Bianca Iulia Ciocan

PhD Student

Field of Interests

Bianca Iulia Ciocan

My fundamental research intrest is the formation and evolution of galaxies. Special emphsis is placed on analysing galaxies located in high-density environments, in order to understand the interplay between galaxy evolution and the environment, as it is well established that the environment in which a galaxy resides strongly impacts its evolutionary path. 

To reveal the importance of various mechanisms driving galaxy evolution in the most massive structures of the universe, galaxy clusters, we quantitatively investigate the spatially resolved 2D distributions of star formation rates, gas metallicities, ionising mechanisms, stellar and gas morphologies, as well as the gas kinematics of a representative sample of star-forming cluster members. We probe the cosmic epoch after which cluster assembly peaks, i.e. intermediate redshifts of z0.35 (∼ 4 billion years lookback time) when the inner region of the large-scale structures achieves virialisation. The galaxies we study span a wide range of stellar masses, from the dwarf regime (log(M/M9.5) up to the brightest cluster galaxies (log(M/M∼ 11), allowing us to probe the impact of the environment as a function of the mass of the systems. For this, we employ high-resolution 2D and, more importantly, 3D spectroscopic observations from world- class facilities such as ESO/VLT, using instruments such as VIMOS and MUSE. The 3D spectroscopic data allow us to perform a pixel-by-pixel analysis of the physical properties of the warm ionised gas confined in the interstellar medium of the galaxies under scrutiny. The spectroscopic observations are supplemented by high-resolution optical and infrared photometry from both ground-based telescopes such as SUBARU and VLT/HAWK-I and space-based observatories such as HST. We study different scaling relations including the mass-star formation rate, the mas-gas-phase metallicity, the fundamental metallicity and the Tully-Fisher relation for galaxies in high-density environments, compared to those of isolated field galaxies. This allows us to search for signatures of cluster-specific mechanisms using for example enhanced gas-phase metallicities and/or disturbed gas velocity fields and gas morphologies as tracers.

From the sample of low mass cluster galaxies analysed in Ciocan et al. (2022), we find that 65% have disturbed gas velocity fields and morphologies and that they depart from the different scaling relations, hinting at preprocessing before infall into the cluster and ram pressure stripping as the mechanisms driving these offsets. The low and intermediate-mass systems studied in Ciocan et al. (2022) and (2020) show more enhanced metallicities than predicted by the fundamental metallicity relation, hinting at the cutoff of pristine gas inflow when the galaxies are accreted into the cluster together with ram pressure stripping as the environmental mechanisms responsible for these discrepancies. In Ciocan et al. (2021), we find that the brightest cluster galaxy is affected by ’chaotic cold accretion’, meaning that the system is fuelled by gas, which has condensed from the intra-cluster medium, owing to the feedback from the supermassive black hole.