We observed NH _3 metastable inversion lines from (3, 3) to (18, 18) toward G0.66-0.13 in the Galactic center with the Shanghai Tianma 65 m radio telescope and Yebes 40 m telescope. Highly excited lines of NH _3 (17, 17) and (18, 18) were detected in emission for the first time in the interstellar medium, with upper energy levels up to 3100 K. Mapping observations reveal widespread hot molecular gas traced by NH _3 (13, 13) toward G0.66-0.13. The rotation temperatures of hot gas traced by NH _3 exceed 400 K, which amounts to 5% of the total NH _3 in the Galactic center. Hot gas (>400 K) and warm gas (100–140 K) are found in distinct clumps, with the hot gas located at the interfacing regions between different warm clouds. The theory of intermittency in turbulence reproduces the complex temperature structure in the central molecular zone (CMZ), especially the hot gas observed here. The results presented here demonstrate that turbulence heating dominates the heating of the molecular gas in the CMZ, while the turbulence is induced by the shear motion of molecular clouds under the gravitational potential of the nuclear star clusters and the supermassive black hole. Our results suggest that shear-induced turbulence heating could be a widespread factor influencing galactic evolution.

We present a multiwavelength analysis of 850 μm-selected SMGs (deblended S_ 850≳ 1mJy) in the SSA22 field, where our deepest JCMT/SCUBA-2 observations reach a sensitivity of σ_850∼ 0.80mJy beam^-1. Using multiple identification methods, we have identified 248 deblended SMG candidates for 192 SCUBA-2 sources. The average multiplicity of SCUBA-2 sources is ∼26

We present a study of a near-infrared-dark (NIR-dark) submillimeter galaxy R0600-C67, initially detected in the Atacama Large Millimeter/submillimeter Array (ALMA) Lensing Cluster Survey program. Due to the lack of robust emission lines from spectral line-scan observations at ALMA's 3 mm and 2 mm bands, we utilize two spectral energy distribution (SED) fitting codes, EAZY and CIGALE, to derive a robust photometric redshift of z = 4.7 +/- 0.9, based on the observations from ALMA and James Webb Space Telescope (JWST), making it as a rare NIR-dark object at high redshift. Based on the SED analysis, we derive the physical properties of R0600-C67. Joint spatial imaging analyses suggest that stellar body traced by JWST, significantly larger than the compact dust continuum from ALMA. While we test for an active galactic nucleus (AGN), the current SED fitting analysis provides no conclusive evidence for its presence. Future mid-infrared observations would be essential to clarify the presence of an AGN.

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.

The cycling of carbon between its ionized, atomic, and molecular phases shapes the chemical compositions and physical conditions of the interstellar medium (ISM). However, ground-based studies of the full carbon cycle have been limited by atmospheric absorption. Dome A, the most promising site for submillimeter astronomy, has long resisted successful submillimeter astronomical observations. Using the 60-centimeter Antarctic Terahertz Explorer, we present the first successful CO (4-3) and [CI] ([Formula: see text]) mapping observations of two archetypal triggered massive star-formation regions at Dome A. These data, together with archival [CII], provide the first complete characterization of all three carbon phases in these environments. We find elevated C0/CO abundance ratios in high-extinction regions, plausibly driven by deep penetration of intense radiation fields from massive stars into a clumpy ISM. These findings mark a major milestone for submillimeter astronomy at Dome A and offer valuable insights into the impact of massive star feedback on the surrounding ISM.

The Chinese Space Station Survey Telescope (CSST) is an upcoming Stage-IV sky survey telescope, distinguished by its large field of view (FoV), high image quality, and multi-band observation capabilities. It can simultaneously conduct precise measurements of the Universe by performing multi-color photometric imaging and slitless spectroscopic surveys. The CSST is equipped with five scientific instruments, i.e., Multi-band Imaging and Slitless Spectroscopy Survey Camera (SC), Multi-Channel Imager (MCI), Integral Field Spectrograph (IFS), Cool Planet Imaging Coronagraph (CPI-C), and THz Spectrometer (TS). Using these instruments, CSST is expected to make significant contributions and discoveries across various astronomical fields, including cosmology, galaxies and active galactic nuclei (AGN), the Milky Way and nearby galaxies, stars, exoplanets, Solar System objects, astrometry, and transients and variable sources. This review aims to provide a comprehensive overview of the CSST instruments, observational capabilities, data products, and scientific potential.

Previous studies using p-H2CO J = 3-2 transitions at 218 GHz suggested widespread high-temperature gas exceeding 60 K and even 100 K in the central molecular zone, with heating mechanisms possibly related to cosmic rays or turbulent dissipation. However, at temperatures above 100 K, p-H2CO J = 3-2 line emission may lead to significant overestimates of kinetic temperature. This study combines o-H2CO J = 5-4 data from the James Clerk Maxwell Telescope with p-H2CO J = 3-2 data from APEX to analyze three molecular clouds (the Brick, Sgr A1, and Sgr A2) with high temperatures. We used the non-LTE radiative transfer code RADEX to model spectral lines and constrain physical parameters with multiple line ratios, obtaining more reliable kinetic temperatures. Our results show that the previously reported extreme temperatures (>100 K) based on p-H2CO J = 3-2 line ratios are revised downward, with the average kinetic temperatures now constrained to 84-95 K using o-H2CO J = 5-4 line ratios, indicating systematic overestimation in the earlier studies. Further analysis reveals that the relationship between temperature and gas line width aligns more closely with predictions from models incorporating both a high cosmic-ray ionization rate and turbulent heating, suggesting that these molecular clouds are likely heated by a combination of cosmic-ray and turbulent dissipation mechanisms.

The High Sensitivity Terahertz Detection Module (HSTDM), a key component of the backend modules on board the Chinese Space Station Survey Telescope (CSST), will offer great opportunities for the discovery of terahertz astronomy, with implications that extend well beyond China to the global astronomical community. It is imperative that the raw data collected by HSTDM undergo meticulous calibration and processing through the HSTDM data processing pipeline (HSTDM pipeline for short) to ensure the accuracy and effectiveness of the final science data to be archived for further research. This process necessitates that the HSTDM pipeline address instrumental artifacts and effects as well as the coordination of data flow of the scheduled observing sequences under all observing modes of HSTDM within the CSST automated processing environment. As the understanding of CSST HSTDM data processing develops during the pipeline development stage, it becomes essential to assess the accuracy, robustness and performance of the HSTDM pipeline under all observing modes of HSTDM so that components of the HSTDM pipeline be rationally added, removed, amended or extended within the modular framework. In this paper, we develop practical simulation methods to facilitate this need. The contribution of synthetic data generation of HSTDM observation includes two parts: (1) HSTDM instrumental effect simulation based on both real testing profiles and simulated models; (2) Observing data flow generation based on HSTDM observing mode scenario. The simulation methods have been implemented and shown to be practical in testing the HSTDM pipeline during the development stage.

We analyze the spectral energy distributions (SEDs), star formation histories (SFHs), and infrared-radio correlation (IRRC) of 221 850 μm-selected submillimeter galaxies (SMGs) in the SSA22 deep field. The median mass-weighted age is 567 Myr. Most galaxies in our sample began forming ∼ 1.68 Gyr after the Big Bang, entered the `SMG phase' after ∼ 1 Gyr of evolution – when they are predominantly observed – and largely transitioned out of the `SMG phase' to become quiescent within an additional ∼ 0.2 Gyr. A subset of massive galaxies shows rapid early assembly with high star formation efficiencies (∼0.2-0.8). The majority of SMGs reside at the high-mass end of the star-forming main sequence, with a characteristic stellar mass of M_star∼ 10^11 M_⊙, above which galaxies are predominantly either on the main sequence or already quenched. We observe a downsizing trend: more massive galaxies tend to “mature" earlier, completing their major episodes of star formation at higher redshifts compared to lower-mass systems. Our sample contributes ∼ 21

We present results from Atacama Large Millimeter/submillimeter Array (ALMA) spectral line-scan observations at 3 mm and 2 mm bands of three near-infrared-dark (NIR-dark) galaxies behind two massive lensing clusters MACS J0417.5-1154 and RXC J0032.1+1808. Each of these three sources is a (sub)millimeter faint (delensed S _1.2 mm < 1 mJy) triply lensed system originally discovered in the ALMA Lensing Cluster Survey. We have successfully detected CO and [C i ] emission lines and confirmed that their spectroscopic redshifts are z = 3.652, 2.391, and 2.985. By utilizing a rich multiwavelength data set, we find that the NIR-dark galaxies are located on the star formation main sequence in the intrinsic stellar mass range of log ( M _* / M _⊙ ) = 9.8–10.4, which is about 1 order of magnitude lower than that of typical submillimeter galaxies (SMGs). These NIR-dark galaxies show a variety in gas depletion times and spatial extent of dust emission. One of the three is a normal star-forming galaxy with gas depletion time consistent with a scaling relation, and its infrared surface brightness is an order of magnitude smaller than that of typical SMGs. Since this galaxy has an elongated axis ratio of ∼0.17, we argue that normal star-forming galaxies in an edge-on configuration can be heavily dust-obscured. This implies that existing deep WFC3/F160W surveys may miss a fraction of typical star-forming main-sequence galaxies due to their edge-on orientation.

Early galaxy formation, initiated by the dark matter and gas assembly, evolves through frequent mergers and feedback processes into dynamically hot, chaotic structures. In contrast, dynamically cold, smooth rotating disks have been observed in massive evolved galaxies merely 1.4 billion years after the Big Bang, suggesting rapid morphological and dynamical evolution in the early Universe. Probing this evolution mechanism necessitates studies of young galaxies, yet efforts have been hindered by observational limitations in both sensitivity and spatial resolution. Here we report high-resolution observations of a strongly lensed and quintuply imaged, low-luminosity, young galaxy at $z=6.072$ (dubbed the Cosmic Grapes), 930 million years after the Big Bang. Magnified by gravitational lensing, the galaxy is resolved into at least 15 individual star-forming clumps with effective radii of $r_{\rm e}\simeq$ 10--60 parsec (pc), which dominate $\simeq$ 70\% of the galaxy's total flux. The cool gas emission unveils a smooth, underlying rotating disk characterized by a high rotational-to-random motion ratio and a gravitationally unstable state (Toomre $Q \simeq$ 0.2--0.3), with high surface gas densities comparable to local dusty starbursts with $\simeq10^{3-5}$ $M_{\odot}$/pc$^{2}$. These gas properties suggest that the numerous star-forming clumps are formed through disk instabilities with weak feedback effects. The clumpiness of the Cosmic Grapes significantly exceeds that of galaxies at later epochs and the predictions from current simulations for early galaxies. Our findings shed new light on internal galaxy substructures and their relation to the underlying dynamics and feedback mechanisms at play during their early formation phases, potentially explaining the high abundance of bright galaxies observed in the early Universe and the dark matter core-cusp problem.

Submillimeter astronomy is poised to revolutionize our understanding of the Universe by revealing cosmic phenomena hidden from optical and near-infrared observations, particularly those associated with interstellar dust, molecular gas, and star formation. The Xue-shan-mu-chang 15-meter submillimeter telescope (XSMT-15m), to be constructed at a premier high-altitude site (4813 m) in Qinghai, China, marks a major milestone for Chinese astronomy, establishing the China mainland's first independently developed, world-class submillimeter facility. Equipped with state-of-the-art instruments, XSMT-15m will address a diverse range of frontier scientific questions spanning extragalactic astronomy, Galactic structure, time-domain astrophysics, and astrochemistry. In synergy with current and forthcoming observatories, XSMT-15m will illuminate the formation and evolution of galaxies, unravel the physical and chemical processes shaping the interstellar medium, and explore transient phenomena in the submillimeter regime. These capabilities will advance our understanding across extragalactic astronomy, Galactic ecology, astrochemistry, and time-domain astrophysics, inaugurating a new era for submillimeter research in China and the northern hemisphere.

The short-lived ionized emission lines in early spectroscopy of the nearby Type II supernova SN 2024ggi signify the presence of dense circumstellar matter (CSM) close to its progenitor star. We proposed the Atacama Large Millimeter/submillimeter Array (ALMA) observations by its Director's Discretionary Time program to catch the potential synchrotron radiation associated with the ejecta–CSM interaction. Multiepoch observations were conducted using ALMA band 6 at +8, +13, and +17 days after the discovery. The data show nondetections at the position of SN 2024ggi with a 3 σ upper limit of less than 0.15 mJy, corresponding to a luminosity of approximately 8 × 10 24 erg s −1 Hz −1 . In this paper, we leverage the nondetections to place constraints on the properties of CSM surrounding SN 2024ggi. We investigate both the Wind and Eruptive models for the radial distribution of CSM, assuming a constant mass-loss rate in the Wind model and a distance-variant mass-loss rate in the Eruptive model. The derived CSM distribution for the Wind model does not align with the early-time spectral features, while the ALMA observations suggest a mass-loss rate of ~5 × 10 −3 M ⊙ yr −1 for the Eruptive model. Conducting multiepoch millimeter/submillimeter observations shortly after the explosion, with a cadence of a few days, could offer a promising opportunity to capture the observable signature of the Eruptive model.

In this study, we used the 13.7m telescope at Qinghai Station to observe CO data in 48 galaxies in Virgo clusters, of which 41 sources observed CO signals. The properties of molecular gas are deduced by co-to-$H_2$ factor. We also collected and investigated the relationship between $M_{H_2}$ and other galactic properties ($M_B$, $L_K$, sfr, and $def_{HI}$). We found correlations between $M_{H_2}$ and $M_B$, $L_K$, sfr, and $def_{HI}$. It has the strongest correlation with Lk. There is a certain correlation between MB and MB, but the scattering is larger. For sfr, the more abundant the atomic and molecular gases, the stronger the sfr activity.

We analyze the morphology of 125 submillimeter galaxies (SMGs) in the PRIMER-COSMOS field using double Sérsic modeling on JWST NIRCam images across six bands (F150W, F200W, F277W, F356W, F410M, and F444W), with SMGs being classified by the bulge Sérsic index ( n _ bulge ) and bulge-to-total luminosity ratio (B/T). The Kolmogorov–Smirnov test between the bright (SFR > 175 M _⊙ yr ^−1 ) and the faint groups (SFR < 175 M _⊙ yr ^−1 ) reveals no significant statistical differences in morphology across bands. However, we notice that SMGs skew towards higher B/T ratios and lower n _ bulge from shorter to longer wavelengths. In F444W, bright SMGs exhibit higher B/T and lower n _ bulge , indicating flatter, disturbed bulges, while faint SMGs show lower B/T and higher n _ bulge . Notably, SMGs with higher B / T tend to have low Sérsic, challenging the local Universe dichotomy of classical bulges ( B / T > 0.5, n > 4) versus pseudo-bulges ( B / T < 0.35, n < 2). In the F277W, nonparametric morphological measurements indicate predominantly disk-dominated patterns, with only 24% of SMGs demonstrating merger signatures. After the removal of SMGs with disturbed morphology, the bulge classification scheme in F277W shows pseudo-bulges (21%) and clump migration bulges (16%) from secular evolution, compared to 4% merger-built bulges. Surprisingly, 48% of SMGs defy the classification scheme, showing high B / T (∼0.7) but low Sérsic index ( n _ bulge ≤ 1). Bars are confirmed in 7% of SMGs. This work suggests that secular evolution takes precedence over major mergers, supporting the idea that isolated evolution fueled by filamentary gas inflow plays a nonnegligible role in the formation of SMGs.

The ADF22 line survey reported detections of two high-z line-emitting source candidates above $6\sigma$, both of which were shown to be spurious after follow-up observations. We investigate the detectability of far-infrared emitters in ALMA deep fields using mock observations by injecting artificial line-emitting sources into the visibility planes. We also discuss our investigation, conducted together with the ALMA operations team, of a possible technical problem in the original observations. Finally, we devise a method to estimate the [C ii] luminosity function (LF) at z similar to 6, including a full analysis of signal contamination and sample completeness. The comparison of pixel distributions between the real and mock datacubes does not show significant differences, confirming that the effect of non-Gaussian noise is negligible for the ADF22 datacube. Using 100 blank mock-mosaic datasets, we show 0.43 +/- 0.67 false detections per datacube with the previous source-finding method. We argue that the underestimation of the contamination rate in the previous work is caused by the smaller number of datacubes, using only four real ADF22 datacubes. We compare the results of clump-finding between the time division mode (TDM) and frequency division mode (FDM) correlator datacubes and confirm that the velocity widths of the clumps in the TDM case are up to three times wider than in the FDM case. Additional investigation into technical issues, specifically the "QA3 process," found no technical problems for both Cycle 2 and Cycle 4 data. Therefore, we confirm that false detections of high-SN ratios are unavoidable because clump-like structures already exist in large TDM datacubes. The LF estimation using our model shows that a correction for the number count is required, up to one order of magnitude, in the luminosity range of >= 5 x 10(8) L-circle dot. Our reconstruction method for the line LF can be applied to future blind line surveys.

In this work, we report a study on the relationship between flux and intensity for molecular clouds. Our analysis is established on high-quality CO images from the Milky Way Imaging Scroll Painting project. The new flux–intensity relation characterizes the flux variation of molecular clouds above specific intensity levels. We found that the flux–intensity relation exhibits two prominent features. First, the flux–intensity relation generally follows exponential shapes; second, hierarchical structures of molecular clouds are imprinted on flux–intensity relations. Specifically, ^12 CO flux–intensity relations are composed of one or more exponential segments, and for molecular clouds with segmented flux–intensity relations, the edge and the flux of the high-temperature component are strikingly consistent with ^13 CO emission. Further analysis shows that a similar relationship also exists between ^13 CO flux–intensity relations and C ^18 O emission. The mean brightness temperature of molecular clouds is tightly associated with the decay rate of flux, the break temperature of exponential segments, and, to a certain extent, the flux fraction of the high-temperature component. Broadly, the flux–intensity relation of a molecular tracer, either in optically thick or in optically thin cases, has the capability to outline the silhouette of internal structures of molecular clouds, proving to be a potent tool for probing structures of molecular clouds.

We report physical properties of the brightest ($S_{870\,\mu \rm m}=12.4$-$19.2\,$mJy) and not strongly lensed 18 870$\,\mu$m selected dusty star-forming galaxies (DSFGs), also known as submillimeter galaxies (SMGs), in the COSMOS field. This sample is part of an ALMA band$\,$3 spectroscopic survey (AS2COSPEC), and spectroscopic redshifts are measured in 17 of them at $z=2$-$5$. We perform spectral energy distribution analyses and deduce a median total infrared luminosity of $L_{\rm IR}=(1.3\pm0.1)\times10^{13}\,L_{\odot}$, infrared-based star-formation rate of ${\rm SFR}_{\rm IR}=1390\pm150~M_{\odot}\,\rm yr^{-1}$, stellar mass of $M_\ast=(1.4\pm0.6)\times10^{11}\,M_\odot$, dust mass of $M_{\rm dust}=(3.7\pm0.5)\times10^9\,M_\odot$, and molecular gas mass of $M_{\rm gas}= (\alpha_{\rm CO}/0.8)(1.2\pm0.1)\times10^{11}\,M_\odot$, suggesting that they are one of the most massive, ISM-enriched, and actively star-forming systems at $z=2$-$5$. In addition, compared to less massive and less active galaxies at similar epochs, SMGs have comparable gas fractions; however, they have much shorter depletion time, possibly caused by more active dynamical interactions. We determine a median dust emissivity index of $\beta=2.1\pm0.1$ for our sample, and by combining our results with those from other DSFG samples, we find no correlation of $\beta$ with redshift or infrared luminosity, indicating similar dust grain compositions across cosmic time for infrared luminous galaxies. We also find that AS2COSPEC SMGs have one of the highest dust-to-stellar mass ratios, with a median of $0.02\pm0.01$, significantly higher than model predictions, possibly due to too strong of a AGN feedback implemented in the model. Finally, our complete and uniform survey enables us to put constraints on the most massive end of the dust and molecular gas mass functions.

In this paper, we combine the Early Science radio continuum data from the MeerKAT International GHz Tiered Extragalactic Exploration (MIGHTEE) Survey, with optical and near-infrared data and release the cross-matched catalogues. The radio data used in this work covers 0.86deg(2) of the COSMOS field, reaches a thermal noise of 1.7 mu Jy beam(-1) and contains 6102 radio components. We visually inspect and cross-match the radio sample with optical and near-infrared data from the Hyper Suprime-Cam (HSC) and UltraVISTA surveys. This allows the properties of active galactic nuclei and star-forming populations of galaxies to be probed out to z approximate to 5. Additionally, we use the likelihood ratio method to automatically cross-match the radio and optical catalogues and compare this to the visually cross-matched catalogue. We find that 94 per cent of our radio source catalogue can be matched with this method, with a reliability of 95 per cent. We proceed to show that visual classification will still remain an essential process for the cross-matching of complex and extended radio sources. In the near future, the MIGHTEE survey will be expanded in area to cover a total of similar to 20 deg(2); thus the combination of automated and visual identification will be critical. We compare the redshift distribution of SFG and AGN to the SKADS and T-RECS simulations and find more AGN than predicted at z similar to 1.

We present confusion-limited SCUBA-2 450-$\mu$m observations in the COSMOS-CANDELS region as part of the JCMT Large Program, SCUBA-2 Ultra Deep Imaging EAO Survey (STUDIES). Our maps at 450 and 850 $\mu$m cover an area of 450 arcmin$^2$. We achieved instrumental noise levels of $\sigma_{\mathrm{450}}=$ 0.59 mJy beam$^{-1}$ and $\sigma_{\mathrm{850}}=$ 0.09 mJy beam$^{-1}$ in the deepest area of each map. The corresponding confusion noise levels are estimated to be 0.65 and 0.36 mJy beam$^{-1}$. Above the 4 (3.5) $\sigma$ threshold, we detected 360 (479) sources at 450 $\mu$m and 237 (314) sources at 850 $\mu$m. We derive the deepest blank-field number counts at 450 $\mu$m, covering the flux-density range of 2 to 43 mJy. These are in agreement with other SCUBA-2 blank-field and lensing-cluster observations, but are lower than various model counts. We compare the counts with those in other fields and find that the field-to-field variance observed at 450 $\mu$m at the $R=6^\prime$ scale is consistent with Poisson noise, so there is no evidence of strong 2-D clustering at this scale. Additionally, we derive the integrated surface brightness at 450 $\mu$m down to 2.1 mJy to be $57.3^{+1.0}_{-6.2}$~Jy deg$^{-2}$, contributing to (41$\pm$4)\% of the 450-$\mu$m extragalactic background light (EBL) measured by COBE and Planck. Our results suggest that the 450-$\mu$m EBL may be fully resolved at $0.08^{+0.09}_{-0.08}$~mJy, which extremely deep lensing-cluster observations and next-generation submillimeter instruments with large aperture sizes may be able to achieve.