1,725,171 research outputs found
Multiwavelength observations of the HII region of NGC 6357
No full textreservedIn this thesis, I conducted an analysis of the emissions originating from the NGC 6357, also known as the Lobster Nebula. This nebula exhibits emissions within radio frequency bands. Through observations with ALMA, the J=1-0 emission of Hydrogen Cyanide (HCN), a molecule that traces high-density gas, were successfully detected and identified. Through an examination of these emission lines, I derived some parameters of the source like temperature, column density, and mass.
Subsequently, I embarked on a phase aimed at expanding the scope of observations for NGC 6357 by exploring various wavelengths. Specifically, I conducted an analysis of observations in the WISE W1 (3.4 μm), W2(4.6 μm), and W3(12 μm) bands, which are included in the AllWise catalog. This endeavor was taken in an effort to establish potential correlations with the HCN emission regions. I found that these HCN emission areas indeed represent pre-main sequence regions. This conclusion agrees with the characteristics extracted from ALMA observations. This study demonstrates that the HCN emissions observed with ALMA in NGC 6357 originate from pre-main sequence sources, particularly prestellar cores. These sources exhibit temperatures spanning the range from 10 to 30 K and are characterized by high column densities. These findings contribute significantly to our broader comprehension of star-forming regions of NGC 6357.In this thesis, I conducted an analysis of the emissions originating from the NGC 6357, also known as the Lobster Nebula. This nebula exhibits emissions within radio frequency bands. Through observations with ALMA, the J=1-0 emission of Hydrogen Cyanide (HCN), a molecule that traces high-density gas, were successfully detected and identified. Through an examination of these emission lines, I derived some parameters of the source like temperature, column density, and mass.
Subsequently, I embarked on a phase aimed at expanding the scope of observations for NGC 6357 by exploring various wavelengths. Specifically, I conducted an analysis of observations in the WISE W1 (3.4 μm), W2(4.6 μm), and W3(12 μm) bands, which are included in the AllWise catalog. This endeavor was taken in an effort to establish potential correlations with the HCN emission regions. I found that these HCN emission areas indeed represent pre-main sequence regions. This conclusion agrees with the characteristics extracted from ALMA observations. This study demonstrates that the HCN emissions observed with ALMA in NGC 6357 originate from pre-main sequence sources, particularly prestellar cores. These sources exhibit temperatures spanning the range from 10 to 30 K and are characterized by high column densities. These findings contribute significantly to our broader comprehension of star-forming regions of NGC 6357
<i>Hemato</i> Keeps You Updated on the Research in Hematology
No full textHemato (ISSN 2673-6357) is an open access, peer-reviewed journal that publishes original articles and reviews highlighting important advances in the fundamental areas of Hematology [...
NGC 6334 and NGC 6357: Hα kinematics and the nature of the H II regions
No full textInternational audienceAims: NGC 6334 and NGC 6357 are amongst the most active, optically visible Galactic star-forming complexes. They are composed of several H ii regions that have a significant impact on their surrounding. The aim of this paper is to present a kinematic study of the optical H ii regions that belong to NGC 6334 and NGC 6357. Methods: We use Fabry-Perot interferometer observations of the Hα line, which cover NGC 6334 and NGC 6357. These observations allow us to analyse the Hα line profiles to probe the kinematics of the ionised gas of both regions. We complement the Hα observations with multi-wavelength data to specify the nature of the H ii regions. Results: We determine the dynamical nature of the optical H ii regions that belongs to NGC 6334 and NGC 6357. In NGC 6334, GUM 61 is an expanding wind shell-like H ii region, GUM 64b exhibits a champagne flow, GM1-24 is the Hα counterpart of two larger regions and H ii 351.2+0.5 is, in fact, composed of two H ii regions. In NGC 6357, H ii 353.08+0.28 and H ii 353.09+0.63 are probably stellar wind-shaped bubble H ii regions, while H ii 353.42+0.45 is a classical photo-ionised H ii region. We suggest that, at large scale, star-formation seems to be triggered where large/old H ii regions intersect. Inversely, stellar formation seems to have already started in the NGC 6334 north-east filament, irrespective of any evident external H ii region impact. While NGC 6357 shows more complicated kinematics, NGC 6334 is characterised by a more active stellar formation.The Hα data (FITS cubes) are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/587/A13
OB stars and YSO populations in the region of NGC 6334–NGC 6357 as seen with Gaia DR2
No full textInternational audienceAims. Our goal is to better understand the origin and the star-formation history of regions NGC 6334 and NGC 6357. We focus our study on the kinematics of young stars (young stellar objects and OB stars) in both regions mainly on the basis of the Gaia DR2 data.Methods. For both regions, we compiled catalogs of OB stars and young stellar objects from the literature and complemented them using VPHAS+ DR2 and Spitzer IRAC/GLIMPSE photometry catalogues. We applied a cross-match with the Gaia DR2 catalog to obtain information on the parallax and transverse motion.Results. We confirm that NGC 6334 and NGC 6357 are in the far side of the Saggitarius-Carina arm at a distance of 1.76 kpc. For NGC 6357, OB stars show strong clustering and ordered star motion with Vlon ∼–10.7 km s−1 and Vlat ∼3.7 km s−1, whereas for NGC 6334, no significant systemic motion was observed. The OB stars motions and distribution in NGC 6334 suggest that it should be classified as an association. Ten runaway candidates may be related to NGC 6357 and two to NGC 6334, respectively. The spatial distributions of the runaway candidates in and around NGC 6357 favor a dynamical (and early) ejection during the cluster(s) formation. Because such stars are likely to be ejected during a cluster’s formation, the fact that not as many such stars are observed towards NGC 6334 suggests different formation conditions than have been assumed for NGC 6357
NGC 6334 and NGC 6357 Insights from spectroscopy of their OB star populations
Get PDFInternational audienceAims. The formation of high-mass stars is still debated. For this reason, several projects such as Herschel-HOBYS are focussed on the study of the earliest phases of massive star formation. As a result, massive star-forming complexes such as NGC 6334 and NGC 6357 have been observed in the far-infrared to study their massive dense cores where massive stars are expected to form. However, to better characterise the environments of these cores we need to understand the previous massive star formation history. To better characterise the environment of these massive dense cores we study the previous high-mass star formation and how these stars act on their environments. Methods. This study is based on the spectral classification of the OB stars identified towards NGC 6334 and NGC 6357 with spectra taken with the AAOmega spectrograph on the Anglo-Australian Telescope (AAT). From the subsequent spectral classification of 109 stars across these regions we were able to evaluate the following: distance, age, mass, global star-forming efficiency (SFE), and star formation rate (SFR) of the regions. The physical conditions of the ionised gas for both complexes was also derived. Results. We confirm that NGC 6334 and NGC 6357 belong to the Saggitarius-Carina arm which, in this direction, extends from 1 kpc to 2.2 kpc. From the location of the stars in Hertzprung-Russell diagram we show that stars older than ∼10 Myr are broadly spread across these complexes, while younger stars are mainly located in the H ii regions and stellar clusters. Our data also suggests that some of the young stars can be considered runaway stars. We evaluate a SFE of 0.019 +0.008 −0.007 and 0.021 +0.004 −0.003 and a SFR of 1.1 × 10 3 ± 300 M Myr −1 and 1.7 × 10 3 ± 400 M Myr −1 for NGC 6334 and NGC 6357, respectively. We note that 29 OB stars have X-ray counterparts, most of them belonging to NGC 6357. This suggests that molecular clouds in NGC 6357 are more impacted by X-ray flux and stellar winds than in NGC 6334. Finally, from the analysis of nebular lines (Hα, [NII], and [SII]) from spectra from several regions of ionised gas, we confirm that the filaments in NGC 6357 are shock heated
A possible far-ultraviolet flux-dependent core mass function in NGC 6357
Get PDFContext. NGC 6357 is a galactic star-forming complex (d ~ 1.7 kpc) composed of several HI
Statistical study of OB stars in NGC 6334 and NGC 6357
No full textInternational audienceContext. Star-forming complexes are large structures exhibiting massive star-formation at different stages of evolution, from dense cores to well-developed H ii regions. They are very interesting for the study of the formation and evolution of stars. NGC 6334 and NGC 6357 are two active and relatively nearby star-forming complexes. From the extinction map and the sub-mm cold dust emission, and because they have similar velocities, these regions are most likely connected. However, located in the direction of the Galactic center their radial velocity is not representative of their distance. An alternative is then to determine the distance of NGC 6334 and NGC 6357 from their stellar content. Aims: Our aim is to perform a census of O-B3 ionising stars in NGC 6334 and NGC 6357, to determine the extinction coefficient, and the distance of both regions. A census of O-B3 stars is an essential basis for estimating the statistical lifetime of the earliest massive star-forming phases. Methods: We performed a U, B, V, and R photometric survey of a large area covering NGC 6334 and NGC 6357 with the VIMOS (ESO-VLT) and the MOSAIC (CTIO) instruments. This allows us to have a complete census of O to B3 stars up to V = 22.6 mag. The OB stars are selected based on their U - B and B - V colors. The most robust extinction coefficient is determined from color - color plots before computing the distance of the OB stars. Results: We find a higher value than typical of the diffuse interstellar medium for RV of 3.53 ± 0.08 and 3.56 ± 0.15 for NGC 6357 and NGC 6334, respectively. Adopting these RV values, the distances of NGC 6357 and NGC 6334 are 1.9 ± 0.4 kpc and 1.7 ± 0.3 kpc. We conclude that, within the error bars, both regions are thus at the same distance of 1.75 kpc (weighted mean). We confirm that the value of RV is linked to the large dust grain content. In particular, we found that there are more very small grains in NGC 6357 than in NGC 6334, suggesting that NGC 6357 could be more evolved than NGC 6334. Placed in the Galactic context, the NGC 6334-NGC 6357 complex appears to be located at the inner edge of the Sagittarius-Carina arm. Our census of O to B3 stars leads to a count of ~230, which allows us to determine the statistical lifetime of the earliest phases of the massive stars. The starless and the protostellar phases have a mean statistical lifetime of ~1.5 × 104 yr and ~2.2 × 105 yr, respectively. Based on observations made with the VIMOS instrument at the VLT-ESO. Based on visiting astronomer observations, at Cerro Tololo Inter-American Observatory, National Optical Astronomy Observatory, which is operated by the Association of Universities for Research in Astronomy, under contract with the National Science Foundation.Appendices are available in electronic form at http://www.aanda.orgFull Tables A.1 and A.2 are only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/538/A14
NGC 6334-NGC 6357 complex (Russeil+, 2010)
No full texttablea1.dat 56x89 24 microns flux and signpost of stellar activity; list.dat 519x49 List of FITS file; sp/* 519. Individual fits filesVizieR On-line Data Catalog: J/A+A/515/A55. Originally published in: 2010A&A...515A..55RFrom the SIMBA/SEST 1.2mm data of the NGC 6334-NGC 6357 complex, we extracted dense cores following the method used for Cygnus X. We constrain the properties of the most massive dense cores (M>100Mȯ) thanks to new molecular line observations (among which SiO, N2H+,H13CO+, HCO+ (1-0) and CH3CN) with Mopra and a complete cross-correlation with infrared databases (e.g. MSX, GLIMPSE, MIPSGAL) and literature. (3 data files)
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