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 quadrupole 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 [3] |
3204.019 |
|||||
NeIII |
3343.14 |
|||||
NeV |
3346.783 |
1.38e-1 |
6.2e-5 |
|||
NeV |
3426.864 |
3.82e-1 |
3.9e-4 |
|||
NI [3] |
3467.513 |
|||||
H25 |
3670.5155 |
|||||
H24 |
3672.5279 |
|||||
H23 |
3674.8110 |
|||||
H22 |
3677.4160 |
|||||
H21 |
3680.4065 |
|||||
H20 |
3683.8627 |
|||||
H19 |
3687.8871 |
|||||
H18 |
3692.6119 |
|||||
H17 |
3698.2103 |
|||||
H16 |
3704.9132 |
|||||
H15 |
3713.0334 |
|||||
H14 |
3723.0035 |
3706.3 – 3716.3 |
3738.6 – 3748.6 |
|||
OII |
3727.092 |
1.59e-4 |
1.86e-5 |
3716.3 – 3738.3 |
3706.3 – 3716.3 |
3738.6 – 3748.6 |
OII |
3729.875 |
1.98e-6 |
2.86e-5 |
3706.3 – 3716.3 |
3738.6 – 3748.6 |
|
H13 |
3735.4365 |
3706.3 – 3716.3 |
3738.6 – 3748.6 |
|||
H12 [4] |
3751.2174 |
3746.2 – 3756.2 |
3738.6 – 3748.6 |
3756.6 – 3766.6 |
||
H11 [4] |
3771.7012 |
3761.7 – 3781.7 |
3756.6 – 3766.6 |
3779.1 – 3789.1 |
||
\({\rm H}\theta\) [4] |
3798.9757 |
3789.0 – 3809.0 |
3776.5 – 3791.5 |
3806.5 – 3821.5 |
||
\({\rm H}\eta\) [4] |
3836.4720 |
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 [3] |
3889.749 |
3806.5 – 3826.5 |
3900.2 – 3920.2 |
|||
\({\rm H}\zeta\) [4] |
3890.1506 |
3880.2 – 3900.2 |
3806.5 – 3826.5 |
3900.2 – 3920.2 |
||
NeIII |
3968.59 |
5.40e-2 |
3938.6 – 3958.6 |
3978.6 – 3998.6 |
||
\({\rm H}\epsilon\) [4] |
3971.1951 |
3961.2 – 3981.2 |
3941.2 – 3961.2 |
3981.2 – 4001.2 |
||
HeI [3] |
4027.328 |
4017.3 – 4037.3 |
3997.3 – 4017.3 |
4037.3 – 4057.3 |
||
SII |
4069.749 |
1.92e-1 |
9.53e-8 |
4062.7 – 4073.6 |
4049.7 – 4062.7 |
4082.0 – 4092.9 |
SII |
4077.500 |
7.72e-2 |
1.16e-6 |
4073.6 – 4084.5 |
4049.7 – 4062.7 |
4082.0 – 4092.9 |
\({\rm H}\delta\) [4] |
4102.8922 |
4092.9 – 4112.9 |
4082.0 – 4092.9 |
4112.9 – 4132.9 |
||
\({\rm H}\gamma\) [4] |
4341.6837 |
4331.7 – 4351.7 |
4311.7 – 4331.7 |
4349.7 – 4358.7 |
||
OIII |
4364.436 |
1.71e+0 |
4358.7 – 4374.4 |
4349.7 – 4358.7 |
4374.4 – 4384.4 |
|
HeI [3] |
4472.734 |
4462.7 – 4482.7 |
4442.7 – 4462.7 |
4482.7 – 4502.7 |
||
HeII [3] |
4687.015 |
4677.0 – 4697.0 |
4667.0 – 4677.0 |
4697.0 – 4707.0 |
||
ArIV [2] |
4712.58 |
9.6e-3 |
||||
HeI [3] |
4714.466 |
4707.0 – 4722.0 |
4697.0 – 4707.0 |
4722.0 – 4732.0 |
||
ArIV |
4741.45 |
7.2e-2 |
5.1e-3 |
|||
\({\rm H}\beta\) [4] |
4862.6830 |
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 |
4988.2 – 4983.2 |
5028.2 – 5048.2 |
|||
ArIII |
5193.27 |
3.10e+0 |
||||
NI |
5199.349 |
1.60e-5 |
4.34e-6 |
5189.3 – 5209.3 |
5169.4 – 5189.3 |
5211.7 – 5231.7 |
NI |
5201.705 |
9.71e-7 |
6.59e-6 |
5169.4 – 5189.4 |
5211.7 – 5231.7 |
|
OI |
5578.887 |
1.26e+0 |
||||
NII |
5756.19 |
1.14e+0 |
||||
HeI [3] |
5877.252 |
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 |
6365.536 |
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 |
HeII [3] |
6561.890 |
|||||
\({\rm H}\alpha\) [4] |
6564.608 |
6557.6 – 6571.6 |
6483.0 – 6513.0 |
6623.0 – 6653.0 |
||
NII |
6585.27 |
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 |
6718.295 |
1.39e-5 |
1.88e-4 |
6711.3 – 6725.3 |
6690.0 – 6708.0 |
6748.0 – 6768.0 |
SII |
6732.674 |
5.63e-4 |
1.21e-4 |
6725.7 – 6739.7 |
6690.0 – 6708.0 |
6748.0 – 6768.0 |
HeI [3] |
7067.144 |
7057.1 – 7077.1 |
7037.1 – 7057.1 |
7077.1 – 7097.1 |
||
HeI |
7067.65683 |
|||||
ArIII |
7137.76 |
3.21e-1 |
1.4e-3 |
7127.8 – 7147.8 |
7107.8 – 7127.8 |
7147.8 – 7167.8 |
ArIV |
7172.67 |
8.1e-1 |
9.8e-2 |
|||
ArIV |
7239.77 |
4.44e-1 |
2.26e-1 |
|||
ArIV |
7265.33 |
4.88e-1 |
1.90e-1 |
|||
HeI |
7283.3571 |
|||||
OII |
7320.94 |
5.19e-2 |
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 |
7291.0 – 7311.0 |
7342.8 – 7362.8 |
|
ArIV |
7334.17 |
1.22e-1 |
||||
ArIII |
7753.24 |
8.3e-2 |
1.3e-4 |
7743.2 – 7763.2 |
7703.2 – 7743.2 |
7763.2 – 7803.2 |
ArIII |
8038.73 |
2.9e-5 |
||||
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 |
||
SIII |
8831.8 |
5.25e-6 |
||||
\({\rm P}\theta\) |
8865.216 |
8855.2 – 8875.2 |
8815.2 – 8855.2 |
8875.2 – 8915.2 |
||
\({\rm P}\eta\) |
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 |
HeI [3] |
9212.862 |
|||||
\({\rm P}\zeta\) |
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 |
||
HeI [3] |
9528.778 |
|||||
HeI [3] |
10030.470 |
|||||
\({\rm P}\delta\) |
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
EmissionMomentsDB
object,
which is built using an SDSS-style parameter file.
The columns of the parameter file are:
Parameter |
Format |
Description |
---|---|---|
|
int |
Unique integer identifier of the emission line. Must be unique. |
|
str |
Name of the transition. |
|
float |
Rest frame wavelength of the emission line to analyze. |
|
str |
The reference frame of the wavelengths; must be either ‘air’ for air or ‘vac’ for vacuum. |
|
float[2] |
A two-element vector with the starting and ending wavelength for the primary passband surrounding the emission line(s). |
|
float[2] |
A two-element vector with the starting and ending wavelength for a passband to the blue of the primary band. |
|
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 define
nonsensical passbands with 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 in the DAP MAPS file.
Changing the moment parameters
The moment measurements are performed by
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/mangadap/data/emission_bandpass_filters
. The
database you wish to use is selected by the passbands
parameter in the
relevant parameter block of the Analysis Plans file. The keyword is simply the
capitalized name of the file without the “.par” extension. For example, to use
the elbmpl9.par
database, the plan file would include
[default.eline_moments]
passbands = 'ELBMPL9'
To provide a user-defined database, simply replace the passbands
keyword
with the name of the local file defining the database (in the format given
above). For example,
[default.eline_moments]
passbands = '/path/to/my/local/file/my_elb_database.par'
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
EmissionLineDB
object, which is built
using an SDSS-style parameter file.
The columns of the parameter file are:
Parameter |
Format |
Description |
---|---|---|
|
int |
Unique integer identifier of the emission line. Must be unique. Specifically used when tying line parameters. |
|
str |
Name of the transition. |
|
float |
Rest frame wavelength of the emission line to analyze. |
|
str |
The reference frame of the wavelengths; must be either ‘air’ for air or ‘vac’ for vacuum. |
|
str |
A single character setting how the line should be treated. See Emission-Line “Actions”. |
|
str[2] |
A sequence of 2 10-character strings that indicate how the flux of
the line should be tied to another line. The first element gives the
index of the line to tie (see |
|
str[2] |
A sequence of 2 10-character strings that indicate how the velocity
of the line should be tied to another line. The first element gives
the index of the line to tie (see |
|
str[2] |
A sequence of 2 10-character strings that indicate how the velocity
dispersion of the line should be tied to another line. The first
element gives the index of the line to tie (see |
|
float[2] |
A two-element vector with the starting and ending wavelength for a passband to the blue of the primary band. |
|
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 restwave;
char waveref[3];
char action;
char tie_f[2][10];
char tie_v[2][10];
char tie_s[2][10];
double blueside[2];
double redside[2];
} DAPEML;
DAPEML 2 OII 3727.092 vac f { None None } { 34 = } { None None } { 3706.3 3716.3 } { 3738.6 3748.6 }
DAPEML 3 OII 3729.875 vac f { None None } { 2 = } { 2 = } { 3706.3 3716.3 } { 3738.6 3748.6 }
DAPEML 23 Hb 4862.6830 vac f { None None } { 34 = } { 34 1.4 } { 4798.9 4838.9 } { 4885.6 4925.6 }
DAPEML 33 NII 6549.86 vac f { 35 =0.34 } { 35 = } { 35 = } { 6483.0 6513.0 } { 6623.0 6653.0 }
DAPEML 34 Ha 6564.608 vac f { None None } { None None } { None None } { 6483.0 6513.0 } { 6623.0 6653.0 }
DAPEML 35 NII 6585.27 vac f { None None } { 34 = } { None None } { 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 is true.
- Format changes:
version 3.1.0: Many parameters removed that were used by the deprecated
Elric
fitter.version 4.1.0: Added ability to tie the three parameters to different lines; i.e., velocity can be tied to one line while dispersion is tied to a different one.
Emission-Line “Actions”
The action
parameter allows the emission-line database to be used
both in masking during the stellar-continuum modeling (see
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 itself
s
: 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 Tying
Line tying in the DAP uses the functionality in ppxf in a limited and abstracted way.
Tying fluxes effectively means that the lines are put in the same emission-line template. This is why, currently, any lines with tied fluxes must also tie their velocity and velocity dispersion. Also, the DAP currently does not allow tying fluxes using inequalities.
Tying kinematics can be done with equality or inequality. For equality, use
the =
character, as in the example file above. Unlike the fluxes, the
kinematics cannot be tied to be, e.g., a specific fraction of the value of the
tied line. (I.e., you can’t tie the dispersion to be exactly half of the
dispersion of the tied line). For inequality, there are a couple of options:
Use
>N
or<N
to force the value to be greater or less than the provided fraction of the the value of the tied line. E.g., to force the dispersion of one component to be at least 1.5 times larger than the tied line, use>1.5
. Using>
or<
is equivalent to>1
and<
, respectively.To bound the value between both upper and lower limits, you must use a single fixed fractional bound. For example, setting the tied value for the dispersion to
1.4
means that the best-fitting dispersion must be greater than 1/1.4 and less than 1.4 times the dispersion of the tied line.
Warning
Although line tying has been experimented with for MaNGA data, much of the inequality tying is not well tested.
Emission-Line “Modes”
Warning
This parameter is now DEPRECATED in favor of the tie
parameter.
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 byElric
only. Fit the line with untied parameters, but use a window that includes both this line and the line with indexN
.
xN
: Used byElric
only. Fit the line with its flux tied to the line with indexN
.
vN
: Fit the line with the velocity tied to the line with indexN
.
sN
: Fit the line with the velocity dispersion tied to the line with indexN
.
kN
: Fit the line with the velocity and velocity dispersion tied to the line with indexN
.
aN
: Fit the line with the flux, velocity, and velocity dispersion tied to the line with indexN
.
As noted in the mode description, many of the modes are only
available when using the Elric
module.
For the w
mode, this is simply because the preferred module,
Sasuke
, fits the full spectrum instead
of fitting the lines within small spectral windows. The other
limitation are because Sasuke
is based
on the use of template spectra to fit the emission lines (see
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
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 to 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 moment measurements are performed by
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/mangadap/data/emission_bandpass_filters
. The
database you wish to use is selected by the passbands
parameters in the
relevant parameter block of the Analysis Plans file. The keyword is simply the
capitalized name of the file without the “.par” extension. To provide a
user-defined database, simply replace the passbands
keyword with the name of
the local file defining the database (in the format given above).
The emission-line modeling is performed by
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/mangadap/data/emission_lines
. The database you
wish to use is selected by the emission_lines
parameter in the relevant
parameter block of the Analysis Plans file. The keyword is simply the capitalized
name of the file without the “.par” extension. For example, to use the
elpmpl11.par
database, the plan file would include
[default.eline_fits.fit]
emissionpassbands = 'ELPMPL11'
To provide a user-defined database, simply replace the passbands
keyword
with the name of the local file defining the database (in the format given
above). For example,
[default.eline_fits.fit]
emissionpassbands = '/path/to/my/local/file/my_elp_database.par'