arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 0904.1966astro-ph.CO
收藏

由GMOS-IFU观测到的致密HII星系UM 408:物理条件

On the compact HII galaxy UM 408 as seen by GMOS-IFU: Physical conditions

Patricio Lagos, Eduardo Telles, Casiana Munoz-Tunon, Eleazar R. Carrasco, Francois Cuisinier, Guillermo Tenorio-Tagle

摘要:

我们提出了在双子座南望远镜获得的紧凑型HII星系UM 408的积分场单元GMOS-IFU数据,以获得位于星系中心部分的3“x4”.4(~ 750 x1100 pc)区域内的发射线和线比的空间分布、运动学、等离子体参数和氧丰度以及积分性质。该区域的星暴被分解为两个巨大的区域,直径分别为~375和250 pc。用Hb等效宽度估算的这两个区域的年龄表明,它们是约500万年前的同时代事件,恒星质量约为10^4M_o。我们还使用[OIII]/Hb和[SII]/Ha比值图来探索该星系的激发机制。利用Ha发射谱线测量径向速度和速度弥散。我们得出了12+log(O/H)=7.87的综合氧丰度,在我们的视野中的所有spaxels上求和。考虑到测量氧丰度的所有数据点,发现平均值为12+log(O/H)=7.77,最小值和最大值之间的差值D(O/H)=0.47(7.58+-0.06-8.05+-0.04)。氧丰度的空间分布在整个星系中没有显示出任何明显的梯度。另一方面,大部分数据点位于平均值附近的+-2 σ色散区域(σ =0.1 dex),证实了这个紧凑的HII星系与其他先前研究的矮不规则星系一样是化学均匀的。因此,由当前恒星形成事件处理和注入的新金属可能没有被观察到,并且存在于热气相中,而来自以前事件的金属混合良好,均匀地分布在整个星系范围内。

英文摘要:

We present Integral Field Unit GMOS-IFU data of the compact HII galaxy UM408, obtained at Gemini South telescope, in order to derive the spatial distribution of emission lines and line ratios, kinematics, plasma parameters, and oxygen abundances as well the integrated properties over an area of 3"x4".4(~750x1100 pc) located in the central part of the galaxy. The starburst in this area is resolved into two giant regions of ~375 and 250pc diameter, respectively. The ages of these two regions, estimated using Hb equivalent widths, suggest that they are coeval events of ~5Myr with stellar masses of ~10^4M_o. We have also used [OIII]/Hb and [SII]/Ha ratio maps to explore the excitation mechanisms in this galaxy. The Ha emission line was used to measure the radial velocity and velocity dispersion. We derived an integrated oxygen abundance of 12+log(O/H)=7.87 summing over all spaxels in our field of view. An average value of 12+log(O/H)=7.77 and a difference of D(O/H)=0.47 between the minimum and maximum values (7.58+-0.06-8.05+-0.04) were found, considering all data points where the oxygen abundance was measured. The spatial distribution of oxygen abundance does not show any significant gradient across the galaxy. On the other hand, the bulk of data points are lying in a region of +-2sigma dispersion (with sigma=0.1 dex) around the average value, confirming that this compact HII galaxy as other previously studied dwarf irregular galaxies is chemically homogeneous. Therefore, the new metals processed and injected by the current star formation episode are possibly not observed and reside in the hot gas phase, whereas the metals from previous events are well mixed and homogeneously distributed through the whole extent of the galaxy.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

↑