HOW TO IDENTIFY AND SEPARATE BRIGHT GALAXY CLUSTERS FROM THE LOW-FREQUENCY RADIO SKY

Journal Article · Mon Nov 01 00:00:00 EDT 2010 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/723/1/620· OSTI ID:21467166

Jingying, Wang; Haiguang, Xu; Junhua, Gu; Haijuan, Cui ^[1]; Tao, An ^[2]; Jianxun, Li ^[3]; Zhongli, Zhang ^[4]; Qian, Zheng

---

1. Department of Physics, Shanghai Jiao Tong University, 800 Dongchuan Road, Minhang, Shanghai 200240 (China)
2. Shanghai Astronomical Observatory, Chinese Academy of Sciences, Shanghai 200030 (China)
3. School of Electronic Information and Electrical Engineering, Shanghai Jiao Tong University, 800 Dongchuan Road, Minhang, Shanghai 200240 (China)
4. Max-Planck-Institute of Astrophysics, Karl-Schwarzschild-Str.1, Postfach 1317 85741 Garching, Munich (Germany)

In this work, we simulate the 50-200 MHz radio sky that is constrained in the field of view (5{sup 0} radius) of the 21 Centimeter Array (21CMA), a low-frequency radio interferometric array constructed in the remote area of Xinjiang, China, by carrying out Monte Carlo simulations to model the strong contaminating foreground of the redshifted cosmological reionization signals, including emissions from our Galaxy, galaxy clusters, and extragalactic discrete sources (i.e., star-forming galaxies, radio-quiet active galactic nuclei (AGNs), and radio-loud AGNs). As an improvement over previous works, we consider in detail not only random variations of morphological and spectroscopic parameters within the ranges allowed by multi-band observations, but also the evolution of radio halos in galaxy clusters, assuming that relativistic electrons are re-accelerated in the intracluster medium (ICM) in merger events and lose energy via both synchrotron emission and inverse Compton scattering with cosmic microwave background photons. By introducing a new approach designed on the basis of independent component analysis and wavelet detection algorithm, we prove that, with a cumulative observation of one month with the 21CMA array, about 80% of galaxy clusters (37 out of 48 clusters assuming a mean magnetic field of B = 2 {mu}G in the ICM, or 15 out of 18 clusters assuming B = 0.2 {mu}G) with central brightness temperatures of >10 K at 65 MHz can be safely identified and separated from the overwhelmingly bright foreground. By examining the brightness temperature images and spectra extracted from these identified clusters, we find that the morphological and spectroscopic distortions are extremely small compared to the input simulated clusters, and the reduced {chi}{sup 2} of brightness temperature profiles and spectra are controlled to be {approx}<0.5 and {approx}<1.3, respectively. These results robustly indicate that in the near future a sample of dozens of bright galaxy clusters will be disentangled from the foreground in 21CMA observations, the study of which will greatly improve our knowledge about cluster merger rates, electron acceleration mechanisms in cluster radio halos, and magnetic field in the ICM.

• OSTI ID: 21467166
• Journal Information: Astrophysical Journal, Vol. 723, Issue 1; Other Information: DOI: 10.1088/0004-637X/723/1/620; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTROPHYSICS
COSMOLOGY AND ASTRONOMY
ALGORITHMS
BRIGHTNESS
COMPTON EFFECT
COMPUTERIZED SIMULATION
EMISSION
EMISSION SPECTRA
GALACTIC EVOLUTION
GALAXIES
GALAXY CLUSTERS
GALAXY NUCLEI
IMAGE PROCESSING
MAGNETIC FIELDS
MHZ RANGE
MONTE CARLO METHOD
PHOTONS
RELATIVISTIC RANGE
RELICT RADIATION
STARS
UNIVERSE
BASIC INTERACTIONS
BOSONS
CALCULATION METHODS
ELASTIC SCATTERING
ELECTROMAGNETIC INTERACTIONS
ELECTROMAGNETIC RADIATION
ELEMENTARY PARTICLES
ENERGY RANGE
EVOLUTION
FREQUENCY RANGE
INTERACTIONS
MASSLESS PARTICLES
MATHEMATICAL LOGIC
MICROWAVE RADIATION
OPTICAL PROPERTIES
PHYSICAL PROPERTIES
PROCESSING
RADIATIONS
SCATTERING
SIMULATION
SPECTRA