Low frequency wide field astronomy with paper precision array to probe the epoch of reionization
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Low Frequency, Wide-Field Astronomy with PAPER: Precision Array to Probe the Epoch of Reionization. Nicole Gugliucci Graduate Student, UVa /NRAO Advisor: Rich Bradley. Collaborators: D. Backer, A. Parsons, J. Manley, G. Foster, M . Wright, D. Werthimer , CASPER group (UCB),

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Low frequency wide field astronomy with paper precision array to probe the epoch of reionization

Low Frequency, Wide-Field Astronomy with PAPER:Precision Array to Probe the Epoch of Reionization

Nicole Gugliucci

Graduate Student, UVa/NRAO

Advisor: Rich Bradley

Collaborators: D. Backer, A. Parsons, J. Manley, G. Foster, M. Wright, D. Werthimer, CASPER group (UCB),

C. Parashare, E. Mastrantonio,P. Klima (UVa/NRAO), C. Carilli, A. Datta, (NRAO/NMT)

J. Aguirre, D. Jacobs (U. Colorado) , M. Lynch, D. Herne, T. Colegate (Curtin U.)‏


Outline
Outline

  • What is the epoch of reionization?

  • The PAPER approach

  • Green Bank deployment

  • Early results

  • Ionosphere challenge

  • Future work


What is the eor
What is the EoR?

NASA/WMAP Team

The universe was created in a Big Bang 13.7 billion years ago. 300,000 years later, protons and electrons first came together to create hydrogen and the Cosmic Microwave Background. Today, we see stars, galaxies, and clusters, and all of the hydrogen in intergalactic space is ionized.

What happened in between?


The new [epoch of reionization] map may carry more information than even the cosmic microwave background radiation.

- Avi Loeb, Scientific American, Nov. 06


Seeing in the dark
Seeing in the Dark information than even the cosmic microwave background radiation.

“Spin flip” transition of hydrogen at 21 cm wavelength, unmitigated by dust in the Galaxy

NRAO/AUI


Seeing in the dark1
Seeing in the Dark information than even the cosmic microwave background radiation.

The 21 cm or 1.4 GHz transition marks a protected band for radio astronomy, due to the importance of hydrogen as an astronomical tracer. However, the hydrogen at the EoR is redshifted to a lower frequency.

Doppler Shift + Expanding Universe -> most astronomical objects appear redshifted. The redshift (z) is related to the distance the object is from us and, more importantly, how far back in time we are looking!

z = 0.1 was 1.3 billion years ago

z = 1 was 7.7 billion years ago

z = 7 was 12.9 billion years ago

z = 1100 was time of CMB

Machele Cable of Wake Forest

Ned Wright's Cosmology Tutorial


The story s o far
The Story information than even the cosmic microwave background radiation.So Far

Gunn-Peterson trough at z=6.28 (Becker et al. 2001) indicates end of reionization; Lyman transitions opaque at neutral fraction ~ 10-2 - 10-3

WMAP (Spergel et al. 2007): power spectrum of TE mode of CMB polarization measures the optical depth of free electrons, indicating that if instantaneous, reionization would have occurred at z~10.

Reionization occurs z ~ 6 - 14, redshifted to 100 – 230 MHz


The paper approach
The PAPER Approach information than even the cosmic microwave background radiation.

  • Actual imaging of the neutral hydrogen will take many more times the sensitivity of current telescopes

  • Instead, measure power spectrum of the fluctuating signal at different redshifts, or different times

  • This is natural for an interferometer, which detects spatial frequencies

Condon & Ransom

Christian Deichert


The paper approach1
The PAPER Approach information than even the cosmic microwave background radiation.

21-cm Power Spectrum

Point Sources/1000

PWA-128 Uniform

PWA-128 Gaussian

Synchrotron/1000


The paper approach2
The PAPER Approach information than even the cosmic microwave background radiation.

  • Staggered deployments – learn at each stage

  • Test and measure everything before we do science

    • antenna beam pattern

    • response of receivers, amplifiers, cable, etc.

    • digitization effects of correlator

  • Science and data quality drives instrumentation

  • Develop new methods of imaging to fit our needs: wide bandwidth and full sky without tracking


Paper 16gb
PAPER-16GB information than even the cosmic microwave background radiation.

  • Picture of array and antennas


Paper 16gb1
PAPER-16GB information than even the cosmic microwave background radiation.

  • Block diagram

  • Deployments (set up for position fitting)

  • Configuration decisions


Interferometry 101
Interferometry information than even the cosmic microwave background radiation. 101

  • Need to calibrate the data for precise antenna positions, cable delays, and other effects to produce calibrated visibilities, or measurements at certain spatial frequencies

  • These visibilities are then deconvolved to produce a sky image. Note that the spatial frequency plane is not fully sampled!


Interferometry 1011
Interferometry information than even the cosmic microwave background radiation. 101

  • Position fitting phase plots

  • Preliminary positions results


The next challenge
The Next Challenge… information than even the cosmic microwave background radiation.

http://madrigal.haystack.mit.edu/models/IRI/index.html

http://radiojove.gsfc.nasa.gov


The ionosphere in interferometry
The Ionosphere in information than even the cosmic microwave background radiation.Interferometry

Kassim et al. (2007) defines the isoplanatic patch as more specifically as the region of with a phase difference less than one radian at a particular observing frequency

Isoplanatic Patch

Phase vs. Time for 3 Directions

Work at the VLA at 74 MHz probed different ionospheric disturbances

From Kitchin, Astrophysical Techniques

Phase of three antennas relative to a central

antenna during an approximately 8 hr observation of Vir A illustrating many of the ionospheric phenomena typically observed at the VLA.


The ionosphere in interferometry1
The Ionosphere in information than even the cosmic microwave background radiation.Interferometry

Kassim et al. (2007) defines the isoplanatic patch as more specifically as the region of with a phase difference less than one radian at a particular observing frequency

Isoplanatic Patch

Phase vs. Time for Baseline Lengths

Work at the VLA at 74 MHz probed different ionospheric disturbances

From Kitchin, Astrophysical Techniques

Same as previous except for two antennas at different distances along the same azimuth, indicating that to first order the phase effects of all the phenomena are proportional to baseline length.


The ionosphere in interferometry2
The Ionosphere in information than even the cosmic microwave background radiation.Interferometry

Kassim et al. (2007) defines the isoplanatic patch as more specifically as the region of with a phase difference less than one radian at a particular observing frequency

Isoplanatic Patch

Position vs. Time for RA and Dec

Work at the VLA at 74 MHz probed different ionospheric disturbances

From Kitchin, Astrophysical Techniques

Refraction (or apparent position wander in both right ascension and declination) of Virgo A over the same timescale as before, 8 hours.


Modeling the ionosphere
Modeling the Ionosphere information than even the cosmic microwave background radiation.

  • Simple spherical model and eqn

  • Compare results to data for Cas


Modeling the ionosphere1
Modeling the Ionosphere information than even the cosmic microwave background radiation.

  • Then talk about irregularities and first pass at that

  • Next is to model image effects and try different irregularities


Parallel path through the data
Parallel Path through the Data information than even the cosmic microwave background radiation.

  • Continue w/ 16 and add outriggers b/c effect exaggerated

  • But also improve resolution for point source removal


Outriggers
Outriggers information than even the cosmic microwave background radiation.

  • Technical issues (power, signal, solving positions)

  • So step out!


Outriggers1
Outriggers information than even the cosmic microwave background radiation.

  • Surveyed map and pictures from that


Next step green bank
Next Step… Green Bank information than even the cosmic microwave background radiation.

  • Expand model and bring together model and data

  • Other stability experiments?


Next step australia
Next Step… Australia information than even the cosmic microwave background radiation.

  • 32 elements deployment in the fall w/ pic of groundscreens in GB ready to go…


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