The properties of the high-mass star formation region IRAS22475+5939

Abstract

IRAS22475+5939 has been well researched by previous astronomers. But we still get some new characteristics about it, using the first observations in lines of CO J=2-1,13CO J=2-1,13CO J=3-2 by the KOSMA 3 m telescope. The mapping of the intensity ratio of 13CO J=3-2 and 13CO J=2-1 shows the distribution of the temperature with two peaks, which don't coincide with IRAS22475+5939 source and the center of the HII region, but at the edge of the HII region. The overlays of the Spitzer IRAC 8um and CO contours indicate that they are associated with each other and the strongest polycyclic aromatic hydrocarbons (PAHs) emission is at the position of IRAS22475+5939 source. While the IRAS LRS spectrum at 7-23 um and the PHT-s spectrum at 2-12 um of IRAS22475+5939 source also exhibit strong PAHs emission characters at the main PAH bands. The diversity of PAH family should be responsible for the plateaus of PAHs emission in the PHT-s spectrum and the IRAS-LRS spectrum. An analysis and modeling in infrared bands suggest that IRAS22475+5939 is more likely to be a Class I YSO. Where this is the case, the star is likely to have a temperature T_{EFF} \sim 9995.8 K, mass \sim15.34 M_(sun), luminosity \sim 1.54*10^4 L_(sun) and age \sim 1.54*10^4 yr. The model shows that the circumstellar disc emission is important for the wavelength between 1 and 10 um, otherwise, envelope fluxes for lambda >10 um. The bipolar outflow is confirmed in the molecular cloud. The excited star of the HII region has the chance to be the driving source of the outflow. The high resolution is required.