1810.05168
The signal of decaying dark matter with hydrodynamical simulations
Lovell, et al
DM articles may decay, emitting photons. Drawing on the EAGLE family of hydrodynamic simulations of galaxy formation -- including the APOSTLE and C-EAGLE simulations -- assess the systematic uncertainties and scatter on the decay flux from different galaxy classes, from MW satellites to galaxy clusters, and compare the results to studies of the 3.55 keV line. Demonstrate that previous detections and non-detections of this line are consistent with a DM interpretation. For example, in the simulations the width of the DM decay one for Perseus-Analogue galaxy clusters lies in the range 1300-1700 km/s. Therefore, the non-detection of the 3.55 keV line in the centre of the Perseus cluster by the Hitomi collaboration is consistent with detections by other instruments. Also consider trends with stellar and halo mass and evaluate the scatter in the expected fluxes arising from the anisotropic halo mass distribution and from object-to-object variations. Provide specific predictions for observations with XMM-Newton and with the planned X-ray telescopes XRISM and ATHENA. If future detections of unexplained X-ray lines match the predictions, including line widths, there is strong evidence that we have discovered the DM.
1810.05216
BICEP2 / Keck Array x: Constraints on primordial gravitational waves using Planck, WMAP, and New BICEP2/Keck observations through the 2015 season
Keck Array, BICEP2 collaborations, et al
Present results from an analysis of all data taken by the BICEP2/Keck CMB polarization experiments up to and including the 2015 observing season. This includes the first Keck Array observations at 220 GHz and additional observations at 95 & 150 GHz. The Q/U maps reach depths of 5.2, 2.9 and 26 mu K_cmb arcmin at 95,150 and 220 GHz respectively over an effective area of ~400 square degrees. The 220 GHz maps achieve a signal-to-noise on polarized dust emission approximately equal to that of Planck at 353 GHz. Take auto- and cross-spectra between these maps and publicly available WMAP and Planck maps at frequencies from 23 to 353 GHz. Evaluate the joint likelihood of the spectra versus a multicomponent model of lensed-LCDM+r+dust+synchrotron+noise. The foreground model has seven parameters, and impose priors on some of these using external information from Planck and WMAP derived from larger regions of sky. The model is shown to be an adequate description of the data at the current noise levels. The likelihood analysis yields the constraint r_0.05<0.07 at 95% confidence, which tightens to r_0.05<0.06 in conjunction with Planck temperature measurements and other data. The lensing signal is detected at 8.8 sigma significance. Running maximum likelihood search on simulations, obtain unbiased results and find that sigma(r)=0.020. These are the strongest constrains to date on primordial gravitational waves.
1810.6146
The origin of magnetism in white dwarfs
Ferrario
The absence of magnetic white dwarfs with a non-degenerate low-mass stellar companion in a wide binary is still very intriguing and at odds with the hypothesis that magnetic white dwarfs are the progenies of the magnetically peculiar Ap/Bp stars. On the other hand, we cannot resort to a process that impedes the generation of a strong magnetic field in the main or pre-main sequence progenitors of white dwarfs if they are in a multiple stellar system, because such a process would also prevent the formation of magnetic cataclysmic variables consisting of a magnetic white dwarf accreting mass from a low-mass companion. This is the reason why it has been proposed that fields in white dwarfs may be linked to their binary and are generated through a dynamo mechanism during common envelope evolution.
1810.06200
Intergalactic $\gamma$-ray propagation: basic ideas, processes, and constraints
Dzhatdoev, et al
Review extragalactic gamma-ray propagation models with emphasis on the EM cascade process in the magnetized expanding Universe. Consider cascades initiated by primary protons of ultra-high energy accelerated by blazers and show that the observable spectrum is similar to the universal spectrum of a purely EM cascade. Also present a detailed calculation of the observable energy distribution for the case of EM cascades developing from relatively nearby (<20 Mpc) sources. Finally, calculate the point-like source differential sensitivity of a novel liquid Argon time projection chamber gamma-ray telescope and show that its sensitivity is several times better than the Fermi LAT sensitivity in the 100 MeV -- 100 GeV energy range.
The signal of decaying dark matter with hydrodynamical simulations
Lovell, et al
DM articles may decay, emitting photons. Drawing on the EAGLE family of hydrodynamic simulations of galaxy formation -- including the APOSTLE and C-EAGLE simulations -- assess the systematic uncertainties and scatter on the decay flux from different galaxy classes, from MW satellites to galaxy clusters, and compare the results to studies of the 3.55 keV line. Demonstrate that previous detections and non-detections of this line are consistent with a DM interpretation. For example, in the simulations the width of the DM decay one for Perseus-Analogue galaxy clusters lies in the range 1300-1700 km/s. Therefore, the non-detection of the 3.55 keV line in the centre of the Perseus cluster by the Hitomi collaboration is consistent with detections by other instruments. Also consider trends with stellar and halo mass and evaluate the scatter in the expected fluxes arising from the anisotropic halo mass distribution and from object-to-object variations. Provide specific predictions for observations with XMM-Newton and with the planned X-ray telescopes XRISM and ATHENA. If future detections of unexplained X-ray lines match the predictions, including line widths, there is strong evidence that we have discovered the DM.
1810.05216
BICEP2 / Keck Array x: Constraints on primordial gravitational waves using Planck, WMAP, and New BICEP2/Keck observations through the 2015 season
Keck Array, BICEP2 collaborations, et al
Present results from an analysis of all data taken by the BICEP2/Keck CMB polarization experiments up to and including the 2015 observing season. This includes the first Keck Array observations at 220 GHz and additional observations at 95 & 150 GHz. The Q/U maps reach depths of 5.2, 2.9 and 26 mu K_cmb arcmin at 95,150 and 220 GHz respectively over an effective area of ~400 square degrees. The 220 GHz maps achieve a signal-to-noise on polarized dust emission approximately equal to that of Planck at 353 GHz. Take auto- and cross-spectra between these maps and publicly available WMAP and Planck maps at frequencies from 23 to 353 GHz. Evaluate the joint likelihood of the spectra versus a multicomponent model of lensed-LCDM+r+dust+synchrotron+noise. The foreground model has seven parameters, and impose priors on some of these using external information from Planck and WMAP derived from larger regions of sky. The model is shown to be an adequate description of the data at the current noise levels. The likelihood analysis yields the constraint r_0.05<0.07 at 95% confidence, which tightens to r_0.05<0.06 in conjunction with Planck temperature measurements and other data. The lensing signal is detected at 8.8 sigma significance. Running maximum likelihood search on simulations, obtain unbiased results and find that sigma(r)=0.020. These are the strongest constrains to date on primordial gravitational waves.
1810.6146
The origin of magnetism in white dwarfs
Ferrario
The absence of magnetic white dwarfs with a non-degenerate low-mass stellar companion in a wide binary is still very intriguing and at odds with the hypothesis that magnetic white dwarfs are the progenies of the magnetically peculiar Ap/Bp stars. On the other hand, we cannot resort to a process that impedes the generation of a strong magnetic field in the main or pre-main sequence progenitors of white dwarfs if they are in a multiple stellar system, because such a process would also prevent the formation of magnetic cataclysmic variables consisting of a magnetic white dwarf accreting mass from a low-mass companion. This is the reason why it has been proposed that fields in white dwarfs may be linked to their binary and are generated through a dynamo mechanism during common envelope evolution.
1810.06200
Intergalactic $\gamma$-ray propagation: basic ideas, processes, and constraints
Dzhatdoev, et al
Review extragalactic gamma-ray propagation models with emphasis on the EM cascade process in the magnetized expanding Universe. Consider cascades initiated by primary protons of ultra-high energy accelerated by blazers and show that the observable spectrum is similar to the universal spectrum of a purely EM cascade. Also present a detailed calculation of the observable energy distribution for the case of EM cascades developing from relatively nearby (<20 Mpc) sources. Finally, calculate the point-like source differential sensitivity of a novel liquid Argon time projection chamber gamma-ray telescope and show that its sensitivity is several times better than the Fermi LAT sensitivity in the 100 MeV -- 100 GeV energy range.
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