We present the first survey of dense gas towards Planck Galactic Cold Clumps (PGCCs). Observations in the J=1-0 transitions of HCO+ and HCN towards 621 molecular cores associated with PGCCs were performed using the Purple Mountain Observatory 13.7-m telescope. Among them, 250 sources have detection, including 230 cores detected in HCO+ and 158 in HCN. Spectra of the J=1-0 transitions from CO, 13CO, and C18O at the centers of the 250 cores were extracted from previous mapping observations to construct a multi-line data set. The significantly low detection rate of asymmetric double-peaked profiles, together with the well consistence among central velocities of CO, HCO+, and HCN spectra, suggests that the CO-selected Planck cores are more quiescent compared to classical star-forming regions. The small difference between line widths of C18O and HCN indicates that the inner regions of CO-selected Planck cores are not more turbulent than the exterior. The velocity-integrated intensities and abundances of HCO+ are positively correlated with those of HCN, suggesting these two species are well coupled and chemically connected. The detected abundances of both HCO+ and HCN are significantly lower than values in other low- to high-mass star-forming regions. The low abundances may be due to beam dilution. On the basis of the inspection of the parameters given in the PGCC catalog, we suggest that there may be about 1 000 PGCC objects having sufficient reservoir of dense gas to form stars.
Gas at high Galactic latitude is a relatively little-noticed component of the interstellar medium. In an effort to address this, forty-one Planck Galactic Cold Clumps at high Galactic latitude (HGal; $|b|>25^{\circ}$) were observed in $^{12}$CO, $^{13}$CO and C$^{18}$O J=1-0 lines, using the Purple Mountain Observatory 13.7-m telescope. $^{12}$CO (1-0) and $^{13}$CO (1-0) emission was detected in all clumps while C$^{18}$O (1-0) emission was only seen in sixteen clumps. The highest and average latitudes are $71.4^{\circ}$ and $37.8^{\circ}$, respectively. Fifty-one velocity components were obt…
Planck cold clumps in the $λ$ Orionis complex: I. Discovery of an extremely young Class 0 protostellar object and a proto-brown dwarf candidate in a bright rimmed clump PGCC G192.32-11.88
我们正在用地面望远镜对$λ$ Orionis复合体中的普朗克银河系冷团(PGCC)进行一系列观测,以系统地研究恒星反馈的影响。在PGCC G192.32-11.88的特殊情况下,我们发现了一个非常年轻的0类原恒星天体(G192 N)和一个原棕矮星候选天体(G192 S)。G192 N和G192 S位于一个受重力束缚的亮边团块中。在CO同位素谱线发射中观察到的速度和温度梯度表明PGCC G192.32-11.88受到外部加热和压缩。与猎户座复合体中其他年轻的0级源(例如PACS亮红源(PBRs))相比,G192 N可能具有最低的热光度($\sim0.8$ L $_{\sun}$)和吸积速率(6.3 $\times10^{-7}$ M $_{\sun}$ ~yr $^{-1}$)。它的内部光度($0.21\pm0.01$ L $_{\sun}$)和外流速度($\sim$ 14 km~s $^{-1}$)比第一流体静力学核心(FHSC)的预测值稍大。G192 N可能是最年轻的0级源之一,比FHSC稍微进化。考虑到它的低内部光度($0.08\pm0.01$ L $_{\odot}$)和吸积速率(2.8 $\times10^{-8}$ M $_{\sun}$ ~yr $^{-1}$),G192 S是一颗理想的原棕矮星候选者。PGCC G192.32-11.88中的恒星形成效率($\sim$ …
我们用詹姆斯·克拉克·麦克斯韦望远镜/SCUBA-2和野边山45米射电望远镜观测了13个普朗克冷团。用Nobeyama望远镜得到的N $_2$ H $^+$分布与SCUBA-2尘埃分布非常相似。82 GHz HC $_3$ N、82 GHz CCS和94 GHz CCS发射通常相对于N $_2$ H $^+$发射不同地分布。CCS发射,这是众所周知的,是丰富的无星分子云的核心,往往是非常clusive的观测目标。我们在DNC、HN $^{13}$ C、N $_2$ D $^+$、cyclic-C $_3$ H $_2$中对9个团块进行了深单点观测。N $_2$ D $^+$的检出率为50%。此外,我们还观测了$_3$向15普朗克冷团簇的发射,以估计动力学温度,并证实大多数靶是冷的($\lesssim$ 20 K)。在观测到的两个无星团块中,CCS辐射分布在N $_2$ H $^+$核心(化学演化气体)周围,这与L1544的情况类似,L1544是一个显示坍缩的星前核心。此外,我们还检测到DNC和N $_2$ D $^+$。这两个团块极有可能处于恒星形成的边缘。引入化学演化因子(CEF)来描述无星核的化学演化阶段,并对观测到的普朗克冷团进行了分析。
Astrochemistry Focus and Research on Planck Cold Clumps
在天体化学焦点小组,我们讨论了我们的理解中仍然缺少的东西,即使在这次会议上给出了新的知识,以及从现在开始的10年内可以做些什么。目前尚缺乏对紫外光子和宇宙射线与冰尘埃颗粒的相互作用、硫和磷化学、金属丰度效应、持续时间效应、COM的形成和破坏、相变、尘埃-气体界面、尘埃演化等的认识。我们应该做的是多尺度高光谱分辨率分子观测、实验室工作、理论、辐射转移、我们需要仔细建模,而不是简化事物。接下来,我介绍我们对普朗克冷团簇的研究。我们用詹姆斯·克拉克·麦克斯韦望远镜/SCUBA-2和野边山45米射电望远镜观测了13个普朗克冷团。用Nobeyama望远镜得到的N $_2$ H $^+$分布与SCUBA-2尘埃分布非常相似。82 GHz HC $_3$ N、82 GHz CCS和94 GHz CCS发射通常相对于N $_2$ H $^+$发射不同地分布。CCS发射,这是众所周知的,是丰富的无星分子云的核心,往往是非常clusive的观测目标。我们对DNC、HN $^{13}$ C、N $_2$ D $^+$、cyclic C $_3$ H $_2$等9个星系团进行了单点观测。N $_2$ D $^+$的检出率为50%。在观测到的两个无星团块中,CCS辐射分布在N $_2$ H $^+$核心(化学演化气体)周围,这与L1544的情况类似,L1544是一个显示坍缩的星前核心。此外,我们还检测到DN…
We have selected six sources (G209.55-19.68S2, G205.46-14.56S1$_{-}$A, G203.21-11.20W2, G191.90-11.21S, G205.46-14.56S3, and G206.93-16.61W2) from the Atacama Large Millimeter/submillimeter Array Survey of Orion Planck Galactic Cold Clumps (ALMASOP), in which these sources have been mapped in the CO (J=2-1), SiO (J=5-4), and C$^{18}$O (J=2-1) lines. These sources have high-velocity SiO jets surrounded by low-velocity CO outflows. The SiO jets consist of a chain of knots. These knots have been thought to be produced by semi-periodical variations in jet velocity. Therefore, we adopt a shock-form…
We report the detection of four new hot corino sources, G211.47-19.27S, G208.68-19.20N1, G210.49-19.79W and G192.12-11.10 from a survey study of Planck Galactic Cold Clumps in the Orion Molecular Cloud Complex with the Atacama Compact Array (ACA). Three sources had been identified as low mass Class 0 protostars in the Herschel Orion Protostar Survey (HOPS). One source in the lambda Orionis region is firstly reported as a protostellar core. We have observed abundant complex organic molecules (COMs), primarily methanol but also other oxygen-bearing COMs (in G211.47-19.27S and G208.68-19.20N1) an…
Determining the clumpiness of matter around galaxies is pivotal to a full understanding of the spatially inhomogeneous, multi-phase gas in the circumgalactic medium (CGM). We combine high spatially resolved 3D observations with hydrodynamical cosmological simulations to measure the cold circumgalactic gas clumpiness. We present new adaptive-optics-assisted VLT/MUSE observations of a quadruply lensed quasar, targeting the CGM of 2 foreground $z\sim$1 galaxies observed in absorption. We additionally use zoom-in FOGGIE simulations with exquisite resolution ($\sim$0.1 kpc scales) in the CGM of gal…
The presence of complex organic molecules (COMs) in the interstellar medium (ISM) is of great interest since it may link to the origin and prevalence of life in the universe. Aiming to investigate the occurrence of COMs and their possible origins, we conducted a chemical census toward a sample of protostellar cores as part of the ALMA Survey of Orion Planck Galactic Cold Clumps (ALMASOP) project. We report the detection of 11 hot corino sources, which exhibit compact emissions from warm and abundant COMs, among 56 Class 0/I protostellar cores. All the hot corino sources discovered are likely C…
Sequential Star Formation in the filamentary structures of Planck Galactic cold clump G181.84+0.31
我们提出了一个多波长的研究普朗克冷团G181.84+0.31,这是位于北端的扩展的星系结构S242。我们已经从SCUBA-2 850 μ m地图中提取了9个致密的核心,并根据它们的斯皮策,宽视场红外巡天探测器(WISE)和两微米全天巡天(2 MASS)近红外和中红外颜色确定了18个年轻的恒星物体(YSO,4个I类和14个II类)。致密核和YSO主要分布在G181.84的边界结构上,HCO $^{+}$(1-0)和N $_{2}$ H $^{+}$(1-0)谱线能很好地追踪到致密核和YSO。我们在G181.84中发现了连续恒星形成活动的特征:位于北部和南部子结构的致密核心和YSO比中心区域的年轻。我们还检测到全球速度梯度约0.8 $\pm$ 0.05 km s $^{-1}$ pc $^{-1}$和1. 0 $\pm$ 0.05 km s分别沿北部和南部子结构的$^{-1}$ pc $^{-1}$,中央下部结构的局部速度梯度为1.2 $\pm$ 0.1 km s $^{-1}$ pc $^{-1}$。这些结果可能是由于扩展的丝状结构S242的整体坍缩是由边缘效应驱动的,对于边缘效应,丝状体边缘首先坍缩,然后进一步向内触发恒星形成活动。我们确定了G181.84中的三个亚结构,并估计了它们单位长度的临界质量,它们分别是$\sim$ 101 $\pm$ 15 M $_{\odot}$ pc…
We aim to characterize a diverse selection of dense, potentially star-forming cores, clumps, and clouds within the Milky Way in terms of their dust emission and SF activity. We studied 53 fields that have been observed in the JCMT SCUBA-2 continuum survey SCOPE and have been mapped with Herschel. We estimated dust properties by fitting Herschel observations with modified blackbody functions, studied the relationship between dust temperature and dust opacity spectral index $β$, and estimated column densities. We extracted clumps from the SCUBA-2 850 $μ$m maps with the FellWalker algorithm and e…
Sixty five Planck Galactic cold clumps (PGCCs) from the first quadrant (IQuad) and thirty nine of PGCCs from the Anti-Center direction region (ACent) were observed in $^{12}$CO, $^{13}$CO and C$^{18}$O J=1-0 lines using the PMO 13.7-m telescope. All the targets were detected with all the three lines, except for 12 IQuad and 8 ACent PGCCs without C$^{18}$O detection. Seventy six and 49 velocity components were obtained in IQuad and ACent respectively. One-hundred and forty-six cores were extracted from 76 IQuad clumps and 100 cores from 49 ACent clumps. The average T$_{\mathrm{ex}}$ of IQuad co…
Massive stars have a strong impact on their local environments. However, how stellar feedback regulates star formation is still under debate. In this context, we studied the chemical properties of 80 dense cores in the Orion molecular cloud complex composed of the Orion A (39 cores), B (26 cores), and lambda Orionis (15 cores) clouds using multiple molecular line data taken with the Korean Very Long Baseline Interferometry Network (KVN) 21-m telescopes. The lambda Orionis cloud has an H ii bubble surrounding the O-type star lambda Ori, and hence it is exposed to the ultraviolet (UV) radiation …
The objective of this paper is to help shedding some light on the nature and the properties of the cold structures formed via thermal instability in the magnetized atomic interstellar medium. To this end, we searched for clumps formed in forced (magneto)hydrodynamic simulations with an initial magnetic field ranging from 0 to 8.3$μ$G. We statistically analyzed, through the use of Kernel Density Estimations, the physical and the morphological properties of a sample containing $\sim 1500$ clumps, as well as the relative alignments between the main direction of clumps and the internal velocity an…
We have investigated the protostellar disk around a Class 0/I protostar, L1527 IRS, using multi-wavelength observations of the dust continuum emission at $λ=0.87$, 2.1, 3.3, and 6.8 mm obtained by the Atacama Large Millimeter/submillimeter Array (ALMA) and the Jansky Very Large Array (VLA). Our observations achieved a spatial resolution of $3-13$ au and revealed an edge-on disk structure with a size of $\sim80-100$ au. The emission at 0.87 and 2.1 mm is found to be optically thick within a projected disk radius of $ r_{\rm proj}\lesssim50$ au. The emission at 3.3 and 6.8 mm shows that the powe…
Planck Galactic Cold Clumps (PGCCs) are contemplated to be the ideal targets to probe the early phases of star formation. We have conducted a survey of 72 young dense cores inside PGCCs in the Orion complex with the Atacama Large Millimeter/submillimeter Array (ALMA) at 1.3\,mm (band 6) using three different configurations (resolutions $\sim$ 0$\farcs$35, 1$\farcs$0, and 7$\farcs$0) to statistically investigate their evolutionary stages and sub-structures. We have obtained images of the 1.3\,mm continuum and molecular line emission ($^{12}$CO, and SiO) at an angular resolution of $\sim$ 0$\far…
Aims: Interstellar molecules form early in the evolutionary sequence of interstellar material that eventually forms stars and planets. To understand this evolutionary sequence, it is important to characterize the chemical composition of its first steps. Methods: In this paper, we present the result of a 2 and 3 mm survey of five cold clumps identified by the Planck mission. We carried out a radiative transfer analysis on the detected lines in order to put some constraints on the physical conditions within the cores and on the molecular column densities. We also performed chemical models to rep…