This collaborative project will discover and study a large sample of neutron stars and also search for a variety of radio transient sources using the Arecibo L-band Feed Array (ALFA) at the Arecibo telescope. The science return results from both the hundreds of expected new pulsars and from rare, individual objects that will serve as laboratories for probing fundamental areas in physics and astrophysics.
The pulsar survey will complement and transcend previous surveys by reaching more than twice the distance of the very successful multibeam survey using the Parkes telescope. The work is expected to lead to discoveries of rare objects that will be used as laboratories for basic physics and astrophysics to probe the equation of state of nuclear matter, gravity in compact, high-mass binaries, and gravitational-wave backgrounds. Discoveries may include the first black-hole/neutron-star binary, which would allow unprecedented studies of gravity in the strong-field limit. The large sample of new pulsars, when combined with existing ones, will contribute to the understanding of neutron stars as end products of stellar evolution, and will enable state-of-the-art modeling of the Milky Way Galaxy with respect to its ionized components. Also, use of the large number of pulsars as tracers will allow delineation of some ambiguously defined spiral arms of the Galaxy.
The ultimate goals of the project will be enabled by the availability in 2008 of a new spectrometer that utilizes the full capabilities of the 7-beam system at Arecibo, and the availability of computer and data storage systems that can process and archive the large volume of data generated. Specific tasks include developmental activities related to the commissioning at Arecibo of the large bandwidth spectrometer, the setting up of the infrastructure required to analyze the data, and the intensive data analysis required to find new pulsars, all of which will be conducted in collaboration with the Pulsar ALFA Consortium, an international group of about 30 researchers. Over the 3-year project, about 1000 Terabytes of data will be analyzed using several computer clusters. Post-discovery studies will include timing campaigns and multiwavelength observations. A web-based system will provide access to source catalogs, timing models, and intermediate data products that can be used as a resource for synergistic studies. Raw data will be archived for long-term data mining applications and use in multiwavelength campaigns, such as future gamma-ray space telescope observations that require radio counterpart observations.
The large data volume requires development of data management for streamlined analysis, archival and retrieval. The project therefore serves as a prototype for future data-intensive surveys in astronomy, and will enable eventual connection to multi-user facilities such as national and international virtual observatories. The project will also contribute to the training of graduate students, and to the teaching of undergraduate students by their inclusion in certain aspects of data analysis.
The Milky Way contains several hundred billion stars that, like the Sun, are fusing hydrogen into helium. Eventually, all of these stars will run out of fuel and will transform into a final state that is either a white dwarf, a neutron star or, for the most massive stars, a black hole. This project's primary goal was to conduct a deep census of the Milky Way for neutron stars that appear as radio pulsars, those that emit steady pulses of energy at radio frequencies. Finding more pulsars allows us to better understand how neutron stars form in supernova explosions and also how they convert their spin energy into radiation. Of great interest to astronomers and astrophysicists is the utility of pulsars for probing fundamental physics, including Einstein's General Theory of Relativity, and for detecting gravitational waves, usually described as ripples in spacetime. We are also able to use pulsars to infer the properties of matter under extreme conditions: a neutron star is about the size of a small city and has a density that is greater than that of an atomic nucleus. These objects are also highly magnetized, about a trillion times the magnetic field of the Earth, and because they rotate rapidly, they generate huge voltages (a trillion volts). These voltages are responsible for accelerating particles that produce the radiation that we can detect. The project has discovered more than 100 pulsars and many of them are of special interest for achieving the intellectual goals discussed above. These objects are now being monitored in order to fulfill the goals. Study of the new pulsars is of interest to many researchers who work on neutron stars using a variety of telescopes. Along the way, we have had to create a sophisticated system of computers, massive storage, databases, high-speed networking, and web-based tools. These are necessary because the project involves a collaboration of researchers that are spread all over the world and also because the data we obtain from the Arecibo Observatory in Puerto Rico require significant storage space. Our project has also developed a side project that enables an important citizen science effort. Through collaboration with researchers in Germany and at the University of Wisconsin, Milwaukee, we have supplied data from our survey to the Einstein@Home project, which allows volunteers from anywhere to participate in the survey. About 20 new pulsars have been discovered by Einstein@Home volunteers. The web site for this part of the project (which was developed by the Albert Einstein Institute in Hannover, Germany) includes educational material about neutron stars and pulsars aimed at the general public.
