A Breakthrough in Astronomical Software Development
Margaret Meixner\altaffilmark{1}
Letizia Stanghellini
% Howard Bond
% and the start of your text. \begin{abstract} % Leave intact % Place the text of your abstract here - NO BLANK LINES We have measured the expansion velocities and proper motion of the ansae in NGC\,7009 using high dispersion echelle spectra and archive narrow band HST images. Assuming that the ansae are moving at equal and opposite velocities from the central star we obtain an average system radial velocity of $-54 \pm 2$ km/s, the eastern ansa approaching and the western ansa receding at $v_r=5.5 \pm 1$ km/s relative to this value. Only the proper motion of the eastern ansa could be measured, leading to $2.8 \pm 0.8$ arcsec/century, or $v_t=(130 \pm 40)d$ km/s, where $d$ is the distance to the nebula in $kpc$. Additionally, the electron temperature and density for each ansa was measured using line intensity ratios. The results are $T_e \sim 9000$ K and $n_e \sim 2000$ $cm^{-3}$ for both ansae within the errors.
fernandez.tex
%APN3_PROCEEDINGS_FORM%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
% TEMPLATE.TEX -- APN3 (2003) ASP Conference Proceedings template.
%
% Derived from ADASS VIII (98) ASP Conference Proceedings template
% Updated by N. Manset for ADASS IX (99), F. Primini for ADASS 2000,
% D.Bohlender for ADASS 2001, and H. Payne for ADASS XII and LaTeX2e.
%
% Use this template to create your proceedings paper in LaTeX format
% by following the instructions given below.  Much of the input will
% be enclosed by braces (i.e., { }).  The percent sign, "%", denotes
% the start of a comment; text after it will be ignored by LaTeX.
% You might also notice in some of the examples below the use of "\ "
% after a period; this prevents LaTeX from interpreting the period as
% the end of a sentence and putting extra space after it.
%
% You should check your paper by processing it with LaTeX.  For
% details about how to run LaTeX as well as how to print out the User
% Guide, consult the README file.  You should also consult the sample
% LaTeX papers, sample1.tex and sample2.tex, for examples of including
% figures, html links, special symbols, and other advanced features.
%
% If you do not have access to the LaTeX software or a laser printer
% at your site, you can still prepare your paper following the
% instructions in the User Guide.  In such cases, the editors will
% process the file and make any necessary editorial adjustments.
%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
\documentclass[11pt,twoside]{article}  % Leave intact
\usepackage{apn3conf}

% If you have the old LaTeX 2.09, and not the current LaTeX2e, comment
% out the \documentclass and \usepackage lines above and uncomment
% the following:

%\documentstyle[11pt,twoside,apn3conf]{article}

\begin{document}   % Leave intact


%-----------------------------------------------------------------------
%		            Paper Title
%-----------------------------------------------------------------------
% Enter the title of the paper.
%
% EXAMPLE: \title{A Breakthrough in Astronomical Software Development}
%
% If your title is so long as to fill the page header when you print it,
% then please supply a short form as a \titlemark.
%
% EXAMPLE:
%  \title{Rapid Development for Distributed Computing, with Implications
%         for the Virtual Observatory}
%  \titlemark{Rapid Development for Distributed Computing}
%

\title{Kinematics and Proper Motion of the Ansae in NGC\,7009}
%\titlemark{ }

%-----------------------------------------------------------------------
%		          Authors of Paper
%-----------------------------------------------------------------------
% Enter the authors followed by their affiliations.  The \author and
% \affil commands may appear multiple times as necessary (see example
% below).  List each author by giving the first name or initials first
% followed by the last name.  Authors with the same affiliations
% should grouped together.
%
% EXAMPLE: \author{Margaret Meixner\altaffilmark{1}, Letizia Stanghellini,
%			Howard Bond}
%          \affil{Space Telescope Science Institute,
%                 3700 San Martin Dr.,  Baltimore, MD 21218}
%          \author{Joel Kastner}
%          \affil{Rochester Institute of Technology}
%
%          \altaffiltext{1}{Astronomy Department, UIUC}
%
% In this example, the first three authors, "Meixner", "Stanghellini", and
% "Bond" are affiliated with "STScI".  "Meixner" has an alternate
% affiliation with the "Astronomy Department at UIUC".  The fourth author,
% "Kastner", is affiliated with "Rochester Institute of Technology"

\author{Rodrigo Fern\'andez, Hugo E. Schwarz, Hektor Monteiro}
\affil{Cerro Tololo Inter-American Observatory, NOAO-AURA, Casilla 603, 
La Serena, Chile}

%-----------------------------------------------------------------------
%			 Contact Information
%-----------------------------------------------------------------------
% This information will not appear in the paper but will be used by
% the editors in case you need to be contacted concerning your
% submission.  Enter your name as the contact along with your email
% address.
%
% EXAMPLE:  \contact{Dennis Crabtree}
%           \email{crabtree@cfht.hawaii.edu}
%

\contact{Rodrigo Fern\'andez}
\email{rafernan@puc.cl}

%-----------------------------------------------------------------------
%		      Author Index Specification
%-----------------------------------------------------------------------
% Specify how each author name should appear in the author index.  The
% \paindex{ } should be used to indicate the primary author, and the
% \aindex for all other co-authors.  You MUST use the following
% syntax:
%
% SYNTAX:  \aindex{LASTNAME, F. M.}
%
% where F is the first initial and M is the second initial (if
% used).  This guarantees that authors that appear in multiple papers
% will appear only once in the author index.
%
% EXAMPLE: \paindex{Crabtree, D.}
%          \aindex{Manset, N.}
%          \aindex{Veillet, C.}
%
% NOTE: this information is also used to build the author list that
% appears in the table of contents.  Authors will be listed in the order
% of the \paindex and \aindex commmands.
%

\paindex{Fern\'andez, R.}
\aindex{Schwarz, H.}     % Remove this line if there is only one author
\aindex{Monteiro, H.}

%-----------------------------------------------------------------------
%		      Author list for page header
%-----------------------------------------------------------------------
% Please supply a list of author last names for the page header. in
% one of these formats:
%
% EXAMPLES:
% \authormark{LASTNAME}
% \authormark{LASTNAME1 \& LASTNAME2}
% \authormark{LASTNAME1, LASTNAME2, ... \& LASTNAMEn}
% \authormark{LASTNAME et al.}
%
% Use the "et al." form in the case of seven or more authors, or if
% the preferred form is too long to fit in the header.

\authormark{Fern\'andez, Schwarz \& Monteiro}

%-----------------------------------------------------------------------
%			Subject Index keywords
%-----------------------------------------------------------------------
% Enter up to 6 keywords describing your paper.  These will NOT be
% printed as part of your paper; however, they will be used to
% generate an object index and a subject index for the proceedings.
% There is no standard list,  however, individual object names are
% encouraged and one or two word descriptions of the topics (e.g.MHD,
% ionized gas) are useful.
%
% EXAMPLE:  \keywords{NGC 7027, AFGL 2688, HD 161796, binary stars,
%                      dust,  molecular gas}
%

\keywords{NGC\,7009, ansae}

%-----------------------------------------------------------------------
%			       Abstract
%-----------------------------------------------------------------------
% Type abstract in the space below.  Consult the User Guide and Latex
% Information file for a list of supported macros (e.g. for typesetting
% special symbols). Do not leave a blank line between \begin{abstract}
% and the start of your text.

\begin{abstract}          % Leave intact
% Place the text of your abstract here - NO BLANK LINES
We have measured the expansion velocities and proper motion of the
ansae in NGC\,7009 using high dispersion echelle spectra and archive
narrow band HST images. Assuming that the ansae are moving at equal
and opposite velocities from the central star we obtain an average
system radial velocity of $-54 \pm 2$ km/s, the eastern ansa
approaching and the western ansa receding at $v_r=5.5 \pm 1$ km/s
relative to this value. Only the proper motion of the eastern ansa
could be measured, leading to $2.8 \pm 0.8$ arcsec/century, or
$v_t=(130 \pm 40)d$ km/s, where $d$ is the distance to the nebula in
$kpc$. Additionally, the electron temperature and density for each
ansa was measured using line intensity ratios.  The results are $T_e
\sim 9000$ K and $n_e \sim 2000$ $cm^{-3}$ for both ansae within the errors.
\end{abstract}

%-----------------------------------------------------------------------
%			      Main Body
%-----------------------------------------------------------------------
% Place the text for the main body of the paper here.  You should use
% the \section command to label the various sections; use of
% \subsection is optional.  Significant words in section titles should
% be capitalized.  Sections and subsections will be numbered
% automatically.
%
% EXAMPLE:  \section{Introduction}
%           ...
%           \subsection{Our View of the World}
%           ...
%           \section{A New Approach}
%
% It is recommended that you look at the sample papers, sample1.tex
% and sample2.tex, for examples for formatting references, footnotes,
% figures, equations, html links, lists, and other special features.

\section{Introduction}

NGC\,7009 is a good example of a planetary nebula with
FLIERs\footnote{Fast, Low Ionization Emission Regions (Balick et
al. 1994).}  The nebula shows two pairs of condensations along the
major symmetry axis. The outer pair has been called
\emph{ansae} (=handles, Aller 1941). The condensations show strong 
emission in low ionization lines and weak emission in high excitation
ones. Kinematic studies by Reay \& Atherton~(1985) and Balick, Preston
\& Icke~(1987) have shown that the ansae are moving very near the
plane of the sky at velocities $\sim 10^2$ km/s with respect to the
central star.  Here we aim to better determine the kinematics of the
ansae in NGC\,7009, measuring radial velocities from high dispersion
echelle spectra and proper motions from archive HST images. As a
by-product, the electron temperatures and densities are measured from
line intensity ratios.

\section{Observations and Data Reduction}

The data consist of a set of echelle spectra and two
sets of public HST images taken in 1996 and 2001.  The spectra were
obtained during the night of July\,29, 2002, with the CTIO 4m echelle
spectrograph, which was optimized to cover the spectral range 410\,nm
- 720\,nm. The dimensions of the slit were $1.2\arcsec \times
6.6\arcsec$, and the mean seeing was $1.4\arcsec$. For wavelength
calibration a Th-Ar lamp was used. The flux calibration was done with
observations of the star 58\,Aql (HR\,7596).

The HST images were obtained from the HST archive. The first set was
taken on April\,28, 1996 using the WFPC2 with a [NII]\,6583 narrow band
filter (Balick et al.\,1998). The second set was taken in May\,11, 2001
also with the WFPC2 and the same filter (Palen et al.\,2002).

The echelle spectra were reduced and calibrated using standard IRAF
routines. The dispersion is 0.008\,nm\,pixel$^{-1}$, or
3.7\,km.s$^{-1}$.pixel$^{-1}$ at 650\,nm. The HST images were
retrieved from the archive using the \emph{On The Fly Calibration}
option. The calibrated images of each set were median combined to
eliminate cosmic rays.

\section{Results}

\subsection{Radial Velocities}

The lines that could be identified in the spectra are listed in Table
\ref{spectra}. The central wavelength of each line was measured by
fitting a Voigt profile. Almost every line could be identified in two
echelle orders, thus the value quoted is the average of the two values
in each order. The rest wavelengths of forbidden lines were taken from
Bowen\,(1960), while the values for the permitted lines were taken from
Moore\,(1945). Assuming symmetric expansion with respect to the central
star, the system velocity is the average of the ansae's velocities,
namely $-54\pm 2$\,km.s$^{-1}$, whereas the radial expansion velocity with
respect to the central star is $v_r = \pm 5.5$ km/s.

\begin{deluxetable}{llcc}
\tablecaption{Radial velocities for identified emission lines.}
\tablehead{Line & $\lambda$(nm) & Eastern Ansa (km.s$^{-1}$) & 
Western Ansa (km.s$^{-1}$)}
\startdata
$[$NII$]$ & 575.5 & -59.17 & -47.70\\
HeI       & 587.6 & -56.42 & -48.51\\
$[$OI$]$  & 636.4 & -62.23 & -50.44\\
$[$OI$]$  & 630.0 & -61.19 & -49.05\\
$[$NII$]$ & 654.8 & -59.33 & -48.34\\
H$\alpha$ & 656.3 & -56.69 & -48.46\\
$[$NII$]$ & 658.3 & -57.87 & -46.48\\
$[$SII$]$ & 671.6 & -57.68 & -45.34\\
$[$SII$]$ & 673.1 & -56.83 & -45.46\\
$[$AIII$]$& 713.4 & -57.60 & -48.97\\
\noalign{\smallskip}
{\bf Average} &  & -58.55 $\pm$ 1.9 & -47.82$\pm$ 1.6\\
\enddata
\label{spectra}
\end{deluxetable}

\subsection{Proper Motions}

The HST images have a shift between 1996 and 2001 of $20\arcsec$ in
the east-west direction, which makes the western ansa disappear from
the 2001 images. Therefore, only the proper motion of the eastern ansa
could be measured.  The position of the ansa was determined by
confining it in a box of width $5\arcsec$ and calculating a
centroid. Three stars were selected as reference points for angular
displacement measurements, namely the central star and two background
stars. The results for the angular displacements are listed in Table
\ref{angdisp}. A fourth reference point was determined by looking for
a point that minimized the square of the distances between the three
reference stars, weighted by the error in each position. The angular
displacement relative to this point is listed as \emph{Least
squares}. An average between the displacements with respect to each
star is also listed.  The proper motion is obtained by dividing the
corresponding angular displacement by the time difference between both
set of images, nl. 5.038170123 yrs. All displacements occur in the
same direction, outward from the central star.  Using the least
squares value for the proper motion, one gets a tangential velocity of
$v_t = (130\pm 32) d$ km/s, where $d$ is the distance to the nebula in
kpc.  Computing a weighted average of 14 values from the literature
(Acker et al.\,1992) gave 0.86kpc or $v_t =(112\pm 32) $ km/s

\begin{deluxetable}{lcc}
\tablecaption{Angular displacement and proper motion of the eastern ansa, 
using different reference points}
\tablehead{Ref. point & Ang. displacement (\arcsec) & Prop. motion 
(\arcsec/yr)}
\startdata
Central star & $0.17\pm 0.10$ & $0.03\pm 0.02$\\
Background star 1 & $0.16\pm 0.10$ & $0.03\pm 0.02$\\
Background star 2 & $0.10\pm 0.02$ & $0.020\pm 0.004$\\
Average & $0.13\pm 0.04$ & $0.026\pm 0.008$\\
Least squares & $0.14\pm 0.04$ & $0.028\pm 0.008$
\enddata
\label{angdisp}
\end{deluxetable}

\subsection{Line intensities, Electron Temperatures and Densities}

The line intensities of the [NII] and [SII] lines were measured in
order to derive the electron temperature and density in both
ansae. Voigt profiles were fitted to each line using the IRAF task
\emph{splot}. The interstellar extinction correction was made assuming
a recombination model B with $T = 10^4$\,K and $n_e =
10^4$\,cm$^{-3}$, and an extinction coefficient $c_\beta\,=\,0.26$
(Lame \& Pogge\,1996). The line intensity ratios together with electron
temperatures and densities derived from them are listed in Table
\ref{Tne}. The latter results were obtained using the formulae from
McCall\,(1984).  The errors in the ratios were calculated from the S/N
in each line.

\begin{table}[!htb]
\caption{Line intensity ratios and results obtained from them. 
$T_e$ and $n_e$ are the electron temperature
and density, respectively.}
\begin{tabular}{lccl}
\noalign{\bigskip}
\noalign{\emph{Eastern ansa}}
\noalign{\smallskip}
Ratio &                     Observed &       Corrected &        Result\\
\noalign{\smallskip}
\hline
\noalign{\smallskip}
$[$NII$]$(6548+6583)/5755 &      $111 \pm 15$ &       $103 \pm 15$ &     
   $T_e = 9000 \pm 400$ K\\
\noalign{\smallskip}
$[$SII$]$ 6716/6730 &           $0.67 \pm 0.04$ &    $0.67 \pm 0.04$ &   
   $n_e = 2600 \pm 500$ $cm^{-3}$\\
\noalign{\smallskip}
\hline
\noalign{\vspace{0.3in}}
\noalign{\emph{Western Ansa}}
\noalign{\smallskip}
Ratio &                     Observed &       Corrected &        Result\\
\noalign{\smallskip}
\hline
\noalign{\smallskip}
$[$NII$]$(6548+6583)/5755 &      $120 \pm 12$ &      $110 \pm 12$ &      
    $T_e = 8900 \pm 400$ K\\
\noalign{\smallskip}
$[$SII$]$ 6716/6730  &          $0.64 \pm 0.04$ &    $0.64 \pm 0.04$ &   
     $n_e = 1900 \pm 300$ $cm^{-3}$\\
\noalign{\smallskip}
\hline
\end{tabular}
\label{Tne}
\end{table}


\section{Comparison with previous results}

The results for the radial velocities are in good agreement with
previous determinations. If we take only the results for the [OI] 6300
line, we get a result equal within the errors to that of Reay \&
Atherton\,(1984), who measured $v_r\,=\,\pm 6.2$\,km.s$^{-1}$ with
respect to the central star using a Fabry-Perot interferometer.  The
only available measurement of proper motion is that of Liller\,(1965),
who obtained 1.6\,\arcsec/century using photographic plates, which is
almost a factor of two smaller than the result obtained here. The
electron temperatures are equal within the errors to those reported by
Balick et al.\,(1994) and Bohigas et al.\,(1994), while the electron
density is within a factor of two from the results of the same
authors.

We conclude that the ansae are moving with total velocity
$V\,=\,\sqrt{v_r^2\,+\,v_t^2} \simeq v_t\,=\,(130\pm 32)d$
km.s$^{-1}$, at an angle $i\,=\,\arctan{v_r/V}\,=\,2\pm\,1.6\,^o$ with
respect to the plane of the sky.

\acknowledgments

This work was done as part of the \emph{Programa de Investigaci\'on en
Astronom\'\i a} (PIA) for chilean students at CTIO.


%-----------------------------------------------------------------------
%			      References
%-----------------------------------------------------------------------
% List your references below within the reference environment
% (i.e. between the \begin{references} and \end{references} tags).
% Each new reference should begin with a \reference command which sets
% up the proper indentation.  Observe the following order when listing
% bibliographical information for each reference:  author name(s),
% publication year, journal name, volume, and page number for
% articles.  Note that many journal names are available as macros; see
% the User Guide listing "macro-ized" journals.
%
% EXAMPLE:  \reference Hagiwara, K., \& Zeppenfeld, D.\  1986,
%                Nucl.Phys., 274, 1
%           \reference H\'enon, M.\  1961, Ann.d'Ap., 24, 369
%           \reference King, I.\ R.\  1966, \aj, 71, 276
%           \reference King, I.\ R.\  1975, in Dynamics of Stellar
%                Systems, ed.\ A.\ Hayli (Dordrecht: Reidel), 99
%
% Note the following tricks used in the example above:
%
%   o  \& is used to format an ampersand symbol (&).
%   o  \'e puts an accent agu over the letter e.  See the User Guide
%      and the sample files for details on formatting special
%      characters.
%   o  "\ " after a period prevents LaTeX from interpreting the period
%      as an end of a sentence.
%   o  \aj is a macro that expands to "Astron. J."  See the User Guide
%      for a full list of journal macros
%
\begin{references}
\reference Acker, A., et al. 1992 ``Strasbourg-ESO catalogue of Galactic PNe''
\reference Aller, L.\ H.\ 1941, \apj, 93, 236
\reference Balick, B.\, Preston, H.\ \& Icke, V.\ 1987, \aj, 94, 1641
\reference Balick, B.\ et al. 1994, \apj, 424, 800
\reference Balick, B.\ et al 1998, \aj, 116, 360
\reference Bowen, I.\ 1960, \apj, 132, 1
\reference Lame, N.\ \& Pogge, R.\ 1996, \aj, 111, 2320
\reference Liller, W.\ 1965, \pasp, 104, 533
\reference McCall, M.\ 1984, \mnras, 208, 253
\reference Moore, C.\ ``A Multiplet Table of Astrophysical Interest", 
Cont. of the Princeton U. Obs., No. 20, 1945.
\reference Palen, S.\ et al. 2002, \aj,  123, 2666
\reference Reay, N.\ K.\ \& Atherton, P.\ D.\ 1985, \mnras, 215, 233


\end{references}

% Do not place any material after the references section

\end{document}  % Leave intact
