Hi, I am Marika!

About me

My life has always been driven by a constant curiosity about how everything fits together and what we can learn from the world around us. This curiosity led me to physics, and when I first picked up The Theory of Everything by Stephen Hawking in high school, I became captivated by the mysteries of the universe. Eager to dive deeper into the wonders of the cosmos, I decided to become an astronomer.

I did both my undergraduate course and my masters at La Sapienza University of Rome. After that, I moved to Florence to do my PhD at INAF - Astrophysical Observatory of Arcetri (OAA). Currently, I am a postdoctoral researcher at INAF - OAA.

My research primarily focuses on the study of the formation and evolution of galaxy clusters and protoclusters across cosmic epochs. In particular, I investigate the interplay between the different components of these structures and the processes that shape the large-scale structure of the Universe. If you want to know more about my academic career, you can go to the CV and Research tabs.

Research

My research explores the formation and evolution of galaxy clusters and protoclusters, investigating the interplay between their components and the physical processes that influence their growth and impact on cosmic structure

Exploring the feeding and feedback mechanisms in the Spiderweb Protocluster

Protoclusters are crucial for understanding the evolution of the Universe's large-scale structure and the processes driving galaxy evolution, such as star formation, mergers, gas cooling, and feedback mechanisms. Multiwavelength studies, particularly those involving X-ray and Sunyaev-Zeldovich (SZ) data, are essential for investigating these structures. The Spiderweb protocluster at z=2.16 offers a unique window into the early stages of galaxy cluster formation. At its center, the Spiderweb Galaxy, a powerful radio galaxy embedded in a giant Lyα halo, is surrounded by a >2 Mpc-sized overdensity of star-forming galaxies, dusty starbursts, red galaxies, and active galactic nuclei (AGNs). Indeed, this protocluster exhibits one of the highest AGN fractions observed to date (Tozzi et al., 2022a).
Radio studies reveal 200 kpc-long jets interacting with surrounding gas (Carilli et al., 2022a), while X-ray and submillimeter observations detect diffuse hot gas with temperatures of several keV, marking the emergence of the intracluster medium (ICM) (Tozzi et al., 2022b, Di Mascolo et al., 2024a). Combining deep Chandra X-ray data and ALMA SZ observations has allowed for the first derivation of the ICM's thermodynamical properties in a halo at z>2 (Lepore et al., 2024). This analysis uncovered a strong cool core, comparable to local clusters, with a baryon cooling time of ∼ 0.1 Gyr and evidence of a mass deposition rate of up to ∼ 1000 M_☉/yr. This cooling flow likely fuels both the central supermassive black hole (SMBH) and the high star formation observed in the Spiderweb Galaxy. Mild asymmetries in the X-ray surface brightness suggest cavities in the proto-ICM, potentially carved by radio jets, with feedback power exceeding ∼ 10⁴³ erg/s (Lepore et al., 2024). These findings indicate a highly dynamic baryon cycle, where rapid cooling and AGN feedback work together to shape the Spiderweb protocluster's evolution, transitioning it into a self-regulated phase within less than 1 Gyr.

X-ray and optical composite image of the Spiderweb Galaxy Field. The X-ray emission is shown in purple. The left box represents a zoom-in on the central radio galaxy. Credit: NASA/Chandra Press Release.

• Spiderweb webpage

Galaxy assembly and nuclear activity in the high-redshift cluster XDCP J0044.0-2033

XDCP J0044.0−2033 is the most massive galaxy cluster currently known at z > 1.5. The core of this cluster is characterized by a high density of galaxies undergoing mergers and exhibiting strong nuclear activity, making it one of the prime candidates for studying galaxy evolution at early cosmic epochs.
Lepore et al., 2022 analyzed a high density region (24 kpc × 24 kpc) located 157 kpc from the cluster core, using both photometric and spectroscopic observations in the infrared (HST and KMOS data) and X-ray band (Chandra data).
The analysis reveals that the region contains at least nine distinct sources, six of which are confirmed as cluster members within a narrow redshift range of 1.5728 Among the sources, one is identified as a Type-1 AGN due to the broad Hα emission line detected in its spectrum. The AGN is associated with a point-like X-ray source exhibiting moderate intrinsic absorption (N_H ∼ 10²² cm⁻²), and a central black hole mass of M_BH ∼ 10⁷ M_☉, accreting at an Eddington ratio of approximately 0.2.
The findings suggest that the region is a likely site for the formation of a secondary brightest cluster galaxy (BCG). This conclusion, in conjunction with an in-depth examination of the X-ray morphology, supports a merging scenario for the entire cluster. The cluster contains two massive halos, each hosting rapidly evolving BCGs that are on the verge of merging. Additionally, the AGN activity observed in one of the cluster members is consistent with being triggered by a gas-rich mergers, processes that may play a key role in the formation of the red sequence of elliptical galaxies observed at the centers of local galaxy clusters.

Adapted from Travascio et al., 2020: HST RGB (F105W+F104W+F160W) image of XDCP0044 with overlaid the soft ([0.5-2] keV) bands X-ray contours.

Cooling flows and turbulence in the cool-core cluster Abell 2667

In galaxy cluster evolution, one key question is how much gas cools down to the lowest detectable temperatures of 0.3–0.5 keV and contributes to cooling flows, which are thought to play a role in the formation of BCGs. To explore this, we studied the cool-core cluster Abell 2667 (z = 0.23), which features a BCG with strong ongoing activity and peculiar gas components. This BCG shows prominent activity across optical, radio, and X-ray bands, with highly absorbed X-ray nuclear emission and diffuse ICM emission comparable to the Phoenix cluster, the only convincing CF candidate known to date. However, the nuclear emission and star formation rate in Abell 2667 are much lower than those of Phoenix, making it an interesting case for studying cooling and heating processes in clusters.
Lepore et al., 2025 found that gas cooling rates in the temperature ranges of 0.5–1 keV and 1–2 keV are limited to upper bounds of approximately 40 M_☉/yr and 50–60 M_☉/yr, respectively, with no clear signatures of strong cooling flows. We also detected significantly higher turbulence in the ICM of Abell 2667, with an upper limit of about 320 km/s, suggesting mechanisms that enhance the dynamics of the cluster. While no recent feedback events were identified, the observed turbulence indicates active heating processes that may prevent cooling flows and contribute to future cycles of ICM dynamics. Overall, Abell 2667 shares many traits with other low-redshift cool-core clusters, with limited cooling flows, but shows evidence of turbulence-driven heating, which may regulate the evolution of the cluster and prevent gas cooling.

HST composite image of Abell 2667. Credit: NASA, ESA, and J. Kneib (Laboratorie Astrophysique de Marseille).

• Read papers

Curriculum Vitae

Currently, I am a Postdoctoral Researcher at INAF-OAA. If you want to know more about my work, you can access my CV below.

Contact me

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