Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userSpatial structure of the WMAP-Planck haze
88
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
It was proposed that the two phenomena, WMAP-Planck haze and Fermi bubbles, may have a common origin. In the present paper we analyze the spatial structure of the haze using the Planck 2018 data release. It is found that the spatial dimensions and locations of WMAP-Planck haze and Fermi bubbles are compatible within the experimental uncertainties. No substructures similar to the Fermi bubbles cocoon are identified in the Planck data. Comparison with the spatial extent of possible synchrotron emission caused by the electron-positron pair emitted by the Galactic center pulsar population and by the decay of dark matter particles in the Galactic center region are performed. Both galactic pulsars and dark matter decay remain viable explanations of the WMAP-Planck haze.
rate research
Read More
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 emission 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.
Using precise full-sky observations from Planck, and applying several methods of component separation, we identify and characterize the emission from the Galactic haze at microwave wavelengths. The haze is a distinct component of diffuse Galactic emission, roughly centered on the Galactic centre, and extends to |b| ~35 deg in Galactic latitude and |l| ~15 deg in longitude. By combining the Planck data with observations from the WMAP we are able to determine the spectrum of this emission to high accuracy, unhindered by the large systematic biases present in previous analyses. The derived spectrum is consistent with power-law emission with a spectral index of -2.55 +/- 0.05, thus excluding free-free emission as the source and instead favouring hard-spectrum synchrotron radiation from an electron population with a spectrum (number density per energy) dN/dE ~ E^-2.1. At Galactic latitudes |b|<30 deg, the microwave haze morphology is consistent with that of the Fermi gamma-ray haze or bubbles, indicating that we have a multi-wavelength view of a distinct component of our Galaxy. Given both the very hard spectrum and the extended nature of the emission, it is highly unlikely that the haze electrons result from supernova shocks in the Galactic disk. Instead, a new mechanism for cosmic-ray acceleration in the centre of our Galaxy is implied.
We analyse WMAP 7-year temperature data, jointly modeling the cosmic microwave background (CMB) and Galactic foreground emission. We use the Commander code based on Gibbs sampling. Thus, from the WMAP7 data, we derive simultaneously the CMB and Galactic components on scales larger than 1deg with sensitivity improved relative to previous work. We conduct a detailed study of the low-frequency foreground with particular focus on the microwave haze emission around the Galactic center. We demonstrate improved performance in quantifying the diffuse galactic emission when Haslam 408MHz data are included together with WMAP7, and the spinning and thermal dust emission is modeled jointly. We also address the question of whether the hypothetical galactic haze can be explained by a spatial variation of the synchrotron spectral index. The excess of emission around the Galactic center appears stable with respect to variations of the foreground model that we study. Our results demonstrate that the new galactic foreground component - the microwave haze - is indeed present.
The extraction of a haze from the WMAP microwave skymaps is based on subtraction of known foregrounds, viz. free-free (bremsstrahlung), thermal dust and synchrotron, each traced by other skymaps. While the 408 MHz all-sky survey is used for the synchrotron template, the WMAP bands are at tens of GHz where the spatial distribution of the radiating cosmic ray electrons ought to be quite different because of the energy-dependence of their diffusion in the Galaxy. The systematic uncertainty this introduces in the residual skymap is comparable to the claimed haze and can, for certain source distributions, have a very similar spectrum and latitudinal profile and even a somewhat similar morphology. Hence caution must be exercised in interpreting the haze as a physical signature of, e.g., dark matter annihilation in the Galactic centre.
In this paper we show that dark matter in the form of dense matter/antimatter nuggets could provide a natural and unified explanation for several distinct bands of diffuse radiation from the core of the Galaxy spanning over 12 orders of magnitude in frequency. We fix all of the phenomenological properties of this model by matching to x-ray observations in the keV band, and then calculate the unambiguously predicted thermal emission in the microwave band, at frequencies smaller by 10 orders of magnitude. Remarkably, the intensity and spectrum of the emitted thermal radiation are consistent with--and could entirely explain--the so-called WMAP haze: a diffuse microwave excess observed from the core of our Galaxy by the Wilkinson Microwave Anisotropy Probe (WMAP). This provides another strong constraint of our proposal, and a remarkable nontrivial validation. If correct, our proposal identifies the nature of the dark matter, explains baryogenesis, and provides a means to directly probe the matter distribution in our Galaxy by analyzing several different types of diffuse emissions.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
