Galaxy Zoo Talk

Galaxies without SDSS (or any other!) names

  • JeanTate by JeanTate

    We've all come across these, from time to time; a nice looking galaxy which does not have an SDSS name (i.e. is not a photometric object). Sometimes, you can find it in DR7, sometimes in 2MASS, but sometimes it seems to mock you.

    Hence this thread: if you've ever come across a 'ghost galaxy' (or star, for that matter), post it here ... maybe someone else has better sleuthing abilities than you, and can find at least a name (which often means an entry in a catalog).

    To kick this off, may I present this nice galaxy, centered at (349.9183, 5.4179); next to it is a version showing the nearby DR13 photometric objects (POs):

    enter image description here enter image description here

    Going to DR7 doesn't help in this case:

    enter image description here

    Posted

  • Dolorous_Edd by Dolorous_Edd

    Well, it has 2MASS name

    2MASS 23194036+0525044

    Posted

  • Ghost_Sheep_SWR by Ghost_Sheep_SWR

    Here's a pretty recent thread that touches on the subject, also looks like zoomign out really far shows the areas without photometric objects. I'm not trying that right now in case of PC crash 😃

    https://talk.galaxyzoo.org/?_ga=1.191070186.1751955194.1484309494#/boards/BGZ0000005/discussions/DGZ0002m2r

    Posted

  • Budgieye by Budgieye moderator

    Jean Tate, your image isn't coming through.

    http://skyservice.pha.jhu.edu/DR7/ImgCutout/getjpeg.aspx?ra=349.9183&dec=5.4179&scale=12.0&width=400&height=400&opt=GP

    Posted

  • JeanTate by JeanTate in response to Budgieye's comment.

    Yes, DR7 is often rather unresponsive. All the cutout shows is black/blank, except for a row of POs along the top (N) border. In other words, (349.9183, 5.4179) is outside the DR7 footprint.

    Posted

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

    Definitely related! 😃

    However, in this thread I hope to have obvious SDSS photometric objects without an SDSS ID/name ... and for sleuths like Dolorous_Edd to find names (as he did for the PO in the OP, if you get my drift 😉).

    Posted

  • JeanTate by JeanTate

    Two more:

    The flat galaxy at ~(52.5345, 40.5238) is not a PO, in either DR7 (outside footprint) or DR13 (DR14):

    enter image description here

    The 'blue star' at (209.9543, 10.5488) seems to be the host of a pretty bright radio (FIRST) source, but it's not a PO (in either DR7 of DR13/14)!

    enter image description here enter image description here enter image description here

    I'll see if I can upload a FIRST contour overlay image of this field later.

    Posted

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

    Weird thing, but the first galaxy at RA,Dec 52.53427255 40.52423587 is not a PO, but IS an SDSS object + SDSS designation. No clue how that works. Only name assigned atm AFAIK

    SDSS J033008.22+403127.2 ObjID 1237661055819644977

    http://cas.sdss.org/dr9/en/tools/explore/obj.asp?id=1237661055819644977

    Posted

  • klmasters by klmasters scientist, admin

    A nice demonstration of why human visual inspection is useful! I could try to find out from the SDSS pipeline gurus why they think this might be (or you can try yourself - actually helpdesk@sdss.org is amazingly responsive - within a fairly relaxed timeframe!). The edge-on galaxy I find particularly puzzling....

    Posted

  • JeanTate by JeanTate

    A star this time (likely a QSO, the host of a nice radio source, with a morphology described as "triple"; link to RGZ field; FIRST cutout):

    enter image description here enter image description here

    Posted

  • JeanTate by JeanTate

    Here's a whole field, full of galaxies (and maybe some stars too) without names! 😮

    enter image description here

    Posted

  • Rick_Nowell by Rick_Nowell

    Good find! Could you estimate how many unamed galaxies there are? Worth reporting to someone who might be concerned?

    Posted

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

    Thanks! 😃

    Could you estimate how many unamed galaxies there are?

    Not easily.

    Worth reporting to someone who might be concerned?

    I don't think so 😦 A Discussion thread from earlier today, on a similar topic, hints at why (not) ... Big object it is not recognised by system

    Posted

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

    Some more, all of them are POs in DR7 ...

    Somehow an off-stage bright star spooked the algorithm, but not quite close to the star itself:

    enter image description here

    enter image description here

    This one's really weird! There's an off-center PO, yet in Explore you put your cursor on it, and it says "No objects have been found within 0.2 arcmins"! 😮

    enter image description here

    enter image description here

    In the last two, it isn't just the cool galaxy which gets ignored, but several other (much smaller, fainter) galaxies, and even some stars ...

    Posted