scholarly journals WB89 520: A Small Isolated High Mass Star Forming Region Associated with an Extremely Metal-poor Nebula

2001 ◽  
Vol 205 ◽  
pp. 284-285
Author(s):  
Jun-Jie Wang ◽  
Jing-Yao Hu ◽  
Jian-Yan Wei ◽  
Leonardo Testi
Keyword(s):  
Optical Spectroscopy ◽  
Near Infrared ◽  
Infrared Imaging ◽  
High Mass ◽  
Mass Star ◽  
Molecular Line ◽  
Hii Region ◽  
Stellar Cluster ◽  
Star Forming ◽  
Low Metallicity

In this paper, by discussing and analyzing the observational results of near infrared imaging, optical spectroscopy and 12CO molecular line, together with IRAS and NVSS data, we conclude that WB89 520 is an UC HII region with a very young compact stellar cluster. The spectrum of the UC HII region shows that it is an extremely metal-poor nebula, which has the lowest line ratio of [NII]/Hα (∼ 1/56) discovered in the nebulae of our Galaxy until now. We give two possible explanations for the low metallicity.

Magnetic field structures in star-forming regions revealed by imaging polarimetry at multi-wavelengths

2018 ◽  
Vol 14 (A30) ◽  
pp. 102-102
Author(s):  
Jungmi Kwon
Keyword(s):  
Magnetic Fields ◽  
Near Infrared ◽  
Infrared Imaging ◽  
Young Stellar Objects ◽  
High Mass ◽  
Mass Star ◽  
Stellar Objects ◽  
Star Forming ◽  
Star Forming Regions ◽  
Imaging Polarimetry

AbstractMagnetic fields are ubiquitous in various scales of astronomical objects, and they are considered as playing significant roles from star to galaxy formations. However, the role of the magnetic fields in star forming regions is less well understood because conventional optical polarimetry is hampered by heavy extinction by dust. We have been conducting extensive near-infrared polarization survey of various star-forming regions from low- and intermediate-mass to high-mass star-forming regions, using IRSF/SIRPOL in South Africa. Not only linear but also circular polarizations have been measured for more than a dozen of regions. Both linear and circular polarimetric observations at near-infrared wavelengths are useful tools to study the magnetic fields in star forming regions, although infrared circular polarimetry has been less explored so far. In this presentation, we summarize our results of the near-infrared polarization survey of star forming regions and its comparison with recent submillimeter polarimetry results. Such multi-wavelength approaches can be extended to the polarimetry using ALMA, SPICA in future, and others. We also present our recent results of the first near-infrared imaging polarimetry of young stellar objects in the Circinus molecular cloud, which has been less studied but a very intriguing cluster containing numerous signs of active low-mass star formation.

scholarly journals IRAS 23385+6053: an embedded massive cluster in the making

2019 ◽  
Vol 627 ◽  
pp. A68 ◽  
Author(s):  
R. Cesaroni ◽  
H. Beuther ◽  
A. Ahmadi ◽  
M. T. Beltrán ◽  
T. Csengeri ◽  
...  
Keyword(s):  
Large Scale ◽  
Rotational Temperature ◽  
Line Emission ◽  
Core Sample ◽  
High Mass ◽  
Mass Star ◽  
Molecular Line ◽  
Stellar Cluster ◽  
Star Forming ◽  
The Core

Context. This study is part of the CORE project, an IRAM/NOEMA large program consisting of observations of the millimeter continuum and molecular line emission towards 20 selected high-mass star-forming regions. The goal of the program is to search for circumstellar accretion disks, study the fragmentation process of molecular clumps, and investigate the chemical composition of the gas in these regions. Aims. We focus on IRAS 23385+6053, which is believed to be the least-evolved source of the CORE sample. This object is characterized by a compact molecular clump that is IR-dark shortward of 24 μm and is surrounded by a stellar cluster detected in the near-IR. Our aim is to study the structure and velocity field of the clump. Methods. Observations were performed at ~1.4 mm and employed three configurations of NOEMA and additional single-dish maps, merged with the interferometric data to recover the extended emission. Our correlator setup covered a number of lines from well-known hot core tracers and a few outflow tracers. The angular (~0′′.45–0′′.9) and spectral (0.5 km s−1) resolutions were sufficient to resolve the clump in IRAS 23385+6053 and investigate the existence of large-scale motions due to rotation, infall, or expansion. Results. We find that the clump splits into six distinct cores when observed at sub-arcsecond resolution. These are identified through their 1.4 mm continuum and molecular line emission. We produce maps of the velocity, line width, and rotational temperature from the methanol and methyl cyanide lines, which allow us to investigate the cores and reveal a velocity and temperature gradient in the most massive core. We also find evidence of a bipolar outflow, possibly powered by a low-mass star. Conclusions. We present the tentative detection of a circumstellar self-gravitating disk lying in the most massive core and powering a large-scale outflow previously known in the literature. In our scenario, the star powering the flow is responsible for most of the luminosity of IRAS 23385+6053 (~3000 L⊙). The other cores, albeit with masses below the corresponding virial masses, appear to be accreting material from their molecular surroundings and are possibly collapsing or on the verge of collapse. We conclude that we are observing a sample of star-forming cores that is bound to turn into a cluster of massive stars.

scholarly journals The Formation of Massive Stars: from Herschel to Near-Infrared

2014 ◽  
Vol 1 (1) ◽  
pp. 103-107
Author(s):  
Paolo Persi ◽  
Mauricio Tapia
Keyword(s):  
Near Infrared ◽  
Narrow Band ◽  
Narrow Band Imaging ◽  
Spectral Energy Distribution ◽  
Far Infrared ◽  
High Mass ◽  
Spectral Energy ◽  
Mass Star ◽  
Stellar Cluster ◽  
Star Forming

We have studied a number of selected high mass star forming regions, including high resolution near-infrared broad- and narrow-band imaging, Herschel (70, 160, 250, 350 and 500<em> μ</em>m) and Spitzer (3.6, 4.5, 5.8 and 8.0 m) images. The preliminary results of one of this region, IRAS 19388+2357(MOL110) are discussed. In this region a dense core has been detected in the far-infrared, and a young stellar cluster has been found around this core. Combining near-IR data with Spitzer and Herschel photometry we have derived the spectral energy distribution of Mol110. Finally comparing our H<sub>2</sub> and Kc narrow-band images, we have found an H<sub>2</sub> jet in this region.

scholarly journals Nitrogen and hydrogen fractionation in high-mass star-forming cores from observations of HCN and HNC

2018 ◽  
Vol 609 ◽  
pp. A129 ◽  
Author(s):  
L. Colzi ◽  
F. Fontani ◽  
P. Caselli ◽  
C. Ceccarelli ◽  
P. Hily-Blant ◽  
...  
Keyword(s):  
Solar System ◽  
Solar Nebula ◽  
Rotational Transition ◽  
High Mass ◽  
Evolutionary Stage ◽  
Mass Star ◽  
Stellar Cluster ◽  
Star Forming ◽  
Star Forming Regions ◽  
Dense Cores

The ratio between the two stable isotopes of nitrogen, 14N and 15N, is well measured in the terrestrial atmosphere (~272), and for the pre-solar nebula (~441, deduced from the solar wind). Interestingly, some pristine solar system materials show enrichments in 15N with respect to the pre-solar nebula value. However, it is not yet clear if and how these enrichments are linked to the past chemical history because we have only a limited number of measurements in dense star-forming regions. In this respect, dense cores, which are believed to be the precursors of clusters and also contain intermediate- and high-mass stars, are important targets because the solar system was probably born within a rich stellar cluster, and such clusters are formed in high-mass star-forming regions. The number of observations in such high-mass dense cores has remained limited so far. In this work, we show the results of IRAM-30 m observations of the J = 1−0 rotational transition of the molecules HCN and HNC and their 15N-bearing counterparts towards 27 intermediate- and high-mass dense cores that are divided almost equally into three evolutionary categories: high-mass starless cores, high-mass protostellar objects, and ultra-compact Hii regions. We have also observed the DNC(2–1) rotational transition in order to search for a relation between the isotopic ratios D/H and 14N/15N. We derive average 14N/15N ratios of 359 ± 16 in HCN and of 438 ± 21 in HNC, with a dispersion of about 150–200. We find no trend of the 14N/15N ratio with evolutionary stage. This result agrees with what has been found for N2H+ and its isotopologues in the same sources, although the 14N/15N ratios from N2H+ show a higher dispersion than in HCN/HNC, and on average, their uncertainties are larger as well. Moreover, we have found no correlation between D/H and 14N/15N in HNC. These findings indicate that (1) the chemical evolution does not seem to play a role in the fractionation of nitrogen, and that (2) the fractionation of hydrogen and nitrogen in these objects is not related.

scholarly journals Molecular line survey of the high-mass star-forming region NGC 6334I withHerschel/HIFI and the Submillimeter Array

2012 ◽  
Vol 546 ◽  
pp. A87 ◽  
Author(s):  
A. Zernickel ◽  
P. Schilke ◽  
A. Schmiedeke ◽  
D. C. Lis ◽  
C. L. Brogan ◽  
...  
Keyword(s):  
High Mass ◽  
Mass Star ◽  
Molecular Line ◽  
Star Forming ◽  
Line Survey

scholarly journals Multiwavelength investigation of extended green object G19.88-0.53: revealing a protocluster

2020 ◽  
Vol 497 (4) ◽  
pp. 5454-5472
Author(s):  
Namitha Issac ◽  
Anandmayee Tej ◽  
Tie Liu ◽  
Watson Varricatt ◽  
Sarita Vig ◽  
...  
Keyword(s):  
Infrared Spectroscopy ◽  
Star Formation ◽  
Near Infrared Spectroscopy ◽  
Near Infrared ◽  
High Mass ◽  
Mass Star ◽  
Star Forming ◽  
Gas Kinematics ◽  
Evolutionary Spectrum ◽  
Multiple Shock

ABSTRACT A multiwavelength analysis of star formation associated with the extended green object, G19.88-0.53 is presented in this paper. With multiple detected radio and millimetre components, G19.88-0.53 unveils as harbouring a protocluster rather than a single massive young stellar object. We detect an ionized thermal jet using the upgraded Giant Meterwave Radio Telescope, India, which is found to be associated with a massive, dense and hot ALMA 2.7 mm core driving a bipolar CO outflow. Near-infrared spectroscopy with UKIRT–UIST shows the presence of multiple shock-excited H2 lines concurrent with the nature of this region. Detailed investigation of the gas kinematics using ALMA data reveals G19.88-0.53 as an active protocluster with high-mass star-forming components spanning a wide evolutionary spectrum from hot cores in accretion phase to cores driving multiple outflows to possible UCH ii regions.

scholarly journals Ammonia towards dust clumps in the giant molecular cloud associated with RCW 106

2012 ◽  
Vol 8 (S292) ◽  
pp. 50-50
Author(s):  
Vicki Lowe ◽  
Maria R. Cunningham ◽  
James S. Urquhart ◽  
Shinji Horiuchi
Keyword(s):  
Star Formation ◽  
Radio Telescope ◽  
Molecular Cloud ◽  
Galactic Plane ◽  
High Mass ◽  
Mass Star ◽  
Giant Molecular Clouds ◽  
Molecular Line ◽  
Star Forming ◽  
Star Formation Regions

AbstractHigh-mass stars are known to be born within giant molecular clouds (GMCs); However, the exact processes involved in forming a high-mass star are still not well understood. It is clear that high-mass stars do not form in isolation, and that the processes surrounding high-mass star formation may affect the environment of the entire molecular cloud. We are studying the GMC associated with RCW 106 (G333), which is one of the most active massive-star formation regions in the Galactic plane. This GMC, located at l = 333° b = − 0.5°, has been mapped in over 20 molecular line transitions with the Mopra radio telescope (83-110 GHz), in Australia, and with the Swedish-ESO Submillimeter Telescope (SEST) in the 1.2 mm cool dust continuum. The region is also within the Spitzer GLIMPSE infrared survey (3.6, 4.5, 5.8, and 8.0 μm) area. We have decomposed the dust continuum using a clump-finding algorithm (CLUMPFIND), and are using the multiple molecular line traditions from the Mopra radio telescope to classify the type and stage of star formation taking place therein. Having accurate physical temperatures of the star forming clumps is essential to constrain other parameters to within useful limits. To achieve this, we have obtained pointed NH3 observations from the Tidbinbilla 70-m radio telescope, in Australia, towards these clumps.

The innermost regions of massive protostars traced by masers, high-resolution radio continuum, and near-infrared imaging

2017 ◽  
Vol 13 (S336) ◽  
pp. 289-290
Author(s):  
Fabrizio Massi ◽  
Luca Moscadelli ◽  
Carmelo Arcidiacono ◽  
Francesca Bacciotti
Keyword(s):  
Near Infrared ◽  
Infrared Imaging ◽  
High Spatial Resolution ◽  
Radio Continuum ◽  
High Mass ◽  
Mass Star ◽  
Near Infrared Imaging ◽  
Stellar Objects ◽  
First Results ◽  
Low Mass

AbstractWhether high-mass stars (M > 7M⊙) emerge from a scaled-up version of the low-mass star formation scenario, i. e. through disk-mediated accretion, is still debated. We present the first results of an observational programme aimed to map the innermost regions of high-mass stellar objects by combining together high-spatial resolution maser and radio continuum observations, and near-infrared imaging.

scholarly journals High-mass star formation in Orion possibly triggered by cloud–cloud collision. III. NGC 2068 and NGC 2071

2020 ◽  
Author(s):  
Shinji Fujita ◽  
Daichi Tsutsumi ◽  
Akio Ohama ◽  
Asao Habe ◽  
Nirmit Sakre ◽  
...  
Keyword(s):  
Velocity Structure ◽  
High Mass ◽  
Line Of Sight ◽  
Mass Star ◽  
Molecular Line ◽  
Star Forming ◽  
Star Forming Regions ◽  
Frontal Collisions ◽  
Reflection Nebulae ◽  
Projected Distance

Abstract Using the NANTEN2 Observatory, we carried out a molecular-line study of high-mass star forming regions with reflection nebulae, NGC 2068 and NGC 2071, in Orion in the $^{13}$CO($J = 2$–1) transition. The $^{13}$CO distribution shows that there are two velocity components at ${9.0}$ and ${10.5}\:$km$\:$s$^{-1}$. The blue-shifted component is in the northeast associated with NGC 2071, whereas the red-shifted component is in the southwest associated with NGC 2068. The total intensity distribution of the two clouds shows a gap of $\sim\!\! 1\:$pc, suggesting that they are detached at present. A detailed spatial comparison indicates that the two show complementary distributions. The blue-shifted component lies toward an intensity depression to the northwest of the red-shifted component, where we find that a displacement of ${0.8}\:$pc makes the two clouds fit well with each other. Furthermore, a new simulation of non-frontal collisions shows that observations from $60^\circ$ off the collisional axis agreed well with the velocity structure in this region. On the basis of these results, we hypothesize that the two components collided with each other at a projected relative velocity of ${3.0}\:$km$\:$s$^{-1}$. The timescale of the collision is estimated to be ${0.3}\:$Myr for an assumed axis of the relative motion $60^\circ$ off the line of sight. We assume that the two most massive early B-type stars in the cloud, illuminating stars of the two reflection nebulae, were formed by collisional triggering at the interfaces between the two clouds. Given the other young high-mass star-forming regions, namely, M 42, M 43, and NGC 2024 (Fukui et al. 2018a, ApJ, 859, 166; Ohama et al. 2017, arXiv:1706.05652), it seems possible that collisional triggering has been independently working to form O-type and early B-type stars in Orion in the last Myr over a projected distance of ∼80 pc.

Sign in / Sign up

Export Citation Format

Share Document