A review of RFI mitigation techniques in microwave radiometry

Radio frequency interference (RFI) is a well-known problem in microwave radiometry (MWR). Any undesired signal overlapping the MWR protected frequency bands introduces a bias in the measurements, which can corrupt the retrieved geophysical parameters. This paper presents a literature review of RFI detection and mitigation techniques for microwave radiometry from space. The reviewed techniques are divided between real aperture and aperture synthesis. A discussion and assessment of the application of RFI mitigation techniques is presented for each type of radiometer.Peer ReviewedPostprint (published version

Towards the first detection of strongly lensed HI emission

We report interferometric observations tuned to the redshifted neutral hydrogen (HI) 21cm emission line in three strongly lensed galaxies at $z \sim 0.4$ with the Giant Metrewave Radio Telescope (GMRT). One galaxy spectrum (J1106+5228 at z=0.407) shows evidence of a marginal detection with an integrated signal-to-noise ratio of 3.8, which, if confirmed by follow-up observations, would represent the first strongly lensed and most distant individual galaxy detected in HI emission. Two steps are performed to transcribe the lensed integrated flux measurements into HI mass measurements for all three target galaxies. First, we calculate the HI magnification factor $\mu$ by applying general relativistic ray-tracing to a physical model of the source-lens system. The HI magnification generally differs from the optical magnification and depends largely on the intrinsic HI mass $M_{\rm HI}$ due to the HI mass-size relation. Second, we employ a Bayesian formalism to convert the integrated flux, amplified by the $M_{\rm HI}$-dependent magnification factor $\mu$, into a probability density for $M_{\rm HI}$, accounting for the asymmetric uncertainty due to the declining HI mass function (Eddington bias). In this way, we determine a value of $\log_{\rm 10} (M_{\rm HI}/M_\odot) = 10.2^{+0.3}_{-0.7}$ for J1106+5228, consistent with the estimate of $9.4\pm0.3$ from the optical properties of this galaxy. The HI mass of the other two sources are consistent with zero within a 95 per cent confidence interval however we still provide upper limits for both sources and a $1\sigma$ lower limit for J1250-0135 using the same formalism.Comment: Accepted by MNRAS, no changes made. 12 pages, 7 figure

Observing large-scale structures in the gamma-ray sky

The essence of this doctoral research constitutes the development and application of novel data analysis and modelling techniques to observations from the High Altitude Water Cherenkov (HAWC) gamma-ray observatory. This thesis is organised in three main parts, culminating in the study of extended very-high-energy sources such as the Fermi bubbles. We first develop a novel discriminator to distinguish between gamma-ray-induced and proton-induced atmospheric showers. Our discriminator is independent of core reconstruction and is useful for enhancing the accuracy of the detector simulation. Secondly, we developed a new background model which incorporates the cosmic-ray anisotropy, exploits all statistics available and has fast computation times. Thirdly, we present a profile likelihood approach to calculate the significance and flux from any region of the sky, which allows the combination of data from different shower sizes while consistently accounting for their relative contributions. With the above tools, we perform blind searches for large-scale structures in the TeV gamma-ray sky. We find a candidate source region with significance up to 5.30 sigma at 16 degree integration scale, which could be a TeV halo associated with a pulsar, molecular clouds or a galactic outflow. Finally, with no significant signal from the north Fermi bubble and its base, we compute their integral flux upper limits, at 95% confidence level and present a hadronic model with an estimated proton cut-off energy at 85 TeV

Reverberation: models, estimation and application

The use of reverberation models is required in many applications such as acoustic measurements, speech dereverberation and robust automatic speech recognition. The aim of this thesis is to investigate different models and propose a perceptually-relevant reverberation model with suitable parameter estimation techniques for different applications. Reverberation can be modelled in both the time and frequency domain. The model parameters give direct information of both physical and perceptual characteristics. These characteristics create a multidimensional parameter space of reverberation, which can be to a large extent captured by a time-frequency domain model. In this thesis, the relationship between physical and perceptual model parameters will be discussed. In the first application, an intrusive technique is proposed to measure the reverberation or reverberance, perception of reverberation and the colouration. The room decay rate parameter is of particular interest. In practical applications, a blind estimate of the decay rate of acoustic energy in a room is required. A statistical model for the distribution of the decay rate of the reverberant signal named the eagleMax distribution is proposed. The eagleMax distribution describes the reverberant speech decay rates as a random variable that is the maximum of the room decay rates and anechoic speech decay rates. Three methods were developed to estimate the mean room decay rate from the eagleMax distributions alone. The estimated room decay rates form a reverberation model that will be discussed in the context of room acoustic measurements, speech dereverberation and robust automatic speech recognition individually

Direct Detection of Strongly Interacting Sub-GeV Dark Matter via Electron Recoils

We consider direct-detection searches for sub-GeV dark matter via electron scatterings in the presence of large interactions between dark and ordinary matter. Scatterings both on electrons and nuclei in the Earth's crust, atmosphere, and shielding material attenuate the expected local dark matter flux at a terrestrial detector, so that such experiments lose sensitivity to dark matter above some critical cross section. We study various models, including dark matter interacting with a heavy and ultralight dark photon, through an electric dipole moment, and exclusively with electrons. For a dark-photon mediator and an electric dipole interaction, the dark matter-electron scattering cross-section is directly linked to the dark matter-nucleus cross section, and nuclear interactions typically dominate the attenuation process. We determine the exclusion bands for the different dark-matter models from several experiments - SENSEI, CDMS-HVeV, XENON10, XENON100, and DarkSide-50 - using a combination of Monte Carlo simulations and analytic estimates. We also derive projected sensitivities for a detector located at different depths and for a range of exposures, and calculate the projected sensitivity for SENSEI at SNOLAB and DAMIC-M at Modane. Finally, we discuss the reach to high cross sections and the modulation signature of a small balloon- and satellite-borne detector sensitive to electron recoils, such as a Skipper-CCD. Such a detector could potentially probe unconstrained parameter space at high cross sections for a sub-dominant component of dark matter interacting with a massive, but ultralight, dark photon.Comment: 40 pages, 12 figures. Code available at https://github.com/temken/DaMaSCUS-CRUST and https://doi.org/10.5281/zenodo.2846401 . v2: matches published versio

Sound Source Separation

This is the author's accepted pre-print of the article, first published as G. Evangelista, S. Marchand, M. D. Plumbley and E. Vincent. Sound source separation. In U. Zölzer (ed.), DAFX: Digital Audio Effects, 2nd edition, Chapter 14, pp. 551-588. John Wiley & Sons, March 2011. ISBN 9781119991298. DOI: 10.1002/9781119991298.ch14file: Proof:e\EvangelistaMarchandPlumbleyV11-sound.pdf:PDF owner: markp timestamp: 2011.04.26file: Proof:e\EvangelistaMarchandPlumbleyV11-sound.pdf:PDF owner: markp timestamp: 2011.04.2