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First M87 Event Horizon Telescope Results. III. Data Processing and Calibration
2019
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 μas, with characteristic sensitivity limits of ~1 mJy on baselines to ALMA and ~10 mJy on other baselines. The observations present challenges for existing data processing tools, arising from the rapid atmospheric phase fluctuations, …
GRB 050904 at redshift 6.3: observations of the oldest cosmic explosion after the Big Bang
2005
We present optical and near-infrared observations of the afterglow of the gamma-ray burst GRB 050904. We derive a photometric redshift z = 6.3, estimated from the presence of the Lyman break falling between the I and J filters. This is by far the most distant GRB known to date. Its isotropic-equivalent energy is 3.4x10^53 erg in the rest-frame 110-1100 keV energy band. Despite the high redshift, both the prompt and the afterglow emission are not peculiar with respect to other GRBs. We find a break in the J-band light curve at t_b = 2.6 +- 1.0 d (observer frame). If we assume this is the jet break, we derive a beaming-corrected energy E_gamma = (4-12)x10^51 erg. This limit shows that GRB 050…
First M87 Event Horizon Telescope Results. II. Array and Instrumentation
2019
The Event Horizon Telescope (EHT) is a very long baseline interferometry (VLBI) array that comprises millimeter- and submillimeter-wavelength telescopes separated by distances comparable to the diameter of the Earth. At a nominal operating wavelength of ~1.3 mm, EHT angular resolution (λ/D) is ~25 μas, which is sufficient to resolve nearby supermassive black hole candidates on spatial and temporal scales that correspond to their event horizons. With this capability, the EHT scientific goals are to probe general relativistic effects in the strong-field regime and to study accretion and relativistic jet formation near the black hole boundary. In this Letter we describe the system design of th…
First M87 Event Horizon Telescope Results. I. the Shadow of the Supermassive Black Hole
2019
When surrounded by a transparent emission region, black holes are expected to reveal a dark shadow caused by gravitational light bending and photon capture at the event horizon. To image and study this phenomenon, we have assembled the Event Horizon Telescope, a global very long baseline interferometry array observing at a wavelength of 1.3 mm. This allows us to reconstruct event-horizon-scale images of the supermassive black hole candidate in the center of the giant elliptical galaxy M87. We have resolved the central compact radio source as an asymmetric bright emission ring with a diameter of 42 ± 3 μas, which is circular and encompasses a central depression in brightness with a flux rati…
First M87 Event Horizon Telescope Results. VI. The Shadow and Mass of the Central Black Hole
2019
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 fro…
Evidence for “Celtic migrations”? Strontium isotope analysis at the early La Tène (LT B) cemeteries of Nebringen (Germany) and Monte Bibele (Italy)
2013
Abstract Strontium isotope analysis on human remains from the Iron Age (4th/3rd century BC) cemeteries of Nebringen, Germany and Monte Bibele, Italy were carried out to investigate the role of residential changes during the period of the historic “Celtic migrations”. From an archaeological perspective, the location of the cemeteries in the Celtic core (Nebringen) and expansion area (Monte Bibele), and the distinctive development of their material culture, suggest that the buried populations had differing mobility rates. On the contrary, the strontium results indicate that only few individuals were mobile or non-local. There is, however, a difference in variation of strontium isotope ratios …
Earliest evidence of Neolithic collective burials from Eastern Iberia: Radiocarbon dating at the archaeolgoical site of Les Llometes (Alicante, Spain)
2016
AbstractIn the Valencia region of Spain, the dominant use of natural caves for collective burials during the Late Neolithic and Chalcolithic periods has been documented. Collective burials are central to the hypothesis about social relationships in Copper Age societies from Iberia, and key to interpreting kinship-based societies. Les Llometes (Alcoi, Alicante) is one of the biggest collective burial sites existing in eastern Iberia. This article presents the direct14C dates on 25 skeletal remains at the site. The results indicate that the site was used as a burial place from the end of the 5th millennium cal BC until the end of the 4th millennium cal BC, and is a first milestone for future …
Ecological plant epigenetics: Evidence from model and non-model species, and the way forward
2017
Growing evidence shows that epigenetic mechanisms contribute to complex traits, with implications across many fields of biology. In plant ecology, recent studies have attempted to merge ecological experiments with epigenetic analyses to elucidate the contribution of epigenetics to plant phenotypes, stress responses, adaptation to habitat, and range distributions. While there has been some progress in revealing the role of epigenetics in ecological processes, studies with non-model species have so far been limited to describing broad patterns based on anonymous markers of DNA methylation. In contrast, studies with model species have benefited from powerful genomic resources, which contribute…
Cannibalism facilitates gigantism in a nine-spined stickleback (Pungitius pungitius) population
2016
Cannibalism is a taxonomically widespread phenomenon that can fundamentally affect the structure and stability of aquatic communities, including the emergence of a bimodal size distribution (“dwarfs” and “giants”) in fish populations. Emergence of giants could also be driven or facilitated by parasites that divert host resources from reproduction to growth. We studied the trophic ecology of giant nine-spined sticklebacks (Pungitius pungitius) in a Finnish pond to evaluate the hypotheses that gigantism in this population would be facilitated by cannibalism and/or parasitic infections by Schistocephalus pungitii cestode. Stomach content analyses revealed an initial ontogenetic dietary shift f…
Selection for multicomponent mimicry: equal feature salience and variation in preferred traits
2016
When should multiple traits on Batesian mimics be selected to resemble corresponding traits on model species? Here, we explore two possibilities. First, features of equal salience to predators may be used to categorize prey, selecting for multicomponent mimicry. Second, if different predators use single yet different traits to categorize prey, multicomponent mimicry may still be selected. We studied how blue tits categorized rewarding and unrewarding artificial prey items that are differentiated by a combination of two color dimensions. Many birds used both color dimensions to make decisions, and overall, the population selected for multicomponent mimicry. However, a subset of birds used on…