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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. 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

3. 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

4. The 1.28 GHz MeerKAT DEEP2 Image

Author

K. M. B. Asad, T. E. Monama, E. F. Bauermeister, Bruce Merry, O. Toruvanda, S. J. Marais, B. M. Lunsky, L. C. Schwardt, H. Bester, H. Kriel, M. Geyer, S. February, B. H. Wallace, M. Serylak, S. N. Twum, N. Kriek, B. Taljaard, M. A. Dikgale-Mahlakoana, W. S. New, K. Madisa, R. M. Adam, Oleg Smirnov, S. Fataar, R. Millenaar, Z. R. Ramudzuli, S. Gounden, I. P. Theron, K. J. Ngoasheng, Z. B. Brits, J. Horrell, G. Stone, D. H. Botha, T. W. Kusel, B. Xaia, M. J. Hlakola, B. S. Frank, S. W. P. Esterhuyse, Jason Manley, James J. Condon, A. Robyntjies, J. A. Malan, Gyula I. G. Józsa, A. A. Patel, R. R. G. Gamatham, Justin L. Jonas, S. C. Gumede, R. Siebrits, A. J. T. Ramaila, M. T. O. Ockards, Nadeem Oozeer, J. P. Burger, A. Loots, M. A. Aldera, L. G. Magnus, R. P. M. Julie, B. L. Fanaroff, G. Fadana, Robert Lehmensiek, A. J. Otto, A. van der Byl, T. Mauch, T. J. van Balla, S. K. Sirothia, L. Sofeya, P. P. A. Kotzé, N. Mnyandu, M. S. de Villiers, T. Cheetham, J. S. Kenyon, R. Renil, J. M. Chalmers, Ian Heywood, A. M. Matthews, L. Richter, F. Kapp, S. Salie, A. R. Isaacson, I. P. T. Moeng, A. Peens-Hough, R. T. Lord, Dirk I. L. de Villiers, W. D. Cotton, V. A. Kasper, J. P. L. Main, Sharmila Goedhart, B. Hugo, L. P. Williams, C. Tasse, L. R. S. Brederode, A. Martens, M. G. Welz, S. J. Buchner, T. D. Abbott, Simon Perkins, M. C. Mphego, C.G. Van der Merwe, V. Van Tonder, C. T. G. Schollar, L. J. du Toit, Fernando Camilo, O. J. Mokone, A. J. Tiplady, T. G. H. Bennett, and B. Ngcebetsha

Subjects
Physics, 010504 meteorology & atmospheric sciences, Star formation, Image (category theory), Center (category theory), FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics, 01 natural sciences, Astrophysics - Astrophysics of Galaxies, Galaxy, Luminosity, law.invention, Radio telescope, Telescope, Space and Planetary Science, law, Astrophysics of Galaxies (astro-ph.GA), 0103 physical sciences, 010303 astronomy & astrophysics, 0105 earth and related environmental sciences, Luminosity function (astronomy)
Abstract

We present the confusion-limited 1.28 GHz MeerKAT DEEP2 image covering one $\approx 68'$ FWHM primary beam area with $7.6''$ FWHM resolution and $0.55 \pm 0.01$ $\mu$Jy/beam rms noise. Its J2000 center position $\alpha=04^h 13^m 26.4^s$, $\delta=-80^\circ 00' 00''$ was selected to minimize artifacts caused by bright sources. We introduce the new 64-element MeerKAT array and describe commissioning observations to measure the primary beam attenuation pattern, estimate telescope pointing errors, and pinpoint $(u,v)$ coordinate errors caused by offsets in frequency or time. We constructed a 1.4 GHz differential source count by combining a power-law count fit to the DEEP2 confusion $P(D)$ distribution from $0.25$ to $10$ $\mu$Jy with counts of individual DEEP2 sources between $10$ $\mu$Jy and $2.5$ mJy. Most sources fainter than $S \sim 100$ $\mu$Jy are distant star-forming galaxies obeying the FIR/radio correlation, and sources stronger than $0.25$ $\mu$Jy account for $\sim93\%$ of the radio background produced by star-forming galaxies. For the first time, the DEEP2 source count has reached the depth needed to reveal the majority of the star formation history of the universe. A pure luminosity evolution of the 1.4 GHz local luminosity function consistent with the Madau & Dickinson (2014) model for the evolution of star-forming galaxies based on UV and infrared data underpredicts our 1.4 GHz source count in the range $-5 \lesssim \log[S(\mathrm{Jy})] \lesssim -4$., Comment: 20 pages, 18 figures. Accepted for publication in ApJ

Published
2019
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5. 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

6. Characterization of Optical Frequency Transfer Over 154 km of Aerial Fiber

Author

David R. Gozzard, R. R. G. Gamatham, Keith Grainge, Bruce G. Wallace, and Sascha Schediwy

Subjects
Physics, Time delay and integration, Optical amplifier, Physics - Instrumentation and Detectors, business.industry, FOS: Physical sciences, Instrumentation and Detectors (physics.ins-det), 01 natural sciences, Stability (probability), Signal, Atomic and Molecular Physics, and Optics, 010309 optics, Optics, Polarization mode dispersion, 0103 physical sciences, Phase noise, Fiber, 010306 general physics, business, Astrophysics - Instrumentation and Methods for Astrophysics, Instrumentation and Methods for Astrophysics (astro-ph.IM), Noise (radio)
Abstract

We present measurements of the frequency transfer stability and analysis of the noise characteristics of an optical signal propagating over aerial suspended fiber links up to 153.6 km in length. The measured frequency transfer stability over these links is on the order of 10^-11 at an integration time of one second dropping to 10^-12 for integration times longer than 100 s. We show that wind-loading of the cable spans is the dominant source of short-timescale noise on the fiber links. We also report an attempt to stabilize the optical frequency transfer over these aerial links., 4 pages, submitted to Optics Letters

Published
2017

7. Square Kilometre Array: the radio telescope of the XXI century

Author

Siju Mammen, Vivek Mohile, R. R. G. Gamatham, David Hindley, Bo Wang, John Nicholls, Mark Tearle, Tim Gibbon, Praveen Diwakar, S. W. Amy, Jill Hammond, Neil Wingfield, Supriya Sharma, R. T. Schilizzi, Bruce G. Wallace, Althea Wilkinson, Richard Whitaker, Yicheng Guo, Tim Rayner, SwamI Natarajan, Domingos Barbosa, Simon Stobie, Rajesh Warange, Yashwant Gupta, Uli Horn, Richard Hughes-Jones, Samantha Lloyd, Michelle Hussey, Richard Oberland, Simon Garrington, Ralph Braddock, David R. Gozzard, Simeon Miteff, Murali Bommineni, Lijun Wang, Vishal Francis, Sascha Schediwy, Robert Gabrielczyk, J. A. Davis, Keith Grainge, Bassem Alachkar, Jaco Muller, Michael Pearson, Simon R. Gregory, and Paul Boven

Subjects
Physics, business.industry, media_common.quotation_subject, Big data, Astronomy, Astronomy and Astrophysics, Astrophysics, 01 natural sciences, Universe, Galaxy, law.invention, 010309 optics, Telescope, Radio telescope, Stars, Square kilometre array, Space and Planetary Science, law, 0103 physical sciences, Dark energy, business, 010303 astronomy & astrophysics, media_common
Abstract

The Square Kilometre Array (SKA) will be the world’s largest and most sensitive radio telescope. It will address fundamental unanswered questions about our Universe including how the first stars and galaxies formed after the Big Bang, how dark energy is accelerating the expansion of theUniverse, the role of magnetism in the cosmos, the nature of gravity, and the search for life beyond Earth. This project envisages the construction of 133 15-m antennas in South Africa and 131072 log-periodic antennas in Australia, together with the associated infrastructure in the two desert sites. In addition, the SKA is an exemplar Big Data project, with data rates of over 10 Tbps being transported from the telescope to HPC/HTC facilities.

Published
2017

8. MeerKAT time and frequency reference optical network: Preliminary design analysis

Author

F. Kapp, H. Kriel, S. Malan, Tim Gibbon, Andrew W. R. Leitch, Enoch K. Rotich Kipnoo, and R. R. G. Gamatham

Subjects
Clock signal, Computer science, precursor, optical fibre network, 02 engineering and technology, telescope, timing signals, 01 natural sciences, General Biochemistry, Genetics and Molecular Biology, law.invention, lcsh:Social Sciences, 010309 optics, Telescope, Amplitude modulation, 020210 optoelectronics & photonics, Link budget, law, 0103 physical sciences, Phase noise, 0202 electrical engineering, electronic engineering, information engineering, Electronic engineering, lcsh:Social sciences (General), lcsh:Science, lcsh:Science (General), Jitter, Distributed feedback laser, Astrophysics::Instrumentation and Methods for Astrophysics, phase noise, lcsh:H, General Earth and Planetary Sciences, lcsh:Q, lcsh:H1-99, General Agricultural and Biological Sciences, lcsh:Q1-390, Data transmission
Abstract

The MeerKAT telescope is a precursor to the Square Kilometre Array, which will rely on optical fibres to link the telescope receivers to a central processor point. The main aspects to consider for the fibre transport are astronomical data transmission as well as timing, monitoring and control. The astronomical data streams from individual dishes to a central building, while the clock signal is distributed from a central point to remote dishes in the telescope array. The MeerKAT telescope, for instance, demands highly accurate and stable clock distribution over up to 12 km of optical fibre to remote dishes. The clock distribution is required for digitisation of astronomical signals. Phase stability is thus critical both for short-term and long-term requirements. In this work, we focused on the short-term stability. Phase noise measurements were performed on optical transmitters used to distribute the clock signals so as to ascertain their contribution to the overall clock jitter of the system. A maximum jitter requirement of 130 fs for a 1.712-GHz clock signal for MeerKAT time and reference is achieved using a distributed feedback laser. We found that with optimised modulation depth, additional passive optical components in the link do not significantly degrade the phase noise response. A distributed feedback laser was proven to be a suitable optical source that will meet the performance and link budget requirements for the MeerKAT telescope. Significance: A distributed feedback laser is recommended for the design of the MeerKAT time and reference system as it is a suitable optical source that will meet the performance and link budget requirements.

Published
2017

9. Experimental characterization of the counter-propagating Raman polarization attraction

Author

Marco Santagiustina, Luca Palmieri, Fabrizio Chiarello, Andrea Galtarossa, and R. R. G. Gamatham

Subjects
Raman scattering, Optical amplifier, Materials science, business.industry, Single-mode optical fiber, Polarization mode dispersion, Physics::Optics, Polarization-maintaining optical fiber, Atomic and Molecular Physics, and Optics, Fiber optic amplifiers, symbols.namesake, Optics, Brillouin scattering, Fiber optic amplifiers, High power fibers, Optical fibers, Polarization mode dispersion, Raman scattering, High power fibers, symbols, Optical fibers, Coherent anti-Stokes Raman spectroscopy, Raman spectroscopy, business, Brillouin scattering, Photonic-crystal fiber
Abstract

Recently, fiber Raman amplifiers have proven to be effective in the all-optical control of the state of polarization of signals in single-mode telecommunications optical fibers. Previous works predicted the existence of a quantitative relationship between the achieved degree of polarization and the mean Raman gain. Here, we experimentally validate such a relationship in the case of counter-propagating Raman-based polarization attractors for different pump and signal powers and for different fiber link lengths.

Published
2012

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