Galaxy Zoo Talk

Dark Galaxies

  • Alpha_Aurigae by Alpha_Aurigae

    What kind of objects do astronomers think there are - or might be there - that haven't been found or recognized yet, either on Galaxy Zoo or elsewhere?

    Posted

  • Alpha_Aurigae by Alpha_Aurigae

    Well, here is at least one object, but near to impossible to find on Galaxy Zoo:
    http://en.wikipedia.org/wiki/Dark_galaxy

    Posted

  • Capella05 by Capella05 moderator

    Strangly enough - we came across one today that has been looked at by astronomers in this thread AGZ0002klo

    Posted

  • Alpha_Aurigae by Alpha_Aurigae

    I smell a new challenge: looking for isolated, disturbed galaxies 😉

    Posted

  • Capella05 by Capella05 moderator

    I would start by reading the papers (there were 4 linked to UGC 4722) and looking at comparisons between the galaxies the lastest paper has identitified as having possible 'dark companions' 😃

    Just from a short read of the paper, they are very rare - but I do not think we have actively looked for them on GZ.

    A quick search of the forum would tell you if we have found any previously 😃

    Posted

  • JeanTate by JeanTate in response to Alpha Aurigae's comment.

    IIRC, this is one thing which waveney had on his 'To Do' list, of analyses to be applied to the data he obtained from the Irregulars Project*. As he never published anything (as far as I know), no one knows what he actually found (publicly at least).

    There's also likely overlap with GIGs, so checking on what papers have cited Terao+ (2013) (and which that references) might turn up something interesting.

    Good luck! 😃

    *holler if you can't find it in the GZ forum

    Posted

  • Alpha_Aurigae by Alpha_Aurigae

    Thank you Capella05 and Jean Tate 😃

    If I have got any questions I know who to turn to.
    I am going to handle this in a nice and slow manner, as this is also new territory for me.

    These galaxies are mentioned in the latest paper Capella05 mentioned:

    UGC 04722

    UGC 05101

    UGC 11905

    UGC 11871

    NGC 244

    F 635-02

    ESO 539-7

    ESO 545-5

    I am going to have close look at these galaxies and use them as a starting point to look for similar ones 😃

    Posted

  • Capella05 by Capella05 moderator

    If you find corresponding SDSS images for the ID's above do post them in this thread 😃 It will be fascinating to have a look!

    PS. You might want to change the name of the discussion 😉

    Posted

  • Alpha_Aurigae by Alpha_Aurigae

    I am already looking or the SDSS images, and also new candidates, but I have got a feeling it will be like looking for a needle in a haystack. But if we find anything, I have we can make a contribution to the Dark Galaxy discussion.

    And I will change the title of this thread 😃

    Posted

  • Capella05 by Capella05 moderator in response to Alpha Aurigae's comment.

    Well - we both independently came across the same concept on the same day, so I would say you have a better chance than a 'needle in a haystack'.

    All I was trying to do is work out why a particular galaxy looked like a merger and wasn't, and came across the paper, and remembered reading your post in this thread 😃

    Posted

  • Alpha_Aurigae by Alpha_Aurigae

    This one might be a good candidate:

    enter image description here
    AGZ0002ky8

    #NGC 4656; #UGC 7907

    However, a nearby galaxy might be the cause of the disturbance:

    enter image description here

    Posted

  • Alpha_Aurigae by Alpha_Aurigae in response to Capella05's comment.

    Maybe the universe is trying to tell us something 😉?

    Posted

  • Capella05 by Capella05 moderator in response to Alpha Aurigae's comment.

    Here is the inverted image of NGC 4656

    NGC 4656

    Compared to the top right galaxy (just visible) - the tidal tail is going in a different direction 😃

    Could still be disturbance caused by a fly by, but a closer look is always worth the effort 😃

    Posted

  • Capella05 by Capella05 moderator in response to Alpha Aurigae's comment.

    Next thing is to research NGC 4656 - any papers written about it? what about articles? How about identifying the galaxy in the top right?

    Search NED / SIMBAD etc...

    Tackle one galaxy at a time 😃

    Posted

  • Alpha_Aurigae by Alpha_Aurigae

    NGC 4656: There are a number of papers - among them: Andrew Schechtman-Rook , Kelley M. Hess University of Wisconsin-Madison, University of Cape Town), NGC 4656UV: A UV-selected Tidal Dwarf Galaxy Candidate (2012): http://search.arxiv.org:8081/paper.jsp?r=1203.1319&qid=1412713692145mix_nCnN_2041063659&qs=NGC+4656
    I am checking the paper at the moment.

    Posted

  • Alpha_Aurigae by Alpha_Aurigae

    The UV Dwarf Galaxy is definitely interacting with NGC 4656, so we can rule out Dark Galaxies.

    Posted

  • Capella05 by Capella05 moderator

    Can you identify the dwarf galaxy in the SDSS image? Top left arm? or more distant? Other people reading this discussion may be interested 😄

    It will also help you to remember why you discounted a specific galaxy, when you are analysing future ones 😃

    Science is a long process....

    Posted

  • Alpha_Aurigae by Alpha_Aurigae

    One thing I can do is point readers toward fig 1 and fig 2 on page 3 and 4 of the scientific paper I mentioned.
    The other is get a Sky View Image. Be back in a sec.

    Posted

  • Capella05 by Capella05 moderator in response to Capella05's comment.

    Just read the paper - the UV Dwarf candidate galaxy is the very faint trail above the 'Hook'- what I had identified as a tidal trail.

    Posted

  • Capella05 by Capella05 moderator in response to Capella05's comment.

    BTW I am going to move this thread from chat to the Citizen Science board...

    Posted

  • Alpha_Aurigae by Alpha_Aurigae

    Thanks,
    Here is the Sky View Image, near UV, and the UV Dwarf Galaxy can be seen above the galaxy.

    enter image description here

    Posted

  • Capella05 by Capella05 moderator

    Nice 😃 Even though we don't have a dark galaxy - this was really interesting!

    I would love to have a Scientists opinion on this paper, I am not entirely convinced how the dwarf galaxy could have that 'big' an impact on the larger galaxy.

    Or I might have to read the paper in more depth 😉

    Posted

  • Alpha_Aurigae by Alpha_Aurigae

    Could dark galaxies be responsible for area's of extreme starformation in certain galaxies?

    Posted

  • Alpha_Aurigae by Alpha_Aurigae

    I don't know if it is a merger of two galaxies, one disturbed galaxy, or a barred galaxy in its early stages. If it is only one, it might be worth checking out.
    There are no close neighbours:

    enter image description here
    AGZ0003pni

    enter image description here

    enter image description here

    As far as I can tell there is no paper about this object.

    Posted

  • Budgieye by Budgieye moderator

    Blog: A Dark Secret in Virgo http://blog.galaxyzoo.org/2010/12/17/a-dark-secret-in-virgo/ "VIRGOHI21 is currently the best dark galaxy candidate" NGC4254 is being distorted by an invisible galaxy (!) made of dark matter, and some hydrogen gas and dust.

    Posted

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

    VIRGOH121 might well be a tidal tail of NGC 4254 and not a dark galaxy. A whole galaxy that has no stars but lots of dark matter? As we don't know what DM is, detecting (or not) a whole 'galaxy' made of it seems counter-intuitive. http://en.wikipedia.org/wiki/VIRGOHI21

    Posted

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

    There's also likely overlap with GIGs, so checking on what papers have
    cited Terao+ (2013) (and which that references) might turn up
    something interesting.

    Checking ADS the paper by Terao+ remains unpublished in a refereed journal and it has no citations. I'm guessing the referee noticed the same thing I did, namely the authors failed to do their homework.

    The catalog of "Local Orphan Galaxies" by Karachentsev et al. (2013) might be a good place to start hunting. Clicking the online data link will take you to the catalog on Vizier.

    Posted

  • Alpha_Aurigae by Alpha_Aurigae

    @ mlpeck: thanks for your contribution. I had a quick look at the galaxies and UGC 9588 seems like a good candidate as it is disturbed. However it looks like the galaxy may be the result of a merger, either that or the bright objects are "just" starformation instead of two nuclei.

    UGC 9588 - Image and inverted image Sky View.

    enter image description here

    enter image description here

    Posted

  • Alpha_Aurigae by Alpha_Aurigae

    Here is an interesting one - UGC 02473:

    enter image description here
    AGZ0002a8f

    There are neighbours but I am not sure they are anywhere near UGC 02473, although the tidal tail points to one of them. I am not skilled or experienced enough to find out whether the neighbour is responsible for the tidal tail or not.

    enter image description here

    enter image description here

    Also no results when looking for a paper.

    Any input is welcome 😃.

    Posted

  • Capella05 by Capella05 moderator

    Hey AA,

    I will try to have a look later, but my gut instinct says it is two separate irregular galaxies interacting - rather than a single galaxy that is disturbed by a hidden galaxy 😃

    Posted

  • Alpha_Aurigae by Alpha_Aurigae

    Ok, thanks 😃

    Posted

  • Alpha_Aurigae by Alpha_Aurigae

    The Scythe Galaxy (let's cal it that 😉 ):

    enter image description here
    AGZ00026aj

    There is a galaxy at the top which may have caused the irregularity

    enter image description here

    enter image description here

    Posted

  • ElisabethB by ElisabethB moderator

    I haven't looked at all the galaxies in this thread; But we used to call these disturbed, single galaxies victims of a flyby ! 😄

    Posted

  • Alpha_Aurigae by Alpha_Aurigae

    Now the question is, is the passer-by a galaxy we can see and identify, or might the galaxy be disturbed by a so-called dark galaxy?

    Don't worry Elisabeth, I am not going to flood this thread with galaxies. I will check their immediate surroundings for fly-by candidates and also see if disturbed galaxies are the result of a merger (e.g. 2 nuclei). Those I certainly won't post.
    It is very hard to find a single, isolated and disturbed galaxy which may have an unknown, dark galaxy in the neighbourhood. I don't expect there are that many, but who knows, we may hit the jackpot one day. Or not....

    Posted

  • Alpha_Aurigae by Alpha_Aurigae

    This one might be the result of merger, but in case it is only one disturbed, very isolated galaxy:

    enter image description here
    AGZ00061h7

    enter image description here

    enter image description here

    Posted

  • Alpha_Aurigae by Alpha_Aurigae

    This might be a merger, or it might be a single, irregular galaxy with starformation and no neighbour in sight:

    enter image description here
    AGZ0003d52

    enter image description here

    Inverted:

    enter image description here

    Posted

  • Alpha_Aurigae by Alpha_Aurigae

    Another possibiity. However, the greyish smudge might be a dwarf galaxy responsible for the disturbance.

    enter image description here
    AGZ0002qdf

    enter image description here

    enter image description here

    Posted

  • Alpha_Aurigae by Alpha_Aurigae

    Merger or irregular galaxy with no neighbour in sight?

    enter image description here
    AGZ0001i4f

    enter image description here

    enter image description here

    Posted

  • Alpha_Aurigae by Alpha_Aurigae

    enter image description here
    AGZ0003zke

    There is a small galaxy at the bottom (and also one to the left) which may be responsible for the irregularity

    enter image description here

    enter image description here

    Posted

  • JeanTate by JeanTate

    "Discovery of an Ultra-Faint Dwarf Galaxy in the Intracluster Field of the Virgo Center : A fossil of the First Galaxies?" (Jang&Lee, arXiv:1410.2247) points to the existence of a kind of galaxy previously found only in the Local Group. If there were somewhat more massive examples of such ultra-faint, LSB galaxies, would their existence be betrayed more by their interaction with/influence on neighboring more visible (in SDSS) galaxies?

    Posted

  • Alpha_Aurigae by Alpha_Aurigae

    NGC 7711 looks disturbed, but there isn't a neighbour in sight.

    enter image description here
    AGZ0001xvy

    enter image description here

    enter image description here

    Posted

  • JKD by JKD

    what do you think about this one http://talk.galaxyzoo.org/#/subjects/AGZ0001vdh

    Posted

  • Alpha_Aurigae by Alpha_Aurigae

    Hi Hans,

    This galaxy is probably disturbed by one of its neighbours:

    enter image description here

    Posted

  • Budgieye by Budgieye moderator

    Great find! Looks like it was created by a high speed see Shell ellipticals - created by high speed collisions collison http://www.galaxyzooforum.org/index.php?topic=278085.msg483159#msg483159

    http://talk.galaxyzoo.org/#/subjects/AGZ0001vdh

    Posted

  • JeanTate by JeanTate

    A Search For Star Formation in the Smith Cloud (Stark+ 2014) may be of some interest here.

    The first sentence of the abstract reads (HVC = High-velocity cloudWP):

    Motivated by the idea that a subset of HVCs trace dark matter substructure in the Local Group, we search for signs of star formation in the Smith Cloud, a nearby ~2x10^6 Msun HVC currently falling into the Milky Way.

    And the last two read:

    We also discuss how the newly discovered star forming galaxy Leo P has very similar properties to the Smith Cloud, but its young stellar population would not have been detected at a statistically significant level using our method. Thus, we cannot yet rule out the idea that the Smith Cloud is really a dwarf galaxy.

    Posted

  • Alpha_Aurigae by Alpha_Aurigae

    Thanks, Budgieye and Jean 😃.

    Some background:

    http://en.wikipedia.org/wiki/Smith's_Cloud

    http://astromic.blogspot.nl/2011/03/mystery-of-million-mass-smiths-cloud.html

    Posted

  • Alpha_Aurigae by Alpha_Aurigae

    enter image description here
    AGZ0003yw3

    enter image description here

    Posted

  • Alpha_Aurigae by Alpha_Aurigae

    Disturbed, but by what?

    enter image description here
    AGZ0005gwi

    enter image description here

    enter image description here

    Posted

  • Alpha_Aurigae by Alpha_Aurigae

    This galaxy is disturbed with no neighbour in sight. Or is the disturbance caused by a very small galaxy merging with AGZ0004m49?

    enter image description here
    AGZ0004m49

    enter image description here

    Posted

  • Alpha_Aurigae by Alpha_Aurigae

    Might have been disturbed by the very small galaxy at the top at one o' clock

    enter image description here

    enter image description here

    Posted

  • Alpha_Aurigae by Alpha_Aurigae

    Not sure what to make of this one. Disurbed ring? Semi ring? One-armed spiral galaxy?

    enter image description here

    enter image description here

    Posted

  • Alpha_Aurigae by Alpha_Aurigae

    This one might have been disturbed by a small galaxy at one o'clock:

    enter image description here
    AGZ000550z

    enter image description here

    Posted

  • Alpha_Aurigae by Alpha_Aurigae

    Somewhat disturbed, but no obvious neighbour in sight

    enter image description here

    enter image description here
    AGZ00033ql

    Posted

  • Alpha_Aurigae by Alpha_Aurigae

    Maybe the galaxy at 6.15 caused the disruption

    enter image description here

    enter image description here
    AGZ00022xr

    Posted

  • williamaskew by williamaskew in response to Alpha Aurigae's comment.

    Re AGZ0005gwi this sort of looks like ram pressure stripping

    Posted