Non-parametric reconstruction of cluster mass distribution from strong lensing: modelling Abell 370     

Hanadi M. AbdelSalam  Prasenjit Saha  & Liliya L. R. Williams 《Monthly notices of the Royal Astronomical Society》1998,294(4):734-746

We describe a new non-parametric technique for reconstructing the mass distribution in galaxy clusters with strong lensing, i.e. from multiple images of background galaxies. The observed positions and redshifts of the images are considered as rigid constraints, and through the lens (ray-trace) equation they provide us with linear constraint equations. These constraints confine the mass distribution to some allowed region, which is then found by linear programming. Within this allowed region we study in detail the mass distribution with minimum mass-to-light variation, and also some other distributions, such as the smoothest mass distribution.
The method is applied to the extensively studied cluster Abell 370, which hosts a giant luminous arc and several other multiply imaged background galaxies. Our mass maps are constrained by the observed positions and redshifts (spectroscopic or model-inferred by previous authors) of the giant arc and multiple-image systems. The reconstructed maps obtained for Abell 370 reveal a detailed mass distribution, with substructure quite different from the light distribution. The method predicts the bimodal nature of the cluster, and that the projected mass distribution is indeed elongated along the axis defined by the two dominant cD galaxies. However, the peaks in the mass distribution appear to be offset from the centres of the cDs.
We also present an estimate for the total mass of the central region of the cluster. This is in good agreement with previous mass determinations. The total mass of the central region is M =(2.0–2.7)×10¹⁴ M⊙ h ⁻¹₅₀, depending on the solution chosen.  相似文献   

Remotely sensed canopy temperature based evapotranspiration models for wheat     

S. K. Saha  Ajai 《Journal of the Indian Society of Remote Sensing》1986,14(2):87-97

Field studies were conducted on differentially irrigated wheat (Cv. ‘Sonalika’), on a sandy loam soil at Indian Agricultural Research Institute, New Delhi to evaluate the surface energy balance evapotranspiration (ET) models which use remotely sensed canopy temperature as an input. Four energy balance ET models were used in this study viz. Jackson et. al. (1977) approach; Bartholic et. al. (1970) and stability corrected and uncorrected aerodynamic resistance forms of models. To test the model, ET was estimated using remotely sensed canopy temperatrue, with the remaining to ET measured by water depletion method. Aerodynamic resistance forms of ET models performed well as compared to other models. Results indicate that remotely sensed canopy temperature as an input to surface energy balance models, offers a potential method of estimating ET from a cropped surface.  相似文献   

Models for wheat yield prediction using remotely sensed canopy temperature based indices     

S. K. Saha  Ajai 《Journal of the Indian Society of Remote Sensing》1989,17(4):9-18

Canopy temperature in differentially irrigated and fertilized wheat plots were collected by hand held infrared thermometer from seedling emergence to maturity for two growing seasons (1981–82 and 1982–83). Canopy temperature indices like stress degree day (SDD) and crop water stress index (CWSI) based four-parameter (crop growth stage partitioned) and two-parameter (Non-partitioned) yield models suitable for remote sensing application were developed and tested with observed yield data. From statistical analysis of the models it was concluded that crop growth stage partitioned CWSI or SDD yield model was better than non-partitioned SDD models for predicting wheat grain as well as biological yields.  相似文献   

Tropospheric ozone profiles near equator and meteorological parameters     

Namita Kundu  A. K. Saha 《Journal of Atmospheric Chemistry》1987,5(3):243-253

This is a study of ozone profile shapes in the 800 to 100 millibar range obtained with balloonsonde data over Trivandrum (8.5° N) during 1975–76 and possible associations of these shapes to some meteorological parameters.Whereas monotonic ozone profiles were noted with clear weather conditions, those associated with cloud cover show three basic anomalous features. Some bulges of increased values are observed in the range of 800 to 500 mb. In the 500–100 mb range, short range or localized cloud cover or passing weather disturbances are associated with fluctuation patterns in the ozone profile and an average depleted value of ozone. The fluctuations are also associated with changing wind speed and direction at these heights.Possible causative mechanisms are discussed. Lightning associated with thundestorm, producing additional CO and NO are sought to interpret the bulges at lower heights. The decrease in values as well as the fluctuation patterns are suggested as due to possible incursion of water vapour from troposphere to stratosphere in the tropical region and dynamical effects associated with it.  相似文献   

Rare gases,water, and carbon in kaersutites     

Robert J. Poreda  Asish R. Basu 《Earth and Planetary Science Letters》1984,69(1):58-68

Kaersutites from Kakanui, New Zealand and from three localities in the southwestern United States have been analyzed for rare gases, water and carbon to investigate the volatile signature of the sub-continental mantle. This study does not confirm the high ³He/⁴He and ²¹Ne/²²Ne ratios reported by Saito et al. [1] for the Kakanui kaersutite. Instead, a ³He/⁴He ratio of 6 R_A and atmospheric ²¹Ne/²²Ne ratios were measured which are consistent with our current knowledge of the earth's mantle. A low ⁴⁰Ar/³⁶Ar of 320 and more than 10^?8 cm³/g of ³⁶Ar confirms the argon results of Saito et al. and indicates that significant quantities of ³⁶Ar reside in this portion of the mantle. Kaersutites from the southwestern United States (Arizona) have a heterogeneous helium isotope signature, ranging from 8.8 R_A at San Carlos to 0.46 at Hoover Dam. All D/H ratios for the water in kaersutites (?56‰ to ?78‰) represent typical mantle values with no apparent correlation with ³He/⁴He. The correlation of increasing carbon content (140–400 ppm) with increasing δ¹³C (?24.5‰ to ?16.7‰) may reflect differences in the proportions of oxidized and reduced carbon in these samples.  相似文献   

Sm-Nd,K-Ar and petrologic study of some kimberlites from eastern United States and their implication for mantle evolution     

Asish R. Basu  Eric Rubury  Harald Mehnert  Mitsunobu Tatsumoto 《Contributions to Mineralogy and Petrology》1984,86(1):35-44

We provide new data on Sm-Nd systematics, K-Ar dating and the major element chemistry of kimberlites from the eastern United States (mostly from central New York State) and their constituent mineral phases of olivine, clinopyroxene, garnet, phlogopite and perovskite. In addition, we report Nd-isotopes in a few kimberlites from South Africa, Lesotho and from the eastern part of China. The major element compositions of the New York dike rocks and of their constituent minerals including a xenolith of eclogite are comparable with those from the Kimberley area in South Africa. The K-Ar age of emplacement of the New York dikes is further established to be 143 Ma.We have analyzed the Nd-isotopic composition of the following kimberlites and related rocks: Nine kimberlite pipes from South Africa and Lesotho, two from southern India; one from the U.S.S.R., fifteen kimberlite pipes and related dike rocks from eastern and central U.S. and two pipes from the Shandong Province of eastern China. The age of emplacement of these kimberlites ranges from 1300 million years to 90 million years. The initial Nd-isotopic compositions of these kimberlitic rocks expressed as _Nd ^I with respect to a chondritic bulk-earth growth-curve show a range between 0 and +4, with the majority of the kimberlites being in the range 0 to +2. This range is not matched by any other suite of mantle-derived igneous rocks. This result strengthens our earlier conclusion that kimberlitic liquids are derived from a relatively primeval and unique mantle reservoir with a nearly chondritic Sm/Nd ratio.  相似文献   

Sm-Nd Isotopic and Geochemical Study of the Archean Tonalite-Amphibolite association from the eastern Indian Craton     

Mukul Sharma  Asish R. Basu  Sagar L. Ray 《Contributions to Mineralogy and Petrology》1994,117(1):45-55

We report the results of a Sm-Nd isotopic, major element and rare earth element (REE) study of the Older Metamorphic Group (OMG) tonalite-amphibolite association of the eastern Indian Craton. The Older Metamorphic Tonalite Gneisses (OMTG) have been previously dated to be 3.8 Ga using Sm-Nd isotope systematies, and 3.2–3.4 Ga by Rb-Sr and Pb-Pb dating. The results of this study indicate that the protoliths of the OMG amphibolites are 3.3 Ga isochron age=3.30±0.06 Ga, _Nd= +0.9 ± 0.7), and therefore, the OMTG, which intrude into the associated amphibolites, cannot be any older than 3.3 Ga. The amphibolites display light REE enrichment ((Ce/Yb)_N=2.2–6.7; La=30–100 x chondrite) and nearly flat heavy REE patterns ((Tb/Lu)_N=1.2–1.9); the basaltic parents of the amphibolites were probably generated by the partial melting of a spinel lherzolite mantle. Strong linear relationships between the amphibolites and tonalites in ¹⁴⁷Sm/¹⁴⁴Nd-¹⁴³Nd/¹⁴⁴Nd space (isochron age =3.29±0.04 Ga, _Nd= +0.8 ± 0.8) imply that they are genetically related. The tonalites display fractionated REE patterns (La=100–300 x chondrite) with moderate heavy REE depletions ((Tb/Lu)_N=1.9–3.4). The isotopic, major element and REE data are consistent with the derivation of the OMTG from partial melting of OMG amphibolites or equivalent rocks at amphibolegarnet stabilization depths. An initial _Nd(t) value of +0.9±0.7 for the amphibolites indicates the presence of a slightly depleted mantle source at 3.3 Ga with ¹⁴⁷Sm/¹⁴⁴Nd. between 0.20 and 0.22. It is suggested that the growth of continental crust in the eastern Indian craton occurred in response to magmatic underplating in a plume setting.  相似文献   

Calculation of coronal line intensities for boron-like ions     

H. P. Saha  E. Trefftz 《Solar physics》1983,83(2):233-242

New atomic data (Saha and Trefftz, 1982a) have been used to calculate line intensities of S xii for the physical conditions found in the solar corona. They are compared with similar calculations for S ix (Saha and Trefftz, 1982b) and with published work. For the density sensitive intensity ratio I ₂₂₇/I2₂₁₈ the new values give the observed ratio (Malinovski and Heroux, 1973) for an electron density of logN _e = 8.5 which is more likely than the density deduced from the values of Flower and Nussbaumer (1975), logN _e ? 7.  相似文献   

Experimental studies on sloshing behavior due to horizontal movement of liquids in baffled tanks     

P.K. Panigrahy  U.K. Saha  D. Maity 《Ocean Engineering》2009,36(3-4):213-222

A series of experiments have been carried out in a developed liquid sloshing setup to estimate the pressure developed on the tank walls and the free surface displacement of water from the mean static level. The square tank attached to a shaking table can be moved to and fro by a cam arrangement driven by a DC motor. Pressure and displacement studies are done on the basis of changing excitation frequency of the shaking table and fill level in the tank. Experiments were carried out without and with baffles, and the consequent changes in the parameters are observed.  相似文献   

Erratum to: Simulation of monsoon intraseasonal variability in NCEP CFSv2 and its role on systematic bias     

Bidyut B. Goswami  Medha Deshpande  P. Mukhopadhyay  Subodh K. Saha  Suryachandra A. Rao  Raghu Murtugudde  B. N. Goswami 《Climate Dynamics》2015,44(3-4):1171-1171

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