Open Access266 E+A galaxies selected from the Sloan Digital Sky Survey Data Release 2: the origin of E+A galaxies
Author(s) -
Goto Tomotsugu
Publication year - 2005
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.1365-2966.2005.08701.x
Subject(s) - physics , astrophysics , luminous infrared galaxy , galaxy group , elliptical galaxy , astronomy , galaxy , peculiar galaxy , brightest cluster galaxy , radio galaxy , galaxy cluster , balmer series , lenticular galaxy , sky , emission spectrum , spectral line
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 indicates that E+A galaxies have experienced starburst within the past one gigayear. However, the lack of [O ii ] and Hα emission lines indicates that E+A galaxies do not have any on‐going star formation. Therefore, E+A galaxies are interpreted as post‐starburst galaxies. For many years, however, it has been a mystery why E+A galaxies started starburst and why they quenched star formation abruptly. Using one of the largest samples of 266 E+A galaxies carefully selected from the Sloan Digital Sky Survey Data Release 2, we have investigated the environment of E+A galaxies from 50 kpc to 8 Mpc scale, i.e. from a typical distance to satellite galaxies to the scale of large‐scale structures. We found that E+A galaxies have an excess of local galaxy density only at a scale of <100 kpc (with a 2σ significance), but not at the cluster scale (∼1.5 Mpc) nor at the scale of large‐scale structure (∼8 Mpc). These results indicate that E+A galaxies are not created by the physical mechanisms associated with galaxy clusters or the large‐scale structure, but are likely to be created by dynamical interaction with closely accompanying galaxies at a <100 kpc scale. The claim is also supported by the morphology of E+A galaxies. We have found that almost all E+A galaxies have a bright compact core, and that ∼30 per cent of E+A galaxies have dynamically disturbed signatures or tidal tails, which quite strongly suggest the morphological appearance of merger/interaction remnants.