Survey


Last night (12.10.25 in ALFALFA nomenclature), we completed the ALFALFA drift scan survey, known as Arecibo observing program A2010. Riccardo and Martha conducted the observations from the “Camuy Cave” on the 5th floor of the Space Sciences Building at Cornell. It’s a little hard to believe that we’ve actually done it!

The last telescope schedule showing program A2010, the ALFALFA drift scan survey

It was a memorable night. Even before we began, the awesome Undergraduate ALFALFA team sent us a e-card. Thanks to you all! We look forward to the continuing activities of the UAT!

Riccardo reads a printed version of the UAT e-card. Notice the smile on his face!

Some friends came to celebrate the end of the A2010 era. Martha had on her ALFALFA t-shirt (thanks of course to the UAT) so it was all very official.

Bonnie, Martha and Jim celebrate the moment. As should be clear, Martha was having “more fun than human beings should be allowed to have” (ALFALFA motto #2).

Of course, it is not just all about observing, and with the end of the drift scan program A2010, ALFALFA is not really done yet. There is a lot of work still to do! Once ALFALFA discovers something interesting, a lot of followup work has to be done. For example, we recently discovered a fairly strong signal that turns out to be associated with a really, really, really faint (in terms of starlight) galaxy. We are now trying to determine its precise distance and star formation history using ground (WIYN, LBT, JVLA) and space based telescopes (Hubble, Spitzer). Just this one galaxy could keep us busy for a while. And there are lots of fascinating ALFALFA discoveries!

Riccardo introduces Leo P, a tiny nearby galaxy discovered by ALFALFA, to Anita, Don and Luke.

ALFALFA couldn’t have happened without the participation of the ALFALFA team of all ages and career stages and the support of the dedicated and expert staff of the Arecibo Observatory and the National Astronomy and Ionosphere Center. The survey has been carried out on a low budget with no dedicated full-time staff. So, to all of the people who have participated in one way or another, we thank you – each and every one!

The observing on this last night went swimmingly and, as usual, there wasn’t much actually to do except to monitor the data taking. So there was a little celebration…. Thanks especially to Carlo (BB) for the bottle, Ron (and the UAT) for the culatello and parmigiano, and Edy and Marcia (4F Club) for the chocolates.

Luke, Greg and Mike (rear) keep an eye on the observing while Martha and Riccardo celebrate the end of A2010. As to the observing, it was a boring night, but as we all know: “Boring is good!” (ALFALFA motto #1)

We also note that those 4,741.5 hours do not include all the time spent planning, archiving, flagging, signal extracting, etc, etc, etc… And just because A2010 is done, that doesn’t mean ALFALFA is finished. We still have to “bring in the harvest”!

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Last night, Luke conducted the 800th observing run for ALFALFA. Some of us remember the first observing run, on Friday, Feb 4th, 2005. For some of you younger folks, we do not want to know what you were doing at that time. For those of us who have been along for the whole ride, we are very aware that 800 is a big number!

And, we are now scheduled to complete the legacy drift scan observing program for ALFALFA on Thursday October 25th — well, we will actually finish the observing at about 1:30 am on Friday October 26th. Let the countdown begin….

I’m spending this week at the Arecibo Observatory with the Undergraduate ALFALFA Team (UAT) for our annual January workshop. I like to call these events “Camp ALFALFA” — an opportunity to bring lots of young undergraduate scientists, and their faculty mentors, together at this world-class facility. During the workshop, there are observing opportunities, telescope training sessions, a tour of the Observatory, lectures, and scavenger hunts to get everyone up to speed on ALFALFA. It’s a lot of fun, and a great way to get people involved in ALFALFA so that we can maximize the scientific results of the survey and spread the work around. That’s pretty important when you have a total of 5,000 hours of observing to cover!

Currently, I’m here with Martha and Becky getting everything set up for the arrival of 32 members of the UAT. That involves making sure that everyone, and their laptops, will have a place to sit and to connect to the web. If you’re a member of the team, welcome! That goes double if this is your first trip to Arecibo. For us, Arecibo is a welcome change from upstate New York. It’s 85 degrees here in the day, and at night it dips down to the low 70s (so we can sleep with the windows open and listen to the impressively high-volume sounds of the coqui frogs all night).

Throughout the week, we’ll be updating the blog (and hopefully posting some contributions from members of the team!) to let you know what we’re up to and to give you a better idea of what it’s like to spend time at this amazing facility.

I mentioned in my recent post on astronomy and astrophysicists that I consider myself an astronomer because of the emphasis I place on observations and data in my studies.  While working on a large survey, it’s not surprising that data would have such a large focus for me.  It seems only fair to share the awesomeness and fun of working with all this data.  This post will be a general timeline for the data processing, and follow-up posts will go into more details for each step.

Day 0: The data is observed at Arecibo.

Day 1:  The data is transferred from Arecibo to Cornell.  The initial calibrations are done.

Day N (1 < N < \infty): The data is flagged to mark all the radio frequency interference (RFI).

Day X (N < X < \infty): The data is ‘gridded’ – three-dimensional cubes are produced and source extraction begins.

Day Y (X < Y < \infty):  Source extraction is complete for a strip of sky and the source catalog is officially published.

I’ve mentioned the “spring” and “fall” skies of ALFALFA at least once already, so I thought it was time to explain what I meant. And since a picture is worth a thousand words, here’s a helpful graphic put together by Brian Kent:

ALFALFA footprint with SDSS overlay, by B. Kent

ALFALFA footprint with SDSS overlay, by B. Kent

The map above is a projection of the sky with coordinate lines of right ascension and declination. The blue areas represent the planned survey coverage of ALFALFA. The red shows the coverage of the Sloan Digital Sky Survey (SDSS), an optical survey that has photometry and spectroscopic redshifts for hundreds of thousands of galaxies. The SDSS footprint (sky coverage) is shown for comparison purposes. Where there is overlap, we’ll be able to use the two datasets in a complementary manner.

The middle chunk in the picture is our “spring” sky. This extends from 7hours:30 minutes to 14h:30m in right ascension (R.A) and from 0 to 36 degrees in declination. (R.A. is the equivalent of longitude for stellar coordinates and runs from 0 to 24 hours. Declination is the equivalent of latitude and uses degrees.) We refer to this region as our “spring” sky because this part of the sky is visible at night during spring months. Of course, I use the word “spring” very generally, as we are currently observing the spring sky of our survey, and January and February do not qualify as spring (especially in Ithaca). The other two chunks you see are actually contiguous and constitute our “fall” sky. The declination range is the same as for the spring sky and the R.A. ranges from 22 to 3 hours.  Once again, the “fall” refers to the fact that this part of the sky is visible during fall months and is a loosely used term.  (November and December?  Not really fall in my opinion.)

The declination limits on the survey are placed mostly by the telescope itself; Arecibo can only look so far away from zenith (straight overhead). Arecibo is located at about 18 degrees latitude, so we are looking about 18 degrees north and south of zenith. The R.A. ranges are designed both to include interesting local structures (discussed here) and to avoid the Galactic Plane, as there are lots of other astronomers who study our own Galaxy and use Arecibo to observe that part of the sky.