54. ATOMS: ALMA Three-millimeter Observations of Massive Star-forming regions - XII: Fragmentation and multi-scale gas kinematics in protoclusters G12.42+0.50 and G19.88-0.53 Anindya Saha,**¹  Anandmayee Tej,†¹  Hong-Li Liu,‡²  Tie Liu,³³,⁴  Namitha Issac, 5  Chang Won Lee,°. Guido Garay, 8 Paul F. Goldsmith, 9 Mika Juvela, 10 Sheng-Li Qin, 2 Amelia Stutz, 11,12 Shanghuo Li, 7 Ke Wang, 13, 14 Tapas Baug, 15 Leonardo Bronfman, 8 Feng-Wei Xu, 13, 14 Yong Zhang, 16 Chakali Eswaraiah, 17 - ALMAの3mm帯観測G12.42+0.50とG19.88-53 (protocluster領域) -ビリアルパラメ一タ(α  vir)が2より小さく、重力崩壊中- thermal Jeans fragmentationとconsistent -フィラメントの速度勾配と複数のアウトフローが見られた- astrodendroでブランチ(~0.1 pc)とリーフ(0.03 pc)を同定=>ブランチはLarson則とconsistentな乱流,リーフはtransonic/subsonicリーフ構造はLarson則から外れている。スケール依存の乱流と重力の組み合わせが大質量星形成において重要
Table 6. Comparison between observed parameters and estimated Jeans parameters for G12.42 and G19.88. The values in parenthesis denote the median values.
H13CO+のpeak速.
55.

Ekta Sharma, 1.2.3* Maheswar Gopinathan, 1 Archana Soam, 1.4 Chang Won Lee 5.6 and T. R. Seshadri 7分子雲コアの伸びている方向と磁場を調べた天体: L1512, L1523, L1333, L1521E, L1544, L1517, L1780 and L183観測: Herschel column density map, Planckと光学望遠鏡*の偏光観測結果:コアの方向と磁場の方向はランダムだったmass-to-flux ratio:ほとんどははcriticalだがL1333, L1521E and L183は磁場が強い*ARIES Imaging Polarimeter on 1.04 m Sampurnanand Telescope (ST) at Nainital, India -シエルmap or土橋厳光に黄色線(Planck)青線: H-band偏光黒楕円: dendrogramコア
E. Artur de la Villarmois ¹ .², V. V. Guzmán ¹ ,², J. K. Jørgensen ³ , L. E. Kristensen ³ , E. A. Bergin ⁴ , D. Harsono ⁵ , N. Sakai 6, E. F. van Dishoeck 7,8 , and S. Yamamoto 9目的: S系分子でアクリーションショックなどを見たい観測: ALMAで0“.1 (=14 au)の観測, Oph-IRS 44 (also know YLW 16A)分子種: SO, SO2, and ³⁴SO => RADEXモデリングで物理状態を調べた結果- 30 au以内のinfalling-rotating運動をトレース- 30-50 auで赤方偏移のみ見られた(<=noケプラ一モ一ション?) 。 -より冷たい成分は~400 au離れた位置。 -密度10^8 cm^-3, >70 K,柱密度0.4-1.8 x 10^17 cm^-2 - SO2/SO>1でgas-phaseのSI2のアバンダンスを増加させる結論SO2はアクリーションショックをトレースしていそう。観測天体: Oph-IRS 44 (in L1688) - protobinary with a separation of 0.“3 HSTやVLT等の観測に基づく(らしいが、ALMAではミリ波源はsingle?) Class I, d=139 pc, Tbol ~280 K, Lbol ~7.1 Lo, Menv~0.051 Mo
59.鏡観測のアウトフローの向きとは合ってないM(gas+dust) = 4x10^-3 Mo
binary componentなし
赤方偏移の方がちょっと広がっている(Localized streamerか？) Fig. 3.  Contour maps of SO 2 184,14 – 183,15 for different velocity ranges, shifted to 0 velocity. The contours start at So and follow steps of So. The panel that includes the systemic velocity (3.7 km s-') is shown by the green contours in the first panel, while blue- and redshifted emission is represented by the blue and red contours, respectively. The yellow star shows the position of the source and the synthesized beam is indicated by the black filled ellipse in the bottom left corner of the first panel. Fig. 4.  Emission of the SO 2 5 3 – 422 line. Left: Spectra integrated over a circular region with r = 0?2, centered on the continuum peak position centrifugal barrier内の外側はケプラ一モ一ション以外(disk-envelope構造)の力学に強く影響を受ける(=>大屋さんらの論)
Van der Marel+13
5/8 61. Confirmation of the outflow in L1451-mm: SiO line and CH3OH maser detections V. Wakelam¹, A. Coutens², P. Gratier¹, T. H G Vidal¹, and N. Vaytet³概要- L1451-mmはペルセウスにある有力なファーストコア候補(e.g., Maureira et al. 2020) =>低速度COアウトフロー +コンパクトミリ波源(Pineda+11)  等- NOEMA干渉計(+ IRAM 30m)で3mm帯のいろんなラインを観測* - SiOとメタノール(のメーザー)を検出-ショックで説明可能(H2 density of ～ 3  ×  10 6 cm −3 and a temperature higher than 40 K) -ファーストコアモデルでは20 Kくらいのショックしか予想されていない=>アウトフローは実は天球面上に近く、もっと速度は早いかも？
検出できた分子種/トランジションC-C3H2, CH3OH, SiO, CS, SO, H2CO, HC3N, NDCO, DCN, DCO+ =>このうちH2CO, CS, and SiO linesはアウトフローらしいSiOとメタノールは干渉計とIRAMのFluxがほぼ同じH2CSとCSは広がったものがフィルターアウトされる
*2000年後半くらいに発見(と主張される)論文ブ
Maureira et al. 2020の表より一部改変~14天体中10天体ほどは候補外と認識されつつあるMC35は全く除外されていないMC35-mmをさらに推せる点・最近傍(~140pc)天体で、ACA観測しか行われていない(12m arrayで更なる高解像度観測が実行可能)
ensityカラミ:21.3mmコントア: CO(2-1)力学的時間:数千年程度*と思われる*短いタイムスケールのため、たくさん観測しないと見つからない統計的に予想されるライフタイム(<10 yr)と無矛盾Molecular Fraction in the Galactic Center: The Central Molecular and HI Zones Yoshiaki Sofue ⋆ By mapping the molecular fraction of the Galactic Center (GC), we quantitatively address the question of how much molecular and central the CMZ (Central Molecular Zone) is. For this purpose we analyze the CO and HI-line archivale data, and determine the column- (surface-) and volume-molecular fractions, fact and fact , which are the ratio of column-mass density of H2 projected on the sky to that of total gas (H2 + HI) from the line intensities, and the ratio of volume-mass densities of H 2 to total gas from the brightness temperature, respectively. It is shown that fニュー is as high as ～ 0.9 – 0.95 in the CMZ, and f 2 , s is 0.93 – 0.98 in the GC Arms I and II attaining the highest value of ～ 0.98 toward Sgr B2. The expanding molocular ring (EMR, or the parallelogram) has a slightly smaller f x α as ～ 0.9 − 0.93. We define the CMZ as the region with f x α ≥ 0.8 − 0.9 between the shoulders of plateau-like distribution of H 2 column density from l = −1°.1 to +1°.8 having Gaussian vertical distribution with a half thickness of ±0°.2. The CMZ is embedded in the Central HI Zone (CHZ), which is defined as an HI disc between l ～ −2° and +2°.5, b = −0°.5 and +0°.5. Based on the analysis, we discuss the origin of CMZ and interstellar physics such as the volume filling factors of molecular and HI gases inferred from the difference between fact and from
StraKLIP: A novel pipeline for detection and characterization of close-in faint compan-
ions through Karhunen-Loêve Image Processing algorithm
Giovanni M. Strampelli, Laurent Pueyo, Jonathan Aguilar, Antonio Aparicio, Gaspard Duchêne, Massimo Robberto ⋆ We present a new pipeline developed to detect and characterize faint astronomical companions at small angular separation from the host star using sets of wide-field imaging observations not specifically designed for High Contrast Imaging analysis. The core of the pipeline relies on Karhunen-Loève truncated transformation of the reference PSF library to perform PSF subtraction and identify candidates. Tests of reliability of detections and characterization of companions are made through simulation of binaries and generation of Receiver Operating Characteristic curves for false positive/true positive analysis. The algorithm has been successfully tested on large HST/ACS and WFC3 datasets acquired for two HST Treasury Programs on the Orion Nebula Cluster. Based on these extensive numerical experiments we find that, despite being based on methods designed for observations of single star at a time, our pipeline performs very well on mosaic space based data. In fact, we are able to detect brown dwarf-mass companions almost down to the planetary mass limit. The pipeline is able to reliably detect signals at separations as close as ≥ 0.1" with a completeness of ≥ 10%, or ～ 0.2" with a completeness of ～ 30%. This approach can potentially be applied to a wide variety of space based imaging surveys, starting with data in the existing HST archive, near-future JWST mosaics, and future wide-field Roman images.
Rogue planets and brown dwarfs: Predicting the populations of free-floating planetary
mass objects observable with JWST
Aleks Scholz, Koraljka Muzic, Ray Jayawardhana, Lyra Quinlan, James Wurster ⋆ Free-floating (or rogue) planets are planets that are liberated (or ejected) from their host systems. Although simulations predict their existence in substantial numbers, direct observational evidence for free-floating planets with masses below  5 MJup is still lacking. Several cycle-1 observing programs with JWST alm to hunt for them in four different star-forming clusters. These surveys are designed to be sensitive to masses of 1-15 MJup (assuming a hot-start formation), which corresponds to spectral types of early L to late T for the ages of these clusters. If the existing simulations are not wide off the mark, we show here that the planned programs are likely to find up to 10-20 giant rogue planets in moderate density clusters like NGC1333 or IC348, and several dozen to 100 in high-density regions like NGC2024 and the Orion Nebula Cluster. These numbers correspond to 1-5% of the total cluster population; they could be substantially higher if stars form multiple giant planets at birth. In contrast, the number of free-floating brown dwarfs, formed from core collapse ("like stars") is expected to be significantly lower, only about 0.25number of stars, or 1-7 for the clusters considered here. Below 10 MJup that number drops further by an order of magnitude. We also show that the planned surveys are not at risk of being significantly contaminated by field brown dwarfs in the foreground or background, after spectroscopic confirmation. Taken together, our results imply that if a population of L and T dwarfs were to be found in these JWST surveys, it is expected to be predominantly made up of rogue planets.
ATOMS: ALMA Three-millimeter Observations of Massive Star-forming regions – XII:
Fragmentation and multi-scale gas kinematics in protoclusters G12.42+0.50 and G19.88-
0.53
Anindya Saha, Anandmayce Tej, Hong-Li Liu, Tie Liu, Namitha Issac, Chang Won Lee, Guido Garay, Paul F. Goldsmith, Mika Juvela, Sheng-Li Qin, Amelia Stutz, Shanghuo Li, Ke Wang, Tapas Baug, Leonardo Bronfman, Feng-Wei Xu, Yong Zhang, Chakali Eswaraiah ⋆ We present new continuum and molecular line data from the ALMA Three-millimeter Observations of Massive Star-forming regions (ATOMS) survey for the two protoclusters, G12.42+0.50 and G19.88-0.53. The 3 mm continuum maps reveal seven cores in each of the two globally contracting protoclusters. These cores satisfy the radius-mass relation and the surface mass density criteria for high-mass star formation. Similar to their natal clumps, the virial analysis of the cores suggests that they are undergoing gravitational collapse ( α vir << 2). The clump to core scale fragmentation is investigated and the derived core masses and separations are found to be consistent with thermal Jeans fragmentation. We detect large-scale filamentary structures with velocity gradients and multiple outflows in both regions. Dendrogram analysis of the H 13 CO + map identifies several branch and leaf structures with sizes ～ 0.1 and 0.03 pc, respectively. The supersonic gas motion displayed by the branch structures is in agreement with the Larson power-law indicating that the gas kinematics at this spatial scale is driven by turbulence. The transition to transonic/subsonic gas motion is seen to occur at spatial scales of ~0.1 pc indicating the dissipation of turbulence. In agreement with this, the leaf structures reveal gas motions that deviate from the slope of Larson's law. From the large-scale converging filaments to the collapsing cores, the gas dynamics in G12.42÷0.50 and G19.88-0.53 show scale-dependent dominance of turbulence and gravity and the combination of these two driving mechanisms needs to be invoked to explain massive star formation in the protoclusters.
Core orientations and magnetic fields in isolated molecular clouds
Ekta Sharma, Maheswar Gopinathan, Archana Soam, Chang Won Lee, T. R. Seshadri ⋆ Molecular clouds are sites of star formation. Magnetic fields are believed to play an important role in their dynamics and shaping morphology. We aim to study any possible correlation that might exist between the magnetic fields orientation inside the clouds and the magnetic fields at envelope scales and their connection with respect to the observed morphology of the selected clouds. We examine the magnetic field orientation towards the clouds L1512, L1523, L1333, L1521E, L1544, L1517, L1780, and L183 using optical and Planck polarization observations. We also found the correlation between the ambient magnetic field and core orientations derived using Astrodendrogram on the Herschel 250 μm data. We find that the magnetic fields derived from optical and Planck agree with each other. The derived magnetic fields are aligned along the observed emission of each cloud as seen in Herschel 250 μ m data. We also find that the relative orientation between the cores and the magnetic fields is random. This lack of correlation may arise due to the fact that the core orientation could also be influenced by the different magnetization within individual clouds at higher densities or the foedback effects which may vary from cloud to cloud. The estimated magnetic field strength and the mass-to-flux ratio suggest that all the clouds are in a magnetically critical state except L1333, L1521E, and L183 where the cloud envelope could be strongly supported by the magnetic field lines.
Bird's eye view of molecular clouds in the Milky Way: II. Cloud kinematics from sub-pc
to kpc scales
Andri Spilker, Jouni Kainulainen, Jan Orkisz ⋆ The kinematics of molecular gas are crucial for setting the stage for star formation. One key question related to the kinematic properties of gas is how they depend on the spatial scale. We aim to describe the CO spectra, velocity dispersions, and especially the linewidth-size relation, of molecular gas from cloud (parsec-) scales to kiloparsee scales in a complete region within the Milky Way disk. We utilise the census of molecular clouds within 2 kpc from our earlier work, together with CO emission data for them from the literature. We study the kinematics and the Larson's relations for the sample of individual clouds. We also mimic a face-on view of the Milky Way and analyse the kinematics of the clouds within apertures of 0.25-2 kpc in size. In this way, we describe the scale-dependency of the CO gas kinematics and Larson's relations. We describe the spectra of CO gas at cloud scales and in apertures between 0.25-2 kpc in our survey area. The spectra within the apertures are relatively symmetric but show non-Gaussian high-velocity wings. At cloud-scales, our sample shows a linewidth-size relation σ 。 = 1.5 × R 0.3±0.1 with a large scatter. The mass-size relation in the sample of clouds is Mco − 794 × R 1.5±0.5 . The relations are also present for the apertures at kpc-scales. A suggestive dependency on galactic environment is seen, with apertures closer to the Galactic centre and the Sagittarius spiral arm having slightly higher velocity dispersions. We explore the possible effect of a diffuse component in the survey area, and find that such a component would widen the CO spectra and could flatten the linewidth-size relation. Understanding the nature of the possible diffuse CO component and its effects on observations is crucial for connecting Galactic and extragalactic data.
The imprint of star formation on stellar pulsations
Thomas Steindl, Konstanze Zwintz, Eduard Vorobyov ⋆ In the earliest phases of their evolution, stars gain mass through the acquisition of matter from their birth clouds. The widely accepted classical concept of early stellar evolution neglects the details of this accretion phase and assumes the formation of stars with large initial radii that contract gravitationally. In this picture, the common idea is that once the stars begin their fusion processes, they have forgotten their past. By analysing stellar oscillations in recently born stars, we show that the accretion history leaves a potentially detectable imprint on the stars' interior structures. Carrently available data from space would allow discriminating between these more realistic accretion scenarios and the classical early stellar evolution models. This opens a window to investigate the interior structures of young pulsating stars that will also be of relevance for related fields, such as stellar oscillations in general and exoplanet studies.
Disk Evolution Study Through Imaging of Nearby Young Stars (DESTINYS): Scattered
light detection of a possible disk wind in RY Tau
P. -G. Valegård, C. Ginski, C. Dominik, J. Bae, M. Benisty, T. Birnstiel, S. Facchini, A. Garufi, M. Hogerheijde, R. G. van Holstein, M. Langlois, C. F. Manara, P. Pinilla, Ch. Rab, Á. Ribas, L. B. F. M. Waters, J. Williams ★ 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 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 noeded 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 × 10 − " M ⊙ ≤ M ≤ 5 × 10 − " M ⊙ ≤ M ≤ 5 × 10 − " which corresponds to a lower limit mass loss rate in the wind of about ～ 1 × 10 − 8 M ⊙ yτ − 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.
Physical properties of accretion shocks toward the Class I protostellar system Oph-IRS
44
E. Artur de la Villarmois, V. V. Guzmán, J. K. Jørgensen, L. E. Kristensen, E. A. Bergin, D. Harsono, N. Sakai, E. P. van Dishoeck, S. Yamamoto ★ (Abridged) Physical processes such as accretion shocks are thought to be common in the protostellar phase, where the envelope component is still present, and they can reloase molecules from the dust to the gas phase, altering the original chemical composition of the disk. Consequently, the study of accretion shocks is essential for a better understanding of the physical processes at disk scales and their chemical output. The purpose of this work is to assess the characteristics of accretion shocks traced by sulfur-related species. We present ALMA high angular resolution observations (0.1") of the Class I protostar Oph-IRS 44. The continuum emission at 0.87 mm is observed, together with sulfur-related species such as SO, SO 2 , and 34 SO 2 . Six lines of SO 2 , two lines of 34 SO 2 , and one line of SO are detected toward IRS 44. The emission of all the detocted lines peaks at  0.1" ( 14 au) from the continuum peak and we find infalling-rotating motions inside 30 au. However, only redshifted emission is seen between 50 and 30 au. Colder and more quiescent material is seen toward an offset region located at a distance of  400 au from the protostar, and we do not find evidence of a Keplerian profile in these data. Accretion shocks are the most plausible explanation for the high temperatures, high densities, and velocities found for the SO 2 emission. When material enters the disk–envelope system, it generates accretion shocks that increase the dust temperature and desorb SO 2 molecules from dust grains. High-energy SO 2 transitions ( 200 K) seem to be the best tracers of accretion shocks that can be followed up by future higher angular resolution ALMA observations and compared to other species to assess their importance in releasing molecules from the dust to the gas phase.
Multi-wavelength Observations of MWC 297: Constraints on Disk Inclination and Mass
Outflow
William D. Vacca, Göran Sandell ¥ MWC 297 is a young, early-type star driving an ionized outflow and surrounded by warm, entrained dust. Previous analyses of near- and mid-IR interferometric images suggest that the emission at these wavelengths arises from a compact accretion disk with a moderate ( i < 40 degrees) inclination. We have obtained 5-40 micron images of MWC 297 with FORCAST on SOFIA, as well as near-infrared spectra acquired with SpeX on the IRTF and radio data obtained with the VLA and BIMA, and supplemented these with archival data from Herschel/PACS and SPIRE. The FORCAST images, combined with the VLA data, indicate that the outflow lobes are aligned nearly north-south and are well separated. Simple geometrical modeling of the FORCAST images suggests that the disk driving the outflow has an inclination of 55 ± 5 degrees, in disagreement with the results of the interferometric analyses. Analysis of the SpeX data, with a wind model, suggests the the mass loss rate is on the order of 6.0 ± ± 3 × 10 − 7 M ⊙ yτ − 1 and the extinction to the source is A ν ～ 8.1 ± 2 × mag. We have combined our data with values from the literature to generate the spectral energy distribution of the source from 0.35 μ m to 6 cm and estimate the total luminosity. We find the total luminosity to be about 7900 L σ , if we include emission from an extended region around the star, only slightly below that expected for a B1.5V star. The reddening must be produced by dust along the line of sight, but distant from the star.
Confirmation of the outflow in L1451-mm: SiO line and CH 3 OH maser detections
V. Wakelam, A. Coutens, P. Gratier, T. H G Vidal, N. Vaytet ⋆ The observational counterparts of theoretically prodicted first hydrostatic cores (FHSC) have been searched for in the interstellar modium for nearly two decades now. Dis- tinguishing them from other types of more evolved but still embedded objects remains a challenge because these objects have a short lifetime, are small, and embedded in a dense cocoon. One possible lead to finding them is the characterization of the outflows that are launched by these objects. We observed the L1451-mm FHSC candidate with the NOEMA interferometer in order to study the emission of several molecules. A nonlocal thermodynamic oquilibrium analysis of the CH3OH detected lines was performed to retrieve the physical conditions of the emitting region around the central source, together with the CH 3 OH, SiO, CS, and H 2 CO column densities. Of the targeted molecules, we detected lines of c-C 3 H 2 , CH 3 OH, CS, C 34 S, SO, DCN, DCO*, H 2 CO, HC 3 N , HDCO, and SiO. One of the methanol lines appears to be a maser line. The detection of this class I maser and the SiO line in L1451-mm support the presence of a low-velocity and compact outflow. The excitation conditions of the thermal lines of methanol are also compatible with shocks (H 2 density of ～ 3 × 10 6 cm −3 and a temperature higher than 40 K). Although these low-velocity outflows are theoretically prodicted by some models of FHSC, these models also prodict the shock temperature to be below 20 K, that is, not evaporating methanol. In addition, the predicted velocities would not erode the grains and release silicon in the gas phase. We therefore conclude that these new observations favor the hypothesis that L1451-mm would be at a very early protostellar stage, launching an outflow nearly on the plane of the sky with a higher velocity than is observed.
ALMA uncovers highly filamentary structure towards the Sgr E region
J. Wallace, C. Battersby, E. A. C. Mills, J. D. Henshaw, M. C. Sormani, A. Ginsburg, A. T. Barnes, H. P. Hatchfield, S. C. O. Glover, L. D. Anderson ⋆ We report on the discovery of linear filaments observed in CO(1-0) emission for a ~ 2 ′ field of view toward the Sgr E star forming region centered at (l,b)−(358.720°, 0.011°). The Sgr E region is thought to be at the turbulent intersection of the "far dust lane" associated with the Galactic bar and the Central Molecular Zone (CMZ). This region is subject to strong accelerations which are generally thought to inhibit star formation, yet Sgr E contains a large number of HII regions. We present 12 CO(1-0), 12 CO(1-0), and C 18 O(1-0) spectral line observations from ALMA and provide measurements of the physical and kinematic properties for two of the brightest filaments. These filaments have widths (FWHM) of ～ 0.1 pc and are oriented nearly parallel to the Galactic plane, with angles from the Galactic plane of ～ 2 ° . The filaments are elongated, with lower limit aspect ratics of ~5:1. For both filaments we detect two distinct velocity components that are separated by about 15 km s − 1 . In the C 18 O spectral line data with ～0.09 pc spatial resolution, we find that these velocity components have relatively narrow (~1-2 km s − 1 ) FWHM linewidths when compared to other sources towards the Galactic center. The properties of these filaments suggest that the gas in the Sgr E complex is being "stretched" as it is rapidly accelerated by the gravitational field of the Galactic bar while falling towards the CMZ, a result that could provide insight into the extreme environment surrounding this region and the largo-scale processes which fuel this environment.
Discovery of Line Pressure Broadening and Direct Constraint on Gas Surface Density
in a Protoplanetary Disk
Tomohiro C. Yoshida, Hideko Nomura, Takashi Tsukagoshi, Kenji Furuya, Takahiro Ueda ⋆ The gas surface density profile of protoplanetary disks is one of the most fundamental physical properties to understand planet formation. However, it is challenging to determine the surface density profile observationally, because the H 2 emission cannot be observed in low-temperature regions. We analyzed the Atacama Large Millimeter/submillimeter Array (ALMA) archival data of the CO line toward the protoplanetary disk around TW Hya and discovered extremely broad line wings due to the pressure broadening. In conjunction with a previously reported optically thin CO isotopologue line, the pressure broadened line wings enabled us to directly determine the midplane gas density for the first time. The gas surface density at ～ 5 au from the central star reaches ~ 10³ g cm¯ 2, which suggests that the inner region of the disk has enough mass to form a Jupiter-mass planet. Additionally, the gas surface density drops at the inner cavity by ～ 2 orders of magnitude compared to outside the cavity. We also found a low CO abundance of ～ 10−6 with respect to H 2 , even inside the CO snowline, which suggests conversion of CO to less volatile species. Combining our results with previous studies, the gas surface density jumps at r ～ 20 au, suggesting that the inner region (3 < r < 20 au) might be the magnetorotational instability dead zone. This study sheds light on direct gas-surface-density constraint without assuming the CO/H 2 ratio using ALMA.
◆ Directly Detecting the Envelopes of Low-mass Planets Embedded In Protoplanetary
Discs and The Case For TW Hydrae
Zhaohuan Zhu, Avery Bailey, Enrique Macías, Takayuki Muto, Sean M. Andrews ⋆ Despite many methods de- veloped to find young massive planets in protoplanetary discs, it is challenging to directly detect low-mass planets that are embedded in discs. On the other hand, the core-accretion theory suggests that there could be a large population of embedded low-mass young planets at the Kelvin-Helmholtz (KH) contraction phase. We adopt both 1-D models and 3-D simulations to calculate the envelopes around low-mass cores (several to tens of M e ) with different luminosities, and derive their thermal fluxes at radio wavelengths. We find that, when the background disc is optically thin at radio wavelengths, radio observations can see through the disc and probe the denser envelope within the planet's Hill sphere. When the optically thin disc is observed with the resolution reaching one disc scale height, the radio thermal flux from the planetary envelope around a 10 M e core is more than 10% higher than the flux from the background disc. The emitting region can be extended and elongated. Finally, our model suggests that the au-scale chump at 52 au in the TW Hydrae disc revealed by ALMA is consistent with the envelope of an embedded 10-20 M e planet, which can explain the detected flux, the spectral index dip, and the tentative spirals. The observation is also consistent with the planet undergoing pebble accretion. Future ALMA and ngVLA observations may directly reveal more such low-mass planets, enabling us to study core growth and even reconstruct the planet formation history using the embedded "protoplanet" population.
RVSPY – Radial Velocity Survey for Planets around Young Stars. Target characteri-
zation and high-cadence survey
O. Zakhozhay, R. Launhardt, A. Mueller, S. Brems, P. Eigenthaler, M. Gennaro, A. Hempel, M. Hempel, Th. Henning, G. Kennedy, S. Kim, M. Kuerster, R. Lachaume, Y. Manerikar, J. Patel, A. Pavlov, S. Reffert, T. Trifonov ⋆ We introduce our Radial Velocity Survey for Planets around Young stars (RVSPY), characterise our target stars, and search for substellar companions at orbital separations smaller than a few au from the host star. We use the FEROS spectrograph to obtain high signal-to-noise spectra and time series of precise radial velocities (RVs) of 111 stars most of which are surrounded by debris discs. Our target stars have spectral types between early F and late K, a median age of 400 Myr, and a median distance of 45 pc. We determine for all target stars their basic stellar parameters and present the results of the high-cadence RV survey and activity characterization. We achieve a median single-measurement RV precision of 6 m/s and derive the short-term intrinsic RV scatter of our targets (median 22 m/s), which is mostly caused by stellar activity and decays with age from >100 m/s at <20 Myr to <20 m/s at >500 Myr. We discover six previously unknown close companions with orbital periods between 10 and 100 days, three of which are low-mass stars, and three are in the brown dwarf mass regime. We detect no hot companion with an orbital period <10 days down to a median mass limit of  1 Mננfor stars younger than 500 Myr, which is still compatible with the established occurrence rate of such companions around main-sequence stars. We find significant RV periodicities between 1.3 and 4.5 days for 14 stars, which are, however, all caused by rotational modulation due to starspots. We also analyse the TESS photometric time series data and find significant periodicities for most of the stars. For 11 stars, the photometric periods are also clearly detected in the RV data. We also derive stellar rotation periods ranging from 1 to 10 days for 91 stars, mostly from TESS data. From the intrinsic activity-related short-term RV jitter, we derive the expected mass-detection thresholds for longer-period companions.