The Stellar Content of the Infalling Molecular Clump G286.21+0.17

et al. 2020

ApJ

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We study the gas kinematics and dynamics of the massive protocluster G286.21+0.17 with the Atacama Large Millimeter/submillimeter Array using spectral lines of C 18 O(2-1), N 2 D + (3-2), DCO + (3-2) and DCN(3-2). On the parsec clump scale, C 18 O emission appears highly filamentary around the systemic velocity. N 2 D + and DCO + are more closely associated with the dust continuum. DCN is strongly concentrated towards the protocluster center, where no or only weak detection is seen for N 2 D + and DCO + , possibly due to this region being at a relatively evolved evolutionary stage. Spectra of 76 continuum defined dense cores, typically a few 1000 AU in size, are analysed to measure their centroid velocities and internal velocity dispersions. There are no statistically significant velocity offsets of the cores among the different dense gas tracers. Furthermore, the majority (71%) of the dense cores have subthermal velocity offsets with respect to their surrounding, lower density C 18 O emitting gas. Within the uncertainties, the dense cores in G286 show internal kinematics that are consistent with being in virial equilibrium. On clumps scales, the core to core velocity dispersion is also similar to that required for virial equilibrium in the protocluster potential. However, the distribution in velocity of the cores is largely composed of two spatially distinct groups, which indicates that the dense molecular gas has not yet relaxed to virial equilibrium, perhaps due to there being recent/continuous infall into the system.

Section: Core To Core Velocity Dispersionsupporting

confidence: 84%

Gas Kinematics of the Massive Protocluster G286.21+0.17 Revealed by ALMA

Cheng

Tan

et al. 2020

ApJ

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“…G286.21+0.17 (hereafter G286) is a massive protocluster associated with the η Car giant molecular cloud at a distance of 2.5 ± 0.3 kpc, in the Carina spiral arm (e.g., Barnes et al 2010, hereafter B10;Andersen et al 2017). G286 has been claimed to be ∼ 10 4 M (B10), which would make it the most massive and densest of the 300 HCO + (1-0) clumps studied by Barnes et al (2011) and Ma et al (2013), but an assessment of its dust mass from Herschel imaging data suggests a lower mass of ∼ 2000 M (Ma et al, in prep.).…”

Section: Introductionmentioning

confidence: 99%

The Core Mass Function in the Massive Protocluster G286.21+0.17 Revealed by ALMA

Cheng

Tan

et al. 2018

ApJ

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We study the core mass function (CMF) of the massive protocluster G286.21+0.17 with the Atacama Large Millimeter/submillimeter Array via 1.3 mm continuum emission at a resolution of 1.0 (2500 au). We have mapped a field of 5.3 ×5.3 centered on the protocluster clump. We measure the CMF in the central region, exploring various core detection algorithms, which give source numbers ranging from 60 to 125, depending on parameter selection. We estimate completeness corrections due to imperfect flux recovery and core identification via artificial core insertion experiments. For masses M 1 M , the fiducial dendrogram-identified CMF can be fit with a power law of the form dN/dlogM ∝ M −α with α 1.24±0.17, slightly shallower than, but still consistent with, the index of the Salpeter stellar initial mass function of 1.35. Clumpfind-identified CMFs are significantly shallower with α 0.64 ± 0.13. While raw CMFs show a peak near 1 M , completeness-corrected CMFs are consistent with a single power law extending down to ∼ 0.5 M , with only a tentative indication of a shallowing of the slope around ∼ 1 M . We discuss the implications of these results for star and star cluster formation theories.

“…Based on the previous studies, G286 clump is on the edge of HII region A (see B10). Both G286 and HII region A are found to be near HII region B (Gum31), which is at the same distance (d∼2.5 kpc) and is excited by a young stellar cluster NGC3324 (Cappa et al 2008;Barnes et al 2010;Ohlendorf et al 2013;Andersen et al 2017). HII region B is strongly interacting with the surrounding interstellar medium, and it may likely also affect the evolution of G286 and HII region A.…”

Section: Continuum Emissionmentioning

confidence: 99%

“…This work is focused on the dense clump. Andersen et al (2017) suggests the cluster are very young with a rich population of pre-main-sequence stars with a disk fraction ranging from 27% to 44% for a magnitude and extinction limited sample. Cheng et al (2020b) presents a near-infrared (NIR) variability analysis toward the G286 protocluster, suggesting it as being an extreme case of an outburst event that is still ongoing.…”

Section: Introductionmentioning

confidence: 97%

“…G286.21+0.17 (hereafter G286) is a massive protocluster site associated with the η Car giant molecular cloud at a distance of 2.5±0.3kpc, in the Carina spiral arm (e.g., Barnes et al 2010, hereafter B10;Andersen et al 2017). Through observations of molecular lines, B10 determined several parameters about G286 region: the size ∼ 0.9 pc, the luminosity ∼ (2 − 3) × 10 4 L , and the mass ∼ 20000 M .…”

Section: Introductionmentioning

confidence: 99%

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ATOMS: ALMA Three-millimeter Observations of Massive Star-forming regions–VI. On the formation of the ‘L’ type filament in G286.21+0.17

Zhou

Monthly Notices of the Royal Astronomical Society

et al. 2021

Filaments play an important role in star formation, but the formation process of filaments themselves is still unclear. The high-mass star forming clump G286.21+0.17 (G286 for short) that contains an “L” type filament was thought to undergo global collapse. Our high resolution ALMA band 3 observations resolve the gas kinematics of G286 and reveal two sub-clumps with very different velocities inside it. We find that the “blue profile” (an indicator of gas infall) of HCO+ lines in single dish observations of G286 is actually caused by gas emission from the two sub-clumps rather than gas infall. We advise great caution in interpreting gas kinematics (e.g. infall) from line profiles toward distant massive clumps in single dish observations. Energetic outflows are identified in G286 but the outflows are not strong enough to drive expansion of the two sub-clumps. The two parts of the “L” type filament (“NW-SE” and “NE-SW” filaments) show prominent velocity gradients perpendicular to their major axes, indicating that they are likely formed due to large-scale compression flows. We argue that the large-scale compression flows could be induced by the expansion of nearby giant H ii regions. The “NW-SE” and “NE-SW” filaments seem to be in collision, and a large amount of gas has been accumulated in the junction region where the most massive core G286c1 forms.