NGC 5466, a globular cluster in Bootes with a bunch of quasars

[Martin Meredith]

I was out last night testing the new native live capture feature that will be released in the upcoming version of Jocular (initially supporting the Lodestar X2 mono, but with support for the Ultrastar planned shortly afterwards) and trying it out on a varied bunch of objects, mainly to ensure I was reading the sensor correctly (not a given -- quite a complex beast to program, for me at least!).

I happened upon the only globular cluster in Bootes, NGC 5466, and noticed that the field contained a lot of quasars ranging in brightness from 18.7 down to 21.2. These provided a good test of the limiting magnitude that I could compare with earlier captures using StarlightLive. 

It is also a rather nice cluster! 

 

Here's a negative version where I've marked the locations of 5 quasars along with their (V) magnitudes and redshifts, as well as type Sc (though hardly recognisable as such) mag 17.4 galaxy at around three-quarters of a billion light years distant. Checking with Aladin I can confirm the presence of 4 quasars but the 5th, magnitude 21.2, eluded me. I'm never totally sure which is the preferred way to compute redshift to light years as it depends on the cosmological model, but using Ned Wright's calculator I get the following range of estimated distances in billions of light years

z = 0.25: 2.77 - 2.97

z = 1.43: 7.75 - 9.26

z = 1.95: 8.59 - 10.3

z = 3.25: 9.7 - 11.7

(not seen) z = 3.89: 10.0 - 12.1 

The lower value is from the 'open' model while the upper estimate is from the 'flat' model. I'd be interested in hearing from anyone who could explain the differences, and which is the better one to use based on current understanding!

I also wonder if anyone fancies trying to catch the mag 21.2 quasar? This was quite a brief exposure with 10s subs and absolutely no calibration, so those with lower read noise cameras and a better process might conceivably stand a chance.

 

 

cheers

Martin

 

 

 

[Knight of Clear Skies]

z=3.25 - is that over 12 billion light years away in lookback time?

[Martin Meredith]

48 minutes ago, Knight of Clear Skies said:

z=3.25 - is that over 12 billion light years away in lookback time?

According to Ned Wright's calculator it is 11.7 if one assumes the 'flat' model, whatever that is ....

http://astro.ucla.edu/~wright/CosmoCalc.html

Any insights appreciated!

Martin

[Mike JW]

Hi Martin, good to see another globular posting. This one has the 3D effect.

Flat universe - is what it says. Flat and nice square edges

Open Universe - is curved in such a way that it would never meet up on itself (I think they call it negative curvature). A curved and positive ends up as a sphere and is known as closed model.  As if I know or understand relativity............Most folk go for flat or open curve but a paper in 2019 raised the idea of the closed model again based on some latest data analysis but doubted by others.......Majority opinion is for a flat universe based on current data.

Z values do my head in!!!! There is the light travel time (distance), let's say 6 billion lyrs away. So the light took 6 biilion lyrs to reach us but shifted to the red end because the universe is expanding. Thus if we could instantly go the spot the galaxy would not be there. It would now be further away - its actual distance (not sure what term is given to this) However because the universe is expanding at an increasing rate just to add confusion then the true distance will be even more.........

I disclaim all knowledge of the subject!!!!!!!!! Not sure the above is totally correct but hopefully gives a feel for the distance lark. It was all so much easier a few centuries ago when everything circled the earth!!!!

Mike

Edited May 19, 2020 by Mike JW

[Paul M]

The mind boggles. Perhaps some day I'll understand these cosmological distances and light-travel times in terms of the age of the Universe and a Big Bang beginning.

Until then I'll continue to just think "Wow!"

[Bill S]

As Mike JW said, 'It would now be further away...'

Yep according to my look at Ned Wright's calculator that Martin referred to and a handy table based on it in the RAS diary for a Z  of 3.25, so a look back time of 11.7 Gyr then the current distance (the term used in the RAS diary table) is around 21.9 Gly. If you think I have got this wrong you may well be correct!

It's definitely not close!

 

[Bill S]

OK!

Here are a couple of snapshots. Have I caught the quasar, a hot pixel or my wishful thinking? It was very handy that I could use Jocular to flip and orient my image to match yours.

 

 

 

As you'll see I left the capture running a long time.

Martin - do you have the RA and Dec for this object so I can I try looking at the right place in a plate solved image. (Assuming I can plate solve it, of course.)

Best regards

 

[Martin Meredith]

Hi Bill

That's a fine capture! 

The purple cross is where Aladin tells me it is located on the DSS image (the RA/Dec correspond to the object). 

 

In this zoom it is marked with the green square. It is very faint and somewhat reddish on the DSS image. 

Now I must quickly fix a few bugs and get the scope out to cool.....

Best

Martin

 

 

[Mike JW]

Hi Martin and Bill,

I took a look at this area the other night. NGC 5466 is a lovely sight. The image below shows 5466 offset to enable a closer look at the area where Quasar (z=3.89) is - centre and near the top. 

Mike

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

The image below is  close up and rotated to more nearly match Aladin. I have located the  triangle of stars and have labelled approx mag data for two of them. Unable to find data on the third star. No sign of the z=3.89 (in fact I could not find the Z data for this object - SDSS J140508.77+282621.1 (mag 22.4 (g) or mag 22.06 (r) ). It looks like from my site, using the 15" Dob I can at a push get down to around mag 20 but not fainter. Also too easy to imagine conveniently placed bits of noise as a star/DSO.

Fun trying to see how deep I could go.

[Bill S]

I took my snapshot and put it into All Sky Plate Solver. I then took the plate solved image and moved the cursor to the coordinates for the quasar (z=3.89). I have not managed to see even a blemish that I could claim was the object. (Even with my wishful thinking amplifier turned up to 11. )

Best regards

Bill

[Mike JW]

We need to rush out and get fully motorised 20" Dobs and give that a go!!!!!!!!!!!!!!!!!!!!!

Mike