We present nonparametric radial mass profiles for 10 QSO strong-lensing galaxies. Five of the galaxies have profiles close to rho (r) alpha r super(-2), while the rest are closer to r super(-1), ...consistent with an NFW profile. The former are all relatively isolated early types and dominated by their stellar light. The latter-although the modeling code did not know this-are either in clusters, or have very high mass-to-light ratios, suggesting dark matter-dominant lenses (one is actually a pair of merging galaxies). The same models give unk = unk Gyr ( unk = unk km unk unk), consistent with a previous determination. When tested on simulated lenses taken from a cosmological hydrodynamical simulation, our modeling pipeline recovers both unk and rho (r) within estimated uncertainties. Our result is contrary to some recent claims that lensing time delays imply either a low unk or galaxy profiles much steeper than r super(-2). We diagnose these claims as resulting from an invalid modeling approximation: that small deviations from a power-law profile have a small effect on lensing time delays. In fact, as we show using both perturbation theory and numerical computation from a galaxy formation simulation, a first-order perturbation of an isothermal lens can produce a zeroth-order change in the time delays.
Supernovae feedback driven expansion has proven to be a viable mechanism to explain the average properties of Ultra Diffuse Galaxies (UDGs) such as the sizes, colors, mass and internal kinematics. ...Here, we explore the origin of stellar metallicity gradients in feedback driven simulated UDGs from the NIHAO project and compare them with the observed distribution of metallicity gradients of both Local Group dwarfs as well as of the recently observed UDG DF44. Simulated UDGs display a large variety of metallicity profiles, showing flat to negative gradients, similarly to what is observed in LG dwarfs, while DF44 data suggest a flat to positive gradient. The variety of metallicity gradients in simulations is set by the interplay between the radius at which star formation occurs and the subsequent supernovae feedback driven stellar redistribution: rotation supported systems tend to have flat metallicity profiles while dispersion supported galaxies show negative and steep profiles. Our results suggest that UDGs are not peculiar in what regards their metallicity gradients, when compared to regular dwarfs. Desirably, a larger observational sample of UDGs' gradients shall be available in the future, in order to test our predictions.
Modeling Dynamical Dark Energy Mainini, R; Macciò, A. V; Bonometto, S. A ...
The Astrophysical journal,
12/2003, Letnik:
599, Številka:
1
Journal Article
It has been argued that the flux anomalies detected in gravitationally lensed quasi-stellar objects (QSOs) are evidence for substructures in the foreground lensing haloes. In this paper, we ...investigate this issue in greater detail, focusing on the cusp relation which corresponds to images of a source located to the cusp of the inner caustic curve. We use numerical simulations combined with a Monte Carlo approach to study the effects of the expected power-law distribution of substructures within Λ cold dark matter (ΛCDM) haloes on the multiple images.
Generally, the high number of anomalous flux ratios in the cusp configurations is unlikely to be explained by 'simple' perturbers (subhaloes) inside the lensing galaxy, modelled by either point masses or extended Navarro, Frenk & White subhaloes. We considered in our analysis a mass range of 105-107 M⊙ for the subhaloes. We also demonstrate that including the effects of the surrounding mass distribution, such as other galaxies close to the primary lens, does not change the results. We conclude that triple images of lensed QSOs do not show any direct evidence for dark dwarf galaxies such as CDM substructure.
Strongly Coupled Cosmologies Bonometto, S.A.; Mezzetti, M.; Musco, I. ...
Nuclear and particle physics proceedings,
August-September 2015, 2015-08-00, Letnik:
265-266
Journal Article
Recenzirano
Odprti dostop
Models including an energy transfer from CDM to DE were widely considered in the literature, namely to allow DE a significant high-z density. Strongly Coupled cosmologies assume a much larger ...coupling between DE and CDM, together with an uncoupled warm DM component, the role of Cbeing mostly restricted to radiative eras. This allows us to preserve small scale fluctuations even if the warm particle is quite light, O(100 eV). Linear theory shows full agreement between these cosmologies and ΛCDM on supergalactic scales; e.g., CMB spectra are identical. Simultaneously, simulations show that they ease problems related to the properties of MW satellites and cores in dwarfs. While opening new perspectives on early black hole formation and possibly leading towards unificating DE and inflationary fields, the critical prediction of SC cosmologies is a sterile neutrino or gravitino of mass ∼ 100 eV.
Abstract
We examine the chemical properties of five cosmological hydrodynamical simulations of an M33-like disc galaxy which have been shown previously to be consistent with the morphological ...characteristics and bulk scaling relations expected of late-type spirals. These simulations are part of the Making Galaxies in a Cosmological Context Project, in which stellar feedback is tuned to match the stellar mass-halo mass relationship. Each realization employed identical initial conditions and assembly histories, but differed from one another in their underlying baryonic physics prescriptions, including (a) the efficiency with which each supernova energy couples to the surrounding interstellar medium, (b) the impact of feedback associated with massive star radiation pressure, (c) the role of the minimum shut-off time for radiative cooling of Type II supernovae remnants, (d) the treatment of metal diffusion and (e) varying the initial mass function. Our analysis focusses on the resulting stellar metallicity distribution functions (MDFs) in each simulated (analogous) 'solar neighbourhood' (2-3 disc scalelengths from the galactic centre) and central 'bulge' region. We compare and contrast the simulated MDFs' skewness, kurtosis and dispersion (inter-quartile, inter-decile, inter-centile and inter-tenth-percentile regions) with that of the empirical solar neighbourhood MDF and Local Group dwarf galxies. We find that the MDFs of the simulated discs are more negatively skewed, with higher kurtosis, than those observed locally in the Milky Way and Local Group dwarfs. We can trace this difference to the simulations' very tight and correlated age-metallicity relations (compared with that of the Milky Way's solar neighbourhood), suggesting that these relations within 'dwarf' discs might be steeper than in L
★ discs (consistent with the simulations' star formation histories and extant empirical data), and/or the degree of stellar orbital redistribution and migration inferred locally has not been captured in their entirety, at the resolution of our simulations. The important role of metal diffusion in ameliorating the overproduction of extremely metal-poor stars is highlighted.
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