Dr Kevin Pimbblet K.Pimbblet@hull.ac.uk
Director of DAIM
© 2019 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society The ratio of calcium II H plus H∊ to calcium II K inverts as a galaxy stellar population moves from being dominated by older stars to possessing more A and B class stars. This ratio – the H:K ratio – can serve as an indicator of stellar populations younger than 200 Myr. In this work, we provide a new method to determine H:K, and apply it to spectra taken of cluster galaxies in Abell 3888. Although H:K is on average systematically lower for the cluster than for a wider field sample, we show that H:K does not have a simple relationship with other indices such as the equivalent widths of Hδ and [O II] beyond having a high value for strong [O II] emission. Moreover, strongly inverted galaxies with H:K > 1.1 have no preferred location within the cluster and are only slightly lower in their velocity dispersions around the cluster compared to strongly emitting [O II] galaxies. Our results indicate that selecting galaxies on H:K inversion results in a heterogeneous sample formed via a mixture of pathways that likely includes, but may not be limited to, merging spiral galaxies, and quiescent galaxies accreting lower mass, gas-rich companions. In concert with other selection criteria, H:K can provide a means to select a more ‘pure’ passive sample or to aid in the selection of highly star-forming galaxies, especially where other spectral line indicators such as H α may not have been observed.
Pimbblet, K. A., Crossett, J. P., & Fraser-McKelvie, A. (2019). Heterogeneity of inverted calcium II H:K ratio cluster galaxies. Monthly notices of the Royal Astronomical Society, 490(1), 455-466. https://doi.org/10.1093/mnras/stz2549
Journal Article Type | Article |
---|---|
Acceptance Date | Sep 10, 2019 |
Online Publication Date | Sep 12, 2019 |
Publication Date | 2019-11 |
Deposit Date | Nov 26, 2019 |
Publicly Available Date | Oct 27, 2022 |
Journal | Monthly Notices of the Royal Astronomical Society |
Print ISSN | 0035-8711 |
Electronic ISSN | 1365-2966 |
Publisher | Oxford University Press |
Peer Reviewed | Peer Reviewed |
Volume | 490 |
Issue | 1 |
Pages | 455-466 |
DOI | https://doi.org/10.1093/mnras/stz2549 |
Keywords | Space and Planetary Science; Astronomy and Astrophysics |
Public URL | https://hull-repository.worktribe.com/output/2715647 |
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© 2019 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society
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