We present wide-field and high-sensitivity CO (1-0) molecular line observations toward the Galactic anticenter region, using the 13.7 m millimeter telescope of the Purple Mountain Observatory. Based on the CO observations, we report the discovery of a giant spiral molecular cloud, which covers the region of 183 .degrees 75 >= l >= 181 .degrees 25 and -2 .degrees 25 <= b <= 0 .degrees 75, and the velocity range from approximately -16 to -8 km s-1. The distance of the cloud is measured to be similar to 1650 pc, while the derived dimension and gas mass of the cloud are similar to 75 pc & times; 90 pc and similar to 8 & times; 104 M circle dot, respectively. Spiral arms and concentric rings are clearly detected in the cloud, which mimics a typical spiral galaxy observed in the local Universe. The oscillation of radial velocities is observed across the cloud, with a spatial wavelength of similar to 4.8-5.3 pc and a velocity amplitude of similar to 0.11-0.13 km s-1. The spiral cloud is undergoing slow rotation with an approximately constant velocity gradient (similar to 2-3 km s-1 deg-1 or similar to 0.07-0.10 km s-1 pc-1). Similar to many spiral galaxies, the observed structure and kinematics of the cloud can be explained by the density wave theory. The discovery provides a unique cloud sample in the solar neighborhood, which may help us to understand the nature of spiral structures in distant galaxies.

We investigate the relationships between Large High Altitude Air Shower Observatory (LHAASO) TeV gamma-ray sources and various kinds of objects, including pulsar wind nebulae (PWNe), supernova remnants (SNRs), H ii regions, microquasars, and OB associations. We propose a Randomization-Adjusted Overlap Correlation method to statistically assess association probabilities and evaluate association proportions across catalogs. The results reveal statistically significant overlaps between LHAASO sources and SNRs, PWNe, and microquasars, supporting their role as important contributors to TeV gamma-ray emission. The estimated association proportions of LHAASO sources are 0.19 +/- 0.08 with SNRs, 0.20 +/- 0.04 with PWNe, and 0.027 +/- 0.008 with microquasars. The proportion of the gamma-ray sources associated with the subsample of shell-type SNRs is similar to 0.1. While H ii regions also show potential association, particularly with the Kilometer Squared Array (KM2A) component, their large self-overlap ratio complicates precise estimation. In contrast, OB associations exhibit a high probability of chance coincidence, suggesting their limited contribution to TeV gamma-ray emission. Our analysis of TeV gamma-ray emission capabilities shows that similar to 60% of PWNe are gamma-ray bright in both the Water Cherenkov Detector Array (WCDA) and KM2A energy ranges. For SNRs and microquasars, the TeV gamma-ray bright fraction is similar to 10%. The subsample of PWNe associated with molecular clouds (MCs) shows enhanced gamma-ray emission. Furthermore, positional analysis reveals a systematic offset of the gamma-ray sources overlapping with PWNe toward the associated MCs. These findings imply a role for MCs in PWN gamma-ray production. Additionally, self-correlation analysis indicates that about 70% of the WCDA and KM2A gamma-ray components share a common origin. The study also identifies selection effects in existing SNR catalogs and notes clustering among approximately 30% of H ii regions within larger star-forming regions. Further multi-wavelength studies are needed to elucidate the physical mechanisms underlying these associations.

Accurate astrometric measurements for star-forming regions located on the far side of the Milky Way remain scarce. In this work, we present the astrometric results for a 22 GHz water maser associated with star-forming region G040.96+02.48 located on the far side of the Milky Way, using the East Asian Very Long Baseline Interferometry Network. The target water maser's proper motion was determined to be ( mu alpha cos delta,mu delta ) = ( -2.06-0.51+0.53 , -2.95-0.44+0.45 ) mas yr-1. The derived three-dimensional kinematic distance to the star-forming region is 20.2 +/- 3.2 kpc, placing it slightly outside the Outer Scutum-Centaurus Arm. The corresponding vertical height of 872 +/- 139 pc indicates a significant warp of the outer Galactic disk, which is in good agreement with the latest precessing warp model. Moreover, the resulting peculiar motions reveal a complex kinematic pattern, characterized by a large outward radial velocity of -32 +/- 18 km s-1. Our observations substantially expand the valuable sample of star-forming regions with accurate astrometric measurements in the Extreme Outer Galaxy.

Using Gaia astrometry of young stars combined with CO observations, we present the first systematic three-dimensional (3D) analysis of the structure, kinematics, and evolutionary history of the star-forming regions in the environs of the H II region Sh 2-205 (S205). S205 exhibits a complex morphology and coherent expansion on both global and subregional scales. We identify several O9-B1 stars and a 0.56 Myr old pulsar that are likely associated with the region. A momentum estimate suggests that feedback from these objects may account for the observed overall expansion. Trace-back analysis of the expansion, combined with color-magnitude diagram fitting for young star clusters, indicates at least two episodes of star formation. These results reveal a complex star-formation history of S205 and provide new insights into its 3D evolution.

The alignment between the radio-based International Celestial Reference Frame (ICRF) and the optical Gaia Celestial Reference Frame (Gaia-CRF) is critical for multi-waveband astronomy, yet systematic offsets at the optical bright end (G less than or similar to 13) limit their consistency. While radio stars offer a potential link between these frames, their utility has been restricted by the scarcity of precise Very Long Baseline Interferometry (VLBI) astrometry. In this study, we present new VLBI astrometry of 11 radio stars using the Very Long Baseline Array (VLBA), expanding the existing sample with positions, parallaxes, and proper motions measured. All 11 radio stars were detected, for 10 of which parallaxes and proper motions can be estimated, achieving median uncertainties better than 0.1 mas and 0.1 mas yr(-1), respectively. These new samples greatly contribute to the link between ICRF and Gaia-CRF at the optical bright end.

The origin of the multiphase gas within the Fermi/eROSITA bubbles is crucial for understanding Galactic center (GC) feedback. We use HI4PI data to investigate the kinematics and physical properties of high-velocity clouds (HVCs) toward the GC region ( l = +25° to −10°). Our results reveal that the HVCs exhibit a distinct asymmetric distribution, closely associated with bar-driven tilted dust lanes and distorted overshooting streams. We propose that powerful nuclear outflows interact with these gas-rich, off-plane structures, striping and entraining cold gas from the outer Galactic regions ( R _GC ∼ 0.5–1.7 kpc) rather than solely from the central molecular zone (CMZ; R _GC ≲ 0.3 kpc). In this scenario, as the Galactic bar drives gas inflows along the dust lanes, nuclear outflows simultaneously break through the CMZ, sweeping up and ablating cold gas from the boundary layer of these preexisting structures. This process naturally accounts for the observed high turbulence, complex spectral signatures, and anomalous spatial-kinematic gas patterns, as well as multiwavelength asymmetries of the bubbles. The HVCs are accelerated to about 230–340 km s ^−1 over a dynamical time of ∼3–6 Myr. When the multiphase, inhomogeneous composition of the gas is included, the estimated gas outflow rate in on the order of ∼1 M _⊙ yr ^−1 . This value is comparable to the bar-driven inflow rate, indicating a tightly coupled gas cycle in the inner Galaxy. Our research highlights the critical role of bar-driven gas dynamics and nuclear feedback in the secular evolution of the Milky Way, offering a valuable paradigm for investigating the gas outflow–inflow cycle in external galaxies.

Recent studies have shown that the star formation rate (SFR) correlates tightly and linearly with the mass of gravitationally bound gas, which can be delineated from the power-law tail of the column-density probability distribution function (N-PDF) derived from dust emission observations. This relationship holds across four orders of magnitude within the Milky Way–spanning low-mass to high-mass star-forming regions and encompassing the extreme environment of the Central Molecular Zone. Building on this framework, we present a new approach for estimating the mass of gravitationally bound gas in molecular clouds using multi-line CO isotopologue observations. Our sample includes 16 molecular clouds with robust detections in ^12CO, ^13CO, and C^18O J = 1-0, spanning both massive inner Galaxy clouds and nearby star-forming regions. We find that the N-PDFs derived from combined CO isotopologue data recover the characteristic log-normal plus power-law profiles seen in dust-based studies. The mass and spatial distribution of the self-gravitating structures estimated from both dust-based and CO-based methods agree well throughout the sample. This indicates that the CO isotopologue combination can robustly trace the self-gravitating component via the N-PDF method and provides a reliable, scalable, and velocity-resolved alternative to dust emission for identifying the star-forming gas in molecular clouds.

Vertical corrugations—wave-like undulations in galactic disks—are potential imprints of past dynamical events that offer key constraints on galaxy evolution. While large-scale corrugations superimposed on the Galactic warp have recently been detected using young stellar tracers, the corresponding widespread structure within the molecular gas remains largely unexplored due to the challenge of disentangling subtle amplitudes from the dominant warp signal. By analysing over 30,000 molecular clouds from the Milky Way Imaging Scroll Painting survey, we systematically characterize widespread corrugations across the outer CO disk. After subtracting a global CO warp model, residual vertical displacements reveal coherent wave-like structures spanning much of the outer disk. Quantitative modelling yields characteristic vertical amplitudes of ~100–200 pc and radial wavelengths of ~3.9–7.9 kpc, and identifies a coherent azimuthal corrugation mode with a 52.6° (~11.6 kpc) wavelength at Galactocentric radius R ≈ 12.7 kpc, extending ~40 kpc. These findings provide direct evidence that vertical corrugations are a common large-scale feature of the outer Galactic molecular disk, offering insights into the three-dimensional structure and dynamics of spiral galaxies. Using more than 30,000 molecular clouds, this study reveals widespread wave-like corrugations superimposed on the warp of the Milky Way’s outer molecular disk, offering insight into its three-dimensional structure and dynamics.

We present the first Galactic-scale validation of flux scaling relations among CO isotopologues, using an enlarged sample from the Milky Way Imaging Scroll Painting Phase I survey. We identified 10,843 ^13 CO-emitting clouds and 746 C ^18 O-emitting clouds using a stacking algorithm from the ^12 CO cloud sample of Q.-Z. Yan et al. We obtained flux scaling relations ${F}_{{}^{13}{\rm{CO}}}=0.11\,{F}_{{}^{12}{\rm{CO}}}$ within the ^12 CO-bright region and ${F}_{{}^{13}{\rm{CO}}}=0.16\,{F}_{{}^{12}{\rm{CO}}}$ within the ^13 CO-bright region. Additionally, we found the relation ${F}_{{{\rm{C}}}^{18}{\rm{O}}}\,=\,0.11\,{F}_{{}^{13}{\rm{CO}}}$ in C ^18 O-emitting regions, which indicates their abundance ratio ${X}_{{}^{13}{\rm{CO}}}/{X}_{{{\rm{C}}}^{18}{\rm{O}}}\sim 8.0$ . It suggests large-scale chemical homogeneity in molecular clouds. Flux ratios within individual clouds demonstrate a general pattern that gradually decreases outward. The cumulative distributions of flux in ^12 CO, ^13 CO, and C ^18 O are all close to “top heavy,” suggesting that a small number of high-flux molecular clouds dominate the total flux in the Galaxy.

We present the first data release (DR1) of the Milky Way Imaging Scroll Painting (MWISP) survey, a mapping in the J = 1 -> 0 transition lines of 12CO, 13CO, and C18O toward the northern Galactic plane during 2011-2022. The MWISP survey was conducted using the Purple Mountain Observatory 13.7 m telescope at a spatial resolution of approximately 50 '' and a velocity resolution of 0.16 km s-1 at 115 GHz. DR1 fully covered 2310 deg2 within the Galactic longitude (l) and latitude (b) range of 9 .degrees 75 <= l <= 229 .degrees 75 and divided by b divided by <= 5 .degrees 25. The surveyed area was divided into cell units of 30 ' x30 ' for practical purposes and on-the-fly mapping was performed toward each target cell unit. The data were regridded into a regular three-dimensional data cube in l-b-VLSR with a pixel size of 30 '' in l-b axes and 0.16 km s-1 in the VLSR axis. The median rms noise is 0.47, 0.25, and 0.25 K for 12CO, 13CO, and C18O, respectively. The equivalent 3 sigma sensitivity in 12CO luminosity is approximately 0.23 K km s-1, making MWISP the most sensitive survey of its kind. In this paper, we describe the survey data, including the calibration, data cleaning, data mosaic processes, and the data products. The final mosaicked data cubes contain about 3.33 x 107 spectra (pixels) for each CO isotopologue line. Color composite images, made from the intensities of the isotopologue lines, and some concise descriptions are provided. We constructed a molecular cloud catalog based on the mosaicked 12CO data cube using the clustering algorithm DBSCAN, detecting 103,517 molecular clouds, 10,790 of which exhibit 13CO emission and 304 of which show C18O emission. Based on the histogram of voxel brightness temperature, we estimated a total 12CO flux of 7.69 +/- 0.38 x 107 K km s-1 arcmin2, 82% of which is captured by the DBSCAN algorithm. The properties of molecular clouds show a large dynamic range, facilitating more accurate statistics. The data, together with the cloud sample, provide unique information on molecular gas in the northern Milky Way.

A giant spiral molecular cloud is recently discovered in the Galactic anticenter, within a wide-field and high-sensitivity CO line survey. We present multiwavelength observational data of this cloud in this work. Radio continuum images find in the geometric center of the spiral molecular cloud a nonthermal bright source, which drives a wiggly radio jet. No optical or X-ray counterparts are found for this radio source. The CO observations reveal a molecular jet from the center of the cloud. The kinematics of the jet lobes suggests that the CO jet is driven by a source located at the cloud geometric center, where no other alternative driving source is found, except the radio source. Based on the multiwavelength images, we suggest that the radio source represents either an active galactic nucleus or a black hole in the Galaxy. Further observations are needed to study the nature of the radio source, including its distance and radial velocity. If the radio source is associated with the spiral molecular cloud, the mass of the candidate black hole is ∼1.5 × 10 ^3 M _⊙ , estimated from the CO gas kinematics and supported by complementary radio and X-ray data. The discovery of the radio source may provide a unique sample in the Galaxy to study the origin of intermediate-mass black holes.

Molecular bubbles are widely used as tracers of stellar feedback; yet, their identification in spectral-line surveys remains challenging because both cavity morphology and kinematic structure must be assessed consistently in position–position–velocity (PPV) space. We present the Bubble-Weight Fields (BWFields) framework, a PPV-based method that for the first time enables the automated and objective identification and analysis of enclosed molecular bubbles directly from spectral-line data cubes. BWFields constructs a bubble-weight field, W_l,b,v, which encodes cumulative evidence for cavity interiors by aggregating topological signatures across multiple signal-to-noise tiers and velocity-integration scales. Contiguous cavity interiors are segmented as weight-clumps and associated with surrounding molecular gas, linking candidate bubbles to the structure of their host clouds. Shell morphology is characterized using radial intensity profiles and emission-defined intensity skeletons, which capture the shell geometry as traced by the observed emission. Bubble kinematics are quantified using azimuthally sampled position-velocity (PV) diagnostics, along with a turbulence-normalized expansion significance, which serves as a direct measure of the expansion-like velocity organisation. Applied to MWISP ^13CO observations of the G17 region, BWFields identifies a population of bubble candidates with a broad range of morphologies and velocity structures in complex environments. BWFields establishes a scalable and physically interpretable framework for molecular-bubble studies in large surveys, enabling systematic investigations of stellar feedback in the Galactic interstellar medium.

Using CO data from Phase I of the Milky Way Imaging Scroll Painting (MWISP) survey, we present a systematic study of molecular structures with narrow lines. We identify 57 CO structures, most of which exhibit low densities and subsonic/transonic turbulence. Among them, structures with large projected areas and diffuse, sheet-like geometries are identified as veil clouds. The low LSR velocities and the concentration of these CO structures toward both the Galactic center (e.g., Ophiuchus, Aquila) and anticenter (e.g., Cepheus, Taurus) regions suggest a local origin for the sample, as supported by distance measurements of about 200–300pc for a subset with relatively large angular extents. These nearby structures likely arise from large-scale compression driven by past supernova activity within the Local Bubble. The observed low-velocity-dispersion emission may trace quiescent regions where turbulence has decayed due to a lack of sustained energy injection. For diffuse veil clouds with an assumed magnetic field of 10uG, ion-neutral friction may provide an additional mechanism for turbulent dissipation on sub-parsec scales corresponding to their thickness of 0.1–0.3pc. Tracing the atomic-to-molecular transition, veil clouds provide a unique window into the diffuse, quiescent precursor state of dense gas. They likely represent a widespread but previously overlooked component of the Galactic molecular gas reservoir, with significant implications for cloud formation and evolution, the total mass budget and spatial distribution of molecular gas, and the initial conditions of star formation as a related consequence.

We present a comprehensive statistical analysis of molecular cloud (MC) properties using the MWISP survey's 12CO, 13CO, and C18O (J = 1–0) data toward the inner (l = 45^∘–60^∘) and outer (l = 120^∘–130^∘) Galaxy. From a strict selection of 24,724 identified MCs, a final sample of 3,161 well-resolved MCs is established. We investigate the distributions of observational, morphological, and derived physical parameters, as well as their environmental dependencies and intercorrelations. Our analysis reveals that MCs are typically oblate and tend to align with the Galactic disk. A critical evaluation using a nearby subsample confirms significant distance-dependent selection effects for some parameters, nevertheless, the direction of changes in these parameters can indicate distance influence. We also examine several specific subsamples, revealing the distinct characteristics of MCs in the G120 spiral shock region, MCs in the G50 interarm spurs, C18O-bright MCs, and MCs with supra-Larson velocity dispersion. For instance, MCs with supra-Larson velocity dispersion are predominantly small and likely young clouds inheriting turbulence from the diffuse ISM. Notably, a comparison across tracers reveals that typical MCs have a turbulent, diffuse, 12CO-bright gas structure in their outer layers that does not contribute directly to star formation. In contrast, 13CO-bright gas represents a turning point where gravity becomes significant; C18O-bright gas is about gravity-dominated. Comprehensive correlation analysis confirms a flatter σ_v-size relation than classic Larson's law and a strong mass-size relation. Incorporating dimensional analysis, we derive minimal sets of eigenparameters from which most other observational and physical parameters can be estimated. This highlights the underlying scaling relations that governing cloud properties.

Many theories on the evolutionary process of molecular clouds have been proposed, but direct observational evidence remains scarce. The diverse cloud structures may preserve the history of cloud formation and evolution, making the search for critical evidence hidden in cloud structures essential to unraveling the history of clouds. To address this, we analysed the geometric structure of molecular clouds by measuring the fractal dimension (D-H ) across intensity contours of individual clouds and examining its behaviour within cloud samples. For a sample of 10 866 molecular clouds with both (CO)-C-12 and( 13)CO emissions, D-H was measured for 2163 clouds. In general, the D-H distribution peaks at 1.37, with a 95 per cent Highest Density Interval (HDI) of [1.05, 1.54]. Individual molecular clouds exhibit two prominent features: (1) D-H generally decreases linearly with increasing intensity, indicating that molecular clouds are multifractal; (2) D-H undergoes one or more abrupt changes at specific intensity contours. The D-H profiles can be classified into three distinct categories: no jumps (1814 clouds, 84 per cent), one jump (262 clouds, 12 per cent), and two jumps (87 clouds, 4 per cent). The intensity at which these jumps occur is strongly correlated with both the mean and peak temperatures of clouds. Strikingly, these jumps align closely with the breakpoints of recently discovered flux-intensity relations, while the D-H slope exhibits a linear correlation with the exponential flux decay rate. The gradual and abrupt changes in D-H and flux are indicative of historical global events, providing concrete observational evidence for cloud evolution.

Nonthermal plasma enables sustainable bio-oil upgrading, yet the atomic-scale interplay between H radicals and oxygenated functionalities remains insufficient. This study pioneers an innovative approach that integrates reactive molecular dynamics simulations with density functional theory calculations to elucidate these complex interactions. Our findings reveal that H2O removal is the dominant deoxygenation pathway, achieving an efficiency of 36.21 %-42.59 %, approximately 20-fold higher than hydrogenation. Notably, phenolic Cring-OH bonds exhibit extreme recalcitrance (4.68 eV dissociation energy), establishing their role as key upgrading bottlenecks. A parameterized strategy, employing 100H radicals at 500 K, enhances calorific value by 13.3 %, from 27.6 to 31.28 MJ/kg. This approach provides the first mechanistic blueprint for plasma-driven bio-oil upgrading, effectively bridging molecular-level insights with industrial process optimization.

Molecular clouds (MCs) are cradles of star and planet formation, thereby playing an important role in the evolution of galaxies. Based on the unbiased Milky Way Imaging Scroll Painting survey data of 12CO, 13CO, and C18O (J = 1-0) line emission in two regions toward the inner and outer Galaxy, i.e., the G50 (44 .degrees 75 <= l <= 60 .degrees 25) and G120 (119 .degrees 75 <= l <= 130 .degrees 25) regions, the distribution of molecular gas is studied. Both regions have Galactic latitudes of divided by b divided by <= 5 .degrees 25. A catalog containing 24,724 MCs is constructed from the data. In our proximity, several molecular structures with large angular scales and small velocity dispersions are discovered, resembling curtains of mist. Beyond the nearby molecular gas, a clear aggregation of MCs along coherent structures in the Galactic plane is visible, sketching spiral arm structures. Nevertheless, the aggregation of MCs is also detected in the inter-arm region between the Perseus and Outer arms in the G50 region. The Galactic molecular disk in this inter-arm region is found to be thinner than that in the adjacent spiral arm region. In addition, the thickness of the Galactic molecular disk examined here is found to be correlated with the warp of it, indicating their homologous origins. The molecular disk has a typical thickness of similar to 220 pc in the inner Galaxy. Moreover, the dispersion of the MC systemic velocity decreases with increasing galactocentric radius, resulting in lower kinematic distance uncertainties at larger radii. However, the Perseus arm segment in the G120 region exhibits a relatively large cloud-to-cloud velocity dispersion and split components in its MC velocity distribution.

Stars form from molecular gas under complex conditions influenced by multiple competing physical mechanisms, such as gravity, turbulence, and magnetic fields. However, accurately identifying the fraction of gas actively involved in star formation remains challenging. Using dust continuum observations from the Herschel Space Observatory, we derived column density maps and their associated probability distribution functions (N-PDFs). Assuming that the power-law component in the N-PDFs corresponds to gravitationally bound (and thus star-forming) gas, we analyzed a diverse sample of molecular clouds spanning a wide range of mass and turbulence conditions. This sample included 21 molecular clouds from the solar neighborhood (d < 500 pc) and 16 high-mass star-forming molecular clouds. For these two groups, we employed the counts of young stellar objects (YSOs) and mid to far-infrared luminosities as proxies for star formation rates (SFRs), respectively. Both groups revealed a tight linear correlation between the mass of the gravitationally bound gas and the SFR, suggesting a universally constant star formation efficiency in the gravitationally bound gas phase. The star-forming gas mass derived from threshold column densities (Nthreshold) varies from cloud to cloud and is widely distributed over the range of similar to 1-17x10(21) cm(-2) based on N-PDF analysis. However, in solar neighborhood clouds it is in rough consistency with the traditional approach using A(V)>= 8 mag. In contrast, in highly turbulent regions (e.g., the Galactic Central Molecular Zone) where the classical approach fails, the gravitationally bound gas mass and SFR still follow the same correlation as other high-mass star-forming regions in the Milky Way. Our findings also strongly support the interpretation that gas in the power-law component of the N-PDF is undergoing self-gravitational collapse to form stars.

We report the first measurement of the orbital period of a long-period colliding-wind binary (CWB) system WR 146, derived by tracing the rotational morphology of its wind-colliding region (WCR) and the relative orientation of the two binary components. This result is based on our imaging observations using the Very Long Baseline Array (VLBA) and the European Very Long Baseline Interferometry (VLBI) Network (EVN), combined with archival data from VLBA, EVN, the Very Large Array (VLA), the enhanced Multi-Element Radio-Linked Interferometer Network (eMERLIN) arrays, and optical images from the Hubble Space Telescope (HST). We evaluated two methods for determining the binary's orbital period based on the images of the WCR: (I) fitting the shock cone of the WCR and (II) stacking images using the cross-correlation function. Using these techniques, we find orbital period estimates of 810+120-90 years from method I and 1120+540-270 years from method II, both of which support a long orbital period of approximately 1,000 years. Furthermore, we analyzed archival spectral data of WR 146 to estimate the stellar wind velocities of the binary components, finding no significant orbital phase lag between the binary orientation and the WCR rotation. We also estimate the range of the binary's mass using the currently measured parameters.