OVERVIEW

This software package was originally used to fit the Spitzer mid-infrared spectra of the QUEST (Quasar ULIRG and Evolution STudy) sample, as described in Schweitzer et al. 2006, Schweitzer et al. 2008, and Veilleux et al. 2009. It uses two PAH templates from Smith et al. 2007 atop an extincted and absorbed continuum model to fit the mid-IR spectra of galaxies that are heavily-absorbed and AGN with silicate emission.

The current version of QUESTFIT is optimized for processing spectra from the CASSIS (Combined Atlas of Sources with Spitzer IRS Spectra) portal to produce PAH fluxes for heavily absorbed sources. This method is described in Spoon et al. 2021 (submitted). These PAH fluxes will appear in the IDEOS (Infrared Database of Extragalactic Observables from Spitzer) portal.

REQUIREMENTS

IDL (tested with v8.5; may work with pre-v8.0 versions)

IDL libraries:

• IDL Astronomy User's Library
• Coyote, for graphics AND undefine.pro
  • or from the GitHub repository
• ISAP

Notes:

• The Spitzer IRS data reduction software SMART ships with a slightly modified version of the ISAP library. At least one instance of errors has been documented using this version of the library.
• The IDL Astronomy User's Library ships with some Coyote routines. However, it's not clear how well these libraries keep track of each other, so it may be preferable to download each package separately and delete the redundant routines that ship within other packages.

QUICK TEST

See files in the questfit/test subdirectory:

IDEOS ID 4978688_0 = Mrk 231

IDL> questfit, control file='4978688_0.ideos.cf',pathin='[path-to-questfit]/questfit/test/',pathout='[output-directory]',/res,/ps,/data,/log

IRAS21219

IDL> questfit, control file='IRAS21219m1757_dlw_qst.cf',pathin='[path-to-questfit]/questfit/test/',pathout='[output-directory]',/res,/ps,/data,/log

DETAILED USAGE

questfit and ideos_readcf are used to peform the spectral fitting. The other ideos_* routines are for collating the PAH fluxes for input to the IDEOS database.

The control file (*.cf) consists of 10 space-separated text columns of any width:

A	B	C	D	E	F	G	H	I	J
source	spectrum.xdr	-1	-1.	dummy	0.0	0.	X	0.0	0.0
template	si1.xdr	0.1	0.	DRAINE03	10.0	0.	S	0.0	0.0
absorption	tau1.xdr	1.0	0.	H2Oice6	0.0	0.	S	0.0	0.0
blackbody	BB	0.1	0.	DRAINE03	1.0	0.	S	100.	0.0
absorption	tau1.xdr	0.0	1.	H2Oice6	1.0	0.	S	0.0	0.0
powerlaw	PL	0.1	0.	DRAINE03	1.0	0.	S	-3.4	0.0
absorption	tau1.xdr	1.0	0.	H2Oice3	1.0	0.	S	0.0	0.0
absorption	tau2.xdr	1.0	0.	H2Oice6	1.0	0.	S	0.0	0.0
extinction	draine03.xdr	0.0	0.	DRAINE03	0.0	0.	X	0.0	0.0

Meaning of the columns:

• A

  • The type of data. Include at least one of each datatype (template, BB, PL, absorption, extinction). You have to use for at least one of each datatype (template, BB, PL) an absorption (as in the file above). And at least one extinction file has to be given. If you want to use more then one absorption on a certain datatype just add them up under the regarding datatype and they will all work on the datatype above (like for the powerlaw in the example above).

• B

  • source, template, absorption, extinction: filename
  • 'BB, PL`: any string

• C

  • source: lower wavelength limit. "-1" will use the lowest possible common wavelength.
  • template, blackbody, powerlaw: normalization factor
  • absorption: tau_peak
  • extinction: any float

• D

  • source: upper wavelength limit. "-1" will use the largest possible common wavelength.
  • template, blackbody, powerlaw: fix/free parameter for the normalization. 1=fixed, 0=free
  • absorption: fix/free parameter for tau_peak. 1=fixed, 0=free
  • extinction: any float

• E

  • source, absorption: any string
  • template, blackbody, powerlaw: shorthand for the extinction curve
  • extinction: shorthand for the extinction curve is defined and connected to the xdr.file

• F

  • source, extinction, absorption: any float
  • template, blackbody, powerlaw: extinction value (A_V)

• G

  • source, extinction, absorption: any float
  • template, bl, powerlaw: fix/free parameter for A_V. 1=fixed, 0=free

• H

  • source, extinction, absorption: any string
  • template, blackbody, powerlaw: S=screen extinction, M=mixed extinction

• I

  • source, template, absorption, extinction: any float
  • blackbody: temperature (in K)
  • powerlaw: index

• J

  • source, template, absorption, extinction: any float
  • blackbody: fix/free parameter for temperature. 1=fixed, 0=free
  • powerlaw: fix/free parameter for powerlaw index. 1=fixed, 0=free

To run:

IDL> questfit,control file='control.cf'

The fit will start and produce a plot with the model spectra fitted to the source. In addition the contribution of each model depending on wavelength is plotted. This is not in multicolor. If you want to have a nicer view, create a eps file by typing :

IDL> questfit,control file='control.cf',ps=1

This creates an eps-file into the 'pathout' directory At the same time the fitoutput which appears in your shell (after the fit) will be written into a file if you use ps=1.

The filename for the eps file is fit:sourcename.xdr_par:control file.cf.eps.

The filename for the data file is fitresult:sourcename.xdr_par:control file.cf.dat.

In the eps plot each data type (template, BB, PL) has a common color. Within one type the spectra differ from each other by the linestyle.

At the same time on the command shell at the end of the fit some information appears. The output is translated as follows:

• Each value P(X) is the program internal definition for the fitting parameter.

• The numbers of the contributors describe the order of appearance in the control file.

• norm factor is total normalization factor/local maximum. This is the factor you have to put fixed into the control file if you like the result. Be careful if you fix the parameters and you change the wavelength range, as the norm factor depends on the maximum found in the wavlength range.

• total normalization factor is the value which you have to multiply to the original template to get the fitted result.

• integral [W/cm^2] of XX is the flux integrated over frequency.

• contribution [%] to integrated source flux is the contribution to the integrated flux of each contributor

• Sum of all contributions [%] relative to int. sourceflux adds up all contributions; should be 100% in the case of a perfect fit.

Additional options:

• IDL> questfit,control file='control.cf',res=1: shows the residual (Data/Model)

• IDL> questfit,control file='control.cf',log=1: uses log xy-axis

• IDL> questfit,control file='control.cf',data=1 will produce output-data files of each model with norm-factors not equal to 0. The content of this output file is wavelength in microns, flux in Jy.The filenames are for example:

  • sourcename.xdr_par:controlfile.cf_template1.fit
  • sourcename.xdr_par:controlfile.cf_BB2.fit
  • sourcename.xdr_par:controlfile.cf_total.fit

• IDL> questfit,controlfile='control.cf',ident=1: shows an identification index for the spectra

QUESTIONS? BUGS? WANT TO MODIFY THE CODE?

Feel free to contact David Rupke at drupke@gmail.com with questions, bug reports, etc.

Modifications are encouraged, but subject to the license.

LICENSE AND COPYRIGHT

Copyright (C) 2016--2021 David S. N. Rupke, Vince Viola, Henrik Sturm, Mario Schweitzer, Dieter Lutz, Eckhard Sturm, Dong-Chan Kim, Sylvain Veilleux

These programs are free software: you can redistribute them and/or modify them under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License or any later version.

These programs are distributed in the hope that they will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License along with these programs. If not, see http://www.gnu.org/licenses/.