Galaxy Zoo Talk

Amazing

  • GoldenRule by GoldenRule

    http://skyserver.sdss.org/dr9/en/tools/chart/chart.asp?ra=184.29100681&dec=3.67795849

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  • GoldenRule by GoldenRule

    What is the foggy cloud around the top? And if it's just gas why no stars?

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  • Budgieye by Budgieye moderator

    This is unusual. Many references in NED, but I can't find an simple explanation right now. But the cloudy area is composed of stars. Gas does not usually shine and is invisible.

    I would think that the unusual shape is due to a past merger.

    Are there any volunteers to wade through 112 referemces om NED? http://ned.ipac.caltech.edu/cgi-bin/datasearch?search_type=Ref_id&objid=29802&objname=NGC 4234&img_stamp=YES&hconst=73.0&omegam=0.27&omegav=0.73&corr_z=1&of=table

    #NGC 4234

    NGC4234

    UGC 07309

    enter image description here

    http://skyservice.pha.jhu.edu/DR9/ImgCutout/getjpeg.aspx?ra=184.29100681&dec=3.67795849&scale=0.1980635&width=800&height=800&opt=&query=

    http://skyserver.sdss.org/dr9/en/tools/explore/obj.asp?id=1237651737906315311
    SDSS J121709.14+034059.2

    UGC 07309

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  • GoldenRule by GoldenRule

    That makes sense, but it's weird there's a uniform glow instead of speckled. Thanks for looking into it I found it looking around on Aladdin. I looked through the references when I found it bc I'd never seen so many but I don't understand alot of em. If you do figure more out I'd love to no.

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  • vrooje by vrooje admin, scientist

    Wow, what an interesting galaxy.

    There are, as @Budgieye notes, a lot of references to this object in the literature. At first glance they mostly look like this galaxy was included in lots of papers studying populations of galaxies, and I haven't had time to check whether any of those papers single this one out as special.

    The first thing I thought was it looks like there are two stellar populations in this galaxy -- the featureless "fog" is an older population of stars, in which all the blue (massive) stars have lived their (short) lives and died out, leaving mostly the smaller, redder stars to continue their slower evolution. And, later, there was an episode of new star formation, recently enough that the blue stars are still there and still a bit more clumped together than the older stars, so their distribution looks more mottled in the image. The older disk and the younger disk populations have different overall "scale lengths" (by which I mean the older disk is bigger and likely more massive than the younger one).

    Lots of disks have two populations, including our own Milky Way. Some galaxies appear to have two distinct disks, and with some it's harder to tell where one population ends and the other begins. I happened to have a 2-disk galaxy in my initial sample of bulgeless galaxies hosting growing black holes (a Galaxy Zoo paper; the galaxy I'm thinking of is in the top left of the image mosaic in that paper), and there are people who spend their whole careers studying systems like these.

    What strikes me about this one is that the two disks are clearly offset with respect to one another. Specifically, this galaxy has a bar, and the larger & older disk is centered with respect to that bar, whereas the smaller & younger disk is not. Theoretical models of offset disk-bar systems seem to show that less massive disks can "slosh" around the bar (which stays at the gravitational center of the system), perhaps triggered by galaxy interactions, whereas larger disks are much less likely to do this. I wonder if we might be seeing both these outcomes in a single galaxy?

    Galaxy Zoo PhD student Sandor Kruk has been studying bars and disks; his paper on offset bars and disks in the GZ SDSS sample has just been published. I will notify him of this thread. Thank you for posting it!

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  • Budgieye by Budgieye moderator

    Thank you for the detailed explanation Dr Simmons. Good find, GoldenRule.

    I hope we get to hear more about this galaxy in the future.

    If there is information in the NED references, it would take hours to dig it out. I did a search of Google, Google scholar, and the Forum for something that didn't have 10,000 NED objects.

    It is not in the Hubble Space Telescope survey area.

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  • mlpeck by mlpeck

    Binggeli, Popescu & Tammann (1993) assign NGC 4243 to a cloud that's probably in the background of the Virgo cluster and may be dynamically associated with it.

    I think the consensus is Virgo is still in the process of assembling itself and the late type galaxies in the area are falling into the cluster environment for the first time, so maybe this one got a fresh supply of material recently. It's a pity none of the 4 SDSS spectra targeted the (apparently) old disk, although one is centered on the bar:

    enter image description here

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  • GoldenRule by GoldenRule

    That's absolutely amazing. Thank you all very much for the explanation! It's very intriguing, is there any way I can save it in my favorites since I didn't actually classify it?

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  • Budgieye by Budgieye moderator

    It has appeared before, so you could collect on https://talk.galaxyzoo.org/#/subjects/AGZ0001jvw

    Or you can click the Follow button at the top.

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  • GoldenRule by GoldenRule

    Thank you

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