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J. Preston

Publications and source records attributed to J. Preston.

3 recordsLinked to original sources

ARRAKIHS: The observability of tidally stripped satellites in a Milky Way-like halo

Deep imaging surveys are revealing increasing numbers of low surface brightness stellar streams around Milky Way-like galaxies. These streams trace the orbital evolution and internal structure of their disrupted dwarf galaxy progenitors. We investigate the evolution and observability of tidal features from dwarf galaxies consistent with the $Λ$CDM framework and Local Group observations. We performed high-resolution $N$-body simulations of dwarf galaxies orbiting in a static Milky Way-like potential comprising a disc, bulge, and dark matter halo. Each dwarf comprised a Plummer stellar distribution embedded in a cuspy or cored generalised Navarro--Frenk--White dark matter halo. Idealised integrated surface brightness maps were constructed every 0.5 Gyr over 10 Gyr, and detectability was quantified through the projected area of stellar light brighter than limiting surface brightnesses, $μ_{\rm lim}=29$--$32$ mag arcsec$^{-2}$, chosen to span depths relevant to ARRAKIHS, LSST, and Euclid. The detectability of tidal features depends most strongly on progenitor stellar mass, orbital configuration, parameterised by the eccentricity proxy $e_0$, and evolutionary stage. Across this range, extended tidal debris is predominantly recovered for initially more radial configurations, mainly those with $e_0 \gtrsim 0.75$. In the simulated grid, detectable area is dominated by $M_\star=10^8$--$10^9 M_\odot$ progenitors, whereas $M_\star=10^6$--$10^7 M_\odot$ systems can undergo stripping without detectable debris. The detectable area evolves non-monotonically with time, reflecting the competition between stream formation, phase mixing, and the fading of diffuse debris below the adopted surface brightness limits. Cuspy and cored progenitors show similar evolution of the detectable area, with differences smaller than the scatter induced by orbital diversity.

astro-ph.GA↗

Microwave Spectroscopy of Thermally Excited Quasiparticles in YBa_2Cu_3O_{6.99}

We present here the microwave surface impedance of a high purity crystal of $YBa_2Cu_3O_{6.99}$ measured at 5 frequencies between 1 and 75 GHz. This data set reveals the main features of the conductivity spectrum of the thermally excited quasiparticles in the superconducting state. Below 20 K there is a regime of extremely long quasiparticle lifetimes, due to both the collapse of inelastic scattering below $T_c$ and the very weak impurity scattering in the high purity $BaZrO_3$-grown crystal used in this study. Above 20 K, the scattering increases dramatically, initially at least as fast as $T^4$.

cond-mat.supr-con↗

Low temperature penetration depth and the effect of quasi-particle scattering measured by millimeter wave transmission in YBaCuO thin films

Measurement of the penetration depth as a function of temperature using millimeter wave transmission in the range 130-500GHz are reported for three YBCO thin films. The experiment provides the absolute value for the penetration depth at low temperature: the derivation from the transmission data and the experimental uncertainty are discussed. We find a zero temperature penetration depth of 199+/-20nm, 218+/-20nm and 218+/-20nm, for YBCO-50nm/LaAlO3 (pristine), YBCO-130nm/MgO and YBCO-50nm/LaAlO3 (irradiated) respectively. The penetration depth exhibits a different behavior for the three films. In the pristine sample, it shows a clear temperature and frequency dependence, namely the temperature dependence is consistent with a linear variation, whose slope decreases with frequency: this is considered as an evidence for the scattering rate being of the order of the measuring frequency. A two fluids analysis yields 1.7 10^{12} s^{-1}. In the two other samples, the penetration depth does not display any frequency dependence, suggesting a significantly larger scattering rate. The temperature dependence is different in these latter samples. It is consistent with a linear variation for the YBCO/MgO sample, not for the YBCO/LaAlO3 irradiated one, which exhibits a T^2 dependence up to 40K. We have compared our data to the predictions of the d-wave model incorporating resonant scattering and we do not find a satisfactory agreement. However, the large value of the penetration depth at zero Kelvin in the pristine sample is a puzzle and sheds some doubt on a straightforward comparison with the theory of data from thin films, considered as dirty d-wave superconductors.

cond-mat.supr-con↗