Hickson 44a NGC 3190 (Arp 316)
Constellation: Leo
Type: Galaxy Sa(s)a pec
RA: 10h 18m
DEC: +21° 49'
Mag(B): 11.9
Size: 3.6’ x 1.3’
Hickson 44b NGC 3193 (Arp 316)
Constellation: Leo
Type: Galaxy E2
RA: 10h 18.5m
DEC: +21° 53'
Mag(B): 12.0
Size: 2.5’ x 2.3’
Hickson 44c NGC 3185
Constellation: Leo
Type: Galaxy (R)SB(r)a
RA: 10h 17.7m
DEC: +21° 41'
Mag(B): 12.9
Size: 2.1’ x 1.2’
Hickson 44d NGC 3187 (Arp 316)
Constellation: Leo
Type: Galaxy SB(s)c pec
RA: 10h 17.8m
DEC: +21° 52'
Mag(B): 13.8
Size: 2.4’ x 0.8’
After a full year of pandemic lockdown and a winter that just wouldn’t stop and go away, I am especially excited about the arrival of Spring Equinox next week. Why? Because when Spring arrives so does Galaxy Season! So many incredible galaxies to observe! Let’s visit 4 of them in this week’s Object of the Week: HCG 44 and Arp 316.
The galaxies of Arp 316 and HCG 44, located in the constellation Leo, give us a view of eye-catching contrast in galaxy types: spiral, elliptical, barred and irregular, and all with a range of distortion due to their strong interactions with each other.
HCG44.jpeg
Arp 316, categorized as a Group of Galaxies, contains three member galaxies: NGC 3187, NGC 3190, and NGC 3193. With the addition of a fourth galaxy, NGC 3185, this expanded group is designated as the 44th entry in the Hickson Compact Groups of Galaxy (HCG) catalog, from a 1982 study published by Paul Hickson of compact galaxy groups visible from the Northern Hemisphere. Compact galaxy groups selected for inclusion had to have a minimum of four members. The best known entries in the Hickson catalog are Copeland’s Septet (57), Seyfert’s Sextet (79) and Stephan’s Quintet (92).
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According to Hickson: “Most compact groups contain a high fraction of galaxies having morphological or kinematical peculiarities, nuclear radio and infrared emission, and starburst or active galactic nuclei (AGN) activity. They contain large quantities of diffuse gas and are dynamically dominated by dark matter. They most likely form as subsystems within looser associations and evolve by gravitational processes. Strong galaxy interactions result and merging is expected to lead to the ultimate demise of the group. Compact groups are surprisingly numerous, and may play a significant role in galaxy evolution.”
Hickson 44a: NGC 3190 Deformed peculiar edge-on spiral The brightest member of the group, NGC 3190 is a striking spiral that we see nearly edge on. Note the thick tilted main dust lane and the smaller intersecting dust lane, reflecting tidal interactions with nearby galaxies. The distortion is so severe that this galaxy has two designations - NGC 31891 and NGC 3190 - because it was thought to be 2 objects as noted by Herschel in his discovery notes2. The faint star streams at each end of this galaxy also indicate some tidal distortion.
My observation notes: “3189 star, 3190 edge-on with dark dust lane, bright core, very elongated”
n3189-3190.jpeg
Hickson 44b: NGC 3193 Elliptical Although it is the second brightest member of the group, NGC 3193 presents itself as a large featureless fuzzy elliptical galaxy.
My observation notes: “3193 circular, diffuse with center brighter, mottled
n3193.jpeg
Hickson 44c NGC 3185 Deformed barred spiral with outer ring NGC 3185 appears to have a complete external ring. The bar seems to terminate on the ring, but close inspection shows that the "ring" is composed of two closely coiled spiral arms. Each arm can be traced from its starting place at the end of the bar, through 180 degrees, until it passes near and almost joins the opposite end of the bar. Each arm passes beyond the opposite end of the bar and can be traced on the outside of the beginning of the other arm. This galaxy also has a small and very bright Active Galactic Nucleus.
My observation notes: “3185 difficult, very faint, very slight brightening in center”
n3185.jpeg
Hickson 44d: NGC 3187 Highly deformed spiral The faintest member of the group, NGC 3187 is an S-shaped spiral. Its interactions with nearby galaxies have not only severely distorted the arms, but it also looks like this interaction has initiated the formation of numerous bright blue star clusters throughout the galaxy.
My observation notes: “3187 very faint and diffuse, large elongation, brighter toward center”
n3187.jpeg
1The RNGC (Sulentic and Tifft 1973) notes NGC 3189 as a nonexistent object
2Discovered in 1784 by William Herschel with an 18.7-inch f/13 speculum telescope. He called it "Two. Both faint, elongated, a little brighter in the middle, resolvable."
Now it is your turn. Give it a go and let us know!
hcg44abcd.jpeg hcg44ngc.jpeg
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