Plunging fireworks: why do infalling galaxies light up on the outskirts of clusters?

Mahajan, Smriti, Raychaudhury, Somak and Pimbblet, Kevin A. (2012) Plunging fireworks: why do infalling galaxies light up on the outskirts of clusters?. Monthly Notices of the Royal Astronomical Society, 427 2: 1252-1265. doi:10.1111/j.1365-2966.2012.22059.x


Author Mahajan, Smriti
Raychaudhury, Somak
Pimbblet, Kevin A.
Title Plunging fireworks: why do infalling galaxies light up on the outskirts of clusters?
Journal name Monthly Notices of the Royal Astronomical Society   Check publisher's open access policy
ISSN 0035-8711
1365-2966
Publication date 2012-12-01
Sub-type Article (original research)
DOI 10.1111/j.1365-2966.2012.22059.x
Open Access Status DOI
Volume 427
Issue 2
Start page 1252
End page 1265
Total pages 14
Place of publication Oxford, United Kingdom
Publisher Oxford University Press
Language eng
Formatted abstract
Integrated star formation rate (SFR) and specific star formation rate (SFR/M*), derived from the spectroscopic data obtained by the Sloan Digital Sky Survey (SDSS) data release 4 (DR4), are used to show that the star formation activity in galaxies (M r ≤ -20.5) found on the outskirts (1-2r 200) of some nearby clusters (0.02 ≤ z ≤ 0.15) is enhanced. By comparing the mean SFR of galaxies in a sample of clusters with at least one starburst galaxy (log SFR/M* ≥ -10yr -1 and SFR ≥ 10 M ⊙yr -1) to a sample of clusters without such galaxies ('comparison' clusters), we find that despite the expected decline in the mean SFR of galaxies towards the cluster core, the SFR profile of the two samples is different. Compared to the clusters with at least one starburst galaxy on their outskirts, the galaxies in the 'comparison' clusters show a lower mean SFR at all radius (≤3r 200) from the cluster centre. Such an increase in the SFR of galaxies is more likely to be seen in dynamically unrelaxed (σ v ≳ 500kms -1) clusters. It is also evident that these unrelaxed clusters are currently being assembled via galaxies falling in through straight filaments, resulting in high velocity dispersions. On the other hand, 'comparison' clusters are more likely to be fed by relatively low density filaments. We find that the starburst galaxies on the periphery of clusters are in an environment of higher local density than other cluster galaxies at similar radial distances from the cluster centre. We conclude that a relatively high galaxy density in the infalling regions of clusters promotes interactions amongst galaxies, leading to momentary bursts of star formation. Such interactions play a crucial role in exhausting the fuel for star formation in a galaxy, before it is expelled due to the environmental processes that are operational in the dense interiors of the cluster.
Keyword Galaxies: clusters: general
Galaxies: evolution
Galaxies: starburst
Cosmology: observations
Large-scale structure of Universe
Q-Index Code C1
Q-Index Status Confirmed Code
Institutional Status UQ

Document type: Journal Article
Sub-type: Article (original research)
Collections: School of Mathematics and Physics
Official 2013 Collection
 
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