Analysing the visual dynamics of spatial morphology

Recently there has been a revival of interest in visibility analysis of architectural configurations. The new analyses rely heavily on computing power and statistical analysis, two factors which, according to the postpositivist school of geography, should immediately cause us to be wary. Thedanger, they would suggest, is in the application of a reductionist formal mathematical description in order to `explain' multilayered sociospatial phenomena. The author presents an attempt to rationalise how we can use visibility analysis to explore architecture in this multilayered context by considering the dynamics that lead to the visual experience. In particular, it is recommended that we assess the visualprocess of inhabitation, rather than assess the visibility in vacuo. In order to investigate the possibilities and limitations of the methodology, an urban environment is analysed by means of an agent-based model of visual actors within the configuration. The results obtained from the model are compared with actual pedestrian movement and other analytic measurements of the area: the agents correlate well both with human movement patterns and with configurational relationship as analysed by space-syntax methods. The application of both methods in combination improves on the correlation with observed movement of either, which in turn implies that an understanding of both the process of inhabitation and the principles of configuration may play a crucial role in determining the social usage of space

Analysis of CCD images of the coma of comet P/Halley

The modeling analysis objective of this project is to make use of the skill acquired in the development of Monte Carlo particle trajectory models for the distributions of gas species in cometary comae as a basis for a new dust coma model. This model will include a self-consistent picture of the time-dependent dusty-gas dynamics of the inner coma and the three-dimensional time-dependent trajectories of the dust particles under the influence of solar gravity and solar radiation pressure in the outer coma. Our purpose is to use this model as a tool to analyze selected images from two sets of data of the comet P/Halley with the hope that we can help to understand the effects of a number of important processes on the spatial morphology of the observed dust coma. The study will proceed much in the same way as our study of the spatially extended hydrogen coma where we were able to understand the spatial morphology of the Lyman-alpha coma in terms of the partial thermalization of the hot H atoms produced by the photodissociation of cometary H2O and OH. The processes of importance to the observed dust coma include: (1) the dust particle size distribution function; (2) the terminal velocities of various sized dust particles in the inner coma; (3) the radiation scattering properties of dust particles, which are important both in terms of the observed scattered radiation and the radiation pressure acceleration on dust particles; (4) the fragmentation and/or vaporization of dust particles; (5) the relative importance of CHON and silicate dust particles as they contribute both to the dusty-gas dynamics in the inner coma (that produce the dust particle terminal velocities) and to the observed spatial morphology of the outer dust coma; and (6) the time and direction dependence of the source of dust

HiRes deconvolution of Spitzer infrared images

Spitzer provides unprecedented sensitivity in the infrared (IR), but the spatial resolution is limited by a relatively small aperture (0.85 m) of the primary mirror. In order to maximize the scientific return it is desirable to use processing techniques which make the optimal use of the spatial information in the observations. We have developed a deconvolution technique for Spitzer images. The algorithm, "HiRes" and its implementation has been discussed by Backus et al. in 2005. Here we present examples of Spitzer IR images from the Infrared Array Camera (IRAC) and MIPS, reprocessed using this technique. Examples of HiRes processing include a variety of objects from point sources to complex extended regions. The examples include comparison of Spitzer deconvolved images with high-resolution Keck and Hubble Space Telescope images. HiRes deconvolution improves the visualization of spatial morphology by enhancing resolution (to sub-arcsecond levels in the IRAC bands) and removing the contaminating sidelobes from bright sources. The results thereby represent a significant improvement over previously-published Spitzer images. The benefits of HiRes include (a) sub-arcsec resolution (~0".6-0".8 for IRAC channels); (b) the ability to detect sources below the diffraction-limited confusion level; (c) the ability to separate blended sources, and thereby provide guidance to point-source extraction procedures; (d) an improved ability to show the spatial morphology of resolved sources. We suggest that it is a useful technique to identify features which are interesting enough for follow-up deeper analysis

ARCADE 2 Observations of Galactic Radio Emission

We use absolutely calibrated data from the ARCADE 2 flight in July 2006 to model Galactic emission at frequencies 3, 8, and 10 GHz. The spatial structure in the data is consistent with a superposition of free-free and synchrotron emission. Emission with spatial morphology traced by the Haslam 408 MHz survey has spectral index beta_synch = -2.5 +/- 0.1, with free-free emission contributing 0.10 +/- 0.01 of the total Galactic plane emission in the lowest ARCADE 2 band at 3.15 GHz. We estimate the total Galactic emission toward the polar caps using either a simple plane-parallel model with csc|b| dependence or a model of high-latitude radio emission traced by the COBE/FIRAS map of CII emission. Both methods are consistent with a single power-law over the frequency range 22 MHz to 10 GHz, with total Galactic emission towards the north polar cap T_Gal = 0.498 +/- 0.028 K and spectral index beta = -2.55 +/- 0.03 at reference frequency 1 GHz. The well calibrated ARCADE 2 maps provide a new test for spinning dust emission, based on the integrated intensity of emission from the Galactic plane instead of cross-correlations with the thermal dust spatial morphology. The Galactic plane intensity measured by ARCADE 2 is fainter than predicted by models without spinning dust, and is consistent with spinning dust contributing 0.4 +/- 0.1 of the Galactic plane emission at 22 GHz.Comment: 10 poges, 9 figures. Submitted to The Astrophysical Journa

Diffuse emission measurement with INTEGRAL/SPI as indirect probe of cosmic-ray electrons and positrons

Significant advances have been made in the understanding of the diffuse Galactic hard X-ray continuum emission using data from the INTEGRAL observatory. The diffuse hard power-law component seen with the INTEGRAL/SPI spectrometer has been identified with inverse-Compton emission from relativistic (GeV) electrons on the cosmic microwave background and Galactic interstellar radiation field. In the present analysis, SPI data from 2003 to 2009, with a total exposure time of ~ 10^8 s, are used to derive the Galactic ridge hard X-ray spatial distribution and spectrum between 20 keV and 2.4 MeV. Both are consistent with predictions from the GALPROP code. The good agreement between measured and predicted emission from keV to GeV energies suggests that the correct production mechanisms have been identified. We discuss the potential of the SPI data to provide an indirect probe of the interstellar cosmic-ray electron distribution, in particular for energies below a few GeV.Comment: 39 pages, 11 figures. Accepted for publication in The Astrophysical Journa

H.E.S.S. deeper observations on SNR RX J0852.0-4622

Supernova Remnants (SNRs) are believed to be acceleration sites of Galactic cosmic rays. Therefore, deep studies of these objects are instrumental for an understanding of the high energy processes in our Galaxy. RX J0852.0-4622, also known as Vela Junior, is one of the few (4) shell-type SNRs resolved at Very High Energies (VHE; E > 100 GeV). It is one of the largest known VHE sources (~ 1.0 deg radius) and its flux level is comparable to the flux level of the Crab Nebula in the same energy band. These characteristics allow for a detailed analysis, shedding further light on the high-energy processes taking place in the remnant. In this document we present further details on the spatial and spectral morphology derived with an extended data set. The analysis of the spectral morphology of the remnant is compatible with a constant power-law photon index of 2.11 +/- 0.05_stat +/- 0.20_syst from the whole SNR in the energy range from 0.5 TeV to 7 TeV. The analysis of the spatial morphology shows an enhanced emission towards the direction of the pulsar PSR J0855-4644, however as the pulsar is lying on the rim of the SNR, it is difficult to disentangle both contributions. Therefore, assuming a point source, the upper limit on the flux of the pulsar wind nebula (PWN) between 1 TeV and 10 TeV, is estimated to be ~ 2% of the Crab Nebula flux in the same energy range

A modeling analysis program for the JPL Table Mountain Io sodium cloud data

The abundant Io sodium cloud data obtained at JPL Table Mountain was reviewed. Images of the sodium cloud important to this modeling analysis program are contained in the 1976-1979 data set and the 1981 data set. A preliminary assessment of the 263 images in the 1981 data set for Region B/C was initiated. The spatial morphology of some of these images revealed the presence of the forward sodium cloud (Region B) and the directional features (Region C) as expected. Plans for the second quarter to initiate preliminary modeling analysis and to define further data processing are discussed