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arXiv 0909.0111astro-ph.COastro-ph.GA
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z=4.9恒星形成星系的运动学、恒星形成和恒星质量集合的空间分辨地图

A Spatially Resolved Map of the Kinematics, Star-Formation and Stellar Mass Assembly in a Star-Forming Galaxy at z=4.9

Mark Swinbank, Tracy Webb, Johan Richard, Richard Bower, Richard Ellis, Garth Illingworth, Tucker Jones, Mariska Kriek, Ian Smail, Dan Stark, Pieter Van Dokkum

摘要:

本文详细研究了透镜星系团MS 1358 +62后面一个z=4.92的高度放大星系的空间分辨运动学、恒星形成和恒星质量。我们使用HST ACS & NICMOS和Spitzer IRAC观测到的光学,近红外和中红外成像来推导恒星质量,并使用Gemini/NIFS IFU从星云[OII]发射中研究星系的速度结构。使用详细的引力透镜模型,我们考虑了透镜放大因子12 +/-。2.0发现这个L* 星系的恒星质量为M*=7+/-2x10^8Mo,动力学质量为Mdyn=3+/-1x10^9csc^2(i)Mo(在2kpc以内),恒星形成速率为42+/-8Mo/yr。这个星系的源平面紫外/光学形态主要由五个离散的恒星形成区域组成。利用动力学信息,我们得到了Mcl~10^(8-9)Mo单个恒星形成区的质量,其大小约为200 pc。我们发现,在一个固定的大小,在这些HII区域内的恒星形成率密度大约是两个数量级大于当地的螺旋/星暴星系中观察到的,但与最大的HII地区在当地的宇宙,如30 Dor一致。最后,我们将空间分辨的星云发射线速度与Ly-alpha和UV-ISM线进行了比较,发现该星系被星系尺度的外流所包围,其中Ly-alpha线相对于(系统)星云发射线红移约150 km/s,UV-ISM线相对于(系统)星云发射线蓝移约200 km/s。外流的速度结构反映了星云辐射的速度结构,这表明外流是年轻的(~ 1500万年),还没有爆发出系统。总的来说,这些结果表明,这个年轻的星系正在经历它的第一个主要的大规模组装时代。

英文摘要:

We present a detailed study of the spatially resolved kinematics, star-formation and stellar mass in a highly amplified galaxy at z=4.92 behind the lensing cluster MS1358+62. We use the observed optical, near- and mid-infrared imaging from HST ACS & NICMOS and Spitzer IRAC to derive the stellar mass and the Gemini/NIFS IFU to investigate the velocity structure of the galaxy from the nebular [OII] emission. Using a detailed gravitational lens model, we account for lensing amplification factor 12.+/-2.0 and find that this intrinsically L* galaxy has a stellar mass of M*=7+/-2x10^8Mo, a dynamical mass of Mdyn=3+/-1x10^9csc^2(i)Mo (within of 2kpc) and a star-formation rate of 42+/-8Mo/yr. The source-plane UV/optical morphology of this galaxy is dominated by five discrete star-forming regions. Exploiting the dynamical information we derive masses for individual star-forming regions of Mcl~10^(8-9)Mo with sizes of ~200pc. We find that, at a fixed size, the star-formation rate density within these HII regions is approximately two orders of magnitude greater than those observed in local spiral/starburst galaxies, but consistent with the most massive HII regions in the local Universe such as 30Dor. Finally, we compare the spatially resolved nebular emission line velocity with the Ly-alpha and UV-ISM lines and find that this galaxy is surrounded by a galactic scale outflow in which the Ly-alpha appears redshifted by ~150km/s and the UV-ISM lines blue-shifted by -200km/s from the (systemic) nebular emission. The velocity structure of the outflow mirrors that of the nebular emission suggesting the outflow is young (~15Myr), and has yet to burst out of the system. Taken together, these results suggest that this young galaxy is undergoing its first major epoch of mass assembly.

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