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1. 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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2. A Giant Shell of Ionized Gas Discovered near M82 with the Dragonfly Spectral Line Mapper Pathfinder

   https://doi.org/10.3847/1538-4357/ac50b6  

   Lokhorst, Deborah; Abraham, Roberto; Pasha, Imad; van Dokkum, Pieter; Chen, Seery; Miller, Tim; Danieli, Shany; Greco, Johnny; Zhang, Jielai; Merritt, Allison; et al (March 2022, The Astrophysical Journal)

   Abstract We present the discovery of a giant cloud of ionized gas in the field of the starbursting galaxy M82. Emission from the cloud is seen in H α and [N ii ] λ 6583 in data obtained though a small pathfinder instrument used to test the key ideas that will be implemented in the Dragonfly Spectral Line Mapper, an upcoming ultranarrow-bandpass imaging version of the Dragonfly Telephoto Array. The discovered cloud has a shell-like morphology with a linear extent of 0.°8 and is positioned 0.°6 northwest of M82. At the heliocentric distance of the M81 group, the cloud’s longest angular extent corresponds to 55 kpc and its projected distance from the nucleus of M82 is 40 kpc. The cloud has an average H α surface brightness of 2 × 10 −18 erg cm − 2 s − 1 arcsec − 2 . The [N ii ] λ 6583/H α line ratio varies from [N ii ]/H α ∼ 0.2 to [N ii ]/H α ∼ 1.0 across the cloud, with higher values found in its eastern end. Follow-up spectra obtained with Keck LRIS confirm the existence of the cloud and yield line ratios of [N ii ] λ 6583/H α = 0.340 ± 0.003 and [S ii ] λλ 6716, 6731/H α = 0.64 ± 0.03 in the cloud. This giant cloud of material could be lifted from M82 by tidal interactions or by its powerful starburst. Alternatively, it may be gas infalling from the cosmic web, potentially precipitated by the superwinds of M82. Deeper data are needed to test these ideas further. The upcoming Dragonfly Spectral Line Mapper will have 120 lenses, 40× more than in the pathfinder instrument used to obtain the data presented here. 

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3. The lifecycle of molecular clouds in nearby star-forming disc galaxies

   https://doi.org/10.1093/mnras/stz3525  

   Chevance, Mélanie; Kruijssen, J M; Hygate, Alexander P; Schruba, Andreas; Longmore, Steven N; Groves, Brent; Henshaw, Jonathan D; Herrera, Cinthya N; Hughes, Annie; Jeffreson, Sarah M; et al (April 2020, Monthly Notices of the Royal Astronomical Society)

   ABSTRACT It remains a major challenge to derive a theory of cloud-scale ($$\lesssim100$$ pc) star formation and feedback, describing how galaxies convert gas into stars as a function of the galactic environment. Progress has been hampered by a lack of robust empirical constraints on the giant molecular cloud (GMC) lifecycle. We address this problem by systematically applying a new statistical method for measuring the evolutionary timeline of the GMC lifecycle, star formation, and feedback to a sample of nine nearby disc galaxies, observed as part of the PHANGS-ALMA survey. We measure the spatially resolved (∼100 pc) CO-to-H α flux ratio and find a universal de-correlation between molecular gas and young stars on GMC scales, allowing us to quantify the underlying evolutionary timeline. GMC lifetimes are short, typically $$10\!-\!30\,{\rm Myr}$$, and exhibit environmental variation, between and within galaxies. At kpc-scale molecular gas surface densities $$\Sigma _{\rm H_2}\ge 8\,\rm {M_\odot}\,{{\rm pc}}^{-2}$$, the GMC lifetime correlates with time-scales for galactic dynamical processes, whereas at $$\Sigma _{\rm H_2}\le 8\,\rm {M_\odot}\,{{\rm pc}}^{-2}$$ GMCs decouple from galactic dynamics and live for an internal dynamical time-scale. After a long inert phase without massive star formation traced by H α (75–90 per cent of the cloud lifetime), GMCs disperse within just $$1\!-\!5\,{\rm Myr}$$ once massive stars emerge. The dispersal is most likely due to early stellar feedback, causing GMCs to achieve integrated star formation efficiencies of 4–10 per cent. These results show that galactic star formation is governed by cloud-scale, environmentally dependent, dynamical processes driving rapid evolutionary cycling. GMCs and H ii regions are the fundamental units undergoing these lifecycles, with mean separations of $$100\!-\!300\,{{\rm pc}}$$ in star-forming discs. Future work should characterize the multiscale physics and mass flows driving these lifecycles. 

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4. Dissecting the Local Environment of FRB 190608 in the Spiral Arm of its Host Galaxy

   https://doi.org/10.3847/1538-4357/ac2818  

   Chittidi, Jay S.; Simha, Sunil; Mannings, Alexandra; Prochaska, J. Xavier; Ryder, Stuart D.; Rafelski, Marc; Neeleman, Marcel; Macquart, Jean-Pierre; Tejos, Nicolas; Jorgenson, Regina A.; et al (November 2021, The Astrophysical Journal)

   Abstract We present a high-resolution analysis of the host galaxy of fast radio burst (FRB) 190608, an SB(r)c galaxy at z = 0.11778 (hereafter HG 190608), to dissect its local environment and its contributions to the FRB properties. Our Hubble Space Telescope Wide Field Camera 3 ultraviolet and visible light image reveals that the subarcsecond localization of FRB 190608 is coincident with a knot of star formation (Σ SFR = 1.5 × 10 −2 M ⊙ yr −1 kpc −2 ) in the northwest spiral arm of HG 190608. Using H β emission present in our Keck Cosmic Web Imager integral field spectrum of the galaxy with a surface brightness of μ H β = ( 3.36 ± 0.21 ) × 10 − 17 erg s − 1 cm − 2 arcsec − 2 , we infer an extinction-corrected H α surface brightness and compute a dispersion measure (DM) from the interstellar medium of HG 190608 of DM Host,ISM = 94 ± 38 pc cm −3 . The galaxy rotates with a circular velocity v circ = 141 ± 8 km s −1 at an inclination i gas = 37° ± 3°, giving a dynamical mass M halo dyn ≈ 10 11.96 ± 0.08 M ⊙ . This implies a halo contribution to the DM of DM Host,Halo = 55 ± 25 pc cm −3 subject to assumptions on the density profile and fraction of baryons retained. From the galaxy rotation curve, we infer a bar-induced pattern speed of Ω p = 34 ± 6 km s −1 kpc −1 using linear resonance theory. We then calculate the maximum time since star formation for a progenitor using the furthest distance to the arm’s leading edge within the localization, and find t enc = 21 − 6 + 25 Myr. Unlike previous high-resolution studies of FRB environments, we find no evidence of disturbed morphology, emission, or kinematics for FRB 190608. 

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5. Timescale of Stellar Feedback-driven Turbulence in the ISM: A Deep Dive into UGC 4305

   https://doi.org/10.3847/1538-3881/aced8e  

   Hunter, Laura Congreve; van Zee, Liese; McQuinn, Kristen B.; Cohen, Roger E.; Markham, Madison; Dolphin, Andrew E. (September 2023, The Astronomical Journal)

   Abstract Understanding the interplay of stellar feedback and turbulence in the interstellar medium (ISM) is essential to modeling the evolution of galaxies. To determine the timescales over which stellar feedback drives turbulence in the ISM, we performed a spatially resolved, multiwavelength study of the nearby star-forming dwarf galaxy UGC 4305. As indicators of turbulence on local scales (400 pc), we utilized ionized gas velocity dispersion derived from IFU H α observations and atomic gas velocity dispersion and energy surface densities derived from H i synthesis observations with the Very Large Array. These indicators of turbulence were tested against star formation histories over the past 560 Myr derived from color–magnitude diagrams using Spearman’s rank correlation coefficient. The strongest correlation identified at the 400 pc scale is between measures of H i turbulence and star formation 70–140 Myr ago. We repeated our analysis of UGC 4305's current turbulence and past star formation activity on multiple physical scales (∼560 and 800 pc) to determine whether there are indications of changes in the correlation timescale with changes to the physical scale. No notable correlations were found at larger physical scales, emphasizing the importance of analyzing star formation-driven turbulence as a local phenomenon. 

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