Most Galaxies May Not Have Black Holes

Jared writes: "A story at space.com reports that new research indicates that black hole formation is tied directly to the amount of mass in a galaxy's central bulge, an ancient and dense sphere of stars that populates the central regions of many galaxies, including our own Milky Way."

3,000 * our Sun = Puny.

[SyniK]

Quotes from the article:
"One of the new studies, led by Rutgers University Professor David Merritt, found that if (Galaxy) M33 contains a black hole, it is not more than 3,000 times the mass of our Sun."

"Gebhardt refers to these possibly numerous groupings of stars as "very puny disk-only galaxies." Some researchers think there may be more of them in the universe than any other type of galaxy. And so if they in fact do not harbor black holes, then galaxies with black holes would be in the minority."

The jury is in! We know nothing conclusive about the universe! (Or why goatse.cx is so popular a troll spot.)

Re:Resampling

[KjetilK]

OK, that makes it more reasonable. I guess I have to read that article.... :-) However, to achieve close to twice the resolution, they have to be very sure they are actually shifting with pretty exactly half a pixel, and something tells me that would be difficult (just take the photon statistics). BTW, there are plans for a new CCD for HST, isn't it?

Good to hear VLTI is doing so great!

Re:Resampling/Drizzle

[KjetilK]

OK. I did some search, and it seems [stsci.edu] like the pointing error is about 10 mas. What is the pixel scale? About 100 mas? I that case, I guess it is quite sufficient, yes.

Resampling

[KjetilK]

From the article:

Gebhardt said his team had developed a "resampling technique" that infers a spatial resolution of the Hubble data that is improved by a factor of two,

Hm, claims of improvement in spatial resolution always makes me veeeery skeptical. Unless they can prove that the resampling technique works, by showing that it correctly reproduces an image taken with higher resolution, I just don't believe it. And with galaxies and with the HST (that has pretty much the best resolution right now (until optical interferometers get into "everyday" use)), you can't do that.

That doesn't mean I reject this study, but I would view it with additional skepticism.

Re:Resampling/Drizzle

[BjornHeijligers]

Great, yes 150mas i think..

Grtz

Bjorn

Re:Resampling

[BjornHeijligers]

The resampling of works for the HST because the resolution of the camera is UNDERsampling the signal coming from it's mirror.. That is the HST could see sharper if it would have a higher resolution CCD camera.. the trick now is to take 2 images with one picture shifted HALF a pixel with respect to the other, thereby creating an image with twice the resolution. Regarding optical interferometry: I'm working on that :)) commisioning of the VLTI (Very Large Telescope Interferometer) is currently in progress, and i will go observing sometime next month :)

Bjorn Heijligers

http://www.heijligers.com

Re:Resampling/Drizzle

[BjornHeijligers]

Well the pointing of any telescope has to be rather good, otherwise one would not be able to integrate for very long, because otherwise the image would be smeared due to the movements of the telescope. (this is controlled by a so called guide camera that locks on nearby guide stars for which the position is very accurately determined)

If i remember correctly they not only move the telescope but also rotate the ccd with a 45 degree angle with respect to the first image, which gives the best result..

The algorithm that does this is called "Drizzle" and is now a very standard technica. (students down the hall here are doing it right now at the Leiden Observatory here :) )

I think i have heard something about a new ccd, but i'm not at all sure how soon that would be..

The first light (fringes) of the VLTI can be found here:
http://www.eso.org/outreach/press-rel/pr-2001/pr -0 6-01.html

(I actually spend 2 months programming one of the microcontrollers on the carriage you can see on one of the images)

Grtz

Bjorn