What is it with me and astronomical blobs? I just seem to find them interesting... First it was Lyman Alpha Blobs (these are found at high redshift and span several kpcs in size). Now, during our Galaxy Research Meeting, I have been introduced to Duilia de Mello's "blue blobs" and find them intriguing. Even more so once I did a little reading: news article and scientific paper.
This discussion led to another interesting object, Hanny's Voorwerp. This was a really odd object first discovered by an amateur astronomy while classifying galaxies using Galaxy Zoo and then much speculation and additional observations ensued. Finally, it appears that some conclusion has been reached. According to one study and supported by this other paper, this object is consistent with having an embedded, obscured AGN and the surrounding galaxy is reflecting the light from this source, in a light echo.
But there are several open questions, I think. For example-- What is the surrounding material? There are strong emission lines (OIII, Neon V and HeII). Is there star formation? There is surrounding HI gas. Why is the continuum so faint compared to the emission lines? Is the relative location of IC2497 significant? Why is the GALEX color so blue? Hmmmm...
there's definitely alot of dusty galaxies in the green valley - i saw this in my 2007 paper, and it has been known for awhile. It's easy to see if you use spectroscopic indices as measures of sSFR, since these are less sensitive to dust. However, there still *are* green valley galaxies after dereddening, and these are interesting. Note also that the location and width of the green valley moves alot after dereddening.
ReplyDeleteAlso, they are getting their attenuations from SED fits with broadband data, and have to be careful there that the model library they are fitting to actually *has* 'true' green valley models, or the fits will always require dust to get green colors.
And if you are fitting SEDs, it makes more sense to talk about the green valley in terms of sSFR than color anyway.....
oops, wrong post
ReplyDelete