Context. Protoplanetary disks are the birthplaces of planets. As such, they set the initial chemical abundances available for planetary atmosphere formation. Thus, studying elemental abundances, molecular compositions, and abundance ratios in protoplanetary disks is key to linking planetary atmospheres to their formation sites.Aims. We aim to derive the sulfur abundance and the C/O ratio in the AB Aur disk using interferometric observations of CS and SO.Methods. New NOEMA observations of CS 3-2 toward AB Aur are presented. We used velocity-integrated intensity maps to determine the inclination and position angles. Keplerian masks were constructed for all observed species to assess the presence of non-Keplerian motions. We used the CS/SO ratio to study the C/O ratio. We compared our present and previous interferometric observations of AB Aur with a NAUTILUS disk model to gain an insight into the S elemental abundance and C/O ratio.Results. We derived an observational CS/SO ratio ranging from 1.8 to 2.6. Only NAUTILUS models with C/O greater than or similar to 1 can reproduce such ratios. The comparison with models points to strong sulfur depletion, with [S/H]=8 & times; 10(-8), but we note that no single model can simultaneously fit all observed species.

(Abridged) We aim to investigate the inner regions of large and massive disks orbiting T Tauri stars, thought to be progenitors of systems with wide-orbit planets and possible cases of halted pebble drift. We analyze the MIRI spectra of three disks from the MINDS program: V1094 Sco, DL Tau, and IM Lup. The spectra reveal a striking diversity. V1094 Sco and DL Tau exhibit the highest C_2H_2/H_2O flux ratio in the MINDS sample of T Tauri disks. In V1094 Sco, even cold C_4H_2 is seen. In contrast, the IM Lup spectrum is dominated by O-bearing species. No one-to-one correspondence is found between the gas in the outer disk, as traced by the C_2H/C^18O flux ratio, and that of the inner disk as traced by the C_2H_2/H_2O flux ratio. To explain these results, we propose a scenario based on a toy model of halted pebble drift. We show that a volatile C/O ratio close to unity and low C and O abundances in inner disks arise only if: (1) 95% of the icy grains are blocked in the outer disk, (2) the outer disk is chemically evolved, and (3) the gas in the outer disk has had time to reach the inner disk. DL Tau and perhaps V1094 Sco would be the rare examples for which all these conditions are met. Therefore, a high C_2H_2/H_2O flux ratio in pebble-rich disks would have a different origin than proposed for very-low mass stars, for which fast drift of O-rich pebbles would eventually leave a C-rich inner disk. We also show for the first time that the disks with high C_2H_2/H_2O flux ratio exhibit a prominent silica dust component, a result found in four disks published so far (V1094 Sco, DL Tau, CY Tau, DoAr 33). We propose that the reformation of dust at the sublimation front of silicates in a gas with super-solar (but below unity) C/O ratio leads to a silica stoichiometry (SiO_2). In turn, silica is a promising diagnostic of the C/O ratio in the inner disks.

Late infall episodes are emerging as an important driver of disk evolution. Observed as filamentary streamers in molecular lines and scattered light, such accretion perturbs disk structures, yet its chemical consequences remain unconstrained. We present NOEMA 1.2 mm observations of AB Aur, a structured young Herbig disk showing evidence for ongoing infall and planet formation. We detect azimuthal chemical diversity: SO emission is enhanced in the northern disk near the inferred streamer-disk interaction region, while C_2H peaks on the opposite southern side; CS forms a nearly axisymmetric ring. HCN and HCO^+ peak near the dust continuum overdensity in the dust ring. Rotational diagram analyses show higher SO rotational temperatures and column densities in the north, whereas CS remains axisymmetric with lower rotational temperatures, suggesting that the species probe different disk layers. For C_2H, temperature variations may contribute to but cannot fully explain the asymmetries. The HCO^+/H^13CO^+ line ratio indicates that HCO^+ is optically thick across the molecular ring, while the elevated ratio inside the cavity suggests enhanced gas-phase ^12C/^13C, consistent with isotope-selective photodissociation. Comparison with chemical models favors gas-phase C/O ratios near or above unity, with higher effective C/O in the C_2H-bright sector. We discuss two origins for the chemical asymmetries: (i) infall-induced heating and desorption of O-bearing ices enhance SO and lower gas-phase C/O near the streamer's impact site, and (ii) planet-driven substructures and localized heating or enhanced UV irradiation promote hydrocarbon-rich chemistry in the southern disk. These results highlight that environmental accretion and planet formation can jointly imprint azimuthal variations in disk chemistry, with potential impacts on forming planets' compositions.

Context. Recently, streamers have been observed causing shocks at the outer edge of protoplanetary disks. The study of sulfur-bearing species can help us to understand the physical and chemical changes caused by infalling streamers toward their landing positions. Aims. We study the physical properties traced by the emission of SO2 and SO toward the Class I protostar Per-emb 50, which is possibly related to the streamer infalling toward its disk. Methods. We present new NOrthern Extended Millimeter Array (NOEMA) A-array observations as part of the large program "Protostars and Disks: Global Evolution" (PRODIGE). We analyzed the morphology of SO2 and SO, and complement our interpretations with additional H2CO and CO data from the same program. We compared the SO2 and SO morphology with an infalling-rotating model. We applied Bayesian model selection to the brightest SO2 line to disentangle the different kinematic components traced by this molecule. We used local thermodynamic equilibrium (LTE) and non-LTE analyses to determine the temperature and density of the SO2 emission. Results. There are two separate peaks of SO2 emission offset toward the southwest of Per-emb 50: one brighter (peak 1) at about 180 au from the protostar, and a weaker one (peak 2) at about 400 au. Peak 2 is blueshifted with respect to an infalling-rotating envelope. We propose that this peak is caused by the shock between the inner envelope and the streamer. Peak 1 is consistent with the expected envelope motion, and could thus be caused by shocks at the disk-envelope interface, but potential streamer influence cannot be neglected. Both peaks show abundance ratios consistent with a low-velocity shock (similar to 3-4 km s(-1)) when compared with shock models. Conclusions. Streamers can affect the physical and chemical structure of both disks and envelopes, suggesting that streamers can play an important role in shaping both structures in the embedded stages of star formation.

We present JWST NIRSpec spectroimaging observations of jets from four edge-on protoplanetary disks that exhibit clear signatures of MHD disk winds. Bipolar jets are detected and spatially resolved in over 30 shock-excited forbidden lines, multiple Paschen and Brackett series lines of atomic hydrogen, and the high-energy excitation line of atomic helium (1.083 μ m). This helium line is the brightest jet tracer toward HH 30 and FS TauB, which also exhibit asymmetric intensity between their red- and blueshifted lobes in all tracers, including the [Fe ii ] and He i lines. Extinction maps reveal no significant differences across the lobes, suggesting an asymmetric jet-launching mechanism rather than environmental effects. Diagnostic line ratios yield consistent shock speeds of 50–60 km s ^−1 , jet ionization fractions of 0.1–0.2, and pre-shock electron densities of 1000 cm ^−3 . Combined with pixel-by-pixel electron density maps and [Fe ii ] line luminosities, we estimate jet mass-loss rates using three independent methods, averaging around a few 10 ^−9 M _⊙ yr ^−1 . We estimate the accretion rates for these sources as 10× the jet mass-loss rates and find them to match well with the independently derived accretion estimates of other Class II sources in the Taurus star-forming region. Owing to JWST’s high precision, we also investigate jet wiggling and find Tau 042021 to showcase the perfect case of mirror-symmetric wiggling, which can only be explained by the motion of the jet source around a stellar companion. Modeling this wiggling suggests Tau 042021 to host a 0.33 and 0.07 M _⊙ binary at the center with a binary separation of 1.35 au and an orbital period of 2.5 yr.

As we learn more about the multi-scale interstellar medium (ISM) of our Galaxy, we develop a greater understanding for the complex relationships between the large-scale diffuse gas and dust in Giant Molecular Clouds (GMCs), how it moves, how it is affected by the nearby massive stars, and which portions of those GMCs eventually collapse into star forming regions. The complex interactions of those gas, dust and stellar populations form what has come to be known as the ecology of our Galaxy. Because we are deeply embedded in the plane of our Galaxy, it takes up a significant fraction of the sky, with complex dust lanes scattered throughout the optically recognizable bands of the Milky Way. These bands become bright at (sub-)millimetre wavelengths, where we can study dust thermal emission and the chemical and kinematic signatures of the gas. To properly study such large-scale environments, requires deep, large area surveys that are not possible with current facilities. Moreover, where stars form, so too do planetary systems, growing from the dust and gas in circumstellar discs, to planets and planetesimal belts. Understanding the evolution of these belts requires deep imaging capable of studying belts around young stellar objects to Kuiper belt analogues around the nearest stars. Here we present a plan for observing the Galactic Plane and circumstellar environments to quantify the physical structure, the magnetic fields, the dynamics, chemistry, star formation, and planetary system evolution of the galaxy in which we live with AtLAST; a concept for a new, 50m single-dish sub-mm telescope with a large field of view which is the only type of facility that will allow us to observe our Galaxy deeply and widely enough to make a leap forward in our understanding of our local ecology.

Mechanisms such as collisions of rocky bodies or cometary activity give rise to dusty debris disks. Debris disks trace the leftover building blocks of planets, and thus also planetary composition. HD 172555, a stellar twin of β Pic, hosts a debris disk thought to have resulted from a giant collision. It is known for its extreme mid-infrared silica dust feature, indicating a warm population of silica-rich grains in the asteroid belt (∼5 au), cold CO observed by Atacama Large Millimeter/submillimeter Array (ALMA), and small bodies evaporating as they approach close to the star. Our JWST Mid-InfraRed Instrument/Medium Resolution Spectroscopy (MIRI MRS) observations now reveal emission from an inner gaseous disk (<0.5 au) that arises from the evaporation of close-in material. For the first time in a debris disk, we detect neutral atomic chlorine and sulfur, as well as ionized nickel. We recovered the neutral sulfur line in ∼20 yr old Spitzer data, showing it is long-lived and stable. Ionized iron, previously seen only in β Pic, is also detected. All lines are broadened by Keplerian rotation, pinpointing the gas location. The HD 172555 system serves as a unique laboratory to study the composition of planetesimals, asteroids, and comets beyond the solar system. The comparison to β Pic reveals that the gas in HD 172555 is hotter, closer to the star, and poor in argon—suggesting it originates from evaporating rocky bodies near the star, while β Pic’s gas may trace volatile-rich bodies from larger separations.

Context. The fragmentation of high-mass star-forming regions depends on a variety of physical parameters, including density, the magnetic field, and turbulent gas properties. Aims. We evaluate the importance of the density and magnetic field structures in relation to the fragmentation properties during high-mass star formation. Methods. Observing the large parsec-scale Stokes I millimeter dust continuum emission with the IRAM 30 m telescope and the intermediate-scale (<0.1 pc) polarized submillimeter dust emission with the Submillimeter Array toward a sample of 20 high-mass star-forming regions allows us to quantify the dependence of the fragmentation behavior of these regions on the density and magnetic field structures. Results. Based on the IRAM 30 m data, we infer density distributions n ∝ r−p of the regions with typical power-law slopes p around ~1.5. There is no obvious correlation between the power-law slopes of the density structures on larger clump scales (~1 pc) and the number of fragments on smaller core scales (<0.1 pc). Comparing the large-scale single-dish density profiles to those derived earlier from interferometric observations at smaller spatial scales, we find that the smaller-scale power-law slopes are steeper, typically around ~2.0. The flattening toward larger scales is consistent with the star-forming regions being embedded in larger cloud structures that do not decrease in density away from a particular core. The magnetic fields of several regions appear to be aligned with filamentary structures that lead toward the densest central cores. Furthermore, we find different polarization structures; some regions exhibit central polarization holes, whereas other regions show polarized emission also toward the central peak positions. Nevertheless, the polarized intensities are inversely related to the Stokes I intensities, following roughly a power-law slope of ∝ SI−0.62. We estimate magnetic field strengths between ~0.2 and ~4.5 mG, and we find no clear correlation between magnetic field strength and the fragmentation level of the regions. A comparison of the turbulent to magnetic energies shows that they are of roughly equal importance in this sample. The mass-to-flux ratios range between ~2 and ~7, consistent with collapsing star-forming regions. Conclusions. Finding no clear correlations between the present-day large-scale density structure, the magnetic field strength, and the smaller-scale fragmentation properties of the regions, indicates that the fragmentation of high-mass star-forming regions may not be affected strongly by the initial density profiles and magnetic field properties. However, considering the limited evolutionary range and spatial scales of the presented CORE analysis, future research directions should include density structure analysis of younger regions that better resemble the initial conditions, as well as connecting the observed intermediate-scale magnetic field structure with the larger-scale magnetic fields of the parental molecular clouds.

Context. The physics and chemistry of planet-forming disks are far from being fully understood. To make further progress, both broad line surveys and observations of individual tracers in a statistically significant number of disks are required. Aims. Our aim is to perform a line survey of eight planet-forming Class II disks in Taurus with the IRAM NOrthern Extended Millimeter Array (NOEMA), as a part of the MPG-IRAM Observatory Program PRODIGE (PROtostars and DIsks: Global Evolution; PIs: P. Caselli and Th. Henning). Methods. Compact and extended disks around T Tauri stars CI, CY, DG, DL, DM, DN, IQ Tau, and UZ Tau E are observed in similar to 80 lines from > 20 C-, O,- N-, and S-bearing species. The observations in four spectral settings at 210-280 GHz with a 1 sigma rms sensitivity of similar to 8-12 mJy beam(-1) at a 0.9 '' and 0.3 km s(-1) resolution will be completed in 2024. The uv visibilities are fitted with the DiskFit model to obtain key stellar and disk properties. Results. In this first paper, the combined (CO)-C-12, (CO)-C-13, and (CO)-O-18 J = 2-1 data are presented. We find that the CO fluxes and disk masses inferred from dust continuum tentatively correlate with the CO emission sizes. We constrained dynamical stellar masses, geometries, temperatures, the CO column densities, and gas masses for each disk. The best-fit temperatures at 100 au are similar to 17-37 K, and decrease radially with the power-law exponent q similar to 0.05-0.76. The inferred CO column densities decrease radially with the power-law exponent p similar to 0.2-3.1. The gas masses estimated from (CO)-C-13 (2-1) are similar to 0.001-0.2 M-circle dot. Conclusions. Using NOEMA, we confirm the presence of temperature gradients in our disk sample. The best-fit CO column densities point to severe CO freeze-out in these disks. The DL Tau disk is an outlier, and has either stronger CO depletion or lower gas mass than the rest of the sample. The CO isotopologue ratios are roughly consistent with the observed values in disks and the low-mass star-forming regions. The high (CO)-C-13/(CO)-O-18 ratio of similar to 23 in DM Tau could be indicative of strong selective photodissociation of (CO)-O-18 in this disk.

Radially extended disk winds could be the key to unlocking how protoplanetary disks accrete and how planets form and migrate. A distinctive characteristic is their nested morphology of velocity and chemistry. Here we report James Webb Space Telescope near-infrared spectrograph spectro-imaging of four young stars with edge-on disks, three of which have already dispersed their natal envelopes. For each source, a fast collimated jet traced by [Fe ii] is nested inside a hollow cavity within wider lower-velocity H2. In one case, a hollow structure is also seen in CO ro-vibrational (v = 1 → 0) emission but with a wider opening angle than the H2, and both of those are nested inside an Atacama Large Millimeter Array CO (J = 2 → 1) cone with an even wider opening angle. This nested morphology, even for sources with no envelope, strongly supports theoretical predictions for wind-driven accretion and underscores the need for theoretical work to assess the role of winds in the formation and evolution of planetary systems. JWST observations of outflows from four young stars reveal in each case a molecular wind with a central cavity surrounding a fast jet. These results point to disk winds driving accretion, with implications for planet formation and evolution.

Deuterated molecules and their molecular D/H-ratios (RD(D)) are important diagnostic tools to study the physical conditions of star-forming regions. The degree of deuteration, RD(D), can be significantly enhanced over the elemental D/H-ratio depending on physical parameters. Within the Cygnus Allscale Survey of Chemistry and Dynamical Environments (CASCADE), we aim to explore the large-scale distribution of deuterated molecules in the nearby Cygnus-X region. We focus on the analysis of large-scale structures of deuterated molecules in the filamentary region hosting the prominent Hii region DR21 and DR21(OH). Here we discuss the HCO+, HNC and HCN molecules and their deuterated isotopologues DCO+, DNC and DCN. The spatial distributions of integrated line emissions from DCO+, DNC, and DCN reveal morphological differences. DCO+ displays the most extended emission, characterized by several prominent peaks. Likewise, DNC exhibits multiple peaks, although its emission appears less extended compared to DCO+. In contrast to the extended emission of DCO+ and DNC, DCN appears the least extended, with distinct peaks. Focusing only on the regions where all three molecules are observed, the mean deuteration ratios for each species are 0.01 for both DNC and DCN, and = 0.005 for DCO+. Anti-correlations are found with deuterated molecules and dust temperature or N(H2). The strongest anti-correlation is found with RD(DCO+) and N(H2). The anti-correlation of RD(DCO+) and N(H2) is suggested to be a result of a combination of an increased photodissociation degree and shocks. A strong positive correlation between the ratio of integrated intensities of DCN and DNC with their 13C-isotopologues, are found in high column density regions. The positive relationship between the ratios implies that the D-isotopologue of the isomers could potentially serve as a tracer for the kinetic gas temperature.

Resolved molecular line observations are essential for gaining insight into the physical and chemical structure of protoplanetary disks, particularly in cold, dense regions where planets form and acquire their chemical compositions. However, tracing these regions is challenging because most molecules freeze onto grain surfaces and are not observable in the gas phase. We investigated cold molecular chemistry in the triple stellar T Tauri disk GG Tau A, which harbours a massive gas and dust ring and an outer disk, using Atacama Large Millimeter/submillimeter Array (ALMA) Band 7 observations. We present high angular resolution maps of N2H+ and DCO+ emission, with upper limits reported for H2D+, 13CS, and SO2. The radial intensity profile of N2H+ shows most emission near the ring's outer edge, while DCO+ exhibits a double peak, one near the ring's inner edge and the other in the outer disk. With complementary observations of lower-lying transitions, we constrained the molecular surface densities and rotation temperatures. We compared the derived quantities with model predictions across different cosmic-ray ionization (CRI) rates, carbon-to-oxygen (C/O) ratios, and stellar UV fluxes. Cold molecular chemistry, affecting the N2H+, DCO+, and H2D+ abundances, is most sensitive to the CRI rate, while the stellar UV fluxes and C/O ratios have minimal impact on these three ions. Our best model requires a low CRI rate of 10-18 s-1. However, it fails to match the low temperatures derived from N2H+ and DCO+, 12-16 K, which are much lower than the CO freezing temperature.

FU Ori stars (FUors) are undergoing powerful luminosity outbursts of ∼100 L ⊙ in magnitude and of several decades in duration. Such outbursts inevitably affect physical and chemical structure of the surrounding protoplanetary disk. Using astrochemical and radiative transfer modelling, we study the lasting impact of the outburst on disks with and without an envelope and how it changes flux in chosen molecular lines. We formulate a number of criteria indicative of a recent outburst activity based on the molecular emission, analyze the chemistry behind the flux change and apply the criteria to available observations of quiescent protoplanetary disks. The latter revealed ten objects with possible outbursts in the past and four of them satisfy multiple proposed criteria.

Context. The formation of stars has been subject to extensive studies in the past decades from molecular cloud to protoplanetary disk scales. It is still not fully understood how the surrounding material in a protostellar system, that often shows asymmetric structures with complex kinematic properties, feeds the central protostar(s) and their disk(s). Aims. We study the spatial morphology and kinematic properties of the molecular gas surrounding the IRS3A and IRS3B protostellar systems in the L1448N region located in the Perseus molecular cloud. Methods. We present 1 mm NOEMA observations of the PRODIGE large program and analyze the kinematic properties of molecular lines. Given the complexity of the spectral profiles, the lines are fitted with up to three Gaussian velocity components. The clustering algorithm DBSCAN is used to disentangle the velocity components into the underlying physical structure. Results. We discover an extended gas bridge ( 3000 au) surrounding both the IRS3A and IRS3B systems in six molecular line tracers (C18O, SO, DCN, H2CO, HC3N, and CH3OH). This gas bridge is oriented along the northeast-southwest direction and shows clear velocity gradients on the order of 100 km/s/pc towards the IRS3A system. We find that the observed velocity profile is consistent with analytical streamline models of gravitational infall towards IRS3A. The high-velocity C18O (2-1) emission towards IRS3A indicates a protostellar mass of 1.2 Msun. Conclusions. While high angular resolution continuum data often show IRS3A and IRS3B in isolation, molecular gas observations reveal that these systems are still embedded within a large-scale mass reservoir with a complex spatial morphology as well as velocity profiles. The kinematic properties of the extended gas bridge are consistent with gravitational infall toward the IRS3A protostar.

Submillimeter and millimeter wavelengths provide a unique view of the Universe, from the gas and dust that fills and surrounds galaxies to the chromosphere of our own Sun. Current single-dish facilities have presented a tantalising view of the brightest (sub-)mm sources, and interferometers have provided the exquisite resolution necessary to analyse the details in small fields, but there are still many open questions that cannot be answered with current facilities. In this report we summarise the science that is guiding the design of the Atacama Large Aperture Submillimeter Telescope (AtLAST). We demonstrate how tranformational advances in topics including star formation in high redshift galaxies, the diffuse circumgalactic medium, Galactic ecology, cometary compositions and solar flares motivate the need for a 50m, single-dish telescope with a 1-2 degree field of view and a new generation of highly multiplexed continuum and spectral cameras. AtLAST will have the resolution to drastically lower the confusion limit compared to current single-dish facilities, whilst also being able to rapidly map large areas of the sky and detect extended, diffuse structures. Its high sensitivity and large field of view will open up the field of submillimeter transient science by increasing the probability of serendipitous detections. Finally, the science cases listed here motivate the need for a highly flexible operations model capable of short observations of individual targets, large surveys, monitoring programmes, target of opportunity observations and coordinated observations with other observatories. AtLAST aims to be a sustainable, upgradeable, multipurpose facility that will deliver orders of magnitude increases in sensitivity and mapping speeds over current and planned submillimeter observatories.

The Cryogenic IR echelle Spectrometer (CRIRES) instrument at the Very Large Telescope (VLT) was in operation from 2006 to 2014. Great strides in characterizing the inner regions of protoplanetary disks were made using CRIRES observations in the L- and M-band at this time. The upgraded instrument, CRIRES+, became available in 2021 and covers a larger wavelength range simultaneously. Here we present new CRIRES+ Science Verification data of the binary system S Coronae Australis (S CrA). We aim to characterize the upgraded CRIRES+ instrument for disk studies and provide new insight into the gas in the inner disk of the S CrA N and S systems. We analyze the CRIRES+ data taken in all available L- and M-band settings, providing spectral coverage from 2.9 to 5.5 $\mu$m. We detect emission from $^{12}$CO (v=1-0, v=2-1, and v=3-2), $^{13}$CO (v=1-0), hydrogen recombination lines, OH, and H$_2$O in the S CrA N disk. In the fainter S CrA S system, only the $^{12}$CO v=1-0 and the hydrogen recombination lines are detected. The $^{12}$CO v=1-0 emission in S CrA N and S shows two velocity components, a broad component coming from $\sim$0.1 au in S CrA N and $\sim$0.03 au in S CrA S and a narrow component coming from $\sim$3 au in S CrA N and $\sim$5 au in S CrA S. We fit local thermodynamic equilibrium slab models to the rotation diagrams of the two S CrA N velocity components and find that they have similar column densities ($\sim$1-7$\times$10$^{17}$ cm$^{-2}$), but that the broad component is coming from a hotter and narrower region. Two filter settings, M4211 and M4368, provide sufficient wavelength coverage for characterizing CO and H$_2$O at $\sim$5 $\mu$m, in particular covering low- and high-$J$ lines. CRIRES+ provides spectral coverage and resolution that are crucial complements to low-resolution observations, such as those with JWST, where multiple velocity components cannot be distinguished.

With new and upcoming observing facilities (JWST and the ELTs), the exoplanet community is poised to precisely measure the chemical inventory of exoplanet atmospheres. This will allow, for the first time, to start investigating whether one of the greatest promises of atmospheric characterization studies holds up: inverting the atmospheric composition to infer the planet formation history encoded in it. In my talk, I will show how such measurements allow to run so-called formation retrievals, which constrain a planet’s formation history using its atmospheric abundances in a Bayesian retrieval framework. I will demonstrate how simple and popular models for the composition of the protoplanetary disk and planet formation could lead to interesting insights when applied in formation retrievals. At the same time, I will discuss how such assumptions are too strongly simplified for making the exoplanet atmosphere — formation connection in practice, and what the most pressing theoretical challenges are. Achieving this connection will be a formidable and interdisciplinary challenge, but the exciting exoplanet observations that lie ahead will allow the community to tackle it in earnest.

We performed a deep search for CCS, SO, SO2, OCS, H2S, H2CS and other molecules in the DM Tau protoplanetary disk at 2mm with PolyFiX@NOEMA. With a beam of ~2''x1'' and a spectral resolution of 0.3 km/s, a high sensitivity of ~3.8 mJy/beam was achieved. We detected o-H2S, o-H2CS, and DNC (first time in DM Tau) as well as H13CO+, N2D+, and, tentatively, HC3N. We have not detected SO2, our main target molecule. We used the non-LTE radiative transfer code RADEX to derive disk-averaged column densities and their upper limits. These values, together with our previous ALMA CS data were used for disk chemical modeling. The presence of CS and the lack of SO2 in the DM Tau disk molecular layer can only be reliably explained by the disk model with a non-solar gas-phase C/O ratio of ~1, supporting previous findings.