4,948 research outputs found

    The stellar mass-halo mass relation of isolated field dwarfs: a critical test of Λ\LambdaCDM at the edge of galaxy formation

    Get PDF
    We fit the rotation curves of isolated dwarf galaxies to directly measure the stellar mass-halo mass relation (M∗−M200M_*-M_{200}) over the mass range 5×105<M∗/M⊙<1085 \times 10^5 < M_{*}/{\rm M}_\odot < 10^{8}. By accounting for cusp-core transformations due to stellar feedback, we find a monotonic relation with little scatter. Such monotonicity implies that abundance matching should yield a similar M∗−M200M_*-M_{200} if the cosmological model is correct. Using the 'field galaxy' stellar mass function from the Sloan Digital Sky Survey (SDSS) and the halo mass function from the Λ\Lambda Cold Dark Matter Bolshoi simulation, we find remarkable agreement between the two. This holds down to M200∌5×109M_{200} \sim 5 \times 10^9M⊙_\odot, and to M200∌5×108M_{200} \sim 5 \times 10^8M⊙_\odot if we assume a power law extrapolation of the SDSS stellar mass function below M∗∌107M_* \sim 10^7M⊙_\odot. However, if instead of SDSS we use the stellar mass function of nearby galaxy groups, then the agreement is poor. This occurs because the group stellar mass function is shallower than that of the field below M∗∌109M_* \sim 10^9M⊙_\odot, recovering the familiar 'missing satellites' and 'too big to fail' problems. Our result demonstrates that both problems are confined to group environments and must, therefore, owe to 'galaxy formation physics' rather than exotic cosmology. Finally, we repeat our analysis for a Λ\Lambda Warm Dark Matter cosmology, finding that it fails at 68% confidence for a thermal relic mass of mWDM<1.25m_{\rm WDM} < 1.25keV, and mWDM<2m_{\rm WDM} < 2keV if we use the power law extrapolation of SDSS. We conclude by making a number of predictions for future surveys based on these results.Comment: 22 pages; 2 Tables; 10 Figures. This is the version accepted for publication in MNRAS. Key changes: (i) added substantially more information on the surveys used to measure the stellar mass functions; (ii) added tests of the robustness of our results. Results and conclusions unchanged from previously. Minor typos corrected from previous versio

    Expectations for first single-top studies in CMS proton-proton collisions

    Get PDF
    We report on the expectations for first single top studies at the LHC with the CMS experiment. The Standard Model predicts the production of single top quark through three electroweak processes at LHC, referred to as t, s and tW channels. The t-channel has the highest cross section and the most potential for early observation. We describe the search strategy for the t-channel applied on a Monte Carlo sample at 10TeV p-p collision energy with an integrated luminosity of 200 pb−1 and on the expectations for the search of single top t-channel in the 7TeV scenario

    The search for the single top at the LHC

    Get PDF
    We report on the predictions of the Standard Model for the single top-quark production at LHC and on the analysis strategies adopted by CMS and ATLAS for the single top-quark search. The Standard Model predicts the production of single top quark through three electroweak processes in the LHC energy reach, referred to as t, s and tW channels, resulting in distinct topologies and backgrounds. Different analysis strategies to search for the single top have been developed by CMS and ATLAS experiments. For the 14TeV center-of-mass energy scenario all the channels have been considered, while for the 10TeV scenario a specific strategy has been developed only for the t-channel and has been applied on Monte Carlo samples assuming an integrated luminosity of 200 pb−1

    Multiple abnormalities in the skull of a prostitute. An autopsy report (1900)

    Get PDF
    OBJECTIVE: The study presents and comments on the publication of an autopsy report. CASE REPORT: In 1900 De Blasio published an article entitled "Multiple abnormalities in a prostitute's skull" in the "Journal of Psychiatry, Criminal Anthropology and related sciences". In this work De Blasio related anomalies at the cranial level to the presence of mental pathologies. The skull belonged to a 24-year-old prostitute who died of syphilitic hepatitis. In his article, De Blasio described the life of the woman, after which he gave a macroscopic description of the skull. De Blasio believed that the subject's amoral behavior was caused by the anomalous shape of the subject's skull. CONCLUSION: From the study, it is evident that the school of criminal anthropology influenced De Blasio's autopsy medical practice, and it is interesting to note the interpretation of anthropologists of the time who tried to describe the link between physical and behavioral anomalies

    The Pioneer anomaly and the holographic scenario

    Full text link
    In this paper we discuss the recently obtained relation between the Verlinde's holographic model and the first phenomenological Modified Newtonian dynamics. This gives also a promising possible explanation to the Pioneer anomaly.Comment: 5 pages, Accepted for publication in Astrophysics & Space Scienc

    Phenomenology of the Lense-Thirring effect in the Solar System

    Full text link
    Recent years have seen increasing efforts to directly measure some aspects of the general relativistic gravitomagnetic interaction in several astronomical scenarios in the solar system. After briefly overviewing the concept of gravitomagnetism from a theoretical point of view, we review the performed or proposed attempts to detect the Lense-Thirring effect affecting the orbital motions of natural and artificial bodies in the gravitational fields of the Sun, Earth, Mars and Jupiter. In particular, we will focus on the evaluation of the impact of several sources of systematic uncertainties of dynamical origin to realistically elucidate the present and future perspectives in directly measuring such an elusive relativistic effect.Comment: LaTex, 51 pages, 14 figures, 22 tables. Invited review, to appear in Astrophysics and Space Science (ApSS). Some uncited references in the text now correctly quoted. One reference added. A footnote adde

    Gravitomagnetism and Relative Observer Clock Effects

    Get PDF
    The gravitomagnetic clock effect and the Sagnac effect for circularly rotating orbits in stationary axisymmetric spacetimes are studied from a relative observer point of view, clarifying their relationships and the roles played by special observer families. In particular Semer\'ak's recent characterization of extremely accelerated observers in terms of the two-clock clock effect is shown to be complemented by a similarly special property of the single-clock clock effect.Comment: 19 pages, LaTeX, IOP macros with package epsf and 1 eps figure, to appear in Classical and Quantum Gravity, slight revisio

    Angular momentum effects in weak gravitational fields

    Get PDF
    It is shown that, contrary to what is normally expected, it is possible to have angular momentum effects on the geometry of space time at the laboratory scale, much bigger than the purely Newtonian effects. This is due to the fact that the ratio between the angular momentum of a body and its mass, expressed as a length, is easily greater than the mass itself, again expressed as a length.Comment: LATEX, 8 page

    Noncommutativity and Lorentz Violation in Relativistic Heavy Ion Collisions

    Get PDF
    The experimental detection of the effects of noncommuting coordinates in electrodynamic phenomena depends on the magnitude of |\theta B|, where \theta is the noncommutativity parameter and B a background magnetic field. With the present upper bound on \theta, given by \theta_{\rm bound} \simeq 1/(10 {\rm TeV})^2, there was no large enough magnetic field in nature, including those observed in magnetars, that could give visible effects or, conversely, that could be used to further improve \theta_{\rm bound}. On the other hand, recently it has been proposed that intense enough magnetic fields should be produced at the beginning of relativistic heavy ion collisions. We discuss here lepton pair production by free photons as one kind of signature of noncommutativity and Lorentz violation that could occur at RHIC or LHC. This allows us to obtain a more stringent bound on \theta, given by 10^{-3} \theta_{\rm bound}, if such "exotic" events do not occur.Comment: Five pages, no figures
    • 

    corecore