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[Abridged] Gas kinematics is a new and unique way to study planet-forming environments by an accurate characterization of disk velocity fields. High angular resolution ALMA observations allow deep kinematical analysis of disks, by observing molecular line emission at high spectral resolution. In particular, rotation curves are key tools for studying the disk pressure structure and estimating fundamental disk parameters, such as mass and radius. In this work, we explore the potential of a multi-molecule approach to gas kinematics to provide a 2D characterization of the HD 163296 disk. From the high quality data of the MAPS Large Program we extracted the rotation curves of rotational lines from seven distinct molecular species, spanning a wide radial and vertical range. To obtain reliable rotation curves for hyperfine lines, we extended standard methodologies to fit multi-component line profiles. We then sampled the likelihood of a thermally stratified model that reproduces all the rotation curves simultaneously, taking into account the molecular emitting layers and disk thermal structure. We obtained dynamical estimates of the stellar mass $M_\star=1.89$ M$_\odot$, the disk mass $M_\text{d}=0.12$ M$_\odot$, and scale radius $R_\text{c}=143$ au. We also explore how rotation curves and the parameter estimates depend on the adopted emitting layers: the disk mass proves to be the most affected by these systematics, yet the main trends we find do not depend on the adopted parameterization. Finally, we investigated the impact of thermal structure on gas kinematics, showing that the thermal stratification can efficiently explain the measured rotation velocity discrepancies between tracers at different heights. Our results show that such a multi-molecule approach, tracing a large range of emission layers, can provide unique constraints on the ($R,z$) pressure structure of protoplanetary disks., Comment: Accepted for publication in A&A; 17 pages, 17 figures. Fixed typos

Disk winds play a crucial role in the evolution of protoplanetary disks. Typical conditions for star and planet formation are in regions with intermediate or strong UV radiation fields produced by massive stars. The $\sigma$-Orionis cluster is the ideal site to study disk winds under these conditions; its outer parts can be used to study disk evolution, while its innermost regions to study the effect of external irradiation. For this, we analyze the $\rm [OI]\,\lambda$6300, $\rm [NII]\,\lambda$6583, and $\rm [SII]\,\lambda$6731,$\lambda$6716 lines using high-resolution MIKE spectra of 27 classical T Tauri stars and complemented by intermediate-resolution X-shooter data. We decompose the line profiles into multiple Gaussian components. We calculated luminosities, line ratios, and kinematic properties of these components. We found that the $\rm [OI]\,\lambda$6300 line luminosity and kinematic properties are similar to those found in low-mass star-forming regions (SFRs). The frequency of single-component $\rm [OI]\,\lambda$6300 line profiles reflects the expected evolutionary stage given the intermediate age of $\sigma$-Orionis. This points to internal processes contributing to the line emission. However, the highly irradiated disks do not follow the accretion - [OI] luminosity relation found in low-mass SFRs, and all exhibit single-component line profiles. Line ratios of highly ionized species of [NII] and [SII] show higher ratios than typical values found in low-mass SFRs. The innermost regions of $\sigma$-Orionis are clearly affected by external irradiation, evidenced by the lack of correlation in the accretion - [OI] luminosity relation. The broad line widths of close-in sources, however, indicate a contribution from internal processes, such as magnetohydrodynamical winds and/or internal photoevaporation. This suggests a coevolution of internal and external winds in $\sigma$-Orionis., Comment: Accepted for publication on Astronomy & Astrophysics. 14 pages, 11 figures + appendix. Abstract abridged to meet arXiv requirements

The dynamical interactions between young binaries can perturb the material distribution of their circumstellar disks, and modify the planet formation process. In order to constrain the impact and nature of the binary interaction in the RW Aur system (bound or unbound), we analyzed the circumstellar material at 1.3 mm wavelengths, as observed at multiple epochs by ALMA. We analyzed the disk properties through parametric visibility modeling, and we used this information to constrain the dust morphology and the binary orbital period. We imaged the dust continuum emission of RW Aur with a resolution of 3 au, and we find that the radius enclosing 90% of the flux (R90%) is 19 au and 14 au for RW Aur A and B, respectively. By modeling the relative distance of the disks at each epoch, we find a consistent trend of movement for the disk of RW Aur B moving away from the disk of RW Aur A at an approximate rate of 3 mas/yr (about 0.5 au/yr in sky-projected distance). By combining ALMA astrometry, historical astrometry, and the dynamical masses of each star, we constrain the RW Aur binary stars to be most likely in a high-eccentricity elliptical orbit with a clockwise prograde orientation relative to RW Aur A, although low-eccentricity hyperbolic orbits are not ruled out by the astrometry. Our analysis does not exclude the possibility of a disk collision during the last interaction, which occurred $295_{-74}^{+21}$ yr ago relative to beginning of 2024. Evidence for the close interaction is found in a tentative warp of 6 deg in the inner 3 au of the disk of RW Aur A, in the brightness temperature of both disks, and in the morphology of the gas emission. A narrow ring that peaks at 6 au around RW Aur B is suggestive of captured material from the disk around RW Aur A., Comment: Accepted in A&A. All self-calibrated data and products are publicly available in https://doi.org/10.5281/zenodo.12825068 . Short video summary in https://youtu.be/IOjEW8Vrj9Q

With two directly detected protoplanets, the PDS 70 system is a unique source in which to study the complex interplay between forming planets and their natal environment. The large dust cavity carved by the two giant planets can affect the disk chemistry, and therefore the molecular emission morphology. On the other hand, chemical properties of the gas component of the disk are expected to leave an imprint on the planetary atmospheres. In this work, we reconstruct the emission morphology of a rich inventory of molecular tracers in the PDS 70 disk, and we look for possible chemical signatures of the two actively accreting protoplanets, PDS b and c. We leverage Atacama Large Millimeter/submillimeter Array (ALMA) band 6 high-angular-resolution and deep-sensitivity line emission observations, together with image and $uv$-plane techniques, to boost the detection of faint lines. We robustly detect ring-shaped emission from $^{12}$CO, $^{13}$CO, C$^{18}$O, H$^{13}$CN, HC$^{15}$N, DCN, H$_2$CO, CS, C$_2$H, and H$^{13}$CO$^{+}$ lines in unprecedented detail. Most of the molecular tracers show a peak of the emission inside the millimeter dust peak. We interpret this as the direct impact of the effective irradiation of the cavity wall, as a result of the planet formation process. Moreover, we have found evidence of an O-poor gas reservoir in the outer disk, which is supported by the observations of bright C-rich molecules, the non-detection of SO, and a lower limit on the $\mathrm{CS/SO}$ ratio of $\sim1$. Eventually, we provide the first detection of the c-C$_3$H$_2$ transitions at 218.73 GHz, and the marginal detection of an azimuthal asymmetry in the higher-energy H$_2$CO (3$_{2,1}$-2$_{2,0}$) line, which could be due to accretion heating near PDS 70b., Comment: 25 pages, 10 figures, 3 tables, 8 figures and one table in appendix. Accepted for publication in A&A

The sample of planet-forming disks observed by high-contrast imaging campaigns over the last decade is mature enough to enable the demographical analysis of individual star-forming regions. We present the full census of Taurus sources with VLT/SPHERE polarimetric images available. The whole sample sums up to 43 targets (of which 31 have not been previously published) corresponding to one-fifth of the Class II population in Taurus and about half of such objects that are observable. A large fraction of the sample is apparently made up of isolated faint disks (equally divided between small and large self-shadowed disks). Ambient signal is visible in about one-third of the sample. This probes the interaction with the environment and with companions or the outflow activity of the system. The central portion of the Taurus region almost exclusively hosts faint disks, while the periphery also hosts bright disks interacting with their surroundings. The few bright disks are found around apparently older stars. The overall picture is that the Taurus region is in an early evolutionary stage of planet formation. Yet, some objects are discussed individually, as in an intermediate or exceptional stage of the disk evolution. This census provides a first benchmark for the comparison of the disk populations in different star forming regions., Comment: Accepted by A&A

We present SPHERE/IRDIS H-band data for a sample of 23 stars in the Orion Star forming region observed within the DESTINYS (Disk Evolution Study Through Imaging of Nearby Young Stars) program. We use polarization differential imaging in order to detect scattered light from circumstellar dust. From the scattered light observations we characterize the disk orientation, radius and contrast. We analyse the disks in context of the stellar parameters and the environment of the Orion star-forming region. We use ancillary X-shooter spectroscopic observations to characterize the central stars in the systems. We furthermore use a combination of new and archival ALMA mm-continuum observations to characterize the dust masses present in the circumstellar disks. Within our sample we detect extended circumstellar disks in 10 of 23 systems. Of these, three are exceptionally extended (V351 Ori, V599 Ori and V1012 Ori) and show scattered light asymmetries which may indicate perturbations by embedded planets or (in the case of V599 Ori) by an outer stellar companion. Our high resolution imaging observations are also sensitive to close (sub)stellar companions and we detect 9 such objects in our sample of which 5 were previously unknown. We find in particular a possible sub-stellar companion (either a very low mass star or a high mass brown dwarf) 137 au from the star RY Ori. We find a strong anti-correlation between disk detection and multiplicity, with only 2 of our 10 disk detections located in stellar multiple systems. We also find a correlation between scattered light contrast and the millimetre flux suggesting that disks that have a high dust content are typically bright in near-infrared scattered light. Conversely we do not find significant correlations between scattered light contrast of the disks and the stellar mass or age., Comment: Accepted by A&A

We used VLT/SPHERE to observe 20 systems in the Cha I cloud in polarized scattered light in the near-infrared. We combined the scattered light observations with existing literature data on stellar properties and with archival ALMA continuum data to study trends with system age and dust mass. We also connected resolved near-infrared observations with the spectral energy distributions of the systems. In 13 of the 20 systems included in this study we detected resolved scattered light signals from circumstellar dust. For the CR Cha, CT Cha, CV Cha, SY Cha, SZ Cha, and VZ Cha systems we present the first detailed descriptions of the disks in scattered light. The observations found typically smooth or faint disks, often with little substructure, with the notable exceptions of SZ Cha, which shows an extended multiple-ringed disk, and WW Cha, which shows interaction with the cloud environment. New high S/N K- band observations of the HD 97048 system in our survey reveal a significant brightness asymmetry that may point to disk misalignment and subsequent shadowing of outer disk regions, possibly related to the suggested planet candidate in the disk. We resolve for the first time the stellar binary in the CS Cha system. Multiple wavelength observations of the disk around CS Cha have revealed that the system contains small, compact dust grains that may be strongly settled, consistent with numerical studies of circumbinary disks. We find in our sample that there is a strong anti-correlation between the presence of a (close) stellar companion and the detection of circumstellar material with five of our seven nondetections located in binary systems., Comment: Accepted by A&A

Context. The study of protoplanetary disks is fundamental to understand their evolution and interaction with the surrounding environment, and to constrain planet formation mechanisms. Aims. We aim at characterising the young binary system HD 34700 A, which shows a wealth of structures. Methods. Taking advantage of the high-contrast imaging instruments SPHERE at the VLT, LMIRCam at the LBT, and of ALMA observations, we analyse this system at multiple wavelengths. We study the rings and spiral arms morphology and the scattering properties of the dust. We discuss the possible causes of all the observed features. Results. We detect for the first time, in the H${\alpha}$ band, a ring extending from $\sim$65 au to ${\sim}$120 au, inside the ring already known from recent studies. These two have different physical and geometrical properties. Based on the scattering properties, the outer ring may consist of grains of typical size $a_{out} > 4 {\mu}m$, while the inner ring of smaller grains ($a_{in} <= 0.4 {\mu m}$). Two extended logarithmic spiral arms stem from opposite sides of the disk. The outer ring appears as a spiral arm itself, with a variable radial distance from the centre and extended substructures. ALMA data confirm the presence of a millimetric dust substructure centred just outside the outer ring, and detect misaligned gas rotation patterns for HD 34700 A and B. Conclusions. The complexity of HD 34700 A, revealed by the variety of observed features, suggests the existence of one or more disk-shaping physical mechanisms. Possible scenarios, compatible with our findings, involve the presence inside the disk of a yet undetected planet of several Jupiter masses and the system interaction with the surroundings by means of gas cloudlet capture or flybys. Further observations with JWST/MIRI or ALMA (gas kinematics) could shed more light on these., Comment: Accepted for publication on A&A. 14 + 5 pages, 9 + 7 figures (text + appendix)

The evolution of protoplanetary disks is regulated by an interplay of several processes, either internal to the system or related to the environment. As most of the stars and planets have formed in massive stellar clusters, studying the effects of UV radiation on disk evolution is of paramount importance. Here we test the impact of external photoevaporation on the evolution of disks in the $\sigma$ Orionis cluster by conducting the first combined large-scale UV to IR spectroscopic and mm-continuum survey of this region. We study a sample of 50 targets located at increasing distances from the central, OB system $\sigma$ Ori. We combine new VLT/X-Shooter spectra with new and previously published ALMA measurements of disk dust and gas fluxes and masses. We confirm the previously found decrease of $M_{\rm dust}$ in the inner $\sim$0.5 pc of the cluster. This is particularly evident when considering the disks around the more massive stars ($\ge$ 0.4 $M_{\odot}$), where those located in the inner part ($<$ 0.5 pc) have $M_{\rm dust}$ about an order of magnitude lower than the more distant ones. About half of the sample is located in the region of the $\dot{M}_{\rm acc}$ vs $M_{\rm disk}$ expected by models of external photoevaporation, namely showing shorter disk lifetimes. These are observed for all targets with projected separation from $\sigma$ Ori $<$ 0.5 pc, proving that the presence of a massive stellar system affects disk evolution. External photoevaporation is a viable mechanism to explain the observed shorter disk lifetimes and lower $M_{\rm dust}$ in the inner $\sim$0.5 pc of the cluster. Follow-up observations of the low stellar mass targets are crucial to confirm the dependence of the external photoevaporation process with stellar host mass. This work confirms that the effects of external photoevaporation are significant down to impinging radiation as low as $\sim 10^{4}$ G$_0$., Comment: Accepted for publication on Astronomy & Astrophysics. 13 pages, 7 figures + appendix. Abstract abridged to meet arXiv requirements

Embedded planets are potentially the cause of substructures like gaps and cavities observed in several protoplanetary disks. Thus, the substructures observed in the continuum and in line emission encode information about the presence of planets in the system and how they interact with the natal disk. The pre-transitional disk around the star PDS 70 is the first case of two young planets imaged within a dust depleted gap that was likely carved by themselves. We aim to determine the spatial distribution of the gas and dust components in the PDS 70 disk. The axisymmetric substructures observed in the resulting profiles are interpreted in the context of planet-disk interactions. We develop a thermo-chemical forward model for an axisymmetric disk to explain a subset of the Atacama Large Millimeter/Submillimeter Array (ALMA) band 6 observations of three CO isotopologues plus the continuum towards PDS 70. Combining the inferred gas and dust distributions, the model results in a variable gas-to-dust ratio profile throughout the disk that spans two orders of magnitude within the first $130$ au and shows a step gradient towards the outer disk, which is consistent with the presence of a pressure maxima driven by planet-disk interactions. We find a gas density drop factor of ${\sim} 19$ at the location of the planet PDS 70 c with respect to the peak gas density at $75$ au. Combining this value with literature results on the hydrodynamics of planet-disk interactions, we find this gas gap depth to be consistent with independent planet mass estimates from infrared observations. Our findings point towards gas stirring processes taking place in the common gap due to the gravitational perturbation of both planets., Comment: Accepted for publication in A&A

Understanding the chemical link between protoplanetary disks and planetary atmospheres is complicated by the fact that the popular targets in the study of disks and planets are widely separated both in space and time. The 5 Myr PDS 70 systems offers a unique opportunity to directly compare the chemistry of a giant planet's atmosphere to the chemistry of its natal disk. To that end, we derive our current best physical and chemical model for the PDS 70 disk through forward modelling of the $^{12}$CO, C$^{18}$O, and C$_2$H emission radial profiles with the thermochemical code DALI and find a volatile C/O ratio above unity in the outer disk. Using what we know of the PDS 70 disk today, we analytically estimate the properties of the disk as it was 4 Myr in the past when we assume that the giant planets started their formation, and compute a chemical model of the disk at that time. We compute the formation of PDS 70b and PDS 70c using the standard core accretion paradigm and account for the accretion of volatile and refractory sources of carbon and oxygen to estimate the resulting atmospheric carbon-to-oxygen number ratio (C/O) for these planets. Our inferred C/O ratio of the gas in the PDS 70 disk indicates that it is marginally carbon rich relative to the stellar C/O = 0.44 which we derive from an empirical relation between stellar metallicity and C/O. Under the assumption that the disk has been carbon rich for most of its lifetime, we find that the planets acquire a super-stellar C/O in their atmospheres. If the carbon-rich disk is a relatively recent phenomenon (i.e. developed after the formation of the planets at $\sim 1$ Myr) then the planets should have close to the stellar C/O in their atmospheres. This work lays the groundwork to better understand the disk in the PDS 70 system as well as the planet formation scenario that produce its planets., Comment: 18 pages, 14 figures, 5 tables, accepted for publication in A&A

In this work we present the highest spatial and spectral resolution integral field observations to date of the bipolar jet from the Orion proplyd 244-440 using MUSE NFM) observations on the VLT. We observed a previously unreported chain of six distinct knots in a roughly S-shaped pattern, and by comparing them with HST images we estimated proper motions in the redshifted knots of 9.5 mas yr$^{-1}$ with an inclination angle of $73^{\circ}$, though these quantities could not be measured for the blueshifted lobe. Analysis of the [FeII] and [NiII] lines suggests jet densities on the order of $\sim 10^5$ cm$^{-3}$. We propose that the observed S-shaped morphology originates from a jet launched by a smaller source with $M_\star < 0.2$ M$_{\odot}$ in orbital motion around a larger companion of $M_\star \simeq 0.5$ M$_{\odot}$ at a separation of 30-40 au. The measured luminosities of the knots using the [OI]$\lambda6300$ and [SII]$\lambda6731$ lines were used to estimate a lower limit to the mass-loss rate in the jet of $1.3 \times 10^{-11}$ M$_{\odot}$ yr$^{-1}$ and an upper limit of $10^{-9}$ M$_{\odot}$ yr$^{-1}$, which is typical for low-mass driving sources. While the brightness asymmetry between the redshifted and blueshifted lobes is consistent with external irradiation, further analysis of the [NiII] and [FeII] lines suggests that photoionization of the jet is not likely to be a dominant factor, and that the emission is dominated by collisional excitation. The dynamical age of the jet compared to the anticipated survival time of the proplyd demonstrates that photoevaporation of the proplyd occurred prior to jet launching, and that this is still an active source. These two points suggest that the envelope of the proplyd may shield the jet from the majority of external radiation, and that photoionization of the proplyd does not appear to impact the ability of a star to launch a jet., Comment: 30 pages, 20 figures

Birth environments of young stars have strong imprints on the star itself and their surroundings. We present a detailed analysis of the wealthy circumstellar environment around the young Herbig Ae/Be star TCrA. Our aim is to understand the nature of the stellar system and the extended circumstellar structures as seen in scattered light images. We conduct our analysis combining archival data, and new adaptive optics high-contrast and high-resolution images. The scattered light images reveal the presence of a complex environment composed of a bright forward scattering rim of the disk's surface that is seen at very high inclination, a dark lane of the disk midplane, bipolar outflows, and streamer features likely tracing infalling material from the surrounding birth cloud onto the disk. The analysis of the light curve suggests the star is a binary with a period of 29.6yrs. The comparison of the scattered light images with ALMA continuum and 12CO line emission shows the disk is in keplerian rotation, with the northern side of the outflowing material receding, while the southern side approaching the observer. The disk is itself seen edge-on. The direction of the outflows seen in scattered light is in agreement with the direction of the more distant molecular hydrogen emission-line objects (MHOs) associated to the star. Modeling of the SED using a radiative transfer scheme well agrees with the proposed configuration, as well as the hydrodynamical simulation performed using a Smoothed Particle Hydrodynamics code. We find evidence of streamers of accreting material around TCrA. These streamers connect the filament along which TCrA is forming with the outer parts of the disk, suggesting that the strong misalignment between the inner and outer disk is due to a change in the direction of the angular momentum of the material accreting on the disk during the late phase of star formation., Comment: 17 pages, 14 figures

ALMA observations of line emission from planet forming discs have demonstrated to be an excellent tool to probe the internal disc kinematics, often revealing subtle effects related to important dynamical processes occurring in them, such as turbulence, or the presence of planets, that can be inferred from pressure bumps perturbing the gas motion, or from detection of the planetary wake. In particular, we have recently shown for the case of the massive disc in Elias 2-27 how one can use such kind of observations to measure deviations from Keplerianity induced by the disc self-gravity, thus constraining the total disc mass with good accuracy and independently on mass conversion factors between the tracer used and the total mass. Here, we refine our methodology and extend it to two additional sources, GM Aur and IM Lup, for which archival line observations are available for both the 12CO and the 13CO line. For IM Lup, we are able to obtain a consistent disc mass of Mdisc=0.1 Msun, implying a disc-star mass ratio of 0.1 (consistent with the observed spiral structure in the continuum emission) and a gas/dust ratio of ~ 65 (consistent with standard assumptions), with a systematic uncertainty by a factor ~2 due to the different methods to extract the rotation curve. For GM Aur, the two lines we use provide slightly inconsistent rotation curves, that cannot be attributed only to a difference in the height of the emitting layer, nor to a vertical temperature stratification. Our best fit disc mass measurement is Mdisc=0.26Msun, implying a disc-star mass ratio of ~0.35 and a gas/dust ratio of ~130... ABRIDGED, Comment: 14 pages, 10 figures, MNRAS in press

We aim to directly trace the vertical location of the emitting surface of multiple molecular tracers in protoplanetary disks. Our sample of disks includes Elias 2-27, WaOph 6 and the sources targeted by the MAPS ALMA Large Program. The set of molecules studied include CO isotopologues in various transitions, HCN, CN, H2CO, HCO+, C2H and c-C3H2. The vertical emitting region is determined directly from the channel maps, implementing accurate masking of the channel emission to recover the vertical location of the emission surface even at large radial distances from the star and for low-SNR lines. The vertical location of the emitting layer is obtained for 4-10 lines in each disk. IM Lup, HD163296 and MWC 480 12CO and 13CO show vertical modulations, which are coincident with dust gaps and kinematical perturbations. We also present estimates of the gas pressure scale height in the disks from the MAPS sample. Compared to physical-chemical models we find good agreement with the vertical location of CO isotopologues. In HD 163296 CN and HCN trace a similar intermediate layer, for the other disks, the UV flux tracers and the vertical profiles of HCN and C2H are lower than predicted in theoretical models. HCN and H2CO show a highly structured vertical profile, possibly indicative of different formation pathways. It is possible to trace the vertical locations of multiple molecular species that trace a wide variety of physical and chemical disk properties. The distribution of CO isotopologues are found at a wide range of vertical heights $z/r = $ 0.5-0.05. Other molecular lines are mostly found at $z/r \leq $0.15. The vertical layering of molecules is in agreement with theory in some systems, but not in all, therefore dedicated chemical-physical models are needed to further study and understand the emission surfaces., Comment: Accepted for publication in A&A. 29 pages, 28 figures

Disk winds are an important mechanism for accretion and disk evolution around young stars. The accreting intermediate-mass T-Tauri star RY Tau has an active jet and a previously known disk wind. Archival optical and new near-infrared observations of the RY Tau system show two horn-like components stretching out as a cone from RY Tau. Scattered light from the disk around RY Tau is visible in near-infrared but not seen at optical wavelengths. In the near-infrared, dark wedges that separates the horns from the disk, indicating we may see the scattered light from a disk wind. We use archived ALMA and SPHERE/ZIMPOL I-band observations combined with newly acquired SPEHRE/IRDIS H-band observations and available literature to build a simple geometric model of the RY Tau disk and disk wind. We use Monte Carlo radiative transfer modelling \textit{MCMax3D} to create comparable synthetic observations that test the effect of a dusty wind on the optical effect in the observations. We constrain the grain size and dust mass needed in the disk wind to reproduce the effect from the observations. A model geometrically reminiscent of a dusty disk wind with small micron to sub-micron size grains elevated above the disk can reproduce the optical effect seen in the observations. The mass in the obscuring component of the wind has been constrained to $1\times10^{-9} M_{\odot} \leq M \leq 5\times10^{-8} M_{\odot}$ which corresponds to a lower limit mass loss rate in the wind of about $\sim 1\times10^{-8}M_{\odot}\mathrm{yr}^{-1}$. While an illuminate dust cavity cannot be ruled out without measurements of the gas velocity, we argue that a magnetically launched disk wind is the most likely scenario., Comment: 11 pages, 5 figures

Elias 2-27 is a young star that hosts an extended, bright and inclined disk of dust and gas. The inclination and extreme flaring of the disk make Elias 2-27 an ideal target to study the vertical distribution of molecules, particularly CN. We directly trace the emission of CN in Elias 2-27 and compare it to previously published CO isotopologue data. CN $N = 3-2$ emission is analyzed in two different transitions $J = 7/2 - 5/2$ and $J = 5/2 - 3/2$, for which we detect two hyperfine group transitions. The vertical location of CN emission is traced directly from the channel maps, following geometrical methods that have been previously used to analyze the CO emission of Elias 2-27. Analytical models are used to parametrize the vertical profile of each molecule and study the extent of each tracer, additionally we compute radial profiles of column density and optical depth. We show that the vertical location of CN and CO isotopologues in Elias 2-27 is layered and consistent with predictions from thermochemical models. A north/south asymmetry in the radial extent of CN is detected and we find that the CN emission is mostly optically thin and constrained vertically to a thin slab at $z/r \sim$0.5. A column density of 10$^{14}$\,cm$^{-2}$ is measured in the inner disk which for the north side decreases to 10$^{12}$\,cm$^{-2}$ and for the south side to 10$^{13}$\,cm$^{-2}$ in the outer regions. In Elias 2-27, CN traces a vertically elevated region above the midplane, very similar to that traced by $^{12}$CO. The inferred CN properties are consistent with thermo-chemical disk models, in which CN formation is initiated by the reaction of N with UV-pumped H$_2$. The observed north/south asymmetry may be caused by either ongoing infall or by a warped inner disk. This study highlights the importance of tracing the vertical location of various molecules to constrain the disk physical conditions., Comment: Accepted for publication in A&A, 19 pages, 14 figures

(Abridged) Exoplanetary research has provided us with exciting discoveries of planets around very low-mass (VLM) stars (e.g., TRAPPIST-1 and Proxima Centauri). However, current theoretical models strive to explain planet formation in these conditions and do not predict the development of giant planets. Recent high-resolution observations from ALMA of the disk around CIDA 1, a VLM star in Taurus, show substructures hinting at the presence of a massive planet. We aim to reproduce the dust ring of CIDA 1, observed in the dust continuum emission in ALMA Band 7 (0.9 mm) and Band 4 (2.1 mm), along with its $^{12}$CO (J=3-2) and $^{13}$CO (J=3-2) channel maps, assuming the structures are shaped by the interaction of the disk with a massive planet. We seek to retrieve the mass and position of the putative planet. We model the protoplanetary disk with a set of hydrodynamical simulations, varying the mass and locations of the embedded planet. We compute the dust and gas emission using radiative transfer simulations, and, finally, we obtain the synthetic observations treating the images as the actual ALMA observations. Our models indicate that a planet with a minimum mass of $\sim1.4\,\text{M}_\text{Jup}$ orbiting at a distance of $\sim 9-10$ au can explain the morphology and location of the observed dust ring at Band 7 and Band 4. We can reproduce the low spectral index ($\sim 2$) observed where the dust ring is detected. Our synthetic images reproduce the morphology of the $^{12}$CO and $^{13}$CO observed channel maps where the cloud absorption allowed a detection. Applying an empirical relation between planet mass and gap width in the dust, we predict a maximum planet mass of $\sim4 - 8\,\text{M}_\text{Jup}$. Our results suggest the presence of a massive planet orbiting CIDA 1, thus challenging our understanding of planet formation around VLM stars., Comment: Accepted for publication in A&A, 22 pages, 21 figures, 3 tables

[Abridged] Most disks observed at high angular resolution show substructures. Knowledge about the gas surface density and temperature is essential to understand these. The aim of this work is to constrain the gas temperature and surface density in two transition disks: LkCa15 and HD 169142. We use new ALMA observations of the $^{13}$CO $J=6-5$ transition together with archival $J=2-1$ data of $^{12}$CO, $^{13}$CO and C$^{18}$O to observationally constrain the gas temperature and surface density. Furthermore, we use the thermochemical code DALI to model the temperature and density structure of a typical transition disk. The $6-5/2-1$ line ratio in LkCa15 constrains the gas temperature in the emitting layers inside the dust cavity to be up to 65 K, warmer than in the outer disk at 20-30 K. For the HD 169142, the peak brightness temperature constrains the gas in the dust cavity of HD 169142 to be 170 K, whereas that in the outer disk is only 100 K. Models also show that a more luminous central star, a lower abundance of PAHs and the absence of a dusty inner disk increase the temperature of the emitting layers and hence the line ratio in the gas cavity. The gas column density in the LkCa15 dust cavity drops by a factor >2 compared to the outer disk, with an additional drop of an order of magnitude inside the gas cavity at 10 AU. In the case of HD 169142, the gas column density drops by a factor of 200$-$500 inside the gas cavity, which could be due to a massive companion of several M$_{\mathrm{J}}$. The broad dust-depleted gas region from 10-68 AU for LkCa15 may imply several lower mass planets. This work demonstrates that knowledge of the gas temperature is important to determine the gas surface density and thus whether planets, and if so what kind of planets, are the most likely carving the dust cavities., Comment: Accepted for publication in Astronomy and astrophysics

The composition of planets may be largely determined by the chemical processing and accretion of icy pebbles in protoplanetary disks. Recent observations of protoplanetary disks hint at wide-spread depletion of gaseous carbon. The missing volatile carbon is likely frozen in CO and/or CO$_2$ ice on grains and locked into the disk through pebble trapping in pressure bumps or planetesimals. We present the results of the first successful ACA (Atacama Compact Array) [C I] $J$ = 1-0 mini-survey of seven protoplanetary disks. Using tailored azimuthally symmetric DALI (Dust And LInes) thermo-chemical disk models, supported by the [C I] $J$ = 1-0 and resolved CO isotopologue data, we determine the system-averaged elemental volatile carbon abundance in the outer disk of three sources. Six out of seven sources are detected in [C I] $J$ = 1-0 with ACA, four of which show a distinct disk component. Based on the modeling we find severe cold gaseous carbon depletion in the outer disk of DL Tau and moderate depletion in the outer disks of DR Tau and DO Tau. Combining the outer and inner disk carbon abundances, we demonstrate definitive evidence for radial drift in the disk of DL Tau, where the existence of multiple dust rings points to either short lived or leaky dust traps. We find dust locking in the compact and smooth disks of DO Tau and DR Tau, hinting at unresolved dust substructure. Comparing our results with stars of different ages and luminosities, we identify an observational evolutionary trend in gaseous carbon depletion that is consistent with dynamical models of CO depletion processes. Transport efficiency of solids in protoplanetary disks can significantly differ from what we expect based on the current resolved substructure in the continuum observations. This has important implications for our understanding of the impact of radial drift and pebble accretion on planetary compositions., Comment: 23 pages, 19 figures, accepted to A&A

The formation of multiple stellar systems is a natural by-product of the star-formation process, and its impact on the properties of protoplanetary discs and on the formation of planets is still to be fully understood. To date, no detailed uniform study of the gas emission from a sample of protoplanetary discs around multiple stellar systems has been performed. Here we analyse new ALMA observations at a $\sim$21 au resolution of the molecular CO gas emission targeting discs in eight multiple stellar systems in the Taurus star-forming regions. $^{12}$CO gas emission is detected around all primaries and in seven companions. With these data, we estimate the inclination and the position angle for all primary discs and for five secondary or tertiary discs, and measure the gas disc radii of these objects with a cumulative flux technique on the spatially resolved zeroth moment images. When considering the radius including 95\% of the flux as a metric, the estimated gas disc size in multiple stellar systems is found to be on average $\sim 4.2$ times larger than the dust disc size. This ratio is higher than what was recently found in a population of more isolated and single systems. On the contrary, when considering the radius including 68\% of the flux, no difference between multiple and single discs is found in the distribution of ratios. This discrepancy is due to the sharp truncation of the outer dusty disc observed in multiple stellar systems. The measured gas disc sizes are consistent with tidal truncation models in multiple stellar systems assuming eccentricities of $\sim0.15$-$0.5$, as expected in typical binary systems., Comment: 25 pages, 29 figures, 9 tables. Accepted for publication in A&A

For several transition disks (TDs), dark regions interpreted as shadows have been observed in scattered light imaging and are hypothesized to originate from misalignments between distinct disk regions. We aim to investigate the presence of misalignments in TDs. We study the inner disk geometries of 20 well-known transition disks with VLTI/GRAVITY observations and use complementary $^{12}$CO and $^{13}$CO molecular line data from ALMA to derive the orientation of the outer disk regions. We fit simple models to the GRAVITY data to derive the inner disks inclination and position angles. The outer disk geometries were derived from Keplerian fits to the ALMA velocity maps and compared to the inner disk constraints. We also predicted the locations of shadows for significantly misaligned systems. Our analysis reveals six disks to exhibit significant misalignments between their inner and outer disks. The predicted shadow positions agree well with the scattered light images of HD100453 and HD142527, and we find supporting evidence for a shadow in the disk around CQ Tau. In the other three targets for which we infer significantly misaligned disks, V1247 Ori, V1366 Ori, and RY Lup, we do not see any evident sign of shadows in the scattered light images. The scattered light shadows observed in DoAr44, HD135344B, and HD139614 are consistent with our observations, yet the underlying morphology is likely too complex to be described by our models and the accuracy achieved by our observations. Whereas we can derive precise constraints on the potential shadow positions for well-resolved inner disks around HAeBe stars, the statistical uncertainties for the marginally resolved inner disks around the TTS of our sample make it difficult to extract conclusive constraints for the presence of shadows in these systems., Comment: Accepted for publication in Astronomy \& Astrophysics

To date, nearly two hundred planet-forming disks have been imaged with high resolution. Our propensity to study bright and extended objects is however biasing our view of the disk demography. In this work, we contribute to alleviate this bias by analyzing fifteen disks targeted with VLT/SPHERE that look faint in scattered light. Sources were selected based on a low far-IR excess from the spectral energy distribution. The comparison with the ALMA images available for a few sources shows that the scattered light surveyed by these datasets is only detected from a small portion of the disk extent. The mild anti-correlation between the disk brightness and the near-IR excess demonstrates that these disks are self-shadowed: the inner disk rim intercepts much starlight and leaves the outer disk in penumbra. Based on the uniform distribution of the disk brightness in scattered light across all spectral types, self-shadowing would act similarly for inner rims at a different distance from the star. We discuss how the illumination pattern of the outer disk may evolve with time. Some objects in the sample are proposed to be at an intermediate stage toward bright disks from the literature with either no shadow or with sign of azimuthally confined shadows., Comment: Accepted for publication in A\&A

The evolution of young stars and disks is driven by the interplay of several processes, notably accretion and ejection of material. Critical to correctly describe the conditions of planet formation, these processes are best probed spectroscopically. About five-hundred orbits of the Hubble Space Telescope (HST) are being devoted in 2020-2022 to the ULLYSES public survey of about 70 low-mass (M<2Msun) young (age<10 Myr) stars at UV wavelengths. Here we present the PENELLOPE Large Program that is being carried out at the ESO Very Large Telescope (VLT) to acquire, contemporaneous to HST, optical ESPRESSO/UVES high-resolution spectra to investigate the kinematics of the emitting gas, and UV-to-NIR X-Shooter medium-resolution flux-calibrated spectra to provide the fundamental parameters that HST data alone cannot provide, such as extinction and stellar properties. The data obtained by PENELLOPE have no proprietary time, and the fully reduced spectra are made available to the whole community. Here, we describe the data and the first scientific analysis of the accretion properties for the sample of thirteen targets located in the Orion OB1 association and in the sigma-Orionis cluster, observed in Nov-Dec 2020. We find that the accretion rates are in line with those observed previously in similarly young star-forming regions, with a variability on a timescale of days of <3. The comparison of the fits to the continuum excess emission obtained with a slab model on the X-Shooter spectra and the HST/STIS spectra shows a shortcoming in the X-Shooter estimates of <10%, well within the assumed uncertainty. Its origin can be either a wrong UV extinction curve or due to the simplicity of this modelling, and will be investigated in the course of the PENELLOPE program. The combined ULLYSES and PENELLOPE data will be key for a better understanding of the accretion/ejection mechanisms in young stars., Comment: Accepted for publication on Astronomy & Astrophysics. 15 pages + appendix, language edited version

Gas-rich circumstellar disks are the cradles of planet formation. As such, their evolution will strongly influence the resulting planet population. In the ESO DESTINYS large program, we study these disks within the first 10 Myr of their development with near-infrared scattered light imaging. Here we present VLT/SPHERE polarimetric observations of the nearby class II system SU Aur in which we resolve the disk down to scales of ~7 au. In addition to the new SPHERE observations, we utilize VLT/NACO, HST/STIS and ALMA archival data. The new SPHERE data show the disk around SU Aur and extended dust structures in unprecedented detail. We resolve several dust tails connected to the Keplerian disk. By comparison with ALMA data, we show that these dust tails represent material falling onto the disk. The disk itself shows an intricate spiral structure and a shadow lane, cast by an inner, misaligned disk component. Our observations suggest that SU Aur is undergoing late infall of material, which can explain the observed disk structures. SU Aur is the clearest observational example of this mechanism at work and demonstrates that late accretion events can still occur in the class II phase, thereby significantly affecting the evolution of circumstellar disks. Constraining the frequency of such events with additional observations will help determine whether this process is responsible for the spin-orbit misalignment in evolved exoplanet systems., Comment: 18 pages, 12 figures, published in ApJL on 18-02-2021

We perform a comprehensive demographic study of the CO extent relative to dust of the disk population in the Lupus clouds, in order to find indications of dust evolution and possible correlations with other properties. We increase up to 42 the number of disks of the region with measured CO and dust sizes ($R_{\mathrm{CO}}$, $R_{\mathrm{dust}}$) from observations with the Atacama Large Millimeter/submillimeter Array (ALMA). The sizes are obtained from modeling the ${^{12}}$CO $J = 2-1$ line emission and continuum emission at $\sim 0.89$ mm with an empirical function (Nuker profile or Gaussian function). The CO emission is more extended than the dust continuum, with a $R_{68\%}^{\mathrm{CO}}$/$R_{68\%}^{\mathrm{dust}}$ median value of 2.5, for the entire population and for a sub-sample with high completeness. 6 disks, around $15\%$ of the Lupus disk population have a size ratio above 4. Based on thermo-chemical modeling, this value can only be explained if the disk has undergone grain growth and radial drift. These disks do not have unusual properties in terms of stellar mass ($M_{\star}$), disk mass ($M_{\mathrm{disk}}$), CO and dust sizes ($R_{\mathrm{CO}}$, $R_{\mathrm{dust}}$), and mass accretion. We search for correlations between the size ratio and $M_{\star}$, $M_{\mathrm{disk}}$, $R_{\mathrm{CO}}$ and $R_{\mathrm{dust}}$: only a weak monotonic anti-correlation with the $R_{\mathrm{dust}}$ is found. The lack of strong correlations is remarkable and suggests that the bulk of the population may be in a similar evolutionary stage, independent of the stellar and disk properties. These results should be further investigated, since the optical depth difference between CO and dust continuum may play a role in the inferred size ratios. Lastly, the CO emission for the majority of the disks is consistent with optically thick emission and an average CO temperature of around 30 K., Comment: Accepted for publication on A&A, 14 pages of main text with 5 figures, and 11 pages of appendices A, B, C, D, E and F with 13 figures

We present K-band interferometric observations of the PDS 70 protoplanets along with their host star using VLTI/GRAVITY. We obtained K-band spectra and 100 $\mu$as precision astrometry of both PDS 70 b and c in two epochs, as well as spatially resolving the hot inner disk around the star. Rejecting unstable orbits, we found a nonzero eccentricity for PDS 70 b of $0.17 \pm 0.06$, a near-circular orbit for PDS 70 c, and an orbital configuration that is consistent with the planets migrating into a 2:1 mean motion resonance. Enforcing dynamical stability, we obtained a 95% upper limit on the mass of PDS 70 b of 10 $M_\textrm{Jup}$, while the mass of PDS 70 c was unconstrained. The GRAVITY K-band spectra rules out pure blackbody models for the photospheres of both planets. Instead, the models with the most support from the data are planetary atmospheres that are dusty, but the nature of the dust is unclear. Any circumplanetary dust around these planets is not well constrained by the planets' 1-5 $\mu$m spectral energy distributions (SEDs) and requires longer wavelength data to probe with SED analysis. However with VLTI/GRAVITY, we made the first observations of a circumplanetary environment with sub-au spatial resolution, placing an upper limit of 0.3~au on the size of a bright disk around PDS 70 b., Comment: 30 pages, 9 figures, Accepted for publication in AJ

To understand the formation of planetary systems, one needs to understand the initial conditions of planet formation, i.e. the young gas-rich planet forming disks. Spatially resolved high-contrast observations are of particular interest, since substructures in disks, linked to planet formation, can be detected and close companions or even planets in formation embedded in the disk can be revealed. In this study we present the first result of the DESTINYS survey (Disk Evolution Study Through Imaging of Nearby Young Stars). DESTINYS is an ESO/SPHERE large program that aims at studying disk evolution in scattered light, mainly focusing on a sample of low-mass stars (<1$M_\odot$) in nearby (~200 pc) star-forming regions. In this particular study we present the observations of the ET Cha (RECX 15) system, a nearby 'old' classical T Tauri star (5-8 Myr, ~100 pc), which is still strongly accreting. We use SPHERE/IRDIS in H-band polarimetric imaging mode to obtain high contrast images of the ET Cha system to search for scattered light from the circumstellar disk as well as thermal emission from close companions. We additionally employ VLT/NACO total intensity archival data taken in 2003. We report here the discovery of a low-mass (sub)stellar companion with SPHERE/IRDIS to ET Cha. We are estimating the mass of this new companion based on photometry. Depending on the system age it is a 5 Myr, 50 $M_{Jup}$ brown dwarf or an 8 Myr, 0.10 $M_\odot$ M-type pre-main-sequence star. We explore possible orbital solutions and discuss the recent dynamic history of the system. Independent of the precise companion mass we find that the presence of the companion likely explains the small size of the disk around ET Cha. The small separation of the binary pair indicates that the disk around the primary component is likely clearing from the outside in, explaining the high accretion rate of the system., Comment: 14 pages, 9 figures, accepted for publication in A&A on 09-07-2020

We present high resolution millimeter continuum ALMA observations of the disks around the T Tauri stars LkCa 15 and J1610. These disks host dust-depleted inner regions, possibly carved by massive planets, and are of prime interest to study the imprints of planet-disk interactions. While at moderate angular resolution they appear as a broad ring surrounding a cavity, the continuum emission resolves into multiple rings at a resolution of ~60$\times$40 mas (~7.5 au for LkCa 15, ~6 au for J1610) and ~$7\,\mu$Jy beam$^{-1}$ rms at 1.3 mm. In addition to a broad extended component, LkCa 15 and J1610 host 3 and 2 narrow rings, respectively, with two bright rings in LkCa 15 being radially resolved. The rings look marginally optically thick, with peak optical depths of ~0.5 (neglecting scattering), in agreement with high angular resolution observations of full disks. We perform hydrodynamical simulations with an embedded, sub-Jovian-mass planet and show that the observed multi-ringed substructure can be qualitatively explained as the outcome of the planet-disk interaction. We note however that the choice of the disk cooling timescale alone can significantly impact the resulting gas and dust distributions around the planet, leading to different numbers of rings and gaps and different spacings between them. We propose that the massive outer disk regions of transition disks are favorable places for planetesimals and possibly second generation planet formation of objects with a lower mass than the planets carving the inner cavity (typically few $M_{\rm Jup}$), and that the annular substructures observed in LkCa 15 and J1610 may be indicative of planetary core formation within dust-rich pressure traps. Current observations are compatible with other mechanisms being at the origin of the observed substructures, in particular with narrow rings generated at the edge of the CO and N$_2$ snowlines., Comment: 17 pages, accepted for publication in Astronomy & Astrophysics

Recent ALMA surveys of protoplanetary disks have shown that for most disks the extent of the gas emission is greater than the extent of the thermal emission of the millimeter-sized dust. Both line optical depth and the combined effect of radially dependent grain growth and radial drift may contribute to this observed effect. For a sample of 10 disks from the Lupus survey we investigate how well dust-based models without radial dust evolution reproduce the observed 12CO outer radius, and determine whether radial dust evolution is required to match the observed gas-dust size difference. We used the thermochemical code DALI to obtain 12CO synthetic emission maps and measure gas and dust outer radii (Rco, Rmm) using the same methods as applied to the observations, which were compared to observations on a source-by-source basis. For 5 disks we find that the observed gas-dust size difference is larger than the gas-dust size difference due to optical depth, indicating that we need both dust evolution and optical depth effects to explain the observed gas-dust size difference. For the other 5 disks the observed gas-dust size difference can be explained using only line optical depth effects. We also identify 6 disks not included in our initial sample but part of a survey of the same star-forming region that show significant 12CO emission beyond 4 x Rmm. These disks, for which no Rco is available, likely have gas-dust size differences greater than 4 and are difficult to explain without substantial dust evolution. Our results suggest that radial drift and grain growth are common features among both bright and fain disks. The effects of radial drift and grain growth can be observed in disks where the dust and gas radii are significantly different, while more detailed models and deeper observations are needed to see this effect in disks with smaller differences., Comment: 17 pages, 11 figures, accepted in A&A

Shadows in scattered light images of protoplanetary disks are a common feature and support the presence of warps or misalignments between disk regions. These warps are possibly due to an inclined (sub-)stellar companion embedded in the disk. We study the morphology of the protoplanetary disk around the Herbig Ae star HD 139614 based on the first scattered light observations of this disk, which we model with the radiative transfer code MCMax3D. We obtained J- and H-band observations in polarized scattered light with VLT/SPHERE that show strong azimuthal asymmetries. In the outer disk, beyond ~30 au, a broad shadow spans a range of ~240{\deg} in position angle, in the East. A bright ring at ~16 au also shows an azimuthally asymmetric brightness, with the faintest side roughly coincidental with the brightest region of the outer disk. Additionally, two arcs are detected at ~34 au and ~50 au. We created a simple 4-zone approximation to a warped disk model of HD 139614 in order to qualitatively reproduce these features. The location and misalignment of the disk components were constrained from the shape and location of the shadows they cast. We find that the shadow on the outer disk covers a range of position angle too wide to be explained by a single inner misaligned component. Our model requires a minimum of two separate misaligned zones -- or a continuously warped region -- to cast this broad shadow on the outer disk. A small misalignment of ~4{\deg} between adjacent components can reproduce most of the observed shadow features. Multiple misaligned disk zones, potentially mimicing a warp, can explain the observed broad shadows in the HD 139614 disk. A planetary mass companion in the disk, located on an inclined orbit, could be responsible for such a feature and for the dust depleted gap responsible for a dip in the SED., Comment: Accepted for publication in A&A

We present new 890 $\mu m$ continuum ALMA observations of 5 brown dwarfs (BDs) with infrared excess in Lupus I and III -- which, in combination with 4 BDs previously observed, allowed us to study the mm properties of the full known BD disk population of one star-forming region. Emission is detected in 5 out of the 9 BD disks. Dust disk mass, brightness profiles and characteristic sizes of the BD population are inferred from continuum flux and modeling of the observations. Only one source is marginally resolved, allowing for the determination of its disk characteristic size. We conduct a demographic comparison between the properties of disks around BDs and stars in Lupus. Due to the small sample size, we cannot confirm or disprove if the disk mass over stellar mass ratio drops for BDs, as suggested for Ophiuchus. Nevertheless, we find that all detected BD disks have an estimated dust mass between 0.2 and 3.2 $M_{\bigoplus}$; these results suggest that the measured solid masses in BD disks can not explain the observed exoplanet population, analogous to earlier findings on disks around more massive stars. Combined with the low estimated accretion rates, and assuming that the mm-continuum emission is a reliable proxy for the total disk mass, we derive ratios of $\dot{M}_{\mathrm{acc}} / M_{\mathrm{disk}}$ significantly lower than in disks around more massive stars. If confirmed with more accurate measurements of disk gas masses, this result could imply a qualitatively different relationship between disk masses and inward gas transport in BD disks., Comment: Accepted for publication on A&A, 14 pages of main text with 13 figures, and 9 pages of appendices A, B, C and D with 14 figures

ALMA surveys have shown that CO emission in protoplanetary disks is much fainter than expected. Accordingly, CO-based gas masses and gas/dust ratios are orders of magnitude lower than previously thought. This may be explained either as fast gas dispersal, or as chemical evolution and locking up of volatiles in larger bodies leading to the low observed CO fluxes. The latter processes lead to enhanced C/O ratios in the gas, which may be reflected in enhanced abundances of molecules like C2H. The goal of this work is to employ C2H observations to understand whether low CO fluxes are caused by volatile depletion, or by fast gas dissipation. We present ALMA Cycle 4 C2H observations of a subsample of nine sources in Lupus. The integrated C2H emission is determined and compared to previous CO observations and model predictions. Seven out of nine disks are detected in C2H, whose line emission is almost as bright as 13CO. All detections are significantly brighter than the typical sensitivity of the observations, hinting at a bimodal distribution of the C2H line intensities. When compared with DALI models, the observed C2H fluxes can be reproduced only if some level of volatile carbon and oxygen depletion is allowed and C/O>1 in the gas. Models with reduced gas/dust ratios fail instead to reproduce the observations. A steeper than linear correlation between C2H and CN emission line is found. This is linked to the fact that C2H emission lines are affected more strongly by C/O variations than CN lines. Ring-like structures are detected both in C2H and in continuum emission but, as for CN, they do not seem to be connected. Sz 71 shows ring shaped emission in both C2H and CN with the location of the peak intensity coinciding. Our new ALMA C2H observations favour volatile carbon and oxygen depletion rather than fast gas dispersal to explain the faint CO observations for most of the disks., Comment: 11 pages, 12 figures, accepted for publication on A&A

The large majority of protoplanetary disks have very compact ($\lesssim15\,$AU) continuum emission at mm wavelengths. However, high angular resolution observations that resolve these small disks are still lacking, due to their intrinsically fainter emission compared with large bright disks. In this letter, we present $1.3\,$mm ALMA data of the faint ($\sim10\,$mJy) disk orbiting the TTauri star CX Tau at a resolution of $\sim40\,$mas, $\sim5\,$AU in diameter. The mm-dust disk is compact, with a 68$\%$ enclosing flux radius of 14$\,$AU, and the intensity profile exhibits a sharp drop between 10-20$\,$AU, and a shallow tail between 20-40$\,$AU. No clear signatures of substructure in the dust continuum are observed, down to the same sensitivity level of the DSHARP large program. However, the angular resolution does not allow to detect substructures at a scale of the disk aspect ratio in the inner regions. The radial intensity profile resembles well the inner regions of more extended disks imaged at the same resolution in DSHARP, but with no rings present in the outer disk. No inner cavity is detected, even though the disk has been classified as a transition disk from the spectral energy distribution in the near infrared. The emission of $^{12}$CO is much more extended, with a 68$\%$ enclosing flux radius of 75$\,$AU. The large difference of the mm dust and gas extents ($>5$) strongly points to the occurrence of radial drift, and matches well the predictions of theoretical models., Comment: Accepted for publication in A&A Letters

In recent years, the disk populations in a number of young star-forming regions have been surveyed with ALMA. Understanding the disk properties and their correlation with those of the central star is critical to understand planet formation. In particular, a decrease of the average measured disk dust mass with the age of the region has been observed. We conducted high-sensitivity continuum ALMA observations of 43 Class II young stellar objects in CrA at 1.3 mm (230 GHz). The typical spatial resolution is 0.3". The continuum fluxes are used to estimate the dust masses of the disks, and a survival analysis is performed to estimate the average dust mass. We also obtained new VLT/X-Shooter spectra for 12 of the objects in our sample. 24 disks are detected, and stringent limits have been put on the average dust mass of the non-detections. Accounting for the upper limits, the average disk mass in CrA is $6\pm3\,\rm M_\oplus$, significantly lower than that of disks in other young (1-3 Myr) star forming regions (e.g. Lupus) and appears consistent with the 5-10 Myr old Upper Sco. The position of the stars in our sample on the HR diagram, however, seems to confirm that that CrA has age similar to Lupus. Neither external photoevaporation nor a lower than usual stellar mass distribution can explain the low disk masses. On the other hand, a low-mass disk population could be explained if the disks are small, which could happen if the parent cloud has a low temperature or intrinsic angular momentum, or if the the angular momentum of the cloud is removed by some physical mechanism such as magnetic braking. In order to fully explain and understand the dust mass distribution of protoplanetary disks and their evolution, it may also be necessary to take into consideration the initial conditions of star and disk formation process, which may vary from region to region, and affect planet formation., Comment: 20 pages, 8 Figures, accepted for publication on A&A. The abstract has been shortened in order to fit arXiv requirements

Despite their importance in the star formation process, measurements of magnetic field strength in proto-planetary discs remain rare. While linear polarisation of dust and molecular lines can give insight into the magnetic field structure, only observations of the circular polarisation produced by Zeeman splitting provide a direct measurement of magnetic field strenghts. One of the most promising probes of magnetic field strengths is the paramagnetic radical CN. Here we present the first Atacama Large Millimeter/submillimeter Array (ALMA) observations of the Zeeman splitting of CN in the disc of TW~Hya. The observations indicate an excellent polarisation performance of ALMA, but fail to detect significant polarisation. An analysis of eight individual CN hyperfine components as well as a stacking analysis of the strongest (non-blended) hyperfine components yields the most stringent limits obtained so far on the magnetic field strength in a proto-planetary disc. We find that the vertical component of the magnetic field $|B_z|<0.8$~mG ($1\sigma$ limit). We also provide a $1\sigma$ toroidal field strength limit of $<30$~mG. These limits rule out some of the earlier accretion disc models, but remain consistent with the most recent detailed models with efficient advection. We detect marginal linear polarisation from the dust continuum, but the almost purely toroidal geometry of the polarisation vectors implies that his is due to radiatively aligned grains., Comment: 10 pages, 5 figures, accepted for publication in A&A letters

RW Aur A is a CTTS that has suddenly undergone three major dimming events since 2010. We aim to understand the dimming properties, examine accretion variability, and derive the physical properties of the inner disc traced by the CO ro-vibrational emission at NIR wavelengths (2.3 mic). We compared two epochs of X-Shooter observations, during and after the dimming. We modelled the rarely detected CO bandhead emission in both epochs to examine whether the inner disc properties had changed. The SED was used to derive the extinction properties of the dimmed spectrum and compare the infrared excess between the two epochs. Lines tracing accretion were used to derive the mass accretion rate in both states. The CO originates from a region with physical properties of T=3000 K, N$_{CO}$=1x10$^{21}$ cm$^{-2}$ and vsini=113 km/s. The extinction properties of the dimming layer were derived with the effective optical depth ranging from teff 2.5-1.5 from the UV to the NIR. The inferred mass accretion rate Macc is $1.5x 10^{-8}$ Msun/yr and $\sim 2x 10^{-8}$ Msun/yr after and during the dimming respectively. By fitting the SED, additional emission is observed in the IR during the dimming event from dust grains with temperatures of 500-700K. The physical conditions traced by the CO are similar for both epochs, indicating that the inner gaseous disc properties do not change during the dimming events. The extinction curve is flatter than that of the ISM, and large grains of a few hundred microns are thus required. When we correct for the observed extinction, Macc is constant in the two epochs, suggesting that the accretion is stable and therefore does not cause the dimming. The additional hot emission in the NIR is located at about 0.5 au from the star. The dimming events could be due to a dust-laden wind, a severe puffing-up of the inner rim, or a perturbation caused by the recent star-disc encounter., Comment: Accepted by Astronomy & Astrophysics

The extent of the gas in protoplanetary disks is observed to be universally larger than the extent of the dust. This is often attributed to radial drift and grain growth of the mm grains, but line optical depth produces a similar observational signature. We investigate in what parts of the disk structure parameter space dust evolution and line optical depth are the dominant drivers of the observed gas and dust size difference. Using the thermochemical model DALI with dust evolution included we ran a grid of models aimed at reproducing the observed gas and dust size dichotomy. The relation between R_dust and dust evolution is non-monotonic and depends on the disk structure. R_gas is directly related to the radius where the CO column density drops below 10^15 cm^-2 and CO becomes photodissociated. R_gas is not affected by dust evolution but scales with the total CO content of the disk. R_gas/R_dust > 4 is a clear sign for dust evolution and radial drift in disks, but these cases are rare in current observations. For disks with a smaller R_gas/R_dust, identifying dust evolution from R_gas/R_dust requires modelling the disk structure including the total CO content. To minimize the uncertainties due to observational factors requires FWHM_beam < 1x the characteristic radius and a peak SNR > 10 on the 12CO emission moment zero map. For the dust outer radius to enclose most of the disk mass, it should be defined using a high fraction (90-95%) of the total flux. For the gas, any radius enclosing > 60% of the 12CO flux will contain most of the disk mass. To distinguish radial drift and grain growth from line optical depth effects based on size ratios requires disks to be observed at high enough angular resolution and the disk structure should to be modelled to account for the total CO content of the disk., Comment: 18 pages, 27 figures, accepted in A&A

PDS 70b is the most robustly detected young planet imaged in the gap of a transition disk so far, found at a separation of ~195 mas (~22 au) from its host star and at a position angle of about 155 deg. This system is therefore a unique laboratory to characterize the properties of young planetary systems at the stage of their formation. We aim to trace direct and indirect imprints of PDS 70b on the gas and dust emission of the circumstellar disk in order to study the properties of this ~5 Myr young planetary system. We obtained ALMA band 7 observations of PDS 70 in dust continuum and $^{12}CO$ (3-2) and combined them with archival data resulting in an unprecedented angular resolution of about 70 mas (~8 au). We derive an upper limit on circumplanetary material at the location of PDS 70b of ~0.01 $M_{\oplus}$ and find a highly structured circumstellar disk in both dust and gas. The outer dust ring peaks at ~0.65" (74 au) and reveals a possible second unresolved peak at ~0.53" (60 au). The integrated intensity of CO also shows evidence of a depletion of emission at ~0.2" (23 au) with a width of ~0.1" (11 au). The gas kinematics show evidence of a deviation from Keplerian rotation inside $\lesssim$0.8" (91 au). This implies a pressure gradient that can account for the location of the dust ring well beyond the location of PDS 70b. Further in, we detect an inner disk which appears to be connected to the outer disk by a possible bridge feature in the North-West region in both gas and dust. We compare the observations to hydrodynamical simulations including a planet with different masses covering the estimated mass range previously derived from NIR photometry (~5-9 M$_{Jup}$). We find that even a planet with a mass of 10 M$_{Jup}$ may not be sufficient to explain the extent of the wide gap and an additional low-mass companion may be needed to account for the observed disk morphology., Comment: Accepted for publication in A&A

The cyanide radical CN is abundant in protoplanetary disks, with line fluxes often comparable to those of $^{13}$CO. It is known to be sensitive to UV irradiation of the upper disk atmosphere, with models predicting ring-shaped emission. We seek to characterize the CN emission from 94 Class II disks in the Lupus star forming region, compare it to observations in other regions, and interpret our observations with a grid of models. The CN emission morphology is discussed for two primordial disks, Sz 71 and Sz 98, and modeled in more detail. ALMA observed CN N=3-2 in Lupus disks down to sensitivities better than previous surveys. Models constructed with the physico-chemical code DALI are used to study the integrated fluxes of the disks and resolved emission of CN in disks without (dust) substructures. We find that CN N=3-2 is bright, and detected in 38% of sources, but its disk-integrated flux is not strongly correlated to either $^{13}$CO or continuum flux. Compared to pre-ALMA single-dish surveys, no significant difference in the CN flux distributions in Lupus and Taurus-Auriga is found, although $\rho$ Ophiuchus disks may be fainter on average. We find ring-shaped CN emission with peak radii of ~50 AU in two resolved disks. We conclude that a large fraction of sources is faint in CN; only exponential gas surface density cutoffs at $R_{c} \leq 15$ AU can reconcile observations with models. This is the first observational evidence of such a compact gas disk population in Lupus. Absolute intensities and the emission morphology of CN are reproduced by DALI models without the need for any continuum substructure; they are unrelated to the CO snowline location. These observations and the successful modeling of these rings provide a new probe of the structure and conditions in disks, and particularly their incident UV radiation field, if disk size is determined by the data., Comment: 22 pages, 14 figures, A&A accepted

Spiral arms, rings and large scale asymmetries are structures observed in high resolution observations of protoplanetary disks, and it appears that some of the disks showing spiral arms in scattered light also show asymmetries in millimeter-sized dust. HD~135344B is one of these disks. Planets are invoked as the origin of these structures, but no planet has been observed so far. We investigate the nature of the asymmetric structure in the HD~135344B disk in order to understand the origin of the spirals and of the asymmetry seen in this disk. Ultimately, we aim at understanding whether or not one or more planets are needed to explain such structures. We present new ALMA sub-0.1" resolution observations in Band 3 and 4. The high spatial resolution allows us to characterize the mm-dust morphology of the disk. The low optical depth of continuum emission probes the bulk of the dust in vortex. Moreover, we combine the new observations with archival data to perform a multi-wavelength analysis and to obtain information about the dust distribution and properties inside the asymmetry. We resolve the asymmetric disk into a symmetric ring + asymmetric crescent, and observe that: (1) the spectral index strongly decreases at the center of the vortex, consistent with the presence of large grains; (2) for the first time, an azimuthal shift of the peak of the vortex with wavelength is observed; (3) the azimuthal width of the vortex decreases at longer wavelengths, as expected for dust traps. These features allow to confirm the nature of the asymmetry as a vortex. Finally a lower limit to the total mass of the vortex is $0.3 M_{\rm Jupiter}$. Considering the uncertainties involved in this estimate, it is possible that the actual mass of the vortex is higher and possibly within the required values ($\sim 4\,\rm M_{\rm Jupiter}$) to launch spiral arms similar to those observed in scattered light., Comment: 14 pages, 13 figures, accepted for publication on A&A. The abstract has been shortened in order to fit arXiv requirements

While planet formation is thought to occur early in the history of a protoplanetary disk, the presence of planets embedded in disks, or of other processes driving disk evolution, might be traced from their imprints on the disk structure. We observed the T Tauri star HD 143006, located in the 5-11 Myr-old Upper Sco region, in polarized scattered light with VLT/SPHERE at near-infrared wavelengths, reaching an angular resolution of ~0.037" (~6 au). We obtained two datasets, one with a 145 mas diameter coronagraph, and the other without, enabling us to probe the disk structure down to an angular separation of ~0.06" (~10 au). In our observations, the disk of HD 143006 is clearly resolved up to ~0.5" and shows a clear large-scale asymmetry with the eastern side brighter than the western side. We detect a number of additional features, including two gaps and a ring. The ring shows an overbrightness at a position angle (PA) of ~140 deg, extending over a range in position angle of ~60 deg, and two narrow dark regions. The two narrow dark lanes and the overall large-scale asymmetry are indicative of shadowing effects, likely due to a misaligned inner disk. We demonstrate the remarkable resemblance between the scattered light image of HD 143006 and a model prediction of a warped disk due to an inclined binary companion. The warped disk model, based on the hydrodynamic simulations combined with 3D radiative transfer calculations, reproduces all major morphological features. However, it does not account for the observed overbrightness at PA~140 deg. Shadows have been detected in several protoplanetary disks, suggesting that misalignment in disks is not uncommon. However, the origin of the misalignment is not clear. As-yet-undetected stellar or massive planetary companions could be responsible for them, and naturally account for the presence of depleted inner cavities., Comment: Accepted for publication in A&A

Extensive surveys of star-forming regions with Spitzer have revealed populations of disk-bearing young stellar objects. These have provided crucial constraints, such as the timescale of dispersal of protoplanetary disks, obtained by carefully combining infrared data with spectroscopic or X-ray data. While observations in various regions agree with the general trend of decreasing disk fraction with age, the Lupus V and VI regions appeared to have been at odds, having an extremely low disk fraction. Here we show, using the recent Gaia data release 2 (DR2), that these extremely low disk fractions are actually due to a very high contamination by background giants. Out of the 83 candidate young stellar objects (YSOs) in these clouds observed by Gaia, only five have distances of 150 pc, similar to YSOs in the other Lupus clouds, and have similar proper motions to other members in this star-forming complex. Of these five targets, four have optically thick (Class II) disks. On the one hand, this result resolves the conundrum of the puzzling low disk fraction in these clouds, while, on the other hand, it further clarifies the need to confirm the Spitzer selected diskless population with other tracers, especially in regions at low galactic latitude like Lupus V and VI. The use of Gaia astrometry is now an independent and reliable way to further assess the membership of candidate YSOs in these, and potentially other, star-forming regions., Comment: Accepted for publication on Astronomy&Astrophysics Letters

A wide variety of ring-like dust structures has been detected in protoplanetary disks, but their origin and frequency are still unclear. We characterize the structure of an extended, multi-ringed disk discovered serendipitously in the ALMA Lupus disk survey and put it in the context of the Lupus disk population. ALMA observations in Band 6 at 234 GHz and Band 7 at 328 GHz at 0.3" resolution toward the K6 star V1094 Sco in Lupus III are presented, and its disk structure is analyzed. The spectral index $\alpha_{mm}$ is determined in the inner 150 AU of the disk. The ALMA continuum data show a very extended disk with two gap/ring pairs. The gaps are located at 100 AU and 170 AU, the bright rings at 130 AU and 220 AU. Continuum emission is detected out to a 300 AU distance, similar to IM Lup but a factor of 5 larger than typically found for Lupus disks at this sensitivity and resolution. The bright central region of the disk (within 35 AU) is possibly optically thick at 1 mm wavelengths, and has a brightness temperature of only 13 K. The spectral index increases between the inner disk and the first ring, at the location of the first gap. Due to the low temperature of the disk midplane, snow lines can be excluded as the drivers behind the ring and gap formation in this disk. Disks the size of V1094 Sco are rare, and only 2.1+-1.5% of disks in Lupus show continuum emission beyond 200 AU. Possible connections between the large primordial disk population, transition disks, and exoplanets are discussed., Comment: 12 pages, 7 figures. Accepted for publication in Astronomy & Astrophysics

We present ALMA Band 6 observations of a complete sample of protoplanetary disks in the young (1-3 Myr) Lupus star-forming region, covering the 1.33 mm continuum and the 12CO, 13CO, and C18O J=2-1 lines. The spatial resolution is 0.25 arcsec with a medium 3-sigma continuum sensitivity of 0.30 mJy, corresponding to M_dust ~ 0.2 M_earth. We apply "Keplerian masking" to enhance the signal-to-noise ratios of our 12CO zero-moment maps, enabling measurements of gas disk radii for 22 Lupus disks; we find that gas disks are universally larger than mm dust disks by a factor of two on average, likely due to a combination of the optically thick gas emission as well as the growth and inward drift of the dust. Using the gas disk radii, we calculate the dimensionless viscosity parameter, alpha_visc, finding a broad distribution and no correlations with other disk or stellar parameters, suggesting that viscous processes have not yet established quasi-steady states in Lupus disks. By combining our 1.33 mm continuum fluxes with our previous 890 micron continuum observations, we also calculate the mm spectral index, alpha_mm, for 70 Lupus disks; we find an anti-correlation between alpha_mm and mm flux for low-mass disks (M_dust < 5), followed by a flattening as disks approach alpha_mm = 2, which could indicate faster grain growth in higher-mass disks, but may also reflect their larger optically thick components. In sum, this work demonstrates the continuous stream of new insights into disk evolution and planet formation that can be gleaned from unbiased ALMA disk surveys., Comment: 22 pages, 10 figures; accepted to ApJ

Disk warps around classical T Tauri stars (CTTS) can periodically obscure the central star for some viewing geometries. For these so-called AA Tau-like variables, the obscuring material is located in the inner disk and absorption spectroscopy allows one to characterize its dust and gas content. Since the observed emission from CTTS consists of several components (photospheric, accretion, jet, and disk emission), which can all vary with time, it is generally challenging to disentangling disk features from emission variability. Multi-epoch, flux-calibrated, broadband spectra provide us with the necessary information to cleanly separate absorption from emission variability. We applied this method to three epochs of VLT/X-Shooter spectra of the CTTS V354 Mon (CSI Mon-660) located in NGC 2264 and find that: (a) the accretion emission remains virtually unchanged between the three epochs; (b) the broadband flux evolution is best described by disk material obscuring part of the star, and (c) the Na and K gas absorption lines show only a minor increase in equivalent width during phases of high dust extinction. The limits on the absorbing gas column densities indicate a low gas-to-dust ratio in the inner disk, less than a tenth of the ISM value. We speculate that the evolutionary state of V354 Mon, rather old with a low accretion rate, is responsible for the dust excess through an evolution toward a dust dominated disk or through the fragmentation of larger bodies that drifted inward from larger radii in a still gas dominated disk., Comment: 9 pages, 7 figures, A&A accepted

Protoplanetary discs around brown dwarfs and very low mass stars offer some of the best prospects for forming Earth-sized planets in their habitable zones. To this end, we study the nature of the disc around the very low mass star V410 X-ray 1, whose SED is indicative of an optically thick and very truncated dust disc, with our modelling suggesting an outer radius of only 0.6 au. We investigate two scenarios that could lead to such a truncation, and find that the observed SED is compatible with both. The first scenario involves the truncation of both the dust and gas in the disc, perhaps due to a previous dynamical interaction or the presence of an undetected companion. The second scenario involves the fact that a radial location of 0.6 au is close to the expected location of the H$_2$O snowline in the disc. As such, a combination of efficient dust growth, radial migration, and subsequent fragmentation within the snowline leads to an optically thick inner dust disc and larger, optically thin outer dust disc. We find that a firm measurement of the CO $J=2$--1 line flux would enable us to distinguish between these two scenarios, by enabling a measurement of the radial extent of gas in the disc. Many models we consider contain at least several Earth-masses of dust interior to 0.6 au, suggesting that V410 X-ray 1 could be a precursor to a system with tightly-packed inner planets, such as TRAPPIST-1., Comment: 10 pages, 8 figures, accepted for publication in MNRAS

HD$\,$169142 is an excellent target to investigate signs of planet-disk interaction due to the previous evidence of gap structures. We performed J-band (~1.2{\mu}m) polarized intensity imaging of HD169142 with VLT/SPHERE. We observe polarized scattered light down to 0.16" (~19 au) and find an inner gap with a significantly reduced scattered light flux. We confirm the previously detected double ring structure peaking at 0.18" (~21 au) and 0.56" (~66 au), and marginally detect a faint third gap at 0.70"-0.73" (~82-85 au). We explore dust evolution models in a disk perturbed by two giant planets, as well as models with a parameterized dust size distribution. The dust evolution model is able to reproduce the ring locations and gap widths in polarized intensity, but fails to reproduce their depths. It, however, gives a good match with the ALMA dust continuum image at 1.3 mm. Models with a parameterized dust size distribution better reproduce the gap depth in scattered light, suggesting that dust filtration at the outer edges of the gaps is less effective. The pile-up of millimeter grains in a dust trap and the continuous distribution of small grains throughout the gap likely require a more efficient dust fragmentation and dust diffusion in the dust trap. Alternatively, turbulence or charging effects might lead to a reservoir of small grains at the surface layer that is not affected by the dust growth and fragmentation cycle dominating the dense disk midplane. The exploration of models shows that extracting planet properties such as mass from observed gap profiles is highly degenerate., Comment: 21 pages, 14 figures. Accepted for publication in ApJ

Bright ring-like structure emission of the CN molecule has been observed in protoplanetary disks. We investigate whether such structures are due to the morphology of the disk itself or if they are instead an intrinsic feature of CN emission. With the intention of using CN as a diagnostic, we also address to which physical and chemical parameters CN is most sensitive. A set of disk models were run for different stellar spectra, masses, and physical structures via the 2D thermochemical code DALI. An updated chemical network that accounts for the most relevant CN reactions was adopted. Ring-shaped emission is found to be a common feature of all adopted models; the highest abundance is found in the upper outer regions of the disk, and the column density peaks at 30-100 AU for T Tauri stars with standard accretion rates. Higher mass disks generally show brighter CN. Higher UV fields, such as those appropriate for T Tauri stars with high accretion rates or for Herbig Ae stars or for higher disk flaring, generally result in brighter and larger rings. These trends are due to the main formation paths of CN, which all start with vibrationally excited H2* molecules, that are produced through far ultraviolet (FUV) pumping of H2. The model results compare well with observed disk-integrated CN fluxes and the observed location of the CN ring for the TW Hya disk. CN rings are produced naturally in protoplanetary disks and do not require a specific underlying disk structure such as a dust cavity or gap. The strong link between FUV flux and CN emission can provide critical information regarding the vertical structure of the disk and the distribution of dust grains which affects the UV penetration, and could help to break some degeneracies in the SED fitting. In contrast with C2H or c-C3H2, the CN flux is not very sensitive to carbon and oxygen depletion., Comment: New version of paper, correcting too high H2 excitation rates and consequently too high CN column densities. Qualitative conclusions of the paper remain unchanged. Quantitatively, the CN column densities are an order of magnitude lower whereas fluxes decrease by a factor of 3-4. Rings are larger by up to a factor of 2. 13 pages, 19 figures, accepted for publication in A&A

We present multi-wavelength radio observations obtained with the VLA of the protoplanetary disk surrounding the young brown dwarf 2MASS J04442713+2512164 (2M0444) in the Taurus star forming region. 2M0444 is the brightest known brown dwarf disk at millimeter wavelengths, making this an ideal target to probe radio emission from a young brown dwarf. Thermal emission from dust in the disk is detected at 6.8 and 9.1 mm, whereas the 1.36 cm measured flux is dominated by ionized gas emission. We combine these data with previous observations at shorter sub-mm and mm wavelengths to test the predictions of dust evolution models in gas-rich disks after adapting their parameters to the case of 2M0444. These models show that the radial drift mechanism affecting solids in a gaseous environment has to be either completely made inefficient, or significantly slowed down by very strong gas pressure bumps in order to explain the presence of mm/cm-sized grains in the outer regions of the 2M0444 disk. We also discuss the possible mechanisms for the origin of the ionized gas emission detected at 1.36 cm. The inferred radio luminosity for this emission is in line with the relation between radio and bolometric luminosity valid for for more massive and luminous young stellar objects, and extrapolated down to the very low luminosity of the 2M0444 brown dwarf., Comment: 9 pages, 5 figures, accepted for publication in ApJ