arXiv subjects

M. De Simone

Publications and source records attributed to M. De Simone.

At least 19 recordsLinked to original sources

arXiv2026

Probing outflow physics through CH$_3$CN and CH$_3$OH chemistry

Chemical correlations between molecules provide powerful diagnostics to probe the physical conditions of protostellar outflows. In particular, the relationship between methanol (CH$_3$OH) and methyl cyanide (CH$_3$CN) offers a promising tool to investigate the chemistry and irradiation environment of shocked gas. In this Letter, we use the CH$_3$OH/CH$_3$CN abundance ratio to constrain the physical properties of the outflow driven by the Class 0 protostar S68N using ALMA Band 3 and Band 6 observations. Assuming local thermodynamic equilibrium (LTE), we derive excitation temperatures of 50-60 K and column densities of 2-3$\times$10$^{13}$ cm$^{-2}$ for CH$_3$CN and 3-5$\times$10$^{15}$ cm$^{-2}$ for CH$_3$OH. The resulting CH$_3$OH/CH$_3$CN abundance ratio is nearly constant along the outflow, with values of $\sim$100-200, similar to those found in other protostellar environments. Using an up-to-date astrochemical model, we test whether gas-phase formation of CH$_3$CN can account for the observed ratios. We find that they are reproduced only by assuming enhanced cosmic-ray ionization rates $\zeta_{\rm CR}$ up to $\sim$10$^{-14}$ s$^{-1}$. These results suggest that the CH$_3$OH-CH$_3$CN correlation can be used as a probe of the irradiation conditions in protostellar outflows. Further studies are required to explore the possible contribution of grain-surface formation of CH$_3$CN which could lead to a lower $\zeta_{\rm CR}$ and to extend the analysis to a larger sample of sources.

astro-ph.GA↗

arXiv2026

FAUST XXXI. Grain properties and variability of three sources in GSS 30

To advance our understanding of dust properties in class 0/I young stellar objects, it is crucial to resolve their structures at multiple wavelengths and investigate how grain growth and environmental effects shape their spectral properties. We present 0.5 arcsec resolution ALMA observations of the GSS 30 complex at 1.2-3.0 mm from the FAUST large programme, achieving a linear resolution of 69 au. We analyse the dust continuum emission and perform modelling to constrain dust properties and disk structures. For IRS3, the spectral index increases radially from 2.0 at the centre to 2.5 at the disk edge, while decreasing to 1.6-1.8 along the outflow direction. The asymmetric low-alpha region towards the northeastern blueshifted lobe may result from cold outer envelope dust obscuring warmer inner regions. SED fitting suggests maximum grain sizes of tens of microns and a dust mass of 650-1510 M_earth. IRS1 is associated with an extended north-eastern structure, which may represent an outflow-disk complex, a trailing structure linked to a circumbinary disk, or a gas streamer accreting onto IRS1. The central IRS1 shows alpha < 0.8, consistent with marginally optically thick free-free emission. IRS2 displays brightness variations over 420 s, and multi-epoch comparison suggests a flare lasting tens of minutes, likely caused by magnetic activity in the protostar. Our results highlight the importance of environmental effects, including dust obscuration and streamer structures, in shaping the observed properties of young disks, and reveal millimetre variability associated with possible protostellar magnetic flares.

astro-ph.SR↗

arXiv2026

The environmental imprint on molecular layering in the dusty streamer of M512

Protostellar streamers are elongated structures that channel material from larger scale onto disks, influencing their physical and chemical evolution. The M512 protostar in Orion/Lynds 1641 hosts one of the most massive and extended streamer discovered so far, offering a unique opportunity to study these processes. We investigate the morphology, chemistry, and origin of this streamer,and its potential impact on the protostellar disk. Using archival ALMA observations of C18O, DCO+, N2D+, and HCO+, we compare their spatial distributions through moment maps and spatial profiles. The streamer shows clear chemical stratification: C18O lies on the western side of the protostar, N2D+ is farther out to the east, and DCO+ is in the middle. This suggests that the structure has been shaped by environmental effects rather than tracing a single coherent infalling flow, with only the densest gas near the protostar likely to accrete onto the disk. Overall, the bulk of the streamer reflects the physical and chemical imprint of the surrounding cloud, highlighting the importance of environmental shaping in interpreting streamer-disk connections and their role in disk growth.

astro-ph.GA↗

arXiv2025

FAUST XXVI. The dust opacity spectral indices of protostellar envelopes bridge the gap between interstellar medium and disks

The sub-millimetre dust opacity spectral index is a critical observable to constrain dust properties, such as the maximum grain size of an observed dust population. It has been widely measured at galactic scales and down to protoplanetary disks. However, because of observational and analytical challenges, quite a gap exists in measuring dust properties in the envelopes that feed newborn protostars and their disks. To fill this gap, we use sensitive dust continuum emission data at 1.2 and 3.1 mm from the ALMA FAUST Large Program and constrain the dust opacity millimetre spectral index around a sample of protostars. Our high-resolution data, along with a more refined methodology with respect to past efforts, allow us to disentangle disk and envelope contributions in the uv-plane, and thus measure spectral indices for the envelopes uncontaminated by the optically thick emission of the inner regions. First, we find that the young disks are small and optically thick. Secondly, we measure the dust opacity spectral index at envelope scales for n=11 sources: the beta of n=9 sources had never been constrained in the literature. We effectively double the number of sources for which the dust opacity spectral index beta has been measured at these scales. Third, combining the available literature measurements with our own (total n=18), we show how envelope spectral indices distribute between ISM-like and disk-like values, bridging the gap in the inferred dust evolution. Finally, we statistically confirm a significant correlation between beta and the mass of protostellar envelopes, previously suggested in the literature. Our findings indicate that the dust optical properties smoothly vary from the ISM, through envelopes and all the way down to disks. Multi-wavelength surveys are needed to further this study and make more general claims on dust evolution in its pathway from cloud to disks.

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arXiv2025

FAUST XXIV. Large dust grains in the protostellar outflow cavity walls of the Class I binary L1551 IRS5

Planet formation around young stars requires the growth of interstellar dust grains from mm-sized particles to km-sized planetesimals. Numerical simulations have shown that large ($\sim$mm-sized) grains found in the inner envelope of young protostars could be lifted from the disc via winds. However we are still lacking unambiguous evidence for large grains in protostellar winds/outflows. We investigate dust continuum emission in the envelope of the Class I binary L1551 IRS5 in the Taurus molecular cloud, aiming to identify observational signatures of grain growth, such as variations in the dust emissivity index ($\beta_{\rm mm}$). In this context, we present new, high-angular resolution (50 au), observations of thermal dust continuum emission at 1.3 mm and 3 mm in the envelope ($\sim$3000 au) of L1551 IRS5 , obtained as part of the ALMA-FAUST Large Program. We analyse dust emission along the cavity walls of the CO outflow, extended up to $\sim$1800 au. We find an H$_2$ volume density $>2\times10^5$ cm$^{-3}$, a dust mass of $\sim$58 M$_\oplus$, and $\beta_{\rm mm}$<1, implying the presence of grains $\sim$10$^3$ times larger than the typical ISM sizes. We provide the first spatially resolved observational evidence of large grains within an outflow cavity wall. Our results suggest that these grains have been transported from the inner disc to the envelope by protostellar winds and may subsequently fall back into the outer disc by gravity and/or via accretion streamers. This cycle provides longer time for grains to grow, playing a crucial role in the formation of planetesimals.

astro-ph.GA↗

arXiv2025

FAUST XXV. A potential new molecular outflow in [BHB2007] 11

During the early stages of star formation, accretion processes such as infall from the envelope and molecular streamers, and ejection of matter through winds and jets take place simultaneously. The Class 0/I binary [BHB2007] 11 shows evidence for accretion and ejection at the scales of the circumbinary disk and the inner close binary. Recent H$_2$CO observations showed two elongated structures with hints of outflowing motion almost perpendicular to the main CO outflow, which is launched from the circumbinary disk. With the aim of verifying the nature of these elongated structures, we analyze the line emission of H$^{13}$CO$^+$, CCH, c-C$_3$H$_2$ and SiO observed with ALMA within the Large Program FAUST. These molecules trace material moving at velocities close to the ambient cloud velocity. The images of H$^{13}$CO$^+$, CCH, c-C$_3$H$_2$ show the elongated structures, whose gas kinematics are consistent with outflowing motions and with rotation in the opposite sense to the main CO outflow. The derived mass loss rate from these large-scale structures is $(1.8\pm0.5)\times10^{-6}M_{\odot}\textrm{ yr}^{-1}$, in agreement with those measured in outflows driven by Class 0/I protostars. The SiO image reveals compact emission close to the binary system, with a slight elongation aligned with the larger-scale structures. This suggests that SiO is released from the sputtering of dust grains in the shocked material at the base of the potential new outflow, with a relative abundance of $\geq(0.11-2.0)\times10^{-9}$. However, higher angular and spectral resolution observations are needed to accurately estimate the outflow launching radius and its powering source. Given the location and the abundance of the SiO emission, we propose that the second outflow may be launched from inside the circumbinary disk, likely by the less massive companion, which is actively accreting material from its surroundings.

astro-ph.GA↗

arXiv2025

SOLIS. XIX. The chemically rich SVS13-B protostellar jet

As part of the IRAM NOEMA Large Program SOLIS, we imaged the protostellar sources SVS13-A and SVS13-B in SiO, SO, CS, and CH3OH at a spatial resolution of 2"-3" (600-900 au). The CS and SO emission traces the 5000 au envelope that hosts the SVS13-A and VLA3 young stellar objects, and CH3OH probes the compact hot corino associated with SVS13-A. In addition, CS blue-shifted emission reveals a molecular shell in the direction of the jet driven by SVS13-A that is revealed by high-velocity SiO, SO and low-velocity H_2 emission. We also imaged the protostellar jet driven by SVS13-B in SiO, and in SO, CS, and CH3OH for the first time as well. The molecules peak at different distances from the driving source: SiO(2-1) peaks at about 1600 au, and SO(2_3-1_2), CS(2--1) and CH3OH(2_k,k-1_k,k) peak at about 2000-2850 au. Moreover, SiO(2-1) emits at larger distances than SiO(5--4), indicating a lower excitation at a larger distance from the protostar. The multi-species observations revealed a stratified chemical structure in the jet of SVS13-B. A jet-like component with a transversal size < 450 au is traced by SiO, which is efficiently formed in high-velocity shocks (> 25 km/s) by sputtering and vaporisation of the grain cores and mantles. A slower and wider (transversal size of about 750 au) component is probed by methanol, which is released from dust mantles at lower shock velocities (< 10 km/s). The SO and CS emission traces an intermediate component with respect to the components probed by SiO and CH3OH. High spatial resolution imaging (down to 10 au) of the jet of SVS13-B in multiple species will aid in reconstructing the chemistry of shocked material in protostellar jets.

astro-ph.SR↗

arXiv2025

FAUST-XXII. Deuteration in the VLA1623-2417 protostellar hot-corinos, cavities, and streamers

The study of deuterium fractionation is a valuable tool for reconstructing our chemical history from the early prestellar stages to the formation of planets. In the context of the ALMA Large Programme FAUST, we observed formaldehyde, H$_2$CO, and its singly and doubly deuterated forms, HDCO and D$_2$CO, towards the protostellar cluster VLA1623-2417, on scales of ~ 2000 - 50 au. Formaldehyde probes the inner envelopes of the protostars VLA1623A, B, and W, the rotating cavities opened by the VLA1623A outflow, and several streamers. The HDCO and D$_2$CO emissions are observed towards VLA1623A, in its outflow cavities, and in one of the streamers. We estimate the gas temperature from the HDCO lines: T~ 125 K towards VLA1623A, indicating hot-corino emission, lower temperatures in the outflow cavities (20 - 40 K), and in the streamers ($\le15$ K). The D$_2$CO lines also trace the flattened envelope of VLA1623A, where H$_2$CO and HDCO are fainter. This may be due to D$_2$CO formation on dust grains in the cold prestellar phase, and subsequent photodesorption caused by the enhanced UV flux from two nearby B stars. We inferred the molecular deuteration: [HDCO]/[H$_2$CO] ~ 0.16, ~ 0.07 - 0.13, and ~ 0.3; [D$_2$CO]/[H$_2$CO] ~ 0.003, ~ 0.05 - 0.13, and ~ 0.03 in the hot corino, in the outflow cavities, and in the streamer, respectively. The spatial distribution of D$_2$CO, which points to formation on dust grains, and the similar values of [HDCO]/[H$_2$CO] and [D$_2$CO]/[H$_2$CO] in the components of the system, suggest that deuterium fractionation occurs at the prestellar stage and is then inherited, mostly unaltered, in the protostellar phase.

astro-ph.SR↗

arXiv2025

FAUST XX. The chemical structure and temperature profile of the IRAS 4A2 hot corino at 20-50 au

Young low-mass protostars often possess hot corinos, compact, hot and dense regions bright in interstellar Complex Organic Molecules (iCOMs). Besides of their prebiotic role, iCOMs can be used as a powerful tool to characterize the chemical and physical properties of hot corinos. Using ALMA/FAUST data we aim to explore the iCOMs emission at < 50 au scale around the Class 0 prototypical hot corino IRAS 4A2. We imaged IRAS 4A2 in six abundant, common iCOMs (CH$_3$OH, HCOOCH$_3$, CH$_3$CHO, CH$_3$CH$_2$OH, CH$_2$OHCHO, and NH$_2$CHO), and derived their emitting size. The column density and gas temperature for each species were derived at 1$\sigma$ from a multi-line analysis by applying a non-LTE approach for CH$_3$OH, and LTE population or rotational diagram analysis for the other iCOMs. Thanks to the unique estimates of the absorption from foreground millimeter dust toward IRAS 4A2, we derived for the first time unbiased gas temperatures and column densities. We resolved the IRAS 4A2 hot corino finding evidence for a chemical spatial distribution in the inner 50 au, with the outer emitting radius increasing from ~ 22-23 au for NH$_2$CHO and CH$_2$OHCHO, followed by CH$_3$CH$_2$OH (~ 27 au), CH$_3$CHO (~ 28 au), HCOOCH$_3$ (~ 36 au), and out to ~ 40 au for CH$_3$OH. Combining our estimate of the gas temperature probed by each iCOM with their beam-deconvolved emission sizes, we inferred the gas temperature profile of the hot corino on scales of 20-50 au in radius, finding a power-law index $q$ of approximately -1. We observed, for the first time, a chemical segregation in iCOMs of the IRAS 4A2 hot corino, and derived the gas temperature profile of its inner envelope. The derived profile is steeper than when considering a simple spherical collapsing and optically-thin envelope, hinting at a partially optically-thick envelope or a gravitationally unstable disk-like structure.

astro-ph.EP↗

arXiv2024

Interaction between the Supernova Remnant W44 and the Infrared Dark Cloud G034.77-00.55: shock induced star formation?

How Supernova Remnant (SNR) shocks impact nearby molecular clouds is still poorly observationally constrained. It is unclear if SNRs can positively or negatively affect clouds star formation potential. We have studied the dense gas morphology and kinematics toward the Infrared Dark Cloud (IRDC) G034.77-00.55, shock-interacting with the SNR W44, to identify evidence of early stage star formation induced by the shock. We have used high-angular resolution N2H+(1-0) images across G034.77-00.55, obtained with ALMA. N2H+ is a well known tracer of dense and cold material, optimal to identify gas with the highest potential to harbour star formation. The N2H+ emission is distributed into two elongated structures, one toward the dense ridge at the edge of the source and one toward the inner cloud. Both elongations are spatially associated with well-defined mass-surface density features. The velocities of the gas in the two structures i.e., 38-41 km s-1 and 41-43 km s-1 are consistent with the lowest velocities of the J- and C-type parts of the SNR-driven shock, respectively. A third velocity component is present at 43-45.5 km s-1. The dense gas shows a fragmented morphology with core-like fragments of scales consistent with the Jeans lengths, masses $\sim$1-20 M$_{\odot}$, densities (n(H$_2$)$\geq$10$^5$ cm$^{-3}$) sufficient to host star formation in free-fall time scales (few 10$^4$ yr) and with virial parameters that hint toward possible collapse. The W44 driven shock may have swept up the encountered material which is now seen as a dense ridge, almost detached from the main cloud, and an elongation within the inner cloud, well constrained in both N2H+ emission and mass surface density. This shock compressed material may have then fragmented into cores that are either in a starless or pre-stellar stage. Additional observations are needed to confirm this scenario and the nature of the cores.

astro-ph.GA↗

arXiv2024

Molecular complexity of young solar analogues

How does molecular complexity emerge and evolve during the process leading to the formation of a planetary system? Astrochemistry is experiencing a golden age, marked by significant advancements in the observation and understanding of the chemical processes occurring in the inner regions of protostellar systems. However, many questions remain open, such as the origin of the chemical diversity observed in the early evolutionary stages, which may influence the chemical composition of the forming planets. Additionally, astrochemistry provides us with powerful tools to investigate the accretion/ejection processes occurring in the inner regions of young embedded objects, such as jets, winds, accretion streamers, and shocks. In this chapter, we review the observational efforts carried out in recent years to chemically characterize the inner regions of Solar-System analogs. We summarize our current understanding of molecular complexity in planet-forming disks and shed light on the existing limitations and unanswered questions. Finally, we highlight the important role of future radio facilities, like SKAO and ngVLA, in exploring the chemical complexity of the regions where planetary systems are emerging.

astro-ph.SR↗

arXiv2024

FAUST XVII: Super deuteration in the planet forming system IRS 63 where the streamer strikes the disk

Recent observations suggest that planets formation starts early, in protostellar disks of $\le10^5$ yrs, which are characterized by strong interactions with the environment, e.g., through accretion streamers and molecular outflows. To investigate the impact of such phenomena on disk physical and chemical properties it is key to understand what chemistry planets inherit from their natal environment. In the context of the ALMA Large Program Fifty AU STudy of the chemistry in the disk/envelope system of Solar-like protostars (FAUST), we present observations on scales from ~1500 au to ~60 au of H$_2$CO, HDCO, and D$_2$CO towards the young planet-forming disk IRS~63. H$_2$CO probes the gas in the disk as well as in a large scale streamer (~1500 au) impacting onto the South-East (SE) disk side. We detect for the first time deuterated formaldehyde, HDCO and D$_2$CO, in a planet-forming disk, and HDCO in the streamer that is feeding it. This allows us to estimate the deuterium fractionation of H$_2$CO in the disk: [HDCO]/[H$_2$CO]$\sim0.1-0.3$ and [D$_2$CO]/[H$_2$CO]$\sim0.1$. Interestingly, while HDCO follows the H$_2$CO distribution in the disk and in the streamer, the distribution of D$_2$CO is highly asymmetric, with a peak of the emission (and [D]/[H] ratio) in the SE disk side, where the streamer crashes onto the disk. In addition, D$_2$CO is detected in two spots along the blue- and red-shifted outflow. This suggests that: (i) in the disk, HDCO formation is dominated by gas-phase reactions similarly to H$_2$CO, while (ii) D$_2$CO was mainly formed on the grain mantles during the prestellar phase and/or in the disk itself, and is at present released in the gas-phase in the shocks driven by the streamer and the outflow. These findings testify on the key role of streamers in the build-up of the disk both concerning the final mass available for planet formation and its chemical composition.

astro-ph.EP↗

arXiv2024

FAUST XV. A disk wind mapped by CH$_3$OH and SiO in the inner 300 au of the NGC 1333 IRAS 4A2 protostar

Context. Understanding the connection between outflows, winds, accretion and disks in the inner protostellar regions is crucial for comprehending star and planet formation process. Aims. We aim to we explore the inner 300 au of the protostar IRAS 4A2 as part of the ALMA FAUST Large Program. Methods. We analysed the kinematical structures of SiO and CH$_3$OH emission with 50 au resolution. Results. The emission arises from three zones: i) a very compact and unresolved region ($<$50 au) dominated by the ice sublimation zone, at $\pm$1.5 km s$^{-1}$ with respect to vsys, traced by methanol; ii) an intermediate region (between 50 au and 150 au) traced by both SiO and CH$_3$OH, between 2 and 6 km s$^{-1}$ with respect to vsys, with an inverted velocity gradient (with respect to the large scale emission), whose origin is not clear; iii) an extended region ($>$150 au) traced by SiO, above 7 km s$^{-1}$ with respect to vsys, and dominated by the outflow. In the intermediate region we estimated a CH$_3$OH/SiO abundance ratio of about 120-400 and a SiO/H$_2$ abundance of 10$^{-8}$. We explored various possibilities to explain the origin of this region such as, rotating disk/inner envelope, jet on the plane of the sky/precessing, wide angle disk wind. Conclusions. We propose that CH$_3$OH and SiO in the inner 100 au probe the base of a wide-angle disk wind. The material accelerated in the wind crosses the plane of the sky, giving rise to the observed inverted velocity gradient, and sputtering the grain mantles and cores releasing CH$_3$OH and SiO. This is the first detection of a disk wind candidate in SiO, and the second ever in CH$_3$OH.

astro-ph.SR↗

arXiv2024

FAUST XIII. Dusty cavity and molecular shock driven by IRS7B in the Corona Australis cluster

The origin of the chemical diversity observed around low-mass protostars probably resides in the earliest history of these systems. We aim to investigate the impact of protostellar feedback on the chemistry and grain growth in the circumstellar medium of multiple stellar systems. In the context of the ALMA Large Program FAUST, we present high-resolution (50 au) observations of CH$_3$OH, H$_2$CO, and SiO and continuum emission at 1.3 mm and 3 mm towards the Corona Australis star cluster. Methanol emission reveals an arc-like structure at $\sim$1800 au from the protostellar system IRS7B along the direction perpendicular to the major axis of the disc. The arc is located at the edge of two elongated continuum structures that define a cone emerging from IRS7B. The region inside the cone is probed by H$_2$CO, while the eastern wall of the arc shows bright emission in SiO, a typical shock tracer. Taking into account the association with a previously detected radio jet imaged with JVLA at 6 cm, the molecular arc reveals for the first time a bow shock driven by IRS7B and a two-sided dust cavity opened by the mass-loss process. For each cavity wall, we derive an average H$_2$ column density of $\sim$7$\times$10$^{21}$ cm$^{-2}$, a mass of $\sim$9$\times$10$^{-3}$ M$_\odot$, and a lower limit on the dust spectral index of $1.4$. These observations provide the first evidence of a shock and a conical dust cavity opened by the jet driven by IRS7B, with important implications for the chemical enrichment and grain growth in the envelope of Solar System analogues.

astro-ph.GA↗

arXiv2024

FAUST XI: Enhancement of the complex organic material in the shocked matter surrounding the [BHB2007] 11 protobinary system

iCOMs are species commonly found in the interstellar medium. They are believed to be crucial seed species for the build-up of chemical complexity in star forming regions as well as our own Solar System. Thus, understanding how their abundances evolve during the star formation process and whether it enriches the emerging planetary system is of paramount importance. We use data from the ALMA Large Program FAUST to study the compact line emission towards the [BHB2007] 11 proto-binary system (sources A and B), where a complex structure of filaments connecting the two sources with a larger circumbinary disk has previously been detected. More than 45 CH3OCHO lines are clearly detected, as well as 8 CH3OCH3 transitions , 1 H2CCO transition and 4 t-HCOOH transitions. We compute the abundance ratios with respect to CH3OH for CH3OCHO, CH3OCH3, H2CCO, t-HCOOH (as well as an upper limit for CH3CHO) through a radiative transfer analysis. We also report the upper limits on the column densities of nitrogen bearing iCOMs, N(C2H5CN) and N(C2H3CN). The emission from the detected iCOMs and their precursors is compact and encompasses both protostars, which are separated by only 0.2" (~ 28 au). The integrated intensities tend to align with the Southern filament, revealed by the high spatial resolution observations of the dust emission at 1.3 mm. A PV and 2D analysis are performed on the strongest and uncontaminated CH3OCH3 transition and show three different spatial and velocity regions, two of them being close to 11B (Southern filament) and the third one near 11A. All our observations suggest that the detected methanol, as well as the other iCOMs, are generated by the shocked gas from the incoming filaments streaming towards [BHB2007] 11A and 11B, respectively, making this source one of the few where chemical enrichment of the gas caused by the streaming material is observed.

astro-ph.SR↗

arXiv2024

FAUST XII. Accretion streamers and jets in the VLA 1623--2417 protocluster

The ALMA interferometer has played a key role in revealing a new component of the Sun-like star forming process: the molecular streamers, i.e. structures up to thousands of au long funneling material non-axisymmetrically to disks. In the context of the FAUST ALMA LP, the archetypical VLA1623-2417 protostellar cluster has been imaged at 1.3 mm in the SO(5$_6$--4$_5$), SO(6$_6$--5$_5$), and SiO(5--4) line emission at the spatial resolution of 50 au. We detect extended SO emission, peaking towards the A and B protostars. Emission blue-shifted down to 6.6 km s$^{-1}$ reveals for the first time a long ($\sim$ 2000 au) accelerating streamer plausibly feeding the VLA1623 B protostar. Using SO, we derive for the first time an estimate of the excitation temperature of an accreting streamer: 33$\pm$9 K. The SO column density is $\sim$ 10$^{14}$ cm$^{-2}$, and the SO/H$_2$ abundance ratio is $\sim$ 10$^{-8}$. The total mass of the streamer is 3 $\times$ 10$^{-3}$ $Msun$, while its accretion rate is 3--5 $\times$ 10$^{-7}$ Msun yr$^{-1}$. This is close to the mass accretion rate of VLA1623 B, in the 0.6--3 $\times$ 10$^{-7}$ Msun yr$^{-1}$ range, showing the importance of the streamer in contributing to the mass of protostellar disks. The highest blue- and red-shifted SO velocities behave as the SiO(5--4) emission, the latter species detected for the first time in VLA1623-2417: the emission is compact (100-200 au), and associated only with the B protostar. The SO excitation temperature is $\sim$ 100 K, supporting the occurrence of shocks associated with the jet, traced by SiO.

astro-ph.SR↗

arXiv2023

Protostellar chimney flues: are jets and outflows lifting submillimetre dust grains from discs into envelopes?

Low dust opacity spectral indices ($\beta < 1$) measured in the inner envelopes of class 0/I young stellar objects (age $\sim 10^{4-5}$ yr) have been interpreted as the presence of (sub-)millimetre dust grains in these environments. The density conditions and the lifetimes of collapsing envelopes have proven unfavorable for the growth of solids up to millimetre sizes. As an alternative, magneto-hydrodynamical simulations suggest that protostellar jets and outflows might lift grains from circumstellar discs and diffuse them in the envelope. We reframe available data for the CALYPSO sample of Class 0/I sources and show tentative evidence for an anti-correlation between the value of $\beta_{1-3mm}$ measured in the inner envelope and the mass loss rate of their jets and outflows, supporting a connection between the two. We discuss the implications that dust transport from the disc to the inner envelope might have for several aspects of planet formation. Finally, we urge for more accurate measurements of both correlated quantities and extension of this work to larger samples, necessary to further test the transport scenario.

astro-ph.EP↗

arXiv2023

A Collection of German Science Interests in the Next Generation Very Large Array

The Next Generation Very Large Array (ngVLA) is a planned radio interferometer providing unprecedented sensitivity at wavelengths between 21 cm and 3 mm. Its 263 antenna element array will be spatially distributed across North America to enable both superb low surface brightness recovery and sub-milliarcsecond angular resolution imaging. The project was developed by the international astronomy community under the lead of the National Radio Astronomy Observatory (NRAO), and is anticipated to be built between 2027 and 2037. Two workshops have been held in 2022 and 2023 with the goal to discuss and consolidate the scientific interests in the ngVLA within the German astronomical community. This community paper constitutes a collection of 48 science ideas which the German community aims to pursue with the ngVLA in the 2030s. This is not a complete list and the ideas are not developed at the level of a "Science Book", such that the present document is mainly meant provide a basis for further discussion within the community. As such, additional contributions are welcome, and will be considered for inclusion in future revisions.

astro-ph.IM↗