A universal framework for Space Resource Utilisation (SRU)

Space Resource Utilisation (SRU) or In Situ Resource Utilisation (ISRU) is the use of natural resources from the Moon, Mars and other bodies for use in situ or elsewhere in the Solar System. The implementation of SRU technologies will provide the breakthrough for humankind to explore further into space. A range of extraction processes to produce usable resources have been proposed, such as oxygen production from lunar regolith, extraction of lunar ice and construction of habitation by 3D printing. Practical and successful implementation of SRU requires that all the stages of the process flowsheet (excavation, beneficiation and extraction) are considered. This requires a complete ‘mine-to-market’ type approach, analogous to that of terrestrial mineral extraction. One of the key challenges is the unique cross-disciplinary nature of SRU; it integrates space systems, robotics, materials handling and beneficiation, and chemical process engineering. This is underpinned by knowledge of the lunar or planetary geology, including mineralogy, physical characteristics, and the variability in local materials. Combining such diverse fields in a coordinated way requires the use of a universal framework. The framework will enable integration of operations and comparison of technologies, and will define a global terminology to be used across all fields. In this paper, a universal SRU flowsheet and terminology are described, and a matrix approach to describing regolith characteristics specifically for SRU is proposed. This is the first time that such an approach has been taken to unify this rapidly-developing sector

Constraining stellar assembly and AGN feedback at the peak epoch of star formation

We study stellar assembly and feedback from active galactic nuclei (AGN) around the epoch of peak star formation (1<z<2), by comparing hydrodynamic simulations to rest-frame UV-optical galaxy colours from the Wide Field Camera 3 (WFC3) Early-Release Science (ERS) Programme. Our Adaptive Mesh Refinement simulations include metal-dependent radiative cooling, star formation, kinetic outflows due to supernova explosions, and feedback from supermassive black holes. Our model assumes that when gas accretes onto black holes, a fraction of the energy is used to form either thermal winds or sub-relativistic momentum-imparting collimated jets, depending on the accretion rate. We find that the predicted rest-frame UV-optical colours of galaxies in the model that includes AGN feedback is in broad agreement with the observed colours of the WFC3 ERS sample at 1<z<2. The predicted number of massive galaxies also matches well with observations in this redshift range. However, the massive galaxies are predicted to show higher levels of residual star formation activity than the observational estimates, suggesting the need for further suppression of star formation without significantly altering the stellar mass function. We discuss possible improvements, involving faster stellar assembly through enhanced star formation during galaxy mergers while star formation at the peak epoch is still modulated by the AGN feedback.Comment: 6 pages, 4 figures, accepted for publication in MNRAS Letter

Extreme AGN Feedback and Cool Core Destruction in the X-ray Luminous Galaxy Cluster MACS J1931.8-2634

We report on a deep, multiwavelength study of the galaxy cluster MACS J1931.8-2634 using Chandra X-ray, Subaru optical, and VLA 1.4 GHz radio data. This cluster (z=0.352) harbors one of the most X-ray luminous cool cores yet discovered, with an equivalent mass cooling rate within the central 50 kpc is approximately 700 solar masses/yr. Unique features observed in the central core of MACSJ1931.8-2634 hint to a wealth of past activity that has greatly disrupted the original cool core. We observe a spiral of relatively cool, dense, X-ray emitting gas connected to the cool core, as well as highly elongated intracluster light (ICL) surrounding the cD galaxy. Extended radio emission is observed surrounding the central AGN, elongated in the east-west direction, spatially coincident with X-ray cavities. The power input required to inflate these `bubbles' is estimated from both the X-ray and radio emission to reside between 4 and 14e45 erg/s, putting it among the most powerful jets ever observed. This combination of a powerful AGN outburst and bulk motion of the cool core have resulted in two X-ray bright ridges to form to the north and south of the central AGN at a distance of approximately 25 kpc. The northern ridge has spectral characteristics typical of cool cores and is consistent with being a remnant of the cool core after it was disrupted by the AGN and bulk motions. It is also the site of H-alpha filaments and young stars. The X-ray spectroscopic cooling rate associated with this ridge is approximately 165 solar masses/yr, which agrees with the estimate of the star formation rate from broad-band optical imaging (170 solar masses/yr). MACS J1931.8-2634 appears to harbor one of most profoundly disrupted low entropy cores observed in a cluster, and offers new insights into the survivability of cool cores in the context of hierarchical structure formation.Comment: 19 pages, 15 figures, 5 tables. Accepted by MNRAS for publication September 30 201

Numerical simulations of the Warm-Hot Intergalactic Medium

In this paper we review the current predictions of numerical simulations for the origin and observability of the warm hot intergalactic medium (WHIM), the diffuse gas that contains up to 50 per cent of the baryons at z~0. During structure formation, gravitational accretion shocks emerging from collapsing regions gradually heat the intergalactic medium (IGM) to temperatures in the range T~10^5-10^7 K. The WHIM is predicted to radiate most of its energy in the ultraviolet (UV) and X-ray bands and to contribute a significant fraction of the soft X-ray background emission. While O VI and C IV absorption systems arising in the cooler fraction of the WHIM with T~10^5-10^5.5 K are seen in FUSE and HST observations, models agree that current X-ray telescopes such as Chandra and XMM-Newton do not have enough sensitivity to detect the hotter WHIM. However, future missions such as Constellation-X and XEUS might be able to detect both emission lines and absorption systems from highly ionised atoms such as O VII, O VIII and Fe XVII.Comment: 18 pages, 5 figures, accepted for publication in Space Science Reviews, special issue "Clusters of galaxies: beyond the thermal view", Editor J.S. Kaastra, Chapter 14; work done by an international team at the International Space Science Institute (ISSI), Bern, organised by J.S. Kaastra, A.M. Bykov, S. Schindler & J.A.M. Bleeke

Emission from the circumgalactic medium: from cosmological zoom-in simulations to multiwavelength observables

We simulate the flux emitted from galaxy haloes in order to quantify the brightness of the circumgalactic medium (CGM). We use dedicated zoom-in cosmological simulations with the hydrodynamical adaptive mesh refinement code ramses, which are evolved down to z = 0 and reach a maximum spatial resolution of 380 h−1 pc and a gas mass resolution up to 1.8×105h−1M⊙ in the densest regions. We compute the expected emission from the gas in the CGM using cloudy emissivity models for different lines (e.g. Lyα, C iv, O vi, C vi, O viii) considering UV background fluorescence, gravitational cooling and continuum emission. In the case of Lyα, we additionally consider the scattering of continuum photons. We compare our predictions to current observations and find them to be in good agreement at any redshift after adjusting the Lyα escape fraction. We combine our mock observations with instrument models for Faint Intergalactic Redshifted Emission Balloon-2 (FIREBall-2; UV balloon spectrograph) and HARMONI (visible and NIR IFU on the ELT) to predict CGM observations with either instrument and optimize target selections and observing strategies. Our results show that Lyα emission from the CGM at a redshift of 0.7 will be observable with FIREBall-2 for bright galaxies (NUV∼18 mag), while metal lines like O vi and C iv will remain challenging to detect. HARMONI is found to be well suited to study the CGM at different redshifts with various tracers

Emission from the circumgalactic medium: from cosmological zoom-in simulations to multiwavelength observables

We simulate the flux emitted from galaxy haloes in order to quantify the brightness of the circumgalactic medium (CGM). We use dedicated zoom-in cosmological simulations with the hydrodynamical adaptive mesh refinement code RAMSES, which are evolved down to z = 0 and reach a maximum spatial resolution of 380 h−1 pc and a gas mass resolution up to 1.8×105 h−1 M⊙ in the densest regions. We compute the expected emission from the gas in the CGM using CLOUDY emissivity models for different lines (e.g. Lyα, C IV, O VI, C VI, O VIII) considering UV background fluorescence, gravitational cooling and continuum emission. In the case of Lyα, we additionally consider the scattering of continuum photons. We compare our predictions to current observations and find them to be in good agreement at any redshift after adjusting the Lyα escape fraction. We combine our mock observations with instrument models for Faint Intergalactic Redshifted Emission Balloon-2 (FIREBall-2; UV balloon spectrograph) and HARMONI (visible and NIR IFU on the ELT) to predict CGM observations with either instrument and optimize target selections and observing strategies. Our results show that Lyα emission from the CGM at a redshift of 0.7 will be observable with FIREBall-2 for bright galaxies (NUV∼18 mag), while metal lines like O VI and C IV will remain challenging to detect. HARMONI is found to be well suited to study the CGM at different redshifts with various tracers.</p