Astrophysics of Galaxies (astro-ph.GA)

Abstract: We investigate the impact of environment on the internal mass distribution of galaxies using the Middle Ages Galaxy Properties with Integral field spectroscopy (MAGPI) survey. We use 2D resolved stellar kinematics to construct Jeans dynamical models for galaxies at mean redshift $z \sim 0.3$, corresponding to a lookback time of $3-4$ Gyr. The internal mass distribution for each galaxy is parameterised by the combined mass density slope $\gamma$ (baryons $+$ dark matter), which is the logarithmic change of density with radius. We use a MAGPI sample of 28 galaxies from low-to-mid density environments and compare to density slopes derived from galaxies in the high density Frontier Fields clusters in the redshift range $0.29 <z < 0.55$, corresponding to a lookback time of $\sim 5$ Gyr. We find a median density slope of $\gamma = -2.22 \pm 0.05$ for the MAGPI sample, which is significantly steeper than the Frontier Fields median slope ($\gamma = -2.01 \pm 0.04$), implying the cluster galaxies are less centrally concentrated in their mass distribution than MAGPI galaxies. We also compare to the distribution of density slopes from galaxies in Atlas3D at $z \sim 0$, because the sample probes a similar environmental range as MAGPI. The Atlas3D median total slope is $\gamma = -2.25 \pm 0.02$, consistent with the MAGPI median. Our results indicate environment plays a role in the internal mass distribution of galaxies, with no evolution of the slope in the last 3-4 Gyr. These results are in agreement with the predictions of cosmological simulations.

Abstract: We study active galactic nucleus (AGN) feedback in nearby (z<0.35) galaxy clusters from the Planck Sunyaev-Zeldovich (SZ) sample using Chandra observations. This nearly unbiased mass-selected sample includes both relaxed and disturbed clusters and may reflect the entire AGN feedback cycle. We find that relaxed clusters better follow the one-to-one relation of cavity power versus cooling luminosity, while disturbed clusters display higher cavity power for a given cooling luminosity, likely reflecting a difference in cooling and feedback efficiency. Disturbed clusters are also found to contain asymmetric cavities when compared to relaxed clusters, hinting toward the influence of the intracluster medium (ICM) weather on the distribution and morphology of the cavities. Disturbed clusters do not have fewer cavities than relaxed clusters, suggesting that cavities are difficult to disrupt. Thus, multiple cavities are a natural outcome of recurrent AGN outbursts. As in previous studies, we confirm that clusters with short central cooling times, tcool, and low central entropy values, K0, contain warm ionized (10000 K) or cold molecular (<100 K) gas, consistent with ICM cooling and a precipitation/chaotic cold accretion (CCA) scenario. We analyzed archival MUSE observations that are available for 18 clusters. In 11/18 of the cases, the projected optical line emission filaments appear to be located beneath or around the cavity rims, indicating that AGN feedback plays an important role in forming the warm filaments by likely enhancing turbulence or uplift. In the remaining cases (7/18), the clusters either lack cavities or their association of filaments with cavities is vague, suggesting alternative turbulence-driven mechanisms (sloshing/mergers) or physical time delays are involved.

Abstract: We search for Milky Way-like galaxies among a sample of approximately 500 galaxies. The characteristics we considered of the candidate galaxies are the following: stellar mass M_star, optical radius R_25, rotation velocity V_rot, central oxygen abundance (O/H)_0, and abundance at the optical radius (O/H)_R25. If the values of R_25 and M_star of the galaxy were close to that of the Milky Way, then the galaxy was referred to as a structural Milky Way analogue (sMWA). The oxygen abundance at a given radius of a galaxy is defined by the evolution of that region, and we then assumed that the similarity of (O/H)_0 and (O/H)_R25 in two galaxies suggests a similarity in their evolution. If the values of (O/H)_0 and (O/H)_R25 in the galaxy were close to that of the Milky Way, then the galaxy was referred to as an evolutionary Milky Way analogue (eMWA). If the galaxy was simultaneously an eMWA and sMWA, then the galaxy was considered a Milky Way twin. We find that the position of the Milky Way on the (O/H)_0 - (O/H)_R25 diagram shows a large deviation from the general trend in the sense that the (O/H)_R25 in the Milky Way is appreciably lower than in other galaxies of similar (O/H)_0. This feature of the Milky Way evidences that its (chemical) evolution is not typical. We identify four galaxies (NGC~3521, NGC~4651, NGC~2903, and MaNGA galaxy M-8341-09101) that are simultaneously sMWA and eMWA and can therefore be considered as Milky Way twins. In previous studies, Milky Way-like galaxies were selected using structural and morphological characteristics, that is, sMWAs were selected. We find that the abundances at the centre and at the optical radius (evolutionary characteristics) provide a stricter criterion for selecting real Milky Way twins

Abstract: Galaxy evolution is an important topic, and our physical understanding must be complete to establish a correct picture. This includes a thorough treatment of feedback. The effects of thermal-mechanical and radiative feedback have been widely considered, however cosmic rays (CRs) are also powerful energy carriers in galactic ecosystems. Resolving the capability of CRs to operate as a feedback agent is therefore essential to advance our understanding of the processes regulating galaxies. The effects of CRs are yet to be fully understood, and their complex multi-channel feedback mechanisms operating across the hierarchy of galaxy structures pose a significant technical challenge. This review examines the role of CRs in galaxies, from the scale of molecular clouds to the circum-galactic medium. An overview of their interaction processes, their implications for galaxy evolution, and their observable signatures is provided and their capability to modify the thermal and hydrodynamic configuration of galactic ecosystems is discussed. We present recent advancements in our understanding of CR processes and interpretation of their signatures, and highlight where technical challenges and unresolved questions persist. We discuss how these may be addressed with upcoming opportunities.

Abstract: The alignment of striated intensity structures in thin neutral hydrogen (HI) spectroscopic channels with Galactic magnetic fields has been observed. However, the origin and nature of these striations are still debatable. Some studies suggest that the striations result solely from real cold-density filaments without considering the role of turbulent velocity fields, i.e., the velocity caustics effect in shaping the channel's intensity distribution. To determine the relative contribution of density and velocity in forming the striations in channel maps, we analyze synthetic observations of channel maps obtained with simulations that represent realistic magnetized multi-phase HI. We vary the thickness of the channel maps and apply the Velocity Decomposition Algorithm to separate the velocity and density contributions. In parallel, we analyze GALFA HI observations and compare the results. Our analysis shows that the thin channels are dominated by velocity contribution, and velocity caustics mainly generate the HI striations. We show that velocity caustics can cause a correlation between unsharp-masked HI structures and far-infrared emission. We demonstrate that the linear HI fibers revealed by the Rolling Hough Transform (RHT) in thin velocity channels originate from velocity caustics. As the thickness of channel maps increases, the relative contribution of density to fluctuations in channel maps also increases. As a result, more RHT-detected fibers tend to be perpendicular to the magnetic field. Conversely, the alignment with the magnetic field is the most prominent in thin channels. We conclude that similar to the Velocity Channel Gradients (VChGs) approach, RHT traces magnetic fields through the analysis of velocity caustics in thin channel maps.

Abstract: Ions and neutrals in the interstellar medium play a key role in the dynamics of magnetohydrodynamic (MHD) turbulence, but challenging to study. In this study, we investigate the damping of MHD turbulence using 3D two-fluid simulations generated with the AthenaK code. Specifically, we examine the density, velocity, and magnetic field statistics of the two-fluid turbulence. Our results demonstrate that when ions and neutrals are strongly coupled, the velocity statistics resemble those of single-fluid MHD turbulence. However, when neutrals begin to decouple from ions, turbulence in both neutrals and ions is damped, resulting in steep kinetic energy spectra compared to Kolmogorov-type turbulence. We attribute the damping of turbulence in neutrals to their local coupling with ions, caused by local variations in the ionization fraction and Alfv\'en speed. The neutral-ion decoupling scale is not fixed but extends to a range of values. After neutrals completely decouple from ions, the neutrals have a Kolmogorov-type kinetic energy spectrum, while the ions' spectrum remains steep. We find that ion and neutral densities can be different when their coupling is weak but velocity statistics remain similar, indicating that densities are more sensitive to neutral-ion decoupling than velocities. The density structures of ions are filamentary, while those of neutrals are clumpy. Using the probability distribution function of logarithmic mass density, we find density fluctuations in ions can be enhanced when neutral and ions are weakly coupled. We confirm that the magnetic field spectrum can be steep due to the damping of MHD turbulence by neutral-ion collision.