ALMA Results

I propose to merge all threads concerning ALMA findings in this topic, starting from the latest ones:

Led_Zep wrote:

http://www.spacedaily.com/reports/ALMA_Sheds_Light_on_Planet_Forming_Gas_Streams_999.html

 

Sirius_Alpha wrote:

First Detection of the Simplest Organic Acid in a Protoplanetary Disk
https://arxiv.org/abs/1807.05768

Quote :

The formation of asteroids, comets and planets occurs in the interior of protoplanetary disks during the early phase of star formation. Consequently, the chemical composition of the disk might shape the properties of the emerging planetary system. In this context, it is crucial to understand whether and what organic molecules are synthesized in the disk. In this Letter, we report the first detection of formic acid (HCOOH) towards the TW Hydrae protoplanetary disk. The observations of the trans-HCOOH 6(1,6)−5(1,5) transition were carried out at 129~GHz with ALMA. We measured a disk-averaged gas-phase t-HCOOH column density of ∼ (2-4)×1012~cm−2, namely as large as that of methanol. HCOOH is the first organic molecules containing two oxygen atoms detected in a protoplanetary disk, a proof that organic chemistry is very active even though difficult to observe in these objects. Specifically, this simplest acid stands as the basis for synthesis of more complex carboxylic acids used by life on Earth.

Sirius_Alpha wrote:

ALMA observations of the nearby AGB star L2 Puppis - I. Mass of the central star and detection of a candidate planet
https://arxiv.org/abs/1611.06231

Quote :

Six billion years from now, while evolving on the asymptotic giant branch (AGB), the Sun will metamorphose from a red giant into a beautiful planetary nebula. This spectacular evolution will impact the Solar System planets, but observational confirmations of the predictions of evolution models are still elusive as no planet orbiting an AGB star has yet been discovered. The nearby AGB red giant L2 Puppis (d = 64 pc) is surrounded by an almost edge-on circumstellar dust disk. We report new observations with ALMA at very high angular resolution (18 x 15 mas) in band 7 (f ~ 350 GHz) that allow us to resolve the velocity profile of the molecular disk. We establish that the gas velocity profile is Keplerian within the central cavity of the dust disk, allowing us to derive the mass of the central star L2 Pup A, mA = 0.659 +/- 0.011 +/- 0.041 Msun (+/- 6.6%). From evolutionary models, we determine that L2 Pup A had a near-solar main sequence mass, and is therefore a close analog of the future Sun in 5 to 6 Gyr. The continuum map reveals the presence of a secondary source (B) at a radius of 2 AU contributing fB/ fA = 1.3 +/- 0.1% of the flux of the AGB star. L2 Pup B is also detected in CO emission lines at a radial velocity of vB = 12.2 +/- 1.0 km/s. The close coincidence of the center of rotation of the gaseous disk with the position of the continuum emission from the AGB star allows us to constrain the mass of the companion to mB = 12 +/- 16 MJup. L2 Pup B is most likely a planet or low mass brown dwarf with an orbital period around 5 years. Its continuum brightness and molecular emission suggest that it may be surrounded by an extended molecular atmosphere or an accretion disk. L2 Pup therefore emerges as a promising vantage point on the distant future of our Solar System.

Latest news

Kinematics signature of a giant planet in the disk of AS 209

Quote :

ALMA observations of dust in protoplanetary disks are revealing the existence of sub-structures such as rings, gaps and cavities. Such morphology are expected to be the outcome of dynamical interaction between the disk and planets. However, other mechanisms are able to produce similar dust sub-structures. A solution is to look at the perturbation induced by the planet to the gas surface density and/or to the kinematics. In the case of the disk around AS 209, a prominent gap has been reported in the surface density of CO at r∼100au. Recently, Bae et al. (2022) detected a localized velocity perturbation in the 12CO J=2−1 emission along with a clump in 13CO J=2−1 at nearly 200 au, interpreted as a gaseous circumplanetary disk. We report a new analysis of ALMA archival observations of 12CO and 13CO J=2-1. A clear kinematics perturbation (kink) is detected in multiple channels and over a wide azimuth range in both dataset. We compared the observed perturbation with a semi-analytic model of velocity perturbations due to planet-disk interaction. The observed kink is not consistent with a planet at 200\,au as this would require a low gas disk scale height (<0.05) in contradiction with previous estimate (h/r∼0.118 at r=100 au). When we fix the disk scale height to 0.118 (at r=100 au) we find instead that a planet of 3-5 MJup at 100 au induces a kinematics perturbation similar to the observed one. Thus, we conclude that a giant protoplanet orbiting at r∼100au is responsible of the large scale kink as well as of the perturbed dust and gas surface density previously detected. The position angle of the planet is constrained to be between 60∘-100∘. Future observations with high contrast imaging technique in the near- and mid- infrared are needed to confirm the presence and position of such a planet.

The ALMA view of MP Mus (PDS 66): a protoplanetary disk with no visible gaps down to 4 au scales

Quote :

We present ALMA multiwavelength observations of the protoplanetary disk around the nearby (d∼100 pc) young solar analog MP Mus (PDS 66). These observations at 0.89 mm, 1.3 mm, and 2.2 mm have angular resolutions of ∼ 1", 0.05", and 0.25", respectively, and probe the dust and gas in the system with unprecedented detail and sensitivity. The disk appears smooth down to the 4 au resolution of the 1.3 mm observations, in contrast with most disks observed at comparable spatial scales. The dust disk has a radius of 60±5 au, a dust mass of 0.14+0.11−0.06MJup, and a mm spectral index <2 in the inner 30 au, suggesting optically thick emission from grains with high albedo in this region. Several molecular gas lines are also detected extending up to 130±15 au, similar to small grains traced by scattered light observations. Comparing the fluxes of different CO isotopologues with previous models yields a gas mass of 0.1−1MJup, implying a gas to dust ratio of 1-10. We also measure a dynamical stellar mass of Mdyn=1.30±0.08 M⊙ and derive an age of 7-10 Myr for the system. The survival of large grains in an evolved disk without gaps/rings is surprising, and it is possible that existing substructures remain undetected due to optically thick emission at 1.3 mm. Alternatively, small structures may still remain unresolved with the current observations. Based on simple scaling relations for gap-opening planets and gap widths, this lack of substructures places upper limits to the masses of planets in the disk as low as 2 M⊕-0.06 MJup at r>40 au. The lack of mm emission at radii r>60 au also suggests that the gap in scattered light between 30-80 au is likely not a gap in the disk density, but a shadow cast by a puffed-up inner disk.