Magnetically regulated collapse in the B335 protostar?

Cabedo, V.; Maury, A.; Girart, Josep Miquel; Padovani, M.; Hennebelle, P.; Houde, Martin; Zhang, Q.

doi:10.1051/0004-6361/202243813

Cited by 20 publications

(13 citation statements)

References 88 publications

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“…The latter span values in between 10 −16 and 10 −13 s −1 , i.e., from 1 to 2 orders of magnitude larger than the ones obtained with the method of Bovino et al (2020). In addition, they tend to overestimate the upper limits provided by the CR propagation model with All the values reported in Figures 4(a), (b), and (c) are similar to those obtained by Cabedo et al (2023), even if the analyzed samples show very different physical conditions. From this result, we conclude that the method proposed by Caselli et al (1998) shows significant limitations in its applicability.…”

Section: Discussionsupporting

confidence: 66%

“…However, recent studies have used this method to estimate the H ion 2 z in a protostellar source (Cabedo et al 2023), where the physical conditions are far from the range of applicability of the original formula (determined at 10 K and for early stages of star-forming regions). For the Bok Globule B335, which hosts a Class-0 protostar with already developed outflow, Cabedo et al (2023) as a local effect of the protostellar activity, which, however, would also affect f D that will decrease at T gas > 20 K, when CO is efficiently desorbed in the gas phase. However, their resulting f D present values of about 80 at the position of the protostellar embryo, i.e., an unexpected extremely high depleted region.…”

Section: Discussionmentioning

confidence: 99%

“…It is also worth noting that any other process that might affect the estimates of f D (such as the UV photodissociation of CO due to protostellar activity or the CO conversion to other species such as HCO + by CRs) would prevent the application of the method proposed by Caselli et al (1998), since the underlying assumptions imply that only a fraction of C and O (i.e., 1/f D ) remains in the gas phase, while the rest is frozen, in the form of CO, on the surface of the grains. To understand the results reported by Cabedo et al (2023), we then decided to apply the formula proposed by Caselli et al (1998) to our sources, which fall in the correct range of applicability being prestellar in nature. From the comparison between a prestellar and a protostellar source we can then inspect the validity of the method and its reliability.…”

Section: Discussionmentioning

confidence: 99%

“…The limitations of this formulation are also discussed in Caselli et al (2002) and lie primarily in the lack of some terms in the chemistry of H 2 D + and the reactions involving electrons, and it appears to greatly overestimate x(e) and the associated ζ ion H2 . However, recent studies have used this method to estimate the ζ ion H2 in a protostellar source (Cabedo et al 2023), where the physical conditions are far from the range of applicability of the original formula (determined at 10 K and for early stages of star-forming regions). For the Bok Globule B335, which hosts a Class 0 protostar with already developed outflow, Cabedo et al (2023) obtained a ζ ion H2 ∼7×10 −14 s −1 , by assuming a T ex = 25 K for each species.…”

Section: B Comparison With Previous Methodsmentioning

confidence: 99%

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First ALMA Maps of Cosmic-Ray Ionization Rate in High-mass Star-forming Regions

Sabatini¹,

Bovino²,

Redaelli³

2023

ApJL

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Low-energy cosmic rays (<1 TeV) are a pivotal source of ionization of the interstellar medium, where they play a central role in determining the gas chemical composition and drastically influence the formation of stars and planets. Over the past few decades, H3 + absorption line observations in diffuse clouds have provided reliable estimates of the cosmic-ray ionization rate relative to H2 ( ζ H 2 ion ). However, in denser clouds, where stars and planets form, this method is often inefficient due to the lack of H3 + rotational transitions. The ζ H 2 ion estimates are, therefore, still provisional in this context and represent one of the least understood components when it comes to defining general models of star and planet formation. In this Letter, we present the first high-resolution maps of the ζ H 2 ion in two high-mass clumps obtained with a new analytical approach recently proposed to estimate the ζ H 2 ion in the densest regions of molecular clouds. We obtain 〈 ζ H 2 ion 〉 that span from 3 × 10−17 to 10−16 s−1, depending on the different distribution of the main ion carriers, in excellent agreement with the most recent cosmic-ray propagation models. The cores belonging to the same parental clump show comparable ζ H 2 ion , suggesting that the ionization properties of prestellar regions are determined by global rather than local effects. These results provide important information for the chemical and physical modeling of star-forming regions.

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Section: Discussionsupporting

confidence: 66%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: B Comparison With Previous Methodsmentioning

confidence: 99%

See 2 more Smart Citations

First ALMA Maps of Cosmic-Ray Ionization Rate in High-mass Star-forming Regions

Sabatini¹,

Bovino²,

Redaelli³

2023

ApJL

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“…This is illustrated by the dichotomy found in BHR71 IRS2 between the outflow cavity and inner envelope traced by CO and C 18 O, respectively, and the cold envelope traced by N 2 D + where CO freezes out onto dust grains (Hull et al 2020; see also the unpolarized southern region of B335 in Fig. 1 compared to these same molecular lines presented in Cabedo et al 2021Cabedo et al , 2023. The dust polarization detected in the outflow cavity walls of IRS2 lies precisely between the regions where the N 2 D + and CO emission lines peak, suggesting that dust grains cannot become aligned in these areas.…”

Section: Effect Of C/o In the Gas Phase And The Cch Abundancementioning

confidence: 91%

Physical conditions for dust grain alignment in Class 0 protostellar cores

Gouellec

Maury

Hull

2023

A&A

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Context. High angular resolution observations of Class 0 protostars have produced detailed maps of the polarized dust emission in the envelopes of these young embedded objects. Interestingly, the improved sensitivity brought by ALMA has revealed wide dynamic ranges of polarization fractions, with specific locations harboring surprisingly large amounts of polarized dust emission. Aims. Our aim is to characterize the grain alignment conditions and dust properties responsible for the observed polarized dust emission in the inner envelopes (≤1000 au) of Class 0 protostars. Methods. We analyzed the polarized dust emission maps obtained with ALMA and compared them to molecular line emission maps of specific molecular tracers, mainly C2H, which allowed us to probe one of the key components in dust grain alignment theories: the irradiation field. Results. We show that C2H peaks toward outflow cavity walls, where the polarized dust emission is also enhanced. Our analysis provides a tentative correlation between the morphology of the polarized intensity and C2H emission, suggesting that the radiation field impinging on the cavity walls favors both the grain alignment and the warm carbon chain chemistry in these regions. We propose that shocks happening along outflow cavity walls could potentially represent an additional source of photons contributing to dust grain alignment. However, some parts of the cores, such as the equatorial planes, exhibit enhanced polarized flux, although no radiation driven chemistry is observed, for example where radiative torques are theoretically not efficient enough. This suggests that additional physical conditions, such as source geometry and dust grain evolution, may play a role in grain alignment. Conclusions. Comparing chemical processes with grain alignment physics opens a promising avenue to develop our understanding of the dust grain evolution (i.e., their origin, growth, and structure) in the interior of Class 0 protostars. The source geometry and evolution can represent important factors that set the environmental conditions of the inner envelope, determining whether the radiation field strength and spectrum can drive efficient dust grain alignment via radiative torques.

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Is the mm/submm dust polarization a robust tracer of the magnetic field topology in protostellar envelopes? A model exploration

Valdivia

Maury

Hennebelle

2022

A&A

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Context. High-resolution millimeter and submillimeter (mm and submm) polarization observations have opened a new era in the understanding of how magnetic fields are organized in star forming regions, unveiling an intricate interplay between the magnetic fields and the gas in protostellar cores. However, to assess the role of the magnetic field in the process of solar-type star formation, it is important to understand to what extent these polarized dust emission are good tracers of the magnetic field in the youngest protostellar objects. Aims. In this paper, we present a thorough investigation of the fidelity and limitations of using dust polarized emission to map the magnetic field topologies in low-mass protostars. Methods. To assess the importance of these effects, we performed an analysis of magnetic field properties in 27 realizations of magnetohydrodynamics (MHD) models following the evolution of physical properties in star-forming cores. Assuming a uniform population of dust grains the sizes of which follow the standard MRN size distribution, we analyzed the synthetic polarized dust emission maps produced when these grains align with the local B-field because of radiative torques (B-RATs). Results. We find that mm and submm polarized dust emission is a robust tracer of the magnetic field topologies in inner protostellar envelopes and is successful at capturing the details of the magnetic field spatial distribution down to radii ∼ 100 au. Measurements of the line-of-sight-averaged magnetic field line orientation using the polarized dust emission are precise to < 15 • (typical of the error on polarization angles obtained with observations from large mm polarimetric facilities such as ALMA) in about 75% − 95% of the independent lines of sight that pass through protostellar envelopes. Large discrepancies between the integrated B-field mean orientation and the orientation reconstructed from the polarized dust emission are mostly observed in (i) lines of sight where the magnetic field is highly disorganized and (ii) those that probe large column densities. Our analysis shows that the high opacity of the thermal dust emission and low polarization fractions could be used to avoid using the small fraction of measurements affected by large errors.

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Magnetically regulated collapse in the B335 protostar?

Cited by 20 publications

References 88 publications

First ALMA Maps of Cosmic-Ray Ionization Rate in High-mass Star-forming Regions

First ALMA Maps of Cosmic-Ray Ionization Rate in High-mass Star-forming Regions

Physical conditions for dust grain alignment in Class 0 protostellar cores

Is the mm/submm dust polarization a robust tracer of the magnetic field topology in protostellar envelopes? A model exploration

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