scholarly journals Radio and optical observations at high spatial and spectral resolution of compact young Planetary Nebulae

1997 ◽  
Vol 180 ◽  
pp. 360-360
Author(s):  
L. F. Miranda ◽  
J. M. Torrelles ◽  
C. Eiroa
Keyword(s):  
Spatial Resolution ◽  
Spectral Resolution ◽  
Spatial Scales ◽  
Planetary Nebulae ◽  
Radio Continuum ◽  
Optical Observations ◽  
Optical Data ◽  
Electron Density And Temperature ◽  
Spectrally Resolved ◽  
Mass Ejection

We present VLA-A radio continuum at 3.6 cm and H92α observations, and optical long-slit spectra at high spectral and spatial resolution of the compact Planetary Nebulae (PNs) Hu 2-1, IC 4997, IC 5117 and NGC 6884. The radio continuum maps show the subarcsecond structure of the PNs in detail. From the optical spectra, the basic kinematical properties can be deduced. The H92α emission line, spatially and spectrally resolved in IC 5117 and Hu 2-1, allows us to observe the kinematics of the PNs in spatial scales of ∼ 0.3″. By combining the radio and optical data, it is possible to identify the components present in the nebulae, to deduce their spatio-kinematical structure, and to obtain estimates for the electron density and temperature, ionized masses and kinematical ages. All this information permits to impose constraints about the mass ejection processes involved in the formation of PNs and when they have occurred.

scholarly journals AMBER/VLTI Snapshot Survey on Circumstellar Environments

2014 ◽  
Vol 9 (S307) ◽  
pp. 297-300 ◽  
Author(s):  
Th. Rivinius ◽  
W.J. de Wit ◽  
Z. Demers ◽  
A. Quirrenbach ◽  
Keyword(s):  
Spatial Resolution ◽  
Spectral Resolution ◽  
Spatial Scales ◽  
Line Emission ◽  
High Spectral Resolution ◽  
Unique Combination ◽  
Hot Stars ◽  
Circumstellar Environments ◽  
Colour Terms ◽  
Neutral Colour

AbstractOHANA is an interferometric snapshot survey of the gaseous circumstellar environments of hot stars, carried out by the VLTI group at the Paranal observatory. It aims to characterize the mass-loss dynamics (winds/disks) at unexplored spatial scales for many stars. The survey employs the unique combination of AMBER's high spectral resolution with the unmatched spatial resolution provided by the VLTI. Because of the spatially unresolved central OBA-type star, with roughly neutral colour terms, their gaseous environments are among the easiest objects to be observed with AMBER, yet the extent and kinematics of the line emission regions are of high astrophysical interest.

scholarly journals Radio continuum and long-slit optical spectroscopy of the Planetary Nebulae Cn 3-1 and M 3-27

1997 ◽  
Vol 180 ◽  
pp. 283-283
Author(s):  
R. Vázquez ◽  
L. F. Miranda ◽  
J. M. Torrelles ◽  
C. Eiroa ◽  
J.A. López
Keyword(s):  
Optical Spectroscopy ◽  
Stellar Wind ◽  
Planetary Nebulae ◽  
Radio Continuum ◽  
Emission Lines ◽  
Optical Data ◽  
Expansion Velocity ◽  
Polar Regions ◽  
Neutral Material ◽  
Hα Emission

Long-slit optical spectroscopy and VLA-B radio continuum (λ = 3.6 cm) observations toward the compact planetary nebulae Cn 3-1 and M 3-27 are presented. Optical spectra were taken at different position angles (PAs) with the 2.2 m telescope at Calar Alto (Spain), covering the range from 6549 to 6751 Å. The radio and optical data show that the ionized shell of Cn 3-1 is an ellipsoid (size ≃ 6″ × 5″, PA ≃ 72°) containing a bright ring-like equatorial zone (size ≃ 2″.6, expansion velocity ≃ 14 km s–1) and two bright point-symmetric arcs, extending from the equator towards the polar regions of the ellipsoid (Fig. 1). These arcs seem to be filamentary structures embedded in the ellipsoid. An ionized stellar wind has been detected through faint extended wings in the Hα (≃ 660 km s–1) and [N II] (≃ 460 km s–1) emission lines. M 3-27 is unresolved at 3.6 cm (size ≤ 0″6). The detected [N II] and [S II] emission lines arise in a compact (≤ 1″4) probably non-spherical region which is identified with the ionized shell of M 3-27. The Hα emission from M 3-27 is dominated by strong emission from an ionized stellar wind and exhibits a Type III P Cygni profile with very extended wings (≃ 3000 km s–1). The estimated kinematic age and ionized mass of Cn 3-1 (≃ 1300 yr, 4 × 10–2 M⊙) and M 3-27 (≤ 530 yr, ≃ 3 × 10–4 M⊙) indicate that both objects are young planetary nebulae. Extended halos (size ≃ 36″ in Cn 3-1, ≃ 24″ in M 3-27) have been spectroscopically detected in both objects. An analysis of the kinematic and emission properties shows that both halos are reflection nebulosities and suggests that the distribution of neutral material in them probably is largely isotropic. The results suggest that the halos correspond to isotropic mass ejections occurred in the last ≃ 2 × 104 yr of the AGB phase of the Cn 3-1 and M 3-27 progenitors.

scholarly journals Radio continuum emission from HII regions in the Magellanic Clouds

1964 ◽  
Vol 20 ◽  
pp. 283-289 ◽  
Author(s):  
D. S. Mathewson ◽  
J. R. Healey
Keyword(s):  
Hii Regions ◽  
Magellanic Clouds ◽  
Radio Continuum ◽  
Optical Observations ◽  
Optical Data ◽  
Continuum Emission ◽  
Considerable Proportion ◽  
Galactic Emission ◽  
The Galaxy ◽  
Thermal Origin

A considerable proportion of the radio emission at high frequencies from the Galaxy is of thermal origin. This thermal radiation appears to originate both in very extended regions and in discrete sources. It has always been difficult to compare the radio and optical data for these HII regions as galactic optical observations are hampered by heavy obscuration. However, the HII regions in the Magellanic Clouds are relatively free from obscuration, and spectrophotometry by Dickel, Aller, and Faulkner (this volume, paper 63) and Henize (1956) have provided very good measurements of Hβ and Hα flux densities and the relative intensities of the OII, OIII lines. Also the distance to the Clouds is fairly well known (about 55 kpc) so that the linear dimensions of the HII regions may be estimated with some degree of accuracy in contrast to the galactic emission nebulae.

High spatial resolution x-ray microanalysis of interfaces

1995 ◽  
Vol 53 ◽  
pp. 284-285
Author(s):  
J. R. Michael
Keyword(s):  
Spatial Resolution ◽  
Electron Probe ◽  
Solid Angle ◽  
Collection Efficiency ◽  
Spatial Scales ◽  
Energy Dispersive Spectrometer ◽  
X Rays ◽  
X Ray ◽  
Probe Size ◽  
Brightness Field

X-ray microanalysis in the analytical electron microscope (AEM) refers to a technique by which chemical composition can be determined on spatial scales of less than 10 nm. There are many factors that influence the quality of x-ray microanalysis. The minimum probe size with sufficient current for microanalysis that can be generated determines the ultimate spatial resolution of each individual microanalysis. However, it is also necessary to collect efficiently the x-rays generated. Modern high brightness field emission gun equipped AEMs can now generate probes that are less than 1 nm in diameter with high probe currents. Improving the x-ray collection solid angle of the solid state energy dispersive spectrometer (EDS) results in more efficient collection of x-ray generated by the interaction of the electron probe with the specimen, thus reducing the minimum detectability limit. The combination of decreased interaction volume due to smaller electron probe size and the increased collection efficiency due to larger solid angle of x-ray collection should enhance our ability to study interfacial segregation.

Implementation of an Urban Parameterization Scheme into the Regional Climate Model COSMO-CLM

2013 ◽  
Vol 52 (10) ◽  
pp. 2296-2311 ◽  
Author(s):  
Kristina Trusilova ◽  
Barbara Früh ◽  
Susanne Brienen ◽  
Andreas Walter ◽  
Valéry Masson ◽  
...  
Keyword(s):  
Spatial Resolution ◽  
Climate Model ◽  
Spatial Scales ◽  
Regional Climate ◽  
Coupled Model ◽  
Urban Land ◽  
Urban Land Use ◽  
Small Scale ◽  
Model Simulations ◽  
Scale Modelling

AbstractAs the nonhydrostatic regional model of the Consortium for Small-Scale Modelling in Climate Mode (COSMO-CLM) is increasingly employed for studying the effects of urbanization on the environment, the authors extend its surface-layer parameterization by the Town Energy Budget (TEB) parameterization using the “tile approach” for a single urban class. The new implementation COSMO-CLM+TEB is used for a 1-yr reanalysis-driven simulation over Europe at a spatial resolution of 0.11° (~12 km) and over the area of Berlin at a spatial resolution of 0.025° (~2.8 km) for evaluating the new coupled model. The results on the coarse spatial resolution of 0.11° show that the standard and the new models provide 2-m temperature and daily precipitation fields that differ only slightly by from −0.1 to +0.2 K per season and ±0.1 mm day−1, respectively, with very similar statistical distributions. This indicates only a negligibly small effect of the urban parameterization on the model's climatology. Therefore, it is suggested that an urban parameterization may be omitted in model simulations on this scale. On the spatial resolution of 0.025° the model COSMO-CLM+TEB is able to better represent the magnitude of the urban heat island in Berlin than the standard model COSMO-CLM. This finding shows the importance of using the parameterization for urban land in the model simulations on fine spatial scales. It is also suggested that models could benefit from resolving multiple urban land use classes to better simulate the spatial variability of urban temperatures for large metropolitan areas on spatial scales below ~3 km.

scholarly journals Global downscaling of remotely sensed soil moisture using neural networks

2018 ◽  
Vol 22 (10) ◽  
pp. 5341-5356 ◽  
Author(s):  
Seyed Hamed Alemohammad ◽  
Jana Kolassa ◽  
Catherine Prigent ◽  
Filipe Aires ◽  
Pierre Gentine
Keyword(s):  
Soil Moisture ◽  
Spatial Resolution ◽  
Land Surface ◽  
Vegetation Index ◽  
Spatial Scales ◽  
Ancillary Data ◽  
Repeat Time ◽  
Spatiotemporal Scales ◽  
Better Than

Abstract. Characterizing soil moisture at spatiotemporal scales relevant to land surface processes (i.e., of the order of 1 km) is necessary in order to quantify its role in regional feedbacks between the land surface and the atmospheric boundary layer. Moreover, several applications such as agricultural management can benefit from soil moisture information at fine spatial scales. Soil moisture estimates from current satellite missions have a reasonably good temporal revisit over the globe (2–3-day repeat time); however, their finest spatial resolution is 9 km. NASA's Soil Moisture Active Passive (SMAP) satellite has estimated soil moisture at two different spatial scales of 36 and 9 km since April 2015. In this study, we develop a neural-network-based downscaling algorithm using SMAP observations and disaggregate soil moisture to 2.25 km spatial resolution. Our approach uses the mean monthly Normalized Differenced Vegetation Index (NDVI) as ancillary data to quantify the subpixel heterogeneity of soil moisture. Evaluation of the downscaled soil moisture estimates against in situ observations shows that their accuracy is better than or equal to the SMAP 9 km soil moisture estimates.

scholarly journals Hyperspectral and Multispectral Remote Sensing Image Fusion Based on Endmember Spatial Information

2020 ◽  
Vol 12 (6) ◽  
pp. 1009
Author(s):  
Xiaoxiao Feng ◽  
Luxiao He ◽  
Qimin Cheng ◽  
Xiaoyi Long ◽  
Yuxin Yuan
Keyword(s):  
Image Fusion ◽  
Spatial Resolution ◽  
Spectral Resolution ◽  
Spatial Information ◽  
Spectral Unmixing ◽  
High Spectral Resolution ◽  
Remote Sensing Image Fusion ◽  
Fusion Methods ◽  
Invariant Regions ◽  
The Difference

Hyperspectral (HS) images usually have high spectral resolution and low spatial resolution (LSR). However, multispectral (MS) images have high spatial resolution (HSR) and low spectral resolution. HS–MS image fusion technology can combine both advantages, which is beneficial for accurate feature classification. Nevertheless, heterogeneous sensors always have temporal differences between LSR-HS and HSR-MS images in the real cases, which means that the classical fusion methods cannot get effective results. For this problem, we present a fusion method via spectral unmixing and image mask. Considering the difference between the two images, we firstly extracted the endmembers and their corresponding positions from the invariant regions of LSR-HS images. Then we can get the endmembers of HSR-MS images based on the theory that HSR-MS images and LSR-HS images are the spectral and spatial degradation from HSR-HS images, respectively. The fusion image is obtained by two result matrices. Series experimental results on simulated and real datasets substantiated the effectiveness of our method both quantitatively and visually.

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