TY - JOUR
T1 - Near-infrared imaging of 222 nearby Hδ-strong galaxies from the Sloan Digital Sky Survey
AU - Balogh, Michael L.
AU - Miller, Chris
AU - Nichol, Robert
AU - Zabludoff, Ann
AU - Goto, Tomo
N1 - Copyright:
Copyright 2011 Elsevier B.V., All rights reserved.
PY - 2005/6/21
Y1 - 2005/6/21
N2 - We present UFTI K-band imaging observations of 222 galaxies that are selected from the Sloan Digital Sky Survey to have unusually strong Hδ absorption equivalent widths, W o(Hδ) > 4 Å. Using GIM2D, the images are fitted with two-dimensional surface-brightness models consisting of a simple disc and bulge component to derive the fraction of luminosity in the bulge B/T. We find that the galaxies with weak or absent Hα or [O II]λ3727 emission (known as k+a galaxies) are predominantly bulge-dominated (with a mode of B/T ∼ 0.6), while galaxies with nebular emission [known as e(a) galaxies] are mostly disc-dominated (B/T ∼ 0.1). The morphologies and (r - k) colours of most k+a galaxies are inconsistent with the hypothesis that they result from the truncation of star formation in normal, spiral galaxies. However, their (u - g) and (r - k) colours, as well as their Hδ line strengths, form a sequence that is well matched by a model in which >5 per cent of the stellar mass has been produced in a recent starburst. The lack of scatter in the dust-sensitive (r - k) colours suggests that the unusual spectra of k+a galaxies ate not due to the effects of dust. The e(a) galaxies, on the other hand, have a colour distribution that is distinct from the k+a population, and typical of normal or dusty (τ V ∼ 2) spiral galaxies. We conclude that many e(a) galaxies are not progenitors of k+a galaxies, but are a separate phenomenon. Both k+a and e(a) galaxies reside in environments (characterized by the local density of galaxies brighter than M r = -20) that are typical of normal galaxies and that are inconsistent with overdense regions like rich galaxy clusters.
AB - We present UFTI K-band imaging observations of 222 galaxies that are selected from the Sloan Digital Sky Survey to have unusually strong Hδ absorption equivalent widths, W o(Hδ) > 4 Å. Using GIM2D, the images are fitted with two-dimensional surface-brightness models consisting of a simple disc and bulge component to derive the fraction of luminosity in the bulge B/T. We find that the galaxies with weak or absent Hα or [O II]λ3727 emission (known as k+a galaxies) are predominantly bulge-dominated (with a mode of B/T ∼ 0.6), while galaxies with nebular emission [known as e(a) galaxies] are mostly disc-dominated (B/T ∼ 0.1). The morphologies and (r - k) colours of most k+a galaxies are inconsistent with the hypothesis that they result from the truncation of star formation in normal, spiral galaxies. However, their (u - g) and (r - k) colours, as well as their Hδ line strengths, form a sequence that is well matched by a model in which >5 per cent of the stellar mass has been produced in a recent starburst. The lack of scatter in the dust-sensitive (r - k) colours suggests that the unusual spectra of k+a galaxies ate not due to the effects of dust. The e(a) galaxies, on the other hand, have a colour distribution that is distinct from the k+a population, and typical of normal or dusty (τ V ∼ 2) spiral galaxies. We conclude that many e(a) galaxies are not progenitors of k+a galaxies, but are a separate phenomenon. Both k+a and e(a) galaxies reside in environments (characterized by the local density of galaxies brighter than M r = -20) that are typical of normal galaxies and that are inconsistent with overdense regions like rich galaxy clusters.
KW - Galaxies: evolution
KW - Galaxies: interactions
KW - Galaxies: stellar content
KW - Galaxies: structure
KW - Infrared: galaxies
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U2 - 10.1111/j.1365-2966.2005.09047.x
DO - 10.1111/j.1365-2966.2005.09047.x
M3 - Article
AN - SCOPUS:20744441505
VL - 360
SP - 587
EP - 609
JO - Monthly Notices of the Royal Astronomical Society
JF - Monthly Notices of the Royal Astronomical Society
SN - 0035-8711
IS - 2
ER -