The Astrophysical Journal Letters最新文献

{"title":"Calibration of Complementary Metal-oxide-semiconductor Sensor–based Photometry to a Few-millimagnitude Precision: The Case of the Mini-SiTian Array","authors":"Kai Xiao, Yang Huang, Haibo Yuan, Zhirui Li, Yongkang Sun, Timothy C. Beers, Min He, Jifeng Liu, Hong Wu, Yongna Mao, Bowen Huang, Mingyang Ma, Chuanjie Zheng, Hongrui Gu, Beichuan Wang, Lin Yang and Shuai Xu","doi":"10.3847/2041-8213/adbd3c","DOIUrl":"https://doi.org/10.3847/2041-8213/adbd3c","url":null,"abstract":"We present a pioneering achievement in the high-precision photometric calibration of CMOS-based photometry, by application of the Gaia Blue Photometer or Red Photometer (XP) spectra–based synthetic photometry method to the mini-SiTian array (MST) photometry. Through 79 repeated observations of the f02 field on the night, we find good internal consistency in the calibrated MST GMST-band magnitudes for relatively bright stars, with a precision of about 4 mmag for GMST ∼ 13. Results from more than 30 different nights (over 3100 observations) further confirm this internal consistency, indicating that the 4 mmag precision is stable and achievable over timescales of months. An independent external validation using spectroscopic data from the Large Sky Area Multi-Object Fiber Spectroscopic Telescope DR10 and high-precision photometric data using CCDs from Gaia DR3 reveals a zero-point consistency better than 1 mmag. Our results clearly demonstrate that CMOS photometry is on par with CCD photometry for high-precision results, highlighting the significant capabilities of CMOS cameras in astronomical observations, especially for large-scale telescope survey arrays.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"56 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-03-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143661487","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Constraining the Cosmic-Ray Energy Based on Observations of Nearby Galaxy Clusters by LHAASO","authors":"Zhen Cao, F. Aharonian, Y. X. Bai, Y. W. Bao, D. Bastieri, X. J. Bi, Y. J. Bi, W. Bian, A. V. Bukevich, C. M. Cai, W. Y. Cao, Zhe Cao, J. Chang, J. F. Chang, A. M. Chen, E. S. Chen, H. X. Chen, Liang Chen, Long Chen, M. J. Chen, M. L. Chen, Q. H. Chen, S. Chen, S. H. Chen, S. Z. Chen, T. L. Chen, X. B. Chen, X. J. Chen, Y. Chen, N. Cheng, Y. D. Cheng, M. C. Chu, M. Y. Cui, S. W. Cui, X. H. Cui, Y. D. Cui, B. Z. Dai, H. L. Dai, Z. G. Dai, Danzengluobu, Y. X. Diao, X. Q. Dong, K. K. Duan, J. H. Fan, Y. Z. Fan, J. Fang, J. H. Fang, K. Fang, C. F. Feng, H. Feng, L. Feng, S. H. Feng, X. T. Feng, Y. Feng, Y. L. Feng, S. Gabici, B. Gao, C. D. Gao, Q. Gao, W. Gao, W. K. Gao, M. M. Ge, T. T. Ge, L. S. Geng, G. Giacinti, G. H. Gong, Q. B. Gou, M. H. Gu, F. L. Guo, J. Guo, X. L. Guo, Y. Q. Guo, Y. Y. Guo, Y. A. Han, O. A. Hannuksela, M. Hasan, H. H. He, H. N. He, J. Y. He, X. Y. He, Y. He, S. Hernández-Cadena, Y. K. Hor, B. W. Hou, C. Hou, X. Hou, H. B. Hu, S. C. Hu, C. Huang, D. H. Hua..","doi":"10.3847/2041-8213/adb97d","DOIUrl":"https://doi.org/10.3847/2041-8213/adb97d","url":null,"abstract":"Galaxy clusters act as reservoirs of high-energy cosmic rays (CRs). As CRs propagate through the intracluster medium, they generate diffuse γ-rays detectable by arrays such as LHAASO. These γ-rays result from proton–proton (pp) collisions of very high-energy cosmic rays or inverse Compton (IC) scattering of positron-electron pairs created by pγ interactions of ultra-high-energy cosmic rays (UHECRs). We analyzed diffuse γ-ray emission from the Coma, Perseus, and Virgo clusters using LHAASO data. Diffuse emission was modeled as a disk of radius R500 for each cluster while accounting for point sources. No significant diffuse emission was detected, yielding 95% confidence level (C.L.) upper limits on the γ-ray flux: for WCDA (1–25 TeV) and KM2A (>25 TeV), less than (49.4, 13.7, 54.0) and (1.34, 1.14, 0.40) × 10−14 ph cm−2 s−1 for Coma, Perseus, and Virgo, respectively. The γ-ray upper limits can be used to derive model-independent constraints on the integral energy of cosmic ray protons above 10 TeV (corresponding to the LHAASO observational range >1 TeV under the pp scenario) to be less than (1.96, 0.59, 0.08) × 1061 erg. The absence of detectable annuli/ring-like structures, indicative of cluster accretion or merging shocks, imposes further constraints on models in which the UHECRs are accelerated in the merging shocks of galaxy clusters.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"33 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-03-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143653950","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The First Chemical Census of the Milky Way’s Nuclear Star Cluster","authors":"Govind Nandakumar, Nils Ryde, Mathias Schultheis, R. Michael Rich, Paola di Matteo, Brian Thorsbro and Gregory Mace","doi":"10.3847/2041-8213/adbb6d","DOIUrl":"https://doi.org/10.3847/2041-8213/adbb6d","url":null,"abstract":"An important step in understanding the formation and evolution of the nuclear star cluster (NSC) is to investigate its chemistry and chemical evolution. Additionally, exploring the NSC’s relationship to the other structures in the Galactic center and the Milky Way disks is of great interest. Extreme optical extinction has previously prevented optical studies, but near-IR high-resolution spectroscopy is now possible. Here, we present a detailed chemical abundance analysis of 19 elements—more than 4 times as many as previously published—for nine stars in the NSC of the Milky Way, observed with the Immersion GRating INfrared Spectrometer on the Gemini South telescope. This study provides new, crucial observational evidence to shed light on the origin of the NSC. We demonstrate that it is possible to probe a variety of nucleosynthetic channels, reflecting different chemical evolution timescales. Our findings reveal that the NSC trends for the elements F, Mg, Al, Si, S, K, Ca, Ti, Cr, Mn, Co, Ni, Cu, and Zn, as well as for the s-process elements Ba, Ce, Nd, and Yb, generally follow the inner-bulge trends within uncertainties. This suggests a likely shared evolutionary history, and our results indicate that the NSC population is consistent with the chemical sequence observed in the inner Galaxy (the inner-disk sequence). However, we identify a significant and unexplained difference in the form of higher Na abundances in the NSC compared to the inner bulge. This is also observed in few Galactic globular clusters and may suggest a common enrichment process at work in all these systems.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"51 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-03-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143635262","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A Large Molecular Gas Reservoir in the Protocluster SPT2349−56 at z = 4.3","authors":"Dazhi Zhou, Scott C. Chapman, Nikolaus Sulzenauer, Ryley Hill, Manuel Aravena, Pablo Araya-Araya, Jared Cathey, Daniel P. Marrone, Kedar A. Phadke, Cassie Reuter, Manuel Solimano, Justin S. Spilker, Joaquin D. Vieira, David Vizgan, George C. P. Wang, Axel Weiss","doi":"10.3847/2041-8213/adb8d8","DOIUrl":"https://doi.org/10.3847/2041-8213/adb8d8","url":null,"abstract":"We present Atacama Compact Array (ACA) Band-3 observations of the protocluster SPT2349−56, an extreme system hosting >10 ultraluminous infrared galaxies (ULIRGs; <italic toggle=\"yes\">L</italic><sub>IR</sub> ≳ 10<sup>12</sup><italic toggle=\"yes\">L</italic><sub>⊙</sub>) in a 200 kpc diameter region at <italic toggle=\"yes\">z</italic> = 4.3, to study its integrated molecular gas content via CO(4–3) and the long-wavelength dust continuum. The ∼30 hr integration represents one of the longest exposures yet taken on a single pointing with the ACA 7 m. The low-resolution ACA data (21<inline-formula>\u0000<tex-math>\u0000<?CDATA $mathop{.}limits^{unicode{x02033}}$?>\u0000</tex-math>\u0000<mml:math overflow=\"scroll\"><mml:mover><mml:mrow><mml:mo>.</mml:mo></mml:mrow><mml:mrow><mml:mtext>″</mml:mtext></mml:mrow></mml:mover></mml:math>\u0000<inline-graphic xlink:href=\"apjladb8d8ieqn1.gif\"></inline-graphic>\u0000</inline-formula>0 × 12<inline-formula>\u0000<tex-math>\u0000<?CDATA $mathop{.}limits^{unicode{x02033}}$?>\u0000</tex-math>\u0000<mml:math overflow=\"scroll\"><mml:mover><mml:mrow><mml:mo>.</mml:mo></mml:mrow><mml:mrow><mml:mtext>″</mml:mtext></mml:mrow></mml:mover></mml:math>\u0000<inline-graphic xlink:href=\"apjladb8d8ieqn2.gif\"></inline-graphic>\u0000</inline-formula>2) reveal a 75% excess CO(4–3) flux compared to the sum of individual sources detected in higher-resolution Atacama Large Millimeter/submillimeter Array (ALMA) data (1<inline-formula>\u0000<tex-math>\u0000<?CDATA $mathop{.}limits^{unicode{x02033}}$?>\u0000</tex-math>\u0000<mml:math overflow=\"scroll\"><mml:mover><mml:mrow><mml:mo>.</mml:mo></mml:mrow><mml:mrow><mml:mtext>″</mml:mtext></mml:mrow></mml:mover></mml:math>\u0000<inline-graphic xlink:href=\"apjladb8d8ieqn3.gif\"></inline-graphic>\u0000</inline-formula>0 × 0<inline-formula>\u0000<tex-math>\u0000<?CDATA $mathop{.}limits^{unicode{x02033}}$?>\u0000</tex-math>\u0000<mml:math overflow=\"scroll\"><mml:mover><mml:mrow><mml:mo>.</mml:mo></mml:mrow><mml:mrow><mml:mtext>″</mml:mtext></mml:mrow></mml:mover></mml:math>\u0000<inline-graphic xlink:href=\"apjladb8d8ieqn4.gif\"></inline-graphic>\u0000</inline-formula>8). Our work also reveals a similar result by tapering the ALMA data to 10″. In contrast, the 3.2 mm dust continuum shows little discrepancy between ACA and ALMA. A single-dish [C <sc>ii</sc>] spectrum obtained by APEX/FLASH supports the ACA CO(4–3) result, revealing a large excess in [C <sc>ii</sc>] emission relative to ALMA. The missing flux is unlikely due to undetected faint sources but instead suggests that high-resolution ALMA observations might miss extended and low-surface-brightness gas. Such emission could originate from the circumgalactic medium or the preheated protointracluster medium (proto-ICM). If this molecular gas reservoir replenishes the star formation fuel, the overall depletion timescale will exceed 400 Myr, reducing the requirement for the simultaneous ULIRG activity in SPT2349−56. Our results highlight the role of an extended gas reservoir in sustaining a high star formation rate in SPT2349−56 and potentially establishing the ICM du","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"24 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-03-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143635582","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Formation of Ultra-short-period Planets in Hot Jupiter Systems: Application to WASP-47","authors":"Su Wang, Mengrui Pan, Yao Dong, Gang Zhao and Jianghui Ji","doi":"10.3847/2041-8213/adbae6","DOIUrl":"https://doi.org/10.3847/2041-8213/adbae6","url":null,"abstract":"The WASP-47 system is notable as the first known system hosting both inner and outer low-mass planetary companions around a hot Jupiter, with an ultra-short-period (USP) planet as the innermost planetary companion. The formation of such a unique configuration poses challenges to the lonely hot Jupiter formation model. Hot Jupiters in multiple planetary systems may have a similar formation process with warm Jupiter systems, which are more commonly found with companions. This implies that the WASP-47 system could bridge our understanding of both hot and warm Jupiter formation. In this work, we propose a possible formation scenario for the WASP-47 system based on its orbital configuration. The mean motion resonance trapping, giant planet perturbations, and tidal effects caused by the central star are key factors in the formation of USP planets in multiple planetary systems with hot Jupiters. Whether a planet can become a USP planet or a short-period super-Earth planet depends on the competition between eccentricity excitation by nearby giant planet perturbations and the eccentricity damping due to tidal effects. The value of the innermost planet is essential for the final planetary configuration. Our results suggest that a in the range of [1, 10] is favorable for the formation of the WASP-47 system. Based on the formation scenario, we estimate an occurrence rate of 8.4% ± 2.4% for USP planets in systems similar to WASP-47.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"55 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-03-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143635258","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Cascaded Gamma-Ray Emission Associated with the KM3NeT Ultrahigh-energy Event KM3-230213A","authors":"Ke Fang, Francis Halzen and Dan Hooper","doi":"10.3847/2041-8213/adbbec","DOIUrl":"https://doi.org/10.3847/2041-8213/adbbec","url":null,"abstract":"A neutrino-like event with an energy of ∼220 PeV was recently detected by the KM3NeT/ARCA telescope. If this neutrino comes from an astrophysical source or from the interaction of an ultrahigh-energy cosmic ray in the intergalactic medium, the ultrahigh-energy gamma rays that are coproduced with the neutrinos will scatter with the extragalactic background light, producing an electromagnetic cascade and resulting in emission at GeV-to-TeV energies. In this Letter, we compute the gamma-ray flux from this neutrino source considering various source distances and strengths of the intergalactic magnetic field (IGMF). We find that the associated gamma-ray emission could be observed by existing imaging air Cherenkov telescopes and air shower gamma-ray observatories, unless the strength of the IGMF is B ≳ 3 × 10−13 G or the ultrahigh-energy gamma rays are attenuated inside of the source itself. In the latter case, this source is expected to be radio-loud.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"24 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-03-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143635261","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Disk Draining in LIGO Progenitor Black Hole Binaries and Its Significance to Electromagnetic Counterparts","authors":"Xiaoshan Huang, Sierra Dodd, Sophie Lund Schrøder, Shane W. Davis and Enrico Ramirez-Ruiz","doi":"10.3847/2041-8213/adbb62","DOIUrl":"https://doi.org/10.3847/2041-8213/adbb62","url":null,"abstract":"The effect of tidal forces on transport within a relic accretion disk in binary black holes is studied here with a suite of two-dimensional hydrodynamic simulations. As the binary contracts owing to the emission of gravitational waves, the accretion disk is truncated, and a two-armed spiral wave is excited, which remains stationary in the rotating reference frame of the coalescing binary. Such spiral waves lead to increased transport of mass and angular momentum. Our findings suggest that even in the case of weakly ionized accretion disks spiral density waves will drain the disk long before the orbit of the two black holes decays enough for them to merge, thus dimming prospects for a detectable electromagnetic counterpart.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"89 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-03-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143618711","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The Critical Role of Dark Matter Halos in Driving Star Formation*","authors":"Jing Dou, Yingjie Peng, Qiusheng Gu, Luis C. Ho, Alvio Renzini, Yong Shi, Emanuele Daddi, Dingyi Zhao, Chengpeng Zhang, Zeyu Gao, Di Li, Cheqiu Lyu, Filippo Mannucci, Roberto Maiolino, Tao Wang and Feng Yuan","doi":"10.3847/2041-8213/adb95c","DOIUrl":"https://doi.org/10.3847/2041-8213/adb95c","url":null,"abstract":"Understanding the physical mechanisms that drive star formation is crucial for advancing our knowledge of galaxy evolution. We explore the interrelationships between key galaxy properties associated with star formation, with a particular focus on the impact of dark matter (DM) halos. Given the sensitivity of atomic hydrogen (H i) to external processes, we concentrate exclusively on central spiral galaxies. We find that the molecular-to-atomic gas mass ratio ( /MH i) strongly depends on stellar mass and specific star formation rate (sSFR). In the star formation efficiency (SFE)–sSFR plane, most galaxies fall below the H2 fundamental formation relation, with SFEH i being consistently lower than . Using the improved halo masses derived by D. Zhao et al., for star-forming galaxies, both SFEH i and /MH iincrease rapidly and monotonically with halo mass, indicating a higher efficiency in converting H i to H2 in more massive halos. This trend ultimately leads to the unsustainable state where SFEH i exceeds at halo mass around 1012M⊙. For halos with masses exceeding 1012M⊙, galaxies predominantly experience quenching. We propose a plausible evolutionary scenario in which the growth of halo mass regulates the conversion of H i to H2, star formation, and the eventual quenching of galaxies. The disk size, primarily regulated by the mass, spin and concentration of the DM halo, also significantly influences H i to H2 conversion and star formation. These findings underscore the critical role of DM halos as a global regulator of galaxy-wide star formation, a key factor that has been largely under-appreciated in previous studies.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"21 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-03-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143607844","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Quasiperiodic Super-Alfvénic Slippage along Flare Ribbons Observed by the Interface Region Imaging Spectrograph","authors":"Yining Zhang, Ting Li, Yijun Hou, Xuchun Duan, Zheng Sun and Guiping Zhou","doi":"10.3847/2041-8213/adbb6e","DOIUrl":"https://doi.org/10.3847/2041-8213/adbb6e","url":null,"abstract":"The apparent slipping motion of flare loops is regarded as a key feature of the 3D magnetic reconnection in the solar flares. The slippage with a super-Alfvénic speed could be defined as slipping–running reconnection, while the slippage with a sub-Alfvénic speed is called slipping reconnection. Due to the limitation of the observational instrument temporal resolution, the apparent slippage of the flare loop footpoints along the flare ribbons with super-Alfvénic speed is quite rare to our knowledge. In this Letter, we report a unique event that exhibits not only the sub-Alfvénic slippage but also the quasiperiodic super-Alfvénic slippage of ribbon substructures during a C3.4-class flare (SOL2023-01–18-T15:23), using the high-temporal-resolution observations of the Interface Region Imaging Spectrograph (∼2 s). The super-Alfvénic slippage with a speed of up to ∼1688 km s−1 is directly observed in this study. The calculated period of the apparent super-Alfvénic slippage in both ribbons is between 8.4 and 11.9 s. This work provides the first observational evidence of the periodicity for the slipping–running magnetic reconnection.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"37 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-03-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143618489","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Subclustering and Star Formation Efficiency in Three Protoclusters in the Central Molecular Zone","authors":"Suinan Zhang, 遂楠 张, Xing Lu, 行 吕, Adam Ginsburg, Nazar Budaiev, Yu Cheng, Hauyu Baobab Liu, Tie Liu, Qizhou Zhang, Keping Qiu, Siyi Feng, Thushara Pillai, Xindi Tang, Elisabeth A. C. Mills, Qiuyi Luo, Shanghuo Li, Namitha Issac, Xunchuan Liu, Fengwei Xu, Jennifer Wallace, Xiaofeng Mai, Yan-Kun Zhang, Cara Battersby, Steven N. Longmore and Zhiqiang Shen","doi":"10.3847/2041-8213/adb30b","DOIUrl":"https://doi.org/10.3847/2041-8213/adb30b","url":null,"abstract":"We present the highest-resolution (∼0 04) Atacama Large Millimeter/submillimeter Array 1.3 mm continuum observations so far of three massive star-forming clumps in the Central Molecular Zone (CMZ), namely 20 km s−1 C1, 20 km s−1 C4, and Sgr C C4, which reveal prevalent compact millimeter emission. We extract the compact emission with astrodendro and identify a total of 199 fragments with a typical size of ∼370 au, which represent the first sample of candidates of protostellar envelopes and disks and kernels of prestellar cores in these clumps that are likely forming star clusters. Compared with the protoclusters in the Galactic disk, the three protoclusters display a higher level of hierarchical clustering, likely a result of the stronger turbulence in the CMZ clumps. Compared with the mini-starbursts in the CMZ, Sgr B2 M and N, the three protoclusters also show stronger subclustering in conjunction with a lack of massive fragments. The efficiency of high-mass star formation of the three protoclusters is on average 1 order of magnitude lower than that of Sgr B2 M and N, despite a similar overall efficiency of converting gas into stars. The lower efficiency of high-mass star formation in the three protoclusters is likely attributed to hierarchical cluster formation.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"69 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-03-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143618710","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}