91 research outputs found
Einsatz internetbasierter Projektplattformen im Bereich der Bauausführung - "Digitales Bautagebuch"
Der Einsatz internetbasierter Projektplattformen in der Bauausführung wurde bisher kaum thematisiert. Die typischen Vorteile des Einsatzes solcher Werkzeuge, wie etwa die Unterstützung kooperativer, geographisch und zeitlich verteilter Prozesse, scheinen für diesen Einsatzbereich nicht so offensichtlich zu sein wie für den Bereich der Gebäudeplanung. Vor dem Hintergrund der anhaltend problematischen Situation der Bauwirtschaft und der Tatsache, dass im Bereich der Bauausführung oftmals die wesentlichen Ursachen für einen unplanmäßigen Ablauf von Bauprojekten oder ein Verfehlen von Kosten-, Termin- oder Qualitätszielen zu finden sind, kommt diesen Anwendungen eine große Bedeutung zu. Im Rahmen eines größeren Forschungsprojektes des BMWi (TK3 GIT Siegen / Projektträger PTJ-BEO) wurde unter dem Arbeitstitel >Digitales Bautagebuch< ein ausführungsorientiertes Modul für eine schon in den Planungsphasen des Projektes eingesetzte Projektplattform entwickelt. Dabei wurde projektbegleitend eine Umgebung implementiert, welche sowohl die Bauleitung bei ihrer täglichen Arbeit unterstützt als auch Entscheidungsträgern und anderen Projektbeteiligten einen schnellen Überblick über den Stand der Arbeiten ermöglicht. Dieser Beitrag setzt sich mit dem Einsatz internetbasierter Projektplattformen im Bereich der Bauausführung auseinander und beschreibt deren Möglichkeiten unter Einbringung der Erfahrungen aus der Anwendung im Bauprojekt TK3 GIT Siegen
Einsatz internetbasierter Projektplattformen im Bereich der Bauausführung - "Digitales Bautagebuch"
Der Beitrag setzt sich mit dem Einsatz internetbasierter
Projektplattformen im Bereich der Bauausführung auseinander und
beschreibt deren Möglichkeiten unter Einbringung der Erfahrungen
aus der Anwendung im Bauprojekt TK3 GIT Siegen.
Keywords
Kooperatives Arbeiten, anforderungsorientierte
Projektabwicklung, internetbasierte Projektplattform, Digitales
Bautagebuc
Constraints on Assembly Bias from Galaxy Clustering
We constrain the newly-introduced decorated Halo Occupation Distribution
(HOD) model using SDSS DR7 measurements of projected galaxy clustering or
r-band luminosity threshold samples. The decorated HOD is a model for the
galaxy-halo connection that augments the HOD by allowing for the possibility of
galaxy assembly bias: galaxy luminosity may be correlated with dark matter halo
properties besides mass, Mvir. We demonstrate that it is not possible to rule
out galaxy assembly bias using DR7 measurements of galaxy clustering alone.
Moreover, galaxy samples with Mr < -20 and Mr < -20.5 favor strong central
galaxy assembly bias. These samples prefer scenarios in which
high-concentration are more likely to host a central galaxy relative to
low-concentration halos of the same mass. We exclude zero assembly bias with
high significance for these samples. Satellite galaxy assembly bias is
significant for the faintest sample, Mr < -19. We find no evidence for assembly
bias in the Mr < -21 sample. Assembly bias should be accounted for in galaxy
clustering analyses or attempts to exploit galaxy clustering to constrain
cosmology. In addition to presenting the first constraints on HOD models that
accommodate assembly bias, our analysis includes several improvements over
previous analyses of these data. Therefore, our inferences supersede
previously-published results even in the case of a standard HOD analysis.Comment: 15 pages, 8 figures. To be submitted to MNRAS. Comments Welcome.
Python scripts to perform this analysis and MCMC chains will all be made
publicly availabl
Maturing Satellite Kinematics into a Competitive Probe of the Galaxy-Halo Connection
The kinematics of satellite galaxies moving in a dark matter halo are a
direct probe of the underlying gravitational potential. Thus, the phase-space
distributions of satellites represent a powerful tool to determine the
galaxy-halo connection from observations. By stacking the signal of a large
number of satellite galaxies this potential can be unlocked even for haloes
hosting a few satellites on average. In this work, we test the impact of
various modelling assumptions on constraints derived from analysing satellite
phase-space distributions in the non-linear, 1-halo regime. We discuss their
potential to explain the discrepancy between average halo masses derived from
satellite kinematics and gravitational lensing previously reported.
Furthermore, we develop an updated, more robust analysis to extract constraints
on the galaxy-halo relation from satellite properties in spectroscopic galaxy
surveys such as the SDSS. We test the accuracy of this approach using a large
number of realistic mock catalogues. Furthermore, we find that constraints
derived from such an analysis are complementary and competitive with respect to
the commonly used galaxy clustering and galaxy-galaxy lensing observables.Comment: 24 pages, 15 figures; resubmitted to MNRAS after first referee repor
Updated Results on the Galaxy-Halo Connection from Satellite Kinematics in SDSS
We present new results on the relationship between central galaxies and dark
matter haloes inferred from observations of satellite kinematics in the Sloan
Digital Sky Survey (SDSS) DR7. We employ an updated analysis framework that
includes detailed mock catalogues to model observational effects in SDSS. Our
results constrain the colour-dependent conditional luminosity function (CLF) of
dark matter haloes, as well as the radial profile of satellite galaxies.
Confirming previous results, we find that red central galaxies live in more
massive haloes than blue galaxies at fixed luminosity. Additionally, our
results suggest that satellite galaxies have a radial profile less centrally
concentrated than dark matter but not as cored as resolved subhaloes in dark
matter-only simulations. Compared to previous works using satellite kinematics
by More et al., we find much more competitive constraints on the galaxy-halo
connection, on par with those derived from a combination of galaxy clustering
and galaxy-galaxy lensing. We compare our results on the galaxy-halo connection
to other studies using galaxy clustering and group catalogues, showing very
good agreement between these different techniques. We discuss future
applications of satellite kinematics in the context of constraining cosmology
and the relationship between galaxies and dark matter haloes.Comment: 18 pages, 10 figures, submitted to MNRAS, comments welcom
Brightest galaxies as halo centre tracers in SDSS DR7
Determining the positions of halo centres in large-scale structure surveys is
crucial for many cosmological studies. A common assumption is that halo centres
correspond to the location of their brightest member galaxies. In this paper,
we study the dynamics of brightest galaxies with respect to other halo members
in the Sloan Digital Sky Survey DR7. Specifically, we look at the line-of-sight
velocity and spatial offsets between brightest galaxies and their neighbours.
We compare those to detailed mock catalogues, constructed from high-resolution,
dark-matter-only -body simulations, in which it is assumed that satellite
galaxies trace dark matter subhaloes. This allows us to place constraints on
the fraction of haloes in which the brightest galaxy is not the
central. Compared to previous studies we explicitly take into account the
unrelaxed state of the host haloes, velocity offsets of halo cores and
correlations between and the satellite occupation. We find that
strongly decreases with the luminosity of the brightest galaxy
and increases with the mass of the host halo. Overall, in the halo mass range
we find , in good
agreement with a previous study by Skibba et al. We discuss the implications of
these findings for studies inferring the galaxy--halo connection from satellite
kinematics, models of the conditional luminosity function and galaxy formation
in general.Comment: 24 pages, 15 figures. Accepted for publication in MNRA
Galaxy Assembly Bias: A Significant Source of Systematic Error in the Galaxy-Halo Relationship
It is common practice for methods that use galaxy clustering to constrain the
galaxy-halo relationship, such as the halo occupation distribution (HOD) and/or
conditional luminosity function (CLF), to assume that halo mass alone suffices
to determine a halo's resident galaxy population. Yet, the clustering strength
of cold dark matter halos depends upon halo properties in addition to mass,
such as formation time, an effect referred to as assembly bias. If galaxy
characteristics are correlated with any of these auxiliary halo properties, the
basic assumption of HOD/CLF methods is violated. We estimate the potential for
assembly bias to induce systematic errors in inferred halo occupation
statistics. We use halo abundance matching and age matching to construct
fiducial mock galaxy catalogs that exhibit assembly bias as well as additional
mock catalogs with identical HODs, but with assembly bias removed. We fit a
parameterized HOD to the projected two-point clustering of mock galaxies in
each catalog to assess the systematic errors induced by reasonable levels of
assembly bias. In the absence of assembly bias, the inferred HODs generally
describe the true underlying HODs well, validating the basic methodology.
However, in all of the cases with assembly bias, the inferred HODs have
systematic errors that are statistically significant. In most cases, these
systematic errors cannot be identified using void statistics as auxiliary
observables. We conclude that the galaxy-halo relationship inferred from galaxy
clustering should be subject to a non-negligible systematic error induced by
assembly bias. Our work suggests that efforts to model and/or constrain
assembly bias should be high priorities as it is a threatening source of
systematic error in galaxy evolution studies as well as the precision cosmology
program.Comment: 28 pages, 15 figures including an appendix. v2 includes minor
revisions based upon referee comments. Accepted for publication in the MNRAS.
Title changed from original "Phantom Menace of Galaxy Clustering
The Galaxy Clustering Crisis in Abundance Matching
Galaxy clustering on small scales is significantly under-predicted by
sub-halo abundance matching (SHAM) models that populate (sub-)haloes with
galaxies based on peak halo mass, . SHAM models based on the peak
maximum circular velocity, , have had much better success. The
primary reason based models fail is the relatively low abundance
of satellite galaxies produced in these models compared to those based on
. Despite success in predicting clustering, a simple based SHAM model results in predictions for galaxy growth that are at
odds with observations. We evaluate three possible remedies that could "save"
mass-based SHAM: (1) SHAM models require a significant population of "orphan"
galaxies as a result of artificial disruption/merging of sub-haloes in modern
high resolution dark matter simulations; (2) satellites must grow significantly
after their accretion; and (3) stellar mass is significantly affected by halo
assembly history. No solution is entirely satisfactory. However, regardless of
the particulars, we show that popular SHAM models based on
cannot be complete physical models as presented. Either truly is
a better predictor of stellar mass at and it remains to be seen how
the correlation between stellar mass and comes about, or SHAM
models are missing vital component(s) that significantly affect galaxy
clustering.Comment: 25 pages, 22 figures, submitted to MNRAS, comments welcom
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