Follow-Up Observations

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.


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.


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.

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!

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

I’ve been at Kitt Peak (along with Mike Jones) for the past several days doing optical follow-up on ALFALFA HI detections. Specifically,we’re searching for stellar counterparts to potential nearby gas-rich low mass galaxies. I’ll write more about the science at some point in the future, but for now I want to focus on the observing we’re doing.


The WIYN telescope looking up through the dome slit. (Photo courtesy Mike Jones.)

We’ve been using pODI on the WIYN 3.5m telescope. ODI stands for One Degree Imager, and pODI is the partially filled ODI – rather than a one degree field of view it has a ~24′ field of view, with a few outlying chips sampling the full field of view. The instrument is still being commissioned, meaning it is offered as “shared-risk” observing. This is pretty common for new instruments. Not only does it allow science observations to begin sooner, it also lets the engineering and instrument team know what needs further work and development. There’s nothing like bringing in an outside observer to break your instrument – they don’t know all the ins and outs and will naively try things that don’t work.


Looking at the primary and tertiary mirrors of WIYN. (Photo courtesy Mike Jones.)

We’ve experienced some of the shared-risk with the “penalty box”. Last night we had to cycle power to the detectors two separate times because some of the controllers stopped responding. Unfortunately, every time you cycle the power you have to wait an hour for the system to become stable. Any data you take during that time can’t be calibrated, so you end up twiddling your thumbs a bit. Following the observer previous to me, I’ve been referring to this waiting time as being in the “penalty box”.

There are other aspects that go along with using an instrument that is being commissioned. For example, not all of the control software is complete yet. We have everything we need to run the telescope, but not everything is integrated fully so we have lots of windows open. Some of the windows also have a few quirks that can be confusing, but we’ve developed a routine and it seems to be working well.


All our monitors and windows. (Photo courtesy Mike Jones.)

While there are always issues that go along with using a brand new instrument, it’s also super exciting. And new instruments bring new capabilities.

I’ve recently returned from a trip to Socorro, NM where I was working with data from the Very Large Array (recently renamed the Jansky Very Large Array or JVLA). Specifically, we had observations of galaxies found in the ALFALFA survey. While walking into the office one morning I saw the following vanity plate on a truck in the parking lot:

ALFALFA: New Mexico's No. 1 Crop

ALFALFA: New Mexico's No. 1 Crop

It was just too perfect because we jokingly refer to the sort of work I was doing in New Mexico as “harvesting ALFALFA”, so of course I whipped out my cell phone to take the picture above. The ALFALFA survey is nearing completion which means we’re starting on the next phase (harvesting ALFALFA) – following up on all the intriguing sources found by ALFALFA. The recent posts from the Undergraduate ALFALFA Team detail part of that effort – confirming detections using the L-Band Wide (LBW) receiver at Arecibo.

This is only part of effort to understand the interesting sources. ALFALFA is great for finding galaxies based on their gas content and figuring out which galaxies are unusual, and hence interesting. Unfortunately, we don’t get any information about the distribution of gas within a galaxy from ALFALFA; the “beam” (or resolving unit) of the Arecibo telescope is larger than the galaxies we observe. This means that if we want to localize and understand the gas within galaxies we need a larger telescope since larger telescopes have smaller beam sizes.

It’s not physically feasible to build a single telescope that is large enough to resolve structure on the scales astronomers are interested in – it would need to be a kilometre or more across! Instead, individual telescopes spread out over those distances work together to function as a single telescope. This is called interferometry and I’ve describe the idea behind it in more detail before. One important aspect of interferometry is that it’s not easy – combining the data from the individual telescopes together to create a single image is tricky (and figuring it out was worth a Nobel prize!).

The main reason I was in Socorro was to get help from experts and figure out the secret tips and tricks for making the best images. That way, as we find more and more sources from ALFALFA that we want to “harvest” with the JVLA we can have a strategy in place for dealing with the data calibration, imaging and analysis, just like we have a method in place for handling ALFALFA data. I’d like to explain those general steps one day, but for now I’m still working on figuring it out!

This post is by Rachel Almodovar, Union College ’15

My name is Rachel Almodovar and I am a freshman astronomy major at Union College. For spring break I went to the Observatory of Arecibo with my astronomy professor. It had been a few years since the last time I had been there during my childhood in Puerto Rico! At that
time I was twelve years old and the observatory fascinated me. I said to my mother that I wanted to work in a place like the observatory someday. And well, to my surprise Prof. Koopmann, my astronomy professor, invited me to go there during spring break and I had the amazing opportunity to do radio astronomy observing. In my first two nights of observing, I learned how to use CIMA, which is the program that allows you to control the observing mode and the setup of the receiver and also the spectrometer; I also learned how to type in the log the information of the sources like the local sidereal time, zenith angle, the scan number and the source number; and I also learned how to use IDL to reduce the data obtained from the on and off position 3 min exposures and how to look at the spectrum and tell if it had been a detection or not.

Rachel on the Arecibo platform

In my third night observing, Prof. Koopmann taught me how to do flagging of data from the ALFALFA survey. Flagging became my favorite thing to do while I was in Arecibo. Flagging is the technique where you have to examine the spectrum recorded in different drifts and polarizations for bad data like GPS and radars and flag (mark) bad data. One also looks in the spectrum for the detection of galaxies, and records them in the information of the drift.

Well, overall it was a amazing and remarkable experience where besides learning a lot of techniques on how to do radio observing and going up to the Gregorian dome and seeing how it all functions, I also got the opportunity to meet and share time and experiences with a lot of wonderful people at Arecibo that inspired me in a unique way to keep learning about what I am passionate about, which is and will always be Astronomy. I will never forget such an extraordinary experience.

(Left to right): Rachel '15, Becky, Halley Darling '13 and Lucas Viani '14

The following contribution was written by Parker Trosicht, Assistant Professor at Hartwick College, during an observing run at Arecibo Observatory. The observations are pointed observations with the L-Band Wide receiver to confirm ALFALFA detections.

Greetings from the rain soaked Arecibo observatory! We had a couple of downpours today as we drove to a nearby town to get some food for observing tonight (the cafeteria is closed over the weekend). Luckily, our car made it through a small river that poured across the road and we made safely it back to the NAIC. On to the good stuff.. observing. This has been my first extensive experience with the L-Band Wide (LBW) observing method, building on the training received a few months ago at the UAT Workshop (thanks Martha, Betsey and Greg!). Accompanying me are two Hartwick students (Jaclyn Patterson and Kyle Murray) as well as Dr. Ron Olowin from St. Mary’s College in California. We also briefly overlapped with Dr. Rebecca Koopmann and her three students from Union College (Halle, Lucas and Rachel), which allowed us to look over the shoulder of one of the most experienced ALFALFA team members before taking the reins on Saturday (thanks Becky!). So far, the experience has been terrific!! The LBW follow up is more exciting for all of us as we are continually getting to look at recent HI detections and then quickly check with SDSS and AGC Browse to look up the probable optical counterparts and locations. We’ve seen everything from very clear double-horned spiral galaxy spectra, to strong OH Megamaser type signals, to high velocity clouds, and even some HI detections with no apparent optical counterpart at all (which could be very interesting!). The students are now comfortable with all the controls and are working on the log.

Jaclyn is a junior triple major (physics/math/philosophy) who worked with me this past summer on galaxy groups/clusters research and has participated in several nights of ALFALFA remote observing from Hartwick. This is, however, her first experience with the LBW follow up. Kyle is a freshman triple major (physics/music/math) who is newer to the project, but is picking it up quickly. He participated last fall in some remote observing from Hartwick and decided to take the introductory astronomy course this spring. We just discussed radio astronomy in class a few days before traveling down here. My students see photos of Arecibo in slides and textbooks, but these certainly don’t do it justice and there is no substitute for being on site at the NAIC itself. Talk about experiential learning!

Seeing the tangible progress made from the initial “blind” ALFALFA survey to the LBW follow up of several of the more interesting targets has been uplifting for myself as well as several of the more experienced students. It is also important for them to see that the large amount of effort put into ALFALFA for several years is now paying off. Personally, I can’t wait to see what other follow-up observations (including optical) tell us. As usual, it is always great to see the staff at Arecibo as well and they are always very willing to help us out. The operators have been especially helpful (Thanks Elliot, Israel and Edwin!) over the past few days.

Well, a fresh pot of coffee was just brought out and it is time to see what the most recent observations look like.. so, stay tuned!!

Kyle, Parker, Ron and Jaclyn. If you look closely at the monitor on the left you can see a detection!

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