428 research outputs found
The evolution of the galaxy mass assembly and star formation activity from z=1 to z=0 as a function of environment
No full textAim of this thesis is to investigate the role of the galaxy mass and environment in shaping the galaxy properties, characterising the history of stellar evolution, the stellar mass assembly, and the structure development of galaxies in different environments, by tracing the star formation rate, the total stellar mass of galaxies and the morphology at different redshifts.
The data exploited in this thesis come from four surveys which focus on different environments and redshifts in the range z=0 to z=1: the Wide-field Nearby Galaxy-cluster Survey (WINGS - Fasano et al. 2006), the Padova-Millennium Galaxy and Group catalogue (PM2GC - Calvi, Poggianti, Vulcani 2011), the IMACS Cluster Building Survey (ICBS - Oemler et al. 2012a,b, in preparation), and the ESO Distant Cluster Survey (EDisCS - White et al. 2005).
First, analysing a sample of galaxies from EDisCS and using field data from literature, I study the ongoing Star Formation Rate (SFR) and the Specific Star Formation Rate (SSFR) at z=0.4-0.8 for different stellar masses and environments.
In mass-limited samples, the SFR at a fixed galaxy mass declines with time. The SSFR declines as galaxy stellar mass increases, showing that the current star formation contributes more to the fractional growth of low-mass galaxies than high-mass galaxies.
The median SFR is lower in cluster star-forming galaxies than in the field, by a factor of ~1.5. I conclude that the average SFR in star-forming galaxies varies with galaxy environment at a fixed galaxy mass.
Subsequently, using both WINGS and EDisCS data, I examine the morphology-mass relation (the way the proportion of galaxies of different morphological types changes with galaxy mass), and find it strongly depends on redshift. Both at z=0 and z~0.6, ~40% of the stellar mass is in elliptical galaxies. Another ~43% of the mass is in S0 galaxies in local clusters, while it is in late-types in distant clusters.
Using data from all the surveys, I then analyse the galaxy stellar mass function in mass-limited samples, focusing on a number of aspects, such as the role of the global and local environment in shaping the mass distribution, its evolution in clusters compared to the field, and what simulations predict for galaxies located in haloes of different mass. The main results are: (1) at intermediate redshift I do not detect any dependence of the mass function on the global environment: galaxies in clusters, groups and in the field are regulated by similar mass distributions, at least for M_star/M_sun >10.5.
(2) In clusters, I investigate the evolution of the total mass function from z~0.6 to z\sim 0, and I find that in the local Universe there are proportionally more low-mass galaxies than at high-z. This evolution is mainly driven by the galaxy mass growth due to star formation and by morphological transformations from one type to the other. (3) I contrast the evolution of the mass function in clusters and in the field from z~ 0.4 and z~ 0.6 to z~ 0 and find that it is very similar, hence independent of global environment. (4) I analyse the role of the local galaxy density in shaping the mass function, both at low and intermediate redshift, in clusters and in the field. Galaxies in different local density regions follow different mass functions. This result, coupled with point (1) above, suggests that galaxy properties such as galaxy mass are not much dependent on halo mass, but do depend on local scale processes. (5) Simulations are able to reproduce the observed mass function for field galaxies in the local Universe, while they fail in reproducing clusters at both low- and high-z and the field at high-z, suggesting that the current treatment of star formation performed in simulations has to be improved to well reproduce the galaxy mass distribution at different epochs and in different environments.
Having found that both the morphological fractions and the mass functions vary with redshift, I then study how this evolution influences the ellipticity distribution of cluster early-type galaxies,
finding that the variation with redshift is due to a change both of
the median and of the shape of the distributions with redshift.
The evolution of early-type galaxies is not simply related to the different mass distributions at high- and low-z, but it is mainly related to the evolution of the morphological mix with redshift and hence to the relative
contribution of ellipticals and S0s at the two epochs.
Finally, I present the spectroscopic analysis of galaxies in a field containing a z=0.96 cluster, Cl 1103.7-1245C, as part of the EDisCS project, for which I carried out the data reduction. I characterise the galaxy population of the two structures I singled out (the ``main cluster'' and a ``secondary structure'') and I compare my results with the galaxy populations of the other EDisCS clusters that have comparable values of velocity dispersions, but are located at lower redshifts. In general, the properties of the main cluster are in line with the other clusters and the expected evolution, while the secondary structure is an outstanding system, composed only of low-mass, strongly star-forming and morphologically peculiar galaxies.
To conclude, the role of the galaxy stellar mass is undisputed in driving galaxy evolution: galaxies are characterised
by a wide range of total stellar masses and the evolution of their properties strongly depends on their mass.
Anyway, mass and environment are not independent.
The environment, besides affecting some galaxy properties, is partially able to influence the mass distribution:
more massive galaxies are preferentially found at higher densities.Lo scopo principale di questa tesi e` quello di verificare l'importanza della massa delle galassie e dell'ambiente per l'evoluzione delle proprieta` delle galassie. Per fare cio`, ho studiato il tasso di formazione stellare, la massa stellare e le morfologie di galassie situate a diversi redshift, per caratterizzare la storia dell'evoluzione stellare, l'aggregazione della massa stellare e l'evoluzione della struttura delle galassie situate in ambienti diversi.
I dati utilizzati per questo lavoro derivano da quattro campagne osservative che hanno lo scopo di campionare galassie in ambienti differenti e a diverse epoche cosmiche nell'intervallo z=0-1: la Wide-field Nearby Galaxy-cluster Survey (WINGS - Fasano et al. 2006), il Padova-Millennium Galaxy and Group Catalogue (PM2GC - Calvi, Poggianti, Vulcani2011), l'IMACS Cluster Building Survey (ICBS - Oemler et al. 2012a,b, in preparazione) e l'ESO Distant Cluster Survey (EDisCS - White et al. 2005).
I primi risultati presentati in questa tesi riguardano l'analisi del tasso di formazione stellare e del tasso specifico di formazione stellare per galassie di varie masse stellari e situate in vari ambienti. Prendendo in esame un campione di galassie di EDisCS e dati di letteratura, ho trovato che il tasso di formazione stellare per ogni massa diminuisce con il tempo. Inoltre, il tasso specifico di formazione stellare diminuisce all'aumentare della massa, a prova del fatto che a la formazione stellare contribuisce maggiormente alla crescita delle galassie di piccola massa piuttosto che a quella delle galassie pi\`u massive. In generale, le galassie di ammasso presentano un tasso di formazione stellare minore di quelle di campo, di un fattore ~1.5. In conclusione, il tasso di formazione stellare medio delle galassie che formano stelle dipende sia dalla massa che dall'ambiente.
Successivamente, utilizzando dati provenienti da WINGS e EDisCS, presento uno studio sulla relazione tra massa e morfologia (ossia come variano le frazioni morfologiche con la massa), mostrando come questa relazione dipenda dal redshift. Sia a z=0 che a z~0.6, circa il 40% della massa stellare e' racchiusa in galassie ellittiche, mentre il 43% della massa stellare e' nelle S0 in ammassi vicini e in galassie di tipi morfologici piu' avanzati in ammassi lontani.
Di seguito, in base ai dati di tutti i campioni disponibili, presento l'analisi della distribuzione di massa stellare delle galassie in campioni limitati in massa, focalizzandomi su alcuni aspetti principali: l'influenza dell'ambiente globale e locale sull'anda-mento della distribuzione di massa, l'evoluzione della distribuzione stessa, sia in galassie di ammasso che in galassie di campo, e le predizioni delle simulazioni per la distribuzione di massa di galassie in aloni di massa differente. I principali risultati possono essere cos\`i riassunti: (1) Per galassie a redshift intermedio la funzione di massa non dipende dall'ambiente globale: le galassie di ammasso, di gruppo e di campo sono regolate da distribuzioni simili, almeno per galassie con M_star/M_sun >10.5. (2) La distribuzione di massa in ammasso evolve da z~ 0.6 a z~0: il numero di galassie di piccola massa negli ammassi vicini e' proporzionalmente maggiore rispetto a quello di galassie negli ammassi lontani. Quest'evoluzione e' per la maggior parte dovuta al fatto che,le galassie di piccola massa, a questi redshift, continuano a formare stelle e crescono in massa. Contemporaneamente, le galassie cambiano anche tipo morfologico. (3) Confrontando l'evoluzione della funzione di massa in ammassi e nel campo, da z~0.4 e z~0.6 fino a z~0, si trova che e' molto simile nei diversi ambienti, pertanto l'evoluzione sembra essere indipendente dall'ambiente stesso. (4) La densita' locale influenza la distribuzione di massa, sia in diversi ambienti globali sia a diversi redshift. Le galassie situate in zone a diversa densita' sono regolate da distribuzioni di massa differenti. Riassumendo i risultati, si puo' concludere che proprieta' delle galassie come la massa sono maggiormente influenzate dalla densita' locale che dall'ambiente globale in cui si trovano. (5) Le simulazioni riescono a riprodurre la distribuzione di massa osservata solo per il campo a basso redshift, mentre negli altri casi danno risultati in disaccordo con le osservazioni. Questo significa che i modelli non sono ancora in grado di trattare nel modo corretto la formazione stellare, soprattutto a basse masse.
Dal momento che sia le frazioni morfologiche che la distribuzione di massa variano con il redshift, e' interessante studiare l'effetto della loro evoluzione sull'evoluzione della distribuzione di ellitticita' delle galassie dei primi tipi morfologici (ellittiche ed S0) in ammasso. In base ai dati di WINGS ed EDisCS, l'evoluzione totale e' dovuta sia alla variazione della mediana che della forma della distribuzione ai diversi redshift. Tale evoluzione non e' semplicemente dovuta alle diverse distribuzioni di massa di ellittiche ed S0 ai diversi redshift, bensi' alla variazione delle frazioni morfologiche e quindi del diverso contributo di ellittiche ed S0 alla popolazione totale.
Come ultimo argomento, presento la riduzione dati e l'analisi spettroscopica di galassie situate in un campo contenente un ammasso a z=0.96, Cl1103.7-1245C, che fa parte del progetto di EDisCS. Mostro il confronto tra le popolazioni delle galassie localizzate nelle due principali strutture del campo (``ammasso principale'' e ``struttura secondaria'') con le popolazioni di altri ammassi di EDisCS, localizzati a redshift piu' bassi, ma caratterizzati da una dispersione di velocita' simile. In generale, risulta che le proprieta' dell'ammasso principale sono molto simili a quelle degli altri ammassi ed in linea con l'evoluzione delle propriet\`a con il redshift, mentre la struttura secondaria e' una struttura peculiare composta principalmente da galassie di piccola massa, con elevata formazione stellare e di morfologia peculiare.
Concludendo, la massa stellare galattica gioca un ruolo molto importante nell'influenzare l'evoluzione: le galassie possono assumere diversi valori di massa e la loro evoluzione \`e fortemente legata alla massa stessa. Comunque,
massa e ambiente non sono indipendenti. L'effetto dell'ambiente in cui la galassia si trova si esplica sia su alcune proprieta' delle galassie che, in qualche modo, sulla distribuzione di massa: galassie piu' massive si trovano preferibilmente in ambienti piu' densi
The importance of the local density in shaping the galaxy stellar mass functions
No full textExploiting the capabilities of four different surveys - the Padova-Millennium Galaxy and Group Catalogue (PM2GC), the WIde-field Nearby Galaxy-cluster Survey (WINGS), the IMACS (Inamori-Magellan Areal Camera and Spectrograph) Cluster Building Survey (ICBS) and the ESO (European Southern Observatory) Distant Cluster Survey (EDisCS) - we analyse the galaxy stellar mass distribution as a function of local density in mass-limited samples, in the field and in clusters from low (z>0.04) to high (z<0.8) redshift. We find that at all redshifts and in all environments, local density plays a role in shaping the mass distribution. In the field, it regulates the shape of the mass function at any mass above the mass limits. In clusters, it seems to be important only at low masses, otherwise it seems not to influence the mass distribution. Putting together our results with those of Calvi et al. and Vulcani et al. for the global environment, we argue that at least at z~0.8 local density is more important than global environment in determining the galaxy stellar mass distribution, suggesting that galaxy properties are not much dependent on halo mass, but do depend on local scale processes.
Within these groups a few very massive groups (?), comparable to clusters, are included (see Calvi et al. 2011). ? is defined as the radius delimiting a sphere with interior mean density 200 times the critical density of the Universe at that redshift and is commonly used as an approximation for the cluster virial radius. The ? values for our structures are computed from the velocity dispersions using the formula We remind the reader that the normalization adopted in displaying the mass functions does not influence the KS test and hence our results. For the sake of completeness, 'other galaxies' are also plotted; they include all galaxies that belong to groups but are outside each group radial limit or the redshift range for groups. From now on, when we change the mass limit, we always compute again the limits of the density bins: each time, above the adopted mass limit we subdivide galaxies so that in the two central bins galaxies are twice as numerous as galaxies in the outer bins. e remind the reader that the WINGS sample is not spectroscopically complete, so in all the following analyses, we always take into account WINGS' weights. The fact that at low and intermediate redshifts we find the same fraction of massive galaxies indicates that the evolution of the fraction is independent of environment
Gas-phase Metallicity of Local Active Galactic Nuclei in the GASP and MaNGA Surveys: The Role of Ram Pressure Stripping
No full textGrowing evidence in support of a connection between active galactic nuclei (AGN) activity and the ram pressure stripping (RPS) phenomenon has been found both observationally and theoretically in the past decades. In this work, we further explore the impact of RPS on the AGN activity by estimating the gas-phase metallicity of nuclear regions and the mass–metallicity relation of galaxies at z ≤ 0.07 and with stellar masses , either experiencing RPS or not. To measure oxygen abundances, we exploit Integral Field Spectroscopy data from the GASP and MaNGA surveys, photoionization models generated with the code Cloudy and the code Nebulabayes to compare models and observations. In particular, we build Cloudy models to reproduce line ratios induced by photoionization from stars, AGN, or a contribution of both. We find that the distributions of metallicity and [O iii ] λ 5007 luminosity of galaxies undergoing RPS are similar to the ones of undisturbed galaxies. Independently of the RPS, we do not find a correlation between stellar mass and AGN metallicity in the mass range , while for the star-forming galaxies we observe the well-known mass–metallicity relation between with a scatter mainly driven by the star formation rate and a plateau around . The gas-phase metallicity in the nuclei of AGN hosts is enhanced with respect to those of star-forming galaxies by a factor of ∼ 0.05 dex regardless of the RPS
The surprising lack of effect from stellar feedback on the gas stripping rate from massive jellyfish galaxies
No full textWe study the role of star formation and stellar feedback in a galaxy being ram pressure (RP) stripped on its infall into a cluster. We use hydrodynamical wind-tunnel simulations of a massive galaxy (Mstar = 1011 M⊙) moving into a massive cluster (Mcluster = 1015 M⊙). We have two types of simulations: with and without star formation and stellar feedback, SF, and radiative cooling (RC), respectively. For each type, we simulate four realizations of the same galaxy: a face-on wind, edge-on wind, 45◦ angled wind, and a control galaxy not subject to RP. We directly compare the stripping evolution of galaxies with and without star formation. We find that stellar feedback has no direct effect on the stripping process, i.e. there is no enhancement in stripping via a velocity kick to the interstellar medium (ISM) gas. The main difference between RC and SF galaxies is due to the indirect effect of stellar feedback, which produces a smoother and more homogeneous ISM. Hence, while the average gas surface density is comparable in both simulation types, the scatter is broader in the RC galaxies. As a result, at the galaxy outskirts overdense clumps survive in RC simulation, and the stripping proceeds more slowly. At the same time, in the inner disc, underdense gas in the RC holes is removed faster than the smoothly distributed gas in the SF simulation. For our massive galaxy, we therefore find that the effect of feedback on the stripping rate is almost negligible, independent of wind angle
The active role of the environment in driving galaxy evolution
No full textGalaxy Clusters Across Cosmic Time : invited review tal
Recensione a G. Comandè, Medical Law in Italy,Wolters Kluwer, 2014
No full textThe review analyses G. Comandè's work Medical Law in Italy focusing on the main issues analysed by the Author under a criminal law perspectiv
Müller Deutschland 1979-1989. L'istituzione Heiner Müller nella Repubblica Federale Tedesca attraverso l'esempio di Berlino Ovest
No full textObject of this essay is role of the GDR author and dramatist Heiner Müller in West Berlin between 1979 and 1989, contextualizing him in the specific and peculiar artistic and intellectual scenario of the so called "two hearted city"
Los apuntes autobiográficos de un morisco expulsado: algunas reflexiones sobre el prólogo del Ms. S2 de la Colección Gayangos de la Biblioteca de la Real Academia de la Historia de Madrid
No full textThis paper aims to study some details, concerning style and themes, that the anonymous Moorish author determined to provide in the prologue of the manuscript S2 of the Gayangos Collection of the Library of the Real Academia de la Historia in Madrid [ff. 2r-16v]. Particularly, the attention is focused on the autobiographical notes inserted in the prologue, important narrative sequences in which the author tells the tough conditions suffered as a crypto-Muslim in Seventeenth-century Spain.El presente trabajo procura realizar una observación sobre algunos detalles estilísticos y temáticos que el autor morisco anónimo determina brindar en la sección del prólogo del manuscrito S2 perteneciente a la Colección Gayangos de la Biblioteca de la Real Academia de la Historia de Madrid [ff. 2r-16v]. De manera particular, la atención se focaliza en los apuntes autobiográficos intercalados en el mismo prefacio, importantes secuencias narrativas en las que el autor relata la durísima condición que sufrió como criptomusulmán en la España del siglo XVII
GASP - XVI. Does cosmic web enhancement turn on star formation in galaxies?
No full textGalaxy filaments are a peculiar environment, and their impact on the galaxy properties is still controversial. Exploiting the data from the GAs Stripping Phenomena in galaxies with MUSE, we provide the first characterization of the spatially resolved properties of galaxies embedded in filaments in the local Universe. The four galaxies we focus on show peculiar ionized gas distributions: H α clouds have been observed beyond four times the effective radius. The gas kinematics, metallicity map, and the ratios of emission-line fluxes confirm that they do belong to the galaxy gas disc; the analysis of their spectra shows that very weak stellar continuum is associated with them. Similarly, the star formation history and luminosity weighted age maps point to a recent formation of such clouds. The clouds are powered by star formation, and are characterized by intermediate values of dust absorption. We hypothesize a scenario in which the observed features are due to `Cosmic Web Enhancement': we are most likely witnessing galaxies passing through or flowing within filaments that assist the gas cooling and increase the extent of the star formation in the densest regions in the circumgalactic gas. Targeted simulations are mandatory to better understand this phenomenon...
Per un teatro che crede nella storia. Pier Paolo Pasolini nell'opera di Heiner Müller
No full textAim of this essay is to analyse the role of Pier Paolo Pasolini in the work and poetics of the GDR-author Heiner Müller. After an analysis of the reception of Pasolini’s works and persona in Germany and in the specific context of the GDR, the current work focuses on the influence of PPP in Müller’s approach to language, identity and history
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