Proyecto de Investigación: Understanding our Galactic ecosystem: From the disk of the Milky Way to the formation sites of stars and planets
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855130
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Singly and doubly deuterated formaldehyde in massive star-forming regions
(EDP Sciences, 2021-09-07) Zahorecz, S.; Jiménez Serra, I.; Testi, L.; Immer, K.; Fontani, F.; Caselli, P.; Wang, K.; Onishi, T.; European Research Council (ERC); Agencia Estatal de Investigación (AEI); National Natural Science Foundation of China (NSFC); National Key Research and Development Program of China (NKRDPC); Zahorecz, S. [0000-0001-6149-1278]
Context. Deuterated molecules are good tracers of the evolutionary stage of star-forming cores. During the star formation process, deuterated molecules are expected to be enhanced in cold, dense pre-stellar cores and to deplete after protostellar birth.
Aims. In this paper, we study the deuteration fraction of formaldehyde in high-mass star-forming cores at different evolutionary stages to investigate whether the deuteration fraction of formaldehyde can be used as an evolutionary tracer.
Methods. Using the APEX SEPIA Band 5 receiver, we extended our pilot study of the J = 3 →2 rotational lines of HDCO and D2CO to eleven high-mass star-forming regions that host objects at different evolutionary stages. High-resolution follow-up observations of eight objects in ALMA Band 6 were performed to reveal the size of the H2CO emission and to give an estimate of the deuteration fractions HDCO/H2CO and D2CO/HDCO at scales of ~6″ (0.04–0.15 pc at the distance of our targets).
Results. Our observations show that singly and doubly deuterated H2CO are detected towards high-mass protostellar objects (HMPOs) and ultracompact H II regions (UC H II regions), and the deuteration fraction of H2CO is also found to decrease by an order of magnitude from the earlier HMPO phases to the latest evolutionary stage (UC H II), from ~0.13 to ~0.01. We have not detected HDCO and D2CO emission from the youngest sources (i.e. high-mass starless cores or HMSCs).
Conclusions. Our extended study supports the results of the previous pilot study: the deuteration fraction of formaldehyde decreases with the evolutionary stage, but higher sensitivity observations are needed to provide more stringent constraints on the D/H ratio during the HMSC phase. The calculated upper limits for the HMSC sources are high, so the trend between HMSC and HMPO phases cannot be constrained.
Magnetic field morphology and evolution in the Central Molecular Zone and its effect on gas dynamics
(EDP Sciences, 2024-11-22) Tress, Robin; Sormani, Mattia Carlo; Girichidis, P.; Glover, Simon; Klessen, Ralf Stephan; Smith, Rowan; Sobacchi, E.; Armillotta, Lucia; Barnes, A. T.; Battersby, C.; Bogue, Kamran R. J.; Brucy, Noé; Colzi, Laura; Federrath, C.; García, Pablo; Ginsburg, A.; Göller, Junia Aletta Beatrix; Hatchfield, H. P.; Henkel, C.; Hennebelle, P.; Henshaw, J. D.; Hirschmann, M.; Hu, Y.; Kauffmann, J.; Kruijssen, J. M. D.; Lazarian, A.; Lipman, Dani R.; Longmore, S. N.; Morris, Mark; Nogueras Lara, Francisco; Petkova, Maya A.; Pillai, Thushara; Rivilla, Victor M.; Sanchez-Monge, Alvaro; Soler, Juan Diego; Whitworth, David; Zhang, Qizhou; European Research Council (ERC); Royal Society; National Science Foundation (NSF); Consejo Superior de Investigaciones Científicas (CSIC); European Commission (EC); Deutsche Forschungsgemeinschaft (DFG); Ministerio de Ciencia e Innovación (MICINN); Agencia Estatal de Investigación (AEI); Chinese Academy of Science (CAS); Consejo Nacional de Ciencia y Tecnología (CONACyT); Unidad de Excelencia Científica María de Maeztu INSTITUTO DE CIENCIAS DEL ESPACIO, CEX2020-001058-M
The interstellar medium in the Milky Way’s Central Molecular Zone (CMZ) is known to be strongly magnetised, but its large-scale morphology and impact on the gas dynamics are not well understood. We explore the impact and properties of magnetic fields in the CMZ using three-dimensional non-self gravitating magnetohydrodynamical simulations of gas flow in an external Milky Way barred potential. We find that: (1) The magnetic field is conveniently decomposed into a regular time-averaged component and an irregular turbulent component. The regular component aligns well with the velocity vectors of the gas everywhere, including within the bar lanes. (2) The field geometry transitions from parallel to the Galactic plane near ɀ = 0 to poloidal away from the plane. (3) The magneto-rotational instability (MRI) causes an in-plane inflow of matter from the CMZ gas ring towards the central few parsecs of 0.01−0.1 M⊙ yr−1 that is absent in the unmagnetised simulations. However, the magnetic fields have no significant effect on the larger-scale bar-driven inflow that brings the gas from the Galactic disc into the CMZ. (4) A combination of bar inflow and MRI-driven turbulence can sustain a turbulent vertical velocity dispersion of σɀ = 5 km s−1 on scales of 20 pc in the CMZ ring. The MRI alone sustains a velocity dispersion of σɀ ≃ 3 km s−1. Both these numbers are lower than the observed velocity dispersion of gas in the CMZ, suggesting that other processes such as stellar feedback are necessary to explain the observations. (5) Dynamo action driven by differential rotation and the MRI amplifies the magnetic fields in the CMZ ring until they saturate at a value that scales with the average local density as B ≃ 102 (n/103 cm−3)0.33 µG. Finally, we discuss the implications of our results within the observational context in the CMZ.
