Cosmology / Active Galactic Nuclei
We present a summary of the posters of this astronomical topic. If you want to see the full poster, click on the document:
Title: Singularities and Soft-Big Bang in a viscous ΛCDM model
Norman Cruz,1, 2, Esteban González,3, and Jose Jovel ,1
1Departamento de Física, Universidad de Santiago de Chile,
Avenida Ecuador 3493, Santiago, Chile
2Center for Interdisciplinary Research in Astrophysics and Space Exploration (CIRAS),
Universidad de Santiago de Chile, Av. Libertador Bernardo O’Higgins 3363, Estación Central, Chile.
3Dirección de Investigación y Postgrado, Universidad de Aconcagua,
Pedro de Villagra 2265, Vitacura, 7630367 Santiago, Chile
Abstract: We explore the different types of singularities that arise in the ΛCDM model when dissipative processes are considered, in the framework of Eckart’s theory. In particular, we study the late-time behavior of ΛCDM model with viscous cold dark matter (CDM) and an early-time viscous radiation domination era with cosmological constant (CC). The fluids are described by the barotropic equation of state (EoS) p=(𝛾−1)𝜌, where p is the equilibrium pressure of the fluid, ρ their energy density, and γ is the barotropic index. We found that future singularities like Big-Rip types are allowed but without having a phantom EoS associated with the dark energy (DE) fluid. Big-Crunch singularities also appear with negative CC, but also de Sitter and even Big-Rip types are allowed, which opens the possibility of an accelerated expansion in AdS cosmologies. We also discuss a very particular solution without the Big Bang singularity that arises in the early-time radiation dominant era of our model known as Soft-Big Bang.
Title: AGN-driven molecular outflows
Ávila, Patricio J.
Patricio J. Ávila, Universidad de Concepción , Stefano Bovino , Universidad de Concepción, Alessandro Lupi, Universita degli Studi di Milano-Bicocca
Abstract: Fast molecular outflows have been observed in AGN since the last decade, however, their origin is not fully understood. One possibility is that preexisting molecular clouds can be accelerated by AGN-driven wind, although the survivability of these clouds is difficult. A more plausible scenario is that the detected molecules are formed in situ as a consequence of efficient cooling behind the shocked gas. To study this scenario, non-equilibrium chemistry and the connected microphysics is necessary. In this talk I will present hydrodynamical simulations of an isotropic AGN wind which result in a fast outflow performed with the magneto-hydrodynamics code GIZMO, coupled with chemistry, through the code KROME. We follow the time-dependent chemistry of 34 species, including key molecules detected in these outflows such as CO, OH, H2, and HCO+. The thermodynamics is consistently solved along with the hydrodynamics by including important processes like photoheating and the photoelectric process induced by a quasar radiation flux Sazonov (2004), scaled with our bolometric luminosity. We analyze under what conditions the molecular outflows can form and study the time scale for such formation.
Title: Black hole mass estimation for lensed systems using spectroscopy
Melo, A (Universidade de Valparaíso); Motta, V (Universidade de Valparaíso); Godoy, N (Universidade de Valparaíso); Mejía-Restrepo, J; Assef R (Universidad Diego Portales),; Jerez-Nicurcar (Universidade de Valparaíso), R; Ávila-Vera; F (Universidade de Valparaíso).
Abstract: The quadruple lensed system WGD2038-4008 (zs = 0.777) was recently discovered with the help of new techniques
and observations. Even though black hole mass (MBH) has been estimated for lensed quasars, it has been calculated mostly for one broad emission line of one image, but the images could be affected by microlensing, affecting the results. We present spectroscopic observations using X-shooter instrument (VLT) taking advantage of its wide spectral range (UVB, VIS and NIR arm). MBH was estimated for images A and B using the three most prominent broad emission lines (Hα, Hβ and MgII) obtained in one single-epoch spectra. This is the first time the mass is estimated in a lensed quasar in two images, allowing us to disentangle the effects of microlensing.
Title: ACTIVE GALACTIC NUCLEI in the Zwicky Transient Facility (ZTF)
Priyanjali Patel (Universidad de Chile) , Paulina Lira (Universidad de Chile), Patricia Arévalo (Universidad de Valparaíso, Chile)
Abstract: We analyze a sample of optical light curves for AGNs in the r-band (6339.61 Å) and the g-band (4722.74 Å). We take advantage of a homogeneous analysis of SDSS DR14 quasars spectra by Rakshit et al., 2020 to define a sample with well-measured Black Hole mass (MBH) and Eddington ratio/accretion rate (Ṁ) in different redshift bin. The emission from quasars is highly variable, and the variability is a potential key to understand the accretion process. Here we calculate the amplitude of variability, or the variance at different time scales in the resulting power spectrum using the ‘Mexican-Hat’ filter (Arévalo, P. et al., 2012) for a large population of AGN. By separating the variance on different timescales, we find an anti-correlation between rest-frame wavelengths and variance by using the redshift as the tool to study different rest-frame wavelengths. Furthermore, our approach is not affected by biases introduced from redshift effects such as time dilation since the light curves have been corrected for the redshift.