Galaxy Zoo Talk

Two colour galaxy center

  • mkurnell by mkurnell

    This object has two distinct colours in the center. I am not sure if this would be caused by two objects in the same system or by two overlapping objects.

    Posted

  • Rick_Nowell by Rick_Nowell

    The galaxy definitely has a Active Galactic Nucleus as it's in The 'Active Galactic Nuclei in the Sloan Digital Sky Survey. I. Sample Selection' (2005). Nothing immediately revealing in DECaLS DR5:

    http://legacysurvey.org/viewer?ra=216.47807887&dec= -0.19162667&zoom=16&layer=decals-dr5

    or SDSS DR9

    http://skyserver.sdss.org/dr9/en/tools/explore/obj.asp?ra=216.47807733&dec=-0.19163935

    Posted

  • CeciliaB by CeciliaB

    In the DECaLS image there is a red object along the ring of the galaxy, to the right of the bulge. That red object isn't visible in other surveys.

    But if one clicks on the 'SDSS images'-button to the left on the DECaLS' page, one will notice that all bright red objects on the page have lost a lot of their brightness. So the red object near the galaxy may just be too dim to be seen in other surveys.

    enter image description hereDECaLS DR5

    DECaLS 5 http://legacysurvey.org/viewer?ra=216.4779&dec=-0.1918&zoom=16&layer=decals-dr5

    Posted

  • Budgieye by Budgieye moderator

    Yes, in DECaLS that is an interesting red patch, and there is a faint patch on the opposite side. Almost like a #buriedring

    I suppose there is a possibility that the red colour affected the ccds and there is leakage of the red colour.

    https://zooniverse-static.s3.amazonaws.com/www.galaxyzoo.org/subjects/standard/58580d16d369fd00400001ed.png

    Posted

  • Ghost_Sheep_SWR by Ghost_Sheep_SWR

    Definitely an object there in VIKING images in all bands ZYJHK. DECaLS is probably just sensitive enough in NIR /IR to pick it up.

    VSTKIDS gri and VIKING JHK images;

    enter image description hereenter image description here

    Background galaxy, dwarf star (BD?) or something else?

    All PSI bands: http://cutout.icrar.org/tmp/15166622862286/index_temp.php

    Posted

  • Rick_Nowell by Rick_Nowell

    SDSS has perhaps a change of colour (near ojid 1237648721246683517)

    J142554.73

    The object is present in DECaLS DR3

    http://legacysurvey.org/viewer?ra=216.47807887&dec= -0.19162667&zoom=16&layer=decals-dr3

    Does anyone else see in DECaLS DR5 and VSTKIDS gri (the left picture) an arc at, say, 1 o'clock above the object? Most noticeable in DR5. Perhaps just the edge of the galaxy.

    Posted

  • Rick_Nowell by Rick_Nowell

    I´m intrigued by the mystery object first noticed in DECaLS DR5 by CeciliaB. The SDSS picture above is what it is. So I put together a combination of four images that shows the object DECaLS 216.47808__-0.19164, or doesn't show it. The arrows mark the same coordinates as the primary DR5 image reasonably accurately. The object comes and goes mysteriously when looking at different images!

    http://legacysurvey.org/viewer?ra=216.47807887&dec= -0.19162667&zoom=16&layer=decals-dr5

    DR5_216.47808

    Clockwise from top: DECaLS DR5, VIKING, DECaLS DR3 and VSTKIDS bottom left.

    Posted

  • Ghost_Sheep_SWR by Ghost_Sheep_SWR in response to Rick_Nowell's comment.

    Bright in IR, faint in optical far red / NIR, as posted January 23 2018 12:14 AM

    Posted

  • Rick_Nowell by Rick_Nowell in response to Ghost_Sheep_SWR's comment.

    Forgive my slowness. So, a galaxy SDSS J142554.73 is 1.7 billion years distant and has an object which when observed by infrared sources, is very bright in the "higher infrared" and shows up on one visible survey. Ghost Sheep mentions two reasonable sources: a brown dwarf or a galaxy behind J142554.73. The type of star called a brown dwarf is very rare and there are only a couple of thousand known. Isn't the scale a bit big to be a dwarf star, especially when looked at in DR3? Would it be that big and if yes, would it be so bright in the high infrared? https://en.wikipedia.org/wiki/Brown_dwarf

    Which leaves a galaxy (G_red) behind somehow showing through J142554.73 in the infrared. The more redshifted an object is the further away it is. So a galaxy that red must be a long way distant. But G_red is bright in the high infrared, which might mean that it is an energetic object but very distant. It would have to be very energetic to show through: would an overlap of a distant galaxy be that visble through a more local galaxy? If G_red is in front of J142554.73, would it show so? Perhaps something with or near J142554.73 is aiding G_red's visibility? DR3 and VIKING show what appears to be a large object approximately15-20% the size of J142554.73, which could be a guide to how big G_red might be, if it were a distant galaxy.

    What might aid our view of G_red, taking it as a distant galaxy behind J142554.73? A lucky line of sight through a "non-dense" part of J142554.73? A lensed distant galaxy can be shown as arcs, and are very rare as well. Yet looking at a picture of Abell 2744 the lensed galaxies are red blobs rather than beautiful arcs. Yet there are so many objects that turn out not to be lensed and have a simple explanation. It would be interesting to me to find out what that simple explanation might be. https://en.wikipedia.org/wiki/Gravitational_lens

    Posted

  • Ghost_Sheep_SWR by Ghost_Sheep_SWR in response to Rick_Nowell's comment.

    Haha no problems here man.

    Yeah if it indeed is a BD and that bright in VIKING bands it should be also visible in WISE. Also shape seems extended instead of point source.

    Regular BD’s are:

    • bright in W2, faint in W1 or not visible. Not visible in W3 W4. Cant see anything in WISE.
    • If closeby movement through parrallax / PM, but cant see it in WISE to confirm. Perhaps too faint for WISE but seems implausible checking the VIKING bands.

    So probably not a BD IMHO.

    But indeed strange object if that bright in IR but not optical, yes must be energetic then.Perhaps a spectrum available from GAMA / VSTKIDS? No time now 😕

    Posted

  • Rick_Nowell by Rick_Nowell

    Not an imaging anomaly because it is visible in DR3, DR5 and VIKING. Not a foreground star of any sort in our galaxy- scale wrong not a single round point source or round like other stars. Not likely to be an overlap with G_red in front of J142554.73 as it would have to be near invisible. Thus i) a companion galaxy or overlap with G_red behind J142554.73, but hardly optically visible or ii) a very distant and redshifted energetic galaxy being lensed by something not obvious to me. Without a spectrum to say where it's at, nothing can be certain.

    So who can knock us out a spectrum, please?

    Posted

  • Ghost_Sheep_SWR by Ghost_Sheep_SWR

    No spectrum available, it's not even a separate GAMA target.

    enter image description here

    http://www.gama-survey.org/dr2/tools/sov.php?cataid=593407#sigmatop

    Classified by UKIDSS and VIKING as 'Galaxy', that's about it

    Posted

  • Rick_Nowell by Rick_Nowell

    If you go to the DECaLS site link below, on the right handside panel there are options, among many, for both DECaLS DR5 and DR3 'residuals'. I haven't been able to find out what a residual is, so if anyone can help me that would be appreciated. G_red is very prominent in both DECaLS residual images whatever that means.

    DECaLS DR3 residuals are worth looking at as G_Red is almost as bright as the central AGN, which we know J142554.73 has. But I don't know what a residual is.

    http://legacysurvey.org/viewer?ra=216.47807887&dec= -0.19162667&zoom=16&layer=decals-dr5

    Posted

  • Ghost_Sheep_SWR by Ghost_Sheep_SWR in response to Rick_Nowell's comment.

    There is also a 'Model' option. With that they try to mimic all the stars and galaxies as good as possible (shape / size / magnitude etc.). But the models are rarely perfect in the case of galaxies.

    So when the model galaxy image is substracted from the real galaxy image there are some 'leftovers'; the Residuals. It is an indication of how well the modelling software is; a lot of residuals means it's not a good fit.

    Posted

  • Rick_Nowell by Rick_Nowell in response to Ghost_Sheep_SWR's comment.

    Thankyou that was helpful. If you go the GAMA viewer page, address below, and then scroll down to the More Information section. Scroll down that section and you come to an option Sersic Photometry. Click on 'SersicCat' and a table of figures appears to the right including two small pictures, labelled URL_R and URL_K. If you click on URL_K, you are presented with four pictures. They are labelled G00593407 and have indivdual labels for the four pics.

    G_red is in picture UKIDSS K, picture marked Model and picture marked Ellipses + Masks. Quite clearly in UKIDSS K. Info on SersicCat below.

    http://www.gama-survey.org/dr2/tools/sov.php?cataid=593407

    http://www.gama-survey.org/dr2/schema/table.php?id=176 Table: SersicCat

    Posted

  • Ghost_Sheep_SWR by Ghost_Sheep_SWR in response to Rick_Nowell's comment.

    Yeah I saw it was imaged / cataloged by UKIDSS from VIZIER, classified as galaxy.

    If on the main object page you look at ‘From SercicCat:’ just above the four model images already there you can directly flip through all the images / models / residuals with the links in the band designations u g r i z Y J H K 😃

    Its visible in both H and K bands.

    Posted

  • Rick_Nowell by Rick_Nowell

    I suggest it is within J142554.73. A large molecular cloud hides energetic starburst within it. And I think if you look at the orginal GAMA picture, there is the faintest of blue arcs near where the molecular cloud is that shows some of that star formation. Maybe the same could be said of the VSTKIDS image: there is an arc of brightness near where the object is. It would do away with theories on overlaps or lenses. Much simpler. A big stellar nursery obscured by clouds.

    On or near the ring that is round the main galactic centre of J142554.73 is a large cloud at the position of the object. Hidden from view within it is active star formation for what ever reason that has happened. The star formation would give rise to lots of energy, which we see vaguely in the high infrared as everything else that is visible is cut out by the dust and gas. Fits the facts; does away with the need for a spectrum; reasonably simple explanation. Within the galaxy is easy to live with. Perhaps the size of the cloud is remarkable, say 10-15% the size of the whole galaxy, and what is powering such star formation might be interesting to find out. The star formation is big, we just can't see it.

    Ring galaxies like J142554.73 are thought to be caused by mergers. Maybe the object is what's left of the nucleus of that former galaxy or a part of it somehow. There's a lot of dust and gas from that defunct galaxy. The cloud of dust and gas is so large, it obscures part of the central nucleus, explaining why the centre has two colours, which was the original question. An example might be found here:

    A Cosmic Hit and Run. European Southern Observatory http://www.eso.org/public/images/potw1619a/

    Hubble Space Telescope http://www.spacetelescope.org/images/potw1310a/

    https://en.wikipedia.org/wiki/Molecular_cloud

    Posted

  • Budgieye by Budgieye moderator

    This reminds me of

    Is this a lensed galaxy? / red ring (8µm) https://talk.galaxyzoo.org/#/boards/BGZ0000003/discussions/DGZ0002h43?page=1

    Posted

  • Rick_Nowell by Rick_Nowell

    I think this article from Universe Today gives big clues: "The gravity of the smaller galaxy collapses vast clouds of gas and dust, and creates a burst of star formation around the edge of the larger galaxy." We don't see the star formation in J142554.73 because of the dust and gas, perhaps contributed by one of the two merged galaxies. Infrared astronomy allows us to peer through the murkiness and reveals what's beneath. J142554.73's 'cloud' might be a very large example and so is of interest. The picture of AM 0644-741 (below) has the suggestion of a dusty nucleus which would give it two colours.

    Ring Galaxy https://www.universetoday.com/30697/ring-galaxy/

    Ring Galaxy AM 0644-741

    AM 0644-741

    Posted

  • Ghost_Sheep_SWR by Ghost_Sheep_SWR in response to Rick_Nowell's comment.

    Hmm I don’t think anything can be asserted from the two-coloured core; nearly every bright object in GZ GAMA subject images is two-coloured due to misalignment. Also all GZ GAMA subject images are only two colours (2 bands) so not much can be asserted from present or missing colours comparing with SDSS.

    Thats why I create the 3 colour images from gri VSTKIDS bands. Check the one on this thread, core isn’t two-coloured anymore.

    Posted

  • Rick_Nowell by Rick_Nowell

    A different SDSS spectrum has it as Class=GALAXY STARFORMING.

    SpecObjID = 344612261265958912

    http://skyserver.sdss.org/dr9/en/tools/explore/obj.asp?sid=344612261265958912

    34461226_Spec

    Posted