Itziar de Gregorio-Monsalvo

Context. The mechanisms responsible for the formation of the majority of brown dwarfs (BDs) remain a matter of debate. It is unclear whether the majority of BDs form in molecular cloud cores in a process akin to a scaled-down version of low-mass star formation or via disc fragmentation in the circumstellar discs surrounding young stars. To pinpoint these processes, detailed studies of the youngest, most embedded sources are required. Aims. We aim to uncover morphological and kinematic signatures of outflowing and/or infalling gas structures in the vicinity of the very low luminosity object (VeLLO) IRAM 04191+1522. Methods. Our study uses archival ALMA sub-millimetre observations. In particular, we focus on the morphological and kinematic analysis of ¹³ CO (3–2), C ¹⁸ O (2–1) and SO 6 ₅ –5 ₄ molecular emission lines that trace molecular gas at small spatial scales (a few tens to hundreds of au) close to the central source, IRAM 04191+1522. Results. The redshifted and blueshifted emission traced by ¹³ CO (3–2) have very different morphologies and kinematics. The blueshifted emission to the north-west of IRAM 04191+1522 may trace shocked material in a different direction from that of the previously reported 0.1 pc (∼21 000 au) outflow seen in CO. The redshifted emission is mainly seen to the south-east and south-west of IRAM 04191+1522 and could trace the base of an outflow cavity. The presence of an outflow cavity in a direction different from that of any previously reported molecular jet or outflow may suggest the presence of a second outflow in the IRAM 04191+1522 system. The emission traced by C ¹⁸ O (2–1) is highly complex and shows several structures at different spatial scales and separations from the central source. The origin of these components is likely mixed, possibly tracing a combination of emission from a molecular outflow, an outflow cavity, and gas in a rotating disc surrounding the central source. The SO 6 ₅ –5 ₄ emission shows evidence of gas in anti-clockwise rotation around the central source. There is also a structure of undetermined origin to the north of IRAM 04191+1522, traced in SO 6 ₅ –5 ₄ . Conclusions. We detect a new complex set of emission structures traced in ¹³ CO (3–2) and C ¹⁸ O (2–1) indicating the presence of a new outflow cavity at a position angle different from the previously detected outflow. This new finding reinforces the scenario that IRAM 04191+1522 is a binary system. The structure to the north of IRAM 04191+1522 detected in SO 6 ₅ –5 ₄ remains of unknown origin and requires further investigation. Follow-up observations at high spectral and high spatial resolution at intermediate spatial scales are needed to study these newly detected substructures and their relationship to the previously detected large-scale structures in greater depth. This will allow for further characterisation of this system and hence determination of its final fate.

Context . The wide cavity in the PDS 70 protoplanetary disk harbors two directly imaged confirmed protoplanets. Several studies have proposed the existence of a third inner planet candidate at ~13 au, labeled as PDS 70 d. While its motion is consistent with a Keplerian orbit, its unusually blue spectrum challenges a planetary interpretation. Aims . We investigated the presence and nature of a third inner planet using new SPHERE and GRAVITY observations. Methods . Using the star-hopping strategy, we obtained new coronagraphic SPHERE/IRDIS observations of PDS 70 in dual-polarization imaging mode in the H band, as well as non-coronagraphic observations with SPHERE/IRDIFS covering the YJHK bands. We also searched for a planetary-like signal using GRAVITY+ in astrometric mode with the four-unit-telescope configuration. Results . We consistently detect two inner emission features with SPHERE: one corresponding to the previously proposed planet candidate at ~13 au and another that appears to share the same orbit but leads it by ~120° (clockwise) with a more elongated morphology. Both features exhibit dust-scattered light spectra while displaying different colors, which may indicate differences in dust grain sizes. We show that such a configuration is consistent with co-orbital dust accumulated at the stable Lagrangian regions of a yet undetected planet, distinct from the previously proposed candidate. The analysis of GRAVITY data at the predicted position of this newly proposed planet has resulted in a marginal (3 σ ) detection located between the two clumps along the same orbit ( ρ = 76.2 ± 0.29 mas, and position angle PA = 226.50 ± 0.21°), and consistent with a ~3 M _Jup planet. This planet-like signal aligns with a narrow shadow detected in the outer disk with SPHERE. Additionally, with SPHERE we detect polarized emission very close to the star, which likely arise from the inner disk, with an inclination of 50° and a PA of ~135°. The fact that the two dust clumps appear embedded within this polarized emission motivates an inner disk-related alternative scenario. Conclusions . We conclude that the emission from the previously reported third planet candidate could arise either from a dust clump trailing a yet undetected planet along the same orbit, or from a rotating substructure within the inner disk. Additional observations are required to further test these two proposed scenarios. In particular, confirming the new GRAVITY planet-like signal would support the use of co-orbital substructures as indirect tracers of embedded planets.

As part of the ALMA Large Program “Early Planet Formation in Embedded Disks,” ¹² CO (2–1) was observed towards 19 nearby low-mass protostars. Of these objects, 15 sources are found to show molecular outflow emission. Based on their morphological and kinematical structures, the CO outflows are classified into three types: a wind-driven shell, where ambient material is swept up by a wide-angle wind from the star, a bow shock, and a slow disk wind, which is a conical or parabolic flow with onion-like velocity structure. We categorize 11 outflows as a slow disk wind, 7 as a wind-driven shell, and 1 as a bow shock. Four of these outflows were found to show signs of both slow disk wind and wind-driven shell characteristics. Five objects show misalignment between the red- and blueshifted outflows. Seven objects show significant misalignment between the outflow axis (either or both of the red- and blueshifted outflows) and the minor axis of the dust continuum emission around the protostar. For the objects showing wind-driven shell emission, we compare simple parametrized models with the observations to derive physical properties of the observed shells, such as their dynamical ages. This shows evidence of a time variability in the outflows, such as changes in their direction. In some objects, large differences are seen between the properties of the red- and blueshifted outflows, possibly indicating differences in the properties of the ambient medium with which the outflow interacts.

Water, an essential molecule for sustaining life on Earth, plays a crucial role in the physical and chemical processes governing the formation of stars and planets, serving as a primary coolant in the environments surrounding emerging stars. The journey of water from the earliest stages of star and planet formation to its eventual incorporation to exoplanetary atmospheres and its potential oceans is still a matter of debate. Very recent works using ALMA and JWST data reveals that water can be found in the inner astronomical units in protoplanetary disks, in the terrestrial planet-forming zone. Detecting water molecules from ground-based telescopes is challenging due to the water vapor content within Earth’s atmosphere, severely limiting atmospheric transmissivity. Nevertheless, water is one of the few compounds capable of generating bright maser emission within star-forming regions. Their exceptional brightness, narrow spectral profiles, and their origin in highly compact regions offer a unique set of characteristics that render them invaluable tools for investigating circumstellar structure and dynamics at sub-arcsecond spatial scales. In this work we present our efforts to search and characterize water maser emission at submillimeter frequencies in a sample of young stellar objects.

Stars such as the Sun expel their outer layers and form planetary nebulae (PNe) as they evolve into white dwarfs. PNe exhibit diverse morphologies, the origins of which are not fully understood. PNe with OH (OHPNe) and H ₂ O (H ₂ OPNe) masers are thought to be nascent PNe. However, the number of known OHPNe and H ₂ OPNe remains small, and only in eight cases has the position of the maser emission been found to coincide with the PN, using the high astrometric accuracy of interferometric observations. In order to identify more OHPNe and H ₂ OPNe, we used public databases and our own ATCA/VLA observations to match the positions of OH and H ₂ O masers with known PNe and radio continuum emitters, considering radio continuum emission as a possible tracer of the photoionized gas that characterizes PNe. Here we report the confirmation of positional coincidence of maser emission with one more PN, and 12 PN candidates. Moreover, we have confirmed three evolved stars as ‘water fountains’ (WFs) hosting H ₂ O masers. These WFs are associated with radio continuum emission, but their possible nature as PNe has not yet been confirmed. Although a final characterization of maser-emitting PNe as a group still requires confirmation of more objects, their distribution in the infrared color-color diagrams suggests that they are a heterogeneous group of PNe. In particular, the new OHPN IRAS 07027–7934 has been reported to contain a late [WC]-type central star, while the maser emission implies an O-rich envelope. This property is found in only one other known maser-emitting PN, although we found evidence that other confirmed and candidate OHPNe may also have mixed chemistry, since they show emission from polycyclic aromatic hydrocarbons. The new WF IRAS 18443–0231 shows radio continuum that is dominated by strong and variable non-thermal emission, as in magnetized outflows.

We present high-resolution (∼0 . ″ 05; 8 au) dust continuum and molecular line observations toward the Class I protostellar system IRAS 04169+2702 in the Taurus B213 region, as part of the Atacama Large Millimeter/submillimeter Array Large Program Early Planet Formation in Embedded Disks. The 1.3 mm dust continuum emission traces a circumstellar disk with a central depression toward the protostar. Our Karl G. Jansky Very Large Array observations of the same target reveal a single central peak dominated by free–free emission, which coincides with the depression of the thermal dust emission. The mean spectral index of the thermal dust emission from 1.3 mm to 1.4 cm is approximately 2.8, suggestive of the presence of grains grown to millimeter or centimeter sizes in the disk. Velocity gradients along the disk’s major axis are seen in emission from the ¹² CO (2–1), ¹³ CO (2–1), and C ¹⁸ O (2–1) molecular lines. The position–velocity diagrams of these lines unveil a Keplerian-rotating disk with a radius of ∼21 au around a 1.3 M _⊙ protostar, as well as an infalling and rotating envelope with the angular momentum conserved. In addition to the compact disk, large-scale infalling spiral structures extending up to approximately 1400 au, i.e., streamers, are discovered in C ¹⁸ O (2–1), SO (6 ₅ –5 ₄ ), and H ₂ CO (3 _0,3 –2 _0,2 ) as well as in the 1.3 mm continuum emission. Notably, in the region closer to the protostar, the spatial coincidence of C ¹⁸ O and SO may indicate the presence of a shock related to accretion through the spiral arms.

The detection of planets in protoplanetary disks has proven to be extremely challenging. By contrast, rings and gaps, usually attributed to planet–disk interactions, have been found in virtually every large protoplanetary (Class II) disk observed at 0.9–1.3 mm with sufficient spatial resolution (5 au). The nearby disk around MP Mus (PDS 66) stands as an exception to this rule, and its advanced age (7–10 Myr) is particularly difficult to reconcile with its apparent lack of substructures. Despite the disk’s smooth appearance, Gaia data of MP Mus show a significant proper motion anomaly, signalling the presence of a companion. Here we present ALMA 3-mm observations of the system with high spatial resolution comparable to previous 1.3-mm data. The new observations pierce deeper into the disk midplane and reveal an inner cavity (<3 au) and a ring at 10 au. The disk structure inferred from ALMA observations narrows down the properties of the companion to a gas giant orbiting at 1–3 au, and hydrodynamic simulations further confirm that such a planet can produce the observed cavity. These independent pieces of evidence constitute an indirect but compelling detection of an exoplanet within a protoplanetary disk using Gaia astrometry. The detection of dust substructures in MP Mus, thanks to the lower optical depths at longer wavelengths, suggests that rings and gaps are even more abundant than previously thought.

We present high-resolution Atacama Large Millimeter/submillimeter Array (ALMA) observations at 0.89 mm of the Class II brown dwarf 2MASS J04442713+2512164 (2M0444), achieving a spatial resolution of 0 . ″ 046 (∼6.4 au at the distance to the source). These observations targeted continuum emission together with ¹²CO (3–2) molecular line. The line emission traces a Keplerian disk, allowing us to derive a dynamical mass between 0.043 and 0.092 M _⊙ for the central object. We constrain the gas-to-dust disk size ratio to be ∼7, consistent with efficient radial drift. However, the observed dust emission suggests that a dust trap is present, enough to retain some dust particles. We perform visibility fitting of the continuum emission, and under the assumption of annular substructure, our best fit shows a gap and a ring at 98.1 − 8.4 + 4.2 mas (∼14 au) and 116.0 − 4.8 + 4.2 mas (∼16 au), respectively, with a gap width of 20 mas (∼3 au). To ensure robustness, the data were analyzed through a variety of methods in both the image and uv planes, employing multiple codes and approaches. This tentative disk structure could be linked to a possible planetary companion in the process of formation. These results provide the first dynamical mass of the lowest mass object to date, together with the possible direct detection of a substructure, offering new insights into disk dynamics and planet formation in the very low-mass regime. Future higher spatial resolution ALMA observations will be essential to confirm these findings and further investigate the link between substructures and planet formation in brown dwarf disks.

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