| 摘要: | 我們透過SDSS MaNGA提供的積分場光譜觀測資料，研究16個具恆星形成的早型星系（SFETGs）的性質。本研究中的早型星系均由星系動物園2（Galaxy Zoo 2）提供的星系型態資料篩選後得出，並以各個星系的BPT圖將其細分為具恆星形成的早型星系與不具恆星形成的早型星系（NSFETGs）。這兩類星系的性質差異在於SFETGs的質量較小、顏色較藍，且恆星形成活動旺盛，而NSFETGs則質量較大、顏色偏紅、無恆星形成活動。藉由空間解析的觀測圖我們發現部分的SFETGs其氣體與恆星的旋轉方向角度不一致，推論出供應恆星形成活動的氣體源自於星系外部。從游離氫發射線的等效寬度之空間分布圖的樣貌，我們將SFETGs再細分為圓型、偏移型、雙峰型、多峰型四類。為了了解星系旋轉的比角動量（specific angular momentum），我們採用了λ_R這個參數。這四類SFETGs其氣體的λ_R有所不同，其中圓型、偏移型這兩類的λ_R較小，而雙峰、多峰型則較大。我們發現氣體角動量較少的星系，其恆星形成活動較強烈。此外，為了驗證已知的sSFR-Dn4000關係是否在局域同樣適用，我們採用了局部的Hα等效寬度作為局部sSFR，發現這個反相關不僅適用於廣域，也適用於局域。至於恆星年齡剖面的梯度，對於圓型、偏移型、雙峰型與多峰型四類分別為正向、混和、反－正向及反向，這些梯度反映出不同類型的星系的氣體分布。;We investigate the properties of 16 star-forming early-type galaxies (SFETGs) with
the integral field spectroscopy (IFS) from SDSS MaNGA. The ETGs are selected from
the morphological parameters provided by Galaxy Zoo 2 and then classified into SFETGs and Non-SFETGs (NSFETGs) through the BPT maps. The differences of the galaxy properties between the SFETGs and NSFETGs are that the SFETGs are less massive, showing bluer color, and, of course, more star-forming, while the NSFETGs are massive, red, and passive. The origins of the gas fueling the star formation may be external because of the existence of the kinematically misaligned gas and stars in some SFETGs. We further classify the SFETGs into round, shifted, double-peaked, and multiple-peaked using the morphology derived from the maps of the equivalent width (EW) of the Hα emission line. To express the specific angular momentum of the gas of the galaxies, we employ the λ_R parameter. These four types of morphology correspond to different levels of λ_R of gas; the round and the shifted SFETGs are at the lower levels, whereas the double- and multiple-peaked ones are at the higher ones. Based on the relation between λ_R and local Hα EW, the loss of the angular momentum of gas may enhance the star formation. To verify the well-known sSFR-Dn4000 relation on the local scale, we adopt the Hα EW to be the local sSFR. We find that the anti-correlation works on the local scale as well. The gradients of the stellar age profiles of the round, shifted, double-peaked, and multiple-peaked SFETGs are positive, mixed, negative-positive, and negative, respectively, which reflect the distribution of gas while forming stars. |
