Stellar evolution in the Outer Galaxy

Ryszard Szczerba, A. Lesniewska, N. Siodmiak & M. Sewilo

N. Copernicus Astronomical Centre, Poland

We are working on a systematic study of star formation in the Outer Galaxy, starting with some regions carefully selected to sample a range of environments and star formation activities. Our analysis is based on the data from the Spitzer surveys: SMOG and GLIMPSE360, combined with the infrared (IR) data from the 2MASS, UKIDSS, MSX, WISE and AKARI. The general strategy on Young Stellar Objects identification is to select IR excess sources, and then apply a series of filters to remove various populations of other sources. These include unresolved extragalactic sources (starbust galaxies and obscured AGNs), as well as evolved stars, specifically Asymptotic Giant Branch (AGB) stars, post-AGB objects and unresolved planetary nebulae (PNe). We have found that application of our hydrodynamical models developed for investigation of AGB and post-AGB phase of stellar evolution (Steffen, Szczerba, Schoenberner, 1998, A&A 337, 449) is of a crucial importance for selecting the whole population of evolved stars. I will discuss the method, describe the properties of the selected evolved stars in the Outer Galaxy, and present comparison with the similar population of evolved stars from the Inner Galaxy.

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