Found 5 talks width keyword galaxy merger
Majority of galaxies reside in groups and clusters where they are understood to evolve also through galaxy-galaxy interactions. Multiple mergers at the core of galaxy groups can develop a luminosity deficiency or gap, which is quantified as the difference between the luminosity of the two brightest galaxies in groups and clusters. This observable carries important information about the evolution of galaxy groups, for instance, there are indications that collapsed groups with a large luminosity gap, known as fossil groups, are associated with the halos that are relatively old. In a series of recent studies, employing X-ray, optical and radio observations complemented by cosmological simulations, we have utilised the luminosity gap to probe the formation scenarios for galaxies and specially the most luminous galaxies in groups and clusters, introduce a powerful age-date routine for galaxy groups, and also obtain clues about the AGN activities and the IGM heating.
Two competing effects appear to govern galaxy multiplicity (pairs orgroups) at low masses: while associations of low-mass haloes are naturally expected in a LCDM cosmology, galaxy formation within these haloes is thought to be rendered inefficient due to the action of several ionizing agents. Yet associations of dwarf galaxies are known to exist in the Local Volume, and their frequency appears to be unexpectedly high for LCDM expectations even in our own Local Group. Unfortunately, it is not yet well understood what role do interactions between low-mass galaxies play in determining their star formation histories, structural properties, and neutral gas content. Here I will present an investigation of the impact of dwarf-dwarf galaxy tidal interactions on their morphological and star formation properties. The UGC5205 close pair consists of two low-mass (M* ~ 5E7 Msun), late-type galaxies with a relative projected distance of only 10 kpc, and no nearby massive companions. I will show that these equal-mass interactions can be an important 'pre-processing' mechanism that acts before dwarfs are affected by a more massive central galaxy, profoundly impacting their star formation histories and morphologies.
In the 50 years since their discovery, it has become increasingly recognised that quasars are not merely signposts to the distant Universe, but also play a key role in the overall galaxy evolution process. However, if we are to incorporate quasars into models of galaxy evolution, it's important to understand how, when and where they are triggered. In this talk I will review the latest observational results on the triggering of quasars, based on the morphologies of their host galaxies and star formation properties; I will also discuss the future prospects for understanding quasar triggering using Herschel and ALMA data.
The detection and number estimates of supermassive binary black holes (SMBBHs) provide important constraints on the hierarchical models for galaxy formation and evolution. I will present two different approaches for the possible identification of SMBBHs. 1.Radio-optical studies of X-shaped radio sources:X-shaped radio galaxies are extragalactic radio sources that present two pairs of radio lobes passing symmetrically through the center of the host galaxy, giving the galaxy the X-shaped morphology seen on radio maps.This morphology can reflect either a recent merger of two supermassive black holes or the presence of a second active black hole in the galactic nucleus. This scenario is studied by determining the mass, luminosity, jet dynamic age and starburst of a sample of X-shaped sources and comparing the results to a sample of radio-loud active nuclei with similar redshift and luminosities. 2.Compact radio emission in ULX objects: Ultraluminous X-ray sources (ULXs) have luminosities exceeding 10E39 erg/s, suggesting either the presence of black holes larger than stellar mass black holes or sources apparently radiating above the Eddington limit. I will present milliarcsecond-scale radio observations of some ULXs located within optical bright galaxies, resolving their compact radio emission, and measuring its brightness temperature and spectral properties. This allows us to uncover the nature of these sources and investigate whether they are intermediate mass black holes or supermassive black holes stripped of their accretion disks in post-merger systems.
I will review the status of our understanding of galaxy formation in the prevailing cold dark matter paradigm. After reviewing the successes and failures of the most natural predictions of this scenario I will focus on the consequences of two of its main predictions: the presence of large numbers of low-mass dark matter halos and the prevalence of accretion events during the formation of normal galaxies. In particular, I will discuss the interpretation of the recent discovery of a population of ultra-faint galaxies in the Local Group, and its relation to the profuse cold dark matter substructure expected in the Galactic halo. I will also discuss the importance that accretion events might have had in shaping not only the stellar halo but also the disk component(s) of the Milky Way.
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- Gamma-ray AstrophysicsDr. Mónica Vázquez AcostaTuesday July 23, 2019 - 12:30 (Aula)
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