Object of the Week, October 29, 2018 - NGC 1097

[Steve Gottlieb]

RA: 02 46 18.9, Dec: -30 16 28 (Fornax)
Type: SB(rs)b pec
Aliases: Arp 77 = ESO 416-020 = UGCA 41 = PGC 10488
Size: 9.3' x 6.3'
MagV: 9.5, MagB = 10.2
Distance: ~50 million l.y. (Virgo cluster)
NGC description: very bright, large, very much elongated 151°, very bright middle and nucleus

NGC 1097 may be overshadowed by better known NGC 1365 in Fornax, but it’s a remarkable barred spiral that certainly deserves to be featured as an "Object of the Week"!

3240

William Herschel discovered NGC 1097 on 9 Oct 1790 (sweep 972) and logged "vB; E 75° np to sf; about 8' long. A very bright nucleus confined to a small part about 1' diameter." From his latitude of Slough in England this galaxy culminated only 9° above his southern horizon. On the same sweep, he also discovered NGC 1344, NGC 1266 and NGC 1425, all near -30° declination in Fornax.

NGC 1097 is a powerful radio and x-ray Seyfert I galaxy with a circumnuclear starburst ring and a supermassive black hole with a mass of 140 million solar masses.

A rather unique feature are four striking optical "jets" (http://www.pbase.com/strongmanmike2002/image/152760644) that were discovered in 1975. The jets extend out 300,000 light years with one having a bizarre "dog-leg" right-angle turn. As they appear to radiate from the Seyfert 1 nucleus, it was initially thought they were related to the AGN (such as M87's relativistic jet), but it was discovered the jets are composed of ordinary main-sequence stars similar to tidal streams seen in the Milky Way. Another theory is that they were tidal tails drawn out of NGC 1097's disk by the interaction with nearby NGC 1097A.

But more recent studies and models suggests they are the remains of a previously cannibalized dwarf spheroidal galaxy that passed within the inner few kilo parsecs of NGC 1097's disk and one or two knots in the so-called jets may be the stripped nuclei of a former dwarf. As far as the "dog-leg" jet, this may simply be two unrelated intersecting tidal streams.

You don't need to view NGC 1097 from the southern hemisphere to see its strong bar and spiral arms, but here's my best observation with a 30-inch from Coonabarabran in 2015:

At 303x; this showpiece barred spiral contains a bright central bar ~4.5'x1.5' NW-SE. The bar is sharply concentrated with an extremely bright, slightly elongated NW-SE core but no distinct stellar nucleus.

A prominent spiral arm is attached on the northwest end of the bar. The arm is relatively thin, well defined and knotty as it curls counterclockwise to the east, dimming out gradually about 3' ENE of center. A large bright knot is close to the northwest end of the bar, just inside the beginning of the arm and close east of a superimposed mag 14.5 star. NED catalogues this region with the multiple designations NGC 1097:[EKS96] 148 and [EKS96] 151 from the 1996 "An Atlas of H II Regions in Nearby Seyfert Galaxies" in ApJS, 105, 93. Roughly halfway along its length is a pair of fairly prominent HII knots. The first is [EKS96] 245, a 12" knot 2.5' NNE of center. Close east is slightly larger [EKS96] 300/304, 2.5' NE of center. The arm then fades as it passes just south of a mag 15 star.

At the southeast end of the bar a delicate, thin spiral arm unfurls counterclockwise towards the northwest. About halfway along its length is a slightly brighter elongated patch extending ~30" in length, with designations [EKS96] 100/105/119 and others. The arm dims out about 3' WSW of center. The arms stretch about 6' tip to tip, giving overall dimensions of perhaps 7'x6'.

As always,
"Give it a go and let us know!

[Bertrand Laville]

Hi All,

Great choice and very beautiful galaxy.
Here is my observation , Tivoli Namibia, SQM 22.10!, very good seeing. 20" dobson Obsession, 195x
http://www.deepsky-drawings.com/ngc-1097-1097a/dsdlang/fr

x195 Nagler 13mm: You have to stay long on the galaxy to see the details appear. The bar is seen first course: it is V1 (obvious). My drawing shows the a / b ~ 3.5 to ~ 4.25 'x 1.7'. Then the satellite NGC 1097A, seen V2 (easy), very clear. After these two first markers must identify nearby stars or the halo, and position them.

Once the field is well understood and integrated intellectually turns appear, quite easily. They are VI1. The turn N is shorter, compact, visible until star E1 *, which is clearly seen. S coil is more remote, more refined, and I have "seen" since leaving the S end of the bar, to the satellite NGC 1097A. I drew 2 brightness bulges: the first spot between the AP 195 ° and 220 ° relative to the core, the second one, 1.20 'of the nucleus of NGC 1097A in AP 207 ° . But I have not seen the disruption of the regularity of the curve of the coil S. (Note 2006 11 19: this description validated by photos NGC 1097 Capella Observatory, observatory and Rose)

A "thing" non-referenced to the GSC, UCAC2 and A2.0, but B1.0 0596 0028926, m15.2V (unreliable because embedded b) I pointed at my sketches in situ, which I took for a term star, and I said "fake". Yet the images show that "my" star is the exact location of the main HII region of the coil S, halfway between the bulge luminosity, spot one described above, and the star B * . Coincidence?)
B * 19058026 UCAC2, m14.26R, E1 * 0525 00940344 A2.0, m16.6V

Clear skies
Bertrand
http://www.deepsky-drawings.com

3241

[Steve Gottlieb]

Here's Robert Gendler's image of the main jets. If you look carefully at the "dog-leg" jet #2, it includes a couple of very small knots, perhaps remnants of a digested dwarf.

3242

[Ivan Maly]

Great stuff, Steve and Bertrand! This galaxy is on my list for a large telescope in the Southern Hemisphere. That 22.10 reading is fantastic; I sensed that it could be that during my observing in Central Australia, but had no photometer with me.

I looked at this galaxy just earlier this month with my new 20 (250x, latitude 41N). The conditions could be better, with an SQM 21.4 glow overhead and some noticeable horizon haze. Nonetheless, in addition to be bar, the arms were obvious through much of their length, with an enhanced segment in each. As was the companion. I did not spend a lot of time on it, but the dark lane on the W side of the bar was far from definite. I saw this feature quite well before in my 12-inch (125-375x, same dastardly SQM), along with the two enhanced arcs in the arms as floating freely on the background. The dark lane that I mean is not the dust but a gap between the bar proper and the inner arm along its W side.

[Uwe Glahn]

Beside the "dog-leg" jets there is another unike and very astonishing detail around NGC 1097 - its quasar concentration. After Arp and Carosati [ arXiv:0706.0143] there are a lot of more quasars around the galaxy than it should be. Note the ring structure and the double quasars.

chart of the paper by Arp/Carosati
3243

From Austria (47°N) I noted with 16-inch: bright with showy companion, both arms faint, but surely detectable

But like Steve and Bertrand I had my best views from the south (Namibia). The amount of details is difficult to describe so the sketch has to speak.

sketch: 24", 185x - 300x, NELM 7m5+, Seeing II
3244

[Bertrand Laville]

Hi again,

Thanks to Steve, I had a look at [EKS96] An Altlas of HII regions in nearby Seyfert galaxies, and a new look at my sketch of 2006.
Here it is.

3245

a: [EKS96] 123, 124, 126, 127, 131, 133

b: 143, 145, 149

c: many HII regions, located between 235 and 294

d: large HII regions, located between 327 and 344

e: 132, 137, 144, 153, 16.

f: 99, 100, 105, 117, 119

g: 37, 38, 41, 48, 50, 51

h: many HII regions located between 54 and 82

i: 45, 52, 55, 60

It's pretty amazing to validate the details of an observation 12 years later!

Bertrand
http://www.deepsky-drawings.com

[Steve Gottlieb]

As far as I know the excess of quasars around NGC 1097 was never investigated further. In fact, Arp's paper was never published in one of the principal journals (other than on arXiv and perhaps the Max-Planck-Institut website), perhaps because he also insisted it demonstrated that quasars were ejected from the cores of galaxies.

Arp added this epilogue to the paper, which effectively announced he was being blackballed from mainstream astronomy:

It was commented on the title page of this web posting that the paper had been rejected by the Astrophysical Journal Letters. Thus the editor spake: “Your paper has not been able to convince either of two independent referees. . . . “No suppression of your work has been done through my action since you are welcome to submit your paper to a different journal.”

The information supplied here should enable the readers to decide for themselves the value of the data and its discussion. But perhaps more important it enables a judgment on the core structure of current science.

[Ivan Maly]

There were specific objections - quite valid, as I recall - which were expressed close to the time of Arp's original studies, to the statistical method behind the discovery of the "quasar overabundance", like in this example. This is discussed somewhere in Arp's Seeing Red. If my memory is to be trusted, the correction for multiple comparisons was not applied.

[KidOrion]

Observed this for the first and only time from southeast Missouri; I've gotten a little better at estimating distances and magnitudes since then, although not as much better as I'd like. Conditions deteriorated quickly and dramatically.

10/26-27/14

MILL CREEK RETREAT, VAN BUREN, MO
MOON: 3 days, set by observation time
SEEING: 8
TRANSPARENCY: 8, later 3
NELM: 7.1
WEATHER CONDITIONS: temps in 50s-60s, later heavy dew/fog

1:02
NGC 1097 (For)—about 15’ N of little triangle of 8th/9th stars—triangle at widest side is 7’ long—galaxy is v. bright—long halo, 4-5’ by half that—v. bright core, almost blazing—core about 1.5’ round—averted stretches halo to 6’—10’ to NP is 9th star—amazingly-large galaxy—to F side is pair of 11th stars about 10’ away—same distance to P side is pair of 10th/11th stars—no NGC 1097A visible

[Howard B]

I've never had a great view of 1097, but I finally got a half decent look at it last October with my 28-inch:

"This is a gorgeous barred spiral! Only one arm is seen well though as it sweeps by the companion galaxy NGC 1097A. Only a segment of the other arm is seen, but my eye really wants to connect it to the end of the bar. The core is sharply defined and almost seems to have a brighter rim, rather like a planetary nebula. 408x, 21.56 SQM"

3246

My sketch was done quickly, but conveys what I saw well enough - but I sure would like to see it as well as Uwe has!

Also, I just read in the November issue of Sky & Telescope that gravitational lensing can boost the number of quasars seen in the background around galaxy clusters by up to 70%. It doesn't look like there's a galaxy cluster behind 1097, but perhaps 1097 is massive enough to lens quasars by itself.

[MikeWiles]

Last week I had an eight night trip for first light on my 20" f/3 dobsonian. 7 of 8 nights were perfectly clear. I arrived in the dark skies of Portal, Arizona armed with a pretty diverse observing list, including most of the recent OOTW's. This is my first post to this forum.....here's what I saw.

8mm, 219x - Beautiful barred spiral about 8' in the long axis. A very bright core 1' in diameter features the bar coming away NW and SE. From the NW end, the bar extends 3' from the core and then a spiral arm turns sharply north and then away from the body, extending another couple of arc minutes before fading. There is an obvious separation of the spiral arm from the body of the galaxy. There is a 15th magnitude star next to the bar and turn in the arm. From the southeastern end, the bar extends 3' as well and then appears to turn to the west back tightly onto itself. With averted vision there is a dark lane on this arm, but not the same obvious separation from the body of the galaxy.

NGC 1097A is 3' removed from the main body of the galaxy and elongated perpendiculat to 1097. It's perhaps 1' in length and has a stellar core.

Mike
Phoenix, AZ
20 inch f/3 Newtonian

[Dragan]

Hi Mike and welcome! We hope you find DSF a valuable resource for you and your new scope!