Open AccessAbundance diagnosis of E+A (post‐starburst) galaxies
Author(s) -
Goto Tomotsugu
Publication year - 2007
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1111/j.1365-2966.2007.11674.x
Subject(s) - physics , astrophysics , luminous infrared galaxy , balmer series , peculiar galaxy , elliptical galaxy , galaxy , radio galaxy , astronomy , disc , galaxy group , lenticular galaxy , emission spectrum , spectral line
ABSTRACT E+A galaxies are characterized as galaxies with strong Balmer absorption lines but without any [O ii ] or Hα emission lines. The existence of strong Balmer absorption lines means that E+A galaxies have experienced a starburst within the last <1–1.5 Gyr. However, the lack of [O ii ] or Hα emission lines indicates that E+A galaxies do not have any ongoing star formation. Therefore, E+A galaxies are interpreted as post‐starburst galaxies. Morphologically, E+A galaxies appear as early‐type galaxies, implying that E+A galaxies may be one of the progenitors of present‐day elliptical galaxies. However, there remain other possibilities, such as the dusty starburst scenario, where E+A galaxies have ongoing star formation, but optical emission lines are invisible as a result of heavy obscuration by dust. Therefore, additional evidence of the post‐starburst phenomenon has been eagerly awaited. Using one of the largest samples of 451 E+A galaxies carefully selected from the Sloan Digital Sky Survey Data Release 4, here we show the abundance diagnosis of E+A galaxies using Mg and Fe lines. Our findings are as follows. (i) E+A galaxies have an enhanced α‐element abundance ratio compared to star‐forming galaxies with similar Balmer absorption strength. Because the truncation of strong starburst is required to enhance the α‐element ratio, this is additional evidence that E+A galaxies are in the post‐starburst phase. (ii) The metallicity and α‐element abundance of E+A galaxies are consistent with those of elliptical galaxies, suggesting that E+A galaxies could be one of the progenitors of present‐day elliptical galaxies in terms of chemical abundances.