Constraining the local radiation field and the grain size distribution in dust SED modelling of dwarf galaxies
Fr\'ed\'eric {\sc Galliano}
I present a simple self-consistent dust spectral energy distribution (SED) model that has been applied to fit the well-sampled observed UV-to-radio SED of four nearby starbursting dwarf galaxies. The main originality of this model is that numerous multi-wavelength observations, from UV to millimeter (mm), constrain in a self-consistent manner, both the local radiation field and the grain size distribution. I finally present the results of our model and discuss the average dust properties in these dwarf galaxies.
aipcheck.tex
%
% $Id: aipcheck.tex,v 1.7 2002/01/11 19:50:46 frank Exp $
%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% Testing for potential problems with this class
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

\newif\ifproblem
\newif\iftimesok

\makeatletter
\def\IfStandaloneCheck{\def\next{aipcheck}
  \edef\currjob{\jobname}
  \edef\next{\meaning\next}
  \edef\currjob{\meaning\currjob}
  \ifx\currjob\next
    \expandafter\@firstoftwo
  \else
    \expandafter\@secondoftwo
  \fi
}
\makeatother

\typeout{***********************************************}
\typeout{*}
\typeout{* Testing if all files required for the aipproc}
\typeout{* class are available ...}
\typeout{*}
\typeout{***********************************************}

\typeout{*}
\typeout{* Looking for LaTeX2e ... }
\ifx\documentclass\undefined
 \typeout{*}
 \typeout{* Sorry this is a fatal error:}
 \typeout{*}
 \typeout{* The aipproc class can only be used with LaTeX2e which is}
 \typeout{* the standard LaTeX since 1994!}
 \typeout{*}
 \typeout{* Please make sure that your version of LaTeX is up-to-date}
 \typeout{* before attempting to use this class.}
 \typeout{*}
 \expandafter\stop
\else
 \typeout{* ... ok }
\fi


\def\next#1/#2/#3\next{#1#2}
\typeout{*}
\typeout{* Testing that LaTeX2e is not too old ... }
\ifnum\expandafter\next\fmtversion\next<199612 \relax
 \typeout{* ... what a vintage! }
 \typeout{*}
 \typeout{* Sorry this is a fatal error:}
 \typeout{*}
 \typeout{* The aipproc class can only be used with a recent version}
 \typeout{* of LaTeX2e. Your version is dated \fmtversion\space --- but}
 \typeout{* at least the 1996/12/01 version is required!}
 \typeout{*}
 \typeout{* Please make sure that your version of LaTeX is up-to-date}
 \typeout{* before attempting to use this class.}
 \typeout{*}
 \expandafter\stop
\else
 \ifnum\expandafter\next\fmtversion\next<199806 \relax
   \typeout{* ... probably ok }
   \typeout{*}
   \typeout{* Your version of LaTeX2e is quite old --- the aipproc class}
   \typeout{* hasn't been tested with your release.}
   \typeout{*}
   \typeout{* We believe that it will probably work, but if you encounter}
   \typeout{* problems you will need upgrade your installation.}
   \typeout{*}
   \typein{* Type <return> to continue ...}
   \problemtrue
 \else
   \typeout{* ... ok }
 \fi
\fi


\typeout{*}
\typeout{* Looking for aipproc.cls ... }
\IfFileExists{aipproc.cls}
    {
     \typeout{* ... ok }
    }
    {
     \typeout{* ... not found! }
     \typeout{*}
     \typeout{* Sorry this is a fatal error:}
     \typeout{*}
     \typeout{* Before you can use the aipproc class you have to unpack}
     \typeout{* it from the documented source.}
     \typeout{*}
     \typeout{* Run LaTeX on the file 'aipproc.ins', e.g.,}
     \typeout{*}
     \typeout{* \space\space latex aipproc.ins}
     \typeout{*}
     \typeout{* or whatever is necessary on your installation to process}
     \typeout{* a file with LaTeX. This should unpack a number of files for you:}
     \typeout{*}
     \typeout{* aipproc.cls \space and \space aip-*.clo}
     \typeout{*}
     \typeout{* After that retry processing this guide.}
     \typeout{*}
     \stop
}

\typeout{*}
\typeout{* Looking for aipxfm.sty ... }
\IfFileExists{aipxfm.sty}
    {
     \typeout{* ... ok }
    }
    {
     \typeout{* ... not found! }
     \typeout{*}
     \typeout{* Sorry this is a fatal error:}
     \typeout{*}
     \typeout{* The aipxfm.sty file which is part of the aipproc distribution}
     \typeout{* must be installed in a directory which is searched by LaTeX.}
     \typeout{*}
     \typeout{* Please install this file and retry.}
     \typeout{*}
     \stop
}

\typeout{*}
\typeout{* Looking for aip-8s.clo ... }
\IfFileExists{aip-8s.clo}
    {
     \typeout{* ... ok }
    }
    {
     \typeout{* ... not found! }
     \typeout{*}
     \typeout{* Sorry this is a fatal error:}
     \typeout{*}
     \typeout{* The aip-8s.clo file which is part of the aipproc distribution}
     \typeout{* must be installed in a directory which is searched by LaTeX.}
     \typeout{*}
     \typeout{* Please install this file and retry.}
     \typeout{*}
     \stop
}

\typeout{*}
\typeout{* Looking for aip-8d.clo ... }
\IfFileExists{aip-8d.clo}
    {
     \typeout{* ... ok }
    }
    {
     \typeout{* ... not found! }
     \typeout{*}
     \typeout{* Sorry this is a fatal error:}
     \typeout{*}
     \typeout{* The aip-8d.clo file which is part of the aipproc distribution}
     \typeout{* must be installed in a directory which is searched by LaTeX.}
     \typeout{*}
     \typeout{* Please install this file and retry.}
     \typeout{*}
     \stop
}


\typeout{*}
\typeout{* Looking for aip-6s.clo ... }
\IfFileExists{aip-6s.clo}
    {
     \typeout{* ... ok }
    }
    {
     \typeout{* ... not found! }
     \typeout{*}
     \typeout{* Sorry this is a fatal error:}
     \typeout{*}
     \typeout{* The aip-6s.clo file which is part of the aipproc distribution}
     \typeout{* must be installed in a directory which is searched by LaTeX.}
     \typeout{*}
     \typeout{* Please install this file and retry.}
     \typeout{*}
     \stop
}


\typeout{*}
\typeout{* Looking for aip-arlo.clo ... }
\IfFileExists{aip-arlo.clo}
    {
     \typeout{* ... ok }
    }
    {
     \typeout{* ... not found! }
     \typeout{*}
     \typeout{* Sorry this is a fatal error:}
     \typeout{*}
     \typeout{* The aip-arlo.clo file which is part of the aipproc distribution}
     \typeout{* must be installed in a directory which is searched by LaTeX.}
     \typeout{*}
     \typeout{* Please install this file and retry.}
     \typeout{*}
     \stop
}

\typeout{*}
\typeout{* Looking for fixltx2e.sty ... }
\IfFileExists{fixltx2e.sty}
    {
     \typeout{* ... ok }
    }
    {
     \typeout{* ... not found, trying fix2col.sty instead ... }
     \typeout{*}
     \IfFileExists{fix2col.sty}
	 {
	  \typeout{* ... ok }
	 }
	 {
	  \typeout{* ... not found! }
	  \typeout{*}
	  \typeout{* Sorry this is a fatal error:}
	  \typeout{*}
	  \typeout{* Your LaTeX distribution contains neither fixltx2e.sty}
	  \typeout{* nor fix2col.sty.}
	  \typeout{*}
	  \typeout{* This means that it is either too old or incompletely}
	  \typeout{* installed.}
	  \typeout{*}
	  \typeout{* fixltx2e.sty is part of the standard LaTeX distribution}
	  \typeout{* since 1999; fix2col.sty is an earlier version of this}
	  \typeout{* package.}
	  \typeout{*}
	  \typeout{* Best solution is to get the latest LaTeX distribution.}
	  \typeout{* If this is impossible for you, download fix2col.sty.}
	  \typeout{* You can get this software from a CTAN host.}
          \typeout{* Refer to http://www.ctan.org and search for "fix2col".}
	  \typeout{*}
	  \typeout{* After you have updated your LaTeX distribution}
	  \typeout{* retry processing this guide.}
	  \stop
     }
}

\typeout{*}
\typeout{* Looking for fontenc.sty ... }
\IfFileExists{fontenc.sty}
    {
     \typeout{* ... ok }
    }
    {
     \typeout{* ... not found! }
     \typeout{*}
     \typeout{* Sorry this is a fatal error:}
     \typeout{*}
     \typeout{* The fontenc package, which is part of standard LaTeX}
     \typeout{* (base distribution) has to be installed at the site to}
     \typeout{* run the aipproc class.}
     \typeout{*}
     \typeout{* The fact that it cannot be found either means that}
     \typeout{* this LaTeX release is too old or that it was installed}
     \typeout{* improperly.}
     \typeout{*}
     \typeout{* Please make sure that your version of LaTeX is okay}
     \typeout{* before attempting to use this class. The LaTeX distribution}
     \typeout{* contains the file "ltxcheck.tex" which can be used to}
     \typeout{* test the basic functionality and integrity of your installation.}
     \typeout{*}
     \stop
    }

\typeout{*}
\typeout{* Looking for calc.sty ... }
\IfFileExists{calc.sty}
    {
     \typeout{* ... ok }
    }
    {
     \typeout{* ... not found! }
     \typeout{*}
     \typeout{* Sorry this is a fatal error:}
     \typeout{*}
     \typeout{* The calc package, which is part of standard LaTeX}
     \typeout{* (tool distribution) has to be installed at the site}
     \typeout{* to run the aipproc class.}
     \typeout{*}
     \typeout{* The fact that it cannot be found either means that}
     \typeout{* this LaTeX release is too old or that it was installed}
     \typeout{* only in parts.}
     \typeout{*}
     \typeout{* Please make sure that the tools distribution of LaTeX}
     \typeout{* is installed before attempting to use this class.}
     \typeout{*}
     \typeout{* (You might be able to get calc.sty separately for your}
     \typeout{* installation if you are unable to upgrade to a recent}
     \typeout{* distribution for some reason.)}
     \typeout{*}
     \stop
    }

\typeout{*}
\typeout{* Looking for varioref.sty ... }
\IfFileExists{varioref.sty}
    {
     \typeout{* ... ok }
     \gdef\variorefoptionifavailable{varioref,}
    }
    {
     \typeout{* ... not found! }
     \typeout{*}
     \typeout{* Problem detected:}
     \typeout{*}
     \typeout{* The varioref package, which is part of standard LaTeX}
     \typeout{* (tool distribution) is not installed at this site.}
     \typeout{*}
     \typeout{* The fact that it cannot be found either means that}
     \typeout{* this LaTeX release is too old or that it was installed}
     \typeout{* only in parts.}
     \typeout{*}
     \typeout{* You can use the aipproc class without this package but }
     \typeout{* you cannot make use of the options "varioref" or "nonvarioref".}
     \typeout{*}
     \typeout{* Please also note that the aipguide.tex documentation}
     \typeout{* normally uses the "varioref" option to show its}
     \typeout{* effects (which  will now fail).}
     \typeout{*}
     \typein{* Type <return> to continue ...}
     \problemtrue
     \gdef\variorefoptionifavailable{}
     \let\vpageref\pageref
     \let\vref\ref
    }

\typeout{*}
\typeout{* Looking for times.sty ... }
\IfFileExists{times.sty}
    {
     \begingroup
% load times and forget it immediately again
       \RequirePackage{times}
       \global\expandafter\let\csname ver@times.sty\endcsname\relax    
       \long\def\next{ptm}
       \ifx\rmdefault\next
         \typeout{* ... ok }
         \gdef\psnfssproblemoption{}
         \endgroup
         \timesoktrue
       \else
         \endgroup
     \typeout{* ... obsolete! }
     \typeout{*}
     \typeout{* Serious problem detected:}
     \typeout{*}
     \typeout{* The times package, which is part of standard LaTeX}
     \typeout{* (psnfss distribution) is obsolete at this site.}
     \typeout{*}
     \typeout{* The fact that it contains incorrect code either means that}
     \typeout{* this LaTeX release is too old or that it was installed}
     \typeout{* only in parts with old files remaining!}
     \typeout{*}
     \typeout{* You can use the aipproc class without this package but}
     \typeout{* you have to specify the option "cmfonts" which result in}
     \typeout{* documents which are not conforming to the AIP layout specification!}
     \typeout{*}
     \typeout{* You can also try using the class in the following way:}
     \typeout{*}
     \typeout{* \space\space \string\documentclass[cmfonts]{aipproc}}
     \typeout{* \space\space \string\usepackage{times}}
     \typeout{* \space\space ...}
     \typeout{*}
     \typeout{* With luck this will result in Times Roman output but chances}
     \typeout{* are that you will get a larger number of error messages in}
     \typeout{* which case you have to remove the \string\usepackage declaration.}
     \typeout{*}
     \typein{* Type <return> to continue ...}
          \problemtrue
          \gdef\psnfssproblemoption{cmfonts}
          \def\textdegree{$^\circ$}            % used below but now
                                               % not setup
       \fi
    }
    {
     \typeout{* ... not found! }
     \typeout{*}
     \typeout{* Serious problem detected:}
     \typeout{*}
     \typeout{* The times package, which is part of standard LaTeX}
     \typeout{* (psnfss distribution) can not be found.}
     \typeout{*}
     \typeout{* The fact that this package cannot be found either means that}
     \typeout{* this LaTeX release is too old or that it was installed}
     \typeout{* only in parts!}
     \typeout{*}
     \typeout{* You can use the aipproc class without this package but }
     \typeout{* you have to specify the option "cmfonts" which result in}
     \typeout{* documents which are not conforming to the AIP layout specification!}
     \typeout{*}
     \typein{* Type <return> to continue ...}
     \problemtrue
     \gdef\psnfssproblemoption{cmfonts,}
    }

\iftimesok % don't bother testing other font options if times already
           % bad

\typeout{*}
\typeout{* Looking for t1ptm.fd or T1ptm.fd ... }
\IfFileExists{t1ptm.fd}
    {
     \typeout{* ... ok }
    }
    {
     \typeout{* ... not found, trying T1ptm.fd ... }
     \IfFileExists{T1ptm.fd}
          {
           \typeout{* ... ok }
          }
          {
           \typeout{* ... not found}
           \typeout{* Serious problem detected:}
           \typeout{*}
           \typeout{* The times package, which is part of standard LaTeX}
           \typeout{* (psnfss distribution) is available but the corresponding}
           \typeout{* .fd file (defining how to load Times Roman) is missing.}
           \typeout{*}
           \typeout{* The fact that this package is only partially installed}
           \typeout{* means that you LaTeX installation is unable to use Times}
           \typeout{* Roman fonts!}
           \typeout{*}
           \typeout{* You can use the aipproc class without this package but }
           \typeout{* you have to specify the option "cmfonts" which result in}
           \typeout{* documents which are not conforming to the AIP layout}
           \typeout{* specification!}
           \typeout{*}
           \typein{* Type <return> to continue ...}
           \problemtrue
           \timesokfalse
           \gdef\psnfssproblemoption{cmfonts,}
          }
    }

\fi


\newcommand\CheckFDFile[3]{%
  \typeout{*}
  \typeout{* Looking for #1#3.fd or #2#3.fd ... }
  \IfFileExists{#1#3.fd}
    {
     \typeout{* ... ok }
    }
    {
     \IfFileExists{#2#3.fd}
      {
       \typeout{* ... ok }
      }
      {\problemtrue
       \typeout{* ... not found! }
      }
    }
}

\iftimesok % don't bother testing other font options if Times already bad

%\CheckFDFile{ot1}{OT1}{ot1ztmcm}
%\CheckFDFile{oml}{OML}{omlztmcm}
%\CheckFDFile{oms}{OMS}{omsztmcm}
%\CheckFDFile{omx}{OMX}{omxztmcm}

\typeout{*}
\typeout{* Looking for mathptm.sty ... }
\IfFileExists{mathptm.sty}
    {
     \typeout{* ... ok }
     \CheckFDFile{ot1}{OT1}{ptmcm}
     \CheckFDFile{oml}{OML}{ptmcm}
     \CheckFDFile{oms}{OMS}{pzccm}
     \CheckFDFile{omx}{OMX}{psycm}
     \ifproblem
      \typeout{*}
      \typeout{* Problem detected:}
      \typeout{*}
      \typeout{* The mathptm package, which is part of standard LaTeX}
      \typeout{* (psnfss distribution) was found but some or all of its}
      \typeout{* support files describing which fonts to load are missing!}
      \typeout{*}
      \typeout{*}
      \typeout{* The fact that this package is only partially installed}
      \typeout{* means that the mathptm package cannot be used!}
      \typeout{*}
      \typeout{* You can use the aipproc class without this package but }
      \typeout{* you have to specify the option "nomathfonts" so that}
      \typeout{* math formulas will be typeset using Computer Modern.}
      \typeout{*}
      \typein{* Type <return> to continue ...}
      \problemtrue
      \gdef\psnfssproblemoption{nomathfonts,}
     \else
      \typeout{*}
      \typeout{* Looking for mathptmx.sty ... }
      \IfFileExists{mathptmx.sty}
       {
        \typeout{* ... ok }
        \CheckFDFile{ot1}{OT1}{ztmcm}
        \CheckFDFile{oml}{OML}{ztmcm}
        \CheckFDFile{oms}{OMS}{ztmcm}
        \CheckFDFile{omx}{OMX}{ztmcm}
        \ifproblem
	  \typeout{*}
	  \typeout{* Problem detected:}
	  \typeout{*}
	  \typeout{* The mathptmx package, which is part of standard LaTeX}
	  \typeout{* (psnfss distribution) was found but some or all of its}
	  \typeout{* support files describing which fonts to load are missing!}
	  \typeout{*}
	  \typeout{*}
	  \typeout{* The fact that this package is only partially installed}
	  \typeout{* means that the mathptmx package cannot be used!}
	  \typeout{*}
	  \typeout{* You can use the aipproc class without this package but }
	  \typeout{* you have to specify the option "mathptm" (no x) so that}
	  \typeout{* math formulas use the older version with upright greek letters.}
	  \typeout{*}
	  \typein{* Type <return> to continue ...}
	  \problemtrue
	  \gdef\psnfssproblemoption{mathptm,}
        \fi
       }
       {
	\typeout{* ... not found! }
	\typeout{*}
	\typeout{* Problem detected:}
	\typeout{*}
	\typeout{* The mathptmx package, which is part of standard LaTeX}
	\typeout{* (psnfss distribution) can not be found.}
	\typeout{*}
	\typeout{* This is unfortunate but not a disaster as the older}
	\typeout{* version of the package "mathptm" (no x) seems to exist.}
	\typeout{*}
	\typeout{* You can use the aipproc class without this package but }
	\typeout{* you have to specify the option "mathptm" so that}
	\typeout{* math formulas use the older version with upright greek letters.}
	\typeout{*}
	\typein{* Type <return> to continue ...}
	\problemtrue
	\gdef\psnfssproblemoption{mathptm,}
       }
      \fi
    }
    {
     \typeout{* ... not found! }
     \typeout{*}
     \typeout{* Problem detected:}
     \typeout{*}
     \typeout{* The mathptm package, which is part of standard LaTeX}
     \typeout{* (psnfss distribution) can not be found.}
     \typeout{*}
     \typeout{* The fact that this package cannot be found either means that}
     \typeout{* this LaTeX release is too old or that it was installed}
     \typeout{* only in parts!}
     \typeout{*}
     \typeout{* You can use the aipproc class without this package but }
     \typeout{* you have to specify the option "nomathfonts" so that}
     \typeout{* math formulas will be typeset using Computer Modern.}
     \typeout{*}
     \typein{* Type <return> to continue ...}
     \problemtrue
     \gdef\psnfssproblemoption{nomathfonts,}
    }

\typeout{*}
\typeout{* Looking for mathtime.sty ... }
\IfFileExists{mathtime.sty}
    {
     \typeout{* ... ok }
    }
    {
     \typeout{* ... not found! }
     \typeout{*}
     \typeout{* The mathime package can not be found.}
     \typeout{*}
     \typeout{* This is not a serious problem because this package is}
     \typeout{* only of interest if you own the commerical MathTime fonts.}
     \typeout{*}
     \typeout{* You can use the aipproc class without this package but }
     \typeout{* you cannot use the "mathtime" option of the class.}
     \typeout{*}
     \typein{* Type <return> to continue ...}
     \problemtrue
    }
\else
\fi % iftimesok

\typeout{*}
\typeout{* Looking for graphicx.sty ... }
\IfFileExists{graphicx.sty}
    {
     \typeout{* ... ok }
    }
    {
     \typeout{* ... not found! }
     \typeout{*}
     \typeout{* Problem detected:}
     \typeout{*}
     \typeout{* The graphics package, which is part of standard LaTeX}
     \typeout{* (graphics distribution) can not be found.}
     \typeout{*}
     \typeout{* The fact that this package cannot be found either means that}
     \typeout{* this LaTeX release is too old or that it was installed}
     \typeout{* only in parts!}
     \typeout{*}
     \typeout{* You can use the aipproc class without this package but }
     \typeout{* you cannot use commands like \protect\includegraphics
                or \protect\resizebox}
     \typeout{* in this case.}
     \typeout{*}
     \typeout{* Please note that you will get a further error message below}
     \typeout{* about: "graphicx.sty not found" because the class will try}
     \typeout{* to load this package! Type return in response to that error.}
     \typeout{*}
     \typeout{* As a result the illustrations in aipguide will look strange.}
     \typeout{*}
     \typein{* Type <return> to continue ...}

     \gdef\resizebox##1##2{}
     \gdef\includegraphics{\textbf{graphics package missing:}}
     \problemtrue
    }

\typeout{*}
\typeout{* Looking for textcomp.sty ... }
\IfFileExists{textcomp.sty}
    {
     \typeout{* ... ok }
    }
    {
     \typeout{* ... not found! }
     \typeout{*}
     \typeout{* Problem detected:}
     \typeout{*}
     \typeout{* The textcomp package, which is part of standard LaTeX}
     \typeout{* (base distribution) can not be found.}
     \typeout{*}
     \typeout{* The fact that this package cannot be found either means that}
     \typeout{* this LaTeX release is too old or that it was installed}
     \typeout{* only in parts!}
     \typeout{*}
     \typeout{* You can use the aipproc class without this package but }
     \typeout{* you will always get the error: "textcomp.sty not found"}
     \typeout{* because the class will try to load this package!}
     \typeout{* Type return in response to that error.}
     \typeout{*}
     \typein{* Type <return> to continue ...}

     \def\textdegree{$^\circ$}         % used below but now
                                       % not set up
     \problemtrue
    }


\typeout{*}
\typeout{* Looking for url.sty ... }
\IfFileExists{url.sty}
    {
     \typeout{* ... ok }
    }
    {
     \typeout{* ... not found! }
     \typeout{*}
     \typeout{* Problem detected:}
     \typeout{*}
     \typeout{* The url package, which should be part of a good LaTeX}
     \typeout{* distribution, can not be found.}
     \typeout{*}
     \typeout{* Without this package you will not be able to use the \string\url}
     \typeout{* command. Try to download this package from a CTAN  host.}
     \typeout{* Refer to http://www.ctan.org and search for "url".}
     \typeout{*}
     \typein{* Type <return> to continue ...}

     \problemtrue
    }


\makeatletter

\typeout{*}
\typeout{* Looking for natbib.sty ... }
\IfFileExists{natbib.sty}
    {
     \IfStandaloneCheck
       {\begingroup
        \let\@listi\relax
        \let\thebibliography\@empty
        \let\bibstyle\@empty
        \RequirePackage{natbib}
        \@ifpackagelater{natbib}{1999/05/29}
	  {
           \typeout{* ... ok }
	  }{
           \typeout{* ... might be too old! }
           \typeout{*}
           \typeout{* Your version of the natbib package might be too}
           \typeout{* old to be usable. This class was designed to}
           \typeout{* work with the version 7.0 dated 1999/05/28}
           \typeout{*}
           \typeout{* If problems occur download a}
           \typeout{* recent version from a CTAN host.}
           \typeout{*}
           \typeout{* Refer to http://www.ctan.org and search for "natbib".}
           \typeout{*}
           \typein{* Type <return> to continue ...}

           \global\problemtrue
	  }
        \endgroup
        }{}
    }
    {
     \typeout{* ... not found! }
     \typeout{*}
     \typeout{* Serious problem detected:}
     \typeout{*}
     \typeout{* The natbib package, which should be part of a good LaTeX}
     \typeout{* distribution, can not be found.}
     \typeout{*}
     \typeout{* Without this package you will not be able to use certain}
     \typeout{* citation styles. See the aipguide documentation!}
     \typeout{*}
     \typeout{* Especially the layout for ARLO requires this package!}
     \typeout{*}
     \typeout{* Try to download this package from a CTAN  host.}
     \typeout{* Refer to http://www.ctan.org and search for "natbib".}
     \typeout{*}
     \typein{* Type <return> to continue ...}

     \problemtrue
    }

\makeatother


\typeout{*}
\typeout{* ... finished testing}
\typeout{*}
\ifproblem
\typeout{* The tests have revealed some problems in your TeX installation.}
\typeout{*}
\typeout{* Please review the above comments carefully and read the file}
\typeout{* README for further information.}
\typeout{*}
\typeout{*****************************************************************}
\typein{* Type <return> to continue ...}
\else
\typeout{****************************************************************}
\typeout{*}
\typeout{* The tests have reveiled no problems in your TeX installation.}
\typeout{*}
\typeout{****************************************************************}
\fi


% if this file is run standalone stop otherwise continue

\makeatletter
\IfStandaloneCheck
 {
\typeout{*}
\typeout{* This document only produces terminal output.}
\typeout{*}
\stop
 }
 {
\AtBeginDocument{\relax\ifx\xfm@address@loop\@undefined
  \typeout{***************************}
  \typeout{* Oooops ... you seem to have picked up an obsolete}
  \typeout{* aipproc.cls file from a previous installation!}
  \typeout{*}
  \typeout{* Please check that LaTeX finds the right one.}
  \typeout{*}
  \typeout{* Sorry have to give up ....}
  \typeout{***************************}
  \stop
 \fi}
 }
\makeatother

\endinput

heidelberg04.tex
% Version 1.0: Fred, 28-NOV-2004
% Version 1.1: Fred, 30-NOV-2004


\input{aipcheck}

\documentclass[
    ,final            % use final for the camera ready runs
%%  ,draft            % use draft while you are working on the paper
%%  ,numberedheadings % uncomment this option for numbered sections
%%  ,                 % add further options here if necessary
  ]
  {aipproc}

\layoutstyle{6x9}

% New commands
\newcommand{\dbp}{DBP90}
\newcommand{\peg}{P\'EGASE}
\newcommand{\clo}{CLOUDY}
\newcommand{\sms}[1]{{\mbox{{\tiny #1}}}}
\newcommand{\msol}{\mbox{M$_\odot$}}
\newcommand{\lsol}{\mbox{L$_\odot$}}
\newcommand{\zsol}{\mbox{Z$_\odot$}}
\newcommand{\mic}{\mbox{$\mu$m}}
\newcommand{\ngc}[1]{NGC$\,$#1}
\newcommand{\M}[1]{M$\,$#1}
\newcommand{\mw}{Milky Way}
\newcommand{\iizw}{II$\,$Zw$\,$40}
\newcommand{\hen}{He$\,$2-10}
\newcommand{\sfr}{$\rm M_\odot\, yr^{-1}$}
\newcommand{\hmol}{H$_2$}
\newcommand{\hi}{H$\,${\sc i}}
\newcommand{\hii}{H$\,${\sc ii}}
\newcommand{\ha}{H$\alpha$}
\newcommand{\neiii}{Ne$\,${\sc iii}}
\newcommand{\neii}{Ne$\,${\sc ii}}
\newcommand{\siv}{S$\,${\sc iv}}
\newcommand{\ariii}{Ar$\,${\sc iii}}
\newcommand{\neiiiline}{[\neiii] $\lambda 15.56\,\mic$}
\newcommand{\neiiline}{[\neii] $\lambda 12.81\,\mic$}
\newcommand{\sivline}{[\siv] $\lambda 10.51\,\mic$}

\newcommand{\aap}{A\&A}
\newcommand{\apj}{ApJ}
\newcommand{\apjs}{ApJS}

\newcounter{textlistctr}
\newcommand{\thetextlist}{, }
\newcommand{\textlist}[1]
           {\setcounter{textlistctr}{1}
            \renewcommand{\thetextlist}
            {{\it (\roman{textlistctr})}\stepcounter{textlistctr}}#1}


\graphicspath{{Figures/}}

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%% FRONTMATTER
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

\begin{document}

\title{Constraining the local radiation field and the grain size distribution 
       in dust SED modelling of dwarf galaxies}


\author{Fr\'ed\'eric {\sc Galliano}}{
  address={SAp, CEA/Saclay, l'Orme des Merisiers, 91191 Gif, France \\
           Infrared Astrophysics branch, code 685, NASA GSFC, Greenbelt MD 
              20771, USA}
  }

\begin{abstract}
I present a simple self-consistent dust spectral energy distribution (SED) 
model that has been applied to fit the well-sampled observed UV-to-radio SED of
four nearby starbursting dwarf galaxies.
The main originality of this model is that numerous multi-wavelength 
observations, from UV to millimeter (mm), constrain in a self-consistent 
manner, both the local radiation field and the grain size distribution.
I finally present the results of our model and discuss the average dust 
properties in these dwarf galaxies.
\end{abstract}

\maketitle


%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%% MAINMATTER
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%


% Degeneracies
%-------------
\section{Introduction: the difficulties to interpret an observed dust SED}

Most of the current dust models 
\citep{desert+90,li+01,draine+01,zubko+04} have been
developed to describe the emission from the diffuse Galactic ISM.
Consequently, their application to other galaxies is not straightforward.

First, the dust abundances and grain size distribution are
likely to depend significantly on the local physical conditions.
Indeed, the grains can undergo coagulation and accretion of material in dense 
media; fragmentation and erosion in diffuse shocked media; evaporation
of smaller grains in \hii\ regions and injection of newly-formed grains by 
evolved stars and supernovae.
Second, the interpretation of an observed IR-to-millimeter SED of a galaxy in 
terms of dust properties (composition, mass, size distribution) is 
difficult due to the fact that the hardness and intensity of the local 
interstellar radiation field (ISRF) vary strongly from quiescent to 
starforming regions.
This ISRF being the heating source of the dust, its spectral shape 
and intensity have a direct effect on the spectrum emitted by the dust.

\begin{figure}[htbp]
  \centering
  \begin{tabular}{cc}
    \includegraphics[width=0.5\linewidth]{app_SEDisrf.eps}  & \hspace*{-0.6cm}
    \includegraphics[width=0.5\linewidth]{app_SEDsize.eps}  \\
    \includegraphics[width=0.5\linewidth]{app_ISRFsolv.eps} & \hspace*{-0.6cm}
    \includegraphics[width=0.5\linewidth]{app_SIZEsolv.eps} \\
  \end{tabular}
  \caption{Demonstration of the degeneracy in dust SED modelling.
           The model used to fit these SEDs is the \citet{desert+90} model.
           The three dust components are the PAHs (polycyclic aromatic 
           hydrocarbons), the VSGs (very small grains) and the BGs (big 
           grains).
           The grain radius is $a$, and $dm/da$ is the mass of grains
           between $a$ and $a+da$.
           From \citet{galliano+04}.}
  \label{fig:degeneracy}
\end{figure}
Figure~\ref{fig:degeneracy} illustrates the degeneracy between the effects
of the ISRF and those of the size distribution.
The two top plots show an observed dust SED (the grey crosses;
these fluxes are identical in the two plots).
They have been fitted with the \citet{desert+90} model (hereafter DBP90), by 
varying two different sets of 
parameters:\textlist{\thetextlist~the top-left plot has been fitted by 
             varying the ISRF and keeping the Galactic size distribution
           \thetextlist~the top-right plot has been fitted by varying the 
             size distribution and keeping the Galactic ISRF.}
The bottom-left plot shows the radiation field required to produce the
top-left plot, compared to the Galactic one.
This ISRF is harder and more intense, thus the grains are hotter, emitting at
shorter wavelengths.
The bottom-right plot shows the size distribution required for the
top-right plot, compared to the Galactic one.
To fit this SED with a soft and low ISRF, we need to increase the abundance 
of small grains which are the hottest ones.

These figures emphasize the necessity to constrain independently both the 
ISRF and the grain size distribution when modelling a dust SED.


% Ze model
%---------
\section{The choice of a simple self-consistent model}

  \subsection{The multiwavelength observations}

\begin{figure}[htbp]
  \centering
  \begin{tabular}{cc}
    \includegraphics[width=0.5\linewidth]{scuNGC1140lowres.eps}  & \hspace*{-0.6cm}
    \includegraphics[width=0.5\linewidth]{scuNGC1569lowres.eps}  \\
    \includegraphics[width=0.5\linewidth]{scuIIZw40lowres.eps}   & \hspace*{-0.6cm}
    \includegraphics[width=0.5\linewidth]{scuHe2-10lowres.eps}   \\
  \end{tabular}
  \caption{850$\mic$ SCUBA images of the four dwarf galaxies.
           From \citet{galliano+03} and \citet{galliano+04}.}
  \label{fig:scuba}
\end{figure}
We have built the observed UV-to-radio SED of four nearby starburst dwarf 
galaxies (\ngc{1140}, \ngc{1569}, \iizw\ and \hen) by collecting data from the 
literature together with our mid-IR ISOCAM and submm SCUBA 
(Figure~\ref{fig:scuba}) and MAMBO observations.
The broadband fluxes constrain the stellar continuum, the dust emission and
the free-free/synchrotron contribution.
The mid-IR ionic lines observed by ISOCAM are used to constrain the ionized
gas properties, and the CO line measurements are used to remove the molecular 
gas contribution to the submillimeter broadbands.


  \subsection{The model}

The strategy we adopted to model the dust SED of these four nearby dwarf 
galaxies is motivated by the degeneracy shown in Figure~\ref{fig:degeneracy}.
The different steps are the following.
\begin{enumerate}
  \item~An ISRF is synthesized using \peg\ \citep{pegase}.
    We consider two age populations: one accounting for the old 
    underlying stars and a young one accounting for the stars formed 
    during the recent starburst.
    This ISRF fits the unreddened UV-optical broadband fluxes.
    The mean internal optical depth is computed from the energy balance
    between the IR-mm emission and the UV-optical absorption.
    The young stellar population is not well constrained since we lack
    UV data (at shorter wavelengths than U band).
  \item~The ratio of the mid-IR ionic lines (\neiiiline, \neiiline, \sivline) 
    observed by ISOCAM are very sensitive to the hardness of the radiation 
    field and are not significantly affected by extinction.
    The uncertainty of the UV part of the ISRF is removed by constraining
    the photoionisation model \clo\ \citep{cloudy} by these mid-IR ionic line
    ratios.
  \item~The synthesized ISRF is used as the heating source of the 
    DBP90 dust model.
    We vary the grain size distribution in order to fit the IR-mm emission.
    The dust properties deduced from this fit allow us to synthesize an
    average extinction curve for each galaxy.
  \item~This extinction curve is used to unredden the UV-optical observations.
    We iterate these four steps until we reach an agreement between
    extinction and emission properties.
\end{enumerate}

\begin{figure}[htbp]
  \centering
  \includegraphics[width=0.6\linewidth]{method.eps}
  \caption{General method used to fit the SEDs of the four dwarf galaxies
           \citep{galliano+03,galliano+04}.}
  \label{fig:method}
\end{figure}
Figure~\ref{fig:method} summarizes the different steps of our modelling.
This method allow us to independently constrain the local ISRF and the average
size distribution in a self-consistent way, taking into account the emission
and extinction properties of the dust.


% Results
%--------
\section{Average dust properties in four starbursting dwarf galaxies}

\begin{figure}[htbp]
  \centering
  \begin{tabular}{cc}
    \includegraphics[width=0.5\linewidth]{sedtot_1140.eps} &
    \includegraphics[width=0.5\linewidth]{sedtot_1569.eps} \\
    \includegraphics[width=0.5\linewidth]{sedtot_iizw.eps} &
    \includegraphics[width=0.5\linewidth]{sedtot_hen.eps}  \\
  \end{tabular}
  \caption{Multiwavelength observed and modelled global SEDs of four dwarf 
           galaxies \citep{galliano+03,galliano+04}.
           The grey diamonds are the observations and the lines are the model.}
  \label{fig:sedtot}
\end{figure}
Figure~\ref{fig:sedtot} shows the global SEDs of our four galaxies.
The IR-mm part, emitted by the dust is hotter than in the Milky Way.
There remain a submillimeter emission excess in each of the SEDs that
we cannot explain with regular dust properties or radio-molecular 
contributions.
In the next section, I will present the modeled dust properties.
Then, I will discuss the consequences of this submillimeter excess.


  \subsection{The modeled dust properties}

We first notice that the PAHs are underabundant in these galaxies.
They are very weak in \ngc{1569}, \iizw\ and \hen.
Only \ngc{1140}, which is the most quiescent of these objects, 
present some relatively strong mid-IR band emission \citep{madden+04}.

Second, the silicate and graphite size distributions constrained by the fit 
of the dust SED are different from those of the Galaxy.
The grains are on average smaller ($\sim 3-4\,$nm) than those in the 
Milky Way.
Figure~\ref{fig:shocks} shows the size distribution of \ngc{1569} compared to
the Galactic size distribution before and after a shock \citep{jones+96}.
The grain size segregation is consistent with the erosion and the 
fragmentation of the grains by the numerous supernovae shock waves
that these galaxies have recently experienced.
\begin{figure}[htbp]
  \centering
  \includegraphics[width=0.6\textwidth]{shocks.eps}
  \caption{Grain size distribution for \ngc{1569} compared to a graphite 
           and silicate size distribution before (distribution of
           \citep{mathis+77}) and after a shock wave \citep{jones+96}.
           From \citet{galliano+03}.}
  \label{fig:shocks}
\end{figure}

A consequence of this small average grain size is that the bulk of the 
dust emission originates into stochastically heated particles.
Another consequence is that the synthesized extinction curves are 
qualitatively similar to those observed toward several lines of sight 
in the Magellanic Clouds.
Their slope is almost linear in $1/\lambda$ and they have a lower 
extinction bump, except in one galaxy (figure~\ref{fig:compext}).
\begin{figure}[htbp]
  \centering
  \includegraphics[width=0.6\textwidth]{compExt.eps}
  \caption{Synthesized extinction curves for our four galaxies compared to the
           Galactic and the Magellanic extinction curves.
           These curves have been shifted for clarity.
           From \citet{galliano+04}.}
  \label{fig:compext}
\end{figure}


  \subsection{The submillimeter excess}

The submillimeter excess could be either due to peculiar grain optical 
properties or to a component of very cold dust.
Laboratory data show that the emissivity index drops at low temperature
\citep{agladze+96,mennella+98}.
However, these data can not account for this excess, since
the actual change in the slope occurs at a longer wavelength 
\citep{galliano+03}.

Thus, we explore the second hypothesis which is fully quantifiable.
The temperatures required to fit the excess are low ($T\simeq 5-9\,$K).
The dust mass deduced from this component is a large fraction of the total
dust mass ($40-80\,\%$).
A detailed treatment \citep{galliano+03,galliano+04} shows that this 
very cold grain (VCG) hypothesis is consistent with very small and dense
clumps.
Figure~\ref{fig:clump} shows the structure of such a clump.
The very cold dust is embedded and heated only by the IR radiation.
\begin{figure}[htbp]
  \centering
  \includegraphics[width=0.6\textwidth]{clump.eps}
  \caption{Structure of a clump consistent with the very cold dust hypothesis.
           From \citet{galliano+03}.}
  \label{fig:clump}
\end{figure}


% Perpsectives
%-------------
\section{Prospectives}

This modelling was a first step to investigate the detailed dust properties in 
low-metallicity environments.
A further improvement would be to take into account the geometry of the
environment, by using the spatial information that we have on these galaxies,
and treating the radiative transfer.

The second extension of this study would be to consider a larger sample in
order to disentangle the effects of the low-metallicity of the medium and
the effects of the radiation field.
The knowledge of galaxy SEDs is very important to prepare the future missions
like Herschel.


%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%% BACKMATTER
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

\begin{theacknowledgments}
  This presentation was performed while the author held a National Research
  Council Research Associateship Award at NASA GSFC.
\end{theacknowledgments}

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%% You may have to change the BibTeX style below, depending on your
%% setup or preferences.
%%
%% If the bibliography is produced without BibTeX comment out the
%% following lines and see the aipguide.pdf for further information.
%%
%% For The AIP proceedings layouts use either
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

\bibliographystyle{aipproc}   % if natbib is available
%\bibliographystyle{aipprocl} % if natbib is missing

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%% You probably want to use your own bibtex database here
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\bibliography{../../BibTeX/article,../../BibTeX/techreport}

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%% Just a reminder that you may have to run bibtex
%% All of it up to \end{document} can be removed
%% if you don't like the warning.
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\IfFileExists{\jobname.bbl}{}
 {\typeout{}
  \typeout{******************************************}
  \typeout{** Please run "bibtex \jobname" to optain}
  \typeout{** the bibliography and then re-run LaTeX}
  \typeout{** twice to fix the references!}
  \typeout{******************************************}
  \typeout{}
 }

\end{document}

\endinput
%%
%% End of file `template-6s.tex'.

heidelberg04.bbl
\begin{thebibliography}{13}
\expandafter\ifx\csname natexlab\endcsname\relax\def\natexlab#1{#1}\fi
\providecommand{\enquote}[1]{``#1''}
\expandafter\ifx\csname url\endcsname\relax
  \def\url#1{\texttt{#1}}\fi
\expandafter\ifx\csname urlprefix\endcsname\relax\def\urlprefix{URL }\fi

\bibitem[{D\'esert} et~al.(1990)]{desert+90}
{D\'esert}, F.-X., {Boulanger}, F., and {Puget}, J.-L., \emph{\aap},
  \textbf{237}, 215--236 (1990).

\bibitem[{Li} and {Draine}(2001)]{li+01}
{Li}, A., and {Draine}, B.~T., \emph{\apj}, \textbf{554}, 778--802 (2001).

\bibitem[{Draine} and {Li}(2001)]{draine+01}
{Draine}, B.~T., and {Li}, A., \emph{\apj}, \textbf{551}, 807--824 (2001).

\bibitem[{Zubko} et~al.(2004)]{zubko+04}
{Zubko}, V., {Dwek}, E., and {Arendt}, R.~G., \emph{\apjs}, \textbf{152},
  211--249 (2004).

\bibitem[{Galliano} et~al.(2004)]{galliano+04}
{Galliano}, F., {Madden}, S.~C., {Jones}, A.~P., {Wilson}, C.~D., and
  {Bernard}, J.-P., \emph{\aap}, \textbf{\it submitted} (2004).

\bibitem[{Galliano} et~al.(2003)]{galliano+03}
{Galliano}, F., {Madden}, S.~C., {Jones}, A.~P., {Wilson}, C.~D., {Bernard},
  J.-P., and {Le Peintre}, F., \emph{\aap}, \textbf{407}, 159--176 (2003).

\bibitem[{Fioc} and {Rocca-Volmerange}(1997)]{pegase}
{Fioc}, M., and {Rocca-Volmerange}, B., \emph{\aap}, \textbf{326}, 950--962
  (1997).

\bibitem[{Ferland}(1996)]{cloudy}
{Ferland}, G.~J., Hazy, a brief introduction to cloudy, Tech. rep., University
  of Kentucky, department of physics and astronomy (1996).

\bibitem[{Madden} et~al.(2004)]{madden+04}
{Madden}, S.~C., {Galliano}, F., {Jones}, A.~P., and {Sauvage}, M.,
  \emph{\aap}, \textbf{{\it to be submitted}} (2004).

\bibitem[{Jones} et~al.(1996)]{jones+96}
{Jones}, A.~P., {Tielens}, A.~G.~G.~M., and {Hollenbach}, D.~J., \emph{\apj},
  \textbf{469}, 740--764 (1996).

\bibitem[{Mathis} et~al.(1977)]{mathis+77}
{Mathis}, J.~S., {Rumpl}, W., and {Nordsieck}, K.~H., \emph{\apj},
  \textbf{217}, 425--433 (1977).

\bibitem[{Agladze} et~al.(1996)]{agladze+96}
{Agladze}, N.~I., {Sievers}, A.~J., {Jones}, S.~A., {Burlitch}, J.~M., and
  {Beckwith}, S.~V.~W., \emph{\apj}, \textbf{462}, 1026--1040 (1996).

\bibitem[{Mennella} et~al.(1998)]{mennella+98}
{Mennella}, V., {Brucato}, J.~R., {Colangeli}, L., {Palumbo}, P., {Rotundi},
  A., and {Bussoletti}, E., \emph{\apj}, \textbf{496}, 1058--1066 (1998).

\end{thebibliography}
