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ntplot analysis.nebular


NAME · USAGE_ · DESCRIPTION · PARAMETERS · EXAMPLES · BUGS
REFERENCES · SEE_ALSO

NAME

ntplot -- Plot curves on the N_e, T_e plane for observed diagnostic line ratios

USAGE

ntplot intable

DESCRIPTION

This task computes and plots curves that show the range of electron temperatures (T_e) and electron densities (N_e) that are consistent with various observed diagnostic line ratios. The diagnostics from an ionized nebular gas are computed within the N-level atom approximation. (For more details about this approximation, type "help nlevel".) The user specifies the name of the STSDAS binary table containing the observed line fluxes and ratios, and the task plots one curve in the N_e, T_e plane for each diagnostic. An optional output table will contain each of the computed curves, one per column. The output table is useful for identifying the individual curves, and for customized plotting (with, e.g., the `stplot.igi' task). This task is particularly useful for flagging unreasonable input line ratios, and for determining whether a detailed photoionization model is necessary for calculating the physical conditions and ionic abundances. If a detailed model is necessary, the output from this task will be useful for specifying the initial conditions; if not, the `zones' and `abund' tasks may be sufficient for determining the physical conditions and the ionic abundances.

The input table may contain line fluxes for many nebulae and/or many regions within a nebula, one object/region per row. A particular object in the table is selected with the "object" parameter. The flux for each emission line or line ratio must be given in separate columns. The task locates particular emission line fluxes via names of specific columns in the input table. These columns have suggestive default names, but are entirely user-definable; type "help fluxcols" for more details. (An example of an input table can be found in the file "nebular$data/flux.fits".) Note that the input table need not actually contain all the diagnostic lines specified in this p-set: if a named column is not found, the corresponding curve will be skipped. The plot limits can also be specified.

The diagnostic line ratios are derived from the input line fluxes, corrected for interstellar reddening. The reddening corrected line flux "I" is derived from the input line flux "F" by:

			           {-c * f(lambda)}
	     I(line) = F(line) * 10

where "c" is the extinction constant (i.e. the logarithmic extinction at H-beta, 4861 Ang), and "f(lambda)" is derived from one of a few possible extinction functions. The choices for Galactic extinction are: Savage & Mathis (1979), Cardelli, Clayton, & Mathis (1989), and the function of Kaler (1976), which is based on Whitford (1958). The choices for extra-Galactic extinction laws are Howarth (1983) for the LMC, and Prevot et al. (1984) for the SMC. The value of "c" must be given in the input table if a correction for reddening is desired. However, the correction may be disabled if a correction flag (stored in another table column), is set to "yes". By default no reddening correction is performed unless a valid value for "c" is available, and unless the correction flag is set to "no" or is not present. The extinction law will default to that of Savage & Mathis ("gal") unless another choice is specified (one of "gal", "ccm", "jbk", "lmc", or "smc") in the input table.

The available diagnostic line ratios and the ionization potential of the associated ion are listed by ion below. The line ratio is in the form I(wave1)/I(wave2), where "wave1" and "wave2" are in units of Angstroms; ratios involving sums of line strengths are given as I(wave1+wave2)/I(wave3+wave4).

              Table 1. Electron Density Diagnostics

    Ion    Spectrum       Line Ratio              I.P.   Zone
  -------------------------------------------------------------
    C(+1)    C ii]        I(2326) / I(2328)       11.3   Low
    C(+2)    C iii]       I(1907) / I(1909)       24.4   Med
    N(0)    [N i]         I(5198) / I(5200)        0.0   Low
    N(+2)    N iii]       I(1749) / I(1752)       29.6   Med
    O(+1)   [O ii]        I(3726) / I(3729)       13.6   Low
    O(+3)    O iv]        I(1401) / I(1405)       54.9   High
   Ne(+3)  [Ne iv]        I(2423) / I(2425)       63.5   High
   Al(+1)  [Al ii]        I(2661) / I(2670)              Low
   Si(+2)   Si iii]       I(1883) / I(1892)       16.3   Low
    S(+1)   [S ii]        I(6716) / I(6731)       10.4   Low
   Cl(+2)  [Cl iii]       I(5517) / I(5537)       23.8   Med
   Ar(+3)  [Ar iv]        I(4711) / I(4740)       40.9   Med
    K(+4)   [K v]         I(6223) / I(6349)              High
   -------------------------------------------------------------

             Table 2. Electron Temperature Diagnostics

    Ion    Spectrum       Line Ratio              I.P.   Zone
  -------------------------------------------------------------
    N(+1)   [N ii]   I(6548+6583) / I(5755)       14.5   Low
    O(+0)   [O i]    I(6300+6363) / I(5577)        0.0   Low
    O(+1)   [O ii]   I(3726+3729) / I(7320+7330)  13.6   Low
    O(+2)   [O iii]  I(4959+5007) / I(4363)       35.1   Med
   Ne(+2)  [Ne iii]  I(3869+3969) / I(3342)       41.1   Med
   Ne(+3)  [Ne iv]   I(2422+2425) / I(1601+1602)  63.5   High
   Ne(+4)  [Ne v]    I(3426+3346) / I(2975)       97.0   High
   Al(+1)  [Al ii]   I(2661+2670) / I(1671)        6.0   Low
   Si(+2)   Si iii]  I(1883+1892) / I(1206)       16.3   Low 
    S(+1)   [S ii]   I(6716+6731) / I(4068+4076)  10.4   Low
    S(+2)   [S iii]  I(9069+9532) / I(6312)       23.4   Med
   Cl(+3)  [Cl iv]   I(7530+8045) / I(5323)       39.9   Med 
   Ar(+2)  [Ar iii]  I(7136+7751) / I(5192)       27.6   Med
   Ar(+3)  [Ar iv]   I(4711+4740) / I(2854+2868)  40.9   Med 
   Ar(+4)  [Ar v]    I(6435+7006) / I(4626)       59.8   High
    K(+3)   [K iv]   I(6102+6796) / I(4511)       46.0   Med
  -------------------------------------------------------------

Different line types in the plot are used to denote diagnostics from ions with different ionization potential, organized into three zones. Solid lines are used for low ionization species (I.P. < 20 eV), dashed lines for intermediate ionization (20 < I.P. < 50 eV), and dotted lines for the highest ionization diagnostics (I.P. > 50 eV).

PARAMETERS

fluxtab = "" [string]
Input table of diagnostic line fluxes.
(outtab = "") [string]
Optional output table of computed diagnostic curves. If blank, no output table will be produced.
(object = "") [string]
Object to select within the input table, if more than one is present. Individual objects, and regions within objects, must be stored one per row in the input table.
(min_dens = 10.) [real]
Minimum density for plot, in units of 1/cm^3; must lie in the range 1. to 1.e+6, and must be less than "max_dens".
(max_dens = 1.e+6) [real]
Maximum density for plot, in units of 1/cm^3; must lie in the range 100. to 1.e+8, and must exceed "min_dens".
(min_temp = 5000.) [real]
Minimum temperature for plot, in units of Kelvins; must lie in the range 1000. to 30,000 K, and must be less than "max_temp".
(max_temp = 2.0e+4) [real]
Maximum temperature for plot, in units of Kelvins; must lie in the range 10,000. to 100,000 K, and must exceed "min_temp".
(log_ne = yes) [boolean]
Plot the electron density (X-axis) with a log scale?
(log_te = no) [boolean]
Plot the electron temperature (Y-axis) with a log scale?
(resolution = 201) [int]
Max number of data points to plot per curve. Increasing this number improves the fidelity of the curve, at the expense of execution time.
(fluxcols = "") [pset]
Parameter set to specify column names for certain line fluxes, the nebula name and the region code (which must both be present) in the input table. Otherwise, no error is generated if a named column does not exist in the input table; rather, the calculation proceeds as if the associated line flux is INDEF.
(faluminum = "") [pset]
Parameter set to specify column names for aluminum line fluxes.
(fargon = "") [pset]
Parameter set to specify column names for argon line fluxes.
(fcalcium = "") [pset]
Parameter set to specify column names for calcium line fluxes.
(fcarbon = "") [pset]
Parameter set to specify column names for carbon line fluxes.
(fchlorine = "") [pset]
Parameter set to specify column names for chlorine line fluxes.
(fmagnesium = "") [pset]
Parameter set to specify column names for magnesium line fluxes.
(fneon = "") [pset]
Parameter set to specify column names for neon line fluxes.
(fnitrogen = "") [pset]
Parameter set to specify column names for nitrogen line fluxes.
(foxygen = "") [pset]
Parameter set to specify column names for oxygen line fluxes.
(fpotassium = "") [pset]
Parameter set to specify column names for potassium line fluxes.
(fsilicon = "") [pset]
Parameter set to specify column names for silicon line fluxes.
(fsodium = "") [pset]
Parameter set to specify column names for sodium line fluxes.
(fsulfur = "") [pset]
Parameter set to specify column names for sulfur line fluxes.
(device = stdgraph) [string]
Output device for plot.
(at_data = at_data) [string]
Atomic reference data directory name.

EXAMPLES

1. Plot the range of electron densities and temperatures that are consistent with the diagnostic ratios found in the example input table for the object "Test_123". Adjust the density limits to 500 < N_e < 1.e4.

    cl> tcopy nebular$data/flux.fits .
    cl> ntplot flux.tab object=Test_123 min_dens=500. max_dens=1.e4

2. Plot curves in the N_e, T_e plane that are consistent with the diagnostic ratios found in the table nebula.tab, and store the results in the table curves.tab. Adjust the default plot limits to 100 < N_e < 1.e+6/cm^3 and 5000 < T_e < 30,000 K.

    cl> ntplot nebula.tab outtab=curves.tab min_dens=100. \ 
    >>> max_temp=3.e+4

BUGS

REFERENCES

The 5-level atom program, upon which this package is based, was originally written by M.M. DeRobertis, R. Dufour, and R. Hunt. This package was written by R.A. Shaw (STScI); a description was published by R.A. Shaw & R.J. Dufour (1994). Type "help nlevel" for additional information about the N-level atom approximation, and for references to the atomic parameters and the other literature references. Support for this software development was provided by the Astrophysics Data Program through NASA grant NAG5-1432, and through STScI internal research funds.

SEE ALSO

nlevel, temden, zones

For general information about this package, type "help nebular opt=sysdoc".


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