A. Fausti Neto - The DES Collaboration

A. Fausti Neto
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Name
A. Fausti Neto
Affiliation
The DES Collaboration
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Cosmology and Nongalactic Astrophysics (18)
 
Physics - Mesoscopic Systems and Quantum Hall Effect (11)
 
Astrophysics of Galaxies (9)
 
Physics - Materials Science (7)
 
High Energy Astrophysical Phenomena (4)
 
Mathematics - Complex Variables (3)
 
Instrumentation and Methods for Astrophysics (3)
 
Mathematics - Dynamical Systems (3)
 
Physics - Strongly Correlated Electrons (3)
 
Solar and Stellar Astrophysics (3)
 
Mathematics - Number Theory (2)
 
High Energy Physics - Phenomenology (1)
 
Mathematics - Classical Analysis and ODEs (1)
 
Mathematics - Differential Geometry (1)
 
Physics - Superconductivity (1)
 
Quantum Physics (1)
 
Mathematics - Algebraic Geometry (1)

Publications Authored By A. Fausti Neto

We use density functional theory to study intrinsic defects and oxygen related defects in indium selenide. We find that \ch{InSe} is prone to oxidation, but however not reacting with oxygen as strongly as phosphorene. The dominant intrinsic defects in \ch{In}-rich material are the \ch{In} interstitial, a shallow donor, and the \ch{Se} vacancy, which introduces deep traps. Read More

We introduce a new four-parameters sequence that simultaneously generalizes some well-known integer sequences, including Fibonacci, Padovan, Jacobsthatl, Pell, and Lucas numbers. Combinatorial interpretations are discussed and many identities for this general sequence are derived. As a consequence, a number of identities for Fibonacci, Lucas, Pell, Jacobsthal, Padovan, and Narayana numbers as well as some of their generalizations are obtained. Read More

We propose a novel model for including spin-orbit interactions in buckled two dimensional systems. Our results show that in such systems, intrinsic spin-orbit coupling leads to a formation of Dirac cones, similar to Rashba model. We explore the microscopic origins of this behaviour and confirm our results using DFT calculations. Read More

Chemically peculiar stars in dwarf galaxies provide a window for exploring the birth environment of stars with varying chemical enrichment. We present a chemical abundance analysis of the brightest star in the newly discovered ultra-faint dwarf galaxy candidate Tucana III. Because it is particularly bright for a star in an ultra-faint Milky Way satellite, we are able to measure the abundance of 28 elements, including 13 neutron-capture species. Read More

The extreme mechanical resilience of graphene and the peculiar coupling it hosts between lattice and electronic degrees of freedom have spawned a strong impetus towards strain-engineered graphene where, on the one hand, strain augments the richness of its phenomenology and makes possible new concepts for electronic devices and, on the other hand, where new and extreme physics might take place. Here, we demonstrate that the shape of substrates supporting graphene sheets can be optimized for approachable experiments where strain-induced pseudomagnetic fields (PMF) can be tailored by pressure for directionally selective electronic transmission and pinching-off of current flow down to the quantum channel limit. The Corbino-type layout explored here furthermore allows filtering of charge carriers according to valley and current direction, which can be used to inject or collect valley-polarized currents, thus realizing one of the basic elements required for valleytronics. Read More

We study the condition of spontaneously generating an excitonic mass gap due to Coulomb interaction between anisotropic Dirac fermions in an uniaxially strained graphene. The mass gap equation is realized as a self-consistent solution for the self-energy within Hartree-Fock mean-field and static random phase approximation. It depends not only on the momentum because of long-range nature of the interaction but also on the velocity anisotropy due to uniaxial strain. Read More

Measurements of the galaxy stellar mass function are crucial to understand the formation of galaxies in the Universe. In a hierarchical clustering paradigm it is plausible that there is a connection between the properties of galaxies and their environments. Evidence for environmental trends has been established in the local Universe. Read More

We report the discovery of a stellar over-density 8$^{\circ}$ north of the center of the Small Magellanic Cloud (Small Magellanic Cloud Northern Over-Density; SMCNOD) using data from the first two years of the Dark Energy Survey (DES) and the first year of the MAGellanic SatelLITEs Survey (MagLiteS). The SMCNOD is indistinguishable in age, metallicity and distance from the nearby SMC stars, being primarly composed of intermediate-age stars (6 Gyr, Z=0.001), with a small fraction of young stars (1 Gyr, Z=0. Read More

We search for excess gamma-ray emission coincident with the positions of confirmed and candidate Milky Way satellite galaxies using 6 years of data from the Fermi Large Area Telescope (LAT). Our sample of 45 stellar systems includes 28 kinematically confirmed dark-matter-dominated dwarf spheroidal galaxies (dSphs) and 17 recently discovered systems that have photometric characteristics consistent with the population of known dSphs. For each of these targets, the relative predicted gamma-ray flux due to dark matter annihilation is taken from kinematic analysis if available, and estimated from a distance-based scaling relation otherwise, assuming that the stellar systems are dark-matter-dominated dSphs. Read More

The physics of two-dimensional (2D) materials and heterostructures based on such crystals has been developing extremely fast. With new 2D materials, truly 2D physics has started to appear (e.g. Read More

The excitonic spectra of single layer GeS and GeSe are predicted by ab initio GW-Bethe Salpeter equation calculations. G 0 W 0 calculations for the band structures find a fundamental band gap of 2.85 eV for GeS and 1. Read More

We present a new list of irreducible components for the space of k-dimensional holomorphic foliations on $\mathbb P^{n}$, $n\geq3$, $k\ge2$. They are associated to pull-back of dimension one foliations on $\mathbb P^{n-k+1}$ by non-linear rational maps. Read More

To understand complex physics of a system with strong electron electron interactions, it is ideal to control and monitor its properties while tuning an external electric field applied to the system. Indeed, complete electric field control of many body states in strongly correlated electron systems is fundamental to the next generation of condensed matter research and devices. However, the material must be thin enough to avoid shielding of the electric field in bulk material. Read More

The correlation between active galactic nuclei (AGN) and environment provides important clues to AGN fueling and the relationship of black hole growth to galaxy evolution. In this paper, we analyze the fraction of galaxies in clusters hosting AGN as a function of redshift and cluster richness for X-ray detected AGN associated with clusters of galaxies in Dark Energy Survey (DES) Science Verification data. The present sample includes 33 AGN with L_X > 10^43 ergs s^-1 in non-central, host galaxies with luminosity greater than 0. Read More

2016Jun

We report the results of a Dark Energy Camera (DECam) optical follow-up of the gravitational wave (GW) event GW151226, discovered by the Advanced LIGO detectors. Our observations cover 28.8 deg$^2$ of the localization region in the $i$ and $z$ bands (containing 3% of the BAYESTAR localization probability), starting 10 hours after the event was announced and spanning four epochs at $2-24$ days after the GW detection. Read More

We conclusively show that the entanglement- and the mutual information-based measures of quantum non-Markovianity are inequivalent. To this aim, we first analytically solve the optimization problem in the definition of the entanglement-based measure for a two-level system. We demonstrate that the optimal initial bipartite state of the open system and the ancillary is always given by one of the Bell states for any one qubit dynamics. Read More

This paper is devoted to the study of codimension two holomorphic foliations and distributions. We prove the stability of complete intersection of codimension two distributions and foliations in the local case. Converserly we show the existence of codimension two foliations which are not contained in any codimension one foliation. Read More

We study the Sunyaev-Zel'dovich effect (SZE) signature in South Pole Telescope (SPT) data for an ensemble of 719 optically identified galaxy clusters selected from 124.6 deg$^2$ of the Dark Energy Survey (DES) science verification data, detecting a stacked SZE signal down to richness $\lambda\sim20$. The SZE signature is measured using matched-filtered maps of the 2500 deg$^2$ SPT-SZ survey at the positions of the DES clusters, and the degeneracy between SZE observable and matched-filter size is broken by adopting as priors SZE and optical mass-observable relations that are either calibrated using SPT selected clusters or through the Arnaud et al. Read More

Galaxies and their dark matter halos populate a complicated filamentary network around large, nearly empty regions known as cosmic voids. Cosmic voids are usually identified in spectroscopic galaxy surveys, where 3D information about the large-scale structure of the Universe is available. Although an increasing amount of photometric data is being produced, its potential for void studies is limited since photometric redshifts induce line-of-sight position errors of $\sim50$ Mpc/$h$ or more that can render many voids undetectable. Read More

Exfoliated black phosphorus has recently emerged as a new two-dimensional crystal that, due to its peculiar and anisotropic crystalline and electronic band structures, may have potentially important applications in electronics, optoelectronics and photonics. Despite the fact that the edges of layered crystals host a range of singular properties whose characterization and exploitation are of utmost importance for device development, the edges of black phosphorus remain poorly characterized. In this work, the atomic structure and the behavior of phonons near different black phosphorus edges are experimentally and theoretically studied using Raman spectroscopy and density functional theory calculations. Read More

In this paper, we study the topology of real analytic map-germs with isolated critical value $f: (\mathbb{R}^m,0) \to (\mathbb{R}^n,0)$, with $1 Read More

We prove that foliations on the projective plane admitting a Liouvillian first integral but not admitting a rational first integral always have invariant algebraic curves of degree comparatively small with respect to the degree of the foliation. We present a similar result for foliations with intermediate Kodaira dimension admitting a rational first integral. Read More

Point defects in the binary group-IV monochalcogenide monolayers of SnS, SnSe, GeS, GeSe are investigated using density-functional-theory calculations. Several stable configurations are found for oxygen defects, however we give evidence that these materials are less prone to oxidation than phosphorene, with which monochalcogenides are isoelectronic and share the same orthorhombic structure. Concurrent oxygen defects are expected to be vacancies and substitutional oxygen. Read More

We present galaxy-galaxy lensing results from 139 square degrees of Dark Energy Survey (DES) Science Verification (SV) data. Our lens sample consists of red galaxies, known as redMaGiC, which are specifically selected to have a low photometric redshift error and outlier rate. The lensing measurement has a total signal-to-noise of 29 over scales $0. Read More

2016Mar
Affiliations: 1The Dark Energy Survey Collaboration, 2The Dark Energy Survey Collaboration, 3The Dark Energy Survey Collaboration, 4The Dark Energy Survey Collaboration, 5The Dark Energy Survey Collaboration, 6The Dark Energy Survey Collaboration, 7The Dark Energy Survey Collaboration, 8The Dark Energy Survey Collaboration, 9The Dark Energy Survey Collaboration, 10The Dark Energy Survey Collaboration, 11The Dark Energy Survey Collaboration, 12The Dark Energy Survey Collaboration, 13The Dark Energy Survey Collaboration, 14The Dark Energy Survey Collaboration, 15The Dark Energy Survey Collaboration, 16The Dark Energy Survey Collaboration, 17The Dark Energy Survey Collaboration, 18The Dark Energy Survey Collaboration, 19The Dark Energy Survey Collaboration, 20The Dark Energy Survey Collaboration, 21The Dark Energy Survey Collaboration, 22The Dark Energy Survey Collaboration, 23The Dark Energy Survey Collaboration, 24The Dark Energy Survey Collaboration, 25The Dark Energy Survey Collaboration, 26The Dark Energy Survey Collaboration, 27The Dark Energy Survey Collaboration, 28The Dark Energy Survey Collaboration, 29The Dark Energy Survey Collaboration, 30The Dark Energy Survey Collaboration, 31The Dark Energy Survey Collaboration, 32The Dark Energy Survey Collaboration, 33The Dark Energy Survey Collaboration, 34The Dark Energy Survey Collaboration, 35The Dark Energy Survey Collaboration, 36The Dark Energy Survey Collaboration, 37The Dark Energy Survey Collaboration, 38The Dark Energy Survey Collaboration, 39The Dark Energy Survey Collaboration, 40The Dark Energy Survey Collaboration, 41The Dark Energy Survey Collaboration, 42The Dark Energy Survey Collaboration, 43The Dark Energy Survey Collaboration, 44The Dark Energy Survey Collaboration, 45The Dark Energy Survey Collaboration, 46The Dark Energy Survey Collaboration, 47The Dark Energy Survey Collaboration, 48The Dark Energy Survey Collaboration, 49The Dark Energy Survey Collaboration, 50The Dark Energy Survey Collaboration, 51The Dark Energy Survey Collaboration, 52The Dark Energy Survey Collaboration, 53The Dark Energy Survey Collaboration, 54The Dark Energy Survey Collaboration, 55The Dark Energy Survey Collaboration, 56The Dark Energy Survey Collaboration, 57The Dark Energy Survey Collaboration, 58The Dark Energy Survey Collaboration, 59The Dark Energy Survey Collaboration, 60The Dark Energy Survey Collaboration, 61The Dark Energy Survey Collaboration, 62The Dark Energy Survey Collaboration, 63The Dark Energy Survey Collaboration, 64The Dark Energy Survey Collaboration, 65The Dark Energy Survey Collaboration, 66The Dark Energy Survey Collaboration, 67The Dark Energy Survey Collaboration, 68The Dark Energy Survey Collaboration, 69The Dark Energy Survey Collaboration, 70The Dark Energy Survey Collaboration, 71The Dark Energy Survey Collaboration, 72The Dark Energy Survey Collaboration, 73The Dark Energy Survey Collaboration, 74The Dark Energy Survey Collaboration, 75The Dark Energy Survey Collaboration, 76The Dark Energy Survey Collaboration, 77The Dark Energy Survey Collaboration, 78The Dark Energy Survey Collaboration, 79The Dark Energy Survey Collaboration, 80The Dark Energy Survey Collaboration, 81The Dark Energy Survey Collaboration, 82The Dark Energy Survey Collaboration, 83The Dark Energy Survey Collaboration, 84The Dark Energy Survey Collaboration

Shear peak statistics has gained a lot of attention recently as a practical alternative to the two point statistics for constraining cosmological parameters. We perform a shear peak statistics analysis of the Dark Energy Survey (DES) Science Verification (SV) data, using weak gravitational lensing measurements from a 139 deg$^2$ field. We measure the abundance of peaks identified in aperture mass maps, as a function of their signal-to-noise ratio, in the signal-to-noise range $0<\mathcal S / \mathcal N<4$. Read More

Motivated by the emergence of materials with mean free paths on the order of microns, we propose a novel class of solid state radiation sources based on reimplementing classical vacuum tube designs in semiconductors. Using materials with small effective masses, these devices should be able to access the terahertz range. We analyze the DC and AC operation of the simplest such device, the cylindrical diode magnetron, using effective quantum models. Read More

We measure the correlation of galaxy lensing and cosmic microwave background lensing with a set of galaxies expected to trace the matter density field. The measurements are performed using pre-survey Dark Energy Survey (DES) Science Verification optical imaging data and millimeter-wave data from the 2500 square degree South Pole Telescope Sunyaev-Zel'dovich (SPT-SZ) survey. The two lensing-galaxy correlations are jointly fit to extract constraints on cosmological parameters, constraints on the redshift distribution of the lens galaxies, and constraints on the absolute shear calibration of DES galaxy lensing measurements. Read More

The interaction between two different materials can present novel phenomena that are quite different from the physical properties observed when each material stands alone. Strong electronic correlations, such as magnetism and superconductivity, can be produced as the result of enhanced Coulomb interactions between electrons. Two-dimensional materials are powerful candidates to search for the novel phenomena because of the easiness of arranging them and modifying their properties accordingly. Read More

The relation between unusual Mexican-hat band dispersion, ferromagnetism and ferroelasticity is investigated using a combination of analytical, first-principles and phenomenological methods. The class of material with Mexican-hat band edge is studied using the $\alpha$-SnO monolayer as a prototype. Such band edge causes a van Hove singularity diverging with $\frac{1}{\sqrt{E}}$, and in p-type material leads to spatial and/or time-reversal spontaneous symmetry breaking. Read More

Understanding magnetoresistance, the change in electrical resistance upon an external magnetic field, at the atomic level is of great interest both fundamentally and technologically. Graphene and other two-dimensional layered materials provide an unprecedented opportunity to explore magnetoresistance at its nascent stage of structural formation. Here, we report an extremely large local magnetoresistance of ~ 2,000% at 400 K and a non-local magnetoresistance of > 90,000% in 9 T at 300 K in few-layer graphene/boron-nitride heterostructures. Read More

In this paper we give a detailed proof that the Milnor fiber $X_t$ of an analytic complex isolated singularity function defined on a reduced $n$-equidimensional analytic complex space $X$ is a regular neighborhood of a polyhedron $P_t \subset X_t$ of real dimension $n-1$. Moreover, we describe the degeneration of $X_t$ onto the special fiber $X_0$, by giving a continuous collapsing map $\Psi_t: X_t \to X_0$ which sends $P_t$ to $\{0\}$ and which restricts to a homeomorphism $X_t \backslash P_t \to X_0 \backslash \{0\}$. Read More

We use first principles calculations to investigate the lattice properties of group-IV monochalcogenides. These include static dielectric permittivity, elastic and piezoelectric tensors. For the monolayer, it is found that the static permittivity, besides acquiring a dependence on the interlayer distance, is comparatively higher than in the 3D system. Read More

We analyze the problem of electronic transmission through different regions of a graphene sheet that are characterized by different types of connections between the Dirac points. These valley symmetry breaking Hamiltonians might arise from electronic self-interaction mediated by the dielectric environment of distinct parts of the substrate on which the graphene sheet is placed. We show that it is possible to have situations in which we can use these regions to select or filter states of one desired chirality. Read More

Strongly bound excitons confined in two-dimensional (2D) semiconductors are dipoles with a perfect in-plane orientation. In a vertical stack of semiconducting 2D crystals, such in-plane excitonic dipoles are expected to efficiently couple across van der Waals gap due to strong interlayer Coulomb interaction and exchange their energy. However, previous studies on heterobilayers of group 6 transition metal dichalcogenides (TMDs) found that the exciton decay dynamics is dominated by interlayer charge transfer (CT) processes. Read More

Tin (II) sulfide (SnS) is a layered mineral found in nature. In this paper, we study the two-dimensional form of this material using a combination of \emph{ab initio} calculation and $\mathbf{k}\cdot\mathbf{p}$ theory. In particular, we address the valley properties and the optical selection rules of 2D SnS. Read More

We report the discovery of eight new ultra-faint dwarf galaxy candidates in the second year of optical imaging data from the Dark Energy Survey (DES). Six of these candidates are detected at high confidence, while two lower-confidence candidates are identified in regions of non-uniform survey coverage. The new stellar systems are found by three independent automated search techniques and are identified as overdensities of stars, consistent with the isochrone and luminosity function of an old and metal-poor simple stellar population. Read More

The Dark Energy Survey (DES) is a 5000 sq. degree survey in the southern hemisphere, which is rapidly reducing the existing north-south asymmetry in the census of MW satellites and other stellar substructure. We use the first-year DES data down to previously unprobed photometric depths to search for stellar systems in the Galactic halo, therefore complementing the previous analysis of the same data carried out by our group earlier this year. Read More

2015Aug

We present spectroscopic confirmation of two new lensed quasars via data obtained at the 6.5m Magellan/Baade Telescope. The lens candidates have been selected from the Dark Energy Survey (DES) and WISE based on their multi-band photometry and extended morphology in DES images. Read More

We introduce redMaGiC, an automated algorithm for selecting Luminous Red Galaxies (LRGs). The algorithm was specifically developed to minimize photometric redshift uncertainties in photometric large-scale structure studies. redMaGiC achieves this by self-training the color-cuts necessary to produce a luminosity-thresholded LRG sample of constant comoving density. Read More

We measure the cross-correlation between the galaxy density in the Dark Energy Survey (DES) Science Verification data and the lensing of the cosmic microwave background (CMB) as reconstructed with the Planck satellite and the South Pole Telescope (SPT). When using the DES main galaxy sample over the full redshift range $0.2 < z < 1. Read More

2015Jul
Authors: The Dark Energy Survey Collaboration, T. Abbott, F. B. Abdalla, S. Allam, A. Amara, J. Annis, R. Armstrong, D. Bacon, M. Banerji, A. H. Bauer, E. Baxter, M. R. Becker, A. Benoit-Lévy, R. A. Bernstein, G. M. Bernstein, E. Bertin, J. Blazek, C. Bonnett, S. L. Bridle, D. Brooks, C. Bruderer, E. Buckley-Geer, D. L. Burke, M. T. Busha, D. Capozzi, A. Carnero Rosell, M. Carrasco Kind, J. Carretero, F. J. Castander, C. Chang, J. Clampitt, M. Crocce, C. E. Cunha, C. B. D'Andrea, L. N. da Costa, R. Das, D. L. DePoy, S. Desai, H. T. Diehl, J. P. Dietrich, S. Dodelson, P. Doel, A. Drlica-Wagner, G. Efstathiou, T. F. Eifler, B. Erickson, J. Estrada, A. E. Evrard, A. Fausti Neto, E. Fernandez, D. A. Finley, B. Flaugher, P. Fosalba, O. Friedrich, J. Frieman, C. Gangkofner, J. Garcia-Bellido, E. Gaztanaga, D. W. Gerdes, D. Gruen, R. A. Gruendl, G. Gutierrez, W. Hartley, M. Hirsch, K. Honscheid, E. M. Huff, B. Jain, D. J. James, M. Jarvis, T. Kacprzak, S. Kent, D. Kirk, E. Krause, A. Kravtsov, K. Kuehn, N. Kuropatkin, J. Kwan, O. Lahav, B. Leistedt, T. S. Li, M. Lima, H. Lin, N. MacCrann, M. March, J. L. Marshall, P. Martini, R. G. McMahon, P. Melchior, C. J. Miller, R. Miquel, J. J. Mohr, E. Neilsen, R. C. Nichol, A. Nicola, B. Nord, R. Ogando, A. Palmese, H. V. Peiris, A. A. Plazas, A. Refregier, N. Roe, A. K. Romer, A. Roodman, B. Rowe, E. S. Rykoff, C. Sabiu, I. Sadeh, M. Sako, S. Samuroff, C. Sánchez, E. Sanchez, H. Seo, I. Sevilla-Noarbe, E. Sheldon, R. C. Smith, M. Soares-Santos, F. Sobreira, E. Suchyta, M. E. C. Swanson, G. Tarle, J. Thaler, D. Thomas, M. A. Troxel, V. Vikram, A. R. Walker, R. H. Wechsler, J. Weller, Y. Zhang, J. Zuntz

We present the first constraints on cosmology from the Dark Energy Survey (DES), using weak lensing measurements from the preliminary Science Verification (SV) data. We use 139 square degrees of SV data, which is less than 3\% of the full DES survey area. Using cosmic shear 2-point measurements over three redshift bins we find $\sigma_8 (\Omega_{\rm m}/0. Read More

We present measurements of weak gravitational lensing cosmic shear two-point statistics using Dark Energy Survey Science Verification data. We demonstrate that our results are robust to the choice of shear measurement pipeline, either ngmix or im3shape, and robust to the choice of two-point statistic, including both real and Fourier-space statistics. Our results pass a suite of null tests including tests for B-mode contamination and direct tests for any dependence of the two-point functions on a set of 16 observing conditions and galaxy properties, such as seeing, airmass, galaxy color, galaxy magnitude, etc. Read More

We present weak lensing shear catalogues for 139 square degrees of data taken during the Science Verification (SV) time for the new Dark Energy Camera (DECam) being used for the Dark Energy Survey (DES). We describe our object selection, point spread function estimation and shear measurement procedures using two independent shear pipelines, IM3SHAPE and NGMIX, which produce catalogues of 2.12 million and 3. Read More

2015Jul

We present photometric redshift estimates for galaxies used in the weak lensing analysis of the Dark Energy Survey Science Verification (DES SV) data. Four model- or machine learning-based photometric redshift methods -- ANNZ2, BPZ calibrated against BCC-Ufig simulations, SkyNet, and TPZ -- are analysed. For training, calibration, and testing of these methods, we construct a catalogue of spectroscopically confirmed galaxies matched against DES SV data. Read More

Spatially-varying depth and characteristics of observing conditions, such as seeing, airmass, or sky background, are major sources of systematic uncertainties in modern galaxy survey analyses, in particular in deep multi-epoch surveys. We present a framework to extract and project these sources of systematics onto the sky, and apply it to the Dark Energy Survey (DES) to map the observing conditions of the Science Verification (SV) data. The resulting distributions and maps of sources of systematics are used in several analyses of DES SV to perform detailed null tests with the data, and also to incorporate systematics in survey simulations. Read More

We study the clustering of galaxies detected at $i<22.5$ in the Science Verification observations of the Dark Energy Survey (DES). Two-point correlation functions are measured using $2. Read More