This post was written by Mariella A. Mestres-Villanueva, a fourth year Biology major at the University of Puerto Rico-Río Piedras.

One of the perks of my father growing up and being from Arecibo is that I was taken as an impressionable young child to the Arecibo Observatory many times. I was always fascinated by the night sky and all that it contained and I relished each chance I got to visit.

Now during my fourth year of my undergrad career I was given the opportunity to not only go once again to the Observatory but to participate in the ALFALFA survey! Myself and two other students— Jean Casellas and Yenuel Jones— from the University of Puerto Rico Río Piedras Campus went to the Arecibo Observatory on Saturday, November 28th (still full of turkey from Thanksgiving, mind you) to participate in a night of observing. Of course, the bonus was staying overnight at the Observatory and getting a very cool tour of restricted areas.

When the time came to report to our posts at 5:00 PM, I was feeling pretty excited. We would be getting an overview of the systems and programs used for the survey and observation by Dr. Gregory Hallenbeck and other fellow undergrads, Ryan and Kamin, and then would spend five and a half hours recording and analyzing the data we obtained from the telescope’s L-band wide receiver.

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Two thumbs up for a successful calibration.

IMG_9960.JPG  I would not have understood any of this a few weeks ago, but glad to say I now do! (LST is still a weird concept for my AST—or Arecibo Standard Time—adapted brain.)

As a biology major, I admit that I thought I would just type in data that would seem like gibberish to my brain but I’m proud to say I got the hang of it and actually understood what I was doing. It was fantastic seeing how interference and detections are identified, and also interesting seeing how the San Juan Airport could cause interference (I would soon recognize this as “Our Greatest Nemesis” due to the interference it caused). I never thought I would be able to identify galaxies and even understand readings from the telescope, let alone actually be in its control room! Even using SDSS so we could get a visual of the galaxies we were observing was fulfilling.

All in all, the experience was fantastic. When 11 o’clock rolled around, signaling the end of our observation we celebrated and our names were logged in alongside the information analyzed, a—I’d like to think—permanent reminder of my time living out my astronomy dreams.

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The very awesome people I worked with and geeked out with during the observations. Special shout-out to Dr. Mayra Lebrón who gave me this amazing opportunity!

From left to right: Jean Casellas ’16 (UPR), Dr. Mayra Lebrón (UPR), Dr. Gregory Hallenbeck (Union), Yenuel Jones ’18 (Union), Ryan Muther ’16 (Union), Kamin Sylvia ’18 (Union), Mariella Mestres-Villanueva ’16 (UPR)

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.


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.


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??)


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

St. Lawrence University astronomers Jeff Miller, Aileen O’Donoghue and Bryan Geiger ’16 reporting in again from rapidly-thawing northern New York. We’re in the middle of our first LBW remote observing session. So far, everything is going smoothly, and we’ve detected many sources. We learned a lot about LBW observing during our November 2013 observing run at Arecibo, but our observing at the January workshop was cut short by the earthquake, so we were wondering if we would remember everything we learned. It’s nice to know that the procedure has come back to us so quickly. And with LBW observing, it’s very exciting when we get a detection of a galaxy!

We’ve had a steady stream of our students coming through to see how real observing works. They have all been very excited with what we have been able to show them. But so far, no one has been will to stay up with us until 3:30 in the morning!

SLU astronomers

SLU astronomers Jeff Miller & Aileen O’Donoghue, getting into the island spirit

O'Donoghue & Geiger

Aileen and Bryan Geiger ’16 check on a source detection

About 90 astronomers from all over the world participated in a meeting of the Pathfinder Square Kilometre Array HI Survey Coordinating Committee PHISCC at the Netherlands Institute for Radio Astronomy ASTRON in Holland. There were a lot of members of the ALFALFA team members with Cornell roots but who are now working around the world. It was a nice reunion and a great meeting!

Cornell ALFALFA team at the meeting

ALFALFA Cornellians team at the meeting

From left to right: Barbara Catinella (Cornell PhD; now at Swinburne U., Australia), Martha Haynes (Cornell faculty), Betsey Adams (Cornell Ph.D.; now at ASTRON, NL), Luke Leisman (Cornell grad student), Manolis Papastergis (Cornell Ph.D.; now at Kapteyn Inst./U. Groningen, NL), Karen Masters (Cornell Ph.D.; now at U. Portsmouth, UK), Kristine Spekkens (Cornell, PhD; now at RMCC/Queen's, Canada), Kelley Hess (Cornell B.A.; now at U. Cape Town, South Africa)

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.


SLU astronomers Jeffrey Miller & Aileen O’Donoghue


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!

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