We review here the interplay of cluster and galaxy evolution. As a case study, we consider the Butcher-Oemler effect and propose that it is the result of the changing rate of cluster merger events in ...a hierarchical universe. This case study highlights the need for new catalogs of clusters and groups that possess quantified morphologies. We present such a sample here, namely the Sloan Digital Sky Survey (SDSS) C4 Catalog, which has been objectively-selected from the SDSS spectroscopic galaxy sample. We outline here the C4algorithm and present first results based on the SDSS Early Data Release, including an X-ray luminosity-velocity dispersion (L^sub x^-σ^sub v^) scaling relationship (as a function of cluster morphology) and the density-SFR relation of galaxies within C4 clusters (Gomez et al., 2003). We also discuss the merger of Coma and the NGC4839 group and its effect on the galaxy populations in these systems. We finish with a brief discussion of a new sample ofHΔ-selected galaxies (i.e., k+a, post-starburst galaxies) obtained from the SDSS spectroscopic survey.PUBLICATION ABSTRACT
We study the stellar populations of Type Ia supernova (SN Ia) host galaxies using Sloan Digital Sky Survey (SDSS)-II spectroscopy. The main focus is on the relationships of SN Ia properties with ...stellar velocity dispersion and the stellar population parameters age, metallicity and element abundance ratios. We concentrate on a sub-sample of 84 SNe Ia from the SDSS-II Supernova Survey and find that SALT2 stretch factor values show the strongest dependence on stellar population age. Hence, more luminous SNe Ia appear in younger stellar progenitor systems. No statistically significant trends in the Hubble residual with any of the stellar population parameters studied are found. Moreover, the method of photometric stellar mass derivation affects the Hubble residual-mass relationship. For an extended sample (247 objects), including SNe Ia with SDSS host galaxy photometry only, the Hubble residual-mass relationship behaves as a sloped step function. In the high-mass regime, probed by our host spectroscopy sample, this relationship is flat. Below a stellar mass of ∼2 × 1010 M, i.e. close to the evolutionary transition mass of low-redshift galaxies, the trend changes dramatically such that lower mass galaxies possess lower luminosity SNe Ia after light-curve corrections. The sloped step function of the Hubble residual-mass relationship should be accounted for when using stellar mass as a further parameter for minimizing the Hubble residuals.
Previously, we investigated the role of the Rift Valley fever virus (RVFV) virulence genes NSs and NSm in mosquitoes and demonstrated that deletion of NSm significantly reduced the infection, ...dissemination, and transmission rates of RVFV in Aedes aegypti mosquitoes. The specific aim of this study was to further characterize midgut infection and escape barriers of RVFV in Ae. aegypti infected with reverse genetics-generated wild type RVFV (rRVF-wt) or RVFV lacking the NSm virulence gene (rRVF-ΔNSm) by examining sagittal sections of infected mosquitoes for viral antigen at various time points post-infection.
Ae. aegypti mosquitoes were fed an infectious blood meal containing either rRVF-wt or rRVF-ΔNSm. On days 0, 1, 2, 3, 4, 6, 8, 10, 12, and 14 post-infection, mosquitoes from each experimental group were fixed in 4% paraformaldehyde, paraffin-embedded, sectioned, and examined for RVFV antigen by immunofluorescence assay. Remaining mosquitoes at day 14 were assayed for infection, dissemination, and transmission. Disseminated infections were observed in mosquitoes as early as three days post infection for both virus strains. However, infection rates for rRVF-ΔNSm were statistically significantly less than for rRVF-wt. Posterior midgut infections in mosquitoes infected with rRVF-wt were extensive, whereas midgut infections of mosquitoes infected with rRVF-ΔNSm were confined to one or a few small foci.
Deletion of NSm resulted in the reduced ability of RVFV to enter, replicate, and disseminate from the midgut epithelial cells. NSm appears to have a functional role in the vector competence of mosquitoes for RVFV at the level of the midgut barrier.
We present the angular diameter distance measurement obtained with the
Baryonic Acoustic Oscillation feature from galaxy clustering in the completed
Dark Energy Survey, consisting of six years (Y6) ...of observations. We use the Y6
BAO galaxy sample, optimized for BAO science in the redshift range 0.6<$z$<1.2,
with an effective redshift at $z_{\rm eff}$=0.85 and split into six tomographic
bins. The sample has nearly 16 million galaxies over 4,273 square degrees. Our
consensus measurement constrains the ratio of the angular distance to sound
horizon scale to $D_M(z_{\rm eff})/r_d$ = 19.51$\pm$0.41 (at 68.3% confidence
interval), resulting from comparing the BAO position in our data to that
predicted by Planck $\Lambda$CDM via the BAO shift parameter
$\alpha=(D_M/r_d)/(D_M/r_d)_{\rm Planck}$. To achieve this, the BAO shift is
measured with three different methods, Angular Correlation Function (ACF),
Angular Power Spectrum (APS), and Projected Correlation Function (PCF)
obtaining $\alpha=$ 0.952$\pm$0.023, 0.962$\pm$0.022, and 0.955$\pm$0.020,
respectively, which we combine to $\alpha=$ 0.957$\pm$0.020, including
systematic errors. When compared with the $\Lambda$CDM model that best fits
Planck data, this measurement is found to be 4.3% and 2.1$\sigma$ below the
angular BAO scale predicted. To date, it represents the most precise angular
BAO measurement at $z$>0.75 from any survey and the most precise measurement at
any redshift from photometric surveys. The analysis was performed blinded to
the BAO position and it is shown to be robust against analysis choices, data
removal, redshift calibrations and observational systematics.
Kyasanur Forest disease virus (KFDV) is enzootic to India and maintained in ticks, mammals, and birds. It causes severe febrile illness in humans and was first recognized in 1957 associated with a ...high number of deaths among monkeys in Kyasanur Forest. Genetic analysis of 48 viruses isolated in India during 1957-2006 showed low diversity (1.2%). Bayesian coalescence analysis of these sequences and those of KFDVs from Saudi Arabia and the People's Republic of China estimated that KFDVs have evolved at a mean rate of approximately 6.4 x 10(-4) substitutions/site/year, which is similar to rates estimated for mosquito-borne flaviviruses. KFDVs were estimated to have shared a common ancestor in approximately 1942, fifteen years before identification of the disease in India. These data are consistent with the view that KFD represented a newly emerged disease when first recognized. Recent common ancestry of KFDVs from India and Saudi Arabia, despite their large geographic separation, indicates long-range movement of virus, possibly by birds.
We present measurements of the angular diameter distance to and Hubble parameter at z = 0.57 from the measurement of the baryon acoustic peak in the correlation of galaxies from the Sloan Digital Sky ...Survey III Baryon Oscillation Spectroscopic Survey. Our analysis is based on a sample from Data Release 9 of 264 283 galaxies over 3275 square degrees in the redshift range 0.43 < z < 0.70. We use two different methods to provide robust measurement of the acoustic peak position across and along the line of sight in order to measure the cosmological distance scale. We find DA(0.57) = 1408 ± 45 Mpc and H(0.57) = 92.9 ± 7.8 km s-1 Mpc-1 for our fiducial value of the sound horizon. These results from the anisotropic fitting are fully consistent with the analysis of the spherically averaged acoustic peak position presented in Anderson et al. Our distance measurements are a close match to the predictions of the standard cosmological model featuring a cosmological constant and zero spatial curvature.
While serological and virological evidence documents the exposure of bats to medically-important arboviruses, their role as reservoirs or amplifying hosts is less well-characterized. We describe a ...novel orbivirus (
) isolated from an Egyptian fruit bat (
) trapped in 2013 in Uganda and named Bukakata orbivirus. This is the fifth orbivirus isolated from a bat, however genetic information had previously only been available for one bat-associated orbivirus. We performed whole-genome sequencing on Bukakata orbivirus and three other bat-associated orbiviruses (Fomede, Ife, and Japanaut) to assess their phylogenetic relationship within the genus
and develop hypotheses regarding potential arthropod vectors. Replication kinetics were assessed for Bukakata orbivirus in three different vertebrate cell lines. Lastly, qRT-PCR and nested PCR were used to determine the prevalence of Bukakata orbivirus RNA in archived samples from three populations of Egyptian fruit bats and one population of cave-associated soft ticks in Uganda. Complete coding sequences were obtained for all ten segments of Fomede, Ife, and Japanaut orbiviruses and for nine of the ten segments for Bukakata orbivirus. Phylogenetic analysis placed Bukakata and Fomede in the tick-borne orbivirus clade and Ife and Japanaut within the
/phlebotomine sandfly orbivirus clade. Further, Bukakata and Fomede appear to be serotypes of the
species. Bukakata orbivirus replicated to high titers (10⁶⁻10⁷ PFU/mL) in Vero, BHK-21 C-13, and R06E (Egyptian fruit bat) cells. Preliminary screening of archived bat and tick samples do not support Bukakata orbivirus presence in these collections, however additional testing is warranted given the phylogenetic associations observed. This study provided complete coding sequence for several bat-associated orbiviruses and in vitro characterization of a bat-associated orbivirus. Our results indicate that bats may play an important role in the epidemiology of viruses in the genus
and further investigation is warranted into vector-host associations and ongoing surveillance efforts.
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