E+A galaxies

E+A galaxies: galaxies with post-starburst spectra -- strong Balmer absorption lines, but no ongoing star formation. The most extreme examples are thought to be recent merger remnants.

A schematic sequence of galaxy evolution:
 
 
Spiral
Interaction
Merger/ULIRG
Remnant/E+A
Elliptical
M31
The Antennae (Whitmore etal)
IC 883 
(Hibbard & Yun)
NGC 7727 
(DSS)
M87 
(Malin/AAT)

 
 
 
 
 
 
 

Zabludoff etal (1996) identified a sample of ~20 extreme E+A galaxies from the LCRS:
  • EW(Habg > 5.5 A)
  • EW(OIII < 2.5 A)
Using HST, we (Zabludoff etal 2001 in prep) have imaged the 5 most extreme objects.

Four of them are morphologically what we expect 

 
 
 

But EA1 is a head-scratcher:
 
A young merger(?)... 
...with a post-starburst spectrum(?)
21cm VLA imaging Chang etal (2001):
  • MHI ~ 4x109 Msun
  • SFR(1.4 Ghz) < 0.6 Msun/yr