Results 1 to 4 of 4

Thread: Object Of The Week April 9, 2017 - The Tidal Ring/Arm of interacting Arp 107

  1. #1
    Member Steve Gottlieb's Avatar
    Join Date
    Feb 2012
    Location
    Northern California
    Posts
    804

    Object Of The Week April 9, 2017 - The Tidal Ring/Arm of interacting Arp 107

    Arp 107 (Interacting Pair)
    Aliases: VV 233 = UGC 5984 = MCG +05-26-024 = CGCG 155-031 = PGC 32620/32628

    RA: 10 52 16.7, Dec: +30 03 55 (Leo Minor)
    Size: 1.6' x 1.2' and 0.5' x 0.4'
    Mag: 14.0V and 14.5V

    Light-travel time: ~466 million years

    Arp classified his #107 under "Elliptical and elliptical-like Galaxies connected to spirals". He noted "Double arms leads to E galaxy, diffuse material out other side of E galaxy." Here's Arp's photo using the Palomar 200-inch.

    Arp.jpg

    But like many of the galaxies in Arp's Atlas, this interacting system first appeared in Boris Vorontsov-Velyaminov's 1959 Atlas and Catalogue of Interacting Galaxies as VV 233. The system consists of disrupted spiral with a small bar-like bulge and a single strong spiral arm with a pretty circular ring-like shape and a straight extension to the northwest. The nucleus is active, exhibiting Seyfert 2 features. A (double) tidal bridge connects the spiral with a small elliptical companion (MCG +05-26-025) to the northeast and a diffuse halo extends mostly east of the companion. Here's the SDSS image of the pair---

    SDSS.jpg

    In mid-infrared images (Spitzer), the spiral looks more like an asymmetric colliding ring galaxy -- probably an off-center collision. In fact, Arp 107 is listed as a collisional ring in the 2009 "Atlas and Catalog of Collisional Ring Galaxies" by Barry Madore et al. In this Spitzer image (color-coded by infrared wavelength) can you imagine a grinning Cheshire cat?

    Infrared.jpg

    Both galaxies were easily visible in my 18-inch, though I didn't log much structure in this observation from 5 years ago --

    Arp 107 consists of a close pair: MCG +05-26-024, an unusual one-armed spiral and MCG +05-26-025, a compact elliptical off the northeast side. MCG +05-26-024 appeared very faint, moderately large, low surface brightness, very small slightly brighter core, ill-defined oval halo, ~1.4'x1.0', the arm structure wasn't noticed. MCG +05-26-025, situated just off the northeast edge side [1.1' between centers] appeared faint, very small, round, 12" diameter. It has a higher surface brightness than larger MCG +05-26-025.


    I took another look at Arp 107 last May in Jimi's 48-inch and of course recorded the unusual arm/ring structure --

    VV 233a = MCG +05-26-024 is the disrupted member of Arp 107 = VV 233 with a long single spiral arm/tidal tail. At 375x it appeared moderately large, slightly elongated, ~1.3' diameter, sharply concentrated with a very small nucleus 12"-15" diameter. The outer portion of the halo resolves into a single, long spiral arm; it begins on the northeast side and rotates counterclockwise for perhaps 150°, fading out on the southwest side. The fainter tail portion to the northwest was not seen. A mag 16.5 star is superimposed [21" SW of center], just inside the end of the arm.

    VV 233b = MCG +05-26-025 is 1.2' NE of center. It appeared fairly bright, very small, round, high surface brightness, surrounded by a small halo ~15" diameter. This compact galaxy (considered the colider in the 2009 Madore et al "Atlas and Catalog of Collisional Ring Galaxies") has a much higher surface brightness than the RING system MCG +05-26-024.


    This amateur image is from Rick Johnson using a 14" LX200R @ f/10, L=4x10' RGB=2x10', STL-11000XM, Paramount ME

    Rick J..jpg

    There are a few challenges here. What aperture will reveal the single spiral arm/ring? What about the edge-on spiral 5' ENE? (visible on Rick Johnson's image).

    Give it a go and let us know!
    Last edited by Steve Gottlieb; April 9th, 2017 at 09:54 PM.
    Steve
    24" f/3.7 Starstructure
    18" f/4.3 Starmaster
    Adventures in Deep Space
    Contributing Editor, Sky & Tel

  2. #2
    Member
    Join Date
    Feb 2012
    Location
    Germany
    Posts
    813
    Nice catch Steve.

    With 27" I could resolve the (heavy) spiral arm of VV 233a but not the tidal between a and b nor the fainter extensions from a to the northwest.

    sketch: 27", 293x, NELM 6m5+, Seeing II
    UGC5984.jpg
    Clear Skies, uwe
    http://www.deepsky-visuell.de
    Germany

    27" f/4,2

  3. #3
    Member Steve Gottlieb's Avatar
    Join Date
    Feb 2012
    Location
    Northern California
    Posts
    804
    Excellent sketch, Uwe. It captures the visually appearance of this pair in a large scope.
    Steve
    24" f/3.7 Starstructure
    18" f/4.3 Starmaster
    Adventures in Deep Space
    Contributing Editor, Sky & Tel

  4. #4
    Member Ciel Extreme's Avatar
    Join Date
    May 2014
    Location
    Limerick, SK, Great White North
    Posts
    81
    My notes from this past Friday (April 14), backyard with stars mag. +5.8-6.0 visible naked eye, 22-inch reflector at 303x: “This interacting pair is very faint and seen at both medium and high magnification. MCG+5-26-24 is larger; a hazy round disk a little brighter to the middle. The spiral arm surrounding the core is not seen. MCG+5-26-25 (to the NE) is smaller, brighter and more condensed, round and well defined.” Hell of a catch seeing spiral structure in a galaxy almost 500 million light years away. Congrats, Uwe...
    Mark Bratton
    18" f/4.5 Litebox reflector (travel scope)
    22" f/3.3 SpicaEyes Slipstream reflector (LittleTime Observatory)
    25x100mm binoculars
    “The Complete Guide to the Herschel Objects” (CUP 2011)

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •