First M87 Event Horizon Telescope Results. III. Data Processing and Calibration

We present the calibration and reduction of Event Horizon Telescope (EHT) 1.3 mm radio wavelength observations of the supermassive black hole candidate at the center of the radio galaxy M87 and the quasar 3C 279, taken during the 2017 April 5-11 observing campaign. These global very long baseline interferometric observations include for the first time the highly sensitive Atacama Large Millimeter/submillimeter Array (ALMA); reaching an angular resolution of 25 mu as, with characteristic sensitivity limits of similar to 1 mJy on baselines to ALMA and similar to 10 mJy on other baselines. The observations present challenges for existing data processing tools, arising from the rapid atmospheric phase fluctuations, wide recording bandwidth, and highly heterogeneous array. In response, we developed three independent pipelines for phase calibration and fringe detection, each tailored to the specific needs of the EHT. The final data products include calibrated total intensity amplitude and phase information. They are validated through a series of quality assurance tests that show consistency across pipelines and set limits on baseline systematic errors of 2% in amplitude and 1 degrees in phase. The M87 data reveal the presence of two nulls in correlated flux density at similar to 3.4 and similar to 8.3 G lambda and temporal evolution in closure quantities, indicating intrinsic variability of compact structure on a. timescale of days, or several light-crossing times for a. few billion solar-mass black hole. These measurements provide the first opportunity to image horizon-scale structure in M87.Academy of Finland [274477, 284495, 312496]; European Commission Framework Programme Horizon 2020 Research and Innovation action [731016]; Black Hole Initiative at Harvard University through John Templeton Foundation [60477]; Comision Nacional de Investigacion Cientifica y Tecnologica (CONICYT, Chile) [PIA ACT172033, Fondecyt 1171506, BASAL AFB-170002, ALMA-conicyt 31140007]; Consejo Nacional de Ciencia y Tecnologia (CONACYT, Mexico) [104497, 275201, 279006, 281692]; Direccion General de Asuntos del Personal Academico-Universidad Nacional Autonoma de Mexico (DGAPA-UNAM) [IN112417]; European Research Council Synergy Grant "BlackHoleCam: Imaging the Event Horizon of Black Holes" [610058]; Generalitat Valenciana postdoctoral grant [APOSTD/2018/177]; Gordon and Betty Moore Foundation [GBMF 947, GBMF-3561, GBMF-5278]; Japanese Government (Monbukagakusho: MEXT) Scholarship; Japan Society for the Promotion of Science (JSPS) [JP17J08829]; JSPS Overseas Research Fellowships; Key Research Program of Frontier Sciences, Chinese Academy of Sciences (CAS) [QYZDJ-SSW-SLH057, QYZDJ-SSW-SYS008]; Leverhulme Trust Early Career Research Fellowship; MEXT/JSPS KAKENHI [18KK0090, JP18K13594, JP18K03656, JP18H03721, 18K03709, 18H01245, 25120007]; MIT International Science and Technology Initiatives (MISTI) Funds; Ministry of Science and Technology (MOST) of Taiwan [105-2112-M-001-025-MY3, 106-2112-M-001-011, 106-2119-M-001-027, 107-2119-M-001-017, 107-2119-M-001-020, 107-2119-M-110-005]; National Aeronautics and Space Administration (NASA) [80NSSC17K0649]; National Key Research and Development Program of China [2016YFA0400704, 2016YFA0 400702]; National Science Foundation (NSF) [AST-0096454, AST-0352953, AST-0521233, AST-0705062, AST-0905844, AST-0922984, AST-1126433, AST-1140030, DGE-1144085, AST-1207704, AST-1207730]; Natural Science Foundation of China [11573051, 11633006, 11650110427, 10625314, 11721303, 11725312, 11873028, 11873073, U1531245, 11473010]; Natural Sciences and Engineering Research Council of Canada (NSERC); National Research Foundation of Korea [2015-R1D1A1A01056807, NRF-2015H1A2A1033752, NRF-2015H1D3A1066561]; Netherlands Organization for Scientific Research (NWO) VICI award [639.043.513]; Spinoza Prize [SPI 78-409]; Swedish Research Council [2017-00648]; Government of Canada through the Department of Innovation, Science and Economic Development Canada; Province of Ontario through the Ministry of Economic Development, Job Creation and Trade; Russian Science Foundation [17-12-01029]; Spanish Ministerio de Economia y Competitividad [AYA2015-63939-C2-1-P, AYA2016-80889-P]; US Department of Energy (USDOE) through the Los Alamos National Laboratory [89233218CNA000001]; Italian Ministero dell'Istruzione Universita e Ricerca through the grant Progetti Premiali 2012-iALMA [CUP C52I13000140001]; ALMA North America Development Fund; NSF [ACI-1548562, DBI-0735191, DBI-1265383, DBI-1743442]; Smithsonian Institution; Academia Sinica; National Key R&D Program of China [2017YFA0402700]; Science and Technologies Facility Council (UK); CNRS (Centre National de la Recherche Scientifique, France); MPG(Max-Planck-Gesellschaft, Germany); IGN (Instituto Geografico Nacional, Spain); State of Arizona; NSF Physics Frontier Center award [PHY-0114422]; Kavli Foundation; National Science Foundation [PLR-1248097]; NSF Physics Frontier Center [PHY-1125897]; Jansky Fellowship program of the National Radio Astronomy Observatory (NRAO); South African Radio Astronomy Observatory (SARAO), which is a facility of the National Research Foundation (NRF), an agency of the Department of Science and Technology (DST) of South Africa; State Agency for Research of the Spanish MCIU through the "Center of Excellence Severo Ochoa" award [SEV-2017-0709]; European Union' s Horizon 2020 research and innovation programme [730562 RadioNet]; GBMF [GBMF-947]; Compute Ontario; Calcul Quebec; Compute Canada; NSF; CyVerse; [Chandra TM6-17006X]; [AST-1207752]; [MRI-1228509]; [OPP-1248097]; [AST-1310896]; [AST-1312651]; [AST-1337663]; [AST-1440254]; [AST-1555365]; [AST-1715061]; [AST-1615796]; [AST-1716327]; [OISE-1743747]; [AST-1816420]; [AST-1614868]This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

Intermixing-Driven Surface and Bulk Ferromagnetism in the Quantum Anomalous Hall Candidate MnBi6Te10

The recent realizations of the quantum anomalous Hall effect (QAHE) in MnBi2Te4 and MnBi4Te7 benchmark the (MnBi2Te4)(Bi2Te3)n family as a promising hotbed for further QAHE improvements. The family owes its potential to its ferromagnetically (FM) ordered MnBi2Te4 septuple layers (SLs). However, the QAHE realization is complicated in MnBi2Te4 and MnBi4Te7 due to the substantial antiferromagnetic (AFM) coupling between the SLs. An FM state, advantageous for the QAHE, can be stabilized by interlacing the SLs with an increasing number n of Bi2Te3 quintuple layers (QLs). However, the mechanisms driving the FM state and the number of necessary QLs are not understood, and the surface magnetism remains obscure. Here, robust FM properties in MnBi6Te10 (n = 2) with Tc ≈ 12 K are demonstrated and their origin is established in the Mn/Bi intermixing phenomenon by a combined experimental and theoretical study. The measurements reveal a magnetically intact surface with a large magnetic moment, and with FM properties similar to the bulk. This investigation thus consolidates the MnBi6Te10 system as perspective for the QAHE at elevated temperatures

A VLBI receiving system for the South Pole Telescope

The Event Horizon Telescope (EHT) is a very-long-baseline interferometry (VLBI) experiment that aims to observe supermassive black holes with an angular resolution that is comparable to the event horizon scale. The South Pole occupies an important position in the array, greatly increasing its north-south extent and therefore its resolution. The South Pole Telescope (SPT) is a 10-meter diameter, millimeter-wavelength telescope equipped for bolometric observations of the cosmic microwave background. To enable VLBI observations with the SPT we have constructed a coherent signal chain suitable for the South Pole environment. The dual-frequency receiver incorporates state-of-the-art SIS mixers and is installed in the SPT receiver cabin. The VLBI signal chain also includes a recording system and reference frequency generator tied to a hydrogen maser. Here we describe the SPT VLBI system design in detail and present both the lab measurements and on-sky results.Comment: 14 pages, 11 figures, to appear in the Proceedings of the SPIE (SPIE Astronomical Telescopes + Instrumentation 2018; Millimeter, Submillimeter, and Far-Infrared Detectors and Instrumentation for Astronomy IX

“Deep drilling“ requires “surfing“

ISSN:2504 - 185

On computable numbers

ISSN:2504 - 185

Solving Mysteries and Outwitting Transitions : Investigating the Incommensurate Crystal Structures of AuIn and Sn3Sb2

This thesis introduces two new incommensurate alloys. AuIn shows variable amounts of modulation, depending on the measurement temperature. At 400°C the diffraction pattern shows diffuse scattering and a thallium iodide type Cmcm space group. The diffuse scattering condenses into first order satellites on cooling to 300°C and the space group transforms to the incommensurate C-1(α, β, γ)0. I.e. the structure is becoming more ordered. If the measurement temperature is lowered even further to room temperature, satellites up to third order can be found. However the space group and the network structure do not change. The second alloy Sn3Sb2 is a high temperature modification of stistaite, SnSb. It can only be accessed when a pre-grown crystal is mounted in a capillary, with an additional piece of tin and heated to a temperature of 250°C. This way a structure made of 7x7x7 NaCl-type clusters interleaved with single layers of Sn with the space group Xm-3m can be found. If only the pre-grown crystal is measured, be it room or elevated temperatures, the diffraction pattern shows a twinned SnSb structure, with parasitic $\beta$-Sn reflections. In the future, further structures that crystallize in the TlI structure will be investigated, to see if they behave similar to AuIn

Temperature Dependent in situ Studies of two Simple Structure Types Revealing Modulation : or the Art of Making Glitter

In the first part of this thesis, three intermetallic compounds are discussed, that were originally thought of as thallium iodide type compounds. Starting from small evidence that there is more than meets the eye, investigations began to find the true structure of AuIn. AuIn emerged to be modulated with various domain sizes over temperatures between room temperature and 400◦C, where at room temperature it shows satellite reflections up to third order that are fully replaced by diffuse scattering at 400◦C. While the atomic network is optically thesame at all temperatures, the space group changes from the incommensurate C-1(αβγ)0 at room temperature to Cmcm at 400◦C and the gold network appears as a Peierls type distorted version of the thallium network in TlI.In addition the alloys PdBi and PdPb were examined with PdBi showing a very similar behaviour to AuIn, i.e. showcasing various degrees of modulation between room temperature and 300◦C and Pd adopting a Peierls type distorted version of the thallium network in TlI. For PdPb only room temperature data was measured so far, which also shows promising features of a Peierls type distorted thallium network for Pd.The second part of the thesis addresses the alloy Sn3Sb2, which is a high temperature modification of stistaite, SnSb. Its structure can only be accessed in situ when a pre-grown crystal is mounted in a capillary with an additionalpiece of tin. This sample has to be heated to a temperature of 250◦C to enable the structural transition. If the sample is monitored by X-ray diffraction during the heating process, the decay of the -tin reflections and the upsurge of the ordered Sn3Sb2 can be witnessed. Resulting is a structure consisting of 7x7x7 NaCl-type clusters interleaved by single Sn layers, presenting the space group Xm-3m.These two parts are unified by both of them dealing with a simple structure type, which reveals modulation that can be studied in situ

Y₃Ru_2−x—A Representative of a Composite Modulated Family of Intermetallics

The compound Y3Ru2−x was synthesized from the elements and the structure was solved from single crystal synchrotron data. The high quality of the data allowed the determination of the incommensurate ordering of the compound, previously reported as disordered, with respect to the second subsystem. The compound crystallizes in the super space group X-3(00γ)0 with the q-vector axial along c*, q = 00γ, λ = 0.4276(7) and the centering vectors (1/3 2/3 0 1/3), (2/3 1/3 0 2/3)