Stunning Hubble image of Hanny's Voorwerp

[SkyViking (Rolf)]

Finally Hubble has had a go at Hanny's Voorwerp:
http://www.universetoday.com/82358/h...annys-voorwerp

Full resolution image: http://www.universetoday.com/wp-cont.../01/hanny1.jpg

[CraigS]

Its gotta make you wonder what else there is out there that we can't see !
(Ie: 'dark' gases etc).

They're saying this was spotted simply because the quasar jets illuminated one part of one of the galaxy's trailing arms of gas, about one million years ago. (The jet then stopped less than about 200,000 years ago).

There has to be a lot of dark cold gases floating out there. (And thus, plenty of exotic gravitational fields as well).

Thanks Rolf !

Cheers
PS: Interesting that its Oxygen as well !! Hmm ..

[astroron (Ron)]

IC 2497 at only 700 Million light years away, Seems to me to be a little bit close to have a Quasar turn off only a million years ago
This could encourage Arp devotees who say that Quasars are always not Billions of light years away
It should be a very interesting discussion
Cheers

[CraigS]

Originally Posted by astroron

IC 2497 at only 700 Million light years away, Seems to me to be a little bit close to have a Quasar turn off only a million years ago
This could encourage Arp devotees who say that Quasars are always not Billions of light years away
It should be a very interesting discussion
Cheers

OMG Ron !!

What are you doing to us !!

Just remember who started this !! (It wasn't me !!)



Cheers

[astroron (Ron)]

Originally Posted by CraigS

OMG Ron !!

What are you doing to us !!

Just remember who started this !! (It wasn't me !!)



Cheers

Hi Craig, I was surprised this point has not been picked by anyone else,as it was the first thing that came into my mind as I read the article
Bring on the dancing girls
Cheers

[CraigS]

I'm just reading the latest paper I can find on this ..

"The Sudden Death of the Nearest Quasar" by Schawinski, Evans et al, Dated 1st Nov 2010 (ie: prior to the GalaxyZoo's announcement at the beginning of the thread).

They say …

The Voorwerp is a large (11 × 16 kiloparsec) cloud of ionized gas 45,000-70,000 lightyears away from the nucleus of the galaxy IC 2497, embedded in a larger reservoir of atomic hydrogen (J ́ozsa et al. 2009), with a mass of several times 109M⊙ (see Figure 1). The optical spectrum of the Voorwerp is dominated by a powerful [O iii] λ5007 emission line and shows little detectable continuum.
The presence of other emission lines with high ionization potentials, such as [He ii] and [Ne v], together with the narrowness of the emission lines suggest that the Voorwerp is being photoionized by the hard continuum of an active galactic nucleus (AGN; an accreting supermassive black hole), rather than by other processes such as star formation or shocks (such as might be induced by a jet; Lintott et al. 2009).
Radio observations of IC 2497 reveal a nuclear source and a jet hotspot in the nucleus, and a large kiloparsec-scale structure that may be a jet (J ́ozsa et al. 2009; Rampadarath et al. 2010).
The Voorwerp lies where this jet meets the Hi reservoir and coincides with a local decrement in atomic hydrogen presumably due to photoionization. An actively accreting black hole at the centre of IC 2497 is therefore the only plausible source of ionization that can account for the emission seen from the Voorwerp.

More in next post.

Cheers

[CraigS]

Moving on in the same paper ..

However, IC 2497 poses a challenge: the optical image reveals no strong point source, the nuclear spectrum shows very weak optical line emission (Lintott et al. 2009), and it also has a weak (∼ 10⌃38 ergs−1) nuclear radio source (J ́ozsa et al. 2009). These observations are difficult to reconcile with the presence of a currently active L(bol) ∼ 10⌃46 ergs−1 quasar. There are two possible scenarios that can account for these apparently contradictory observations as argued by Lintott et al. (2009):
1) the quasar in IC 2497 features a novel geometry of obscuring material and is obscured at an unprecedented level only along our line of sight, while being virtually unobscured towards the Voorwerp;
or 2) the quasar in IC 2497 has shut down within the last 70,000 years, while the Voorwerp remains lit up due to the light travel time from the nucleus.
If the latter is the case, the IC 2497–Voorwerp system gives for the first time an upper limit of the shutdown timescale of an individual quasar central engine. In this Letter, we present observations to distinguish these two scenarios.

Interesting that these guys are sticking to the shut down occurring only 70,000 years ago, whereas the GalaxyZoo guys are saying that it stopped less than about 200,000 years ago (bit of a difference there .. but probably not that significant).

Cheers

[mswhin63 (Malcolm)]

Originally Posted by CraigS

Moving on in the same paper ..



Interesting that these guys are sticking to the shut down occurring only 70,000 years ago, whereas the GalaxyZoo guys are saying that it stopped less than about 200,000 years ago (bit of a difference there .. but probably not that significant).

Cheers

200,000 years ago is a short time in astro, I suspect this is an acceptble margin of error, especially for a short discovery. Over time it could be narrowed down.

[renormalised (Carl)]

Originally Posted by astroron

IC 2497 at only 700 Million light years away, Seems to me to be a little bit close to have a Quasar turn off only a million years ago
This could encourage Arp devotees who say that Quasars are always not Billions of light years away
It should be a very interesting discussion
Cheers

Not really....the simple, prosaic and most likely explanation is that quasar like activity occurred in the nucleus of this galaxy just recently and only lasted for a limited period of time. The fact that it appears it turned off only about 70,000-200,000 years ago is just our good fortune to be observing it at the right time. The light still had to take 700 million years to get here, so what we're seeing (like a lot of astronomy) is nothing more than an illusion. It never shut off 200,000 years ago in our own perception of time, but over 700 million years ago in reality. The Voorwerp is nowhere near, now, where we see it as it is in the piccies. It might not even exist anymore for all we know.

A quasar, or quasar like activity, can switch itself on or off at anytime in a galaxy during its lifetime. All the quasar needs is an infall of material into the nucleus of the galaxy in which it resides to trigger it off. That could happen at any time, for a great many reasons. The only reasons why quasars and such were more prevalent in the past than now and shut off at similar times is because the galaxies in the earlier times had more material in their nuclei as dust, gas etc...especially during their formative years. More material meant more activity as the central holes gathered the materials to generate the quasars. But that activity will only last as long as the supply of material continues. In many ways, the central BH's are their own worst enemies because the high energy radiation given off in the quasar activity eventually drives the activity to a halt, by expelling the last of the material that's gathered in the near vicinity of the BH. That, and the fact that the hole can only suck in what it can during the life of the activity...which to generate a quasar only needs to be on the order of 1 solar mass/year. It can be more, though, but it's not like what most people would think (hundreds or thousands of solar masses in days, weeks or months).

There's no need for Arp's ideas to even be considered...not that they really hold any water, anyway.

[CraigS]

Its interesting that they compare SMBHs to scaled up versions of X-Ray Binaries because the physics is similar to BHs, namely because rapid transition between accretion states is observed fairly routinely, in XRBs.

In the case of IC 2497, there is a four order of magnitude drop in luminosity, which doesn't stack up too well with the XRB analogy. They attempt to scale up using the XRB model to the estimated mass of IC 2497, which leads to a period of turn off, significantly longer than what appears to be the case for IC 2497 ….

We therefore conclude that the sudden death of IC 2497 is a vital clue to how quasars accrete and shut down, but that we do not yet understand the physics of this process.

They then go on to say that it could turn on again in a similar timescales .. but this would just be a possibility.

The beauty of this beast, is that its so close to us, we can observe the host galaxy "in greater detail than any other system". This would lead to a study of the BH/surrounding matter interactions.

Great stuff. Will be interesting to see what the GalaxyZoo people have to say in their report, (which should follow shortly).

Cheers