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1 TAUVEX and AGNs T TAUVEX=Tel A Aviv University UV Ex UV Explorer
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2 Outline Background Technical description Projected performance Scientific projects (AGNs) Conclusions
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3 IUE: all targets Why UV? Earth atmosphere opaque to UV Low sky background! UV range Background
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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)
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5 Generic UV Targets Comets Hot stars (high-mass, evolved [WD]) Galaxies: evolution Interstellar & Inter- Galactic matter AGNs SMC Hyakutake Hale-Bopp 40 deg
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6 TAUVEX history 1989: chosen as 1 st 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 SRG=Spectrum Roentgen-Gamma (incarnation I) Prime contractor: El-Op, Electro-optical Industries
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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! To allow unrestricted access to the sky, TAUVEX is mounted on orientable platform (MDP). The Indian connection
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8 Toward Earth MDP in launch orientation. MDP motion is up to 180º from the launch position, to -90≤δ≤+90 δ=0º δ=+90º
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9 3x20cm RC telescopes ~One-degree images Angular resolution ~7” UV “solar blind” sensitivity Unblocked area ~266 cm²(3x) On GSAT-4, sky scans TAUVEX basics Technical description
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10 TAUVEX: filter setup Each telescope with 4- position wheel One position blocked (shutter=CLS) Three positions with filters Filter arrangement SF1 T1: SF1, SF2, BBF, CLS SF3 T2: SF2, SF3, BBF, CLS SF1SF3 T3: SF1, NBF3, SF3, CLS Includes geometric shadowing, 2 mirrors, lenses+windows, filter trasmission & detector QE CaF_2 cutoff
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11 Simulated image 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) TAUVEX performance (and constrains) Projected performance
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12 Confusing magnitudes…
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13 TAUVEX vs. HST 144x more collecting area than TAUVEX 70-700x better resolution 400x smaller FOV (STIS) 200-400x higher cost Only operating UV instruments at present are ACS & WFPC-2! HST has:
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14 GALEX 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 AIS like TAUVEX single pass (AB mag limit=18 mono) GALEX NUV= TAUVEX BBF
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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 SunStrongest source=Sun Operational solutions: –Filter choice (solar spectrum) –Sky strip selection –Baffle extension Scattered into baffle Reflected by solar panels & thrusters
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16 Sensitivity (best case) SF-1 SF-2 SF-3 BBF-worst case BBF-best case To Sun Equal-area projection of celestial hemisphere
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17 GALEX vs. TAUVEX 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 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
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18 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) Projected results
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19 How many low-z AGNs? AGNs per square degree, with z<1, to different limiting magnitudes. Conclusion: TAUVEX will find significant numbers of low-z AGNs N
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20 Red≡stars, green ≡ galaxies, light blue ≡ AGNs.+reddening GALEX+SDSS (Bianchi et al 2004) GALEX AGNs: UV vs. optical colors
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21 TAUVEX: UV+optical colors z Nearby AGNs (z<1) UV-UV
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22 z z TAUVEX: UV+optical colors
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23 z AGNs@.5<z<4, including Ly limit and Ly forest Importance of simultaneous UV & optical measurements! UV-UV
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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
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26 TAUVEX on GSAT4: GENERAL VIEW New features: Rotating plate Front radiator Extra baffle Extra shielding Thermal couplings MDP
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27 Performance: SF-1 Equal-area plot, hemisphere
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28 Performance: SF-2
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29 Performance: SF-3
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30 Performance: BBF
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31 TAUVEX: detection system Wedge (A) Strip (B) Zig-zag (C) Detection=(x, y, t) (Approx. 700 “pixels” across FOV)
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32 TD-1A & IUE All-sky photometric survey to 9 mag Targeted mission: spectroscopy
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33 TAUVEX science: stars & ISM B star UV spectrum Use SF2 and NBF3 to measure the EW of the ISM band TD-1 PAHs distribution?
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34 TAUVEX science: galaxies UV light understand physics of star-forming processes, extinction Late-type galaxies=good targets GALEX 1300 sec image
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35 Antennae galaxies (NGC4039/4039): importance of the UV sensitivity to establish the nature of stellar populations and determine the full IMF TAUVEX science: galaxies II Lyman cont`.HαHα Hot stars (O,B,A)FUV, NUV Stars (F,G,K,M)Optical (UBVRI) Stars (K, M)Near-IR Almoznino & Brosch 1998
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36 TAUVEX science: galaxies III UV observations track the history of star formation in the last billion years
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37 TAUVEX science: UV-dropouts (cosmology) Select z=1-2 galaxies from UV dropouts
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38 Real image: distortion pattern “Flat-field” (collimator) TAUVEX: lab performance Next More? Edge discharge
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39 Comments Volume log #Gals m lim Expos [ksec] Length [Month] Area [deg] SURVEY Galactic caps first0.11720.50.1440,000All-sky (AIS) SDSS, 2dF overlap0.6~16.5231.521000Medium Imaging (MIS) Fields0.851.072530480Deep Imaging (DIS) Fields0.90.055.5262000.21Ultra-Deep Image (UDIS) Galaxy List--- 2.5 27.5 m per sq. deg. 0.5 300Nearby Galaxy (NGS) Same fields as DIS0.150.034.52030480Wide Spectroscopic (WSS) Centers of WSS0.50.044.521-2330028 Medium Spectroscopic (MSS) Fields0.90.054.522.5-24200042Deep Spectroscopic (DSS) --- 4 Guest Investigator Cycle 1 GALEX surveys (AB)
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40 GALEX-technical Uses dichroic beamsplitter Two crossed-delay line MCP detectors (2kx2k) Insertable grism for low-resolution spectra Pegasus launch to LEO Pegasus launch
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41 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 BA G (better than GALEX!) TAUVEX: performance (GSAT-4)
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