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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. Q. Mao \& Q. Zeng:
    Submillimeter Dust and Massive Star Formation %%（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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    \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 \bc {\Large\bf An Imaging Survey of Submillimeter Dust
Emission
\\[2mm]in Massive Star Forming Regions  %%（文题）
%\\[1ex]
%$\!\!^*$
}

\vs\vs{\normalsize\zihao{4}\fangsong R.Q. Mao\up{1,2}\hs\&\hs  Q. Zeng\up{1}}  %%（本文作者）

\vs
({\footnotesize 1~\pmo}) \\%%（本文作者单位）
 (\footnotesize 2~ \nao)
\vs\ec

%\documentclass[referee]{aa}
%\documentstyle[11pt,newpasp,twoside,epsf]{article}
%\usepackage{psfig}
%\usepackage{graphicx}
%
%  Abbreviations
%
\def\etal {et al.}
\def\ie {i.\,e.}
\def\etseq {{\em et seq.}}
%\def\vs {{it vs.}}
\def\perse {{it per se}}
\def\adhoc {{\em ad hoc}}
\def\eg {e.\,g.}
\def\etc {etc.}
\def\ccpers {\hbox{${\rm cm}^3{\rm s}^{-1}$}}
\def\vlsr {\hbox{${v_{\rm LSR}}$}}
\def\vhel {\hbox{${v_{\rm HEL}}$}}
\def\delv {\hbox{$\Delta v_{1/2}$}}
\def\TL {$T_{\rm L}$}
\def\TC {$T_{\rm c}$}
\def\TEX {$T_{\rm ex}$}
\def\TMB {$T_{\rm MB}$}
\def\TKIN {$T_{\rm kin}$}
\def\TREC {$T_{\rm rec}$}
\def\TSYS {$T_{\rm sys}$}
\def\TVIB {$T_{\rm vib}$}
\def\TROT {$T_{\rm rot}$}
\def\TDUST {$T_{\rm d}$}
\def\TASTAR {$T_{\rm A}^{*}$}
\def\TVIBST {$T_{\rm vib}^*$}
%
\def\H0 {$H_{\rm o}$}
\def\mic {$\mu\hbox{m}$}
\def\micro {\mu\hbox{m}}
\def\SDOZ {\hbox{$S_{12\mu \rm m}$}}
\def\STWE {\hbox{$S_{25\mu \rm m}$}}
\def\SSIX {\hbox{$S_{60\mu \rm m}$}}
\def\SHUN {\hbox{$S_{100\mu \rm m}$}}
\def\solmass {\hbox{M$_{\odot}$}}
\def\solum {\hbox{L$_{\odot}$}}
\def\irlum {\hbox{$L_{\rm IR}$}}
\def\ohlum {\hbox{$L_{\rm OH}$}}
\def\blum {\hbox{$L_{\rm B}$}}
\def\numd {\hbox{$n\,({\rm H}_2$)}}
\def\rhounit {$\hbox{M}_\odot\,\hbox{pc}^{-3}$}
\def\kms {\hbox{${\rm km\,s}^{-1}$}}
\def\kmsyr {\hbox{${\rm km\,s}^{-1}\,{\rm yr}^{-1}$}}
\def\kmspc {\hbox{${\rm km\,s}^{-1}\,{\rm pc}^{-1}$}}
\def\kmsmpc {\hbox{${\rm km\,s}^{-1}\,{\rm Mpc}^{-1}$}}
\def\Kkms {\hbox{${\rm K\,km\,s}^{-1}$}}
\def\percc {$\hbox{{\rm cm}}^{-3}$}    %cm-3
\def\cmsq  {$\hbox{{\rm cm}}^{-2}$}    %cm-2
\def\cmsix  {$\hbox{{\rm cm}}^{-6}$}   %cm-6
\def\arcsec {\hbox{$^{\prime\prime}$}}
\def\arcmin {\hbox{$^{\prime}$}}
\def\ffam {\hbox{$\,.\!\!^{\prime}$}}
\def\ffas {\hbox{$\,.\!\!^{\prime\prime}$}}
\def\ffM {\hbox{$\,.\!\!\!^{\rm M}$}}
\def\ffm {\hbox{$\,.\!\!\!^{\rm m}$}}
\def\HI  {\hbox{HI}}
\def\HII {\hbox{HII}}
%
%   Greek and abbreviations for radio recomb lines etc
%
\def \AL {$\alpha $}    % gr. alpha
\def \BE {$\beta $}     % gr. beta
\def \GA {$\gamma $}    % gr. gamma
\def \DE {$\delta $}    % gr. delta
\def \EP {$\epsilon $}  % gr. epsilon
\def \alde {($\Delta \alpha ,\Delta \delta $)}
%
\def \MU {$\mu $}       % gr. mue
\def \TAU {$\tau $}     % gr. tau
\def \tapp {$\tau _{\rm app}$}
\def \tuns {$\tau _{\rm uns}$}
\def \RH {\hbox{$R_{\rm H}$}}         % OH main line ratio
\def \RT {\hbox{$R_{\rm \tau}$}}      % OH main tau  ratio
\def \BN  {\hbox{$b_{\rm n}$}}        % bn
\def \BETAN {\hbox{$\beta _n$}}       % beta factor
\def \TE {\hbox{$T_{\rm e}$}}         % Electron Temp.
\def \NE {\hbox{$N_{\rm e}$}}         % Electron Dens.
% molecules
%
\def\MOLH {\hbox{${\rm H}_2$}}                    %H2
\def\HDO {\hbox{${\rm HDO}$}}                     %HDO
\def\AMM {\hbox{${\rm NH}_{3}$}}                  %NH3
\def\NHTWD {\hbox{${\rm NH}_2{\rm D}$}}           %NH2D
\def\CTWH {\hbox{${\rm C_{2}H}$}}                 %C2H
\def\TCO {\hbox{${\rm ^{12}CO}$}}                 %12CO
\def\CEIO {\hbox{${\rm C}^{18}{\rm O}$}}          %C18O
\def\THCO {\hbox{$^{13}{\rm CO}$}}                %13CO
\def\CSEO {\hbox{${\rm C}^{17}{\rm O}$}}          %C17O
\def\CTHFOS {\hbox{${\rm C}^{34}{\rm S}$}}        %C34S
\def\WAT {\hbox{${\rm H}_2{\rm O}$}}              %H2O
\def\WATEI {\hbox{${\rm H}_2^{18}{\rm O}$}}       %H218O
\def\CYAC {\hbox{${\rm HC}_3{\rm N}$}}            %HC3N
\def\CYACFI {\hbox{${\rm HC}_5{\rm N}$}}          %HC5N
\def\CYACSE {\hbox{${\rm HC}_7{\rm N}$}}          %HC7N
\def\CYACNI {\hbox{${\rm HC}_9{\rm N}$}}          %HC9N
\def\METH {\hbox{${\rm CH}_3{\rm OH}$}}           %CH3OH
\def\MECN {\hbox{${\rm CH}_3{\rm CN}$}}           %CH3CN
\def\CH3C2H {\hbox{${\rm CH}_3{\rm C}_2{\rm H}$}} %CH3C2H
\def\FORM {\hbox{${\rm H}_2{\rm CO}$}}            %H2CO
\def\MEFORM {\hbox{${\rm HCOOCH}_3$}}             %HCOOCH3
\def\THFO {\hbox{${\rm H}_2{\rm CS}$}}            %H2CS
\def\ETHAL {\hbox{${\rm C}_2{\rm H}_5{\rm OH}$}}  %C2H5OH
\def\CHTHOD {\hbox{${\rm CH}_3{\rm OD}$}}         %CH3OD
\def\CHTDOH {\hbox{${\rm CH}_2{\rm DOH}$}}        %CH2DOH
\def\CYCP {\hbox{${\rm C}_3{\rm H}_2$}}           %C3H2
\def\CTHHD {\hbox{${\rm C}_3{\rm HD}$}}           %C3HD
\def\HTCN {\hbox{${\rm H^{13}CN}$}}               %H13CN
\def\HNTC {\hbox{${\rm HN^{13}C}$}}               %HN13C
\def\HCOP {\hbox{${\rm HCO}^+$}}                  %HCO+
\def\HTCOP {\hbox{${\rm H^{13}CO}^{+}$}}          %H13CO+
\def\NNHP {\hbox{${\rm N}_2{\rm H}^+$}}           %N2H+
\def\CHTHP {\hbox{${\rm CH}_3^+$}}                %CH3+
\def\CHP {\hbox{${\rm CH}^{+}$}}                  %CH+
\def\ETHCN {\hbox{${\rm C}_2{\rm H}_5{\rm CN}$}}  %C2H5CN
\def\DCOP {\hbox{${\rm DCO}^+$}}                  %DCO+
\def\HTHP {\hbox{${\rm H}_{3}^{+}$}}              %H3+
\def\HTWDP {\hbox{${\rm H}_{2}{\rm D}^{+}$}}      %H2D+
\def\CHTWDP {\hbox{${\rm CH}_{2}{\rm D}^{+}$}}    %CH2D+
\def\CNCHPL {\hbox{${\rm CNCH}^{+}$}}             %CNCH+
\def\CNCNPL {\hbox{${\rm CNCN}^{+}$}}             %CNCN+
%
% Abbreviations for T. Wiklind article
%
\def\In {\hbox{$I^{n}(x_{\rm k},y_{\rm k},u_{\rm l}$})}
\def\Iobs {\hbox{$I_{\rm obs}(x_{\rm k},y_{\rm k},u_{\rm l})$}}
\def\Ingl {I^{n}(x_{\rm k},y_{\rm k},u_{\rm l})}
\def\Iobsgl {I_{\rm obs}(x_{\rm k},y_{\rm k},u_{\rm l})}
\def\Pbgl {P_{\rm b}(x_{\rm k},y_{\rm k}|\zeta _{\rm i},\eta _{\rm j})}
\def\Pbgm {P(x_{\rm k},y_{\rm k}|r_{\rm i},u_{\rm l})}
\def\Pbgn {P(x,y|r,u)}
\def\Pugm {P_{\rm u}(u_{\rm l}|w_{\rm ij})}
\def\Pdem {P_{\rm b}(x,y|\zeta (r,\theta ),\eta (r,\theta ))}
\def\Pden {P_{\rm u}(u,w(r,\theta ))}
\def\greekgl {(\zeta _{\rm i},\eta _{\rm j},u_{\rm l})}
\def\greekg1 {(\zeta _{\rm i},\eta _{\rm j})}

\normalsize
\begin{quotation}

 \no{\bf A{\scriptsize\bf BSTRACT }}~~~\small
We present some preliminary results of an 870\,$\mu$m continuum
imaging survey of a sample of 76 massive star forming regions. Strong submillimeter
dust emission is detected in
almost all sources associated with 6.7\,GHz methanol masers. The absence of dust
emission in  only three exceptions may be interpreted by different maser pumping
mechanism(s). Five morphology types of emission distributions are
classified. About 130 submillimeter sources are detected
in 76 regions, among which 17 sources are found to be hot core candidates and about
40 are promising for Class---0 candidates.
Some interesting sources were also mapped in the CO(3---2) and outflow activities
are found to be quite common in massive star forming regions.

\end{quotation}

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

\vs In recent years the formation of massive stars (M $\ge$ 8
\solmass) has received growing attention, because of their
important role in galactic evolution and the recognition that the
majority of low-mass stars are formed together with high-mass
stars in clusters (Clarke et al. 2000). At present, however, the
formation and early evolution of massive stars still remains a
major puzzle, not only due to the large distances of massive star
forming sites, but also due to their clustered appearance which
makes it very hard to isolate individual young massive objects.

Hot molecular cores are thought to be the precursors of UC\,H{\sc ii}s, and
therefore the formation sites of the massive stars. Being related to the
formation of massive stars, 6.7 GHz methanol masers provide ideal sites to
probe the earliest stages of massive stellar evolution (e.g. Menten 1992).
At present, about 400 IRAS sources are known to be associated with
6.7 GHz methanol masers (MacLeod et al., 1998; Slysh et al., 1999;
Szymczak et al., 2000 and references therein).
We can use these masers as a beacon searching for hot cores.
Since 1998, we have been searching for new hot cores from a catalog
of massive young objects (Chan et al. 1996) in which many are 6.7\,GHz methanol
masers.  New hot core candidates were identified,
based on the presence of high velocity molecular CO emission and high rotational
temperatures derived from \AMM\ metastable inversion lines (Mao 1999; Mao et al. 2002).

Submillimeter dust emission is a good tracer of column density in star forming
regions as it is mostly  optically thin. Dust temperatures, column densities
and masses can be easily estimated from observed fluxes. Hatchell et al. (2000)
found that sources with hot cores can be identified much faster from submillimeter
imaging than from spectral line observations. Previously identified hot core
sources show more strongly centrally peaked emission. Therefore, submillimeter
continuum imaging of molecular cloud is the most efficient way to pick up
hot cores.

In this contribution, we present some preliminary results of an 870\,$\mu$m dust continuum
imaging survey towards a sample of massive star forming regions.

\newpage
\para{\large\bf{2}~~ Samples and Observations}

\vs\vs
To select the sample, we combine the massive
YSO catalog from Chan et al.
(1996) and the list of detected 6.7 GHz methanol masers from Szymczak et al.
(2000). This results in a list of about 210 sources with $\delta$$>$--20$^\circ$.
Excluding those sources already observed at 870\,$\mu$m
(Walsh 2000 priv. comm.) and 1300\,$\mu$m (Beuther et al. 2002), 123 objects
remain as our sample. It contains 18 overlaps with the sample of Beuther et al.
(2002) who selected only those sources not detected in centimeter radio
continuum survey.

\begin{figure}[h]
%\vspace{-6mm}
\center {\includegraphics [angle=270,scale=0.8]{fig1.eps}}

   \parbox[tb]{14cm}
   %{\hspace{3.5cm}
   {\center
   \footnotesize

      Fig.\,1~~ HHT 870\,$\mu$m continuum images of some representative
      morphologies (see text for details)}

    \end{figure}

\begin{figure}[h]
\hspace{5mm} \center {\includegraphics
[angle=270,scale=0.5]{fig2.eps}}
   \parbox[tb]{12cm}
   %{\hspace{3.5cm}
   {%\center
  \vspace{5mm} \footnotesize

      Fig.\,2~~ CO(3--2) red- (dashed) and blue-shifted (dark solid) emission ,
      NH$_{\rm 3}$(1,1)
total integrated intensity contours (light solid) overlaid on 870\,$\mu$m continuum
(grey) in three selected regions.)}

    \end{figure}

870\,$\mu$m dust continuum emission was imaged with the 10-m Heinrich Hertz Telescope
(HHT; see Baars et al 1999) on Mt. Graham in Southern Arizona
during April and May, 2000. A 19-channel bolometer array served as a backend for
continuum imaging. The array covers a hexagonal 200$''$ field of view.
The beam width of the HHT is
about 22$''$ at 870\,$\mu$m. Maps were taken using the On-The-Fly (OTF) method with
a beam throw of
120$''$ and a scanning speed of 8$''$ per second. For most of the sources a single coverage
(400$''\times$300$''$ in size) centered at IRAS position is taken. The
average r.m.s noise level is about 150\,mJy in the maps. All maps were
calibrated using 870\,$\mu$m skydips and the standard calibrators {Uranus} and
{G\,34.3+0.2}, and a peak flux density of 60\,Jy\,beam$^{-1}$ was assumed for the latter one.
At 870\,$\mu$m, the typical atmospheric opacity was about 0.4 during the observations.
The calibration accuracy should be better than $\pm$20\%.



\para{\large\bf{3}~~ Results}

\vs\vs
A total of 76 sources are mapped in 870\,$\mu$m continuum. Fig.~1 shows some
examples for five types of representative morphologies, i.e. from the
1st to the 5th row of Fig.~1 are {\bf a)} strongly centrally peaked; {\bf b)}
multiple centrally
peaked; {\bf c)} elongated and/or filamented; {\bf d)} a compact core with a
diffused envelope surrounded and {\bf e)} diffused or less centrally peaked, respectively.
A systematic study of a complete sample of these different morphologies will help
understand the formation mechanism of massive stars. Different morphologies may
in fact reflect different evolution stages or even different star forming modes. While
those strongly centrally peaked sources are preferable hot core candidates, those
filamented regions with many fragments or multiple centrally peaked cores are
very good sites for studying the clustered forming mode of massive stars.
For example, most recently, about 50 fragments are revealed in a filamentary
structure of the W43 main complex (Motte et al. 2002; see also IRAS\,18449-0158
of Fig.~1). A detailed study on the physical conditions of these fragments suggests that they are
protoclusters. The whole region is likely undergoing a Galactic mini-starburst.
Those regions with diffused or less centrally peaked dust emission can hardly be
the forming sites of massive stars. They are more likely undergoing a more evolved
phase of massive star formation. Our main results are,

1) 130 individual sub-mm sub-sources are found in 76 regions, or 1.7 sub-sources per
regions on average. Beuther et al. (2002) found a higher number 2.2 in their samples,
but their 1.3\,mm images were taken at a spatial resolution of 11$''$, two times higher
than ours. As Beuther et al. (2002) have already pointed out in their paper that most of such
single-dish cores split up into a number of subcores again at even higher resolution
because of their clustered forming trend of massive stars.

2) 17 sources are found to contain strongly centrally peaked submillimeter emission.
We use a criteria of $F_{\rm peak}/F_{\rm total}>$0.5, where $F_{\rm peak}$ and
$F_{\rm total}$ are the peak flux and total flux, respectively.
They are candidates for hot cores which are worthy of further high resolution
study. About a dozen of them show a single
centrally peaked simple structure. These sources can be used as candidates of
calibrators for the submillimeter inteferometer like the SMA and the ALMA.

3) About 40 sources are found to be spatially not coincided with any IRAS source.
These sources are most likely at earlier evolution stages than those sources with
IRAS associations and therefore the promising candidates for Class 0 protostellar
objects.

4) Three 6.7\,GHz methanol maser sources (IRAS\,18021---1950, IRAS\,18141---1626,\linebreak[4]
IRAS\,18321--- 0845) show very weak or even no detection of 870\,$\mu$m continuum
emission within a radius of 1$'$ to the maser sites. These sources
are interesting and need to be further studied. It's possible that the pumping
mechanism for the 6.7\,GHz methanol masers in these regions is different from generally thought
radiative pumping.

We have also calculated the masses of each source.
The masses of the clouds can be estimated via
{\it M=F$_{\rm \nu}$D$^{\rm 2}$/$\kappa_{\rm \nu}$B$_{\rm \nu}$(T$_{\rm d}$)},
where $F_{\rm \nu}$ is the flux density, $D$ denotes the distance
towards the cloud, $B_{\rm \nu}(T_{\rm d})$ is the Plank function
for temperature $T_{\rm d}$, and $\kappa_{\rm \nu}$ is the dust
opacity per unit gas and dust mass. The determination of
$\kappa_{\rm \nu}$ has been discussed in our another paper (Mao et al. 2002),
and the results of these calculations will be published in a separate paper.

\para{\large\bf{4}~~Molecular line follow-up and case studies}

\vs\vs
While we are still going on this continuum survey, some interesting regions
have been selected for molecular line follow-up studies. This includes
NH$_{\rm 3}$ mapping with the Effelsberg 100-m telescope, CO(3--2), CS(5--4),
HCO$^+$(3--2) and some other molecular line emission mapping with the HHT-10m.
Molecular outflows are found to be quite common in these regions.
Observation details is as described in Mao et al. (2002) and
a separate paper of the results is under preparation. Here we only present three
examples.

\vn{\bf{4.1~~IRAS\,18537+0749}}

The cold IRAS color and the high far-infrared luminosity along with the
presence of the water masers, outflows, and radio recombination lines (RRL)
and the absence of UC\,H{\sc ii} regions indicate the very early
stage of the ongoing massive star forming activities in this region.
A total gas/dust mass of about  1200\,M$_{\odot}$ estimated from the
870\,$\mu$m continuum makes the region a promising site forming clusters.
A slightly elongated centrally peaked core with a deconvolved FWHM size
of about 40$''$ ($\sim$0.5\,pc) appears in both the 870\,$\mu$m continuum  and
the CS(5--4) line emission, indicative of
a disk-like envelope and/or the existence of multiple cores. Strong red wings
extending to $\sim$\,50~km\,s$^{-1}$ are detected in CO(3--2).
The bulk of the blue-shifted emission is, however, hidden in the CO emission
due to a strong
self-absorption that is most likely from the foreground cloud(s). An outflowing
gas mass of about 15\,M$_{\odot}$ is estimated from our CO(3--2)
observations.

\vn{\bf{4.2~~IRAS\,19410+2336}}

This source has, to our knowledge, not been studied in detail before.
It has not been found in the 5\,GHz VLA survey by Becker \etal (1994).
Our CO map of this region shows some interesting outflow structures.
While a prominent pair of lobs (red and blue) centered close to the IRAS
point source as well as the main peak of 870\,$\mu$m continuum map, we
found there is another
outflow to the north with two lobs located at either side of a weaker continuum
peak. Two straight lines in middle panel of Fig.~2 imply the possible axis for
two outflows. Missed in the IRAS survey, the later one may trace a much younger
star formation. Relative narrow \AMM\, line width  may also indicate the  cooler
gas and thus an early star forming phase of this source.

\vn{\bf{4.3~~IRAS\,23033+5951}}

This source has not been found in the 5 GHz VLA survey by Becker \etal (1994),
but detected in 6.7GHz \METH\, maser.
We have mapped this region
in CO(3-2) and \AMM\, (1,1), (2,2) line as well. An outflow is clearly shown, but centered
somewhat away from IRAS source. \AMM\, core appearance resembles very much that of 870\,$\mu$m
continuum core, indicating the tight relation between gas and dust in this region.
We suppose this source to be in a phase before a HII region evolved to be visible,
and therefore a good candidate protostar.

\vspace*{1mm}\para{\large\bf{5}~~ Future works}

\vs\vs
Firstly, we need to finish the survey to have a comprehensive statistics.
Since our samples are mostly 6.7\,GHz methanol masers, after such a survey
we can study the correlations between maser luminousities and
core masses, dust temperatures.
Secondly, to identify the hot cores, molecular line observations
are needed. So as a follow-up program, we will concentrate on those
hot core candidates only for line observations of selected molecules
like CH$_{\rm 3}$CN, CH$_{\rm 3}$OH, HNCO and HCO$^+$ etc..
Finally, to eventually dig out the hot cores, high resolution line and
continuum observations are crucial.

\vs\vn{\bf ACKNOWLEDGEMENTS}~~ We appreciate the assistance of the HHT staff
during the observations. The HHT is operated by the Submillimeter Telescope
Observatory on behalf of Steward Observatory and the Max-Planck-Institut
f{\"u}r Radioastronomie (MPIfR).
R.Q.M. acknowledges support by the exchange program between the Chinese
Academy of Sciences and the Max-Planck-Gesellschaft and the hospitality
of MPIfR. This work was
supported in part by NSFC grants 10133020 \& 19973017 and by CMST grant
G19990754.

\bc
{\bf References}
\ec

\vspace{-4mm}
\no \fns

 \nref Baars J, Martin R N, Mangum J G, et al. PASP, 1999, 1111: 627
  \nref Bacmann A, Andr\'e P, Puget J-L, Abergel A, et al. A\&A, 2000,  361: 555
\nref Becker R H, White R L, Helfand D J, et al. ApJS, 1994,  91:
347 \nref Beuther H, Schilke P, Menten K, et al. ApJ, 2002,  566:
945 \nref Chan S J, Henning T, Schreyer K. A\&AS, 1996, 115: 285
 \nref Clarke C J, Bonnell I A, Hillenbrand L A. 2000 in PPIV, eds. V.Mannings,
  A.Boss \& S.S Russell (Tucson: Univ. Arizona Press), 151
\nref Hatchell J, Fuller G A, Millar T J, et al. A\&A, 2000,  357:
637 \nref MacLeod G C, van der Walt D J, North A, et al. AJ, 1998,
116: 2936 \nref Menten K. ApJ, 1991, 380: L75 \nref Mao R Q. PhD
Thesis, Purple Mountain Observatory, CAS, 1999 \nref Mao R Q, Yang
J, Henkel C, Jiang Z B.  A\&A, 2002, 389: 589 \nref Motte F,
Schilke P, Lis D C. ApJ, 2002,  in press \nref Slysh V I, Dzura A
M, et al. A\&AS, 1997,  124: 85 \nref Szymczak M, Hrynek G, Kus A
J. A\&AS, 2000, 143: 269

\end{CJK}
\end{document}
