Near infrared standard stars

Adam wrote on Feb 10, 2009

Is there any external package that includes a set of near-infrared standard stars for use with the 'standard' and 'sensfunc' applications? I found mid-IR calibrators in the Gemini package, but nothing in the 1.0-2.4 micron range.

Thanks,
Adam

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James Turner wrote on Feb 10, 2009

I understand people typically use a model black-body curve in the NIR, appropriate for the spectral type of the observed standard. Whether there are some real tabluated standards available for IRAF I'm not sure. Does that help?

Cheers,

James.

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Adam wrote on Feb 10, 2009

That's what I ended up using, but I know that spectra of, e.g., Vega, are tabulated on the NOAO archive (ftp://ftp.noao.edu/catalogs/medresIR/) and I'd prefer to use a real spectrum if possible. I think it would be useful for dealing with the Brackett and Paschen absorption lines.

Adam

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James Turner wrote on Feb 10, 2009

In that case, I'd just use a small awk script to convert those tables to the right format for IRAF, following the examples in the onedstds$ directory. Alternatively, you might be able to get IRAF to read them directly by adding the right "units" comment at the top of the file. Perhaps Frank can advise on this.

James.

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Adam wrote on Feb 10, 2009

That was also what I was thinking of doing, but my attempt yesterday failed because there are no units provided in the papers or the data tables - I think they're normalized spectra. I should be able to figure out the right units from the zero-magnitude fluxes, I suppose, so if I have success with that I'll post my results here. Otherwise, I would definitely appreciate the help.

Thanks,
Adam

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Adam wrote on Feb 10, 2009

Actually, James, you were quite right: blackbody calibration is good enough for my purposes. On the same note, though, is there any good way to fit to the deep absorption bands at 2.0 and 2.06 microns? Spline fitting in sensfunc does a poor job of matching these features, though it does a very nice job of ignoring the various hydrogen absorption features.

Thanks,
Adam

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James Turner wrote on Feb 10, 2009

I don't have much experience with techniques for removing absorption features (I would suggest asking the instrument support staff), but have you tried the other interpolant options in sensfunc? The splines are piecewise interpolants and maybe a low-order legendre or chebyshev polynomial with rejection will work better.

James.

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Adam wrote on Feb 10, 2009

Whoops, missed this message. Yes, I've used the interpolation in sensfunc, but it's not high enough order (even experimenting with >50 order splines, which I'd never trust) to smoothly fit the absorption features. The low-order ones interpolate across them, as you suggest, but that's not what I'm trying to do in this case.

Adam

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Last post on Feb 10, 2009