Line-of-sight velocity distribution corrections for Lick/IDS indices of early-type galaxies

We investigate line-of-sight velocity distribution (LOSVD) corrections for absorption line-strength indices of early-type galaxies in the Lick/IDS system. This system is often used to estimate basic stellar population parameters such as luminosity weighted ages and metallicities. Using single stellar population model spectral energy distributions by Vazdekis (1999) we find that the LOSVD corrections are largely insensitive to changes in the stellar populations for old galaxies (age >3 Gyr). Only the Lick/IDS Balmer series indices show an appreciable effect, which is on the order of the correction itself. Furthermore, we investigate the sensitivity of the LOSVD corrections to non-Gaussian LOSVDs. In this case the LOSVD can be described by a Gauss-Hermite series and it is shown that typical values of h_3 and h_4 observed in early-type galaxies can lead to significant modifications of the LOSVD corrections and thus to changes in the derived luminosity weighted ages and metallicities. A new, simple parameterisation for the LOSVD corrections, taking into account the h_3 and h_4 terms, is proposed and calibrations given for a subset of the Lick/IDS indices and two additional indices applicable to old (>3 Gyr) stellar populations.Comment: 10 pages, 8 figures, accepted by A&

Spatially resolved spectroscopy of Coma cluster early-type galaxies - II:the minor axis dataset

We present minor axis, off set major axis and one diagonal long slit spectra for 10 E and S0 galaxies of the Coma cluster drawn from a magnitude-limited sample studied before. We derive rotation curves, velocity dispersion profiles and the H-3 and H-4 coefficients of the Hermite decomposition of the line of sight velocity distribution. Moreover, we derive the line index profiles of Mg, Fe and Hbeta line indices and assess their errors. The data will be used to construct dynamical models of the galaxies and study their stellar populations

Steepening mass profiles, dark matter and environment of X-ray bright elliptical galaxies

We use a new non-parametric Bayesian approach to obtain the most probable mass distributions and circular velocity curves along with their confidence ranges, given deprojected density and temperature profiles of the hot gas surrounding X-ray bright elliptical galaxies. For a sample of six X-ray bright ellipticals, we find that all circular velocity curves are rising in the outer parts due to a combination of a rising temperature profile and a logarithmic pressure gradient that increases in magnitude. Comparing the circular velocity curves we obtain from X-rays to those obtained from dynamical models, we find that the former are often lower in the central ~10 kpc. This is probably due to a combination of: i) Non-thermal contributions of up to ~35% in the pressure (with stronger effects in NGC 4486), ii) multiple-temperature components in the hot gas, iii) incomplete kinematic spatial coverage in the dynamical models, and iv) mass profiles that are insufficiently general in the dynamical modelling. Complementing the total mass information from the X-rays with photometry and stellar population models to infer the dark matter content, we find evidence for massive dark matter haloes with dark matter mass fractions of ~35-80% at 2Re, rising to a maximum of 80-90% at the outermost radii. We also find that the six galaxies follow a Tully-Fisher relation with slope ~4 and that their circular velocities at 1Re correlate strongly with the velocity dispersion of the local environment. As a result, the galaxy luminosity at 1Re also correlates with the velocity dispersion of the environment. These relations suggest a close link between the properties of central X-ray bright elliptical galaxies and their environments (abridged).Comment: 20 pages, 11 figures, accepted for publication in MNRA

The Search for the Dark Matter: WIMPs and MACHOs

Review talk presented at the Texas/PASCOS Symposium, Berkeley, CA, Dec 1992. We review the status of experiments and ideas relevant for the detection of the dark matter which is suspected to be the dominant constituent of the Universe. Great progress is being made and the chances are non-negligible that one of the many currently in-progress experiments will discover the nature of the dark matter. We discuss the main dark matter candidates, and review the experiments relevant to each of them.Comment: 17 pages, tex, figures not include

Zur Situation bei wichtigen Infektionskrankheiten – Importierte Infektionskrankheiten 2022

Der im Epidemiologischen Bulletin 46/2023 veröffentlichte Bericht zu reiseassoziierten Erkrankungen 2022 basiert auf den Meldedaten gemäß Infektionsschutzgesetz, die dem RKI mit Datenstand 1. März 2023 übermittelt wurden. Dabei wird das Auftreten von Erkrankungen wie z. B. Malaria, Shigellose, Typhus abdominalis, Hepatitis A und weiteren mit den Vorjahren verglichen. Die Jahre 2020 und 2021 waren durch Reisebeschränkungen im Rahmen der COVID-19-Pandemie und dem damit verbundenen deutlichen Rückgang aller Erkrankungen gekennzeichnet, die in Deutschland überwiegend als im Ausland erworbene Infektionen auftreten. 2022 sind die Fallzahlen gegenüber 2021 – mutmaßlich aufgrund intensiverer Reiseaktivität – bei fast allen gemeldeten Erkrankungen wieder deutlich angestiegen. Sie liegen jedoch mit wenigen Ausnahmen weiterhin unter dem vorpandemischen Niveau von 2019

The Galactic Mergers and Gravitational Unbound Populations

Motivated by the observations on the intra-cluster light (ICL) and inter-galactic stellar populations, n-body simulations are used to model the galactic merging events as a goal to investigate the production and distribution of gravitational unbound populations (GUPs). Both the parabolic and hyperbolic mergers are considered and each category includes six models with different relative orientations between two galaxies. Our results show that there are more (about a factor of two) GUP after a hyperbolic merging event than after a parabolic one. In general, depending on the relative orientation and also the relative velocity of the two galaxies in a merging pair, a head-on collision of a galaxy pair would only make a tiny fraction (less than one percent) of the initial stellar mass become luminous GUP but a considerable fraction (eight to fourteen percent) of the dark matter become dark GUP.Comment: 29 pages, 14 figures, published in MNRAS, Online Earl

Dissipationless Mergers of Elliptical Galaxies and the Evolution of the Fundamental Plane

We carry out numerical simulations of dissipationless major mergers of elliptical galaxies using initial galaxy models that consist of a dark matter halo and a stellar bulge with properties consistent with the observed fundamental plane. By varying the density profile of the dark matter halo (standard NFW versus adiabatically contracted NFW), the global stellar to dark matter mass ratio, and the orbit of the merging galaxies, we are able to assess the impact of each of these factors on the structure of the merger remnant. Our results indicate that the properties of the remnant bulge depend primarily on the angular momentum and energy of the orbit; for a cosmologically motivated orbit, the effective radius and velocity dispersion of the remnant bulge remain approximately on the fundamental plane. This indicates that the observed properties of elliptical galaxies are consistent with significant growth via late dissipationless mergers. We also find that the dark matter fraction within the effective radius of our remnants increases after the merger, consistent with the hypothesis that the tilt of the fundamental plane from the virial theorem is due to a varying dark matter fraction as a function of galaxy mass.Comment: 14 pages, 6 figures; MNRAS, in press. Minor revisions, results from an additional simulation adde

On the tilt of Fundamental Plane by Clausius' virial maximum theory

The theory of the Clausius' virial maximum to explain the Fundamental Plane (FP) proposed by Secco (2000, 2001,2005) is based on the existence of a maximum in the Clausius' Virial (CV) potential energy of a early type galaxy (ETG) stellar component when it is completely embedded inside a dark matter (DM) halo. At the first order approximation the theory was developed by modeling the two-components with two cored power-law density profiles. An higher level of approximation is now taken into account by developing the same theory when the stellar component is modeled by a King-model with a cut-off. Even if the DM halo density remains a cored power law the inner component is now more realistic for the ETGs. The new formulation allows us to understand more deeply what is the dynamical reason of the FP tilt and in general how the CV theory may really be the engine to produce the FP main features. The degeneracy of FP in respect to the initial density perturbation spectrum may be now full understood in a CDM cosmological scenario. A possible way to compare the FPs predicted by the theory with those obtained by observations is also exemplified.Comment: 35 pages, 8 figure

Zur Situation bei wichtigen Infektionskrankheiten – Importierte Infektionskrankheiten 2022

Der im Epidemiologischen Bulletin 46/2023 veröffentlichte Bericht zu reiseassoziierten Erkrankungen 2022 basiert auf den Meldedaten gemäß Infektionsschutzgesetz, die dem RKI mit Datenstand 1. März 2023 übermittelt wurden. Dabei wird das Auftreten von Erkrankungen wie z. B. Malaria, Shigellose, Typhus abdominalis, Hepatitis A und weiteren mit den Vorjahren verglichen. Die Jahre 2020 und 2021 waren durch Reisebeschränkungen im Rahmen der COVID-19-Pandemie und dem damit verbundenen deutlichen Rückgang aller Erkrankungen gekennzeichnet, die in Deutschland überwiegend als im Ausland erworbene Infektionen auftreten. 2022 sind die Fallzahlen gegenüber 2021 – mutmaßlich aufgrund intensiverer Reiseaktivität – bei fast allen gemeldeten Erkrankungen wieder deutlich angestiegen. Sie liegen jedoch mit wenigen Ausnahmen weiterhin unter dem vorpandemischen Niveau von 2019

Baryonic Dark Matter: Theory and Experiment. Overview

The general arguments for baryonic and galactic dark matter are presented. Limits coming from a variety of theoretical considerations and observations are discussed. The surviving candidates for galactic baryonic dark matter seem most likely to be in the form of compact objects and could be in one of two mass windows: either in the brown dwarf regime or in the mass range corresponding to supermassive black holes. Microlensing towards LMC is probing the first window. It is important to keep in mind that these experiments may detect compact heavy objects, independent of their constituency.Comment: Written version of a talk at IV Workshop on Theoretical and Phenomenological Aspects of Underground Physics, TAUP95, Toledo (Spain), Sept. 17-2