arXiv subjects

Jaime E. Pineda

Publications and source records attributed to Jaime E. Pineda.

At least 37 records · Page 2Linked to original sources

arXiv2026

Deuterium fractionation and CO depletion in Barnard 5

Deuterium fractionation provides a key diagnostic of the physical and chemical evolution of prestellar and protostellar cores, where it is strongly linked to CO depletion in cold, dense gas. We present the first spatially resolved maps of deuterium fraction and CO depletion in the Barnard 5 (B5) region of the Perseus molecular cloud, covering both a starless core and the protostellar core hosting the Class 0/I source IRAS 03445+3242. Using IRAM 30~m observations of N$_2$H$^+$(1--0), N$_2$D$^+$(1--0), H$^{13}$CO$^+$(1--0), and DCO$^+$(2--1), complemented by C$^{18}$O(2--1) data, we derive column density, deuterium fraction, and CO depletion maps. We find that the deuterium fraction in both mentioned nitrogen- and carbon-bearing species increases from the protostellar to the starless core, reaching $R_D^{\rm N_2H^+}=0.43\pm0.10$ and $R_D^{\rm HCO^+}=0.09\pm0.02$ in the starless core, compared with $0.15\pm0.03$ and $0.05\pm0.01$, respectively, in the protostellar core. The CO depletion factor also rises from $4.1\pm0.1$ to $5.0\pm0.1$ across the same transition. While the embedded YSO reduces deuteration in the dense inner gas, the less dense envelope traced by HCO$^+$ is only slightly affected at our resolution. Our analysis confirms that CO freeze-out and the presence of a protostar jointly regulate deuterium chemistry in star-forming regions.

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arXiv2026

Unveiling the 3D structure of the central molecular zone from stellar kinematics and photometry: The 50 and 20 km/s clouds

The central molecular zone (CMZ), surrounding the Galactic centre, is the largest reservoir of dense molecular gas in the Galaxy. Despite its relative proximity, the 3D structure of the CMZ remains poorly constrained, primarily due to projection effects. We aim to constrain the line-of-sight location of two molecular clouds in the CMZ -- the 50 and 20 km/s clouds -- and to investigate their possible physical connection using stellar kinematics and photometry. This study serves as a pilot for future applications across the full CMZ. We estimated the line-of-sight position of the clouds by analysing stellar kinematics, stellar densities, and stellar populations towards the cloud regions and a control field. We find an absence of westward moving stars in the cloud regions, which indicates that they lie on the near side of the CMZ. This interpretation is supported by the stellar density distributions. The similar behaviour observed in the two clouds, as well as in the region between them (the ridge), suggests that they are located at comparable distances and are physically linked. We also identified an intermediate-age stellar population (2-7 Gyr) in both regions, consistent with that observed on the near side of the CMZ. We estimated the line-of-sight distances at which the clouds and the ridge become kinematically detectable (i.e. where the proper motion component parallel to the Galactic plane differs from that of the control field at the 3 sigma level) by converting their measured proper motions parallel to the Galactic plane using a theoretical model of the stellar distribution. We find that the 50 and 20 km/s clouds are located at $43\pm8$ pc and $56\pm11$ pc from Sgr A*, respectively, and that the ridge lies at $56\pm11$ pc; this supports the idea that the clouds are physically connected through the ridge.

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arXiv2025

First mapping of prebiotic molecule CH2NH in a pre-stellar core

We present the first spatially resolved map of methanimine CH2NH in the prestellar core L1544 using the IRAM 30m telescope. The 2$_{0,2}$-1$_{0,1}$ line at 127 GHz was mapped with 20" resolution ($\sim$2800 au), revealing extended CH2NH emission across the core. The peak line intensity coincides with the well-known c-C3H2 peak, while the integrated intensity peaks between the HNCO and dust continuum peaks due to broader linewidths in the latter region. Column densities of CH2NH are $\sim$(0.5-1.4$\times$)10$^{12}$ cm$^{-2}$, corresponding to fractional abundances of $5\times10^{-11}$-$1\times10^{-10}$, with a trend decreasing from the southern, carbon-chain rich region to the dust and HNCO peak in the north. Comparison with complementary molecular maps and the gas-grain chemical model of Sipilä et al. suggests that neutral-neutral gas-phase reactions and dissociative recombination dominate in the outer carbon-chain shell. This study demonstrates that CH2NH, a simple nitrogen- and carbon-bearing molecule previously detected with pointed observations in other cold cores, is present and spatially extended in the evolved pre-stellar core L1544. This indicates that prebiotic nitrogen-carbon chemistry continues efficiently up to the onset of gravitational collapse, providing key constraints for astrochemical models and the early stages of chemical complexity leading to amino acids.

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arXiv2025

The Green Bank Ammonia Survey: Data Release 2

We present an overview of the final data release (DR2) from the Green Bank Ammonia Survey (GAS). GAS is a Large Program at the Green Bank Telescope to map all Gould Belt star-forming regions with $A_\mathrm{V} \gtrsim 7$~mag visible from the northern hemisphere in emission from NH$_3$ and other key molecular tracers. This final release includes the data for all the regions observed: Heiles Cloud 2 and B18 in Taurus; Barnard 1, Barnard 1-E, IC348, NGC 1333, L1448, L1451, and Per7/34 in Perseus; L1688 and L1689 in Ophiuchus; Orion A (North and South) and Orion B in Orion; Cepheus, B59 in Pipe; Corona Australis (CrA) East and West; IC5146; and Serpens Aquila and MWC297 in Serpens. Similar to what was presented in GAS DR1, we find that the NH$_3$ emission and dust continuum emission from Herschel correspond closely. We find that the NH$_3$ emission is generally extended beyond the typical 0.1 pc length scales of dense cores, and we find that the transition between coherent core and turbulent cloud is a common result. This shows that the regions of coherence are common throughout different star forming regions, with a substantial fraction of the high column density regions displaying subsonic non-thermal velocity dispersions. We produce maps of the gas kinematics, temperature, and NH$_3$ column densities through forward modeling of the hyperfine structure of the NH$_3$ (1,1) and (2,2) lines. We show that the NH$_3$ velocity dispersion, $σ_v$, and gas kinetic temperature, $T_{\rm kin}$, vary systematically between the regions included in this release, with an increase in both the mean value and spread of $σ_v$ and $T_{\rm kin}$ with increasing star formation activity. The data presented in this paper are publicly available via \dataset[DOI: 10.11570/24.0091]{https://doi.org/10.11570/24.0091}.

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arXiv2025

Chemical templates of the Central Molecular Zone. Shock and protostellar object signatures under Galactic Center conditions

(Abridged) The Central Molecular Zone (CMZ) of the Milky Way exhibits extreme conditions, including high gas densities, elevated temperatures, enhanced cosmic-ray ionization rates, and large-scale dynamics. Large-scale molecular surveys reveal increasing chemical and physical complexity in the CMZ. A key step to interpreting the molecular richness found in the CMZ is to build chemical templates tailored to its diverse conditions. The combined impact of high ionization, elevated temperatures, and dense gas remains insufficiently explored for observable tracers. In this study, we utilized UCLCHEM, a gas-grain time-dependent chemical model, to link physical conditions with their corresponding molecular signatures and identify key tracers of temperature, density, ionization, and shock activity. We ran a grid of models of shocks and protostellar objects representative of typical CMZ conditions, focusing on twenty-four species, including complex organic molecules. Shocked and protostellar environments show distinct evolutionary timescales ($\lesssim 10^4$ vs. $\gtrsim 10^4$ years), with 300 K emerging as a key temperature threshold for chemical differentiation. We find that cosmic-ray ionization and temperature are the main drivers of chemical trends. HCO$^+$, H$_2$CO, and CH$_3$SH trace ionization, while HCO, HCO$^+$, CH$_3$SH, CH$_3$NCO, and HCOOCH$_3$ show consistent abundance contrasts between shocks and protostellar regions over similar temperature ranges. While our models underpredict some complex organics in shocks, they reproduce observed trends for most species, supporting scenarios involving recurring shocks in Galactic Center clouds and enhanced ionization towards Sgr B2(N2). Future work should assess the role of shock recurrence and metallicity in shaping chemistry.

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arXiv2025

CAMPOS II. The onset of protostellar disk substructures and planet formation

The 1.3 mm CAMPOS survey has resolved 90 protostellar disks with ~15 au resolution across the Ophiuchus, Corona Australis, and Chamaeleon star-forming regions. To address the fundamental question, `When does planet formation begin?', we combined the CAMPOS sample with literature observations of Class 0-II disks (bolometric temperature, $T_{bol} \le 1900 K$). To investigate substructure detection rates as a function of $T_{bol}$, we restricted the sample to disks observed at the 1.3 mm wavelength, with inclinations below 75$^\circ$, linear resolution $\le 20$ au and resolved with at least 4 resolution elements ($θ_{disk}/θ_{res} \ge 4$). We also considered the effects of extinction correction and the inclusion of Herschel Space Telescope data on the $T_{bol}$ measurements to constrain the lower and upper limits of $T_{bol}$ for each source. We find that by $T_{bol}$ ~200-400 K, substructure detection rates increased sharply to ~60%, corresponding to an age of ~0.2-0.4 Myr. No substructures are detected in Class 0 disks. The ratio of disk-averaged brightness temperature to predicted dust temperature shows a trend of increasing values toward the youngest Class 0 disks, suggesting higher optical depths in these early stages. Our statistical analysis confirms that substructures similar to those in Class II disks are already common by the Class I stage, and the emergence of structures at early Class I could represent only an upper limit. Classifying disks with substructures into those with and without large central cavities, we find both populations coexisting across evolutionary stages, suggesting they are not necessarily evolutionarily linked. If protostellar disk substructures do follow an evolutionary sequence, then our results imply that disk substructures evolve very rapidly and thus can be present in all Class I/II stages and/or that they can be triggered at different times.

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arXiv2025

Circum-nuclear eccentric gas flow in the Galactic Center revealed by ALMA CMZ Exploration Survey (ACES)

We analyze the CS (J=2-1) line cube from the internal data release obtained by the large-scale program "ALMA CMZ Exploration Survey (ACES)" to investigate the kinematic structure of the innermost $\sim 10$ pc region of the Galaxy, which contains the high-velocity compact cloud (HVCC) at $(l,b,v_{\rm lsr})\sim(+0^\circ.02,-0^\circ.02, 100 {\rm km~s}^{-1})$ (hereafter G0.02). The longitude-velocity diagram (LVD) of the cloud draws an elliptical structure, which is interpreted as an orbital trajectory in the $(l,V_{\rm lsr})$ space of a noncircular (eccentric) motion of the molecular gas in the gravitational potential of an extended mass distribution in the central 10 pc of the Galaxy. We argue that G0.02 is a kinematic tracer of the inner potential, a rare case of a dense gas following an eccentric orbit in the nuclear gravitational field.

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arXiv2025

Asymmetric accretion through a streamer onto the pre-stellar core H-MM1

CONTEXT: Dense cores are thought to be isolated from the surrounding cloud. However, observations of streamers and subsonic material outside core boundaries challenges this idea. AIMS: In this study, we aim to probe the extended subsonic region observed around the pre-stellar core H-MM1 in L1688 using multi-component kinematical analysis of very high-sensitivity NH3 data. METHODS: We used observations of NH3 (1,1) and (2,2) using GBT. We then fitted up to two components towards the core and its surrounding molecular cloud. RESULTS: We detect an extended region of subsonic turbulence in addition to the ambient cloud, which show supersonic turbulence. This extended subsonic region is approximately 12 times the size of and more than two times as massive as the previously detected subsonic material. The subsonic region is further split into two well-separated, velocity-coherent components, one of which is kinematically and spatially connected to the dense core. The two subsonic components are red- and blue-shifted with respected to the cloud component. We also detect a flow of material onto the dense core from the extended subsonic region via a streamer of length ~0.15 pc (~30000 au). CONCLUSIONS: We find that the extended subsonic component kinematically associated with the dense core contains 27% more mass than the core. This material could be further accreted by the core. The other subsonic component contains a mass similar to that of the core mass, and could be tracing material in the early stage of core formation. The H-MM1 streamer is kinematically similar to the ones observed towards protostellar systems, but is the first instance of such an accretion feature onto a core in its pre-stellar phase. This accretion of chemically fresh material by the pre-stellar core challenges our current understanding of a core evolving with a mass unchanged since the time of its formation.

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arXiv2025

Mapping the merging zone of late infall in the AB Aur planet-forming system

Late infall events challenge the traditional view that planet formation occurs without external influence. Here we present deep ALMA $^{12}$CO $J=2-1$ and SO $J_{N}=5_6-4_5$ observations toward AB Aurigae, a Class II disk system with strong signs of gravitational instability and ongoing planet formation. By applying Keplerian and anti-Keplerian masks, we separate disk-like and non-disk-like motions of $^{12}$CO, considering the two outputs as the 'disk' and 'exo-disk' (out of disk) emission components, respectively. The disk component of $^{12}$CO extends to $\sim 1600$ au in radius and exhibits a stunningly rich architecture of global spiral structure. The exo-disk emission consists predominantly of three spiral structures -- S1, S2 and S3 -- whose projections are co-spatial with the disk. We successfully reproduce their trajectories with a ballistic accretion flow model, finding that S1 and S2 (both redshifted) are infalling toward the disk from in front, and S3 (blueshifted) is infalling from behind. Where the terminal ends of S1 and S2 become indistinguishable from the disk, we observe a brightness peak in SO emission $2.5\times$ the azimuthal average of a background SO ring. This merging zone lies within a relatively confined region $15-100$ degrees east of north, and between $\sim150-300$ au from the star, at scales relevant to where planet candidates have been previously identified. The AB Aur system provides a unified picture of late infall inducing replenishment of the disk, triggering gravitational instability, and modifying the conditions of forming planets.

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arXiv2025

Characterising the multiple protostellar system VLA 1623-2417 with JWST, ALMA and VLA: outflow origins, dust growth and an unsettled disk

Utilising JWST, ALMA and the VLA we present high angular resolution (0.06''- 0.42''), multi-wavelength (4 micron - 3cm) observations of the VLA 1623-2417 protostellar system to characterise the origin, morphology and, properties of the continuum emission. JWST observations at 4.4 micron reveal outflow cavities for VLA 1623 A and, for the first time, VLA 1623 B, as well as scattered light from the upper layers of the VLA 1623 W disk. We model the millimetre-centimetre spectral energy distributions to quantify the relative contributions of dust and ionised gas emission, calculate dust masses, and use spectral index maps to determine where optical depth hinders this analysis. In general, all objects appear to be optically thick down to ~90 GHz, show evidence for significant amounts (10's - 100's M_Earth) of large (>1 mm) dust grains, and are dominated by ionised gas emission for frequencies ~<15 GHz. In addition, we find evidence of unsettled millimetre dust in the inclined disk of VLA 1623 B possibly attributed to instabilities within the circumstellar disk, adding to the growing catalogue of unsettled Class 0/I disks. Our results represent some of the highest resolution observations possible with current instrumentation, particularly in the case of the VLA. However, our interpretation is still limited at low frequencies (~<22 GHz) and thus motivates the need for next-generation interferometers operating at centimetre wavelengths.

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arXiv2024

Filament Accretion and Fragmentation in the Perseus Molecular Cloud

Observations suggest that filaments in molecular clouds can grow by mass accretion while forming cores via fragmentation. Here we present one of the first large sample studies of filament accretion using velocity gradient measurements of star-forming filaments on the $\sim 0.05$ pc scale with NH$_3$ observations of the Perseus Molecular Cloud, primarily obtained as a part of the GBT Ammonia Survey (GAS). In this study, we find significant correlations between velocity gradient, velocity dispersion, mass per unit length, and the number of cores per unit length of the Perseus filaments. Our results suggest a scenario in which filaments not only grow through mass accretion but also form new cores continuously in the process well into the thermally supercritical regime. Such behavior is contrary to that expected from isolated filament models but consistent with how filaments form within a more realistic cloud environment, suggesting that the cloud environment plays a crucial role in shaping core formation and evolution in filaments. Furthermore, even though velocity gradients within filaments are not oriented randomly, we find no correlation between velocity gradient orientation and the filament properties we analyzed. This result suggests that gravity is unlikely the dominant mechanism imposing order on the $\sim 0.05$ pc scale for dense star-forming gas.

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arXiv2024

The ALMA Legacy survey of Class 0/I disks in Corona australis, Aquila, chaMaeleon, oPhiuchus north, Ophiuchus, Serpens (CAMPOS). I. Evolution of Protostellar disk radii

We surveyed nearly all the embedded protostars in seven nearby clouds (Corona Australis, Aquila, Chamaeleon I & II, Ophiuchus North, Ophiuchus, Serpens) with the Atacama Large Millimeter/submillimeter Array at 1.3mm observations with a resolution of 0.1$"$. This survey detected 184 protostellar disks, 90 of which were observed at a resolution of 14-18 au, making it one of the most comprehensive high-resolution disk samples across various protostellar evolutionary stages to date. Our key findings include the detection of new annular substructures in two Class I and two flat-spectrum sources, while 21 embedded protostars exhibit distinct asymmetries or substructures in their disks. We find that protostellar disks have a substantially large variability in their radii across all evolutionary classes. In particular, the fraction of large disks with sizes above 60\,au decreases as the protostar evolves from Class 0 to Class I. Compiling the literature data, we discovered an increasing trend of the gas disk radii to dust disk radii ratio ($R_{\rm gas,Kep}/R_{\rm mm}$) with increasing bolometric temperature (${\rm T}_{\rm bol}$). Our results indicate that the dust and gas disk radii decouple during the early Class I stage. However, in the Class 0 stage, the dust and gas disk sizes are similar, which allows a direct comparison between models and observational data at the earliest stages of protostellar evolution. We show that the distribution of radii in the 52 Class 0 disks in our sample is in high tension with various disk formation models, indicating that protostellar disk formation remains an unsolved question.

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arXiv2024

Probing the Physics of Star-Formation (ProPStar) III. No evidence for dissipation of turbulence down to 20 mpc (4 000 au) scale

Context. Turbulence is a key component of molecular cloud structure. It is usually described by a cascade of energy down to the dissipation scale. The power spectrum for subsonic incompressible turbulence is $k^{-5/3}$, while for supersonic turbulence it is $k^{-2}$. Aims. We aim to determine the power spectrum in an actively star-forming molecular cloud, from parsec scales down to the expected magnetohydrodynamic (MHD) wave cutoff (dissipation scale). Methods. We analyze observations of the nearby NGC 1333 star-forming region in three different tracers to cover the different scales from $\sim$10 pc down to 20 mpc. The largest scales are covered with the low density gas tracer $^{13}$CO (1-0) obtained with single dish, the intermediate scales are covered with single-dish observations of the C$^{18}$O (3-2) line, while the smallest scales are covered in H$^{13}$CO$^+$ (1-0) and HNC (1-0) with a combination of NOEMA interferometer and IRAM 30m single dish observations. The complementarity of these observations enables us to generate a combined power spectrum covering more than two orders of magnitude in spatial scale. Results. We derive the power spectrum in an active star-forming region spanning more than 2 decades of spatial scales. The power spectrum of the intensity maps shows a single power-law behavior, with an exponent of 2.9$\pm$0.1 and no evidence of dissipation. Moreover, there is evidence for the power-spectrum of the ions to have more power at smaller scales than the neutrals, which is opposite from theoretical expectations. Conclusions. We show new possibilities of studying the dissipation of energy at small scales in star-forming regions provided by interferometric observations.

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arXiv2024

The Evolution of Protostellar Outflow Opening Angles and the Implications for the Growth of Protostars

We use 1-4" (300-1200 au) resolution 12CO(2-1) data from the MASSES (Mass Assembly of Stellar Systems and their Evolution with the SMA) project to measure the projected opening angles of 46 protostellar outflows in the Perseus Molecular Cloud, 37 of which are measured with sufficiently high confidence to use in further analysis. We find that there is a statistically significant difference in the distributions of outflow opening angles for Class 0 and Class I outflows, with a distinct lack of both wide-angle Class 0 outflows and highly collimated Class I outflows. Synthesizing our results with several previous studies, we find that outflows widen with age through the Class 0 stage but do not continue to widen in the Class I stage. The maximum projected opening angle reached is approximately 90 degrees +/- 20 degrees, with the transition between widening and remaining constant occurring near the boundary between the Class 0 and Class I phases of evolution. While the volume fractions occupied by these outflows are no more than a few tens of percent of the total core volume, at most, recent theoretical work suggests outflows may still be capable of playing a central role in setting the low star formation efficiencies of 25%-50% observed on core scales.

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arXiv2024

A low cosmic-ray ionisation rate in the prestellar core Ophiuchus/H-MM1. Mapping of the molecular ions ortho-H2D+, N2H+, and DCO+

(abridged) We have mapped the prestellar core H-MM1 in Ophiuchus in rotational lines of ortho-H2D+ (oH2D+), N2H+, and DCO+ at the wavelength 0.8 mm with the Large APEX sub-Millimeter Array (LAsMA) multibeam receiver of the Atacama Pathfinder EXperiment (APEX) telescope. We also ran a series of chemistry models to predict the abundance distributions of the observed molecules, and to estimate the effect of the cosmic-ray ionisation rate on their abundances. The three line maps show different distributions. The oH2D+ map is extended and outlines the general structure of the core, while N2H+ mainly shows the density maxima, and the DCO+ emission peaks are shifted towards one edge of the core where a region of enhanced desorption has been found previously. According to the chemical simulation, the fractional oH2D+ abundance remains relatively high in the centre of the core, and its column density correlates strongly with the cosmic-ray ionisation rate. Simulated line maps constrain the cosmic-ray ionisation rate per hydrogen molecule to be low, between 5e-18/s and 1e-17/s in the H-MM1 core. This estimate agrees with the gas temperature measured in the core. Modelling line emission of oH2D+ provides a straightforward method of determining the cosmic-ray ionisation rate in dense clouds, where the primary ion, H3+, is not observable.

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arXiv2024

On the magnetic field properties of protostellar envelopes in Orion

We present 870 um polarimetric observations toward 61 protostars in the Orion molecular clouds, with ~400 au (1") resolution using the Atacama Large Millimeter/submillimeter Array. We successfully detect dust polarization and outflow emission in 56 protostars, in 16 of them the polarization is likely produced by self-scattering. Self-scattering signatures are seen in several Class 0 sources, suggesting that grain growth appears to be significant in disks at earlier protostellar phases. For the rest of the protostars, the dust polarization traces the magnetic field, whose morphology can be approximately classified into three categories: standard-hourglass, rotated-hourglass (with its axis perpendicular to outflow), and spiral-like morphology. 40.0% (+-3.0%) of the protostars exhibit a mean magnetic field direction approximately perpendicular to the outflow on several 100--1000 au scales. However, in the remaining sample, this relative orientation appears to be random, probably due to the complex set of morphologies observed. Furthermore, we classify the protostars into three types based on the C17O (3--2) velocity envelope's gradient: perpendicular to outflow, non-perpendicular to outflow, and unresolved gradient (<1.0~km/s/arcsec). In protostars with a velocity gradient perpendicular to outflow, the magnetic field lines are preferentially perpendicular to outflow, most of them exhibit a rotated hourglass morphology, suggesting that the magnetic field has been overwhelmed by gravity and angular momentum. Spiral-like magnetic fields are associated with envelopes having large velocity gradients, indicating that the rotation motions are strong enough to twist the field lines. All of the protostars with a standard-hourglass field morphology show no significant velocity gradient due to the strong magnetic braking.

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arXiv2024

A broad linewidth, compact, millimeter-bright molecular emission line source near the Galactic Center

A compact source, G0.02467-0.0727, was detected in ALMA \threemm observations in continuum and very broad line emission. The continuum emission has a spectral index $α\approx3.3$, suggesting that the emission is from dust. The line emission is detected in several transitions of CS, SO, and SO$_2$ and exhibits a line width FWHM $\approx160$ \kms. The line profile appears Gaussian. The emission is weakly spatially resolved, coming from an area on the sky $\lesssim1"$ in diameter ($\lesssim10^4$ AU at the distance of the Galactic Center; GC). The centroid velocity is $v_{LSR}\approx40$-$50$ \kms, which is consistent with a location in the Galactic Center. With multiple SO lines detected, and assuming local thermodynamic equilibrium (LTE) conditions, $T_\mathrm{LTE} = 13$ K, which is colder than seen in typical GC clouds, though we cannot rule out low-density, subthermally excited, warmer gas. Despite the high velocity dispersion, no emission is observed from SiO, suggesting that there are no strong ($\gtrsim10~\mathrm{km~s}^{-1}$) shocks in the molecular gas. There are no detections at other wavelengths, including X-ray, infrared, and radio. We consider several explanations for the Millimeter Ultra-Broad Line Object (MUBLO), including protostellar outflow, explosive outflow, collapsing cloud, evolved star, stellar merger, high-velocity compact cloud, intermediate mass black hole, and background galaxy. Most of these conceptual models are either inconsistent with the data or do not fully explain it. The MUBLO is, at present, an observationally unique object.

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arXiv2024

Probing the Physics of Star-Formation (ProPStar): II. The first systematic search for streamers toward protostars

The detection of narrow channels of accretion toward protostellar disks, known as streamers, have increased in number in the last few years. However, it is unclear if streamers are a common feature around protostars that were previously missed, or if they are a rare phenomenon. Our goals are to obtain the incidence of streamers toward a region of clustered star formation and to trace the origins of their gas, to determine if they originate within the filamentary structure of molecular clouds or from beyond. We used combined observations of the nearby NGC 1333 star-forming region, carried out with the NOEMA interferometer and the IRAM 30m single dish. Our observations cover the area between the IRAS 4 and SVS 13 systems. We traced the chemically fresh gas within NGC 1333 with HC3N molecular gas emission and the structure of the fibers in this region with N2H+ emission. We fit multiple velocity components in both maps and used clustering algorithms to recover velocity-coherent structures. We find streamer candidates toward 7 out of 16 young stellar objects within our field of view. This represents an incidence of approximately 40\% of young stellar objects with streamer candidates when looking at a clustered star forming region. The incidence increases to about 60\% when we considered only embedded protostars. All streamers are found in HC3N emission. Given the different velocities between HC3N and N2H+ emission, and the fact that, by construction, N2H+ traces the fiber structure, we suggest that the gas that forms the streamers comes from outside the fibers. This implies that streamers can connect cloud material that falls to the filaments with protostellar disk scales.

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