اشترك بالحزمة الذهبية واحصل على وصول غير محدود شمرا أكاديميا
تسجيل مستخدم جديدMaking sense of the local Galactic escape speed estimates in direct dark matter searches
188
0
0.0
(
0
)
اسأل ChatGPT حول البحث
ﻻ يوجد ملخص باللغة العربية
Direct detection (DD) of dark matter (DM) candidates in the $lesssim$10 GeV mass range is very sensitive to the tail of their velocity distribution. The important quantity is the maximum WIMP speed in the observers rest frame, i.e. in average the sum of the local Galactic escape speed $v_{rm esc}$ and of the circular velocity of the Sun $v_c$. While the latter has been receiving continuous attention, the former is more difficult to constrain. The RAVE Collaboration has just released a new estimate of $v_{rm esc}$ (Piffl {em et al.}, 2014 --- P14) that supersedes the previous one (Smith {em et al.}, 2007), which is of interest in the perspective of reducing the astrophysical uncertainties in DD. Nevertheless, these new estimates cannot be used blindly as they rely on assumptions in the dark halo modeling which induce tight correlations between the escape speed and other local astrophysical parameters. We make a self-consistent study of the implications of the RAVE results on DD assuming isotropic DM velocity distributions, both Maxwellian and ergodic. Taking as references the experimental sensitivities currently achieved by LUX, CRESST-II, and SuperCDMS, we show that: (i) the exclusion curves associated with the best-fit points of P14 may be more constraining by up to $sim 40$% with respect to standard limits, because the underlying astrophysical correlations induce a larger local DM density; (ii) the corresponding relative uncertainties inferred in the low WIMP mass region may be moderate, down to 10-15% below 10 GeV. We finally discuss the level of consistency of these results with other independent astrophysical constraints. This analysis is complementary to others based on rotation curves.
قيم البحث
اقرأ أيضاً
The mirror dark matter (MDM) model of Berezhiani et al. has been shown to reproduce observed galactic rotational curves for a variety of spiral galaxies, and has been presented as an alternative to cold dark matter (CDM) models. We investigate possib
le additional tests involving the properties of stellar orbits, which may be used to discriminate between the two models. We demonstrate that in MDM and CDM models fitted equally well to a galactic rotational curve, one generally expects predictable differences in escape speeds from the disc. The recent radial velocity (RAVE) survey of the Milky Way has pinned down the escape speed from the solar neighbourhood to $v_{esc}=544^{+64}_{-46}$ km s$^{-1}$, placing an additional constraint on dark matter models. We have constructed an MDM model for the Milky Way based on its rotational curve, and find an escape speed that is just consistent with the observed value given the current errors, which lends credence to the viability of the MDM model. The Gaia-ESO spectroscopic survey is expected to lead to an even more precise estimate of the escape speed that will further constrain dark matter models. However, the largest differences in stellar escape speeds between both models are predicted for dark matter dominated dwarf galaxies such as DDO 154, and kinematical studies of such galaxies could prove key in establishing, or abolishing, the validity of the MDM model.
If dark matter (DM) is composed by particles which are non-gravitationally coupled to ordinary matter, their annihilations or decays in cosmic structures can result in detectable radiation. We show that the most powerful technique to detect a particl
e DM signal outside the Local Group is to study the angular cross-correlation of non-gravitational signals with low-redshift gravitational probes. This method allows to enhance signal-to-noise from the regions of the Universe where the DM-induced emission is preferentially generated. We demonstrate the power of this approach by focusing on GeV-TeV DM and on the recent cross-correlation analysis between the 2MASS galaxy catalogue and the Fermi-LAT gamma-ray maps. We show that this technique is more sensitive than other extragalactic gamma-ray probes, such as the energy spectrum and angular autocorrelation of the extragalactic background, and emission from clusters of galaxies. Intriguingly, we find that the measured cross-correlation can be well fitted by a DM component, with thermal annihilation cross section and mass between 10 and 100 GeV, depending on the small-scale DM properties and gamma-ray production mechanism. This solicits further data collection and dedicated analyses.
Line-of-sight integrals of the squared density, commonly called the J-factor, are essential for inferring dark matter annihilation signals. The J-factors of dark matter-dominated dwarf spheroidal satellite galaxies (dSphs) have typically been derived
using Bayesian techniques, which for small data samples implies that a choice of priors constitutes a non-negligible systematic uncertainty. Here we report the development of a new fully frequentist approach to construct the profile likelihood of the J-factor. Using stellar kinematic data from several classical and ultra-faint dSphs, we derive the maximum likelihood value for the J-factor and its confidence intervals. We validate this method, in particular its bias and coverage, using simulated data from the Gaia Challenge. We find that the method possesses good statistical properties. The J-factors and their uncertainties are generally in good agreement with the Bayesian-derived values, with the largest deviations restricted to the systems with the smallest kinematic datasets. We discuss improvements, extensions, and future applications of this technique.
Gamma rays and microwave observations of the Galactic Center and surrounding areas indicate the presence of anomalous emission, whose origin remains ambiguous. The possibility of dark matter (DM) annihilation explaining both signals through prompt em
ission at gamma-rays and secondary emission at microwave frequencies from interactions of high-energy electrons produced in annihilation with the Galactic magnetic fields has attracted much interest in recent years. We investigate the DM interpretation of the Galactic Center gamma-ray excess by searching for the associated synchrotron in the WMAP-Planck data. Considering various magnetic field and cosmic-ray propagation models, we predict the synchrotron emission due to DM annihilation in our Galaxy, and compare it with the WMAP-Planck data at 23-70GHz. In addition to standard microwave foregrounds, we separately model the microwave counterpart to the Fermi Bubbles and the signal due to DM, and use component separation techniques to extract the signal associated with each template from the total emission. We confirm the presence of the Haze at the level of 7% of the total sky intensity at 23GHz in our chosen region of interest, with a harder spectrum $I sim u^{-0.8}$ than the synchrotron from regular cosmic-ray electrons. The data do not show a strong preference towards fitting the Haze by either the Bubbles or DM emission only. Inclusion of both components provides a better fit with a DM contribution to the Haze emission of 20% at 23GHz, however, due to significant uncertainties in foreground modeling, we do not consider this a clear detection of a DM signal. We set robust upper limits on the annihilation cross section by ignoring foregrounds, and also report best-fit DM annihilation parameters obtained from a complete template analysis. We conclude that the WMAP-Planck data are consistent with a DM interpretation of the gamma-ray excess.
A self-interacting dark matter halo can experience gravothermal collapse, resulting in a central core with an ultrahigh density. It can further contract and collapse into a black hole, a mechanism proposed to explain the origin of supermassive black
holes. We study dynamical instability of the core in general relativity. We use a truncated Maxwell-Boltzmann distribution to model the dark matter distribution and solve the Tolman-Oppenheimer-Volkoff equation. For given model parameters, we obtain a series of equilibrium configurations and examine their dynamical instability based on considerations of total energy, binding energy, fractional binding energy, and adiabatic index. The numerical results from our semi-analytical method are in good agreement with those from fully relativistic N-body simulations. We further show for the instability to occur in the classical regime, the boundary temperature of the core should be at least $10%$ of the mass of dark matter particles; for a $10^9~{rm M_odot}$ seed black hole, the particle mass needs to be larger than a few keV. These results can be used to constrain different collapse models, in particular, those with dissipative dark matter interactions.
سجل دخول لتتمكن من نشر تعليقات
التعليقات
جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
