Galaxy Zoo Talk

Explanation?

  • jhanson50 by jhanson50

    Wanted to get input on how to classify as well as ideas about this shape.
    Thanks,
    Julie

    Posted

  • lovermann by lovermann

    It's a #PGC_53078 galaxy.

    Better image: enter image description here

    Posted

  • ElisabethB by ElisabethB moderator

    Hi Julie and welcome to the Zoo,

    It is a disk with a bar and a big bulge. And it has an inner ring. A real beauty!

    Happy hunting !

    Els

    Posted

  • JeanTate by JeanTate in response to jhanson50's comment.

    To add to what Els said, at the two ends of the bar, where it meets the ring, there's a kinda bright spot (short arc in the SDSS image lovermann posted). These are "ansae", and are very interesting features (source):

    Figure 22 shows "ansae"-type bars, referring to bars which have "handles" or bright enhancements at the ends. Martinez-Valpuesta et al. (2007) carried out a statistical study and found that ansae are present in approx 40% of early-type barred galaxies and are very rare for types later than stage Sb. Ansae are usually detectable in direct images, but their visibility can be enhanced using unsharp-masking (all the right frames for each galaxy in Figure 22). Morphologically, ansae may be small round enhancements like those seen in NGC 5375 and 7020, but in some cases, ansae are approximately linear enhancements, giving the bar a parallelogram appearance as in NGC 7098, or curved arcs, giving the bar a partial ring appearance as in NGC 1079. Color index maps in the dVA show that ansae are generally as red as the rest of the bar, indicating the features are stellar dynamical in origin, rather than gas-dynamical. Nevertheless, ansae made of star-forming regions are known. Martinez-Valpuesta et al. (2007) illustrate the case of NGC 4151, a well-known Seyfert 1 galaxy with a strong bar-like inner oval. The appearance of this galaxy's ansae in the 1.65µm H-band is shown in the lower right frames of Figure 22, where the ansae are seen to have irregular shapes compared to the others shown.

    enter image description here

    Figure 22. Examples showing ansae bar morphologies as compared to one mostly non-ansae bar. For each galaxy, the left frame is the full image while the right frame is an unsharp masked image, both in units of mag arcsec-2. The galaxies are: (left to right): Row 1 - NGC 5375 (SDSS g) and 7020 (I) (both round ansae type); Row 2 - NGC 7098 (I, linear, partly wavy ansae) and NGC 1079 (Ks, curved ansae); Row 3 - NGC 4643 (I, mostly non-ansae type with trace of ring arcs at bar ends) and NGC 4151 (OSUBSGS H, irregular ansae).

    Posted