Welcome to ALFALFA!

ALFALFA is a blind survey using the Arecibo telescope designed to detect neutral hydrogen in other galaxies. A brief overview of the survey is available in the About page. If that’s not nearly enough information for you, don’t worry! Future posts will describe various aspects of the survey, data, and follow-up observations in detail. Another goal of this blog is to share the excitement (and trials) of ALFALFA, including observing reports and summaries of new science and papers as they’re published.

We’d also love to hear from you. Do you have a general question about ALFALFA that you would like answered? Post it in the comment section of this entry, and we’ll do our best to answer it. Are you a member of the ALFALFA team and would like to contribute content to this blog? Contact Betsey and your help will be gratefully accepted.

 

600th Observing Session

We recently celebrated the 600th observing session of the ALFALFA survey. This landmark occurred during Thanksgiving week, so we had a large contingent of observers at Arecibo taking advantage of the break from university classes. Two of the institutions from the ALFALFA Undergraduate Team, Humboldt State University and Colgate University, were represented. The observers, including two faculty advisors and seven undergraduate students, met in the control room for a celebration before observations started. Pictures, courtesy of Tom Balonek, are featured below. You can also find the pictures on the ALFALFA website located here.

600 observing sessions completed and 79% of the survey observations completed – we’re nearing completion of the observations for the survey. There’s still plenty of science to do, though!

 

ALFA’s Back!

The receiver we use for our observations, ALFA (more details here), is back in use after being out of commission for a month and a half for service. ALFA was put back into place at the beginning of the month and has been working ever since; we’ve been observing over the last two weeks and things seem to be mostly working.

Servicing ALFA is no simple task. You want to get the receiver into the shop so that it can be tinkered and twiddled with easily, but it’s installed in a dome that is suspended 400 ft above the dish of the telescope and kept chilled to very cold temperatures (well below freezing). You want to have a very good reason for needing to service the receiver. There’s the hassle of uninstalling and reinstalling the receiver, but also the risk that every time you let it warm up to room temperature when it’s in the shop that it might not cool back down without breaking. Then there’s also all of the observing time you lose while the receiver is in the shop. (Of course, Arecibo was still being used for observations, it’s just that any of the projects using ALFA – including us – couldn’t observe.) In this case, ALFA was taken down for servicing because several programs that use the receiver needed it be to improved and tweaked a little bit so that they could actually make the observations they wanted.

Unfortunately, like with everything, once you fix one problem, another appears. In this case, one of the beams of ALFA has been acting up. Fortunately, it seems like this isn’t a problem that will require ALFA coming off the telescope again to fix. Instead, it seems to be something that can be fixed while ALFA is installed in the dome, allowing the problem to be worked on during telescope maintenance time without impacting observations.

 

Arecibo is Awesome

Arecibo is an amazing, amazing telescope. It’s often easy to forget just how impressive it is, but I had the point driven home the other day, and I wanted to share. The sensitivity of a telescope is driven by the collecting area of the dish (or mirror, for optical telescopes) since a dish with a bigger collecting area can collect more photons from distant objects. Arecibo has a 300 meter diameter – it is the world’s largest telescope and hence is extremely sensitive.

I realized just how sensitive Arecibo is last week. I was working on a proposal to observe some sources from the ALFALFA survey with the Very Large Array (VLA) in New Mexico in order to see structure in these sources more clearly. (I talk here about how the VLA achieves better resolution of astronomical sources.) In order to write this proposal, I had to calculate how long we needed to observe my sources in order to have a good detection. These were all objects that were strong detections in the ALFALFA survey where they were observed for only 43 seconds in all (less than a minute!) by Arecibo. I calculated that in order to have a decent detection level with the VLA, it would take upwards of 10 hours of observation time. This strong difference comes from the vast difference in collection areas; the VLA only has twenty-seven 25 meter dishes while Arecibo is a 300 meter dish. I had always known that Arecibo is an awesome facility, but looking at this difference in time necessary to detect the same sources really impressed upon me what an amazing and unique facility Arecibo is.

43 seconds or 10 hours? I know which I’d choose.

 

The 5BAA Tour, Part Two

The 5BAA tour has successfully ended – Sabrina is all settled in and starting her new job. The trip went extremely smoothly, including having nice weather the whole time. We took one day of slight detours to visit Bryce Canyon and Zion National Parks. The scenery and rock formations were spectacular. We thought of our planetary science colleagues at Cornell who could explain the formation processes behind everything, but we were happy to just enjoy the views.

A view of Bryce Canyon.

Chewie enjoying the view at Bryce Canyon.

A view at Zion National Park.

Chewie and Bella enjoying the sand at Zion National Park.

 

The 5BAA Tour

Sabrina recently (five days ago) defended her dissertation to her committee. She gave a very excellent talk on her work over the last few years to a full room. (Once she has some time, I’ll try to convince her to write a brief explanation for here.) Now that she’s done with her graduate work, Sabrina is off to start a post-doctoral position at CalTech in Pasadena, CA where she’ll be working with data from the Spitzer and Herschel space telescopes.

Now, Sabrina has two lovely bulldogs that need to move across the country with her. Rather than leaving her to handle the drive with two dogs by herself, Ann and I are along for the ride (actually, a lot of the driving). We’ve been referring to this trip as the 5BAA Tour: The Five B’s Across America Tour. The five B’s are:

Brie (Sabrina)
Banana (Ann)
Betsey (That’s me!)
Bella (The beautiful bulldog.)
Bad Dog (Chewie, the other bulldog.)

We’ve done two long days of driving to make it part way into Kansas and have three days of shorter drives ahead of us. The internet access is spotty, but I’ll try to include a picture or two at some point.

 

Papers!

I’m going to do some bragging for Ann and Sabrina here. They both have had papers recently accepted to astronomical journals for publication (and Sabrina’s has been published online already because I’m a little slow), which means they posted these papers to the astro-ph arXiv. The arXiv is an online preprint server where scientists post their papers before publication so that the community can see exciting results as soon as possible.

Ann’s paper is a presentation of a catalog of sources from the ALFALFA survey. Ann took a strip of the survey area and found all the sources – both galaxies and high velocity clouds. This work is part of the legacy aspect of the survey. The catalog is made available to the community so that people can use the information about the hydrogen content of that part of the sky in future scientific work.

Sabrina’s paper also includes a catalog but is focused on examining the Leo Group. The Leo Group is a relatively nearby collection of galaxies. This means that lots of small galaxies were found in this region that would be too faint to see if they were further away. Sabrina also found a number of small galaxies that had a substantial portion of their mass in gas, but are so faint optically that they hadn’t been found in previous optical searches. Since the Leo Group is a bound collection of galaxies, Sabrina was able to look at the distribution of galaxy masses and compare the number of big galaxies to small galaxies. This helps us understand how structure forms in the universe. (For example, see Ann’s post explaining the HI Mass Function.)

 

Around the World in 80 Telescopes

If you haven’t heard, 2009 is the International Year of Astronomy and, accordingly, lots of events are planned for the year. About a month ago, ESO (the European Southern Observatory) organized an event called “Around the World in 80 Telescopes” which had live webcasts from eighty telescopes in twenty-four hours. Of course, you can’t visit eighty telescopes and not include Arecibo Observatory. I can’t get the embedding to work right now, so head here to watch the video on Arecibo.

Of course, you should check out all the other telescopes, too. I’m making my way through them slowly.

 

The HI Mass Function: What Do We Do With All These Galaxies?

As Betsey has mentioned, ALFALFA is a great way to find hydrogen-rich galaxies regardless of their stellar content. With ALFALFA, we can find lots of galaxies, including a lot that have very few stars and are therefore incredibly dim. This is just another way to learn about the incredible diversity and structure in the Universe around us, and when we’re done we’ll have a big pile of about 30,000 galaxies to work with. There’s a lot that we can learn about the Universe in this way, but I’d like to tell you about just one: the HI Mass Function. We call it the HIMF for short.

 

Observing at Arecibo

I’ve been back from observing at Arecibo for a bit now, but I thought I would summarize the observing experience. Mostly, observing at Arecibo isn’t much different from observing remotely in Ithaca. The biggest difference in terms of running the observations is that I get many more monitors to watch, as you can see in the pictures below. When observing in Ithaca, I have two monitors (running with one computer) for everything – one to display the program that controls the telescope and one for data monitoring. At Arecibo I have two computers, one with six monitors (telescope and observations control) and one with two (data monitoring). The set-up with all the monitors is very nice, especially because a lot of programs that monitor the status of the telescope and system set-up are displayed (the four peripheral monitors). Occasionally though, the different set-up would cause me to have a mild panic. I would glance at the data monitoring, for example, and then become uneasy when I didn’t see the program controlling the observations and telescope out of the corner of my eye. I managed to keep forgetting that it was on another set of monitors, a few feet away. All that extra monitor space could be disturbing at times.

The computer, and all its monitors, used to control the telescope.

The computer for monitoring data quality.

While the observing set-up is nicer at Arecibo and slightly more responsive since there’s no remote connection delay, that’s not the motivation for traveling all that way. The real reason to travel to Arecibo is to interact with people. Now, there are lots of people to meet at the observatory, but, in terms of observing, it was great to finally meet the telescope operators. The telescope operators are there to help make science observations run as smoothly as possible, which means they help with telescope set-up and are the first people you turn to for help when troubleshooting. When observing remotely, I would call the operator about fifteen minutes before the start of our observations to let him know that I was ready to take control of the telescope and to request the telescope be slewed to our desired position. What this means is that the extent of my interaction with the operators had been occasional 30-60 second phone conversations and snippets of dialog through a chat window in the telescope control program. One of the most productive parts of my trip was having the opportunity to meet the telescope operators in person and chat with them (especially during the long nights). It wasn’t just that it was nice to be able to put faces to the names of the operators I had worked with remotely; having interacted with the operators more has left me more confident of dealing with observing troubles remotely. Now, if I have to call the operator because of troubles (WAPP failures, network failures, etc.), it’s not calling a stranger and explaining the situation from scratch. Instead, I know the operators and they know me, and we can jump right into solving the problem and starting observations as soon as possible.

 

Arecibo and Exo-planets

You may have heard about the recent discovery of an Earth-sized planet that is not quite twice the mass of Earth. Remember, this isn’t an Earth-like planet because it is much too close to the star it orbits to be habitable. I happened to find this announcement especially interesting because I had just attended a talk the day before where Arecibo’s role in exo-planet detection was mentioned. Pulsar B1257+12 was observed at Arecibo and, through close examination of the data, astronomers were able to determine that it hosted two planets, of a few Earth masses, in 1992. Since then, they have detected a third planet and a possible fourth. These extra-solar planets were discovered several years before the “first” exoplanet detection around 51 Pegasi in 1995. I think it’s worth remembering that the first exoplanets, and the first approximately Earth-mass planets, were discovered by the Arecibo radio telescope. Now, you aren’t going to be able to find habitable planets around a pulsar (at least, not habitable to any sort of life we know), but the fact that planets can exist there offers a lot of insight into theories of planet formation and stellar evolution.