Search results for "ODS"

Euclid preparation : XI. Mean redshift determination from galaxy redshift probabilities for cosmic shear tomography

2021

The analysis of weak gravitational lensing in wide-field imaging surveys is considered to be a major cosmological probe of dark energy. Our capacity to constrain the dark energy equation of state relies on an accurate knowledge of the galaxy mean redshift ⟨z⟩. We investigate the possibility of measuring ⟨z⟩ with an accuracy better than 0.002 (1 + z) in ten tomographic bins spanning the redshift interval 0.2  99.8%. The zPDF approach can also be successful if the zPDF is de-biased using a spectroscopic training sample. This approach requires deep imaging data but is weakly sensitive to spectroscopic redshift failures in the training sample. We improve the de-biasing method and confirm our fi…

Euclid preparation : XXII. Selection of quiescent galaxies from mock photometry using machine learning

2023

The Euclid Space Telescope will provide deep imaging at optical and near-infrared wavelengths, along with slitless near-infrared spectroscopy, across ~15 000deg2 of the sky. Euclid is expected to detect ~12 billion astronomical sources, facilitating new insights into cosmology, galaxy evolution, and various other topics. In order to optimally exploit the expected very large dataset, appropriate methods and software tools need to be developed. Here we present a novel machine-learning-based methodology for the selection of quiescent galaxies using broadband Euclid IE, YE, JE, and HE photometry, in combination with multi-wavelength photometry from other large surveys (e.g. the Rubin LSST). The…

Mass-Metallicity Relation from Cosmological Hydrodynamical Simulations and X-ray Observations of Galaxy Groups and Clusters

2018

Recent X-ray observations of galaxy clusters show that the distribution of intra-cluster medium (ICM) metallicity is remarkably uniform in space and time. In this paper, we analyse a large sample of simulated objects, from poor groups to rich clusters, to study the dependence of the metallicity and related quantities on the mass of the systems. The simulations are performed with an improved version of the Smoothed-Particle-Hydrodynamics \texttt{GADGET-3} code and consider various astrophysical processes including radiative cooling, metal enrichment and feedback from stars and active galactic nuclei (AGN). The scaling between the metallicity and the temperature obtained in the simulations ag…

The origin of ICM enrichment in the outskirts of present-day galaxy clusters from cosmological hydrodynamical simulations

2018

The uniformity of the intra-cluster medium (ICM) enrichment level in the outskirts of nearby galaxy clusters suggests that chemical elements were deposited and widely spread into the intergalactic medium before the cluster formation. This observational evidence is supported by numerical findings from cosmological hydrodynamical simulations, as presented in Biffi et al. (2017), including the effect of thermal feedback from active galactic nuclei. Here, we further investigate this picture, by tracing back in time the spatial origin and metallicity evolution of the gas residing at z=0 in the outskirts of simulated galaxy clusters. In these regions, we find a large distribution of iron abundanc…

Cosmological hydrodynamical simulations of galaxy clusters: X-ray scaling relations and their evolution

2018

We analyse cosmological hydrodynamical simulations of galaxy clusters to study the X-ray scaling relations between total masses and observable quantities such as X-ray luminosity, gas mass, X-ray temperature, and $Y_{X}$. Three sets of simulations are performed with an improved version of the smoothed particle hydrodynamics GADGET-3 code. These consider the following: non-radiative gas, star formation and stellar feedback, and the addition of feedback by active galactic nuclei (AGN). We select clusters with $M_{500} > 10^{14} M_{\odot} E(z)^{-1}$, mimicking the typical selection of Sunyaev-Zeldovich samples. This permits to have a mass range large enough to enable robust fitting of the r…

Is ram-pressure stripping an efficient mechanism to remove gas in galaxies?

2017

We study how the gas in a sample of galaxies (M* > 10e9 Msun) in clusters, obtained in a cosmological simulation, is affected by the interaction with the intra-cluster medium (ICM). The dynamical state of each elemental parcel of gas is studied using the total energy. At z ~ 2, the galaxies in the simulation are evenly distributed within clusters, moving later on towards more central locations. In this process, gas from the ICM is accreted and mixed with the gas in the galactic halo. Simultaneously, the interaction with the environment removes part of the gas. A characteristic stellar mass around M* ~ 10e10 Msun appears as a threshold marking two differentiated behaviours. Below this mas…

Soda noteikšana par vairākiem noziedzīgiem nodarījumiem

2018

Sodīšana ir atbilde uz personas izdarītu noziedzīgu nodarījumu. Personai, izdarot vairākus noziedzīgus nodarījumus, sods tiek noteikts, izanalizējot katru noziedzīgu nodarījumu atsevišķi, bet pēc tam, atsaucoties uz tiesību normas konkrētu daļu, tiek noteikts galīgais sods, pēc izdarīto noziedzīgo nodarījuma kopības. Sods tiek noteikts atbilstoši Krimināllikumam, lai īstenotu soda mērķi, proti, nodrošinātu sabiedrības drošību, panāktu taisnīgumu, sodītu vainīgo pesonu par tās izdarīto noziedzīgo nodarījumu, resocialzētu sodīto personu, kā arī, lai notiesātā persona, un arī citas personas ievērotu likumus, un atturētos no noziedzīgu nodarījumu izdarīšnas. Bakalaura darba temats ir “Soda note…

“Kun pääsee irti pulpetista, niin kummasti asiat menevät paremmin perille”: teachers' perspectives of effective teaching strategies for students with…

2015

Inklusiivinen opetus on yleistymässä suomalaisissa kouluissa myös vieraan kielen tunneilla. Oppilaiden hyvin erilaiset taitotasot luovat opettajalle haasteen toteuttaa kaikille sopivaa opetusta samassa tilassa. Lisäksi erilaiset oppimisvaikeudet tulisi ottaa huomioon opetusta suunniteltaessa ja toteuttaessa. Tämän tutkimuksen tarkoituksena oli selvittää laadullisen kyselytutkimuksen avulla suomalaisten vieraan kielen opettajien käyttämiä sekä tehokkaaksi kokemia opetusmenetelmiä. Tutkimuksen aineisto koostuu kyselytutkimuksen vastauksista. Kyselyyn vastasi 32 vieraan kielen opettajaa eri puolilta Suomea. Tuloksia verrattiin muutamaan tutkimuskirjallisuudessa yleisesti tehokkaaksi todettuun …

Assortment, but not knowledge of assortment, affects cooperation and individual success in human groups

2017

The success or failure of human collective action often depends on the cooperation tendencies of individuals in groups, and on the information that individuals have about each other's cooperativeness. However, it is unclear whether these two factors have an interactive effect on cooperation dynamics. Using a decision-making experiment, we confirm that groups comprising individuals with higher cooperation tendencies cooperate at a higher level than groups comprising individuals with low cooperation tendencies. Moreover, assorting individuals with similar cooperation tendency together affected behaviour so that the most cooperative individuals tended to cooperate more and the least cooperativ…

2015

The combination of local orientation collinearity and spatial frequency contrast in contour integration was studied in two experiments using a 2AFC contour detection and discrimination task. Target contours were defined by local orientation collinearity, spatial frequency contrast between contour and background elements, or both cues. Experiments differed in the source of spatial frequency contrast by manipulating the spatial frequency of either contour or background elements. Cue summation gains, defined as the performance benefit of double cue conditions over single cue conditions, were evaluated and tested against the predictions derived from probability summation and linear summation. S…