Synergistic Science Capabilities of NRAO Telescopes
Observations at radio wavelengths address some of the most fundamental questions in astrophysics. The Cosmic Microwave Background Radiation, the Dark Ages before the onset of the first stars or galaxies, the baryonic and dark-matter content of proto-galaxies, the process of reionization of the universe by galaxies, and the earliest stages of star and planet formation are all observed using radio techniques.
The NRAO facilities working together study a wide range of astronomical phenomena in detail. The 100 m GBT, the largest fully steerable radio telescope in the world, is a very sensitive and highly versatile instrument for surveys, detection, and pathfinder observations. Both the EVLA and ALMA can reveal structure within the gaseous components of the earliest galaxies and quasars by imaging redshifted molecular-line radiation and the dust continuum, whereas optical/infrared (OIR) imaging and spectroscopic observations will define stellar components and AGN activities. Together, these observations will provide a complete picture of how stars, galaxies, and quasars form and evolve. The VLBA (and the High Sensitivity Array that combines the VLBA with the GBT and EVLA) can measure accurate distances and proper motions of megamasers in the nuclei of distant galaxies, complementing OIR approaches to determining the Hubble constant and the expansion rate of the Universe. ALMA will resolve details in circumstellar disks as planets form by mapping their mm and submm continuum and line emission, complementing near- and far-IR observations of the later stages of the debris disks and exoplanets.
Examples of Synergistic Science with NRAO
Astrochemistry
Telescopes: GBT, VLA, ALMA
NRAO instrumentations are used to explore the molecular complexity in astronomical environments, and provide the necessary observations for theorists to advance the foundations of astrochemistry and astrobiology. Since its commission and science verification, the GBT is not only leading in astrochemistry but has single-handedly rejuvenated the field. Observations by several groups with the GBT have led to the discovery of 11 new interstellar species including the first detection of anions in astronomical environments as well as the detection of the largest molecules important in pre-biotic chemistry such as acetamide, the largest molecule with a peptide bond currently detected in space. The GBT and subsequent VLA observations of these species have shown a widespread spatial distribution which is in complete contrast to previous thinking on the formation of large molecules in astronomical environments. Finally, these observations will only complement and serve as pathfinder observations for the next large NRAO instruments including the SKA and ALMA. Low frequency observations of large pre-biotic molecular species will be easily detected and imaged at SKA wavelengths and light ions and molecules rich in deuterium, essential to the understanding of molecular clouds and star formation theories, will be easily detected and imaged with ALMA.
Dark Matter & Dark Energy
Telescopes: GBT, EVLA, VLBA
The distribution of dark matter in the local universe can be probed using the VLBA, the most accurate astrometric telescope in existence. Distance determinations using gigamasers are also significant. Recent searches with the GBT already have doubled the number of extragalactic water-megamaser galaxies to more than 40, and the recent GBT discovery of a gigamaser in the Sloan quasar J0804+3607 at z = 0.66 strongly suggests that other cosmologically distant masers will be discovered. This raises the hope that geometric distance determinations at redshifts relevant to the EOS of dark energy will take place in the next decade. Sources such as NGC 6323 will be observed with the High Sensitivity Array (HSA) combination of the VLBA, EVLA, and GBT for direct and accurate measurements of its geometric distance and black-hole mass over the next few years.
Pulsar Search & Timing
Telescopes: GBT, VLBA
Radio observations are critical for studying phenomena that constrain frontier physics. GBT timing observations of the relativistic binary pulsar J0739-3039 are providing the most stringent tests of Einstein’s General Theory of Relativity (GR) in strong gravitational fields. The high masses and short rotation periods of pulsars recently discovered by the GBT in the globular cluster Terzan 5 are providing constraints on the equation of state (EOS) of matter at supra-nuclear densities, which may be a quark-gluon plasma. Distances and proper motions of galaxies in the Local Group are being measured directly by high-precision astrometry with the VLBA, which can yield geometrical distance measurements of distant quasars that could constrain the Hubble constant and perhaps even the dark-energy EOS. Pulsars, relativistic jets from black holes and neutron stars, gamma-ray bursts and soft-gamma-ray repeaters reveal themselves via emission from electrons accelerated to ultrarelativistic energies. Radio emission can trace energetic events at milliarcsecond resolution and on millisecond timescales even through dense gas and dust. Synoptic observations constitute a frontier area of astrophysics with close symbiotic links between radio and current and planned high-energy astrophysics missions (Chandra, Swift, GLAST, Constellation X, etc).
The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc.