Emission-Line Measurements¶
Emission-Line Parameters¶
The table below provides a compilation of emission line parameters gathered through the development of the DAP. Many of them have not actually been fit by the DAP in any survey-level runs of the software and are simply collected here for reference.
Rest wavelengths are Ritz wavelengths in vacuum, collected from the NIST Atomic Spectra Database.
The “M1” and “E2” values are the Einstein \(A_{ki}\) coefficients for the magnetic dipole and electric quadrapole transitions, respectively. These are collected to fix the expected flux ratio between specific line doublets. The expected flux ratio is:
where, e.g., \(\lambda_1\) is the rest wavelength of the first line in the doublet.
Additionally, we have defined some nominal passbands used for calculations of the line equivalent width (EW), including the main passband centered on the line and blue and red sidebands that are used to construct a linear continuum beneath the emission line.
Name | Rest \(\lambda\) (Å) | M1 | E2 | EW Passband (Å) | Blue Passband (Å) | Red Passband (Å) |
---|---|---|---|---|---|---|
HeII | 3204.038 | |||||
NeV | 3346.783 | |||||
NeV | 3426.863 | |||||
H25 | 3670.5154 | |||||
H24 | 3672.5279 | |||||
H23 | 3674.8109 | |||||
H22 | 3677.4160 | |||||
H21 | 3680.4065 | |||||
H20 | 3683.8627 | |||||
H19 | 3687.8870 | |||||
H18 | 3692.6119 | |||||
H17 | 3698.2104 | |||||
H16 | 3704.9133 | |||||
H15 | 3713.0334 | |||||
H14 | 3723.0035 | [1] | 3706.3 – 3716.3 | 3738.6 – 3748.6 | ||
OII | 3727.092 | 3716.3 – 3738.3 | 3706.3 – 3716.3 | 3738.6 – 3748.6 | ||
OII | 3729.875 | [1] | 3706.3 – 3716.3 | 3738.6 – 3748.6 | ||
H13 | 3735.4365 | [1] | 3706.3 – 3716.3 | 3738.6 – 3748.6 | ||
H12 | 3751.2243 | 3746.2 – 3756.2 | 3738.6 – 3748.6 | 3756.6 – 3766.6 | ||
H11 | 3771.7080 | 3761.7 – 3781.7 | 3756.6 – 3766.6 | 3779.1 – 3789.1 | ||
\({\rm H}\theta\) | 3798.9826 | 3789.0 – 3809.0 | 3776.5 – 3791.5 | 3806.5 – 3821.5 | ||
\({\rm H}\eta\) | 3836.4790 | 3826.5 – 3846.5 | 3806.5 – 3826.5 | 3900.2 – 3920.2 | ||
NeIII | 3869.86 | 1.74e-1 | 3859.9 – 3879.9 | 3806.5 – 3826.5 | 3900.2 – 3920.2 | |
HeI | 3889.749 | [1] | 3806.5 – 3826.5 | 3900.2 – 3920.2 | ||
\({\rm H}\zeta\) | 3890.1576 | 3880.2 – 3900.2 | 3806.5 – 3826.5 | 3900.2 – 3920.2 | ||
NeIII | 3968.59 | 5.40e-2 | [1] | 3938.6 – 3958.6 | 3978.6 – 3998.6 | |
\({\rm H}\epsilon\) | 3971.2020 | 3961.2 – 3981.2 | 3941.2 – 3961.2 | 3981.2 – 4001.2 | ||
HeI | 4027.3238 | 4017.3 – 4037.3 | 3997.3 – 4017.3 | 4037.3 – 4057.3 | ||
SII | 4069.749 | 4062.7 – 4073.6 | 4049.7 – 4062.7 | 4082.0 – 4092.9 | ||
SII | 4077.500 | 4073.6 – 4084.5 | 4049.7 – 4062.7 | 4082.0 – 4092.9 | ||
\({\rm H}\delta\) | 4102.8991 | 4092.9 – 4112.9 | 4082.0 – 4092.9 | 4112.9 – 4132.9 | ||
\({\rm H}\gamma\) | 4341.691 | 4331.7 – 4351.7 | 4311.7 – 4331.7 | 4349.7 – 4358.7 | ||
OIII | 4364.435 | 4358.7 – 4374.4 | 4349.7 – 4358.7 | 4374.4 – 4384.4 | ||
HeI | 4472.729 | 4462.7 – 4482.7 | 4442.7 – 4462.7 | 4482.7 – 4502.7 | ||
HeII | 4687.015 | 4677.0 – 4697.0 | 4667.0 – 4677.0 | 4697.0 – 4707.0 | ||
ArIV | 4712.58 | |||||
HeI | 4714.4578 | 4707.0 – 4722.0 | 4697.0 – 4707.0 | 4722.0 – 4732.0 | ||
ArIV | 4741.45 | |||||
\({\rm H}\beta\) | 4862.691 | 4852.7 – 4872.7 | 4798.9 – 4838.9 | 4885.6 – 4925.6 | ||
HeI | 4923.3051 | 4913.3 – 4933.3 | 4898.3 – 4913.3 | 4933.3 – 4948.3 | ||
OIII | 4960.295 | 6.21e-3 | 4.57e-6 | 4950.3 – 4970.3 | 4930.3 – 4950.3 | 4970.3 – 4990.3 |
OIII | 5008.240 | 1.81e-2 | 3.52e-5 | 4998.2 – 5018.2 | 4978.2 – 4998.2 | 5028.2 – 5048.2 |
HeI | 5017.0769 | [1] | 4988.2 – 4983.2 | 5028.2 – 5048.2 | ||
NI | 5199.3490 | 5189.3 – 5209.3 | 5169.4 – 5189.3 | 5211.7 – 5231.7 | ||
NI | 5201.7055 | [1] | 5169.4 – 5189.4 | 5211.7 – 5231.7 | ||
NII | 5756.19 | |||||
HeI | 5877.243 | 5867.2 – 5887.2 | 5847.2 – 5867.2 | 5887.2 – 5907.2 | ||
NaI | 5891.583 | |||||
NaI | 5897.558 | |||||
OI | 6302.046 | 5.63e-3 | 2.11e-5 | 6292.0 – 6312.0 | 6272.0 – 6292.0 | 6312.0 – 6332.0 |
OI | 6365.535 | 1.82e-3 | 3.39e-6 | 6355.5 – 6375.5 | 6335.5 – 6355.5 | 6375.5 – 6395.5 |
NII | 6549.86 | 9.84e-4 | 9.22e-7 | 6542.9 – 6556.9 | 6483.0 – 6513.0 | 6623.0 – 6653.0 |
\({\rm H}\alpha\) | 6564.632 | 6557.6 – 6571.6 | 6483.0 – 6513.0 | 6623.0 – 6653.0 | ||
NII | 6585.271 | 2.91e-3 | 8.65e-6 | 6575.3 – 6595.3 | 6483.0 – 6513.0 | 6623.0 – 6653.0 |
HeI | 6679.9956 | 6670.0 – 6690.0 | 6652.0 – 6670.0 | 6690.0 – 6708.0 | ||
SII | 6718.294 | 6711.3 – 6725.3 | 6690.0 – 6708.0 | 6748.0 – 6768.0 | ||
SII | 6732.674 | 6725.7 – 6739.7 | 6690.0 – 6708.0 | 6748.0 – 6768.0 | ||
HeI | 7067.1252 | 7057.1 – 7077.1 | 7037.1 – 7057.1 | 7077.1 – 7097.1 | ||
ArIII | 7137.76 | 3.21e-1 | 1.4e-3 | 7127.8 – 7147.8 | 7107.8 – 7127.8 | 7147.8 – 7167.8 |
ArIV | 7172.68 | |||||
ArIV | 7239.76 | |||||
ArIV | 7265.33 | |||||
OII | 7321.003 | 5.19e-2 | [1] | 7291.0 – 7311.0 | 7342.8 – 7362.8 | |
OII | 7322.01 | 8.37e-3 | 9.07e-2 | 7313.8 – 7326.8 | 7291.0 – 7311.0 | 7342.8 – 7362.8 |
OII | 7331.68 | 9.32e-3 | 7.74e-2 | 7326.8 – 7339.8 | 7291.0 – 7311.0 | 7342.8 – 7362.8 |
OII | 7332.75 | 1.49e-2 | 3.85e-2 | [1] | 7291.0 – 7311.0 | 7342.8 – 7362.8 |
ArIV | 7334.17 | |||||
ArIII | 7753.24 | 8.3e-2 | 1.3e-4 | 7743.2 – 7763.2 | 7703.2 – 7743.2 | 7763.2 – 7803.2 |
P20 | 8394.703 | |||||
P19 | 8415.630 | |||||
P18 | 8440.274 | |||||
P17 | 8469.581 | |||||
P16 | 8504.819 | 8494.8 – 8514.8 | 8474.8 – 8494.8 | 8514.8 – 8534.8 | ||
P15 | 8547.731 | 8534.8 – 8557.7 | 8514.8 – 8534.8 | 8557.7 – 8587.7 | ||
P14 | 8600.754 | 8587.7 – 8610.8 | 8557.7 – 8587.7 | 8610.8 – 8650.8 | ||
P13 | 8667.398 | 8657.4 – 8677.4 | 8617.4 – 8657.4 | 8677.4 – 8717.4 | ||
P12 | 8752.876 | 8742.9 – 8762.9 | 8702.9 – 8742.9 | 8762.9 – 8802.9 | ||
\({\rm P}\theta\) | 8865.216 | 8855.2 – 8875.2 | 8815.2 – 8855.2 | 8875.2 – 8915.2 | ||
SIII | 8831.8 | |||||
\({\rm P}\eta\) | 9017.384 | 9007.4 – 9027.4 | 8977.4 – 9007.4 | 9027.4 – 9057.4 | ||
SIII | 9071.1 | 1.85e-2 | 3.94e-5 | 9061.1 – 9081.1 | 9026.1 – 9061.1 | 9081.1 – 9116.1 |
\({\rm P}\zeta\) | 9231.546 | 9221.5 – 9241.5 | 9181.5 – 9221.5 | 9241.5 – 9281.5 | ||
SIII | 9533.2 | 4.78e-2 | 2.09e-4 | 9525.5 – 9540.9 | 9483.2 – 9523.2 | 9558.6 – 9598.6 |
\({\rm P}\epsilon\) | 9548.588 | 9540.9 – 9556.3 | 9483.2 – 9523.2 | 9558.6 – 9598.6 | ||
\({\rm P}\delta\) | 10052.123 | 10042.1 – 10062.1 | 10002.1 – 10042.1 | 10062.1 – 10102.1 |
Non-parametric Emission-Line Measurements¶
The DAP performs non-parametric measurements of the emission lines using
a simple moment analysis. See mangadap.proc.emissionlinemoments
and Emission-line Moments. In survey-level runs of the DAP, we
have typically paired the set of moment measurements and Gaussian
models; however, the number of emission-line moment measurements need
not be matched to the number of emission-line Gaussian models and vice
versa.
Input Data Format¶
The parameters that define the emission-line moments to calculate are
provided via the
mangadap.par.emissionmomentsdb.EmissionMomentsDB
object, which
is built using an SDSS-style parameter file.
The columns of the parameter file are:
Parameter | Format | Description |
---|---|---|
index |
int | Unique integer identifier of the emission line. Must be unique. |
name |
str | Name of the transition. |
lambda |
float | Rest frame wavelength of the emission line to analyze. |
waveref |
str | The reference frame of the wavelengths; must be either ‘air’ for air or ‘vac’ for vacuum. |
primary |
float[2] | A two-element vector with the starting and ending wavelength for the primary passband surrounding the emission line(s). |
blueside |
float[2] | A two-element vector with the starting and ending wavelength for a passband to the blue of the primary band. |
redside |
float[2] | A two-element vector with the starting and ending wavelength for a passband to the red of the primary band. |
and an example file might look like this:
typedef struct {
int index;
char name[6];
double lambda;
char waveref[3];
double primary[2];
double blueside[2];
double redside[2];
} DAPELB;
DAPELB 2 OIId 3728.4835 vac { 3716.3 3738.3 } { 3706.3 3716.3 } { 3738.6 3748.6 }
DAPELB 3 OII 3729.875 vac { -1 -1 } { -1 -1 } { -1 -1 }
Note in the above example that the second set of parameters set the
passbands to have nonsensical limits of {-1 -1}
. This is used to
signify that the moment parameters are “dummy” or placeholder
parameters. This is used to create an empty channel in the output MAPS
file and is used just to synchronize the channel indices between the
non-parametric and Gaussian-fit results. That is, it’s used to ensure
that, e.g., the \({\rm H}\alpha\) measurements are in the same
channel for both the EMLINE_SFLUX
and EMLINE_GFLUX
extensions.
Changing the moment parameters¶
The moment measurements are performed by
mangadap.proc.emissionlinemoments.EmissionLineMoments
; see
Emission-line Moments. A set of parameter files that define a
list of emission-line moment sets are provided with the DAP source
distribution and located at
$MANGADAP_DIR/data/emission_bandpass_filters
. There are a few
methods that you can use to change the set of emission-line parameters
used by mangadap.proc.emissionlinemoments.EmissionLineMoments
:
- To use one of the existing parameter databases, you can change the
emission_passbands
keyword in themangadap.proc.emissionlinemoments.EmissionLineMoments
configuration file. The keyword should be the capitalized root of the parameter filename. E.g., to use$MANGADAP_DIR/data/emission_bandpass_filters/elbmpl9.par
, set the keyword toELBMPL9
.- To use a new parameter database, write the file and save it in the
$MANGADAP_DIR/data/emission_bandpass_filters/
directory, and then change the relevant configuration file in the same way as described above.
Gaussian Emission-Line Modeling¶
The DAP models the emission lines using single component Gaussian
functions. See mangadap.proc.emissionlinemoments
and
Emission-line Modeling. In survey-level runs of the DAP, we have
typically paired the set of moment measurements and Gaussian models;
however, the number of emission-line moment measurements need not be
matched to the number of emission-line Gaussian models and vice versa.
Input Data Format¶
The parameters that define the emission-line models to fit are provided
via the mangadap.par.emissionlinedb.EmissionLineDB
object,
which is built using an SDSS-style parameter file.
The columns of the parameter file are:
Parameter | Format | Description |
---|---|---|
index |
int | Unique integer identifier of the emission line. Must be unique. Specifically used when tying line parameters. |
name |
str | Name of the transition. |
lambda |
float | Rest frame wavelength of the emission line to analyze. |
waveref |
str | The reference frame of the wavelengths; must be either ‘air’ for air or ‘vac’ for vacuum. |
action |
str | A single character setting how the line should be treated. See Emission-Line “Actions”. |
relative_flux |
float | Relative flux of the emission lines. This should most often be unity when the flux is not tied to another line; see Emission-Line “Modes”. |
mode |
str | Fitting mode for the line. See Emission-Line “Modes”. |
profile |
str | The name of the class used to construct the line profile. The
available options are any of the classes in
mangadap.util.lineprofiles . This functionality will likely be
deprecated because the lineprofile should essentially always be
mangadap.util.lineprofiles.FFTGaussianLSF ; selected by
setting this parameter to “FFTGaussianLSF”. |
ncomp |
int | The number of components to fit. NOT TYPICALLY USED! |
output_model |
int | Flag to include the best-fitting model of the line in the emission-line model spectrum. NOT TYPICALLY USED! |
par |
float[3] | A list of the initial guess for the line profile parameters. NOT TYPICALLY USED! The number of parameters must match the struct declaration at the top of the file. The initial parameters are automatically adjusted to provide any designated flux ratios, and the center is automatically adjusted to the provided redshift for the spectrum. For example, for a GaussianLineProfile, this is typically set to “{1.0 0.0 100.0}”. |
fix |
int[3] | A list of flags for fixing the input guess parameters during the fit. NOT TYPICALLY USED! Use 0 for a free parameter, 1 for a fixed parameter. The parameter value is only fixed AFTER adjusted in the flux and or center based on the redshift and the implied tied parameters. For a free set of parameters using a GaussianLineProfile, this is set to “{ 0 0 0 }”. |
lower_bound |
str[3] | A list of lower bounds for the parameters. NOT TYPICALLY USED! For each parameter, use None to indicate no lower bound. For a GaussianLineProfile with positive flux and standard deviation, this is set to ‘{ 0.0 None 0.0 }’. |
upper_bound |
str[3] | A list of upper bounds for the parameters. NOT TYPICALLY USED! For each parameter, use None to indicate no upper bound. For a GaussianLineProfile with maximum standard deviation of 800 km/s, this is set to ‘{ None None 800.0 }’. |
log_bounded |
int[3] | A list of flags used when determining if a fit parameter is near the imposed boundary. NOT TYPICALLY USED! If true, the fraction of the boundary range used is done in logarithmic, not linear, separation. Use 0 for False, 1 for True. |
blueside |
float[2] | A two-element vector with the starting and ending wavelength for a passband to the blue of the primary band. |
redside |
float[2] | A two-element vector with the starting and ending wavelength for a passband to the red of the primary band. |
and an example file might look like this:
typedef struct {
int index;
char name[6];
double lambda;
char waveref[3];
char action;
double relative_flux;
char mode[6];
char profile[30];
int ncomp;
int output_model;
double par[3];
int fix[3];
char lower_bound[3][10];
char upper_bound[3][10];
int log_bounded[3];
double blueside[2];
double redside[2];
} DAPEML;
DAPEML 2 OII 3727.092 vac f 1.00 v34 FFTGaussianLSF 1 1 { 1.0 0.0 100.0 } { 0 0 0 } { 0.0 None 30.0 } { None None 400. } { 0 0 1 } { 3706.3 3716.3 } { 3738.6 3748.6 }
DAPEML 3 OII 3729.875 vac f 1.00 k2 FFTGaussianLSF 1 1 { 1.0 0.0 100.0 } { 0 0 0 } { 0.0 None 30.0 } { None None 400. } { 0 0 1 } { 3706.3 3716.3 } { 3738.6 3748.6 }
DAPEML 33 NII 6549.86 vac f 0.34 a35 FFTGaussianLSF 1 1 { 1.0 0.0 100.0 } { 0 0 0 } { 0.0 None 30.0 } { None None 400. } { 0 0 1 } { 6483.0 6513.0 } { 6623.0 6653.0 }
DAPEML 34 Ha 6564.632 vac f 1.00 f FFTGaussianLSF 1 1 { 1.0 0.0 100.0 } { 0 0 0 } { 0.0 None 30.0 } { None None 400. } { 0 0 1 } { 6483.0 6513.0 } { 6623.0 6653.0 }
DAPEML 35 NII 6585.271 vac f 1.00 v34 FFTGaussianLSF 1 1 { 1.0 0.0 100.0 } { 0 0 0 } { 0.0 None 30.0 } { None None 400. } { 0 0 1 } { 6483.0 6513.0 } { 6623.0 6653.0 }
Note
- Both the emission-line moments database and the emission-line modeling database define the sidebands used for the equivalent width calculations. Nominally, these should be the same, but it’s up to the person that writes the two parameter files to make sure that’s true.
- Many of the current parameters in the emission line modeling
parameter file are hold-overs from when
mangadap.proc.elric.Elric
was the standard class used for the emission-line fitting. Anything marked as “NOT TYPICALLY USED” hasn’t been adapted for use with the currently preferred module,mangadap.proc.sasuke.Sasuke
.
Emission-Line “Actions”¶
The action
parameter allows the emission-line database to be used
both in masking during the stellar-continuum modeling (see
mangadap.util.pixelmask.SpectralPixelMask
) and during the
emission-line modeling itself.
The valid actions are:
i
: ignore the line, as if the line were commented out.f
: fit the line and mask the line when fitting the stellar continuum.m
: mask the line when fitting the stellar continuum but do not fit the line itselfs
: defines a sky line that should be masked. When masked, the wavelength of the line is not adjusted for the redshift of the object spectrum.
I.e., when using the emission-line database for the emission-line
modeling, lines with the action set to f
are fit, whereas all other
lines are ignored.
Emission-Line “Modes”¶
The mode
parameter sets how the emission line should be treated with
respect of the rest of the lines being modeled.
The valid modes are:
f
: Fit the line independently of all others.wN
: Used bymangadap.proc.elric.Elric
only. Fit the line with untied parameters, but use a window that includes both this line and the line with index N.xN
: Used bymangadap.proc.elric.Elric
only. Fit the line with its flux tied to the line with index N.vN
: Fit the line with the velocity tied to the line with index N.sN
: Fit the line with the velocity dispersion tied to the line with index N.kN
: Fit the line with the velocity and velocity dispersion tied to the line with index N.aN
: Fit the line with the flux, velocity, and velocity dispersion tied to the line with index N.
As noted in the mode description, many of the modes are only available
when using the mangadap.proc.elric.Elric
module. For the w
mode, this is simply because the preferred module,
mangadap.proc.sasuke.Sasuke
, fits the full spectrum instead of
fitting the lines within small spectral windows. The other limitation
are because mangadap.proc.sasuke.Sasuke
is based on the use of
template spectra to fit the emission lines (see
mangadap.proc.emissionelinetemplates.EmissionLineTemplates
): To
tie line fluxes, the lines to be tied are included in the same template
spectrum, meaning that their kinematics are also automatically tied.
That means that, for mangadap.proc.sasuke.Sasuke
, the x
and a
modes are identical.
In the Input Data Format example, the modes set the
\({\rm H}\alpha\) line as the “reference” line. I.e., there should
always be one line whose mode is f
. This requirement is simply
practical in setting up the tied parameter structure; there is no more
weight given to the fit of the reference line than any other line. The
blue [OII] and red [NII] lines have their velocities tied to the
\({\rm H}\alpha\) line, all kinematics of the red [OII] line are
tied to the blue [OII] line, and all parameters of the blue [NII] line
are tied to the red [NII] line with a fixed flux ratio of
NII-6550/NII-6585 == 0.34
. By virtue of being tied to lines that
have their velocites tied to the \({\rm H}\alpha\) line, the
velocities of the red [OII] and blue [NII] lines are also tied to the
\({\rm H}\alpha\) line. Again, this doesn’t mean that the fit to
the \({\rm H}\alpha\) line is given any more weight than any other
line, it just means that there is one model parameter that defines the
velocity of all lines.
Changing the modeling parameters¶
The emission-line modeling is performed by
mangadap.proc.emissionlinemodel.EmissionLineModel
; see
Emission-line Modeling. A set of files that define a list of
emission-line model parameter sets are provided with the DAP source
distribution and located at $MANGADAP_DIR/data/emission_lines
.
There are a few methods that you can use to change the set of
emission-line parameters used by
mangadap.proc.emissionlinemodel.EmissionLineModel
:
- To use one of the existing parameter databases, you can change the
emission_lines
keyword in themangadap.proc.emissionlinemodel.EmissionLineModel
configuration file. The keyword should be the capitalized root of the parameter filename. E.g., to use$MANGADAP_DIR/data/emission_lines/elpmpl9.par
, set the keyword toELPMPL9
.- To use a new parameter database, write the file and save it in the
$MANGADAP_DIR/data/emission_lines/
directory, and then change the relevant configuration file in the same way as described above.
[1] | (1, 2, 3, 4, 5, 6, 7, 8, 9) No primary band defined because it overlaps with another line. |