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Heterogeneity of inverted calcium?ii H:K ratio cluster galaxies

Pimbblet, K. A.; Crossett, J. P.; Fraser-McKelvie, A.

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Authors

K. A. Pimbblet

J. P. Crossett

A. Fraser-McKelvie



Abstract

© 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.

Citation

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 Nov 21, 2019
Deposit Date Dec 10, 2019
Publicly Available Date Mar 28, 2024
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 Methods: data analysis – techniques: spectroscopic – galaxies: clusters: individual: Abell 3888 – galaxies: evolution – galaxies: stellar content.
Public URL https://nottingham-repository.worktribe.com/output/3524069
Publisher URL https://academic.oup.com/mnras/article/490/1/455/5568382
Additional Information This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society ©: 2019 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.

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