The unusual Niv)-emitter galaxy GDS J033218.92-275302.7: star formation or AGN-driven winds from a massive galaxy at z=5.56
The unusual Niv)-emitter galaxy GDS J033218.92-275302.7: star formation or AGN-driven winds from a massive galaxy at z=5.56
复制标题
不寻常的 Niv) 发射星系 GDS J033218.92-275302.7：来自 z=5.56 的大质量星系的恒星形成或 AGN 驱动的风
DOI：
10.1051/0004-6361/200913042
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发表时间：
2009
影响因子：
6.5
通讯作者：
P. Rosati
中科院分区：
文献类型：
--
作者：
E. Vanzella;A. Grazian;M. Hayes;L. Pentericci;D. Schaerer;D. Schaerer;M. Dickinson;S. Cristiani;M. Giavalisco;A. Verhamme;M. Nonino;P. Rosati
目标。我们研究了GDS J033218.92-275302.7的性质，红移为5.56。方法.利用紫外光（HST和VLT）、近红外、近红外（VLT）、中红外（Spitzer）等16个波段的光度测量方法，对源的光谱能量分布进行了较好的采样。在中红外斯皮策/IRAC波段5.8、8.0 μ m（星云发射贡献不太有效）检测到的信号表明存在巴尔末破裂，这是早期形成的潜在恒星群的特征。高质量的VLT/FORS 2光谱显示出清晰的Lyemission线，以及半禁戒Niv）1483.3-1486.5也在发射中。这些线条暗示着一个年轻的恒星群体。特别是Niv）1483.3- 1486.5的特征（如果源不是活动星系核的宿主）是大质量和热恒星的特征，伴随着星云发射。相反，它可能是活动星系核的特征。对所观察到的SED和Lyemission谱线轮廓进行了仔细建模，以研究源的内部性质。结果从单星和双星星族的SED拟合和Lymodeling中，我们发现这个源似乎有一个演化的成分，恒星质量为5 - 10 10 M，年龄为0.4 Gyrs，还有一个年轻的成分，年龄为0.01 Gyrs，星星形成速率在30-200 Myr −1之间。从ACS/z 850和VLT/Ks波段得出的有效半径的极限表明，该星系比具有类似质量的本地星系密度更大。Lyline模型（NHI = 10 21 cm −2）支持相对较高的星云气柱密度。从光谱中测量到了一个强有力的外流（450公里/秒），与Lymodeling一致。从ACS的观测结果来看，Lyphotons的发射区域在空间上是紧凑的，并且在1400埃的静止坐标系波长处估计有类似的有效半径（0.1 kpc物理），其发射主要由恒星连续体和/或AGN控制。气体从中心区域喷出，但是，考虑到星系的质量，不确定它是否会污染IGM到很远的距离。我们认为，在致密气体环境中的星星形成的爆发是活跃的（可能包含热和大质量的恒星和/或低光度活动星系核），叠加在已经形成的恒星质量的一部分。
Aims. We investigate the nature of the source GDS J033218.92-275302.7 at redshift�5.56. Methods. The spectral energy distribution of the source is well-sampled by 16 bands photometry from UV-optical (HST and VLT), near infrared, near infrared (VLT) to mid-infrared (Spitzer). The detection of a signal in the mid-infrared Spitzer/IRAC bands 5.8, 8.0 � m - where the nebular emission contribution is less effective - suggests that there is a Balmer break, the signature of an underlying stellar population formed at earlier epochs. The high-quality VLT/FORS2 spectrum shows a clear Lyemission line, together with semi-forbidden Niv) 1483.3-1486.5 also in emission. These lines imply a young stellar population. In particular, the Niv) 1483.3- 1486.5 feature (if the source is not hosting an AGN) is a signature of massive and hot stars with an associated nebular emission. Conversely, it may be a signature of an AGN. The observed SED and the Lyemission line profile were modeled carefully to investigate the internal properties of the source. Results. From the SED-fitting with a single and a double stellar popula tion and from the Lymodeling, it turns out that the source seems to have an evolved component with a stellar mass of� 5� 10 10 Mand age�0.4 Gyrs, and a young component with an age of �0.01 Gyrs and star formation rate in the range of 30-200 Myr −1 . The limits on the effective radius derived from the ACS/z850 and VLT/Ks bands indicate that this galaxy is denser than the local ones with similar mass. A relatively high nebular gas column density is favored from the Lyline modeling (NHI�10 21 cm −2 ). A vigorous outflow (�450 km/s) has been measured from the optical spectrum, consistent with the Lymodeling. From ACS observations it turns out that the region emitting Lyphotons is spatially compact and has a similar effective radius (�0.1 kpc physical) estimated at the� 1400A rest-frame wavelength, whose emission is dominated by the stellar continuum and/or AGN. The gas is blown out from the central region, but, given the mass of the galaxy, it is uncertain whether it will pollute the IGM to large distances. We argue that a burst of star formation in a dense gas environment is active (possibly containing hot and massive stars and/or a low luminosity AGN), superimposed on an already formed fraction of stellar mass.