Cosmic axion background propagation in galaxies

Many extensions of the Standard Model include axions or axion-like particles (ALPs). Here we study ALP to photon conversion in the magnetic field of the Milky Way and starburst galaxies. By modelling the effects of the coherent and random magnetic fields, the warm ionized medium and the warm neutral medium on the conversion process, we simulate maps of the conversion probability across the sky for a range of ALP energies. In particular, we consider a diffuse cosmic ALP background (CAB) analogous to the CMB, whose existence is suggested by string models of inflation. ALP-photon conversion of a CAB in the magnetic fields of galaxy clusters has been proposed as an explanation of the cluster soft X-ray excess. We therefore study the phenomenology and expected photon signal of CAB propagation in the Milky Way. We find that, for the CAB parameters required to explain the cluster soft X-ray excess, the photon flux from ALP-photon conversion in the Milky Way would be unobservably small. The ALP-photon conversion probability in galaxy clusters is 3 orders of magnitude higher than that in the Milky Way. Furthermore, the morphology of the unresolved cosmic X-ray background is incompatible with a significant component from ALP-photon conversion. We also consider ALP-photon conversion in starburst galaxies, which host much higher magnetic fields. By considering the clumpy structure of the galactic plasma, we find that conversion probabilities comparable to those in clusters may be possible in starburst galaxies.Comment: Version accepted by Physics Letters

Predictors of Involvement in Head Start Services Among Diverse Immigrant Families

Nearly 86% of Head Start preschools serve non-English speaking families. The Head Start preschool program has been shown to increase academic proficiencies in children entering kindergarten and has been particularly successful in helping immigrant children entering the U.S. education system. Family involvement in their child’s education as early as preschool has been correlated with positive academic and behavioral outcomes throughout childhood. Given the importance of Head Start services for immigrant families, this study seeks to better understand variables associated with involvement in Head Start among immigrant families. Data was collected from a diverse sample of immigrant and U.S. born families to better understand what factors influence a family member’s level of involvement in their Head Start program (n = 196). Participating parents and caregivers were from 17 different countries and completed surveys regarding a variety of demographic information, caregiver’s level of satisfaction in Head Start services, and caregiver’s level of involvement in Head Start services. Results indicate a family’s language and birthplace have no significant relationship with a family’s level of involvement in their child’s education. Rather, a family’s satisfaction in the services provided by the school shows the strongest associations with a family’s involvement in services. Demographic variables associated with involvement in a child’s education include a caregiver’s level of education and a caregiver’s relation to the child. Findings indicate that caregivers with low educational attainment and in non-traditional families may be in need of targeted intervention focused on increasing levels of satisfaction in services

Detecting fluorescent dark matter with X-ray lasers.

Fluorescent dark matter has been suggested as a possible explanation of both the 3.5 keV excess in the diffuse emission of the Perseus Cluster and of the deficit at the same energy in the central active galaxy within that cluster, NGC 1275. In this work we point out that such a dark matter candidate can be searched for at the new X-ray laser facilities that are currently being built and starting to operate around the world. We present one possible experimental set up where the laser is passed through a narrow cylinder lined with lead shielding. Fluorescent dark matter would be excited upon interaction with the laser photons and travel across the lead shielding to decay outside the cylinder, in a region which has been instrumented with X-ray detectors. For an instrumented length of 7 cm at the LCLS-II laser we expect O (1-10) such events per week for parameters which explain the astronomical observations.Peterhous

Axion superradiance in rotating neutron stars

It is a well-known fact that compact gravitating objects admit bound state configurations for massive bosonic fields. In this work we describe a new class of superradiant instabilities of axion bound states in neutron star magnetospheres. The instability arises from the mixing of axion and photon modes in the magnetic field of the neutron star which extract energy from the rotating magnetosphere. Unlike for black holes, where the dissipation required for superradiance is provided by an absorbative horizon, the non-hermitian dynamics in this paper come from the resistivity in the stellar magnetosphere arising from a finite bulk conductivity. The axion field mixes with photon modes which superradiantly scatter off the magnetosphere, extracting rotational energy which is then deposited back into the axion sector leading to an instability. We derive the superradiant eigenfrequencies for the axion-photon system using quantum mechanical perturbation theory on the axion boundstate, drawing an analogy with atomic selection rules. We then compare the characteristic time scale of the instability to the spin-down measurements of pulsars which limit the allowed rate of angular momentum extraction from neutron stars

Axion superradiance in rotating neutron stars

It is a well-known fact that compact gravitating objects admit bound state configurations for massive bosonic fields. In this work we describe a new class of superradiant instabilities of axion bound states in neutron star magnetospheres. The instability arises from the mixing of axion and photon modes in the magnetic field of the neutron star which extract energy from the rotating magnetosphere. Unlike for black holes, where the dissipation required for superradiance is provided by an absorbative horizon, the non-hermitian dynamics in this paper come from the resistivity in the stellar magnetosphere arising from a finite bulk conductivity. The axion field mixes with photon modes which superradiantly scatter off the magnetosphere, extracting rotational energy which is then deposited back into the axion sector leading to an instability. We derive the superradiant eigenfrequencies for the axion-photon system using quantum mechanical perturbation theory on the axion boundstate, drawing an analogy with atomic selection rules. We then compare the characteristic time scale of the instability to the spin-down measurements of pulsars which limit the allowed rate of angular momentum extraction from neutron stars

Multilevel Model of Sport Injury (MMSI): Can Coaches Impact and be Impacted by Injury?

No Abstrac

Neutron star-axion star collisions in the light of multimessenger astronomy

Axions are increasingly favoured as a candidate particle for the dark matter in galaxies, since they satisfy the observational requirements for cold dark matter and are theoretically well mo- tivated. Fluctuations in the axion field give rise to stable localised overdensities known as ax- ion stars, which, for the most massive, compact cases, are potential neutron star mimickers. In principle, there are no fundamental arguments against the multi-messenger observations of GW170817/GRB170817A/AT2017gfo arising from the merger of a neutron star with a neutron star mimicker, rather than from a binary neutron star. To constrain this possibility and better un- derstand the astrophysical signatures of a neutron star–axion star (NSAS) merger, we present in this work a detailed example case of a NSAS merger based on full 3D numerical relativity simula- tions, and give an overview of the many potential observables - ranging from gravitational waves, to optical and near-infrared electromagnetic signals, radio flares, fast radio bursts, gamma ray bursts, and neutrino emission. We discuss the individual channels and estimate to which distances current and future observatories might be able to detect such a NSAS merger. Such signals could con- strain the unknown axion mass and its couplings to standard baryonic matter, thus enhancing our understanding of the dark matter sector of the Universe

Constraints on axion-like particles from non-observation of spectral modulations for X-ray point sources

We extend previous searches for X-ray spectral modulations induced by ALP-photon conversion to a variety of new sources, all consisting of quasars or AGNs located in or behind galaxy clusters. We consider a total of seven new sources, with data drawn from the Chandra archive. In all cases the spectrum is well fit by an absorbed power-law with no evidence for spectral modulations, allowing constraints to be placed on the ALP-photon coupling parameter ga(γ)(γ). Two sources are particularly good: the Seyfert galaxy 2E3140 in A1795 and the AGN NGC3862 within the cluster A1367, leading to 95% bounds for light ALPs (ma lesssim 10(−)(12) eV) of ga(γ)(γ) lesssim 1.5 × 10(−)(12) GeV(−)(1) and ga(γ)(γ) lesssim 2.4 × 10(−)(12) GeV(−)(1) respectively

Consistency of Hitomi, XMM-Newton, and Chandra 3.5 keV data from Perseus

Hitomi observations of Perseus with the Soft X-ray Spectrometer (SXS) provide a high-resolution look at the 3.5 keV feature reported by multiple groups in the Perseus cluster. The Hitomi spectrum—which involves the sum of diffuse cluster emission and the pointlike central active galactic nucleus (AGN)—does not show any excess at E∼3.5  keV, giving an apparent inconsistency with previous observations of excess diffuse emission. We point out that 2009 Chandra data reveals a strong dip in the AGN spectrum at E=(3.54±0.02)  keV (cluster frame)—the identical energy to the diffuse excess observed by XMM-Newton. Scaling this dip to the 2016 AGN luminosity and adding it to the diffuse XMM-Newton excess, this predicts an overall dip in the SXS field of view of (-5.9±4.4)×10-6  ph cm-2 s-1 at E=3.54  keV—a precise match to the Hitomi data when broadened by the dark matter virial velocity. We describe models of fluorescent dark matter that can reproduce this physics, in which dark matter absorbs and then reemits 3.5 keV photons emitted from the central AGN.European Research Counci