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Introduzione alla Radioastronomia Parte I

Introduzione alla Radioastronomia Parte I. Nichi D’Amico. Dipartimento di Fisica, Universita’ degli Studi di Cagliari INAF – Osservatorio Astronomico di Cagliari. I Radiotelescopi italiani. Medicina (BO) [CNR]. Matera 20 mt [ASI]. Noto (SR) 32 mt [CNR].

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Introduzione alla Radioastronomia Parte I

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  1. Introduzione alla Radioastronomia Parte I Nichi D’Amico Dipartimento di Fisica, Universita’ degli Studi di Cagliari INAF – Osservatorio Astronomico di Cagliari

  2. I Radiotelescopi italiani Medicina (BO) [CNR] Matera 20 mt [ASI] Noto (SR) 32 mt [CNR] 32 mt [CNR]

  3. 1998: Accordo CNR - ASI - RAS per la costruzione, in Sardegna, di un grande radiotelescopio, versatile, di concezione moderna: il Sardinia Radio Telescope (SRT) Finanziamenti: 59.0 G £ MURST (Antenna) 10.6 G £RAS (Infrastrutture tecnologiche) 6.5 G £ ASI (Progetto Vertex) Sito: Pranu Sanguni (San Basilio, CA)

  4. I problemi osservativi della radioastronomia: • Risoluzione angolare • Campionamento del piano focale • Cambio di frequenza

  5. Risoluzione angolare ~ /d Sistema Ricevente feed Piano focale

  6. Sorgente puntiforme a distanza infinita Figura di diffrazione (sorgente in asse) Offset in posizione  Feed Risposta del sistema riflettore-feed -4 -3 -2 -1 0 1 2 3 4 Offset in posizione 

  7. Alcuni esempi di radiotelescopi ~4 arcmin x 2° (70 cm) ~30 arcmin (21 cm) Medicina, 32mt Medicina, Croce del Nord ~3 arcmin (21 cm) ~30 arcmin (21 cm) Arecibo, Porto Rico, 300mt Jodrell Bank, UK 70mt

  8. Mappa della Via Lattea in coordinate galattiche (falsi colori) • = 70 cm (408 MHz); A=70m  ~ 40 arcmin

  9. Come risolvere il problema della risoluzione angolare: Interferometria e sintesi d’apertura

  10. Sorgente puntiforme a distanza infinita Fronte d’onda Offset in posizione  Baseline D + /D Baseline Offset in posizione  Ritardo t

  11. a) A’ A B B’ b)

  12. M82 E-W 10hr N-S 3hr E-W 3hr Merlin (UK) 10hr

  13. Alcuni esempi di sistemi interferometrici

  14. VLA (Very Large Array) Configurations: A 21.0 km B 6.4 km C 1.9 km D 0.6 km

  15. 1 arcmin 4.9 GHz 0.4 arcsec resolution 4.9 GHz 0.4 arcsec resolution A unified model of Active Galactic Nuclei (AGN), accounts for the features observed in Radiogalaxies (often identified with elliptical galaxies), in Quasars (which are also found at the center of spirals), and Seyfert galaxies. 8 GHz 0.3 arcsec resolution 1.4 GHz 1.4 arcsec resolution 1.4 GHz 5 arcsec resolution

  16. The elliptical galaxy NGC 4261 HST RADIO

  17. VLA observations of the Radiogalaxy NGC326 1.4 GHz (A+C array) 5 arcsec 1.4 GHz (A array) 1 arcmin

  18. The most distant radiogalaxy known TN J0924-2201 at z = 5.19 VLA contour map at 4.8 GHz, superimposed on a near-IR image obtained at Keck-I telescope Spectroscopic observations made at Keck-I telescope show a redshift z = 5.19 5 arcsec At a redshift of 5.19 (nearly 11 billion light years from Earth, back in time ~90% of the age of the Universe), the radio galaxy is very young and still forming through merging of smaller galaxy components.

  19. The European VLBI Network (EVN) Imaging the expansion of a SNR shell in the M82 galaxy, at 12 million light-year distance

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