[daip] problems measuring flux

[Leonia Kogan]

Hi Kristy,

May I start answering your second question:

>2. If there is no beam size information in the head (that I can see),
>how is IMEAN/IMSTAT calculating 

>1.5103E-02 Rms= 8.1310E-03 in JY/BEAM?

Both IMEAN and IMSTAT should consider that all pixel values at the map
are measured at JY/BEAM. And this information is given at the header:


Minimum=-7.00000022E-03      Maximum= 1.34000003E-01 JY/BEAM
                                                     ^^^^^^^
Therefore IMEAN and IMSTAT do not carry out any conversion from 
JY/PIXEL to JY/BEAM or vice versa. They simple use the label.

I think so

Let me think about the first question

Leonia


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>From owner-daip at kochab.cv.nrao.edu Sat Apr 21 15:51 MDT 2001
Date: Sat, 21 Apr 2001 17:48:33 -0400
From: "K. Dyer" <kkdyer at unity.ncsu.edu>
Reply-To: Kristy_Dyer at ncsu.edu
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To: daip at cv3.cv.nrao.edu
Subject: [daip] problems measuring flux
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I have the a map of single dish + interferometer data with header thus:

AIPS 1: Image=SNR1006   (MA)         Filename=PARKES      .IMAP  .   1
AIPS 1: Telescope=                   Receiver=Molonglo
AIPS 1: Observer=Roger-Mi            User #= 1010
AIPS 1: Observ. date=01-JUN-1983     Map date=12-OCT-2000
AIPS 1: Minimum=-7.00000022E-03      Maximum= 1.34000003E-01 JY/BEAM
AIPS 1: ----------------------------------------------------------------
AIPS 1: Type    Pixels   Coord value     at Pixel     Coord incr   Rotat
AIPS 1: RA---NCP   256    15 02 46.281     129.00        -11.000    0.00
AIPS 1: DEC--NCP   256   -41 55 45.265     129.00         11.000    0.27
AIPS 1: FREQ         1   8.4300000E+08       1.00  1.0000000E+00    0.00
AIPS 1: STOKES       1   1.0000000E+00       1.00  1.0000000E+00    0.00
AIPS 1: ----------------------------------------------------------------
AIPS 1: Coordinate equinox 2000.00
AIPS 1: Maximum version number of extension files of type HI is   1
AIPS 1: Maximum version number of extension files of type SL is   2
AIPS 1: Maximum version number of extension files of type PL is   3

I want to know the flux density [Jy] in a particular area but instead I
get:

IMSTAT
AIPS 1: Mean= 1.8883E-02 rms= 6.9834E-03 JY/BEAM   over     840. pixels
AIPS 1: Maximum= 3.4000E-02 at   103    61    1    1    1    1    1
AIPS 1: Skypos: RA 15 03 12.304  DEC -42 08 10.03
AIPS 1: Skypos: IPOL  843.000 MHZ
AIPS 1: Minimum= 3.0000E-03 at   78   56    1    1    1    1    1
AIPS 1: Skypos: RA 15 03 37.061  DEC -42 09 02.38
AIPS 1: Skypos: IPOL  843.000 MHZ

IMEAN
localh> IMEAN1: Task IMEAN  (release of 15OCT99) begins
localh> IMEAN1: ZTXOP2: using translated file name =
localh> IMEAN1: ZTXOP2: /marcielocal/aips/FITS/parkes.ps
localh> IMEAN1: Image= PARKES      .CLIP  .   8 2   xywind=   64   56 
194  196
localh> IMEAN1: Mean and rms found by fitting peak in histogram:
localh> IMEAN1: Mean= 1.2134E-02 Rms= 5.2291E-03  **** from histogram
localh> IMEAN1: Mean and rms found by including all data:
localh> IMEAN1: Mean= 1.5103E-02 Rms= 8.1310E-03 JY/BEAM   over    9226.
pixels
localh> IMEAN1: Minimum= 4.0000E-03 at  150  161    1    1
localh> IMEAN1: Skypos: RA 15 02 25.467  DEC -41 49 53.74
localh> IMEAN1: Maximum= 6.6000E-02 at  149   70    1    1
localh> IMEAN1: Skypos: RA 15 02 26.782  DEC -42 06 33.91
localh> IMEAN1: Skypos: IPOL  843.000 MHZ
localh> IMEAN1: Appears to have ended successfully
localh> IMEAN1: marcie       15OCT99 TST: Cpu=       0.0  Real=       0

Some times IMSTAT or IMEAN will give a line:

AIPS 1: Flux density = -3.2719E-02 Jy.   Beam area = 100.63 pixels  

Sometimes it doesn't.

Two questions:

1. Why doesn't it always give that line?

2. If there is no beam size information in the head (that I can see),
how is IMEAN/IMSTAT calculating 

1.5103E-02 Rms= 8.1310E-03 in JY/BEAM?

-- Kristy Dyer



-- 
Work: Kristy_Dyer at ncsu.edu     
NCSU Astrophysics
http://wonka.physics.ncsu.edu/~kkdyer/kristy.html


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