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arXiv 0911.2344astro-ph.CO
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恒星形成矮星系的新发现:蓝色致密矮星系Mrk 409的PMAS积分视场图

New Light in Star-Forming Dwarf Galaxies: The PMAS Integral Field View of the Blue Compact Dwarf Galaxy Mrk 409

L. M. Cairos, N. Caon, P. Papaderos, C. Kehrig, P. Weilbacher, M. M. Roth, C. Zurita

摘要:

我们利用波茨坦多孔径分光光度计对蓝矮星系Mrk 409的中心2 × 2 kpc ^2进行了积分场分光研究。本研究着重于星暴成分中电离星际介质的形态、二维化学丰度模式、激发性质和运动学。我们还调查了Mrk 409明亮的核星暴区域周围的电离气体发射的扩展环的性质。用演化模型和星族合成模型对环上选定区域的PMAS光谱进行了解释,结果表明它们的电离辐射主要来自一个总质量约为1.5 × 10 ^6 M_sun的年轻恒星星族,该恒星族在大约1000万年前开始形成。这个恒星成分很可能局限于一个球形膨胀的、由星暴驱动的超级气泡的碰撞界面上,这个超级气泡具有密度更大的、被扫过的环境气体,距离中心星暴核约600 pc。后者的光谱性质暗示了一个大的消光(C_H-β>0.9),以及一个额外的非热电离源的存在,很可能是一个低光度的活动星系核。Mrk 409显示出相对较大的氧丰度(12+log(O/H)~8.4),并且在R~600 pc外没有化学丰度梯度。电离气体的运动学显示出一个整体的规则旋转,轴向为西北-西南,最大速度为60 km/s;恒星形成环内的总质量约为1.4x10^9 M_sun。

英文摘要:

We present an integral field spectroscopic study of the central 2x2 kpc^2 of the blue compact dwarf galaxy Mrk 409, observed with the Potsdam MultiAperture Spectrophotometer. This study focuses on the morphology, two-dimensional chemical abundance pattern, excitation properties and kinematics of the ionized interstellar medium in the starburst component. We also investigate the nature of the extended ring of ionized gas emission surrounding the bright nuclear starburst region of Mrk 409. PMAS spectra of selected regions along the ring, interpreted with evolutionary and population synthesis models, indicate that their ionized emission is mainly due to a young stellar population with a total mass of ~1.5x10^6 M_sun, which started forming almost coevally ~10 Myr ago. This stellar component is likely confined to the collisional interface of a spherically expanding, starburst-driven super-bubble with denser, swept-up ambient gas, ~600 pc away from the central starburst nucleus. The spectroscopic properties of the latter imply a large extinction (C_H-beta>0.9), and the presence of an additional non-thermal ionization source, most likely a low-luminosity Active Galactic Nucleus. Mrk 409 shows a relatively large oxygen abundance (12+log(O/H)~8.4) and no chemical abundance gradients out to R~600 pc. The ionized gas kinematics displays an overall regular rotation on a northwest-southwest axis, with a maximum velocity of 60 km/s; the total mass inside the star-forming ring is about 1.4x10^9 M_sun.

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