Void Statistics in Large Galaxy Redshift Surveys: Does Halo Occupation of Field Galaxies Depend on Environment?

We use measurements of the projected galaxy correlation function w_p and galaxy void statistics to test whether the galaxy content of halos of fixed mass is systematically different in low density environments. We present new measurements of the void probability function (VPF) and underdensity probability function (UPF) from Data Release Four of the Sloan Digital Sky Survey, as well as new measurements of the VPF from the full data release of the Two-Degree Field Galaxy Redshift Survey. We compare these measurements to predictions calculated from models of the Halo Occupation Distribution (HOD) that are constrained to match both w_p and the space density of galaxies. The standard implementation of the HOD assumes that galaxy occupation depends on halo mass only, and is independent of local environment. For luminosity-defined samples, we find that the standard HOD prediction is a good match to the observations, and the data exclude models in which galaxy formation efficiency is reduced in low-density environments. More remarkably, we find that the void statistics of red and blue galaxies (at L ~ 0.4L_*) are perfectly predicted by standard HOD models matched to the correlation function of these samples, ruling out "assembly bias" models in which galaxy color is correlated with large-scale environment at fixed halo mass. We conclude that the luminosity and color of field galaxies are determined predominantly by the mass of the halo in which they reside and have little direct dependence on the environment in which the host halo formed. In broader terms, our results show that the sizes and emptiness of voids found in the distribution of L > 0.2L_* galaxies are in excellent agreement with the predictions of a standard cosmological model with a simple connection between galaxies and dark matter halos. (abridged)Comment: 20 emulateapj pages, 9 figures. submitted to Ap

The spectral-type/luminosity and the spectral type/satellite-density relations in the 2dFGRS

We examine the relative fractions of passive (Type 1), quiet-SF (Type 2) and active-SF (Type 3+4) galaxies as a function of luminosity and number of neighbours in several volume limited samples selected from the 2dFGRS. Neighbours are counted within 1 $h_{75}^{-1}$ Mpc projected distance, and $\pm$ 1000 km s$^{-1}$ depth. We apply a maximum magnitude difference criterion and require neighbours to be fainter than the galaxy itself. We show that, whatever the environment, passive galaxies dominate in bright samples and active-SF galaxies in faint samples, whereas quiet-SF galaxies never dominate. We further show that in bright samples (M$_{B}$ -- 5 $\log$ $h_{75}$ $\leq$$- 19$) the fraction of passive galaxies grows steadily with fainter neighbour density, whereas in faint samples a threshold like dependence is observed. This suggests that the spectral-type / density ($\approx$ morphology / density) relation extends to intermediate dense environment, but only in the surrounding of luminous galaxies and that it reflects an enhancement of the number of satellites rather than stronger clustering among galaxies themselves. Our analysis indicates that, in general, luminosity is a good tracer of a galaxy halo mass and that it dominates over environment (satellite density) in setting the spectral type mix of a population. However, minority populations exist, such as luminous SF galaxies and faint passive galaxies, whose luminosity is an unfair tracer of halo mass.Comment: 8 pages, 5 figur

The angular correlations of galaxies in the COSMOS field

We present measurements of the two-point galaxy angular correlation function w(\theta) in the COSMOS field. Independent determinations of w(\theta) as a function of magnitude limit are presented for both the HST ACS catalog and also for the ground-based data from Subaru and the CFHT. Despite having significantly different masks, these three determinations agree well. At bright magnitudes (IAB<22), our data generally match very well with existing measurements and with mock catalogs based on semi-analytic galaxy formation calculations of Kitzbichler and White from the Millennium Simulation. The exception is that our result is at the upper end of the expected cosmic variance scatter for \theta > 10 arcmin, which we attribute to a particularly rich structure known to exist at z~0.8. For fainter samples, however, the level of clustering is somewhat higher than reported by some previous studies: in all three catalogues we find w(\theta=1')~0.014 at a median IAB magnitude of 24. At these very faintest magnitudes, our measurements agree well with the latest determinations from the Canada-France Legacy Survey. This level of clustering is approximately double what is predicted by the semi-analytic catalogs (at all angles). The semi-analytic results allow an estimate of cosmic variance, which is too small to account for the discrepancy. We therefore conclude that the mean amplitude of clustering at this level is higher than previously estimated.Comment: Six pages, five figures. Accepted for publication in the ApJS COSMOS special issue, Sept. 200

INTEROP deliverable DTG 6.2 : Method repository

This deliverable presents the INTEROP method chunks repository (MCR), its architecture and provided services. It includes the definition of a reusable method chunk, its structure, illustrated with examples of method chunks stored in the repository and guidelines for method chunks definition and characterisation covering tasks TG6.2 and TG6.3 of the work plan of the task group. The main result is the definition of the structure of the method chunk repository emphasizing the link to interoperability. Interoperability is a first-class concept in the structure of the method chunk repository. It not only characterizes method chunks, i.e. procedures to solve interoperability problems, but also interoperability cases, i.e. the presentation of actual problems involving interoperability issues. TG 6 has produced three MCR prototypes. Two experiments were undertaken using the Metis system and one using ConceptBase. The task group attended a two-day intense workshop on Metis. As a result, two experiments with Metis as platform for the method chunk repository are under way and reported in this deliverable. One is realizing the structure of the MCR as specified in this report. The other is an alternative approach that serves as a benchmark and is reported in the appendix. The ConceptBase prototype utilizes the metamodel presented in this deliverable. We have analysed three cases involving various aspects of interoperability. One case is about establishing a broker platform for insurance agents, the second about linking the information systems in the public utility sector, and the third case is establishing the relation of the ATHENA Model-Driven Interoperability Framework to the goals of the MCR. The results of the TG6 have been published at the ISD conference 2006 and the ER conference 2006. Copies of the papers are included in the appendix. The report of the example session with the method chunk repository has been shifted towards deliverable TG6.3 (Tutorial of the MCR). This is the more logical place. We want to emphasize that TG6 was not only busy in drafting concepts, exploring the state of the art, and analyzing cases. We are actually experimenting with a prototype and consider this a valuable contribution to the network. As soon as the prototype is stable, knowledge about interoperability solutions can be coded in this repository and can guide designers of interoperable systems by experience knowledge

Forecasting neutrino masses from galaxy clustering in the Dark Energy Survey combined with the Planck Measurements

We study the prospects for detecting neutrino masses from the galaxy angular power spectrum in photometric redshift shells of the Dark Energy Survey (DES) over a volume of 20 (Gpc/h)^3 combined with the Cosmic Microwave Background (CMB) angular fluctuations expected to be measured from the Planck satellite. We find that for a Lambda-CDM concordance model with 7 free parameters in addition to a fiducial neutrino mass of M_nu = 0.24 eV, we recover from DES &Planck the correct value with uncertainty of +- 0.12 eV (95 % CL), assuming perfect knowledge of the galaxy biasing. If the fiducial total mass is close to zero, then the upper limit is 0.11 eV (95 % CL). This upper limit from DES &Planck is over 3 times tighter than using Planck alone, as DES breaks the parameter degeneracies in a CMB-only analysis. The analysis utlilizes spherical harmonics up to 300, averaged in bin of 10 to mimic the DES sky coverage. The results are similar if we supplement DES bands (grizY) with the VISTA Hemisphere Survey (VHS) near infrared band (JHK). The result is robust to uncertainties in non-linear fluctuations and redshift distortions. However, the result is sensitive to the assumed galaxy biasing schemes and it requires accurate prior knowledge of the biasing. To summarize, if the total neutrino mass in nature greater than 0.1eV, we should be able to detect it with DES &Planck, a result with great importance to fundamental Physics.Comment: Submitted to MNRAS, 9 pages, 10 figure

Genetic Predisposition to Long-Term Nondiabetic Deteriorations in Glucose Homeostasis: Ten-Year Follow-Up of the GLACIER Study

Objective: To assess whether recently discovered genetic loci associated with hyperglycemia also predict long-term changes in glycemic traits. Research Design and Methods: Sixteen fasting glucose-raising loci were genotyped in middle-aged adults from the Gene x Lifestyle interactions And Complex traits Involved in Elevated disease Risk (GLACIER) Study, a population-based prospective cohort study from northern Sweden. Genotypes were tested for association with baseline fasting and 2-h postchallenge glycemia (N = 16,330), and for changes in these glycemic traits during a 10-year follow-up period (N = 4,059). Results: Cross-sectional directionally consistent replication with fasting glucose concentrations was achieved for 12 of 16 variants; 10 variants were also associated with impaired fasting glucose (IFG) and 7 were independently associated with 2-h postchallenge glucose concentrations. In prospective analyses, the effect alleles at four loci (GCK rs4607517, ADRA2A rs10885122, DGKB-TMEM195 rs2191349, and G6PC2 rs560887) were nominally associated with worsening fasting glucose concentrations during 10-years of follow-up. MTNR1B rs10830963, which was predictive of elevated fasting glucose concentrations in cross-sectional analyses, was associated with a protective effect on postchallenge glucose concentrations during follow-up; however, this was only when baseline fasting and 2-h glucoses were adjusted for. An additive effect of multiple risk alleles on glycemic traits was observed: a weighted genetic risk score (80th vs. 20th centiles) was associated with a 0.16 mmol/l (P = 2.4 × 10$^{−6}$) greater elevation in fasting glucose and a 64% (95% CI: 33–201%) higher risk of developing IFG during 10 years of follow-up. Conclusions: Our findings imply that genetic profiling might facilitate the early detection of persons who are genetically susceptible to deteriorating glucose control; studies of incident type 2 diabetes and discrete cardiovascular end points will help establish whether the magnitude of these changes is clinically relevant

Objective and Subjective Factors as Predictors of Post-Traumatic Stress Symptoms in Parents of Children with Cancer – A Longitudinal Study

BACKGROUND: Parents of children with cancer report post-traumatic stress symptoms (PTSS) years after the child's successful treatment is completed. The aim of the present study was to analyze a number of objective and subjective childhood cancer-related factors as predictors of parental PTSS. METHODS: Data were collected from 224 parents during and after their child's cancer treatment. Data sources include self-report questionnaires and medical records. RESULTS: In a multivariate hierarchical model death of the child, parent's perception of child psychological distress and total symptom burden predicted higher levels of PTSS. In addition, immigrants and unemployed parents reported higher levels of PTSS. The following factors did not predict PTSS: parent gender, family income, previous trauma, child's prognosis, treatment intensity, non-fatal relapse, and parent's satisfaction with the child's care. CONCLUSIONS: Although medical complications can be temporarily stressful, a parent's perception of the child's distress is a more powerful predictor of parental PTSS. The vulnerability of unemployed parents and immigrants should be acknowledged. In addition, findings highlight that the death of a child is as traumatic as could be expected