Ram pressure stripping candidates in the coma cluster: evidence for enhanced star formation

ABSTRACT The Coma cluster is the nearest massive ($M \gtrsim 10^{15}\, \mathrm{M_\odot }$) galaxy cluster, making it an excellent laboratory to probe the influence of the cluster environment on galaxy star formation. Here, we present a sample of 41 galaxies with disturbed morphologies consistent with ram pressure stripping. These galaxies are identified visually using high-quality, multiband imaging from the Canada–France–Hawaii telescope covering ${\sim}9\, \mathrm{deg^2}$ of the Coma cluster. These ‘stripping candidates’ are clear outliers in common quantitative morphological measures, such as concentration-asymmetry and Gini-M20, confirming their disturbed nature. Based on the orientations of observed asymmetries, as well as the galaxy positions in projected phase space, these candidates are consistent with galaxies being stripped shortly after infall on to the Coma cluster. Finally, the stripping candidates show enhanced star formation rates, both relative to ‘normal’ star-forming Coma galaxies and isolated galaxies in the field. Ram pressure is likely driving an enhancement in star formation during the stripping phase, prior to quenching. On the whole, ram pressure stripping appears to be ubiquitous across all regions of the Coma cluster.

Optical properties of undoped, Eu3+ doped and Li+ co-doped Y2Hf2O7 nanoparticles and polymer nanocomposite films

Li+ co-doping of Y2Hf2O7:Eu3+ nanoparticles improve their quenching concentration, asymmetry ratio, quantum yield, and radioluminescence intensity due to the enhanced covalent character of Eu3+–O2− bonding.

Simultaneous effects of variable viscosity and thermal conductivity on peristaltic flow in a vertical asymmetric channel

This paper discusses the effects of variable viscosity and thermal conductivity on peristaltic flow of a Newtonian fluid in a vertical asymmetric channel. Both viscosity and thermal conductivity are considered as a function of temperature. The long wavelength approximation is used to linearize the governing equations. The system of the governing nonlinear partial differential equation is solved using the perturbation method. Solutions are obtained for the velocity field, the temperature and the concentration. Asymmetry in the flow is induced by traveling waves of different phase and amplitude that propagate along the channel walls. The numerical results show that variable viscosity and thermal conductivity have significant influence on velocity, temperature, and mass transfer. The importance of pertinent flow parameters entering into the flow modeling is discussed.

Morphology of z ~ 1 galaxies from deep K-band AO imaging

We present the results of observations of distant galaxies (z ~ 0.8) at high spatial resolution (~0.1"). We observed 7 fields of 1' × 1' with the NACO Adaptive Optics system (VLT) in Ks (2.2μm) band with typical V ~ 14 guide stars and 3h integration time per field. Observed fields are selected within the COSMOS survey area. We analyze the morphologies by means of B/D (Bulge/Disk) decomposition with GIM2D and CAS (Concentration-Asymmetry) estimators for 79 galaxies with magnitudes between Ks = 17 − 23 and classify them in three main morphological types (Late Type, Early Type and Irregulars). We obtain for the first time an estimate of the distribution of galaxy types at redshift z ~ 1 as measured from the near infrared at high spatial resolution.

The Nature of UV-selected Galaxies in the Chandra Deep Field South

We report the first results of the ongoing survey using HST/WFPC2 (F300W) in parallel with ACS within the Chandra Deep Field South. A sample of 34 objects were identified in the WFPC2 images and their counterparts were found in the ACS images taken by the GOODS team; 6 of them are stars. Galaxies were classified as early-, late-types, and starbursts by template fitting which was also used to determine their photometric redshifts (z< 1). Analysis of the light concentration, asymmetry and clumpiness shows that this sample is a mixed bag, containing dwarf ellipticals, early- and late-spirals, and peculiar objects which resemble mergers in progress. This result has important implications for galaxy evolution since the intermediate redshifts are the epoch when the rise in the volume-averaged star formation rate occurs.

Environmental and Genetic Effects on the Asymmetry Phenotype: Diazinon Resistance in the Australian Sheep Blowfly, Lucilia cuprina

The asymmetry phenotype of diazinon-resistant flies lacking a fitness/asymmetry Modfier (+/+; R/−) was dominant and independent of developmental temperature, larval density and diazinon concentration. Asymmetry score, pooled over three bristle characters, was ~50% greater for these phenotypes than for those of modified genotypes (M/−; −/− ) and unmodified susceptibles (+ /+ ; S/S) reared under standard laboratory conditions. Modified and susceptible phenotypes showed increased asymmetry score for temperatures and larval densities above and below standard rearing conditions; a positive correlation was observed between diazinon concentration and asymmetry score. Single and multiple environmental stresses resulted in similar scores that approached, but never exceeded, those of unmodified resistant phenotypes. Irrespective of the developmental conditions anti-symmetry and fluctuating asymmetry were typically observed for each bristle character of unmodified resistant and the modified and susceptible phenotypes, respectively. Thus while similar asymmetry scores could arise from genetic or environmental effects, asymmetry pattern was genetically based. Population cage analyses at different temperatures and larval densities showed a negative association between mean asymmetry and relative fitness.

Intracellular monosaccharide and amino acid concentrations and activities and the mechanisms of insulin action

Current amino acid and monosaccharide transport models are based on an assumption which equates the intracellular chemical activity of a solute with its concentration. This assumption was tested for alpha-aminoisobutyric acid and 3-O-methylglucose in a giant cell, the amphibian oocyte, by using recently developed cryomicrodissection and internal reference phase techniques. We found the following. (i) alpha-Aminoisobutyric acid and 3-O-methylglucose activities were much greater in cytoplasm than was suggested by concentration data; i.e., activity coefficients were higher than in ordinary water solutions. This is attributable to the inaccessibility of considerable water as solvent (solute exclusion). (ii) Solute concentrations varied regionally as follows: nucleus > > animal cytoplasm > vegetal cytoplasm. Insulin increased the nucleus/cytoplasm concentration asymmetry, apparently by increasing cytoplasmic solute exclusion. (iii) Nuclear activity coefficients more closely resembled those of ordinary saline solutions so that nucleus/ extracellular concentration ratios reflected transmembrane activity gradients better than did cytoplasm (or whole cell)/extracellular ratios. (iv) Mediated passive alpha-aminoisobutyric acid and 3-O-methylglucose transport were constituent oocyte membrane properties. Membrane active transport was initiated with time (in the presence of substrate) and by insulin. (v) Increased temperature mimicked insulin in enhancing transmembrane alpha-aminoisobutyric acid activity gradients and increasing the nucleus/cytoplasm concentration asymmetry. These results indicated that concentration data are a misleading measure of cellular amino acid and monosaccharide activity; some consequences of this observation were explored. A model is proposed in which cell water has reduced solvent capacity or is compartmentalized (considered less likely) and is susceptible to physiological modulation. The model accounts for many observations in small cells, suggesting generality of the exclusion phenomenon and a previously unrecognized metabolic control mechanism.