Interacting galaxy system Arp 102

About this image

About this image
This is a combination of several exposures taken on the night of June 22nd 1995 (UT of observation 23/06/95:06:18 to 09:34) with a CCD detector on loan from Morley Block and the manufacturer, Scientific Imaging Technologies (SITe), Inc. This was one of the first of their new 2048x4096, 15 micron, three side buttable, thinned, back-illuminated devices, quickly inserted into a Kitt Peak standard dewar and installed on the WIYN 3.5m telescope. Three exposures were taken through each of three different filters approximating red (five minutes each), blue (fifteen minutes each), and green (ten minutes each). The result is therefore a combination of an hour and a half of observations. The individual colors were aligned and combined in the computer to create this (approximately) true color picture. The pixel size on the sky is 0.139 arc seconds; after combination, the final size is 1900x3960, or about 4.4x9.2 arc minutes. The image quality was changing during the exposure sequence, and to make the final picture the "seeing" measurement (average full-width half-maximum (FWHM) for several stars) had to be matched across all nine of the original frames, for a final value of about 1.0 arc seconds, although the best single frame measured at 0.7 arc seconds.
Orientation: N to the right, E up.

About this object
This interesting interacting spiral/elliptical pair of galaxies was first described in the Catalogue of Peculiar Galaxies, compiled by Halton Arp in 1966. It is also pair number 508 in Igor Karachentsev's catalog of binary galaxies. The large spiral galaxy (type SABb pec) shows long blue tidal tails caused by its interaction with the southerly elliptical. In fact, this "elliptical" is much the more interesting galaxy, despite its more nondescript appearance. It is a broad line radio galaxy with an unresolved core and a sub-parsec VLBI component at 6cm. It is also an intermediate type Seyfert, meaning it has an active nucleus, and it shows a double-peaked emission line profile (separation about 5000 km/s), which is considered to be strong evidence for the presence of an accretion disk, probably around a central supermassive black hole.
In this picture we also see the presence of numerous more distant background galaxies, showing as clusters of small, diffuse red objects and scattered diffuse blue objects. These objects are very difficult to detect and require excellent conditions and superb optics.

Location: 17 18 00 +49 04 (1950.0), constellation of Hercules (just!).
Distance: approximately 320 million light-years.

More: galaxies page, spiral galaxies page, elliptical galaxies page, WIYN galaxies page, WIYN spiral galaxies page, WIYN elliptical galaxies page.

Minimum credit line: C.F.Claver, N.A.Sharp (NOAO)/WIYN/NOAO/NSF

Downloadable versions:
417 x 200 6 kb color JPEG (on this page)
834 x 400 14 kb color JPEG
3960 x 1900 360 kb color JPEG
3960 x 1900 7.3 Mb 8-bit color TIFF
3960 x 1900 22.0 Mb 24-bit color TIFF
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