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\title{HEAVILY-OBSCURED STAR FORMATION IN THE II~Zw~96 GALAXY MERGER}

\author{Jeffrey D.\ Goldader\/\thanks{Visiting Astronomer at the 
United Kingdom Infrared Telescope, which is operated by the Royal 
Observatory Edinburgh on behalf of the U.K. Science and Engineering
Research Council}\morethanks{Institute for Astronomy, University of Hawaii,
2680 Woodlawn Drive, Honolulu, HI 96822}\\
\\
Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, 
MD 21218\\
e-mail: I:goldader@stsci.edu\\
\and
Deborah L.\ Goldader,\thanks{Current address: Department of Physics and 
Astronomy, University of Pennsylvania, 209 S.\ 33rd St., 
Philadelphia, PA 19104-6396} R.~D.\ Joseph\/\samethanks{1}\\
\\
Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, 
Honolulu, HI 96822\\
\and
Ren\'{e} Doyon\/\samethanks{1}\\
\\
D\'{e}partment de Physique, Universit\'{e} de Montr\'{e}al\\
C.P.\ 6128, Succ.~A., Montr\'{e}al (Qc), H3C~3J7, Canada\\
\and
D.~B.\ Sanders\/\samethanks{1}\\
\\
Institute for Astronomy, University of Hawaii}

\tobe{May 1997}{Astronomical Journal}
\recacc{25 November 1996}{31 January 1997}

\maketitle

\abstract{We present evidence that the luminous infrared galaxy II~Zw~96
(log$(L_{IR}/L_{\sun})=11.89$)
is a merger containing powerful, young starburst regions, 
similar to VV~114 and the well-studied Arp~299 system.
Our analysis is based on spatially-resolved $K$-band spectroscopy and
new optical and high-resolution near-infrared images.
Four primary infrared sources are found.
One (source~A) may be a galaxy nucleus, since it shows morphological hints
of a stellar bar, and is in the throes of powerful starburst activity.
Another~(B) seems to be a relatively quiescent spiral galaxy.
The remaining two sources (C~and~D) are very red with
strong near-infrared emission lines from atomic and molecular hydrogen
and helium.  They do
not seem identifiable as galaxy nuclei, based on morphological
grounds. Therefore, they are most likely highly obscured,
luminous ($M_K \sim -21$) starburst regions. Comparison of the near-infrared 
spectroscopic diagnostics of sources A, C, and~D with starburst models
suggests that these starbursts are younger than those in most other 
infrared-luminous galaxies.

We note both qualitative and quantitative similarities between 
regions~A, C, and D and ones in the interacting galaxies Arp~299 and VV~114. 
We suggest that these three systems are in a similar evolutionary stage,
containing very young starbursts and seen before
the final dissipative collapse and dynamical relaxation which numerical
simulations predict for major mergers.  If this analogy is correct, 
the starburst regions are probably 
groups of the super star clusters, rich in OB stars, which are
ubiquitous in starburst galaxies.  An important, yet open, question is
whether these galaxies represent part of an evolutionary sequence, a
stage through which most or even all infrared-luminous mergers will pass.}