Neutral and ionized gas distribution in and around the radio galaxy Coma A
R. Morganti
T. Oosterloo
and
morganti.tex
% vla2000.tex 
%%
%% tex file for Gas & Galaxy Evolution Conference 
%% PLEASE EDIT THIS FILE AS NECESSARY AND SUBMIT
%% NOTE: DO NOT DEFINE ANY COMMANDS (\def, \newcommand)
%% OF YOUR OWN FOR ANY REASON!!!
%
% For an example of this file, see the files vla2000_sample*.*
% at http://www.nrao.edu/vla2000/proceedings/ or
% ftp over the file vla2000.tar.gz via anonymous ftp to 
% ftp.cv.nrao.edu/NRAO-staff/jhibbard/vla2000
% For more detailed instructions, see the file 
% vla2000_man.ps at the same site. 

% The first item in the LaTeX file must be the \documentclass command to
% declare the overall style of the paper.  Next, the \usepackage
% commands specify that we will use the definitions from the newpasp.sty 
% style file (available from http://www.aspsky.org/pubs/authors.html
% as well as the above web and ftp sites)

\documentclass[11pt,twoside]{article}
\usepackage{newpasp}

% Many authors like to format figure with the commands in the
% epsf.sty, so I have included a line to include that file. Without it, 
% you can still include figures using the \plotone, \plottwo, and 
% \plotfiddle commands. See vla2000_sample.tex and vla2000_man.ps for
% more details. 
%\usepackage{epsf}
\input{psfig}
\newcommand{\HI}{H{\,\small I}}

% Authors should supply running head information.  The left head contains a
% list of author surnames, usually three allowed---otherwise use et al.  
% The right head is a modified title of up to roughly 44 characters.  

\markboth{R. Morganti et al. }{Neutral Hydrogen in Coma A}

% the \setcounter{page}{#} command will uncommented and filled in by 
% the editorial staff, so just ignore it for now
%%\setcounter{page}{1}

% include each authors name and initials in an index command for
% help in constructing the author index for the proceedings.

\index{Morganti, R.}
\index{Oosterloo, T.A.}
\index{Tadhunter, C.N.}
\index{Wills, K.A.}


% This is the end of the "preamble".  Now we wish to start with the
% real material for the paper, which we indicate with \begin{document}.
% Following the \begin{document} command is the front matter for the
% paper, viz., the title, author and address data, the abstract, and
% any keywords or subject headings that are relevant.
% The \affil command should be used to give the author's full postal 
% address. The address will be broken over several lines automatically;
% do NOT use LaTex's "\\" command to indicate the line breaks.
% Please use mixed case text for ALL these fields rather than supplying 
% all capitals; the style file will convert to upper case as necessary.

\begin{document}

\title{Neutral and ionized gas distribution in and around the radio galaxy Coma A}
\author{R. Morganti, T. Oosterloo}
\affil{ASTRON - NFRA, Postbus 2, 7990 AA
Dwingeloo, The Netherlands}
\author{C.N. Tadhunter, K. A. Wills}
\affil{Dep. Physics and Astronomy,
University of Sheffield,  S7 3RH, UK}


% A concise abstract is recommended.  Enter the text of the abstract in
% between the \begin{abstract} and \end{abstract} commands.  Do NOT
% include the word ``Abstract'' in your text; it is insterted
% automatically. Do NOT  make a paragraph break between \begin{abstract} 
% and the first line of the text of the abstract!  Abstracts are required 
% for all papers.

\begin{abstract}

\HI\ absorption has been detected with the WSRT against {\sl both lobes} of
the radio galaxy Coma~A.  This radio galaxy could be expanding in a
particularly gas rich environment, perhaps the result from interactions/mergers
between the dominant giant galaxy (associated with the radio galaxy) and less
massive galaxies in the same group. 
\end{abstract}

% Include keywords if you wish. The keywords.apj file, found on aas.org 
% in the pubs/aastex-misc directory, contains a list of keywords used 
% with the ApJ and Letters.  

%%\keywords{infrared: galaxies -- galaxies: nuclei -- galaxies: starburst}

% That's it for the front matter.  On to the main body of the paper.

Powerful radio galaxies are frequently associated with kpc-sized emission line
nebulosities, extending up to tens of kpc from the nucleus.  These
nebulosities can be either lit up by interactions between the radio jet/lobe
and the environment or photoionized by anisotropic UV radiation from the
active nucleus. Little is known in radio galaxies to what extent this ionized
gas is related to the overall ISM.  A key element for studies of these
extended emission line regions is to know the intrinsic distribution of the
gas in and around the galaxy, i.e.  to know the distribution of the neutral
gas together with that of the ionized gas.  Coma~A is an ideal object for this
study.  It is a well-known radio galaxy (\( z=0.0857 \)) studied in detail by
van Breugel et al. (1985).  The radio structure is mainly formed
by two lobes (see Fig.~1) and the total size is $\sim 65$ kpc (for \( H_{\circ
}=75 \) km s\( ^{-1} \) Mpc\( ^{-1} \), 1.45 kpc/arcsec).  A spectacular
system of interlocking emission line arcs and filaments has been observed in
H$\alpha$ (see Fig.~1) using the Taurus Tunable Filter (on the WHT, Tadhunter
et al. 2000).  A striking match between the ionized gas and the radio
structures (see Fig.~1) makes the origin of the ionized gas even more puzzling
and {\sl strongly suggests the presence of a complex interaction between the radio
structure and the gas around Coma~A}.

\section{HI observations with the Westerbork Synthesis Radio Telescope}

We have observed Coma A at the frequency of the redshifted \HI\ line (1343
MHz) with the WSRT using 10 MHz bandwidth and a velocity resolution of $\sim
20$ km s$^{-1}$.  At the resolution of our observations (about 13 arcsec), the
radio structure of Coma A appears just resolved in two structures
corresponding to the northern and southern lobes.  The preliminary results
show that we have detected \HI\ in absorption against {\sl both radio lobes}.
In both lobes the peak of the absorption is at a very low optical depth
($\sim 0.4$ \%).  This low optical depth is likely to be due (at least in part) to
dilution.  The velocity of the absorption is about 200 km s\( ^{-1} \)
redshifted for the northern lobe and between 100 and 150 km s\( ^{-1} \)
blueshifted for the southern lobe compared to the systemic velocity.  The FWHM
is between 150 and 200 km s\( ^{-1} \).  Assuming a spin temperature of 100 K,
this gives a column density of \( 5\cdot 10^{19} \) atoms cm\( ^{-2} \). 
Velocities of the ionized gas derived from a slit aligned with the radio axis
show the same trend with position.  Thus, {\sl the HI appears kinematically
associated with the ionized gas}. 

% Fig. 1
%\begin{figure}
\centerline{\psfig{figure=morganti.fig1.ps,height=6.0cm,angle=-90}}
{\it {\bf Fig.1} Panel showing the approximate location of the \HI\ absorption.
In the plots, the dashed line  represents the systemic velocity.
In the middle, is the H$\alpha$ image with superimposed the contours from a
20cm VLA image.}


\subsection{Preliminary conclusions}


One of the very few objects in which spatially extended 21-cm \HI\ absorption
has been detected against the radio lobes is the central radio galaxy in the
cooling flow cluster Abell 2597 (O'Dea et al. 1994).  This has been
interpreted as indication that the radio lobes are surrounded by a collection
of clouds containing both neutral and ionized gas.
The same could apply to Coma A, with the main difference that {\sl the scale of the
phenomena is larger} (several tens of kpc instead of few kpc).  Indeed, in the
case of Coma A, the complicated H\( \alpha \) structure has been explained by
a particularly gas rich environment surrounding the galaxy and that the close
morphological association is due to the radio lobes expanding into this
gas-rich environment (Tadhunter et al. 2000). The detected \HI\ would just
be part of this system.

Coma A could be the result of interactions/mergers between the dominant giant
galaxy and less massive galaxies in the same group.  Although we cannot yet
say how spatially extended the observed absorption is, it is quite likely
that Coma A indeed possesses extended \HI\ structures. 



% comment this out if you want to include acknowledgements

%\acknowledgements

\begin{references}
{\small
\reference Tadhunter C.N., Villar-Martin M., Morganti R., Axon D. 2000, \mnras, 314, 849
\reference van Breugel W., Miley G., Heckman T., Butcher H., Bridle A. 1985, \apj, 290, 496
\reference O'Dea C., Baum S., Gallimore J., 1994, \apj, 436, 669

}
\end{references}

\end{document}

% OK, you're done. Now:
%   __ Make sure you can successfully LaTeX your contribution and
%      produce a postscript file from it, including figures.  Make sure
%      the the postscript file so produce can be successfully printed out.
%    
%   __ Check your paper carefully, making sure to obey the pagelimits,
%      and that no figures plot into the margins. The final version 
%      must be photo-ready, and anything in the margins will not 
%      be reproduced. 
% 
%   __ if possible, tar and gzip the completed tex file, the resulting 
%      postscript file, and any accompanying figures, and rename the 
%      gzipped tar file to [yourlastname firstinitial].tar.gz
%      (if you can't tar or gzip, just ftp the whole mess) 
%    
%   __ anonymous ftp the gzipped tar file to the directory 
%      Incoming/vla2000 on the node ftp.cv.nrao.edu:
%          % ftp ftp.cv.nrao.edu (or ftp 192.33.115.108)
%       ftp> [log in as anonymous]
%       ftp> [use your email address as the password]
%       ftp> cd Incoming/vla2000
%       ftp> bin
%       ftp> put [yourlastname firstinitial].tar.gz
%       ftp> [exit]
