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11 results on '"S. S. Passmoor"'

1. The 1.28 GHz MeerKAT Galactic Center Mosaic

Author

I. Heywood, I. Rammala, F. Camilo, W. D. Cotton, F. Yusef-Zadeh, T. D. Abbott, R. M. Adam, G. Adams, M. A. Aldera, K. M. B. Asad, E. F. Bauermeister, T. G. H. Bennett, H. L. Bester, W. A. Bode, D. H. Botha, A. G. Botha, L. R. S. Brederode, S. Buchner, J. P. Burger, T. Cheetham, D. I. L. de Villiers, M. A. Dikgale-Mahlakoana, L. J. du Toit, S. W. P. Esterhuyse, B. L. Fanaroff, S. February, D. J. Fourie, B. S. Frank, R. R. G. Gamatham, M. Geyer, S. Goedhart, M. Gouws, S. C. Gumede, M. J. Hlakola, A. Hokwana, S. W. Hoosen, J. M. G. Horrell, B. Hugo, A. I. Isaacson, G. I. G. Józsa, J. L. Jonas, A. F. Joubert, R. P. M. Julie, F. B. Kapp, J. S. Kenyon, P. P. A. Kotzé, N. Kriek, H. Kriel, V. K. Krishnan, R. Lehmensiek, D. Liebenberg, R. T. Lord, B. M. Lunsky, K. Madisa, L. G. Magnus, O. Mahgoub, A. Makhaba, S. Makhathini, J. A. Malan, J. R. Manley, S. J. Marais, A. Martens, T. Mauch, B. C. Merry, R. P. Millenaar, N. Mnyandu, O. J. Mokone, T. E. Monama, M. C. Mphego, W. S. New, B. Ngcebetsha, K. J. Ngoasheng, M. T. Ockards, N. Oozeer, A. J. Otto, S. S. Passmoor, A. A. Patel, A. Peens-Hough, S. J. Perkins, A. J. T. Ramaila, N. M. R. Ramanujam, Z. R. Ramudzuli, S. M. Ratcliffe, A. Robyntjies, S. Salie, N. Sambu, C. T. G. Schollar, L. C. Schwardt, R. L. Schwartz, M. Serylak, R. Siebrits, S. K. Sirothia, M. Slabber, O. M. Smirnov, L. Sofeya, B. Taljaard, C. Tasse, A. J. Tiplady, O. Toruvanda, S. N. Twum, T. J. van Balla, A. van der Byl, C. van der Merwe, V. Van Tonder, R. Van Wyk, A. J. Venter, M. Venter, B. H. Wallace, M. G. Welz, L. P. Williams, and B. Xaia

Subjects
Space and Planetary Science, Astrophysics::High Energy Astrophysical Phenomena, Astrophysics of Galaxies (astro-ph.GA), FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics - Astrophysics of Galaxies, Astrophysics::Galaxy Astrophysics
Abstract

The inner $\sim$200 pc region of the Galaxy contains a 4 million M$_{\odot}$ supermassive black hole (SMBH), significant quantities of molecular gas, and star formation and cosmic ray energy densities that are roughly two orders of magnitude higher than the corresponding levels in the Galactic disk. At a distance of only 8.2 kpc, the region presents astronomers with a unique opportunity to study a diverse range of energetic astrophysical phenomena, from stellar objects in extreme environments, to the SMBH and star-formation driven feedback processes that are known to influence the evolution of galaxies as a whole. We present a new survey of the Galactic center conducted with the South African MeerKAT radio telescope. Radio imaging offers a view that is unaffected by the large quantities of dust that obscure the region at other wavelengths, and a scene of striking complexity is revealed. We produce total intensity and spectral index mosaics of the region from 20 pointings (144 hours on-target in total), covering 6.5 square degrees with an angular resolution of 4$"$,at a central frequency of 1.28 GHz. Many new features are revealed for the first time due to a combination of MeerKAT's high sensitivity, exceptional $u,v$-plane coverage, and geographical vantage point. We highlight some initial survey results, including new supernova remnant candidates, many new non-thermal filament complexes, and enhanced views of the Radio Arc Bubble, Sgr A and Sgr B regions. This project is a SARAO public legacy survey, and the image products are made available with this article., Comment: 29 pages, 15 figures, 3 tables, accepted for publication in the The Astrophysical Journal. Replacement arXiv version with higher quality figures

Published
2022
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2. A MeerKAT view of pre-processing in the Fornax A group

Author

Oleg Smirnov, S. S. Passmoor, A. Sivitilli, D. Kleiner, Fabio Vitello, M. Ramatsoku, M. A. Raj, Aku Venhola, Kshitij Thorat, D. Cs. Molnár, Gyula I. G. Józsa, Reynier Peletier, A. Loni, S. I. Loubser, W. J. G. de Blok, Enrichetta Iodice, Kana Morokuma-Matsui, A. Comrie, F. M. Maccagni, Peter Kamphuis, Paolo Serra, and Astronomy

Subjects
groups: individual: Fornax A [galaxies], Stellar mass, FOS: Physical sciences, Astrophysics, 01 natural sciences, Group (periodic table), galaxies: groups: general, 0103 physical sciences, galaxies: interactions, Lagrangian coherent structures, Fornax Cluster, 010303 astronomy & astrophysics, evolution [galaxies], Physics, radio lines: galaxies, ISM [galaxies], groups: general [galaxies], interactions [galaxies], 010308 nuclear & particles physics, Astronomy and Astrophysics, galaxies: groups: individual: Fornax A, Astrophysics - Astrophysics of Galaxies, galaxies [radio lines], Redshift, Galaxy, Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA), Content (measure theory), Halo, galaxies: evolution, galaxies: ISM
Abstract

We present MeerKAT neutral hydrogen (HI) observations of the Fornax A group, that is likely falling into the Fornax cluster for the first time. Our HI image is sensitive to 1.4 x 10$^{19}$ cm$^{-2}$ over 44.1 km s$^{-1}$, where we detect HI in 10 galaxies and a total of 1.12 x 10$^{9}$ Msol of HI in the intra-group medium (IGM). We search for signs of pre-processing in the 12 group galaxies with confirmed optical redshifts that reside within our HI image. There are 9 galaxies that show evidence of pre-processing and we classify the pre-processing status of each galaxy, according to their HI morphology and gas (atomic and molecular) scaling relations. Galaxies yet to experience pre-processing have extended HI disks, a high HI content with a H$_2$-to-HI ratio an order of magnitude lower than the median for their stellar mass. Galaxies currently being pre-processed display HI tails, truncated HI disks with typical gas ratios. Galaxies in the advanced stages of pre-processing are HI deficient. If there is any HI, they have lost their outer HI disk and efficiently converted their HI to H$_2$, resulting in H$_2$-to-HI ratios an order of magnitude higher than the median for their stellar mass. The central, massive galaxy in our group underwent a 10:1 merger 2 Gyr ago, and ejected 6.6 - 11.2 x 10$^{8}$ Msol of HI that we detect as clouds and streams in the IGM, some forming coherent structures up to 220 kpc in length. We also detect giant (100 kpc) ionised hydrogen (H$\alpha$) filaments in the IGM, likely from cool gas being removed (and ionised) from an infalling satellite. The H$\alpha$ filaments are situated within the hot halo of NGC 1316 and some regions contain HI. We speculate that the H$\alpha$ and multiphase gas is supported by magnetic pressure (possibly assisted by the AGN), such that the hot gas can condense and form HI that survives in the hot halo for cosmological timescales., Comment: 18 pages, 9 figured. Accepted for publication in Astronomy and Astrophysics (A&A)

Published
2021

3. Anomalous gas in ESO 149-G003: A MeerKAT-16 View

Author

Sharmila Goedhart, Elmar Körding, D. Kleiner, W. J. G. de Blok, Kshitij Thorat, L. A. L. Andati, Patrick Woudt, Steven Bloemen, Dániel Cs. Molnár, J.A. Wang, Marc Klein-Wolt, Eric Maina, L. Sebokolodi, B. Hugo, Gyula I. G. Józsa, S. Makhathini, M. Serylak, S. S. Passmoor, Vanessa McBride, M. Ramatsoku, Paul J. Groot, Paolo Serra, F. M. Maccagni, Oleg Smirnov, Peter Kamphuis, P. M. Vreeswijk, A. J. T. Ramaila, R. S. Le Poole, R. J. Dettmar, Kerry Paterson, D. L. A. Pieterse, and Astronomy

Subjects
media_common.quotation_subject, Astronomy, Minimum mass, FOS: Physical sciences, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, 01 natural sciences, Asymmetry, Radio telescope, 0103 physical sciences, 010303 astronomy & astrophysics, Scaling, Astrophysics::Galaxy Astrophysics, galaxies: kinematics and dynamics, media_common, Physics, 010308 nuclear & particles physics, Astronomy and Astrophysics, galaxies: dwarf, Mass ratio, Astrophysics - Astrophysics of Galaxies, Galaxy, Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA), Intergalactic travel, Irregular galaxy, galaxies: evolution, galaxies: individual: ESO 149-G003, galaxies: ISM
Abstract

ESO 149-G003 is a close-by, isolated dwarf irregular galaxy. Previous observations with the ATCA indicated the presence of anomalous neutral hydrogen (HI) deviating from the kinematics of a regularly rotating disc. We conducted follow-up observations with the MeerKAT radio telescope during the 16-dish Early Science programme as well as with the MeerLICHT optical telescope. Our more sensitive radio observations confirm the presence of anomalous gas in ESO 149-G003, and further confirm the formerly tentative detection of an extraplanar HI component in the galaxy. Employing a simple tilted-ring model, in which the kinematics is determined with only four parameters but including morphological asymmetries, we reproduce the galaxy's morphology, which shows a high degree of asymmetry. By comparing our model with the observed HI, we find that in our model we cannot account for a significant (but not dominant) fraction of the gas. From the differences between our model and the observed data cube we estimate that at least 7%-8% of the HI in the galaxy exhibits anomalous kinematics, while we estimate a minimum mass fraction of less than 1% for the morphologically confirmed extraplanar component. We investigate a number of global scaling relations and find that, besides being gas-dominated with a neutral gas-to-stellar mass ratio of 1.7, the galaxy does not show any obvious global peculiarities. Given its isolation, as confirmed by optical observations, we conclude that the galaxy is likely currently acquiring neutral gas. It is either re-accreting gas expelled from the galaxy or accreting pristine intergalactic material., 16 pages, 14 figures, MNRAS, Accepted 2020 December 2, in original form 2019 September 18

Published
2021

4. Blind HI and OH absorption line search: first results with MALS and uGMRT processed using ARTIP

Author

Kavilan Moodley, J. K. Krogager, C. Kaski, Peter Kamphuis, C. M. Cress, Varsha P. Kulkarni, J. Jose, George Heald, Kenda Knowles, Preshanth Jagannathan, Gyula I. G. Józsa, Raghunathan Srianand, Erin Boettcher, V. Krishnan, Anja Schroeder, S. K. Pandey, Francoise Combes, Sinenhlanhla P. Sikhosana, O. I. Wong, Emmanuel Momjian, Pasquier Noterdaeme, Hans-Rainer Klöckner, S. S. Passmoor, Hsiao We Chen, Sanjay Bhatnagar, Patrick Petitjean, J. Kerp, E. Kamau, J. Wagenveld, Srikrishna Sekhar, N. Gupta, Sharmila Goedhart, R. Dutta, S. Balashev, Andrew J. Baker, Inter-University Centre for Astronomy and Astrophysics [Pune] (IUCAA), Institut d'Astrophysique de Paris (IAP), Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Laboratoire d'Etude du Rayonnement et de la Matière en Astrophysique (LERMA (UMR_8112)), Observatoire de Paris, and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-CY Cergy Paris Université (CY)

Subjects
Physics, [PHYS]Physics [physics], [SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph], Analytical chemistry, Radio-loud quasars, FOS: Physical sciences, Astronomy and Astrophysics, 01 natural sciences, Astrophysics - Astrophysics of Galaxies, Spectral line, Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA), 0103 physical sciences, Quasar absorption line spectroscopy, 010306 general physics, 010303 astronomy & astrophysics
Abstract

We present details of the Automated Radio Telescope Imaging Pipeline (ARTIP) and results of a sensitive blind search for HI and OH absorbers at $z5.4\times10^{19}$ cm$^{-2}$, the survey has probed only the outskirts of star-forming galaxies at $\rho>30$ kpc. MALS with the expected $\Delta z\sim10^{3-4}$ will overcome this limitation and provide stringent constraints on the cold gas fraction of galaxies in diverse environments over $0, Comment: 30 pages, 15 figures, accepted in ApJ

Published
2020
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5. The MeerKAT Galaxy Cluster Legacy Survey

Author

K. Knowles, W. D. Cotton, L. Rudnick, F. Camilo, S. Goedhart, R. Deane, M. Ramatsoku, M. F. Bietenholz, M. Brüggen, C. Button, H. Chen, J. O. Chibueze, T. E. Clarke, F. de Gasperin, R. Ianjamasimanana, G. I. G. Józsa, M. Hilton, K. C. Kesebonye, K. Kolokythas, R. C. Kraan-Korteweg, G. Lawrie, M. Lochner, S. I. Loubser, P. Marchegiani, N. Mhlahlo, K. Moodley, E. Murphy, B. Namumba, N. Oozeer, V. Parekh, D. S. Pillay, S. S. Passmoor, A. J. T. Ramaila, S. Ranchod, E. Retana-Montenegro, L. Sebokolodi, S. P. Sikhosana, O. Smirnov, K. Thorat, T. Venturi, T. D. Abbott, R. M. Adam, G. Adams, M. A. Aldera, E. F. Bauermeister, T. G. H. Bennett, W. A. Bode, D. H. Botha, A. G. Botha, L. R. S. Brederode, S. Buchner, J. P. Burger, T. Cheetham, D. I. L. de Villiers, M. A. Dikgale-Mahlakoana, L. J. du Toit, S. W. P. Esterhuyse, G. Fadana, B. L. Fanaroff, S. Fataar, A. R. Foley, D. J. Fourie, B. S. Frank, R. R. G. Gamatham, T. G. Gatsi, M. Geyer, M. Gouws, S. C. Gumede, I. Heywood, M. J. Hlakola, A. Hokwana, S. W. Hoosen, D. M. Horn, J. M. G. Horrell, B. V. Hugo, A. R. Isaacson, J. L. Jonas, J. D. B. Jordaan, A. F. Joubert, R. P. M. Julie, F. B. Kapp, V. A. Kasper, J. S. Kenyon, P. P. A. Kotzé, A. G. Kotze, N. Kriek, H. Kriel, V. K. Krishnan, T. W. Kusel, L. S. Legodi, R. Lehmensiek, D. Liebenberg, R. T. Lord, B. M. Lunsky, K. Madisa, L. G. Magnus, J. P. L. Main, A. Makhaba, S. Makhathini, J. A. Malan, J. R. Manley, S. J. Marais, M. D. J. Maree, A. Martens, T. Mauch, K. McAlpine, B. C. Merry, R. P. Millenaar, O. J. Mokone, T. E. Monama, M. C. Mphego, W. S. New, B. Ngcebetsha, K. J. Ngoasheng, M. T. Ockards, A. J. Otto, A. A. Patel, A. Peens-Hough, S. J. Perkins, N. M. Ramanujam, Z. R. Ramudzuli, S. M. Ratcliffe, R. Renil, A. Robyntjies, A. N. Rust, S. Salie, N. Sambu, C. T. G. Schollar, L. C. Schwardt, R. L. Schwartz, M. Serylak, R. Siebrits, S. K. Sirothia, M. Slabber, L. Sofeya, B. Taljaard, C. Tasse, A. J. Tiplady, O. Toruvanda, S. N. Twum, T. J. van Balla, A. van der Byl, C. van der Merwe, C. L. van Dyk, V. Van Tonder, R. Van Wyk, A. J. Venter, M. Venter, M. G. Welz, L. P. Williams, and B. Xaia

Subjects
Physics, Cosmology and Nongalactic Astrophysics (astro-ph.CO), Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA), FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics, Astrophysics - Astrophysics of Galaxies, Galaxy cluster, Astrophysics - Cosmology and Nongalactic Astrophysics
Abstract

MeerKAT's large number of antennas, spanning 8 km with a densely packed 1 km core, create a powerful instrument for wide-area surveys, with high sensitivity over a wide range of angular scales. The MeerKAT Galaxy Cluster Legacy Survey (MGCLS) is a programme of long-track MeerKAT L-band (900-1670 MHz) observations of 115 galaxy clusters, observed for $\sim$6-10 hours each in full polarisation. The first legacy product data release (DR1), made available with this paper, includes the MeerKAT visibilities, basic image cubes at $\sim$8" resolution, and enhanced spectral and polarisation image cubes at $\sim$8" and 15" resolutions. Typical sensitivities for the full-resolution MGCLS image products are $\sim$3-5 {\mu}Jy/beam. The basic cubes are full-field and span 4 deg^2. The enhanced products consist of the inner 1.44 deg^2 field of view, corrected for the primary beam. The survey is fully sensitive to structures up to $\sim$10' scales and the wide bandwidth allows spectral and Faraday rotation mapping. HI mapping at 209 kHz resolution can be done at $0, Comment: 43 pages, 33 figures, 6 tables. Accepted for publication in Astronomy and Astrophysics

Published
2022

6. Inflation of 430-parsec bipolar radio bubbles in the Galactic Centre by an energetic event

Author

Jasper Horrell, M. Serylak, T. D. Abbott, P. P. A. Kotzé, J. P. Burger, L. G. Magnus, A. A. Pate, P. S. Swart, A. Loots, S. Tshongweni, A. van der Byl, S. Buchner, Farhad Yusef-Zadeh, Jason Manley, T. W. Kusel, R. Renil, T. J. van Balla, D. H. Botha, A. R. Foley, N. Mnyandu, O. Mahgoub, A. G. Botha, B. M. Lunsky, L. C. Schwardt, Bruce Merry, A. J. Tiplad, C. J. Hoek, R. Siebrits, Dirk I. L. de Villiers, C. L. van Dyk, T. Cheetham, J. A. Malan, C.G. Van der Merwe, D. M. Horn, S. Salie, T. E. Monama, A. R. Isaacson, I. P. T. Moeng, Kshitij Thorat, E. F. Bauermeister, Roy Booth, F. Kapp, B. L. Fanaroff, Simon Perkins, M. C. Mphego, A. Rust, V. Van Tonder, W. S. New, Oleg Smirnov, S. Gounden, H. Kriel, J. D. B. L. Jordaan, M. A. Dikgale-Mahlakoana, R. T. Lord, L. J. du Toit, B. Ngcebetsha, S. W. P. Esterhuyse, P. Macfarlane, Sharmila Goedhart, D. T. Taylor, Justin L. Jonas, R. van Rooyen, C. Magozore, M. J. Hlakola, Dehann Fourie, Robert Lehmensiek, A. F. Joubert, Fernando Camilo, B. H. Wallace, D. Liebenberg, R. van Wyk, R. R. G. Gamatham, Gyula I. G. Józsa, Nadeem Oozeer, J. S. Kenyon, R. D. Malgas, Robert P. Millenaar, Matthys Maree, A. Hokwana, J. M. Chalmers, C. Tasse, L. P. Williams, R. M. Adam, Z. B. Brits, L. R. S. Brederode, W. D. Cotton, J. P. L. Main, M. G. Welz, B. Hugo, A. Peens-Hough, L. Sofeya, Ian Heywood, S. Ratcliffe, I. P. Theron, S. S. Passmoor, M. A. Aldera, A. J. Otto, S. K. Sirothia, R. P. M. Julie, Galaxies, Etoiles, Physique, Instrumentation (GEPI), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Active galactic nucleus, Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, Cosmic ray, Context (language use), Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, 01 natural sciences, Relativistic particle, 0103 physical sciences, Disc, 010306 general physics, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics, ComputingMilieux_MISCELLANEOUS, Physics, [PHYS]Physics [physics], Supermassive black hole, Multidisciplinary, Star formation, Galactic plane, Astrophysics - Astrophysics of Galaxies, 13. Climate action, Astronomy and astrophysics, Astrophysics of Galaxies (astro-ph.GA), [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph]
Abstract

The Galactic Centre contains a supermassive black hole with a mass of 4 million suns within an environment that differs markedly from that of the Galactic disk. While the black hole is essentially quiescent in the broader context of active galactic nuclei, X-ray observations have provided evidence for energetic outbursts from its surroundings. Also, while the levels of star formation in the Galactic Centre have been approximately constant over the last few hundred Myr, there is evidence of elevated short-duration bursts, strongly influenced by interaction of the black hole with the enhanced gas density present within the ring-like Central Molecular Zone at Galactic longitude |l| < 0.7 degrees and latitude |b| < 0.2 degrees. The inner 200 pc region is characterized by large amounts of warm molecular gas, a high cosmic ray ionization rate, unusual gas chemistry, enhanced synchrotron emission, and a multitude of radio-emitting magnetised filaments, the origin of which has not been established. Here we report radio imaging that reveals bipolar bubbles spanning 1 degree x 3 degrees (140 parsecs x 430 parsecs), extending above and below the Galactic plane and apparently associated with the Galactic Centre. The structure is edge-brightened and bounded, with symmetry implying creation by an energetic event in the Galactic Centre. We estimate the age of the bubbles to be a few million years, with a total energy of 7 x 10^52 ergs. We postulate that the progenitor event was a major contributor to the increased cosmic-ray density in the Galactic Centre, and is in turn the principal source of the relativistic particles required to power the synchrotron emission of the radio filaments within and in the vicinity of the bubble cavities., 25 pages, 3 figures, 3 tables, authors' version of a Letter published in Nature on 11 September 2019

Published
2019

7. H i in group interactions: HCG 44

Author

Claude Carignan, Sahba Yahya, Paolo Serra, D. M. Lucero, S. S. Passmoor, Lukas Leisman, Michelle E. Cluver, Kelley M. Hess, Department of Astronomy, Faculty of Science, and Astronomy

Subjects
History, TIDAL DEBRIS, FAST ALPHA SURVEY, Density, Astrophysics, 01 natural sciences, Example, law.invention, Synthesis, Group (periodic table), law, histoire, Galaxy group, galaxies: interactions, Radio telescopes, 010303 astronomy & astrophysics, Observations, Physics, Ecology, galaxies: groups: individual: HCG 44, Astrophysics::Instrumentation and Methods for Astrophysics, Atomic hydrogen, COLD GAS, environnement, ATOMIC GAS, HICKSON COMPACT-GROUPS, Order, Astrophysics - Instrumentation and Methods for Astrophysics, galaxies: evolution, environment, galaxies: ISM, colonne, FOS: Physical sciences, Astrophysics::Cosmology and Extragalactic Astrophysics, STAR-FORMATION, Radio telescope, Telescope, 0103 physical sciences, survey, GALAXY GROUPS, Nature and nurture, prospection, Instrumentation and Methods for Astrophysics (astro-ph.IM), Astrophysics::Galaxy Astrophysics, radio lines: galaxies, CLUSTER GALAXIES, 010308 nuclear & particles physics, Star formation, Order (ring theory), Astronomy, Astronomy and Astrophysics, Astrophysics - Astrophysics of Galaxies, NEUTRAL HYDROGEN, jeNne, Compact group, Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA), Adaptation (Biology), SKY SURVEY, Euthenics, Telescopes
Abstract

Extending deep observations of the neutral atomic hydrogen (HI) to the environment around galaxy groups can reveal a complex history of group interactions which is invisible to studies that focus on the stellar component. Hickson Compact Group 44 (HCG 44) is a nearby example and we have combined HI data from the Karoo Array Telescope, Westerbork Synthesis Radio Telescope, and Arecibo Legacy Fast ALFA survey, in order to achieve high column density sensitivity (N_HI < 2x10^18 cm^-2) to the neutral gas over a large field-of-view beyond the compact group itself. We find the giant HI tail north of HCG 44 contains 1.1x10^9 M_Sun of gas and extends 450 kpc from the compact group: twice as much mass and 33% further than previously detected. However, the additional gas is still unable to account for the known HI deficiency of HCG 44. The tail likely formed through a strong tidal interaction and HI clouds in the tail have survived for 1 Gyr or more after being stripped. This has important implications for understanding the survival of neutral clouds in the intragroup and circumgroup medium, and we discuss their survival in the context of simulations of cold gas in hot halos. HCG 44 is one of a growing number of galaxy groups found to have more extended HI in the intragroup and circumgroup medium than previously measured. Our results provide constraints for simulations on the properties of galaxy group halos, and reveal a glimpse of what will be seen by future powerful HI telescopes and surveys., 12 pages, 6 figures. Accepted for publication in MNRAS

Published
2016
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8. Early Observations of the MHONGOOSE Galaxies: Getting Ready for MeerKAT

Author

S. K. Sirothia, A. Sorgho, Claude Carignan, Sharmila Goedhart, Nickolas M. Pingel, S. S. Passmoor, Daniel J. Pisano, Amy Sardone, M. Korsaga, Tom Oosterloo, A. Dikgale, W. J. G. de Blok, Astronomy, Laboratoire d'Astrophysique de Marseille (LAM), and Aix Marseille Université (AMU)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)

Subjects
HIPASS CATALOG, NEWTONIAN DYNAMICS, NGC 7424, Dark matter, FOS: Physical sciences, Astrophysics, 01 natural sciences, dark matter, galaxies: individual: NGC 625, HI, law.invention, MASS MODELS, Telescope, IRREGULAR GALAXIES, surveys, law, 0103 physical sciences, IC 4951, 010303 astronomy & astrophysics, Galaxy rotation curve, ISM: kinematics and dynamics, Physics, NGC 7793, Spiral galaxy, 010308 nuclear & particles physics, CLOUDS, Sigma, Astronomy and Astrophysics, Astrophysics - Astrophysics of Galaxies, Galaxy, Accretion (astrophysics), NEUTRAL HYDROGEN, ESO 300-G014, [SDU]Sciences of the Universe [physics], techniques: interferometric, GAS, Space and Planetary Science, ROTATION CURVES, Astrophysics of Galaxies (astro-ph.GA), NGC 3621, Irregular galaxy, SPIRAL GALAXIES, galaxies: individual: NGC 625, ESO 300-G014, IC 4951, NGC 3621, NGC 7424, NGC 7793
Abstract

We present early observations of 20 galaxies in the MHONGOOSE survey galaxies using KAT-7, the GBT, and MeerKAT. We present the best calibrators for five of the MHONGOOSE galaxies observed with the KAT-7, and search for signs of gas accretion in the GBT data, down to $3\sigma$ column density levels of $\rm 2.2\times10^{18}\, cm^{-2}$ over a $\rm 20\, km\, s^{-1}$ linewidth, but identify none. Using the KAT-7 and MeerKAT data, we have derived rotation curves and mass models for NGC 3621 and NGC 7424 out to an unprecedented extent. As a precursor to the SKA, the MeerKAT telescope combines both a high spatial resolution and a large field of view, necessary to map the extended neutral hydrogen in local galaxies. The mass models of the two galaxies were constructed for both the Dark Matter (DM) models (the pseudo-isothermal model and the Navarro-Frenk-White model) and MOND. Overall, we find that the DM models provide a better fit than MOND to the galaxies' rotation curves. Furthermore, the pseudo-isothermal model is found to be the most consistent with the observations., Comment: 16 pages (+ 9 pages appendix), 16 figures. Accepted for publication in MNRAS

Published
2018

9. Revival of the Magnetar PSR J1622-4950:Observations with MeerKAT, Parkes, XMM-Newton, Swift, Chandra, and NuSTAR

Author

G C Du Toit, T. D. Abbott, A. J. T. Ramaila, P. S. Swart, P. Ntuli, G. de Bruin, Stephanie Smith, T. E. Monama, C. Stuart, Andrew Jameson, R. Spann, H. Kriel, N. Matthysen, J. Horrell, K. M. B. Asad, D. H. Botha, L. P. Williams, L. D. Mc Nally, R. T. Lord, A. Struthers, W. de Villiers, H. Niehaus, E. F. Bauermeister, John Sarkissian, B. Jordaan, R. Andreas, T. G. H. Bennett, J. P. Conradie, Riana Geschke, I. Wait, B. Ngcebetsha, A. van der Byl, Ben Stappers, A. Robyntjies, J. P. Jansen van Rensburg, N. Mabombo, D. H. Hoorn, A. Nzama, Bruce Merry, L. Sofeya, Sharmila Goedhart, L. R. S. Brederode, M. J. Hlakola, I. Rammala, O. Toruvanda, S. Rakoma, B. L. Fanaroff, A. Rust, A. Martens, M. G. Welz, Y. Padayachee, C. T. G. Schollar, S. J. Marais, B. Xaia, J. P. van Staden, F. Karels, T. Baloyi, B. de Swardt, I. Liebenberg, Vanessa A. Moss, A. L. Walker, C.G. Van der Merwe, W. S. New, E. C. Knox-Davies, R. Millenaar, P. Prozesky, L. J. du Toit, O. J. Mokone, K. Madisa, G. Sethosa, Griffin Foster, T. L. Grobler, Tom Alberts, S. S. Passmoor, F. Joubert, A. A. Patel, D. Koch, Ramesh Karuppusamy, L. Richter, Kshitij Thorat, O. Mahgoub, Jason Manley, C. Sharpe, M. J. Slabber, P. L. van der Merwe, S. Fataar, G. B. Taylor, M. Rasivhaga, P. Sunnylall, MacCalvin Kariseb, Gyula I. G. Józsa, A. R. Foley, N. Marais, M. A. Dikgale, J. P. Burger, C. Olyn, S. Paula, A. J. Otto, S. Ratcliffe, B. Pholoholo, R. Renil, T. Macdonald, Justin L. Jonas, R. van Rooyen, P. Scholz, Oleg Smirnov, B. H. Wallace, Fernando Camilo, A. Peens-Hough, S. Lamoor, F. Obies, L. Marais, T. J. Steyn, M. T. O. Ockards, O. Jacobs, C. Mjikelo, A. J. Tiplady, Roy Booth, D. Liebenberg, R. Strong, T. J. van Balla, P. C. van Niekerk, S. D. Matshawule, V. Van Tonder, C. de Waal, S. K. Sirothia, D. Rosekrans, R. M. Adam, L. Mafhungo, Matthew Bailes, G. Adams, P. P. A. Kotzé, D. M. Horn, S. Salie, M. S. de Villiers, Howard C. Reader, A. R. Isaacson, Dehann Fourie, B. Taljaard, C. de Villiers, A. F. Joubert, M. Serylak, T. Mauch, N. Sambu, Victoria M. Kaspi, C. C. Julius, N. Mnyandu, S. Seranyane, A. Krebs, Simon Johnston, N. Young, L. van den Heever, M. Manzini, R. van Wyk, M. Obrocka, N. Songqumase, T. W. Kusel, M. C. Mphego, J. A. Malan, I. P. T. Moeng, P. Malgas, K. J. Ngoasheng, B. M. Lunsky, L. C. Schwardt, M. Merryfield, W. van Straten, V. Thondikulam, B. Hugo, Nadeem Oozeer, Robert F. Archibald, P. Macfarlane, T. Cheetham, Aris Karastergiou, J. Conradie, D. Steyn, S. C. Gumede, S. Makhathini, S. W. P. Esterhuyse, N. Mkhabela, D. Booisen, R. P. M. Julie, Gianni Bernardi, L. Boyana, N. Kriek, Dirk I. L. de Villiers, T. Baxana, Cyril Tasse, M. Maree, Robert Lehmensiek, R. R. G. Gamatham, S. Zitha, D. E. Baker, K. Montshiwa, C. Magozore, Z. R. Ramudzuli, T. Gatsi, George Hobbs, S. J. Buchner, I. P. Theron, R. Siebrits, John Reynolds, A. Hokwana, F. Kapp, L. G. Magnus, V. A. Kasper, J. P. L. Main, J. van Aardt, David B. Davidson, ZAF, Unité Scientifique de la Station de Nançay (USN), Centre National de la Recherche Scientifique (CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO), Galaxies, Etoiles, Physique, Instrumentation (GEPI), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL), Université d'Orléans (UO)-Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, PSL Research University (PSL)-Centre National de la Recherche Scientifique (CNRS), and PSL Research University (PSL)-PSL Research University (PSL)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Swift, individual (PSR J16224950) [pulsars], 010504 meteorology & atmospheric sciences, Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, Magnetosphere, Flux, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Ephemeris, Magnetar, 01 natural sciences, general [pulsars], stars: neutron, stars: magnetars, neutron [stars], Pulsar, pulsars: general, 0103 physical sciences, magnetars [stars], 010303 astronomy & astrophysics, 0105 earth and related environmental sciences, computer.programming_language, High Energy Astrophysical Phenomena (astro-ph.HE), Physics, Quiescent state, Astronomy and Astrophysics, Neutron star, pulsars: individual, Space and Planetary Science, Astrophysics - High Energy Astrophysical Phenomena, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], computer
Abstract

New radio (MeerKAT and Parkes) and X-ray (XMM-Newton, Swift, Chandra, and NuSTAR) observations of PSR J1622-4950 indicate that the magnetar, in a quiescent state since at least early 2015, reactivated between 2017 March 19 and April 5. The radio flux density, while variable, is approximately 100x larger than during its dormant state. The X-ray flux one month after reactivation was at least 800x larger than during quiescence, and has been decaying exponentially on a 111+/-19 day timescale. This high-flux state, together with a radio-derived rotational ephemeris, enabled for the first time the detection of X-ray pulsations for this magnetar. At 5%, the 0.3-6 keV pulsed fraction is comparable to the smallest observed for magnetars. The overall pulsar geometry inferred from polarized radio emission appears to be broadly consistent with that determined 6-8 years earlier. However, rotating vector model fits suggest that we are now seeing radio emission from a different location in the magnetosphere than previously. This indicates a novel way in which radio emission from magnetars can differ from that of ordinary pulsars. The torque on the neutron star is varying rapidly and unsteadily, as is common for magnetars following outburst, having changed by a factor of 7 within six months of reactivation., Comment: Published in ApJ (2018 April 5); 13 pages, 4 figures

Published
2018

10. KAT-7 science verification

Author

Thomas H. Jarrett, Sharmila Goedhart, Claude Carignan, S. S. Passmoor, Kelley M. Hess, and Astronomy

Subjects
Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, 01 natural sciences, infrared: galaxies, 0103 physical sciences, Astrophysics::Solar and Stellar Astrophysics, Brightest cluster galaxy, 010303 astronomy & astrophysics, Galaxy cluster, Astrophysics::Galaxy Astrophysics, galaxies: kinematics and dynamics, Luminous infrared galaxy, Physics, radio lines: galaxies, 010308 nuclear & particles physics, Star formation, Astronomy, Astronomy and Astrophysics, galaxies: clusters: individual: Antlia Cluster, Astrophysics - Astrophysics of Galaxies, Galaxy, Accretion (astrophysics), Ram pressure, Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA), Elliptical galaxy, galaxies: distances and redshifts, galaxies: evolution
Abstract

The Antlia Cluster is a nearby, dynamically young structure, and its proximity provides a valuable opportunity for detailed study of galaxy and group accretion onto clusters. We present a deep HI mosaic completed as part of spectral line commissioning of the Karoo Array Telescope (KAT-7), and identify infrared counterparts from the WISE extended source catalog to study neutral atomic gas content and star formation within the cluster. We detect 37 cluster members out to a radius of ~0.9 Mpc with M_HI > 5x10^7 M_Sun. Of these, 35 are new HI detections, 27 do not have previous spectroscopic redshift measurements, and one is the Compton thick Seyfert II, NGC 3281, which we detect in HI absorption. The HI galaxies lie beyond the X-ray emitting region 200 kpc from the cluster center and have experienced ram pressure stripping out to at least 600 kpc. At larger radii, they are distributed asymmetrically suggesting accretion from surrounding filaments. Combining HI with optical redshifts, we perform a detailed dynamical analysis of the internal substructure, identify large infalling groups, and present the first compilation of the large scale distribution of HI, and star forming galaxies within the cluster. We find that elliptical galaxy NGC 3268 is at the center of the oldest substructure and argue that NGC 3258 and its companion population are more recent arrivals. Through the presence of HI and on-going star formation, we rank substructures with respect to their relative time since accretion onto Antlia., 22 pages, 12 figures. Accepted for publication in MNRAS

Published
2015

11. Engineering and science highlights of the KAT-7 radio telescope

Author

W. New, D. Rosekrans, Nadeem Oozeer, F. Curtolo, M. Fijalkowski, S. Seranyane, A. Rust, J. R. Manley, I. P. Theron, N. Marais, A. C. Schröder, P. A. Woudt, R. T. Lord, Sharmila Goedhart, M. S. de Villiers, R. P. M. Julie, B. L. Fanaroff, Rob Fender, G. Coreejes, L. Sofeya, Claude Carignan, D. S. Shepherd, R. Lehmensiek, L. P. Williams, S. J. Marais, O. J. Mokone, Jonathan T. L. Zwart, R. Springbok, P. Gibbs, I. Liebenberg, P. Prozesky, Vanessa A. Moss, J. Horrell, Justin L. Jonas, R. van Rooyen, D. H. Botha, Roy Booth, A. Martens, L. G. Magnus, M. G. Welz, L. Richter, J. A. Malan, Tom Alberts, A. J. Tiplady, S. Mthembu, M. Madlavana, P. P. A. Kotzé, J. Grobbelaar, L. van den Heever, A. Langman, Venkatasubramani L. Thondikulam, S. Rajan, K. Cloete, S. Tshongweni, A. Peens-Hough, P. C. van Niekerk, N. J. Young, P. Herselman, S. J. Buchner, A. L. Walker, P. Macfarlane, F. Kapp, R. P. Armstrong, R. Spann, A. Dikgale, Kelley M. Hess, L. J. du Toit, M. Wolleben, M. Maree, J. Ludick, S. S. Passmoor, R. Siebrits, S. Blose, T. Cheetham, D. George, R. Renil, G. D. Nicholson, L. C. Schwardt, B. S. Frank, P. S. Swart, A. Loots, S. W. P. Esterhuyse, S. Wakhaba, C. J. T. van der Merwe, C. Magozore, T. W. Kusel, S. Ratcliffe, R. C. Crida, S. C. Gumede, M. Serylak, A. R. Foley, H. Bester, J. D. B. L. Jordaan, L. Marais, D. M. Lucero, S. D. Cross, D. Liebenberg, A. Barta, A. B. Pińska, E. F. Bauermeister, Dehann Fourie, O. Toruvanda, N. Hoek, Research School of Earth Sciences, Australian National University ( ANU ), Estrato Research and Development Ltd, Interdisciplinary Centre for Security, Reliability and Trust [Luxembourg] ( SnT ), Université du Luxembourg ( Uni.lu ), Faculty of Science, Technology and Communication [Luxembourg] ( FSTC ), University of Luxembourg [Luxembourg], Département de Physique [Montréal], Université de Montréal, Department of Paediatric Endocrinology, Royal Victoria Infirmary, Institute of Human Genetics, Centre for Life, Newcastle University [Newcastle], Développement et Communication Chimique chez les Insectes ( DCCI ), Centre National de la Recherche Scientifique ( CNRS ) -Université de Bourgogne ( UB ) -AgroSup Dijon - Institut National Supérieur des Sciences Agronomiques, de l'Alimentation et de l'Environnement, Animal Demography Unit, University of Cape Town, University of Southampton (Southampton, UK), Institute of Physics, University of Silesia, Rapita Systems Ltd [York], Department of Medical Oncology, Royal Melbourne Hospital, Brain and Mind Institute, Ecole Polytechnique Fédérale de Lausanne ( EPFL ), Service d'Explorations fonctionnelles multidisciplinaires [CHU Tenon], CHU Tenon [APHP]-Assistance publique - Hôpitaux de Paris - AP-HP (FRANCE), Service d'urologie [Mondor], Assistance publique - Hôpitaux de Paris (AP-HP)-Hôpital Henri Mondor-Université Paris-Est Créteil Val-de-Marne - Paris 12 ( UPEC UP12 ), OMedical Oncology, Guy's and St Thomas' Hospital [London], Institute of Cardiovascular and Medical Sciences, Electrocardiology Section, University of Glasgow, Glasgow, United Kingdom, Department of Computer and Information Science [Trondheim], Norwegian University of Science and Technology [Trondheim] ( NTNU ), Bordeaux Imaging Center ( BIC ), Université de Bordeaux ( UB ) -Institut François Magendie-Institut National de la Santé et de la Recherche Médicale ( INSERM ) -Centre National de la Recherche Scientifique ( CNRS ), Laboratoire de l'Accélérateur Linéaire ( LAL ), Université Paris-Sud - Paris 11 ( UP11 ) -Institut National de Physique Nucléaire et de Physique des Particules du CNRS ( IN2P3 ) -Centre National de la Recherche Scientifique ( CNRS ), School of Mathematics [Birmingham], University of Birmingham [Birmingham], Institut für Spezielle Botanik und Funktionelle Biodiversität, University of Leipzig, German Aerospace Center ( DLR ), University of the Western Cape, Unité Scientifique de la Station de Nançay ( USN ), Institut national des sciences de l'Univers ( INSU - CNRS ) -Observatoire de Paris-Université d'Orléans ( UO ) -Centre National de la Recherche Scientifique ( CNRS ), Materials Laboratory Rand Afrikaans University, Rand Afrikaans University, Jodrell Bank Centre for Astrophysics, University of Manchester [Manchester], School of Physics & DST-NRF, University of the Witwatersrand, University of the Witwatersrand [Johannesburg] ( WITS ), University of Southampton, Unité Scientifique de la Station de Nançay (USN), Centre National de la Recherche Scientifique (CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO), Jodrell Bank Centre for Astrophysics (JBCA), University of the Witwatersrand [Johannesburg] (WITS), and Astronomy

Subjects
Cryogenic system, radio continuum: general, FOS: Physical sciences, 01 natural sciences, law.invention, Radio telescope, Telescope, Pulsar, law, 0103 physical sciences, Very-long-baseline interferometry, Aerospace engineering, Open architecture, instrumentation: interferometers, 010303 astronomy & astrophysics, Instrumentation and Methods for Astrophysics (astro-ph.IM), [ SDU.ASTR ] Sciences of the Universe [physics]/Astrophysics [astro-ph], Physics, Protocol data unit, 010308 nuclear & particles physics, business.industry, Astronomy, Astronomy and Astrophysics, [SDU.ASTR.IM]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Instrumentation and Methods for Astrophysic [astro-ph.IM], Space and Planetary Science, business, Astrophysics - Instrumentation and Methods for Astrophysics, radio lines: general, [ SDU ] Sciences of the Universe [physics]
Abstract

The construction of the seven-dish Karoo Array Telescope (KAT-7) array in the Karoo region of the Northern Cape in South Africa was intended primarily as an engineering prototype for technologies and techniques applicable to the MeerKAT telescope. This paper looks at the main engineering and scientific highlights from this effort, and discusses their applicability to both MeerKAT and other next-generation radio telescopes. In particular, we found that the composite dish surface works well, but it becomes complicated to fabricate for a dish lacking circular symmetry; the Stirling cycle cryogenic system with ion pump to achieve vacuum works but demands much higher maintenance than an equivalent Gifford-McMahon cycle system; the ROACH (Reconfigurable Open Architecture Computing Hardware)-based correlator with SPEAD (Streaming Protocol for Exchanging Astronomical Data) protocol data transfer works very well and KATCP (Karoo Array Telescope Control Protocol) control protocol has proven very flexible and convenient. KAT-7 has also been used for scientific observations where it has a niche in mapping low surface-brightness continuum sources, some extended H I haloes and OH masers in star-forming regions. It can also be used to monitor continuum source variability, observe pulsars, and make Very Long Baseline Interferometry observations.

Published
2016

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