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Tidal interactions and mergers in intermediate redshift EDisCS clusters

Deger, Sinan; Rudnick, Gregory; Kelkar, Kshitija; Aragón-Salamanca, Alfonso; Desai, Vandana; Lotz, Jennifer M.; Jablonka, Pascale; Moustakas, John; Zaritsky, Dennis


Sinan Deger

Gregory Rudnick

Kshitija Kelkar

Vandana Desai

Jennifer M. Lotz

Pascale Jablonka

John Moustakas

Dennis Zaritsky


We study the fraction of tidal interactions and mergers with well identified observability timescales (fTIM) in group, cluster, and accompanying field galaxies and its dependence on redshift (z), cluster velocity dispersion (sigma) and environment analyzing HST-ACS images and catalogs from the ESO Distant Cluster Survey (EDisCS). Our sample consists of 11 clusters, 7 groups, and accompanying field galaxies at 0:4 equal or less z equal or less 0:8. We derive fTIM using both a visual classification of galaxy morphologies and an automated method, the G-M20 method. We calibrate this method using the visual classifications that were performed on a subset of our sample. We find marginal evidence for a trend between fTIM and z, in that higher z values correspond to higher fTIM. However, we also cannot rule out the null hypothesis of no correlation at higher than 68% confidence. No trend is present between fTIM and z. We find that fTIM shows suggestive peaks in groups, and tentatively in clusters at R > 0:5 x R200, implying that fTIM gets boosted in these intermediate density environments. However, our analysis of the local densities of our cluster sample does not reveal a trend between fTIM and density, except for a potential enhancement at the very highest densities. We also perform an analysis of projected radius-velocity phase space for our cluster members. Our results reveal that tidal interactions and mergers (TIM), and undisturbed galaxies only have a 6% probability of having been drawn from the same parent population in their velocity distribution and 37% in radii, in agreement with the modest differences obtained in fTIM at the clusters.


Deger, S., Rudnick, G., Kelkar, K., Aragón-Salamanca, A., Desai, V., Lotz, J. M., …Zaritsky, D. (2018). Tidal interactions and mergers in intermediate redshift EDisCS clusters. Astrophysical Journal, 869(1),

Journal Article Type Article
Acceptance Date Sep 27, 2018
Online Publication Date Dec 5, 2018
Publication Date Dec 5, 2018
Deposit Date Oct 10, 2018
Publicly Available Date Oct 10, 2018
Journal The Astrophysical Journal
Print ISSN 0004-637X
Publisher American Astronomical Society
Peer Reviewed Peer Reviewed
Volume 869
Issue 1
Public URL
Publisher URL
Additional Information Journal title: The Astrophysical Journal; Article type: paper; Article title: Tidal Interactions and Mergers in Intermediate-redshift EDisCS Clusters; Copyright information: © 2018. The American Astronomical Society. All rights reserved.; Date received: 2018-02-09; Date accepted: 2018-09-26; Online publication date: 2018-12-05


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