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In the recent years my research has been focused on the investigation of distant brightest cluster galaxies (BCGs) and cluster core galaxies. The main goal is to unveil the co-evolution of these galaxies with their super massive engines and the surrounding intra-cluster medium (ICM), which may fuel and regulate the star formation via accretion of cold gas, as often observed so far only in local cool-core clusters. Since 2016 I led several studies based on IRAM observations (IRAM 30m and NOEMA) with the aim to investigate the molecular gas properties of distant cluster galaxies, as they evolve from the outskirts to the cluster cores.
Please visit the links and the description below for more details about the results of this ongoing campaign!
Publications:
Castignani, Combes et al. 2018, A&A "Molecular gas in two companion cluster galaxies at z = 1.2"
Castignani, Combes, et al. 2019, A&A "Molecular gas in radio galaxies in dense megaparsec-scale environments at z = 0.4-2.6"
Castignani, Combes et al. 2020, A&A "Molecular gas in distant brightest cluster galaxies"
Castignani, Combes & Salomé et al. 2020, A&AL "Environmental processing in cluster core galaxies at z = 1.7"
Castignani, Pandey-Pommier et al. 2020, A&A "Molecular gas in CLASH brightest cluster galaxies at z∼0.2−0.9"
Castignani, Jablonka et al. 2020, A&A "Molecular gas and star formation activity in LIRGs in intermediate redshift clusters"
Castignani, Meyer et al. 2022, A&AL "NOEMA observations support a recoiling black hole in 3C 186"
Castignani, Radovich et al. 2022, A&A "Star-forming and gas-rich brightest cluster galaxies at z ∼ 0.4 in the Kilo-Degree Survey"
Castignani, Radovich et al. 2023, A&A "Star-forming brightest cluster galaxies at z ∼ 0.4 in KiDS. Further studies of cold gas and stellar properties"
Castignani, Combes et al. 2025, A&A "Molecular gas in cool-core brightest cluster galaxies at z ≃ 0.4"
By using forefront mm-wavelength observational facilities I investigated the molecular gas and star formation properties of the rare sub-population of distant star forming Brightest Cluster Galaxies (BCGs), over a broad range in redshift (z~0.2-2.6) and cosmic time (~9 Gyr).
Distant BCGs and radio galaxies in dense Mpc-scale environments
Distant BCGs and radio galaxies in dense Mpc-scale environments
Castignani, Combes, et al. 2019, A&A
Castignani, Combes et al. 2020, A&A
Castignani, Combes & Salomé et al. 2020, A&A Letters
Castignani, Pandey-Pommier et al. 2020, A&A
Castignani, Meyer et al. 2022, A&A Letters
Castignani, Radovich et al. 2022, A&A
Cluster LIRGs at z~0.2-0.5 in the HLS and LoCuSS surveys
Cluster LIRGs at z~0.2-0.5 in the HLS and LoCuSS surveys
Molecular gas and star formation properties of the largest samples of cluster Luminous Infrared Galaxies (LIRGs) at intermediate redshifts.
In Castignani, Jablonka et al. 2020 I report the study based on several PdBI and NOEMA observations of cluster galaxies within the Herschel Lensing Survey and the Local Cluster Substructure Survey (LoCuSS), trying to unveil the impact of the cluster environment on processing molecular gas in the rare population of LIRGs in clusters. I studied the largest sample of cluster LIRGs (∼ 20) in CO, from the outskirts down to the cores of intermediate-z clusters. Surprisingly, a deficit of LIRGs with normal (main sequence) depletion times is found, towards the cluster cores. This is the first direct observational evidence that environmental effects (e.g., gas-compression) are effective in exhausting rapidly the molecular gas reservoirs of cluster LIRGs. Forthcoming NOEMA observations (n. W19BZ) will complete the sample of intermediate-z cluster LIRGs in CO, thus enabling to unveil the mechanisms responsible for processing the gas in this rare sub-population of cluster galaxies
Depletion timescale, τdep = M (H2)/SFR, normalized to the main sequence as a function of the normalized projected cluster centric radius r/r200 . Surprisingly, short depletion time scales are found for cluster core LIRGs (Castignani, Jablonka et al. 2020)
Two companion cluster galaxies at z=1.2
Two companion cluster galaxies at z=1.2
Castignani, Combes et al. 2018, A&A, 617, 103
I reported the first detection in CO of distant cluster galaxies at 1 < z < 1.4 with no clear sign of AGN. This is a still overlooked epoch, where nevertheless morphological and star formation properties (e.g., red sequence) of cluster galaxies are being shaped.
Low depletion time τdep ~ 0.4 Gyr and low MH2/Mstar ~ 0.2 are found, suggesting that the cluster environment might have played a role in preventing the refueling of gas via environmental mechanisms such as galaxy harassment, strangulation, ram-pressure, or tidal stripping.
ISCS J1426.5+3339 cluster at z=1.2; target pair of cluster galaxies, unresolved by NOEMA, with overlaid CO(2-1) contours; CO(2-1) spectrum (Castignani et al. 2018)
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