\begin{table}%T4
\caption{Values for submillimeter and millimeter emissivity, $Q(\lambda)$, collated from the literature.
Estimates are given as $\frac{Q(V)}{Q(\lambda)}$ where the extinction efficiency in the $V$-band [$Q(V)$]
 has been taken, where necessary, to be 1.5 (Whittet 1992). The absorption mass coefficient $\kappa(\lambda)$ is
calculated from $Q(\lambda)$ assuming a classical grain radius of $0.1~\mu$m and a material density of
$\rho =3 \times 10^{3}~$kg~m$^{-3}$. For each measurement the column "Medium'' denotes the type of astrophysical
environment where the corresponding grains are believed to be situated.}
\label{tab_emissivity}
%\centering
\par
\begin{tabular}{llllll}
\hline
\hline
\noalign{\smallskip}
$\lambda$ & $\frac{Q(V)}{Q(\lambda)}$ & $\kappa(\lambda)$ & Medium &
 Reference & Comment \\
($\mu$m)  &  & (cm$^{2}$ g$^{-1}$) & & & \\ \hline
100 & 760 & 49 & diffuse \ion{H}{i} (Milky Way) & Bianchi et~al. (1999)       & \\
125 & 2000 & 19 & reflection nebula & Hildebrand (1983)    & $\frac{Q(V)}{Q(\lambda)}$ up to 5000 if $\beta=1$ \\
240 & 3900 & 9.7 & diffuse \ion{H}{i} (Milky Way) & Boulanger et~al. (1996) & DIRBE data; values also given \\
    &      &     &                  &                                      & at 100 and 140$~\mu$m \\
250 & 2500 & 15  & reflection nebula & Casey (1991)                 & 5 objects; $\frac{Q(V)}{Q(\lambda)}$ up to 30~000  \\
    &      &     &                   &                              &   depending on the method   \\
250 & 4400 & 8.5 & diffuse \ion{H}{i} (model) & Draine \& Lee (1984)   & Uses laboratory data; oscillator  \\
    &      &     &                    &                                    & model for $\lambda>60~\mu$m \\
400 & 1900 & 20 & late-type star & Sopka (1985)                 &    \\
736 & 34~000 & 1.1 & diffuse \ion{H}{i} (Milky Way) & Boulanger et~al. (1996) & FIRAS data; values also given \\
    &       &     &                 &                                      & at 346, 490, 535 and 1100$~\mu$m \\
850 & 9100 & 4.1 & cold core        & Rengarajan (1984)        &  \\
850 & 30~000 & 1.3 & cold core       & Kramer et~al. (2003)          &  \\
850 & 54~000 & 0.69 & diffuse \ion{H}{i}   & James et~al. (2002)        & Using $N_{\rm H}$, metallicity \& SCUBA data \\
850 & 16~000 & 2.4 & H$_{2}$ (NGC~891) & Alton et~al. (2000)        & RT model of this work \& SCUBA data \\
850 & 14~000 & 3.2 & H$_{2}$ (NGC~4013) & this work                           &  \\
850 & 12~000 & 2.7 & H$_{2}$ (NGC~5907) & this work                           &  \\
850 & 25~000 & 1.5 & cold core       & Bianchi et~al. (2003)    & SCUBA data\ \\
1000 & 18~000 & 2.1 & diffuse \ion{H}{i} (model) & Mathis \& Whiffen (1989)  & \\
1000 & 180~000 & 0.22 & laboratory (Si crystalline) & Agladze et~al. (1996);  & Mean value of both works \\
     &       &       &                             & Mennella et~al. (1996)  & (150~000 and 197~000) \\
1000 & 40~000 & 0.95 & laboratory (Si amorphous) &  Agladze et~al. (1996);    & Mean value of both works \\
     &       &       &                          &  Mennella et~al. (1996)    &  (36~100 and 43~600) \\
1000 & 1600   & 24    & laboratory (C amorphous)   & Mennella et~al. (1996)  &                  \\
1200 & 120~000 & 0.315 & diffuse \ion{H}{i} (NGC~4565)      & Neininger et~al. (1996) & Authors claim emissivity 2--4 \\
     &        &       &                            &           &   higher for molecular regions \\
1200 & 110~000 & 0.35 & diffuse \ion{H}{i} (NGC~5907) & Dumke et~al. (1997) & Outer regions of the galactic disk \\
1200 & 110~000 & 0.34 &  cold core & Bianchi et~al. (2003) & IRAM data \\
1200 & 66~000 & 0.57 & H$_{2}$ (NGC~4565) & this work & \\
\hline
\end{tabular}
\end{table}