北极方向AKARI/IRC监测场中18 μ m选择星系的多波长分析
Multi-wavelength analysis of 18um-selected galaxies in the AKARI/IRC monitor field towards the North Ecliptic Pole
摘要：
我们提出了一个初步的分析AKARI 18微米选定的星系使用所有9个光度波段在2- 24微米可用的在红外相机（IRC），以证明新的能力AKARI宇宙学调查。我们在AKARI/IRC监测场中的北极（NEP）50.2弧分^[2]的区域内探测到了72个18微米的源。从该样本中，通过单色切割（N2-N3>0.1）选择了25个可能红移z>~ 0.5的星系，以便使用地基BVRi 'z'JK数据进行详细的SED分析。利用覆盖紫外-亚毫米波段的星暴的SED辐射转移模型，我们从18 μ m选定星系的光学-MIR SED中获得光度红移。从最佳拟合的SED模型，我们表明，IRC全波段测光是能够跟踪在PAH 6.2um发射功能的蓝色侧的流量急剧上升。这表明IRC全波段测光对限制红外星系的红移是有用的，特别是对于4000 A破裂不太突出的尘埃星系。此外，我们还发现，在观测到的星系在z~1的SED中，PAH 7.7和11.2um发射特征之间的通量骤降是可识别的。通过利用PAH和硅酸盐吸收特征所导致的这种颜色异常，可以从AKARI朝向NEP的大型宇宙学巡天（即NEP-Deep和NEP-Wide巡天）中构造z~1处的ULIRG（“硅酸盐断裂”星系）的独特样本。这项试点研究表明，在NEP深，宽调查，如系统的差异，在SED之间的高，低z ULIRGs，和一个大的变化PAH带间强度比在星系高红移的可能性检测到许多有趣的星系属性。[删节]
英文摘要：
We present an initial analysis of AKARI 18um-selected galaxies using all 9 photometric bands at 2-24um available in the InfraRed Camera (IRC), in order to demonstrate new capabilities of AKARI cosmological surveys. We detected 72 sources at 18um in an area of 50.2 arcmin^2 in the AKARI/IRC monitor field towards the North Ecliptic Pole (NEP). From this sample, 25 galaxies with probable redshifts z>~ 0.5 are selected with a single colour cut (N2-N3>0.1) for a detailed SED analysis with ground-based BVRi'z'JK data. Using an SED radiative transfer model of starbursts covering the wavelength range UV -- submm, we derive photometric redshifts from the optical-MIR SEDs of 18um-selected galaxies. From the best-fit SED models, we show that the IRC all-band photometry is capable of tracing the steep rise in flux at the blue side of the PAH 6.2um emission feature. This indicates that the IRC all-band photometry is useful to constrain the redshift of infrared galaxies, specifically for dusty galaxies with a less prominent 4000A break. Also, we find that the flux dip between the PAH 7.7 and 11.2um emission feature is recognizable in the observed SEDs of galaxies at z~1. By using such a colour anomaly due to the PAH and silicate absorption features, unique samples of ULIRGs at z~1, `silicate-break' galaxies, can be constructed from large cosmological surveys of AKARI towards the NEP, i.e. the NEP-Deep and NEP-Wide survey. This pilot study suggests the possibility of detecting many interesting galaxy properties in the NEP-Deep and Wide surveys, such as a systematic difference in SEDs between high- and low-z ULIRGs, and a large variation of the PAH inter-band strength ratio in galaxies at high redshifts. [abridged]
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