Embedded Files
Main research topics:
Main research topics:
Interstellar/Circumgalactic medium and large scale environment of high-z galaxies and quasar hosts.
Co-evolution between supermassive black holes and their host galaxies across cosmic time.
Structure formation and Intergalactic medium.
High-z quasar discovery and identification.
Techniques:
Techniques:
Interferometry at (sub)millemeter wavelengths (ALMA, IRAM PdBI/NOEMA, JVLA)
Optical and near-infrared imaging and long-slit spectroscopy (VLT, HST, JWST)
Archive data querying, data modelling and statistics.
The Dawn of Cosmic Time
The Dawn of Cosmic Time
Understanding the early Universe and the formation of galaxies and black holes is one of the greatest challenges in extragalactic astronomy. The first observable light — the Cosmic Microwave Background (CMB) — emerged when baryons and radiation decoupled around 400,000 years after the Big Bang (z ~ 1200), marking the start of the cosmic “dark ages.” During this period, neutral hydrogen filled the Universe, while baryons began assembling into dark matter halos, forming the first protogalaxies.
The ignition of nuclear fusion in the first stars brought the Universe into its luminous era, releasing UV radiation that ionized the intergalactic medium (IGM) and enriched the surrounding gas with heavy elements. These early massive stars likely collapsed into black holes, seeding the growth of the first supermassive black holes (SMBHs) and quasars. This transformative period, known as the Epoch of Reionization (EoR, z ~ 10 to z ~ 6), saw galaxies driving the reionization of the IGM, shaping the Universe as we observe it today.
Pushing the redshift frontier to discover and characterize the most distant quasars and galaxies is essential to test this evolutionary picture. Thanks to advances in selection techniques and wide-field surveys, hundreds of galaxies and quasars have now been identified at z > 6, when the Universe was less than 1 billion years old. These galaxies were already actively forming stars and assembling significant stellar mass, while luminous quasars at z ~ 7 reveal SMBHs with masses exceeding 10⁹ solar masses — a remarkable challenge for our understanding of early black hole growth.
Credits: NAOJ
The Birth of the Giants
High-redshift quasars (z > 6) are among the brightest objects in the Universe and are believed to be the progenitors of today’s massive elliptical galaxies. Their extraordinary luminosity stems from rapid gas accretion onto central SMBHs, which outshines the starlight from their host galaxies. This rapid growth is accompanied by vigorous star formation, fueled by vast gas reservoirs, but also regulated by AGN feedback — powerful outflows that expel gas, suppressing further star formation and influencing the host's final mass and structure.
This interconnected growth drives the black hole-galaxy co-evolution, setting the stage for the scaling relations between SMBHs and host galaxies observed in the local Universe. Quasar host galaxies at z > 6 are thus prime laboratories for studying the ISM under extreme conditions, providing insights into the balance between star formation and black hole accretion. Additionally, quasars serve as cosmic beacons, illuminating the IGM at the end of the EoR and revealing the properties of the surrounding gas. Simulations predict that such early quasars reside in densest regions of the cosmic web — marking the locations of the first galaxy overdensities and protoclusters.
Artist's concept of a galaxy with a luminous quasar at its center. A quasar is a very bright, distant and active supermassive black hole. Among the brightest objects in the Universe, a quasar’s light outshines that of all the stars in its host galaxy combined. Quasars feed on infalling matter and unleash torrents of winds and radiation, shaping the galaxies in which they reside.
Credits: NASA, ESA and J. Olmsted (STScI)
My research
My research has played a pivotal role in advancing this field. I contributed to the discovery of numerous quasars at z > 5, helping expand our census of early SMBHs and their host galaxies. By leading (sub-)mm observational campaigns with ALMA (Atacama Large sub-Millemeter Array) and NOEMA (Northern Extended Millimeter Array), I have explored the physical conditions of the ISM in these extreme environments. Using key tracers like [CII] 158μm and CO rotational lines, I systematically mapped the cold gas kinematics of quasar host galaxies down to the earliest cosmic epochs.
Through multi-line spectroscopy, I developed diagnostic tools to measure gas density, temperature, and dissect the ISM excitation mechanisms — essential to disentangle star formation from AGN-driven heating. My work provided some of the first quantitative constraints on the ISM properties of quasar hosts at cosmic dawn, offering new insights into the complex interplay between SMBH growth, star formation, and galaxy evolution in the early Universe.
With the most advanced facilities now available and the next generation of telescopes, including JWST and AtLAST, I aim to extend these investigations, investigating the galaxy-CGM connections, and the large-scale environment around high-redshift quasars — ultimately contributing to a more complete picture of early galaxy assembly and black hole formation.
Page updated
Google Sites
Report abuse