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Velo city values derived from ICOR and WAPP sp ectra p ost 08-Feb-2007 correction ­C.Salter, T.Ghosh, M.Lebron

This rep ort describ es the velo city values for various sp ectral lines using b oth the ICOR and the WAPPs, after the correction implemented by Mikael on 8th Feb 2007. Part 1: A galactic OH maser source These observations were taken on 27 Feb 07, using a Galactic OH-Maser source, S269, with the velo cityz entry in the list file to b e 0, and we changed the velo city-frame b etween LSR and Helio. Explanation: i = ICOR, w = WAPP, l = LSR, h = Helio, v = velo city, z = redshift, d = DPS Just ON: ------Scan ----ilv1 ilv2 wlv1 ihv1 whv1 ilz1 wlz1 ihz1 whz1

Frq_obs -------1665.0853 1665.0852 1665.0855 1665.0853 1665.0855 1665.0852 1665.0854 1665.0852 1665.0855

Frq_rest -------1665.3133 1665.3132 1665.3137 1665.2333 1665.2336 1665.3132 1665.3136 1665.2333 1665.2337

Vel(km/s) Factor Velorz Freqbcrest ------ -------- ----- --------15.943 0.99986311 0 1666.3804 15.959 0.99986308 0 1666.3804 15.8737 0.99986300 0 1665.4018 30.3498 0.99991112 30.2756 0.99991104 15.953 0.99986306 15.8737 0.99986297 30.3427 0.99991110 30.2718 0.99991101 0 0 0 0 0 0 1666.3804 1665.4018 1666.3804 1665.4018 1666.3804 1665.4018

velobsproj ---------41.0437 -41.0521 -41.0781 -26.6465 -26.6715 -41.0589 -41.0865 -26.6533 -26.6803

Inference: (1) The numb ers are self consistent within the ICOR and the WAPP. For a particular choice of the velo city frame (i.e. LSR or Helio), the velo city values derived from the sp ectra agree quite well regardless of the choice of velz (compare, for instance, the pairs: wlv1/wlz1 or ihv1/ihz1). (2) However, there is a discrepancy b etween the velo city values derived from ICOR and WAPP for the same selection of velo city frame and velz option. For instance, check the pair, ihz1/whz1. The difference in the velo city values is ab out 0.07 kms. There are two p ossibilities (or more?) which could give rise to this: (a) WAPPs calculate the Doppler correction for the middle of the scan, and ICOR for the b eginning.


(b) The magnitude of this error happ ens to b e ab out the same as the V-geo terms printed out on the screen at the time of observing.

DPS with WAPP: ------------Scan Frq_obs Frq_rest ------------------ON/OFF-T + ON/OFF-BP: dwhv1 dwhz1 1665.0854 1665.0852 1665.2337 1665.2336

Vel ------

Factor --------

Velorz Freqbcrest velobsproj ----- --------- ---------

30.2737 0.99991096 30.2737 0.99991091

0 0

1665.4018 1665.4018

-26.69529 -26.71185

OFF/ON-T + OFF/ON-BP: dwhv2 dwhz2 1665.0851 1665.0850 1665.2336 1665.2337 30.2737 0.99991080 30.2756 0.99911074 0 0 1665.4018 1665.4018 -26.743902 -26.762446

Inference: The velo city values are internally consistent, and matches with the wapp ONs in the table ab ove. However, as they are again a bit off from the ICOR-ON values (30.342730.2737=0.069) the same error might have crept in here as well via the combination of WAPP FITS headers and their interpretations in was2 routines OR the time of setting of the dopplar correction ?

DPS with ICOR: ON/OFF-T On/OFF-BP -----------------------------------Scan Frq_obs Frq_rest Vel Factor Velorz ------------------- ------ -------------dihv1 1665.0845 1665.2333 57.1323 0.99991067 26.782661 (30.3470 with correction, see dihz1 1665.0844 1665.2333

Freqbcrest velobsproj --------- --------1666.3804 0 below) 0

57.1473 0.99991061 26.800041 1666.3804 (30.3432 with correction)

Inference: The velo city values derived were completely wrong. However, the line is seen loud and clear, and the observing (Top o centric) frequency is correct, same as all the other entries b efore these. The correction we implemented was to move the header variable "velorz" to "velobspro j" with the sign reversed. i.e, velobspro j=-1.0*velorz I think, this is b ecause to run DPS with ICOR, Jeff tried to "fo ol" the dopset program. He did his own calculations to determine where the observing frequency should b e, and then told ICOR to just observe at that frequency considering it to b e a top o centric observation with velo city 0. Part2: Observing an extragalactic source at higher redshift Source = DLA toward OI363 at z=0.09103, observed with ICOR - just ON


(A WAPP counterpart of these didn't show the lines at all for no discernible reason at that time. The allo cated time ran out b efore we could investigate it fully. We reobserved them later) Scan ----OIhz1 OIhv1 Frq_obs -------1301.5577 1301.5575 Frq_rest Vel Factor -------- ------ -------1420.1619 27351.428 0.91649975 1420.1538 27351.667 0.91650518 Velorz ------0.09103 27290.107 Freqbcrest --------1420.4058 1420.4058 velobsproj ---------21.369560 -21.376945

Part2-A: On 8th March, we got 15 mins to cross check the velo city of this line using the WAPP (the non-detection of the 27th Feb observation was due to a wrong filter selection. This was corrected. Also, the redshift and velo city in the source catalog was up dated to the NED value, of 0.09118+/- 0.00001 (HI-Jayaram & nissim, GMRT) and 27335.0763 kms. The observation on 27th feb used z=0.09103 (and c*z). Scan ----owhz1 Frq_obs Frq_rest -------- -------1301.5577 1420.1619 Vel Factor Velorz Freqbcrest velobsproj ---------------------------- --------+14.97 0.91636463 9.118e-5 1420.4058 -27361.657 (27349.039 with correction A) -26.585374 -26.592914

owhv1 owhv2

1301.5443 1420.341 27349.128 0.91650518 27335.076 1420.4058 1301.5447 1420.3409 27349.064 0.91636459 27335.076 1420.4058

Inference: (1) The header entries in the FITS file for the WAPP+helio+Z option is not translated into was2 header correctly. "velorz" parameter is getting wrongly divided by 1000. Also, the parameter, "velobspro j" has the complete velo city vector into it, i.e. V el recessional + V elhelio (+V elgeo ?). This, by itself, is not a problem if "velorz" parameter is never used in was2's corfrq program which generates the velo city scale. The velo city scale will b e relative to cz .However, it may b e go o d to get these parameters set correctly. Correction A: Enter the velobspro j value from the next scan (owhv1) in the lo cation for velobspro j for the "owhz1" scan. (2) The literature value of Velo city/z for this DLA do esn't match with the value we derive ab ove, even though the ICOR and the WAPP values agree within 3 kms. We found an earlier measurement of this line in Lane et.al. (... taken at Arecib o using the ICOR, which gives a z-value 0.0912348 or velo city, 27351.505 kms.


Part-2B : Checking the higher z-DLA (0.221249 - Ar value of 2003+ICOR) towards this same source (10-Mar-2007) Scan Frq_obs Frq_rest ------------ -------oid2whz 1162.9788 1420.405 Vel Factor Velorz Freqbcrest velobsproj ---------------------------- --------0.2508 0.81876582 0.000221249 1420.4058 -66359.193 66329.1221 - when velobsproj=-24.8478 (as noted down during obs)

(2.i) Velo city of this line seems to b e matching with previous Ar measurement. This is the most accurate measurement in the literature. So, for the lower-z DLA, were the GMRT values wrong? (3) The 3kms discrepancy b etween ICOR and WAPP needs to b e explained. Part3 :A nearer source at z=0.06, 0116+319 (test on 15th Feb07) Scan Frq_obs Frq_rest -------- -----------whz 1339.1918 1419.7007 Vel Factor Velorz Freqbcrest velobsproj ------ ----------------------- --------+157.83 0.94331671 0.00006 1420.4058 -18014.336 (18151.1 - with Correction A described above) 18151.4 0.94331667 17987.547 1420.4058 -26.801776

whv

1339.1975

1419.7086

ihz ihv

1339.1922 1339.1932

1419.7057

18154 0.94331659 0.06 1543.8824 -25.308792 (+/-1.4) 1419.7007 18154 0.94332106 17987.547 1543.8824 -25.321032

Inference: (1) Comparing the velo city values b etween ICOR and WAPP, we see that there is still a difference of ab out 3 kms b etween the V option of WAPP and the ICOR velo cities. (2) The literature value for the velo city of this line is 18150 kms. These were 1987 observations at Arecib o by Mirab el et al. with the pre-upgrade telescop e/receiver/correlator and software. (ref: ApJ 352, L37, 1990) Overall Summary: · All mo des of ICOR and WAPP are internally consistent. · There is ab out 3kms difference b etween ICOR and WAPP velo city values. · WAPP FITS data translated to IDL by WAS2 routine generates two inconsistent header parameters in the .h.dop section. · WAPP p olarization channels are not lab eled in a IDL-routine compatible way so that was2-routines can translate these prop erly when observing in 1p ol/b oard mo de. · The exact velo cityz value for the z 0.09 DLA towards OI363 do esn't agree with the GMRT measurement which is adopted in NED as the standard at present.