Low luminosity elliptical galaxies

Long-slit spectra for the photometric axes of a sample of 14 elliptical galaxies, predominantly low-luminosity ellipticals, in the Virgo cluster and in nearby groups, are studied to investigate the galaxy kinematical structure and stellar evolutionary history. To determine the galaxy kinematical structure, the shape of the line-of-sight velocity distribution (hereafter LOSVD) is measured using the Fourier Correlation Quotient method of Bender (1990), adopting the parametrisation of the LOSVD due to van der Marel and Franx (1993). This parametrisation enables the asymmetrical and symmetrical deviations of the LOSVD from a Gaussian function to be measured by the amplitudes H(_3) and H(_4) of the Gauss-Hermite series respectively. Rotation, velocity dispersion (σ), H(_3) and H(_4) are determined as a function of radius for both the major and minor axes of our sample. To summarise, LOSVD asymmetries were measured for the major axes of 12 galaxies which in the majority of cases have been interpreted as evidence for central disk-like components; evidence of both radial and tangential anisotropy were found from the measurement of H(_4); central decreases in σ are measured for 3 galaxies, which is interpreted as evidence that they have undergone some form of merger or interaction. On the basis of their measurements, galaxies are classified into 3 classes: types 1, 2 and 3. "Type 1" galaxies show strong evidence for both disk and bulge components and have the greatest measured values of H(_3) for our sample. Galaxies of "type 2" show strong evidence for embedded disk components and most (3 of 4) are measured to have central decreases in a. "Type 3" galaxies have kinematically-decoupled cores. Other galaxies, not classified, are NGC 3379 and NGC 4468.Measurements of the line-strength indices Mg(_b), Mg(_2), Hβ, Fe5270, Fe5335 and are determined as a function of radius for all spectra and established to the Lick/IDS scale. The relations Mg’(_b)-Mg(_2), Mg’(_b), - log(σ), Mg(_b)- and Hβ-[Mg(_b) ] are then studied. The Mg’(_b),-Mg(_2) relation of Wegner et al. (1998) and the calibrations of Worthey (1994) are compared with measurements here: this is used as a check of our calibration of Mg’(b), and Mg(_2). Measurements in the Mg’(_b)-log(σ) plane are considered separately for each galaxy and compared with the central relation of Colless et al. (1998). Measurements for most galaxies are found to be in good agreement with this relation. Measurements of Mg(_b) and are similarly considered for each galaxy and compared with the predictions of the models of Worthey (1994). For the majority of galaxies, measurements are clearly offset from the Mg(_b)- model grid of Worthey (1994), representing an [(^Mg)-(_Fe)] overabundance. This is an important result which shows that the [(^Mg)-(_Fe)] overabundance detected previously for the giant ellipticals similarly exists for ellipticals of the low luminosities studied here. For most galaxies this overabundance is found to be a constant function of radius. For the "type 2" galaxy NGC 3605, and NGC 4468, measurements are consistent with solar abundance ratios. Finally, measurements of Hβ and [Mg(_b) ] are compared with the models of Worthey (1994) to distinguish gradients in both age and metallicity. For all galaxies, gradients in metallicity are found with metallicity decreasing as a function of radius. For 5 galaxies (NGC 4564, NGC 3377, NGC 4478, NGC 4339 and NGC 3605) age gradients are also detected, with the galaxy centre shown to be younger than the surrounding galaxy. Interpreting these results together, different formation scenarios are proposed for the different galaxy types. For galaxies of "type 1", formation by homogenous, dissipational collapse is proposed. Galaxies of "type 2" show evidence for a less homogenous evolutionary history involving dissipationless collapse. No conclusive scenario is proposed for galaxies of "type 3"

Abnormal connectivity between the default mode and the visual system underlies the manifestation of visual hallucinations in Parkinson’s disease:A task-based fMRI study

Background: The neural substrates of visual hallucinations remain an enigma, due primarily to the difficulties associated with directly interrogating the brain during hallucinatory episodes. Aims: To delineate the functional patterns of brain network activity and connectivity underlying visual hallucinations in Parkinson’s disease. Methods: In this study, we combined functional magnetic resonance imaging (MRI) with a behavioral task capable of eliciting visual misperceptions, a confirmed surrogate for visual hallucinations, in 35 patients with idiopathic Parkinson’s disease. We then applied an independent component analysis to extract time series information for large-scale neuronal networks that have been previously implicated in the pathophysiology of visual hallucinations. These data were subjected to a task-based functional connectivity analysis, thus providing the first objective description of the neural activity and connectivity during visual hallucinations in patients with Parkinson’s disease. Results: Correct performance of the task was associated with increased activity in primary visual regions; however, during visual misperceptions, this same visual network became actively coupled with the default mode network (DMN). Further, the frequency of misperception errors on the task was positively correlated with the strength of connectivity between these two systems, as well as with decreased activity in the dorsal attention network (DAN), and with impaired connectivity between the DAN and the DMNs, and ventral attention networks. Finally, each of the network abnormalities identified in our analysis were significantly correlated with two independent clinical measures of hallucination severity. Conclusions: Together, these results provide evidence that visual hallucinations are due to increased engagement of the DMN with the primary visual system, and emphasize the role of dysfunctional engagement of attentional networks in the pathophysiology of hallucinations

Halpha-Derived Star-Formation Rates For Three z ~ 0.75 EDisCS Galaxy Clusters

We present Halpha-derived star-formation rates (SFRs) for three z ~ 0.75 galaxy clusters. Our 1 sigma flux limit corresponds to a star-formation rate of 0.10-0.24 solar mass per year, and our minimum reliable Halpha + [N II] rest-frame equivalent width is 10\AA. We show that Halpha narrowband imaging is an efficient method for measuring star formation in distant clusters. In two out of three clusters, we find that the fraction of star-forming galaxies increases with projected distance from the cluster center. We also find that the fraction of star-forming galaxies decreases with increasing local galaxy surface density in the same two clusters. We compare the median rate of star formation among star-forming cluster galaxies to a small sample of star-forming field galaxies from the literature and find that the median cluster SFRs are \~50% less than the median field SFR. We characterize cluster evolution in terms of the mass-normalized integrated cluster SFR and find that the z ~ 0.75 clusters have more SFR per cluster mass on average than the z <= 0.4 clusters from the literature. The interpretation of this result is complicated by the dependence of the mass-normalized SFR on cluster mass and the lack of sufficient overlap in the mass ranges covered by the low and high redshift samples. We find that the fraction and luminosities of the brightest starburst galaxies at z ~ 0.75 are consistent with their being progenitors of the post-starburst galaxies at z ~ 0.45 if the post-starburst phase lasts several (~5) times longer than the starburst phase.Comment: Accepted for publication in ApJ, 20 pages, 24 figure

Implementer and recipient perspectives of community-wide mass drug administration for soil-transmitted helminths in Kwale County, Kenya.

Soil-transmitted helminthiases (STH) are one of 17 neglected tropical diseases (NTDs) earmarked for control or elimination by 2020 in the WHO's Roadmap on NTDs. Deworming programs for STH have thus far been focused on treating pre-school and school-aged children; however, there is a growing consensus that to achieve elimination of STH transmission, programs must also target adults, potentially through community-wide mass drug administration (MDA). There is currently a gap in the literature on what components are required to deliver community-wide MDA for STH in order to achieve high intervention reach and uptake. Nested within the TUMIKIA Project, a cluster randomized trial in Kenya evaluating the effectiveness of school-based deworming versus community-wide MDA, we collected qualitative data from program implementers and recipients in eight clusters where community-wide MDA was delivered. Data collection included semi-structured in-depth interviews (n = 72) and focus group discussions (n = 32). A conceptual framework for drug distribution was constructed to help build an analysis codebook. Case memos were developed for each top-level theme. Community-wide MDA for STH was perceived as a complex intervention with key administrative and social mobilization domains. Key actionable themes included: (1) developing an efficient strategy to allocate reasonable workload for implementers to cover all targeted households; (2) maximizing community drug distributors' motivation through promoting belief in the effectiveness of the intervention and providing sufficient financial incentives; (3) developing effective capacity building strategies for implementers; and (4) implementing a context-adapted community engagement strategy that leverages existing community structures and takes into consideration past community experiences of MDAs. Transitioning from STH control to elimination goals requires significant planning and action to ensure community-wide MDA is delivered with sufficient reach and uptake. We present findings that can inform national deworming programs to increase intervention delivery capacity

Cerebellar atrophy in Parkinson's disease and its implication for network connectivity.

Pathophysiological and atrophic changes in the cerebellum are documented in Parkinson's disease. Without compensatory activity, such abnormalities could potentially have more widespread effects on both motor and non-motor symptoms. We examined how atrophic change in the cerebellum impacts functional connectivity patterns within the cerebellum and between cerebellar-cortical networks in 42 patients with Parkinson's disease and 29 control subjects. Voxel-based morphometry confirmed grey matter loss across the motor and cognitive cerebellar territories in the patient cohort. The extent of cerebellar atrophy correlated with decreased resting-state connectivity between the cerebellum and large-scale cortical networks, including the sensorimotor, dorsal attention and default networks, but with increased connectivity between the cerebellum and frontoparietal networks. The severity of patients' motor impairment was predicted by a combination of cerebellar atrophy and decreased cerebellar-sensorimotor connectivity. These findings demonstrate that cerebellar atrophy is related to both increases and decreases in cerebellar-cortical connectivity in Parkinson's disease, identifying potential cerebellar driven functional changes associated with sensorimotor deficits. A post hoc analysis exploring the effect of atrophy in the subthalamic nucleus, a cerebellar input source, confirmed that a significant negative relationship between grey matter volume and intrinsic cerebellar connectivity seen in controls was absent in the patients. This suggests that the modulatory relationship of the subthalamic nucleus on intracerebellar connectivity is lost in Parkinson's disease, which may contribute to pathological activation within the cerebellum. The results confirm significant changes in cerebellar network activity in Parkinson's disease and reveal that such changes occur in association with atrophy of the cerebellum

The build-up of the colour-magnitude relation in galaxy clusters since z~0.8

Using galaxy clusters from the ESO Distant Cluster Survey, we study how the distribution of galaxies along the colour-magnitude relation has evolved since z~0.8. While red-sequence galaxies in all these clusters are well described by an old, passively evolving population, we confirm our previous finding of a significant evolution in their luminosity distribution as a function of redshift. When compared to galaxy clusters in the local Universe, the high redshift EDisCS clusters exhibit a significant "deficit" of faint red galaxies. Combining clusters in three different redshift bins, and defining as `faint' all galaxies in the range 0.4 > L/L* > 0.1, we find a clear decrease in the luminous-to-faint ratio of red galaxies from z~0.8 to z~0.4. The amount of such a decrease appears to be in qualitative agreement with predictions of a model where the blue bright galaxies that populate the colour-magnitude diagram of high redshift clusters, have their star formation suppressed by the hostile cluster environment. Although model results need to be interpreted with caution, our findings clearly indicate that the red-sequence population of high-redshift clusters does not contain all progenitors of nearby red-sequence cluster galaxies. A significant fraction of these must have moved onto the red-sequence below z~0.8.Comment: 15 pages, 10 figures, accepted for publication in MNRA

Preprocessing Among the Infalling Galaxy Population of EDisCS Clusters

We present results from a low-resolution spectroscopic survey for 21 galaxy clusters at $0.4 < z < 0.8$ selected from the ESO Distant Cluster Survey. We measured spectra using the low-dispersion prism in IMACS on the Magellan Baade telescope and calculate redshifts with an accuracy of $\sigma_z = 0.007$. We find 1763 galaxies that are brighter than $R = 22.9$ in the large-scale cluster environs. We identify the galaxies expected to be accreted by the clusters as they evolve to $z = 0$ using spherical infall models and find that $\sim30\%$ to $\sim70\%$ of the $z = 0$ cluster population lies outside the virial radius at $z \sim 0.6$. For analogous clusters at $z = 0$, we calculate that the ratio of galaxies that have fallen into the clusters since $z \sim 0.6$ to those that were already in the core at that redshift is typically between $\sim0.3$ and $1.5$. This wide range of ratios is due to intrinsic scatter and is not a function of velocity dispersion, so a variety of infall histories is to be expected for clusters with current velocity dispersions of $300 \lesssim\sigma\lesssim 1200$ km s$^{-1}$. Within the infall regions of $z \sim 0.6$ clusters, we find a larger red fraction of galaxies than in the field and greater clustering among red galaxies than blue. We interpret these findings as evidence of "preprocessing", where galaxies in denser local environments have their star formation rates affected prior to their aggregation into massive clusters, although the possibility of backsplash galaxies complicates the interpretation.Comment: Accepted for publication in Ap