ANÁLISE DO ESTÁGIO DINÂMICO DE ABELL 3571 POR MEIO DE ESPECTROSCOPIA ESPACIALMENTE RESOLVIDA EM RAIOS X

2025-01-10T16:58:42Z

ANÁLISE DO ESTÁGIO DINÂMICO DE ABELL 3571 POR MEIO DE ESPECTROSCOPIA ESPACIALMENTE RESOLVIDA EM RAIOS X PATRICK PRADO DOS SANTOS DE ALENCAR DUPKE, RENATO Thermodynamic maps of galaxy clusters created from X-ray observations are capable of revealing structures within these systems much more effectively than analyses in optical frequencies, for example. Understanding the nature of these structures facilitates the correct determination of the cluster’s dynamical stage. In this work, a Python code was developed to create such maps, from selecting regions for spectrum extraction to smoothing the points obtained using the Kriging method. The test system chosen to evaluate the developed code was the galaxy cluster Abell 3571 (A3571). Despite being a nearby cluster ($z=0.039$) and the sixth brightest X-ray cluster, there are few studies on it, and its dynamical stage is still unclear in the literature. Using an observation made with the Chandra X-ray Observatory we created temperature, pressure, and entropy maps, which revealed features not previously seen in earlier works, such as the presence of a cold front south of the cluster core and a low-entropy elongation whose direction does not coincide with the X-ray brightness elongation direction. The entropy map obtained in this work, along with maps from previous studies using the XMM-Newton telescope and the structure mentioned above, led to the suggestion of a scenario where a group of galaxies is colliding with the center of A3571. Therefore, we conclude that the code was successful in creating the thermodynamic maps, and these play a fundamental role in determining the dynamical stage of the cluster. The work will continue by adapting the code for use with XMM-Newton observations and applying it to this and other systems. Observatorio Nacional Dissertação

EVOLUÇÃO DE GALÁXIAS EM SUPERGRUPOS DE AGLOMERADOS DE GALÁXIAS EM BAIXO REDSHIFT

2024-10-11T18:30:11Z

EVOLUÇÃO DE GALÁXIAS EM SUPERGRUPOS DE AGLOMERADOS DE GALÁXIAS EM BAIXO REDSHIFT GOIS DA SILVA, FILIPE CORREIA OGANDO, RICARDO LOURENCO Supergroups are “groups of galaxy groups” and/or galaxy clusters with substructures that might collapse into a single cluster. Since galaxy clusters have singular characteristics, such as a well-defined red sequence and a concentration of early-type galaxies, it is important to understand how these properties came to be and which factors — such as preprocessing in these structures — might have led to this configuration. There are few studies about Supergroups (e.g., Brough et al., 2006; Sengupta et al., 2022; Smit et al., 2015). Besides, the studies generally focus on the analysis of one Supergroup at a time. In this context, we will study a set of Supergroups over a significant redshift range (z<0.5), expanding the list of these objects, and understanding their common characteristics concerning galaxy evolution and stellar population distribution. We identified Supergroups in the RedMaPPer galaxy clusters catalog using data from the 5,000 sq. deg. DES footprint in the griz bands. We analyzed the galaxy evolution inside them using colors, understanding how factors, such as the radius and the mass of the Supergroup, might influence these populations. To find Supergroups, we searched for cluster overdensities in redshift bins of 0.1 out to z=0.5 and with 5 cMpc wide pixels in RA and Dec. We used the K correction of Blanton and Roweis (2007) to correct the magnitude in all bands and a Gaussian Mixture Model (GMM) to separate populations in blue and red galaxies. We found 8 Supergroup candidates with 0.1

EXPLORANDO VARIÁVEIS CATACLÍSMICAS COM SIMILARIDADES OBSERVACIONAIS DE ANÃS BRANCAS ACRETANTES MAGNÉTICAS E NÃO-MAGNÉTICAS

2024-10-11T18:23:37Z

EXPLORANDO VARIÁVEIS CATACLÍSMICAS COM SIMILARIDADES OBSERVACIONAIS DE ANÃS BRANCAS ACRETANTES MAGNÉTICAS E NÃO-MAGNÉTICAS SILVA DE ARAUJO, AMANDA LOPES DE OLIVEIRA FILHO, RAIMUNDO Cataclysmic Variables (CVs) are binary systems in which a white dwarf (WD) accretes matter from a companion star on or near the main sequence. Some of the uncertainties about these systems revolve around the following points: population studies and determination of parameter space at the threshold between systems harboring accreting magnetic and non-magnetic white dwarfs. These points were addressed in this work through a multispectral analysis. In the first approach, we used a sample of systems classified as dwarf novae (DNs), yet with optical spectral characteristics similar to those of low-luminosity intermediate polar-like X-ray sources (LLIPs), LLIPs, and polars. In the second approach, we focused on characterizing CVs identified in S-PLUS. The work utilized (i) a collection of observations, with optical spectroscopy performed using GMOS/Gemini-South and X-ray observations with the Swift satellite, along with optical and ultraviolet photometry from the same satellite, (ii) observations and information from public databases such as light curves from the TESS satellite and the ASAS-SN project, optical spectroscopy from LAMOST and SDSS, magnitude and distance measurements from the GAIA satellite, and flux measurements from the eROSITA satellite, and (iii) information available in the literature. In terms of population, we characterized and confirmed 11 new CVs based on characteristic lines from Balmer Series of H, HeI, and HeII at 4686 Å. Additional confirmation of this nature for four systems came through X-ray observations performed with the Swift telescope. The observed X-ray luminosities were consistent with those expected for LLIPs and DNs. One system stands out, in which we determined an orbital period of 1.81 hours, revealed in TESS light curves, whose orbital and spectral characteristics are consistent with those of IPs and certain NAs. However, the non-detection of the white dwarf spin period from TESS observations suggests it is an DN. Furthermore, two of these eleven systems were identified, based on spectral similarities (notably in HeII 4686 emissions, Hα, and Hβ), as polars. Regarding the parameter space between CVs, polars tend to have lower equivalent widths for Hα and Hβ lines, with a relationship suggesting higher EW(Hα) values are associated with higher Hβ values. In polars, the ratio EW(Hα)/EW(Hβ) as a function of EW(HeII 4686) indicates that intense emissions of HeII at 4686 Å are preferentially associated with optically thick astrophysical environments to Hα photons. Additionally, polars exhibit greater variation in EW(HeII 4686)/EW(Hα), always exceeding 0.2, but without correlation with EW(Hα) values. On the other hand, DNs and LLIPs show greater dispersion in EW(Hα) and EW(Hβ) values, extending up to approximately 200 Å. HeII emission at 4686 Å in DNs and LLIPs is always associated with EW(HeII 4686) values below 15 Å indicating relatively weak emissions compared to polars. There is no distinction among HeII 4686, Hα, and Hβ emissions between DNs and LLIPs studied, making differentiation based solely on these lines impossible. The ratio EW(HeII 4686)/EW(Hα) for DNs and LLIPs is consistently low, below 0.2, reflecting weak HeII emissions at 4686 Å compared to Hα. Furthermore, no significant trends were observed between equivalent widths and orbital periods of the systems in any of the classes. Observatorio Nacional Dissertação

TESTE DO PRINCÍPIO COSMOLÓGICO UTILIZANDO RECONSTRUÇÕES NÃO-PARAMÉTRICAS

2024-10-11T18:19:30Z

TESTE DO PRINCÍPIO COSMOLÓGICO UTILIZANDO RECONSTRUÇÕES NÃO-PARAMÉTRICAS LOPES DA SILVA DIAS, MARIANA PAES BENGALY JUNIOR, CARLOS ANDRE This work aims to conduct a consistency test of the Cosmological Principle, one of the fundamental hypotheses of the Standard Cosmological Model. This principle postulates that the Universe is homogeneous and isotropic on large scales. By testing it, we end up reviewing the foundations of the Standard Cosmological Model. Through a consistency relationship between measurements of ages and cosmological distances, we verify, in this work, whether there is evolution in the redshift of the curvature parameter, . If we find that is not constant, we have evidence of a deviation from the homogeneity hypothesis and, consequently, there is no consistency with the Cosmological Principle. We use a compilation of distance measurements from type Ia Supernovae from the Pantheon+SH0ES collaboration and a compilation of Hubble parameter measurements, Hpzq, obtained by galaxy ages and baryon acoustic oscillations, to calculate Ωk. Through non-parametric reconstructions via Gaussian Processes, we show that there is no significant evolution of the curvature parameter, , as a function of redshift, and that there is in agreement with the Standard Cosmological Model. However, the uncertainties in our analyses are still quite high. We also show that these uncertainties can be significantly reduced through simulations of redshift survey data, as well as gravitational waves. Observatorio Nacional Dissertação

Dissertações de Mestrado PPGA

ANÁLISE DO ESTÁGIO DINÂMICO DE ABELL 3571 POR MEIO DE ESPECTROSCOPIA ESPACIALMENTE RESOLVIDA EM RAIOS X

EVOLUÇÃO DE GALÁXIAS EM SUPERGRUPOS DE AGLOMERADOS DE GALÁXIAS EM BAIXO REDSHIFT

EXPLORANDO VARIÁVEIS CATACLÍSMICAS COM SIMILARIDADES OBSERVACIONAIS DE ANÃS BRANCAS ACRETANTES MAGNÉTICAS E NÃO-MAGNÉTICAS

TESTE DO PRINCÍPIO COSMOLÓGICO UTILIZANDO RECONSTRUÇÕES NÃO-PARAMÉTRICAS