Search

It is now well known that certain massive galaxies undergo enormous enhancements in their SFR when they undergo major mergers(100x). To analyse the SF enhancement and AGN fraction evolution during the merger process, we use a more timeline-like merger sequence. Also, to determine the relation between the SF enhancement in mergers and the morphology of the galaxies involved. Taking advantage of the Mstr and SFR of 600 nearby isolated mergers from our previous study, we calculate the distance of our galaxies from the SF MS, which we refer to as SFmode. We analyse how the SFmode varies during the merger process, for morphology and Mstr. We also analyse the AGN content of our mergers, using multiple diagnostics based on emission line ratios and WISE colours. We observe that, overall, merging galaxies show a SFmode that is governed by their morphology. Spirals typically show high SFmode values while highly-disturbed galaxies are generally even more enhanced (0.8dex and 1dex above the MS, resp). On the contrary, elliptical and lenticular galaxies show the lowest SF modes, as expected. However, even they show SF enhancement compared to their unperturbed counterparts (their median SFmode is within the 1-sigma scatter of the MS, and this can occur even before the galaxies have coalesced). We see a trend for SFmode to gradually increase with increasing merger stage. We do not find a clear dependency of the observed AGN fraction on merger stage for the majority of our classification methods. We find mergers can significantly enhance SF in galaxies of all morphologies. For early-type galaxies, this could suggest that some gas was present prior to the merger which may be triggered to form stars by the tidal interaction. As the SF enhancement continues throughout the merger process, this suggests that the enhancement may be a long-lived event, contrary to the short starbursts seen in some models., Comment: A&A accepted. 16 pages, 13+5 figures

Ram pressure stripping is perhaps the most efficient mechanism for removing gas and quenching galaxies in dense environments as they move through the intergalactic medium. Extreme examples of on-going ram pressure stripping are known as jellyfish galaxies, characterized by a tail of stripped material that can be directly observed in multiple wavelengths. Using the largest homogeneous broad-band optical jellyfish candidate sample in local clusters known to date, we measure the angle between the direction of the tails visible in the galaxies, and the direction towards the host cluster center. We find that $33\%$ of the galaxy tails point away from the cluster center, $18\%$ point towards the cluster center, and $49\%$ point elsewhere. Moreover, we find stronger signatures of ram pressure stripping happening on galaxies with a tail pointing away and towards the cluster center, and larger velocity dispersion profiles for galaxies with tails pointing away. These results are consistent with a scenario where ram pressure stripping has a stronger effect for galaxies following radial orbits on first infall. The results also suggest that in many cases, radially infalling galaxies are able to retain their tails after pericenter and continue to experience significant on-going ram pressure stripping. We further constrain the lifespan of the optical tails from the moment they first appear to the moment they disappear, by comparing the observed tail directions with matched N-body simulations through Bayesian parameter estimation. We obtain that galaxy tails appear for the first time at $\sim 1.16$ R$_{200}$ and disappear $\sim660$ Myr after pericenter., Comment: 19 pages, 17 figures

Our objectives are to map the filamentary network around the Fornax-Eridanus Complex and probe the influence of the local environment on galaxy morphology. We employ the novel machine-learning tool, 1-DREAM (1-Dimensional, Recovery, Extraction, and Analysis of Manifolds) to detect and model filaments around the Fornax cluster. We then use the morphology-density relation of galaxies to examine the variation in the galaxies' morphology with respect to their distance from the central axis of the detected filaments. We detect 27 filaments that vary in length and galaxy-number density around the Fornax-Eridanus Complex. These filaments showcase a variety of environments; some filaments encompass groups/clusters, while others are only inhabited by galaxies in pristine filamentary environments. We also reveal a well-known structure -- the Fornax Wall, that passes through the Dorado group, Fornax cluster, and Eridanus supergroup. Regarding the morphology of galaxies, we find that early-type galaxies (ETGs) populate high-density filaments and high-density regions of the Fornax Wall. Furthermore, the fraction of ETGs decreases as the distance to the filament spine increases. Of the total galaxy population in filaments, ~7% are ETGs and ~24% are late-type galaxies (LTGs) located in pristine environments of filaments, while ~27% are ETGs and ~42% are LTGs in groups/clusters within filaments. This study reveals the Cosmic Web around the Fornax Cluster and asserts that filamentary environments are heterogeneous in nature. When investigating the role of the environment on galaxy morphology, it is essential to consider both, the local number-density and a galaxy's proximity to the filament spine. Within this framework, we ascribe the observed morphological segregation in the Fornax Wall to pre-processing of galaxies within groups embedded in it., Comment: Accepted for publication in A&A. 21 pages with 15 figures

We explore the formation of the intragroup light (IGL) and intracluster light (ICL), representing diffuse lights within groups and clusters, since $z=1.5$. For this, we perform multi-resolution cosmological N-body simulations using the ``galaxy replacement technique" (GRT) and identify the progenitors in which the diffuse light stars existed when they fell into the groups or clusters. Our findings reveal that typical progenitors contributing to diffuse lights enter the host halo with the massive galaxies containing a stellar mass of $10 < \log M_{\rm{gal}}~[M_{\odot}]< 11$, regardless of the mass or dynamical state of the host halos at $z=0$. In cases where the host halos are dynamically unrelaxed or more massive, diffuse lights from massive progenitors with $\log M_{\rm{gal}}~[M_{\odot}]> 11$ are more prominent, with over half of them already pre-processed before entering the host halo. Additionally, we find that the main formation mechanism of diffuse lights is the stripping process of satellites, and a substantial fraction ($40-45\%$) of diffuse light stars is linked to the merger tree of the BCG. Remarkably, all trends persist for groups and clusters at higher redshifts. The fraction of diffuse lights in the host halos with a similar mass decreases as the redshift increases, but they are already substantial at $z=1.5$ ($\sim10\%$). However, it's crucial to acknowledge that detection limits related to the observable radius and faint-end surface brightness may obscure numerous diffuse light stars and even alter the main formation channel of diffuse lights., Comment: 18 pages, 13 figures. Accepted for publication in The Astrophysical Journal, May 10th, 2024

During cluster assembly, a cluster's virialization process leaves behind signatures that can provide information on its dynamical state. However, no clear consensus yet exists on the best way to achieve this. Therefore, we attempt to derive improved recipes for classifying the dynamical state of clusters in observations using cosmological simulations. Cluster halo mass and their subhalos' mass are used to $ 10^{14}M_{\odot} h^{-1}$ and $10^{10}M_{\odot} h^{-1}$ to calculate five independent dynamical state indicators. We experiment with recipes by combining two to four indicators for detecting specific merger stages like recent and ancient mergers. These recipes are made by plotting merging clusters and a control sample of relaxed clusters in multiple indicators parameter space, and then applying a rotation matrix method to derive the best way to separate mergers from the control sample. The success of the recipe is quantified using the success rate and the overlap percentage of the merger and control histograms along the newly rotated $x$-axis. This provides us with recipes using different numbers of combined indicators and for different merger stage. Among the recipes, the stellar mass gap and center offset are the first and second most dominant of the indicators, and using more indicators improves the effectiveness of the recipe. When applied to observations, our results show good agreement with literature values of cluster dynamical state., Comment: 17pages, 9 figures, 3 tables, ApJ Accepted

It is currently unknown how matter behaves at the extreme densities found within the cores of neutron stars. Measurements of the neutron star equation of state probe nuclear physics that is otherwise inaccessible in a laboratory setting. Gravitational waves from binary neutron star mergers encode details about this physics, allowing the equation of state to be inferred. Planned third-generation gravitational-wave observatories, having vastly improved sensitivity, are expected to provide tight constraints on the neutron star equation of state. We combine simulated observations of binary neutron star mergers by the third-generation observatories Cosmic Explorer and Einstein Telescope to determine future constraints on the equation of state across a plausible neutron star mass range. In one year of operation, a network consisting of one Cosmic Explorer and the Einstein Telescope is expected to detect $\gtrsim 3\times 10^5$ binary neutron star mergers. By considering only the 75 loudest events, we show that such a network will be able to constrain the neutron star radius to at least $\lesssim 200$ m (90% credibility) in the mass range $1-1.97$ $M_{\odot}$ -- about ten times better than current constraints from LIGO-Virgo-KAGRA and NICER. The constraint is $\lesssim 75$ m (90% credibility) near $1.4-1.6$ $M_{\odot}$ where we assume the the binary neutron star mass distribution is peaked. This constraint is driven primarily from the loudest $\sim 20$ events., Comment: 6 pages, 3 figures. Submitted to Physical Review Letters