Interstellar Gas and Star Formation Near the Peculiar Radio Galaxy NGC 4410A
Beverly J. Smith
and
smithb.tex
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\index{Donahue, M.}
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\title{Interstellar Gas and Star Formation Near the Peculiar Radio Galaxy
NGC 4410A}
\author{Beverly J. Smith}
\affil{East Tennessee State University, Physics and Astronomy 
Department,
Johnson City TN  37604}
\author{Megan Donahue}
\affil{Space Telescope Science Institute, Baltimore
MD  21218}
\author{John Stocke}
\affil{University of Colorado, APS Dept, Box 391, Boulder CO  80309}

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\begin{abstract}

We present new multi-wavelength
data for the NGC 4410 galaxy group.
This group contains the peculiar radio galaxy NGC 4410A,
which has a distorted double-lobed radio structure.
NGC 4410A is strongly interacting with three nearby galaxies,
and has a peculiar ring-like optical morphology, a number
of luminous H~II regions, as well
as tidal tails and bridges variously visible in optical,
HI, and X-ray light.  
The gravitational interaction
has affected the interstellar matter, the star formation rate,
and the radio lobes in this system.

\end{abstract}

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\section{Introduction}

The large radio lobes of radio
galaxies both affect and are affected by their
environment.  They may be distorted by motion
through an intracluster medium
or by an encounter with interstellar matter in the
host galaxy or a companion
galaxy.
In addition, impacts between jets and interstellar matter
may trigger star formation.
To investigate the interplay between radio lobes and the
interstellar matter in radio galaxies, detailed studies
of the interstellar matter in nearby radio galaxies
are essential.  In this paper, we present a study
of the interstellar matter in the nearby low
luminosity radio galaxy NGC 4410A.

\section{A Multi-Wavelength View of the NGC 4410 Group}

NGC 4410A is part of a small group containing a dozen
known members.  
NGC 4410A has a prominent bulge surrounded by a ring-like
or loop-like structure (Figure 1a).  East and southeast
of the nucleus, luminous H~II regions
are detected (Figure 1b).
There is an HI tail extending
to the southeast of the NGC 4410A+B pair, coincident with
a stellar tail (Figure 2).  
NGC 4410A was also detected in CO (1 $-$ 0),
yielding
M$_{H_2}$ $\sim$ 4 $\times$ 10$^9$ M$_{\sun}$.
NGC 4410A has two 
distorted radio lobes;
the southeastern lobe 
is superposed on the optical/HI tidal tail.
X-ray maps
show a 2$'$ long `tail'
coincident
with the NGC 4410A+B/NGC 4410C stellar bridge.



\section{Conclusions}

The NGC 4410 group shows
clear evidence for gravitational interactions between
galaxies as well as evidence for an external force acting upon
the radio lobes.  
The peculiar ring-like structure of
NGC 4410A suggests that a near-head-on
collision with NGC 4410B has occurred.
We suggest that the distortion of the radio lobes was caused
by ram pressure from the interstellar medium,
due to the motion of this gas relative to the radio
source during a gravitational interaction 
between galaxies.
The X-ray extension may
be due to shocked tidal gas or
intragroup gas coincidently superposed
on the stellar bridge.
The 
star formation may have been induced by the collision or 
by a jet/interstellar medium impact.

{\bf Captions}

1a) a red continuum image of NGC 4410A (right)
and its companion NGC 4410B.  1b) an H$\alpha$+[N~II] image
of NGC 4410A+B.  The field of view is $\sim$1$'$.

2) A VLA D Array 21 cm HI map of the inner
part of the NGC 4410 group, superposed on an R-band image
from the SARA 0.9m telescope.  The field of view is 6$'$ $\times$
5$'$.

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%\begin{references}
{\small

%\reference Smith, B. J. 2000, \apj, in press.

}
%\end{references}

\end{document}

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<TITLE>Interstellar Gas and Star Formation Near the 
Peculiar Radio Galaxy NGC 4410A</TITLE>

<font size=+2>

<font color="#ZZZZZZ">

<P><b><center><font size=+3>ABSTRACT</font></center></b>

 
<TITLE>Interstellar Gas and Star Formation Near the 
Peculiar Radio Galaxy NGC 4410A</TITLE>

<font size=+2>

<P>
<B><font size=+3>
<center>
INTRODUCTION:</center>
<center>THE INTERSTELLAR MEDIUM</center>
<center>IN</center>
<center>RADIO GALAXIES</center>
</font>
</b>

<P>
 
<TITLE>Interstellar Gas and Star Formation Near the 
Peculiar Radio Galaxy NGC 4410A</TITLE>

<font color="#0000ff">
<body vlink=#AA00FF>

<font size=+2>

<P><center><b>REFERENCES</b></center>

<ul>

\reference Hummel, E., Kotanyi, C. G., and van Gorkom, J. H. 1986,
AA, 155, 161 

In Figure 1, a VLA 21 cm HI map, a radio continuum map, and an R-band optical 
image of the inner part of this group
are compared with an archival ROSAT X-ray map.
Five galaxies are visible in this image,
four of which appear to be interacting.

Optical spectroscopy confirm
that these knots are indeed H~II regions, while the nuclei
of both galaxies show LINER-like line ratios.  The extended
ionized gas to the west of the nucleus has line ratios
typical of shock ionization.

An HI tail is also seen near the
barred spiral NGC 4410D.
HI was also detected in the small galaxy NGC 4410F 
and four galaxies in the outer
part of the group.
