Lake Sonoma 11/13/07

Steve Gottlieb

After last Monday's little excitement at Lone Rock flat, I was hoping for a more serene evening and that's just what we got. We had a little breeze and a little dew, but not enough to be an issue at all. This was fall observing at its best, with no need to put on winter gear. Seeing started off quite good and I was able to use 450x and even higher on several planetaries, but by 11:00 the seeing softened, particularly looking lower in the south. The transparency was typical for Lake Sonoma on a good night -- last Monday, Greg recorded 21.30 on his SQM and on Tuesday night, it registered between 21.3 and 21.4 (perhaps he'll report the numbers), not bad for a bay area site. Contrast was excellent on galaxies with the dust lane in NGC 891 showing off a scalloped appearance in my 18-inch and showing up as a faint streak in my 80mm finder at 25x. Obviously 891 doesn't require much aperture if the transparency is good.

After checking out 891, Bill spent some time on Abell Galaxy Cluster (AGC) 262, situated roughly 45' SE of 891 and counted quite a number of galaxies in the central core. That reminded me about another remarkable field nearby. Moving just 45' due north of 891 is a group of three UGC galaxies at the northern outskirts of AGC 262 in addition to one of the most optically variable galaxies -- 3C 66A -- a blazar which resides in the distant background.

The first UGC galaxy I looked at, U1832, had a very strange appearance at 225x. The galaxy is dominated by a sharply concentrated 25"x20" core that appears to be elongated NW-SE. Surrounding the core is a much larger, low surface brightness halo at least 2' in diameter. The galaxy appears odd with the contrast between the halo and bright core and it happens to be sandwiched between a mag 8.4 at the north end of the halo and a mag 10.9 star at the south end! The glare of these stars make it is difficult to gauge the edge of the halo, but it appears to extend perhaps 3/4 of the way between the stars.

Then I noticed the core was closely bracketed by two faint "stars -- one just off the SE edge and a second star jammed up against the NW end. This probably contributed to the impression of elongation. I had a suspicion these might not be stars due to their locations and checking NED the "star" at the SE end is a virtually stellar galaxy, V Zw 230 (a classification by Zwicky of compact galaxies), just 25" SE of the center of U1841. It turns out that U1841 is a well-studied Seyfert (radio) galaxy with a designation 3C 66A and a short jet extending from the nucleus has been detected in radio, x-ray, infrared and optical wavelengths. SIMBAD shows 337 journal references for this interesting galaxy.

A second UGC galaxy, U1837, is located 2.7' NW, just beyond a mag 11 star close NW of U1832. I logged this one as "faint, small, slightly elongated SW-NE, 24"x18", weak concentration with a slightly brighter core." A mag 11 star sits less than 1' ESE and a mag 8.4 star is 2.4' E. The third UGC galaxy, U1832 was easily visible another 6' NW of U1837. I recorded this final galaxy as "very faint, fairly small, elongated 2:1 NW-SE, 0.6'x0.3'. The major axis closely parallels a 1.5' string of mag 12-13 stars that is just west of the galaxy."

Finally, just 2.4' SE of UGC 1837 is the variable blazar 3C 66A. We're looking at an active galactic nucleus (BL Lacertae type) with a relativistic jet shooting directly in our line of sight. This blazar displays infrared, optical, ultraviolet, and X-ray variability on both short-term and long-term timescales. Visually, it varies between ~13.8-15.6 and it happens to be near its maximum right now. With a redshift of 0.444, the light travel time for this galaxy is roughly 4.6 billion years -- pretty close to the age of our solar system! VIsually, it appeared as just a 14th magnitude "star", but it was fun to contemplate that this light left the blazar in the same timeframe as when the earth was forming!

-- Steve