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arXiv 1902.04124astro-ph.GA
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ALMA空间分辨致密分子气探测超铝红外探测器

ALMA Spatially-resolved Dense Molecular Gas Survey of Nearby Ultraluminous Infrared Galaxies

Masatoshi Imanishi, Kouichiro Nakanishi, Takuma Izumi

摘要:

本文给出了我们对z < 0.15的邻近超亮红外星系(ULIRGs)的均匀选择样本(>25个)的ALMA HCN J=3-2和HCO+ J=3-2谱线观测结果。这些密集的分子气体示踪剂和连续的发射空间分辨在大多数观察到的ULIRGs的第一次实现合成光束的大小为~0.2 arcsec或~500 pc。在大多数ULIRG中,在束流尺寸内的核区域中的HCN与HCO+ J=3-2的通量比系统地高于空间延伸区域中的那些。升高的核HCN J=3-2发射可能与(a)发光的掩埋活动星系核,(b)ULIRG核中的高分子气体密度和温度,和/或(c)空间紧凑的核流出的机械加热有关。一小部分的观察到的ULIRGs显示更高的HCN-HCO+ J=3-2的流量比在本地化的非核区域比那些的核,这可能是由于机械加热的空间扩展流出。观测到的附近超重红外星系通常富含致密(>10^5 cm^-3)分子气体,在核区域(几千秒差距)内的质量估计为>10^9兆太阳能,致密气体可能在那里的总分子质量中占主导地位。我们发现一个低的检测率(<20%)的振动激发(v2=1f)HCN J=3 -2发射线的可能签名附近的明亮的HCO+ J= 3 -2线,这可能是由于,部分,大分子线宽度的ULIRGs。

英文摘要:

We present the results of our ALMA HCN J=3-2 and HCO+ J=3-2 line observations of a uniformly selected sample (>25) of nearby ultraluminous infrared galaxies (ULIRGs) at z < 0.15. The emission of these dense molecular gas tracers and continuum are spatially resolved in the majority of observed ULIRGs for the first time with achieved synthesized beam sizes of ~0.2 arcsec or ~500 pc. In most ULIRGs, the HCN-to-HCO+ J=3-2 flux ratios in the nuclear regions within the beam size are systematically higher than those in the spatially extended regions. The elevated nuclear HCN J=3-2 emission could be related to (a) luminous buried active galactic nuclei, (b) the high molecular gas density and temperature in ULIRG's nuclei, and/or (c) mechanical heating by spatially compact nuclear outflows. A small fraction of the observed ULIRGs display higher HCN-to-HCO+ J=3-2 flux ratios in localized off-nuclear regions than those of the nuclei, which may be due to mechanical heating by spatially extended outflows. The observed nearby ULIRGs are generally rich in dense (>10^5 cm^-3) molecular gas, with an estimated mass of >10^9 Msun within the nuclear (a few kpc) regions, and dense gas can dominate the total molecular mass there. We find a low detection rate (<20%) regarding the possible signature of a vibrationally excited (v2=1f) HCN J=3-2 emission line in the vicinity of the bright HCO+ J=3-2 line that may be due, in part, to the large molecular line widths of ULIRGs.

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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