Resumen:

Luminous, high-redshift ($z>6$) quasars are formidable probes of the universe in the Epoch of Reionization. They are observed to already host super-massive black holes (BHs) in their centers, and to reside in the earliest, most massive galaxies, where they are thought to be surrounded by large galactic over-densities. How BHs and hosts get this massive in such short amount of time after the Big Bang is one of the key open questions of current astrophysics. Here, we present bolometric luminosities, BH masses and Eddington ratios for 42 luminous quasars at z>6 using, for the first time, high signal-to-noise ratio VLT/X-Shooter spectra, acquired as part of the ESO Large Programme XQR-30. We find that quasars at high-redshift host slightly less massive BHs which accrete slightly more rapidly than a bolometric luminosity matched quasars sample at $z\sim 1$, and we explore the repercussion of such results with respect to BH seeds formation and evolution scenarios.

Resumen:

In this work, we study the number density of Lyman Alpha Emitter (LAE) galaxies, their physical properties, and synthetic spectra at redshift ~ 6 using high-resolution hydrodynamical simulations with radiative transfer from the Thesan project. By recreating the scenario described in Becker et al. 2018, we test the hypothesis that observations to date are missing the vast majority of the high-redshift galaxies' signal since they are extremely faint and, thus, are out of the observational limits of our current telescopes. We also follow the evolution of the neutral Hydrogen fraction, the chemical enrichment of the circum- and intergalactic medium, and specific star formation rate of galaxies in the simulation at the end of Reionization, and evaluate why the detections from HST and the Silverrush project significantly underestimate the number of faint galaxies. Our study indicates an observational bias to massive galaxies in the field. Thus, we forecast the properties of the dwarf galaxies responsible for completing the budget of ionizing photons that concluded the Epoch of Reionization.

Resumen:

Observations and models indicate that the fraction of active galaxies in the local Universe is about 10\% . As most large galaxies host a supermassive black hole (SMBH), this can be interpreted as a duty cycle, where 10\% of galaxies are active at any given time. Estimating this activation rate is important to constrain central black hole feeding mechanisms in galaxy evolution models. Black hole ignition events, which involve a galaxy transitioning from a quiescent or star-forming state to a an AGN are, however, exceptionally challenging to detect. For our work, we took advantage of the very large public photometric monitorings that are currently ongoing together with machine-learning algorithms for selecting interesting objects. Black hole ignition event candidates were selected form a parent sample of spectrally classified non-active galaxies ($>2.300.000$ objects), that currently show optical flux variability indicative of a type I AGN, according to the ALeRCE light curve classifier. In this talk we will present spectral results for the most convincing case of new AGN activity, for a galaxy with a previous star-forming optical classification, where the confirmation spectrum shows the appearance of prominent, broad Balmer lines without significant changes in the narrow line flux ratios. MIR colors have also evolved from typical non active galaxy colors to AGN-like colors.

Resumen:

Structural analyses of high-redshift galaxies are key to understanding the physical processes that drive galaxy evolution across cosmic time. While high-resolution observations from the HST and JWST open a window into dust-unobscured star formation and stellar mass content of high-redshift galaxies, radio continuum imaging at sub-arcsec resolution is needed to trace dust-obscured star formation that dominates the star formation rate density of the Universe out to $z\approx5$. To address this open issue, we have conducted the first high-resolution (0.2 arcsec), high-frequency observational campaign to fully map an extragalactic deep field at unprecedented sensitivity: ``The VLA 10GHz Survey of GOODS-N’’. Surveying the extragalactic sky at 10GHz has the advantage of yielding higher angular resolution imaging while probing thermal (free-free) radiation of high-redshift galaxies, which is more directly proportional to the rate of massive star formation. The deep 10GHz images of GOODS-N, thereby, provide an extinction-free view for the morphologies of massive star-forming galaxies out to $z\approx3$ on 1.7kpc scales. In this talk, I will review the key science goals of the “VLA 10GHz Survey of GOODS-N”, present the initial results, and describe the plans for the data release. Finally, I will discuss how the ``VLA 10GHz Survey of GOODS-N’’ will serve as a pathfinder for future ngVLA observations to trace the sub-kpc scale distribution of star formation of high-redshift galaxies.

Resumen:

Quasars and QSOs are the most luminous objects in the Universe, having bolometric luminosities Lbol > 10$^{46}$ erg/s produced by a Supermassive Black Hole (SMBH) with a high accretion rate in the nucleus of their host galaxies. The SMBH is surrounded by an accretion disk and emitting clouds with velocities in excess of 1000 km/s, surrounded by a dusty molecular torus at ~pc scales. In the Unified Model of AGN (Active Galactic Nuclei), this torus blocks the view of the inner region if observed "edge-on", in the so-called type 2 QSOs. Type 1 QSOs, on the other hand, are supposed to be seen face-on and do not show obscuration. However, there has been some evidence suggesting that these two types of objects do not differ only due to orientation. The goal of this work is to investigate this for a QSO sample, comparing the optical spectral properties of QSO 1 with those of QSOs 2 using, in particular, the [O III] emission-line doublet for the quasar sample from SDSS DR 16, named DR16Q, to investigate a QSO 1 and 2 subsample within 0.4 < z < z 0.5. We found that the [O III] kinematic profile, traced by the W80 parameter, shows that the QSO 2 population has a broader profile than those for the QSOs 1. Moreover, the [O III] luminosity is higher for the QSOs 2 than for the QSOs 1. Both results suggest that there is a difference between these two QSO populations that cannot be fully explained by the AGN Unified Model. Our next step is to check if this difference persists up to z = 1 (when the [O III] doublet goes out of the SDSS wavelength range).