Very faint and diffuse but very blue object


http://legacysurvey.org//viewer/?ra=102.1759&dec=70.4866&layer=dr8-north&zoom=14

There is no data available in Simbad Search. When clicked on the link from Simbad Search it jumps to a star in the naberhood. Nothing in SDSS DR14 with coordinates RA,Dec = 102.1744, 70.4865.

So I think: #faint-blue-galaxy #unclassified.
On the Galaxy Zoo website we have a whole collection of #unclassified #faint-blue-galaxies

http://skyserver.sdss.org/dr14/en/tools/chart/navi.aspx?ra=217.72857804193444&dec=22.890613386968063&scale=0.1&width=120&height=120

http://simbad.u-strasbg.fr/simbad/sim-coo?Coord=102.1744d70.4865d&CooFrame=ICRS&CooEpoch=2000&CooEqui=2000&Radius=2&Radius.unit=arcmin&submit=submit+query

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Now for something completely different …

It’s widely known - including to many here - that AGN in elliptical galaxies can produce jets, which can be seen in the radio, optical (e.g. M87, 3C 273), and even x-ray. Less well known is that the jets end in a “hotspot” (yes, that’s the technical term!) and around this hotspot are “lobes”, which are cavities in the IGM (intra-galactic medium) full of hot, low density plasma. Until recently, I thought that these lobes were visible in the radio only (OK, maybe the microwave too). However, it turns out that some have been detected in the IR, optical, and even (if memory serves) x-rays. :open_mouth:

I’ve been meaning to follow up on this, but haven’t yet gotten around to it.

Maybe some fraction of these faint blue “galaxies” are, in fact, lobes? If so, it may not be as easy as you might image to confirm the association.

That’s an interesting theory. I have been seeing quite a few of these fuzzy bluish areas recently - they are much easier to pick out in the DR8 images that have improved signal-to-noise ratio. I will start hunting for matching opposites to see if the lobe theory might be right…

To counter that idea though, some of them do have star formation too, which indicates that the gas must be pretty dense if it is forming stars.

Jean - check out the latest image I posted - they could be the lobes you mention!

Update - here is a REALLY speculative one…

I’ll check the literature, and post some images (SDSS, DECaLS) of lobes reported therein. That will provide some context, and also a rough check on just how similar (or not) they are to at least some faint blue things.

For sure, many faint blue things are relatively local (z<~0.1), small, star-forming (because they’re so blue), somewhat diffuse, mostly irregular (no obvious nucleus, nor arms) galaxies. Some may be similar to a class of such reported in one (more?) of the GAMA papers (I forget the acronym they used).

Thanks for your interesting theory jeantate. :slightly_smiling_face:

Thanks One.

I’ve made some progress, if only identifying hotspots that are not in either SDSS or DECaLS! No blue smudges yet, however (although a couple are interesting indeed).