Closed dirkscholte closed 1 year ago
Just adding a few other plots that I had lying around. In case they might be useful. The yellow bands at z ~0.45 and ~0.9 is where the 4000A break passes through the edges of the different cameras.
DN4000_OBS:
Looking as expected!
DN4000:
@dirkscholte thank you for this report. This is a clear bug in DN4000
right here:
https://github.com/desihub/fastspecfit/blob/2.1.2/py/fastspecfit/emlines.py#L2624
TL;DR: in my call to get_dn4000()
I should have explicitly set rest=True
; the line-free spectra I'm passing are in the observed frame but even though I'm passing the redshift to move things in the rest-frame, get_dn4000()
doesn't use this redshift if rest=True
, which is the default for the code, blarg!
When plotting
DN4000_OBS
andDN4000
I found that their values are very different. The plots below are using data from the fuji v2.0, guadalupe v2.0 and iron v1.0 catalogs. The log(Mstar) vsDN4000_OBS
plot looks as expected but theDN4000
does not. Selection is BGS galaxies between 0.05<z<0.09.