Multi-Wavelength Surveys

Portrait of our Milky Way galaxy
A dynamic portrait of our Milky Way galaxy shows a frenzy of gas, charged particles and dust.
Credits: ESA/NASA/JPL-Caltech.
Click for a full-size image.

Multi-wavelength surveys allow astronomers to map the sky in different bands, providing a different view of the Universe. Surveys are often focused on answering particular astrophysical questions, but are becoming a vital tool for the community, which can be used for years to come.

Mapping the sky at different frequencies/wavelengths, in different emission/absorption bands, and in polarization, allows astronomers to get a complete picture of the Universe. JBCA is involved in a number of large surveys, covering the entire electromagnetic spectrum. 

Research activities

We are involved in a number of sky surveys, which allow us to study a range of astrophysical phenomena across a wide range of wavelengths.

  • C-Band All Sky Survey (C-BASS)
    A preliminary C-BASS map showing polarised emission at 5GHz from the northern survey
    A preliminary C-BASS map showing polarised emission at 5GHz from the northern survey.
    Copyright: C-BASS Collaboration.
     
    C-BASS North in the snow
    C-BASS North in the snow.
    Copyright: Mike Peel, CC-BY-SA-4.0.
    C-BASS South at night
    C-BASS South at night.
    Copyright: Mike Peel, CC-BY-SA-4.0.

    The C-Band All Sky Survey (C-BASS) is an experiment that is mapping the whole sky at a frequency of 5GHz in both temperature and polarization. Its aim is to enable the accurate subtraction of foreground synchrotron emission from our Galaxy in both intensity and polarization from maps of the Cosmic Microwave Background (CMB).

    C-BASS is observing the universe using two telescopes, one at Owens Valley Radio Observatory, California, and the other at the Square Kilometre Array in the Karoo desert, South Africa.

    C-BASS data will have a wide range of applications including the study of astrophysical emission mechanism, Galactic structure, Galactic magnetic field, and component separation for CMB experiments.

    See also:

    1. C-BASS: C-Band All Sky Survey - The C-BASS project website.
    2. C-Band All Sky Survey - on Wikipedia.
     
  • GALFACTS
    The 300-m diameter Arecibo telescope is surveying all the sky it can see in a broad range of frequencies centred
    near 1420 MHz, using its ALFA multi-beam receiver: the Galactic ALFA Continuum Transity Survey. GALFACTS traces the synchrotron and free-free emission from the Milky Way, and detects many thousands of radio sources in distant galaxies. The main aim is to use the variation of polarization with frequency across the band to measure the Faraday effect, which traces the magnetic fields in interstellar and intergalactic space. See also: Astrophysical Magnetism
  • Halpha surveys of ionised gas

    Coming Soon.

  • Multi-beam surveys

    Coming Soon.

  • JCMT

    Coming Soon

  • Radio Recombination Lines (RRLs)
    An image showing the integrated RRL intensity map covering a large area of the Galactic plane
    The image above shows the integrated RRL intensity map covering a large area of the Galactic plane.
    Click for a full-size image.
     

    Manchester has pioneered observations of radio recombination lines (RRLs) since the 1960s. RRLs are the emission lines from atoms when electrons in ionized gas fall from a high-to-law quantum number. They are a probe of the warm ionized gas in the interstellar medium and can be used to probe the density, temperature, and ionization state of interstellar gas. Since they emit at radio wavelengths, the emission is not absorbed as it travels through the Galaxy, providing an unimpeded view.

    JBCA researchers have re-analysed the data from the HI-Parkes-All-Sky-Survey (HIPASS) to make the first contiguous large-area RRL survey of the Galaxy. The final Galactic plane survey, covering longitudes 248-0-52 degrees is now available online. The data reduction and analysis is described in Alves et al. (2015, MNRAS, 450, 2025).

  • SKA and SKA pathfinder extragalactic surveys

    The JBCA SSG group is involved with many large international survey projects using SKA pathfinder and precursor telescopes, including e-MERLIN, VLA, EVN, MeerKAT, ASKAP, LOFAR and APERFIF. A number of JBCA staff are also involved in the scientific development of the SKA itself and are leading members in the SKA Science working groups.

     

    These surveys include:

    1. e-MERLIN Legacy Surveys:

    JBCA leads and is involved in a number of major extragalactic legacy surveys using the e-MERLIN telescope these including:

    1. The e-MERGE Survey: e-MERlin Galaxy Evolution Survey
    2. LeMMINGs : Legacy e-MERLIN Multi-band Imaging of Nearby Galaxies Survey
    3. LIRGI : Luminous Infrared Galaxies Inventory
    4. SuperCLASS: The Super-Cluster Assisted Shear Survey – A weak lensing deep field with e-MERLIN
    5. AGATE - Astrophysics of Galaxy Transformation and Evolution
    6. Resolving Key Questions in Extragalactic Jet Physics

     

    JBCA researchers are also involved in number of current and future key survey projects using SKA Pathfinders and precursors including those using MeerKAT, ASKAP, VLA, EVN, APERTIF and LOFAR.

  • SKA and SKA pathfinder Galactic surveys

    Coming Soon.

  • Planck satellite
    PLANCK FSM 03 Black
    The first Planck all-sky map, showing diffuse Galactic emission at low (red) and high (blue) frequencies, as well as the CMB at high and low latitudes.
    Copyright: Planck Collaboration.
    Click for a full-size image.
     

    The Planck satellite was a project to map the cosmic microwave background anisotropies as fully and accurately as possible. It was launched by the European Space Agency in 2009, and surveyed the entire sky for 4 years from an orbit about the L2 Lagrangian point in the Earth-Sun system, 1.5 million miles from Earth, before being switched off in 2013.

    Planck made very sensitive measurements at nine different frequencies at 30-857 GHz, and polarisation at seven frequencies between 30-353 GHz, using two instruments, the High and Low Frequency Instruments (HFI and LFI). Scientists and engineers at Jodrell Bank designed and built radio receivers at the heart of the LFI. These were the most sensitive receivers ever built to work at these frequencies.

    JBCA was involved throughout the scientific analysis of the Planck data, in particular playing key roles in:

    1. The analysis of the raw data from LFI to minimize systematic effects in the data, and ensure that it was accurately calibrated;
    2. The analysis of the diffuse Galactic foreground emission lying between us and the CMB;
    3. The analysis of dust from nearby galaxies, including the Andromeda Galaxy;
    4. The cosmological parameter analysis using number counts of galaxy clusters through the Sunyaev-Zeldovich effect.
     Cosmic Microwave Background
    The Cosmic Microwave Background as seen by the Planck satellite
    The Cosmic Microwave Background as seen by the Planck satellite.
    Copyright: ESA and the Planck Collaboration.
     

    At the start of time, our Universe consisted of a single point of matter/energy as a result of the Big Bang. This expanded over the next 380,000 years, turning into into a dense, hot, fog of matter and light. Then the fog lifted - the photons were unbound from the atoms, and light streamed free, forming the cosmic microwave background (CMB). Over time, this cooled to a temperature today of just 2.7255K - the coldest natural temperature in the universe.

    At first glance, the CMB is constant across the sky - however by making very sensitive observations of it, small anisotropies (at the level of one part in a million) can be seen. These anisotropies provide measurements of the fundamental cosmological parameters of our Universe, such as the fraction of normal and dark matter, and dark energy, as well as giving the age of the universe. In addition, by looking at the polarisation of the CMB, we can look back to the start of the Universe,

    The existence of the CMB was predicted as early as 1948, but it took until 1965 before it was accidentally discovered by Penzias and Wilson when they were measuring the system temperature of their telecommunications horn antenna. This famously led to them receiving a Nobel Prize for their discovery of the CMB.

     
    The power spectrum of the CMB as seen by the Planck satellite
    The power spectrum of the CMB as seen by the Planck satellite.
    Copyright: ESA and the Planck Collaboration.
     

    Jodrell Bank has played a leading role in studying the CMB since the 1970s. The Tenerife Experiments in the late 1980s and early 1990s provided upper limits on the CMB anisotropies that were comparable to satellite missions at the time. The Very Small Array (VSA) provided the best measurements of the second and third peak of the CMB that were available at the start of this millennium.

    Jodrell Bank constructed the 30 and 44GHz low noise amplifiers for the Planck satellite, which provided the best observations of the CMB in 2013-15. JBCA continues to study the CMB using the successor satellites to Planck (LiteBird and/or CORE++/PRISM), as well as ground-based telescopes such as POLARBEAR.

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