The growth of central and satellite galaxies in cosmological smoothed particle hydrodynamics simulations     

Vimal Simha  David H. Weinberg  Romeel Davé  Oleg Y. Gnedin  Neal Katz  Du&#;an Kere&#; 《Monthly notices of the Royal Astronomical Society》2009,399(2):650-662

We examine the accretion and merger histories of central and satellite galaxies in a smoothed particle hydrodynamics (SPH) cosmological simulation that resolves galaxies down to  7 × 10⁹ M_⊙  . Most friends-of-friends haloes in the simulation have a distinct central galaxy, typically 2–5 times more massive than the most massive satellite. As expected, satellites have systematically higher assembly redshifts than central galaxies of the same baryonic mass, and satellites in more massive haloes form earlier. However, contrary to the simplest expectations, satellite galaxies continue to accrete gas and convert it to stars; the gas accretion declines steadily over a period of 0.5–1 Gyr after the satellite halo merges with a larger parent halo. Satellites in a cluster mass halo eventually begin to lose baryonic mass. Typically, satellites in our simulation are 0.1–0.2 mag bluer than in models that assume no gas accretion on to satellites after a halo merger. Since   z = 1  , 27 per cent of central galaxies (above  3 × 10¹⁰ M_⊙  ) and 22 per cent of present-day satellite galaxies have merged with a smaller system above a 1:4 mass ratio; about half of the satellite mergers occurred after the galaxy became a satellite and half before. In effect, satellite galaxies can remain 'central' objects of halo substructures, with continuing accretion and mergers, making the transition in assembly histories and physical properties a gradual one. Implementing such a gradual transformation in semi-analytic models would improve their agreement with observed colour distributions of satellite galaxies in groups and with the observed colour dependence of galaxy clustering.  相似文献   

Ongoing assembly of massive galaxies by major merging in large groups and clusters from the SDSS     

Daniel H. McIntosh †  Yicheng Guo  Jen Hertzberg ‡  Neal Katz  H. J. Mo  Frank C. van den Bosch  Xiaohu Yang 《Monthly notices of the Royal Astronomical Society》2008,388(4):1537-1556

  相似文献   

A Grid of Metal-Poor Model Stellar Atmospheres for Stars Born in the Early Galaxy     

C. Van 'T Veer-Menneret  D. Katz  R. Cayrel  C. Soubiran 《Astrophysics and Space Science》1999,265(1-4):257-258

  相似文献   

Is use of oil-field brine as a dust-abating agent really benign? Tracing the source and flowpath of contamination by oil brine in a shallow phreatic aquifer     

Yoram Eckstein 《Environmental Earth Sciences》2011,63(1):201-214

In Ohio, 1985 H.R. Bill 501 authorizes the local authorities to issue permits to use oil-field brine surface spreading as a dust and ice control agent. Such permits are usually given without any necessary hydrogeological expertise as to the potential impact on the shallow aquifers, particularly if the brine spreading occurs in a recharge area. One such case occurred recently in the southwestern suburb of the City of Wooster, OH, USA, where a group of home owners were seeking judicial relief when their water wells began yielding salty water as a result of brine spreading on a nearby large open storage area for oil and gas well drilling supplies. The defendant, owner of the storage yard, acted in accordance with the permit issued by the local authorities. Yet, decentralized decision making and an increased emphasis on local and citizen involvement have created a gap between science and society. The local authorities were not required by law to condition the issuance of the permit on an analysis of the potential environmental impact. The decision to issue that permit was made purely on non-scientific grounds. Therefore, the residents had no choice but to embark on a costly process of proving the damages, causation, and liability in court of law. During the protracted, 6-year long conflict, an extensive hydrogeological and hydrochemical data set (including stable isotopes’ analyses along with the complete chemical analyses of major and minor constituents) was amassed at a great cost to both sides. The following article presents the hydrogeological and hydrochemical interpretation of this data set. In addition, the case illustrates a glaring deficiency in the Ohio, 1985 H.R. Bill 501, and one pitfall in the “politically correct” philosophy of delegating decision-making process entirely to the non-professional local authorities.  相似文献   

The Hinode Spectro-Polarimeter     

B. W. Lites  D. L. Akin  G. Card  T. Cruz  D. W. Duncan  C. G. Edwards  D. F. Elmore  C. Hoffmann  Y. Katsukawa  N. Katz  M. Kubo  K. Ichimoto  T. Shimizu  R. A. Shine  K. V. Streander  A. Suematsu  T. D. Tarbell  A. M. Title  S. Tsuneta 《Solar physics》2013,283(2):579-599

The joint Japan/US/UK Hinode mission includes the first large-aperture visible-light solar telescope flown in space. One component of the Focal Plane Package of that telescope is a precision spectro-polarimeter designed to measure full Stokes spectra with the intent of using those spectra to infer the magnetic-field vector at high precision in the solar photosphere. This article describes the characteristics of the flight hardware of the Hinode Spectro-Polarimeter, and summarizes its in-flight performance.  相似文献   

Lyα flux power spectrum and its covariance     

Hu Zhan  Romeel Davé  Daniel Eisenstein  Neal Katz 《Monthly notices of the Royal Astronomical Society》2005,363(4):1145-1154

  相似文献   

How do galaxies get their gas?     

Du&#;an Kere&#;  Neal Katz  David H. Weinberg  Romeel Davé 《Monthly notices of the Royal Astronomical Society》2005,363(1):2-28

  相似文献   

Numerical simulation of groundwater flow in the Peshawar intermontane basin, northwest Himalayas     

Asim Yousafzai  Yoram Eckstein  Peter Dahl 《Hydrogeology Journal》2008,16(7):1395-1409

The hypothesis that abnormal fluid pressure is generated in basins under tectonic compression is tested. The study site, between the Main Karakoram Thrust (MKT), Main Mantle Thrust (MMT), Main Central Thrust (MCT), Main Boundary Thrust (MBT) and Salt Range Thrust (SRT) in northwest Pakistan, is experiencing a tectonic compression of 90 MPa. The Peshawar basin is a broad, oval depression comprising a thick sequence of lacustrine, deltaic and fluvial sediments overlain by loess and alluvial deposits dated at 2.8–0.6 Ma. It is surrounded by the Precambrian and Tertiary intrusive and metamorphic rocks on the north and sedimentary rocks of Paleogene and Neogene to the south. The basin was divided into four hydrostratigraphic units for numerical simulations using the three-dimensional finite-element model FEMWATER within groundwater modeling system (GMS) ver. 5.1. Simulated pressure head data have been compared with the field measurements of hydraulic heads. Transient simulations indicate that topography alone is not sufficient to induce the pressure heads observed in the field, generating consistently positive residuals 0.98–2.90 m over the topography-driven flow. The residuals disappeared after inclusion of the elastic properties of the four hydrostratigraphic units in the model, suggesting the effect of tectonic compression.  相似文献   

Using chemical and microbiological indicators to track the impacts from the land application of treated municipal wastewater and other sources on groundwater quality in a karstic springs basin     

Brian G. Katz  Dale W. Griffin 《Environmental Geology》2008,55(4):801-821

Multiple chemical constituents (nutrients; N, O, H, C stable isotopes; 64 organic wastewater compounds, 16 pharmaceutical compounds) and microbiological indicators were used to assess the impact on groundwater quality from the land application of approximately 9.5 million liters per day of treated municipal sewage effluent to a sprayfield in the 960-km² Ichetucknee Springs basin, northern Florida. Enriched stable isotope signatures (δ¹⁸O and δ²H) were found in water from the effluent reservoir and a sprayfield monitoring well (MW-7) due to evaporation; however, groundwater samples downgradient from the sprayfield have δ¹⁸O and δ²H concentrations that represented recharge of meteoric water. Boron and chloride concentrations also were elevated in water from the sprayfield effluent reservoir and MW-7, but concentrations in groundwater decreased substantially with distance downgradient to background levels in the springs (about 12 km) and indicated at least a tenfold dilution factor. Nitrate-nitrogen isotope (δ¹⁵N–NO₃) values above 10 ‰ in most water samples were indicative of organic nitrogen sources except Blue Hole Spring (δ¹⁵N–NO₃ = 4.6–4.9 ‰), which indicated an inorganic source of nitrogen (fertilizers). The detection of low concentrations the insect repellent N,N-diethyl-metatoluamide (DEET), and other organic compounds associated with domestic wastewater in Devil’s Eye Spring indicated that leakage from a nearby septic tank drainfield likely has occurred. Elevated levels of fecal coliforms and enterococci were found in Blue Hole Spring during higher flow conditions, which likely resulted from hydraulic connections to upgradient sinkholes and are consistent with previoius dye-trace studies. Enteroviruses were not detected in the sprayfield effluent reservoir, but were found in low concentrations in water samples from a downgradient well and Blue Hole Spring during high-flow conditions indicating a human wastewater source. The Upper Floridan aquifer in the Ichetucknee Springs basin is highly vulnerable to contamination from multiple anthropogenic sources throughout the springs basin.  相似文献   

d'Entrecasteaux Zone,trench and western chain of the central New Hebrides island arc: Their significance and tectonic relationship     

J. Daniel  H. R. Katz 《Geo-Marine Letters》1981,1(3-4):213-219

The absence of a trench and the existence of a separate, western chain of islands in the central New Hebrides island arc are a consequence of earlier tectonic evolution, and not the result of subduction of the d'Entrecasteux Zone as was previously suggested. Because of tectonic consolidation in the western islands prior to present subduction, a resistant block was created opposing subduction, and a trench never did form, here. The d'Entrecasteux Zone is responsible only locally for additional deformation of the subducting plate, in a way that can be regarded as an initial stage of obduction.  相似文献