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arXiv 1508.05099astro-ph.GA
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ALMACAL I:第一次从深宽ALMA亚毫米测量中获得双波段计数,不受宇宙变化的影响

ALMACAL I: First dual-band number counts from a deep and wide ALMA submm survey, free from cosmic variance

I. Oteo, M. A. Zwaan, R. J. Ivison, I. Smail, A. D. Biggs

摘要:

我们利用ALMA校准观测进行了一个新的,广泛的和深亚毫米调查,ALMACAL。这些校准数据包括在各种频带和阵列配置中对校准器场的大量观测。收集在多次访问许多ALMA校准器期间获得的数据,有可能达到噪声水平,从而可以在重要区域内检测到暗淡的尘埃,恒星形成星系(DSFG)。在本文中,我们概述了我们的调查策略和报告的第一个结果。我们已经分析了69个校准器的数据,在亚弧秒分辨率下达到$\sim 25 \, {\rm μJy \, beam^{-1}}$的深度。采用基于$\geq 5 σ$探测的保守方法,我们在ALMA波段6和7分别发现了8个和11个DSFG,其通量密度为$S_{\rm 1.2 mm} \geq 0.2 \, {\rm mJy}$。即使是最深的\emph{Herschel}巡天也会错过最暗的星系。我们的累积计数已被确定独立在870 $μ$ m和1.2 mm,从稀疏的采样的天文天空,因此相对自由的宇宙方差。计数低于先前报告的值,至少为$2\times$的系数。未来的分析将产生大的,安全的DSFG样品,通过检测submm谱线确定红移。独特的是,我们的策略,然后允许形态学研究非常微弱的DSFG-代表更正常的恒星形成星系比传统的亚毫米星系(SMG)-在现场的自我校准是可行的,产生毫角秒的空间分辨率。

英文摘要:

We have exploited ALMA calibration observations to carry out a novel, wide and deep submm survey, ALMACAL. These calibration data comprise a large number of observations of calibrator fields in a variety of frequency bands and array configurations. Gathering together data acquired during multiple visits to many ALMA calibrators, it is possible to reach noise levels which allow the detection of faint dusty, star-forming galaxies (DSFGs) over a significant area. In this paper we outline our survey strategy and report the first results. We have analysed data for 69 calibrators, reaching depths of $\sim 25 \, {\rm μJy \, beam^{-1}}$ at sub-arcsec resolution. Adopting a conservative approach based on $\geq 5 σ$ detections, we have found eight and 11 DSFGs in ALMA bands 6 and 7, respectively, with flux densities $S_{\rm 1.2 mm} \geq 0.2 \, {\rm mJy}$. The faintest galaxies would have been missed by even the deepest \emph{Herschel} surveys. Our cumulative number counts have been determined independently at 870 $μ$m and 1.2 mm, from a sparse sampling of the astronomical sky, and are thus relatively free of cosmic variance. The counts are lower than reported previously by a factor of at least $2\times$. Future analyses will yield large, secure samples of DSFGs, with redshifts determined via detection of submm spectral lines. Uniquely, our strategy then allows morphological studies of very faint DSFGs - representative of more normal star-forming galaxies than conventional submm galaxies (SMGs) - in fields where self-calibration is feasible, yielding milliarcsecond spatial resolution.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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