In 2017, the Event Horizon Telescope (EHT) Collaboration succeeded in capturing the first direct image of the center of the M87 galaxy. The asymmetric ring morphology and size are consistent with theoretical expectations for a weakly accreting supermassive black hole of mass ∼6.5 × 10⁹ M _⊙. The EHTC also partnered with several international facilities in space and on the ground, to arrange an extensive, quasi-simultaneous multi-wavelength campaign. This Letter presents the results and analysis of this campaign, as well as the multi-wavelength data as a legacy data repository. We captured M87 in a historically low state, and the core flux dominates over HST-1 at high energies, making it possible to combine core flux constraints with the more spatially precise very long baseline interferometry data. We present the most complete simultaneous multi-wavelength spectrum of the active nucleus to date, and discuss the complexity and caveats of combining data from different spatial scales into one broadband spectrum. We apply two heuristic, isotropic leptonic single-zone models to provide insight into the basic source properties, but conclude that a structured jet is necessary to explain M87’s spectrum. We can exclude that the simultaneous γ-ray emission is produced via inverse Compton emission in the same region producing the EHT mm-band emission, and further conclude that the γ-rays can only be produced in the inner jets (inward of HST-1) if there are strongly particle-dominated regions. Direct synchrotron emission from accelerated protons and secondaries cannot yet be excluded.

We present the initial results of multiepoch VLBI observations of 22 GHz H$$_{2}$$O masers in the Orion KL region with VERA (VLBI Exploration of Radio Astrometry). With the VERA dual-beam receiving system, we carried out phase-referencing VLBI astrometry, and successfully detected the annual parallax of Orion KL to be 2.29$$\;\pm\;$$0.10 mas, corresponding to a distance of 437$$\;\pm\;$$19 pc from the Sun. The distance to Orion KL was determined for the first time with the trigonometric parallax method in these observations. Although this value is consistent with that previously reported, 480$$\;\pm\;$$80 pc, which was estimated from a statistical parallax method using the proper motions and radial velocities of the H$$_{2}$$O maser features, our new results provide a much more accurate value with an uncertainty of only 4%. In addition to the annual parallax, we detected an absolute proper motion of the maser feature, suggesting an outflow motion powered by the radio source I along with the systematic motion of source I itself.

To date, about two dozen low-mass embedded protostars exhibit rich spectra with lines of complex organic molecules (COMs). These protostars seem to possess a different enrichment in COMs. However, the statistics of COM abundance in low-mass protostars are limited by the scarcity of observations. This study introduces the Perseus ALMA Chemistry Survey (PEACHES), which aims at unbiasedly characterizing the chemistry of COMs toward the embedded (Class 0/I) protostars in the Perseus molecular cloud. Of the 50 embedded protostars surveyed, 58% of them have emission from COMs. 56%, 32%, and 40% of the protostars have CH₃OH, CH₃OCHO, and N-bearing COMs, respectively. The detectability of COMs depends neither on the averaged continuum brightness temperature, a proxy of the H₂ column density, nor on the bolometric luminosity and the bolometric temperature. For the protostars with detected COMs, CH₃OH has a tight correlation with CH₃CN, spanning more than two orders of magnitude in column densities normalized by the continuum brightness temperature, suggesting a chemical relation between CH₃OH and CH₃CN and a large chemical diversity in the PEACHES samples at the same time. A similar trend with more scatter is also found between all identified COMs, which hints at a common chemistry for the sources with COMs. The correlation between COMs is insensitive to the protostellar properties, such as the bolometric luminosity and the bolometric temperature. The abundance of larger COMs (CH₃OCHO and CH₃OCH₃) relative to that of smaller COMs (CH₃OH and CH₃CN) increases with the inferred gas column density, hinting at an efficient production of complex species in denser envelopes.

The ATOMS, standing for ALMA Three-millimeter Observations of Massive Star-forming regions, survey has observed 146 active star forming regions with ALMA Band 3, aiming to systematically investigate the spatial distribution of various dense gas tracers in a large sample of Galactic massive clumps, to study the roles of stellar feedback in star formation, and to characterize filamentary structures inside massive clumps. In this work, the observations, data analysis, and example science of the ATOMS survey are presented, using a case study for the G9.62+0.19 complex. Toward this source, some transitions, commonly assumed to trace dense gas, including CS J = 2 − 1, HCO⁺J = 1 − 0 and HCN J = 1 − 0, are found to show extended gas emission in low density regions within the clump; less than 25% of their emission is from dense cores. SO, CH₃OH, H¹³CN and HC₃N show similar morphologies in their spatial distributions and reveal well the dense cores. Widespread narrow SiO emission is present (over ∼1 pc), which may be caused by slow shocks from large–scale colliding flows or H ii regions. Stellar feedback from an expanding H ii region has greatly reshaped the natal clump, significantly changed the spatial distribution of gas, and may also account for the sequential high-mass star formation in the G9.62+0.19 complex. The ATOMS survey data can be jointly analyzed with other survey data, e.g., MALT90, Orion B, EMPIRE, ALMA_IMF, and ALMAGAL, to deepen our understandings of ”dense gas” star formation scaling relations and massive proto-cluster formation.

We report the first evidence of a hot corino in a Bok globule. This is based on ALMA observations in the 1.2 mm band toward the low-mass Class 0 protostar IRAS 19347+0727 in B335. Saturated complex organic molecules (COMs), CH₃CHO, HCOOCH₃, and NH₂CHO, are detected in a compact region within a few 10 au around the protostar. Additionally, CH₃OCH₃, C₂H₅OH, C₂H₅CN, and CH₃COCH₃ are tentatively detected. Carbon-chain related molecules, CCH and c-C₃H₂, are also found in this source, whose distributions are extended over a scale of a few 100 au. On the other hand, sulfur-bearing molecules CS, SO, and SO₂ have both compact and extended components. Fractional abundances of the COMs relative to H₂ are found to be comparable to those in known hot corino sources. Though the COMs lines are as broad as 5–8 km s⁻¹, they do not show obvious rotation motion in the present observation. Thus, the COMs mainly exist in a structure whose distribution is much smaller than the synthesized beam (0.″58 × 0.″52).

The Class 0 protostar, L483, has been observed in various molecular lines in the 1.2 mm band at a subarcsecond resolution with ALMA. An infalling–rotating envelope is traced by the CS line, while a very compact component with a broad velocity width is observed for the CS, SO, HNCO, NH₂CHO, and HCOOCH₃ lines. Although this source is regarded as the warm carbon-chain chemistry (WCCC) candidate source at a 1000 au scale, complex organic molecules characteristic of hot corinos such as NH₂CHO and HCOOCH₃ are detected in the vicinity of the protostar. Thus, both hot corino chemistry and WCCC are seen in L483. Although such a mixed chemical character source has been recognized as an intermediate source in previous single-dish observations, we here report the first spatially resolved detection. A kinematic structure of the infalling–rotating envelope is roughly explained by a simple ballistic model with a protostellar mass of 0.1–0.2 M ⊙ and a radius of the centrifugal barrier (half of the centrifugal radius) of 30–200 au, assuming an inclination angle of 80° (0° for face-on). The broad-line emission observed in the above molecules most likely comes from the disk component inside the centrifugal barrier. Thus, a drastic chemical change is seen around the centrifugal barrier.