1 / 25

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

jennis
Download Presentation

ALMA Band 2: Future Prospects for Scientific Studies

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  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

More Related