arXiv subjects

James W. Trayford

Publications and source records attributed to James W. Trayford.

At least 37 records · Page 2Linked to original sources

arXiv2026

A hybrid active galactic nucleus feedback model with spinning black holes, winds and jets

We present a hybrid active galactic nucleus (AGN) feedback model that features three accretion disc states (the thick, thin, and slim discs at low, moderate, and super-Eddington accretion rates, respectively), and two feedback modes: thermal isotropic and kinetic jets. The model includes black hole (BH) spin evolution due to gas accretion, BH mergers, jet spindown, and Lense-Thirring torques. The BH spin determines the jet directions and affects the feedback efficiencies. The model is implemented in the SWIFT code and coupled with the COLIBRE galaxy formation model. We present the first results from hybrid AGN feedback simulations run as part of the COLIBRE suite, focusing on the impact of new parameters and calibration efforts. Using the new hybrid AGN feedback model, we find that AGN feedback affects not just massive galaxies, but all galaxies down to $M_*\approx10^8$ $\mathrm{M}_\odot$. BH spins are predicted to be near-maximal for intermediate-mass BHs ($M_\mathrm{BH}\in[10^6,10^8]$ $\mathrm{M}_\odot$), and lower for other BH masses. These trends are in good agreement with observations. The intergalactic medium is hotter and impacted on larger scales in the hybrid AGN feedback simulations compared to those using purely thermal feedback. In the hybrid AGN simulations, we predict that half of the cumulative injected AGN energy is in thermal and the other half in jet form, broadly independent of BH mass and redshift. Jet feedback is important at all redshifts and dominates over thermal feedback at $z<0.5$ and $z>1.5$, but only mildly.

astro-ph.GA↗

arXiv2026

Non-explosive pre-supernova feedback in the COLIBRE model of galaxy formation

We present the implementation and testing of a subgrid non-explosive pre-supernova (NEPS) feedback module for the COLIBRE model of galaxy formation. The NEPS module incorporates three key physical processes sourced by young, massive stars that act immediately following star formation: momentum injection from stellar winds and radiation pressure, and thermal energy from photoheating in HII regions. The age- and metallicity-dependent energy and momentum budgets are derived from BPASS stellar population models and are coupled self-consistently to the local gas properties. We test the model using a suite of smoothed particle hydrodynamics simulations of isolated, unstable gaseous disks at various numerical resolutions (gas particle masses in the range $10^4-10^6$ $\rm M_{\odot}$). We find that the NEPS module successfully regulates star formation by providing pressure support that prevents catastrophic gas collapse. This regulation improves the numerical convergence of star formation rates and disk structure. In our model, feedback from HII regions is the dominant regulatory mechanism. Furthermore, we demonstrate a crucial synergy with subsequent supernova feedback; NEPS feedback pre-processes the interstellar medium, creating a more homogeneous environment that moderates the effect of explosive feedback from supernova events. Our NEPS module thus provides a physically motivated and numerically robust framework that mitigates resolution-dependent artefacts and promotes self-regulated galaxy growth.

astro-ph.GA↗

arXiv2026

Modelling the evolution and influence of dust in cosmological simulations that include the cold phase of the interstellar medium

While marginal in mass terms, dust grains play an outsized role in both the physics and observation of the interstellar medium (ISM). However, explicit modelling of this ISM constituent remains uncommon in large cosmological simulations. In this work, we present a model for the life-cycle of dust in the ISM that couples to the forthcoming COLIBRE galaxy formation model, which explicitly simulates the cold ISM. We follow 6 distinct grain types: 3 chemical species, including carbon and two silicate grains, with 2 size bins each. Our dust model accounts for seeding of grains from stellar ejecta, self-consistent element-by-element metal yields and growth by accretion, grain size transfer (shattering and coagulation) and destruction of dust by thermal sputtering in the ISM. We detail the calibration of this model, particularly the use of a clumping factor, to account for unresolved gas clouds in which dust readily evolves. We present a fiducial run in a 25$^3$~cMpc$^3$ cosmological volume that displays good agreement with observations of the cosmic evolution of dust density, as well as the $z=0$ galaxy dust mass function and dust scaling relations. We highlight known tensions between observational datasets of the dust-to-gas ratio as a function of metallicity depending on which metallicity calibrator is used; our model favours higher-normalisation metallicity calibrators, which agree with the observations within 0.1~dex for stellar masses $>10^9 \; {\rm M_\odot}$. We compare the grain size distribution to observations of local galaxies, and find that our simulation suggests a higher concentration of small grains, associated with more diffuse ISM and the warm-neutral medium (WNM), which both play a key role in boosting H$_2$ content. Putting these results and modelling approaches in context, we set the stage for upcoming insights into the dusty ISM of galaxies using the COLIBRE simulations.

astro-ph.GA↗

arXiv2025

Hybrid-chimes: A model for radiative cooling and the abundances of ions and molecules in simulations of galaxy formation

Radiative processes play a pivotal role in shaping the thermal and chemical states of gas across diverse astrophysical environments, from the interstellar medium (ISM) to the intergalactic medium. We present a hybrid cooling model for cosmological simulations that incorporates a comprehensive treatment of radiative processes, including parameterizations of the interstellar radiation field, cosmic ray rates, and dust physics. The model uses the chimes chemical network and combines on-the-fly non-equilibrium calculations with quasi-equilibrium cooling rates. The quasi-equilibrium rates account for the time-dependent free electron fractions of elements tracked in non-equilibrium, balancing computational efficiency with physical accuracy. We evaluate the performance under various conditions, including the thermal evolution of primordial gas at the cosmic mean density, the properties of the warm and cold neutral media in Milky Way-like galaxies, and the atomic-to-molecular hydrogen transition. We demonstrate that thermal equilibrium predictions for the neutral phases of the ISM underestimate the median gas pressures in simulations of isolated galaxies by up to 0.5 dex. Finally we find that the atomic-to-molecular hydrogen transition is shifted to lower densities by up to 1 dex if oxygen is not included in the chemical network. Our work provides a robust framework for studying the multi-phase ISM and its role in galaxy formation and evolution.

astro-ph.GA↗

arXiv2025

A case study of translating sonifications across musical cultures for an educational application

Sonification can be part of educational resources that can be accessible to those who prefer, or require, non-visual learning methods. Furthermore, sonification can contribute to an engaging multi-sensory learning experience, which are known to benefit general learners. Whilst some sonification can be relatively agnostic to musical culture, many sonifications are subject to culturally influenced choices, such as the chosen harmonies, rhythmic structures, and instrumentation. This is important when considering how universally inclusive and relatable sonification-based educational resources will be. Here we present a case study of translating a sonification-based educational show about the Solar System, that was originally designed with influences from Euro-American (Western-classical) music, to be more culturally relevant to the Caribbean region. We describe the motivation, approach, some of the challenges, and the initial feedback of the resulting output of the project. Finally, we provide reflections on the importance of further work exploring how educational sonifications can transcend international borders and musical cultures.

physics.ed-ph↗

arXiv2025

STRAUSS: Sonification Tools & Resources for Analysis Using Sound Synthesis

Sonification, or conveying data using non-verbal audio, is a relatively niche but growing approach for presenting data across multiple specialist domains including astronomy, climate science, and beyond. The STRAUSS Python package aims to provide such a tool, which builds upon previous approaches to provide a powerful means to explore different ways of expressing data, with fine control over the output audio and its format. STRAUSS is a free, open source (FOSS) package, designed to allow flexible and effective sonification to be integrated into data workflows, in analogy to widely used visualisation packages. The remit of STRAUSS is broad; it is intended to be able to bridge between ad-hoc solutions for sonifying very particular datasets, and highly technical compositional and sound-design tools that are not optimised for sonification, or may have a steep learning curve. The code offers a range of approaches to sonification for a variety of contexts (e.g. science education, science communication, technical data analysis, etc). To this end, STRAUSS is packaged with a number of examples of different sonification approaches, and preset configurations to support "low-barrier, high-ceiling" approach. STRAUSS has been used to produce both educational resources and analysis tools.

astro-ph.IM↗

arXiv2023

Introducing STRAUSS: A flexible sonification Python package

We introduce STRAUSS (Sonification Tools and Resources for Analysis Using Sound Synthesis) a modular, self-contained and flexible Python sonification package, operating in a free and open source (FOSS) capacity. STRAUSS is intended to be a flexible tool suitable for both scientific data exploration and analysis as well as for producing sonifications that are suitable for public outreach and artistic contexts. We explain the motivations behind STRAUSS, and how these lead to our design choices. We also describe the basic code structure and concepts. We then present output sonification examples, specifically: (1) multiple representations of univariate data (i.e., single data series) for data exploration; (2) how multi-variate data can be mapped onto sound to help interpret how those data variables are related and; (3) a full spatial audio example for immersive Virtual Reality. We summarise, alluding to some of the future functionality as STRAUSS development accelerates.

cs.SD↗

arXiv2023

Inspecting spectra with sound: proof-of-concept & extension to datacubes

We present a novel approach to inspecting galaxy spectra using sound, via their direct audio representation ('spectral audification'). We discuss the potential of this as a complement to (or stand-in for) visual approaches. We surveyed 58 respondents who use the audio representation alone to rate 30 optical galaxy spectra with strong emission lines. Across three tests, each focusing on different quantities measured from the spectra (signal-to-noise ratio, emission-line width, & flux ratios), we find that user ratings are well correlated with measured quantities. This demonstrates that physical information can be independently gleaned from listening to spectral audifications. We note the importance of context when rating these sonifications, where the order examples are heard can influence responses. Finally, we adapt the method used in this promising pilot study to spectral datacubes. We suggest that audification allows efficient exploration of complex, spatially-resolved spectral data.

astro-ph.IM↗

arXiv2020

Massive Low Surface Brightness Galaxies in the EAGLE Simulation

We investigate the formation and properties of low surface brightness galaxies (LSBGs) with $M_{*} > 10^{9.5} \mathrm{M_{\odot}}$ in the EAGLE hydrodynamical cosmological simulation. Galaxy surface brightness depends on a combination of stellar mass surface density and mass-to-light ratio ($M/L$), such that low surface brightness is strongly correlated with both galaxy angular momentum (low surface density) and low specific star formation rate (high $M/L$). This drives most of the other observed correlations between surface brightness and galaxy properties, such as the fact that most LSBGs have low metallicity. We find that LSBGs are more isolated than high surface brightness galaxies (HSBGs), in agreement with observations, but that this trend is driven entirely by the fact that LSBGs are unlikely to be close-in satellites. The majority of LSBGs are consistent with a formation scenario in which the galaxies with the highest angular momentum are those that formed most of their stars recently from a gas reservoir co-rotating with a high-spin dark matter halo. However, the most extended LSBG disks in EAGLE, which are comparable in size to observed giant LSBGs, are built up via mergers. These galaxies are found to inhabit dark matter halos with a higher spin in their inner regions ($<0.1r_{200c}$), even when excluding the effects of baryonic physics by considering matching halos from a dark matter only simulation with identical initial conditions.

astro-ph.GA↗

arXiv2019

Non-parametric Morphologies of Galaxies in the EAGLE Simulation

We study the optical morphology of galaxies in a large-scale hydrodynamic cosmological simulation, the EAGLE simulation. Galaxy morphologies were characterized using non-parametric statistics (Gini, $M_{20}$, Concentration and Asymmetry) derived from mock images computed using a 3D radiative transfer technique and post-processed to approximate observational surveys. The resulting morphologies were contrasted to observational results from a sample of $\log_{10}(M_{*}/M_\odot) > 10$ galaxies at $z \sim 0.05$ in the GAMA survey. We find that the morphologies of EAGLE galaxies reproduce observations, except for asymmetry values which are larger in the simulated galaxies. Additionally, we study the effect of spatial resolution in the computation of non-parametric morphologies, finding that Gini and Asymmetry values are systematically reduced with decreasing spatial resolution. Gini values for lower mass galaxies are especially affected. Comparing against other large scale simulations, the non-parametric statistics of EAGLE galaxies largely agree with those found in IllustrisTNG. Additionally, EAGLE galaxies mostly reproduce observed trends between morphology and star formation rate and galaxy size. Finally, We also find a significant correlation between optical and kinematic estimators of morphologies, although galaxy classification based on an optical or a kinematic criteria results in different galaxy subsets. The correlation between optical and kinematic morphologies is stronger in central galaxies than in satellites, indicating differences in morphological evolution.

astro-ph.GA↗

arXiv2019

From the far-ultraviolet to the far-infrared -- galaxy emission at $0\le z \le 10$ in the Shark semi-analytic model

We combine the Shark semi-analytic model of galaxy formation with the ProSpect software tool for spectral energy distribution (SED) generation to study the multi-wavelength emission of galaxies from the far-ultraviolet (FUV) to the far-infrared (FIR) at $0\le z\le 10$. We produce a physical model for the attenuation of galaxies across cosmic time by combining a local Universe empirical relation to compute the dust mass of galaxies from their gas metallicity and mass, attenuation curves derived from radiative transfer calculations of galaxies in the EAGLE hydrodynamic simulation suite, and the properties of Shark galaxies. We are able to produce a wide range of galaxies, from the $z=8$ star-forming galaxies with almost no extinction, $z=2$ submillimeter galaxies, down to the normal star-forming and red sequence galaxies at $z=0$. Quantitatively, we find that Shark reproduces the observed (i) the $z=0$ FUV-to-FIR, (ii) $0\le z\le 3$ rest-frame $K$-band, and (iii) $0\le z\le 10$ rest-frame FUV luminosity functions, (iv) $z\le 8$ UV slopes, (v) the FUV-to-FIR number counts (including the widely disputed 850$μ$m), (vi) redshift distribution of bright $850μ$m galaxies and (vii) the integrated cosmic SED from $z=0$ to $z=1$ to an unprecedented level. This is achieved without the need to invoke changes in the stellar initial mass function, dust-to-metal mass ratio, or metal enrichment timescales. Our model predicts star formation in galaxy disks to dominate in the FUV-to-optical, while bulges dominate at the NIR at all redshifts. The FIR sees a strong evolution in which disks dominate at $z\le 1$ and starbursts (triggered by both galaxy mergers and disk instabilities, in an even mix) dominate at higher redshifts, even out to $z=10$.

astro-ph.GA↗

arXiv2019

Fade to grey: systematic variation of the galaxy attenuation curves with galaxy properties in EAGLE

We present a simple model for galaxy attenuation by distilling SKIRT radiative transfer calculations for ~100,000 EAGLE galaxies at redshifts z=2-0. Our model adapts the two component screen model of Charlot & Fall (2000), parametrising the optical depth and slope of the ISM screen using the average dust surface density, $Σ_{\rm dust}$. We recover relatively tight relations between these parameters for the EAGLE sample, but also provide the scatter in these parameter owing to the morphological variation and orientation of galaxies. We also find that these relations are nearly independent of redshift in the EAGLE model. By pairing our model with an empirical prescription for birth clouds below the resolution scale of the simulation, we reproduce the observed relation between attenuation slope and optical depth for the first time in a cosmological simulation. We demonstrate that this result is remarkably independent of the attenuation properties assumed for birth cloud screen, merely requiring a boosted attenuation for infant stars. We present this model with a view to interpreting observations, as well as processing semi-analytic models and other hydrodynamic simulations.

astro-ph.GA↗

arXiv2019

Quenching timescales of galaxies in the EAGLE simulations

We use the \eagle\ simulations to study the connection between the quenching timescale, $τ_{\rm Q}$, and the physical mechanisms that transform star-forming galaxies into passive galaxies. By quantifying $τ_{\rm Q}$ in two complementary ways - as the time over which (i) galaxies traverse the green valley on the colour-mass diagram, or (ii) leave the main sequence of star formation and subsequently arrive on the passive cloud in specific star formation rate (SSFR)-mass space - we find that the $τ_{\rm Q}$ distribution of high-mass centrals, low-mass centrals and satellites are divergent. In the low stellar mass regime where $M_{\star}<10^{9.6}M_{\odot}$, centrals exhibit systematically longer quenching timescales than satellites ($\approx 4$~Gyr compared to $\approx 2$~Gyr). Satellites with low stellar mass relative to their halo mass cause this disparity, with ram pressure stripping quenching these galaxies rapidly. Low mass centrals are quenched as a result of stellar feedback, associated with long $τ_{\rm Q}\gtrsim 3$~Gyr. At intermediate stellar masses where $10^{9.7}\,\rm M_{\odot}<M_{\star}<10^{10.3}\,\rm M_{\odot}$, $τ_{\rm Q}$ are the longest for both centrals and satellites, particularly for galaxies with higher gas fractions. At $M_{\star}\gtrsim 10^{10.3}\,\rm M_{\odot}$, galaxy merger counts and black hole activity increase steeply for all galaxies. Quenching timescales for centrals and satellites decrease with stellar mass in this regime to $τ_{\rm Q}\lesssim2$~Gyr. In anticipation of new intermediate redshift observational galaxy surveys, we analyse the passive and star-forming fractions of galaxies across redshift, and find that the $τ_{\rm Q}$ peak at intermediate stellar masses is responsible for a peak (inflection point) in the fraction of green valley central (satellite) galaxies at $z\approx 0.5-0.7$.

astro-ph.GA↗

arXiv2019

An evolving and mass dependent ${\rm σ_{\text{sSFR}}}$-${\rm M_{\star}}$ relation for galaxies

The scatter (${\rmσ_{\text{sSFR}}}$) of the specific star formation rates (sSFRs) of galaxies is a measure of the diversity in their star formation histories (SFHs) at a given mass. In this paper we employ the EAGLE simulations to study the dependence of the ${\rm σ_{\text{sSFR}}}$ of galaxies on stellar mass (${\rm M_{\star}}$) through the ${\rm σ_{\text{sSFR}}}$-${\rm M_{\star}}$ relation in $ {\rm z \sim 0-4}$. We find that the relation evolves with time, with the dispersion depending on both stellar mass and redshift. The models point to an evolving U-shape form for the ${\rm σ_{\text{sSFR}}}$-${\rm M_{\star}}$ relation with the scatter being minimal at a characteristic mass $M^{\star}$ of ${\rm 10^{9.5}}$ ${\rm M_{\odot}}$ and increasing both at lower and higher masses. This implication is that the diversity of SFHs increases towards both at the low- and high-mass ends. We find that active galactic nuclei feedback is important for increasing the ${\rm σ_{\text{sSFR}}}$ for high mass objects. On the other hand, we suggest that SNe feedback increases the ${\rm σ_{\text{sSFR}}}$ of galaxies at the low-mass end. We also find that excluding galaxies that have experienced recent mergers does not significantly affect the ${\rm σ_{\text{sSFR}}}$-${\rm M_{\star}}$ relation. Furthermore, we employ the combination of the EAGLE simulations with the radiative transfer code SKIRT to evaluate the effect of SFR/stellar mass diagnostics in the ${\rm σ_{\text{sSFR}}}$-${\rm M_{\star}}$ relation and find that the ${\rm SFR/M_{\star}}$ methodologies (e.g. SED fitting, UV+IR, UV+IRX-$β$) widely used in the literature to obtain intrinsic properties of galaxies have a large effect on the derived shape and normalization of the ${\rm σ_{\text{sSFR}}}$-${\rm M_{\star}}$ relation.

astro-ph.GA↗

arXiv2019

Feedback from supermassive black holes transforms centrals into passive galaxies by ejecting circumgalactic gas

Davies et al. (2019) established that for L^* galaxies the fraction of baryons in the circumgalactic medium (CGM) is inversely correlated with the mass of their central supermassive black holes (BHs) in the EAGLE hydrodynamic simulation. The interpretation is that, over time, a more massive BH has provided more energy to transport baryons beyond the virial radius, which additionally reduces gas accretion and star formation. We continue this research by focusing on the relationship between the 1) BH masses, 2) physical and observational properties of the CGM, and 3) galaxy colours for Milky Way-mass systems. The ratio of the cumulative BH feedback energy over the gaseous halo binding energy is a strong predictor of the CGM gas content, with BHs injecting >~10x the binding energy resulting in gas-poor haloes. Observable tracers of the CGM, including CIV, OVI, and HI absorption line measurements, are found to be effective tracers of the total z~0 CGM halo mass. We use high-cadence simulation outputs to demonstrate that BH feedback pushes baryons beyond the virial radius within 100 Myr timescales, but that CGM metal tracers take longer (0.5-2.5 Gyr) to respond. Secular evolution of galaxies results in blue, star-forming or red, passive populations depending on the cumulative feedback from BHs. The reddest quartile of galaxies with M_*=10^{10.2-10.7} M_solar (median u-r = 2.28) has a CGM mass that is 2.5x lower than the bluest quartile (u-r=1.59). We propose strategies for observing the predicted lower CGM column densities and covering fractions around galaxies hosting more massive BHs using the Cosmic Origins Spectrograph on Hubble.

astro-ph.GA↗

arXiv2019

The nature of sub-millimeter and highly star-forming galaxies in the EAGLE simulation

We exploit EAGLE, a cosmological hydrodynamical simulation, to reproduce the selection of the observed sub-millimeter (submm) galaxy population by selecting the model galaxies at $z \geq 1$ with mock submm fluxes $S_{850} \geq 1$ mJy. There is a reasonable agreement between the galaxies within this sample and the properties of the observed submm population, such as their star formation rates (SFRs) at $z<3$, redshift distribution and many integrated galaxy properties. We find that the bulk of the $S_{850} \geq 1$ mJy model population is at $z = 2.5$, and that they are massive galaxies ($M_* \sim 10^{11}$ Msol) with high dust masses ($M_{\mathrm{dust}} \sim 10^{8}$ Msol), gas fractions ($f_{\mathrm{gas}} \approx 50$%) and SFRs ($\dot M_* \approx 100$ Msol/yr). They have major and minor merger fractions similar to the general population, suggesting that mergers are not the primary driver of the model submm galaxies. Instead, the $S_{850} \geq 1$ mJy model galaxies yield high SFRs primarily because they maintain a significant gas reservoir as a result of hosting an undermassive black hole. In addition, we find that not all highly star-forming EAGLE galaxies have submm fluxes $S_{850} > 1$ mJy. Thus, we investigate the nature of $z \geq 1$ highly star-forming Submm-Faint galaxies (i.e., $\dot M_* \geq 80$ Msol/yr but $S_{850}< 1$ mJy). We find they are similar to the model submm galaxies; being gas rich and hosting undermassive black holes, however they are typically lower mass ($M_* \sim 10^{10}$ Msol) and are at higher redshifts ($z>4$). These typically higher-$z$ galaxies show stronger evidence for having been triggered by major mergers, and critically, they are likely missed by current submm surveys due to their higher dust temperatures. This suggests a potentially even larger contribution to the SFR density at $z > 3$ from dust-obscured systems than implied by current observations.

astro-ph.GA↗

arXiv2018

Resolved galaxy scaling relations in the EAGLE simulation: star formation, metallicity and stellar mass on kpc scales

We explore scaling relations between the physical properties of spatially resolved regions within the galaxies that emerge in the Evolution and Assembly of GaLaxies and their Environments (EAGLE) hydrodynamical, cosmological simulations. Using 1 kpc-scale spaxels, we compute the relationships between the star formation rate and stellar mass surface densities, i.e. the spatially resolved star-forming main sequence (rSFMS), and between the gas metallicity and the stellar mass surface density, i.e. the spatially resolved mass-metallicity relation (rMZR). We compare to observed relations derived from integral field unit surveys and imaging of galaxies. EAGLE reproduces the slope of the local ($z\approx0.1$) rSFMS well, but with a $\approx-0.15$ dex offset, close to that found for the galaxy-integrated relation. The shape of the rMZR agrees reasonably well with observations, replicating the characteristic turnover at high surface density, which we show is due to AGN feedback. The residuals of the rSFMS and rMZR are negatively (positively) correlated at low (high) surface density. The rSFMS becomes shallower as the simulation evolves from $z=2$ to 0.1, a manifestation of inside-out galaxy formation. The shape of the rMZR also exhibits dramatic evolution, from a convex profile at $z=2$ to the observed concave profile at $z=0.1$, such that the gas in regions of high stellar density is more enriched at higher redshift. The redshift independence of the relationship between the galaxy-wide gas fraction and metallicity in EAGLE galaxies is not preserved on 1 kpc scales, implying that chemical evolution is non-local due to the transport of gas and metals within galaxies.

astro-ph.GA↗

arXiv2018

The origin of the red sequence galaxy population in the EAGLE simulation

We investigate the evolution in colour and morphology of the progenitors of red-sequence galaxies in the EAGLE cosmological hydrodynamical simulation. We quantify colours with $u^{*}-r^{*}$ intrinsic magnitudes and morphologies with a measure of the stellar kinematics. The time when galaxies moved onto the red sequence depends on their morphology. Disc-type galaxies tend to have become red during the last 3 Gyr, while elliptical-type galaxies joined the red sequence earlier, with half the sample already being red 5 Gyr ago. The time-scale, $τ_{\rm{Green}}$, of colour transition through the `green valley' depends weakly on the galaxy's morphological type. Elliptical-type galaxies cross the green valley slightly faster ($τ_{\rm{Green}}{\approx}1$ Gyr) than disc-type galaxies ($τ_{\rm{Green}}{\approx}$1.5 Gyr). While $τ_{\rm{Green}}$ is similar for central and satellite galaxies, for satellites $τ_{\rm{Green}}$ decreases with increasing stellar mass to host-halo mass ratio. Coupled with our finding that galaxies tend to become green after becoming satellites, this indicates that satellite-specific processes are important for quenching red-sequence galaxies. The last time central, elliptical-type red-sequence galaxies left the blue cloud is strongly correlated with the time the luminosity of the central black hole peaked, but this is not the case for discs. This suggests that AGN feedback is important for quenching ellipticals, particularly centrals, but not for discs. We find only a weak connection between transformations in colour and morphology.

astro-ph.GA↗