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This is the homepage of the of the weekly Astrophysics journal club at the Division of Particle physics and astrophysics at the University of Helsinki. The meetings are of an unofficial nature and the main driver is to get together and discuss recent interesting papers. This meeting differs from the Seminar series in that people are not expected to talk about their own research and in that no credits will be awarded to students. The meetings are open to everyone and the aim is to stimulate discussion about recent results and provide the possibility to
 learn about research that is not necessarily connected to one's own field of expertise.

All topics are welcome ranging from planetary science to larger scales involving stellar
 astrophysics, Milky Way studies, galaxies and cosmology.
The only requirement is that the
 presented papers should be interesting to a wider audience and that they should be presented 
in such a way that also a non-expert can follow the presentation. In the meetings we discuss one paper each week for about 45 minutes.
 All meetings are in English.

Location: In the Spring semester 2021 the Journal club will be organised remotely on Zoom
Normal location: Conference room C310 on the third floor.

Time: Thursdays at 10.15-11.00am during term time.

Speakers: Please contact Peter Johansson or Mikael Granvik if you want to present a paper.

Present Program: The next talk will be on the 23rd of September - Organised remotely on Zoom

Presenter: Alexander Rawlings
Paper title: The SAMI Galaxy Survey: Mass and Environment as Independent Drivers of Galaxy Dynamics
Authors: van de Sande, J. et al.
References:  2021, MNRAS in press, ArXiv: 2109.06189

Abstract:  The kinematic morphology-density relation of galaxies is normally attributed to a changing distribution of galaxy stellar masses with the local environment. However, earlier studies were largely focused on slow rotators; the dynamical properties of the overall population in relation to environment have received less attention. We use the SAMI Galaxy Survey to investigate the dynamical properties of 1800 early and late-type galaxies with log(M/M)>9.5 as a function of mean environmental overdensity (Σ5) and their rank within a group or cluster. By classifying galaxies into fast and slow rotators, at fixed stellar mass above log(M/M)>10.5, we detect a higher fraction (3.4σ) of slow rotators for group and cluster centrals and satellites as compared to isolated-central galaxies. Focusing on the fast-rotator population, we also detect a significant correlation between galaxy kinematics and their stellar mass as well as the environment they are in. Specifically, by using inclination-corrected or intrinsic λRe values, we find that, at fixed mass, satellite galaxies on average have the lowest λRe,intr, isolated-central galaxies have the highest λRe,intr, and group and cluster centrals lie in between. Similarly, galaxies in high-density environments have lower mean λRe,intr values as compared to galaxies at low environmental density. However, at fixed Σ5, the mean λRe,intr differences for low and high-mass galaxies are of similar magnitude as when varying Σ5 {(ΔλRe,intr0.05. Our results demonstrate that after stellar mass, environment plays a significant role in the creation of slow rotators, while for fast rotators we also detect an independent, albeit smaller, impact of mass and environment on their kinematic properties.

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