1,723,816 research outputs found
A kinematical study of the NGC 7538 IRS 1 region
No full textWe present high angular resolution images of both NH3 (1, 1) and (2, 2) lines toward NGC 7538 IRS 1. The density and velocity-position plots have been used to study the interaction among the outflows, winds and their environment. For the first time we have found an expanding half-shell of molecular gas around the HII region associated with IRS 1, which may be produced by the interaction of the bipolar outflows and the winds originating in IRS 1-3, and optical HII region NGC 7538 with ambient molecular gas
An infrared study of the NGC 7538 region
Get PDFInfrared observations of the NGC 7538 region at wavelengths from 1 μm to 1 mm are presented and analysed with the aim of understanding both the large-scale structure of this region of current star formation and the properties of the individual compact objects within it. At far-infrared wavelengths (25–130 μm), emission is seen from the visible H II region, from the vicinity of the previously known maser sources and dust-embedded compact H II regions, and from a new region called NGC 7538(E). Coincident with NGC 7538(E) are a point-like 1–25 μm infrared source, NGC 7538-IRS9, which probably provides the power for the far-infrared emission, and an extended source of 2.2 μm emission which appears to be an infrared reflection nebula. NGC 7538-IRS9 strongly resembles the compact H II region NGC 7538-IRS1 in its infrared properties but shows no radio continuum emission. The compact H II regions, the maser sources and IRS9 are located within a dense molecular cloud at the edge of the optical H II region. This cloud, which has M∼9×10³M⊙, is detected in emission at 1 mm. The NGC 7538 region appears to contain examples of different stages in the formation of massive stars; it is suggested that the centre of star formation is moving systematically to the south-east in this region
Discovery of two new methanol masers in NGC 7538
Get PDFContext.NGC 7538 is known to host a
6.7 and 12.2 GHz methanol maser cospatial with a Ultra Compact (UC) \ion{H}{ii}
region, IRS 1.Aims.We report on the
serendipitous discovery of two additional 6.7 GHz
methanol masers in the same region, not associated
with IRS 1.Methods.Interferometry maser positions are compared with recent single-dish and
interferometry continuum observations.Results.The positions of the masers agree to high
accuracy with the 1.2 mm continuum peak
emission in NGC 7538 IRS 9 and NGC 7538 S. This
clear association is also confirmed by the positional agreement of the
masers with existing high resolution continuum observations at cm and/or mm
wavelengths.Conclusions.Making use
of the established strong relation between methanol masers and high-mas
star formation, we claim that we have accurately positioned the high-mass
protostars within the regions where they are detected. The variety of
objects hosting a 6.7 GHz methanol maser in NGC 7538 shows that
this emission probably traces different evolutionary stages within the
protostellar phase
Near-infrared spectroscopy in NGC 7538
No full text<BR /> Aims: The characterisation of the stellar population in young high-mass star-forming regions allows fundamental cluster properties like distance and age to be constrained. These are essential when using high-mass clusters as probes for conducting Galactic studies. <BR /> Methods: NGC 7538 is a star-forming region with an embedded stellar population unearthed only in the near-infrared (NIR). We present the first near-infrared spectro-photometric study of the candidate high-mass stellar content in NGC 7538. We obtained H and K spectra of 21 sources with both the multi-object and long-slit modes of LIRIS at the WHT, and complement these data with subarcsecond JHKs photometry of the region using the imaging mode of the same instrument. <BR /> Results: We find a wide variety of objects within the studied stellar population of NGC 7538. Our results discriminate between a stellar population associated to the H ii region, but not contained within its extent, and several pockets of more recent star formation. We report the detection of CO bandhead emission toward several sources, as well as other features indicative of a young stellar nature. We infer a spectro-photometric distance of 2.7 ñ 0.5 kpc, an age spread in the range 0.5-2.2 Myr and a total mass 1.7 Ãâ 103 Msun for the older population. Based on observations made with the WHT operated on the island of La Palma by the Isaac Newton Group in the Spanish Observatorio del Roque de los Muchachos of the Instituto de AstrofÃsica de Canarias
Aperture synthesis observations of recombination lines from compact H II regions V - NGC 7538
No full textThe NGC 7538 (S158) complex has been mapped in the H110-alpha line using the Westerbork Synthesis Radio Telescope at 4.8 GHz. It is shown that the compact source IRS-2 has a velocity of -68 km/s, which is significantly different from the velocity of NGC 7538 (-61 km/s) and the velocity of nearby molecular velocities. In addition, it is noted that IRS-2 may be another example of a compact H II region within a collapsing neutral cloud
HERSCHEL REVEALS MASSIVE COLD CLUMPS IN NGC 7538
Get PDFWe present the first overview of the Herschel observations of the nearby high-mass star-forming region NGC 7538, taken as part of the Herschel imaging study of OB young stellar objects (HOBYS) Key Programme. These PACS and SPIRE maps cover an approximate area of one square degree at five submillimeter and far-infrared wavebands. We have identified 780 dense sources and classified 224 of those. With the intention of investigating the existence of cold massive starless or class 0-like clumps that would have the potential to form intermediate- to high-mass stars, we further isolate 13 clumps as the most likely candidates for follow-up studies. These 13 clumps have masses in excess of 40 M 99and temperatures below 15 K. They range in size from 0.4 pc to 2.5 pc and have densities between 3
7 103 cm -3 and 4
7 104 cm-3. Spectral energy distributions are then used to characterize their energetics and evolutionary state through a luminosity-mass diagram. NGC 7538 has a highly filamentary structure, previously unseen in the dust continuum of existing submillimeter surveys. We report the most complete imaging to date of a large, evacuated ring of material in NGC 7538 which is bordered by many cool sources.Peer reviewed: YesNRC publication: Ye
Herschel reveals massive cold clumps in NGC 7538
No full textWe present the first overview of the Herschel observations of the nearby high-mass star-forming region NGC 7538, taken as part of the Herschel imaging study of OB young stellar objects (HOBYS) Key Programme. These PACS and SPIRE maps cover an approximate area of one square degree at five submillimeter and far-infrared wavebands. We have identified 780 dense sources and classified 224 of those. With the intention of investigating the existence of cold massive starless or class 0-like clumps that would have the potential to form intermediate- to high-mass stars, we further isolate 13 clumps as the most likely candidates for follow-up studies. These 13 clumps have masses in excess of 40 M ⊙and temperatures below 15 K. They range in size from 0.4 pc to 2.5 pc and have densities between 3 × 103 cm -3 and 4 × 104 cm-3. Spectral energy distributions are then used to characterize their energetics and evolutionary state through a luminosity-mass diagram. NGC 7538 has a highly filamentary structure, previously unseen in the dust continuum of existing submillimeter surveys. We report the most complete imaging to date of a large, evacuated ring of material in NGC 7538 which is bordered by many cool sources. © 2013. The American Astronomical Society. All rights reserved
Aperture synthesis observations of recombination lines from compact H II regions V - NGC 7538
No full textThe NGC 7538 (S158) complex has been mapped in the H110-alpha line using the Westerbork Synthesis Radio Telescope at 4.8 GHz. It is shown that the compact source IRS-2 has a velocity of -68 km/s, which is significantly different from the velocity of NGC 7538 (-61 km/s) and the velocity of nearby molecular velocities. In addition, it is noted that IRS-2 may be another example of a compact H II region within a collapsing neutral cloud
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