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quick extinction coefficient questions

quick extinction coefficient questions  

  By: Adrian Lucy on May 13, 2019, 6:39 a.m.

Two quick questions:

(1) I just wanted to double-check my understanding that the Rband values available here (http://skymapper.anu.edu.au/filter-transformations/) correspond to 

Aband = Rband * E(B-V)true

and not

Aband = Rband * E(B-V)SFD

Is that right? (Where, e.g., E(B-V)true=0.86*E(B-V)SFD per the S&F 2011 correction to SFD 1998.)

(2) The SFD E(B-V) value in SkyMapper master generally isn't exactly what you'd get searching on those exact coordinates in IRSA (https://irsa.ipac.caltech.edu/applications/DUST/), although it's close. Is there some spatial binning in the SkyMapper catalog, or something?

Of course, that's all pretty insubstantial relative to other typical uncertainties (Rband being from a flat-spectrum calculation, differences with empirical coefficients like in Huang et al. 2019, airmass/leak issues, or patching together different southern hemisphere 3D dust maps that all have their own problems), but I thought I'd check anyway.



Re: quick extinction coefficient questions  

  By: SkyMapper Team on May 29, 2019, 3:32 p.m.

Hi Adrian,

1) The absorption coefficients are to be used as Aband = Rband * E(B-V)SFD, so the coefficients already include the 0.86 factor in them. Some authors find higher R_band values than we do, because they use those with E(B-V)true instead.

2) The E(B-V) values are not exactly the ones you find at the location of the objects, because they are indeed determined from a resampled SFD map, but they are close enough.