CMB spectral distortions from ultra light axions

DO AXIONS EXIST? DO THEY INTERACT WITH PHOTONS AND OTHER STANDARD MODEL PARTICLES?
Myself along with R. Khatri, D. Spergel and B. Wandelt have provided a new observational probe to the Lagrangian of the Universe which is accessible from the upcoming ground based CMB experiments. Ultra light axions in the presence of magnetic field get converted into photons and vice-versa. This process can produce a unique spectral distortion in the blackbody spectrum of the CMB. This signal can arise from our own galaxy 'The Milky Way', galaxy clusters, voids producing a unique spatially varying polarised and unpolarised spectral distortion in CMB black body.

Distortion from Milky Way

In the presence of the magnetic field of Milky Way, CMB photons can undergo resonant conversion into axions producing a polarised spectral distortion in the CMB with a unique spatial shape as shown in the figure. This signal is calculated using the data-driven model of galactic magnetic field and electron density. This work is done with R. Khatri and B. Wandelt. The details on this work can be found in JCAP04(2018)045.

Polarised spectral distortion of CMB at 150 GHz from ultra light axion of mass 0.5 peV.

Distortion from galaxy clusters

Resonant photon-axion conversion in the presence of cluster magnetic field can produce polarised spectral distortion around galaxy clusters. This method can provide the strongest constraints on ultra light axions over the mass range 0.01-1 peV using the upcoming ground based CMB experiments such as Simons Observatory and CMB-S4. This work is in preparation with D. Spergel, R. Khatri and B. Wandelt.

Simulated spectral distortion signal from ultra light axions originating in the magnetic field of galaxy clusters.

Full sky axion distortion map using the multi-frequency temperature sky maps from Planck satellite

The spatial variation of the axion spectral distortion makes it feasible to be measured from the multi-frequency sky maps of Planck satellite. Using the temperature data of the Planck satellite, we provide the first axion distortion map using 45% most cleaned part of the sky. The details on this work can be found in arXiv:1811.11177

Axion distortion map from Planck over 45% sky part.

Making map of cosmological parameters

Influence of foreground contaminations and other spatially varying systematics can cause bias in the estimated cosmological parameters. Me and B. Wandelt proposed a fast method to scrutinize any such contaminations by measuring the spatial variation in the estimated cosmological parameters. Details on this work can be found in JCAP 01 (2018) 042.

The spatial variation in the cosmological parameters with direction are shown from the Planck SMICA temperature map. The variations are negligible in comparison to the error-model indicating no severe contaminations from foregrounds.

CMB anomalies

'CMB-Anomalies' are enigmatic observational signatures which are not highly statistically significant nor ignorable. Most of these anomalies such as hemispherical power asymmetry, low amplitude of the temperature variance, etc., are observed by both WMAP and Planck in the large angular scales with 2-3 σ statistical significance. However, we neither understand its origin nor sure about its statistical properties. Myself and T. Souradeep had explored several aspects of these anomalies after the confirmation of its existence also in the Planck sky maps.

Simulating statistically anisotropic maps: Code for non-Isotropic Gaussian Sky (CoNIGS)

The true understanding of the CMB Anomalies requires 'SIMULATIONS'. I have developed a very generic and fast numerical algorithm called 'Code for non-Isotropic Gaussian Sky (CoNIGS)' which can generate statistically anisotropic CMB simulations, useful to study the statistical properties of these anomalies. Details about this algorithm is available in Phys. Rev. D 89, 063013 (2014) .

Simulated temperature map of hemispherical power asymmetry.

Exploring the origin of CMB anomalies from lensed B-mode polarization

We observed CMB anomalies in the temperature field, but do not understand its origin. One of the best method to probe its origin is to search for possible signatures from other cosmological observables. We proposed a new window which can probe the imprints of hemispherical asymmetry in the scalar perturbations through lensing field and is capable to rule out the cosmological origin of the hemispherical asymmetry from scalar perturbations. Details about this work can be found in Phys. Rev. Lett. 116, 221301 (2016).

The expected asymmetry in the B-mode polarization if the observed hemispherical asymmetry has a cosmological origin from the scalar perturbations. This signal strength and shape can be determined by the observed hemispherical asymmetry signal in the temperature field.