92 research outputs found
Synthesis and in vitro evaluation of a multifunctional and surface-switchable nanoemulsion platform
We present a multifunctional nanoparticle platform that has targeting moieties shielded by a matrix metalloproteinase-2 (MMP2) cleavable PEG coating. Upon incubation with MMP2 this surface-switchable coating is removed and the targeting ligands become available for binding. The concept was evaluated in vitro using biotin and αvβ3-integrin-specific RGD-peptide functionalized nanoparticles.National Heart, Lung, and Blood InstituteNational Institutes of Health (U.S.) (Program of Excellence in Nanotechnology (PEN) Award Contract HHSN268201000045C
Synthesis and in vitro evaluation of a multifunctional and surface-switchable nanoemulsion platform
We present a multifunctional nanoparticle platform that has targeting moieties shielded by a matrix metalloproteinase-2 (MMP2) cleavable PEG coating. Upon incubation with MMP2 this surface-switchable coating is removed and the targeting ligands become available for binding. The concept was evaluated in vitro using the biotin and αvβ3-integrin-specific RGD-peptide functionalized nanoparticles
First M87 Event Horizon Telescope Results and the Role of ALMA
In April 2019, the Event Horizon Telescope (EHT) collaboration revealed the
first image of the candidate super-massive black hole (SMBH) at the centre of
the giant elliptical galaxy Messier 87 (M87). This event-horizon-scale image
shows a ring of glowing plasma with a dark patch at the centre, which is
interpreted as the shadow of the black hole. This breakthrough result, which
represents a powerful confirmation of Einstein's theory of gravity, or general
relativity, was made possible by assembling a global network of radio
telescopes operating at millimetre wavelengths that for the first time included
the Atacama Large Millimeter/ submillimeter Array (ALMA). The addition of ALMA
as an anchor station has enabled a giant leap forward by increasing the
sensitivity limits of the EHT by an order of magnitude, effectively turning it
into an imaging array. The published image demonstrates that it is now possible
to directly study the event horizon shadows of SMBHs via electromagnetic
radiation, thereby transforming this elusive frontier from a mathematical
concept into an astrophysical reality. The expansion of the array over the next
few years will include new stations on different continents - and eventually
satellites in space. This will provide progressively sharper and
higher-fidelity images of SMBH candidates, and potentially even movies of the
hot plasma orbiting around SMBHs. These improvements will shed light on the
processes of black hole accretion and jet formation on event-horizon scales,
thereby enabling more precise tests of general relativity in the truly strong
field regime.Comment: 11 pages + cover page, 6 figure
Monitoring the Morphology of M87* in 2009–2017 with the Event Horizon Telescope
The Event Horizon Telescope (EHT) has recently delivered the first resolved images of M87*, the supermassive black hole in the center of the M87 galaxy. These images were produced using 230 GHz observations performed in 2017 April. Additional observations are required to investigate the persistence of the primary image feature—a ring with azimuthal brightness asymmetry—and to quantify the image variability on event horizon scales. To address this need, we analyze M87* data collected with prototype EHT arrays in 2009, 2011, 2012, and 2013. While these observations do not contain enough information to produce images, they are sufficient to constrain simple geometric models. We develop a modeling approach based on the framework utilized for the 2017 EHT data analysis and validate our procedures using synthetic data. Applying the same approach to the observational data sets, we find the M87* morphology in 2009–2017 to be consistent with a persistent asymmetric ring of ~40 μas diameter. The position angle of the peak intensity varies in time. In particular, we find a significant difference between the position angle measured in 2013 and 2017. These variations are in broad agreement with predictions of a subset of general relativistic magnetohydrodynamic simulations. We show that quantifying the variability across multiple observational epochs has the potential to constrain the physical properties of the source, such as the accretion state or the black hole spin
First M87 Event Horizon Telescope Results. VI. The Shadow and Mass of the Central Black Hole
We present measurements of the properties of the central radio source in M87 using Event Horizon Telescope data obtained during the 2017 campaign. We develop and fit geometric crescent models (asymmetric rings with interior brightness depressions) using two independent sampling algorithms that consider distinct representations of the visibility data. We show that the crescent family of models is statistically preferred over other comparably complex geometric models that we explore. We calibrate the geometric model parameters using general relativistic magnetohydrodynamic (GRMHD) models of the emission region and estimate physical properties of the source. We further fit images generated from GRMHD models directly to the data. We compare the derived emission region and black hole parameters from these analyses with those recovered from reconstructed images. There is a remarkable consistency among all methods and data sets. We find that >50% of the total flux at arcsecond scales comes from near the horizon, and that the emission is dramatically suppressed interior to this region by a factor >10, providing direct evidence of the predicted shadow of a black hole. Across all methods, we measure a crescent diameter of 42 +/- 3 mu as and constrain its fractional width to b
First M87 Event Horizon Telescope Results. IV. Imaging the Central Supermassive Black Hole
We present the first Event Horizon Telescope (EHT) images of M87, using observations from April 2017 at 1.3 mm wavelength. These images show a prominent ring with a diameter of similar to 40 mu as, consistent with the size and shape of the lensed photon orbit encircling the "shadow" of a supermassive black hole. The ring is persistent across four observing nights and shows enhanced brightness in the south. To assess the reliability of these results, we implemented a two-stage imaging procedure. In the first stage, four teams, each blind to the others' work, produced images of M87 using both an established method (CLEAN) and a newer technique (regularized maximum likelihood). This stage allowed us to avoid shared human bias and to assess common features among independent reconstructions. In the second stage, we reconstructed synthetic data from a large survey of imaging parameters and then compared the results with the corresponding ground truth images. This stage allowed us to select parameters objectively to use when reconstructing images of M87. Across all tests in both stages, the ring diameter and asymmetry remained stable, insensitive to the choice of imaging technique. We describe the EHT imaging procedures, the primary image features in M87, and the dependence of these features on imaging assumptions
First M87 Event Horizon Telescope Results. VI. The Shadow and Mass of the Central Black Hole
We present measurements of the properties of the central radio source in M87 using Event Horizon Telescope data obtained during the 2017 campaign. We develop and fit geometric crescent models (asymmetric rings with interior brightness depressions) using two independent sampling algorithms that consider distinct representations of the visibility data. We show that the crescent family of models is statistically preferred over other comparably complex geometric models that we explore. We calibrate the geometric model parameters using general relativistic magnetohydrodynamic (GRMHD) models of the emission region and estimate physical properties of the source. We further fit images generated from GRMHD models directly to the data. We compare the derived emission region and black hole parameters from these analyses with those recovered from reconstructed images. There is a remarkable consistency among all methods and data sets. We find that >50% of the total flux at arcsecond scales comes from near the horizon, and that the emission is dramatically suppressed interior to this region by a factor >10, providing direct evidence of the predicted shadow of a black hole. Across all methods, we measure a crescent diameter of 42 +/- 3 mu as and constrain its fractional width to be <0.5. Associating the crescent feature with the emission surrounding the black hole shadow, we infer an angular gravitational radius of GM/Dc(2) = 3.8 +/- 0.4 mu as. Folding in a distance measurement of 16.8(-0.7)(+0.8) gives a black hole mass of M = 6.5. 0.2 vertical bar(stat) +/- 0.7 vertical bar(sys) x 10(9) M-circle dot. This measurement from lensed emission near the event horizon is consistent with the presence of a central Kerr black hole, as predicted by the general theory of relativity
The science case and challenges of space-borne sub-millimeter interferometry
Ultra-high angular resolution in astronomy has always been an important vehicle for making fundamental discoveries. Recent results in direct imaging of the vicinity of the supermassive black hole in the nucleus of the radio galaxy M87 by the millimeter VLBI system Event Horizon Telescope and various pioneering results of the Space VLBI mission RadioAstron provided new momentum in high angular resolution astrophysics. In both mentioned cases, the angular resolution reached the values of about 10–20 microarcseconds (0.05–0.1 nanoradian). Further developments towards at least an order of magnitude “sharper” values, at the level of 1 microarcsecond are dictated by the needs of advanced astrophysical studies. The paper emphasis that these higher values can only be achieved by placing millimeter and submillimeter wavelength interferometric systems in space. A concept of such the system, called Terahertz Exploration and Zooming-in for Astrophysics, has been proposed in the framework of the ESA Call for White Papers for the Voyage 2050 long term plan in 2019. In the current paper we present new science objectives for such the concept based on recent results in studies of active galactic nuclei and supermassive black holes. We also discuss several approaches for addressing technological challenges of creating a millimeter/sub-millimeter wavelength interferometric system in space. In particular, we consider a novel configuration of a space-borne millimeter/sub-millimeter antenna which might resolve several bottlenecks in creating large precise mechanical structures. The paper also presents an overview of prospective space-qualified technologies of low-noise analogue front-end instrumentation for millimeter/sub-millimeter telescopes. Data handling and processing instrumentation is another key technological component of a sub-millimeter Space VLBI system. Requirements and possible implementation options for this instrumentation are described as an extrapolation of the current state-of-the-art Earth-based VLBI data transport and processing instrumentation. The paper also briefly discusses approaches to the interferometric baseline state vector determination and synchronisation and heterodyning system. The technology-oriented sections of the paper do not aim at presenting a complete set of technological solutions for sub-millimeter (terahertz) space-borne interferometers. Rather, in combination with the original ESA Voyage 2050 White Paper, it sharpens the case for the next generation microarcsecond-level imaging instruments and provides starting points for further in-depth technology trade-off studies.</p
Event Horizon Telescope observations of the jet launching and collimation in Centaurus A
Very-long-baseline interferometry (VLBI) observations of active galactic nuclei at millimetre wavelengths have the power to reveal the launching and initial collimation region of extragalactic radio jets, down to 10–100 gravitational radii (rg ≡ GM/c2) scales in nearby sources. Centaurus A is the closest radio-loud source to Earth2. It bridges the gap in mass and accretion rate between the supermassive black holes (SMBHs) in Messier 87 and our Galactic Centre. A large southern declination of −43° has, however, prevented VLBI imaging of Centaurus A below a wavelength of 1 cm thus far. Here we show the millimetre VLBI image of the source, which we obtained with the Event Horizon Telescope at 228 GHz. Compared with previous observations, we image the jet of Centaurus A at a tenfold higher frequency and sixteen times sharper resolution and thereby probe sub-lightday structures. We reveal a highly collimated, asymmetrically edge-brightened jet as well as the fainter counterjet. We find that the source structure of Centaurus A resembles the jet in Messier 87 on ~500 rg scales remarkably well. Furthermore, we identify the location of Centaurus A’s SMBH with respect to its resolved jet core at a wavelength of 1.3 mm and conclude that the source’s event horizon shadow should be visible at terahertz frequencies. This location further supports the universal scale invariance of black holes over a wide range of masses.A.C. is an Einstein Fellow of the NASA Hubble Fellowship Program. J.P is an EACOA
fellow. Z.Y. is a UKRI Stephen Hawking Fellow. We thank the following organizations
and programmes: the Academy of Finland (projects 274477, 284495, 312496, 315721);
the Agencia Nacional de Investigación y Desarrollo (ANID), Chile via NCN19_058
(TITANs) and Fondecyt 3190878; the Alexander von Humboldt Stiftung; an Alfred P.
Sloan Research Fellowship; Allegro, the European ALMA Regional Centre node in the
Netherlands, the NL astronomy research network NOVA and the astronomy institutes
of the University of Amsterdam, Leiden University and Radboud University; the Black
Hole Initiative at Harvard University, through a grant (60477) from the John Templeton
Foundation; the China Scholarship Council; Consejo Nacional de Ciencia y Tecnología
(CONACYT, Mexico, projects U0004-246083, U0004-259839, F0003-272050, M0037-
279006, F0003-281692, 104497, 275201, 263356, 57265507); the Delaney Family via the Delaney Family John A. Wheeler Chair at Perimeter Institute; Dirección General
de Asuntos del Personal Académico-Universidad Nacional Autónoma de México
(DGAPA-UNAM, projects IN112417 and IN112820); the EACOA Fellowship of the
East Asia Core Observatories Association; the European Research Council Synergy
Grant “BlackHoleCam: Imaging the Event Horizon of Black Holes” (grant 610058);
the Generalitat Valenciana postdoctoral grant APOSTD/2018/177 and GenT Program
(project CIDEGENT/2018/021); MICINN Research Project PID2019-108995GB-C22;
the Gordon and Betty Moore Foundation (grants GBMF- 3561, GBMF-5278); the
Istituto Nazionale di Fisica Nucleare (INFN) sezione di Napoli, iniziative specifiche
TEONGRAV; the International Max Planck Research School for Astronomy and
Astrophysics at the Universities of Bonn and Cologne; Joint Princeton/Flatiron and
Joint Columbia/Flatiron Postdoctoral Fellowships, research at the Flatiron Institute is
supported by the Simons Foundation; the Japanese Government (Monbukagakusho:
MEXT) Scholarship; the Japan Society for the Promotion of Science (JSPS) Grant-in-Aid
for JSPS Research Fellowship (JP17J08829); the Key Research Program of Frontier
Sciences, Chinese Academy of Sciences (CAS, grants QYZDJ-SSW-SLH057, QYZDJSSWSYS008,
ZDBS-LY-SLH011).
We further thank the Leverhulme Trust Early Career Research Fellowship; the
Max-Planck-Gesellschaft (MPG); the Max Planck Partner Group of the MPG and
the CAS; the MEXT/JSPS KAKENHI (grants 18KK0090, JP18K13594, JP18K03656,
JP18H03721, 18K03709, 18H01245, JP19H01943, 25120007); the Malaysian
Fundamental Research Grant Scheme (FRGS) FRGS/1/2019/STG02/UM/02/6; the
MIT International Science and Technology Initiatives (MISTI) Funds; the 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, 108-2112-M-001-048, and 109-2124-M-001-005); the
National Aeronautics and Space Administration (NASA, Fermi Guest Investigator
grant 80NSSC20K1567, NASA Astrophysics Theory Program grant 80NSSC20K0527,
NASA grant NNX17AL82G, and Hubble Fellowship grant HST-HF2-51431.001-A
awarded by the Space Telescope Science Institute, which is operated by the Association
of Universities for Research in Astronomy, Inc., for NASA, under contract NAS5-
26555, and NASA NuSTAR award 80NSSC20K0645); the National Institute of Natural
Sciences (NINS) of Japan; the National Key Research and Development Program of
China (grant 2016YFA0400704, 2016YFA0400702); the National Science Foundation
(NSF, grants AST-0096454, AST-0352953, AST-0521233, AST-0705062, AST-0905844,
AST-0922984, AST-1126433, AST-1140030, DGE-1144085, AST-1207704, AST-
1207730, AST-1207752, MRI-1228509, OPP-1248097, AST-1310896, AST-1337663,
AST-1440254, AST-1555365, AST-1615796, AST-1715061, AST-1716327, AST-
1716536, OISE-1743747, AST-1816420, AST-1903847, AST-1935980, AST-2034306);
the Natural Science Foundation of China (grants 11573051, 11633006, 11650110427,
10625314, 11721303, 11725312, 11933007, 11991052, 11991053); a fellowship of
China Postdoctoral Science Foundation (2020M671266); the Natural Sciences and
Engineering Research Council of Canada (NSERC, including a Discovery Grant and
the NSERC Alexander Graham Bell Canada Graduate Scholarships-Doctoral Program);
the National Research Foundation of Korea (the Global PhD Fellowship Grant: grants
2014H1A2A1018695, NRF-2015H1A2A1033752, 2015- R1D1A1A01056807, the Korea
Research Fellowship Program: NRF-2015H1D3A1066561, Basic Research Support Grant
2019R1F1A1059721); the Netherlands Organization for Scientific Research (NWO)
VICI award (grant 639.043.513) and Spinoza Prize SPI 78-409; the New Scientific
Frontiers with Precision Radio Interferometry Fellowship awarded by the South African
Radio Astronomy Observatory (SARAO), which is a facility of the National Research
Foundation (NRF), an agency of the Department of Science and Innovation (DSI) of
South Africa; the South African Research Chairs Initiative of the Department of Science
and Innovation and National Research Foundation; the Onsala Space Observatory
(OSO) national infrastructure, for the provisioning of its facilities/observational support (OSO receives funding through the Swedish Research Council under grant 2017-
00648) the Perimeter Institute for Theoretical Physics (research at Perimeter Institute
is supported by the Government of Canada through the Department of Innovation,
Science and Economic Development and by the Province of Ontario through the
Ministry of Research, Innovation and Science); the Spanish Ministerio de Economía
y Competitividad (grants PGC2018-098915-B-C21, AYA2016-80889-P, PID2019-
108995GB-C21); the State Agency for Research of the Spanish MCIU through the ‘Center
of Excellence Severo Ochoa’ award for the Instituto de Astrofísica de Andalucía (SEV-
2017- 0709); the Toray Science Foundation; the Consejería de Economía, Conocimiento,
Empresas y Universidad of the Junta de Andalucía (grant P18-FR-1769), the Consejo
Superior de Investigaciones Científicas (grant 2019AEP112); the US Department of
Energy (US DOE) through the Los Alamos National Laboratory (operated by Triad
National Security, LLC, for the National Nuclear Security Administration of the US
DOE (Contract 89233218CNA000001); the European Union’s Horizon 2020 research
and innovation programme under grant agreement No 730562 RadioNet; ALMA North
America Development Fund; the Academia Sinica; Chandra TM6- 17006X and DD7-
18089X; the GenT Program (Generalitat Valenciana) Project CIDEGENT/2018/021.
This work used the Extreme Science and Engineering Discovery Environment
(XSEDE), supported by NSF grant ACI-1548562, and CyVerse, supported by NSF grants
DBI-0735191, DBI-1265383, and DBI-1743442. XSEDE Stampede2 resource at TACC
was allocated through TG-AST170024 and TG-AST080026N. XSEDE JetStream resource
at PTI and TACC was allocated through AST170028. The simulations were performed
in part on the SuperMUC cluster at the LRZ in Garching, on the LOEWE cluster in
CSC in Frankfurt, and on the HazelHen cluster at the HLRS in Stuttgart. This research was enabled in part by support provided by Compute Ontario (http://computeontario.
ca), Calcul Quebec (http://www.calculquebec.ca) and Compute Canada (http://www.
computecanada.ca). We thank the staff at the participating observatories, correlation
centres, and institutions for their enthusiastic support.
This paper makes use of the following ALMA data: ADS/JAO.ALMA#2016.1.01198.V.
ALMA is a partnership of the European Southern Observatory (ESO; Europe,
representing its member states), NSF, and National Institutes of Natural Sciences of Japan,
together with National Research Council (Canada), Ministry of Science and Technology
(MOST; Taiwan), Academia Sinica Institute of Astronomy and Astrophysics (ASIAA;
Taiwan), and Korea Astronomy and Space Science Institute (KASI; Republic of Korea), in
cooperation with the Republic of Chile. The Joint ALMA Observatory is operated by ESO,
Associated Universities, Inc. (AUI)/NRAO, and the National Astronomical Observatory of
Japan (NAOJ). The NRAO is a facility of the NSF operated under cooperative agreement
by AUI. APEX is a collaboration between the Max-Planck-Institut für Radioastronomie
(Germany), ESO, and the Onsala Space Observatory (Sweden). The SMA is a joint project
between the SAO and ASIAA and is funded by the Smithsonian Institution and the
Academia Sinica. The JCMT is operated by the East Asian Observatory on behalf of the
NAOJ, ASIAA, and KASI, as well as the Ministry of Finance of China, Chinese Academy
of Sciences, and the National Key R&D Program (No. 2017YFA0402700) of China.
Additional funding support for the JCMT is provided by the Science and Technologies
Facility Council (UK) and participating universities in the UK and Canada. The LMT is a
project operated by the Instituto Nacional de Astrófisica, Óptica, y Electrónica (Mexico)
and the University of Massachusetts at Amherst (USA), with financial support from
the Consejo Nacional de Ciencia y Tecnología and the National Science Foundation.
The IRAM 30-m telescope on Pico Veleta, Spain is operated by IRAM and supported
by CNRS (Centre National de la Recherche Scientifique, France), MPG (Max-Planck-
Gesellschaft, Germany) and IGN (Instituto Geográfico Nacional, Spain). The SMT is
operated by the Arizona Radio Observatory, a part of the Steward Observatory of the
University of Arizona, with financial support of operations from the State of Arizona and
financial support for instrumentation development from the NSF. The SPT is supported
by the National Science Foundation through grant PLR- 1248097. Partial support is also
provided by the NSF Physics Frontier Center grant PHY-1125897 to the Kavli Institute of
Cosmological Physics at the University of Chicago, the Kavli Foundation and the Gordon
and Betty Moore Foundation grant GBMF 947. The SPT hydrogen maser was provided
on loan from the GLT, courtesy of ASIAA. The EHTC has received generous donations
of FPGA chips from Xilinx Inc., under the Xilinx University Program. The EHTC has benefited from technology shared under open-source license by the Collaboration for
Astronomy Signal Processing and Electronics Research (CASPER). The EHT project is
grateful to T4Science and Microsemi for their assistance with Hydrogen Masers. This
research has made use of NASA’s Astrophysics Data System. We gratefully acknowledge
the support provided by the extended staff of the ALMA, both from the inception of the
ALMA Phasing Project through the observational campaigns of 2017 and 2018. We would
like to thank A. Deller and W. Brisken for EHT-specific support with the use of DiFX. We
acknowledge the significance that Maunakea, where the SMA and JCMT EHT stations are
located, has for the indigenous Hawaiian people.
The grants listed above collectively fund the Event Horizon Telescope project.http://www.nature.com/natureastronomyam2023Physic
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