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

Perception of biological motion by form analysis

Detection of other living beings’ movements is a fundamental property of the human visual system. Viewing their movements, categorizing their actions, and interpreting social behaviors like gestures constitutes a framework of our everyday lives. These observed actions are complex and differences among them are rather subtle. However, humans recognize these actions without ma jor efforts and without being aware of the complexity of the observed tasks. In point-light walkers, the visual information about the human body is reduced to only a handful point-lights placed on the ma jor joints of the otherwise invisible body. But even this sparse information does not effectively reduce humans’ abilities to perceive the performed actions. Neurophysiological and neuroimaging studies suggested that the movement of the human body is represented in specific brain areas. Nonetheless, the underlying network is still issue of controversial discussion. To investigate the role of form information, I developed a model and conducted psychophysical experiments using point-light walkers. A widely accepted theory claims that in point-light walkers, form information is decreased to a non-usable minimum and, thus, the perception of biological motion is driven by the analysis of motion signals. In my study, I could show that point-light walker indeed contain useful form information. Moreover, I could show that temporal integration of this information is sufficient to explain results from psychophysical, neurophysiological, and neuroimaging studies. In opposition to the standard models of biological motion perception, I could also show that all results can be explained without the analysis of local motion signals

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

Sprachniveau in Online- und TV-Nachrichten: Eine quantitative computergestützte Textanalyse der Online- und TV-Berichterstattung von ARD, ZDF, Sat.1 und RTL

Nachrichten stellen ein beliebtes Forschungsfeld der Kommunikationsforschung dar. In der entsprechenden deutschsprachigen Forschung werden vielfach die Hauptnachrichten der beiden deutschen Rundfunksysteme (öffentlich-rechtlich vs. privat) miteinander verglichen – zuletzt z. B. hinsichtlich ihres Sprachniveaus. Allerdings existiert wenig Forschung, die sich dem Online-Nachrichtenangebot widmet. Daher lag unser Ziel in der Analyse des Sprachniveaus von deutschen Online-Nachrichtenangeboten beider Systeme sowie einzelner Sender (ARD, ZDF, RTL SAT.1) mit Hilfe von vier Kategorien des Textanalyseprogramms Linguistic Inquiry and Word Count sowie von zwei weiteren Massen (Umgangssprache, Flesch-Index), die unterschiedliche Dimensionen des Sprachniveaus erfassen. In Form einer künstlichen Nachrichtenwoche wurden insgesamt 84 Online-Nachrichtentexte hinsichtlich ihres Sprachniveaus analysiert. Online-Nachrichten der Privatsender wiesen durchschnittlich längere Texte und mehr Wörter pro Satz auf. Ein Unterschied hinsichtlich Wortschatzdiversität und Wortkomplexität konnte nicht gefunden werden. Die Ergebnisse zum Flesch-Index zeigen, dass Online-Nachrichten beider Systeme ähnlich schwer verständlich sind. Diese Ergebnisse wurden aktuellen Daten zum Sprachniveau klassischer TV-Nachrichten gegenübergestellt. Dabei wurde evident, dass Online-Nachrichten höhere Werte bei einigen Markern des Sprachniveaus aufwiesen, was u. a. mit Hilfe des Kontinuums Mündlichkeit-Schriftlichkeit kontextualisierbar ist, und dass sich das Sprachniveau in Online-Nachrichten zwischen den Systemen und Sendern, im Unterschied zu TV-Nachrichten, eher ähnelte, was im ersten Fall als Konvergenz, im zweiten als Konkurrenz interpretiert werden kann

Bist du schlau? Dann guckst du(,) logo! Ein Vergleich der Wissensvermittlung durch die Nachrichtensendungen Tagesschau und logo! und ihrer sprachlichen Gestaltung

Die vorliegende empirische Studie beschäftigt sich mit dem Vergleich der Tagesschau mit den Kindernachrichten von logo! Es wurde vermutet, dass der Wissenserwerb durch logo! höher ausfällt und sich logo! durch ein niedrigeres Sprachniveau auszeichnet, was zu höherem Wissen beitragen könnte. Zur Überprüfung der Annahmen wurde ein Online-Experiment konzipiert, welches das durch beide Sendungen in Form konkreter Beiträge vermittelte Wissen von 260 Versuchspersonen empirisch überprüfte. Die verwendete Sprache wurde mit der Software LIWC analysiert; zudem wurde der Flesch-Index bestimmt. Die Ergebnisse zeigen, dass logo! zu einem höheren Wissen führt, allerdings nicht für alle Beiträge gleichermassen, und teils ein niedrigeres Sprachniveau aufweist (geringere Wortkomplexität und kürzere Sätze sowie höherer Flesch-Index). Das höhere Wissen in der logo!-Bedingung könnte dabei teils durch die eingesetzte Sprache erklärbar sein, obwohl die Befunde nicht eindeutig sind. Schliesslich zeigte sich, dass der logo!-Vorteil bei Personen mit Hochschulabschluss grösser war als bei anderen Personen, was vor dem Hintergrund der Wissenskluft-Hypothese verständlich wird. Aus unseren Befunden lassen sich Praxisempfehlungen u. a. zur sprachlichen Gestaltung von TV-Nachrichten ableiten, um den Wissenserwerb zu verbessern. The present empirical study deals with the comparison of the Tagesschau with the children’s news from logo! It was assumed that the acquisition of knowledge by logo! is higher and that logo! is characterized by a lower language level, which could contribute to higher knowledge. To test the assumptions, an online experiment was designed which empirically tested the knowledge conveyed by both programs in the form of concrete contributions from 260 study participants. The language used was analyzed with the LIWC software; the Flesch-Index was also determined. The results show that logo! leads to a higher level of knowledge, although not equally for all contributions, and in some cases has a lower language level (lower word complexity and shorter sentences as well as a higher Flesch-Index). The higher knowledge in the logo! condition could thereby be partly explained by the language used, although the findings are not entirely clear. Finally, the logo! advantage was found to be greater for individuals with a university degree than for others, which becomes understandable in light of the knowledge gap hypothesis. From our findings, practical recommendations can be derived, among other things, for the linguistic design of TV news in order to improve knowledge acquisition

Night lights and regional GDP

Night lights could be a valuable proxy of economic activity at the subnational level when GDP data are lacking or of poor quality. Supplementing Henderson et al.'s (2012) analysis at the national level, we assess the stability of the elasticity of GDP with regard to night lights across regions in Brazil, India, the United States, and Western Europe. The relationship between regional GDP and night lights proves to be unstable, not only where regional GDP data may be unreliable but also where such data are of high quality. This suggests that night lights tend to be a poor proxy of regional economic activity

Oceanic lithospheric S wave velocities from the analysis of P wave polarization at the ocean floor

Our knowledge of the absolute S wave velocities of the oceanic lithosphere is mainly based on global surface wave tomography, local active seismic or compliance measurements using oceanic infragravity waves. The results of tomography give a rather smooth picture of the actual S wave velocity structure and local measurements have limitations regarding the range of elastic parameters or the geometry of the measurement. Here, we use the P wave polarization (apparent P wave incidence angle) of teleseismic events to investigate the S wave velocity structure of the oceanic crust and the upper tens of kilometres of the mantle beneath single stations. In this study, we present an up to our knowledge new relation of the apparent P wave incidence angle at the ocean bottom dependent on the half space S wave velocity. We analyse the angle in different period ranges at ocean bottom stations (OBS) to derive apparent S wave velocity profiles. These profiles are dependent on the S wave velocity as well as on the thickness of the layers in the subsurface. Consequently, their interpretation results in a set of equally valid models. We analyse the apparent P wave incidence angles of an OBS data set which was collected in the Eastern Mid Atlantic. We are able to determine reasonable S wave velocity-depth models by a three step quantitative modelling after a manual data quality control, although layer resonance sometimes influences the estimated apparent S wave velocities. The apparent S wave velocity profiles are well explained by an oceanic PREM model in which the upper part is replaced by four layers consisting of a water column, a sediment, a crust and a layer representing the uppermost mantle. The obtained sediment has a thickness between 0.3 km and 0.9 km with S wave velocities between 0.7 km s−1 and 1.4 km s−1. The estimated total crustal thickness varies between 4 km and 10 km with S wave velocities between 3.5 km s−1 and 4.3 km s−1. We find a slight increase of the total crustal thickness from ∼5 km to ∼8 km towards the South in the direction of a major plate boundary, the Gloria Fault. The observed crustal thickening can be related with the known dominant compression in the vicinity of the fault. Furthermore, the resulting mantle S wave velocities decrease from values around 5.5 km s−1 to 4.5 km s−1 towards the fault. This decrease is probably caused by serpentinization and indicates that the oceanic transform fault affects a broad region in the uppermost mantle. Conclusively, the presented method is useful for the estimation of the local S wave velocity structure beneath ocean bottom seismic stations. It is easy to implement and consists of two main steps: (1) measurement of apparent P wave incidence angles in different period ranges for real and synthetic data, and (2) comparison of the determined apparent S wave velocities for real and synthetic data to estimate S wave velocity-depth models

Redesigned Human Metabolic Simulator

A design has been formulated for a proposed improved version of an apparatus that simulates atmospheric effects of human respiration by introducing controlled amounts of carbon dioxide, water vapor, and heat into the air. Denoted a human metabolic simulator (HMS), the apparatus is used for testing life-support equipment when human test subjects are not available. The prior version of the HMS, to be replaced, was designed to simulate the respiratory effects of as many as four persons. It exploits the catalytic combustion of methyl acetate, for which the respiratory quotient (the molar ratio of carbon dioxide produced to oxygen consumed) is very close to the human respiratory quotient of about 0.86. The design of the improved HMS provides for simulation of the respiratory effects of as many as eight persons at various levels of activity. The design would also increase safety by eliminating the use of combustion. The improved HMS (see figure) would include a computer that would exert overall control. The computer would calculate the required amounts of oxygen removal, carbon dioxide addition, water addition, and heat addition by use of empirical equations for metabolic profiles of respiration and heat. A blower would circulate air between the HMS and a chamber containing a life-support system to be tested. With the help of feedback from a mass flowmeter, the blower speed would be adjusted to regulate the rate of flow according to the number of persons to be simulated and to a temperature-regulation requirement (the air temperature would indirectly depend on the rate of flow, among other parameters). Oxygen would be removed from the circulating air by means of a commercially available molecular sieve configured as an oxygen concentrator. Oxygen, argon, and trace amounts of nitrogen would pass through a bed in the molecular sieve while carbon dioxide, the majority of nitrogen, and other trace gases would be trapped by the bed and subsequently returned to the chamber. If, as recommended, the oxygen concentrator were of a rotating twelve-bed design, then variations in the product stream could be made very small. Carbon dioxide would be added directly to the circulating air by simple injection from a supply tank. The rate of injection would be maintained at the required rate by use of a mass flowmeter/controller. In the same way, nitrogen would be added to make up for the small amount of nitrogen lost through the oxygen concentrator. Water vapor would be added to the circulating air by heating the corresponding required flow of water to steam in a heat exchanger. More heat, required to complete the simulation of the thermal effect of respiration, would be added through another heat exchanger. Heat would be supplied to both heat exchangers via a hot-oil loop

Discrete-Continuous ADMM for Transductive Inference in Higher-Order MRFs

This paper introduces a novel algorithm for transductive inference in higher-order MRFs, where the unary energies are parameterized by a variable classifier. The considered task is posed as a joint optimization problem in the continuous classifier parameters and the discrete label variables. In contrast to prior approaches such as convex relaxations, we propose an advantageous decoupling of the objective function into discrete and continuous subproblems and a novel, efficient optimization method related to ADMM. This approach preserves integrality of the discrete label variables and guarantees global convergence to a critical point. We demonstrate the advantages of our approach in several experiments including video object segmentation on the DAVIS data set and interactive image segmentation