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Title: MODELING VERY LONG BASELINE INTERFEROMETRIC IMAGES WITH THE CROSS-ENTROPY GLOBAL OPTIMIZATION TECHNIQUE

Abstract

We present a new technique for obtaining model fittings to very long baseline interferometric images of astrophysical jets. The method minimizes a performance function proportional to the sum of the squared difference between the model and observed images. The model image is constructed by summing N{sub s} elliptical Gaussian sources characterized by six parameters: two-dimensional peak position, peak intensity, eccentricity, amplitude, and orientation angle of the major axis. We present results for the fitting of two main benchmark jets: the first constructed from three individual Gaussian sources, the second formed by five Gaussian sources. Both jets were analyzed by our cross-entropy technique in finite and infinite signal-to-noise regimes, the background noise chosen to mimic that found in interferometric radio maps. Those images were constructed to simulate most of the conditions encountered in interferometric images of active galactic nuclei. We show that the cross-entropy technique is capable of recovering the parameters of the sources with a similar accuracy to that obtained from the very traditional Astronomical Image Processing System Package task IMFIT when the image is relatively simple (e.g., few components). For more complex interferometric maps, our method displays superior performance in recovering the parameters of the jet components. Our methodologymore » is also able to show quantitatively the number of individual components present in an image. An additional application of the cross-entropy technique to a real image of a BL Lac object is shown and discussed. Our results indicate that our cross-entropy model-fitting technique must be used in situations involving the analysis of complex emission regions having more than three sources, even though it is substantially slower than current model-fitting tasks (at least 10,000 times slower for a single processor, depending on the number of sources to be optimized). As in the case of any model fitting performed in the image plane, caution is required in analyzing images constructed from a poorly sampled (u, v) plane.« less

Authors:
;  [1];  [2]; ;  [3]
  1. Nucleo de Astrofisica Teorica, Universidade Cruzeiro do Sul, R. Galvao Bueno 868, Liberdade, 01506-000 Sao Paulo, SP (Brazil)
  2. UNIFEI, Instituto de Ciencias Exatas, Universidade Federal de Itajuba, Av. BPS 1303, Pinheirinho, 37500-903, Itajuba, MG (Brazil)
  3. Instituto de Astronomia, Geofisica e Ciencias Atmosfericas, Universidade de Sao Paulo, R. do Matao 1226, Cidade Universitaria, 05508-900 Sao Paulo, SP (Brazil)
Publication Date:
OSTI Identifier:
21578311
Resource Type:
Journal Article
Journal Name:
Astrophysical Journal
Additional Journal Information:
Journal Volume: 736; Journal Issue: 1; Other Information: DOI: 10.1088/0004-637X/736/1/68; Journal ID: ISSN 0004-637X
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; BL LACERTAE OBJECTS; DATA ANALYSIS; ENTROPY; GALAXIES; IMAGE PROCESSING; IMAGES; INTERFEROMETRY; JETS; OPTIMIZATION; SIMULATION; COSMIC RADIO SOURCES; PHYSICAL PROPERTIES; PROCESSING; THERMODYNAMIC PROPERTIES

Citation Formats

Caproni, A., Toffoli, R. T., Monteiro, H., Abraham, Z., and Teixeira, D. M., E-mail: anderson.caproni@cruzeirodosul.edu.br. MODELING VERY LONG BASELINE INTERFEROMETRIC IMAGES WITH THE CROSS-ENTROPY GLOBAL OPTIMIZATION TECHNIQUE. United States: N. p., 2011. Web. doi:10.1088/0004-637X/736/1/68.
Caproni, A., Toffoli, R. T., Monteiro, H., Abraham, Z., & Teixeira, D. M., E-mail: anderson.caproni@cruzeirodosul.edu.br. MODELING VERY LONG BASELINE INTERFEROMETRIC IMAGES WITH THE CROSS-ENTROPY GLOBAL OPTIMIZATION TECHNIQUE. United States. doi:10.1088/0004-637X/736/1/68.
Caproni, A., Toffoli, R. T., Monteiro, H., Abraham, Z., and Teixeira, D. M., E-mail: anderson.caproni@cruzeirodosul.edu.br. Wed . "MODELING VERY LONG BASELINE INTERFEROMETRIC IMAGES WITH THE CROSS-ENTROPY GLOBAL OPTIMIZATION TECHNIQUE". United States. doi:10.1088/0004-637X/736/1/68.
@article{osti_21578311,
title = {MODELING VERY LONG BASELINE INTERFEROMETRIC IMAGES WITH THE CROSS-ENTROPY GLOBAL OPTIMIZATION TECHNIQUE},
author = {Caproni, A. and Toffoli, R. T. and Monteiro, H. and Abraham, Z. and Teixeira, D. M., E-mail: anderson.caproni@cruzeirodosul.edu.br},
abstractNote = {We present a new technique for obtaining model fittings to very long baseline interferometric images of astrophysical jets. The method minimizes a performance function proportional to the sum of the squared difference between the model and observed images. The model image is constructed by summing N{sub s} elliptical Gaussian sources characterized by six parameters: two-dimensional peak position, peak intensity, eccentricity, amplitude, and orientation angle of the major axis. We present results for the fitting of two main benchmark jets: the first constructed from three individual Gaussian sources, the second formed by five Gaussian sources. Both jets were analyzed by our cross-entropy technique in finite and infinite signal-to-noise regimes, the background noise chosen to mimic that found in interferometric radio maps. Those images were constructed to simulate most of the conditions encountered in interferometric images of active galactic nuclei. We show that the cross-entropy technique is capable of recovering the parameters of the sources with a similar accuracy to that obtained from the very traditional Astronomical Image Processing System Package task IMFIT when the image is relatively simple (e.g., few components). For more complex interferometric maps, our method displays superior performance in recovering the parameters of the jet components. Our methodology is also able to show quantitatively the number of individual components present in an image. An additional application of the cross-entropy technique to a real image of a BL Lac object is shown and discussed. Our results indicate that our cross-entropy model-fitting technique must be used in situations involving the analysis of complex emission regions having more than three sources, even though it is substantially slower than current model-fitting tasks (at least 10,000 times slower for a single processor, depending on the number of sources to be optimized). As in the case of any model fitting performed in the image plane, caution is required in analyzing images constructed from a poorly sampled (u, v) plane.},
doi = {10.1088/0004-637X/736/1/68},
journal = {Astrophysical Journal},
issn = {0004-637X},
number = 1,
volume = 736,
place = {United States},
year = {2011},
month = {7}
}