Cloudy & Associates

Commit 42059912 authored by Ferland, Gary's avatar Ferland, Gary
Browse files

explain relationships between coarse & fine continua, and lines

There have been FAQs on the user forum in which
people expect to resolve the lines in the coarse continuum.
This add a discussion of the coarse and fine continua,
and explains that the lines are in their own space.
We recommend using SAVE LINE LIST to extract line intensities
and point to a second of Hazy 2 describing how to post process
our output to obtain line profiles.

 Changes to be committed:
	modified:   ../QuickStart/QuickStart.tex
	modified:   ../hazy1/conout.tex
	modified:   ../hazy1/cont-def.tex
	modified:   observed.tex
parent fc1b0378
......@@ -1445,6 +1445,21 @@ either the \cdCommand{background} or \cdCommand{table HM} commands.
Pairs of intensity and shape commands should be kept together. They
may be misinterpreted if they are not.
\subsection{The coarse and fine continua, and lines}
\Cloudy\ solves the line and continuum radiative transfer in three different spaces.
The \emph{coarse continuum} is the broad-band spectrum shown in plots
like Figure \ref{fig:PN_spectrum}.
The \emph{fine continuum} is used to map line opacities onto the continuum and was designed
to fully account for line overlap.
Finally, the line transfer is solved separately and self consistently,
using information from the coarse and fine continua.
Each emergent line is mapped into a single bin in the coarse continuum.
Although the coarse continuum shows the line intensities, that is not its purpose.
The family of \cdCommand{save line list} commands is the most helpful way
to extract line predictions.
\section{Other commands}
......@@ -2513,6 +2513,7 @@ reported with the \cdCommand{save line data} command, described in
\subsection{Save line list [absolute]}
This reads in a list of emission lines from a file and reports the
predicted line intensities. It is designed as a way to obtain predictions
......@@ -10,7 +10,8 @@ The shape and its intensity or luminosity are usually specified
There are many ways to do this.
\section{The coarse and fine continua}
\section{The coarse and fine continua, and lines}
The code uses multi-grid methods to compute the overall spectral emission while
including interactions among the
......@@ -76,6 +77,30 @@ The \cdCommand{set fine continuum} command described on
page \pageref{sec:CommandSetFineContinuum}
can also adjust this resolution.
Emission lines are included in the coarse continuum shown in the right panel of
Figure \ref{fig:CoarseFineContinua}.
Lines are transferred in their own space and are treated self-consistently with both
coarse and fine continua.
The fine continuum, the left panel of Figure \ref{fig:CoarseFineContinua}, includes all
line opacities evaluated using a Voigt function with the appropriate turbulent and damped line broadening.
The line transfer is done independently with the continuum attenuation shown in the left panel
taken into account in continuum fluorescent excitation.
Broadband photoelectric and grain opacities are evaluated on the coarse continuum.
Line destruction by these background opacities is taken into account in the line-transfer solution.
After the calculation is complete, the predicted emergent intensity of each line is placed into a single
wavelength bin in the coarse continuum.
Although the lines are transferred with a full Voigt function, and line broadening is
done self consistently in that space, no attempt is made to map the line profile onto the
coarse continuum.
Line profiles can be generated by post processing the predictions, as described in
Section~\ref{Hazy2-sec:obs_line_profiles} of \Hazy\ 2.
Although line intensities are shown in the coarse continuum, that is not its purpose.
The \cdCommand{save line list} family of commands
(Section \ref{sec:save_line_list}) is the most helpful way
to extract line predictions.
\section{Defining a single component of the incident radiation field}
Two quantities, the \emph{shape} and \emph{intensity},
......@@ -430,6 +430,7 @@ This is correct if the continuum
source is included in the beam, but is not if only the gas is observed.
\section{Column densities}
The column densities of all constituents are printed at the end of the
......@@ -442,6 +443,7 @@ accompanies the description of the \cdTerm{cdColm} command
identifies the various labels.
\section{A synthetic spectrum}
A table of emission-line intensities is part of the normal output.
Sometimes a synthetic spectrum, rather than a table, is desired.
......@@ -464,6 +466,7 @@ Write a small program or script to read these tables and create a final
synthesized spectrum.
\section{Line profiles}
The observed line profile can be predicted by integrating the emissivity
of the line over the computed structure while taking the local velocity
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