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The SOAR Optical Imager

The SOAR Optical Imager. Hugo E. Schwarz. and the people who did the work:. Michael Ashe, Max Boccas, Marco Bonati, Francisco Delgado, Ramón Gálvez, Manuel Martínez, Ricardo Schmidt, Patricio Schurter, Roberto Tighe, led by Alistair Walker. + SOAR, CTIO & AOSS teams.

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The SOAR Optical Imager

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  1. The SOAR Optical Imager Hugo E. Schwarz and the people who did the work: Michael Ashe, Max Boccas, Marco Bonati, Francisco Delgado, Ramón Gálvez, Manuel Martínez, Ricardo Schmidt, Patricio Schurter, Roberto Tighe, led by Alistair Walker. + SOAR, CTIO & AOSS teams.

  2. Instrument concept. High resolution images over medium FoV. Part of “system” with 4m VMB and Gemini south. Blanco (wide FoV) Gemini (8m) complementary.

  3. In optical Both seeing limited  ~ comparable for 4m & 8m t  (1/D)2 ~1/4 The “very” blue 0.7 0.6 Strehl width “ In near IR  ~ 1.5 x smaller for 4m Makes up much of difference in D. 0.5 0.4 0.3 0.2 0.1 0.5 1.2 1.6 2.2 3.5 5.0 Wavelength (μm) SOAR’s Niche Tip-Tilt 4m • In mid-IR • Both diffraction limited •  1/D, t  (1/D)4 ~ 1/16 SOAR not competitive 8m Background-limited Case,time to reach given S/N on given object t (/D)2  = image diameter, D = telescope diameter

  4. What has been/will be done to preserve image quality. At the telescope: Active M1, Tip-Tilt M3, integrated M1 laminar air flow, active dome flow, cooling everywhere, a well insulated “minimal building”. Height above ground layer….

  5. What has been/will be done to preserve image quality. Around the telescope: Minimal building, no thermal mass exposed to Sun, short thermal time scale material, dust control, environmental monitoring system.

  6. Site characterization DIMM to monitor the seeing. Meteo station on El Peñon. PASCA to monitor the whole sky.

  7. Typical weather+DIMM page

  8. Optical Imager • f/16 to f/9 focal reducer optics • Dual 2kx4k E2V 4282 CCDs, 15m pixels • Scale 0.08” pix-1, 5.6’ x 5.6’ FoV • Linear ADC • Two filter slides, 5 positions each • Installed at bent/broken Cassegrain • Only CCD & filters rotate

  9. Optics module Cable wrap CCDs LN2 Prism 1 Prism 2 Filter slides

  10. How we observed…. 6” lens 45º mirror Scale: 2” pix; 2.9º FoV

  11. Linear ADC Atmospheric dispersion is: Band (nm) z = 30° 50° 65° U 310-400 0.8 1.7 3.0 B 370-470 0.4 0.8 1.4 V 490-600 0.2 0.5 0.8 R 570-730 0.2 0.3 0.5 I 730-860 0.1 0.2 0.3 And worse for white light imaging, so: We need an ADC!

  12. Why a linear ADC? • Cannot tolerate tilt in pupil/optical axis (WFS) • Single prism: NO because of tilt. • Double prism (0 deviation): thick & costly • Linear ADC: best option. • For SOI at 70° BVRI <0.3”; U~0.4” d80.

  13. Science with the SOI. • Census of galaxies d < 5Mpc • Used 2.5m NOT, 0.6”, LG galaxies. • M31 fine, Leo I&II a nightmare. • SOAR 4.2m with SOI, best 0.3”, 11xdeeper. • Less sky concentration, better photometry. • Go further out, (a bit) beyond local group.

  14. Good separation of C- and M stars, using Wing filters, Centered on CN band & cont. TiO band & cont.

  15. Derived magnitudes & luminosities: NGC185 NGC147

  16. Results • Photometry for 8000 stars per frame. • Separate C- and M-stars by < 1.5mag • Distance 24.04 & [Fe/H]=-0.89 for NGC185 • Distance 24.44 & [Fe/H]=-1.11 for NGC147 • 300 new C-stars, C/M = 0.089 & 0.154 resp. • M(C-stars)=-4.24 and bolometric mags. • Try Antlia (25.5), DDO210 (24.6) go further out • Efficient use of telescope time, good project for SOAR/SOI.

  17. Summary of SOI status Done: Light comes through when on the telescope To do: Flexure tests, guide probe tests. Movements of filters, ADCs, rotator. Autoguider. Tuning of science CCDs. Calibrations Documentation, website. ALSO: delivery of LL CCDs, much improved blue response to be expected. Obrigado!

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