Real-Time Galaxy Image

I apologize for my silence of the last few weeks; real life gets busy at times. This time, I was in a crunch finishing up things before running off to an observing run at the CTIO Observatory in Chile. That's where I am right now. I'm at the 0.9 meter telescope doing imaging of "blazars," a class of active galactic nuclei that sometimes vary on timescale of minutes (which is surprising if you know how big galaxies are). My graduate student Katie Chynoweth is observing on the 1.5 meter telescope, doing spectroscopy of infrared-luminous galaxies.

Below is an image — really, a composite of 27 images taken over the course of about 2 hours through red, green, and blue filters — i took with the 0.9m telescope:


The target I'm interested in is the galaxy that's right at the center:


This galaxy goes by the romantic name ESO 264-G057, and is in fact one of the infrared luminous galaxies that is a part of Katie's project. She's been observing that galaxy and one other (whose picture will probably show up here in a day or two!) this week, and I took this image in support of that project.

So this is an image of the galaxy that's only two days old! Well, plus the 230 million years it took the light to reach Earth....

More like this

That depends on your definition of fast....

The blazar I'm spending most of my time on has a lookback time of 5.3 billion years. At z=0.54, it's at what people nowadays call merely "moderate" redshift....

...imaging of "blazars," a class of active galactic nuclei that sometimes vary on timescale of minutes (which is surprising if you know how big galaxies are)....

Does this imply that the nucleus is no more than a few light minutes wide? That would make them very small objects.

By Chris' Wills (not verified) on 14 Apr 2007 #permalink

Chris --

Sort of. In fact, the black holes that are at the cores of these galaxies are thought to have Schwarzschild Radii that are a few billion km, which is about a light-hour. So, the nuclei are larger.

This does say, though, that the primary source of emission for a *blazar* is no more than light-minutes across, which is very tiny. The thought is that we're looking at relativistic gas clouds crashing into each other at or near the base of the jet. It's pretty boggling how well collimated that jet must be, esp. considering the size of the black hole.

YAY, more galaxy blogging!

Mollishka -- I'll write more about that at some point assuredly.

What I'm looking for is microvarability, or intranight variability. Part of what I'm hoping to do with a previous run and with this run is to push the shortest timescale of variation that have been observed. I'm also starting to work with Mike Carini on some ways of detecting small time-lags between different colors (or lags between flux and color vairations -- same thing).


Do the distances you mention, 230 million LY and 5.3 billion LY, indicate "blazers" are more common in the middle history of the universe; thus that you have not been able to locate any much nearer (less than 200 million LY) or much farther away(more than 6 billion LY)? Or are these simly the ones you've found convenient to investigate?

Barry Wood

By Barry Wood (not verified) on 15 Apr 2007 #permalink

The thought is that we're looking at relativistic gas clouds crashing into each other at or near the base of the jet.
Posted by: Rob Knop

As the galaxy, in the wonderful picture, is seen from the top, is the jet pointing our way (I'm guessing that the black hole spins on the same axis as the galaxy) does it emit in the visible spectrum at all or is it all x-rays?

By Chris' Wills (not verified) on 16 Apr 2007 #permalink

Barry-- multiple things.

Blazars are very *rare*. The jets are quite narrow, so the orientation has to be just right for it to be pointing at you. What this means is that in order to find one, you have to look in a very large volume that includes a lot of galaxies. The higher redshift you go to, the larger the volume you search, and as such the more likely you are to find a blazar. They're also very bright, so they're easier to see at high redshift than normal galaxies. This is the primary reason that most blazars we look at tend to be at pretty high redshifts.

It's also true that as you go back in time, AGN activity was more common, but the difference between now and z=0.5 isn't all that great. THe difference is a lot bigger if you look back to z=1-2.

I'm looking at this blazar because it's one that is known to vary, and because it's coming off of a long-term flare over the last few months.

Chris -- the galaxy in that picture actually doesn't have a jet (or much of a jet) associated with it. It's not the blazar-- the blazar is a different galaxy.

However, your assumption turns out not to be necessarily right -- the rotation axis of the black hole and the rotation axis of the galaxy as a whole do *not* need to be the same.

The jets we see : if they're pointed at us (as in a blazar), we see them in all wavelengths. If you're looking at them edge-on, it's usually easiest to see them with radio waves (where you're looking at synchrotron radiation of relativistic electrons spiralling around magnetic fields), but you can also sometimes see them optically.

One classic case of a relatively weak nearby jet is the one at the core of the giant elliptical galaxy M87. You can find some classic HST images of that jet, visible in optical wavelengths.


So...which galaxy is the host for the blazar?

Also, do you happen to have a visual magnitude for ESO 264-G057? I'm curious if it's even vaguely possible to see in an amateur telescope. (It's too far south for me anyway, but....) I couldn't find it on Wikisky, possibly because the ESO catalog doesn't seem to be in their dataset.

Great of luck with the data reduction. Clear skies!

By David Williamson (not verified) on 19 Apr 2007 #permalink

David -- use SIMBAD or NED, you can probably get magnitude estimates there.

I haven't published any blazar images, because they're boring.... Mostly they look just like stars. The one I was spending most of my time on (3c279) is a point source. The other one I looked at (AP Librae) has a bit of fuzz around it, but is still not very interesting.....

These are the "secondary project" images I've been posting.


Oh. Duh. SINBAD. Right. For the record, B=14.5. It's nice and dim, but it's possible with a decent sized scope.

On the blazar images point, I think I earn another slap in the forehead. You did say z=0.54, which is far enough to generally make for a very faint image, outside of the point source.

By David Williamson (not verified) on 20 Apr 2007 #permalink

Can you please explain. I am quite challenged :-) When you say that you saw an image 2days ago, is that image something that is happening at that time or is it so that 2days ago you were looking at an image of something that was occuring 230 million years ago?