Current Studies - Software Development

 AIDA: Astronomical Image Decomposition and Analysis

AIDA is a software package  (see the flow chart) specifically designed to analyse images of galaxies with a bright nucleus and to perform the decomposition into the nuclear and galactic components, in particular in the case where the nucleus is dominant. The image of this kind of objects in the focal plane of a telescope is described by: (galaxy+nucleus)⊗PSF.

Plot
Figure 1:AIDA view. A GUI assists the user in choosing sources and preparing them for subsequent analysis. For each selected source, information about its characteristics (FWHM, apparent magnitude, ellipticity, position angle, local background) are displayed, along with a 4-panels visualization of the object (image, contour plot, 3D surface and radial profile). Several interactive controls are available in the right side of the GUI, allowing changing the visualization appearance. Each plot can be exported in eps files and a text report of the characteristics of all the sources can be generated.

The decomposition into the galactic and nuclear components thus requires a careful characterization of the PSF, and then the information about the components can be retrieved by fitting the image with a model obtained by convolving the galaxy model with the PSF and adding the nucleus. AIDA can model the PSF in 2D by using reference stars in the images and can manage complex models (including any combination of available, even user-supplied, functions and/or empirical look-up tables). The PSF model can be variable in the Field Of View, making it suitable for Adaptive Optics observations. With the use of graphical interfaces, AIDA assists interactively the user in selecting sources for the analysis, preparing them (masking bad pixels and contamination from other sources, selecting regions to be included in the analysis, evaluating the local background), providing reasonable initial guess for the fit parameters and checking every step of the analysis process. When a large number of objects have to be analysed, a fully interactive analysis is unpractical. For this reason, we are also implementing a non-interactive mode, which bypass the graphical interfaces and allow using batch procedures. AIDA has been developed in IDL 6.0 and tested under Linux SuSE, Linux Red Hat, Windows XP. The software can also run under Virtual Machine, thus not requiring an IDL license.

People:R. Falomo  

Collaboration: M.Uslenghi (IASF-Mi)

Publications: Uslenghi & Falomo (2007), MSS Conf, 313

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