Object of the Week March 14, 2021 – HCG (Hickson) 44 and Arp 316

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.

Attachment 4246

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).

Attachment 4247

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”

Attachment 4248

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

Attachment 4249

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”

Attachment 4251

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”

Attachment 4250

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!

Attachment 4252 Attachment 4253

Hi here's my observation from 6/3/2016: ngc 3190 magnitude:11.2, ngc 3193 magnitude:10.9 and ngc 3187 magnitude:13.4 galaxies in Leo aka Hickson 44, beautiful collection of different types of galaxies. Ngc gives the appearance of a dust lane,Ngc 3193 is roundish with a brighter central area, ngc 3187 was just barely perceived. I used a 8mm Ethos at 198x with my 14.5 Starstructure Dob f/4.3Attachment 4254

An observation in February 2018 from dark (and cold! -10C) northern Germany. 14" SCT @ 168x / 29':

All four galaxies are visible, a beautiful group.
A - NGC3190 is elongated NW-SE and is suddenly brighter in a core that is slightly elongated in the same direction with a bright nucleus that is visible without AV. Has somewhat irregular structure and is flattened on the south side on a line from SE to NW; that will be due to the dark lane in the galaxy but the lane can not be discerned. To the NW is D - NGC3187, to the NE is B - NGC3193, 1/3 FoV to the SSW is C - NGC3185.
B - NGC3193 is a round glow, suddenly brighter in a round core with a bright nucleus that is visible without AV. To the NNW is a mag. 9 star (SAO81279).
C - NGC3185 is a NW-SE elongated glow, quite suddenly brighter in a core that is slightly elongated in the same direction, with AV the extremely faint nucleus is at the limit of visibility. To the SW is a mag. 15 star.
D - NGC3187 is an extremely faint, NE-SW elongated glow, even in brightness, no detail visible and difficult to observe without AV.

I rated the group 7/10.

Attachment 4256 Attachment 4257 Attachment 4255

Click here to download the observing guide above, in multiple images orientations.

Some observations through Jimi's 48"...

NGC 3185: very bright, oval halo 5:3 NW-SE, ~1.8' major axis. Strongly concentrated with a very bright roundish core which increases to a slightly brighter stellar nucleus. The halo has a brighter arcs at the ends of the major axis (northwest and southeast ends) and is slightly weaker inside, creating a weak ring. A low contrast bar connects the ends of the major axis and the core, creating a subtle barred ring.

NGC 3187: elongated 3:1 NW-SE, ~1.8'x0.6', weak concentration with no well defined core. At both the NW and SE ends of the bar are faint spiral arms. The arm at the NW end bends sharply towards the south in the direction of a mag 13.8 star 1.0' SW of center, though doesn't reach this star. On the SW end of the bar a second faint arm hooks at a right angle to the NE. Both arms give the galaxy a distinctive zig-zag shape.

NGC 3190: extremely bright, nearly edge-on 7:2 WNW-ESE, perhaps 3.7'x1.0', very bright core with a dazzling stellar nucleus. A sharp, contrasty dust lane that is relatively wide runs along the full length of the galaxy, passing just south of the core. A thin strip of the galaxy parallels the dust lane on the outer southwest side of the galaxy. This strip has a well-defined southern edge and dims at the southeast end of the galaxy.

I can contribute a low-end sketch concerning aperture - HCG 44 with a 4-inch Newton.

I wrote: "A" visible as an easy noticeable glow which seems 1:2 elongated SE-NW; "B" also visible as a direct visible somewhat concentrated round glow, "C" visible with averted vision as a faint glow, "D" beyond the range of the scope

sketch: 4", 54x, NELM 6m5+
Attachment 4268
home

Wow that's a beautiful galaxy group with members of different morphologies.

I observed it twice this week. On the first evening it was a race against cirrus clouds that were moving towards the constellation of Leo. On the second evening conditions were better.

With my new 20" Dobsonian I tried to observe the dark lane in NGC 3190, but was unable to see it. On the first evening I saw a sharp edge on the SW side. But under better conditons I saw a diffuse continuation of the galaxy beyond that edge. I couldn't resolve a dark lane, though. Maybe it was a seeing issue?

Please find attached my sketch.

Clear skies,

Robin