Phosphorus Chemistry in Circumstellar Envelopes: PN in IRC+10216, VY CMa,

and CRL 2688

Aldo J. Apponi, Stefanie N. Milam, DeWayne T. Halfen, Emily D. Tenenbaum, and Lucy M. Ziurys

University of Arizona, Steward Observatory, Arizona Radio Observatory

Arizona

ObservatoryRadio

Arizona

ObservatoryRadio

• Gas Phase– C-rich: Carbon Chains (HCnN, HCn)

– O-rich: Sulfur (SO, SO2 and CS)

• Compounds of refractory elements– Silicon (SiO, SiS and SiC2)

– Sodium, Aluminum and Magnesium

• Where is the Phosphorus?– Until very recently, only CP and tentatively PN in IRC+10216– Depleted in dense gas (Orion-KL)

• Models indicate that Phosphorus is depleted by a factor of 100

• Phosphorus forms refractory compounds like Schreibersite (NiP)

– Higher sensitivity telescope receivers

C-rich EnvelopeIRC+10216

Cernicharo et al. 2000

2.0

1.5

1.0

0.5

0.0

TR

* (K)

260x103 250240230220

Frequency (MHz)

SiO (5-4)

SiS

(12-1

1)

SO

2 (1

1 1,1

1-10 0

,10)

29 S

iO V

2 (6-5

)

CO

(2-1

)

SO

2 (2

4 2,2

2-24 1

,23)

SiO

V2 (6-5

)

29 S

iO (6-5

)SO

(6 6

-55)

SiO

V1 (6-5

)SO

2 (9

3,7-9

2,9)

SiO

(6-5

)

HC

N (3-2

)

O-rich EnvelopeVY CMa

Circumstellar Chemistry

Pasek (2007)

ALMA Band 6 (211 – 275 GHz)

ALMA Memo 553

15 August 2006

First Astronomical Observations with an ALMA Band 6 (211-275 GHz) Sideband-Separating SIS Mixer-Preamp

E. F. Lauria1, A. R. Kerr2, G. Reiland1, R. F. Freund1, A.W. Lichtenberger3, L. M. Ziurys1,M. Metcalf1 and D. Forbes1

1 University of Arizona, Arizona Radio Observatory (ARO), Tucson, AZ2National Radio Astronomy Observatory (NRAO), Charlottesville, VA

3University of Virginia Microfabrication Laboratory (UVML), Charlottesville, VA

Abstract - A 211-275 GHz SIS receiver using an ALMA Band 6 sideband-separating mixer-preamp has been installed on the Submillimeter Telescope (SMT) on Mt. Graham, Arizona, a facility of the University of Arizona. Initial observations have yielded single-sideband system noise temperatures as low as 107 K referred to outside the atmosphere. The image rejection, measured on the sky, was > 12 dB (15 dB typical) for the upper sideband, and > 20 dB for the lower sideband. Excellent baseline stability was also observed: a 4° position offset in galactic latitude yielded a peak-to-peak baseline of only 10 mK. The receiver has separate 4-8 GHz IF outputs for the upper and lower sidebands, although in the present observations the bandwidth was limited by the available spectrometers to 2 GHz in each sideband .

On the Sky… • First time ALMA Receiver on a telescope (SMT) First test of ALMA technology Improved Sensitivity (factor of 10 in time) Tsys ~ 107 K, SSB (20 dB rejection) Excellent baseline stability Wide IF Bandwidth

High sensitivity:4 mK rms in 3.7hours

SMT

IRC+10216

..and happy Fred Lo

Introduction to Phosphorus Chemistry

• What was looked for, what was found and when– No detection: PH3 or HCP (Hollis et al. 1980, 1981)

– PN: Orion-KL (Ziurys 1987; Turner & Bally 1987)– CP: IRC+10216 (Guelin et al. 1990)

• No detection of PN or HCP in that work

– No detection of PS (Ohishi et al. 1990)• VY CMa

• IRC+10216

• OH231

– PN in IRC+10216• Blended line at 140 GHz (Cernicharo et al. 2000)

• Confirming line at 94 GHz (Guelin et al. 2000)

• Re-confirmed (Milam et al. in prep.)

– HCP detected in IRC+10216 (Agundez et al. 2007)– Tenenbaum and Ziurys independently detect HCP less than a month

later

-147 -87 -27 33 93

-0.006

0.000

0.006

0.012

0.000

0.006

0.012

0.000

0.004

0.008PN IRC+10216

N = 2 1

N = 3 2

N = 5 4 SiC2 v3=1

NaCN

NaCN

SiC2

30SiC2

VLSR (km s-1)

TA

* (K

)T

R* (

K)

TR

* (K

)

VLSR (km s-1)

-181 -81 19 119 219

0.000

0.012

0.024

-0.006

0.000

0.006

0.012-0.002

0.000

0.002

0.004

PN VY CMa

N = 3 2

N = 5 4

N = 6 5SO2

SO2

SO2SiS v=1

TA

* (K

)T

A* (

K)

TR

* (K

)

141 GHz

95 GHz

235 GHz

282 GHz

Cernicharo, Guelin and Kahane 2000

M. Guelin, S. Muller, J. Cernicharo, A. J. Apponi, M .C. McCarthy, C.A. Gottlieb, and P. Thaddeus 2000

Observations of PN

-0.004

0.000

0.004

0.008

-153 -93 -33 27 87

-0.006

0.000

0.006

0.012

-0.002

0.000

0.002

0.004

PN CRL 2688

N = 2 1

N = 3 2

N = 5 4

VLSR (km s-1)

SiC230SiC2

NaCN

NaCN

TA

* (K

)T

R* (

K)

TR

* (K

)

Rotational Diagram

9.5

10.0

10.5

11.0

11.5

12.0

12.5

13.0

13.5

14.0

0 5 10 15 20 25 30 35 40 45 50

log

(3kW

/8p3 S

nm2 )

Eu / k (K)

Rotational Diagram for PN in Circumstellar Envelopes

VY CMa

CRL2688

IRC+10216

Ntot = 2 x 1015 cm-2; 57 K

Ntot = 3 x 1012 cm-2; 14 K

Ntot = 1 x 1012 cm-2; 34 K

• Millar et al. 1987– Depletion factor of about 100 or more– “…searches should be carried out (for PN) in O-rich

circumstellar envelopes.”

• MacKay & Charnley 2001– HCP (C-rich) and PS (O-rich) dominate the chemistry– No PN observable in either case– CP abundance reproduced as a daughter product of

HCP (C-rich)– PS remains undetected (O-rich)

C-rich O-rich

HCPCP

PS P

Models on PN Chemistry

Agundez et al. 2007

Two reactions added to produce the observed PNN + CP → PN + CP + CN → PN + C

Spatial extent crucial for validation of the model

Estimating the Source Size

• Compare lines– 30m horned profile– 12m flat top

• Compare intensities– TR = 9 mK vs. 18 mK

– Compute the ratio of filling factors

– 30 arcsec source size

-147 -87 -27 33 93

-0.006

0.000

0.006

0.012

0.000

0.006

0.012

0.000

0.004

0.008PN IRC+10216

N = 2 1

N = 3 2

N = 5 4 SiC2 v3=1

NaCN

NaCN

SiC2

30SiC2

VLSR (km s-1)

TA

* (K)

TR

* (K)

TR

* (K)

40” beam

16” beam

TR = 18 mK

TR = 9 mK

Agundez et al. 2007

30 arcsec

Phosphorus model in IRC+10216

• HCP– 20 mK vs. 9 mK– ~20 arcsec source

• CP– 25 mK vs. ~10 mK– ~20 to 30 arcsec

source

HCP

Agundez et al. 2007

0.006

0.003

0.000

-0.003

T R* (K

)

159900159850159800159750159700Frequency (MHz)

159 GHzGuelin (1990)

Agundez et al. 2007

20 arcsec

Phosphorus model in IRC+10216

Summary• PN observed in circumstellar envelopes

– C-rich envelopes of IRC+10216 and CRL 2688– O-rich envelope VY CMa

• Models of IRC+10216– Reproduce PN in the outer envelope

• Required the addition of two new reactions• N + CP → PN + C and P + CN → PN + C

– Reproduces HCP and CP• CP a daughter product of HCP• Both HCP and CP depleted in the outer envelope onto grains

Summary• Models of O-rich envelopes less successful

– No available observations to guide the models– Current O-rich models vary

• PS dominant (MacKay and Charnley 2001)

• P2O4 dominant (Agundez et al. 2007)

– Absence of PS detection• Dipole moment estimated to be 2.0 D• No calculation or measurement available• Could be much smaller (NO: 0.16 D)

– PN not predicted to be abundant in the current available models

• Millar et al. 1987 suggested looking for it in O-rich envelopes• PN is an inner envelope component in VY CMa• Could be an LTE product

PO

PN

PS

PH

High “freeze-out” tempsHigh abundance ofPO, PN, PS and PH

Acknowledgements• Funding from NASA Astrobiology Institute and NSF

Astronomy• Research Associates: Lucy Ziurys and Neville Woolf• The Ziurys research group

– Stefanie Milam– DeWayne Halfen– Emily Tenenbaum