高山 - 阿尔玛[CII]调查：关于极度遮盖的偶然星系的性质

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高山 - 阿尔玛[CII]调查：关于极度遮盖的偶然星系的性质

The ALPINE-ALMA [CII] Survey: On the nature of an extremely obscured serendipitous galaxy

论文作者

Romano, Michael, Cassata, P., Morselli, L., Lemaux, B. C., Bethermin, M., Capak, P., Faisst, A., Fevre, O. Le, Schaerer, D., Silverman, J., Yan, L., Bardelli, S., Boquien, M., Cimatti, A., Dessauges-Zavadsky, M., Enia, A., Fudamoto, Y., Fujimoto, S., Ginolfi, M., Gruppioni, C., Hathi, N. P., Ibar, E., Jones, G. C., Koekemoer, A. M., Loiacono, F., Mancini, C., Riechers, D. A., Rodighiero, G., Rodriguez-Munoz, L., Talia, M., Vallini, L., Vergani, D., Zamorani, G., Zucca, E.

论文摘要

我们报告了偶然发现的明亮星系（GAL-A）是ALMA大型计划的一部分，该计划是在早期研究[CII]（Alpine）。尽管在Alma频段7中同时检测到该星系在线和连续发射中，但它在紫外线/光学滤镜中完全是黑暗的，并且仅在Ultravista KS频段中呈现边缘检测。我们讨论了观察到的ALMA线的性质，即发射是来自Z〜4.6的[CII]，还是来自Z〜2.2时的High-J Co转换。在第一种情况下，我们发现log（l_ [cii]/l_fir）= - 2.5的[CII]与fir亮度比率，与局部星形星系（SFGS）的平均值一致；相反，在第二种情况下，来源将不在文献中发现的L_CO和L_FIR之间的经验关系之外。在这两个红移中，我们通过使用恒星种群合成模型作为Lephare光谱能量分布（SED）拟合的输入来得出来自Alma Continuum的恒星形成速率（SFR），而恒星质量（M*）。利用我们的结果，我们认为GAL-A是一个主要序列（MS），Z = 4.6时Dusty Sfg（即[CII]发射极），log（sfr/[m/yr]）〜1.4和log（m*/m）〜9.7。这项工作强调了高山调查在对这类对象进行普查中的至关重要作用，以便在复兴时期结束时揭示其对宇宙全球恒星形成率密度（SFRD）的贡献。

We report the serendipitous discovery of a bright galaxy (Gal-A) observed as part of the ALMA Large Program to INvestigate [CII] at Early times (ALPINE). While this galaxy is detected both in line and continuum emission in ALMA Band 7, it is completely dark in UV/optical filters and only presents a marginal detection in the UltraVISTA Ks band. We discuss the nature of the observed ALMA line, i.e. whether the emission comes from [CII] at z~4.6, or from high-J CO transitions at z~2.2. In the first case we find a [CII]-to-FIR luminosity ratio of log(L_[CII]/L_FIR)=-2.5, consistent with the average value for local star-forming galaxies (SFGs); in the second case, instead, the source would lie outside of the empirical relations between L_CO and L_FIR found in the literature. At both redshifts, we derive the star-formation rate (SFR) from the ALMA continuum, and the stellar mass (M*) by using stellar population synthesis models as input for LePHARE spectral energy distribution (SED) fitting. Exploiting our results, we believe that Gal-A is a Main-Sequence (MS), dusty SFG at z=4.6 (i.e. [CII] emitter) with log(SFR/[M/yr])~1.4 and log(M*/M)~9.7. This work underlines the crucial role of the ALPINE survey in making a census of this class of objects, in order to unveil their contribution to the global star-formation rate density (SFRD) of the Universe at the end of the Reionisation epoch.

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