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

   https://doi.org/10.1051/0004-6361/202040141  

   Castignani, G.; Combes, F.; Jablonka, P.; Finn, R. A.; Rudnick, G.; Vulcani, B.; Desai, V.; Zaritsky, D.; Salomé, P. (January 2022, Astronomy & Astrophysics)

   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 H 2 -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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2. Virgo Filaments. V. Disrupting the Baryon Cycle in the NGC 5364 Galaxy Group

   https://doi.org/10.3847/1538-4357/adc566  

   Finn, Rose A; Rudnick, Gregory; Jablonka, Pascale; Ramatsoku, Mpati; Nagaraj, Gautam; Vulcani, Benedetta; Koopmann, Rebecca A; Fossati, Matteo; Agostino, James; Bahé, Yannick; et al (May 2025, The Astrophysical Journal)

   Abstract The Virgo Filament Survey (VFS) is a comprehensive study of galaxies that reside in the extended filamentary structures surrounding the Virgo Cluster, out to 12 virial radii. The primary goal is to characterize all of the dominant baryonic components within galaxies and to understand whether and how they are affected by the filament environment. A key constituent of VFS is a narrowband Hαimaging survey of over 600 galaxies, VFS-Hα. The Hαimages reveal detailed, resolved maps of the ionized gas and massive star formation. This imaging is particularly powerful as a probe of environmentally induced quenching because different physical processes affect the spatial distribution of star formation in different ways. In this paper, we present the first results from the VFS-Hαfor the NGC 5364 group, a low-mass ( ${\log }_{10}(M_{\mathrm{dyn}}/M_{\odot })<13$) system located at the western edge of the Virgo III filament. We combine Hαimaging with resolved Hiobservations from MeerKAT for eight group members. These galaxies exhibit peculiar morphologies, including strong distortions in the stars and the gas, truncated Hiand Hαdisks, H itails, extraplanar Hαemission, and off-center Hαemission. These signatures are suggestive of environmental processing such as tidal interactions, ram pressure stripping, and starvation. We quantify the role of ram pressure stripping expected in this group, and find that it can explain the cases of Hitails and truncated Hαfor all but one of the disk-dominated galaxies. Our observations indicate that multiple physical mechanisms are disrupting the baryon cycle in these group galaxies. 

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3. Dark No More: The Low-luminosity Stellar Counterpart of a Dark Cloud in the Virgo Cluster*

   https://doi.org/10.3847/2041-8213/ad3ef5  

   Jones, Michael_G; Janowiecki, Steven; Dey, Swapnaneel; Sand, David_J; Bennet, Paul; Crnojević, Denija; Fielder, Catherine_E; Karunakaran, Ananthan; Kent, Brian_R; Mazziotti, Nicolas; et al (April 2024, The Astrophysical Journal Letters)

   Abstract We have discovered the stellar counterpart to the ALFALFA Virgo 7 cloud complex, which has been thought to be optically dark and nearly star-free since its discovery in 2007. This ∼190 kpc long chain of enormous atomic gas clouds (M_Hi∼ 10⁹M_⊙) is embedded in the hot intracluster medium of the Virgo galaxy cluster but is isolated from any galaxy. Its faint, blue stellar counterpart, BC6, was identified in a visual search of archival optical and UV imaging. Follow-up observations with the Green Bank Telescope, Hobby–Eberly Telescope, and Hubble Space Telescope demonstrate that this faint counterpart is at the same velocity as the atomic gas, actively forming stars, and metal-rich (12 + (O/H) = 8.58 ± 0.25). We estimate its stellar mass to be only $\log \left(M_{*}/M_{\odot }\right)\sim 4.4$, making it one of the most gas-rich stellar systems known. Aside from its extraordinary gas content, the properties of BC6 are entirely consistent with those of a recently identified class of young, low-mass, isolated, and star-forming clouds in Virgo that appear to have formed via extreme ram pressure stripping events. We expand the existing discussion of the origin of this structure and suggest NGC 4522 as a likely candidate; however, the current evidence is not fully consistent with any of our proposed progenitor galaxies. We anticipate that other “dark” gas clouds in Virgo may have similarly faint, star-forming counterparts. We aim to identify these through the help of a citizen science search of the entire cluster. 

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4. A Gradual Decline of Star Formation since Cluster Infall: New Kinematic Insights into Environmental Quenching at 0.3 < z < 1.1

   https://doi.org/10.3847/1538-4357/acecff  

   Kim, Keunho J; Bayliss, Matthew B; Noble, Allison G; Khullar, Gourav; Cronk, Ethan; Roberson, Joshua; Ansarinejad, Behzad; Bleem, Lindsey E; Floyd, Benjamin; Grandis, Sebastian; et al (September 2023, The Astrophysical Journal)

   Abstract The environments where galaxies reside crucially shape their star formation histories. We investigate a large sample of 1626 cluster galaxies located within 105 galaxy clusters spanning a large range in redshift (0.26 <z< 1.13). The galaxy clusters are massive (M₅₀₀≳ 2 × 10¹⁴M_⊙) and uniformly selected from the SPT and ACT Sunyaev–Zel’dovich surveys. With spectra in hand for thousands of cluster members, we use the galaxies’ position in projected phase space as a proxy for their infall times, which provides a more robust measurement of environment than quantities such as projected clustercentric radius. We find clear evidence for a gradual age increase of the galaxy’s mean stellar populations (∼0.71 ± 0.4 Gyr based on a 4000 Å break, D_n4000) with the time spent in the cluster environment. This environmental quenching effect is found regardless of galaxy luminosity (faint or bright) and redshift (low or high-z), although the exact stellar age of galaxies depends on both parameters at fixed environmental effects. Such a systematic increase of D_n4000 with infall proxy would suggest that galaxies that were accreted into hosts earlier were quenched earlier due to longer exposure to environmental effects such as ram pressure stripping and starvation. Compared to the typical dynamical timescales of 1–3 Gyr of cluster galaxies, the relatively small age increase (∼0.71 ± 0.4 Gyr) found in our sample galaxies seems to suggest that a slow environmental process such as starvation is the dominant quenching pathway. Our results provide new insights into environmental quenching effects spanning a large range in cosmic time (∼5.2 Gyr,z= 0.26–1.13) and demonstrate the power of using a kinematically derived infall time proxy. 

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5. DESI Massive Poststarburst Galaxies at z ∼ 1.2 Have Compact Structures and Dense Cores

   https://doi.org/10.3847/1538-4357/ad7c45  

   Zhang, Yunchong; Setton, David_J; Price, Sedona_H; Bezanson, Rachel; Khullar, Gourav; Newman, Jeffrey_A; Aguilar, Jessica_Nicole; Ahlen, Steven; Andrews, Brett_H; Brooks, David; et al (November 2024, The Astrophysical Journal)

   Abstract Poststarburst galaxies (PSBs) are young quiescent galaxies that have recently experienced a rapid decrease in star formation, allowing us to probe the fast-quenching period of galaxy evolution. In this work, we obtained Hubble Space Telescope (HST)/WFC3 F110W imaging to measure the sizes of 171 massive ( $\log (M_{*}/M_{\odot })\sim 11)$spectroscopically identified PSBs at 1 <z1.3 selected from the DESI Survey Validation luminous red galaxy sample. This statistical sample constitutes an order of magnitude increase from the ∼20 PSBs with space-based imaging and deep spectroscopy. We perform structural fitting of the target galaxies withpysersicand compare them to quiescent and star-forming galaxies in the 3D-HST survey. We find that these PSBs are more compact than the general population of quiescent galaxies, lying systematically ∼0.1 dex below the established size–mass relation. However, their central surface mass densities are similar to those of their quiescent counterparts ( $\log \left({\mathrm{\Sigma }}_{1\mathrm{kpc}}/\right(M_{\odot }{\mathrm{kpc}}^{-2}\left)\right)\sim 10.1$). These findings are easily reconciled by later ex situ growth via minor mergers or a slight progenitor bias. These PSBs are round in projection (b/a_median∼ 0.8), suggesting that they are primarily spheroids, not disks, in 3D. We find no correlation between the time since quenching and light-weighted PSB sizes or central densities. This disfavors apparent structural growth due to the fading of centralized starbursts in this galaxy population. Instead, we posit that the fast quenching of massive galaxies at this epoch occurs preferentially in galaxies with preexisting compact structures. 

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