Molecular Line Research Articles

Early Phases of Star Formation: Testing Chemical Tools

Star-forming processes strongly influence the ISM chemistry. Nowadays, many high-quality databases are available at millimeter wavelengths. Using them, it is possible to carry out studies that review and deepen previous results. If these studies involve large samples of sources, it is preferred to use direct tools to study the molecular gas. With the aim of testing these tools such as the use of the HCN/HNC ratio as a thermometer, and the use of H13CO+, HC3N, N2H+ and C2H as “chemical clocks,” we present a molecular line study toward 55 sources representing massive young stellar objects at different evolutionary stages: infrared dark clouds (IRDCs), high-mass protostellar objects (HMPOs), hot molecular cores (HMCs) and ultracompact H ii regions. We found that the use of the HCN/HNC ratio as a universal thermometer in the ISM should be taken with care because the HCN optical depth is a big issue that can affect the method. Hence, this tool should be utilized only after a careful analysis of the HCN spectrum, checking that no line, neither the main nor the hyperfine ones, presents absorption features. We point out that the analysis of the emission of H13CO+, HC3N, N2H+ and C2H could be useful to trace and distinguish regions among IRDCs, HMPOs and HMCs. The molecular line widths of these four species increase from the IRDC to the HMC stage, which can be a consequence of the gas dynamics related to the star-forming processes taking place in the molecular clumps. Our results not only contribute with more statistics, acting as a probe of such chemical tools, useful to obtain information in large samples of sources, but also complement previous works through the analysis of other types of sources.

The prediction of acute toxicity (LD50) for organophosphorus-based chemical warfare agents (V-series) using toxicology in silico methods.

Nerve agents are organophosphate chemical warfare agents that exert their toxic effects by irreversibly inhibiting acetylcholinesterase, affecting the breakdown of the neurotransmitter acetylcholine in the synaptic cleft. Due to the risk of exposure to dangerous nerve agents and for animal welfare reasons, in silico methods have been used to assess acute toxicity safely. The next-generation risk assessment (NGRA) is a new approach for predicting toxicological parameters that can meet modern requirements for toxicological research. The present study explains the acute toxicity of the examined V-series nerve agents (n = 9) using QSAR models. Toxicity Estimation Software Tool (ver. 4.2.1 and ver. 5.1.2), QSAR Toolbox (ver. 4.6), and ProTox-II browser application were used to predict the median lethal dose. The Simplified Molecular Input Line Entry Specification (SMILES) was the input data source. The results indicate that the most deadly V-agents were VX and VM, followed by structural VX analogues: RVX and CVX. The least toxic turned out to be V-sub x and Substance 100A. In silico methods for predicting various parameters are crucial for filling data gaps ahead of experimental research and preparing for the upcoming use of nerve agents.

Computational drug discovery on human immunodeficiency virus with a customized long short-term memory variational autoencoder deep-learning architecture.

Despite attempts to control the spread of human immunodeficiency virus (HIV) through the use of anti-HIV medications, the absence of an effective vaccine continues to present a significant obstacle. In addition, the development of drug resistance by HIV underscores the necessity for computational drug discovery methods to identify novel therapies. This investigation specifically focused on employing a long short-term memory (LSTM) variational autoencoder deep-learning architecture for computational drug discovery in relation to HIV. Our data set comprised simplified molecular input line entry system (SMILES)-encoded compounds, which were used to train the LSTM autoencoder. Remarkably, our model achieved a training accuracy of 91%, with a data set containing 1377 compounds. Leveraging the generative model derived from the training phase, we generated potential new drugs for combating HIV and assessed their interaction with the virus using a previously developed artificial intelligence model. Lastly, we verified the drug likeliness of our computationally generated compounds in accordance with Lipinski's rule of five. Overall, our study presents a promising approach to computational drug discovery in the ongoing battle against HIV.

Surveying the Whirlpool at Arcseconds with NOEMA (SWAN)

We present the first results from “Surveying the Whirlpool at Arcseconds with NOEMA” (SWAN), an IRAM Northern Extended Millimetre Array (NOEMA)+30 m large program that maps emission from several molecular lines at 90 and 110 GHz in the iconic nearby grand-design spiral galaxy M 51 at a cloud-scale resolution (∼3″ = 125 pc). As part of this work, we have obtained the first sensitive cloud-scale map of N2H+(1–0) of the inner ∼5 × 7 kpc of a normal star-forming galaxy, which we compared to HCN(1–0) and 12CO(1–0) emission to test their ability in tracing dense, star-forming gas. The average N2H+-to-HCN line ratio of our total FoV is 0.20 ± 0.09, with strong regional variations of a factor of ≳2 throughout the disk, including the south-western spiral arm and the center. The central ∼1 kpc exhibits elevated HCN emission compared to N2H+, probably caused by AGN-driven excitation effects. We find that HCN and N2H+ are strongly super-linearily correlated in intensity (ρSp ∼ 0.8), with an average scatter of ∼0.14 dex over a span of ≳1.5 dex in intensity. When excluding the central region, the data are best described by a power law of an exponent of 1.2, indicating that there is more N2H+ per unit HCN in brighter regions. Our observations demonstrate that the HCN-to-CO line ratio is a sensitive tracer of gas density in agreement with findings of recent galactic studies utilising N2H+. The peculiar line ratios present near the AGN and the scatter of the power-law fit in the disk suggest that in addition to a first-order correlation with gas density, second-order physics (such as optical depth, gas temperature) or chemistry (abundance variations) are encoded in the N2H+/12CO, HCN/12CO, and N2H+/HCN ratios.

JWST: Deuterated PAHs, PAH Nitriles, and PAH Overtone and Combination Bands. I. Program Description and First Look

A first look is taken at the NIRSpec 1–5 μm observations from James Webb Space Telescope program 1591 that targets seven objects along the low-mass stellar life cycle with polycyclic aromatic hydrocarbon (PAH) emission. Spectra extracted from a 1.″5 radius circular aperture are explored, showing a wealth of features, including the 3 μm PAH complex, the PAH continuum, and atomic and molecular emission lines from H i, He, H2, and other species. CO2- and H2O-ice absorption and CO emission is also seen. Focusing on the bright-PDR position in M17, the PAH CH stretch falls at 3.29 μm (FWHM = 0.04 μm). Signs of its 1.68 μm overtone are confused by line emission in all targets. Multicomponent decomposition reveals a possible aliphatic deuterated PAH feature centered at 4.65 μm (FWHM = 0.02 μm), giving [D/H]alip. = 31% ± 12.7%. However, there is little sign of its aromatic counterpart between 4.36 and 4.43 μm. There is also little sign of PAH nitrile emission between 4.34 and 4.39 μm. A PAH continuum rises from ∼1 to 3.2 μm, after which it jumps by about a factor of 2.5 at 3.6 μm, with bumps at 3.8, 4.04, and 4.34 μm adding structure. The CO2 absorption band in M17 is matched with 10:1 H2O:CO2 ice at 10 K. The v = 0 pure rotational molecular hydrogen population diagram reveals >2200 K UV-pumped gas. The hydrogen Pfund series runs from levels 10 to >30. Considering Brα/Brβ = 0.381 ± 0.01966 and Case B recombination results in A V ≃ 8. CO emission in IRAS 21282+5050 originates from 258 K gas. In-depth spectral–spatial analysis of all features and targets is planned for a series of forthcoming papers.

Constraining the halo-ISM connection through multi-transition carbon monoxide line-intensity mapping

Line-intensity mapping (LIM) surveys will characterise the cosmological large-scale structure of emissivity in a range of atomic and molecular spectral lines, but existing literature rarely considers whether these surveys can recover excitation properties of the tracer gas species, such as the carbon monoxide (CO) molecule. Combining basic empirical and physical assumptions with the off-the-shelf Radex radiative transfer code or a Gaussian process emulator of Radex outputs, we devise a basic dark matter halo model for CO emission by tying bulk CO properties to halo properties, exposing physical variables governing CO excitation as free parameters. The CO Mapping Array Project (COMAP) is working towards a multi-band survey programme to observe both CO(1–0) and CO(2–1) at z ∼ 7. We show that this programme, as well as a further `Triple Deluxe' extension to higher frequencies covering CO(3–2), is fundamentally capable of successfully recovering the connection between halo mass and CO abundances, and constraining the molecular gas kinetic temperature and density within the star-forming interstellar medium in ways that single-transition CO LIM cannot. Given a fiducial thermal pressure of ∼ 104 K cm-3 for molecular gas in halos of ∼ 1010 M ⊙, simulated multi-band COMAP surveys successfully recover the thermal pressure within 68% interval half-widths of 0.5–0.6 dex. Construction of multi-frequency LIM instrumentation to access multiple CO transitions is crucial in harnessing this capability, as part of a cosmic statistical probe of gas metallicity, dust chemistry, and other physical parameters in star-forming regions of the first galaxies and proto-galaxies out of reionisation.

Digging into the Interior of Hot Cores with ALMA: Spiral Accretion into the High-mass Protostellar Core G336.01–0.82

We observed the high-mass star-forming core G336.01–0.82 at 1.3 mm and 0.″05 (∼150 au) angular resolution with the Atacama Large Millimeter/submillimeter Array (ALMA) as part of the Digging into the Interior of Hot Cores with ALMA survey. These high-resolution observations reveal two spiral streamers feeding a circumstellar disk at opposite sides in great detail. Molecular line emission from CH3OH shows velocity gradients along the streamers consistent with infall. Similarly, a flattened envelope model with rotation and infall implies a mass larger than 10 M ☉ for the central source and a centrifugal barrier of 300 au. The location of the centrifugal barrier is consistent with local peaks in the continuum emission. We argue that gas brought by the spiral streamers is accumulating at the centrifugal barrier, which can result in future accretion burst events. A total high infall rate of ∼4 × 10−4 M ☉ yr−1 is derived by matching models to the observed velocity gradient along the streamers. Their contribution accounts for 20%–50% the global infall rate of the core, indicating streamers play an important role in the formation of high-mass stars.

Observational chemical signatures of the past FU Ori outbursts

Abstract FU Ori-type stars are young stellar objects (YSOs) experiencing luminosity outbursts by a few orders of magnitude, which last for ∼102 years. A dozen of FUors are known up to date, but many more currently quiescent YSOs could have experienced such outbursts in the last ∼103 years. To find observational signatures of possible past outbursts, we utilise ANDES, RADMC-3D code as well as CASA ALMA simulator to model the impact of the outburst on the physical and chemical structure of typical FU Ori systems and how it translates to the molecular lines’ fluxes. We identify several combinations of molecular lines that may trace past FU Ori objects both with and without envelopes. The most promising outburst tracers from an observational perspective are the molecular flux combinations of the N2H+J = 3 − 2, C18O J = 2 − 1, H2CO $(J_{\rm K_a, K_c}) = 4_{04}-3_{03}$, and HCN J = 3 − 2 lines. We analyse the processes leading to molecular flux changes and show that they are linked with either thermal desorption or enhanced chemical reactions in the molecular layer. Using observed CO, HCN, N2H+ and H2CO line fluxes from the literature, we identify ten nearby disc systems that might have undergone FU Ori outbursts in the past ∼103 years: [MGM2012] 556, [MGM2012] 371 and [MGM2012] 907 YSOs in L1641, Class II protoplanetary discs around CI Tau, AS 209 and IM Lup and transitional discs DM Tau, GM Aur, LkCa 15 and J1640-2130.

The Detection of Higher-order Millimeter Hydrogen Recombination Lines in the Large Magellanic Cloud

We report the first extragalactic detection of the higher-order millimeter hydrogen recombination lines (Δn > 2). The γ-, ϵ-, and η-transitions have been detected toward the millimeter continuum source N 105–1 A in the star-forming region N 105 in the Large Magellanic Cloud with the Atacama Large Millimeter/submillimeter Array. We use the H40α line, the brightest of the detected recombination lines (H40α, H36β, H50β, H41γ, H57γ, H49ϵ, H53η, and H54η), to determine the electron temperature and study ionized gas kinematics in the region, and the 3 mm free–free continuum emission to determine the physical parameters: the size, emission measure, and electron density. We compare the physical properties of N 105–1 A to a large sample of Galactic compact and ultracompact (UC) H ii regions and conclude that N 105–1 A is similar to the most luminous (L > 105 L ⊙) UC H ii regions in the Galaxy. N 105–1 A is ionized by an O5.5 V star; it is deeply embedded in its natal molecular clump, and likely associated with a (proto)cluster. We incorporate high-resolution molecular line data including CS, SO, SO2, and CH3OH (∼0.12 pc), and HCO+ and CO (∼0.087 pc) to explore the molecular environment of N 105–1 A. Based on the CO data, we find evidence for a cloud–cloud collision that likely triggered star formation in the region. We find no clear outflow signatures, but the presence of filaments and streamers indicates ongoing accretion onto the clump hosting the UC H ii region. Sulfur chemistry in N 105–1 A is consistent with the accretion shock model predictions.

Investigating Graph Invariants for Predicting Properties of Chemical Structures of Antiviral Drugs

In the study of the Quantitative Structure-Activity Relationship (QSAR) model, the topological index of a molecular structure as a molecular descriptor is used to analyze their molecular characteristics. Theoretical evaluation of the drug’s molecular structure helps to accelerate the process of design and discovery of drugs by understanding its mechanism of action. In this paper, we study the molecular structure of antiviral drugs, namely, Ritonavir and Lopinavir using the graph theory and the edge-partition approach. We determine the exact formula of some new Sombor-type topological indices and Sombor-type topological coindices of the molecular graph and line graph of the chemical structures of the antiviral drugs Ritonavir and Lopinavir. In this study, we apply Matlab and Mathematica software to evaluate the results and accuracy of calculations. The linear regression approach in the quantitative structure-property relationships model is used to investigate the relationships between Sombor indices and coindices and physicochemical properties.

Modelling molecular clouds and CO excitation in AGN-host galaxies

ABSTRACT We present a new physically motivated model for estimating the molecular line emission in active galaxies. The model takes into account (i) the internal density structure of giant molecular clouds (GMCs), (ii) the heating associated with both stars and the active galactic nuclei (AGNs), respectively, producing photodissociation regions (PDRs) and X-ray-dominated regions (XDRs) within the GMCs, and (iii) the mass distribution of GMCs within the galaxy volume. The model needs, as input parameters, the radial profiles of molecular mass, far-UV flux and X-ray flux for a given galaxy, and it has two free parameters: the CO-to-H2 conversion factor αCO, and the X-ray attenuation column density NH. We test this model on a sample of 24 local (z ≤ 0.06) AGN-host galaxies, simulating their carbon monoxide spectral-line energy distribution (CO SLED). We compare the results with the available observations and calculate, for each galaxy, the best (αCO, NH) with a Markov chain Monte Carlo algorithm, finding values consistent with those present in the literature. We find a median αCO = 4.8 M⊙ (K km s−1 pc2)−1 for our sample. In all the modelled galaxies, we find the XDR component of the CO SLED to dominate the CO luminosity from Jupp ≥ 4. We conclude that, once a detailed distribution of molecular gas density is taken into account, PDR emission at mid-/high-J becomes negligible with respect to XDR.

Modelling CN Zeeman effect observations of the envelopes of a low-mass protostellar disc and a massive protostar

ABSTRACT We use the polaris radiative transfer code to produce simulated circular polarization Zeeman emission maps of the cyanide (CN) J = 1–0 molecular line transition for two types of protostellar envelope magnetohydrodynamic simulations. Our first model is a low-mass disc envelope system (box length L = 200 au), and our second model is the envelope of a massive protostar (L = 104 au) with a protostellar wind and a CN-enhanced outflow shell. We compute the velocity-integrated Stokes I and V, as well as the implied V/I polarization percentage, for each detector pixel location in our simulated emission maps. Our results show that both types of protostellar environments are in principle accessible with current circular polarization instruments, with each containing swaths of envelope area that yield percentage polarizations that exceed the 1.8 per cent nominal sensitivity limit for circular polarization experiments with the Atacama Large Millimeter/submillimeter Array. In both systems, high-polarization (≳1.8 per cent) pixels tend to lie at an intermediate distance away from the central star and where the line-centre opacity of the CN emission is moderately optically thin (τLC ∼ 0.1–1). Furthermore, our computed V/I values scale roughly with the density-weighted mean line-of-sight magnetic field strength, indicating that Zeeman observations can effectively diagnose the strength of envelope-scale magnetic fields. We also find that pixels with large V/I are preferentially co-located where the absolute value of the velocity-integrated V is also large, suggesting that locations with favourable percentage polarization are also favourable in terms of raw signal.

A Low-mass line-rich Core Found in Massive Star-forming Region IRAS 16351-4722

We present Atacama Large Millimeter/submillimeter Array subarcsecond-resolution observations of both continuum and molecular lines at 345 GHz toward the massive star-forming region IRAS 16351-4722 (hereafter I16351). A total of 12 dust cores were detected based on high-spatial-resolution observations of the continuum. Among them, a high-mass core (11.6 M ⊙) and a low-mass core (1.7 M ⊙) show abundant molecular line emissions. 164 molecular transitions from 29 species and 104 molecular transitions from 25 species are identified in the high-mass and low-mass cores, respectively. Complex organic molecules (COMs) such as CH3OH, CH3OCHO, CH3OCH3, C2H5OH, and C2H5CN are detected in the two cores. Under the assumption of local thermodynamic equilibrium, the rotational temperatures and column densities of the COMs are derived with the XCLASS software. The maximum rotation temperature values in the low-mass core and the high-mass core were found to be approximately 130 K and 198 K, respectively. Additionally, the line widths in the high-mass core are larger than those in the low-mass one. The abundant COM line transitions, high gas temperatures, and smaller line widths indicate the presence of a low-mass line-rich core in the massive star formation region for the first time, while the high-mass line-rich core shows hot core properties. When comparing the molecular abundances of CH3OH, CH3OCHO, CH3OCH3, and C2H5OH of the two cores with other hot cores and hot corinos reported in the literature, we further confirm that both a hot core and a low-mass line-rich core are simultaneously detected in I16351.

Collisional broadening of molecular rovibronic lines

To meet burning needs of high-resolution pressure-induced line-shape parameters in the UV/visible regions for hot-temperature industrial and atmospheric applications as well as current and future space missions, phase-shift theory is examined in its historical context, tested and revisited using accurate numerical potentials and advanced trajectory models. First, a general analysis for arbitrary molecular systems is conducted in terms of the dimensionless parameter α determined by the differences of the Lennard-Jones parameters in the final and initial electronic absorber’s states. Temperature dependence, use of the power law and influence of Maxwell–Boltzmann averaging over relative velocities are addressed. Then, interaction-potential calculations are attempted for some representative molecular pairs (NO-Ar, NO-N2, OH-Ar and OH-N2) and the isotropic parts are fitted using the 12-6 Lennard-Jones form to get room and high-temperature line-broadening and line-shift coefficients which are compared to available measurements. It is shown that the phase-shift theory in its standard rectilinear-trajectory formulation provides linewidth and shift estimates accurate within 30%–40%. Attempted improvements using numerical potentials and curved trajectories lead to closer matches with measurements for some cases but also worsen the agreement for others. To ensure better theoretical predictions, introduction of correction terms to the usual phase-shift integral is suggested.

SOFIA FEEDBACK Survey: The Pillars of Creation in [C ii] and Molecular Lines

We investigate the physical structure and conditions of photodissociation regions (PDRs) and molecular gas within the Pillars of Creation in the Eagle Nebula using SOFIA FEEDBACK observations of the [C ii] 158 μm line. These observations are velocity resolved to 0.5 km s−1 and are analyzed alongside a collection of complimentary data with similar spatial and spectral resolution: the [O i] 63 μm line, also observed with SOFIA, and rotational lines of CO, HCN, HCO+, CS, and N2H+. Using the superb spectral resolution of SOFIA, APEX, CARMA, and BIMA, we reveal the relationships between the warm PDR and cool molecular gas layers in context of the Pillars’ kinematic structure. We assemble a geometric picture of the Pillars and their surroundings informed by illumination patterns and kinematic relationships and derive physical conditions in the PDRs associated with the Pillars. We estimate an average molecular gas density cm−3 and an average atomic gas density n H ∼ 1.8 × 104 cm−3 and infer that the ionized, atomic, and molecular phases are in pressure equilibrium if the atomic gas is magnetically supported. We find pillar masses of 103, 78, 103, and 18 M ⊙ for P1a, P1b, P2, and P3, respectively, and evaporation times of ∼1–2 Myr. The dense clumps at the tops of the pillars are currently supported by the magnetic field. Our analysis suggests that ambipolar diffusion is rapid and these clumps are likely to collapse within their photoevaporation timescales.

Cygnus A obscuring torus: ionized, atomic, or molecular?

ABSTRACT The prototypical powerful FR II radio galaxy Cygnus A fits extremely well into the quasar/radio galaxy unified model: high polarization with an angle almost perpendicular to the radio jet and polarized flux showing broad permitted lines. It has been claimed that ionized gas in the torus reveals a very clear torus shape via Bremmstrahlung emission. We rule out the later with an energetic argument, and we constrain the molecular and atomic gas properties with existing observations. The atomic absorption against the core has been shown to match the X-ray column only if the spin temperature is an implausible Ts = 1 × 106 K. This points to a molecular medium for the X-ray column $\log (N_{\rm H} ~[\rm {cm^{-2}}]) \sim 23.5$. Yet not low-J CO absorption is detected to sensitive limits. The non-detection is surprising given that this powerful radio galaxy hosts a luminous, dust-obscured active nucleus and copious warm molecular hydrogen. These conditions suggest a detectable level of emission. Furthermore, the torus X-ray column density suggests detectable absorption. We explore various possibilities to explain the lack of a signature from warm CO (200–250 K). Specifically, that the radiative excitation by the radio core renders low-J CO absorption below current sensitivities, and that high-J levels are well populated and conducive to producing absorption. We test this hypothesis using archival Hershel/SPIRE FTS observations of Cygnus A of high-J CO lines (14 ≥ J ≥ 4 transitions). Still high-J CO lines are not detected. We suggest that ALMA observations near its high frequency limit can be critical to obtain the signature of molecular line of the torus of Cygnus A.

Early Planet Formation in Embedded Disks (eDisk). VIII. A Small Protostellar Disk around the Extremely Low Mass and Young Class 0 Protostar IRAS 15398–3359

Protostellar disks are an ubiquitous part of the star formation process and the future sites of planet formation. As part of the Early Planet Formation in Embedded Disks large program, we present high angular resolution dust continuum (∼40 mas) and molecular line (∼150 mas) observations of the Class 0 protostar IRAS 15398–3359. The dust continuum is small, compact, and centrally peaked, while more extended dust structures are found in the outflow directions. We perform a 2D Gaussian fitting and find the deconvolved size and 2σ radius of the dust disk to be 4.5 × 2.8 au and 3.8 au, respectively. We estimate the gas+dust disk mass assuming optically thin continuum emission to be 0.6M J–1.8M J, indicating a very low mass disk. The CO isotopologues trace components of the outflows and inner envelope, while SO traces a compact, rotating disk-like component. Using several rotation curve fittings on the position–velocity diagram of the SO emission, the lower limits of the protostellar mass and gas disk radius are 0.022 M ⊙ and 31.2 au, respectively, from our Modified 2 single power-law fitting. A conservative upper limit of the protostellar mass is inferred to be 0.1 M ⊙. The protostellar mass accretion rate and the specific angular momentum at the protostellar disk edge are found to be in the range of (1.3–6.1) × 10−6 M ⊙ yr−1 and (1.2–3.8) × 10−4 km s−1 pc, respectively, with an age estimated between 0.4 × 104 yr and 7.5 × 104 yr. At this young age with no clear substructures in the disk, planet formation would likely not yet have started. This study highlights the importance of high-resolution observations and systematic fitting procedures when deriving dynamical properties of deeply embedded Class 0 protostars.

Correlations between laboratory line lists for FeH, CrH, and NiH and M-star spectra collected with ESPaDOnS and SPIRou

Context. Molecular bands of metal oxides and hydrides dominate the optical and near-infrared spectra of M dwarfs. High-resolution spectra of these bands have immense potential for determining many properties of these stars, such as effective temperature, surface gravity, elemental abundances, radial velocity, or surface magnetic fields. Techniques are being developed to do this but remain limited by the current availability and accuracy of molecular data and spectral line lists. Aims. This paper reports metal monohydride line lists selected from near-infrared and visible laboratory data to show that specific bands in several electronic transitions can be used to identify CrH, NiH, and FeH in M stars and to determine radial velocities from Doppler shifts. The possibility of measuring magnetic fields is also investigated for FeH and CrH. Methods. We used systematic cross-correlation analysis between unpolarised spectra from a selection of M stars and state-specific laboratory line lists. These lists were generated from a combination of existing data and new laboratory laser-excitation spectra recorded at Doppler-limited resolution, in zero-field conditions or in magnetic fields up to 0.6 tesla. Results. We show that transitions at visible wavelengths in FeH and NiH, usually neglected in the analysis of the spectra of M-type stars, do in fact contribute to the spectra, and we demonstrate the influence of magnetic sensitivity on selected transitions in CrH and FeH. Conclusions. Although the new line lists focus on transitions recorded at temperatures significantly lower than those of stellar objects, they remain pertinent because they cover some band-head regions of high spectral density. FeH bands can provide a useful supplement to atomic lines for the analysis of high-resolution optical and near-infrared spectra of M dwarfs. We demonstrate the influence of a magnetic field on CrH signatures around 862 nm.

TRAO Survey of Nearby Filamentary Molecular Clouds, the Universal Nursery of Stars (TRAO-FUNS). III. Filaments and Dense Cores in the NGC 2068 and NGC 2071 Regions of Orion B

We present the results of molecular line observations performed toward the NGC 2068 and NGC 2071 regions of the Orion B cloud as the TRAO-FUNS project to study the roles of the filamentary structure in the formation of dense cores and stars in the clouds. Gaussian decomposition for the C18O spectra with multiple velocity components and the application of a friends-of-friends algorithm for the decomposed components allowed us to identify a few tens of velocity-coherent filaments. We also identified 48 dense cores from the observations of N2H+ using a core finding tool, FellWalker. We performed a virial analysis for these filaments and dense cores, finding that the filaments with N2H+ dense core are thermally supercritical, and the filaments with a larger ratio between the line mass and the thermal critical line mass tend to have more dense cores. We investigated the contribution of the nonthermal motions in dense cores and filaments, showing the dense cores are mostly in transonic/subsonic motions while their natal filaments are mostly in supersonic motions. This may indicate that gas turbulent motions in the filaments have been dissipated at the core scale to form the dense cores there. The filaments with (dynamically evolved) dense cores in infalling motions or with NH2D bright (or chemically evolved) dense cores are all found to be gravitationally critical. Therefore, the criticality of the filament is thought to provide a key condition for its fragmentation, the formation of dense cores, and their kinematical and chemical evolution.

Dissecting the morphology of star forming complex S193

ABSTRACT We have studied a star-forming complex S193 using near-infrared (NIR) observations and other archival data covering optical to radio wavelengths. We identified stellar clusters in the complex using the NIR photometric data and estimated the membership and distance of the clusters. Using the mid-infrared (MIR) and far-infrared (FIR) images, the distribution of the dust emission around H ii regions is traced in the complex. The Herschel column density and temperature maps analysis reveal 16 cold dust clumps in the complex. The H α image and 1.4 GHz radio continuum emission map are employed to study the ionized gas distribution and infer the spectral type and the dynamical age of each H ii region/ionized clump in the complex. The 12CO(J = 3 − 2) and 13CO(J = 1 − 0) molecular line data hint at the presence of two velocity components around [−43, −46] and [−47, −50] km s−1, and their spatial distribution reveals two overlapping zones toward the complex. By investigating the immediate surroundings of the central cluster [BDS2003]57 and the pressure calculations, we suggest that the feedback from the massive stars seems responsible for the observed velocity gradient and might have triggered the formation of the central cluster [BDS2003]57.