Molecular gas in distant brightest cluster galaxies

Castignani, G.; Combes, F.; Salomé, P.; Freundlich, Jonathan

doi:10.1051/0004-6361/201936148

Cited by 13 publications

(30 citation statements)

References 195 publications

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“…The latter are instead a population of more star forming ETGs, with low H 2 gas content and thus relatively low depletion time (upper limits) of τ dep 10 8−9 yr. They correspond to ETGs still forming stars, but in a rapid phase of quenching, similarly to their higher-z star forming analogs found in cluster cores (Castignani et al 2020). They are experiencing a rapid phase of quenching and will possibly turn, in less than 1 Gyr, into red and dead galaxies, that are commonly seen in cluster cores.…”

Section: S G Xmentioning

confidence: 70%

Virgo Filaments I: Processing of gas in cosmological filaments around the Virgo cluster

Castignani,

Combes,

Jablonka

et al. 2021

Preprint

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It is now well established that galaxies have different morphology, gas content and star formation rate in dense environments like galaxy clusters. The impact of environmental density extends to several virial radii, and galaxies appear to be pre-processed in filaments and groups, before falling into the cluster. Our goal is to quantify this pre-processing, in terms of gas content, and star formation rate, as a function of density in cosmic filaments. We have observed the two first CO transitions in 163 galaxies with the IRAM-30m telescope, and added 82 more measurements from the literature, for a sample of 245 galaxies in the filaments around Virgo. We gathered HI-21cm measurements from the literature, and observed 69 galaxies with the Nançay telescope, to complete our sample. We compare our filament galaxies with comparable samples from the Virgo cluster and with the isolated galaxies of the AMIGA sample. We find a clear progression from field galaxies to filament and cluster ones for decreasing star formation rate, increasing fraction of galaxies in the quenching phase, increasing proportion of early-type galaxies and decreasing gas content. Galaxies in the quenching phase, defined as having star formation rate below one third of the main sequence rate, are only between 0-20% in the isolated sample, according to local galaxy density, while they are 20-60% in the filaments and 30-80% in the Virgo cluster. Processes that lead to star formation quenching are already at play in filaments. They depend mostly on the local galaxy density, while the distance to filament spine is a secondary parameter. While the HI to stellar mass ratio decreases with local density by an order of magnitude in the filaments, and two orders of magnitude in the Virgo cluster with respect to the field, the decrease is much less for the H 2 to stellar mass ratio. As the environmental density increases, the gas depletion time decreases, since the gas content decreases faster than the star formation rate. This suggests that gas depletion significantly precedes star formation quenching.

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Section: S G Xmentioning

confidence: 70%

Virgo Filaments I: Processing of gas in cosmological filaments around the Virgo cluster

Castignani,

Combes,

Jablonka

et al. 2021

Preprint

Self Cite

View full text Add to dashboard Cite

show abstract

“…The latter are instead a population of more star forming ETGs, with low H 2 gas content and thus relatively low depletion time (upper limits) of τ dep 10 8−9 yr. These correspond to ETGs that are still forming stars, but are in a rapid phase of quenching, similarly to their higher-z star forming analogs found in cluster cores (Castignani et al 2020); they are experiencing a rapid phase of quenching and will possibly turn, in less than 1 Gyr, into red and dead galaxies, which are commonly seen in cluster cores. On the other hand, the observed population of filament and Virgo cluster galaxies with low M HI 10 8 M can be explained as galaxies having already experienced the removal of the HI envelope, likely via ram-pressure stripping in dense environments.…”

Section: C2 Sfr Versus Gas Massmentioning

confidence: 77%

Virgo filaments

Castignani

Combes

Jablonka

et al. 2021

A&A

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It is now well established that galaxies have different morphologies, gas contents, and star formation rates (SFR) in dense environments like galaxy clusters. The impact of environmental density extends to several virial radii, and galaxies appear to be pre-processed in filaments and groups before falling into the cluster. Our goal is to quantify this pre-processing in terms of gas content and SFR, as a function of density in cosmic filaments. We have observed the two first CO transitions in 163 galaxies with the IRAM-30 m telescope, and added 82 more measurements from the literature, thus forming a sample of 245 galaxies in the filaments around the Virgo cluster. We gathered HI-21cm measurements from the literature and observed 69 galaxies with the Nançay telescope to complete our sample. We compare our filament galaxies with comparable samples from the Virgo cluster and with the isolated galaxies of the AMIGA sample. We find a clear progression from field galaxies to filament and cluster galaxies for decreasing SFR, increasing fraction of galaxies in the quenching phase, an increasing proportion of early-type galaxies, and decreasing gas content. Galaxies in the quenching phase, defined as having a SFR below one-third of that of the main sequence (MS), are only between 0% and 20% in the isolated sample, according to local galaxy density, while they are 20%–60% in the filaments and 30%–80% in the Virgo cluster. Processes that lead to star formation quenching are already at play in filaments; they depend mostly on the local galaxy density, while the distance to the filament spine is a secondary parameter. While the HI-to-stellar-mass ratio decreases with local density by an order of magnitude in the filaments, and two orders of magnitude in the Virgo cluster with respect to the field, the decrease is much less for the H2-to-stellar-mass ratio. As the environmental density increases, the gas depletion time decreases, because the gas content decreases faster than the SFR. This suggests that gas depletion precedes star formation quenching.

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“…This work is part of a larger search done over a wide range of redshifts, z ∼ 0.4−2.6, to detect molecular gas in distant BCGs (Castignani et al 2019(Castignani et al , 2020a. The paper is structured as follows: in Sect.…”

Section: Introductionmentioning

confidence: 99%

Molecular gas in CLASH brightest cluster galaxies at z ∼ 0.2 – 0.9

Castignani

Pandey-Pommier

Hamer

et al. 2020

A&A

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Brightest cluster galaxies (BCGs) are excellent laboratories for the study of galaxy evolution in dense Mpc-scale environments. We used the IRAM-30 m to observe, in CO(1→0), CO(2→1), CO(3→2), or CO(4→3), 18 BCGs at z ∼ 0.2 − 0.9 drawn from the Cluster Lensing And Supernova survey with Hubble (CLASH) survey. Our sample includes RX1532, which is our primary target as it is among the BCGs with the highest star formation rate (SFR ≳100 M⊙ yr−1) in the CLASH sample. We unambiguously detected both CO(1→0) and CO(3→2) in RX1532, yielding a large reservoir of molecular gas, MH2 = (8.7 ± 1.1)×1010 M⊙, and a high level of excitation, r31 = 0.75 ± 0.12. A morphological analysis of the Hubble Space Telescope I-band image of RX1532 reveals the presence of clumpy substructures both within and outside the half-light radius re = (11.6 ± 0.3) kpc, similarly to those found independently both in ultraviolet and in Hα in previous works. We tentatively detected CO(1→0) or CO(2→1) in four other BCGs, with molecular gas reservoirs in the range of MH2 = 2 × 1010 − 11 M⊙. For the remaining 13 BCGs, we set robust upper limits of MH2/M⋆ ≲ 0.1, which are among the lowest molecular-gas-to-stellar-mass ratios found for distant ellipticals and BCGs. In comparison with distant cluster galaxies observed in CO, our study shows that RX1532 (MH2/M⋆ = 0.40 ± 0.05) belongs to the rare population of star-forming and gas-rich BCGs in the distant universe. By using the available X-ray based estimates of the central intra-cluster medium entropy, we show that the detection of large reservoirs of molecular gas MH2 ≳ 1010 M⊙ in distant BCGs is possible when the two conditions are met: (i) high SFR and (ii) low central entropy, which favors the condensation and the inflow of gas onto the BCGs themselves, similarly to what has been previously found for some local BCGs.

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Molecular gas in distant brightest cluster galaxies

Cited by 13 publications

References 195 publications

Virgo Filaments I: Processing of gas in cosmological filaments around the Virgo cluster

Virgo Filaments I: Processing of gas in cosmological filaments around the Virgo cluster

Virgo filaments

Molecular gas in CLASH brightest cluster galaxies at z ∼ 0.2 – 0.9

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