaxy transformation and the Arrow of Time

  8. 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.

  9. 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

  10. 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

  11. LOCAL TADPOLE GALAXIES

    SciTech Connect

    Elmegreen, Debra Meloy; Putko, Joseph; Dewberry, Janosz; Elmegreen, Bruce G.; Sanchez Almeida, Jorge; Munoz-Tunon, Casiana

    2012-05-10

    Tadpole galaxies have a giant star-forming region at the end of an elongated intensity distribution. Here we use Sloan Digital Sky Survey data to determine the ages, masses, and surface densities of the heads and tails in 14 local tadpoles selected from the Kiso and Michigan surveys of UV-bright galaxies, and we compare them to tadpoles previously studied in the Hubble Ultra Deep Field. The young stellar mass in the head scales linearly with rest-frame galaxy luminosity, ranging from {approx}10{sup 5} M{sub Sun} at galaxy absolute magnitude U = -13 mag to 10{sup 9} M{sub Sun} at U = -20 mag. The corresponding head surface density increases from several M {sub Sun} pc{sup -2} locally to 10-100 M{sub Sun} pc{sup -2} at high redshift, and the star formation rate (SFR) per unit area in the head increases from {approx}0.01 M{sub Sun} yr{sup -1} kpc{sup -2} locally to {approx}1 M{sub Sun} yr{sup -1} kpc{sup -2} at high z. These local values are normal for star-forming regions, and the increases with redshift are consistent with other cosmological SFRs, most likely reflecting an increase in gas abundance. The tails in the local sample look like bulge-free galaxy disks. Their photometric ages decrease from several Gyr to several hundred Myr with increasing z, and their surface densities are more constant than the surface densities of the heads. The far-outer intensity profiles in the local sample are symmetric and exponential. We suggest that most local tadpoles are bulge-free galaxy disks with lopsided star formation, perhaps from environmental effects such as ram pressure or disk impacts, or from a Jeans length comparable to half the disk size.

  12. 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).

  13. 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

  14. 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.

  15. 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.

  16. Supermassive disk galaxies

    NASA Astrophysics Data System (ADS)

    Buson, L. M.; Galletta, G.; Saglia, R. P.; Zeilinger, W. W.

    1991-03-01

    In order to investigate the properties of supermassive disk galaxies (SDGs), an extensive optical survey of SDG candidates in the Southern Hemisphere was performed with the 2.2-m ESO/MPI telescope at La Silla. The question of whether SDGs have in general an unusually high content of dark matter in the inner regions or, perhaps, an unusual stellar population is addressed. It is suggested that SDGs are formed as the result of a series of accretion events, possibly induced also by the progressive deepening of the galaxy potential well.

  17. Validating a dark galaxy

    NASA Astrophysics Data System (ADS)

    Disney, Michael

    2005-07-01

    VIRGOHI21 is an object detected in the Virgo Cluster HI survey of Davies et al {2004}, with a velocity width typical of a disc galaxy {220 km/s} but which does not appear to have an optical counterpart down to a surface brightness level of 27.5 B mag/sq. arcsec. Altogether, it is the best ever candidate for a Dark Galaxy. We propose to image this object with the ACS through the F814W filter for 9 orbits to see if this object contains a population of individually very faint stars which would be missed by ground-based telescopes.

  18. 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.

  19. 7 CFR 1220.625 - Counting requests.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 7 Agriculture 10 2011-01-01 2011-01-01 false Counting requests. 1220.625 Section 1220.625 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (MARKETING... CONSUMER INFORMATION Procedures To Request a Referendum Definitions § 1220.625 Counting requests. (a)...

  20. 7 CFR 1220.625 - Counting requests.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 7 Agriculture 10 2012-01-01 2012-01-01 false Counting requests. 1220.625 Section 1220.625 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (MARKETING... CONSUMER INFORMATION Procedures To Request a Referendum Definitions § 1220.625 Counting requests. (a)...

  1. 7 CFR 1220.625 - Counting requests.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 7 Agriculture 10 2013-01-01 2013-01-01 false Counting requests. 1220.625 Section 1220.625 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (MARKETING... CONSUMER INFORMATION Procedures To Request a Referendum Definitions § 1220.625 Counting requests. (a)...

  2. 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…

  3. Photon counts from stellar occultation sources

    NASA Technical Reports Server (NTRS)

    Buglia, James J.

    1987-01-01

    The feasibility of using stars as radiation sources for Earth atmospheric occultation experiments is investigated. Exoatmospheric photon counts of the order of 10 to the 6th power photons/sq cm/sec are realized for the 15 visually brightest stars. Most photon counts appear to be marginally detectable unless photomultiplier or cascade detection devices can be used.

  4. 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…

  5. 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…

  6. 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…

  7. 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…

  8. 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

  9. Kids Count in Indiana: 1996 Data Book.

    ERIC Educational Resources Information Center

    Erickson, Judith B.

    This Kids Count report is the third in a series examining statewide trends in the well-being of Indiana's children. The report combines statistics of special concern in Indiana with 10 national Kids Count well-being indicators: (1) percent low birthweight; (2) infant mortality rate; (3) child death rate; (4) birth rate to unmarried teens ages 15…

  10. 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.

  11. Kids Count in Delaware: Fact Book 1999 [and] Families Count in Delaware: Fact Book, 1999.

    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 10 main indicators of child well-being: (1) births to teens; (2) low birth weight babies; (3) infant mortality; (4) child deaths; (5) teen…

  12. 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)…

  13. 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

  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. Supernovae in paired host galaxies

    NASA Astrophysics Data System (ADS)

    Nazaryan, T. A.; Petrosian, A. R.; Hakobyan, A. A.; Adibekyan, V. Zh.; Kunth, D.; Mamon, G. A.; Turatto, M.; Aramyan, L. S.

    2014-12-01

    We investigate the influence of close neighbor galaxies on the properties of supernovae (SNe) and their host galaxies using 56 SNe located in pairs of galaxies with different levels of star formation (SF) and nuclear activity. The mean distance of type II SNe from nuclei of hosts is greater by about a factor of 2 than that of type Ibc SNe. For the first time it is shown that SNe Ibc are located in pairs with significantly smaller difference of radial velocities between components than pairs containing SNe Ia and II. We consider this as a result of higher star formation rate (SFR) of these closer systems of galaxies. SN types are not correlated with the luminosity ratio of host and neighbor galaxies in pairs. The orientation of SNe with respect to the preferred direction toward neighbor galaxy is found to be isotropic and independent of kinematical properties of the galaxy pair.

  16. IRAS observations of active galaxies

    NASA Technical Reports Server (NTRS)

    Neugebauer, G.; Soifer, B. T.; Rowan-Robinson, M.

    1985-01-01

    The IRAS survey gives an unbiased view of the infrared properties of the active galaxies. Seyfert galaxies occupy much the same area in color-color plots as to normal infrared bright galaxies, but extend the range towards flatter 60 to 25 mm slopes. Statistically the Seyfert 1 galaxies can be distinguished from the Seyfert 2 galaxies, lying predominantly closer to the area with constant slopes between 25 and 200 mm. The infrared measurements of the Seyfert galaxies cannot distinguish between the emission mechanisms in these objects although they agree with the currently popular ideas; they do provide a measure of the total luminosity of the Seyferts. The quasar's position in the color-color diagrams continue the trend of the Seyferts. The quasar 3C48 is shown to be exceptional among the radio loud quasars in that it has a high infrared luminosity which dominates the power output of the quasar and is most likely associated with the underlying host galaxy.

  17. 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

  18. The Galaxy Evolution Explorer

    NASA Astrophysics Data System (ADS)

    Martin, Christopher; Barlow, Thomas; Barnhart, William; Bianchi, Luciana; Blakkolb, Brian K.; Bruno, Dominique; Bushman, Joseph; Byun, Yong-Ik; Chiville, Michael; Conrow, Timothy; Cooke, Brian; Donas, Jose; Fanson, James L.; Forster, Karl; Friedman, Peter G.; Grange, Robert; Griffiths, David; Heckman, Timothy; Lee, James; Jelinsky, Patrick N.; Kim, Sug-Whan; Lee, Siu-Chun; Lee, Young-Wook; Liu, Dankai; Madore, Barry F.; Malina, Roger; Mazer, Alan; McLean, Ryan; Milliard, Bruno; Mitchell, William; Morais, Marco; Morrissey, Patrick F.; Neff, Susan G.; Raison, Frederic; Randall, David; Rich, Michael; Schiminovich, David; Schmitigal, Wes; Sen, Amit; Siegmund, Oswald H. W.; Small, Todd; Stock, Joseph M.; Surber, Frank; Szalay, Alexander; Vaughan, Arthur H.; Weigand, Timothy; Welsh, Barry Y.; Wu, Patrick; Wyder, Ted; Xu, C. Kevin; Zsoldas, Jennifer

    2003-02-01

    The Galaxy Evolution Explorer (GALEX), a NASA Small Explorer Mission planned for launch in Fall 2002, will perform the first Space Ultraviolet sky survey. Five imaging surveys in each of two bands (1350-1750Å and 1750-2800Å) will range from an all-sky survey (limit mAB~20-21) to an ultra-deep survey of 4 square degrees (limit mAB~26). Three spectroscopic grism surveys (R=100-300) will be performed with various depths (mAB~20-25) and sky coverage (100 to 2 square degrees) over the 1350-2800Å band. The instrument includes a 50 cm modified Ritchey-Chrétien telescope, a dichroic beam splitter and astigmatism corrector, two large sealed tube microchannel plate detectors to simultaneously cover the two bands and the 1.2 degree field of view. A rotating wheel provides either imaging or grism spectroscopy with transmitting optics. We will use the measured UV properties of local galaxies, along with corollary observations, to calibrate the UV-global star formation rate relationship in galaxies. We will apply this calibration to distant galaxies discovered in the deep imaging and spectroscopic surveys to map the history of star formation in the universe over the red shift range zero to two. The GALEX mission will include an Associate Investigator program for additional observations and supporting data analysis. This will support a wide variety of investigations made possible by the first UV sky survey.

  19. 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.

  20. 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.

  1. Automated galaxy recognition

    NASA Astrophysics Data System (ADS)

    Rappaport, Barry; Anderson, Kurt

    Previous approaches to automated image processing have used both deterministic and nondeterministic techniques. These have not used any form of conceptual learning nor have they employed artificial intelligence techniques. Addition of such techniques to the task of image processing may significantly enhance the efficiencies and accuracies of the recognition and classification processes. In our application, the objects to be recognized and classified are galaxies.

  2. 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)

  3. Tides in Colliding Galaxies

    NASA Astrophysics Data System (ADS)

    Duc, Pierre-Alain; Renaud, Florent

    Long tails and streams of stars are the most noticeable traces of galaxy collisions. However, their tidal origin was recognized only less than 50 years ago and more than 10 years after their first observations. This review describes how the idea of galactic tides has emerged thanks to advances in numerical simulations, from the first simulations that included tens of particles to the most sophisticated ones with tens of millions of them and state-of-the-art hydrodynamical prescriptions. Theoretical aspects pertaining to the formation of tidal tails are then presented. The third part turns to observations and underlines the need for collecting deep multi-wavelength data to tackle the variety of physical processes exhibited by collisional debris. Tidal tails are not just stellar structures, but turn out to contain all the components usually found in galactic disks, in particular atomic/molecular gas and dust. They host star-forming complexes and are able to form star-clusters or even second-generation dwarf galaxies. The final part of the review discusses what tidal tails can tell us (or not) about the structure and the content of present-day galaxies, including their dark components, and explains how they may be used to probe the past evolution of galaxies and the history of their mass assembly. On-going deep wide-field surveys disclose many new low-surface brightness structures in the nearby Universe, offering great opportunities for attempting galactic archeology with tidal tails.

  4. 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

  5. Uncovering blue diffuse dwarf galaxies

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

    Extremely metal poor (XMP) galaxies are known to be very rare, despite the large numbers of low-mass galaxies predicted by the local galaxy luminosity function. This paper presents a subsample of galaxies that were selected via a morphology-based search on Sloan Digital Sky Survey images with the aim of finding these elusive XMP galaxies. By using the recently discovered XMP galaxy, Leo P, as a guide, we obtained a collection of faint, blue systems, each with isolated H II regions embedded in a diffuse continuum, that have remained optically undetected until now. Here we show the first results from optical spectroscopic follow-up observations of 12 of ˜100 of these blue diffuse dwarf (BDD) galaxies yielded by our search algorithm. Oxygen abundances were obtained via the direct method for eight galaxies, and found to be in the range 7.45 < 12 + log (O/H) < 8.0, with two galaxies being classified as XMPs. All BDDs were found to currently have a young star-forming population (<10 Myr) and relatively high ionization parameters of their H II regions. Despite their low luminosities (-11 ≲ MB ≲ -18) and low surface brightnesses (˜23-25 mag arcsec-2), the galaxies were found to be actively star forming, with current star formation rates between 0.0003 and 0.078 M⊙ yr-1. From our current subsample, BDD galaxies appear to be a population of non-quiescent dwarf irregular galaxies, or the diffuse counterparts to blue compact galaxies and as such may bridge the gap between these two populations. Our search algorithm demonstrates that morphology-based searches are successful in uncovering more diffuse metal-poor star-forming galaxies, which traditional emission-line-based searches overlook.

  6. 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

  7. 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.

  8. Where do Galaxies End?

    NASA Astrophysics Data System (ADS)

    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 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 vir(M *, Mh , za ) for stellar mass M * and halo mass Mh , half of which formed at "assembly redshifts" ranging from za ≈ 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 langR virrang ≈ 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 * = 10.7 ± 0.1, would correspond to R_vir = 153^{+25}_{-16} kpc for half-mass halo assembly at za = 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.

  9. Non-circular motion estimation of the grand-design spiral galaxy NGC 628

    NASA Astrophysics Data System (ADS)

    Colombo, D.

    2013-09-01

    I present a harmonic decomposition analysis of the grand-design spiral galaxy NGC 628 using the H I data from The H I Nearby Galaxy Survey (THINGS), Walter et al., Astron. J. 136, 2563 (2008). The harmonic decomposition analysis allows the estimation of the peculiar motion magnitude of the galaxy not counted in the rotation of the disk. The rotation curve is obtained through a tilted ring analysis and reaches a maximum velocity not higher than 200 km s-1. The residual from the velocity field shows a morphology shift from a m = 1 to a m = 3 feature at R = 120", typical of two spiral arms perturbation of the potential. The non-circular motion have a magnitude of ~10 km s-1, in agreement with previous studies of similar Hubble type galaxies.

  10. Assigning Star-galaxy Probabilities to SDSS Stripe 82 Point Sources

    NASA Astrophysics Data System (ADS)

    Preston, Annie; Willman, B.; Fadely, R.; Bochanski, J. J.; Hogg, D. W.

    2013-01-01

    Sloan Digital Sky Survey (SDSS) Stripe 82 imaging covers 275 deg^2 in ugriz. Reaching ~ 1-2 magnitudes deeper than the SDSS main survey (50% point source completeness at r ~24.2 mag), the public Stripe 82 catalog provides new opportunities in Galactic structure, weak lensing, and large scale structure. However, at magnitudes fainter than r ~ 22, unresolved galaxies dominate star counts in the point source catalog. The resulting contamination of point sources by galaxies can be mitigated by using multi-color information to derive star-galaxy probabilities. In this poster, we quantify the expected demographics of the Stripe 82 point source catalog. We use ugriz magnitudes to assign star-galaxy classification probabilities to Stripe 82 point sources with maximum likelihood, hierarchical Bayesian, and SVM techniques. We thank NSF AST-0908193 and NSF AST-1151462 for support.

  11. Weak lensing effects on the galaxy three-point correlation function

    SciTech Connect

    Schmidt, Fabian; Vallinotto, Alberto; Sefusatti, Emiliano; Dodelson, Scott

    2008-08-15

    We study the corrections to the galaxy three-point correlation function induced by weak lensing magnification due to the matter distribution along the line of sight. We consistently derive all the correction terms arising up to second order in perturbation theory and provide analytic expressions as well as order-of-magnitude estimates for their relative importance. The magnification contributions depend on the geometry of the projected triangle on the sky plane and scale with different powers of the number count slope and redshift of the galaxy sample considered. We evaluate all terms numerically and show that, depending on the triangle configuration as well as the galaxy sample considered, weak lensing can in general significantly contribute to and alter the three-point correlation function observed through galaxy and quasar catalogs.

  12. Cosmic Infrared Background and Early Galaxy Evolution

    NASA Technical Reports Server (NTRS)

    Kashlinsky, Alexander

    2005-01-01

    The cosmic infrared background (CIB) reflects the sum total of galactic luminosities integrated over the entire age of the universe. From its measurement the red-shifted starlight and dust-absorbed and re-radiated starlight of the CIB can be used to determine (or constrain) the rates of star formation and metal production as a function of time and deduce information about objects at epochs currently inaccessible to telescopic studies. This review discusses the state of current CIB measurements and the (mostly space-based) instruments with which these measurements have been made, the obstacles (the various foreground emissions) and the physics behind the CIB and its structure. Theoretical discussion of the CIB levels can now be normalized to the standard cosmological model narrowing down theoretical uncertainties. We review the information behind and theoretical modeling of both the mean (isotropic) levels of the CIB and their fluctuations. The CIB is divided into three broad bands: near-IR (NIR), mid-IR (MIR) and far-IR (FIR). For each of the bands we review the main contributors to the CIB flux and the epochs at which the bulk of the flux originates. We also discuss the data on the various quantities relevant for correct interpretation of the CIB levels: the star-formation history, the present-day luminosity function measurements, resolving the various galaxy contributors to the CIB, etc. The integrated light of all galaxies in the deepest NIR galaxy counts to date fails to match the observed mean level of the CIB, probably indicating a significant high-redshift contribution to the CIB. Additionally, Population III stars should have left a strong and measurable signature via their contribution to the CIB anisotropies for a wide range of their formation scenarios, and measuring the excess CIB anisotropies coming from high z would provide direct information on the epoch of the first stars.

  13. 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%.

  14. 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.

  15. 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.

  16. 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

  17. THE GALAXY LUMINOSITY FUNCTION DURING THE REIONIZATION EPOCH

    SciTech Connect

    Trenti, M.; Shull, J. M.; Stiavelli, M.; Bradley, L. D.; Bouwens, R. J.; Illingworth, G. D.; Oesch, P.; Carollo, C. M.

    2010-05-10

    The new Wide Field Camera 3/IR observations on the Hubble Ultra-Deep Field (HUDF) started investigating the properties of galaxies during the reionization epoch. To interpret these observations, we present a novel approach inspired by the conditional luminosity function method. We calibrate our model to observations at z = 6 and assume a non-evolving galaxy luminosity versus halo mass relation. We first compare model predictions against the luminosity function (LF) measured at z = 5 and z = 4. We then predict the LF at z {>=} 7 under the sole assumption of evolution in the underlying dark-matter halo mass function. Our model is consistent with the observed z {approx_gt} 7 galaxy number counts in the HUDF survey and suggests a possible steepening of the faint-end slope of the LF: {alpha}(z {approx_gt} 8) {approx_lt} -1.9 compared to {alpha} = -1.74 at z = 6. Although we currently see only the brightest galaxies, a hidden population of lower luminosity objects (L/L {sub *} {approx_gt} 10{sup -4}) might provide {approx_gt}75% of the total reionizing flux. Assuming escape fraction f {sub esc} {approx} 0.2, clumping factor C {approx} 5, top-heavy initial mass function (IMF), and low metallicity, galaxies below the detection limit produce complete reionization at z {approx_gt} 8. For solar metallicity and normal stellar IMF, reionization finishes at z {approx_gt} 6, but a smaller C/f {sub esc} is required for an optical depth consistent with the Wilkinson Microwave Anisotropy Probe measurement. Our model highlights that the star formation rate in sub-L {sub *} galaxies has a quasi-linear relation to dark-matter halo mass, suggesting that radiative and mechanical feedback were less effective at z {>=} 6 than today.

  18. 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.

  19. 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.

  20. 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.

  1. 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

  2. Detecting gravitationally lensed Population III galaxies with the Hubble Space Telescope and the James Webb Space Telescope

    NASA Astrophysics Data System (ADS)

    Zackrisson, Erik; Zitrin, Adi; Trenti, Michele; Rydberg, Claes-Erik; Guaita, Lucia; Schaerer, Daniel; Broadhurst, Tom; Östlin, Göran; Ström, Tina

    2012-12-01

    Small galaxies consisting entirely of Population III (pop III) stars may form at high redshifts, and could constitute one of the best probes of such stars. Here, we explore the prospects of detecting gravitationally lensed pop III galaxies behind the galaxy cluster J0717.5+3745 (J0717) with both the Hubble Space Telescope (HST) and the upcoming James Webb Space Telescope (JWST). By projecting simulated catalogues of pop III galaxies at z ≈ 7-15 through the J0717 magnification maps, we estimate the lensed number counts as a function of flux detection threshold. We find that the ongoing HST survey Cluster Lensing And Supernova survey with Hubble (CLASH), targeting a total of 25 galaxy clusters including J0717, potentially could detect a small number of pop III galaxies if ˜1 per cent of the baryons in these systems have been converted into pop III stars. Using JWST exposures of J0717, this limit can be pushed to ˜0.1 per cent of the baryons. Ultradeep JWST observations of unlensed fields are predicted to do somewhat worse, but will be able to probe pop III galaxies with luminosities intermediate between those detectable in HST/CLASH and in JWST observations of J0717. We also explain how current measurements of the galaxy luminosity function at z = 7-10 can be used to constrain pop III galaxy models with very high star formation efficiencies (˜10 per cent of the baryons converted into pop III stars).

  3. 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.

  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. 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.

  6. 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.

  7. 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.

  8. 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.

  9. Time Variant Floating Mean Counting Algorithm

    Energy Science and Technology Software Center (ESTSC)

    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.

  10. Clicks counting system for a riflescope

    NASA Astrophysics Data System (ADS)

    Drumea, Andrei; Granciu, Dana

    2015-02-01

    A very useful requirement for a zoom aiming scope with high magnification used for long range rifle shooting is counting and display of knob's clicks number needed for elevation corrections. The paper analyzes one method for clicks counting usable with existing mechanical knobs and describes a microcontroller based system that implements it. Practical aspects like required changes in mechanical construction, influence of perturbations, complexity of electronics or power consumption are also analyzed.

  11. 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.

  12. Results and analyses of faint field galaxy surveys with the Keck Telescope

    NASA Astrophysics Data System (ADS)

    Hogg, D. W.

    1996-12-01

    A large collaboration at Caltech has been using the Keck and other telescopes to perform UBVRIKL imaging and take spectra of faint galaxies. The spectroscopic samples contain several hundred objects to K=20 mag or R=24 mag and the imaging samples contain thousands of sources to R~ 27. Faint field galaxies are found to be strongly clustered in velocity space; the angular coherence, masses and morphologies in configuration space of these structures are investigated. In cooperation with the University of Hawaii group, the luminosity function of galaxies is computed in the near-infrared; strong evolution is found in the number of low-luminosity galaxies to z~ 1, although the statistical properties of high-luminosity objects are relatively constant. A range of models for the faint galaxy counts are constructed, not on the basis of a priori information about galaxy properties (from, say, cosmogonic theory) but rather by ``inverting'' the data under a range of qualitatively distinct simplifying assumptions. Predictions are made for ongoing or future imaging and spectroscopy surveys which will clearly distinguish the models. The prospects for a ``meta-analysis'' of a large collection of heterogeneous surveys to create consistent galaxy evolution models from z=0 to the highest observed redshifts are discussed.

  13. Power counting to better jet observables

    NASA Astrophysics Data System (ADS)

    Larkoski, Andrew J.; Moult, Ian; Neill, Duff

    2014-12-01

    Optimized jet substructure observables for identifying boosted topologies will play an essential role in maximizing the physics reach of the Large Hadron Collider. Ideally, the design of discriminating variables would be informed by analytic calculations in perturbative QCD. Unfortunately, explicit calculations are often not feasible due to the complexity of the observables used for discrimination, and so many validation studies rely heavily, and solely, on Monte Carlo. In this paper we show how methods based on the parametric power counting of the dynamics of QCD, familiar from effective theory analyses, can be used to design, understand, and make robust predictions for the behavior of jet substructure variables. As a concrete example, we apply power counting for discriminating boosted Z bosons from massive QCD jets using observables formed from the n-point energy correlation functions. We show that power counting alone gives a definite prediction for the observable that optimally separates the background-rich from the signal-rich regions of phase space. Power counting can also be used to understand effects of phase space cuts and the effect of contamination from pile-up, which we discuss. As these arguments rely only on the parametric scaling of QCD, the predictions from power counting must be reproduced by any Monte Carlo, which we verify using Pythia 8 and Herwig++. We also use the example of quark versus gluon discrimination to demonstrate the limits of the power counting technique.

  14. Contribution of hand motor circuits to counting.

    PubMed

    Andres, Michael; Seron, Xavier; Olivier, Etienne

    2007-04-01

    The finding that number processing activates a cortical network partly overlapping that recruited for hand movements has renewed interest in the relationship between number and finger representations. Further evidence about a possible link between fingers and numbers comes from developmental studies showing that finger movements play a crucial role in learning counting. However, increased activity in hand motor circuits during counting may unveil unspecific processes, such as shifting attention, reciting number names, or matching items with a number name. To address this issue, we used transcranial magnetic stimulation to measure changes in corticospinal (CS) excitability during a counting task performed silently and using either numbers or letters of the alphabet to enumerate items. We found an increased CS excitability of hand muscles during the counting task, irrespective of the use of numbers or letters, whereas it was unchanged in arm and foot muscles. Control tasks allowed us to rule out a possible influence of attention allocation or covert speech on CS excitability increase of hand muscles during counting. The present results support a specific involvement of hand motor circuits in counting because no CS changes were found in arm and foot muscles during the same task. However, the contribution of hand motor areas is not exclusively related to number processing because an increase in CS excitability was also found when letters were used to enumerate items. This finding suggests that hand motor circuits are involved whenever items have to be put in correspondence with the elements of any ordered series. PMID:17381248

  15. Factors affecting leukocyte count in healthy adults.

    PubMed

    Carel, R S; Eviatar, J

    1985-09-01

    The relationships between white blood cell (WBC) count, smoking, and other health variables were determined among 35,000 apparently healthy men and women. The effect of smoking on the WBC count was greater than that of all other variables. The leukocyte level and the variance in WBC count values increased with increased smoking intensity. The relationship between smoking intensity and leukocyte level is expressed quantitatively by the following regression equation: WBC (10(3)/mm3) = 7.1 + 0.05(SM), where SM has seven values according to the smoking level. Multiple regression analysis with additional variables other than smoking did not much improve the predictive value of the equation. The effect of smoking on WBC count could be only partially explained by an inflammatory process, e.g., chronic bronchitis. Relationships of statistical significance (but mostly with r values of less than 0.10) were found between WBC count and the following variables: hemoglobin, heart rate, weight (or Quetelet index), cholesterol, uric acid, creatinine, sex, ethnic origin, systolic blood pressure, height, blood sugar, and diastolic blood pressure. The normal WBC count range for smokers differs from that of nonsmokers and is shifted to the right according to the smoking level. This may have both a diagnostic and prognostic significance in different clinical settings. PMID:4070192

  16. The Hubble Space Telescope Wide Field Camera 3 Early Release Science Data: Panchromatic Faint Object Counts for 0.2-2 μm Wavelength

    NASA Astrophysics Data System (ADS)

    Windhorst, Rogier A.; Cohen, Seth H.; Hathi, Nimish P.; McCarthy, Patrick J.; Ryan, Russell E., Jr.; Yan, Haojing; Baldry, Ivan K.; Driver, Simon P.; Frogel, Jay A.; Hill, David T.; Kelvin, Lee S.; Koekemoer, Anton M.; Mechtley, Matt; O'Connell, Robert W.; Robotham, Aaron S. G.; Rutkowski, Michael J.; Seibert, Mark; Straughn, Amber N.; Tuffs, Richard J.; Balick, Bruce; Bond, Howard E.; Bushouse, Howard; Calzetti, Daniela; Crockett, Mark; Disney, Michael J.; Dopita, Michael A.; Hall, Donald N. B.; Holtzman, Jon A.; Kaviraj, Sugata; Kimble, Randy A.; MacKenty, John W.; Mutchler, Max; Paresce, Francesco; Saha, Abihit; Silk, Joseph I.; Trauger, John T.; Walker, Alistair R.; Whitmore, Bradley C.; Young, Erick T.

    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 (Ys ), 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 arcmin2 at 0.2-1.7 μm in wavelength at 0farcs07-0farcs15 FWHM resolution and 0farcs090 Multidrizzled pixels to depths of AB sime 26.0-27.0 mag (5σ) for point sources, and AB sime 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 0farcs07-0farcs15 FWHM resolution of HST/WFC3 and ACS makes star-galaxy separation straightforward over a factor of 10 in wavelength to AB sime 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-1 (4.6σ), 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 <~ AB lsim 20 mag) and the Hubble Ultra Deep Field counts in the BVizYsJH filters at the faint end (24 mag <~ AB lsim 30 mag) yields galaxy counts that are well measured over the entire

  17. 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

  18. Galaxy collisions - A preliminary study

    NASA Technical Reports Server (NTRS)

    Miller, R. H.; Smith, B. F.

    1980-01-01

    Collisions of spherical galaxies were studied in a series of numerical experiments to see what happens when galaxies collide. Each experiment starts with two model galaxies, each consisting of 50,000 stars, moving toward each other along a specified orbit. The series of experiments provides a systematic sampling of the parameter space spanned by the initial orbital energy and the initial angular momentum. Deeply penetrating collisions are emphasized. The collisions reported here scale to relative velocities as great as 500 km/s, well into the range for collisions within clusters of galaxies. It is found that: (1) the galaxies contract momentarily to about half their original sizes shortly after close passage; and (2) the initial galaxies blend into a single dynamical system while they are near each other.

  19. Applying galactic archeology to massive galaxies using deep imaging surveys

    NASA Astrophysics Data System (ADS)

    Duc, Pierre-Alain

    2015-04-01

    Various programs aimed at exploring the still largely unknown low surface brightness Universe with deep imaging optical surveys have recently started. They open a new window for studies of galaxy evolution, pushing the technique of galactic archeology outside the Local Group (LG). The method, based on the detection and analysis of the diffuse light emitted by collisional debris or extended stellar halos (rather than on stellar counts as done for LG systems), faces however a number of technical difficulties, like the contamination of the images by reflection halos and Galactic cirrus. I review here the on-going efforts to address them and highlight the preliminary promising results obtained with a systematic survey with MegaCam on the CFHT of nearby massive early-type galaxies done as part of the ATLAS3D, NGVS and MATLAS collaborations.

  20. Young Elliptical Galaxies

    NASA Astrophysics Data System (ADS)

    Kim, Dong-Woo

    2005-10-01

    We propose deep XMM-Newton observations of two young, post-merger elliptical galaxies, NGC 3377 and NGC 5018. Because their X-ray to optical luminosity ratios are the lowest among ellipticals and their stellar populations are significantly metal-enriched, they are the best candidates to address two biggest unsolved problems of the X-ray study of elliptical galaxies: large L_X/L_B scatter and ISM Fe discrepancy. Our XMM-Newton data, in conjunction with the existing Chandra data will allow us to accurately determine Fe and alpha-elements abundances. We will then address the origin of the large L_X/L_B scatter in terms of ISM removal mechanisms by merger-induced galactic winds.

  1. Spokes in ring galaxies

    NASA Technical Reports Server (NTRS)

    Hernquist, Lars; Weil, Melinda L.

    1993-01-01

    We examine the response of self-gravitating primary galaxies consisting of dark matter halos and disks containing both stars and gas to collisions with less massive companions. The primaries were constructed using a technique which makes it possible to realize multi-component systems that are stable and virtually in precise equilibrium. A total of 65,536 particles were employed to represent the primary and 4096 to represent the companion. Half the particles in the primary comprise its halo and the other half its disk. Gas makes up 10 percent of the disk mass and is represented by 8192 of the disk particles. A system of units is used where the gravitational constant, total disk mass, and disk exponential scale length are unity. The primary motivation of the present study is to determine whether effects associated with dissipation and self-gravity can account for the unusual morphology of the Cartwheel galaxy.

  2. The Galaxy's Eating Habits

    NASA Astrophysics Data System (ADS)

    Putman, M. E.; Thom, C.; Gibson, B. K.; Staveley-Smith, L.

    2004-06-01

    The possibility of a gaseous halo stream which was stripped from the Sagittarius dwarf galaxy is presented. The total mass of the neutral hydrogen along the orbit of the Sgr dwarf in the direction of the Galactic Anti-Center is 4 - 10 × 106 M⊙ (at 36 kpc, the distance to the stellar debris in this region). Both the stellar and gaseous components have negative velocities in this part of the sky, but the gaseous component extends to higher negative velocities. We suggest this gaseous stream was stripped from the main body of the dwarf 0.2 - 0.3 Gyr ago during its current orbit after a passage through a diffuse edge of the Galactic disk with a density > 10-4 cm-3. The gas would then represent the dwarf's last source of star formation fuel and explains how the galaxy was forming stars 0.5-2 Gyr ago.

  3. 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.

  4. 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.

  5. Abundances in dwarf irregular galaxies

    NASA Technical Reports Server (NTRS)

    Dufour, Reginald J.

    1986-01-01

    The results of abundance studies of dwarf irregular galaxies and similar objects are reviewed with special attention to variations in the CNO element group. Observations of the forbidden N II and semiforbidden C III lines in the most metal-poor galaxy known, IZw 18, are presented for the first time and CNO abundances are derived via a photoionization model and discussed in the context of the abundances found in other metal-poor H II regions and galaxies.

  6. Very high redshift radio galaxies

    SciTech Connect

    van Breugel, W.J.M., LLNL

    1997-12-01

    High redshift radio galaxies (HzRGs) provide unique targets for the study of the formation and evolution of massive galaxies and galaxy clusters at very high redshifts. We discuss how efficient HzRG samples ae selected, the evidence for strong morphological evolution at near-infracd wavelengths, and for jet-induced star formation in the z = 3 800 HzRG 4C41 17

  7. 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.

  8. Structural Properties of Barred Galaxies

    NASA Astrophysics Data System (ADS)

    Kim, Taehyun; Gadotti, D. A.; Sheth, K.; Lee, M.; S4G Team

    2014-01-01

    We have performed two-dimensional multicomponent decomposition of 144 local barred spiral galaxies using 3.6 micron images from the Spitzer Survey of Stellar Structure in Galaxies. Our model fit includes up to four components (bulge, disk, bar, and a point source) and, most importantly, takes into account disk breaks. We present that ignoring the disk break and using a single disk scale length in the model fit for Type II (down- bending) disk galaxies can lead to differences of 40% in the disk scale length, 10% in bulge-to-total luminosity ratio (B/T), and 25% in bar-to-total luminosity ratios. We show that for galaxies with B/T > 0.1, the break radius to bar radius, r_br/R_bar, varies between 1 and 3, but as a function of B/T the ratio remains roughly constant. This suggests that in bulge-dominated galaxies the disk break is likely related to the outer Lindblad Resonance (OLR) of the bar, and thus the OLR also moves outwards at the same rate as the bar grows. For galaxies with B/T < 0.1, r_br/R_bar, spans a wide range from 1 to 6. This suggests that the mechanism that produces the break in these galaxies may be different from that in galaxies with more massive bulges. Consistent with previous studies, we conclude that disk breaks in galaxies with small bulges may originate from bar resonances that may be also coupled with the spiral arms, or be related to star formation thresholds. We quantifiy shapes of bar radial surface brightness profiles by measuring their Sersic indices and show that bars in higher B/T galaxies have flatter radial surface brightness profile than bulgeless galaxies do. In particular, bulgeless galaxies mostly have bars with steep profiles. We show that the normalized bar length is correlated with B/T, which is consistent with bars growing longer with time.

  9. ARCHANGEL: Galaxy Photometry System

    NASA Astrophysics Data System (ADS)

    Schombert, James

    2011-07-01

    ARCHANGEL is a Unix-based package for the surface photometry of galaxies. While oriented for large angular size systems (i.e. many pixels), its tools can be applied to any imaging data of any size. The package core contains routines to perform the following critical galaxy photometry functions: sky determinationframe cleaningellipse fittingprofile fittingtotal and isophotal magnitudes The goal of the package is to provide an automated, assembly-line type of reduction system for galaxy photometry of space-based or ground-based imaging data. The procedures outlined in the documentation are flux independent, thus, these routines can be used for non-optical data as well as typical imaging datasets. ARCHANGEL has been tested on several current OS's (RedHat Linux, Ubuntu Linux, Solaris, Mac OS X). A tarball for installation is available at the download page. The main routines are Python and FORTRAN based, therefore, a current installation of Python and a FORTRAN compiler are required. The ARCHANGEL package also contains Python hooks to the PGPLOT package, an XML processor and network tools which automatically link to data archives (i.e. NED, HST, 2MASS, etc) to download images in a non-interactive manner.

  10. 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.

  11. 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.

  12. 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.

  13. The Assembly of Galaxy Groups

    NASA Astrophysics Data System (ADS)

    Ponman, Trevor

    2001-09-01

    The most interesting phase in the evolution of a galaxy group is the virialisation stage, at which the infall velocities of the galaxies are randomised and the interstellar gas compressed and heated. The violently fluctuating environment experienced by galaxies during this phase may have long-lasting effects on their properties. Such virialising groups appear to be quite rare, since the phase is transient, but we have identified three strong candidates from an extensive study of groups with ROSAT. We propose to obtain high quality spectral images of these with ACIS in order to study the way in which the intergalactic medium is heated, and the effects of strong interactions on galaxy properties.

  14. 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

  15. Chemical Signatures in Dwarf Galaxies

    NASA Astrophysics Data System (ADS)

    Venn, Kim A.; Hill, Vanessa M.

    2008-12-01

    Chemical signatures in dwarf galaxies describe the examination of specific elemental abundance ratios to investigate the formation and evolution of dwarf galaxies, particularly when compared with the variety of stellar populations in the Galaxy. Abundance ratios can come from HII region emission lines, planetary nebulae, or supernova remnants, but mostly they come from stars. Since stars can live a very long time, for example, a 0.8 MSun star born at the time of the Big Bang would only now be ascending the red giant branch, and, if, for the most part, its quiescent main sequence lifetime had been uneventful, then it is possible that the surface chemistry of stars actually still resembles their natal chemistry. Detailed abundances of stars in dwarf galaxies can be used to reconstruct their chemical evolution, which we now find to be distinct from any other component of the Galaxy, questioning the assertion that dwarf galaxies like these built up the Galaxy. Potential solutions to reconciling dwarf galaxy abundances and Galaxy formation models include the timescale for significant merging and the possibility for uncovering different stellar populations in the new ultra-faint dwarfs.

  16. 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.

  17. Colliding Galaxies: Hubble Space Telescope

    NASA Astrophysics Data System (ADS)

    1997-10-01

    NASA's Hubble Space Telescope looks deep within the violent center where the two Antennae Galaxies were merging. The Hubble's high resolution and sensitivity reveals the birth of young star clusters formed in the collision. New Hubble images of young star clusters help investigators put the evolutionary sequence into the right order. The Hubble Space Telescope images are: (1) zoom into the antennae galaxies; (2) galaxy merger evolution sequence; (3) the formation of the antennae pair; and (4) artist's conception of the collision of Milky-Way Galaxy with the Andromeda.

  18. 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.

  19. Giant disc galaxies: where environment trumps mass in galaxy evolution

    NASA Astrophysics Data System (ADS)

    Courtois, H. M.; Zaritsky, D.; Sorce, J. G.; Pomarède, D.

    2015-04-01

    We identify some of the most H I-massive and fastest rotating disc galaxies in the local universe with the aim of probing the processes that drive the formation of these extreme disc galaxies. By combining data from the Cosmic Flows project, which has consistently reanalysed archival galaxy H I profiles, and 3.6 μm photometry obtained with the Spitzer Space Telescope, with which we can measure stellar mass, we use the baryonic Tully-Fisher (BTF) relationship to explore whether these massive galaxies are distinct. We discuss several results, but the most striking is the systematic offset of the H I-massive sample above the BTF. These galaxies have both more gas and more stars in their discs than the typical disc galaxy of similar rotational velocity. The `condensed' baryon fraction, fC, the fraction of the baryons in a dark matter halo that settle either as cold gas or stars into the disc, is twice as high in the H I-massive sample than typical, and almost reaches the universal baryon fraction in some cases, suggesting that the most extreme of these galaxies have little in the way of a hot baryonic component or cold baryons distributed well outside the disc. In contrast, the star formation efficiency, measured as the ratio of the mass in stars to that in both stars and gas, shows no difference between the H I-massive sample and the typical disc galaxies. We conclude that the star formation efficiency is driven by an internal, self-regulating process, while fC is affected by external factors. Neither the morphology nor the star formation rate of these galaxies is primarily determined by either their dark or stellar mass. We also found that the most massive H I detected galaxies are located preferentially in filaments. We present the first evidence of an environmental effect on galaxy evolution using a dynamical definition of a filament.

  20. Giant disk galaxies : Where environment trumps mass in galaxy evolution

    NASA Astrophysics Data System (ADS)

    Courtois, Helene M.; Zaritsky, Dennis; Sorce, Jenny G.; Pomarede, Daniel

    2015-08-01

    We identify some of the most HI massive and fastest rotating disk galaxies in the local universe with the aim of probing the processes that drive the formation of these extreme disk galaxies. By combining data from the Cosmic Flows project, which has consistently reanalyzed archival galaxy HI profiles, and 3.6 micron photometry obtained with the Spitzer Space Telescope, with which we can measure stellar mass, we use the baryonic Tully-Fisher relationship to explore whether these massive galaxies are distinct.We discuss several results, but the most striking is the systematic offset of the HI-massive sample above the baryonic Tully-Fisher. These galaxies have both more gas and more stars in their disks than the typical disk galaxy of similar rotational velocity. The ``condensed" baryon fraction, fC, the fraction of the baryons in a dark matter halo that settle either as cold gas or stars into the disk, is twice as high in the HI-massive sample than typical, and almost reaches the universal baryon fraction in some cases, suggesting that the most extreme of these galaxies have little in the way of a hot baryonic component or cold baryons distributed well outside the disk. In contrast, the star formation efficiency, measured as the ratio of the mass in stars to that in both stars and gas, shows no difference between the HI-massive sample and the typical disk galaxies. We conclude that the star formation efficiency is driven by an internal, self-regulating process, while fC is affected by external factors. Neither the morphology nor the star formation rate of these galaxies is primarily determined by either their dark or stellar mass. We also found that the most massive HI detected galaxies are located preferentially in filaments. We present the first evidence of an environmental effect on galaxy evolution using a dynamical definition of a filament.

  1. 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.

  2. Deep 2mm Surveys with GISMO : Searching for submillimeter galaxies at the highest redshifts

    NASA Astrophysics Data System (ADS)

    Staguhn, Johannes Gunter; Kovacs, Attila; Karim, Alexander; Arendt, Richard; Benford, Dominic J.; Decarli, Roberto; Dwek, Eli; Fixsen, Dale; Gene, Hilton; Irwin, Kent; Moseley, S. Harvey; Sharp, Elmer; Walter, Fabian; Edward, Wollack

    2015-08-01

    The GISMO 2 mm camera at the IRAM 30m telescope has been available to the astronomical community for years through the semi-annual IRAM call for proposals. The 2 mm band is in particular well suited to trace the first dusty galaxies in the universe, since their redshifted SEDs peak close to GISMO's observing frequency, whereas the medium redshift galaxy foreground is almost invisible in this band. This effect makes GISMO's deep field observations a valuable complement, rather than a redundancy, to the HERSCHEL far-infrared and sub-mm surveys. Two survey projects aiming at obtaining 2mm galaxy number counts are at the core of GISMO’s science. Simple models predict an appreciable number of galaxies detected in these surveys to be be at very high redshifts (z~5-6 and above) with intrinsic luminosities of a few 10^12 L_sol.The first of these projects is the GISMO Deep Field (GDF) survey, which is centered on the Hubble Deep Field North. This survey by now has reached the confusion limit (we measure a confusion noise of 60 microJy). Our detailed statistical analysis of the GDF data provides a solid estimate of the expected rate of false detections among those source identifications. Furthermore, numerical simulations were used, to estimate the "completeness" of our set of extracted sources. A comparison of our observations with model predictions shows that our results are in good agreement with galaxy count models.The second survey covers a ~ 1/4 square degree region in the COSMOS field, in which by now we have obtained sufficient sensitivity to extract statistically relevant galaxy number counts, and by using auxiliary data, redshift distributions. We will present first results that complement those obtained in the deeper GDF.

  3. 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.

  4. 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.

  5. 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.

  6. Density normalization of the thick disc of the Galaxy

    NASA Astrophysics Data System (ADS)

    Evans, Dafydd Wyn

    1987-07-01

    In the present resolution of the discrepancy between the 10-percent value of Sandage and Fouts (1987) and the 2-percent value of Gilmore and Reid (1983) for the normalization of the thick disk of the Galaxy relative to the thin disk, it is demonstrated that the former work's density laws, in combination with that 10-percent normalization figure, are inconsistent with star count data from the Hazard 8-Hour Field. It is also shown that a local thick disk normalization of 10 percent is compatible with Gilmore and Reid's exponential density law normalization of 2 percent.

  7. An excess of star-forming galaxies in the fields of high-redshift QSOs

    NASA Astrophysics Data System (ADS)

    Stevens, J. A.; Jarvis, Matt J.; Coppin, K. E. K.; Page, M. J.; Greve, T. R.; Carrera, F. J.; Ivison, R. J.

    2010-07-01

    We present submillimetre (submm) and mid-infrared (MIR) imaging observations of five fields centred on quasi-stellar objects (QSOs) at 1.7< z<2.8. All five QSOs were detected previously at submm wavelengths. At 850 (450) m, we detect 17 (11) submillimetre galaxies (SMGs) in addition to the QSOs. The total area mapped at 850 m is arcmin2 down to rms noise levels of 1-2 mJybeam-1, depending on the field. Integral number counts are computed from the 850-m data using the same analytical techniques adopted by `blank-field' submm surveys. We find that the `QSO-field' counts show a clear excess over the blank-field counts at deboosted flux densities of mJy at higher flux densities, the counts are consistent with the blank-field counts. Robust MIR counterparts are identified for all four submm detected QSOs and per cent of the SMGs. The MIR colours of the QSOs are similar to those of the local ultraluminous infrared galaxy (ULIRG)/active galactic nuclei (AGN) Mrk 231 if placed at 1< z<3 whilst most of the SMGs have colours very similar to those of the local ULIRG Arp 220 at 1< z<3. MIR diagnostics therefore find no strong evidence that the SMGs host buried AGN although we cannot rule out such a possibility. Taken together our results suggest that the QSOs sit in regions of the early universe which are undergoing an enhanced level of major star formation activity, and should evolve to become similarly dense regions containing massive galaxies at the present epoch. Finally, we find evidence that the level of star formation activity in individual galaxies appears to be lower around the QSOs than it is around more powerful radio-loud AGN at higher redshifts.

  8. The APM bright galaxy Surveys: the Equatorial Galaxy Catalog

    NASA Astrophysics Data System (ADS)

    Raychaudhury, S.; Lynden-Bell, D.; Scharf, C.; Hudson, M. J.

    1994-05-01

    The catalogs of bright galaxies (B_J<16.5) compiled from APM scans of UKST IIIa-J Sky Survey plates have now covered most of the southern sky (|b|>20(deg) ). This presentation reviews the current status of these catalogs, and the ongoing scientific research supported by them. In particular, the first results from the catalog of galaxies (B_J<17, D>0(') .5) compiled from the IIIa--J plates of the UKST Equatorial Survey are presented. This covers a part of the sky (-17(deg) < delta < -2(deg) , |b|>20(deg) ) that was not surveyed for the UGC and ESO catalogs, and hence is the first equivalent galaxy catalog in the Equatorial Sky. All galaxy candidates from a preliminary star-galaxy separation exercise were visually inspected, and the identified galaxies were assigned a morphological type. This catalog of over 50,000 galaxies from 200 plates lists accurate positions and shape parameters for all galaxies, together with their diameters and B_J magnitudes, measured by edge-matching and CCD calibration.

  9. Magellanic Irregular Galaxies and Chemical Evolution of Galaxies

    NASA Astrophysics Data System (ADS)

    Comte, G.; Lequeux, J.; Stasińska, G.; Vigroux, L.

    1982-03-01

    Abundance determination provides a way to study the evolution of galaxies. In conjunction with other properties of galaxies, such as the gas mass fraction, the present rate of star formation or the luminosity, they can help to determine the 3 major quantities which govern the chemical evolution of galaxies: the Initial Mass Function (IMF), the past rate of star formation (SFR), and the amount of heavy elements produced at each generation of stars. Possibilities of abundance determinations in external galaxies are rare. Even in the closest galaxy, the Large Magellanic Cloud, stellar spectra are restricted to supergiants whose complex atmospheres prevent us from obtaining accurate abundances. Spectra or colours of the integrated light of clusters, or galaxies themselves, can give some information. However, this integrated light comes from a mixture of stars of different spectral type, luminosity c1asses and luminosity, its interpretation in terms of abundances is not straightforward (e. g. Tinsley 1980, Fund. Cosm. Phys., 5,287). For external galaxies, H I1 regions provide the most reliable abundances. They are bright enough to be observed in distant galaxies and the emission line intensities are proportional to the abundances of the emitting ions. Two major problems remain in the way to elemental abundances: correction for unseen ions, and the amount of different elements locked in dust grains.

  10. Galaxy coordinates. III. Accurate positions for 17124 galaxies including 3301 new companions of UGC galaxies

    NASA Astrophysics Data System (ADS)

    Paturel, G.; Petit, C.; Garnier, R.; Prugniel, P.

    2000-06-01

    This paper gives accurate coordinates and diameters for 3301 galaxies, companions of UGC galaxies. (about 2764 companions were not yet available in electronic form). In addition previously poor equatorial coordinates are re-measured for 13823 galaxies. These coordinates which have an accuracy of 5'' or better will be used for facilitating the cross-identification with forthcoming catalogues of millions of galaxies. Full Tables 1 and 2 are available in electronic form at CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/Abstract.html

  11. Protecting count queries in study design

    PubMed Central

    Sarwate, Anand D; Boxwala, Aziz A

    2012-01-01

    Objective Today's clinical research institutions provide tools for researchers to query their data warehouses for counts of patients. To protect patient privacy, counts are perturbed before reporting; this compromises their utility for increased privacy. The goal of this study is to extend current query answer systems to guarantee a quantifiable level of privacy and allow users to tailor perturbations to maximize the usefulness according to their needs. Methods A perturbation mechanism was designed in which users are given options with respect to scale and direction of the perturbation. The mechanism translates the true count, user preferences, and a privacy level within administrator-specified bounds into a probability distribution from which the perturbed count is drawn. Results Users can significantly impact the scale and direction of the count perturbation and can receive more accurate final cohort estimates. Strong and semantically meaningful differential privacy is guaranteed, providing for a unified privacy accounting system that can support role-based trust levels. This study provides an open source web-enabled tool to investigate visually and numerically the interaction between system parameters, including required privacy level and user preference settings. Conclusions Quantifying privacy allows system administrators to provide users with a privacy budget and to monitor its expenditure, enabling users to control the inevitable loss of utility. While current measures of privacy are conservative, this system can take advantage of future advances in privacy measurement. The system provides new ways of trading off privacy and utility that are not provided in current study design systems. PMID:22511018

  12. Genetic regulatory networks that count to 3.

    PubMed

    Lehmann, Malte; Sneppen, Kim

    2013-07-21

    Sensing a graded input and differentiating between its different levels is at the core of many developmental decisions. Here, we want to examine how this can be realized for a simple system. We model gene regulatory circuits that reach distinct states when setting the underlying gene copy number to 1, 2 and 3. This distinction can be considered as counting the copy number. We explore different circuits that allow for counting and keeping memory of the count after resetting the copy number to 1. For this purpose, we sample different architectures and parameters, only considering circuits that contain repressive links, which we model by Michaelis-Menten terms. Interestingly, we find that counting to 3 does not require a hierarchy in Hill coefficients, in contrast to counting to 2, which is known from lambda phage. Furthermore, we find two main circuit architectures: one design also found in the vertebrate neural tube in a development governed by the sonic hedgehog morphogen and the more robust design of a repressilator supplemented with a weak repressilator acting in the opposite direction. PMID:23567648

  13. 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.

  14. 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.

  15. 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.

  16. 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/

  17. 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.

  18. The ESO Slice Project (ESP) galaxy redshift survey. II. The luminosity function and mean galaxy density.

    NASA Astrophysics Data System (ADS)

    Zucca, E.; Zamorani, G.; Vettolani, G.; Cappi, A.; Merighi, R.; Mignoli, M.; Stirpe, G. M.; MacGillivray, H.; Collins, C.; Balkowski, C.; Cayatte, V.; Maurogordato, S.; Proust, D.; Chincarini, G.; Guzzo, L.; Maccagni, D.; Scaramella, R.; Blanchard, A.; Ramella, M.

    1997-10-01

    The ESO Slice Project (ESP) is a galaxy redshift survey we have recently completed as an ESO Key-Project over about 23 square degrees, in a region near the South Galactic Pole. The survey is nearly complete to the limiting magnitude b_J_=19.4 and consists of 3342 galaxies with reliable redshift determination. The ESP survey is intermediate between shallow, wide angle samples and very deep, one-dimensional pencil beams: spanning a volume of ~5x10^4^h^-3^Mpc^3^ at the sensitivity peak (z~0.1), it provides an accurate determination of the "local" luminosity function and the mean galaxy density. We find that, although a Schechter function (with α=-1.22, M^*^_bJ_=-19.61+5logh and φ^*^=0.020h^3^/Mpc^3^) is an acceptable representation of the luminosity function over the entire range of magnitudes (M_bJ_<=-12.4+5logh), our data suggest the presence of a steepening of the luminosity function for M_bJ_>=-17+5logh. Such a steepening at the faint end of the luminosity function, well fitted by a power law with slope β~-1.6, is almost completely due to galaxies with emission lines: in fact, dividing our galaxies into two samples, i.e. galaxies with and without emission lines, we find significant differences in their luminosity functions. In particular, galaxies with emission lines show a significantly steeper slope and a fainter M^*^. The amplitude and the α and M^*^ parameters of our luminosity function are in good agreement with those of the AUTOFIB redshift survey (Ellis et al. 1996). Vice-versa, our amplitude is significantly higher, by a factor ~1.6 at M~M^*^, than that found for both the Stromlo-APM (Loveday et al. 1992) and the Las Campanas (Lin et al. 1996) redshift surveys. Also the faint end slope of our luminosity function is significantly steeper than that found in these two surveys. The galaxy number density for M_bJ_<=-16+5logh is well determined (n{bar}=0.08+/-0.015h^3^/Mpc^3^). Its estimate for M_bJ_<=-12.4+5logh is more uncertain, ranging from n{bar}=0.28h

  19. Anisotropic magnification distortion of the 3D galaxy correlation. I. Real space

    SciTech Connect

    Hui, Lam; LoVerde, Marilena; Gaztanaga, Enrique

    2007-11-15

    It has long been known that gravitational lensing, primarily via magnification bias, modifies the observed galaxy (or quasar) clustering. Such discussions have largely focused on the 2D angular correlation function. Here and in paper II [L. Hui, E. Gaztanaga, and M. LoVerde, arXiv:0710.4191] we explore how magnification bias distorts the 3D correlation function and power spectrum, as first considered by Matsubara [Astrophys. J. Lett. 537, L77 (2000).]. The interesting point is that the distortion is anisotropic. Magnification bias in general preferentially enhances the observed correlation in the line-of-sight (LOS) orientation, especially on large scales. For instance, at a LOS separation of {approx}100 Mpc/h, where the intrinsic galaxy-galaxy correlation is rather weak, the observed correlation can be enhanced by lensing by a factor of a few, even at a modest redshift of z{approx}0.35. This effect presents an interesting opportunity as well as a challenge. The opportunity: this lensing anisotropy is distinctive, making it possible to separately measure the galaxy-galaxy, galaxy-magnification, and magnification-magnification correlations, without measuring galaxy shapes. The anisotropy is distinguishable from the well-known distortion due to peculiar motions, as will be discussed in paper II. The challenge: the magnification distortion of the galaxy correlation must be accounted for in interpreting data as precision improves. For instance, the {approx}100 Mpc/h baryon acoustic oscillation scale in the correlation function is shifted by up to {approx}3% in the LOS orientation, and up to {approx}0.6% in the monopole, depending on the galaxy bias, redshift, and number count slope. The corresponding shifts in the inferred Hubble parameter and angular diameter distance, if ignored, could significantly bias measurements of the dark energy equation of state. Lastly, magnification distortion offers a plausible explanation for the well-known excess correlations seen in

  20. Modelling the spectral energy distribution of galaxies: introducing the artificial neural network

    NASA Astrophysics Data System (ADS)

    Silva, L.; Schurer, A.; Granato, G. L.; Almeida, C.; Baugh, C. M.; Frenk, C. S.; Lacey, C. G.; Paoletti, L.; Petrella, A.; Selvestrel, D.

    2011-01-01

    The spectral energy distribution (SED) of galaxies is a complex function of the star formation history and geometrical arrangement of stars and gas in galaxies. The computation of the radiative transfer of stellar radiation through the dust distribution is time-consuming. This aspect becomes unacceptable in particular when dealing with the predictions by semi-analytical galaxy formation models populating cosmological volumes, to be then compared with multi-wavelength surveys. Mainly for this aim, we have implemented an artificial neural network (ANN) algorithm into the spectro-photometric and radiative transfer code GRASIL in order to compute the SED of galaxies in a short computing time. This allows to avoid the adoption of empirical templates that may have nothing to do with the mock galaxies output by models. The ANN has been implemented to compute the dust emission spectrum (the bottleneck of the computation), and separately for the star-forming molecular clouds (MC) and the diffuse dust (due to their different properties and dependencies). We have defined the input neurons effectively determining their emission, which means this implementation has a general applicability and is not linked to a particular galaxy formation model. We have trained the net for the disc and spherical geometries, and tested its performance to reproduce the SED of disc and starburst galaxies, as well as for a semi-analytical model for spheroidal galaxies. We have checked that for this model both the SEDs and the galaxy counts in the Herschel bands obtained with the ANN approximation are almost superimposed to the same quantities obtained with the full GRASIL. We conclude that this method appears robust and advantageous, and will present the application to a more complex SAM in another paper.

  1. 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.

  2. 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.

  3. Bacterial colony counting by Convolutional Neural Networks.

    PubMed

    Ferrari, Alessandro; Lombardi, Stefano; Signoroni, Alberto

    2015-08-01

    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. PMID:26738016

  4. EVOLUTION OF QUIESCENT AND STAR-FORMING GALAXIES SINCE z {approx} 1.5 AS A FUNCTION OF THEIR VELOCITY DISPERSIONS

    SciTech Connect

    Bezanson, Rachel; Van Dokkum, Pieter; Franx, Marijn

    2012-11-20

    We measure stellar masses and structural parameters for 5500 quiescent and 20,000 star-forming galaxies at 0.3 < z {<=} 1.5 in the Newfirm Medium Band Survey COSMOS and UKIDSS UDS fields. We combine these measurements to infer velocity dispersions and determine how the number density of galaxies at fixed inferred dispersion, or the velocity dispersion function (VDF), evolves with time for each population. We show that the number of galaxies with high velocity dispersions appears to be surprisingly stable with time, regardless of their star formation history. Furthermore, the overall VDF for star-forming galaxies is constant with redshift, extending down to the lowest velocity dispersions probed by this study. The only galaxy population showing strong evolution are quiescent galaxies with low inferred dispersions, whose number density increases by a factor of {approx}4 since z = 1.5. This buildup leads to an evolution in the quiescent fraction of galaxies such that the threshold dispersion above which quiescent galaxies dominate the counts moves to lower velocity dispersion with time. We show that our results are qualitatively consistent with a simple model in which star-forming galaxies quench and are added to the quiescent population. In order to compensate for the migration into the quiescent population, the velocity dispersions of star-forming galaxies must increase, with a rate that increases with dispersion.

  5. 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.

  6. 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.

  7. 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

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

    PubMed Central

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

    2008-01-01

    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

  9. 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.

  10. Irregular Dwarf Galaxy IC 1613

    NASA Technical Reports Server (NTRS)

    2005-01-01

    Ultraviolet image (left) and visual image (right) of the irregular dwarf galaxy IC 1613. Low surface brightness galaxies, such as IC 1613, are more easily detected in the ultraviolet because of the low background levels compared to visual wavelengths.

  11. Radio galaxies and their environment

    SciTech Connect

    van Breugel, W.

    1993-02-24

    The relationships between radio galaxies and their environment are varied, complex, and evolve with cosmic epoch. Basic questions are what role the environment plays in triggering and fuelling (radio) galaxy activity what the effects of this activity are on its environment, and how radio galaxies and environment evolve. Clearly, this could be the topic of a workshop all in itself and the scope of this review will necessarily be limited. A review of the connections between environment and galaxy activity in general has been given by Heckman. First, I will briefly summarize the relationships between parent galaxy and cluster environments, and radio galaxies. A more detailed discussion of various aspects of this will be given elsewhere by F. Owen, J.0. Burns and R. Perley. I will then discuss the current status of investigations of extended emission-line regions in radio galaxies, again referring elsewhere in this volume for more detailed discussions of some particular aspects (kinematics and ionization mechanisms by K. Meisenheimer; polarization and spectral index lobe asymmetries by G. Pooley). I will conclude with a brief discussion of the current status of observations of high redshift radio galaxies.

  12. 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)

  13. 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

  14. Analytic Time Depending Galaxy Models

    NASA Astrophysics Data System (ADS)

    Sala, F.

    1990-11-01

    RESUMEN. Considerando las hip6tesis de Chandrasekhar para el estudjo de la GalActicaq se han desarrollado varios modelos analiticos integrables con simetria axial y dependientes del . . By considering Chandrasekhar hypotheses +or the study o+ Galactic Dynamics, several integrable analytic axisymmetric time-depending galactic models have been developed. Ke ords; GALAXY-DYNAMICS - GALAXY-STRUCTURE

  15. Which Factors Shape Galaxy Evolution?

    NASA Astrophysics Data System (ADS)

    Iovino, A.; Cucciati, O.; Scodeggio, M.; Knobel, K.; Kovac, K.; Lilly, S.; Zcosmos Team

    2010-10-01

    Using samples of isolated and groups galaxies obtained from the first 10000 zCOSMOS-bright high quality redshifts, we study in detail the complex interplay between environment and galaxy evolution. Our main result is that galaxies of log( M* / Msun) ≍ 10.8 do not show any strong environmental dependency up to z ˜ 1. In contrast, for masses below this value and at redshift lower than z˜ 1, we witness the emergence of what we call nurture red galaxies: galaxies that slightly deviate from the trend of the downsizing scenario displayed by the global galaxy population and do more so as cosmic time progresses. There are various mechanisms occurring in groups (gradual cessation of star formation induced by gentle gas stripping and starvation by a diffuse intragroup medium, or by slow group-scale harassment), and that are more efficient for less massive galaxies. Our analysis implies that these mechanisms begin to significantly influence galaxy evolution after z˜1, a redshift corresponding to the emergence of structures in which these mechanisms take place.

  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. Extragalactic archeology with the GHOSTS Survey. I. Age-resolved disk structure of nearby low-mass galaxies

    NASA Astrophysics Data System (ADS)

    Streich, David; de Jong, Roelof S.; Bailin, Jeremy; Bell, Eric F.; Holwerda, Benne W.; Minchev, Ivan; Monachesi, Antonela; Radburn-Smith, David J.

    2016-01-01

    Aims: We study the individual evolution histories of three nearby low-mass edge-on galaxies (IC 5052, NGC 4244, and NGC 5023). Methods: Using resolved stellar populations, we constructed star count density maps for populations of different ages and analyzed the change of structural parameters with stellar age within each galaxy. Results: We do not detect a separate thick disk in any of the three galaxies, even though our observations cover a wider range in equivalent surface brightness than any integrated light study. While scale heights increase with age, each population can be well described by a single disk. Two of the galaxies contain a very weak additional component, which we identify as the faint halo. The mass of these faint halos is lower than 1% of the mass of the disk. The three galaxies show low vertical heating rates, which are much lower than the heating rate of the Milky Way. This indicates that heating agents, such as giant molecular clouds and spiral structure, are weak in low-mass galaxies. All populations in the three galaxies exhibit no or only little flaring. While this finding is consistent with previous integrated light studies, it poses strong constraints on galaxy simulations, where strong flaring is often found as a result of interactions or radial migration.

  18. 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.

  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. Advances in photon counting for bioluminescence

    NASA Astrophysics Data System (ADS)

    Ingle, Martin B.; Powell, Ralph

    1998-11-01

    Photon counting systems were originally developed for astronomy, initially by the astronomical community. However, a major application area is in the study of luminescent probes in living plants, fishes and cell cultures. For these applications, it has been necessary to develop camera system capability at very low light levels -- a few photons occasionally -- and also at reasonably high light levels to enable the systems to be focused and to collect quality images of the object under study. The paper presents new data on MTF at extremely low photon flux and conventional ICCD illumination, counting efficiency and dark noise as a function of temperature.

  1. Optical planar waveguide for cell counting

    PubMed Central

    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. PMID:22331960

  2. Galaxy dynamics in clustered environments

    NASA Astrophysics Data System (ADS)

    Pereira, Maria J. R. R.

    Galaxy orientations have been studied statistically for over 70 years now, but it is only recently that alignments have been found on scales larger than those of close interacting pairs. Large scale alignments between galaxies and their surrounding tidal fields are expected to occur during formation, but what happens when these galaxies fall into larger systems? Can their orientations tell us anything about the accretion process itself? In this dissertation I will focus on the radial alignment of satellite galaxies, in which a satellite's long axis points preferentially toward the center of its host. I present observational evidence for this type of galaxy alignment in the SDSS DR3 using a sample of X-ray selected massive clusters. Then, using results from N-body cosmological simulations, I will argue that this effect is the result of a secular tidal interaction between the galaxies and their host potential. The analysis shows that subhalos are effectively torqued by their host throughout their orbits, so that their major axes tend to be aligned with the gradient of the host potential. The significant discrepancy between the magnitude of the effect as seen in these simulations and that detected in observations motivates the work of the next chapter, where I perform numerical experiments on idealized, high resolution N-body models of elliptical galaxies. These experiments show that the more centrally concentrated luminous components of galaxies take longer to react to the external torque, and, in the particular case of mildly eccentric orbits, their orientations can figure rotate in periodic patterns that are not radially aligned on average. The mechanism is more effective on galaxies that have larger triaxialities, but the overall effect of torquing is to make galaxies rounder, since radially misaligned galaxies tend to become more spherical as they are torqued towards equilibrium. In the last chapter, I briefly discuss the impact of these results for galaxy

  3. 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

  4. The BlueTides simulation: first galaxies and reionization

    NASA Astrophysics Data System (ADS)

    Feng, Yu; Di-Matteo, Tiziana; Croft, Rupert A.; Bird, Simeon; Battaglia, Nicholas; Wilkins, Stephen

    2016-01-01

    We introduce the BlueTides simulation and report initial results for the luminosity functions of the first galaxies and active galactic nuclei (AGN), and their contribution to reionization. BlueTides was run on the BlueWaters cluster at National Center for Super-computing Applications from z = 99 to 8.0 and includes 2 × 70403 particles in a 400 h-1 Mpc per side box, making it the largest hydrodynamic simulation ever performed at high redshift. BlueTides includes a pressure-entropy formulation of smoothed particle hydrodynamics, gas cooling, star formation (including molecular hydrogen), black hole growth and models for stellar and AGN feedback processes, and a fluctuating ultraviolet background from a patchy reionization model. The predicted star formation rate density is a good match to current observational data at z ˜ 8-10. We find good agreement between observations and the predicted galaxy luminosity function in the currently observable range -18 ≤ MUV ≤ -22.5 with some dust extinction required to match the abundance of brighter objects. The predicted number counts for galaxies fainter than current observational limits are consistent with extrapolating the faint-end slope of the luminosity function with a power-law index α ˜ -1.8 at z ˜ 8 and redshift dependence of α ˜ (1 + z)-0.4. The AGN population has a luminosity function well fit by a power law with a slope α ˜ -2.4 that compares favourably with the deepest CANDELS GOODS fields. We investigate how these luminosity functions affect the progress of reionization, and find that a high Lyman α escape fraction (fesc ˜ 0.5) is required if galaxies dominate the ionizing photon budget during reionization. Smaller galaxy escape fractions imply a large contribution from faint AGN (down to MUV = -12) which results in a rapid reionization, disfavoured by current observations.

  5. Galaxy Properties and Substructure in the Cluster Abell 160

    NASA Astrophysics Data System (ADS)

    Koontz, Craig; Pinkney, Jason

    2008-10-01

    We continue development of a procedure for building a large catalog of cluster galaxies and their photometric properties, as measured with CCDs. Our first case, Abell 160, is relatively nearby and we have already obtained spectroscopic redshifts for its brightest galaxies. We have mosaiced this cluster in R and V filters using a CCD imager on the 1.3-meter McGraw-Hill telescope. For each CCD frame we fit a WCS (world coordinate system), remove bright cosmic rays, and extract sources using ``SExtractor.'' We create software for merging source catalogs in such a way as to reject residual cosmic rays and other invalid sources, and to combine redundant measurements without double counting. The measured properties include magnitude, ellipticity, position angle, size, and color (V-R). We compare our data to those of the HST (Hubble Space Telescope) and SDSS (Sloan Digital Sky Survey) archives to examine the accuracy of our star/galaxy separation and our color measurements. For our substructure investigation, we draw several subsamples of galaxies based on stellarity index, color (the color-magnitude relation), magnitude and velocity. The smallest subsample of spectroscopically confirmed members produces significant substructure signals from 1D (velocity) and 3D (x,y,velocity) diagnostics - a small, offset group may be the culprit. The 2D (x,y) diagnostics applied to the larger samples produce some significant statistics, the cause does not seem to be a large-scale merger, but perhaps several small groups. This is consistent with previous X-ray data showing X-ray emitting gas clumped around small groupings of galaxies.

  6. Direction counts: a comparative study of spatially directional counting biases in cultures with different reading directions.

    PubMed

    Shaki, Samuel; Fischer, Martin H; Göbel, Silke M

    2012-06-01

    Western adults associate small numbers with left space and large numbers with right space. Where does this pervasive spatial-numerical association come from? In this study, we first recorded directional counting preferences in adults with different reading experiences (left to right, right to left, mixed, and illiterate) and observed a clear relationship between reading and counting directions. We then recorded directional counting preferences in preschoolers and elementary school children from three of these reading cultures (left to right, right to left, and mixed). Culture-specific counting biases existed before reading acquisition in children as young as 3 years and were subsequently modified by early reading experience. Together, our results suggest that both directional counting and scanning activities contribute to number-space associations. PMID:22341408

  7. 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

  8. FRACTAL DIMENSION OF GALAXY ISOPHOTES

    SciTech Connect

    Thanki, Sandip; Rhee, George; Lepp, Stephen E-mail: grhee@physics.unlv.edu

    2009-09-15

    In this paper we investigate the use of the fractal dimension of galaxy isophotes in galaxy classification. We have applied two different methods for determining fractal dimensions to the isophotes of elliptical and spiral galaxies derived from CCD images. We conclude that fractal dimension alone is not a reliable tool but that combined with other parameters in a neural net algorithm the fractal dimension could be of use. In particular, we have used three parameters to segregate the ellipticals and lenticulars from the spiral galaxies in our sample. These three parameters are the correlation fractal dimension D {sub corr}, the difference between the correlation fractal dimension and the capacity fractal dimension D {sub corr} - D {sub cap}, and, thirdly, the B - V color of the galaxy.

  9. 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.

  10. 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

  11. Fanaroff-Riley I galaxies as the parent population of BL Lacertae objects. I - X-ray constraints

    NASA Technical Reports Server (NTRS)

    Padovani, P.; Urry, C. M.

    1990-01-01

    The hypothesis that BL Lacertae objects are a special subset of Fanaroff-Riley type I radio galaxies, namely, those dominated by beamed emission from a relativistic jet aligned with the line of sight, is examined by looking at the relative number densities. The calculation depends primarily on observed quantities, including the X-ray luminosity function of Fanaroff-Riley type I galaxies. The model predicts the X-ray luminosity function of BL Lacertae objects, the shape of the X-ray counts below currently observed fluxes, and the velocity of the X-ray emitting jet. With Fanaroff-Riley type I galaxies as the parent population the flat luminosity function, the observed X-ray number counts, and the partial redshift distribution of BL Lacertae objects can be explained.

  12. 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

  13. 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.

  14. Galaxy populations in rich environments

    NASA Astrophysics Data System (ADS)

    Tran, Kim-Vy Huu

    2002-11-01

    Combining two color HST/WFPC2 mosaics with extensive Keck/LRIS spectroscopy, we derive physical properties for over 400 confirmed cluster members at z = 0.33, 0.58, and 0.83 to provide key tests of current CDM models of hierarchical galaxy formation. Morphological characteristics such as bulge to total luminosity, half-light radius, bulge/disk scale length, and galaxy asymmetry are measured by determining the best-fit 2D bulge + disk model for each galaxy. We rigorously test these measurements using extensive mock galaxy catalogs to quantify systematic and random errors. Utilizing quantitative structural parameters, spectral indices ([OII] λ3727, HS, and H-γ), Hubble types, internal velocity dispersions (for a subset), and galaxy colors, we find that: (1)Galaxies spanning the range of Hubble type (-5 ≤ T ≤ 8) are well-fit by a de Vaucouleurs bulge with exponential disk profile; (2)The average [OII] equivalent width of the most disk-dominated members (B/T < 0.25) is significantly higher than the average of the bulge-dominated members (B/T ≥ 0.4); (3)The physical properties, e.g. half-light radii, bulge-to-total luminosities, and bulge ellipticities, of cluster elliptical and S0 galaxies (-17.3 ≥ MBz - 5log h 70 ≥ -19.3) are consistent with the two types sharing a common parent galaxy population; (4)In these three clusters, the distributions of cluster disk sizes are indistinguishable, a result contrary to predictions from current hierarchical formation models; (5)Post- starburst (“E + A”) galaxies are a non- negligible fraction (˜5 20%) of the cluster population at these redshifts; (6)We find compelling evidence that the E + A mass distribution evolves with redshift (“downsizing”) such that E + A galaxies span the range in mass at high redshift but only low mass E + A's exist in nearby clusters.

  15. 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.

  16. 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.

  17. 45 CFR 263.4 - When do educational expenditures count?

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... educational services or activities provided through the public education system do not count unless they meet... 45 Public Welfare 2 2010-10-01 2010-10-01 false When do educational expenditures count? 263.4... do educational expenditures count? (a) Expenditures for educational activities or services count...

  18. 20 CFR 418.3410 - Whose resources do we count?

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 20 Employees' Benefits 2 2011-04-01 2011-04-01 false Whose resources do we count? 418.3410 Section... Subsidies Resources § 418.3410 Whose resources do we count? (a) We count your resources. We count the resources of both you and your spouse regardless of whether one or both of you apply or are eligible for...

  19. 7 CFR 51.1242 - Count per pound.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 7 Agriculture 2 2010-01-01 2010-01-01 false Count per pound. 51.1242 Section 51.1242 Agriculture... Standards for Cleaned Virginia Type Peanuts in the Shell Definitions § 51.1242 Count per pound. Count per pound means the number of peanuts in a pound. When determining the count per pound, one single...

  20. 20 CFR 418.3410 - Whose resources do we count?

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 20 Employees' Benefits 2 2014-04-01 2014-04-01 false Whose resources do we count? 418.3410 Section... Subsidies Resources § 418.3410 Whose resources do we count? (a) We count your resources. We count the resources of both you and your spouse regardless of whether one or both of you apply or are eligible for...

  1. 20 CFR 418.3410 - Whose resources do we count?

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 20 Employees' Benefits 2 2010-04-01 2010-04-01 false Whose resources do we count? 418.3410 Section... Subsidies Resources § 418.3410 Whose resources do we count? (a) We count your resources. We count the resources of both you and your spouse regardless of whether one or both of you apply or are eligible for...

  2. 21 CFR 864.6160 - Manual blood cell counting device.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Manual blood cell counting device. 864.6160... blood cell counting device. (a) Identification. A manual blood cell counting device is a device used to count red blood cells, white blood cells, or blood platelets. (b) Classification. Class I...

  3. 21 CFR 864.6160 - Manual blood cell counting device.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Manual blood cell counting device. 864.6160... blood cell counting device. (a) Identification. A manual blood cell counting device is a device used to count red blood cells, white blood cells, or blood platelets. (b) Classification. Class I...

  4. 21 CFR 864.6160 - Manual blood cell counting device.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Manual blood cell counting device. 864.6160... blood cell counting device. (a) Identification. A manual blood cell counting device is a device used to count red blood cells, white blood cells, or blood platelets. (b) Classification. Class I...

  5. 21 CFR 864.6160 - Manual blood cell counting device.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Manual blood cell counting device. 864.6160... blood cell counting device. (a) Identification. A manual blood cell counting device is a device used to count red blood cells, white blood cells, or blood platelets. (b) Classification. Class I...

  6. 20 CFR 418.3410 - Whose resources do we count?

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 20 Employees' Benefits 2 2012-04-01 2012-04-01 false Whose resources do we count? 418.3410 Section... Subsidies Resources § 418.3410 Whose resources do we count? (a) We count your resources. We count the resources of both you and your spouse regardless of whether one or both of you apply or are eligible for...

  7. 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.

  8. DEPENDENCE OF BARRED GALAXY FRACTION ON GALAXY PROPERTIES AND ENVIRONMENT

    SciTech Connect

    Lee, Gwang-Ho; Lee, Myung Gyoon; Park, Changbom; Choi, Yun-Young E-mail: mglee@astro.snu.ac.kr E-mail: yy.choi@khu.ac.kr

    2012-02-01

    We investigate the dependence of the occurrence of bars in galaxies on galaxy properties and environment. We use a volume-limited sample of 33,391 galaxies brighter than M{sub r} = -19.5 + 5logh at 0.02 {<=} z {<=} 0.05489, drawn from the Sloan Digital Sky Survey Data Release 7. We classify the galaxies into early and late types, and identify bars by visual inspection. Among 10,674 late-type galaxies with axis ratio b/a > 0.60, we find 3240 barred galaxies (f{sub bar} = 30.4%) which divide into 2542 strong bars (f{sub SB1} = 23.8%) and 698 weak bars (f{sub SB2} = 6.5%). We find that f{sub SB1} increases as u - r color becomes redder and that it has a maximum value at intermediate velocity dispersion ({sigma} {approx_equal}150 km s{sup -1}). This trend suggests that strong bars are dominantly hosted by intermediate-mass systems. Weak bars prefer bluer galaxies with lower mass and lower concentration. In the case of strong bars, their dependence on the concentration index appears only for massive galaxies with {sigma} > 150 km s{sup -1}. We also find that f{sub bar} does not directly depend on the large-scale background density when other physical parameters (u - r color or {sigma}) are fixed. We discover that f{sub SB1} decreases as the separation to the nearest neighbor galaxy becomes smaller than 0.1 times the virial radius of the neighbor regardless of neighbor's morphology. These results imply that strong bars are likely to be destroyed during strong tidal interactions and that the mechanism for this phenomenon is gravitational and not hydrodynamical. The fraction of weak bars has no correlation with environmental parameters. We do not find any direct evidence for environmental stimulation of bar formation.

  9. 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.

  10. Multicolor photometry of clusters of galaxies: A3284, A3305, A1942

    NASA Astrophysics Data System (ADS)

    Molinari, E.; Banzi, M.; Buzzoni, A.; Chincarini, G.; Pedrana, M. D.

    1994-02-01

    We present complete multicolor photometry in the Gunn system for the three clusters of galaxies A3284, A3305 and A1942 at redshift z~0.2. INVENTORY magnitudes and colours have been obtained for over 1,000 objects in the three fields down to g=24, and with a good completeness level in the detections (85% or better) about one magnitude brighter. By fitting with King profiles the r counts we derived the total number of galaxies and the core radius down to the r magnitude limit in each cluster. These are N_TOT_=146 galaxies and R_c_=0.24 Mpc for A3284, N_TOT_=129 and R_c_=0.20 Mpc for A3305, N_TOT_=130 and R_c_=0.24 Mpc for A1942. The observed mean redshift of the clusters is z=0.150+/-0.001 for A3284, z=0.157+/-0.001 for A3305, and z=0.226+/-0.001 for A1942. The c-m diagrams and the g-i colour distribution as well as the two-colour diagrams are used to single out early-type galaxies and spirals on the basis of their different photometric properties. This approach aimed at a self-consistent classification of galaxies on the basis of photometric indicators will be further developed for a systematic study of the galaxy population in distant clusters.

  11. An Introduction to Galaxies and Cosmology

    NASA Astrophysics Data System (ADS)

    Jones, Mark H.; Lambourne, Robert J. A.; Serjeant, Stephen

    2015-01-01

    Introduction; 1. The Milky Way - our galaxy; 2. Normal galaxies; 3. Active galaxies; 4. The spatial distribution of galaxies; 5. Introducing cosmology - the science of the Universe; 6. Big bang cosmology - the evolving Universe; 7. Observational cosmology - measuring the Universe; 8. Questioning cosmology - outstanding problems about the Universe; Answers and comments; Appendix; Glossary; Further reading; Acknowledgements; Figure references; Index.

  12. 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.

  13. Maine KIDS COUNT 2001 Data Book.

    ERIC Educational Resources Information Center

    Davey, Lynn

    This KIDS COUNT data book 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 data book presents state level trend data, a…

  14. 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…

  15. Maine Kids Count 1997 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 indictors children's well-being in four areas: (1) physical and mental health; (2) social and economic opportunity; (3) community and family environment; and (4) education and learning. The report's introduction describes…

  16. 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;…

  17. County Data Book 1996: Kentucky Kids Count.

    ERIC Educational Resources Information Center

    Kentucky Youth Advocates, Inc., Louisville.

    This Kids Count data book examines trends in the well-being of Kentucky children on a state-wide, county, and school district basis. An introductory essay finds a strong link between the percentage of adults completing high school in a given school district and various indicators: As the percentage of adults completing high school increases, the…

  18. Kids Count in Nebraska: 1995 Report.

    ERIC Educational Resources Information Center

    Nebraska Univ. Medical Center, Omaha.

    While a vast majority of children in Nebraska are experiencing a safe, healthy, and nurturing childhood, a significant number are not, and some of these numbers are growing. This Kids Count report is the third annual comprehensive review of available data in nine areas of child health and well-being in the state. Presented with these statistics…

  19. 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…

  20. 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…

  1. Kids Count Report in Nebraska, 2002.

    ERIC Educational Resources Information Center

    Johnston, Janet M.

    This Kids Count report examines statewide trend data on the well-being of Nebraska's children. Section 1 of the report presents U.S. Census data on population trends in Nebraska as well as child poverty rates, and urges Nebraskans to work together to ensure that its youngest citizens have the best start possible. Section 2, the bulk of this…

  2. 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…

  3. 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…

  4. 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.

  5. 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…

  6. 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.

  7. Rhode Island Kids Count Factbook, 2001.

    ERIC Educational Resources Information Center

    Rhode Island KIDS COUNT, Providence.

    This Kids Count databook is the seventh annual profile examining statewide trends in the well-being of Rhode Island's children. The statistical portrait is based on 43 indicators in 5 areas: (1) family and community (including child population and children in single-parent families); (2) economic well-being (including median household income,…

  8. 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…

  9. WisKids Count Data Book, 2001.

    ERIC Educational Resources Information Center

    Townsend, Laura; Grigsby, Tamera; Peacock, Jon; Brien, Nan

    This WisKids Count data book provides a statistical portrait of K-12 education in the state of Wisconsin. The introduction to the data book examines financing of education, including special education, and the issue of financing private education with public dollars; barriers to school success, including mobility and racial disparities; what…

  10. 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…

  11. 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)…

  12. Optical Ranicon detectors for photon counting imaging.

    NASA Astrophysics Data System (ADS)

    Clampin, Mark; Crocker, Jim; Paresce, Francesco; Rafal, Marc

    1988-08-01

    The design and development of two detectors, known as Ranicon and advanced Ranicon, for optical photon counting imaging on ground-based telescopes are discussed. The proximity focusing, microchannel-plate stack, resistive anode, and signal processing characteristics are described. The theory behind the overall resolution of the Ranicon system is reviewed. Resolution measurements for the instruments are reported and discussed.

  13. 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…

  14. 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…

  15. 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…

  16. 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…

  17. 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…

  18. 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,...

  19. 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,...

  20. 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,...

  1. 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,...

  2. KIDS COUNT in Missouri 2001 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…

  3. 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)…

  4. 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)…

  5. Wyoming Kids Count in Wyoming Factbook, 1999.

    ERIC Educational Resources Information Center

    Wyoming Children's Action Alliance, Cheyenne.

    This Kids Count factbook details statewide trends in the well-being of Wyoming's children. Following an overview of key indicators and data sources, the factbook documents trends by county for 20 indicators, including the following: (1) poverty and population; (2) welfare reform; (3) certified day care facilities; (4) births; (5) infant deaths;…

  6. 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…

  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. 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;…

  9. 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…

  10. Kids Count Alaska Data Book: 1997.

    ERIC Educational Resources Information Center

    Alaska Univ., Anchorage. Inst. of Social and Economic Research.

    This second annual Kids Count data book examines statewide trends in the well-being of Alaska's children. The statistical portrait is based on key indicators in six areas: (1) early childhood, including prenatal care, infant mortality, and children with developmental disabilities; (2) economic well-being, including children living in poverty and…

  11. Kids Count Alaska Data Book, 2001.

    ERIC Educational Resources Information Center

    Leask, Linda, Ed.

    This Kids Count Data Book examines statewide trends in the well-being of Alaska's children. The statistical portrait is based on key indicators in six areas: (1) infancy, including prenatal care, low birth weight, and infant mortality; (2) economic well-being, including child poverty, children with no parent working full-time, and teen births; (3)…

  12. Estimating mutation rate: how to count mutations?

    PubMed Central

    Fu, Yun-Xin; Huai, Haying

    2003-01-01

    Mutation rate is an essential parameter in genetic research. Counting the number of mutant individuals provides information for a direct estimate of mutation rate. However, mutant individuals in the same family can share the same mutations due to premeiotic mutation events, so that the number of mutant individuals can be significantly larger than the number of mutation events observed. Since mutation rate is more closely related to the number of mutation events, whether one should count only independent mutation events or the number of mutants remains controversial. We show in this article that counting mutant individuals is a correct approach for estimating mutation rate, while counting only mutation events will result in underestimation. We also derived the variance of the mutation-rate estimate, which allows us to examine a number of important issues about the design of such experiments. The general strategy of such an experiment should be to sample as many families as possible and not to sample much more offspring per family than the reciprocal of the pairwise correlation coefficient within each family. To obtain a reasonably accurate estimate of mutation rate, the number of sampled families needs to be in the same or higher order of magnitude as the reciprocal of the mutation rate. PMID:12807798

  13. County Data Book 1995: Kentucky Kids Count.

    ERIC Educational Resources Information Center

    Kentucky Youth Advocates, Inc., Louisville.

    This data book presents findings of the Kids Count project on current conditions faced by Kentucky children age birth through 19. For each county, and for the state, comparisons are provided between the base years of 1980-1982 and the most recent years 1992-1994. Counties are ranked against each other and trend graphs are provided for the studied…

  14. Numbers, Counting, and Infinity in Middle Schools.

    ERIC Educational Resources Information Center

    Meconi, L. J.

    1992-01-01

    Discusses the use of middle-school students' natural understanding of large numbers to introduce the concept of infinity. Presents activities that investigate infinite sets by demonstrating a one-to-one correspondence between the counting numbers and the given set. Examples include prime numbers, Fibonacci numbers, fractions, even and odd numbers,…

  15. Technology Counts 2007: A Digital Decade

    ERIC Educational Resources Information Center

    Education Week, 2007

    2007-01-01

    "Technology Counts 2007" looks back, and ahead, after a decade of enormous upheaval in the educational technology landscape. This special issue of "Education Week" includes the following articles: (1) A Digital Decade; (2) Getting Up to Speed (Andrew Trotter); (3) E-Rate's Imprint Seen in Schools (Andrew Trotter); (4) Teaching Assistants (Rhea R.…

  16. Alabama Kids Count 2001 Data Book.

    ERIC Educational Resources Information Center

    Curtis, Apreill; Bogie, Don

    This Kids Count data book examines statewide trends in well-being for Alabama's children. The statistical portrait is based on 17 indicators in the areas of health, education, safety, and security. The indicators are: (1) infant mortality rate; (2) low weight births; (3) child health index; (4) births to unmarried teens; (5) first grade retention;…

  17. 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.

  18. 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…

  19. Making Academics Count: Action Guide. Successful Strategies.

    ERIC Educational Resources Information Center

    McMahon, Amanda Sodoma; Meeder, Hans; Rosen, Linda P.; Silver, Steve; Williams, Andra

    This document is intended to help communities plan and implement initiatives modeled after Making Academics Count, a campaign that was launched in 1997 by the Business Coalition for Education Reform (BCER) to encourage employers to ask job applicants for their school records and thereby help motivate students to achieve at higher levels. The guide…

  20. Implementing Graduation Counts: State Progress to Date

    ERIC Educational Resources Information Center

    National Governors Association, 2006

    2006-01-01

    This report provides information on states' progress in implementing the graduation rate all 50 governors agreed by signing the Graduation Counts Compact in 2005 to adopt. The governors undertook this commitment because they understand the imperative to gather more accurate, comparable data on how many of their students graduate from high school…