The low-mass end of the Mbh/Mhost relation in quasars

The Mbh-Mhost relation in quasars has been probed only in a limited parameter space, namely at Mbh~10^9 Msun and Mhost~10^12 Msun. Here we present a study of 26 quasars lying in the low-mass end of the relation, down to Mbh~10^7 Msun. We selected quasars from the SDSS and HST-FOS archives, requiring modest Mbh (as derived through the virial paradigm). We imaged our sources in H band from the Nordic Optical Telescope. The quasar host galaxies have been resolved in 25 out of 26 observed targets. Host galaxy luminosities and stellar masses are computed, under reasonable assumptions on their star formation histories. Combining these results with those from our previous studies, we manage to extend the sampled parameter space of the Mbh-Mhost relation in quasars. The relation holds over 2 dex in both the parameters, similarly to what observed in low-luminosity AGN and in quiescent galaxies. For the first time, we are able to measure the slope of the Mbh-Mhost relation in quasars. We find that it is consistent with the linear case (similarly to what observed in quiescent galaxies). We do not find any evidence of a population of massive black holes lying below the relation.Comment: Accepted for publication in Advances in Astronomy. To appear in the special issue: "Seeking for the Leading Actor on the Cosmic Stage: Galaxies versus Supermassive Black Holes

Towards in-cylinder chemical species tomography on large-bore IC engines with pre-chamber

A feasibility study is presented and the achieved key design milestones towards the first application of Chemical Species Tomography by Near-IR Absorption Tomography on a heavy duty, large-bore marine engine to visualise relative mixture strength are described. The engine is equipped with pre-chamber ignition and operates using Liquefied Natural Gas with > 88.9 % methane content. Operation of the engine under maximum-load conditions is a key design requirement, with peak cylinder pressure and mean temperature exceeding 127,510 Torr (170 bar) and 850 K respectively. The near-IR spectroscopic behaviour of methane is examined for suitable absorption and reference regions for the above application. In particular, the spectroscopic absorption around the 2ν3 transition region near 1,666 nm is approximated by simulation using data from the HITRAN database under worst-case conditions. The simulation results are compared with methane spectra experimentally acquired at high temperature and ambient pressure. Interference from other chemical species as well as measurement linearity is also investigated. A 31-laser beam tomographic imaging array is proposed, which has been optimised to achieve higher spatial resolution performance in the vicinity of the pre-chamber’s orifices. To enable optical access, a novel, minimally-intrusive method is presented, utilising standard fibreoptics and collimator

High Speed Combustion Imaging in a Large Bore Gas Engine: The Relationship Between Pre- and Main Chamber Heat Release

An experimental study is carried out to investigate the combustion process in a Wartsila 34SG spark-ignited lean burn four-stroke large bore engine (bore 340 mm) by means of optical diagnostics when operating on natural gas. The main focus of this work is to gain knowledge about in-cylinder combustion phenomena when igniting a lean air/fuel mixture with pre-combustion chamber induced jets. Especially the origin of cyclic variability is of interest. The flame propagation process in a single cycle was captured using a high speed video camera. The analysis is based on apparent heat release rates in the pre-combustion chamber and main chamber, in order to find correlations with the imaged phenomena. The results show that the flame propagation inside the main chamber starts at the end of the pre-chamber combustion heat release and that variation in main chamber heat release does not correlate with variations in the pre-combustion chamber