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arXiv 2102.13563astro-ph.GA
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CON-Quest:寻找最模糊的星系核

CON-quest: Searching for the most obscured galaxy nuclei

N. Falstad, S. Aalto, S. König, K. Onishi, S. Muller, M. Gorski, M. Sato, F. Stanley, F. Combes, E. González-Alfonso, J. G. Mangum, A. S. Evans, L. Barcos-Muñoz… 展开作者

N. Falstad, S. Aalto, S. König, K. Onishi, S. Muller, M. Gorski, M. Sato, F. Stanley, F. Combes, E. González-Alfonso, J. G. Mangum, A. S. Evans, L. Barcos-Muñoz, G. C. Privon, S. T. Linden, T. Díaz-Santos, S. Martín, K. Sakamoto, N. Harada, G. A. Fuller, J. S. Gallagher, P. P. van der Werf, S. Viti, T. R. Greve, S. García-Burillo, C. Henkel, M. Imanishi, T. Izumi, Y. Nishimura, C. Ricci, S. Mühle

摘要:

一些明亮和超明亮的红外星系(LIRGs和ULIRGs)拥有非常紧凑和尘埃的核。这些来源中温暖尘埃产生的强烈红外辐射容易激发分子的振动能级,如HCN。这导致振动激发的HCN(HCN-vib)的旋转跃迁发射,其中最亮的发射出现在致密遮蔽核(CON)中。我们的目标是确定CON在本地宇宙中的常见程度,以及它们的流行程度是否取决于宿主星系的光度或其他属性。我们对46个远红外发光星系样本中HCN-vib的旋转J = 3 - 2跃迁进行了阿塔卡玛大型毫米/亚毫米阵列(ALMA)观测。在38%的ULIRGs、21%的LIRGs和0%的低光度星系中可以识别出致密的暗核。我们发现,与宿主星系的倾角无关,但强有力的证据表明,与其他样本相比,CON中的IRAS 25至60 μ m通量密度比(f25/f60)较低。此外,我们还发现CONs与其他星系相比具有更强的硅酸盐特征(s9.7 μ m),但PAH等效宽度(EQW6.2 μ m)相似。在本机宇宙中,CON主要存在于(U)LIRGs中。需要对单个核进行高分辨率连续观测,以确定CON现象是否与核盘的倾角有关。CON中较低的f25/f60比值以及中红外诊断研究的结果与大型尘埃柱将核辐射转移到更长的波长相一致,使得中红外和远红外“光球”比内部区域显着更冷。为了评估CON在星系演化背景下的重要性,有必要将这项研究扩展到更高的红移,其中(U)LIRG更常见。

英文摘要:

Some luminous and ultraluminous infrared galaxies (LIRGs and ULIRGs) host extremely compact and dusty nuclei. The intense infrared radiation arising from warm dust in these sources is prone to excite vibrational levels of molecules such as HCN. This results in emission from the rotational transitions of vibrationally excited HCN (HCN-vib), with the brightest emission found in compact obscured nuclei (CONs). We aim to establish how common CONs are in the local Universe, and whether their prevalence depends on the luminosity or other properties of the host galaxy. We have conducted an Atacama Large Millimeter/submillimeter Array (ALMA) survey of the rotational J=3-2 transition of HCN-vib in a sample of 46 far-infrared luminous galaxies. Compact obscured nuclei are identified in 38 percent of ULIRGs, 21 percent of LIRGs, and 0 percent of lower luminosity galaxies. We find no dependence on the inclination of the host galaxy, but strong evidence of lower IRAS 25 to 60 μm flux density ratios (f25/f60) in CONs compared to the rest of the sample. Furthermore, we find that CONs have stronger silicate features (s9.7μm) but similar PAH equivalent widths (EQW6.2μm) compared to other galaxies. In the local Universe, CONs are primarily found in (U)LIRGs. High resolution continuum observations of the individual nuclei are required to determine if the CON phenomenon is related to the inclinations of the nuclear disks. The lower f25/f60 ratios in CONs as well as the results for the mid-infrared diagnostics investigated are consistent with large dust columns shifting the nuclear radiation to longer wavelengths, making the mid- and far-infrared "photospheres" significantly cooler than the interior regions. To assess the importance of CONs in the context of galaxy evolution, it is necessary to extend this study to higher redshifts where (U)LIRGs are more common.

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