ORCID Profile
0000-0002-8140-0422
Current Organisation
University of Oxford
Does something not look right? The information on this page has been harvested from data sources that may not be up to date. We continue to work with information providers to improve coverage and quality. To report an issue, use the Feedback Form.
Publisher: Oxford University Press (OUP)
Date: 10-10-2017
Publisher: Cambridge University Press (CUP)
Date: 06-2014
DOI: 10.1017/S1743921316010310
Abstract: Using the Horizon-AGN simulation we find a mass dependent spin orientation trend for galaxies: the spin of low-mass, rotation-dominated, blue, star-forming galaxies are preferentially aligned with their closest filament, whereas high-mass, velocity dispersion- supported, red quiescent galaxies tend to possess a spin perpendicular to these filaments. We explore the physical mechanisms driving galactic spin swings and quantify how much mergers and smooth accretion re-orient them relative to their host filaments.
Publisher: Oxford University Press (OUP)
Date: 26-07-2012
Publisher: American Astronomical Society
Date: 06-2023
Abstract: Based on the recent advancements in numerical simulations of galaxy formation, we anticipate the achievement of realistic models of galaxies in the near future. Morphology is the most basic and fundamental property of galaxies, yet observations and simulations still use different methods to determine galaxy morphology, making it difficult to compare them. We hereby perform a test on the recent NewHorizon simulation, which has spatial and mass resolutions that are remarkably high for a large-volume simulation, to resolve the situation. We generate mock images for the simulated galaxies using SKIRT, which calculates complex radiative transfer processes in each galaxy. We measure morphological and kinematic indicators using photometric and spectroscopic methods following observers’ techniques. We also measure the kinematic disk-to-total ratios using the Gaussian mixture model and assume that they represent the true structural composition of galaxies. We found that spectroscopic indicators such as V / σ and λ R closely trace the kinematic disk-to-total ratios. In contrast, photometric disk-to-total ratios based on the radial profile fitting method often fail to recover the true kinematic structure of galaxies, especially small ones. We provide translating equations between various morphological indicators.
Publisher: Oxford University Press (OUP)
Date: 28-10-2016
Publisher: American Astronomical Society
Date: 24-05-2021
Abstract: There have been many studies aiming to reveal the origins of the star–gas misalignment found in galaxies, but there still is a lack of understanding of the contribution from each formation channel candidate. We aim to answer the question by investigating the misaligned galaxies in the Horizon-AGN simulation. There are 27,903 galaxies of stellar mass M * 10 10 M ⊙ in our s le, of which 5984 are in a group in the halo mass of M 200 10 12 M ⊙ . We have identified four main formation channels of misalignment and quantified their levels of contribution: mergers (35%), interaction with nearby galaxies (23%), interaction with dense environments or their central galaxies (21%), and secular evolution, including smooth accretion from neighboring filaments (21%). We found in the simulation that the gas, rather than stars, is typically more vulnerable to dynamical disturbances hence, misalignment formation is mainly due to the change in the rotational axis of the gas rather than stars, regardless of the origin. We have also inspected the lifetime (duration) of the misalignment. The decay timescale of the misalignment shows a strong anticorrelation with the kinematic morphology ( V / σ ) and the cold gas fraction of the galaxy. The misalignment has a longer lifetime in denser regions, which is linked with the environmental impact on the host galaxy. There is a substantial difference in the length of the misalignment lifetime depending on the origin, and it can be explained by the magnitude of the initial position angle offset and the physical properties of the galaxies.
Publisher: Oxford University Press (OUP)
Date: 16-08-2017
Publisher: SPIE
Date: 14-06-2006
DOI: 10.1117/12.669772
Publisher: EDP Sciences
Date: 07-2001
Publisher: American Astronomical Society
Date: 08-02-2021
Publisher: Oxford University Press (OUP)
Date: 06-2005
Publisher: EDP Sciences
Date: 15-06-2009
Publisher: Oxford University Press (OUP)
Date: 11-11-2003
Publisher: Oxford University Press (OUP)
Date: 08-09-2016
Publisher: Springer Berlin Heidelberg
Date: 2008
Publisher: Oxford University Press (OUP)
Date: 28-08-2014
Publisher: Oxford University Press (OUP)
Date: 21-07-2017
Abstract: The observed massive end of the galaxy stellar mass function is steeper than its predicted dark matter halo counterpart in the standard Λ cold dark matter paradigm. In this paper, we investigate the impact of active galactic nuclei (AGN) feedback on star formation in massive galaxies. We isolate the impact of AGN by comparing two simulations from the HORIZON suite, which are identical except that one also includes supermassive black holes (SMBHs) and related feedback models. This allows us to cross-identify in idual galaxies between simulations and quantify the effect of AGN feedback on their properties, including stellar mass and gas outflows. We find that massive galaxies (M* ≥ 1011 M⊙) are quenched by AGN feedback to the extent that their stellar masses decrease by up to 80 per cent at z = 0. SMBHs affect their host halo through a combination of outflows that reduce their baryonic mass, particularly for galaxies in the mass range 109 M⊙ ≤ M* ≤ 1011 M⊙, and a disruption of central gas inflows, which limits in situ star formation. As a result, net gas inflows on to massive galaxies, M* ≥ 1011 M⊙, drop by up to 70 per cent. We measure a redshift evolution in the stellar mass ratio of twin galaxies with and without AGN feedback, with galaxies of a given stellar mass showing stronger signs of quenching earlier on. This evolution is driven by a progressive flattening of the MSMBH–M* relation with redshift, particularly for galaxies with M* ≤ 1010 M⊙. MSMBH/M* ratios decrease over time, as falling average gas densities in galaxies curb SMBH growth.
Publisher: Oxford University Press (OUP)
Date: 12-12-2017
Publisher: Oxford University Press (OUP)
Date: 24-07-2018
Publisher: EDP Sciences
Date: 05-2018
DOI: 10.1051/0004-6361/201629007
Abstract: Context. The anisotropic distribution of satellites around the central galaxy of their host halo is both well-documented in observations and predicted by the ΛCDM model. However its litude, direction and possible biases associated to the specific dynamics of such satellite galaxies are still highly debated. Aims. Using the cosmological hydrodynamics simulation Horizon-AGN, we aim to quantify the anisotropy of the spatial distribution of satellite galaxies relative to their central counterpart and explore its connexion to the local cosmic web, in the redshift range between 0.3 and 0.8. Methods. Haloes and galaxies were identified and their kinematics computed using their dark matter and stellar particles respectively. Sub-haloes were discarded and galaxies lying within 5 R vir of a given halo are matched to it. The filamentary structure of the cosmic web was extracted from the density field – smoothed over a 3 h −1 Mpc typical scale – as a network of contiguous segments. We then investigated the distribution function of relevant angles, most importantly the angle α between the central-to-satellite separation vector and the group’s nearest filament, aside with the angle between this same separation and the central minor axis. This allowed us to explore the correlations between filamentary infall, intra-cluster inspiralling and the resulting distribution of satellites around their central counterpart. Results. We find that, on average, 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 M ⊙ 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. In that redshift range, we find hints 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. Conclusions. 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.
Publisher: American Astronomical Society
Date: 05-07-2016
Publisher: EDP Sciences
Date: 18-08-2009
Publisher: Oxford University Press (OUP)
Date: 29-07-2015
Publisher: Oxford University Press (OUP)
Date: 05-09-2017
Publisher: Oxford University Press (OUP)
Date: 16-09-2014
Publisher: Oxford University Press (OUP)
Date: 09-02-2018
DOI: 10.1093/MNRAS/STY324
Abstract: Understanding the processes that drive the formation of black holes (BHs) is a key topic in observational cosmology. While the observed MBH–MBulge correlation in bulge-dominated galaxies is thought to be produced by major mergers, the existence of an MBH–M⋆ relation, across all galaxy morphological types, suggests that BHs may be largely built by secular processes. Recent evidence that bulge-less galaxies, which are unlikely to have had significant mergers, are offset from the MBH–MBulge relation, but lie on the MBH–M⋆ relation, has strengthened this hypothesis. Nevertheless, the small size and heterogeneity of current data sets, coupled with the difficulty in measuring precise BH masses, make it challenging to address this issue using empirical studies alone. Here, we use Horizon-AGN, a cosmological hydrodynamical simulation to probe the role of mergers in BH growth over cosmic time. We show that (1) as suggested by observations, simulated bulge-less galaxies lie offset from the main MBH–MBulge relation, but on the MBH–M⋆ relation, (2) the positions of galaxies on the MBH–M⋆ relation are not affected by their merger histories, and (3) only ∼35 per cent of the BH mass in today's massive galaxies is directly attributable to merging – the majority (∼65 per cent) of BH growth, therefore, takes place gradually, via secular processes, over cosmic time.
Location: United Kingdom of Great Britain and Northern Ireland
No related grants have been discovered for Julien Devriendt.