Consistent beta values from density-density and velocity-velocity comparisons

We apply a new algorithm, called the Unbiased Minimal Variance (hereafter UMV) estimator, to reconstruct the cosmic density and peculiar velocity fields in our local universe from the SEcat catalog of peculiar velocities comprising both early (ENEAR) and late type (SFI) galaxies. The reconstructed fields are compared with those predicted from the IRAS PSCz galaxy redshift survey to constrain the value of beta = Omega_m^{0.6}/b, where Omega_m and b are the mass density and the bias parameters. The comparison of the density and velocity fields is carried out within the same methodological framework, and leads, for the first time, to consistent values of beta, yielding beta = 0.57_{-0.13}^{+0.11} and beta = 0.51 +/- {0.06}, respectively. We find that the distribution of the density and velocity residuals, relative to their respective errors, is consistent with a Gaussian distribution with sigma approximately 1, indicating that the density field predicted from the PSCz is an acceptable fit to that deduced from the peculiar velocities of the SEcat galaxies.Comment: 15 pages, 12 figures, accepted for publication in MNRA

Determination of Malmquist Bias and Selection Effects from Monte Carlo Simulations

Maps of the peculiar velocity field derived from distance relations are affected by Malmquist type bias and selection effects. Because of the large number of interdependent effects, they are in most cases difficult to treat analytically. Monte Carlo simulations are used to understand and evaluate these effects. In these simulations the true spatial distribution and relevant properties of galaxies as well as selection effects and observational uncertainties are realistically modeled. The results of the simulation can be directly applied to correct observed peculiar velocity maps. The simulation is used to investigate biases in samples of measured peculiar velocities by Lynden-Bell et al. (ApJ, 326, 19, 1988). Willick (ApJ, 351, L5, 1990) and the new sample of spiral galaxies by Haynes et al. (BAAS, 25, 1403, 1993). Based on the results obtained from the application of our method to toy models we find that the method is a useful tool to estimate the bias induced both by inhomogeneities and selection effects. This is a crucial step for the analysis of the Haynes et al. sample which was selected with a redshift dependent criterion

ENEAR Redshift-Distance Survey: Cosmological Constraints

We present an analysis of the ENEAR sample of peculiar velocities of field and cluster elliptical galaxies, obtained with Dn-σ distances. We use the velocity correlation function ψ1(r) to analyze the statistics of the field object\u27s velocities, while the analysis of the cluster data is based on the estimate of their rms peculiar velocity Vrms. The results are compared with predictions from cosmological models using linear theory. The statistics of the model velocity field is parameterized by the amplitude η8 = σ8Ω and by the shape parameter Γ of the cold dark matter-like power spectrum. This analysis is performed in redshift space, so as to circumvent the need to address corrections due to inhomogeneous Malmquist bias and to the redshift cutoff adopted in the sample selection. From the velocity correlation statistics, we obtain η8 = 0.51 for Γ = 0.25 at the 2 σ level for one interesting fitting parameter. This result agrees with that obtained from a similar analysis of the SFI I-band Tully-Fisher (TF) survey of field Sc galaxies. Even though less constraining, a consistent result is obtained by comparing the measured Vrms of clusters with linear theory predictions. For Γ = 0.25, we find η8 = 0.63 at 1 σ. Again, this result agrees, within the uncertainties, with that obtained from the SCI cluster sample based on TF distances. Overall, our results point toward a statistical concordance of the cosmic flows traced by spiral and early-type galaxies, with galaxy distances estimated using TF and Dn-σ distance indicators, respectively

A Test of the Lauer-Postman Bulk Flow

We use Tully-Fisher distances for a sample of field late spiral galaxies to test the Lauer & Postman result suggestive of a bulk flow with respect to the cosmic microwave background reference frame, of amplitude of +689 km s-1 in the direction l = 343°, b = +52°. A total of 432 galaxies are used, subdivided between two cones, of 30° semiaperture each and pointed toward the apex and antapex of the LP motion, respectively. The peculiar velocities in the two data sets are inconsistent with a bulk flow of the amplitude claimed by Lauer & Postman. When combined in opposition, the peculiar velocity medians in shells of constant redshift width are never larger than half the amplitude of the Lauer & Postman bulk flow. Out to 5000 km s-1 the median bulk velocity in the Lauer & Postman apex-antapex cones is about 200 km s-1 or less, dropping to a value indistinguishable from zero beyond that distance. It can be excluded that field spiral galaxies within 8000 km s-1 partake of a bulk flow of the amplitude and direction reported by Lauer & Postman

Using Lean to Counteract Complexity

Based on a literature review and drawing from the experience of lean implementation in multipleconstruction projects, this paper explores the notion that simplicity and integrality might be crucial for anyproduction system seeking to develop competences against variations derived from both internal andexternal sources. A discussion using different systems thinking approaches is conducted to provide a betterunderstanding of the volatile behaviour of complex organizations. The aim is to encourage initiatives thataddress organizational simplicity and integrality in construction projects and, more important, to highlightthe important role of lean tools and principles for this endeavour

A Project-Based View of the Link Between Strategy, Structure and Lean Construction

Currently, there is a good understanding that companies do not obtain satisfactoryresults when lean practices are implemented alone. The benefits can only be realizedby making a substantial number of organizational changes, which in turn need to becoherent with the business strategy. However, contextual factors drive companies toadopt different business strategies, organizational structures and bundles ofproduction practices. Consequently, the sequence and content of businessdevelopment projects aimed to implement and test lean construction practices canvary according to each firm's internal characteristics and conjunctural needs.This paper argues that lean implementation is not an isolated event, but part of aneffort to create a strategy-structure alignment. Moreover, because leanimplementation is conducted through different internal projects, it is also argued thatprojects constitute the link between business strategy, organizational structure andlean processes. A model is proposed to explain the role that projects play ininterlinking strategy, structure and processes. In doing so, the authors hope to bringawareness to the bigger changes behind lean implementation and to the challenges ofbuilding "finely-tuned" organizations for specific missions

The Tully-Fisher Relation and H0

The use of the Tully-Fisher (TF) relation for the determination of H0 relies on the availability of an adequate template TF relation and of reliable primary distances. Here we use a TF template relation with the best available kinematical zero point, obtained from a sample of 24 clusters of galaxies extending to cz ~ 9000 km s-1, and the most recent set of Cepheid distances for galaxies fit for TF use. The combination of these two ingredients yields H0 = 69 ± 5 km s-1 Mpc-1. The approach is significantly more accurate than the more common application with single cluster (e.g., Virgo, Coma) samples

Peculiar Velocity Dipoles of Field Galaxies

The Tully-Fisher (TF) relation is applied to obtain peculiar velocities of field spiral galaxies and to calculate dipoles of the peculiar velocity field to cz8000 km s-1. The field galaxy sample is spatially coextensive with and completely independent of a cluster sample, for which dipole characteristics are given in a separate paper. Dipoles of the peculiar velocity field are obtained separately by applying (1) an inverse version of the TF relation and selecting galaxies by redshift windowing and (2) a direct TF relation, with velocities corrected for the inhomogeneous Malmquist bias and windowing galaxies by TF distance. The two determinations agree, as they do with the cluster sample. When measured in a reference frame in which the Local Group is at rest, the dipole moment of field galaxies farther than ~4000 km s-1 is in substantial agreement, both in amplitude and direction, with that exhibited by the cosmic microwave background radiation field