Signatures of Galaxy-Cluster Interactions: Spiral Galaxy Rotation Curve Asymmetry, Shape, and Extent

The environmental dependencies of the characteristics of spiral galaxy rotation curves are studied in this work. We use our large, homogeneously collected sample of 510 cluster spiral galaxy rotation curves to test the claim that the shape of a galaxy's rotation curve strongly depends on its location within the cluster, and thus presumably on the strength of the local intracluster medium and on the frequency and strength of tidal interactions with the cluster and cluster galaxies. Our data do not corroborate such a scenario, consistent with the fact that Tully-Fisher residuals are independent of galaxy location within the cluster; while the average late-type spiral galaxy shows more rise in the outer parts of its rotation curve than does the typical early-type spiral galaxy, there is no apparent trend for either subset with cluster environment. We also investigate as a function of cluster environment rotation curve asymmetry and the radial distribution of H II region tracers within galactic disks. Mild trends with projected cluster-centric distance are observed: (i) the (normalized) radial extent of optical line emission averaged over all spiral galaxy types shows a 4%+/-2% increase per Mpc of galaxy-cluster core separation, and (ii) rotation curve asymmetry falls by a factor of two between the inner and outer cluster for early-type spirals (a negligible decrease is found for late-type spirals). Such trends are consistent with spiral disk perturbations or even the stripping of the diffuse, outermost gaseous regions within the disks as galaxies pass through the dense cluster cores.Comment: 17 pages; to appear in the April 2001 Astronomical Journa

Rectangular beam (5 X 40 cm multipole ion source)

A 5 x 40 cm rectangular-beam ion source was designed and fabricated. A multipole field configuration was used to facilitate design of the modular rectangular chamber, while a three-grid ion optics system was used for increased ion current densities. For the multipole chamber, a magnetic integral of 0.000056 Tesla-m was used to contain the primary electrons. This integral value was reduced from the initial design value, with the reduction found necessary for discharge stability. The final value of magnetic integral resulted in discharge losses at typical operating conditions which ranged from 600 to 1000 eV/ion, in good agreement with the design value of 800 eV/ion. The beam current density at the ion optics was limited to about 3.2 mA/sq cm at 500 eV and to about 3.5 mA/sq cm at 1000 ev. The effects of nonuniform ion current, dimension tolerance, and grid thermal warping were considered. The use of multiple rectangular-beam ion sources to process wider areas than would be possible with a single source (approx. 40 cm) was also studied. Beam profiles were surveyed at a variety of operating conditions and the results of various amounts of beam overlap calculated

Galaxy Peculiar Velocities and Infall onto Groups

We perform statistical analyses to study the infall of galaxies onto groups and clusters in the nearby Universe. The study is based on the UZC and SSRS2 group catalogs and peculiar velocity samples. We find a clear signature of infall of galaxies onto groups over a wide range of scales 5 h^{-1} Mpc<r<30 h^{-1} Mpc, with an infall amplitude on the order of a few hundred kilometers per second. We obtain a significant increase in the infall amplitude with group virial mass (M_{V}) and luminosity of group member galaxies (L_{g}). Groups with M_{V}<10^{13} M_{\odot} show infall velocities V_{infall} \simeq 150 km s^{-1} whereas for M_{V}>10^{13} M_{\odot} a larger infall is observed, V_{infall} \simeq 200 km s^{-1}. Similarly, we find that galaxies surrounding groups with L_{g}<10^{15} L_{\odot} have V_{infall} \simeq 100 km s^{-1}, whereas for L_{g}>10^{15} L_{\odot} groups, the amplitude of the galaxy infall can be as large as V_{infall} \simeq 250 km s^{-1}. The observational results are compared with the results obtained from mock group and galaxy samples constructed from numerical simulations, which include galaxy formation through semianalytical models. We obtain a general agreement between the results from the mock catalogs and the observations. The infall of galaxies onto groups is suitably reproduced in the simulations and, as in the observations, larger virial mass and luminosity groups exhibit the largest galaxy infall amplitudes. We derive estimates of the integrated mass overdensities associated with groups by applying linear theory to the infall velocities after correcting for the effects of distance uncertainties obtained using the mock catalogs. The resulting overdensities are consistent with a power law with \delta \sim 1 at r \sim 10 h^{-1}Mpc.Comment: 25 pages, 10 figure

Diffusion of passive scalar in a finite-scale random flow

We consider a solvable model of the decay of scalar variance in a single-scale random velocity field. We show that if there is a separation between the flow scale k_flow^{-1} and the box size k_box^{-1}, the decay rate lambda ~ (k_box/k_flow)^2 is determined by the turbulent diffusion of the box-scale mode. Exponential decay at the rate lambda is preceded by a transient powerlike decay (the total scalar variance ~ t^{-5/2} if the Corrsin invariant is zero, t^{-3/2} otherwise) that lasts a time t~1/\lambda. Spectra are sharply peaked at k=k_box. The box-scale peak acts as a slowly decaying source to a secondary peak at the flow scale. The variance spectrum at scales intermediate between the two peaks (k_box0). The mixing of the flow-scale modes by the random flow produces, for the case of large Peclet number, a k^{-1+delta} spectrum at k>>k_flow, where delta ~ lambda is a small correction. Our solution thus elucidates the spectral make up of the ``strange mode,'' combining small-scale structure and a decay law set by the largest scales.Comment: revtex4, 8 pages, 4 figures; final published versio

The validity and reliability of the my jump 2 app for measuring the reactive strength index and drop jump performance

BACKGROUNDː This is the first study to independently assess the concurrent validity and reliability of the My Jump 2 app for measuring drop jump performance. It is also the first to evaluate the app’s ability to measure the reactive strength index (RSI). METHODSː Fourteen male sport science students (age: 29.5 ± 9.9 years) performed three drop jumps from 20 cm and 40 cm (totalling 84 jumps), assessed via a force platform and the My Jump 2 app. Reported metrics included reactive strength index, jump height, ground contact time, and mean power. Measurements from both devices were compared using the intraclass correlation coefficient (ICC), Pearson product moment correlation coefficient (r), Cronbach’s alpha (α), coefficient of variation (CV) and Bland-Altman plots. RESULTSː Near perfect agreement was seen between devices at 20 cm for RSI (ICC = 0.95) and contact time (ICC = 0.99) and at 40 cm for RSI (ICC = 0.98), jump height (ICC = 0.96) and contact time (ICC = 0.92); with very strong agreement seen at 20 cm for jump height (ICC = 0.80). In comparison with the force plate the app showed good validity for RSI (20 cm: r = 0.94; 40 cm; r = 0.97), jump height (20 cm: r = 0.80; 40 cm; r = 0.96) and contact time (20 cm = 0.96; 40 cm; r = 0.98). CONCLUSIONSː The results of the present study show that the My Jump 2 app is a valid and reliable tool for assessing drop jump performance

Cape Vincent Harbor: Summer Data Report to the Army Corps of Engineers Buffalo District

Fish, benthos, macrophytes and birds were collected or observed over two days (16 July through 17 July 1979) at Cape Vincent Harbor, New York, to evaluate the potential biological impact of dredging on the harbor. Figure 1 is a map of the harbor area indicating the location of sampling sites. Observed fishing pressure and boat traffic were minimal during the two-day sampling trip. This is a preliminary data report. The final report will include both our analysis and interpretation of the data regarding potential impacts of dredging

Spring Thermal Fronts and Salmonine Sport Catches in Lake Ontario

The hypothesis that salmonine catches in Lake Ontario are higher at thermal fronts in spring and early summer was tested in 1990 by comparing catches in nonfrontal water and three types of fronts: thermal bar (4°C); spring thermocline (6-8°C); and thermal break (\u3e=9°C). A thermal front in the spring in Lake Ontario is a pronounced temperature cline across the surface of the lake (in this study defined as 0.15Co/min or greater at standard boat speeds) parallel to shore that extends obliquely from the surface toward shore and the bottom. Surface temperature was recorded every 2 min during 45 h of trolling for fish at a standard 3.2-4.8 km/h. Only 20% of the time was spent fishing in thermal fronts, where 35% of the 88 strikes occurred and 37% of the 59 fish were caught. Catch per unit effort (CPUE) for salmonines at thermal fronts was greater than nonfrontal CPUE (P \u3c 0.001 for all strikes; P \u3c 0.05 for fish caught). Catches were better in thermal breaks (P \u3c 0.002) and the spring thermocline (P \u3c 0.05) than in nonfrontal waters. Relative to nonfrontal water, CPUE for coho salmon Oncorhynchus kisutch was greater in the spring thermocline (P \u3c 0.01). Salmonines were caught deeper in nonfrontal waters than in frontal waters (P = 0.014). Chinook salmon O. tshawytscha and lake trout Salvelinus namaycush were caught deeper than were coho salmon and steelhead O. mykiss (P \u3c 0.05). Anglers can effectively enhance their catch of salmonines by fishing the spring thermocline and thermal breaks. These results likely are applicable to other pelagic habitats utilized by salmonines

Colonization and persistence of Crangonyx pseudogracilis (Bousfield 1958) in temporary pools

Crangonyctid amphipods occupy temporary habitats across northeastern North America, but they are mostly known as permanent-water species. Crangonyx pseudogracilis (Bousfield 1958) is found at high densities in temporary pools in western New York, but the means by which it persists are not well understood. Our objectives were to: 1) assess the dispersal abilities of C. pseudogracilis, 2) explore its ability to descend through inundated porous substrates, 3) assess whether its life cycle and brood releases are related to survival through the dry season, and 4) find their dry-season refugia and measure the period for which they can survive desiccation. During periods of inundation, C. pseudogracilis was found in the top 15 cm of soil in holes \u3c10 m from pools. After pools dried in mid-June or early July, C. pseudogracilis was not found in the soil to a depth of 45 cm, even when rains temporarily refilled the pools. In the laboratory, small C. pseudogracilis descended easily through substrates with ≥ 0.7-mm pore radii but large (≥ 7 mm) and ovigerous C. pseudogracilis were unable to descend. In the field, ovigerous females were found from mid-March until late May. The previous year’s generation of large and ovigerous individuals began dying in May and was gone by the end June. In the laboratory, C. pseudogracilis survived in damp soil (51% average free moisture content) for 15 wk. Crangonyx pseudogracilis lacks specialized strategies for survival in temporary waters (e.g., resting eggs, dormant juvenile stages, active burrowing), but has ecological traits well suited for temporary pools and similar environment

Oak Orchard Harbor Summer Data Report to the Army Corps of Engineers Buffalo District

On 8 and 9 July 1979 benthos, fish, macrophytes and birds were collected or observed at Oak Orchard Harbor, New York, to evaluate the potential biological impact of dredging the harbor area. This is a data report. In the final report, our analysis and interpretation of the data collected will be presented. Figures 1 and 2 are maps of the Oak Orchard Harbor area indicating the location of sample sites. Table 1 provides information on bottom characteristics at the benthos sampling sites. Fishing pressure and boat traffic were heavy compared to the usage during the fall 1978 sampling trip. Water temperature was 19° c