Search

We present version 1.0 of the cosmological simulation code $\rm{{\small CO}{{\small N}}{\small CEPT}}$, designed for simulations of large-scale structure formation. $\rm{{\small CO}{\rm{\small N}}{\small CEPT}}$ 1.0 contains a P3M gravity solver, with the short-range part implemented using a novel (sub)tiling strategy, coupled with individual and adaptive particle time-stepping. A primary objective of $\rm{{\small CO}{\rm{\small N}}{\small CEPT}}$ is ease of use. To this end, it has built-in initial condition generation and can produce output in the form of snapshots, power spectra, and direct visualizations. $\rm{{\small CO}{\rm{\small N}}{\small CEPT}}$ is the first massively parallel cosmological simulation code written in Python. Despite of this, excellent performance is obtained, even comparing favourably to other codes such as gadget at similar precision, in the case of low to moderate clustering. By means of power-spectrum comparisons we find extraordinary good agreement between $\rm{{\small CO}{\rm{\small N}}{\small CEPT}}$ 1.0 and gadget. At large and intermediate scales the codes agree to well below the per mille level, while the agreement at the smallest scales probed ($k \sim 13\ h\, {\rm Mpc}^{-1}$) is of the order of 1 per cent. The $\rm{{\small CO}{\rm{\small N}}{\small CEPT}}$ code is openly released and comes with a robust installation script as well as thorough documentation.

We perform a systematic study of the recently discovered Fundamental Plane of galaxy clusters (CFP) using ∼250 simulated clusters from The Three Hundred project, focusing on the stability of the plane against different temperature definitions and its dependence on the dynamical relaxation state of clusters. The CFP is characterized by T∝Mαsrβs⁠, defined with the gas temperature (T) and the characteristic halo scale radius and mass (rs and Ms) assuming a Navarro–Frenk–White halo description. We explore two definitions of weighted temperatures, namely mass-weighted and spectroscopic-like temperatures, in three radial ranges. The Three Hundred project clusters at z = 0 lie on a thin plane whose parameters (α, β) and dispersion (0.015–0.030 dex) depend on the gas temperature definition. The CFP for mass-weighted temperatures is closer to the virial equilibrium expectation (α = 1, β = −1) with a smaller dispersion. For gas temperatures measured within 500 h−1 kpc, the resulting CFP deviates the most from the virial expectation and shifts towards the similarity solution for a secondary infall model (α = 1.5, β = −2). Independently of the temperature definition, we find that clusters at z = 1 and relaxed clusters form a CFP similar to the virial expectation, unlike disturbed clusters exhibiting stronger evolution. Only systems formed over the last 4 Gyr present a CFP that is closer to the similarity solution. All these findings are compatible with the CFP obtained for a Cluster Lensing And Supernova survey with Hubble subsample excluding the hottest clusters with TX > 12 keV. © 2022 The Author(s)., LADG and KU acknowledge support from the Ministry of Science and Technology of Taiwan (grants MOST 106-2628-M-001-003-MY3 and MOST 109-2112-M-001-018-MY3) and from the Academia Sinica (grant AS-IA-107-M01). LADG thanks for financial support from the State Agency for Research of the Spanish MCIU through the ‘Center of Excellence Severo Ochoa’ award to the Instituto de Astrofísica de Andalucía (SEV-2017-0709), and to the PID2019-109067-GB100. EL receives support by contract ASI-INAF n.2017-14-H.0, whereas WC is supported by the European Research Council under grant number 670193 and by the STFC AGP grant ST/V000594/1 and further acknowledges the science research grants from the China Manned Space Project with no. CMS-CSST-2021-A01 and CMS-CSST-2021-B01. The authors are also grateful to Yutaka Fujita for sharing part of tables employed in his work, as well as the discussions carried out with him during this research, which contributed to improve this work. In addition, the authors thank the constructive and fruitful comments provided by the referee that helped to improve the content of this paper. This work has been made possible by The Three Hundred Collaboration. The simulations used in this paper have been performed in the MareNostrum Supercomputer at the Barcelona Supercomputing Center, thanks to CPU time granted by the Red Española de Supercomputación. As part of The Three Hundred Project, this work has received financial support from the European Union’s Horizon 2020 - Research and Innovation Framework Programme under the Marie Sklodowska-Curie Actions grant agreement number 734374, the LACEGAL project. For this research, we made use of multiple PYTHON packages, such as MATPLOTLIB (Hunter 2007), CORNER (Foreman-Mackey 2016), and NUMPY (Harris et al. 2020).

Within $��$CDM, dwarf galaxies like the Large Magellanic Cloud (LMC) are expected to host numerous dark matter subhalos, several of which should host faint dwarf companions. Recent Gaia proper motions confirm new members of the LMC-system in addition to the previously known SMC, including two classical dwarf galaxies ($M_\ast$ > $10^5$ M$_{\odot}$; Carina and Fornax) as well as several ultra-faint dwarfs (Car2, Car3, Hor1, and Hyd1). We use the Feedback In Realistic Environments (FIRE) simulations to study the dark and luminous (down to ultrafaint masses, $M_\ast$ ~ $6\times10^3$ M$_{\odot}$) substructure population of isolated LMC-mass hosts ($M_\text{200}$ = $1-3\times10^{11}$ M$_{\odot}$) and place the Gaia + DES results in a cosmological context. By comparing number counts of subhalos in simulations with and without baryons, we find that, within 0.2 $r_\text{200}$, LMC-mass hosts deplete ~30% of their substructure, significantly lower than the ~70% of substructure depleted by Milky Way (MW) mass hosts. For our highest resolution runs ($m_\text{bary}$ = 880 M$_{\odot}$), ~5-10 subhalos form galaxies with $M_\ast$ > $10^4$ M$_{\odot}$, in agreement with the 7 observationally inferred pre-infall LMC companions. However, we find steeper simulated luminosity functions than observed, hinting at observation incompleteness at the faint end. The predicted DM content for classical satellites in FIRE agrees with observed estimates for Carina and Fornax, supporting the case for an LMC association. We predict that tidal stripping within the LMC potential lowers the inner dark matter density of ultra faint companions of the LMC. Thus, in addition to their orbital consistency, the low densities of dwarfs Car2, Hyd1, and Hyd2 reinforce their likelihood of Magellanic association., 19 pages, 9 figures, 4 tables. Accepted for publication in MNRAS

This paper has gone through internal review by the DES collaboration. It has Fermilab preprint number 19-115-AE and DES publication number 13387. We acknowledge support from EU/FP7- ERC grant 615929. RCN would like to acknowledge support from STFC grant ST/N000688/1 and the Faculty of Technology at the University of Portsmouth. LG was funded by the European Union’s Horizon 2020 Framework Programme under the Marie Skłodowska- Curie grant agreement no. 839090. This work has been partially supported by the Spanish grant PGC2018-095317-B-C21 within the European Funds for Regional Development (FEDER). Funding for the DES Projects has been provided by the U.S. Department of Energy, the U.S. National Science Foundation, the Ministry of Science and Education of Spain, the Science and Technology Facilities Council of the United Kingdom, the Higher Education Funding Council for England, the National Center for Supercomputing Applications at the University of Illinois at Urbana-Champaign, the Kavli Institute of Cosmological Physics at the University of Chicago, the Center for Cosmology and Astro-Particle Physics at the Ohio State University, the Mitchell Institute for Fundamental Physics and Astronomy at Texas A&M University, Financiadora de Estudos e Projetos, Fundac¸ ˜ao Carlos Chagas Filho de Amparo `a Pesquisa do Estado do Rio de Janeiro, Conselho Nacional de Desenvolvimento Cient´ıfico e Tecnol´ogico and the Minist´erio da Ciˆencia, Tecnologia e Inovac¸ ˜ao, the Deutsche Forschungsgemeinschaft, and the Collaborating Institutions in the Dark Energy Survey. The Collaborating Institutions are Argonne National Laboratory, the University of California at Santa Cruz, the University of Cambridge, Centro de Investigaciones Energ´eticas, Medioambientales y Tecnol ´ogicas-Madrid, the University of Chicago, University College London, the DES-Brazil Consortium, the University of Edinburgh, the Eidgen¨ossische Technische Hochschule (ETH) Z¨urich, Fermi NationalAccelerator Laboratory, theUniversity of Illinois atUrbana- Champaign, the Institut de Ci`encies de l’Espai (IEEC/CSIC), the Institut de F´ısica d’Altes Energies, Lawrence Berkeley National Laboratory, the Ludwig-Maximilians Universit¨at M¨unchen and the associated Excellence Cluster Universe, the University of Michigan, the National Optical Astronomy Observatory, the University of Nottingham, The Ohio State University, the University of Pennsylvania, the University of Portsmouth, SLAC National Accelerator Laboratory, Stanford University, the University of Sussex, Texas A&M University, and the OzDES Membership Consortium. Based in part on observations at Cerro Tololo Inter-American Observatory, National Optical Astronomy Observatory, which is operated by the Association of Universities for Research in Astronomy (AURA) under a cooperative agreement with the National Science Foundation. The DES data management system is supported by the National Science Foundation under grant numbers AST-1138766 and AST-1536171. The DES participants from Spanish institutions are partially supported by MINECO under grants AYA2015- 71825, ESP2015-66861, FPA2015-68048, SEV-2016-0588, SEV- 2016-0597, and MDM-2015-0509, some of which include ERDF funds from the European Union. IFAE is partially funded by the CERCA program of the Generalitat de Catalunya. Research leading to these results has received funding from the European Research Council under the European Union Seventh Framework Programme (FP7/2007-2013) including ERC grant agreements 240672, 291329, and 306478.We acknowledge support from the Australian Research Council Centre of Excellence for All-skyAstrophysics (CAASTRO), through project number CE110001020, and the Brazilian Instituto Nacional de Ciˆencia e Tecnologia (INCT) e-Universe (CNPq grant 465376/2014-2). This paper has been authored by Fermi Research Alliance, LLC under Contract No.DE-AC02-07CH11359 with theU.S.Department of Energy, Office of Science, Office of High Energy Physics. The United States Government retains and the publisher, by accepting the paper for publication, acknowledges that the United States Government retains a non-exclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this paper, or allow others to do so, for United States Government purposes., We present the first Hubble diagram of superluminous supernovae (SLSNe) out to a redshift of two, together with constraints on the matter density, M, and the dark energy equation-of-state parameter, w(≡p/ρ). We build a sample of 20 cosmologically useful SLSNe I based on light curve and spectroscopy quality cuts. We confirm the robustness of the peak–decline SLSN I standardization relation with a larger data set and improved fitting techniques than previous works. We then solve the SLSN model based on the above standardization via minimization of the χ2 computed from a covariance matrix that includes statistical and systematic uncertainties. For a spatially flat cold dark matter ( CDM) cosmological model, we find M = 0.38+0.24 −0.19, with an rms of 0.27 mag for the residuals of the distance moduli. For a w0waCDM cosmological model, the addition of SLSNe I to a ‘baseline’ measurement consisting of Planck temperature together with Type Ia supernovae, results in a small improvement in the constraints of w0 and wa of 4 per cent.We present simulations of future surveys with 868 and 492 SLSNe I (depending on the configuration used) and show that such a sample can deliver cosmological constraints in a flat CDM model with the same precision (considering only statistical uncertainties) as current surveys that use Type Ia supernovae, while providing a factor of 2–3 improvement in the precision of the constraints on the time variation of dark energy, w0 and wa. This paper represents the proof of concept for superluminous supernova cosmology, and demonstrates they can provide an independent test of cosmology in the high-redshift (z > 1) universe., EU/FP7-ERC grant 615929, STFC grant ST/N000688/1, Faculty of Technology at the University of Portsmouth, European Union’s Horizon 2020 Framework Programme under the Marie Skłodowska- Curie grant agreement no. 839090, Spanish grant PGC2018-095317-B-C21 within the European Funds for Regional Development (FEDER), U.S. Department of Energy, U.S. National Science Foundation, Ministry of Science and Education of Spain, Science and Technology Facilities Council of the United Kingdom, Higher Education Funding Council for England, National Center for Supercomputing Applications at the University of Illinois at Urbana-Champaign, Kavli Institute of Cosmological Physics at the University of Chicago, Center for Cosmology and Astro-Particle Physics at the Ohio State University, Mitchell Institute for Fundamental Physics and Astronomy at Texas A&M University, Financiadora de Estudos e Projetos, Fundacão Carlos Chagas Filho de Amparo `a Pesquisa do Estado do Rio de Janeiro, Conselho Nacional de Desenvolvimento Científico e Tecnológico and the Ministério da Ciencia, Tecnologia e Inovacão, Deutsche Forschungsgemeinschaft, Collaborating Institutions in the Dark Energy Survey., National Science Foundation under grant numbers AST-1138766 and AST-1536171., T MINECO under grants AYA2015- 71825, ESP2015-66861, FPA2015-68048, SEV-2016-0588, SEV- 2016-0597, and MDM-2015-0509, some of which include ERDF funds from the European Union., CERCA program of the Generalitat de Catalunya., European Research Council under the European Union Seventh Framework Programme (FP7/2007-2013) including ERC grant agreements 240672, 291329, and 306478., Australian Research Council Centre of Excellence for All-skyAstrophysics (CAASTRO), through project number CE110001020, Brazilian Instituto Nacional de Ciˆencia e Tecnologia (INCT) e-Universe (CNPq grant 465376/2014-2), Fermi Research Alliance, LLC under Contract No.DE-AC02-07CH11359 with theU.S.Department of Energy, Office of Science, Office of High Energy Physics

Cosmological simulations are a powerful tool to test various cosmological and galaxy formation scenarios. The discovery of low surface brightness objects has been a challenge for both of these fields. Our work aims to create a fully reproducible pipeline to generate a realistic dark matter halo catalog with corresponding information on galaxy formation and evolution.

Primordial black holes formed through the collapse of cosmological density fluctuations have been hypothesised as contributors to the dark matter content of the Universe. At the same time, their mergers could contribute to the recently observed population of gravitational-wave sources. We investigate the scenario in which primordial black holes form binaries at late times in the Universe. Specifically, we re-examine the mergers of primordial black holes in small clusters of ~30 objects in the absence of initial binaries. Binaries form dynamically through Newtonian gravitational interactions. These binaries act as heat sources for the cluster, increasing the cluster's velocity dispersion, which inhibits direct mergers through gravitational-wave two-body captures. Meanwhile, three-body encounters of tight binaries are too rare to tighten binaries sufficiently to allow them to merge through gravitational-wave emission. We conclude that in the absence of initial binaries, merger rates of primordial black holes in the Bird et al. (2016) initial cluster configuration are at least an order of magnitude lower than previously suggested, which makes gravitational-wave detections of such sources improbable., Comment: 8 pages, 4 figures

We investigate the relationship of kinematically misaligned galaxies with their large-scale environment, in the context of halo assembly bias. According to numerical simulations, halo age at fixed halo mass is intrinsically linked to the large-scale tidal environment created by the cosmic web. We investigate the relationship between distances to various cosmic web features and present-time gas accretion rate. We select a sub-sample of ~900 central galaxies from the MaNGA survey with defined global position angles (PA; angle at which velocity change is greatest) for their stellar and H$\alpha$ gas components up to a minimum of 1.5 effective radii ($R_e$). We split the sample by misalignment between the gas and stars as defined by the difference in their PA. For each central galaxy we find its distance to nodes and filaments within the cosmic web, and estimate the host halo's age using the central stellar mass to total halo mass ratio $M_{*}/M_{h}$. We also construct halo occupation distributions using a background subtraction technique for galaxy groups split using the central galaxy's kinematic misalignment. We find, at fixed halo mass, no statistical difference in these properties between our kinematically aligned and misaligned galaxies. We suggest that the lack of correlation could be indicative of cooling flows from the hot halo playing a far larger role than `cold mode' accretion from the cosmic web or a demonstration that the spatial extent of current large-scale integral field unit (IFU) surveys hold little information about large-scale environment extractable through this method., Comment: 19 pages, 12 figures. Accepted in MNRAS

Publisher's version (útgefin grein), We use the IllustrisTNG (TNG) cosmological simulations to provide theoretical expectations for the dark matter mass fractions (DMFs) and circular velocity profiles of galaxies. TNG predicts flat circular velocity curves for z = 0 Milky Way (MW)-like galaxies beyond a few kpc from the galaxy centre, in better agreement with observational constraints than its predecessor, Illustris. TNG also predicts an enhancement of the dark matter mass within the 3D stellar half-mass radius (⁠rhalf⁠; M200c=1010−1013M⊙⁠, z ≤ 2) compared to its dark matter only and Illustris counterparts. This enhancement leads TNG present-day galaxies to be dominated by dark matter within their inner regions, with fDM(, MRL is supported by a COFUND/Durham Junior Research Fellowship under EU grant 609412. MRL acknowledges support by a Grant of Excellence from the Icelandic Research Fund (grant number 173929-051). VS, RP, and RW acknowledge support through the European Research Council under ERC-StG grant EXAGAL-308037, and would like to thank the Klaus Tschira Foundation. The Flatiron Institute is supported by the Simons Foundation.

We study projected underdensities in the cosmic galaxy density field known as 'troughs', and their overdense counterparts, which we call 'ridges'. We identify these regions using a bright sample of foreground galaxies from the photometric Kilo-Degree Survey (KiDS), specifically selected to mimic the spectroscopic Galaxy And Mass Assembly survey (GAMA). Using background galaxies from KiDS, we measure the weak gravitational lensing profiles of the troughs/ridges. We quantify the amplitude of their lensing strength $A$ as a function of galaxy density percentile rank $P$ and galaxy overdensity $\delta$, and find that the skewness in the galaxy density distribution is reflected in the total mass distribution measured by weak lensing. We interpret our results using the mock galaxy catalogue from the Marenostrum Institut de Ci\`encies de l'Espai (MICE) simulation, and find a good agreement with our observations. Using signal-to-noise weights derived from the Scinet LIghtCone Simulations (SLICS) mock catalogue we optimally stack the lensing signal of KiDS troughs with an angular radius $\theta_A$ = {5,10,15,20} arcmin, resulting in {16.8,14.9,10.13,7.55} $\sigma$ detections. Finally, we select troughs using a volume-limited sample of galaxies, split into two redshift bins between 0.1 < z < 0.3. For troughs/ridges with transverse comoving radius $R_A$ = 1.9 Mpc/h, we find no significant difference in the comoving Excess Surface Density as a function of $P$ and $\delta$ between the low- and high-redshift sample. Using the MICE and SLICS mocks we predict that trough and ridge evolution could be detected with gravitational lensing using deeper and wider lensing surveys, such as those from the Large Synoptic Survey Telescope and Euclid., Comment: 23 pages, 15 figures, 2 tables; published in MNRAS

We have recently introduced a new model for the distribution of dark matter (DM) in galaxies based on a self-gravitating system of massive fermions at finite temperatures, the Ruffini–Argü elles–Rueda (RAR) model. We show that this model, for fermion masses in the keV range, explains the DM halo of the Galaxy and predicts the existence of a denser quantum core at the center. We demonstrate here that the introduction of a cutoff in the fermion phase-space distribution, necessary to account for the finite Galaxy size, defines a new solution with a central core which represents an alternative to the black hole (BH) scenario for SgrA*. For a fermion mass in the range mc2=48–345 keV, the DM halo distribution is in agreement with the Milky Way rotation curve data, while harbors a dense quantum core of about 4×106M⊙ within the S2-star pericenter., Instituto de Astrofísica de La Plata, Consejo Nacional de Investigaciones Científicas y Técnicas

The expansion of the Universe is not homogeneous. In the Local Group (LG), Andromeda (M31) is approaching the Milky Way (MW) at ~110 km/s. To turn around the cosmic expansion locally to this extent, their combined mass must lie in a narrow range of values. This constrains the gravitational field in the LG. I will describe recent calculations (arXiv:1506.07569) solving test particle trajectories in this gravitational field. The major perturber to the LG, Centaurus A, is directly included in our model. Final radial velocities (RVs) are compared with observed RVs of LG dwarf galaxies. We find a major discrepancy for all plausible initial MW and M31 masses. Although few objects have RVs much below the predictions of the best-fitting model, some have RVs much above them, by as much as 110 km/s. We find that these galaxies tend to lie within a plane. This plane aligns closely with the planes of satellite galaxies recently discovered around M31 and the MW. We suggest that the observations can be explained by a past flyby encounter between these galaxies. This doesn't arise in LCDM but does in MOND. In this context, a simple calculation suggests that their planes of satellites can be formed tidally with their observed orientations only if the MW and M31 orbit within a particular plane. Our analysis of much more distant non-satellite galaxies with anomalously high RVs implies they prefer a very similar plane. The flyby time implied by the positions and velocities of these galaxies (∼9 Gyr ago) roughly agrees with the time expected from a MOND calculation of the MW–M31 orbit. Interestingly, the velocity dispersion of the MW's disk increased suddenly at around this time, forming its thick disk. Postprint

© 2017 by the authors. With the upcoming release of the Gaia catalog and the many multiplexed spectroscopic surveys on the horizon, we are rapidly moving into a new data-driven era in the study of the Milky Way's stellar halo. When combined, these data sets will give us a many-dimensional view of stars in accreted structures in the halo that includes both dynamical information about their orbits and chemical information about their formation histories. Using simulated data from the state-of-the-art Latte simulations of Milky-Way-like galaxies, which include hydrodynamics, feedback, and chemical evolution in a cosmological setting, we demonstrate that while dynamical information alone can be used to constrain models of the Galactic mass distribution in the halo, including the extra dimensions provided by chemical abundances can improve these constraints as well as assist in untangling different accreted components.

We present a temperature map and a temperature profile of the central part (r < 20' or 1/4 virial radius) of the Coma cluster. We combined 5 overlapping pointings made with XMM/EPIC/MOS and extracted spectra in boxes of 3.5' X 3.5'. The temperature distribution around the two central galaxies is remarkably homogeneous (r, 7 pages, 8 figures, Accepted for publication in A&A (special Letter issue on XMM)

The Fermi-LAT collaboration has recently reported the detection of angular power above the photon noise level in the diffuse gamma-ray background between 1 and 50 GeV. Such signal can be used to constrain a possible contribution from Dark-Matter-induced photons. We estimate the intensity and features of the angular power spectrum (APS) of this potential Dark Matter (DM) signal, for both decaying and annihilating DM candidates, by constructing template all-sky gamma-ray maps for the emission produced in the galactic halo and its substructures, as well as in extragalactic (sub)halos. The DM distribution is given by state-of-the-art N-body simulations of cosmic structure formation, namely Millennium-II for extragalactic (sub)halos, and Aquarius for the galactic halo and its subhalos. We use a hybrid method of extrapolation to account for (sub)structures that are below the resolution limit of the simulations, allowing us to estimate the total emission all the way down to the minimal self-bound halo mass. We describe in detail the features appearing in the APS of our template maps and we estimate the effect of various uncertainties such as the value of the minimal halo mass, the fraction of substructures hosted in a halo and the shape of the DM density profile. Our results indicate that the fluctuation APS of the DM-induced emission is of the same order as the Fermi-LAT APS, suggesting that one can constrain this hypothetical emission from the comparison with the measured anisotropy. We also quantify the uncertainties affecting our results, finding "theoretical error bands" spanning more than two orders of magnitude and dominated (for a given particle physics model) by our lack of knowledge of the abundance of low-mass (sub)halos., Comment: 24 pages, 13 figures

Here we present a new particle-mesh galactic N-body code that uses the full multigrid algorithm for solving the modified Poisson equation of the quasi-linear formulation of modified Newtonian dynamics (QUMOND). A novel approach for handling the boundary conditions using a refinement strategy is implemented and the accuracy of the code is compared with analytical solutions of Kuzmin discs. We then employ the code to compute the predicted rotation curves for a sample of five spiral galaxies from the THINGS sample. We generated static N-body realizations of the galaxies according to their stellar and gaseous surface densities and allowed their distances, mass-to-light ratios (M/L values) and both the stellar and gas scale-heights to vary in order to estimate the best-fitting parameters. We found that NGC 3621, NGC 3521 and DDO 154 are well fitted by MOND using expected values of the distance and M/L. NGC 2403 required a moderately larger M/L than expected and NGC 2903 required a substantially larger value. The surprising result was that the scale-height of the dominant baryonic component was well constrained by the rotation curves: the gas scale-height for DDO 154 and the stellar scale-height for the others. In fact, if the suggested stellar scale-height (one-fifth the stellar scale-length) was used in the case of NGC 3621 and NGC 3521 it would not be possible to produce a good fit to the inner rotation curve. For each of the four stellar dominated galaxies, we calculated the vertical velocity dispersions which we found to be, on the whole, quite typical compared with observed stellar vertical velocity dispersions of face-on spirals. We conclude that modelling the gas scale-heights of the gas-rich dwarf spiral galaxies will be vital in order to make precise conclusions about MOND.

The viability of the lightest neutralino as a dark matter candidate in the next-to-minimal supersymmetric standard model is analysed. We carry out a thorough analysis of the parameter space, taking into account accelerator constraints as well as bounds on low-energy observables, such as the muon anomalous magnetic moment and rare K and B meson decays. The neutralino relic density is also evaluated and consistency with present bounds imposed. Finally, the neutralino direct detection cross section is calculated in the allowed regions of the parameter space and compared to the sensitivities of present and projected dark matter experiments. Regions of the parameter space are found where experimental constraints are fulfilled, the lightest neutralino has the correct relic abundance and its detection cross section is within the reach of dark matter detectors. This is possible in the presence of very light singlet-like Higgses and when the neutralino is either light enough so that some annihilation channels are kinematically forbidden, or has a large singlino component.

We examine the systematics affecting the X-ray mass estimators applied to a set of five simulated galaxy clusters. They have been processed through the X-ray Map Simulator, X-MAS, to provide Chandra-like long exposures that are analyzed to reconstruct the gas temperature, density, and mass profiles used as input. We find that at R_2500 the mass profile obtained via a direct application of the hydrostatic equilibrium equation is consistent within 1 sigma with the actual mass; although we notice this estimator shows high statistical errors due to high level of Chandra background. Instead, the poorness of the beta-model in describing the gas density profile makes the evaluated masses to be underestimated by \sim 40 per cent with respect to the true mass, both with an isothermal and a polytropic temperature profile. We also test ways to recover the mass by adopting an analytic mass model, such as those proposed by Navarro et al. (1997) and Rasia et al. (2004), and fitting the temperature profile expected from the hydrostatic equilibrium equation to the observed one. These methods and the one of the hydrostatic equilibrium equation provide a more robust mass estimation than the ones based on the beta-model. In the present work the main limitation for a precise mass reconstruction is to ascribe to the relatively high level of the background chosen to reproduce the Chandra one. After artificially reducing it by a factor of 100, we find that the estimated mass significantly underestimates the true mass profiles. This is manly due (i) to the neglected contribution of the gas bulk motions to the total energy budget and (ii) to the bias towards lower values of the X-ray temperature measurements because of the complex thermal structure of the emitting plasma., submitted to MNRAS, 12 pages

Most of the matter in the Universe appears to be in some form which does not emit or absorb light. While evidence for the existence of this dark matter has accumulated over the last seventy years, its nature remains elusive. In this thesis, quasars and low surface brightness galaxies (LSBGs) are used to investigate the properties of the dark matter. Quasars are extremely bright light sources which can be seen over vast distances. These cosmic beacons may be used to constrain dark matter in the form of low-mass, compact objects along the line of sight, as such objects are expected to induce brightness fluctuations in quasars through gravitational microlensing effects. Using a numerical microlensing model, we demonstrate that the uncertainty in the typical size of the optical continuum-emitting region in quasars represents the main obstacle in this procedure. We also show that, contrary to claims in the literature, microlensing fails to explain the observed long-term optical variability of quasars. Here, quasar distances are inferred from their redshifts, which are assumed to stem from the expansion of the Universe. Some astronomers do however defend the view that quasar redshifts could have a different origin. A number of potential methods for falsifying claims of such non-cosmological redshifts are proposed. As the ratio of dark to luminous matter is known to be unusually high in LSBGs, these objects have become the prime targets for probing dark matter halos around galaxies. Here, we use spectral evolutionary models to constrain the properties of the stellar populations in a class of unusually blue LSBGs. Using rotation curve data obtained at the ESO Very Large Telescope, we also investigate the density profiles of their dark halos. We find our measurements to be inconsistent with the predictions of the currently favoured cold dark matter scenario.

(Abriged) We present a study of the integrated physical properties of a sample of 28 X-ray galaxy clusters observed with Chandra at redshift between 0.4 and 1.3. In particular, we have twelve objects in the redshift range 0.4-0.6, five between 0.6 and 0.8, seven between 0.8 and 1 and four at z>1, compounding the largest sample available for such a study. We focus particularly on the properties and evolution of the X-ray scaling laws. We fit both a single and a double beta-model with the former which provides a good representation of the observed surface brightness profiles, indicating that these clusters do not show any significant excess in their central brightness. By using the best-fit parameters of the beta-model together with the measured emission-weighted temperature (in the range 3-11 keV), we recover gas luminosity, gas mass and total gravitating mass out to R500. We observe scaling relations steeper than expected from self-similar model by a significant (>3 sigma) amount in the L-T and Mgas-T relations. We detect hints of negative evolution in the L-T, Mgas-T and L-Mtot relations, thus suggesting that systems at higher redshift have lower X-ray luminosity and gas mass for fixed temperature. In particular, when the 16 clusters at z>0.6 are considered, the evolution becomes more evident and its power-law modelization is a statistically good description of the data., accepted for publication in A&A; typos corrected

We analyze the internal dynamics of 43 non-interacting clusters which are selected from the 2dF Galaxy Redshift Survey 100k public release. We join together the 43 clusters into an ensemble cluster by appropriately scaling their galaxy velocities and clustercentric distances. We solve the Jeans equation for the hydrostatic equilibrium for the member galaxies within the virial radius of the ensemble cluster, assuming isotropic orbits. We constrain the cluster mass profile within the virial radius by exploring parameterized models for the cluster mass-density profile. We find that both cuspy profiles and profiles with a core are acceptable. In particular, the concentration parameter of the best fit NFW model is as predicted from numerical simulations in a LambdaCDM cosmology. Density profiles with very large core-radii are ruled out. Beyond the virial radius, dynamical equilibrium cannot be taken for granted, and the Jeans equation may not be applicable. In order to extend our dynamical analysis out to ~2 virial radii, we rely upon the method which uses the amplitude of caustics in the space of galaxy clustercentric distances and velocities. We find very good agreement between the mass profile determined with the caustic method and the extrapolation to ~2 virial radii of the best-fit mass profile determined by the Jeans analysis in the virialized inner region. We determine the mass-to-number density profile, and find it is fully consistent with a constant within the virial radius. The mass-to-number density profile is however inconsistent with a constant when the full radial range from 0 to ~2 virial radii is considered, unless the sample used to determine the number density profile is restricted to the early-type galaxies., To be published in ApJ - 20 pages, 9 figures

We analyze the ROSAT Deep Cluster Survey (RDCS) to derive cosmological constraints from the evolution of the cluster X-ray luminosity distribution. The sample contains 103 galaxy clusters out to z=0.85 and flux-limit Flim=3 10^{-14} cgs (RDCS-3) in the [0.5-2.0] keV energy band, with a high-z extension containing four clusters at 0.901 10^{-14} cgs (RDCS-1). Model predictions for the cluster mass function are converted into the X-ray luminosity function in two steps. First we convert mass into intra-cluster gas temperature by assuming hydrostatic equilibrium. Then temperature is converted into X-ray luminosity by using the most recent data on the Lx-T relation for nearby and distant clusters. These include the Chandra data for seven distant clusters at 0.57, Comment: 10 pages, 4 figures, to appear in Astrophysical Journal

The neutralino-nucleon cross section in the context of the MSSM with universal soft supersymmetry-breaking terms is compared with the limits from dark matter detectors. Our analysis is focussed on the stability of the corresponding cross sections with respect to variations of the initial scale for the running of the soft terms, finding that the smaller the scale is, the larger the cross sections become. For example, by taking $10^{10-12}$ GeV rather than $M_{GUT}$, which is a more sensible choice, in particular in the context of some superstring models, we find extensive regions in the parameter space with cross sections in the range of $10^{-6}$--$10^{-5}$ pb, i.e. where current dark matter experiments are sensitive. For instance, this can be obtained for $\tan\beta\gsim 3$., Comment: Improved references, new comments added

We present an in-depth weak lensing analysis of the cluster MS1008.1-1224 based on deep multicolor imaging obtained during the Science Verification of FORS1 at the VLT. The image quality (half arcsec seeing) and depth of the VLT images allow the shear signal to be mapped with high signal-to-noise and to be traced out to 1.2 h50-1 Mpc, near the edge of the 8' 8' field of view. Using BVRI color information, as well as 81 redshifts in the field from the CNOC survey, background galaxies can be effectively separated from cluster and foreground objects. PSF distorsions are found to be moderate across the FORS images and thus easily removed. Due to the small statistical errors in the mass reconstruction, this dataset provides a testing ground where several systematic effects (e.g. mass-sheet degeneracy, redshift distribution of the background sources, cluster galaxy contamination), which are involved in the weak lensing analysis, can be quantified. Several methods are used to remove the mass-sheet degeneracy which is found to dominate the systematic error budget. We measure a lower limit to the mass of 2.6 x 1014 h50-1 Msun within 1 h50-1 Mpc and a ``total'' mass of 5.3x 1014 h50-1 Msun by fitting a softened isothermal sphere. We find the mass distribution fairly uniform, with no significant substructures, in agreement with the virial analysis. The availability of the CNOC redshift data and X-ray observations on this cluster allow a comparison of different determinations of the mass radial profile. We find the lensing and X-ray measurements in excellent agreement, while the mass derived from the virial analysis is marginally (1-2 sigma ) in agreement at radii where both methods are reliable. This analysis underscores the importance of systematics in the mass determination of clusters, particularly when such a high quality dataset is not available or in similar studies at higher redshifts. Based on observations performed at the European Southern Observatory, Paranal, Chile

The possibility of determining cosmological parameters on the basis of a wide set of observational data including the Abell-ACO cluster power spectrum and mass function, peculiar velocities of galaxies, the distribution of Ly-$\alpha$ clouds and CMB temperature fluctuations is analyzed. Using a $\chi^2$ minimization method, assuming $\Omega_{\Lambda}+\Omega_{\rm{matter}} =1 $ and no contribution from gravity waves, we found that a tilted $\Lambda$MDM model with one sort of massive neutrinos and the parameters $n=1.12\pm 0.10$, $\Omega_m=0.41\pm 0.11$ ($\Omega_{\Lambda}=0.59\pm0.11$), $\Omega_{cdm}=0.31\pm 0.15$, $\Omega_{\nu}=0.059\pm 0.028$, $\Omega_b=0.039\pm 0.014$ and $h=0.70\pm 0.12$ matches observational data best. The 1$\sigma$ (68.3%) confidence limits on each cosmological parameter, which are obtained by marginalizing over the other parameters, are $0.82\le n\le1.39$, $0.19\le\Omega_m\le 1$ ($0\le\Omega_{\Lambda}\le 0.81$), $0\le\Omega_{\nu}\le 0.17$, $0.021\le \Omega_b\le 0.13$ and $0.38\le h\le 0.85$ $1.5\le b_{cl}\le 3.5$. Here $b_{cl}$ is the cluster bias parameter. The best-fit parameters for 31 models which are inside of $1\sigma$ range of the best model are presented. It is shown also that observational data set used here rules out the class of CDM models with $h\ge 0.5$, scale invariant primordial power spectrum, zero cosmological constant and spatial curvature at very high confidence level, $>99.99%$. The corresponding class of MDM models are ruled out at $\sim 95%$ C.L., Comment: 19 pages, 9 figures. Accepted for publication in A&A

In this letter we present an idea which reconciles a homogeneous and isotropic Friedmann universe with a fractal distribution of galaxies. We use two observational facts: The flat rotation curves of galaxies and the (still debated) fractal distribution of galaxies with fractal dimension [FORMULA]. Our idea can also be interpreted as a redefinition of the notion of bias.

We perform a forecast analysis on how well a Euclid-like photometric galaxy cluster survey will constrain the total neutrino mass and effective number of neutrino species. We base our analysis on the Monte Carlo Markov Chains technique by combining information from cluster number counts and cluster power spectrum. We find that combining cluster data with CMB measurements from Planck improves by more than an order of magnitude the constraint on neutrino masses compared to each probe used independently. For the LCDM+m_nu model the 2 sigma upper limit on total neutrino mass shifts from M_nu < 0.35 eV using cluster data alone to M_nu < 0.031 eV when combined with CMB data. When a non-standard model with N_eff number of neutrino species is considered, we estimate N_eff, 26 pages 9 figure

DES Collaboration: G. Zacharegkas et al., Galaxy–galaxy lensing is a powerful probe of the connection between galaxies and their host dark matter haloes, which is important both for galaxy evolution and cosmology. We extend the measurement and modelling of the galaxy–galaxy lensing signal in the recent Dark Energy Survey Year 3 cosmology analysis to the highly non-linear scales (∼100 kpc). This extension enables us to study the galaxy–halo connection via a Halo Occupation Distribution (HOD) framework for the two lens samples used in the cosmology analysis: a luminous red galaxy sample (REDMAGIC) and a magnitude-limited galaxy sample (MAGLIM). We find that REDMAGIC (MAGLIM) galaxies typically live in dark matter haloes of mass log10(Mh/M⊙) ≈ 13.7 which is roughly constant over redshift (13.3−13.5 depending on redshift). We constrain these masses to ∼15 per cent ⁠, approximately 1.5 times improvement over the previous work. We also constrain the linear galaxy bias more than five times better than what is inferred by the cosmological scales only. We find the satellite fraction for REDMAGIC (MAGLIM) to be ∼0.1−0.2 (0.1−0.3) with no clear trend in redshift. Our constraints on these halo properties are broadly consistent with other available estimates from previous work, large-scale constraints, and simulations. The framework built in this paper will be used for future HOD studies with other galaxy samples and extensions for cosmological analyses., CC is supported by the Henry Luce Foundation. JP is supported by DOE grant DE-SC0021429. Funding for the DES Projects has been provided by the U.S. Department of Energy, the U.S. National Science Foundation, the Ministry of Science and Education of Spain, the Science and Technology Facilities Council of the United Kingdom, the Higher Education Funding Council for England, the National Center for Supercomputing Applications at the University of Illinois at Urbana-Champaign, the Kavli Institute of Cosmological Physics at the University of Chicago, the Center for Cosmology and Astro-Particle Physics at the Ohio State University, the Mitchell Institute for Fundamental Physics and Astronomy at Texas A&M University, Financiadora de Estudos e Projetos, Fundação Carlos Chagas Filho de Amparo à Pesquisa do Estado do Rio de Janeiro, Conselho Nacional de Desenvolvimento Científico e Tecnológico and the Ministério da Ciência, Tecnologia e Inovação, the Deutsche Forschungsgemeinschaft, and the Collaborating Institutions in the Dark Energy Survey. The Collaborating Institutions are Argonne National Laboratory, the University of California at Santa Cruz, the University of Cambridge, Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas-Madrid, the University of Chicago, University College London, the DES-Brazil Consortium, the University of Edinburgh, the Eidgenössische Technische Hochschule (ETH) Zürich, Fermi National Accelerator Laboratory, the University of Illinois at Urbana-Champaign, the Institut de Ciències de l’Espai (IEEC/CSIC), the Institut de Física d’Altes Energies, Lawrence Berkeley National Laboratory, the Ludwig-Maximilians Universität München and the associated Excellence Cluster Universe, the University of Michigan, NFS’s NOIRLab, the University of Nottingham, The Ohio State University, the University of Pennsylvania, the University of Portsmouth, SLAC National Accelerator Laboratory, Stanford University, the University of Sussex, Texas A&M University, and the OzDES Membership Consortium. Based in part on observations at Cerro Tololo Inter-American Observatory at NSF’s NOIRLab (NOIRLab Prop. ID 2012B-0001; PI: J. Frieman), which is managed by the Association of Universities for Research in Astronomy (AURA) under a cooperative agreement with the National Science Foundation. The DES data management system is supported by the National Science Foundation under grant numbers AST-1138766 and AST-1536171. The DES participants from Spanish institutions are partially supported by MICINN under grants ESP2017-89838, PGC2018-094773,PGC2018-102021, SEV-2016-0588, SEV-2016-0597, and MDM-2015-0509, some of which include ERDF funds from the European Union. IFAE is partially funded by the CERCA programme of the Generalitat de Catalunya. Research leading to these results has received funding from the European Research Council under the European Union’s Seventh Framework Program (FP7/2007-2013) including ERC grant agreements 240672, 291329, and 306478. We acknowledge support from the Brazilian Instituto Nacional de Ciência e Tecnologia (INCT) do e-Universo (CNPq grant 465376/2014-2). This manuscript has been authored by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the U.S. Department of Energy, Office of Science, Office of High Energy Physics.