Reduction with CASA. Kana Sugimoto, Erik Muller, and ALMA-J computing & EA-ARC science team (NAOJ)

Transcription

1 Single ge Dish Data a Reduction with CASA Kana Sugimoto, Erik Muller, and ALMA-J computing & EA-ARC science team (NAOJ) How to reduce and analyze observation data from single dish radio telescopes by CASA single dish tasks Contents CASA single-dish package (ASAP) overview of single dish data reduction steps CASA-SD tasks

2 Single dish CASA and ASAP Common Astronomy t Software Applications (CASA) a software to reduce and analyze astronomical observation data of both single dish and interferometer radio telescopes The single dish capabilities are developed mainly by NAOJ developers (~3FTE) + Single dish spectral analysis functions in CASA are based on ATNF Spectral Analysis Package (ASAP) originally developed in Australia Telescope National Facility (ATNF). + Many enhancements to analyze data from ALMA and the other telescopes such as NRO 45m, ASTE, GBT (partly), and ATNF.

3 Single dish data reduction steps example data import view data calibration flag baseline subtraction spectral data analysis convert data (internal format) list summary, plot spectra, and view numerical values according to observation strategy eliminate bad data line observation line width, statistics, + INT, etc. imaging view image & analyze create images momentum, +INT, etc.

4 Single dish data reduction with CASA data import view data calibration flag baseline subtraction spectral data analysis imaging view image & analyze sdsave, importasdm sdlist, sdplot, browsetable sdaverage sdflag sdbaseline sdfit, sdstat, sdaverage sdimaging viewer, etc.

5 17 CASA single dish tasks Output of taskhelp()

6 Single dish data reduction with CASA data import view data calibration flag baseline subtraction spectral data analysis imaging view image & analyze sdsave, importasdm sdlist, sdplot, browsetable sdaverage sdflag sdbaseline ( sdfit, sdstat, sdaverage) sdimaging viewer, etc.

7 Overview of sample data HST image of Antennae galaxies (NGC ) 4039) Observation ALMA CO(J=1-0) (Band 3) observation of the Antennae galaxies obs. date: 2011/08/06 5 x 5 map in 15 arcsec grids (center: J h01m d52m ) obs. Mode: position switching (15 Ants) (Credit: NASA, ESA, and the Hubble Heritage Team STScI/AURA- ESA/Hubble Collaboration).

8 Step 0! Import single dish package First of all, (1) load casapy > casapy and (2)import ASAP, the single dish reduction package in CASA CASA<>: asap_init() So far, you should explicitly import ASAP to CASA, but this step is supposed to be removed in the next release.

9 Single dish data reduction with CASA data import view data calibration flag baseline subtraction spectral data analysis imaging view image & analyze sdsave, importasdm, sd.splitant sdlist, sdplot, browsetable sdaverage sdflag sdbaseline sdfit, sdstat, sdaverage sdimaging viewer, etc.

10 CASA-SD and ALMA DATA formats ASDM ALMA/EVLA raw data xml + binary table data Contains more info. related to SB, calibration, hardware, etc. Cannot be viewed with CASA Measurement Set (MS) the internal data format of CASA Directory structure of binary tables (Main, ANTENNA, FIELD, ) Can store observations of multiple antennas. scantable the internal data format of ASAP Close to MS but more simple and single-dish friendly data model Stores data of single antenna

11 importasdm - import ALMA (SD) data singledish = False ocorr_mode = ao singledish=false ASDM MSMS singledish=true ASDM scantable (select an antenna ID) Note: An issue in singledish = True (CASA3.3) 3) Solution: ASDM MS scantable

12 sdsave - import / export data Transform data format input: scantable, MS, SDFITS (old), rpfits, NOSTAR, NEWSTAR output: scantable, MS, ASCII, SDFITS (old)

13 sd.splitant Usage: Imports the auto-correlation data in a Measurementset and convert it to scantables Data from different antennas are stored in separate scantables. CASA<>: sd.splitant(filename=msname, outprefix=prefix,overwrite=true/false) MSname: the name of input Measurementset prefix: the prefix of output file Output file names are, prefix.antennaname.asap, e.g., x141.pm01.asap

14 Single dish data reduction with CASA data import view data calibration flag baseline subtraction spectral data analysis imaging view image & analyze sdsave, importasdm, sd.splitant sdlist, sdplot, browsetable sdaverage sdflag sdbaseline sdfit, sdstat, sdaverage sdimaging viewer, etc.

15 sdlist list observation View scantable summary Output CASA logger/text file

16 sdlist list observation WVR load target

17 browsetable view scantable (table data)

18 browsetable view scantable (table data)

19 Baselined spectra (Antennae) sdplot plot scantable

20 sdplot plot scantable plottype = totalpower, azel, pointing row # total power R.A. Dec (FLS3a) time azimuth or elevation

21 Single dish data reduction with CASA data import view data calibration flag baseline subtraction spectral data analysis imaging view image & analyze sdsave, importasdm, sd.splitant sdlist, sdplot, browsetable sdaverage sdflag sdbaseline ( sdfit, sdstat, sdaverage) sdimaging viewer, etc.

22 Workaround for ALMA (filling the Tsys column) In general, ALMA observes target and hot/ambient loads in different spectral resolutions. You should transfer Tsys values calculated from load observations to target scans. General usage: CASA<>: from filltsys import * CASA<>: filltsys(filename, targetif, tsysif=tsysif, mode="linear") filltsys.py fills Tsys values of each channel of target scans (targetif) in a scantable (filename) by interpolating the values of load scans (targetif) in the time and frequency

23 sdaverage calibration

24 sdaverage calibration Observation IRC Calibrated

25 Single dish data reduction with CASA data import view data calibration flag baseline subtraction spectral data analysis imaging view image & analyze sdsave, importasdm, sd.splitant sdlist, sdplot, browsetable sdaverage sdflag sdbaseline ( sdfit, sdstat, sdaverage) sdimaging viewer, etc.

26 sdflag flag out bad data by channel by row ID by flux WARNING: The infile is overwritten by default! WARNING: The infile is overwritten by default! Version management: sdflagmanager task

27 sdflag flag out bad data Interactive=True Per spectrum flagging on the plot First flagged by the task parameter setting

28 Single dish data reduction with CASA data import view data calibration flag baseline subtraction spectral data analysis imaging view image & analyze sdsave, importasdm, sd.splitant sdlist, sdplot, browsetable sdaverage sdflag sdbaseline ( sdfit, sdstat, sdaverage) sdimaging viewer, etc.

29 sdbaseline baseline subtraction Subtracting continuum and bandpass features auto, list, or interact poly, cspline, or sinusoid

30 sdbaseline baseline subtraction interactive mask selection example (IRC+10216) draw rectangle add mask chans: LEFT-mouse delete mask chans: RIGHT-mouse current mask in yellow press Enter to finish selection

31 Single dish data reduction with CASA data import view data calibration flag baseline subtraction spectral data analysis imaging view image & analyze sdsave, importasdm, sd.splitant sdlist, sdplot, browsetable sdaverage sdflag sdbaseline ( sdfit, sdstat, sdaverage) sdimaging viewer, etc.

32 sdsave (again) convert data format Important! Convert data to MeasurementSet before imaging.

33 single dish MS Single dish data is stored in FOAT_DATA or DATA column

34 sdimaging single dish imaging Input: MeasurementSet Output: CASA image imsize i (pixel number) phase center cell (resolution)

35 viewer view CASA image

36 The other single dish tasks sdcal = sdaverage + sdsmooth + sdbaseline sdflagmanager save, restore, and list flag versions sdsmooth channel average spectra sdfit fit emission/absorption lines by Gaussian/Lorenzian sdstat calculate statistics of spectra sdtpimaging total power imaging (incl. scan noise subtraction) sdimprocess subtract scan noise sdscale scale spectra sdmath various arithmetic (+, -, *, /)operations on spectra sdcoadd merge scantables

37 Summary and Future Plans CASA single dish package has basic capabilities to reduce and analyze observation data from single dish radio telescopes including ACA-TP antennas. On going developments and future plans Scantable remodeling (more MS like data model) Speed up operations (performance improvements) Better plotting capabilities more astronomer friendly capabilities (user inputs helps)