Embedded Files
Affiliated with University of Birmingham, under the supervision of Dr Sean McGee and Dr Jacob Crossett, and in collaboration with Dr Callum Bellhouse.
My poster contribution on the topic of "RPS in Groups" got awarded 3rd prize for the best student poster in The STFC Introductory Astronomy School!
As galaxies are drawn into dense cluster/group environments, various environmentally-related physical mechanisms can act on them which can cause transformations and quenching. One of these processes is ram-pressure stripping (RPS) due to hydrodynamical interactions between the host galaxy and the dense intracluster/group medium.
Galaxies that undergo aggressive ram-pressure stripping show features like gas 'tentacles' and debris trails stripped from their main body (see figure on right). Hence, their resemblance to jellyfish gives them their popular definition of "jellyfish galaxies".
Ram-pressure stripping is seen commonly in galaxy clusters but isn't seen as often in galaxy groups, where the intragroup medium density is lower. Due to the expectation that ram pressure isn't as effective in groups, the role of RPS in groups is left largely unexplored.
This composite view of ESO 137-001 includes visible light from Hubble and X-ray light from the Chandra X-ray Observatory (in blue). It reveals a tail of hot gas that has been stripped from the galaxy. Its tail extends across 260,000 light-years of space. Credits: NASA, ESA, CXC
We used the data from Hyper Suprime-Cam (HSC) Subaru Strategic Program (imaging) Galaxy And Mass Assembly (GAMA) (spectroscopy) to identify ram-pressure stripped galaxies in group environments. We imposed an observational systematic search for the features of potential RPS in group candidates.
Depending on the visual strength of RPS, we assigned a class (JF Class, 0-no RPS signs, 3-majority of RPS signs) on each target and created a jellyfish candidate catalogue. We examined 125 galaxy groups totalling 1312 group members. We identified 45 galaxies with jellyfish-like features of which 13 of them showed secure signs and 32 of them had tentative signs of RPS. Some of the classified galaxies are displayed on left.
Simulations vs Observations (Candinates in Phase Space)
Secure candidates appear as recently accreted into the galaxy groups
The time of accretion of galaxies to the main halo shows that 7/13 of our secure candidates are in the first infall to the group
The phase velocity diagram of stacked galaxy groups within the sample. Galaxies with stellar-mass higher and lower than 1010.5 M⊙ marked as black and grey points respectively. The contour lines represent the number density of galaxies combined (darker colour indicates a higher population). The secure and inferior jellyfish candidates were highlighted as red and blue squares respectively.
Same as on left, only secure jellyfish candidates are highlighted (red points). Coloured contours show three different time of accretion ranges of galaxy to the main halo.
General properties of galaxies with respect to our JF class.
We found no correlation between JF class and stellar mass
Candidates are predominantly star-forming and blue
(85% of the secures, 74% of the inferiors)~10% star formation enhancement for both candidate groups
None of the secure candidates show AGN features
Candidates had a high median halo mass.
What can we conclude?
We determine that the secure candidates are located at preferentially high relative velocities and relatively low R200 values, consistent with ram-pressure expectations. They seem to have been recently accreted into galaxy groups.
Combining results from the phase space distribution and the simple analytic model, we deduce that the assumption of ram pressure stripping does not occur in galaxy groups is incorrect.
We show that even with the reduced relative velocities of group galaxies, the densities towards the centre of galaxy groups is sufficient to strip gas from the main galaxy body.
If you are interested of using any content from the page, please use the referral link from here. For more information, feel free to drop me a line!
Page updated
Google Sites
Report abuse