剑鱼座及其成员星系。基团骨架的HA成像
Dorado and its member galaxies. Ha imaging of the group backbone
摘要：
剑鱼座是一个邻近的，丰富的和clusified星系群，在南半球延伸几度。这是第一次，我们映射的哈分布作为一个可能的指标的恒星形成（SF）活动的剑鱼成员的很大一部分显示相互作用和合并签名。用2.5米的杜邦望远镜和1米的斯沃普望远镜，我们获得了14个星系的窄带校准图像，这些星系构成了星系群的骨干，将Ha+[N II]映射到几个10 $^{-17}$ erg~cm $^{-2}$ ~s $^{-1}$ ~arcsec $^{-2}$。我们估计的星系恒星形成率（SFR）的Ha通量，校正星系前景灭绝和[N II]污染。在所有星系中都检测到了Ha+[N II]发射。晚型星系（LTG）中有明显的HII区，而早型星系（ETG）中的Ha+[N II]辐射主要由[N II]辐射控制，特别是在中心区域。然而，HII复合物也显示在四个ETG。将剑鱼座星系群作为一个整体来考虑，我们注意到Ha+[N II]的等效宽度（一种特定SF的度量）随着形态类型的增加而增加，从早期到晚期类型的成员，尽管它仍然低于在螺旋星系的类似调查中观察到的。螺旋成员的SFR在James+（2004）在类似星系巡天中观察到的范围内，尽管在三个螺旋中，SFR远低于其形态类别的中位数。一些早期型成员的SFR往往，在赔率，高于平均来自Ha+[N II]调查这个形态家庭。我们在Ha+[N Ⅱ]中检测到所有观察到的ETG，其中一半显示HII区。这些发现表明，这个星系群中的ETG并不是死星系：它们的SF还没有关闭。机制，如气体剥离和气体吸积，通过星系-星系的相互作用，似乎相关的修改SF在这一演化阶段的剑鱼座。
英文摘要：
ABRIDGED: Dorado is a nearby, rich and clumpy galaxy group that extends for several degrees in the Southern Hemisphere. For the first time, we map the Ha distribution as a possible indicator of star formation (SF) activity of Dorado members a large fraction of which show interaction and merging signatures. With the 2.5m du Pont and the 1m Swope telescopes we obtained narrow-band, calibrated images of 14 galaxies, forming the backbone of the group, mapping Ha+[N II] down to few 10$^{-17}$ erg~cm$^{-2}$~s$^{-1}$~arcsec$^{-2}$. We estimated the galaxy star formation rate (SFR) from the Ha fluxes, corrected for Galaxy foreground extinction and [N II] contamination. Ha+[N II] emission has been detected in all galaxies. HII regions clearly emerge in late-type galaxies (LTGs) , while in early-type galaxies (ETGs) the Ha+[N II] emission is dominated by [N II], especially in the central regions. However, HII complexes are also revealed in four ETGs. Considering the Dorado group as a whole, we notice that the Ha+[N II] equivalent width, a measure of the specific SF, increases with the morphological type, from early to late-type members, although it remains lower that what observed in similar surveys of spiral galaxies. The SFR of the spiral members is in the range of what observed in similar galaxies surveys James+ (2004), although, in three spirals the SFR is well below the median for their morphological classes. The SFR of some early-type members tends, at odds, to be higher than the average derived from Ha+[N II] surveys of this morphological family. We detected in Ha+[N II] all the ETGs observed and half of them show HII regions. These findings suggest that ETGs in this group are not dead galaxies: their SF has not shut down yet. Mechanisms such as gas stripping and gas accretion, through galaxy-galaxy interaction, seem relevant in modifying the SF in this evolutionary phase of Dorado.
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