Browsing by Author "Jaffe, Yara L."

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    Distribution of Merging and Post-merger Galaxies in Nearby Galaxy Clusters
    (2024) Kim, Duho; Sheen, Yun-Kyeong; Jaffe, Yara L.; Kelkar, Kshitija; Ranjan, Adarsh; Piraino-Cerda, Franco; Crossett, Jacob P.; Lourenco, Ana Carolina Costa; Martin, Garreth; Nantais, Julie B.; Demarco, Ricardo; Treister, Ezequiel; Yi, Sukyoung K.
    We study the incidence and spatial distribution of galaxies that are currently undergoing gravitational merging (M) or that have signs of being post-merger (PM) in six galaxy clusters (A754, A2399, A2670, A3558, A3562, and A3716) within the redshift range of 0.05 less than or similar to z less than or similar to 0.08. To this aim, we obtained Dark Energy Camera mosaics in the u ' , g ' , and r ' bands covering up to 3 x R 200 of the clusters, reaching 28 mag arcsec-2 surface brightness limits. We visually inspect u ' g ' r ' color-composite images of volume-limited (M r < -20) cluster member galaxies to identify whether galaxies are of M or PM type. We find 4% M-type and 7% PM-type galaxies in the galaxy clusters studied. By adding spectroscopic data and studying the projected phase-space diagram (PPSD) of the projected clustocentric radius and the line-of-sight velocity, we find that PM-type galaxies are more virialized than M-type galaxies, having a 1%-5% higher fraction within the escape-velocity region, while the fraction of M-type was similar to 10% higher than the PM type in the intermediate environment. Similarly, on a substructure analysis, M types were found in groups in the outskirts, while PM-type populated groups were found in ubiquitous regions of the PPSD. Adopting literature-derived dynamical state indicator values, we observed a higher abundance of M types in dynamically relaxed clusters. This finding suggests that galaxies displaying post-merger features within clusters likely merged in low-velocity environments, including clusters outskirts and dynamically relaxed clusters.
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    Formation of S0s in extreme environments I: clues from kinematics and stellar populations
    (2020) Coccato, Lodovico; Jaffe, Yara L.; Cortesi, Arianna; Merrifield, Michael; Johnston, Evelyn; Rodriguez del Pino, Bruno; Haeussler, Boris; Chies-Santos, Ana L.; Mendes de Oliveira, Claudia L.; Sheen, Yun-Kyeong; Menendez-Delmestre, Karin
    Despite numerous efforts, it is still unclear whether lenticular galaxies (S0s) evolve from spirals whose star formation was suppressed, or formed trough mergers or disc instabilities. In this paper we present a pilot study of 21 S0 galaxies in extreme environments (field and cluster), and compare their spatially resolved kinematics and global stellar populations. Our aim is to identify whether there are different mechanisms that form S0s in different environments. Our results show that the kinematics of S0 galaxies in field and cluster are, indeed, different. Lenticulars in the cluster are more rotationally supported, suggesting that they are formed through processes that involve the rapid consumption or removal of gas (e.g. starvation, ram pressure stripping). In contrast, S0s in the field are more pressure supported, suggesting that minor mergers served mostly to shape their kinematic properties. These results are independent of total mass, luminosity, or disc-to-bulge ratio. On the other hand, the mass-weighted age, metallicity, and star formation time-scale of the galaxies correlate more with mass than with environment, in agreement with known relations from previous work, such as the one between mass and metallicity. Overall, our results re-enforce the idea that there are multiple mechanisms that produce S0s, and that both mass and environment play key roles. A larger sample is highly desirable to confirm or refute the results and the interpretation of this pilot study.