Дисертації з теми "Cluster of galaxie"
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Březina, Karel. "Generátor herní mapy galaxie." Master's thesis, Vysoké učení technické v Brně. Fakulta informačních technologií, 2018. http://www.nusl.cz/ntk/nusl-385941.
Повний текст джерелаZatloukal, Michael. "A search for distant cluster of galaxies in the COSMOS field." [S.l. : s.n.], 2008. http://nbn-resolving.de/urn:nbn:de:bsz:16-opus-88001.
Повний текст джерелаJeltema, Tesla Erin. "Cosmology with clusters of galaxies : high-redshift clusters and the evolution of cluster substructure." Thesis, Massachusetts Institute of Technology, 2004. http://hdl.handle.net/1721.1/28372.
Повний текст джерелаIncludes bibliographical references (p. 85).
Clusters of galaxies have become an important cosmological tool, yet we do not un-erstand many aspects of their formation and development. In this thesis, I pursue two projects aimed at using clusters to constrain cosmology and better understanding cluster evolution. First, I examine the Chandra observation of MS1054-0321. MS1054-0321 is the highest redshift cluster in the Einstein Medium Sensitivity Survey (EMSS), and it was one of the first high-redshift clusters observed with Chandra. I confirm that this cluster is hot and massive, although its temperature is slightly lower than inferred previously. I also detected an iron line in this cluster, one of the first detections of iron in a cluster at these redshifts, with an abundance consistent with early enrichment of the ICM. MS1054-0321 exhibits significant substructure, which I study in detail for the first time. In X-rays, it appears to be a nearly equal mass double cluster in the process of merging. Both the cluster galaxies and mass associated with the western subclump are offset from the X-ray peak, possibly indicating that the gas in the subclump is being stripped off as it falls into the cluster. Despite the lower temperature, I find that the detection of this cluster in the EMSS constrains Qm to be less than one.
(cont.) In the second project, I investigate the evolution of cluster substructure with redshift, quantifying for the first time cluster structure out to z [approx.] 1. My sample includes 40 X-ray selected, luminous clusters from the Chandra archive, and I quantify cluster morphology using the power ratio method (Buote & Tsai 1995). I find that, as expected qualitatively from hierarchical models of structure formation, high-redshift clusters have more substructure and are dynamically more active than low-redshift clusters. Specifically, the clusters with z > 0.5 have significantly higher average third and fourth order power ratios than the lower redshift clusters. This observation of structure evolution indicates that dynamical state may be an important systematic effect in cluster studies seeking to constrain cosmology, and when calibrated against numerical simulations, structure evolution will itself provide interesting bounds on cosmological models.
by Tesla Erin Jeltema.
Ph.D.
Zibetti, Stefano. "Diffuse stellar components in galaxies and galaxy clusters." Diss., lmu, 2004. http://nbn-resolving.de/urn:nbn:de:bvb:19-30331.
Повний текст джерелаMakiya, Ryu. "Cosmic-Ray Acceleration in Galaxies and Galaxy Clusters." 京都大学 (Kyoto University), 2013. http://hdl.handle.net/2433/175125.
Повний текст джерелаBuote, David Augustin. "The structure of elliptical galaxies and galaxy clusters." Thesis, Massachusetts Institute of Technology, 1995. http://hdl.handle.net/1721.1/36556.
Повний текст джерелаYoshikawa, Koji. "Cosmological Hydrodynamic Simulations of Galaxies and Galaxy Clusters." 京都大学 (Kyoto University), 2002. http://hdl.handle.net/2433/149981.
Повний текст джерелаPracy, Michael Benjamin Physics Faculty of Science UNSW. "The properties and evolution of galaxy populations in the rich cluster environment." Awarded by:University of New South Wales. Physics, 2006. http://handle.unsw.edu.au/1959.4/23033.
Повний текст джерелаGupta, Nikhel [Verfasser], and Joseph [Akademischer Betreuer] Mohr. "High frequency cluster radio galaxies and the Sunyaev-Zel’dovich Effect properties of galaxy clusters / Nikhel Gupta ; Betreuer: Joseph Mohr." München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2018. http://d-nb.info/1154385981/34.
Повний текст джерелаVanDalfsen, Marcel L. Harris W. E. "The globular cluster system of the Sombrero galaxy." *McMaster only, 2004.
Знайти повний текст джерелаWong, Kenneth Christopher. "Strong Gravitation Lensing as a Probe of Galaxy Evolution and Cosmology." Diss., The University of Arizona, 2013. http://hdl.handle.net/10150/303637.
Повний текст джерелаNoble, Allison. "Dusty star-forming galaxies within high-redshift galaxy clusters." Thesis, McGill University, 2014. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=123107.
Повний текст джерелаNous présentons une analyse multi-fréquentielle de galaxies à formation d'étoiles situées à l'intérieur d'amas de galaxies fortement décalés vers le rouge. Ces amas en provenance du sondage Red-sequence Cluster Survey (RCS) et de son adaptation par Spitzer (SpARCS) possèdent une large couverture spectroscopique et contiennent plusieurs membres confirmés. Cette thèse représente une collection de travaux distincts mais reliés, qui se concentrent sur les effets environnementaux présents à l'intérieur des régions denses d'amas de galaxies, des structures parmi les plus rares de l'Univers. Nous exploitons la sensibilité élevée des télescopes infrarouges et submillimétriques de pointe pour collecter l'information encodée dans la portion thermale de la distribution spectrale d'énergie, ce qui inclue des mesures de luminosité infrarouge et des températures de poussière. Cette méthode nous permet de dévoiler plusieurs tendances en cours à l'intérieur de la population de galaxies à formation d'étoiles en fonction de l'environnement où se trouvent ces galaxies. De plus, nous développons une nouvelle définition de ce qui constitue l'environnement d'une galaxie basée sur l'espace de phase du rayon et de la vitesse. Cette définition tient compte des nombreux épisodes d'accrétion de galaxies par les amas de galaxies, traçant ainsi la densité moyenne connue par chaque population de galaxies. En utilisant ce nouveau traceur d'environnement, nous trouvons un manque important dans le taux de formation d'étoiles par unité de masse stellaire pour les galaxies à formation d'étoiles situées au coeur d'amas de galaxies entre z~0.9 et z~1.2, ce qui contraste avec le taux constant résultant d'une définition conventionnelle de l'environnement. Nous avons aussi découvert une population de galaxies ayant des températures de poussière plus basse que celles associées à des galaxies qui tombent ou qui ont été accrétées au début de la formation de l'amas de galaxies. Considérées ensemble, ces tendances caractérisant le taux de formation d'étoiles et la température de poussière peuvent aider à mettre en lumière les mécanismes de relaxation actifs à l'intérieur des amas de galaxies. Pour terminer, nous rapportons la détection fortuite d'une surdensité de galaxies submillimétriques situées derrière un superamas de galaxies à z~0.9, ce qui pourrait indiquer la présence d'un proto-amas à haute formation d'étoiles à z~3.
Kim, Stacy Yeonchi. "Constraining Dark Matter Properties with Dwarf Galaxies and Galaxy Clusters." The Ohio State University, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=osu1563515307606673.
Повний текст джерелаAmodeo, Stefania. "Scaling relations and stellar populations of galaxy clusters from their first epochs of assembly to the present." Thesis, Paris Sciences et Lettres (ComUE), 2018. http://www.theses.fr/2018PSLEO012/document.
Повний текст джерелаThis thesis focuses on the role of galaxy clusters in cosmology and galaxy evolution. I use multi-wavelenght photometric and spectroscopic observations (optical, mm, near/mid- IR) which I analyse with statistical methods. For a sample of clusters detected by the Planck satellite and re-observed with the Gemini optical telescope, I have studied the dynamics of member galaxies to probe their mass and understand possible systematics affecting such estimates, of crucial importance in cluster cosmology at present. Within the CARLA (Clusters Around Radio Loud AGN) collaboration, I examine morphology and stellar populations of galaxies in clusters and proto-clusters in their first assembly phases (z>1.4), with the aim of shedding light on the quenching of star formation and the role of the environment on galaxy evolution
Misgeld, Ingo. "Early-type stellar systems in nearby galaxy clusters: from dwarf galaxies to star clusters." Diss., lmu, 2011. http://nbn-resolving.de/urn:nbn:de:bvb:19-131647.
Повний текст джерелаSimanton, Lesley Ann. "Star Cluster Populations in the Spiral Galaxy M101." University of Toledo / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1437587267.
Повний текст джерелаTyler, Krystal D. "Star Formation and Galaxy Evolution in Different Environments, from the Field to Massive Clusters." Diss., The University of Arizona, 2012. http://hdl.handle.net/10150/265395.
Повний текст джерелаCantwell, Therese. "Low frequency radio observations of galaxy clusters and groups." Thesis, University of Manchester, 2018. https://www.research.manchester.ac.uk/portal/en/theses/low-frequency-radio-observations-of-galaxy-clusters-and-groups(35ee5532-96b2-48c9-a064-3a86c4f33747).html.
Повний текст джерелаMartinet, Nicolas. "Galaxy clusters : a probe to galaxy evolution and cosmology." Thesis, Paris 6, 2015. http://www.theses.fr/2015PA066348/document.
Повний текст джерелаThis thesis presents some recent results concerning galaxy evolution and cosmology,based on the observation of galaxy clusters at optical wavelengths. We first introduce the main properties of galaxy clusters (Sect. 1.1) and how they can be used for cosmology within the standard cosmological model (Sect. 1.2). A large fraction of the presented results comes from the study of the DAFT/FADA galaxy cluster survey at redshifts 0.4 < z < 0.9 (Sect. 1.3). We divide our study in two parts according to the observable that is considered: galaxy luminosity or galaxy shape. The distribution of galaxy luminosities is called the galaxy luminosity function (GLF), which can be used to probe the evolution of cluster galaxies (Sect. 2.1). Computing the GLFs for a sub sample of 25 DAFT/FADA clusters, we find that faint blue star forming galaxies are quenched into red quiescent galaxies from high redshift until today. Comparing to the field shows that this transformation is more efficient in high density environments.We also study the fraction of baryons in galaxy groups and clusters (Sect. 2.2). Wefind that in groups, the stars contained in galaxies can reach masses of the same order as those of the intra-cluster gas, while in clusters they are usually negligible relatively to the gas. Taking both stars and gas into account we constrain the matter density parameter Galaxy shapes are distorted by foreground objects that bend light in their vicinity. This lensing signal can be exploited to measure the mass distribution of a foreground cluster. We review the basic theory of weak lensing and shear measurement (Sect. 3.1), and then apply it to a subsample of 16 DAFT/FADA clusters, with Subaru/SuprimeCam or CFHT/MegaCam imaging (Sect. 3.2). We estimate the masses of these clusters, and take advantage of the large fields of view of our images to detect filaments and structures in the cluster vicinity, observationally supporting the hierarchical scenario of cluster growth. Finally, we detect shear peaks in Euclid-like simulations, and use their statistics as a cosmological probe, similarly to cluster counts (Sect. 3.3). We forecast the cosmological constraints that this technique will achieve when applied to the Euclid space mission, and develop a tomographic analysis that adds information from redshifts. We conclude with a discussion of our perspectives on future studies in all the fieldsinvestigated in the present thesis
Huang, Hung-Jin, Rachel Mandelbaum, Peter E. Freeman, Yen-Chi Chen, Eduardo Rozo, and Eli Rykoff. "Intrinsic alignment in redMaPPer clusters – II. Radial alignment of satellites towards cluster centres." OXFORD UNIV PRESS, 2018. http://hdl.handle.net/10150/627131.
Повний текст джерелаMonna, Anna. "Investigating galaxies in and behind Galaxy Clusters using Strong Gravitational Lensing." Diss., Ludwig-Maximilians-Universität München, 2015. http://nbn-resolving.de/urn:nbn:de:bvb:19-182062.
Повний текст джерелаPatej, Anna. "Distributions of Gas and Galaxies From Galaxy Clusters to Larger Scales." Thesis, Harvard University, 2016. http://nrs.harvard.edu/urn-3:HUL.InstRepos:33493358.
Повний текст джерелаPhysics
Fensch, Jérémy. "Star and stellar cluster formation in gas-dominated galaxies." Thesis, Sorbonne Paris Cité, 2017. http://www.theses.fr/2017USPCC207/document.
Повний текст джерелаWe study the formation of stars and stellar clusters in gas-dominated galaxies. This term primarily refers to galaxies from the epoch of the peak of the cosmic star formation history, which occurred at z ~ 2, but also to their local analogues, the tidal dwarf galaxies.Firstly, using numerical simulations, we show that the massive galaxies at z = 2, which have a gas fraction of about 50%, form massive (10**7-8 solar masses) and gravitationally bound structures, which we call clumps thereafter. These clumps do not form in galaxies with a gas fraction below 25%. We then present an observational study of a local analogue of a z = 2 galactic clump, which is the tidal dwarf galaxy NGC 5291N. The analysis of emission lines show the presence of shocks on the outskirts of the object. Photometry of this galaxy’s stellar clusters show that the youngest clusters (< 10 million years) are significantly less massive than older clusters. This could be the sign of ongoing cluster mergers and/or of a strong star formation activity in this system about 500 million years ago).Secondly, we study how the gas fraction impacts the formation of stars and stellar clusters in galaxy mergers at z = 2. Using numerical simulations we show that these mergers only slightly increase the star and stellar cluster formation rate, compared to local galaxy mergers, which have a lower gas fraction. We show that this is due to the saturation of several physical quantities, which are already strong in isolated z=2 galaxies and are thus less enhanced by the merger. These factors are gas turbulence, compressive tides and nuclear gas inflows, We also show that the stellar structures formed in the gaseous clumps are preserved by the fusion: they are ejected from the disk and orbit in the halo of the remnant galaxy, where they may become the progenitors of some globular clusters
Millington, S. J. C. "Clusters of galaxies." Thesis, University of Oxford, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.382461.
Повний текст джерелаHarris, William E., Stephanie M. Ciccone, Gwendolyn M. Eadie, Oleg Y. Gnedin, Douglas Geisler, Barry Rothberg, and Jeremy Bailin. "GLOBULAR CLUSTER SYSTEMS IN BRIGHTEST CLUSTER GALAXIES. III. BEYOND BIMODALITY." IOP PUBLISHING LTD, 2017. http://hdl.handle.net/10150/622870.
Повний текст джерелаRandriamampandry, Solohery Mampionona. "Far-infrared-radio relations in clusters and groups at intermediate redshift." Thesis, University of the Western Cape, 2014. http://hdl.handle.net/11394/4221.
Повний текст джерелаIn this thesis, we present a multi-wavelength analysis of star-forming galaxies to shed new light on the evolution of the far-IR-radio relations in intermediate redshift (0.3 < z < 0.6) galaxy clusters and galaxy groups. The far-infrared (far-IR) emission from galaxies is dominated by thermal dust emission. The radio emission at 1.4 GHz is predominantly produced by non-thermal synchrotron radiation. The underlying mechanisms, which drive the far-IR-radio correlation, are believed to arise from massive star formation. A number of studies have investigated the relationship as a function of redshift in the field and have found no evolution out to at least z _ 2, however few works have been done in galaxy clusters. In nearby clusters, the median logarithmic ratio of the far-IR to radio luminosity is qFIR = 2.07_0.74, which is lower than the value found in the field, and there is an indication of an enhancement of radio emission relative to the far-IR emission. Understanding the properties of the far-IR-radio correlation in a sample of distant and massive cluster and groups plays an important role in understanding the physical processes in these systems. We have derived total infrared luminosities for a sample of cluster, group, and field galaxies through an empirical relation based on Spitzer MIPS 24 _m photometry. The radio flux densities were measured from deep Very Large Array 1.4 GHz radio continuum observations. We have studied the properties of the far-IR-radio correlation of galaxies at intermediate redshift clusters by comparing the relationship of these galaxies to that of low redshift clusters. We have also examined the properties of the galaxies showing radio excess to determine the extent that galaxy type or environment may explain the radio excess in galaxy clusters. We find that the ratio of far-IR to radio luminosity for galaxies in an intermediate redshift cluster to be qFIR = 1.72_0.63. This value is comparable to that measured in low redshift clusters. A higher fraction of galaxies in clusters show an excess in their radio fluxes when compared to low redshift clusters, and corroborates previous evidence of a cluster enhancement of radio excess sources at this earlier epoch as well. We have also investigated the properties of the far-IR-radio correlation for a sample of galaxy groups in the COSMOS field. We find a lower percentage of radio-excess sources in groups as compared to clusters. This provides preliminary evidence that the number of radioexcess sources may depend on galaxy environment. We also find that a larger fraction of radio-excess sources in clusters are red sequence galaxies.
Cluver, Michelle E. "Probing distant clusters : a pre-SALT photometric study of intermediate redshift galaxy cluster." Master's thesis, University of Cape Town, 2005. http://hdl.handle.net/11427/4415.
Повний текст джерелаCuciti, Virginia <1989>. "Cluster-scale radio emission: analysis of a mass-selected sample of galaxy clusters." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2018. http://amsdottorato.unibo.it/8540/1/Tesi_PhD.pdf.
Повний текст джерелаPrice, James. "Galaxies in the coma cluster." Thesis, University of Bristol, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.529836.
Повний текст джерелаDesai, Vandana. "The assembly of cluster galaxies /." Thesis, Connect to this title online; UW restricted, 2004. http://hdl.handle.net/1773/5415.
Повний текст джерелаBlakeslee, John Paul. "The globular cluster luminosity functions of brightest cluster galaxies." Thesis, Massachusetts Institute of Technology, 1997. http://hdl.handle.net/1721.1/42589.
Повний текст джерелаJust, Dennis William. "The Influence of Environment on Galaxy Evolution." Diss., The University of Arizona, 2012. http://hdl.handle.net/10150/265357.
Повний текст джерелаBocquet, Sebastian. "Galaxy cluster cosmology." Diss., Ludwig-Maximilians-Universität München, 2015. http://nbn-resolving.de/urn:nbn:de:bvb:19-183812.
Повний текст джерелаPeery, Tyler Robert. "The Use of Brightest Cluster Galaxies as Standard Candles Since z~1." Ohio University Art and Sciences Honors Theses / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=ouashonors1276623279.
Повний текст джерелаParroni, Carolina. "Cluster mass scaling relations through weak lensing measurements." Thesis, Sorbonne Paris Cité, 2017. http://www.theses.fr/2017USPCC232/document.
Повний текст джерелаGalaxy clusters are essential cosmological and astrophysical tools, since they represent the largest and most massive gravitationally bound structures in the Universe. Through the study of their mass function, of their correlation function, and of the scaling relations between their mass and different observables, we can probe the predictions of cosmological models and structure formation scenarios. They are also interesting laboratories that allow us to study galaxy formation and evolution, and their interactions with the intra-cluster medium, in dense environments. For all of these goals, an accurate estimate of cluster masses is of fundamental importance. I studied the accuracy of the optical richness obtained by the RedGOLD cluster detection algorithm (Licitra et al. 2016) as a mass proxy, using weak lensing and X-ray mass measurements. I measured stacked weak lensing cluster masses for a sample of 1323 galaxy clusters in the CFHTLS W1 and in the NGVS at 0.2
Cooke, Elizabeth A. "How to build a cluster : the formation and evolution of galaxies in high-redshift clusters and protoclusters." Thesis, University of Nottingham, 2016. http://eprints.nottingham.ac.uk/35454/.
Повний текст джерелаBarrientos, Luis Felipe. "The evolution of cluster elliptical galaxies." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/nq41098.pdf.
Повний текст джерелаZhao, Dongyao. "Evolution of the brightest cluster galaxies." Thesis, University of Nottingham, 2016. http://eprints.nottingham.ac.uk/35927/.
Повний текст джерелаWhiley, Ian M. "Evolution of the brightest cluster galaxies." Thesis, University of Nottingham, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.489698.
Повний текст джерелаRandriamampandry, Solohery Mampionona. "Stellar masses of star forming galaxies in clusters." University of the Western Cape, 2010. http://hdl.handle.net/11394/3028.
Повний текст джерелаWe determine the stellar mass of star forming galaxies in the X-ray luminous cluster MS 0451.6-0305 at z ∼ 0.54. The stellar masses are estimated from fitting model spectral energy distributions (SEDs) to deep, optical UBRIz observations obtained from WIYN 3.5m telescope and public NIR K-band image from Palomar Observatory telescope. The model SEDs are based on the stellar population synthesis (SPS) model of Bruzual & Charlot (2003) and Conroy et al. (2009) that span a wide range of age, star formation history, Initial Mass Function (IMF), metallicity and dust content. We measure stellar masses for galaxies down to M∗∼2×10⁸M(.) We find a tight correlation between stellar masses derived from the two SPSs. We compare the derived stellar masses to the dynamical masses for a set of 25 star forming galaxies. The dynamical masses are derived from high resolution, spectroscopic observations of emission lines from the DEIMOS spectrograph on the Keck telescope. A strong correlation is seen between the dynamical and stellar mass for the galaxies; and the star forming galaxies show fairly constant ratio between stellar and dynamical mass. When comparing to the field sample of Guzm ́an et al. (2003) of luminous compact blue galaxies, we see an excess of low mass galaxies in the cluster.
South Africa
Misgeld, Ingo [Verfasser], and Ralf [Akademischer Betreuer] Bender. "Early-type stellar systems in nearby galaxy clusters : from dwarf galaxies to star clusters / Ingo Misgeld. Betreuer: Ralf Bender." München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2011. http://d-nb.info/1015064787/34.
Повний текст джерелаWong, Kenneth Christopher. "Strong Gravitational Lensing as a Probe of Galaxy Evolution and Cosmology." Diss., The University of Arizona, 2013. http://hdl.handle.net/10150/305760.
Повний текст джерелаGiacintucci, Simona <1975>. "Multiwavelenght study of cluster mergers and consequences for the radio emission properties of galaxy clusters." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2007. http://amsdottorato.unibo.it/353/1/tesi_giacintucci.pdf.
Повний текст джерелаGiacintucci, Simona <1975>. "Multiwavelenght study of cluster mergers and consequences for the radio emission properties of galaxy clusters." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2007. http://amsdottorato.unibo.it/353/.
Повний текст джерелаHodson, Alistair. "A non-Newtonian perspective of gravity : testing modified gravity theories in galaxies and galaxy clusters." Thesis, University of St Andrews, 2017. http://hdl.handle.net/10023/12016.
Повний текст джерелаEsposito, Federico. "Proprietà degli ammassi di galassie." Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2015. http://amslaurea.unibo.it/9091/.
Повний текст джерелаMessa, M., A. Adamo, G. Östlin, D. Calzetti, K. Grasha, E. K. Grebel, F. Shabani, et al. "The young star cluster population of M51 with LEGUS – I. A comprehensive study of cluster formation and evolution." OXFORD UNIV PRESS, 2018. http://hdl.handle.net/10150/626277.
Повний текст джерелаEllingson, Erica. "Quasars in galaxy cluster environments." Diss., The University of Arizona, 1989. http://hdl.handle.net/10150/184878.
Повний текст джерелаRuggiero, Rafael. "Galaxy Evolution in Clusters." Universidade de São Paulo, 2018. http://www.teses.usp.br/teses/disponiveis/14/14131/tde-14022019-140755/.
Повний текст джерелаNesta tese, nós visamos a contribuir para o entendimento do fenômeno da evolução de galáxias no ambiente de aglomerados de galáxias usando a metodologia de simulações numéricas. Para isso, desenvolvemos modelos hidrodinâmicos nos quais galáxias idealizadas ricas em gás movem-se em meio ao gás difuso de aglomerados de galáxias idealizados, permitindo um estudo detalhado e controlado da evolução destas galáxias neste ambiente extremo. O principal código usado em nossas simulações é o RAMSES, e nossos resultados tratam das mudanças em composição do gás, taxa de formação estelar, luminosidade e cor de galáxias caindo em aglomerados. Adicionalmente a processos acontecendo dentro das próprias galáxias, nós também descrevemos a dinâmica do gás que é varrido dessas galáxias com resolução sem precedentes para simulações dessa natureza (122 pc em uma caixa incluindo um aglomerado de 1e14 Msun inteiro), encontrando que aglomerados de gás molecular são formados nas caudas de galáxias que passaram por varrimento de gás por pressão de arraste, aglomerados estes que procedem a viver em isolamento em meio ao gás difuso de um aglomerado de galáxias por até 300 Myr. Esses aglomerados moleculares possivelmente representam uma nova classe de objetos; objetos similares foram previamente observados tanto em aglomerados quanto em grupos de galáxias, mas um tratamento compreensivo deles não foi apresentado até agora. Nós adicionalmente criamos um modelo hidrodinâmico para o sistema multi-aglomerado A901/2, e correlacionamos as condições do gás nesse modelo com a localização de uma amostra de galáxias jellyfish nesse sistema; isso nos permitiu inferir um possível mecanismo para a geração de morfologias jellyfish em colisões de aglomerados de galáxias em geral.
Guglielmo, Valentina. "Groups and clusters of galaxies in the XXL survey." Doctoral thesis, Università degli studi di Padova, 2018. http://hdl.handle.net/11577/3421945.
Повний текст джерелаQuesta tesi presenta uno dei primi censimenti delle proprietà delle galassie in gruppi ed ammassi selezionati nei raggi X a redshift intermedio, con lo scopo di valutare il ruolo dell'ambiente sull'assemblamento della massa stellare delle galassie, l'attività di formazione stellare e le proprietà delle popolazioni stellari osservate. Il mio progetto è inquadrato nella Survey XXL (Pierre et al., 2016), il più grande programma XMM-Newton approvato fino ad oggi, che copre due regioni extra-galattiche di 25 gradi quadrati ciascuna. Le sorgenti di raggi X estese ed identificate come gruppi ed ammassi sono state confermate spettroscopicamente e le loro proprietà principali sono caratterizzate o tramite misurazioni dirette o mediante relazioni di scala. Tra queste, le luminosità e le temperature X, le masse virali ed i raggi viriali sono di fondamentale importanza per lo sviluppo di questa tesi. Il grande vantaggio di XXL è che il campo XXL-Nord (XXL-N) è completamente coperto da osservazioni fotometriche e spettroscopiche provenienti dalle più recenti survey extra-galattiche di galassie. La disponibilità di una tale miniera di informazioni motiva lo sviluppo della mia ricerca sulle popolazioni di galassie nell'intervallo di redshift 0.1≤z≤0.6 nel campo XXL-N, esplorando gli ambienti più diversi dalle regioni di campo, ai gruppi, agli ammassi e ai superammassi. Il primo compito del mio lavoro consiste nella creazione di un campione spettrofotometrico omogeneo di galassie, pubblicato in Guglielmo et al. (2017), e adatto ad essere utilizzato in un'analisi scientifica. Il catalogo contiene redshift spettroscopici, informazioni sull'appartenenza a gruppi e ammassi, pesi di completezza spettroscopica in funzione della posizione nel cielo e magnitudine osservata, le masse stellari e le magnitudini assolute calcolate mediante una tecnica di spectral energy distribution (SED). Il catalogo è fondamentale per tutti gli studi all'interno della collaborazione XXL che mirano a correlare le proprietà ottiche derivate dalle galassie con informazioni sulle strutture X ed è ampiamente utilizzato nell'intera collaborazione XXL. Il catalogo spettrofotometrico pubblicato consente il primo risultato scientifico di questa tesi riguardante lo studio della funzione di massa stellare delle galassie (GSMF). L'obiettivo di questa analisi è di svelare se il processo di assemblamento della massa delle galassie dipende dall'ambiente cosiddetto globale, cioè dall'appartenenza al campo o a gruppi ed ammassi e, tra quest'ultimi, dalla luminosità X, utilizzata come proxy per la massa di alone. Ho eseguito l'analisi in quattro intervalli di redshift nel range 0.1≤z≤0.6, trovando nel complesso che l'ambiente non influenza la GSMF, almeno nell'intervallo di massa campionato. Il risultato è ulteriormente confermato dall'invarianza della massa media delle galassie membre rispetto alla luminosità X. Ho anche esaminato l'evoluzione della GSMF da z = 0.6 fino a z = 0.1, trovando che l'estremità della funzione a masse elevate è già formata nell'epoca più antica e non evolve, e rilevando invece un aumento del numero di galassie a bassa massa nello stesso intervallo di redshift. Questo studio è uno dei primi studi sistematici della GSMF condotto per sorgenti estese a raggi X che vanno da masse di alone tipiche di gruppi fino agli ammassi, ed è pubblicato nella seconda parte di Guglielmo et al. (2017). Avendo valutato l'indipendenza delle distribuzioni di massa rispetto all'ambiente globale, procedo a indagare se e in che misura l'ambiente influisce sull'attività di formazione stellare e sulle proprietà osservate delle popolazioni stellari delle galassie. Ho iniziato questa analisi dal superammasso più ricco identificato in XXL-N, XLSSsC N01, situato a redshift z~0.3 e composto da 14 gruppi ed ammassi. Questo lavoro è stato sottomesso in Guglielmo et al. (2018a). Concentrandosi sulla regione che circonda XLSSsC N01, ho diviso le galassie in diversi ambienti, che vanno dalle regioni virali di gruppi ed ammassi fino al campo, utilizzando una combinazione di parametrizzazioni ambientali globali e locali. I risultati principali di questo studio sono che, nell'ambiente del superammasso, mentre la frazione di galassie che formano stelle e l'efficienza di arresto dell'attività di formazione stellare dipendono fortemente dall'ambiente, lo stesso non vale per la relazione fra massa e tasso di formazione stellare (SFR). La frazione di galassie che formano stelle declina progressivamente dal campo ai filamenti fino alle regioni virializzate di gruppi ed ammassi, con un interessante aumento della stessa nelle regioni esterne delle strutture X. Inoltre, mentre la relazione media fra l'età delle galassie pesata per la luminosità (LW-age) e la massa stellare delle stesse è indipendente dall'ambiente, una chiara evidenza di una recente estinzione della formazione stellare si rileva nelle galassie passive situate nelle regioni virializzate delle strutture X. Infine, si estende l'analisi di questo particolare superammasso all'intero campo XXL-N. Questo lavoro sarà racchiuso in due articoli in preparazione (Guglielmo et al., 2018 b, c in preparazione). Grazie alla statistica più elevata dell'intero campione, ho studiato le proprietà delle galassie e la loro evoluzione nell'intervallo 0.1≤z≤0.5 in diversi ambienti, con l'obiettivo di caratterizzare il cambiamento nelle proprietà delle popolazioni stellari e la formazione della popolazione passiva al variare dell'ambiente. Oltre a distinguere tra le galassie di campo, e in gruppi ed ammassi (regioni virali e periferiche), mi sono concentrata anche su galassie situate in strutture di diversa luminosità X e sulle galassie situate all'interno di superammassi. Contemporaneamente, ho anche studiato le proprietà delle galassie situate a diverse densità locali proiettate (LD). In particolare, ho caratterizzato la frazione galassie con formazione stellare attiva / galassie blu e ho studiato la relazione fra massa e SFR, in funzione sia dell'ambiente globale che di quello locale. La frazione di galassie con formazione stellare attiva e di galassie blu è strettamente correlata all'ambiente, con il valore più basso nelle regioni virali di gruppi ed ammassi e il più alto nel campo. Nei membri esterni, la stessa frazione è simile a quella nel campo a z≥0.2 e assume valori intermedi rispetto ai membri virali e il campo a 0.1≤z<0.2. La relazione fra SFR e massa è anch'essa dipendente dall'ambiente, e in particolare il numero di galassie dei membri virali che hanno una ridotta SFR (galassie in transizione) risulta essere quasi il doppio di quella di galassie di campo. Ancora una volta, i membri esterni mostrano proprietà intermedie: la frazione di galassie in transizione è simile alla popolazione virale a z>0,3, ed in particolare risulta associata all'ambiente dei superammassi, e si riduce successivamente a valori tipici delle galassie di campo a 0.1≤z<0.3. Inoltre, la frazione di galassie attive nella formazione stellare e quella di galassie blu diminuiscono con l'aumentare della LD a tutti i redshift. Al contrario, la frazione di galassie in transizione non varia nello stesso intervallo LD. Queste differenze significative emergenti tra gli ambienti globali e locali sono intrinsecamente correlate al diverso significato fisico delle due parametrizzazioni, quindi ai diversi meccanismi fisici che agiscono sulle galassie quando sono legate al potenziale gravitazionale di un alone di materia oscura (secondo la definizione globale) o quando esposto ad interazioni con altre galassie in regioni densamente popolate (secondo la definizione locale). Durante le prime fasi del mio dottorato di ricerca, ho anche completato l'analisi della mia tesi magistrale, e riporto il testo completo del documento pubblicato in Appendice alla tesi (Guglielmo et al., 2015). I risultati sono strettamente correlati alle domande scientifiche trattate nel mio progetto di dottorato, ma vengono affrontate attraverso un approccio complementare, che mira alla ricostruzione della storia della formazione stellare delle galassie a basso redshift in ammassi e nel campo per studiare la dipendenza dall'ambiente globale, dalla massa stellare e dalla morfologia osservata.