Pair of Galaxies NGC 3395/6 (Arp 270)

History

The galaxy pair NGC 3395/6 was discovered on 7 December 1785 by the German-British astronomer William Herschel with his homemade 18.7 inch f/12.8 reflecting telescope in Slough, England. He listed them under the designations I 116 and I 117. The same night he also encountered NGC 3413 (II 439), NGC 3424 (II 494), and NGC 3430 (I 118). ^{[196, 277, 313]} He classified his discoveries based on purely visual impressions, with I = bright nebulae and II = faint nebulae. ^[269]

The French astronomer Stephane Javelle searched this area of the sky on 17 May 1896 with the 76 cm refractor telescope of the Observatoire de Nice and recorded four other nebulae: IC 2604, IC 2605, IC 2608 and IC 2612, with IC 2605 being a bright node in the galaxy NGC 3995. ^{[196, 277, 315]}

Halton Arp divided his «Atlas of Peculiar Galaxies», published in 1966, into groups based on purely morphological criteria. The pair of galaxies here received the designation Arp 270 as a pair of interacting galaxies. ^[199]

Physical Properties

The interacting galaxy pair NGC 3395/6 is at a distance of 15 to 30 Mpc. ^[145] According to HyperLEDA ^[134] they together form the NGC 3430 galaxy group with a total of 15 members, which also includes NGC 3381, NGC 3424, NGC 3430, NGC 3442, IC 2604 and IC 2608. IC 2612 (PGC 32704) has a much higher redshift of z = 0.04452, which corresponds to a heliocentric velocity of about 13400 km/s. This galaxy is far in the background.

«Catalogue of Principal Galaxies (PGC)», Paturel et al. 1989 ^[144]
Name	RA [hms]	Dec [dms]	mType	Dim [']	Btot [mag]	HRV [km/s]	PA [°]
PGC 32390, IC 2604	10 49 25.7	+32 46 29	SB	1.2 x .9	14.8	1680	40
PGC 32424, NGC 3395	10 49 49.4	+32 58 51	SB M	1.7 x .9	12.5	1621	50
PGC 32434, NGC 3396	10 49 56.1	+32 59 22	IB M	2.9 x 1.2	12.6	1633	100
PGC 32464, IC 2608	10 50 15.4	+32 46 06	S	.9 x .3	15.6
PGC 32543, NGC 3413	10 51 21.1	+32 46 04	L	1.8 x .8	13.1	645	178
PGC 32584, NGC 3424	10 51 46.5	+32 54 02	SB	2.7 x .8	13.2	1497	112
PGC 32614, NGC 3430, IC 2613	10 52 10.9	+32 57 09	SB	4.1 x 2.2	12.2	1585	30
PGC 32704	10 53 34.3	+32 45 01	E	x

Finder Chart

The interacting galaxy pair NGC 3395/6 is located in the constellation Leo Minor. The best viewing time is October to June.

Chart Pair of Galaxies NGC 3395/6 (Arp 270) — Pair of Galaxies NGC 3395/6 (Arp 270) in constellation Leo Minor. Charts created using SkySafari 6 Pro and STScI Digitized Sky Survey. Limiting magnitudes: Constellation chart ≈ 6.5 mag, DSS2 close-ups ≈ 20 mag. ^{[149, 160]}

Visual Observation

762 mm Aperture: Both galaxies are slightly more elongated than wide and are at right angles to each other, one of which is slightly wider compared to the second. The nuclei are each perceptible as points. — 30" SlipStream-Dobson f/3.3, Hasliberg, 14. 2. 2023, Eduard von Bergen

134	Lyon-Meudon Extragalactic Database (LEDA); leda.univ-lyon1.fr
144	Catalogue of Principal Galaxies (PGC); Paturel G., Fouque P., Bottinelli L., Gouguenheim L.; Astron. Astrophys. Suppl. Ser. 80, 299 (1989); cdsarc.unistra.fr/viz-bin/cat/VII/119 (2021-02-18)
145	SIMBAD astronomical database; simbad.u-strasbg.fr/simbad
147	Aladin Lite; aladin.u-strasbg.fr/AladinLite (2020-12-23)
149	SkySafari 6 Pro, Simulation Curriculum; skysafariastronomy.com
160	The STScI Digitized Sky Survey; archive.stsci.edu/cgi-bin/dss_form
196	Celestial Atlas by Curtney Seligman; cseligman.com/text/atlas.htm (2020-12-28)
199	«Atlas Of Peculiar Galaxies», Halton Arp, 1966; Astrophysical Journal Supplement, vol. 14, p.1 (1966); DOI:10.1086/190147; Bibcode:1966ApJS...14....1A; ned.ipac.caltech.edu/level5/Arp/frames.html
269	William Herschel's catalog of Deep Sky objects; messier.seds.org/xtra/similar/herschel.html (2021-12-27)
277	«Historische Deep-Sky Kataloge» von Dr. Wolfgang Steinicke; klima-luft.de/steinicke (2021-02-17)
313	«A New General Catalogue of Nebulae and Clusters of Stars, being the Catalogue of the late Sir John F.W. Herschel, Bart., revised, corrected, and enlarged» Dreyer, J. L. E. (1888); Memoirs of the Royal Astronomical Society. 49: 1–237; Bibcode:1888MmRAS..49....1D; ui.adsabs.harvard.edu/abs/1888MmRAS..49....1D/abstract (2021-04-14)
315	«Second Index Catalogue of Nebulae and Clusters of Stars; containing objects found in the years 1895 to 1907, with Notes and Corrections to the New General Catalogue and to the Index Catalogue for 1888–94» Dreyer, J. L. E. (1910); Memoirs of the Royal Astronomical Society. 59: 105–198; Bibcode:1910MmRAS..59..105D; ui.adsabs.harvard.edu/abs/1910MmRAS..59..105D/abstract (2021-04-14)