- ID:
- ivo://CDS.VizieR/J/A+A/563/L3
- Title:
- NGC1333-IRAS2A CALYPSO IRAM-PdBI SiO and SO maps
- Short Name:
- J/A+A/563/L3
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The earliest evolutionary stages of low-mass protostars are characterised by hot and fast jets which remove angular momentum from the circumstellar disk, thus allowing mass accretion onto the central object. However, the launch mechanism is still being debated. We would like to exploit high-angular (~0.8") resolution and high-sensitivity images to investigate the origin of protostellar jets using typical molecular tracers of shocked regions, such as SiO and SO.
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- ID:
- ivo://CDS.VizieR/J/A+A/637/A63
- Title:
- NGC 1333-IRAS4A radio images
- Short Name:
- J/A+A/637/A63
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Low-mass protostars drive powerful molecular outflows that can be observed with millimetre and submillimetre telescopes. Various sulfuretted species are known to be bright in shocks and could be used to infer the physical and chemical conditions throughout the observed outflows. The evolution of sulfur chemistry is studied along the outflows driven by the NGC1333-IRAS4A protobinary system located in the Perseus cloud to constrain the physical and chemical processes at work in shocks. We observed various transitions from OCS, CS, SO, and SO_2_ towards NGC1333-IRAS4A in the 1.3, 2, and 3mm bands using the {IRAM NOrthern Extended Millimeter Array (NOEMA)} and we interpreted the observations through the use of the Paris-Durham shock model. The targeted species clearly show different spatial emission along the two outflows driven by IRAS4A. OCS is brighter on small and large scales along the south outflow driven by IRAS4A1, whereas SO_2_ is detected rather along the outflow driven by IRAS4A2 that is extended along the north east - south west (NE-SW) direction. SO is detected at extremely high radial velocity up to +25km/s relative to the source velocity, clearly allowing us to distinguish the two outflows on small scales. Column density ratio maps estimated from a rotational diagram analysis allowed us to confirm a clear gradient of the OCS/SO_2_ column density ratio between the IRAS4A1 and IRAS4A2 outflows. Analysis assuming non Local Thermodynamic Equilibrium of four SO$_2$ transitions towards several SiO emission peaks suggests that the observed gas should be associated with densities higher than 10^5^cm^-3^ and relatively warm (T>100K) temperatures in most cases. The observed chemical differentiation between the two outflows of the IRAS4A system could be explained by a different chemical history. The outflow driven by IRAS4A1 is likely younger and more enriched in species initially formed in interstellar ices, such as OCS, and recently sputtered into the shock gas. In contrast, the longer and likely older outflow triggered by IRAS4A2 is more enriched in species that have a gas phase origin, such as SO_2_.
- 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.
- 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/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/A+A/625/A100
- Title:
- NGC 1068 SPHERE-VLT images
- Short Name:
- J/A+A/625/A100
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Establishing precisely how stars and interstellar medium distribute within the central 100 pc area around an AGN, down to the pc scale, is key to understanding the late stages of transfer of matter onto the accretion disc. Using adaptive optics-assisted (SPHERE-VLT) near-IR images in the H band, Ks band, and several narrow bands of the Seyfert 2 galaxy NGC 1068, we analysed the radial distribution of brightness in the central r<100pc area down to the pc scale. The median-averaged radial profiles are fitted by a cusp (power law) plus a central point source. A simple radiative transfer model is also used to interpret the data. We find that the fit of radial brightness profiles beyond 10pc is done quite precisely at Ks band by a cusp of exponent -2.0 plus a central point source and by a cusp of exponent -1.2 at H. The difference of exponents between H band and Ks band can be explained by differential extinction, provided that the distribution of dust is itself cuspy, with an exponent -1.0. However, the derived stellar density is found to follow a r^-4^ cusp, which is much steeper than any other cusp, either theoretically predicted around a massive black hole, or observed in the centre of early- and late-type galaxies or in mergers. Introducing a segregation in the stellar population with a central excess of giant stars leads to a somewhat less steep exponent; however, the de-reddened luminosity of the stellar cusp, as well as the mass of dust and gas all appear much too high to be realistic. An alternative scenario, where the Ks-band profile is well fitted by a combination of radiation from a stellar cusp identical to the H-band profile and thermal emission ofwarm/hot dust heated by the central engine appears much more satisfactory. NGC 1068 is shown to satisfy a relationship between half-light radius, cusp luminosity, and exponent that we established using a sample of luminous infrared galaxies (LIRGs) and ultraluminous infrared galaxies ULIRGs. This suggests that the cusp is the remnant of a recent starburst. We identify the central point-like source with the very hot dust at the internal wall of the putative torus and derive an intrinsic luminosity that requires a central extinction A_K_~8, a value consistent with predictions by several torus models. The overall picture revealed by this study is closely consistent with the scheme of a central rather steep stellar cusp, embedded in a diluted medium of warm dust, while a compact and dense structure identified with the putative torus is required to interpret a highly reddened point-like central source of very hot dust.
- ID:
- ivo://CDS.VizieR/J/A+A/565/A4
- Title:
- NGC 891 70-500um images
- Short Name:
- J/A+A/565/A4
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We investigate the connection between dust and gas in the nearby edge-on spiral galaxy NGC 891, a target of the Very Nearby Galaxies Survey. High resolution Herschel Space Observatory PACS and SPIRE 70, 100, 160, 250, 350, and 500 micron images are combined with JCMT SCUBA 850 micron observations to trace the far-infrared/submillimetre spectral energy distribution (SED). Maps of the HI 21cm line and CO(J=3-2) emission trace the atomic and molecular hydrogen gas, respectively. We fit one-component modified blackbody models to the integrated SED, finding a global dust mass of (8.5+/-2.0)x10^7^M_{sun}_ and an average temperature of 23+/-2K, consistent with results from previous far-infrared experiments. We also fit one-component modified blackbody models to pixel-by-pixel SEDs to produce maps of the dust mass and temperature. A comparison of the dust properties with the gaseous components of the ISM reveals strong spatial correlations between the surface mass densities of dust and the molecular hydrogen and total gas surface densities.