Scripts for Imaging - Continuum:

• image_continuum.py # main script

• dictionary_mask.py # loads mask_dict

• dictionary_data.py # loads data_dict

• JvM_correction_casa6.py # MAPS JvM correction script (Czekala et al. 2021)

Visibility Data for Imaging - Continuum (obtained after step 3):

• ABAur_continuum.bin30s.ms

Links to download the resulting Continuum Images (shown below):

• Continuum image fits files (robust=0.5)

• Continuum image fits files (robust=1.0)

• Continuum image fits files (robust=1.5)

Continuum Images

Below are three sets of continuum images, made with varying Briggs robust weighting (robust=0.5, robust=1.0 and robust=1.5).

The images were cleaned non-interactively, using a circular mask of radius 3 arcsec centered on 04h55m45.8549s +30.33.03.733 (J2000). We used the Hogbom deconvolver. The cell size was set to 0.02 arcsec and the image size to 2048x2048 cells. We cleaned down to a threhold of 2x the rms noise, where the rms noise was measured in the dirty image within an annulus (inner radius 6 arcsec; outer radius 10 arcsec). All the parameter details you’d need to reproduce these images can be found in the CASA log files linked below.

Image made with Briggs robust = 0.5

Link to the CASA log file documenting the calls and parameters in this imaging run.

Key values in imaging process

Dirty Image RMS (uJy/beam)	CLEAN threshold (mJy/beam)	JvM Epsilon (unitless)	Residual Image Peak (mJy/beam)
50.20	0.1004	0.4566	0.0992

Properties of the resulting images

CLEAN Image	Peak Intensity (mJy/beam)	Disk Flux (mJy)	RMS noise (uJy/beam)	SNR
.image	2.13	102.9	13.34	159.5
.JvMcorr.image	2.09	89.9	6.11	342.6
.image.pbcor	2.14	103.1	17.37	123.1
.JvMcorr.image.pbcor	2.09	90.0	7.92	264.1

Peak intensity, disk flux (total flux within cleaning mask), measured RMS noise (within an annulus with inner and outer radii 4’’ and 11’’, respectively) and signal to noise ratio (column 2 / column 4) for each of the 4 image types. .image is the “regular” CLEAN image. .pbcor indicates primary beam corrected, and .JvMcorr indicates JvM corrected.

JvM-corrected and primary beam-corrected continuum image with robust parameter of 0.5. Left: Zoom-out with aggressive colorbar stretch to accentuate background noise. Right: Zoom-in with less aggressive colorbar stretch.

Left: Regular CLEAN image. Middle: Regular CLEAN image, primary beam corrected. Right: JvM corrected image (not primary beam corrected).

Image made with Briggs robust = 1.0

Link to the CASA log file documenting the calls and parameters in this imaging run.

Key values in imaging process

Dirty Image RMS (uJy/beam)	CLEAN threshold (mJy/beam)	JvM Epsilon (unitless)	Residual Image Peak (mJy/beam)
150.3	0.3006	0.3531	0.2998

Properties of the resulting images

CLEAN Image	Peak Intensity (mJy/beam)	Disk Flux (mJy)	RMS noise (uJy/beam)	SNR
.image	4.47	111.65	24.24	184.2
.JvMcorr.image	4.30	89.86	8.45	509.1
.image.pbcor	4.45	111.84	31.33	142.0
.JvMcorr.image.pbcor	4.34	89.96	11.04	393.5

Peak intensity, disk flux (total flux within cleaning mask), measured RMS noise (within an annulus with inner and outer radii 4’’ and 11’’, respectively) and signal to noise ratio (column 2 / column 4) for each of the 4 image types. .image is the “regular” CLEAN image. .pbcor indicates primary beam corrected, and .JvMcorr indicates JvM corrected.

JvM-corrected and primary beam-corrected continuum image with robust parameter of 1.0. Left: Zoom-out with aggressive colorbar stretch to accentuate background noise. Right: Zoom-in with less aggressive colorbar stretch.

Left: Regular CLEAN image. Middle: Regular CLEAN image, primary beam corrected. Right: JvM corrected image (not primary beam corrected).

Image made with Briggs robust = 1.5

Link to the CASA log file documenting the calls and parameters in this imaging run.

Key values in imaging process

Dirty Image RMS (uJy/beam)	CLEAN threshold (mJy/beam)	JvM Epsilon (unitless)	Residual Image Peak (mJy/beam)
253.2	0.5064	0.3383	0.5064

Properties of the resulting images

CLEAN Image	Peak Intensity (mJy/beam)	Disk Flux (mJy)	RMS noise (uJy/beam)	SNR
.image	5.94	117.38	41.83	142.1
.JvMcorr.image	5.73	90.13	14.13	405.6
.image.pbcor	5.95	117.60	54.10	110.0
.JvMcorr.image.pbcor	5.76	90.25	18.34	314.2

Peak intensity, disk flux (total flux within cleaning mask), measured RMS noise (within an annulus with inner and outer radii 4’’ and 11’’, respectively) and signal to noise ratio (column 2 / column 4) for each of the 4 image types. .image is the “regular” CLEAN image. .pbcor indicates primary beam corrected, and .JvMcorr indicates JvM corrected.

JvM-corrected and primary beam-corrected continuum image with robust parameter of 1.5. Left: Zoom-out with aggressive colorbar stretch to accentuate background noise. Right: Zoom-in with less aggressive colorbar stretch.

Left: Regular CLEAN image. Middle: Regular CLEAN image, primary beam corrected. Right: JvM corrected image (not primary beam corrected).