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ALMA Band 2: Future Prospects for Scientific Studies

ALMA Band 2: Future Prospects for Scientific Studies. Lucy M. Ziurys Staff and Students Arizona Radio Observatory University of Arizona. “3 mm Low” at the ARO 12 m. In 2000: Arizona took over the former NRAO 12 m at Kitt Peak

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ALMA Band 2: Future Prospects for Scientific Studies

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  1. ALMA Band 2: Future Prospects for Scientific Studies Lucy M. Ziurys Staff and Students Arizona Radio Observatory University of Arizona

  2. “3 mm Low” at the ARO 12 m • In 2000: Arizona took over the former NRAO 12 m at Kitt Peak • 3 mm Low Receiver (65 – 88 GHz): Previous generation SIS mixers • Used for many science projects over past 12.75 years • Conducted MIC/MMIC test observations at ARO 12 m in spring 2013 3 mm Low receiver ARO 12 m

  3. Importance of 67 – 90 GHz Region • Many known spectral lines • Unique physical and chemical tracers • Contains fundamental transitions of important molecules • H2CO: Abundant molecule, excellent • thermometer and biologically relevant • Deuterated Species: DCO+, N2D+, DCN, HDO, NH2D • HNO: Key species in N/O chemical network • J = 2→1 lines of SiO, SO, HCP: • Refractory and sulfur chemistry

  4. Significance of Deuterated Species in Band 2 • Deuterium: cosmological origin in universe (D/H ~ 10-5) • Abundance not altered by star formation • D/H ratio: Examine chemical fractionation in ion-molecule reactions + + + + • High D/H ratios found in molecular clouds • Particularly high in COLD clouds • Used to examine chemical pathways • Tracer of cloud evolution • J = 1→ 0 transition: veryimportant

  5. Refractory Chemistry • SiO: Related to refractory material, dust grain evolution • Also known to trace jet structures (HH212: Cabrit et. al. 2012) • HCP: Phosphorus analog of HCN • Only observed in circumstellar envelopes (Agundez et al.; Milam et al.) • Tracer of phosphorus chemistry in dense clouds ?

  6. New Molecules: Band 2 • Searching for new molecules • Many blended/contaminated transitions • Band 2 may provide critical and/or confirming lines • Case for FeCN (First Fe-bearing species) • 84 GHz transition (J = 10.5 → 9.5): essential for • identification TR* (mK) VLSR (km s-1) Zack, Halfen, & Ziurys, 2011, ApJ(Letters), 733, L36

  7. Ubiquitous H2CO • Excellent thermometer (multiple transitions) • “Bio-marker”: Precursor to sugar Ribose • (RNA, DNA) • Common molecule in molecular clouds • Abundant in Outer Galaxy (DGC ~ 10 - 23 kpc) • 72 GHz Transition FAVORABLE (101→ 000) H2CO 20.3 kpc Blair et al. 2008

  8. H2CO in Diffuse Clouds • H2CO common in diffuse clouds • Observed in absorption towards many site lines (Liszt and Lucas 2003, 2006, etc.) • Abundance H2CO/H2 ~ 4 x 10-9 • Factor of 5 less than cold molecular clouds 3C111

  9. H2CO in Planetary Nebulae: Helix ~1000" • Helix Nebula: one of oldest known PNe (~ 12, 000 yrs.) • UV impinging on remnant shell material for some time • H2CO widespread in Helix (Zack & Ziurys 2013) • Abundancef (H2CO/H2)~ 0.3–2.1 × 10-7 Helix Nebula TK ~ 30 K N(H2) ~ 105 cm-3

  10. H2CO in Red Spider Nebula • Red Spider (NGC 6537): Young PNe at 1,600 yrs • Highest excitation planetary nebula known • Presence of Si VI emission • Interesting bipolar morphology • H2CO present with f ~ 2 x 10-8(relative to H2) ~2’ Edwards & Ziurys Ap.J. Letters, in press

  11. SgrB 2(N) at Band 2 • Spectrum: 68- 90 GHz: ARO 12 m data • Part of SgrB2(N) survey in 1,2,3 mm windows SgrB2(N): Galactic Center Halfen et al.

  12. Fairly dense in lines at 10 mK level (SSB) • Many organic-type species (C2H5CN, HCOOCH3,CH3OCH3, etc.) • Also unidentified lines (“U”)

  13. Finished survey near 69 GHz as part of MIC testing • Comparative 12 m data: 7. 7 hours integration • POSITION SWITCHING: Off Position: 30‘ in AZ • Frequency of 69.2 GHz (same relative T. scale) SIS MIC

  14. Long integration at 72 GHz (H2CO): 31 hours • Beam-switching towards IRC+10216 • Notice image contamination !! SIS MIC

  15. But additional observations must wait… • 12 m now retired 12 M Retirement: April 1, 2013

  16. Mark Gordon Darrel Emerson Speeches from Past and Current Directors…

  17. Final Blessing of the 12 m Paul Gabor, S.J. Vatican Observatory

  18. Ceremonial Signing of the 12m Panel

  19. A moment of silence as the compressors are turned off for the last time.

  20. April 2, 2013: Work begins to dismantle old 12 m

  21. Lift Elevation Axis, Yoke, Pedestal from Dome

  22. Now outside dome with Tom Folkers

  23. In Conclusion • Observations have already shown Band 2 has much to offer scientifically • 12 tests suggest use of MIC or MMIC may be acceptable instead of SIS • NRAO-style (Kerr/Pan designs) SIS hard to beat • Concerns about stability and image rejection with MMIC/MIC’s receivers • Image rejection: properly-matched mixers in down-converter • Further use of MIC and MMIC needed to draw concrete conclusions • ARO will pursue Band 2 with new 12 m • Next priority after installation of Band 3 receiver

  24. ALMA Development Fund NSF URO

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