Testing Models of the Individual and Cosmological Evolutions of Powerful Radio Galaxies

We seek to develop an essentially analytical model for the evolution of Fanaroff-Riley Class II radio galaxies as they age individually and as their numbers vary with cosmological epoch. Such modeling is required in order to probe in more detail the impact of radio galaxies on the growth of structures in the universe, which appears likely to have been quite significant at z > 1. In this first paper of a series we compare three rather sophisticated analytical models for the evolution of linear size and lobe power of FR II radio galaxies, those of Kaiser, Dennett-Thorpe & Alexander (1997), Blundell, Rawlings & Willott (1999), and Manolakou & Kirk (2002). We perform multi-dimensional Monte Carlo simulations in order to compare the predictions of each model for radio powers, sizes, redshifts and spectral indices with data. The observational samples used here are the low frequency radio surveys, 3CRR, 6CE and 7CRS, which are flux-limited and complete. We search for and describe the best parameters for each model, after doing statistical tests on them. We find that no existing model can give acceptable fits to all the properties of the surveys considered, although the Kaiser, Dennett-Thorpe & Alexander (1997) model gives better overall results than do the Manolakou & Kirk (2002) or Blundell, Rawlings & Willott (1999) models for most of the tests we performed. We suggest ways in which these models may be improved.Comment: 26 pages, 5 figures; substantially improved version, with additional statistical tests; to appear in MNRA

Triple-ionised carbon associated with the low-density neutral hydrogen gas at 1.7 < z < 3.3: the integrated N(HI)-N(CIV) relation

From the Voigt profile fitting analysis of 183 intervening CIV systems at 1.7 < z < 3.3 in 23 high-quality UVES/VLT and HIRES/Keck QSO spectra, we find that a majority of CIV systems (~75%) display a well-characterised scaling relation between integrated column densities of HI and CIV with a negligible redshift evolution, when column densities of all the HI and CIV components are integrated within a given (-150, +150) km/sec range centred at the CIV flux minimum. The integrated CIV column density N(CIV, sys) increases with N(HI, sys) at log N(HI, sys) = 14.0--15.5 and log N(CIV, sys) = 11.8--14.0, then becomes almost independent of N(HI, sys) at log N(HI, sys) > 16, with a large scatter: at log N(HI, sys) = 14--22, log N(CIV, sys) = C1 / (log(NHI, sys) + C2) + C3, with C1 = -1.90+0.55, C2 = -14.11+0.19 and C3 = 14.76+0.17, respectively. The steep (flat) part is dominated by SiIV-free (SiIV-enriched) CIV systems. Extrapolating the N(HI, sys)-N(CIV, sys) relation implies that most absorbers with log N(HI) < 14 are virtually CIV-free. The N(HI, sys)-N(CIV, sys) relation does not hold for individual components, clumps or the integration velocity range less than +-100 km/sec. It is expected if the line-of-sight extent of CIV is smaller than HI and N(CIV, sys) decreases more rapidly than N(HI, sys) at the larger impact parameter, regardless of the location of the HI+CIV gas in the IGM filaments or in the intervening galactic halos.Comment: Accepted for publication on MNRAS, 26 pages, 20 figures, 4 tables. On-line materials are found in the submitted civ.tar.gz file: complete Table 2, complete Table 3, complete Table 4, velocity plots civ1.pdf, civ2.pdf, civ3.pdf, civ4.pdf and civ5.pd

Kinetic or thermal AGN feedback in simulations of isolated and merging disc galaxies calibrated by the M-\ua0 relation

We investigate two modes of coupling the feedback energy from a central active galacticnucleus (AGN) to the neighbouring gas in galaxy simulations: kinetic - velocity boost andthermal - heating. We formulate kinetic feedback models for energy-driven wind (EDW)and momentum-driven wind (MDW), using two free parameters: feedback efficiency \u3b5f and AGN wind velocity \u3bd w. A novel numerical algorithm is implemented in the smoothed particlehydrodynamics code GADGET-3, to prevent the expansion of a hole in the gas distributionaround the black hole (BH). We perform simulations of isolated evolution and merger ofdisc galaxies, of Milky Way mass as well as lower and higher masses. We find that in theisolated galaxy BH kinetic feedback generates intermittent bipolar jet-like gas outflows. Weinfer that current prescriptions for BH subgrid physics in galaxy simulations can grow theBH to observed values even in an isolated disc galaxy. The BH growth is enhanced in agalaxy merger, which consequently requires different model parameters to fit the observationsthan an isolated case. Comparing the [MBH-\u3c3*] relation obtained in our simulations withobservational data, we conclude that it is possible to find parameter sets for a fit in all themodels (e.g. \u3bdw = 10 000 km s-1 and \u3b5f = 0.25 for BH kinetic EDW), except for the casewith MDW feedback in a galaxy merger, in which the BH is always too massive. The BHthermal feedback implementation of Springel et al. within the multiphase star formation modelis found to have negligible impact on gas properties, and the effect claimed in all previousstudies is attributed to gas depletion around the BH by the creation of an artificial hole. TheBH mass accretion rate in our simulations exhibit heavy fluctuations. The star formation rate isquenched with feedback by removal of gas. The circumgalactic medium gas at galactocentricdistances (20-100) h-1 kpc is found to give the best metallicity observational diagnostic todistinguish between BH model

The influence of temperature and charge-discharge rate on open circuit voltage hysteresis of an LFP Li-ion battery

Open circuit voltage (OCV) is a crucial parameter in an equivalent circuit model (ECM). The path dependence of OCV is a distinctive characteristic of a Li-ion battery; this is known as OCV hysteresis. In this manuscript the influence of temperature and charge/discharge rate on OCV hysteresis has been identified. OCV hysteresis was found to be 13mV higher at 0°C while remaining unchanged at 45°C compared to the 25°C result. In general, OCV hysteresis was found to be less dependent on charge/discharge rate than temperature. The potential explanations of these results have been reported