谱线源探测与可视化综述
Overview on spectral line source finding and visualisation
摘要：
在这里，我将概述在噪声占主导地位的大型数据立方体中寻找谱线源的成功和挑战。这是一个3D挑战，因为我们希望编目的源分布在多个空间像素和光谱通道上。虽然可以应用2D搜索，例如，逐个信道地，最佳搜索考虑到源的3维性质。在这篇综述中，我将重点介绍河外巡天中HI 21-cm谱线源探测，特别是HIPASS，即“HI帕克斯全天巡天”和WALLABY，即“ASKAP HI全天巡天”。我使用原始HIPASS数据来突出星系和气体云的光谱特征的多样性，无论是在发射还是吸收。其中，我报告发现的680公里/秒宽HI吸收槽的超脉泽星系NGC 5793。诸如源混淆和基线波纹的问题，通常在单碟HI调查中遇到的，在干涉HI调查中大大减少。计划为澳大利亚平方公里阵列探路者（ASKAP）进行几次大型HI发射和吸收调查：这里我们重点关注WALLABY，这是对天空的21厘米调查（Dec < +30 degr; z < 0.26），ASKAP将花费大约一年的观测时间。新型相控阵馈电（“无线电摄像机”）将提供30平方度的瞬时视场。WALLABY预计将探测超过50万个星系，揭示它们的大尺度结构和宇宙学参数，探测它们扩展的低表面亮度盘以及星系之间的气流和细丝。它是未来使用SKA第一和第二阶段进行HI调查的先驱，探索星系形成和演化。编制高度可靠和完整的源目录将需要复杂的源查找算法以及准确的源参数化。
英文摘要：
Here I will outline successes and challenges for finding spectral line sources in large data cubes that are dominated by noise. This is a 3D challenge as the sources we wish to catalog are spread over several spatial pixels and spectral channels. While 2D searches can be applied, e.g., channel by channel, optimal searches take into account the 3-dimensional nature of the sources. In this overview I will focus on HI 21-cm spectral line source detection in extragalactic surveys, in particular HIPASS, the "HI Parkes All-Sky Survey" and WALLABY, the "ASKAP HI All-Sky Survey". I use the original HIPASS data to highlight the diversity of spectral signatures of galaxies and gaseous clouds, both in emission and absorption. Among others, I report the discovery of a 680 km/s wide HI absorption trough in the megamaser galaxy NGC 5793. Issues such as source confusion and baseline ripples, typically encountered in single-dish HI surveys, are much reduced in interferometric HI surveys. Several large HI emission and absorption surveys are planned for the Australian Square Kilometre Array Pathfinder (ASKAP): here we focus on WALLABY, the 21-cm survey of the sky (Dec < +30 degr; z < 0.26) which will take about one year of observing time with ASKAP. Novel phased array feeds ("radio cameras") will provide 30 square degrees instantaneous field-of-view. WALLABY is expected to detect more than 500 000 galaxies, unveil their large-scale structures and cosmological parameters, detect their extended, low-surface brightness disks as well as gas streams and filaments between galaxies. It is a precursor for future HI surveys with SKA Phase I and II, exploring galaxy formation and evolution. The compilation of highly reliable and complete source catalogs will require sophisticated source-finding algorithms as well as accurate source parametrisation.
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