Undergraduate ALFALFA Team


This post was contributed by Genesis Guerra, a first year physics major at Union College. Over the Thanksgiving break she, along with three faculty and seven other students from Union College, St. Mary’s College of California, and University of Puerto Rico traveled to observe at the Arecibo Observatory.

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Faculty and Students from Union College and St. Mary’s College of California

I had an amazing experience at the Arecibo Observatory! I’ve learned so much about how astronomers observe our universe and derive important information from it. Before coming here I had no idea how to control a telescope or how to analyze a spectrum. I couldn’t tell what was a detection and what was radio interference, or how to baseline a spectrum, subtract background noise, and measure its rotational velocity and HI mass. But, I do now and, I feel very confident on the skills obtained on this research opportunity.

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Faculty and Students from Union College and the University of Puerto Rico

The purpose of our current observations is to observe and detect certain galaxies that weren’t originally detected by the ALFALFA survey because they had too low of an HI mass. Throughout our observing time, we performed two different types of observation. One was a regular targeted observation and the second one was a “search mode”. For regular observing, we observe using narrower frequency bands because we know the velocities and frequencies of the targets. We get better resolution from narrower bands. For search mode, we use wide bands to cover a bigger and wider range of velocities on the sky. We do this because we don’t know the velocities and frequencies of the targets.

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Braving torrential downpours and the ominous tidings of a full moon on Friday the 13th, four Skidmore College students doing research with Mary Crone Odekon made their way from Saratoga Springs NY down to Union College. That night they had the opportunity to remotely control the Arecibo Observatory in Puerto Rico along with Parker Troischt from Hartwick and Becky Koopmann from Union. Observations are currently underway as they look for HI detections from galaxies with detected star formation.

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Margot, Parker, and Yang.

So far, this summer’s work for the Skidmore group has involved confirming previously obtained group selection results from the AGC catalog with the Sloan Survey data. Happily enough the two data sets resulted in the same group identifications and further work is now underway to improve the determination of local density for each galaxy deemed to be a member of the group. The new technique being implemented relies on an absolute magnitude selection after employing the previously implemented red shift cut on the entire survey data set. The goal is to be able to compare the local density for groups at different distances.

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Skye, Pierre-Francois, and Yang examine a possible detection.

Another aspect of their research has involved checking the uncertainties in HI mass and HI deficiency that arise from uncertainties in galaxy distances. This was accomplished using a random number generator to create iterations with distance errors with a gaussian distribution that has a standard deviation of 10% of the galaxy distance. Analysis of the original data and the randomized sets have thus far shown that the estimates of HI mass and HI deficiency statistics are robust.

Finally, they are checking whether their results depend on whether galaxy groups are defined within a fixed radius or depend on the size of the groups. So far the results look similar even when groups are defined in this different way.

The galaxies they are trying to observe right now are elusive in HI… They keep being non-detections! Where is the gas coming from to create stars??? (Wormholes??)

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Yang, Becky, Margot, Pierre-Francois, and Mary.

Jeff Miller here, one of the two astronomers from St. Lawrence University. I’m here with my SLU colleague Aileen O’Donoghue and a group of faculty and students from Union and UPR who are observing during the week of Thanksgiving. Becky Koopmann once again serves as our fearless leader (although why she puts up with me, I’ll never know). There’s nothing better than leaving the cold, icy weather of northern New York behind to bask in the sunshine and radio waves streaming towards Arecibo!

Aileen and I are enjoying our first night of observing, and things are going very well. There was a slight break in the observing while technicians investigated a strange noise in the dome. Fortunately, it turned out that nothing was found, and observing resumed. We’ve had many detections tonight, and consumed many salty snacks. One of the more exciting detections was a “dark” source that Martha suspects is an OH megamaser. A very exciting observation, indeed! We’re here for two more nights before the crew from St. Mary’s arrives, so we’re looking forward to more exciting discoveries.

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SLU astronomers Jeffrey Miller & Aileen O’Donoghue

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Observing on the third night: Jeff Miller (SLU) and UPR students Jorge Padial, Jonathan Perez and Andres Arrieta

A little more than a year ago, while examining a newly made ALFALFA grid, Riccardo noticed a rather bright source in the constellation of Leo, moving away from us with a velocity of only 264 km/sec. It was not (or only barely) resolved by ALFA’s 4 arcminute beam, and its HI line velocity width was very narrow, indicating either a fully face-on and/or a very low mass object. In fact, it met the criteria of a “ultra compact high velocity cloud”, the targets for which Betsey Adams has been hunting. With such a low redshift, it was not clear whether the signal arose from a cloud in the Milky Way’s halo or a previously unidentified, tiny nearby galaxy. Quick checks of the public Sloan Digital Sky Survey (SDSS) and Digital Sky Survey (DSS) images showed no obvious associated stellar population but a suggestion of some faint, blue-ish emission. Could this really be a very faint, very small Milky Way neighbor, a bona fide (almost) optically-invisible (dark) galaxy? We needed to determine its distance and to look for evidence of rotation (which would suggest the presence of dark matter), so the quest to obtain the required additional observations began.

Optical image of the starlight in Leo P.

Optical image of Leo P showing its starlight

Being able to respond quickly to potentially exciting discoveries is one of the reasons ALFALFA is a team effort. So right away, we contacted ALFALFA team members Kathy Rhode and John Salzer at Indiana University, because IU has access to good imaging instruments on the WIYN (Wisconsin-Indiana-Yale-NOAO) 3.5 meter telescope in Arizona, and John Cannon at Macalester College who has been undertaking the SHIELD (Survey of HI in Extremely Low mass Dwarfs) program with the VLA. We made a special plea to the director of the VLA for “director’s discretionary time” to take a quick peek at the HI source to look for rotation. Knowing us not to ask without good reason, the director approved our last minute request. Although we were sure of the reality of the signal, the (awesome) Undergraduate ALFALFA team, during one of the ALFALFA followup runs took a spectrum centered on the optical object to confirm the position and radio characteristics of the ALFALFA signal. Kathy and John S. were able to take some quick images during an already-scheduled observing run. Indeed there were stars, and even more importantly, not very many! And a single HII region, proving that star formation is taking place. The VLA observations were made a few months later and the map that John C. and his student Elijah Bernstein-Cooper (read Elijah’s comments in an earlier post) resolved and localized the HI gas and confirmed that the object is rotating. Rotation signifies the presence of a significant amount of dark matter proving its extragalactic nature. A truly tiny object, Leo P contains only a few hundred thousand stars, in contrast to the Milky Way’s tens of billions, but Kathy and John were able to tease out an H-R diagram of the stars, yielding a distance of about 1.75 Mpc (or 5 million light years). So, while Leo P meets Betsey’s criteria to be an ultra compact high velocity cloud, it is also a bona fide galaxy, discovered because of its hydrogen gas, not its starlight. In fact, it contains more mass in gas than in stars. Most recent spectroscopic observations made by another ALFALFA team member Evan Skillman of the University of Minnesota confirm its pristine nature as an object that has undergone very little enrichment in heavy elements due to nucleosynthesis in stars, earning it the designation “P” for “pristine”. We believe that Leo P has managed to retain its gas without forming stars because, in contrast to most dwarf galaxies which reside near large ones, it lives virtually isolated in the local universe, just outside the Local Group.

Leo P is the first example of the class of gas-bearing tiny galaxy for which ALFALFA was specifically designed to look. Betsey’s thesis has already produced a catalog of similar “dark galaxy” candidates even though the survey data processing is not yet complete. As in the case of Leo P, we are pursuing the required detailed observations of the very best candidates (see her post on her March 2013 observing run at WIYN with its new pODI camera). The ALFALFA hunt for (almost) dark galaxies continues, but now we have shown that they do exist and that we can find them!

This post was contributed by Jonathan Perez, a student at the University of Puerto Rico, who participated in the observing run in March 2013 after attending the UAT workshop at Arecibo in January 2013.

To only say that the experience at the Arecibo Observatory was unique does not reflect in its entirely the true nature of this opportunity. I guess if I had to say what was one of the most significant details of the experience, it would have to be the comprehensive insight that one receives of what a scientific research career would be like. Radio astronomy wise speaking, this experience opens your eyes of how it all goes down, meaning that one can see how all the raw data is receive, collected, analyze and then stored for a later more comprehensive and thorough review. However, I must say that the most awesome moment (which is almost always the little details) was the opportunity to look into the clear night sky next to the world’s biggest radio telescope; giving away a sense of its endless wonders, and the urge to understand its mysteries.

Jonathan (left) and other members of the UAT on the tour of the telescope. The Arecibo telescope is amazing!

Jonathan (left) and other members of the UAT on the tour of the telescope. The Arecibo telescope is amazing!

This post was contributed by Elijah Bernstein-Cooper (Macalester College) during his 2nd trip to Arecibo this year. He and Jesse Watson (U. Wisconsin, Stevens Point) first met at the UAT workshop in January and both volunteered to return to Puerto Rico in March for the ALFALFA followup observations.

Elijah and Jesse discuss neutral gas spectra observed at Arecibo in a follow-up ALFALFA observation with the L-Band Wide receiver.

Elijah and Jesse discuss neutral gas spectra observed at Arecibo in a follow-up ALFALFA observation with the L-Band Wide receiver.

We are now operating in a nocturnal fashion: meeting the bedsheets at 6 AM and having pizza for breakfast (if you can call eating at 1 PM breakfast). Elijah has made many detections while Jesse is lagging (not for a lack of trying), and Parker figures it’s about the magic touch. One night of observing consists of about 100 observations of different sources which Martha has been kind enough to fully map out making the observing run relatively easy and stress free. Jesse and Elijah are doing a push-up after slewing to a new source which helps to keep the heart rate up to combat sleepiness, and is a great way to incorporate exercise into science. As usual, the coquis keep everyone plenty of company throughout the night.

We cross our fingers that we’ll discover a starless galaxy, or a dark galaxy. Jesse and Elijah learned plenty about dark galaxies and follow-up objects during the Undergraduate ALFALFA Workshop in January of 2013. They were so excited about the science they accepted Becky’s and Martha’s offer to observe at Arecibo during their spring break. Weather 50 degrees warmer than their homes made the decision even more attractive.

Overall this has been an amazing experience that never would have happened without both Martha and Becky. We can’t thank them enough. While here we have had the joy of using a professional telescope that not many people in the world have the privilege of using. Additionally we have had the chance to meet a wide variety of incredibly nice and helpful people ranging from the scientists, guard staff, kitchen staff, telescope operators, and of course the other students from around the country. This experience made us even more excited to continue astronomy after undergraduate schooling.

This post was written by Andrés Arrieta, a student at the University of Puerto Rico at Rio Piedras during his first observing experience as a member of the Undergraduate ALFALFA team.

The excitement I felt as I arrived to the Arecibo Observatory was belittled by the growing excitement that I would come to feel with every minute that I spent learning, conversing and investigating the universe throughout the weekend. Every person I met had something beautiful to teach me in all aspects, not only astronomy. I learned about the process of identifying galaxies by interpreting the data produced by the telescope. Also, I learned about the process by which the telescope gathers that data, which involves a period in which it is on source and then a period in which it is off source, which will be subtracted to produce a final result. After this process, one interprets this information and decides whether there is enough evidence to say that the source is a galaxy (also using the SDSS optical information as an aid in our identifications). Overall, it was a great experience; everyone I met during my stay was nice and very willing to answer questions and have enthralling conversations about diverse topics. It is was wonderful to be given the opportunity to spend a weekend doing something I love and getting to know people that fuel the love for science with their presence and knowledge. I cannot wait to do it again!

Jonathan Perez (UPR), Andres Arrieta (UPR) and  Joseph Serrano (UMET) listen to Parker Troischt (Hartwick Coll) explain how the observing program is designed and scheduled.

Jonathan Perez (UPR), Andres Arrieta (UPR) and Joseph Serrano (UMET) listen to Parker Troischt (Hartwick Coll) explain what the observations are revealing

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