Chen, Yi-Ping

Supervisor: Hirano, Naomi

12CO J=2-1 Observation Of M51 With SMA

Physical Department of Tamkang University

August ,27, 2002

Summer Student Program ,Institute of Astronomy and Astrophysics, Academia Sinica

Introduction

• Galaxy M51• SMA• C12O Emission J=2-1• Data Reduction • Analysis Data

Galaxy M51

• Position (J2000):

R.A. 13h 29m 52.37sDec. +47°11' 40.8"

• Constellation:

Canes Venatici

• Distance:About 9.6 Mpc

• Visual Magnitude:8.4

http://oposite.stsci.edu/pubinfo/PR/2001/10/index.html

3arcmin

9.3 kpc

1acrmin

50 arcsec

(Field of view)

Sub-Millimeter Array

• Antenna: 5

• Diameter:6-meter

• Covering bands :230 -350 GHz

• Position:

Summit of Mauna Kea, Hawaii

http://www.asiaa.sinica.edu.tw/Research/SMART/index.html

O C

Because of CO molecule has a permanent dipole moment ,the binary molecule with a simples ladder of rotational level spaced such that the lowest transition are in the millimeter wavelength.

12CO Emission J=2-1

• J is the quantum number of total angular momentum correspond to the rotational level.

• Frequency : 230.538 GHz

• Energy : 16.6 Κ

(upper level above ground)

J=0

J=1

J=2hν= E2-E1

hν =E1-E0

Observation

• Observation date : 2002 Feb 17,18

• Telescope : SMA 6m(diameter)×5(antenna)

10 baseline• Field of view : 50’’ @230 GHZ

• Bandwidth : 320 MHZ ~ 417.39 km/s((82 MHZ ~106.7 km/s)× 4)

• Spectral resolution : 812.5 KHZ ~1.06 km/s

• Gain calibrator : 1310 + 323

• Band pass calibrator : Jupiter

Data Reduction Why using the Gain Calibration?

Phase

Amplitude

t

t

Due to the instrument instability and atmosphere variation , it is necessary to do the gain calibration, and the better calibrator is quasar because it’s has a simple visibility function.

V(u,v)=∫∞-∞∫∞

-∞A(x,y) I(x,y)ei2(ux+vy)dxdy

0

0

constant

I. Gain Calibraiton

• Before Gain Calibration

• Blue *-- (1310+323)

• Red *--

NGC5194

Row data

Blue--NGC5194

Red--

Cailbrator

(1310+323)

Set amplitude—1Jy

After Gain Calibration

After calibration the phase is becoming zero(blue)&M51 drift like function.

II. Band Pass Calibration

• In the SMA Aarry each channel have four chunks

• Before band Pass Calibration

• 1chunk=82MHZ 106.7 km/s≒• 1channel =4×chunk 320MHZ ≒ ≒

417.39

• Calibrator : Jupiter

• This calibrator must be strong enough that can clear display each of the chuck’s pattern.

• After Calibration Jupiter’s Spectra

Spectra

After band Pass Calibration

Analysis Data-- Make Maps

UV Coverage Beam Map

Dirty Map(obtained from the inversion visibility function)

Obtained by convolving the δ-function

Clean Map

UV plane FFT XY plane

(Visibility function)

UV Coverage

Beam mapUV coverage

Dirty Map(Feb 18,chunk 2)

Clean Map(Feb 18,chunk 2)

• Major axis = 4.584 +/- 0.4904 asec• Minor axis = 3.651 +/- 0.3906 asec• Position angle = 93.787 +/- 18.892

degrees

Synthesize beam

Beam map

Combine Map

Total integration intensity

VLSR =374.57~574.34 km/s

VLSR= 479.2~574.3 km/s

VLSR=374~480.7 km/s

Contour MapDue to the sigh of phase is flipped the map must rotate 180°

12CO J=1-0 HCN J=1-0

©The Astrophysical Journal,461:L29-L32,1996 April 10

Compare 12CO J=2-1 & 12CO J=1-0

Compare HCN J=1-0 &C12O J=2-1