The SCUBA HAlf Degree Extragalactic Survey (SHADES) – VII. Optical/IR photometry and stellar masses of submillimetre galaxies     

S. Dye  S. A. Eales  I. Aretxaga  S. Serjeant  J. S. Dunlop  T. S. R. Babbedge  S. C. Chapman  M. Cirasuolo  D. L. Clements  K. E. K. Coppin  L. Dunne  E. Egami  D. Farrah  R. J. Ivison  E. van Kampen  A. Pope  R. Priddey  G. H. Rieke  A. M. Schael  D. Scott  C. Simpson  T. Takagi  T. Takata  M. Vaccari 《Monthly notices of the Royal Astronomical Society》2008,386(2):1107-1130

We present estimates of the photometric redshifts, stellar masses and star formation histories of sources in the Submillimetre Common-User Bolometer Array (SCUBA) HAlf Degree Extragalactic Survey (SHADES). This paper describes the 60 SCUBA sources detected in the Lockman Hole covering an area of ∼320 arcmin². Using photometry spanning the B band to 8 μm, we find that the average SCUBA source forms a significant fraction of its stars in an early period of star formation and that most of the remainder forms in a shorter more intense burst around the redshift it is observed. This trend does not vary significantly with source redshift. However, the sources show a clear increase in stellar mass with redshift, consistent with downsizing. In terms of spectral energy distribution types, only two out of the 51 sources we have obtained photometric redshifts for are best fitted by a quasar-like spectrum, with approximately 80 per cent of the sources being best fitted with late-type spectra (Sc, Im and starburst). By including photometry at 850 μm, we conclude that the average SCUBA source is forming stars at a rate somewhere between 6 and 30 times the rate implied from the rest-frame optical in a dust obscured burst and that this burst creates 15–65 per cent of the total stellar mass. Using a simplistic calculation, we estimate from the average star formation history that between one in five and one in 15 bright  ( L _*+ 2 < L _optical < L _*− 1 mag)  galaxies in the field over the interval  0 < z < 3  will at some point in their lifetime experience a similar energetic dusty burst of star formation. Finally, we compute the evolution of the star formation rate density and find it peaks around   z ∼ 2  .  相似文献   

Comparison of carbon cycle between the western Pacific subarctic and subtropical time-series stations: highlights of the K2S1 project     

Makio C. Honda  Masahide Wakita  Kazuhiko Matsumoto  Tetsuichi Fujiki  Eko Siswanto  Kosei Sasaoka  Hajime Kawakami  Yoshihisa Mino  Chiho Sukigara  Minoru Kitamura  Yoshikazu Sasai  Sherwood L. Smith  Taketo Hashioka  Chisato Yoshikawa  Katsunori Kimoto  Shuichi Watanabe  Toru Kobari  Toshi Nagata  Koji Hamasaki  Ryo Kaneko  Mario Uchimiya  Hideki Fukuda  Osamu Abe  Toshiro Saino 《Journal of Oceanography》2017,73(5):647-667

A comparative study of ecosystems and biogeochemistry at time-series stations in the subarctic gyre (K2) and subtropical region (S1) of the western North Pacific Ocean (K2S1 project) was conducted between 2010 and 2013 to collect essential data about the ecosystem and biological pump in each area and to provide a baseline of information for predicting changes in biologically mediated material cycles in the future. From seasonal chemical and biological observations, general oceanographic settings were verified and annual carbon budgets at both stations were determined. Annual mean of phytoplankton biomass and primary productivity at the oligotrophic station S1 were comparable to that at the eutrophic station K2. Based on chemical/physical observations and numerical simulations, the likely “missing nutrient source” was suggested to include regeneration, meso-scale eddy driven upwelling, meteorological events, and eolian inputs in addition to winter vertical mixing. Time-series observation of carbonate chemistry revealed that ocean acidification (OA) was ongoing at both stations, and that the rate of OA was faster at S1 than at K2 although OA at K2 is more critical for calcifying organisms.  相似文献   

Double-planed deep seismic zone and upper-mantle structure in the Northeastern Japan Arc   总被引：6，自引：0，他引：6  

Akira Hasegawa  Norihito Umino  Akio Takagi 《Geophysical Journal International》1978,54(2):281-296

Summary. The ScSp wave converted from the ScS wave at the boundary between the descending lithospheric slab and the mantle above it was clearly observed from a nearby deep earthquake with magnitude 7.7 at some stations of the seismic network of Tohoku University which covers the Tohoku District, the northeastern part of Honshu, Japan. By applying the three-dimensional seismic-ray tracing method, the location of this boundary was determined from the difference in arrival time between the ScS and ScSp waves. The result shows that the upper boundary of the descending slab lies exactly on the upper plane of the double-planed deep seismic zone found in the Northeastern Japan Arc.
There is an additional evidence that the boundary is located on the upper plane of the double-planed deep seismic zone. The hypocentre distribution of intermediate-depth earthquakes located by the small-scale seismic-array observation is extremely different from that obtained by the relatively large-scale seismic network. The discrepancy in the distribution of hypocentres of the same earthquake independently located is well explained by the inclined lithospheric slab model derived from the difference in arrival time between the ScS and ScSp waves.
The earthquakes with reverse faulting or with down-dip compressional stresses occur at the upper boundary of the descending slab. Within the descending slab, the earthquakes with down-dip extensional stresses also occur in a very narrow zone from 30 to 40 km below the dipping boundary in the depth range from 50 to about 200 km, and these shocks form the lower plane of the double-planed deep seismic zone.  相似文献   

Distribution and photo-physiological condition of phytoplankton in the tropical and subtropical North Pacific     

Tetsuichi Fujiki  Kazuhiko Matsumoto  Toshiro Saino  Masahide Wakita  Shuichi Watanabe 《Journal of Oceanography》2013,69(1):35-43

To better understand the vertical distribution of phytoplankton in the tropical and subtropical North Pacific, we used fast repetition rate fluorometry to investigate the photo-physiological condition of the phytoplankton assemblage in this region between February and March 2007. Along 155°E, between the equator and 24°N, the peak of fluorescence (F _m), an indication of the deep chlorophyll maximum (DCM), was deeper than the top of the nitracline and occurred at the 2.4 ± 1.3 % (mean ± SD) light depth (relative to 0 m). The photochemical efficiency (F _v/F _m) and effective absorption cross-section of photosystem II (σ_PSII) were low at the surface but increased rapidly at depths between the top of the nitracline (40–138 m) and the DCM (70–158 m), an indication that the photo-physiological condition of the phytoplankton improved below the top of the nitracline. The depth of the maximal F _v/F _m [Z(F _v/F _{m max})] was 18–32 m deeper than the DCM and corresponded to the 0.8 ± 0.2 % light depth. The values of F _v/F _m at the Z(F _v/F _{m max}) were 20 % higher than those at the DCM and averaged 0.48 ± 0.01. These results suggest that the phytoplankton assemblage beneath the DCM had a high potential photosynthetic performance capacity and was growing by using the very low ambient light in this region.  相似文献   

Geological and Geochemical Characteristics of the Hydrothermal Clay Alteration in South Korea   总被引：1，自引：1，他引：0  

Sang-Mo KOH  Tetsuichi TAKAGI  Moon–Young KIM  Kazuki NAITO  Sei–Sun HONG  Sadahisa SUDO 《Resource Geology》2000,50(4):229-242

Abstract: Hydrothermally altered areas forming pyrophyllite‐kaolin‐sericite‐alunite deposits are distributed in Chonnam and Kyongsang areas, Cretaceous volcanic field of the Yuchon Group. The Chonnam alteration area is located within depression zone which is composed of volcanic and granitic rocks of late Cretaceous age. The clay deposits of this area show the genetic relationship with silicic lava domes. The Kyongsang alteration area is mainly distributed within Kyongsang Basin comprising volcanic, sedimentary and granitic rocks of Cretaceous and Tertiary age. Most of the clay deposits of this area are closely related to cauldrons. Paleozoic clay deposit occurs in the contact zone between Precambrian Hongjesa granite gneiss and Paleozoic Jangsan quartzite of Choson Supergroup. Cretaceous igneous rocks of the both alteration areas belong to high K calc‐alkaline series formed in the volcanic arc of continental margin by subduction‐related magmatism. Chonnam igneous rocks show more enrichment of crustal components such as K, La, Ce, Sm, Nd and Ba, higher (La/Yb)cn ratio, and higher initial ⁸⁷Sr/⁸⁶Sr ratio (0. 708 to 0. 712) than those of Kyongsang igneous rocks. This might be due to the difference of degree of crustal contamination during Cretaceous magmatism. The most characteristic alteration minerals of Chonnam clay deposits are alunite, kaolin, quartz, pyrophyllite and diaspore which were formed by acidic solution. Those of Kyongsang clay deposits are sericite, quartz and pyrophyllite which were formed by weak acid and neutral solution. The formation ages of the clay deposits of two alteration areas range from 70. 1 to 81. 4 Ma and 39. 7 to 79. 4 Ma, respectively. The Daehyun clay deposit in Ponghwa area of Kyongsang province shows the alteration age range from 290 to 336 Ma. This result shows the different alteration episode from the hydrothermal alteration of Cretaceous to early Tertiary in the Kyongsang and Chonnam alteration areas. These data indicate, at least, three hydrothermal activities of Tertiary (middle to late Eocene), late Cretaceous (Santonian to Maastrichtian) and Paleozoic Carboniferous Periods in South Korea.  相似文献   

Uncovering unnoticed small-scale tsunamis: field survey in Lombok,Indonesia, following the 2018 earthquakes     

Tsimopoulou  Vana  Mikami  Takahito  Hossain  Tajnova Tanha  Takagi  Hiroshi  Esteban  Miguel  Utama  Nuki Agya 《Natural Hazards》2020,103(2):2045-2070

Natural Hazards - In 2018, Lombok island, Indonesia, was hit by a series of destructive earthquakes that caused thousands of casualties and widespread material damage. In response to those events,...  相似文献   

East-west distribution of POC fluxes estimated from <Superscript>234</Superscript>Th in the northern North Pacific in autumn     

Hajime Kawakami  Makio C. Honda  Kazuhiko Matsumoto  Tetsuichi Fujiki  Shuichi Watanabe 《Journal of Oceanography》2010,66(1):71-83

Observations of primary productivity, ²³⁴Th, and particulate organic carbon (POC) were made from west to east across the northern North Pacific Ocean (from station K2 to Ocean Station Papa) during September–October 2005. Primary productivities in this region varied longitudinally from approximately 236 to 444 mgC m⁻²d⁻¹ and clearly indicate the West High East Low (WHEL) trend. We estimated east-west variations in the POC flux from the surface layer (0–100 m) by using ²³⁴Th as a tracer. POC fluxes in the western region (44–53 mgC m⁻²d⁻¹) were higher than those in the eastern region (21–34 mgC m⁻²d⁻¹). However, the export ratios (e-ratios) ranged from approximately 8% to 16% and did not show the WHEL trend. Contrary to our expectation, no relation between POC flux (or e-ratio) and diatom biomass (or dominance) was apparent in autumn in the northern North Pacific.  相似文献