Single Dish Data S g e s a a Reduction with CASAKana Sugimoto, Erik Muller, and ALMA-J

computing & EA-ARC science team (NAOJ)

How to “reduce” and analyze observation data fromsingle dish radio telescopes by CASA single dish tasks

ContentsContentsCASA single-dish package (ASAP)overview of single dish data reduction stepsoverview of single dish data reduction stepsCASA-SD tasks

CASA SD tutorial and workshop @NAASC 2011/12/7

Single dish CASA and ASAP

C A t S ft A li ti (CASA) Common Astronomy Software Applications (CASA) a software to reduce and analyze astronomical observation data of both single dish and interferometer radio telescopesg p

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 ATNF Spectral Analysis Package (ASAP) originally developed in

Australia Telescope National Facility (ATNF).

+ Many enhancements to analyze data from ALMA and the + Many enhancements to analyze data from ALMA and the

other telescopes such as NRO 45m, ASTE, GBT (partly), and

ATNF ATNF.

CASA SD tutorial and workshop @NAASC 2011/12/7

Single dish data reduction steps example

data import … convert data (internal format)

view data … list summary, plot spectra, and view numerical values

fl

calibration … according to observation strategy

baseline subtraction

flag

… line observation

… eliminate bad data

spectral data analysis

baseline subtraction

… line width, statistics, + INT, etc.

… line observation

imaging … create images

view image & analyze … momentum, +INT, etc.CASA SD tutorial and workshop @NAASC 2011/12/7

Single dish data reduction with CASA

data import … sdsave, importasdm

view data … sdlist, sdplot, browsetable

fl

calibration

dfl

… sdaverage

baseline subtraction

flag

… sdbaseline

… sdflag

spectral data analysis

baseline subtraction

… sdfit, sdstat, sdaverage

… sdbaseline

imaging … sdimaging

view image & analyze … viewer, etc.CASA SD tutorial and workshop @NAASC 2011/12/7

17 CASA single dish tasks

Output of taskhelp()

CASA SD tutorial and workshop @NAASC 2011/12/7

Single dish data reduction with CASA

data import … sdsave, importasdm

view data … sdlist, sdplot, browsetable

fl

calibration

dfl

… sdaverage

baseline subtraction

flag

… sdbaseline

… sdflag

spectral data analysis

baseline subtraction

(… sdfit, sdstat, sdaverage)

… sdbaseline

imaging … sdimaging

view image & analyze … viewer, etc.CASA SD tutorial and workshop @NAASC 2011/12/7

Overview of sample data

HST image of Antennae galaxies (NGC 4038 4039)(NGC 4038-4039)

ObservationALMA CO(J=1-0) (Band 3) observation ofthe Antennae galaxiesg• obs. date: 2011/08/06• 5’ x 5’ map in 15 arcsec grids (center:J2000 12h01m53.170 -18d52m37.920‘))• obs. Mode: position switching (15 Ants)

(Credit: NASA, ESA, and the Hubble Heritage Team STScI/AURA-Heritage Team STScI/AURAESA/Hubble Collaboration).

CASA SD tutorial and workshop @NAASC 2011/12/7

Step 0! Import single dish package

First of all

> casapy

First of all, (1) load casapy

> casapy

and

CASA<>: asap init()

(2)import ASAP, the single dish reduction package in CASA

S f h ld li i l i S C S

CASA<>: asap_init()

So far, you should explicitly import ASAP to CASA,

but this step is supposed to be removed in the next release.

CASA SD tutorial and workshop @NAASC 2011/12/7

Single dish data reduction with CASA

data import … sdsave, importasdm, sd.splitant

view data … sdlist, sdplot, browsetable

fl

calibration

dfl

… sdaverage

baseline subtraction

flag

… sdbaseline

… sdflag

spectral data analysis

baseline subtraction

… sdfit, sdstat, sdaverage

… sdbaseline

imaging … sdimaging

view image & analyze … viewer, etc.CASA SD tutorial and workshop @NAASC 2011/12/7

CASA-SD and ALMA DATA formats

ASDM ALMA/EVLA raw dataASDM … ALMA/EVLA raw data• xml + binary table data• Contains more info. related to SB, calibration, hardware, etc.

C t b i d ith C S• 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.

bl th i t l d t f t f Sscantable … the internal data format of ASAP• Close to MS but more simple and single-dish friendly data model• Stores data of single antenna

CASA SD tutorial and workshop @NAASC 2011/12/7

importasdm - import ALMA (SD) data

singledish=False ASDM MS

singledish = False… ASDM→MS

singledish=Trueocorr mode = “ao” … ASDM

→scantable(select an

ocorr_mode = “ao”

(antenna ID)

Note:Note:An issue in singledish = True (CASA3 3)(CASA3.3)Solution:ASDM → MS → scantable

CASA SD tutorial and workshop @NAASC 2011/12/7

scantable

sdsave - import / export data

Transform data format• input: scantable, MS, SDFITS (old), rpfits, NOSTAR, NEWSTAR • output: scantable , MS, ASCII , SDFITS (old)

CASA SD tutorial and workshop @NAASC 2011/12/7

sd.splitant

Imports the auto-correlation data in a Measurementset and convert it to scantablesData from different antennas are stored in separate scantables.

CASA<>: sd splitant(filename=MSname

Usage:

CASA<>: sd.splitant(filename MSname, outprefix=prefix,overwrite=True/False)

MSname: the name of input Measurementsetprefix: the prefix of output file

Output file names are, prefix.antennaName.asap, e.g., ’x141.PM01.asap’

CASA SD tutorial and workshop @NAASC 2011/12/7

Single dish data reduction with CASA

data import … sdsave, importasdm, sd.splitant

view data … sdlist, sdplot, browsetable

fl

calibration

dfl

… sdaverage

baseline subtraction

flag

… sdbaseline

… sdflag

spectral data analysis

baseline subtraction

… sdfit, sdstat, sdaverage

… sdbaseline

imaging … sdimaging

view image & analyze … viewer, etc.CASA SD tutorial and workshop @NAASC 2011/12/7

sdlist – list observation

View scantable summaryView scantable summary

Output CASA logger/text fileOutput → CASA logger/text file

CASA SD tutorial and workshop @NAASC 2011/12/7

sdlist – list observation

← WVR← load← target

CASA SD tutorial and workshop @NAASC 2011/12/7

browsetable – view scantable (table data)

CASA SD tutorial and workshop @NAASC 2011/12/7

browsetable – view scantable (table data)

CASA SD tutorial and workshop @NAASC 2011/12/7

sdplot – plot scantableBaselined spectra (Antennae)

CASA SD tutorial and workshop @NAASC 2011/12/7

sdplot – plot scantableplottype = ‘totalpower’, ‘azel’, ‘pointing’

row # – total power R.A. – Dec (FLS3a)p ( )

time – azimuth or elevation

CASA SD tutorial and workshop @NAASC 2011/12/7

Single dish data reduction with CASA

data import … sdsave, importasdm, sd.splitant

view data … sdlist, sdplot, browsetable

fl

calibration

dfl

… sdaverage

baseline subtraction

flag

… sdbaseline

… sdflag

spectral data analysis

baseline subtraction

(… sdfit, sdstat, sdaverage)

… sdbaseline

imaging … sdimaging

view image & analyze … viewer, etc.CASA SD tutorial and workshop @NAASC 2011/12/7

Workaround for ALMA (filling the Tsys column)

In general, ALMA observes target and hot/ambient loads in g , g /different spectral resolutions. You should transfer Tsys values calculated from load observations to target scans.

CASA<>: from fillTsys import *

General usage:

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

CASA SD tutorial and workshop @NAASC 2011/12/7

sdaverage – calibration

CASA SD tutorial and workshop @NAASC 2011/12/7

sdaverage – calibration

CalibratedObservationIRC+10216

CASA SD tutorial and workshop @NAASC 2011/12/7

Single dish data reduction with CASA

data import … sdsave, importasdm, sd.splitant

view data … sdlist, sdplot, browsetable

fl

calibration

dfl

… sdaverage

baseline subtraction

flag

… sdbaseline

… sdflag

spectral data analysis

baseline subtraction

(… sdfit, sdstat, sdaverage)

… sdbaseline

imaging … sdimaging

view image & analyze … viewer, etc.CASA SD tutorial and workshop @NAASC 2011/12/7

sdflag – flag out bad data

by channelby channel

by row IDby flux

WARNING: The infile is overwritten by default!WARNING: The infile is overwritten by default!Version management: sdflagmanager task

CASA SD tutorial and workshop @NAASC 2011/12/7

sdflag – flag out bad data

Interactive=True

Per spectrum Per spectrum flagging on the plot

First flagged by the task parameter setting

CASA SD tutorial and workshop @NAASC 2011/12/7

Single dish data reduction with CASA

data import … sdsave, importasdm, sd.splitant

view data … sdlist, sdplot, browsetable

fl

calibration

dfl

… sdaverage

baseline subtraction

flag

… sdbaseline

… sdflag

spectral data analysis

baseline subtraction

(… sdfit, sdstat, sdaverage)

… sdbaseline

imaging … sdimaging

view image & analyze … viewer, etc.CASA SD tutorial and workshop @NAASC 2011/12/7

sdbaseline – “baseline” subtraction Subtracting continuum and bandpass features

‘auto’, ‘list’, or ‘interact’or ‘interact’

‘ l ’ ‘ li ’ ‘poly’, ‘cspline’, or ‘sinusoid’

CASA SD tutorial and workshop @NAASC 2011/12/7

sdbaseline – “baseline” subtraction

interactive mask selection example (IRC+10216)

draw rectangledraw rectangle• add mask chans:

LEFT-mousedelete mask chans:• delete mask chans:

RIGHT-mousecurrent mask in

llyellow

press “Enter” to finish selection

CASA SD tutorial and workshop @NAASC 2011/12/7

Single dish data reduction with CASA

data import … sdsave, importasdm, sd.splitant

view data … sdlist, sdplot, browsetable

fl

calibration

dfl

… sdaverage

baseline subtraction

flag

… sdbaseline

… sdflag

spectral data analysis

baseline subtraction

(… sdfit, sdstat, sdaverage)

… sdbaseline

imaging … sdimaging

view image & analyze … viewer, etc.CASA SD tutorial and workshop @NAASC 2011/12/7

sdsave (again) – convert data format

Important!Important!Convert data to MeasurementSet before imaging.

CASA SD tutorial and workshop @NAASC 2011/12/7

single dish MS

Single dish data is stored in FOAT_DATA or DATA column

CASA SD tutorial and workshop @NAASC 2011/12/7

sdimaging – single dish imagingInput: MeasurementSet Output: CASA image

i i ( i l b )imsize (pixel number)

phase center

cell (resolution)

phase center

CASA SD tutorial and workshop @NAASC 2011/12/7

viewer – view CASA image

CASA SD tutorial and workshop @NAASC 2011/12/7

The other single dish tasks

sdcal = sdaverage + sdsmooth + sdbaselinesdcal sdaverage sdsmooth sdbaseline

sdflagmanager … save, restore, and list flag versions

sdsmooth channel average spectrasdsmooth … channel average spectra

sdfit … fit emission/absorption lines by Gaussian/Lorenzian

sdstat calculate statistics of spectrasdstat … calculate statistics of spectra

sdtpimaging … total power imaging (incl. scan noise

b i ) subtraction)

sdimprocess … subtract scan noise

sdscale … scale spectra

sdmath … various arithmetic (+, -, *, /)operations on spectra

sdcoadd … merge scantablesCASA SD tutorial and workshop @NAASC 2011/12/7

Summary and Future Plans

CASA single dish package has basic capabilities CASA single dish package has basic capabilities to reduce and analyze observation data from single dish radio telescopes including ACA-TP 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)• Speed up operations (performance improvements)• Better plotting capabilities• more astronomer friendly capabilities (user inputs more astronomer friendly capabilities (user inputs helps)

CASA SD tutorial and workshop @NAASC 2011/12/7