Virgo filaments

Abstract

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.

SEEDisCS II. Molecular gas in galaxy clusters and their large scale structure: low gas fraction galaxies, the case of CL1301.7$-$1139

“…Most existing datasets have focused on field galaxies, at the exception of Geach et al (2009Geach et al ( , 2011, Jablonka et al (2013), Cybulski et al (2016), Rudnick et al (2017a), Hayashi et al (2018), Noble et al (2017Noble et al ( , 2019 and Castignani et al (2020). The present analysis provides the second largest sample at a fixed given redshift, the other one being our analysis of galaxies related to the CL1411.1−1148 environment.…”

“…However, similar systems without evidence of disks in Figure 6 provides an overview of the galaxy specific star formation rates (sSFR) as a function of redshift from ∼ 0.02 to ∼ 2 for galaxies with existing CO line fluxes. The list of our comparison samples is identical to Paper I where their exact composition, redshift range, selection and CO line transitions, are detailed (Gao & Solomon 2004;García-Burillo et al 2012;Saintonge et al 2017;Baumgartner et al 2013;Lamperti et al 2020;Abdo et al 2010;Bauermeister et al 2013a,b;Morokuma-Matsui et al 2015;Cybulski et al 2016;Castignani et al 2020;Jablonka et al 2013;Geach et al 2009Geach et al , 2011Tacconi et al 2010Tacconi et al , 2013Tacconi et al , 2018Freundlich et al 2019;Spilker et al 2018;Hayashi et al 2018;Daddi et al 2010;Noble et al 2017Noble et al , 2019Rudnick et al 2017a). The galaxy stellar masses of these comparison samples were originally derived by SED fitting, assuming either a 'Chabrier' or a 'Kroupa' IMF (Kroupa 2001;Chabrier 2003).…”

“…As a matter of fact, Bauermeister et al (2013a,b) explicitly selected their targets with sSFR between 1 and 4 times that of MS galaxies. Similarly, prior detection at 24µm (e.g., Daddi et al 2004;Cybulski et al 2016), or some of the Herschel bands (e.g., Daddi et al 2010;Castignani et al 2020) does play a role in this bias toward actively star forming systems, unless it is purposely controlled to include systems below the main sequence, as it was done by the PHIBSS1/2 field surveys at 0.5 < z < 0.8 (e.g., Tacconi et al 2010Tacconi et al , 2013Freundlich et al 2019). Very noticeably, our CL1301.7−1139 and CL1411.1−1148 samples, without any prior on previous FIR detection and in the vicinity of high density environments, are devoid of galaxies above the main sequence.…”

“…The cold molecular gas masses are derived using the same value of α CO , α MW = 4.36 M (K km s −1 pc 2 ) −1 , for most samples (Daddi et al 2010;Geach et al 2011;Tacconi et al 2010Tacconi et al , 2013Bauermeister et al 2013a,b;Cybulski et al 2016;Rudnick et al 2017a;Hayashi et al 2018;Noble et al 2017Noble et al , 2019. The other samples have linked the value of their CO-to-H 2 conversion factor either to metallicity (Freundlich et al 2019), or to the position of the galaxy with respect to the MS (Castignani et al 2020). Considering α MW for these two samples slightly redistributes the position of the galaxies within the distributions, but does not modify their global shapes and mean positions.…”

SEEDisCS

“…So far studies of the cold molecular gas content of galaxies at intermediate redshifts have mostly focussed on distinct environments, isolating the field (Gao & Solomon 2004;Abdo et al 2010;Daddi et al 2010;Tacconi et al 2010Tacconi et al , 2013García-Burillo et al 2012;Baumgartner et al 2013;Bauermeister et al 2013b,a;Morokuma-Matsui et al 2015;Saintonge et al 2017;Hayashi et al 2018;Spilker et al 2018;Freundlich et al 2019;Lamperti et al 2020), from groups (Boselli et al 1996;Martinez-Badenes et al 2012;Lisenfeld et al 2017) and clusters (Geach et al 2009(Geach et al , 2011Jablonka et al 2013;Rudnick et al 2017a;Noble et al 2017Noble et al , 2019Castignani et al 2020). Very few of these cluster studies purposely target galaxies beyond the cluster virial radius (e.g., Morokuma-Matsui et al 2021;Castignani et al 2021).…”