CASA Tutorial 1. For ALMA Archival Data

Transcription

1 CASA Tutorial 1 For ALMA Archival Data

2 Outline - Using ALMA archival data you have searched for - SV data (TWhydra), one archival project - ALMA Data structures. - ALMA Data inspection. - Preparation for hands-on session - Make sure everyone has your own directory in the linux server.

3 More Examples in ALMAguides - SV data - Good for learning calibration step by step manually. - But, a little bit out of date (versions, etc.).

4 ALMA Data Structure Measurement Set (MS): ALMA data = «measurment set».ms directory containing visibilities+ meta data (sources [name, coordinates],antennas [position,diameter], frequency setup...etc. CASA <28>: cd /home/star/workshop/casa_tutorial/demo0629/alma_practice CASA <29>: ls Meta data (Tables): similar to the concept of header in FITS. CASA <29>: ls TWHydra_calibrated.ms CASA <31>: browsetable(tablename='twhydra_calibrated.ms/antenna/')

5 ALMA Data Structure Observing Sequence of standard interferometric observation (different colors represent difference field (source)) Ant 1-Ant 2 Scan 2 Scan 1 One integration =10 second Amplitude Time 6 integration = 1 scan =?second Integration: a record a one time for each baseline. Scan: a set of consecutive integrations toward the same source.

6 ALMA Data Structure Measurement Set contains 3 columns 1. Data : ''raw'' data (not calibrated) 2. Corrected : calibrated data (from calibration) 3. Model : model set (from calibration) From archival, you will have corrected data by default if you don t download the raw data.

7 Information of observations: listobs() Try alias: CASA <61> msname='twhydra_calibrated' CASA <62>: listobs(vis=msname+'.ms',listfile='twhydra.listobs') CASA <63>:!more twhydra.listobs Field, Antenna, Spectral information, integration, scan, etc. ID (number) & Name (string) are identical. e.g. antenna name and ID (index from 0).

8 Information of observations - antenna position CASA<3> plotants(vis=msname+'.ms', figfile='ant') X (meter), Y (meter) Name ID DV04 0 DV06 1

9 Information of observations - uv coverage Plotting UV coverage X (klambda), Y (klambda) CASA<4> plotuv(vis=msname+'.ms')

10 Data Inspection: plotms() Task for plotting and interacting with visibility data. CASA <62>: default plotms CASA <63>: help plotms (hit q to quit) Interactive mode CASA <63>: plotms Try: 1. Control panel 2. Zoom in, zoom out 3. Locate the data 4. X-axis: frequency, uvdistance, time Y-axis: amplitude, phase

11 More Data Inspection on ALMA Archive data

12 ALMA Archival Data Inspection - Pipeline calibration - Manual calibration In principle, users don t need to calibrate the data again. All the ALMA archival data is QA2 passed (quality ensured). However, users might want to make customized images by themselves (tomorrow s tutorial). It is still important to double check the calibration, though. Questions: How to check the calibration and data quality?

13 Inspecting Your Downloading Data structures: <Project code>/sg_ouss_id/group_ouss_id/member_ouss_id/<your data is here> alma_demo]$ cd /home/star/workshop/casa_tutorial/demo0629/alma_demo alma_demo]$ ls S S_uid A001_X12a_X1e4_001_of_001.tar S_uid A002_X960614_X3325.asdm.sdm.tar downloadrequest sh alma_demo]$ cd S/science_goal.uid A001_X12a_X1e2/group.uid A001_X12a_X1e3/member.uid A001_X12a_X1e4/ member.uid A001_X12a_X1e4]$ ls calibrated calibration log product qa raw README script

14 Data Packaging (Directory Structure) The tar files of a delivery contain scripts and logs, calibration tables and representative images, as well as one or more README files. log. The set of log les generated by CASA during the calibration. product. FITS image cubes of (a selection of) frequency channels in the measurement set, ms qa. Several diagnostic plots, related to the data calibration. script. All the scripts used for the data calibration. calibration. All the calibration tables (and plots) (The calibration directory contains subdirectories for each EB (named*.calibration and*.calibration.plots) calibrated. The calibrated measurement set(s) of the EB(s). These are named *.split.cal. raw. The measurement set(s) after a basic a-priori calibration (antenna positions, Tsys, and PWV). These are named *.split. README. Some useful information.

15 Pipeline Calibration Data Process (for reference)

16 S/science_goal.uid A001_X12a_X1e2/group.uid A001_X12a_X1e3/member. uid A001_X12a_X1e4% casa422pl --pipeline (but I actually use casa431pl --pipeline) CASA <1>: ls casapy log log/ qa/ README calibration/ ipython log product/ raw/ script/ CASA <2>: cd script/ CASA <3>: ls casa_piperestorescript.py* PPR_uid A001_X12a_X1e5.xml* scriptforimaging.py casa_pipescript.py* scriptforfluxcalibration.py* scriptforpi.py* CASA <4>: execfile('scriptforpi.py') After 20 min...waiting script to restore the solution and get calibrated MS file CASA <5>: ls calibrated/ casapy log log/ qa/ README calibration/ ipython log product/ raw/ script/ CASA <6>: ls calibrated/ products@ rawdata/ uid A002_X960614_X3325.ms.split.cal/ working/ CASA <49>:!du -hs uid A002_X960614_X3325.ms.split.cal 11G uid A002_X960614_X3325.ms.split.cal

17 Data Inspection of the Calibrated MS

18 Calibrated MS README cd /home/star/workshop/casa_tutorial/demo0629/alma_demo/ S/science_goal.uid A001_X12a_X1e2/group.uid A001_X12a_X1e3/member. uid A001_X12a_X1e4/calibrated uid A002_X960614_X3325.ms.split.cal

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23 Hands-on Tutorial

24 Pipeline reports

25 Reducing the data size CASA <80> cd /home/star/workshop/casa_tutorial/demo0629/alma_practice CASA <81> ls split.ms.ch30.cal/ TWHydra_calibrated.ms/ twhydra.listobs Already binned 30 channels to reduce the data size. You can use this MS for hands-on practicing. CASA<82> listants(vis= split.ms.ch30.cal/ )

26 listobs() Step 1: listobs(vis= split.ms.ch30.cal/ ) Q: Check message window and answer the ID, Name ID J Uranus ngc_1614

27 listobs() Step 1: listobs(vis= split.ms.ch30.cal/ ) Q1: Check message window and answer the ID, Field ID (ans) J Uranus 2 ngc_1614 4,5,6 Q2: spectral window IDs? Ans. 0, 1, 2,3

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30 Plotms()

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