Comparison between 30 micron sources in different galaxies

We present an analysis and comparison of the 30 µ m dust feature in the spectra of carbon-rich objects located in the Milky Way, Magellanic Clouds and the Sagittarius dwarf spheroidal galaxy. These spectra were collected by Spitzer Space Telescope. All of these galaxies are characterized by the different metallicities. We expect that some physical and chemical processes related to the formation of the feature are a function of the metallicity. Our study should allow us to better understand the mass loss process and thus late stages of stellar evolution of carbon-rich stars in these four galaxies. Our analysis uses the "Manchester method" as a basis of estimating the temperature of dust for the carbon-rich stars and the planetary nebulae in our sample. In the case of post-AGB objects we changed the spectral ranges used for the temperature estimation, because of the presence of the 21 µ m feature. We used a blackbody function with a single temperature deduced from the Manchester method to approximate the continuum under the 30 µ m feature. We have produced on-line catalogues of photometric and Spitzer IRS spectra for all objects that show the 30 µ m feature. These resources are available on-line for use by the community. (paper)