The Chemistry and Kinematics of Two Molecular Clouds near Sagittarius A*
John A. P. Lopez, Maria R. Cunningham, Paul A. Jones, Jonathan P. Marshall, Leonardo Bronfman, Nadia Lo, Andrew J. Walsh
备注：
Accepted for publication in MNRAS, on the 5th of August 2016. 39 pages (including online supplementary material). Main manuscript is 27 pages, containing 12 figures and 16 tables. The last 12 pages are the online supplementary material, containing 36 figures
我们分析了银河系中央分子带中20和50 km/s的$^{-1}$分子云的化学和运动学性质，以及连接这两个分子云的分子脊的化学和运动学性质。我们的工作利用了来自Mopra和NANTEN 2望远镜的0.65，3和7毫米波段的37个分子跃迁。0.65毫米NANTEN 2数据突出了20公里/秒$^{-1}$云西部的密集的发射凝结，仅在其他四个过渡中可见，它们是3毫米H $^{13}$ CN（1--0），H $^{13}$ CO $^{+}$（1--0），HNC（1--0）和N $_{2}$ H $^{+}$（1--0），表明凝结是适度的光学厚和冷。我们发现，虽然两个云之间的相对化学丰度是一样的，在许多过渡，这表明在两个云之间的化学变化不大，20公里秒的$^{-1}$，冷云是明亮的比50公里秒的$^{-1}$云在冲击和高密度示踪剂。增强发射的空间分布是广泛的，在20公里秒的$^{-1}$云，通过线比图所示。穿过两个云的位置速度图表明气体混合良好。我们表明，分子脊是最有可能的一部分，20公里秒的$^{-1}$云，他们都可能会扩展到包括50公里秒的$^{-1}$云，作为一个更大的云的一部分。此外，我们预计，20公里秒的$^{-1}$云被潮汐剪切的结果，从Sgr A* 的引力位。
英文摘要：
We have analysed the chemical and kinematic properties of the 20 and 50 km s$^{-1}$ molecular clouds in the Central Molecular Zone of the Milky Way Galaxy, as well as those of the molecular ridge bridging these two clouds. Our work has utilized 37 molecular transitions in the 0.65, 3 and 7-mm wavebands, from the Mopra and NANTEN2 telescopes. The 0.65-mm NANTEN2 data highlights a dense condensation of emission within the western part of the 20 km s$^{-1}$ cloud, visible in only four other transitions, which are 3-mm H$^{13}$CN (1--0), H$^{13}$CO$^{+}$ (1--0), HNC (1--0) and N$_{2}$H$^{+}$ (1--0), suggesting that the condensation is moderately optically thick and cold. We find that while the relative chemical abundances between both clouds are alike in many transitions, suggesting little variation in the chemistry between both clouds; the 20 km s$^{-1}$, cold cloud is brighter than the 50 km s$^{-1}$ cloud in shock and high density tracers. The spatial distribution of enhanced emission is widespread in the 20 km s$^{-1}$ cloud, as shown via line ratio maps. The position velocity diagrams across both clouds indicate that the gas is well mixed. We show that the molecular ridge is most likely part of the 20 km s$^{-1}$ cloud and that both of them may possibly extend to include the 50 km s$^{-1}$ cloud, as part of one larger cloud. Furthermore, we expect that the 20 km s$^{-1}$ cloud is being tidally sheared as a result of the gravitational potential from Sgr A*.
Being one of the most abundant atomic/molecular species observed in dense molecular gas, atomic carbon ($\mathrm{C}^0$) is a potential good tracer of molecular gas mass in many chemical/physical environments, though the $\mathrm{C^0}$ abundance variation outside the Galactic disk region is yet to be fully known. This paper presents a wide-field 500 GHz [CI] map of the Galactic central molecular zone (CMZ) obtained with the ASTE 10-m telescope. Principal component analysis and non-LTE multi-transition analysis have shown that the [CI] emission predominantly originates from the low-excitation ga…
The infall of the Sagittarius (Sgr) Dwarf Spheroidal Galaxy in the Milky Way halo is an unique opportunity to understand how the different components of a dwarf galaxy could be tidally removed. In this work, we reconstruct the Sgr core morphology and kinematics on the basis of a model that has already successfully reproduced the Sgr stream. Here we use a very high resolution model that almost resolves individual stars in the Sgr core. It reproduces most of the observed morphology and kinematic properties, without specific fine-tuning. We also show that the dark matter may have been almost enti…
Neighbors, Not Kin: Kinematic evidence for tidal tails from NGC 7492 along the Sagittarius stream
Université Côte d’Azur, Observatoire de la Côte d’Azur, CNRS, Laboratoire Lagrange（蔚蓝海岸大学，蔚蓝海岸天文台，法国国家科学研究中心，拉格朗日实验室）；Centro de Investigación en Ciencias del Espacio y Física Teórica, Universidad Central de Chile（智利中央大学空间科学与理论物理研究中心）；Departamento de Física, Universidad de Santiago de Chile（智利圣地亚哥大学物理系）；Center for Interdisciplinary Research in Astrophysics and Space Exploration (CIRAS), Universidad de Santiago de Chile（智利圣地亚哥大学天体物理与空间探索跨学科研究中心）；Instituto Interdisciplinario de Ciencias Básicas (ICB), CONICET-UNCuyo（CONICET-门多萨大学基础科学跨研究所）；Consejo Nacional de Investigaciones Científicas y Técnicas（阿根廷国家科学研究委员会）；Instituto de Alta Investigación, Universidad de Tarapacá（塔拉帕卡大学高等研究院）；ESO–European Southern Observatory（欧洲南方天文台）；Miranda House, University of Delhi（德里大学米兰达学院）；Inter University Centre for Astronomy and Astrophysics（大学间天文与天体物理中心）；Institute of Astronomy, University of Cambridge（剑桥大学天文学研究所）
Dynamical Origins of Azimuthal Metallicity Variations in the Galactic Disk: Insights from Kinematic Ridges with Gaia
The University of Texas at Austin（德克萨斯大学奥斯汀分校）；University of Surrey（萨里大学）；Flatiron Institute（平顿研究所）；University of Toronto（多伦多大学）；Princeton University（普林斯顿大学）
The Sagittarius stream is one of the best tools that we currently have to estimate the mass and shape of our Galaxy. However, assigning membership and obtaining the phase-space distribution of the stars that form the tails is quite challenging. Our goal is to produce a catalogue of RR Lyrae stars of Sagittarius and obtain an empiric measurement of the trends along the stream in sky position, distance and tangential velocities. We generate two initial samples from the Gaia DR2 RR Lyrae catalogue: one, selecting only the stars within \pm20deg of the orbital plane of Sagittarius (Strip) and the o…
CII fine-structure line observations of the Sagittarius C Region in the Galaxy's Central Molecular Zone
Max-Planck-Institut für Radioastronomie（马克斯·普朗克射电天文研究所）；Departamento de Astronomía, Universidad de La Serena（拉塞雷纳大学天文学系）；Department of Physics and Astronomy, University of California, Los Angeles（加州大学洛杉矶分校物理与天文学系）；Department of Astronomy, University of Maryland, College Park（马里兰大学天文学系）；Department of Physics, Astronomy, and Geosciences, Towson University（陶森大学物理、天文学和地球科学系）；I. Physikalisches Institut der Universität zu Köln（科隆大学第一物理研究所）；Institut de Radioastronomie Millimètrique（毫米波射电天文研究所）
We present evidence for globular cluster stellar debris in a dwarf galaxy system (Sagittarius: Sgr) based on an analysis of high-resolution \textit{H}-band spectra from the Apache Point Observatory Galactic Evolution Experiment (APOGEE) survey. We add [N/Fe], [Ti/Fe], and [Ni/Fe] abundance ratios to the existing sample of potential members of M~54; this is the first time that [N/Fe] abundances are derived for a large number of stars in M~54. Our study reveals the existence of a significant population of nitrogen- (with a large spread, $\gtrsim1$ dex) and aluminum-enriched stars with moderate M…
Chemical decoding of kinematic substructures in the Galactic halo
Università di Firenze（佛罗伦萨大学）；INAF – Osservatorio Astrofisico di Arcetri（意大利国家天体物理研究所阿切特里天文台）；Observatoire de Paris, Université PSL, Sorbonne Université, Université Paris Cité, CY Cergy Paris Université, CNRS（巴黎天文台，巴黎文理研究大学，索邦大学，巴黎西岱大学，CY塞尔吉巴黎大学，法国国家科学研究中心）；CEA, AIM, Université Paris-Saclay（法国原子能和替代能源委员会，天体物理学和粒子物理研究所，巴黎萨克雷大学）；Leibniz Institut für Astrophysik Potsdam (AIP)（波茨坦莱布尼茨天体物理研究所）；Dipartimento di Fisica e Astronomia “Galileo Galilei”, Università di Padova（帕多瓦大学伽利略·伽利莱物理与天文学系）；Dipartimento di Tecnica e Gestione dei Sistemi Industriali, Università di Padova（帕多瓦大学工业系统技术与管理系）；INAF – Osservatorio Astronomico di Padova（意大利国家天体物理研究所帕多瓦天文台）
The internal kinematics and chemistry of 20 Milky Way strings
INAF - Osservatorio Astronomico di Padova（意大利国家天体物理研究所帕多瓦天文台）；INAF – Osservatorio Astrofisico di Catania（意大利国家天体物理研究所卡塔尼亚天文台）；INAF - Osservatorio di Astrofisica e Scienza dello Spazio di Bologna（意大利国家天体物理研究所博洛尼亚天文与空间科学观测站）；INAF - Osservatorio Astronomico di Roma（意大利国家天体物理研究所罗马天文台）；Fundación Galileo Galilei – INAF（伽利略基金会-意大利国家天体物理研究所）；INAF – Osservatorio Astrofisico di Arcetri（意大利国家天体物理研究所阿切尔菲天文台）
Using of a new N-body simulation, as well as Gaia DR2/EDR3 data complemented by data from the Galah, APOGEE, LAMOST surveys, we explore the possible link between the MW spiral arms, RVphi-ridges and moving groups in local UV space. We show that the tightly wound main spiral arms in the N-body model can be successfully identified using overdensities in angular momentum (AM) or guiding space, as well as in the distribution of dynamically cold stars close to their guiding centers. Stars in the AM overdensities that travel over many kpc in radius trace extended density ridges in RVphi space and ov…
The chemical differentiation of seven COMs in the extended region around Sgr B2 has been observed: CH$_2$OHCHO, CH$_3$OCHO, t-HCOOH, C$_2$H$_5$OH, and CH$_3$NH$_2$ were detected both in the extended region and near the hot cores Sgr B2(N) and Sgr B2(M), while CH$_3$OCH$_3$ and C$_2$H$_5$CN were only detected near the hot cores. The density and temperature in the extended region are relatively low. Different desorption mechanisms have been proposed to explain the observed COMs in cold regions but fail to explain the deficiency of CH$_3$OCH$_3$ and C$_2$H$_5$CN. We explored under what physical c…
The Physical and chemical structure of Sagittarius B2 -- IV. Converging filaments in the high-mass cluster forming region Sgr B2(N)
我们使用了一个无偏的，谱线调查，覆盖的频率范围从211到275 GHz，并获得与ALMA（角分辨率为0.4 arcsec）研究的小尺度结构的稠密气体在人马座B2（北）。发现八个细丝会聚到中心毂并延伸约0.1 pc。空间结构，以及存在的巨大的中心区域，表明这些丝可能与吸积过程。为了推导出像Sgr B2（N）这样化学谱线丰富的源中气体的运动学性质，我们开发了一种新的工具，可以叠加任何分子物种的所有检测到的跃迁谱线。这允许增加我们的观测的信噪比和平均线外混合效应，这是线丰富区域中的常见问题。我们推导出的速度梯度约为20-100公里秒的$^{-1}$ pc $^{-1}$，这是10-100倍，通常发现在其他恒星形成区域的更大的尺度（1 pc）。单个细丝的质量吸积速率约为0.05 M $_\odot$ yr $^{-1}$，这导致总吸积速率为0.16 M $_\odot$ yr $^{-1}$。有些暗条拥有致密的核心，可能正在形成恒星和星团。这些致密核心的恒星含量约占总质量的50%。我们的结论是，当已经形成星团但仍含有大量气体时，核心可能会在中心合并，导致“潮湿”合并。中心区域的高密度和质量，加上高质量的会聚细丝的存在，高吸积率和嵌入的致密核心已经形成恒星，表明Sgr B2（N）可能有潜力演变成超级星团。
Compact Obscured Nuclei (CONs) account for a significant fraction of the population of luminous and ultraluminous infrared galaxies (LIRGs and ULIRGs). These galaxy nuclei are compact, with radii of 10-100~pc, with large optical depths at submm and far-infrared wavelengths, and characterized by vibrationally excited HCN emission. It is not known what powers the large luminosities of the CON host galaxies because of the extreme optical depths towards their nuclei. CONs represent an extreme phase of nuclear growth, hiding either a rapidly accreting supermassive black hole or an abnormal mode of …
We present high angular resolution 1.1mm continuum and spectroscopic ALMA observations of the well-known massive proto-cluster Mon R 2 IRS 3.The continuum image at 1.1mm shows two components, IRS 3 A and IRS 3 B, that are separated by $\sim$0.65$"$. We estimate that IRS 3 A is responsible of $\sim$80 % of the continuum flux, being the most massive component. We explore the chemistry of IRS 3 A based on the spectroscopic observations. In particular, we have detected intense lines of S-bearing species such as SO, SO$_2$, H$_2$CS and OCS, and of the Complex Organic Molecules (COMs) methyl formate…
