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NGC 7793的深Fabry-Perot Half观测:一个非常扩展的Half盘和一个真正下降的旋转曲线

Deep Fabry-Perot Halpha Observations of NGC 7793: a Very Extended Halpha Disk and a Truly Declining Rotation Curve

I. Dicaire, C. Carignan, P. Amram, M. Marcelin, J. Hlavacek-Larrondo, M. -M. de Denus-Baillargeon, O. Daigle, O. Hernandez

摘要:

在智利拉西拉的ESO 3.60米和马赛36厘米望远镜上获得了玉夫座星系群NGC 7793的深Halalpha观测。Halpha辐射一直被探测到HI盘的边缘,使得NGC 7793的HII盘成为在安静的非活动星系核晚型系统中观测到的最大的盘之一。即使在非常外部的部分,HII电离源可能主要是内部的(盘中的大质量恒星),不太可能来自河外电离背景。Halalpha运动学证实了HI观测已经看到的:NGC 7793有一个真正下降的旋转曲线。然而,这种下降不是开普勒式的,仍然需要一个黑暗的晕来解释外部的旋转速度。

英文摘要:

Deep Halpha observations of the Sculptor Group galaxy NGC 7793 were obtained on the ESO 3.60m and the Marseille 36cm telescopes at La Silla, Chile. Halpha emission is detected all the way to the edge of the HI disk, making of the HII disk of NGC 7793 one of the largest ever observed in a quiet non-AGN late-type system. Even in the very outer parts, the HII ionizing sources are probably mainly internal (massive stars in the disk) with an unlikely contribution from the extragalactic ionizing background. The Halpha kinematics confirms what had already been seen with the HI observations: NGC 7793 has a truly declining rotation curve. However, the decline is not Keplerian and a dark halo is still needed to explain the rotation velocities in the outer parts.

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