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    {\small\rm\zihao{6}\songti\thepage\hfill
    \quad\quad ACTA ASTRONOMICA SINICA \hfill
    \hspace{2mm} Vol.44\vspace{2mm}}}} %%%%%%%
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    {\small\rm \zihao{6}\songti suppl.\hfill R. Wielebinski: Warm CO Gas
    and Cold Dust in Galaxies  %%（作者：题目名称）
    \vspace{1.5mm}
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    \normalsize\rm
\zihao{5}\songti

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    \begin{document}

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    \small\rm
    \zihao{6}\songti
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    Vol.44~ Suppl.
    \hfill\hspace{8mm} %%% if ``October/January'' then \hspace{8/10 mm} July
    \small ACTA ASTRONOMICA SINICA
    \hfill
      Feb.,~2003 \\[-1.5 true mm] %%January
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\vs\vs\vs \bc {\Large\bf Warm CO Gas
    and Cold Dust in Galaxies
   %%（文题）
%\\[1ex]
%$\!\!^*$
}

\vs\vs{\normalsize\zihao{4}\fangsong Richard Wielebinski}  %%（本文作者）

\vs
({\footnotesize {\it Max-Planck-Institut f\"ur Radioastronomie, auf dem H\"ugel 69,
       53121 Bonn, Germany}}) %%（本文作者单位）
\vs\vs \ec

\normalsize
\begin{quotation}

 \no{\bf A{\scriptsize\bf BSTRACT }}~~~\small
The recent years have seen the `closing' of the window between radio
astronomy and far infrared observations. Several telescopes exist
capable of sub-mm wavelength observations, more are under
construction. Radio astronomy at cm wavelengths studies thermal
(free-free) emissions from hot gas and nonthermal radiation from
magnetic fields and relativistic electrons. When we move into the mm
wavelengths range we can study many molecular lines as well as
emission from cold dust. At sub-mm wavelengths the lines become a
forest and the continuum emission comes from warm dust.

\end{quotation}

%%%% 正文
 \para{\large\bf{1}~~ Introduction}

\vs\vs
A spectrum of a galaxy at radio wavelengths is made up from
contributions of the nonthermal emission that dominates at low
frequencies, the free-free emission that is best observed at short cm
wavelengths and the dust emission which dominates in the sub-mm
wavelength range. A typical spectrum of a galaxy, that for the
starburst galaxy M82, is shown in Figure 1. The spectrum in
the sub-mm---FIR range can be best fitted by a Planck black-body
spectrum with a temperature of $\sim 50$\,K. The deviation from a one
temperature black-body spectrum led observers to fit two or even three
temperatures. Superposed on this black-body spectrum we have a great
number of spectral lines. The HI line at 1427\,MHz and some of the other
cm wavelength lines (OH, H$_2$CO, H$_2$O, NH$_4$) make no huge
difference to the spectrum. However in the mm and more so in
the sub-mm wavelength range a `forest' of molecular lines comes up
that must be taken into consideration in any interpretation. In
particular the CO lines contribute a significant flux to the overall
spectrum. The `ladder' of CO lines is given in Table 1. It is to be
noted that the higher CO lines require higher temperatures for their
excitation. The information can be inverted and from the observation of
the line ratios a temperature can be derived. Hence in the sub-mm
wavelength astronomy we have a tool to measure the temperature of the
dust by continuum (bolometer) measurements and of the CO gas by
measuring the transitions. A good review on the background can be found
in Hildebrand (1983) or Cox \& Mezger (1989). I will concentrate in this
talk on the results on nearby galaxies.

\bc{\small\bf

 Table 1~~ CO Astronomy
}\\[2mm]

\fns \tabcolsep 10mm
\begin{tabular}{lll}
\hline\\[-3.6mm]\hline
 Line    &Frequency              &T excitation\\
\hline
$^{12}$CO(1-0)  &115.271203\,GHz  &$\sim 5$\,K \\
$^{13}$CO(1-0)  &110.201370\,GHz  & \\
$^{12}$CO(2-1)  &230.538001\,GHz  &$\sim12$\,K \\
$^{13}$CO(2-1)  &220.398714\,GHz  & \\
$^{12}$CO(3-2) &345.79568\,GHz    &$\sim 35$\,K \\
$^{12}$CO(4-3)  &461.04075\,GHz   &$\sim 55$\,K \\
$^{12}$CO(7-6)  &806.65171\,GHz   &$\sim 120$\,K \\
$^{12}$CO(9-8)  &1.03691235\,THz  &$\sim 150$\,K \\
 \hline\\[-3.6mm]\hline%\\[-4.5mm]\hline
 \end{tabular}
 \ec

\begin{figure}[h]
\center {\includegraphics [bb=0 0 442 352,scale=0.8]{rw1-fig1.eps}}

   \parbox[tb]{12cm}
   %{\hspace{3.5cm}
  { %\center
   \footnotesize

   Fig.\,1~~ The spectrum of M82. Below $10^{11}$\,Hz we see nonthermal and
free-free radio emission. Above $10^{11}$\,Hz we see dust emission}

    \end{figure}

    \begin{figure}[tbph]
\center {\includegraphics [bb=0 0 595 842,scale=0.75]{rw1-fig2.eps}}

   %\parbox[tb]{12cm}
   %{\hspace{3.5cm}
  { \center
  \vspace{-12mm} \footnotesize
   Fig.\,2~~ CO(3-2) Observations of some galaxies}
\end{figure}


\para{\large\bf{2}~~Instruments}

\vs\vs
The development of this field of research has a long history. The
first Galactic CO was detected by Wilson et al. (1970) and
extragalactic CO by  Rickard et al. (1975) with the 36-ft Kitt Peak NRAO
mm-telescope. This NRAO telescope has played a major role in this field
of research. Later several new telescopes were constructed, able to
work in the mm wavelength range, notably the 13.7\,m radome enclosed
telescopes of the Five College Radio Astronomy Observatory,
the Onsala dish and the Delingha dish. Also the Haystack facility had mm
capabilities. The CSO 10.4\,m telescope and the 15\,m JCMT, placed on the
high altitude site in Hawaii contributed lots to the opening up of the
higher frequenciy window. The JCMT in particular, equipped with the
SCUBA bolometer, became synonymous with continuum (bolometer)
observations.
The completion of the 30\,m Pico Veleta dish of IRAM
resulted in a major change in the possibilities to study galaxies in
CO(1-0) and CO(2-1) line transitions. Large maps of nearby galaxies
became possible with good angular resolution. By now most of the
extended nearby galaxies have been mapped. The Pico Veleta telescope
was also a major driver in observing red-shifted CO: high line
transitions shifted into the lower mm bands. While the Plateau de Bure
interferometer was constructed near Grenoble the dish no.\,2 was
transferred to Chile and became the SEST telescope. Interferometers
such as BIMA in the USA contributed a lot of data with good angular
resolution. The final instrument in this saga is the 10\,m HHT, placed on
Mt. Graham, Arizona and operated as the SMTO observatory. This
telescope holds the world record in the best surface ($\rm rms =
15\,\mu$) and in the highest radio frequency observation made from
earth: the detection of the CO(9-8) line
in Orion at 1.037\,THz. The
development of sensitive receivers had to keep up with the telescope
developments. All the line receivers are state of art SIS mixers. For
continuum observations multi-channel bolometers are needed. The biggest
bolometer made at the MPIfR for the Pico Veleta telescope at 1.2\,mm
wavelength has 117 pixels. The HHT observation at $870\,\mu$m are made
with a 19-pixel bolometer.

\begin{figure}[h]
\center {\includegraphics [bb=28 56 548 705,scale=0.6]{rw1-fig3.eps}}

   %\parbox[tb]{12cm}
   %{\hspace{3.5cm}
  { \center
   \footnotesize

   Fig.\,3~~ $870\,\mu$m observations of some galaxies}

    \end{figure}


\para{\large\bf{3}~~Our Observations}

\vs\vs
We have made many of our observations with the Pico Veleta 30\,m
telescope in the CO(1-0) and CO(2-1) line (e.g. Reuter et al. 1991;
Golla \& Wielebinski 1994) as well as in $\lambda = 1.2$\,mm radio
continuum (e.g. Braine et al. 1995; Neininger \& Dumke 1999). Some of
the studied galaxies were re-observed with better angular resolution
with the Plateau de Bure interferometer. The HHT telescope on Mt.~Graham
was used to make observations in the CO(3-2) and CO(4-3) lines as well
as in $\lambda = 870\,\mu$m radio continuum. The CO data have been
published in Wielebinski et al. (1999), Nieten et al. (1999), Dumke et
al. (2001) and Walsh et al. (2002). I show a collection of the CO(3-2)
results in Figure 2. The bolometer maps, made at $870\,\mu$m, are shown
in Figure~3. The combination of all these data allow us to study warm
CO gas and cold dust in these galaxies. A surprising result was the
discovery of widely distributed warm gas in galaxies. The warm CO gas,
with temperatures of 50\,K or more is seen over the whole optical image
of many galaxies. The dust emission gave some surprising results.
The fits showed components with typical temperatures of 20\,K and 50\,K
for most galaxies but needed also the fit of a very cold component with
only $\sim 5$\,K in some of the studied objects.

\para{\large\bf{4}~~ The Future}

\vs\vs
The highest frequency at which a galaxy could be studied at the 3400\,m
Mt. Graham site was the CO(7-6) line at 806\,GHz (Mao et al. 1999). The
weather does not permit studies of the higher lines and the shorter
continuum wavelengths at either Mt. Graham or Hawaii. As a result of
this fact a search for an even better site has been made and the
Chajnantor plateau at $\sim5000$\,m was identified. This site is in
the high Andes (Chile) near Antofogasta. This site will be used for the
project ALMA, a joint USA-European mm-wavelength interferometer. In
anticipation of this development the MPIfR proposed the project APEX, a
12\,m pathfinder radio telescope for sub-mm wavelengths to be
constructed on the Chajnantor site in Chile at the elevation of 5080\,m
before ALMA is ready. All the developments at the MPIfR are presently
concentrated to make this a successful observatory. Project APEX is a
cooperation of the MPIfR with the Bochum University, the Onsala Space
Observatory and ESO: the European Southern Observatory that is also the
prime leader in the ALMA development.

\vs\vn{\bf ACKNOWLEDGEMENT}~~ I want to thank Michael Dumke, `our man in
Arizona', who made most of the sub-mm observations and provided
Figures 2 and 3

\bc
{\bf References}
\ec

\vspace{-4mm}
\no \fns

 \no Braine J, Kr\"ugel E, Sievers A. et al, A\&A, 1995, 295: L55\\
\no Cox P, Mezger P G.   A\&AR, 1989, 1: 49\\
\no Dumke M, Nieten Ch, Thuma G. et al, A\&A, 2001, 373: 853\\
\no Golla G, Wielebinski R. A\&A, 1994, 286: 733\\
\no Hildebrand R H. QJRAS, 1983, 24: 267\\
\no Mao R Q, Henkel C, Schulz A, et al. A\&A, 358, 433\\
\no Nieten Ch, Dumke M, Beck R, et al. A\&A, 1999, 347: L5\\
\no Neininger N, Dumke M. , Proc. Natl. Acad. Sci. USA, 1999, 96: 5360\\
\no Reuter H P, Krause M, Wielebinski R, et al. A\&A, 1991: 248, 12\\
\no Rickard L J, Palmer P, Morris M, et al. ApJ, 1975, 199: L75\\
\no Walsh W, Beck R, Thuma G, et al. A\&A, 2002, 388: 7\\
\no Wielebinski R, Dumke M,  Nieten Ch. A\&A, 1999, 347: 634\\
\no Wilson R W, Jefferts K B, Penzias A A. ApJ, 1970, 161: L43\\

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