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We report high angular resolution observations, made with the Atacama Large Millimeter Array in band 6, of high excitation molecular lines of CH 3 CN and SO2 and of the H29 α radio recombination line toward the G345.0061+01.794 B HC H ii region in order to investigate the physical and kinematical characteristics of its surroundings. Emission was detected in all observed components of the J = 14 →13 rotational ladder of CH 3 CN and in the 304,26–303,27, and 324,28–323,29 lines of SO2. The peak of the velocity-integrated molecular emission is located ∼0.″4 northwest of the peak of the continuum emission. The first-order moment images and channel maps show a velocity gradient of 1.1 km s−1 arcsec−1 across the source and a distinctive spot of blueshifted emission toward the peak of the zero-order moment. The rotational temperature is found to decrease from 252±24 K at the peak position to 166±16 K at its edge, indicating that our molecular observations are probing a hot molecular core that is internally excited. The emission in the H29 α line arises from a region of 0.″65 in size, where its peak coincides with that of the dust continuum. We model the kinematical characteristics of the "central blue spot" feature as due to infalling motions, suggesting a central mass of 172.8±8.8 M ⊙. Our observations indicate that this HC H ii region is surrounded by a compact structure of hot molecular gas, which is rotating and infalling toward a central mass, that is most likely confining the ionized region. The observed scenario is reminiscent of a "butterfly pattern" with an approximately edge-on torus and ionized gas roughly parallel to its rotation axis. [ABSTRACT FROM AUTHOR]

Hydrogen radio recombination lines (RRLs) are one of the major diagnostics of the physical properties of H  ii regions. We use RRL H40α, He40α, and 3 mm continuum emission to investigate the properties of a large sample of resolved UC H  ii regions identified in the ATOMS survey. In total, we identify 94 UC H  ii regions from H40α emission. The basic parameters for these UC H  ii regions, such as electron density, emission measure, electron temperature, ionic abundance ratio (n |$_{\rm He^+}$| /n |$_{\rm H^+}$|⁠), and line width are derived. The median electron density and the median n |$_{\rm He^+}$| /n |$_{\rm H^+}$| ratio of these UC H  ii regions derived from RRLs are ∼9000 cm−3 and 0.11, respectively. Within UC H  ii regions, the n |$_{\rm He^+}$| /n |$_{\rm H^+}$| ratios derived from the intensity ratio of the He40α and H40α lines seems to be higher in the boundary region than in the centre. The H40α line width is mainly broadened by thermal motion and microturbulence. The electron temperature of these UC H  ii regions has a median value of ∼6700 K, and its dependence on galactocentric distance is weak. [ABSTRACT FROM AUTHOR]

The parameters FWHM, FWHMdec, and Rcore are derived in the same way as in Table 1. The number of the UC-H ii should be 81 (see above). in appendix B, the number of the COM-containing but not H/UC-H ii-associated cores should change from 90 to 82. The parameters FWHM, FWHMdec, and Rcore are derived in the same way as in Table 1. The parameters FWHM, FWHMdec, and Rcore are derived in the same way as in Table 1. [Extracted from the article]

We have identified 453 compact dense cores in 3 mm continuum emission maps in the ALMA Three-millimetre Observations of Massive Star-forming regions survey, and compiled three catalogues of high-mass star-forming cores. One catalogue, referred to as hyper/ultra compact (H/UC)-H  ii catalogue, includes 89 cores that enshroud H/UC H  ii regions as characterized by associated compact H40α emission. A second catalogue, referred to as pure s-cHMC, includes 32 candidate hot molecular cores (HMCs) showing rich spectra (N ≥ 20 lines) of complex organic molecules (COMs) and not associated with H/UC-H  ii regions. The third catalogue, referred to as pure w-cHMC, includes 58 candidate HMCs with relatively low levels of COM richness and not associated with H/UC-H  ii regions. These three catalogues of dense cores provide an important foundation for future studies of the early stages of high-mass star formation across the Milky Way. We also find that nearly half of H/UC-H  ii cores are candidate HMCs. From the number counts of COM-containing and H/UC-H  ii cores, we suggest that the duration of high-mass protostellar cores showing chemically rich features is at least comparable to the lifetime of H/UC-H  ii regions. For cores in the H/UC-H  ii catalogue, the width of the H40α line increases as the core size decreases, suggesting that the non-thermal dynamical and/or pressure line-broadening mechanisms dominate on the smaller scales of the H/UC-H  ii cores. [ABSTRACT FROM AUTHOR]

We combine Multi-Unit Spectroscopic Explorer and Atacama Large Millimeter/sub-millimeter Array observations with theoretical models to evaluate how a tadpole-shaped globule located in the Carina Nebula has been influenced by its environment. This globule is now relatively small (radius ∼2500 au), hosts a protostellar jet+outflow (HH 900), and, with a blueshifted velocity of ∼10 km s−1, is travelling faster than it should be if its kinematics were set by the turbulent velocity dispersion of the precursor cloud. Its outer layers are currently still subject to heating, but comparing the internal and external pressures implies that the globule is in a post-collapse phase. Intriguingly the outflow is bent, implying that the Young Stellar Object (YSO) responsible for launching it is comoving with the globule, which requires that the star formed after the globule was up to speed since otherwise it would have been left behind. We conclude that the most likely scenario is one in which the cloud was much larger before being subject to radiatively driven implosion, which accelerated the globule to the high observed speeds under the photoevaporative rocket effect and triggered the formation of the star responsible for the outflow. The globule may now be in a quasi-steady state following collapse. Finally, the HH 900 YSO is likely ≳1 M⊙ and may be the only star forming in the globule. It may be that this process of triggered star formation has prevented the globule from fragmenting to form multiple stars (e.g. due to heating) and has produced a single higher mass star. [ABSTRACT FROM AUTHOR]

We present new Atacama Large Millimeter/submillimeter Array observations of the tadpole, a small globule in the Carina Nebula that hosts the HH 900 jet+outflow system. Our data include 12CO, 13CO, C18O J =2–1, 13CO, C18O J =3–2, and serendipitous detections of DCN J =3–2 and CS J =7–6. With angular resolution comparable to the Hubble Space Telescope , our data reveal for the first time the bipolar molecular outflow in CO, seen only inside the globule, that is launched from the previously unseen jet-driving protostar (the HH 900 YSO). The biconical morphology joins smoothly with the externally irradiated outflow seen in ionized gas tracers outside the globule, tracing the overall morphology of a jet-driven molecular outflow. Continuum emission at the location of the HH 900 YSO appears to be slightly flattened perpendicular to outflow axis. Model fits to the continuum have a best-fitting spectral index of ∼2, suggesting cold dust and the onset of grain growth. In position–velocity space, 13CO and C18O gas kinematics trace a C-shaped morphology, similar to infall profiles seen in other sources, although the global dynamical behaviour of the gas remains unclear. Line profiles of the CO isotopologues display features consistent with externally heated gas. We estimate a globule mass of ∼1.9 M⊙, indicating a remaining lifetime of ∼4 Myr, assuming a constant photoevaporation rate. This long globule lifetime will shield the disc from external irradiation perhaps prolonging its life and enabling planet formation in regions where discs are typically rapidly destroyed. [ABSTRACT FROM AUTHOR]

We present new MUSE/VLT observations of a small globule in the Carina H  ii region that hosts the HH 900 jet+outflow system. Data were obtained with the GALACSI ground-layer adaptive optics system in wide-field mode, providing spatially resolved maps of diagnostic emission lines. These allow us to measure the variation of the physical properties in the globule and jet+outflow system. We find high temperatures (T e ≈ 104 K), modest extinction (AV ≈ 2.5 mag), and modest electron densities (n e ≈ 200 cm−3) in the ionized gas. Higher excitation lines trace the ionized outflow; both the excitation and ionization in the outflow increase with distance from the opaque globule. In contrast, lower excitation lines that are collisionally de-excited at densities ≳104 cm−3 trace the highly collimated protostellar jet. Assuming the globule is an isothermal sphere confined by the pressure of the ionization front, we compute a Bonnor–Ebert mass of ∼3.7 M⊙. This is two orders of magnitude higher than previous mass estimates, calling into question whether small globules like the Tadpole contribute to the bottom of the initial mass function. The derived globule properties are consistent with a cloud that has been and/or will be compressed by the ionization front on its surface. At the estimated globule photoevaporation rate of ∼5 × 10−7 M⊙ yr−1, the globule will be completely ablated in ∼7 Myr. Stars that form in globules like the Tadpole will emerge into the H  ii later and may help resolve some of the temporal tension between disc survival and enrichment. [ABSTRACT FROM AUTHOR]

We present subarcsecond observations toward the massive star-forming region G75.78+0.34. We used the Very Large Array to study the centimeter continuum and H2O and CH3OH maser emission, and the Owens Valley Radio Observatory and Submillimeter Array to study the millimeter continuum and recombination lines (H40α and H30α). We found radio continuum emission at all wavelengths, coming from three components: (1) a cometary ultracompact (UC) Hii region with an electron density ~3.7 × 104 cm-3, excited by a B0 type star, and with no associated dust emission; (2) an almost unresolved UCHii region (EAST), located ~6'' to the east of the cometary UCHii region, with an electron density ~1.3 × 105 cm-3, and associated with a compact dust clump detected at millimeter and mid-infrared wavelengths; and (3) a compact source (CORE), located ~2'' to the southwest of the cometary arc, with a flux density increasing with frequency, and embedded in a dust condensation of 30 M☉. The CORE source is resolved into two compact and unresolved sources which can be well fit by two homogeneous hypercompact Hii regions each one photoionized by a B0.5 zero-age main sequence star, or by free-free radiation from shock-ionized gas resulting from the interaction of a jet/outflow system with the surrounding environment. The spatial distribution and kinematics of water masers close to the CORE-N and S sources, together with excess emission at 4.5μm and the detected dust emission, suggest that the CORE source is a massive protostar driving a jet/outflow. [ABSTRACT FROM AUTHOR]