CANDELS中的极端发射线星系：z>1的宽带选择性恒星爆发矮星系
Extreme Emission Line Galaxies in CANDELS: Broad-Band Selected, Star-Bursting Dwarf Galaxies at z>1
摘要：
在哈勃空间望远镜/WFC 3（HST/WFC 3）的宇宙组合近红外深河外遗留巡天（CANDELS）中，我们发现了大量红移z~1.7的极端发射线星系（EELG）。69个EELG候选者是通过异常明亮的发射线对其近红外宽带幅度的巨大贡献来选择的。在光谱学上证实了HST/WFC 3棱镜观测到的四个候选天体的强[OIII]发射线（静止坐标系等效宽度约为1000 μ m）的支持下，我们得出结论，这些天体是恒星质量为10^8 Msol的星系，正在经历一个巨大的星暴阶段，M_*/（dM_*/dt）仅为约1500万年。这些爆发可能会导致外流，其强度足以在低质量星系中产生核心暗物质轮廓。单个恒星的形成速率和同向运动的数密度（3.7x10^-4 Mpc^-3）可以在~4 Gyr内产生目前包含在10^8-10^9 Msol矮星系中的大部分恒星质量密度。因此，我们的观测提供了一个强有力的迹象，即当今矮星系中的许多甚至大多数恒星都是在强烈的、短暂的爆发中形成的，大多数是在z>1时。
英文摘要：
We identify an abundant population of extreme emission line galaxies (EELGs) at redshift z~1.7 in the Cosmic Assembly Near-IR Deep Extragalactic Legacy Survey (CANDELS) imaging from Hubble Space Telescope/Wide Field Camera 3 (HST/WFC3). 69 EELG candidates are selected by the large contribution of exceptionally bright emission lines to their near-infrared broad-band magnitudes. Supported by spectroscopic confirmation of strong [OIII] emission lines -- with rest-frame equivalent widths ~1000Å-- in the four candidates that have HST/WFC3 grism observations, we conclude that these objects are galaxies with 10^8 Msol in stellar mass, undergoing an enormous starburst phase with M_*/(dM_*/dt) of only ~15 Myr. These bursts may cause outflows that are strong enough to produce cored dark matter profiles in low-mass galaxies. The individual star formation rates and the co-moving number density (3.7x10^-4 Mpc^-3) can produce in ~4 Gyr much of the stellar mass density that is presently contained in 10^8-10^9 Msol dwarf galaxies. Therefore, our observations provide a strong indication that many or even most of the stars in present-day dwarf galaxies formed in strong, short-lived bursts, mostly at z>1.
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