Article
Astronomy & Astrophysics
G. C. MacLeod, D. P. Smits, T. R. Hunter, C. Brogan, J. O. Chibueze, S. P. van den Heever
Summary: A new tool for identifying possible Zeeman pairs is introduced in this article: the RCP and LCP components of a pair drift at the same velocity. By monitoring hydroxyl transitions towards NGC 6334I-MM3 over a long period of time, three potential Zeeman pairs have been identified at the 1.667, 6.030, and 6.035 GHz transitions, where the RCP feature's drift rate equals that of the LCP component. Historical observations suggest that their drift has been occurring for 40 years. A fourth pair in the 1.720 GHz OH transition may indicate magnetic field variation over 50 years.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
G. C. MacLeod, Derck P. Smits, J. A. Green, S. P. van den Heever
Summary: This study reports the first confirmed periodically varying 6.031 and 6.035 GHz hydroxyl masers, which vary contemporaneously with the 6.7 GHz methanol masers in G323.459-0.079. Historical excited-state hydroxyl maser observations set a stricter upper limit, and time lags in methanol were confirmed.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
M. Durjasz, M. Szymczak, P. Wolak, A. Bartkiewicz
Summary: This study aimed to search for 12.2 GHz methanol emission in 6.7 GHz methanol masers and revealed its detection in 36 high-mass young stellar objects. The flux density ratio between 6.7 and 12.2 GHz exhibited significant variability among sources, with a median value of 5.1. Comparison with historical data suggested noticeable (>50%) variability in methanol maser emission over the past decade.
ASTRONOMY & ASTROPHYSICS
(2021)
Article
Astronomy & Astrophysics
G. C. MacLeod, J. O. Chibueze, A. Sanna, J. D. Paulsen, M. Houde, S. P. van den Heever, S. Goedhart
Summary: The source G9.62+0.20E shows several methanol masers at different frequencies experiencing contemporaneous and systematic velocity drifts, possibly due to a rotating Keplerian disc. Additionally, distinct periodic variations in some 6.7-GHz methanol maser features have been observed, with unclear causes for these changes.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
A. Kobak, A. Bartkiewicz, M. Szymczak, M. Olech, M. Durjasz, P. Wolak, J. O. Chibueze, T. Hirota, J. Eisloffel, B. Stecklum, A. Sobolev, O. Bayandina, G. Orosz, R. A. Burns, K. -T. Kim, S. P. van den Heever
Summary: Recent studies have shown that 6.7 GHz methanol maser flares can verify maser production mechanisms and specific characteristics of high-mass star formation. In this study, the 6.7 and 12.2 GHz methanol masers and 22.2 GHz water vapor masers of the high-mass young stellar object G24.33+0.14 were monitored using VLBA. The correlation between the 6.7 GHz maser and infrared fluxes was found using WISE data. The results indicate that the maser morphology remains stable during the monitoring period, possibly due to recurring low-energy accretion events.
ASTRONOMY & ASTROPHYSICS
(2023)
Article
Astronomy & Astrophysics
S. Paron, M. E. Ortega, A. Marinelli, M. B. Areal, N. C. Martinez
Summary: This study aims to investigate the spatial distribution of the cyano radical around massive young stellar objects, revealing its presence in ongoing star-forming processes.
ASTRONOMY & ASTROPHYSICS
(2021)
Article
Astronomy & Astrophysics
Onic Shuvo, E. D. Araya, W. S. Tan, P. Hofner, S. Kurtz, Y. M. Pihlstrom, I. M. Hoffman
Summary: Observations with the GBT detected 2cm formaldehyde emission towards NGC 7538 IRS1 in the Galactic star-forming region, revealing a deconvolved size of 50arcsec for the emission. Additionally, 1cm H2CO observations showed emission overlaid on weak absorption, indicative of quasi-thermal radiation from dense gas.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
Tomoya Hirota, Riccardo Cesaroni, Luca Moscadelli, Koichiro Sugiyama, Ross A. Burns, Jungha Kim, Kazuyoshi Sunada, Yoshinori Yonekura
Summary: The study reveals a possible link between the 22 GHz H2O maser outflow in S225 NIRS 3 and past ejection events, while the brightening of the 22 GHz H2O masers may be due to radiative excitation by infrared emissions.
ASTRONOMY & ASTROPHYSICS
(2021)
Article
Astronomy & Astrophysics
V Wakelam, A. Coutens, P. Gratier, T. H. G. Vidal, N. Vaytet
Summary: The emission of several molecules from the L1451-mm FHSC candidate was observed, and a low-velocity and compact outflow was detected, supporting the hypothesis that L1451-mm is at an early protostellar stage.
ASTRONOMY & ASTROPHYSICS
(2022)
Article
Astronomy & Astrophysics
A. Avison, G. A. Fuller, N. Peretto, A. Duarte-Cabral, A. L. Rosen, A. Traficante, J. E. Pineda, R. Guesten, N. Cunningham
Summary: The infrared dark cloud SDC335.579-0.292 is a massive star-forming cloud with high-mass protostellar objects at early evolution stages. Molecular outflow observations reveal that the protostars in SDC335 are in the early stages of evolution (Class 0) with a total accretion rate of 1.4 x 10^-3 solar masses per year.
ASTRONOMY & ASTROPHYSICS
(2021)
Article
Astronomy & Astrophysics
A. Aberfelds, J. Steinbergs, I Shmeld, R. A. Burns
Summary: We present the results of a 5-year monitoring program on 42 6.7 GHz methanol maser sources. More than 55% of the sources showed significant variability, with only a few spectral features being affected. Various types of variability were observed, including low-variable, periodic, irregular, synchronized, and anticorrelated patterns. The program demonstrated the suitability of the Irbene radio telescope for maser research purposes, and also uncovered new variability trends.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
David A. Kinson, Joana M. Oliveira, Jacco Th van Loon
Summary: A supervised machine learning methodology was used to classify stellar populations in NGC6822, achieving high accuracy in identifying different target classes. The study confirmed the nature of known YSO candidates, identified new YSOs, and characterized the star formation environment in the galaxy. The PRF analysis also definitively classified non-YSO candidates and explored the potential of unsupervised methods for stellar population identification.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
G. Perotti, J. K. Jorgensen, W. R. M. Rocha, A. Plunkett, E. Artur de la Villarmois, L. E. Kristensen, M. Sewilo, P. Bjerkeli, H. J. Fraser, S. B. Charnley
Summary: This study aims to constrain the interplay of solid and gaseous methanol in the outer regions of protostellar envelopes and assess the importance of irradiation. The results suggest that the overall CH3OH chemistry in the outer regions of low-mass envelopes is relatively independent of variations in the physical conditions and is set during the prestellar stage.
ASTRONOMY & ASTROPHYSICS
(2023)
Article
Astronomy & Astrophysics
T. P. McCarthy, S. L. Breen, J. F. Kaczmarek, X. Chen, S. Parfenov, A. M. Sobolev, S. P. Ellingsen, R. A. Burns, G. C. MacLeod, K. Sugiyama, A. L. Brierley, S. P. van den Heever
Summary: We report the detection of ammonia masers in various transitions, including the first ever made detection of the (6, 5) transition. Our observations reveal the coexistence of ammonia masers and class II methanol masers in G 358.931-0.030 during an accretion burst event. Radiative transfer calculations support the hypothesis that the (6, 5) transition is excited by high temperature infrared emission and suggest dust temperatures >400 K.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
M. Juvela, E. Mannfors, T. Liu, L. Toth
Summary: This study evaluated the physical conditions within massive star-forming clouds using magnetohydrodynamic simulation data and synthetic observations, with a focus on the potential of the ngVLA interferometer. The ngVLA proved capable of providing accurate data on small-scale structures and physical states in high-mass star-forming regions at kiloparsec distances.
ASTRONOMY & ASTROPHYSICS
(2022)
Article
Astronomy & Astrophysics
F. de Gasperin, L. Rudnick, A. Finoguenov, D. Wittor, H. Akamatsu, M. Brueggen, J. O. Chibueze, T. E. Clarke, W. Cotton, V Cuciti, P. Dominguez-Fernandez, K. Knowles, S. P. O'Sullivan, L. Sebokolodi
Summary: This study presents detailed observations of the radio relic system in Abell 3667, revealing the complexity of the interaction between thermal and non-thermal components in the merging cluster region, as well as the non-trivial magnetic properties of the cluster medium.
ASTRONOMY & ASTROPHYSICS
(2022)
Article
Astronomy & Astrophysics
Andrzej A. Zdziarski, Dakalo G. Phuravhathu, Marek Sikora, Markus Bottcher, James O. Chibueze
Summary: Through studying the jet of 3C 120, we found that the jet is mainly composed of electron-positron pairs and its power exceeds that achievable by the magnetically arrested disk scenario for the maximum black hole spin.
ASTROPHYSICAL JOURNAL LETTERS
(2022)
Article
Astronomy & Astrophysics
James O. Chibueze, Hiroki Akamatsu, Viral Parekh, Haruka Sakemi, Takumi Ohmura, Ruby van Rooyen, Takuya Akahori, Hiroyuki Nakanishi, Mami Machida, Tsutomu T. Takeuchi, Oleg Smirnov, Dane Kleiner, Filippo M. Maccagni
Summary: We present the initial results of our MeerKAT L-band observations of Abell 3376. Our observations achieved higher angular resolution and sensitivity compared to previous observations. We successfully calibrated the data and detected relics and radio galaxies.
PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN
(2023)
Article
Astronomy & Astrophysics
Mikito Kohno, Toshihiro Omodaka, Toshihiro Handa, James O. Chibueze, Takumi Nagayama, Ross A. Burns, Takeru Murase, Ren Matsusaka, Makoto Nakano, Kazuyoshi Sunada, Rin Yamada, John H. Bieging
Summary: We conducted NH3 mapping observations towards the Galactic massive star-forming regions Sh 2-255 and Sh 2-257 using the Nobeyama 45 m telescope. Our findings suggest that NH3 gas in these regions is influenced by stellar feedback from embedded young stellar object (YSO) clusters. We also detected NH3 emission in a region adjacent to an H II region, indicating the possibility of star formation influenced by the older H II region.
PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN
(2022)
Article
Astronomy & Astrophysics
O. S. Bayandina, C. L. Brogan, R. A. Burns, A. Caratti O. Garatti, J. O. Chibueze, S. P. van den Heever, S. E. Kurtz, G. C. MacLeod, L. Moscadelli, A. M. Sobolev, K. Sugiyama, I. E. Val'tts, Y. Yonekura
Summary: This study revealed significant changes in the spatial structure and emission velocity range of 22 GHz water masers associated with the accretion burst of G358.93-0.03-MM1, demonstrating the impact of the accretion event on ejection from the source.
ASTRONOMY & ASTROPHYSICS
(2022)
Article
Astronomy & Astrophysics
R. Kale, V Parekh, M. Rahaman, D. C. Joshi, T. Venturi, K. Kolokythas, J. O. Chibueze, S. Sikhosana, D. Pillay, K. Knowles
Summary: This study conducted a radio survey of 20 massive and nearby southern galaxy clusters, revealing the presence of radio halos, relics, and mini-haloes in some of them. The radio relic in A3399 was found to be formed due to a cluster merger shock, while the relic in RXC J0232.2-4420 had a different origin. The results also showed that 1/9 of the clusters had radio halos and double relics, 1/9 had radio halos, and 2/9 had mini-haloes. The X-ray morphology analysis indicated that A3399 was a disturbed cluster, while RXC J0232.2-4420 was relaxed, and the mini-halo clusters had intermediate morphologies.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
J. O. Chibueze, M. Caleb, L. Spitler, H. Ashkar, F. Schussler, B. W. Stappers, C. Venter, I Heywood, A. M. S. Richards, D. R. A. Williams, M. Kramer, R. Beswick, M. C. Bezuidenhout, R. P. Breton, L. N. Driessen, F. Jankowski, E. F. Keane, M. Malenta, M. Mickaliger, V Morello, H. Qiu, K. Rajwade, S. Sanidas, M. Surnis, T. W. Scragg, C. R. H. Walker, N. Wrigley, F. Aharonian, F. Ait Benkhali, E. O. Anguener, M. Backes, V Baghmanyan, V. Barbosa Martins, R. Batzofin, Y. Becherini, D. Berge, M. Bottcher, C. Boisson, J. Bolmont, M. de Bony de Lavergne, M. Breuhaus, R. Brose, F. Brun, T. Bulik, F. Cangemi, S. Caroff, S. Casanova, J. Catalano, M. Cerruti, T. Chand, A. Chen, O. U. Chibueze, G. Cotter, P. Cristofari, J. Damascene Mbarubucyeye, J. Devin, A. Djannati-Atai, A. Dmytriiev, K. Egberts, J-P Ernenwein, A. Fiasson, G. Fichet de Clairfontaine, G. Fontaine, S. Funk, S. Gabici, S. Ghafourizadeh, G. Giavitto, D. Glawion, M-H Grondin, M. Horbe, C. Hoischen, T. L. Holch, Zhiqiu Huang, M. Jamrozy, F. Jankowsky, V Joshi, I Jung-Richardt, E. Kasai, K. Katarzynski, U. Katz, B. Khelifi, W. Kluzniak, Nu Komin, K. Kosack, D. Kostunin, A. Lemiere, J-P Lenain, F. Leuschner, T. Lohse, A. Luashvili, I Lypova, J. Mackey, D. Malyshev, V Marandon, P. Marchegiani, A. Marcowith, G. Marti-Devesa, R. Marx, A. Mitchell, R. Moderski, L. Mohrmann, E. Moulin, J. Muller, K. Nakashima, M. de Naurois, A. Nayerhoda, J. Niemiec, A. Priyana Noel, P. O'Brien, S. Ohm, L. Olivera-Nieto, E. de Ona Wilhelmi, M. Ostrowski, S. Panny, R. D. Parsons, S. Pita, V Poireau, D. A. Prokhorov, H. Prokoph, G. Puehlhofer, A. Quirrenbach, P. Reichherzer, A. Reimer, O. Reimer, G. Rowell, B. Rudak, E. Ruiz-Velasco, V Sahakian, S. Sailer, H. Salzmann, D. A. Sanchez, A. Santangelo, M. Sasaki, H. M. Schutte, U. Schwanke, J. N. S. Shapopi, A. Specovius, S. Spencer, R. Steenkamp, S. Steinmassl, T. Takahashi, T. Tanaka, C. Thorpe-Morgan, N. Tsuji, C. van Eldik, J. Veh, J. Vink, S. J. Wagner, A. Wierzcholska, Yu Wun Wong, A. Yusafzai, M. Zacharias, D. Zargaryan, A. A. Zdziarski, A. Zech, S. J. Zhu, S. Zouari, N. Zywucka
Summary: We conducted observations using the MeerKAT radio telescope and the H.E.S.S. for persistent radio and gamma-ray emissions from FRBs. We detected persistent radio emission potentially associated with a non-repeating FRB, indicating a possible distinction between repeaters and non-repeaters. However, the search for repeat bursts from these FRBs did not yield any new detections.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
G. C. MacLeod, Y. Yonekura, Y. Tanabe, W. A. Baan, C. L. Brogan, R. A. Burns, J. O. Chibueze, M. Houde, T. R. Hunter, S. E. Kurtz, F. Rajabi, D. P. Smits, B. Stecklum, K. Sugiyama
Summary: The source G9.62+0.20E continues to surprise as analysis reveals a new feature and two periodicities, P = 52.1 +/- 0.3 d and P = 243 d. Possible explanations include harmonic flaring, Dicke's superradiance, a secondary pulsation, or two different periodically varying radio sources with associated methanol masers. It remains unclear which explanation best describes the observations.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
G. C. MacLeod, D. P. Smits, T. R. Hunter, C. Brogan, J. O. Chibueze, S. P. van den Heever
Summary: A new tool for identifying possible Zeeman pairs is introduced in this article: the RCP and LCP components of a pair drift at the same velocity. By monitoring hydroxyl transitions towards NGC 6334I-MM3 over a long period of time, three potential Zeeman pairs have been identified at the 1.667, 6.030, and 6.035 GHz transitions, where the RCP feature's drift rate equals that of the LCP component. Historical observations suggest that their drift has been occurring for 40 years. A fourth pair in the 1.720 GHz OH transition may indicate magnetic field variation over 50 years.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
C. J. Ugwu, J. O. Chibueze, J. Morgan, T. Csengeri, A. E. Chukwude, D. J. van der Walt, J. A. Alhassan
Summary: We investigated the nature and gas kinematics of protostellar objects in G358.46-0.39 using ALMA data to understand the ongoing star formation activities. Multiple cores were identified dominated by MM1a with no free-free emission. Masses, column densities, and molecular transitions were calculated for each object, revealing different excitation conditions. The presence of a bipolar outflow, a rotating envelope, and a possibly rotating structure suggest the early stage formation of a massive young stellar object with outflow activity and accretion.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
Mikito Kohno, James O. Chibueze, Ross A. Burns, Toshihiro Omodaka, Toshihiro Handa, Takeru Murase, Rin I. Yamada, Takumi Nagayama, Makoto Nakano, Kazuyoshi Sunada, Kengo Tachihara, Yasuo Fukui
Summary: NH3(J, K) = (1, 1), (2, 2), and (3, 3) mapping observations were conducted towards the Galactic infrared bubble N49 (G28.83-0.25) using the Nobeyama 45 m telescope, revealing three NH3 clumps (A, B, and C) with different radial velocities. The kinetic temperature showed an elevation at Clump B, coinciding with massive young stellar objects associated with the 6.7 GHz class II methanol maser source, indicating local heating by stellar feedback. The NH3 dense gas formation in Clump B may be explained by a filament-filament interaction scenario, while Clumps A and C might be sites of spontaneous star formation.
PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN
(2023)
Correction
Astronomy & Astrophysics
R. A. Burns, Y. Uno, N. Sakai, J. Blanchard, Z. Rosli, G. Orosz, Y. Yonekura, Y. Tanabe, K. Sugiyama, T. Hirota, Kee-Tae Kim, A. Aberfelds, A. E. Volvach, A. Bartkiewicz, A. Caratti o Garatti, A. M. Sobolev, B. Stecklum, C. Brogan, C. Phillips, D. A. Ladeyschikov, D. Johnstone, G. Surcis, G. C. MacLeod, H. Linz, J. O. Chibueze, J. Brand, J. Eisloeffel, L. Hyland, L. Uscanga, M. Olech, M. Durjasz, O. Bayandina, S. Breen, S. P. Ellingsen, S. P. van den Heever, T. R. Hunter, X. Chen
Article
Astronomy & Astrophysics
R. A. Burns, Y. Uno, N. Sakai, J. Blanchard, Z. Fazil, G. Orosz, Y. Yonekura, Y. Tanabe, K. Sugiyama, T. Hirota, Kee-Tae Kim, A. Aberfelds, A. E. Volvach, A. Bartkiewicz, A. Caratti o Garatti, A. M. Sobolev, B. Stecklum, C. Brogan, C. Phillips, D. A. Ladeyschikov, D. Johnstone, G. Surcis, G. C. MacLeod, H. Linz, J. O. Chibueze, J. Brand, J. Eisloeffel, L. Hyland, L. Uscanga, M. Olech, M. Durjasz, O. Bayandina, S. Breen, S. P. Ellingsen, S. P. van den Heever, T. R. Hunter, X. Chen
Summary: High-mass protostars gain most of their mass through short and intense bursts of growth, facilitated by gravitationally unstable and inhomogeneous accretion disks. Limited observational capabilities and lack of observed accretion burst events have hindered confirmation of the connection between disk accretion, instability, and accretion bursts in high-mass protostars. Using heatwave mapping, researchers observed a heatwave driven by a burst of radiation from the high-mass protostar G358.93-0.03-MM1, tracing the expansion of the accretion disk. They discovered a Keplerian accretion disk with a four-arm spiral pattern, confirming the role of disk accretion and spiral arm instabilities in episodic accretion of high-mass stars.
Article
Astronomy & Astrophysics
Dongting Yang, Hong-Li Liu, Anandmayee Tej, Tie Liu, Patricio Sanhueza, Sheng-Li Qin, Xing Lu, Ke Wang, Sirong Pan, Feng-Wei Xu, Enrique Vazquez-Semadeni, Shanghuo Li, Gilberto C. C. Gomez, Aina Palau, Guido Garay, Paul F. F. Goldsmith, Mika Juvela, Anindya Saha, Leonardo Bronfman, Chang Won Lee, Kenichi Tatematsu, Lokesh Dewangan, Jianwen Zhou, Yong Zhang, Amelia Stutz, Chakali Eswaraiah, L. Viktor Toth, Isabelle Ristorcelli, Xianjin Shen, Anxu Luo, James O. O. Chibueze
Summary: There is evidence that high-mass star formation and hub-filament systems are connected. This paper presents observations of a typical hub-filament cloud, revealing clear evidence of mass inflow from the cloud through the filaments onto the forming protostars at the hub, in accordance with model predictions.
ASTROPHYSICAL JOURNAL
(2023)