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TAUVEX and AGNs

TAUVEX and AGNs. TAUVEX = T el A viv University UV Ex plorer. Outline. Background Technical description Projected performance Scientific projects (AGNs) Conclusions. Background. Why UV?. Earth atmosphere opaque to UV. UV range. Low sky background!. IUE: all targets.

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TAUVEX and AGNs

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  1. TAUVEX and AGNs TAUVEX=Tel Aviv University UVExplorer

  2. Outline • Background • Technical description • Projected performance • Scientific projects (AGNs) • Conclusions

  3. Background Why UV? Earth atmosphere opaque to UV UV range Low sky background! IUE: all targets

  4. Short history of UV astronomy • UV range definition: 10 nm to 380 nm • First observation: Sun, from V2 (US-NRL) • First satellite: TD-1. Sky survey to ~9 mag • First spectroscopy: Copernicus • Longest duration: IUE • Most expensive: HST (only part is UV) TD-1 starlight at 156.5 nm in 3° bins (Sujatha et al. 2004)

  5. Hyakutake Generic UV Targets • Comets • Hot stars (high-mass, evolved [WD]) • Galaxies: evolution • Interstellar & Inter-Galactic matter • AGNs Hale-Bopp 40 deg SMC

  6. TAUVEX history SRG=Spectrum Roentgen-Gamma (incarnation I) Prime contractor: El-Op, Electro-optical Industries 1989: chosen as 1st priority by ISA 1991: agreement to launch with SRG 1994: planned launch date 2000: delays with SRG; start search for alternate launch 2003: ISA-ISRO agreement 2007: planned launch on GSAT-4

  7. GSAT-4 to geo-synchronous orbit. • Platform=technological demonstrator for • new generation of Indian communication • satellites. • TAUVEX has a dedicated communication • channel of 1 Mbps, continuously. • Satellite has fixed orientation w.r.t. the • Earth! The Indian connection • To allow unrestricted • access to the sky, TAUVEX • is mounted on orientable • platform (MDP).

  8. Toward Earth δ=+90º δ=0º MDP in launch orientation. MDP motion is up to 180º from the launch position, to -90≤δ≤+90

  9. Technical description TAUVEX basics • 3x20cm RC telescopes • ~One-degree images • Angular resolution ~7” • UV “solar blind” sensitivity • Unblocked area ~266 cm²(3x) • On GSAT-4, sky scans

  10. TAUVEX: filter setup Each telescope with 4-position wheel One position blocked (shutter=CLS) Three positions with filters CaF_2 cutoff Includes geometric shadowing, 2 mirrors, lenses+windows, filter trasmission & detector QE Filter arrangement T1: SF1, SF2, BBF, CLS T2: SF2, SF3, BBF, CLS T3: SF1, NBF3, SF3, CLS

  11. Projected performance TAUVEX performance(and constrains) Drift rate: “Pixel”=3 arcsec Max. “no-smear” time=1/8 sec Basic timescale for data frame Object in FOV: 224 sec along detector diameter at δ=0 (basic exposure time) High declination advantage! (above 81º, more than 1500 sec per pass) Simulated image

  12. Confusing magnitudes…

  13. TAUVEX vs. HST Only operating UV instruments at present are ACS & WFPC-2! HST has: • 144x more collecting area than TAUVEX • 70-700x better resolution • 400x smaller FOV (STIS) • 200-400x higher cost

  14. GALEX AIS like TAUVEX single pass (AB mag limit=18 mono) GALEX NUV= TAUVEX BBF • GALEX launched April 2003 for all-sky UV survey • GALEX (1x) and TAUVEX (3x) have similar collecting • areas and angular resolution • GALEX has one 50-cm telescope and only two spectral • bands: FUV & NUV • GALEX operates only 1/3 of the orbit

  15. TAUVEX - performance • Exposure depth depends on: • Dwell time of object in FOV(“exposure”) • Level of background (Max count rate~100K/sec) • Background is stray light: light scattered into the detectors from sources external to the FOV • Strongest source=Sun • Operational solutions: • Filter choice (solar spectrum) • Sky strip selection • Baffle extension • Scattered into • baffle • Reflected by • solar panels & • thrusters

  16. Sensitivity (best case) SF-1 To Sun BBF-best case SF-2 SF-3 BBF-worst case Equal-area projection of celestial hemisphere

  17. GALEX: DIS=80 sq. degrees (~70 fields). Limiting AB=25 (1σ); only small part done yet TAUVEX: DEC=+90 to +85 is equivalent area to DIS Limiting mag’s (5σ) for single scan are: SF1-3: 18-20 monochromatic (AB=21-23) BBF: gain one mag GALEX vs. TAUVEX To surpass GALEX DIS, TAUVEX requires 10 scans of the Polar Cap area! This is 1-2 months of observations. GALEX DIS field: Groth region, 14ksec exposure

  18. Projected results TAUVEX science: AGNs • Detection (star-AGN photometric separation) • Rough redshift determination (UV dropouts) • Variability studies Composite AGN spectrum (Telfer et al. 2002, ApJ 565, 773)

  19. How many low-z AGNs? N AGNs per square degree, with z<1, to different limiting magnitudes. Conclusion: TAUVEX will find significant numbers of low-z AGNs

  20. GALEX AGNs: UV vs. optical colors Red≡stars, green≡galaxies,light blue≡AGNs.+reddening GALEX+SDSS (Bianchi et al 2004)

  21. TAUVEX: UV+optical colors Nearby AGNs (z<1) UV-UV z

  22. TAUVEX: UV+optical colors z z

  23. AGNs@.5<z<4, including Ly limit and Ly forest UV-UV z Importance of simultaneous UV & optical measurements!

  24. Conclusions TAUVEX offers similar performance to GALEX, with important enhancements: • Three simultaneous bands • Five different filters (flexibility) • Time-resolved photometry over a number of time scales: 1/8 sec to 100s of sec for single pass; revisits Launch 20 February 2007

  25. TAUVEX on GSAT4: GENERAL VIEW • New features: • Rotating plate • Front radiator • Extra baffle • Extra shielding • Thermal couplings MDP

  26. Performance: SF-1 Equal-area plot, hemisphere

  27. Performance: SF-2

  28. Performance: SF-3

  29. Performance: BBF

  30. Zig-zag (C) Strip (B) Wedge (A) TAUVEX: detection system Detection=(x, y, t) (Approx. 700 “pixels” across FOV)

  31. TD-1A & IUE All-sky photometric survey to 9 mag Targeted mission: spectroscopy

  32. TAUVEX science: stars & ISM TD-1 PAHs distribution? Use SF2 and NBF3 to measure the EW of the ISM band B star UV spectrum

  33. TAUVEX science: galaxies UV light understand physics of star-forming processes, extinction Late-type galaxies=good targets GALEX 1300 sec image

  34. TAUVEX science: galaxies II Antennae galaxies (NGC4039/4039): importance of the UV sensitivity to establish the nature of stellar populations and determine the full IMF Almoznino & Brosch 1998

  35. TAUVEX science: galaxies III UV observations track the history of star formation in the last billion years

  36. TAUVEX science:UV-dropouts (cosmology) Select z=1-2 galaxies from UV dropouts

  37. TAUVEX: lab performance Next Edge discharge More? More? Real image: distortion pattern “Flat-field” (collimator)

  38. GALEX surveys (AB)

  39. GALEX-technical Pegasus launch • Uses dichroic • beamsplitter • Two crossed-delay line MCP detectors (2kx2k) • Insertable grism for low-resolution spectra • Pegasus launch to LEO

  40. TAUVEX: performance (GSAT-4) (better than GALEX!) • Assume best case=no stray light • Performance (S/N=5) with SF-2 for stars of different spectral types • Lines for monochromatic mag. 17, 18, 19, 20, 21 star O B A G

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