The Hα halo distribution of 10 nearby planetary nebulae based on the SHASSA imaging data.

Abstract

Here we present initial results of our search for extensive halos around the planetary nebulae (PNe) in our Galaxy based on imaging data from the Southern H-Alpha Sky Survey Atlas (SHASSA). A threshold surface brightness in H emission was used to help identify the spatially extended features of the PNe. We investigated a sample that included 10 PNe, the large majority of which were found to be surrounded by extensive outer halos. The formation of these halos might be closely related to the AGB phase mass loss and/or the interaction of the stellar outflows with the interstellar medium. Most of these outer halos are nearly spherical. Close investigation of some specific objects, such as He 2-111 and NGC 3242, indicate a kinematic age on the order of 105 yrs. The mass loss history can be traced back to the late AGB phase of the evolution of the progenitors. Two objects form the sample (He 2-111, NGC 3242), were found to have outer halos with fragmented arcs that are apparently the result of their interaction with the interstellar medium. 我們在此呈現對於一些行星狀星雲周圍暗暈的初步研究結果，而這些結果主要是應用一個名為SHASSA(Southern H-Alpha Sky Survey Atlas) Hα射線源的巡天工作所做成的；經過仔細研究10個鄰近我們的行星狀星雲之後，我們發現它們絕大部分都被延展的暗暈結構所圍繞著，而這些暗暈的形成機制又與行星狀星雲在漸進巨星分支(AGB)時期的質量損失或是與周遭的星際介質交互作用有關；且這些暗暈的分佈呈現近似球形，針對He 2-111以及NGC 3242這兩個目標的詳細的研究之後，我們發現其動力學年齡約在105年左右，這意味著它們質量損失的過程可以追溯到AGB階段的晚期；其次，我們也在這兩個目標天體的外圍發現了一些細絲狀結構，而這些結構的出現正是表示著這兩個行星狀星雲與附近的星際物質正在交互作用。