Date: November 28, 2010

Title: ALMA Update with Dr. Carole Lonsdale

Podcaster: Richard Drumm

Link: http://theastronomybum.blogspot.com/

Description: Richard talks to Dr. Carol Lonsdale, the head of the NAASC, the North America ALMA Science Center, about the progress in construction of the ALMA radio telescope array, which is being built in the Atacama Desert in Chile. We also learn about some of the incredible science the array will be doing when it becomes operational.

Bio: Richard Drumm is President of the Charlottesville Astronomical Society in Charlottesville, Virginia.

His blog is at http://theastronomybum.blogspot.com/

He’s the owner of 3D – Drumm Digital Design, an award-winning video production company. He was an observer with the UVa Parallax Program at McCormick Observatory in 1981 & 1982. He’s found that his greatest passion in life is public outreach astronomy and he pursues it at every opportunity.

Today’s sponsor: This episode of “365 Days of Astronomy” is sponsored by — no one. We still need sponsors for many days in 2010, so please consider sponsoring a day or two. Just click on the “Donate” button on the lower left side of this webpage, or contact us at signup@365daysofastronomy.org.

Transcript:

In this podcast we’ll update you on the construction progress and science of the Atacama Large Millimeter/submillimeter Array, or ALMA. It’s being built in the high desert of the Chajnantor Plateau in northern Chile, at an altitude of 5,000 meters, that’s 5 kilometers above sea level.

It’s only there that the array can be located above much of the water vapor in our atmosphere, vapor that blocks important parts of the radio spectrum from reaching the ground. It’s the next best thing to being in outer space.

ALMA will be the most important tool for observing what’s called the “cool universe” composed of the gas & dust from which planets, stars & galaxies form. In order to achieve the sharpness we’re accustomed to seeing in astronomical images, a millimeter radio antenna would have to be many kilometers across, and therefore impossible to build. By combining the signals from smaller antennas scattered across kilometers of the high desert in a special computer called a correlator, these sharp images can be acquired.

Hello, I’m Richard Drumm, outgoing President of the Charlottesville Astronomical Society, and I’m here today at the headquarters of the NRAO, the National Radio Astronomy Observatory, with Dr. Carol Lonsdale, head of the NAASC, the North America ALMA Science Center.

Welcome to the 365 Days of Astronomy Dr. Lonsdale!

CJL:
Thank you.

RBD:
Tell me, Dr. Lonsdale, how did you get interested, in astronomy inn the first place?

CJL:
Oh, gosh, that’s a long story, but um, it actually has to do with the fact that my brother is also an astronomer. And his name is Dr. Colin Lonsdale and he’s now the director of the Haystack Observatory in Massachusetts, which is run by MIT. And we’re just 2 years apart and when we were young he was fascinated by astronomy. And so he was actually the first one to come up with the idea that it was a pretty cool thing to do. He built his own telescope, polished the mirror, and (I) have to say, I got pretty fascinated by the sorts of things he was doing. That was the start and been a fan of astronomy ever since.

RBD:
I’m assuming your career has had a bit of a red shift, starting with optical visual, then optical infra red, and now radio. Has it been a logical progression?

CJL:
Well, in some sense. Actually, its mostly been in the infra red up until this point. So it’s a red shift from the infra red into the radio. I spent most of my career at CalTech, where I worked with the infra red processing and analysis center for most of my career, which is a NASA funded facility, doing the data reduction for, for the most part, infra red missions, including the IRAS satellite back in the 80s, which is when I joined CalTech, and through to the Spitzer mission, sometimes called “the infra red Hubble.”

RBD:
I’ll buy that, yes!

CJL:
Yeah, so my connection to the radio and to the NAASC, the North American Science Center, comes from my background in being involved in running science centers at the CalTech Science Center.

RBD:
And for those of our listeners who uh, aren’t familiar with ALMA, and I’m afraid a lot of you probably aren’t familiar with ALMA, describe for them for a moment just in a couple short sentences what ALMA is.

CJL:
Well ALMA is the uh, Atacama Large Millimeter/submillimeter array, and it is an array of dishes which is being constructed right now in the high desert of Northern Chile in the Atacama Desert at a high elevation of about 16 thousand feet. When it’s finished it will be an array of 66 antennas, most of them are 12 meters in diameter. A small number of them are 7 meters in diameter. And they will be observing the sky in the submillimeter and millimeter wavelength range.

RBD:
So I presume this penetrates dust even better than infra red does.

CJL:
Well, indeed, and not only does it penetrate dust but a lot of the radiation that we receive in this wavelength range comes from dust radiating itself. The dust is warmed by radiation ultimately from stars and then re-radiates in this wavelength region.

RBD:
So how many antennas are up at the AOS, the high site up at the top of the mountain?

CJL:
At the moment there are 8, which is an exciting stage, we’re going to be starting the actual observations at the observatory, involving community members who can propose to use the observatory. They’ll be able to start using the observatory when it has 16 antennas on the high site. So we’re halfway there!

RBD:
Do you have any of the 7 meter ACA, Atacama Compact Array dishes yet?

CJL:
I don’t believe there are any of those at the high site in operation yet, the 8 that are up there are all 12 meters, but there are 7 meters that are completed at the intermediate facility which is somewhat lower on the mountain.

RBD:
And the ACA, they’re basically just gonna stay fixed and, and not be moved around…

CJL:
That’s right, there’s a compact configuration of the antennas in the center of the array, that’s called the ACA, and in addition to that, there’s an extended array of antennas which can be moved around. There are more pads for the antennas than there are antennas, so each of the 66 antennas, minus the ones that stay put in the compact array, can be moved from pad to pad so that we can open up the array to a larger separation between antennas or we can close it down to a smaller configuration. And that allows finer or less detail on the objects, uh, depending on what the science requires.

RBD:
Right, so the ACA, the compact array will serve as sort of like a wide angle lens stuck in the middle of the telescopic lens of the, of the larger dishes.

CJL:
Yeah, that’s a pretty good way to look at it. Yep.

RBD:
So what are the big scientific questions that ALMA will answer?

CJL:
Well, one of the most interesting things that ALMA is going to be able to do is look in detail at molecular lines – emissions from molecules in interstellar space. One of the particularly interesting regions is areas of molecular clouds where new stars are forming. We’ll be able to look at the complex chemistry, and we’ll be able to use the line emissions to give us some information about velocity structures and the overall structure of the material around the young stars as they are in the process of forming.

RBD:
When do you think first science will happen?

CJL:
First science?

RBD:
When you get 16 dishes, but when does it…

CJL:
16 dishes are scheduled to be up at the high site and operating early next year (2011), well in the spring of next year, and then the scientists, the ALMA project scientists will be involved in checking them out and making sure they’re operating correctly, checking out all the different modes of the observatory. That the general community will be able to propose for time on ALMA sometime within the next year, and will be able to start putting community proposed observations onto the array perhaps towards the end of 2011. But that’s still to be defined, exactly when the observatory will start operating.

RBD:
How much of the correlator is up there? Is it half?

CJL:
I believe that 2 of the 4 quadrants are now in operation on the high site and the third quadrant is up there but is not yet installed into the array, so 2 of the quadrants are being used by the 8 antennas that are up there at the moment.

RBD:
And some of the quadrants are made here in Charlottesville, Virginia, and some are being made in Canada, aren’t they?

CJL:
Yeah, that’s correct.

RBD:
For that first science, what sort of things, do you think, that they’ll be looking at?

CJL:
Well, the first science we’ll be using just 16 antennas, whereas by the time we get to a milestone we call the inauguration, there will be 50 antennas. There are 66 antennas in the total array when it’s completely finished, and so over this period of time the capabilities of the array are going to be changing dramatically. Because the more antennas the hat (?) you have, the greater sensitivity is going to be available to the observer.

Plus, the more antennas you have, the finer resolution and more detail you can obtain on the sources you’re looking at. And so some of the early projects will be more focused towards studies that don’t need the full capabilities of the final array. For the most part that means that, uh, we’ll be looking at sources that are, brighter perhaps than we’ll be looking at when the array is finalized.

We’ll also be looking at sources that are, we’re less concerned about knowing the detailed structure of the source on fine scales, where it’s adequate to just collect more of the total flux and look at that. There’s a whole range of astronomical studies that can be done with the early array.

And indeed the early array is much more capable than any other array that’s ever existed in this wavelength region, so it’ll be many steps ahead of what you can do at the moment, so I foresee that we’ll see a wide range of studies of all kinds of astrophysics, even with the early array.

RBD:
I was just wondering what the low hanging fruit was. What they’re gonna go after first! Large Magellanic Cloud or…

CJL:
Oh, I think some of the most interesting star formation regions in the galaxy, some of the most obvious ones in the Southern sky, people will be looking for the strongest lines and the structures of the lines to understand the chemistry that’s going on in the regions of star formation.

People will be looking for lines from circumstellar disks, and another uh, low hanging fruit I think is going to be some of the most distant galaxies in the universe, which might sound like it’s one of the hardest things to do, but in fact, some of the most distant galaxies in the universe emit quite strongly in this wavelength range, partly due to the redshift effect, that a lot of the energy coming from shorter wavelengths is redshifted at these large distances into the submillimeter band.

And also due to the fact that a lot of these objects are intrinsically very luminous in this wavelength band, so they’re not all that faint indeed, when you look at high redshift. So ALMA will be able to detect those quite handily, many of them with the early array and the, the detailed spatial structure is not so important for the early science, we’ll be looking for CO emission lines in particular which will actually tell us how far away those objects are, and ALMA is very well designed for that task.

RBD:
Thank you so much, Dr. Lonsdale!

CJL:
You’re very welcome, it’s been a pleasure.

RBD:
To learn more about ALMA, please visit science.nrao.edu/alma

Remember:
There is no endeavour more enobling for humanity, than understanding the cosmos.

ALMA will serve as our eyes as we throw open the window to the millimeter universe.

End of podcast:

365 Days of Astronomy
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