Line emissivities at high temperatures

[Teja Teppala]

Hi,

I'm using PyNeb to calculate ratios of HeI recombination lines. I need to obtain emissivities for temperatures around 20000-40000 K. Although the Helium table has data at such temperatures, the built-in emissivity function is not working beyond 25000K. Is there a way to get the emissivities for temperatures beyond that?

Thanks,

Teja

--

Teja Teppala (he/him/his)

Doctoral candidate in Astronomy | Graduate Teaching Assistant

Vice President - Graduate Professional Council | President - Mizzou Science Policy Advocacy Network

Department of Physics and Astronomy

University of Missouri - Columbia

Contact: +1 (573) 825-4874 | tt...@mail.missouri.edu | tejateppala.github.io

[Christophe Morisset]

Hi Teja,

The atomic data used by PyNeb for HeI recombination are from Porter et al 2012, and they cover the 5,000-25,000K range only.

Are you aware of public data at higher temperatures?

Thanks,

Christophe

[Christophe Morisset]

Hi again Teja,

Sorry for the mistake, I realized that we actually already have the data you need incorporated in a development branch of PyNeb. They are from Del Zanna & Storey 2022. We still did not merge them into the main branch because we still have to see what we will use as labels for the lines: wavelength or levels. In any case we will need to provide a correspondence table to help the user. And one issue with wavelength is to use the air of vacuum values. Air is more easy, but in this case there will be some issues in the edges (IR and UV being in vacuum).

If you are in some need and take very care of the wavelengths you are using comparing with the data from Del Zanna, you may install the branch and check if this covers your needs:

pip install -U git+https://github.com/Morisset/PyNeb_devel.git@HeI_Zanna

Tell us if anything goes wrong so we can correct before release, thanks a lot,

Christophe

[Teja Teppala]

Hi Christophe,

Thank your response. I have installed the development branch and tested it for higher temperatures. Although the temperatures from Del Zanna & Storey 2022 reach up to 10^4.6 K (~40000K), the getEmissivity function is unable to work beyond 31622 K. Is there a way to fix this? or change the core function to extrapolate to higher temperatures (say > 40000K)?

Their data has so many lines close together, so it is a good idea to provide the correspondence table.

Please let me know if you need any additional information.

Thanks,

Teja

[Christophe Morisset]

Hi Teja,

The data from Del Zanna have been obtained form the supplement data file "stac800_supplemental_file.zip" from the MNRAS. The "allem.d" data file contains emissivities for 9 densities. For each density, the Te are given as:

Log Ne=2.00 log T= 2.60 2.70 2.80 2.90 3.00 3.10 3.20 3.30 3.40 3.50  3.60 3.70 3.80 3.90 4.00 4.10 4.20 4.30 4.40 4.50
As you can see, the upper Te is 10**4.5 = 31,622K, which is what we have in PyNeb (we actually only change the format the data are stored, not the values). The paper claims data up to 4.6 are available, but not in the MNRAS datafile.

I did not find any data on the CDS database related to this paper, I will ask Gulio Del Zanna if he has any data covering high Te.

Best regards,

Ch.

[Teja Teppala]

Thanks for the clarification, Christophe. The supplement data file folder also contains a FORTRAN code to make 2D interpolations for the emissivities. I'm thinking of generating data for temperatures of interest. Can you share the format for the data file so that I can convert the interpolated emissivities into something that PyNeb can read?

Best,

Teja

[Christophe Morisset]

In your case it would be extrapolation, that is mure complicated and risky than interpolation. The HeI_Zanna branch also includes the python routine used to deal with the original data:

https://github.com/Morisset/PyNeb_devel/blob/HeI_Zanna/pyneb/atomic_data_fits/HeI_Zanna/read_zanna.py

Ch.

[Teja Teppala]

Thank you, I got the word wrong. I'm trying to modify that Fortran code to extrapolate, but I'll contact the author directly to see if I can get the data for higher temperatures.

Thank you again, for sending the python code.

I'll update you if something comes up.

Best,

Teja