The present work aims at studying the dense gas of the molecular cloud LDN 1287 (L1287), which harbors a double FU Ori system, an energetic molecular outflow and a still-forming cluster of deeply embedded low-mass, young stellar objects, showing a high level of fragmentation. We present optical Halpha and [SII], and VLA NH$_3$ (1,1) and (2,2) observations with an angular resolution of ~3.5''. The observed NH$_3$ spectra have been analyzed with the HfS tool, fitting simultaneously three different velocity components. The NH$_3$ emission from L1287 comes from four different structures: a core associated with RNO 1, a guitar-shaped core (the "Guitar") and two interlaced filaments (the Blue and Red Filaments) roughly centered towards the binary FU Ori system RNO 1B/C and its associated cluster. Regarding the Guitar Core, there are clear signatures of gas infall onto a central mass that has been estimated to be ~2.1 $M_\odot$. Regarding the two filaments, they have radii ~0.03 pc, masses per unit length ~50 $M_\odot$ pc$^{-1}$, and are near isothermal equilibrium. A central cavity, probably related with the outflow, and also traced by the Halpha and [SII] emission, is identified, with several young stellar objects near its inner walls. Both filaments show clear signs of perturbation by the high-velocity gas of the outflows driven by one or several young stellar objects of the cluster. The Blue and Red filaments are coherent in velocity and have nearly subsonic gas motions, except at the position of the embedded sources. Velocity gradients across the Blue Filament can be interpreted either as infalling material onto the filament or rotation. Velocity gradients along the filaments are interpreted as infall motions towards a gravitational well at the intersection of both filaments.
We report systematic mapping observations of the NH$_{3}$ (1,1) and (2,2) inversion lines towards 62 high-mass star-forming regions using VLA in its D and DnC array configurations. The VLA images cover a spatial dynamic range from 40$"$ to 3$"$, allowing us to trace gas kinematics from $\sim$1 pc scales to $\lesssim$0.1 pc scales. Based on the NH$_3$ morphology and the infrared nebulosity on 1\,pc scales, we categorize three sub-classes in the sample: filaments, hot cores, and NH$_3$ dispersed sources. The ubiquitous gas filaments found on 1 pc scales have a typical width of $\sim$0.1\,pc and …
We present the first astronomical detection of the 14NH3 (J,K) = (10,6) line: nonthermal emission at several velocities in the Galactic star-forming region NGC 7538. Using the VLA we have imaged the (10,6) and (9,6) ammonia masers at several positions within NGC 7538 IRS 1. The individual sources have angular sizes < 0.1 arcseconds corresponding to brightness temperatures T_B > 1E6 K. We apply the pumping model of Brown & Cragg, confirming the conjecture that multiple ortho-ammonia masers can occur with the same value of K. The positions and velocities of the (10,6) and (9,6) masers are modele…
Infrared-dark clouds (IRDCs) are believed to be the birthplaces of rich clusters and thus contain the earliest phases of high-mass star formation. We use the Green Bank Telescope (GBT) and Very Large Array (VLA) maps of ammonia (NH3) in six IRDCs to measure their column density and temperature structure (Paper 1), and here, we investigate the kinematic structure and energy content. We find that IRDCs overall display organized velocity fields, with only localized disruptions due to embedded star formation. The local effects seen in NH3 emission are not high velocity outflows but rather moderate…
The gas kinetic temperature in the centres of starless, high-density cores is predicted to fall as low as 5-6 K. The aim of this study was to determine the kinetic temperature distribution in the low-mass prestellar core Oph D where previous observations suggest a very low central temperature. The densest part of the Oph D core was mapped in the NH3(1,1) and (2,2) inversion lines using the Very Large Array (VLA). The physical quantities were derived from the observed spectra by fitting the hyperfine structure of the lines, and subsequently the temperature distribution of Oph D was calculated u…
The central few 100 pc of galaxies often contain large amounts of molecular gas. The chemical and physical properties of these extragalactic star formation regions differ from those in galactic disks, but are poorly constrained. This study aims to develop a better knowledge of the spatial distribution and kinetic temperature of the dense neutral gas associated with the nuclear regions of three prototypical spiral galaxies, NGC253, IC342, and Maffei2. VLA CnD and D configuration measurements have been made of three ammonia (NH3) inversion transitions. The (J,K)=(1,1) and (2,2) transitions of NH…
We present combined VLA and Green Bank Telescope images of \ammonia\ inversion transitions (1,1) and (2,2) toward OMC2 and OMC3. We focus on the relatively quiescent Orion cores, which are away from the Trapezium cluster and have no sign of massive protostars nor evolved star formation, such as IRAS source, water maser, and methanol maser. The 5\arcsec\ angular resolution and $0.6 \rm{}km\,s^{-1}$ velocity resolution of these data enable us to study the thermal and dynamic state of these cores at $\sim{}0.02 \rm{}pc$ scales, comparable to or smaller than those of the current dust continuum sur…
We present multi-epoch Very Long Baseline Array (VLBA) H$_2$O maser observations toward the massive young stellar objects (YSOs) VLA 2 and VLA 3 in the star-forming region AFGL 2591. Through these observations, we have extended the study of the evolution of the masers towards these objects up to a time span of $\sim$ 10 yrs, measuring their radial velocities and proper motions. The H$_2$O masers in VLA 3, the most massive YSO in AFGL 2591 ($\sim$ 30--40~M$_{\odot}$), are grouped within projected distances of $\lesssim$ 40 mas ($\lesssim$ 130 AU) from VLA 3. In contrast to other H$_2$O masers i…
We use NH3 inversion transitions to trace the dense gas in the NGC 1333 region of the Perseus molecular cloud. NH3(1,1) and NH3(2,2) maps covering an area of 102 square arcminutes at an angular resolution of ~3.7" are produced by combining VLA interferometric observations with GBT single dish maps. The combined maps have a spectral resolution of 0.14 km/s and a sensitivity of 4 mJy/beam. We produce integrated intensity maps, peak intensity maps and dispersion maps of NH3(1,1) and NH3(2,2) and a line-of-sight velocity map of NH3(1,1). These are used to derive the optical depth for the NH3(1,1) …
We want to understand the kinematic and thermal properties of young massive gas clumps prior to and at the earliest evolutionary stages of high-mass star formation. Do we find signatures of gravitational collapse? Do we find temperature gradients in the vicinity or absence of infrared emission sources? Do we find coherent velocity structures toward the center of the dense and cold gas clumps? To determine kinematics and gas temperatures, we used ammonia, because it is known to be a good tracer and thermometer of dense gas. We observed the NH$_3$(1,1) and (2,2) lines within seven very young hig…
Infrared Dark Clouds (IRDCs) harbor the earliest phases of massive star formation, and many of the compact cores in IRDCs, traced by millimeter continuum or by molecular emission in high critical density lines, host massive young stellar objects (YSOs). We used the Robert C. Byrd Green Bank Telescope (GBT) and the Karl G. Jansky Very Large Array (VLA) to map NH$_{3}$ and CCS in nine IRDCs to reveal the temperature, density, and velocity structures and explore chemical evolution in the dense ($>10^{22}$ cm$^{-2}$) gas. Ammonia is an excellent molecular tracer for these cold, dense environments.…
We use 3mm continuum NOEMA and NH$_3$ VLA observations towards the First Hydrostatic Core (FHSC) candidate CB 17 MMS to reveal the dust structure and gas properties down to 600-1,100 au scales and constrain its evolutionary stage. We do not detect any compact source at the previously identified 1.3 mm point source, despite expecting a minimum signal-to-noise of 9. The gas traced by NH$_3$ exhibits subsonic motions, with an average temperature of 10.4 K. A fit of the radial column density profile derived from the ammonia emission finds a flat inner region of radius $\sim$1,800 au and a central …
We present Very Large Array observations of ammonia (NH3) (1,1), (2,2), and CCS (2_1-1_0) emission toward the Infrared Dark Cloud (IRDC) G19.30+0.07 at ~22GHz. The NH3 emission closely follows the 8 micron extinction. The NH3 (1,1) and (2,2) lines provide diagnostics of the temperature and density structure within the IRDC, with typical rotation temperatures of ~10 to 20K and NH3 column densities of ~10^15 cm^-2. The estimated total mass of G19.30+0.07 is ~1130 Msun. The cloud comprises four compact NH3 clumps of mass ~30 to 160 Msun. Two coincide with 24 micron emission, indicating heating by…
Spectral lines of ammonia, NH$_3$, are useful probes of the physical conditions in dense molecular cloud cores. In addition to advantages in spectroscopy, ammonia has also been suggested to be resistant to freezing onto grain surfaces, which should make it a superior tool for studying the interior parts of cold, dense cores. Here we present high-resolution NH$_3$ observations with the Very Large Array (VLA) and Green Bank Telescope (GBT) towards a prestellar core. These observations show an outer region with a fractional NH$_3$ abundance of X(NH$_3$) = (1.975$\pm$0.005)$\times 10^{-8}$ ($\pm 1…
We discuss high-angular resolution observations of ammonia toward four candidate high-mass starless cores (HMSCs). The cores were identified by the Balloon-borne Large Aperture Submillimeter Telescope (BLAST) during its 2005 survey of the Vulpecula region where 60 compact sources were detected simultaneously at 250, 350, and 500 micron. Four of these cores, with no IRAS-PSC or MSX counterparts, were observed with the NRAO Very Large Array (VLA) in the NH3(1,1) and (2,2) spectral lines. Our observations indicate that the four cores are cold (Tk <~ 14K) and show a filamentary and/or clumpy struc…
The gas kinematics in 70 μm dark molecular clumps with ammonia
Guangxi Key Laboratory for Relativistic Astrophysics, School of Physical Science and Technology, Guangxi University（广西大学物理科学与技术学院相对论天体物理广西壮族自治区重点实验室）；School of Astronomy and Space Science, Nanjing University（南京大学天文与空间科学学院）；Key Laboratory of Modern Astronomy and Astrophysics (Nanjing University), Ministry of Education（教育部现代天文与天体物理重点实验室（南京大学））；Korea Astronomy and Space Science Institute（韩国天文与空间科学研究院）；Department of Astronomy, Xiamen University（厦门大学天文系）；Department of Earth, Environment, and Physics, Worcester State University（伍斯特州立大学地球、环境与物理系）；Center for Astrophysics | Harvard & Smithsonian（哈佛-史密森尼天体物理中心）；Shanghai Astronomical Observatory, Chinese Academy of Sciences（中国科学院上海天文台）；State Key Laboratory of Radio Astronomy and Technology（射电天文与技术国家重点实验室）
We present Very Large Array (VLA) high resolution observations of the NH3(1,1) and NH3(2,2) molecular transitions towards the high mass star forming region AFGL 437. Our aim was to investigate if the poorly collimated CO molecular outflow previously detected in the region is the result of a projection effect, with no intrinsic bipolarity, as suggested by Gomez et al. We complemented our observations with radio continuum archived data from the VLA at 2 and 3.6 cm, and with unpublished public data at 450 μm taken with Submillimetre Common-User Bolometer Array at the James Clerk Maxwell Telescope…
[Abridged] We have recently reported on the collapse and fragmentation properties of the northernmost part of this structure, located ~2.4pc north of Orion KL -- the Orion Molecular Cloud 3 (OMC 3, Takahashi et al. 2013). As part of our project to study the integral-shaped filament, we analyze the fragmentation properties of the northern OMC 1 filament. This filament is a dense structure previously identified by JCMT/SCUBA submillimeter continuum and VLA ammonia observations and shown to have fragmented into clumps. We observed OMC1 n with the Submillimeter Array (SMA) at 1.3mm and report on o…
Subarcsecond Multi-line Observations of NH$_3$ with VLA toward the Class 0 Source IRAS 16293-2422
The University of Tokyo（东京大学）；RIKEN Pioneering Research Institute（理化学研究所先导研究本部）；National Radio Astronomy Observatory（美国国家射电天文台）；Niels Bohr Institute, University of Copenhagen（哥本哈根大学尼尔斯玻尔研究所）
