Characterization of Zero-Bias Microwave Diode Power Detectors at Cryogenic Temperature

We present the characterization of commercial tunnel diode low-level microwave power detectors at room and cryogenic temperatures. The sensitivity as well as the output voltage noise of the tunnel diodes are measured as functions of the applied microwave power, the signal frequency being 10 GHz. We highlight strong variations of the diode characteristics when the applied microwave power is higher than few microwatt. For a diode operating at ${4}$ K, the differential gain increases from ${1,000}$ V/W to about ${4,500}$ V/W when the power passes from ${-30}$ dBm to ${-20}$ dBm. The diode present a white noise floor equivalent to a NEP of ${0.8}$ pW/ ${\sqrt{\mathrm{Hz}}}$ and ${8}$ pW/${ \sqrt{\mathrm{Hz}}}$ at 4 K and 300 K respectively. Its flicker noise is equivalent to a relative amplitude noise power spectral density ${S_{\alpha}(1~\mathrm{Hz})=-120}$~dB/Hz at ${4}$ K. Flicker noise is 10 dB higher at room temperature.Comment: 8 pages and 16 figure

The cosmic evolution of massive black holes in the Horizon-AGN simulation

We analyse the demographics of black holes (BHs) in the large-volume cosmological hydrodynamical simulation Horizon-AGN. This simulation statistically models how much gas is accreted onto BHs, traces the energy deposited into their environment and, consequently, the back-reaction of the ambient medium on BH growth. The synthetic BHs reproduce a variety of observational constraints such as the redshift evolution of the BH mass density and the mass function. Strong self-regulation via AGN feedback, weak supernova feedback, and unresolved internal processes result in a tight BH-galaxy mass correlation. Starting at z~2, tidal stripping creates a small population of BHs over-massive with respect to the halo. The fraction of galaxies hosting a central BH or an AGN increases with stellar mass. The AGN fraction agrees better with multi-wavelength studies, than single-wavelength ones, unless obscuration is taken into account. The most massive halos present BH multiplicity, with additional BHs gained by ongoing or past mergers. In some cases, both a central and an off-centre AGN shine concurrently, producing a dual AGN. This dual AGN population dwindles with decreasing redshift, as found in observations. Specific accretion rate and Eddington ratio distributions are in good agreement with observational estimates. The BH population is dominated in turn by fast, slow, and very slow accretors, with transitions occurring at z=3 and z=2 respectively.Comment: Accepted for publication in MNRA

Tests of Sapphire Crystals Produced with Different Growth Processes for Ultra-stable Microwave Oscillators

We present the characterization of 8-12 GHz whispering gallery mode resonators machined in high-quality sapphire crystals elaborated with different growth techniques. These microwave resonators are intended to constitute the reference frequency of ultra-stable Cryogenic Sapphire Oscillators. We conducted systematic tests near 4 K on these crystals to determine the unloaded Q-factor and the turnover temperature for whispering gallery modes in the 8-12 GHz frequency range. These characterizations show that high quality sapphire crystals elaborated with the Heat Exchange or the Kyropoulos growth technique are both suitable to meet a fractional frequency stability better than 1x10-15 for 1 s to 10.000 s integration times.Comment: 7 figure

Process Optimization and Downscaling of a Single Electron Single Dot Memory

This paper presents the process optimization of a single-electron nanoflash electron memory. Self-aligned single dot memory structures have been fabricated using a wet anisotropic oxidation of a silicon nanowire. One of the main issue was to clarify the process conditions for the dot formation. Based on the process modeling, the influence of various parameters (oxidation temperature, nanowire shape) has been investigated. The necessity of a sharp compromise between these different parameters to ensure the presence of the memory dot has been established. In order to propose an aggressive memory cell, the downscaling of the device has been carefully studied. Scaling rules show that the size of the original device could be reduced by a factor of 2. This point has been previously confirmed by the realization of single-electron memory devices

Model Assisted Creativity Sessions for the Design of Mixed Interactive Systems: a Protocol Analysis

Part 1: Long and Short Papers (Continued)International audienceTo help designers face the complexity of mixed interaction and identifying original and adapted solutions, we developed and evaluated an original approach to interaction design. This approach, called MACS, aims to combine the best elements of both a model of mixed interaction, and a collaborative and creative session. The objective is twofold: to support the exploration of the design space, and to establish a common language between participants. To assess the viability of this approach, we relied on a protocol analysis technique on the verbal recordings of two existing design situations. Results show that the model has a strong impact on the generation of ideas and that participants use the model concepts to share their thoughts during the session

Caught in the rhythm: how satellites settle into a plane around their central galaxy

Using the cosmological hydrodynamics simulation Horizon-AGN, we investigate the spatial distribution of satellite galaxies relative to their central counterpart in the redshift range between 0.3 and 0.8. We find that, on average, these satellites tend to be located on the galactic plane of the central object. This effect is detected for central galaxies with a stellar mass larger than 10^10 solar masses and found to be strongest for red passive galaxies, while blue galaxies exhibit a weaker trend. For galaxies with a minor axis parallel to the direction of the nearest filament, we find that the coplanarity is stronger in the vicinity of the central galaxy, and decreases when moving towards the outskirts of the host halo. By contrast, the spatial distribution of satellite galaxies relative to their closest filament follows the opposite trend: their tendency to align with them dominates at large distances from the central galaxy, and fades away in its vicinity. Relying on mock catalogs of galaxies in that redshift range, we show that massive red centrals with a spin perpendicular to their filament also have corotating satellites well aligned with both the galactic plane and the filament. On the other hand, lower-mass blue centrals with a spin parallel to their filament have satellites flowing straight along this filament, and hence orthogonally to their galactic plane. The orbit of these satellites is then progressively bent towards a better alignment with the galactic plane as they penetrate the central region of their host halo. The kinematics previously described are consistent with satellite infall and spin build-up via quasi-polar flows, followed by a re-orientation of the spin of massive red galaxies through mergers.Comment: 26 pages, 28 figures, 2 tables, submitted to A&

Caught in the rhythm II: Competitive alignments of satellites with their inner halo and central galaxy

The anisotropic distribution of satellites around the central galaxy of their host halo is well-documented. However the relative impact of baryons and dark matter in shaping this distribution is still debated. Using the simulation Horizon-AGN, the angular distribution of satellite galaxies with respect to their central counterpart and halo is quantified. Below one Rvir, satellites cluster more strongly in the plane of the central, rather than merely tracing the shape of their host halo. This is due to the increased isotropy of inner haloes acquired through their inside-out assembly in vorticity-rich flows along the cosmic web. While the effect of centrals decreases with distance, halos' triaxiality increases, impacting more and more the satellite's distribution. Effects become comparable just outside one virial radius. Above this scale, the filamentary infall also impacts the satellites distribution, dominating above two virial radii. The central's morphology plays a governing role: the alignment w.r.t. the central plane is four times stronger in haloes hosting stellar discs than in spheroids. But the impact of the galactic plane decreases for lower satellite-to-central mass ratios, suggesting this might not hold for dwarf satellites of the Local group. The orientation of the Milky-Way's satellites traces their cosmic filament, their level of coplanarity is consistent with systems of similar mass and cosmic location in Horizon-AGN. However, the strong impact of galactic planes in massive groups and clusters bounds the likelihood of finding a relaxed region where satellites can be used to infer halo shape. The minor-to-major axis ratios for haloes with log(M0/Msun)>13.5 is underestimated by 10%. This error soars quickly to 30-40% for individual halo measurements.Comment: 30 pages, 28 figures, submitted to A&