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$\begin{figure} \par\includegraphics[width=9cm, angle=0]{5873fig1.eps}\end{figure}$ Figure 1: Brightness distribution around the M0.5 dwarf GJ842.2 at $\lambda = 850~\mu$ m based on the data from all the bolometers of the JCMT/SCUBA array. We made an attempt to identify the general morphology of the source in splitting the field of view in eight sectors and averaging the data in each one of them. As it is seen, the emission is non-uniformly distributed and is oriented along the North East-South West direction, suggesting an inclined disk. The plot at the bottom of the figure is a section of the brightness along this direction. The total flux density (brightness $\times$ surface area) is estimated to be $\sim$ $25 \pm 4.6$ mJy (i.e. S/N = 5.5) by adding the flux densities of the 4 quadrants along this direction. The FWHM beamwidth of the telescope is 14'' at 850 $\mu$ m. Observed position of GJ 842.2 is $\alpha =$ 21h58 m 24.8 s and $\delta = 75^{\circ } 35' 21''$ (J 2000).
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In the text

$\begin{figure} \par\includegraphics[width=7cm, angle=-90]{5873fig2.ps}\end{figure}$ Figure 2: IRAM/MAMBO Signal-to-Noise map of the field around the M3.5 dwarf GJ 628 at $\lambda =1.2$ mm. In this map, Signal-to-Noise ratio (S/N) is computed from the intensity map reduced with the shift-and-add method using the software package mopsic (Zylka 1998) and smoothed to the angular resolution 12''. The S/N is computed by dividing the intensity at each pixel by the local rms ( $10 \times 10$ pixels) which is not uniform across this intensity map made by the scanning technique. The local rms $\sigma$ is $\sim$ 0.4 mJy/11'' beam in the central region (r < 60'') and degrades towards the edges of the map; for example, $1 \sigma$ is 0.75 mJy/11'' beam at $r \sim 150''$ . The countours are $-3 \sigma , -2 \sigma$ (dotted lines), and $2 \sigma , 3 \sigma , 4 \sigma$ ; The map pixel size is 3.5''. The West component (MAMBO-W) is associated with a 1.4 GHz radio source ( $\times$ symbol) of the NVSS catalogue and with an optical object of the USNO-B1.1 catalogue (+ symbol), and so it is a background source. The other four MAMBO components (NW, NE, E, SW) may be dust clumps of a large debris disk around GJ 628 but the lack of diffuse emission between them requires additional observations for confirmation. Observed position of GJ 628 at center of the map is $\alpha =$ 16h 30m 18.0s and $\delta = -12^{\circ } 39' 51''$ (J2000).
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In the text

$\begin{figure} \par\includegraphics[width=6cm, angle=-90]{5873fig3.ps}\end{figure}$ Figure 3: Dust masses of debris disks (filled circles) around A- to K-type main sequence stars (Table 4), around the two M-dwarfs AU Mic and GL 182 from Liu et al. (2004) and around the M-dwarf GJ 842.2 reported in this paper. In addition, we plot the dust mass $3\sigma$ upper limits of potential disks for the non-detections of this paper and for the M-dwarf GJ 799 reported in Liu et al. (2004) (red thin triangles = SCUBA and green thick triangles = MAMBO). The dust mass for the Kuiper Belt is shown here to indicate that present observations provide dust masses that are only the envelope of a possibly much larger population of debris disks. The dashed lines are plotted as a guide.
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In the text