- ID:
- ivo://CDS.VizieR/J/MNRAS/443/3218
- Title:
- NGC 7538 IRS 1-3 and IRS 9 sources
- Short Name:
- J/MNRAS/443/3218
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present deep and high-resolution (FWHM~0.4-arcsec) near-infrared (NIR) imaging observations of the NGC 7538 IRS 1-3 region (in JHK bands), and IRS 9 region (in HK bands) using the 8.2m Subaru telescope. The NIR analysis is complemented with Giant Metrewave Radio Telescope (GMRT) low-frequency observations at 325, 610, and 1280MHz, molecular line observations of H^13^CO^+^ (J=1-0), and archival Chandra X-ray observations. Using the 'J-H/H-K' diagram, 144 Class II and 24 Class I young stellar object (YSO) candidates are identified in the IRS 1-3 region. Further analysis using 'K/H-K' diagram yields 145 and 96 red sources in the IRS 1-3 and IRS 9 regions, respectively. A total of 27 sources are found to have X-ray counterparts. The YSO mass function (MF), constructed using a theoretical mass-luminosity relation, shows peaks at substellar (~0.08-0.18M_{sun}_) and intermediate (~1-1.78M_{sun}_) mass ranges for the IRS 1-3 region. The MF can be fitted by a power law in the low-mass regime with a slope of {Gamma} ~0.54-0.75, which is much shallower than the Salpeter value of 1.35. An upper limit of 10.2 is obtained for the star to brown dwarf ratio in the IRS 1-3 region. GMRT maps show a compact HII region associated with the IRS 1-3 sources, whose spectral index of 0.87+/-0.11 suggests optical thickness. This compact region is resolved into three separate peaks in higher resolution 1280MHz map, and the 'east' subpeak coincides with the IRS 2 source. H^13^CO^+^ (J=1-0) emission reveals peaks in both IRS 1-3 and IRS 9 regions, none of which are coincident with visible nebular emission, suggesting the presence of dense cloud nearby. The virial masses are approximately of the order of 1000 and 500M_{sun}_ for the clumps in IRS 1-3 and IRS 9 regions, respectively.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/558/A81
- Title:
- NGC 7538 IRS1 maps in CH3OH, HCN and HCO+
- Short Name:
- J/A+A/558/A81
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Revealing the fragmentation, infall, and outflow processes in the immediate environment around massive young stellar objects is crucial for understanding the formation of the most massive stars. With this goal in mind we present the so far highest spatial-resolution thermal submm line and continuum observations toward the young high-mass protostar NGC 7538 IRS1. Using the Plateau de Bure Interferometer in its most extended configuration at 843um wavelength, we achieved a spatial resolution of 0.2"x0.17", corresponding to ~500AU at a distance of 2.7kpc.
- ID:
- ivo://CDS.VizieR/J/A+A/606/A52
- Title:
- NGC7538-IRS1 THz water maser
- Short Name:
- J/A+A/606/A52
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The formation of massive stars (M>10M_{sun}_, L>10^3^L_{sun}_) is still not well understood. Accumulating a large amount of mass infalling within a single entity in spite of radiation pressure is possible if, among several other conditions, enough thermal energy is released. Despite numerous water line observations, over a broad range of energies, with the Herschel Space Observatory, in most of the sources observations were not able to trace the emission from the hot core around the newly forming protostellar object. We want to probe the physical conditions and water abundance in the inner layers of the host protostellar object NGC7538-IRS1 using a highly excited H_2_O line. Water maser models predict that several THz water masers should be detectable in these objects. We therefore aim to detect for the first time the o-H_2_O 8_2,7_-7_3,4_ line in a star forming region, which model calculations predict to show maser action. We present SOFIA observations of the o-H_2_O 8_2,7_-7_3,4_ line at 1296.41106GHz and a 6_16_-5_23_ 22GHz e-MERLIN map of the region (first-ever 22GHz images made after the e-MERLIN upgrade). In order to be able to constrain the nature of the emission - thermal or maser - we use near-simultaneous observations of the 22GHz water maser performed with the Elsberg radiotelescope and e-MERLIN. A thermal water model using the RATRAN radiative transfer code is presented based on HIFI pointed observations. Molecular water abundances are derived for the hot core. The of the o-H_2_O 8_2,7_-7_3,4_ line is detected toward NGC7538-IRS1 with one feature at the source velocity (-57.7km/s) and another one at -48.4km/s. We propose that the emission at the source velocity is consistent with thermal excitation and is excited in the innermost part of the IRS1a massive protostellar object's closest circumstellar environment. The other emission is very likely the first detection of a water THz maser line, pumped by shocks due to IRS1b outflow, in a star-forming region. Assuming thermal excitation of the THz line, the water abundance in NGC7538-IRS1's hot core is estimated to be 5.2x10^-5^ with respect to H_2_.
- ID:
- ivo://CDS.VizieR/J/A+A/605/A61
- Title:
- NGC 7538 IRS1 VLA maps in CH_3_OH and NH_3_
- Short Name:
- J/A+A/605/A61
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- High-mass stars have a high degree of multiplicity and most likely form via disk accretion processes. The detailed physics of the binary and disk formation are still poorly constrained. We seek to resolve the central substructures of the prototypical high-mass star-forming region NGC7538IRS1 at the highest possible spatial resolution line and continuum emission to investigate the protostellar environment and kinematics. Using the Karl G. Jansky Very Large Array (VLA) in its most extended configuration at ~24GHz has allowed us to study the NH_3_ and thermal CH_3_OH emission and absorption as well as the cm continuum emission at an unprecedented spatial resolution of 0.06"x0.05", corresponding to a linear resolution of ~150AU at a distance of 2.7kpc.
- ID:
- ivo://CDS.VizieR/J/A+A/625/A134
- Title:
- NGC 6357 massive dense cores
- Short Name:
- J/A+A/625/A134
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- To constrain models of high-mass star formation it is important to identify the massive dense cores (MDCs) able to form high-mass star(s). It is one of purposes of the Herschel/HOBYS key program. Here, we make the census and characterisation of the properties of the MDCs population of the NGC 6357 HII region. Our study is based on the Herschel PACS and SPIRE 70-500 microns images of NGC 6357 complemented with (sub)millimetre and mid-infrared data. We followed the procedure, established by the Herschel/HOBYS consortium, to extract ~0.1pc massive dense cores using the getsources software. We estimated their physical parameters (temperatures, masses, luminosities) from spectral energy distribution (SED) fitting. We have obtained a complete census of 23 massive dense cores, amongs which one is found to be IR-quiet and twelve are starless, representing very early stages of the star-formation process. Focussing on the starless MDCs, we consider their evolutionary status, and suggest that only five are likely to form a high-mass star. We find that, contrarily to the case in NGC 6334, the NGC 6357 region does not exhibit any ridge/hub features that are believed to be crucial to the massive star formation process. This study adds support for an empirical model in which massive dense cores and protostars simultaneously accrete mass from the surrounding filaments. In addition, the massive star formation in NGC 6357 seems to have stopped and the hottest stars in Pismis 24 have disrupted the filaments.
- ID:
- ivo://CDS.VizieR/J/A+A/515/A55
- Title:
- NGC 6334-NGC 6357 complex
- Short Name:
- J/A+A/515/A55
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Our knowledge of high-mass star formation has been mainly based on follow-up studies of bright sources found by IRAS, and has thus been incomplete for its earliest phases, which are inconspicuous at infrared wavelengths. With a new generation of powerful bolometer arrays, unbiased large-scale surveys of nearby high-mass star-forming complexes now search for the high-mass analog of low-mass cores and class 0 protostars. Following the pioneering study of Cygnus X, we investigate the star-forming region NGC 6334-NGC 6357 (~1.7kpc)
- ID:
- ivo://CDS.VizieR/J/A+A/507/227
- Title:
- NGC 7129 pre-main sequence stars
- Short Name:
- J/A+A/507/227
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The reflection nebula NGC 7129 has long been known to be a site of recent star formation as shown, e.g., by the presence of deeply embedded protostars and HH objects. However, studies of the stellar population produced in the star formation process have remained rudimentary. A major step forward has been made with recent Spitzer imaging of the region. This study represents the next step towards a systematic assessment of the pre-main sequence population in NGC 7129. Completeness of the pre-main sequence sample is necessary for studying key features that allow the star-forming process to be understood, such as disk evolution, dynamical evolution, and mass function. At a presumed age of ~3Myr, NGC 7129 is in the critical range where disks around young stars disappear.
- ID:
- ivo://CDS.VizieR/J/AJ/140/266
- Title:
- NGC 1333 X-ray luminous YSOs properties
- Short Name:
- J/AJ/140/266
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present new Chandra X-ray data of the NGC 1333 embedded cluster and combine these data with existing Chandra data, Spitzer photometry, and ground-based spectroscopy of both the NGC 1333 and Serpens cloud core clusters to perform a detailed study of the X-ray properties of two of the nearest embedded clusters to the Sun. We first present new, deeper observations of NGC 1333 with Chandra ACIS-I and combine these with existing Spitzer observations of the region. In NGC 1333, a total of 95 cluster members are detected in X-rays of which 54 were previously identified in the Spitzer data.
- ID:
- ivo://CDS.VizieR/J/A+A/593/A7
- Title:
- NH and AV Towards YSOs in the ONC
- Short Name:
- J/A+A/593/A7
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We characterise the relation between the gas and dust content of the interstellar medium towards young stellar objects in the Orion Nebula Cluster. X-ray observations provide estimates of the absorbing equivalent hydrogen column density NH based on spectral fits. Near-infrared extinction values are calculated from intrinsic and observed colour magnitudes (J-H) and (H-Ks) as given by the VISTA Orion A survey. A linear fit of the correlation between column density and extinction values AV yields an estimate of the N_H_/A_V_ ratio. We investigate systematic uncertainties of the results by describing and (if possible) quantifying the influence of circumstellar material as well as the adopted extinction law, X-ray models, and elemental abundances on the NH/AV ratio. Assuming a Galactic extinction law with R_V=3.1 and solar abundances by Anders et al. (1989), we deduce an N_H_/A_V_ ratio of (1.39+/-0.14)*10^21cm^-2^.mag^-1^ for Class III sources in the Orion Nebula Cluster, where the given error does not include systematic uncertainties. This ratio is consistent with similar studies in other star-forming regions and approximately 31% lower than the Galactic value. We find no obvious trends in the spatial distribution of N_H_/A_V_ ratios. Changes in the assumed extinction law and elemental abundances are demonstrated to have a relevant impact on deduced A_V_ and N_H_ values, respectively. Large systematic uncertainties associated with metal abundances in the Orion Nebula Cluster represent the primary limitation for the deduction of a definitive N_H_/A_V_ ratio and the physical interpretation of these results.
- ID:
- ivo://CDS.VizieR/J/ApJ/739/100
- Title:
- [NII] observations of the Carina Nebula (NGC 3372)
- Short Name:
- J/ApJ/739/100
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of a ~250arcmin^2^ mapping of the 205um [NII] fine-structure emission over the northern Carina Nebula, including the Car I and Car II HII regions. Spectra were obtained using the South Pole Imaging Fabry-Perot Interferometer (SPIFI) at the Antarctic Submillimeter Telescope and Remote Observatory (AST/RO) at the South Pole. We supplement the 205um data with new reductions of far-IR fine-structure spectra from the Infrared Space Observatory (ISO) Long Wavelength Spectrometer (LWS) in 63um [OI], 122um [NII], 146um [OI], and 158um [CII]; the 146um [OI] data include 90 raster positions which have not been previously published. Morphological comparisons are made with optical, radio continuum, and CO maps. The 122/205 line ratio is used to probe the density of the low-ionization gas, and the 158/205 line ratio is used to probe the fraction of C^+^ arising from photodissociation regions (PDRs). The [OI] and [CII] lines are used to construct a PDR model of Carina. When the PDR properties are compared with other sources, Carina is found to be more akin to 30 Doradus than galactic star-forming regions such as Orion, M17, or W49; this is consistent with the view of Carina as a more evolved region, where much of the parent molecular cloud has been ionized or swept away. These data constitute the first ground-based detection of the 205um [NII] line, and the third detection overall since those of COBE FIRAS and the Kuiper Airborne Observatory in the early 1990s.
