Taurus Molecular Cloud Research Articles

Indene is among the first polycyclic aromatic hydrocarbon (PAH) species detected in the gas phase in the Taurus molecular cloud (TMC-1), with high abundances for such a complex organic molecule (COM). Considering the conditions of these dense clouds, and the timescales of the processes at play, there have to be mechanisms driving the desorption of molecules to maintain a high level of gas phase species; otherwise, most of them should condense on dust grains when approaching the cloud core. On the other hand, detections of diamond features in young stellar objects have been reported, sparking interest in diamondoid species such as the cage molecule adamantane. We investigate and quantify the importance of cosmic rays in the sputtering and radiolysis of COMs such as indene and adamantane and the potential release of species from the solid phase. )Fe(^ ) ion beam at the heavy-ion accelerator Grand Accélérateur National d'Ions Lourds (GANIL; Caen, France). Both infrared and quadrupole mass spectrometer measurements were recorded simultaneously throughout the irradiation, enabling the sputtering efficiencies and the radiolysis cross sections of the species to be determined. The intact-to-solid sputtered ratios and the radiolysis cross sections of indene and adamantane were determined. By combining these results with astrophysical models, the expected fraction of indene in the solid phase that would be required to explain the gas phase abundance by this process was calculated with respect to the depth in the cloud and compared to current gas phase abundances observed in TMC-1.

Abstract Observing and characterizing pre- and protostellar cores in the earliest and densest stages of star formation is challenging due to their short timescales and high densities, limiting the suitable tracers and targets. We conducted Atacama Large Millimeter/submillimeter Array-Atacama Compact Array standalone observations of ortho-H2D+ (11,0–11,1) emission, which is believed to trace cold high-density regions, toward three dense cores in the Taurus molecular cloud: (1) L1544, likely in the densest prestellar phase; (2) MC 35 mm, a candidate for the first hydrostatic core; and (3) MC 27/L1521F, which hosts a Class 0 very-low-luminosity object. These observations provide high angular resolution data for the line across a set of cores selected to represent consecutive stages around the onset of star formation, offering a unique opportunity to trace the time evolution of ∼104 yr. With the single-dish total-power array, we detected ortho-H2D+ emission in all three cores, revealing its presence over scales of ∼10,000 au. In the interferometric 7 m array data with a beam size of 3 . ″ 5 (∼500 au), emission was detected only toward the central continuum source of MC 35 mm, with a significance of ∼3σ. No significant detections were found in the other targets, placing an upper limit on the H2D+ abundance of ∼10−11 in the dense components traced by the interferometric continuum emission. These results suggest that ortho-H2D+ predominantly exhibits an extended distribution over several thousand au in the early stages of star formation. Detection in compact, dense central structures may only be achieved within a few ×104 yr immediately before or after protostar formation.

Context. Diffuse interstellar bands (DIBs) are absorption features in the optical-to-near-infrared spectra of stars and they are associated with interstellar medium (ISM) carriers. They are valuable in studying the ISM, offering insights into its physical and chemical conditions, while tracing the distribution and kinematics of interstellar material. Aims. We employed DIB λ6614 as a tracer to probe the distances and spatial distributions of interstellar material in the Perseus, Taurus, and Orion molecular clouds. These key star-forming regions in the solar neighborhood were analyzed to evaluate the feasibility and limitations of using DIB λ6614 as a tracer for distance and kinematic measurements. Methods. We obtained stellar spectra from the Large Sky Area Multi-Object Fiber Spectroscopic Telescope medium-resolution survey within 600 pc. For hot stars (Teff ≥ 7500 K), DIB λ6614 was directly measured due to minimal contamination by stellar lines near the wavelength of 6614 Å. For cool stars (Teff < 7500 K), a template subtraction method was applied to isolate the ISM spectrum. Molecular cloud boundaries were identified based on 12CO emission maps integrated over velocity ranges, with 315, 684, 281, and 275 sources selected for Perseus, Taurus, Orion A, and Orion B, respectively. Results. The DIB λ6614-derived distances to the molecular clouds are 297.2 ± 1.7 pc, 150.2 ± 1.2 pc, 421. 1 ± 0.7 pc, and 409.8 ± 0.7 pc for Perseus, Taurus, Orion A, and Orion B, respectively. These results are consistent with extinction-based distances, with discrepancies of 3–15 pc. In Perseus, two significant jumps in DIB λ6614 equivalent width are detected along the distance direction, with the first at ~152 pc, likely corresponding to the boundary of the Local Bubble. Conclusions. DIB λ6614 is a robust tracer for molecular cloud distances, with estimates closely matching extinction-based measurements. DIB λ6614 is particularly effective for tracing diffuse regions and provides complementary insights into the structural details of molecular clouds.

black Pre-stellar cores are centrally concentrated starless cores on the verge of star formation and they represent the initial conditions for star and planet formation. Pre-stellar cores host an active organic chemistry and isotopic fractionation, kept stored in thick icy mantles, that can be inherited by the future protoplanetary disks and planetesimals. It is therefore important to study pre-stellar cores, but this is difficult as they are short-lived, and thus rare. So far, only a few pre-stellar cores have been studied in detail, with special attention being paid to the prototypical pre-stellar core L1544 in the Taurus Molecular Cloud. black Our aim is to identify nearby ($<$200,pc) pre-stellar cores in an unbiased way, to build a sample that can then be studied in detail. This will also allow us to explore the effect of the environment on the chemical and physical structure of pre-stellar cores. black We first used the archival Herschel Gould Belt Survey data, selecting all those starless cores with central H_2 number densities higher than or equal to 3times10^5 the density of L1544 within the Herschel beam of 20 The selected 40 (out of 1746) cores were then observed in and using the APEX antenna. black Following a simple analysis, a total of 17 bona fide (i.e., with a deuterium fraction larger than 10%) pre-stellar cores have been identified. Another 16 objects can also be considered pre-stellar, as they are dynamically evolved starless cores, but their deuterium fractions is relatively low ($<$10%); thus, they deserve further scrutiny to unveil the source of the low deuteration. Of the remaining seven objects, six have been found to be associated with a young stellar object, and one (CrA,151) presents hints of a very young (or very low-luminosity) stellar object. black Dust continuum emission, together with spectroscopic observations of and is a powerful tool to identify pre-stellar cores in molecular clouds. Detailed modeling of the physical structure of the objects is now required to reconstruct the chemical composition as a function of radius. This work has provided a statistically significant sample of 33 pre-stellar cores, a crucial step in the understanding of the process of star and planet formation.

Abstract The phenyl derivative of ketene, phenylketene (C6H5CHCO), can be considered as a candidate to be observed in the Taurus Molecular Cloud TMC-1. However, due to its high reactivity, there has been no microwave spectroscopic research conducted on it, nor has there been any radioastronomical search for it. In order to enable the interstellar search of phenylketene in TMC-1, in this study, its microwave spectrum was characterized in the laboratory. Gas phase phenylketene was generated by pulsed discharge of mixture of ethynylbenzene (C6H5CCH) and O2, and its rotational signatures were measured using a chirped pulse Fourier transform microwave (CP-FTMW) spectrometer. By assigning 90 pure rotational transitions of phenylketene in the 8-16 GHz range, we obtained accurate rotational constants, enabling broader spectral predictions in high frequency range for interstellar exploration. Discharge microwave spectrum of 18O2 and other oxygen-containing small molecules, in addition to dioxygen, were also measured to validate the discharge products. Subsequently, we searched for phenylketene molecule in TMC-1, but did not detect it. The upper limit to its abundance in this source was derived.

Unsaturated nitriles are significant in prebiotic andastrochemistry.Dicyanoacetylene, in particular, is a possible precursor of uraciland was previously detected in Titan’s atmosphere. Its nulldipole moment hindered detection through rotational spectroscopy ininterstellar clouds, and it escaped identification until recently,when its protonated form NC4NH+ was finallydetected toward the Taurus molecular cloud (TMC-1) (Agúndezet al., Astronom. Astrophys. 2023, 669, L1). Given thelow-temperature conditions of both Titan and TMC-1, a facile formationroute must be available. Low-temperature kinetics experiments andtheoretical characterization of the entrance channel demonstratedthat the CN + HC3N reaction is a compelling candidate forNC4N formation in cold clouds. Here, we report on a combinedcrossed-molecular beams (CMB) and theoretical study of the reactionmechanism up to product formation, demonstrating that NC4N + H is the sole open channel from low to high temperatures (collisionenergies). Indeed, unlike other CN reactions, the formation of theisocyano isomer (3-isocyano-2-propynenitrile) was not seen to occurat the high collision energy (44.8 kJ/mol) of the CMB experiment.Preliminary calculations on the related CN + HC5N reactionindicate that the reaction channel leading to NC6N + His exothermic and occurs via submerged transition states. We thereforeexpect it to be fast and that the mechanism is generalizable to theentire family of CN +cyanopolyyne reactions. Furthermore, we derivesome properties of the related reactions C2H + CNCN (isocyanogen)and CN + HCCNC (isocyanoacetylene): the C2H + CNCN reactionleads to the formation of HC3N + CN, and the main channelof the CN + HCCNC reaction also leads to CN + HC3N. Thislast reaction efficiently converts isocyanoacetylene and, by extension,any isocyanopolyyne into their cyano counterparts without a net lossof cyano radicals. Finally, we also characterized the entrance channelof the reaction C2H + NC4N and verified thatthe addition of C2H to all possible sites of NC4N is characterized by a significant entrance barrier, thus confirmingthat, once formed, dicyanoacetylene terminates the growth of cyanopolyynesvia the sequence of steps involving polyynes, cyanopolyynes, and C2H/CN radicals.

The disparity between predicted sulfur abundances and identified reservoirs of sulfur in cold molecular clouds, also known as the sulfur depletion problem, has remained an ongoing debate over decades. Here, we show in laboratory simulation experiments that hydrogen sulfide (H2S) can be converted on ice-coated interstellar grains in cold molecular clouds through galactic cosmic rays processing at 5 K to sulfanes (H2Sn; n = 2–11) and octasulfur (S8). This locks the processed hydrogen sulfide as high-molecular weight sulfur-containing molecules thus providing a plausible rationale for the fate of the missing interstellar sulfur. These sulfuretted molecules may undergo fractionated sublimation once the molecular cloud transforms into star forming regions. The isomeric identification of octasulfur rings (S8) coincides with the recent identification of elementary sulfur in the carbonaceous asteroid (162173) Ryugu, thus providing compelling evidence on the link between sulfur in cold molecular clouds and in our Solar System with, e.g., the Taurus Molecular Cloud (TMC) potentially accumulating an equivalent of 350 Earth masses of octasulfur.

Context. Cold, dense cores are unique among structures found in the interstellar medium, as they harbor a rich chemical inventory, including complex organic molecules (COMs), which future evolutionary stages, such as protostellar envelopes and protoplanetary disks, will inherit. These molecules exist both in the gas phase and as ices accreted onto grain surfaces. Aims. To model these environments, we present PEGASIS: a new, fast, and extensible three-phase astrochemical code designed to explore the chemistry of cold cores, with an emphasis on the role of diffusive and nondiffusive chemistry in shaping their gas and grain chemical compositions. Methods. We incorporate the latest developments in interstellar chemistry modeling by utilizing the 2024 Kinetic Database for Astrochemistry chemical network and comparing our results with current state-of-the-art astrochemical models. Using a traditional rate-equation-based approach, we implement both diffusive and nondiffusive chemistry, coupled with either an inert or a chemically active ice mantle. Results. We identify crucial reactions that enhance the production of COMs through nondiffusive mechanisms on the grain surface, as well as the mechanisms through which they can accumulate in the gas phase. Across all models with nondiffusive chemistry, we observe a clear enhancement in the concentration of COMs on both the grain surface and in the grain mantle. Finally, our model broadly reproduces the observed abundances of multiple gas-phase species for the Taurus Molecular Cloud (TMC-1) and provides insights into its chemical age. Conclusions. Our work demonstrates the capabilities of PEGASIS in exploring a wide range of grain surface chemical processes and modeling approaches for three-phase chemistry in the interstellar medium, providing robust explanations for observed abundances in cold cores, such as TMC-1 (CP). In particular, it highlights the role of nondiffusive chemistry in the production of gas-phase COMs on grain surfaces, which are subsequently chemically desorbed, especially when the precursors involved in their formation on the surfaces are heavier than atomic hydrogen.

Abstract New measurements of nitrosomethane (CH3NO), a formamide isomer, were done up to 660 GHz. The molecule exhibits internal rotation motion from the CH3 group, and therefore the analysis with a dedicated rho-axis method code, RAM36, was used. A total of 2035 lines for v t = 0 and 1 states of A and E symmetries were fitted with an rms deviation of 41.1 kHz, with the maximum quantum numbers values J = 30 and K a = 15. Using these new data, CH3NO was searched in the cold dark cloud Taurus Molecular Cloud 1 as well as the high mass star-forming regions Sgr B2(N) and NGC 6334I. CH3NO was not observed in any of the sources, 3σ column density upper limits were determined, and we discuss the implications for the chemistry of CH3NO in the interstellar medium. The accurate spectroscopic prediction of its spectra provided in this work will allow astronomers to continue the search of CH3NO in other interstellar sources.

Several small polycyclic aromatic hydrocarbons (PAHs) with closed-shell electronic structure have been identified in the cold, dark environment Taurus Molecular Cloud 1. We measure efficient radiative cooling through the combination of recurrent fluorescence (RF) and IR emission in the closed-shell indenyl cation (C_{9}H_{7}^{+}), finding good agreement with a master equation model including molecular dynamics trajectories to describe internal-energy-dependent properties for RF. We find that C_{9}H_{7}^{+} formed with up to E_{c}=5.85 eV vibrational energy, which is ≈2 eV above the dissociation threshold, radiatively cool rather than dissociate. The efficient radiative stabilization dynamics are likely common to other closed-shell PAHs present in space, contributing to their abundance.

Context. Planet formation around young stars requires the growth of interstellar dust grains from micron-sized (μm-sized) particles to kilometre-sized (km-sized) planetesimals. Numerical simulations have shown that large (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 and outflows. Aims. We investigated 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 (βmm). Methods. 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 (∼3000 au) of L1551 IRS5, obtained as part of the ALMA-FAUST Large Program. Results. We analysed dust emission along the cavity walls of the CO outflow, extended up to ∼1800 au. We found an H2 volume density > 2 × 105 cm−3, a dust mass of ∼58 M⊕, and βmm ≲ 1, implying the presence of grains ∼103 times larger than typical sizes for the interstellar medium (ISM). Conclusions. We present 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, demonstrating their crucial role in the formation of planetesimals.

Abstract Machine learning pipelines for astrochemical inventories have been introduced as a useful addition to the astrochemist toolbox, having first been used to model and predict column densities in the Taurus Molecular Cloud (TMC-1). Rapid changes in the field of machine learning have provided new tools in optimizing this pipeline, including improved vector representations. Furthermore, the addition of new detections since the original model allows for a retrospective analysis of model performance, in addition to new data for the model. This study revisits TMC-1, investigating both effects of an increased detection inventory on the model and changes to various portions of the pipeline, yielding a significant improvement in column density predictions. Through these comparisons, we attempt to derive insight into the ultimate effectiveness of these models, as well as their current limitations and words of caution in their use and interpretation. Finally, we provide suggestions for future machine learning of interstellar sources.

Abstract We report JWST MIRI/MRS observations of the H2 S(1) 17.04 μm transition in two regions in the boundary of the Taurus molecular cloud. The two regions, denoted “Edge” (near the relatively sharp boundary of the 13CO J = 1 → 0 emission) and “Peak” (the location of the strongest H2 emission observed with Spitzer), have average intensities of 14.5 and 32.1 MJy sr−1, respectively. We find small-scale structures of characteristic size 1 . ″ 0–2 . ″ 5, corresponding to 140–350 au, with characteristic intensity above the extended background of 10 MJy sr−1, corresponding to a J = 3 column density of 1.6 × 1017 cm−2. The most plausible explanation for the observed intensities from this level 845 K above the J = 1 ortho-H2 ground-state level is excitation by collisions with H2 molecules (the hydrogen in this region being predominantly molecular). Two mechanisms, turbulent dissipation and shocks, have been proposed for the heating of localized regions of the interstellar medium (ISM) to temperatures ≃1000 K to explain abundances of and emission from particular molecules. While we cannot determine unique values of density and kinetic temperature, the solutions in best agreement with predictions of shock models are n(H2) = 370 cm−3 and T kin = 1000 K. The total H2 column density of the small-scale structures under these conditions is ≃8 × 1017 cm−2. This first direct detection of significantly heated tiny-scale structures in the quiescent molecular ISM has significant implications for the physical structure of this phase of the ISM and the maintaining of supersonic motions within it.

Context. Substellar objects, including brown dwarfs and free-floating planetary-mass objects, are a significant product of star formation. Their sensitivity to initial conditions and early dynamical evolution makes them especially valuable for studying planetary and stellar formation processes. Aims. We search for brown dwarfs and isolated planetary mass objects in a young star-forming region to better constrain their formation mechanisms. Methods. We took advantage of the Euclid unprecedented sensitivity, spatial resolution and wide field of view to search for brown dwarfs and free-floating planetary mass objects in the LDN 1495 region of the Taurus molecular clouds. We combined the recent Euclid Early Release Observations with older very deep ground-based images obtained over more than 20 yr to derive proper motions and multiwavelength photometry and to select members based on their morphology and their position in a proper motion diagram and in nine color-magnitude diagrams. Results. We identified 15 point sources whose proper motions, colors, and luminosity are consistent with being members of LDN 1495. Six of these objects were already known M9–L1 members. The remaining nine are newly identified sources whose spectral types might range from late-M to early-T types, with masses potentially as low as 1∼2 MJup based on their luminosity and according to evolutionary models. However, follow-up observations are needed to confirm their nature, spectral type, and membership. When it is extrapolated to the entire Taurus star-forming region, this result suggests the potential presence of several dozen free-floating planetary mass objects.

Abstract We have compiled the ∼4–400 GHz broad spectra of 32 Class II protoplanetary disks (PPDs) in the Taurus-Auriga region, which represents the brightest one-third of sources detected in the submillimeter band in this region. The spectra at >20 GHz frequency can be described with a piecewise function: (1) a power law with a spectral index of ∼2 at >200 GHz, (2) a power law with a spectral index in the range of 0.3–4.2 at 20–50 GHz, and (3) a transition region in between these two power laws, which can be characterized by a sigmoid function. This suggests that the flux densities at >200 GHz and <50 GHz are dominated by distinct emission components. At >200 GHz, the emission is likely dominated by the optically thick dust thermal emission in the bulk of the disks. In some sources that were not detected at 6.8 GHz or 10 GHz, embedded high-density dust substructures may contribute to a significant fraction of the flux densities at 30–50 GHz, and the spectral indices are mostly consistent with 2.0. Although, at 30–50 GHz, free–free and/or synchrotron emission may be significant, and some sources in our sample have spectral indices <2.0. Based on these results, we hypothesize that high-density dust substructures (e.g., vortices) are often found in resolved Class II PPDs, and are a precursor to the formation of kilometer-sized planetesimals and rocky planets. They may not present high contrast at >200 GHz frequencies owing to the high optical depth. To probe these dust substructures, high angular resolution observations at <100 GHz are necessary to distinguish them from free–free and synchrotron emission sources. Otherwise, in the analyses of the spatially unresolved spectra, one needs to simultaneously constrain the flux densities of free–free, synchrotron, and dust emission with the observations at ∼5–50 GHz.

ABSTRACT The recent interstellar detection of individual polycyclic aromatic hydrocarbons (PAHs) in the Taurus Molecular Cloud (TMC-1) brings with it interest in related species that could be present in this astronomical environment. The interstellar PAHs detected in TMC-1 consist of a few pure PAHs while the majority that have been detected are their cyano-derivative counterparts due to their larger dipole moment components. Bowl-shaped PAHs, such as sumanene (C$_{21}$H$_{12}$), represent another important target for radio astronomy as they are very polar species, in spite of their high symmetry, increasing their chances of detection. Here, we present the laboratory rotational spectroscopic study of the PAH sumanene, characterized in the gas-phase using a chirped-pulse Fourier-transform microwave spectrometer operating between 2 and 8 GHz. Accurate spectroscopic parameters are derived from the spectral analysis and compared to those obtained for corannulene. These parameters have been employed to achieve reliable frequency predictions for their astronomical search in TMC-1. We do not detect either sumanene or corannulene in our QUIJOTE line survey of TMC-1 but upper limits to their abundance in this source are derived.

New discoveries of young stars revise our star formation history in the Taurus Molecular Cloud

Infrared (IR) cooling of polycyclic aromatic hydrocarbon(PAH)molecules is a major radiative stabilization mechanism of PAHs presentin space and is the origin of the aromatic infrared bands (AIBs).Here, we report an anharmonic cascade model in a master equation frameworkto model IR emission rates and emission spectra of energized PAHsas a function of internal energy. The underlying (simple harmoniccascade) framework for fundamental vibrations has been developed throughthe modeling of cooling rates of PAH cations and other carboneaousions measured in electrostatic ion storage ring experiments performedunder “molecular cloud in a box” conditions. The anharmonicextension is necessitated because cyano-PAHs, recently identifiedin Taurus Molecular Cloud-1 (TMC-1), exhibit strong anharmonic couplings,which make substantial contributions to the IR emission dynamics.We report an experimental mid-IR (650–3200 cm–1) absorption spectrum of 2-cyanoindene (2CNI), which is the smallestcyano-PAH that has been identified in TMC-1 and model its IR coolingrates and emission properties. The mid-IR absorption spectrum is reasonablydescribed by anharmonic calculations at the B3LYP/N07D level of theorythat include resonance polyad matrices, although the CN-stretch modefrequency continues to be difficult to describe. The anharmonic cascadeframework can be readily applied to other neutral or charged PAHsand is also readily extended to include competing processes, suchas recurrent fluorescence and isomerization.

The azulene (C10H8) molecule, the simplestpolycyclic aromatic hydrocarbon (PAH) carrying a fused seven- andfive-membered ring, is regarded as a fundamental molecular buildingblock of saddle-shaped carbonaceous nanostructures such as curvednanographenes in the interstellar medium. However, an understandingof the underlying gas-phase formation mechanisms of this nonbenzenoid10π-Hückel aromatic molecule under low-temperature conditionsis in its infancy. Here, by merging crossed molecular beam experimentswith electronic structure calculations and molecular dynamics simulations,our investigations unravel an unconventional low-temperature, barrierlessroute to azulene via the reaction of the simplest organic radical,methylidyne (CH), with indene (C9H8) throughring expansion. This reaction might represent the initial step towardto the formation of saddle-shaped PAHs with seven-membered ring moietiesin hydrocarbon-rich cold molecular clouds such as the Taurus MolecularCloud-1 (TMC-1). These findings challenge conventional wisdom thatmolecular mass growth processes to nonplanar PAHs, especially thosecontaining seven-membered rings, operate only at elevated pressureand high-temperature conditions, thus affording a versatile low-temperatureroute to contorted aromatics in our galaxy.

What if an experiment could combine the power of cycloaddition and cross-coupling with the in situ formation of an aromatic molecule in a single collision? Crossed molecular beam experiments augmented with electronic structure and statistical calculations provided compelling evidence on a novel radical route involving 1,3-butadiynyl (HCCCC; X2∑+) radicals synthesizing (substituted) arylacetylenes in the gas phase upon reactions with 1,3-butadiene (CH2CHCHCH2; X1Ag) and 2-methyl-1,3-butadiene (isoprene; CH2C(CH3)CHCH2; X1A'). This elegant mechanism de facto merges two previously disconnected concepts of cross-coupling and cycloaddition-aromatization in a single collision event via the formation of two new C(sp2)-C(sp2) bonds and bending the 180° moiety of the linear 1,3-butadiynyl radical out of the ordinary by 60° to 120°. In addition to its importance to fundamental organic chemistry, this unconventional mechanism links two previously separated routes of gas-phase molecular mass growth processes of polyacetylenes and polycyclic aromatic hydrocarbons (PAHs), respectively, in low-temperature environments such as in cold molecular clouds like the Taurus Molecular Cloud (TMC-1) and in hydrocarbon-rich atmospheres of planets and their moons such as Titan, which revises the established understanding of low-temperature molecular mass growth processes in the Universe.