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1. SO and SiS Emission Tracing an Embedded Planet and Compact 12 CO and 13 CO Counterparts in the HD 169142 Disk

   https://doi.org/10.3847/2041-8213/acdfd0  

   Law, Charles J. ; Booth, Alice S. ; Öberg, Karin I. ( August 2023 , The Astrophysical Journal Letters)

   Planets form in dusty, gas-rich disks around young stars, while at the same time, the planet formation process alters the physical and chemical structure of the disk itself. Embedded planets will locally heat the disk and sublimate volatile-rich ices, or in extreme cases, result in shocks that sputter heavy atoms such as Si from dust grains. This should cause chemical asymmetries detectable in molecular gas observations. Using high-angular-resolution ALMA archival data of the HD 169142 disk, we identify compact SOJ= 8₈− 7₇and SiSJ= 19 − 18 emission coincident with the position of a ∼ 2M_Jupplanet seen as a localized, Keplerian NIR feature within a gas-depleted, annular dust gap at ≈38 au. The SiS emission is located along an azimuthal arc and has a morphology similar to that of a known¹²CO kinematic excess. This is the first tentative detection of SiS emission in a protoplanetary disk and suggests that the planet is driving sufficiently strong shocks to produce gas-phase SiS. We also report the discovery of compact¹²CO and¹³COJ= 3 − 2 emission coincident with the planet location. Taken together, a planet-driven outflow provides the best explanation for the properties of the observed chemical asymmetries. We also resolve a bright, azimuthally asymmetric SO ring at ≈24 au. While most of this SO emission originates from ice sublimation, its asymmetric distribution implies azimuthal temperature variations driven by a misaligned inner disk or planet–disk interactions. Overall, the HD 169142 disk shows several distinct chemical signatures related to giant planet formation and presents a powerful template for future searches of planet-related chemical asymmetries in protoplanetary disks.

    

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2. PHANGS–JWST First Results: Rapid Evolution of Star Formation in the Central Molecular Gas Ring of NGC 1365

   https://doi.org/10.3847/2041-8213/acac9e  

   Schinnerer, Eva ; Emsellem, Eric ; Henshaw, Jonathan D. ; Liu, Daizhong ; Meidt, Sharon E. ; Querejeta, Miguel ; Renaud, Florent ; Sormani, Mattia C. ; Sun, Jiayi ; Egorov, Oleg V. ; et al ( February 2023 , The Astrophysical Journal Letters)

   Large-scale bars can fuel galaxy centers with molecular gas, often leading to the development of dense ringlike structures where intense star formation occurs, forming a very different environment compared to galactic disks. We pair ∼0.″3 (30 pc) resolution new JWST/MIRI imaging with archival ALMA CO(2–1) mapping of the central ∼5 kpc of the nearby barred spiral galaxy NGC 1365 to investigate the physical mechanisms responsible for this extreme star formation. The molecular gas morphology is resolved into two well-known bright bar lanes that surround a smooth dynamically cold gas disk (R_gal∼ 475 pc) reminiscent of non-star-forming disks in early-type galaxies and likely fed by gas inflow triggered by stellar feedback in the lanes. The lanes host a large number of JWST-identified massive young star clusters. We find some evidence for temporal star formation evolution along the ring. The complex kinematics in the gas lanes reveal strong streaming motions and may be consistent with convergence of gas streamlines expected there. Indeed, the extreme line widths are found to be the result of inter-“cloud” motion between gas peaks;ScousePydecomposition reveals multiple components with line widths of 〈σ_CO,scouse〉 ≈ 19 km s⁻¹and surface densities of$〈{\mathrm{\Sigma }}_{{\mathrm{H}}_2,\mathrm{scouse}}〉\approx 800M_{\odot }{\mathrm{pc}}^{-2}$, similar to the properties observed throughout the rest of the central molecular gas structure. Tailored hydrodynamical simulations exhibit many of the observed properties and imply that the observed structures are transient and highly time-variable. From our study of NGC 1365, we conclude that it is predominantly the high gas inflow triggered by the bar that is setting the star formation in its CMZ.

    

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3. The interstellar medium distribution, gas kinematics, and system dynamics of the far-infrared luminous quasar SDSS J2310+1855 at z = 6.0

   https://doi.org/10.1051/0004-6361/202244610  

   Shao, Yali ; Wang, Ran ; Weiss, Axel ; Wagg, Jeff ; Carilli, Chris L. ; Strauss, Michael A. ; Walter, Fabian ; Cox, Pierre ; Fan, Xiaohui ; Menten, Karl M. ; et al ( December 2022 , Astronomy & Astrophysics)

   We present Atacama Large Millimeter/submillimeter Array (ALMA) sub-kiloparsec- to kiloparsec-scale resolution observations of the [C II], CO (9–8), and OH⁺(1₁–0₁) lines along with their dust continuum emission toward the far-infrared (FIR) luminous quasar SDSS J231038.88+185519.7 atz = 6.0031, to study the interstellar medium distribution, the gas kinematics, and the quasar-host system dynamics. We decompose the intensity maps of the [C II] and CO (9–8) lines and the dust continuum with two-dimensional elliptical Sérsic models. The [C II] brightness follows a flat distribution with a Sérsic index of 0.59. The CO (9–8) line and the dust continuum can be fit with an unresolved nuclear component and an extended Sérsic component with a Sérsic index of ∼1, which may correspond to the emission from an active galactic nucleus dusty molecular torus and a quasar host galaxy, respectively. The different [C II] spatial distribution may be due to the effect of the high dust opacity, which increases the FIR background radiation on the [C II] line, especially in the galaxy center, significantly suppressing the [C II] emission profile. The dust temperature drops with distance from the center. The effective radius of the dust continuum is smaller than that of the line emission and the dust mass surface density, but is consistent with that of the star formation rate surface density. This may indicate that the dust emission is a less robust tracer of the dust and gas distribution but is a decent tracer of the obscured star formation activity. The OH⁺(1₁–0₁) line shows a P-Cygni profile with an absorption at ∼–400 km s⁻¹, which may indicate an outflow with a neutral gas mass of (6.2 ± 1.2)×10⁸ M_⊙along the line of sight. We employed a three-dimensional tilted ring model to fit the [C II] and CO (9–8) data cubes. The two lines are both rotation dominated and trace identical disk geometries and gas motions. This suggest that the [C II] and CO (9–8) gas are coplanar and corotating in this quasar host galaxy. The consistent circular velocities measured with [C II] and CO (9–8) lines indicate that these two lines trace a similar gravitational potential. We decompose the circular rotation curve measured from the kinematic model fit to the [C II] line into four matter components (black hole, stars, gas, and dark matter). The quasar-starburst system is dominated by baryonic matter inside the central few kiloparsecs. We constrain the black hole mass to be 2.97^+0.51_-0.77 × 10⁹M_⊙; this is the first time that the dynamical mass of a black hole has been measured atz ∼ 6. This mass is consistent with that determined using the scaling relations from quasar emission lines. A massive stellar component (on the order of 10⁹ M_⊙) may have already existed when the Universe was only ∼0.93 Gyr old. The relations between the black hole mass and the baryonic mass of this quasar indicate that the central supermassive black hole may have formed before its host galaxy.

    

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4. H I -H 2 transition: Exploring the role of the magnetic field: A case study toward the Ursa Major cirrus

   https://doi.org/10.1051/0004-6361/202142512  

   Skalidis, R. ; Tassis, K. ; Panopoulou, G. V. ; Pineda, J. L. ; Gong, Y. ; Mandarakas, N. ; Blinov, D. ; Kiehlmann, S. ; Kypriotakis, J. A. ( September 2022 , Astronomy & Astrophysics)

   Context. Atomic gas in the diffuse interstellar medium (ISM) is organized in filamentary structures. These structures usually host cold and dense molecular clumps. The Galactic magnetic field is considered to play an important role in the formation of these clumps. Aims. Our goal is to explore the role of the magnetic field in the H I -H 2 transition process. Methods. We targeted a diffuse ISM filamentary cloud toward the Ursa Major cirrus where gas transitions from atomic to molecular. We probed the magnetic field properties of the cloud with optical polarization observations. We performed multiwavelength spectroscopic observations of different species in order to probe the gas phase properties of the cloud. We observed the CO ( J = 1−0) and ( J = 2−1) lines in order to probe the molecular content of the cloud. We also obtained observations of the [C ii ] 157.6 µ m emission line in order to trace the CO-dark H 2 gas and estimate the mean volume density of the cloud. Results. We identified two distinct subregions within the cloud. One of the regions is mostly atomic, while the other is dominated by molecular gas, although most of it is CO-dark. The estimated plane-of-the-sky magnetic field strength between the two regions remains constant within uncertainties and lies in the range 13–30 µG. The total magnetic field strength does not scale with density. This implies that gas is compressed along the field lines. We also found that turbulence is trans-Alfvénic, with M A ≈ 1. In the molecular region, we detected an asymmetric CO clump whose minor axis is closer, with a 24° deviation, to the mean magnetic field orientation than the angle of its major axis. The H i velocity gradients are in general perpendicular to the mean magnetic field orientation except for the region close to the CO clump, where they tend to become parallel. This phenomenon is likely related to gas undergoing gravitational infall. The magnetic field morphology of the target cloud is parallel to the H i column density structure of the cloud in the atomic region, while it tends to become perpendicular to the H i structure in the molecular region. On the other hand, the magnetic field morphology seems to form a smaller offset angle with the total column density shape (including both atomic and molecular gas) of this transition cloud. Conclusions. In the target cloud where the H i –H 2 transition takes place, turbulence is trans-Alfvénic, and hence the magnetic field plays an important role in the cloud dynamics. Atomic gas probably accumulates preferentially along the magnetic field lines and creates overdensities where molecular gas can form. The magnetic field morphology is probed better by the total column density shape of the cloud, and not its H i column density shape. 

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5. The HH 24 Complex: Jets, Multiple Star Formation, and Orphaned Protostars

   https://doi.org/10.3847/1538-3881/acadd4  

   Reipurth, Bo ; Bally, J. ; Yen, Hsi-Wei ; Arce, H. G. ; Rodríguez, L. -F. ; Raga, A. C. ; Geballe, T. R. ; Rao, R. ; Comerón, F. ; Mikkola, S. ; et al ( April 2023 , The Astronomical Journal)

   The HH 24 complex harbors five collimated jets emanating from a small protostellar multiple system. We have carried out a multiwavelength study of the jets, their driving sources, and the cloud core hosting the embedded stellar system, based on data from the Hubble Space Telescope, Gemini, Subaru, Apache Point Observatory 3.5 m, Karl G. Jansky Very Large Array, and Atacama Large Millimeter/submillimeter Array (ALMA) telescopes. The data show that the multiple system, SSV 63, contains at least 7 sources, ranging in mass from the hydrogen-burning limit to proto-Herbig Ae stars. The stars are in an unstable nonhierarchical configuration, and one member, a borderline brown dwarf, is moving away from the protostellar system with 25 km s⁻¹, after being ejected ∼5800 yr ago as an orphaned protostar. Five of the embedded sources are surrounded by small, possibly truncated, disks resolved at 1.3 mm with ALMA. Proper motions and radial velocities imply jet speeds of 200–300 km s⁻¹. The two main HH 24 jets, E and C, form a bipolar jet system that traces the innermost portions of parsec-scale chains of Herbig–Haro and H₂shocks with a total extent of at least 3 pc. H₂CO and C¹⁸O observations show that the core has been churned and continuously fed by an infalling streamer.¹³CO and¹²CO trace compact, low-velocity, cavity walls carved by the jets and an ultracompact molecular outflow from the most embedded object. ChaoticN-body dynamics likely will eject several more of these objects. The ejection of stars from their feeding zones sets their masses. Dynamical decay of nonhierarchical systems can thus be a major contributor to establishing the initial mass function.

    

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