Data Analysis and Simulations of the Large Data Sets in the Galactic Astronomy

Abstract

In the last decades large data sets covering a wide range of both resolution and observed regions have been accumulated in the Astronomy. Follow-up technology involving the storage and the access to these data is also necessary to develop methods and tools that will allow their usage. In this chapter, I will review the use of the large data sets in the galactic astronomy, most of them covering almost entire area of the sky in the several wavelengths, for both the diffuse data provided by IRAS, DIRBE/COBE, molecular and hydrogen surveys and point sources catalogues as provided by stellar large-scale surveys such as DENIS, 2MASS, SDSS, among others. A brief description of these surveys and how to access them in the context of Virtual Observatory will be also presented. Numerical simulations have an important role in understanding and describing the nature of the observations. Particularly, large-scale surveys data can be also used to validate numerical models. I will present models and methods that describe the Galactic structure taking into account the hydrogen atomic distribution in our Galaxy, obtaining galactic parameters such as scale-height, spiral arms parameters, the co-rotation radius. One of the biggest problems describing the spiral arms in the Galaxy from the gas distribution resides in the fact that some interpretations in the literature for  -v the diagrams have not been updated in respect to rotation curves using old values for the distance from the Sun to the Galactic center. Another problem resides of the difficulty in describing the non-circular motion. My choice in the present work is to describe the spiral structure by adopting an empirical model (section 3) which is based on the analysis of HI distribution by means its tangential directions and the observed  -v. One of the aims of the present paper is to carry out self consistent inter-comparisons of our results regarding different tracers of the spiral structure. The models of the spiral structure presented here were first introduced by Amores & Lepine (2005, AL05) in which two models were proposed to describe the interstellar extinction in the Galaxy (see section 4 of this chapter). Model S consists in obtaining extinction predictions taking into account the spiral structure of our Galaxy. In this model, the extinction grows by steps each time a spiral arm is crossed and remains almost constant in the inter-arm regions. The models were also compared with other samples of objects and regions as pointed by Amores & Lepine (2007). As galactic interstellar extinction is a crucial obstacle when observing in the highly obscured regions, it is important to model it properly. I will present the recent efforts in this area. I