Radio Foregrounds for the 21 Centimeter Tomography of the Neutral Intergalactic Medium at High Redshifts

By T. Di Matteo, R. Perna, Tom Abel, Martin J. Rees. 2001

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Absorption or emission against the cosmic microwave background (CMB) radiation may be observed in the redshifted 21 cm line if the spin temperature of the neutral intergalactic medium (IGM) prior to reionization differs from the CMB temperature. This so-called 21 cm tomography should reveal important information on the physical state of the IGM at high redshifts. The fluctuations in the redshifted 21 cm line, due to gas density inhomogeneities at early times, should be observed at meter wavelengths by the next-generation radio telescopes such as the proposed Square Kilometer Array (SKA). Here we show that the extragalactic radio sources provide a serious contamination to the brightness temperature fluctuations expected in the redshifted 21 cm emission from the IGM at high redshifts. Unless the radio source population cuts off at flux levels above the planned sensitivity of SKA, its clustering noise component will dominate the angular fluctuations in the 21 cm signal. The integrated foreground signal is smooth in frequency space, and it should nonetheless be possible to identify the sharp spectral feature arising from the nonuniformities in the neutral hydrogen density during the epoch when the first UV sources reionize the IGM.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/9d4619677396ad4d5343c2226aef1a5d2a6f22b9

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Citations in the corpus

21 Centimeter Fluctuations from Cosmic Gas at High Redshifts (2003, methodology): “We will explicitly consider point source foregrounds, as discussed by Di Matteo et al. (2002) and Oh & Mack (2003), but our method can be easily be extended to other types (such as diffuse Galactic synchrotron emission), provided that their power spectra can be estimated.”
Probing beyond the Epoch of Hydrogen Reionization with 21 Centimeter Radiation (2003, background): “While remaining an extremely challenging project due to foreground contamination from unresolved extragalactic radio sources (Di Matteo et al. 2002) and free-free emission from the same halos that reionize the universe (Oh & Mack 2003), the detection and imaging of large-scale structure prior to…”
The cosmic microwave background radiation fluctuations from H i perturbations prior to reionization (2004, background): “It will be necessary to combine both the angular fluctuations and the frequency domain properties of the CMBR brightness temperature fluctuations in order to detect it (e.g. Shaver et al. 1999; Di Matteo et al. 2002; Oh & Mack 2003; Di Matteo, Ciardi & Miniata 2004).”
Reionization and Cosmology with 21-cm Fluctuations (2009, background): “Di Matteo et al. (2002) and Oh & Mack (2003) showed that the clustering and fluctuations of radio galaxies presents an insurmountable obstacle to angular HI power spectrum measurements.”
Foreground simulations for the LOFAR-epoch of reionization experiment (2008, methodology): “Most of the methods rely on the relative smoothness in the frequency of the foregrounds, with respect to the signal (Shaver et al. 1999; Di Matteo et al. 2002; Zaldarriaga, Furlanetto & Hernquist 2004; Morales, Bowman & Hewitt 2006; Wang et al. 2006; Gleser, Nusser & Benson 2007).”
The First Stars (2003, background): “However, in practice, these observations may be extremely challenging owing to the strong foreground contamination (Di Matteo et al. 2002).”
Early Reionization by Miniquasars (2003, background): “Brightness temperature fluctuations may be detectable by future facilities like the LOw Frequency ARray (LOFAR) if foreground contamination from unresolved extragalactic point sources (Di Matteo et al. 2002; Oh & Mack 2003) can be successfully removed by using spectral structure in frequency space.”
Multifrequency Analysis of 21 Centimeter Fluctuations from the Era of Reionization (2004, methodology): “Synchrotron and free-free emission from the Milky Way (Shaver et al. 1999), low frequency radio point sources (Di Matteo et al. 2002, 2004) and free-free emission from free electrons in the intergalac2http://web.haystack.mit.edu/arrays/MWA/site 3http://www.lofar.org 4http://www.skatelescope.org 1 2…”
FOREGROUND CONTAMINATION IN INTERFEROMETRIC MEASUREMENTS OF THE REDSHIFTED 21 cm POWER SPECTRUM (2008, background): “Initial analyses indicated that these foregrounds were an insurmountable obstacle (Di Matteo et al. 2002; Oh & Mack 2003) because their angular variance dominates the expected fluctuations in the redshifted 21 cm background, but subsequent studies have suggested that multi-frequency observations…”
FOUR FUNDAMENTAL FOREGROUND POWER SPECTRUM SHAPES FOR 21 cm COSMOLOGY OBSERVATIONS (2012, background): “…than the EoR signal, and initial studies of the 21 cm foreground concentrated on identifying all of the potentially offending sources (e.g., Matteo et al. 2002; Oh & Mack 2003; Matteo et al. 2004; Gnedin & Shaver 2004; Santos et al. 2005; McQuinn et al. 2007; reviewed by Morales & Wyithe…”
21 cm Tomography with Foregrounds (2005, methodology): “…on various theoretical and experimental aspects of 21 cm radiation (e.g., Barkana & Loeb 2005b; Carilli et al. 2002, 2004; Ciardi &Madau 2003; Di Matteo et al. 2002, 2004; Furlanetto et al. 2004a, 2004b; Gnedin & Shaver 2004; Iliev et al. 2002, 2003; Loeb & Zaldarriaga 2004; McQuinn et al.…”
The Growth of H II Regions During Reionization (2004, background): “…highredshift 21 cm observations are the many bright foreground sources, which include Galactic synchrotron emission, freefree emission from galaxies (Oh & Mack 2003), faint radioloud quasars (Di Matteo et al. 2002), and synchrotron emission from low-redshift galaxy clusters (Di Matteo et al. 2004).”