Skip to end of metadata
Go to start of metadata

     
  

Summary:
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 9th of December - Organised remotely on Zoom

Presenter: Peter Johansson
Paper title: No need for dark matter: resolved kinematics of the ultra-diffuse galaxy AGC 114905
Authors: Mancera Piña, P. E, et al.  
References: 2021, MNRAS in press, ArXiv: 2112.00017

Abstract: We present new HI interferometric observations of the gas-rich ultra-diffuse galaxy AGC 114905, which previous work, based on low-resolution data, identified as an outlier of the baryonic Tully-Fisher relation. The new observations, at a spatial resolution $\sim 2.5$ times higher than before, reveal a regular HI disc rotating at about 23 km/s. Our kinematic parameters, recovered with a robust 3D kinematic modelling fitting technique, show that the flat part of the rotation curve is reached. Intriguingly, the rotation curve can be explained almost entirely by the baryonic mass distribution alone. We show that a standard cold dark matter halo that follows the concentration-halo mass relation fails to reproduce the amplitude of the rotation curve by a large margin. Only a halo with an extremely (and arguably unfeasible) low concentration reaches agreement with the data. We also find that the rotation curve of AGC 114905 deviates strongly from the predictions of Modified Newtonian dynamics. The inclination of the galaxy, which is measured independently from our modelling, remains the largest uncertainty in our analysis, but the associated errors are not large enough to reconcile the galaxy with the expectations of cold dark matter or Modified Newtonian dynamics.

Present program:


Past program:

Autumn 2021:

Spring 2021:

Spring 2020:

Autumn 2019:

Spring 2019:


Autumn 2018:


Spring 2018:

Autumn 2017:

Spring 2017:

Autumn 2016:

Spring 2016:

Autumn 2015:

Spring 2015:


Autumn 2014:

Spring 2014:

Autumn 2013:

Spring 2013:

Autumn 2012:

Spring 2012:

Autumn 2011:

  • No labels