alma band 2: future prospects for scientific studies

Band 2 Workshop NRAO May 29, 2013

ALMA Band 2: Future Prospects for Scientific Studies

Lucy M. ZiurysStaff and Students

Arizona Radio ObservatoryUniversity of Arizona


“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

ARO 12 m 3 mm Low receiver

Arizona

ObservatoryRadio

Arizona

ObservatoryRadio


Important Molecular TransitionsMolecule Frequency (GHz)

H2CO 10,1 → 00,0 72.84N2D+ J = 1→ 0 77.11HDO 11,0 →11,1 80.56HCP J = 2→ 1 79.90DCO+ J = 1→ 0 72.04DCN J = 1→ 0 72.41SiO J = 2→ 1 86.24

H13CO+ J = 1→ 0 86.75DNC J = 1→ 0 76.31NH2D 1+

1,1→ 1-0,1 85.92

SO 22→11 86.10HNO 10,1 →00,0 80.08

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


• 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

Significance of Deuterated Species in Band 2

++

++

• 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: very important


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 ?


New Molecules: Band 2

Zack, Halfen, & Ziurys, 2011, ApJ(Letters), 733, L36

TR

* (m

K)

VLSR (km s-1)

• 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


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)

H2CO20.3 kpc

Blair et al. 2008


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


H2CO in Planetary Nebulae: Helix• 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)

• Abundance f (H2CO/H2)~ 0.3–2.1 × 10-7 Helix Nebula

~1000"

TK ~ 30 KN(H2) ~ 105 cm-3


~2’

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)

Edwards & Ziurys Ap.J. Letters, in press


SgrB2(N): Galactic Center

SgrB 2(N) at Band 2

1.5

1.0

0.5

0.0

TR

* (K

)

90x10385807570

Frequency (GHz)

• Spectrum: 68- 90 GHz: ARO 12 m data

• Part of SgrB2(N) survey in 1,2,3 mm windows

Halfen et al.


0.35

0.30

0.25

0.20

0.15

0.10

0.05

0.00

TR

* (K

)

74.6x10374.474.274.073.8

Frequency (GHz)

C2H

3CN

C2H

5CN

HC

OO

CH

3

HC

OO

CH

3

CH

3OC

H3

CH

3CN

v8=

1

+ C

H3C

N v

8=1

+ C

H3C

N v

8=1

HC

OO

CH

3C

H3C

N v

8=1

CH

3CN

v8=

1

CH

3OH

C2H

5CN HC

NH

+?

CH

3OC

H3

+ C

2H3C

N v

11=

1C

H3C

ON

H2 HC

OO

CH

3

HC

OO

CH

3

C2H

5OH

34S

O2

HC

5N

C2H5CN + U

U

UU

UUU

UUU

UUU

UU

• Fairly dense in lines at 10 mK level (SSB)

• Many organic-type species (C2H5CN, HCOOCH3,CH3OCH3, etc.)

• Also unidentified lines (“U”)


• 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


• Long integration at 72 GHz (H2CO): 31 hours

• Beam-switching towards IRC+10216

• Notice image contamination !!

SIS MIC


12 M Retirement: April 1, 2013

• But additional observations must wait…

• 12 m now retired


Speeches fromPast and CurrentDirectors…

Mark Gordon

Darrel Emerson


Final Blessing of the 12 mPaul Gabor, S.J.Vatican Observatory


Ceremonial Signing of the 12m Panel


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


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


Lift Elevation Axis, Yoke, Pedestal from Dome


Now outside dome with Tom Folkers


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


ALMA Development FundNSF URO

alma band 2: future prospects for scientific studies

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