Object of the Week - June 10, 2018 - Arp 297 (NGC 5754 - group)

[Uwe Glahn]

Arp 297 = NGC 5752/5753/5754/5755

Bootes

NGC 5754
Ra: 14 45 20
Dec: +38 43 58
Vmag: 13.1

NGC 5752
Vmag: 14.1

NGC 5753
Vmag: 15.0

NGC 5755
Vmag: 13.5

Heard of the Galaxy Group was discovered by William Herschel in 1787. The other NGC companions, the relative faintness indicates that, were discovered nearly 100 years (an observation of NGC 5755 by Herschel was not published) later in 1878 by Lawrence Parsons - the son of the famous "Lord Rosse".
A fifth galaxy, PGC 2135414 (18.2bmag) lies between both pairs and is in reach of larger apertures.

All four galaxies found entry in the Arp Atlas under number 297 (group: "Double galaxies with long filaments"). The question is, why Hickson did not respect and catalogue them. In my mind all Hickson classification terms are complied. So with a missing Hickson number the bright and detailed group is often overlooked.

Both northern (NGC 5753/5755 ~ 450mly ) and both southern (NGC 5754/5752 ~ 210mly) seems to belong together. The long tidal filaments and starburst action confirms the interaction between them. Especially impressive is the long tidal of NGC 5454/5752 (~6') to the west.

In practise the group is interesting in nearly every aperture. While 8-inch to 12-inch telescopes shows the members itself, larger apertures 20-inch+ could show the fainter interaction, especially the arms. I never heard about a visual observation of the very faint long filament to the west, but perhaps Jimi gave or give it a go?

DSS blue 15'x15' (http://archive.stsci.edu/cgi-bin/dss_search?v=poss2ukstu_blue&r=14+45+15&d=%2B38+45+50&e=J2000&h=15.0&w=15.0&f=gif&c=none&fov=NONE&v3=)

Adam Block/Mount Lemmon SkyCenter/University of Arizona (http://www.caelumobservatory.com/gallery/n5754.shtml)

sketch: 8", 160x, seeing V, NELM 6m5+
3085

sketch: 27", 419x, seeing III, NELM 6m5+
3086


"GIVE IT A GO AND LET US KNOW"

[Ivan Maly]

Excellent target, Uwe. I observed it in July (20", 360x, SQM 21.83, 4800 ft, good seeing):

NGC 5753 small, roundish.


In 5755, nonstellar nucleus on E end of extended core. Massive arm loops from E end of core N then almost to E end of core. Short arm opposite, points toward stars E.


5752 comparatively small, extended generally NW-SE and concentrated to the center. It is slightly integral sign-shaped with ends pointing E and W.


The core or bar of 5754 is oriented similarly to -52. It is enclosed in a ring with outer arms emanating CCW from near the ends of the bar. NE arm loops back and is enhanced in P.A. 30. SW arm has a similar enhancement opposite and extends around E [should be W] side of the galaxy inward of -52. Outermost arm or tidal tail on S side of the pair is visible as a diffuse arc, unconnected to either member, and much thicker than in the original photograph.

P.S. Regrettably I did not check for the tail W of -52, but since the N half of the outermost arm of -54 was invisible, so too would probably be the W tail.