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Jean Tate
2015-Sep-07, 10:07 AM
20958

That's an SDSS image, centered on SDSS J160646.74+565139.2 (http://skyserver.sdss.org/dr12/en/tools/explore/Summary.aspx?id=1237665570900345527). Two nearby galaxies have spectroscopic redshifts, of 0.565 and 0.552, and assuming J1606+5651 is a member of the same (rich) cluster, its redshift should be similar.

If the blue fluff is an EELR (extended emission line region), then what are the lines? [OII]3727 would be redshifted to ~5577 \lambda, which would put it into the r-band (displayed as G); MgII 2799 - a prominent emission line in quasars - would be ~4388 \lambda, in the g-band (displayed as B).

What do you think?

George
2015-Sep-08, 05:59 PM
20958

That's an SDSS image, centered on SDSS J160646.74+565139.2 (http://skyserver.sdss.org/dr12/en/tools/explore/Summary.aspx?id=1237665570900345527). Two nearby galaxies have spectroscopic redshifts, of 0.565 and 0.552, and assuming J1606+5651 is a member of the same (rich) cluster, its redshift should be similar.

If the blue fluff is an EELR (extended emission line region), then what are the lines? [OII]3727 would be redshifted to ~5577 \lambda, which would put it into the r-band (displayed as G); MgII 2799 - a prominent emission line in quasars - would be ~4388 \lambda, in the g-band (displayed as B).

What do you think?

I'm getting around 5800 (yellow) for a 3727 emission, but I've been wrong more lately than right.

ngc3314
2015-Sep-08, 11:31 PM
Blue fluff? I have an interest...

5577 is close to the rollover wavelength between g and r, with no more than 25% of peak response in r. So it could fit with an extended emission region having significant Mg II - from memory, some AGN extended clouds do, some don't. A couple of the Schirmer et al. Green Bean systems are known to have significant Mg II (they're at z>0.2 so some are redshifted enough to know this). (Its strength is unknown in Hanny's Voorwerp - the redshift put it just to the red of the GALEX spectroscopic mode).