The Allen Telescope Array     

David Deboer  Rob Ackermann  Leo Blitz  Douglas Bock  Geoffrey Bower  Michael Davis  John Dreher  Greg Engargiola  Matt Fleming  Girmay Keleta  Gerry Harp  John Lugten  Jill Tarter  Doug Thornton  Niklas Wadefalk  Sander Weinreb  William J. Welch 《Experimental Astronomy》2004,17(1-3):19-34

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Orientation dependency of broad-line widths in quasars and consequences for black hole mass estimation     

Matt J. Jarvis  Ross J. McLure 《Monthly notices of the Royal Astronomical Society》2006,369(1):182-188

We have identified two new galaxies with gas counter-rotation (NGC 1596 and 3203) and have confirmed similar behaviour in another one (NGC 128), this using results from separate studies of the ionized-gas and stellar kinematics of a well-defined sample of 30 edge-on disc galaxies. Gas counter-rotators thus represent 10 ± 5 per cent of our sample, but the fraction climbs to 21 ± 11 per cent when only lenticular (S0) galaxies are considered and to 27 ± 13 per cent for S0 galaxies with detected ionized gas only. Those fractions are consistent with but slightly higher than previous studies. A compilation from well-defined studies of S0 galaxies in the literature yields fractions of 15 ± 4 and 23 ± 5 per cent, respectively. Although mainly based on circumstantial evidence, we argue that the counter-rotating gas originates primarily from minor mergers and tidally induced transfer of material from nearby objects. Assuming isotropic accretion, twice those fractions of objects must have undergone similar processes, underlining the importance of (minor) accretion for galaxy evolution. Applications of gas counter-rotators to barred galaxy dynamics are also discussed.  相似文献   

Spectroscopic follow-up of a cluster candidate at z= 1.45     

Caroline van Breukelen  Garret Cotter  Steve Rawlings  Tony Readhead  David Bonfield  Lee Clewley  Rob Ivison  Matt Jarvis  Chris Simpson  Mike Watson 《Monthly notices of the Royal Astronomical Society》2007,382(3):971-984

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The K-band Hubble diagram of submillimetre galaxies and hyperluminous galaxies     

Stephen Serjeant  Duncan Farrah  James Geach  Toshinobu Takagi  Aprajita Verma  Ali Kaviani  Matt Fox 《Monthly notices of the Royal Astronomical Society》2003,346(4):L51-L56

We present the K -band Hubble diagrams ( K – z relations) of submillimetre-selected galaxies and hyperluminous galaxies (HLIRGs). We report the discovery of a remarkably tight K – z relation of HLIRGs, indistinguishable from that of the most luminous radio galaxies. Like radio galaxies, the HLIRG K – z relation at   z ≲ 3  is consistent with a passively evolving ∼3 L _* instantaneous starburst starting from a redshift of   z ∼ 10  . In contrast, many submillimetre-selected galaxies are ≳2 mag fainter, and the population has a much larger dispersion. We argue that dust obscuration and/or a larger mass range may be responsible for this scatter. The galaxies so far proved to be hyperluminous may have been biased towards higher AGN bolometric contributions than submillimetre-selected galaxies due to the 60-μm selection of some, so the location on the K – z relation may be related to the presence of the most massive active galactic nucleus. Alternatively, a particular host galaxy mass range may be responsible for both extreme star formation and the most massive active nuclei.  相似文献   

Non-uniform interhemispheric temperature trends over the past 550 years   总被引：1，自引：0，他引：1  

Richard P. Duncan  Pavla Fenwick  Jonathan G. Palmer  Matt S. McGlone  Chris S. M. Turney 《Climate Dynamics》2010,35(7-8):1429-1438

The warming trend over the last century in the northern hemisphere (NH) was interrupted by cooling from ad 1940 to 1975, a period during which the southern hemisphere experienced pronounced warming. The cause of these departures from steady warming at multidecadal timescales are unclear; the prevailing explanation is that they are driven by non-uniformity in external forcings but recent models suggest internal climate drivers may play a key role. Paleoclimate datasets can help provide a long-term perspective. Here we use tree-rings to reconstruct New Zealand mean annual temperature over the last 550 years and demonstrate that this has frequently cycled out-of-phase with NH mean annual temperature at a periodicity of around 30–60 years. Hence, observed multidecadal fluctuations around the recent warming trend have precedents in the past, strongly implicating natural climate variation as their cause. We consider the implications of these changes in understanding and modelling future climate change.  相似文献   

Hyper‐planning Jakarta: The Great Garuda and planning the global spectacle     

Matt Wade 《Singapore journal of tropical geography》2019,40(1):158-172

After a major flood in Jakarta in 2007, the government of Indonesia partnered with a consortium of Dutch engineers and designers to produce a solution. In 2013, this consortium proposed a plan for the Great Garuda, a megaproject that combined a deep seawall and private real estate, both in an archipelago of reclaimed islands that would be shaped like the mythical garuda eagle, Indonesia's national symbol. Despite a range of infeasibilities and opposition, the Great Garuda became the most prominent vision for the city's future. This article argues that the promotion of the Great Garuda was a process of ‘hyper‐planning’, which projected the city as a national triumph and a global spectacle. The plan served the political objective of creating the mere possibility of a ‘new Jakarta’ apart from the perceived chaos of the current capital. Further, the plan functioned as a performative object through its iconic imagery and its circulations. The process of hyper‐planning simultaneously projected a future of urban success, but also displaced the contingencies of the future to the private sector, beyond the purview of the state.  相似文献   

Cover crops and precipitation influence soluble reactive phosphorus losses via tile drain discharge in an agricultural watershed     

Matt T. Trentman  Jennifer L. Tank  Todd V. Royer  Shannon L. Speir  Ursula H. Mahl  Lienne R. Sethna 《水文研究》2020,34(23):4446-4458

Subsurface tile drainage speeds water removal from agricultural fields that are historically prone to flooding. While managed drainage systems improve crop yields, they can also contribute tothe eutrophication of downstream ecosystems, as tile-drained systems are conduits for nutrients to adjacent waterways. The changing climate of the Midwestern US has already altered precipitation regimes which will likely continue into the future, with unknown effects on tile drain water and nutrient loss to waterways. Adding vegetative cover (i.e., as winter cover crops) is one approach that can retain water and nutrients on fields to minimize export via tile drains. In the current study, we evaluate the effect of cover crops on tile drain discharge and soluble reactive phosphorus (SRP) loads using bi-monthly measurements from 43 unique tile outlets draining fields with or without cover crops in two watersheds in northern Indiana. Using four water years of data (n = 844 measurements), we examined the role of short-term antecedent precipitation conditions and variation in soil biogeochemistry in mediating the effect of cover crops on tile drain flow and SRP loads. We observed significant effects of cover crops on both tile drain discharge and SRP loads, but these results were season and watershed specific. Cover crop effects were identified only in spring, where their presence reduced tile drain discharge in both watersheds and SRP loads in one watershed. Varying effects on SRP loads between watersheds were attributed to different soil biogeochemical characteristics, where soils with lower bioavailable P and higher P sorption capacity were less likely to have a cover crop effect. Antecedent precipitation was important in spring, and cover crop differences were still evident during periods of wet and dry antecedent precipitation conditions. Overall, we show that cover crops have the potential to significantly decrease spring tile drain P export, and these effects are resilient to a wide range of precipitation conditions.  相似文献   

GNSS satellite-based augmentation systems for Australia   总被引：1，自引：0，他引：1  

Suelynn Choy  Joost Kuckartz  Andrew G. Dempster  Chris Rizos  Matt Higgins 《GPS Solutions》2017,21(3):835-848

We provided an overview of various satellite-based augmentation systems (SBAS) options for augmented GNSS services in Australia, and potentially New Zealand, with the aim to tease out key similarities and differences in their augmentation capabilities. SBAS can technically be classified into two user categories, namely SBAS for aviation and “non-aviation” SBAS. Aviation SBAS is an International Civil Aviation Organization (ICAO) certified civil aviation safety-critical system providing wide-area GNSS augmentation by broadcasting augmentation information using geostationary satellites. The primary aim was to improve integrity, availability and accuracy of basic GNSS signals for aircraft navigation. On the other hand, “non-aviation” SBAS support numerous GNSS applications using positioning techniques such as wide-area differential-GNSS (DGNSS) and precise point positioning (PPP). These services mainly focus on delivering high-accuracy positioning solutions and guaranteed levels of availability, and integrity remains secondary considerations. Next-generation GNSS satellites capable of transmitting augmentation signals in the L1, L5 and L6 frequency bands will also be explored. These augmentation signals have the data capacity to deliver a range of augmentation services such as SBAS, wide-area DGNSS and PPP, to meet the demands of various industry sectors. In addition, there are well-developed plans to put in place next-generation dual-frequency multi-constellation SBAS for aviation. Multi-constellation GNSS increases robustness against potential degradation of core satellite constellations and extends the service coverage area. It is expected that next-generation SBAS and GNSS will improve accuracy, integrity, availability and continuity of GNSS performance.  相似文献   

Wetland Loss Patterns and Inundation-Productivity Relationships Prognosticate Widespread Salt Marsh Loss for Southern New England     

Elizabeth Burke Watson  Cathleen Wigand  Earl W. Davey  Holly M. Andrews  Joseph Bishop  Kenneth B. Raposa 《Estuaries and Coasts》2017,40(3):662-681

Tidal salt marsh is a key defense against, yet is especially vulnerable to, the effects of accelerated sea level rise. To determine whether salt marshes in southern New England will be stable given increasing inundation over the coming decades, we examined current loss patterns, inundation-productivity feedbacks, and sustaining processes. A multi-decadal analysis of salt marsh aerial extent using historic imagery and maps revealed that salt marsh vegetation loss is both widespread and accelerating, with vegetation loss rates over the past four decades summing to 17.3 %. Landward retreat of the marsh edge, widening and headward expansion of tidal channel networks, loss of marsh islands, and the development and enlargement of interior depressions found on the marsh platform contributed to vegetation loss. Inundation due to sea level rise is strongly suggested as a primary driver: vegetation loss rates were significantly negatively correlated with marsh elevation (r ²?=?0.96; p?=?0.0038), with marshes situated below mean high water (MHW) experiencing greater declines than marshes sitting well above MHW. Growth experiments with Spartina alterniflora, the Atlantic salt marsh ecosystem dominant, across a range of elevations and inundation regimes further established that greater inundation decreases belowground biomass production of S. alterniflora and, thus, negatively impacts organic matter accumulation. These results suggest that southern New England salt marshes are already experiencing deterioration and fragmentation in response to sea level rise and may not be stable as tidal flooding increases in the future.  相似文献   

Quantification of Tsunami Bathymetry Effect on Finite Fault Slip Inversion     

Quentin Bletery  Anthony Sladen  Bertrand Delouis  Lionel Mattéo 《Pure and Applied Geophysics》2015,172(12):3655-3670

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