The Three Hundred project: connection between star formation quenching and dynamical evolution in and around simulated galaxy clusters

In this work, we combine the semi-analytic model of galaxy formation and evolution SAG with the $102$ relaxed simulated galaxy clusters from The Three Hundred project, and we study the link between the quenching of star formation (SF) and the physical processes that galaxies experience through their dynamical history in and around clusters. We classify galaxies in four populations based on their orbital history: recent and ancient infallers, and backsplash and neighbouring galaxies. We find that $\sim 85$ per cent of the current population of quenched galaxies located inside the clusters are ancient infallers with low or null content of hot and cold gas. The fraction of quenched ancient infallers increases strongly between the first and second pericentric passage, due to the removal of hot gas by the action of ram-pressure stripping (RPS). The majority of them quenches after the first pericentric passage, but a non-negligible fraction needs a second passage, specially galaxies with $M_\star \leq 10^{10.5} \, {\rm M_\odot}$. Recent infallers represent $\sim 15$ per cent of the quenched galaxies located inside the cluster and, on average, they contain a high proportion of hot and cold gas; moreover, pre-processing effects are the responsible for quenching the recent infallers prior to infall onto the main cluster progenitor. The $\sim 65$ per cent of quenched galaxies located around clusters are backsplash galaxies, for which the combination of RPS acting during a pre-processing stage and inside the cluster is necessary for the suppression of SF in this population.Comment: 23 pages, 13 figures + Supplementary material. Accepted for publication in MNRA

Semi-analytic galaxies : I. Synthesis of environmental and star-forming regulation mechanisms

We present results from the semi-analytic model of galaxy formation SAG applied on the MULTIDARK simulation MDPL2. SAG features an updated supernova (SN) feedback scheme and a robust modelling of the environmental effects on satellite galaxies. This incorporates a gradual starvation of the hot gas halo driven by the action of ram pressure stripping (RPS), that can affect the cold gas disc, and tidal stripping (TS), which can act on all baryonic components. Galaxy orbits of orphan satellites are integrated providing adequate positions and velocities for the estimation of RPS and TS. The star formation history and stellar mass assembly of galaxies are sensitive to the redshift dependence implemented in the SN feedback model. We discuss a variant of our model that allows to reconcile the predicted star formation rate density at z ≳ 3 with the observed one, at the expense of an excess in the faint end of the stellar mass function at z= 2. The fractions of passive galaxies as a function of stellar mass, halo mass, and the halo-centric distances are consistent with observational measurements. The model also reproduces the evolution of the main sequence of star-forming central and satellite galaxies. The similarity between them is a result of the gradual starvation of the hot gas halo suffered by satellites, in which RPS plays a dominant role. RPS of the cold gas does not affect the fraction of quenched satellites but it contributes to reach the right atomic hydrogen gas content for more massive satellites (M* ≳1010M⊙).Instituto de Astrofísica de La PlataFacultad de Ciencias Astronómicas y Geofísica

Semi-analytic galaxies : I. Synthesis of environmental and star-forming regulation mechanisms

We present results from the semi-analytic model of galaxy formation SAG applied on the MULTIDARK simulation MDPL2. SAG features an updated supernova (SN) feedback scheme and a robust modelling of the environmental effects on satellite galaxies. This incorporates a gradual starvation of the hot gas halo driven by the action of ram pressure stripping (RPS), that can affect the cold gas disc, and tidal stripping (TS), which can act on all baryonic components. Galaxy orbits of orphan satellites are integrated providing adequate positions and velocities for the estimation of RPS and TS. The star formation history and stellar mass assembly of galaxies are sensitive to the redshift dependence implemented in the SN feedback model. We discuss a variant of our model that allows to reconcile the predicted star formation rate density at z ≳ 3 with the observed one, at the expense of an excess in the faint end of the stellar mass function at z= 2. The fractions of passive galaxies as a function of stellar mass, halo mass, and the halo-centric distances are consistent with observational measurements. The model also reproduces the evolution of the main sequence of star-forming central and satellite galaxies. The similarity between them is a result of the gradual starvation of the hot gas halo suffered by satellites, in which RPS plays a dominant role. RPS of the cold gas does not affect the fraction of quenched satellites but it contributes to reach the right atomic hydrogen gas content for more massive satellites (M* ≳1010M⊙).Instituto de Astrofísica de La PlataFacultad de Ciencias Astronómicas y Geofísica

Yeasts in sustainable bioethanol production: a review

Bioethanol has been identified as the mostly used biofuel worldwide since it significantly contributes to the reduction of crude oil consumption and environmental pollution. It can be produced from various types of feedstocks such as sucrose, starch, lignocellulosic and algal biomass through fermentation process by microorganisms. Compared to other types of microoganisms, yeasts especially Saccharomyces cerevisiae is the common microbes employed in ethanol production due to its high ethanol productivity, high ethanol tolerance and ability of fermenting wide range of sugars. However, there are some challenges in yeast fermentation which inhibit ethanol production such as high temperature, high ethanol concentration and the ability to ferment pentose sugars. Various types of yeast strains have been used in fermentation for ethanol production including hybrid, recombinant and wild-type yeasts. Yeasts can directly ferment simple sugars into ethanol while other type of feedstocks must be converted to fermentable sugars before it can be fermented to ethanol. The common processes involves in ethanol production are pretreatment, hydrolysis and fermentation. Production of bioethanol during fermentation depends on several factors such as temperature, sugar concentration, pH, fermentation time, agitation rate, and inoculum size. The efficiency and productivity of ethanol can be enhanced by immobilizing the yeast cells. This review highlights the different types of yeast strains, fermentation process, factors affecting bioethanol production and immobilization of yeasts for better bioethanol production

Evolución de las propiedades de galaxias en grupos y cúmulos

Las galaxias ubicadas dentro de grupos y cúmulos de galaxias identificados en el Universo local (corrimiento al rojo z ≾ 0.1) presentan tasas de formación estelar más atenuadas, colores más rojos y menos contenido de gas atómico y molecular que galaxias de similar masa estelar ubicadas en ambientes menos densos. Las galaxias se clasifican en centrales o satélites según residan en el pozo de potencial de la estructura en la cual se alojan u orbiten dentro de ella. Para ambos tipos de galaxias, la actividad de formación estelar tiende a disminuir conforme aumenta su masa estelar; en particular, dada una masa estelar fija, este efecto aumenta en satélites que habitan en ambientes más densos. Esta tendencia está determinada por procesos internos que dependen principalmente de la masa estelar, como la retroalimentación energética por núcleo galáctico activo (AGN) y explosiones de supernovas. Además, en las galaxias satélites, la formación estelar se ve afectada por efectos generados por el ambiente en el que residen, como la presión de barrido y fuerzas de marea (llamados efectos de ambiente). En este Trabajo de Tesis abordamos un aspecto fundamental de la formación y evolución de las galaxias: cómo la formación estelar se ve afectada en galaxias que habitan entornos densos, tanto en épocas tempranas del Universo como en el presente. Para ello, utilizamos modelos híbridos de formación y evolución de galaxias que involucran simulaciones cosmológicas de N-cuerpos de materia oscura y modelos semi-analíticos de formación de galaxias. En una primera etapa, estudiamos la distribución espacial de galaxias en proto-cúmulos de galaxias, que conforman las etapas tempranas de la formación de los cúmulos de galaxias. Estas galaxias se caracterizan por tener gran actividad de formación estelar, y son detectadas gracias a las intensas líneas de emisión que presentan, en particular, en Lyα (1216 ˚A) y Hα (6563 ˚A). Para ello, combinamos el modelo semi-analítico Galform con la simulación de N-cuerpos de materia oscura P-Millenium, que contiene 50403 partículas en una caja de 542.5h-1, Mpc de lado, y posee una resolución de masa de 1x108 M⊙. Encontramos que, en términos generales, no debe esperarse una diferencia en la distribución espacial de galaxias que presentan l´ıneas de emisi´on Lyα respecto de aquellas que presentan emisión en Hα en los proto-cúmulos de galaxias (Hough, Gurung-Lòpez, Orsi & Cora, 2020). A continuación, nos enfocamos en la actual población de galaxias pasivas (caracterizadas por la baja tasa de formación estelar), explorando la importancia relativa de mecanismos internos o efectos de ambiente en la supresión de la formación estelar, y determinamos las escalas de tiempo involucradas en este proceso. Para ello, combinamos el modelo semi-analítico sag con la simulación de N-cuerpos de materia oscura mdpl2, que consiste en 38403 partículas de materia oscura en una caja de 1 h−1 Gpc de lado, y una resolución de masa de 1.5 × 109 h−1M por partícula. Encontramos que los procesos internos son determinantes en galaxias con masa estelar M* 1010.5M , tanto en galaxias centrales como satélites, siendo principalmente responsable la retroalimentación por AGN que previene el enfriamiento del gas caliente e interrumpe el aporte al reservorio de gas frío que deviene en la formación estelar. Por otro lado, los efectos de ambiente dominan la supresión de la formación estelar en satélites de baja masa (M* ≾ 1010.1⊙ ). El proceso determinante es la presión de barrido ejercida por el medio intra-cúmulo (o intra-grupo) sobre el halo de gas caliente, removiendo así la materia prima del ciclo de formación estelar. La presión de barrido sobre el disco de gas frío ocupa un lugar secundario en la supresión de la formación estelar. Encontramos que las escalas de tiempo involucradas en este fenómeno de supresión presentan una anti-correlación con la masa estelar, en acuerdo con las observaciones. Para las saélites de bajamasa, los tiempos de supresión son de ∼ 4 − 5 Gyr, mientras que para las de alta masa son de ∼ 2 − 3 Gyr. La evolución de la formación estelar de satélites de baja masa es consistente con el escenario demorado-luego-rápido planteado en la literatura; sin embargo, para las de alta masa proponemos un nuevo escenario que describe más adecuadamente la evolución de estas galaxias, al que llamamos \textit{demorado-luego-apagado} (Cora, Hough, Vega-Martínez &; Orsi, 2019). Por último, utilizamos los 324 cúmulos más masivos (y sus entornos) que fueron extraídos de la simulación sc mdpl2, con el objetivo de explorar el vínculo entre las propiedades de las galaxias en entornos densos y su evolución orbital. Clasificamos a las galaxias en 4 submuestras: galaxias que fueron acretadas hace menos y más de 2 Gyr recent infallers y ancient infallers, respectivamente), galaxias que fueron satélites del cúmulo y ahora se encuentran fuera de él (backsplash) y galaxias que nunca fueron acretadas. Encontramos que el contenido de gas caliente, de gas frío y la actividad de formación estelar dependen de la posición que la galaxia ocupa en el diagrama de fases. Las ancient infallers tienen bajas velocidades y se encuentran cerca del centro del cúmulo, prácticamente no poseen gas caliente ni frío debido a la acción prolongada de la presión de barrido sobre estas componentes gaseosas, y no presentan formación estelar. Las recent infallers ingresan al cúmulo a altas velocidades, pero conservan una alta proporción de gas caliente y frío, aún aquellas que se acercan a la región central y han experimentado un pasaje por el pericentro, y presentan una moderada actividad de formación estelar. Las backsplash sólo han experimentado los efectos de ambiente durante 2 Gyr y aquellas que pierden su contenido de gas y la capacidad de formar estrellas sufren una combinación de efectos de pre-procesado, que tienen lugar en una etapa previa a ser acretadas, y los posteriores efectos de ambiente que ocurren dentro del cúmulo. Los resultados obtenidos en este Trabajo de Tesis constituyen un importante aporte al entendimiento de cómo se distribuyen las galaxias que tienen una fuerte actividad de formación estelar en el Universo temprano, y cómo los procesos internos y externos afectan a la formación de estrellas en galaxias que habitan entornos densos en el Universo local.Facultad de Ciencias Astronómicas y Geofísica

Semi-analytic galaxies : II. Revealing the role of environmental and mass quenching in galaxy formation

We use the semi-analytic model of galaxy formation SAG to study the relevance of mass and environmental quenching on satellite galaxies. We find that environmental processes dominate the star formation (SF) quenching of low-mass satellites (⁠M⋆ ≲ 1010.5 M⊙⁠), whereas high-mass galaxies typically quench as centrals. High-mass galaxies that remain actively forming stars while being accreted are found to be mainly affected by mass quenching after their first infall. For a given stellar mass, our model predicts SF quenching to be less efficient in low-mass haloes both before and after infall, in contradiction with common interpretations of observational data. Our model supports a two-stage scenario to explain the SF quenching. Initially, the SF of satellites resembles that of centrals until the gas cooling rate is reduced to approximately half its value at infall. Then, the SF fades through secular processes that exhaust the cold gas reservoir. This reservoir is not replenished efficiently due to the action of either ram-pressure stripping of the hot gas in low-mass satellites, or feedback from the active galactic nucleus in high-mass satellites. The delay times for the onset of SF quenching are found to range from ≈3 to ≈1Gyr for low-mass (⁠M⋆ ≈ 10¹⁰ M⊙⁠) and high-mass (⁠M⋆ ≈ 10¹¹ M⊙⁠) satellites, respectively. SF fades in ≈1Gyr⁠, largely independent of stellar mass. We find that the SF quenching of low-mass satellites supports the so-called delay-then-rapid quenching scenario. However, the SF history of z = 0 passive satellites of any stellar mass is better described by a delay-then-fade quenching scenario.Facultad de Ciencias Astronómicas y GeofísicasInstituto de Astrofísica de La Plat

Are Lyα emitters segregated in protoclusters regions?

The presence of neutral hydrogen in the inter-stellar medium (ISM) and inter-galactic medium (IGM) induces radiative transfer (RT) effects on Lyα photons which affect the observability of Lyα emitters (LAEs). We use the GALFORM semi-analytic model of galaxy formation and evolution to analyse how these effects shape the spatial distribution of LAEs with respect to Hα emitters (HAEs) around high density regions at high redshift. We find that when a large sample of protoclusters is considered, HAEs showing also Lyα emission (HAEs+LAEs) populate the same regions as those that do not display the Lyα line at z = 2.2. We compare against the protocluster USS1558-003, one of the most massive protoclusters located at z = 2.53. Our results indicate that the strong depletion of HAEs+LAEs present in the high density regions of USS1558-003 may be due to cosmic variance. We find that at z = 2.2 and z = 3.0, RT of the ISM produces a strong decline (30-50 per cent) of the clustering amplitude of HAEs+LAEs with respect to HAEs towards the protoclusters centre. At z = 5.7, given the early evolutionary state of protoclusters and galaxies, the clustering of HAEs+LAEs has a smaller variation (10-20 per cent) towards the protoclusters centre. Depending on the equivalent width and luminosity criteria of the emission-line galaxy sample, the IGM can have a mild or a null effect on galaxy properties and clustering in high density regions

Are Ly α emitters segregated in protoclusters regions?

The presence of neutral hydrogen in the inter-stellar medium (ISM) and inter-galactic medium (IGM) induces radiative transfer (RT) effects on Ly α photons which affect the observability of Lyman alpha emitters (LAEs). We use the GALFORM semi-analytic model of galaxy formation and evolution to analyse how these effects shape the spatial distribution of LAEs with respect to H α emitters (HAEs) around high density regions at high redshift. We find that when a large sample of protoclusters is considered, HAEs showing also Ly α emission (HAEs+LAEs) populate the same regions as those that do not display the Ly α line at z = 2.2. We compare against the protocluster USS1558-003, one of the most massive protoclusters located at z = 2.53. Our results indicate that the strong depletion of HAEs + LAEs present in the high density regions of USS1558-003 may be due to cosmic variance. We find that at z = 2.2 and z = 3.0, RT of the ISM produces a strong decline (30-50 per cent) of the clustering amplitude of HAEs + LAEs with respect to HAEs towards the protoclusters centre. At z = 5.7, given the early evolutionary state of protoclusters and galaxies, the clustering of HAEs + LAEs has a smaller variation (10-20 per cent) towards the protoclusters centre. Depending on the equivalent width and luminosity criteria of the emission-line galaxy sample, the IGM can have a mild or a null effect on galaxy properties and clustering in high density regions.Facultad de Ciencias Astronómicas y GeofísicasInstituto de Astrofísica de La Plat