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N. Castro-Toledo

Publications and source records attributed to N. Castro-Toledo.

3 recordsLinked to original sources

ALMA-IMF. XXI.: N$_2$H$^+$ kinematics in the G012.80 protocluster: Evidence for filament rotation and evolution

(abridged) We aim to characterize kinematic processes in the G012.80 protocluster. We principally focus on the N$_2$H$^+$(1$-$0) emission to trace the dense and cold gas. Additionally, we use lines such as DCN(3$-$2), H41$α$, C$^{18}$O(1$-$0), and SiO(5$-$4), as well as continuum maps. We perform a N$_2$H$^+$ hyperfine spectral line fitting to analyze multiple velocity components and spectral parameters. We estimate velocity gradients, column densities, and line-mass profiles for the two main filaments in G012, named R1 and R2. Line-mass profiles follow $λ$($ω$) = 5660 M$_{\odot}$ pc$^{-1}$($ω$/pc)$^{0.30}$ (R1) and $λ$($ω$) = 6943 M$_{\odot}$ pc$^{-1}$($ω$/pc)$^{0.20}$ (R2), which are much larger than those of typical low-mass filaments. R1 and R2 show disparate position-velocity (PV) features. R1 exhibits a transverse velocity gradient of 10.4 kms$^{-1} $pc$^{-1}$ and few dense cores. This gradient is interpreted with a simple rotation toy model, combined with line-mass profile, and corresponds to a rotational timescale of 0.1 Myr. In contrast, R2 exhibits compact velocity structures ($Δ$V < 2 kms$^{-1}$), likely due to collapse, as evidenced by the presence of a comparatively large number of massive cores and protostellar outflows. R2 is forming prestellar and protostellar cores at a rate of 55.3 M$_{\odot}$ Myr$^{-1}$, with an efficiency similar to the Orion Integral Shaped Filament (ISF). The R1 filament, in contrast, lacks protostellar cores and only contains a few prestellar cores, resulting in an estimated SFR of 4.2 M$_{\odot}$ Myr$^{-1}$, more than an order of magnitude below that of R2. Combining these lines of evidence, we suggest that R1 is younger and still rotating, while R2 has evolved to collapse with a higher SFR. G012 thus hosts filaments at different evolutionary stages.

astro-ph.GA

Estimation of the magnetic field strength from ALMA dust polarization in the protocluster G327.29

Magnetic fields and turbulence may play a crucial role in the evolution of molecular clouds and ultimately in the formation of dense cores and stars. Despite being studied in many molecular clouds, the exact role of magnetic fields and turbulence in star formation is still poorly understood. Here, we report the high resolution plane of sky magnetic field (B_pos) morphology toward the high mass star forming region G327.29, obtained with the 12-meter of the Atacama Large Millimeter/sub-millimeter Array (ALMA) telescope. From our analysis, we obtain a complex B_pos morphology where the magnetic field orientation is uniformly distributed across the entire range from -90 to +90 deg. The observed area is composed of one filament and one dense central clump, which harbor multiple dense cores. The total magnetic field strengths (B_tot) in these regions are 1.4 \pm 0.7 mG and 2.0 \pm 0.8 mG at a number density (n) of 6.8 \pm 1.5 x 10^5 and 1.1 \pm 0.3 x 10^6 cm^-3 , derived from the angular dispersion function (ADF) method. The virial parameters (α vir )in these regions are 7.7 \pm 7.1 and 0.7 \pm 0.6, suggesting that the regions may be gravitationally bound or unbound after accounting for the errors. Moreover, the ratio of turbulent to magnetic energy (~ 0.25) indicates that the magnetic field is dynamically more important than turbulence. The relative influence of turbulence and magnetic fields on core dynamics appears to depend on how the B_tot scales with gas density (\r{ho}) in the densest regions. In summary, this work presents a comprehensive analysis of the relative roles of magnetic fields, turbulence, and gravity in regulating high-mass star formation in G327.29, enabled by high-resolution ALMA observations.

astro-ph.GA

Magnetic field morphological diagnostics with ALMA in the G327.29 protocluster: VGT versus dust polarization

Magnetic fields and turbulence may play a key role in the evolution of protoclusters, influencing the formation of dense cores and stars. Here, we examine the morphology of the magnetic fields in the G327.29 protocluster using both the velocity gradient technique (VGT) extracted from molecular line emissions and linear polarization in the dust continuum emission. The VGT analysis is performed using four molecular tracers: DCN (3-2), C18O (2-1), HN13C (3-2), and H13CO+ (3-2) - which probe gas across different density regimes, observed with the ALMA 12 m array. Owing to its sensitivity to gas dynamics, a comparison between VGT and dust polarization provides a powerful probe of the evolutionary processes in massive star-forming regions. From our analysis we reveal a complex magnetic-field structure, shaped by the combined influence of turbulence and gravity. In addition, it also appears that there is a large-scale (beyond the core scale) gravitational infall from the surrounding medium on to the filament and the central densest region. Furthermore, we observe that cores are dominated by a mix of turbulence and gravity. Overall, this work presents, likely for the first time, the application of VGT to a massive protocluster, G327.29, using high-resolution ALMA observations.

astro-ph.GA