Tracing the cold and warm physico-chemical structure of deeply embedded protostars: IRAS 16293−2422 vs. VLA 1623−2417

Murillo, Nadia M.; Dishoeck, E. F. van; Wiel, M. H. D. van der; Jørgensen, J. K.; Drozdovskaya, M. N.; Calcutt, H.; Harsono, Daniel

doi:10.1051/0004-6361/201731724

Cited by 54 publications

(66 citation statements)

References 134 publications

(214 reference statements)

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“…Santangelo et al (2015a), Ching et al (2016) and Tobin et al (2018) for IRAS4A. Santangelo et al (2015b) and Murillo et al (2018) for VLA 1623. Yeh et al (2008), Kristensen et al (2013), Girart et al (2014) and van der Wiel et al 2019for IRAS 16293.…”

Section: Discussionmentioning

confidence: 93%

A statistical analysis of dust polarization properties in ALMA observations of Class 0 protostellar cores

Gouellec

Maury

Guillet

et al. 2020

A&A

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Context. Recent observational progress has challenged the dust grain-alignment theories used to explain the polarized dust emission routinely observed in star-forming cores. Aims. In an effort to improve our understanding of the dust grain alignment mechanism(s), we have gathered a dozen ALMA maps of (sub)millimeter-wavelength polarized dust emission from Class 0 protostars and carried out a comprehensive statistical analysis of dust polarization quantities. Methods. We analyze the statistical properties of the polarization fraction Pfrac and the dispersion of polarization position angles S. More specifically, we investigate the relationship between S and Pfrac as well as the evolution of the product S × Pfrac as a function of the column density of the gas in the protostellar envelopes. We compare the observed trends with those found in polarization observations of dust in the interstellar medium and in synthetic observations of non-ideal magneto-hydrodynamic (MHD) simulations of protostellar cores. Results. We find a significant S ∝ Pfrac−0.79 correlation in the polarized dust emission from protostellar envelopes seen with ALMA; the power-law index significantly differs from the one observed by Planck in star-forming clouds. The product S × Pfrac, which is sensitive to the dust grain alignment efficiency, is approximately constant across three orders of magnitude in envelope column density (from NH2 = 1022 cm−2 to NH2 = 1025 cm−2), with a mean value of 0.36−0.17+0.10. This suggests that the grain alignment mechanism producing the bulk of the polarized dust emission in star-forming cores may not systematically depend on the local conditions such as the local gas density. However, in the lowest-luminosity sources in our sample, we find a hint of less efficient dust grain alignment with increasing column density. Our observations and their comparison with synthetic observations of MHD models suggest that the total intensity versus the polarized dust are distributed at different intrinsic spatial scales, which can affect the statistics from the ALMA observations, for example, by producing artificially high Pfrac. Finally, synthetic observations of MHD models implementing radiative alignment torques (RATs) show that the statistical estimator S × Pfrac is sensitive to the strength of the radiation field in the core. Moreover, we find that the simulations with a uniform perfect alignment (PA) of dust grains yield, on average, much higher S × Pfrac values than those implementing RATs; the ALMA values lie among those predicted by PA, and they are significantly higher than the ones obtained with RATs, especially at large column densities. Conclusions. Ultimately, our results suggest that dust alignment mechanism(s) are efficient at producing dust polarized emission in the various local conditions typical of Class 0 protostars. The grain alignment efficiency found in these objects seems to be higher than the efficiency produced by the standard RAT alignment of paramagnetic grains. Further studies will be needed to understand how more efficient grain alignment via, for example, different irradiation conditions, dust grain characteristics, or additional grain alignment mechanisms can reproduce the observations.

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Section: Discussionmentioning

confidence: 93%

A statistical analysis of dust polarization properties in ALMA observations of Class 0 protostellar cores

Gouellec

Maury

Guillet

et al. 2020

A&A

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“…Meanwhile, OCS, H 2 S and H 2 CS emit also from the envelope. In fact, H 2 CS is one of the few species detected at large distances from source A (appendices C1 and C2 of Murillo et al 2017), definitively pointing to its origins in the extended envelope. However, the detection of all these molecules with interferometric data testifies to their presence on small scales of the disc and/or inner envelope as well.…”

Section: Comparison With Single Dish Observationsmentioning

confidence: 94%

The ALMA-PILS survey: the sulphur connection between protostars and comets: IRAS 16293–2422 B and 67P/Churyumov–Gerasimenko

Drozdovskaya

Dishoeck

Jørgensen

et al. 2018

Monthly Notices of the Royal Astronomical Society

100

145

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The evolutionary past of our Solar system can be pieced together by comparing analogous lowmass protostars with remnants of our Protosolar Nebula-comets. Sulphur-bearing molecules may be unique tracers of the joint evolution of the volatile and refractory components. ALMA Band 7 data from the large unbiased Protostellar Interferometric Line Survey are used to search for S-bearing molecules in the outer disc-like structure, ∼60 au from IRAS 16293-2422 B, and are compared with data on 67P/Churyumov-Gerasimenko (67P/C-G) stemming from the ROSINA (Rosetta Orbiter Spectrometer for Ion and Neutral Analysis) instrument aboard Rosetta. Species such as SO 2 , SO, OCS, CS, H 2 CS, H 2 S, and CH 3 SH are detected via at least one of their isotopologues towards IRAS 16293-2422 B. The search reveals a first-time detection of OC 33 S towards this source and a tentative first-time detection of C 36 S towards a low-mass protostar. The data show that IRAS 16293-2422 B contains much more OCS than H 2 S in comparison to 67P/C-G; meanwhile, the SO/SO 2 ratio is in close agreement between the two targets. IRAS 16293-2422 B has a CH 3 SH/H 2 CS ratio in range of that of our Solar system (differences by a factor of 0.7-5.3). It is suggested that the levels of UV radiation during the initial collapse of the systems may have varied and have potentially been higher for IRAS 16293-2422 B due to its binary nature; thereby, converting more H 2 S into OCS. It remains to be conclusively tested if this also promotes the formation of S-bearing complex organics. Elevated UV levels of IRAS 16293-2422 B and a warmer birth cloud of our Solar system may jointly explain the variations between the two low-mass systems.

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“…c−C 3 H 2 is often detected in UV-illuminated gas in photodissociation regions (PDRs) and H II regions, together with C 2 H, (see for example Pety et al 2005;Fontani et al 2012;Pilleri et al 2013;Guzmán et al 2015). More recently, c−C 3 H 2 has been found to trace the outflow cavity walls in two prototypical low-mass Class 0 YSOs (Murillo et al 2018), presumably tracing gas which is illuminated by UV radiation generated either in the jet and/or outflow or from accretion. Overall, the distribution of c−C 3 H 2 is consistent with with an origin in UV-illuminated gas, and provides additional support for the proposed direction of the outflow, as also seen in lower-mass Class 0 YSOs.…”

Section: Spatial Intensity Distributionsmentioning

confidence: 99%

From clump to disc scales in W3 IRS4

Mottram

Beuther

Ahmadi

et al. 2020

A&A

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Context. High-mass star formation typically takes place in a crowded environment, with a higher likelihood of young forming stars affecting and being affected by their surroundings and neighbours, as well as links between different physical scales affecting the outcome. However, observational studies are often focused on either clump or disc scales exclusively. Aims. We explore the physical and chemical links between clump and disc scales in the high-mass star formation region W3 IRS4, a region that contains a number of different evolutionary phases in the high-mass star formation process, as a case-study for what can be achieved as part of the IRAM NOrthern Extended Millimeter Array (NOEMA) large programme named CORE: “Fragmentation and disc formation in high-mass star formation”. Methods. We present 1.4 mm continuum and molecular line observations with the IRAM NOEMA interferometer and 30 m telescope, which together probe spatial scales from ~0.3−20′′ (600−40 000 AU or 0.003−0.2 pc at 2 kpc, the distance to W3). As part of our analysis, we used XCLASS to constrain the temperature, column density, velocity, and line-width of the molecular emission lines. Results. The W3 IRS4 region includes a cold filament and cold cores, a massive young stellar object (MYSO) embedded in a hot core, and a more evolved ultra-compact (UC)H II region, with some degree of interaction between all components of the region that affects their evolution. A large velocity gradient is seen in the filament, suggesting infall of material towards the hot core at a rate of 10−3−10−4 M⊙ yr−1, while the swept up gas ring in the photodissociation region around the UCH II region may be squeezing the hot core from the other side. There are no clear indications of a disc around the MYSO down to the resolution of the observations (600 AU). A total of 21 molecules are detected, with the abundances and abundance ratios indicating that many molecules were formed in the ice mantles of dust grains at cooler temperatures, below the freeze-out temperature of CO (≲35 K). This contrasts with the current bulk temperature of ~50 K, which was obtained from H2CO. Conclusions. CORE observations allow us to comprehensively link the different structures in the W3 IRS4 region for the first time. Our results argue that the dynamics and environment around the MYSO W3 IRS4 have a significant impact on its evolution. This context would be missing if only high resolution or continuum observations were available.

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Tracing the cold and warm physico-chemical structure of deeply embedded protostars: IRAS 16293−2422 vs. VLA 1623−2417

Cited by 54 publications

References 134 publications

A statistical analysis of dust polarization properties in ALMA observations of Class 0 protostellar cores

A statistical analysis of dust polarization properties in ALMA observations of Class 0 protostellar cores

The ALMA-PILS survey: the sulphur connection between protostars and comets: IRAS 16293–2422 B and 67P/Churyumov–Gerasimenko

From clump to disc scales in W3 IRS4

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