The first CO+ image: Probing the HI/H2 layer around the ultracompact HII region Mon R2
S. P. Trevino-Morales, A. Fuente, A. Sanchez-Monge, P. Pilleri, J. R. Goicoechea, V. Ossenkopf-Okada, E. Roueff, J. R. Rizzo, M. Gerin, O. Berne, J. Cernicharo,… 展开作者
S. P. Trevino-Morales, A. Fuente, A. Sanchez-Monge, P. Pilleri, J. R. Goicoechea, V. Ossenkopf-Okada, E. Roueff, J. R. Rizzo, M. Gerin, O. Berne, J. Cernicharo, M. Gonzalez-Garcia, C. Kramer, S. Garcia-Burillo, J. Pety
备注：
The main text has 4 pages, 2 pages of Appendix, 4 figures, 1 table. Accepted for publication in Astronomy and Astrophysics letters
The CO+ reactive ion is thought to be a tracer of the boundary between a HII region and the hot molecular gas. In this study, we present the spatial distribution of the CO+ rotational emission toward the Mon R2 star-forming region. The CO+ emission presents a clumpy ring-like morphology, arising from a narrow dense layer around the HII region. We compare the CO+ distribution with other species present in photon-dominated regions (PDR), such as [CII] 158 mm, H2 S(3) rotational line at 9.3 mm, polycyclic aromatic hydrocarbons (PAHs) and HCO+. We find that the CO+ emission is spatially coincident with the PAHs and [CII] emission. This confirms that the CO+ emission arises from a narrow dense layer of the HI/H2 interface. We have determined the CO+ fractional abundance, relative to C+ toward three positions. The abundances range from 0.1 to 1.9x10^(-10) and are in good agreement with previous chemical model, which predicts that the production of CO+ in PDRs only occurs in dense regions with high UV fields. The CO+ linewidth is larger than those found in molecular gas tracers, and their central velocity are blue-shifted with respect to the molecular gas velocity. We interpret this as a hint that the CO+ is probing photo-evaporating clump surfaces.
The dynamics of ionized gas around the W33 Main ultracompact HII region is studied using observations of hydrogen radio recombination lines and a detailed multiwavelength characterization of the massive star-forming region W33 Main is performed. We used the Giant Meterwave Radio Telescope (GMRT) to observe the H167$α$ recombination line at 1.4 GHz at an angular resolution of 10 arcsec, and Karl. G. Jansky Very Large Array (VLA) data acquired in the GLOSTAR survey to study the dynamics of ionized gas. We also observed the radio continuum at 1.4 GHz and 610 MHz with the GMRT and used GLOSTAR 4$-…
In this paper we present the results of a morphological study performed on a sample of 28 ultracompact \hiirs~located near extended free-free emission, using radio continuum observations at 3.6~cm with the C and D VLA~configurations, with the aim of determining a direct connection between them. By using previously published observations in B and D VLA~configurations, we compiled a final catalogue of 21 ultracompact \hiirs ~directly connected with the surrounding extended emission. The observed morphology of most of the ultracompact \hiirs~in radio continuum emission is irregular (single or mul…
许多超致密的HII区在射电连续辐射中表现出彗星的形态。在这样的区域，一颗年轻的大质量恒星可能正在通过紫外线辐射消融产生它的分子云团，在恒星的一侧，辐射驱动电离前沿，在致密的分子气体中停滞。在另一边，电离气体向外流入更稀薄的环境。相对于中性气体，这股风是低压的。压力差吸引了更多的云物质，供给风，直到致密的分子气体消散。最近，对大质量恒星在分子气体中开启的随时间变化的模拟显示，该系统正朝着与刚才描述的方向相似的方向演变。在这里，我们探讨了一个半解析模型，其中风是轴对称的，已经达到了稳定状态。通过这个简化的图片，使我们能够研究的依赖性的风和它的绑定电离前的恒星光度，峰值分子密度，和位移的恒星从中心的团块。对于典型的参数值，风的跨音速加速速度约为15 km / s，并以每年10^-4太阳质量的速率向外输送质量。恒星辐射压的作用是使风的密度梯度变陡。
We present a multiwavelength study of the cometary \hii region G12.21--0.10 using the VLA and OVRO. Both radio continuum (0.3, 0.7, 2 and 3.6~cm) and spectral lines of H41$α$, $^{13}$CS(2$-$1) \& (1$-$0), and NH$_{\rm 3}$(2,2) \& (4,4) observations are included. We find two 3~mm continuum peaks toward G12.21--0.10, one of them is spatially coincident with the UC~H~II region, while the other coincides spatially with a molecular clump. We also find that the 0.7, 2 and 3.6~cm continuum and H41$α$ line are only detected toward the UC~H~II region, while the $^{13}$CS, and NH$_{\rm 3}$ is spatially …
We have carried out a multi-epoch simultaneous survey of 22 GHz H$_2$O and 44 GHz Class I CH$_3$OH masers toward 103 ultracompact HII regions (UCHIIs) between 2010 and 2017. We detected H$_2$O and CH$_3$OH maser emission in 74 (72%) and 55 (53%) UCHIIs, respectively. Among them, 3 H$_2$O and 27 CH$_3$OH maser sources are new detections. These high detection rates suggest that the occurrence periods of both maser species are significantly overlapped with the UCHII phase of massive star formation. The CH$_3$OH maser lines always have small (< 10 km s$^{-1}$) relative velocities with respect to t…
The Karl Jansky Very Large Array (VLA), Owens Valley Radio Observatory (OVRO), Atacama Large Millimetric Array (ALMA), and the infrared \textit{Spitzer} observatories, are powerful facilities to study massive star formation regions and related objects such as ultra--compact (UC) \hii regions, molecular clumps, and cores. We used these telescopes to study the \uchiir G43.89--0.78. The morphological study at arcminute scales using NVSS and \textit{Spitzer} data shows that this region is similar to those observed in the \textit{ bubble--like} structures revealed by \textit{Spitzer} observations. …
Spitzer View of Young Massive Stars in the LMC HII Complex N44
大麦云星云（LMC）中的HII复合体N44提供了一个很好的地点来详细研究温和星暴中的恒星形成，因为它拥有三个处于不同演化阶段的恒星形成区域，并且它不像剑鱼座30巨大的HII区域那样复杂和混乱。我们已经获得了斯皮策太空望远镜的观测和补充的地面4 m uBVIJK观测N44，以确定候选的大质量年轻恒星物体（YSO）。我们进一步分类的YSO类型I，II和III，根据他们的光谱能量分布（SED）。在我们的60个YSO候选样本中，其中约65%在高分辨率地基图像中被分解为多个分量或扩展源。我们模拟了36个YSO的SED，这些YSO在一个组中表现为单一或占主导地位。我们发现I型和I/II型YSO很好地拟合，但II型和II/III型YSO显示出它们观察到的SED和不包括PAH排放的模型之间的偏差。我们还发现，一些III型YSO在其盘组件中具有中心孔。在四个超紧凑的HII区发现了YSO对应物，它们的恒星质量由SED模型拟合确定，与由HII区电离要求估计的结果吻合得很好。的YSO的分布进行了比较的基础恒星星族和星际气体的条件，以说明目前形成的O型恒星和以前形成的大质量恒星之间的相关性。也提出了触发恒星形成的证据。
我们提出了深3.6厘米无线电连续观测的HII区域W40使用甚大阵列在其A和B配置。我们在一个4 x 4弧分的区域内探测到总共20个紧凑的射电源，其中11个集中在一个30弧秒的范围内。我们还介绍了夏威夷大学2.2米望远镜上的QUIRC仪器拍摄的W40星团的JHK测光。这些数据表明，20个VLA源中有15个具有红外对应物，10个显示出周期小于20天的射电变率。基于这些综合的无线电和红外数据，我们提出，8个无线电源的候选人超紧凑的HII区，7可能是年轻的恒星物体，和2可能是星际气体冲击。
We have carried out the largest and most unbiased search for hypercompact (HC) HII regions. Our method combines four interferometric radio continuum surveys (THOR, CORNISH, MAGPIS and White2005) with far-infrared and sub-mm Galactic Plane surveys to identify embedded HII regions with positive spectral indices. 120 positive spectrum HII regions have been identified from a total sample of 534 positive spectral index radio sources. None of these HII regions, including the known HCHII regions recovered in our search, fulfills the canonical definition of an HCHII region at 5 GHz. We suggest that th…
This paper investigates the gravitational trapping of HII regions predicted by steady-state analysis using radiation hydrodynamical simulations. We present idealised spherically symmetric radiation hydrodynamical simulations of the early evolution of HII regions including the gravity of the central source. As with analytic steady state solutions of spherically symmetric ionised Bondi accretion flows, we find gravitationally trapped HII regions with accretion through the ionisation front onto the source. We found that, for a constant ionising luminosity, fluctuations in the ionisation front are…
We investigated the chemical evolution of HC3N in six dense molecular clouds, using archival available data from the Herschel infrared Galactic Plane Survey (Hi-GAL) and the Millimeter Astronomy Legacy Team Survey at 90 GHz (MALT90). Radio sky surveys of the Multi-Array Galactic Plane Imaging Survey (MAGPIS) and the Sydney University Molonglo Sky Survey (SUMSS) indicate these dense molecular clouds are associated with ultracompact HII (UCHII) regions and/or classical HII regions. We find that in dense molecular clouds associated with normal classical HII regions, the abundance of HC3N begins t…
The GUAPOS project -- VII: Physical structure and molecular environment of the G31.41+0.31 HII region
INAF, Osservatorio Astrofisico di Arcetri（意大利国家天体物理研究所，阿切特里天文台）；Centro de Astrobiología (CAB), CSIC-INTA（天体生物学中心（CAB），西班牙高等科学研究理事会-国家航空航天技术研究所）；Institut de Ciències de l’Espai (ICE), CSIC（太空科学研究所（ICE），西班牙高等科学研究理事会）；Institut d’Estudis Espacials de Catalunya (IEEC)（加泰罗尼亚空间研究学院）；INAF, Istituto di Astrofisica e Planetologia Spaziale（意大利国家天体物理研究所，天体物理学与行星科学研究所）
We have compiled the most complete compact and ultracompact HII region catalogue to date via multi-wavelength inspection of survey data. We utilise data from the recently available SASSy 850$μ$m survey to identify massive star forming clumps in the outer Galaxy ($R_{\rm{GC}}>8.5$ kpc) and cross-match with infrared and radio data of known UC HII regions from the RMS database. For the inner Galaxy sample ($R_{\rm{GC}}<8.5$ kpc), we adopt the compact HII regions from previous works that used similar methods to cross match ATLASGAL with either CORNISH or RMS, depending on the location within the G…
We present a detailed characterization of the population of compact radio-continuum sources in W51 A using subarcsecond VLA and ALMA observations. We analyzed their 2-cm continuum, the recombination lines (RL's) H77$α$ and H30$α$, and the lines of $\rm H_{2}CO(3_{0,3}-2_{0,2})$, $\rm H_{2}CO(3_{2,1}-2_{2,0})$, and $\rm SO(6_{5}-5_{4})$. We derive diameters for 10/20 sources in the range $D \sim 10^{-3}$ to $\sim 10^{-2}$ pc, thus placing them in the regime of hypercompact HII regions (HC HII's). Their continuum-derived electron densities are in the range $n_{\rm e} \sim 10^4$ to $10^5$ cm$^{-3…
We present 250~GHz continuum and H29alpha line data toward W49N:A2, a hypercompact HII region ionized by an O9 star. The data obtained with ALMA at a resolution of ~0"05 (600 au) confirmed the presence of an ionized ring with a radius of~700 au inclined by ~50degree (0degree for pole-on). It has a width of ~1000 au and is relatively flat with a scale height of less than several hundred au. The tilted ring, or the apparent ellipse, has a prominent velocity difference between its NW and SE ridges along the minor axis, suggesting that it is expanding in the equatorial plane at a velocity of 13.2 …
The Messenger Interface Monte-Carlo Mappings V (M^3) is a photoionization code adopting the fully self-consistent Monte-Carlo radiative transfer technique, which presents a major advance over previous photoionization models with simple geometries. M^3 is designed for modeling nebulae in arbitrary three-dimensional geometries. In this paper, we describe the Monte-Carlo radiative transfer technique and the microphysics implemented in M^3, including the photoionization, collisional ionization, the free-free and free-bound recombination, and two-photon radiation. We put M^3 through the Lexington/M…
We present 247-GHz molecular line observations of methanol (CH$_3$OH) toward sixteen massive star-forming regions, using the APEX telescope with an angular resolution of $25''$. The sample covers a range of evolutionary states, including warm molecular cores, hot molecular cores, and ultracompact HII regions. The hot cores, all of which include UC HII regions, show rich molecular line spectra, although the strength of different species and transitions varies from source to source. In contrast, the warm cores do not show significant molecular line emission. Multiple methanol transitions are det…
The Internal Nebular Attenuation Curve of Three-Dimensional Turbulent HII regions
Westlake University（西湖大学）；Mount Stromlo Observatory, Australian National University（澳大利亚国立大学斯特罗洛天文台）；Department of Astronomy, Boston University（波士顿大学天文学系）；School of Natural Sciences, Institute for Advanced Study（普林斯顿高等研究院自然科学学院）
The Impact and Environment of Massive Stars and Stellar Clusters
West Virginia University（西弗吉尼亚大学）；Indian Institute of Space Science and Technology（印度空间科学与技术学院）；Tata Institute of Fundamental Research（塔塔基础研究所）；Chalmers University of Technology（查尔姆斯理工大学）；Aix Marseille Univ, CNRS, CNES, LAM Marseille（艾克斯-马赛大学、法国国家科学研究中心、法国国家空间研究中心、拉格朗日天文物理实验室）；University of Amsterdam（阿姆斯特丹大学）；University of Central Florida（中佛罗里达大学）；University of Puerto Rico（波多黎各大学）
We aim to investigate the chemistry of internal photon-dominated regions surrounding deeply embedded hypercompact and ultracompact HII regions. We search for specific tracers of this evolutionary stage of massive star formation that can be detected with current astronomical facilities. We modeled hot cores with embedded HC/UCHII regions, by coupling the astrochemical code Saptarsy to a radiative transfer framework obtaining the spatio-temporal evolution of abundances as well as time-dependent synthetic spectra. In these models where we focused on the internal PDR surrounding the HI region, the…
Complex organic molecules are only detected toward a fraction of high-mass protostars. The goal of this work is to investigate whether high-mass disks can explain the lack of methanol emission from some massive protostellar systems. We consider an envelope-only and an envelope-plus-disk model and use RADMC-3D to calculate the methanol emission. High and low millimeter (mm) opacity dust are considered for both models separately and the methanol abundance is parameterized. Viscous heating is included due to the high accretion rates of these objects in the disk. In contrast with low-mass protosta…
We report the results of a pilot program for a Green Bank Telescope (GBT) MUSTANG Galactic Plane survey at 3 mm (90 GHz), MGPS90. The survey achieves a typical $1σ$ depth of $1-2$ mJy beam$^{-1}$ with a 9" beam. We describe the survey parameters, quality assessment process, cataloging, and comparison with other data sets. We have identified 709 sources over seven observed fields selecting some of the most prominent millimeter-bright regions between $0°< \ell < 50°$ (total area $\approx 7.5 °^2$). The majority of these sources have counterparts at other wavelengths. By applying flux selection c…
