ATCA 3mm Mosaic Data Products

This site provides the HCN and HCO+ mosaics for LMC clouds mapped with ATCA from 2006 to 2009.  The data for most of these clouds were previously presented by Seale et al. (2012), but we have re-processed the data with a single calibration script and re-generated a set of moment images. Unless otherwise noted, all data reduction was performed in the MIRIAD package.

Signal and Noise Cubes

Cubes and images are provided in gzipped FITS format.  These cubes have been CLEANed over an unbiased region (the field of view which extends to where the RMS noise reaches 2 times its minimum value).  The cubes were made with 0.4 km/s channels (except for N159S, which was observed with 1 MHz channels so cubes are made at 4 km/s resolution) with a typical velocity range of 20-30 km/s.  They have been primary gain corrected and masked beyond the 33% sensitivity region.

Moment Maps

To generate the moment maps, the signal and noise cubes were uncompressed and unpacked into a single directory.

The IDL code is freely available on Github: https://github.com/tonywong94/idl_mommaps.  The basic task to run is makemom.pro, which has a number of parameters, as can be seen in the header of the program.  Currently two sets of moment maps are generated using two different calls to makemom:

makemom,'$outname.$freq2.cmmsk.fits',errfile='$outname.$freq2.cmnse.fits',baseroot='$outname_hcop_dil',thresh=3,edge=2,/PVMOM0

makemom,'$outname.$freq2.cmmsk.fits',errfile='$outname.$freq2.cmnse.fits',baseroot='$outname_hcop_smo',thresh=3.5,edge=2,smopar=[9,5],/PVMOM0

The first, "dilated" set of maps, with filenames of the form n113_hcop_dil.mom0.fits, uses a masking approach to exclude noise before taking moments. The mask is created by starting at 3-sigma (or greater) peaks in the cube and expanding down to the surrounding 2-sigma contour.

The second, "smoothed" set of maps, with filenames of the form n113_hcop_smo.mom0.fits, uses pre-smoothing to enhance the signal to noise before creating a mask. The cube is spatially smoothed to a final resolution of 9" x 9" and also smoothed in velocity with a 5 km/s FWHM Gaussian kernel. Then the mask is created by starting at 3.5-sigma (or greater) peaks in the smoothed cube and expanding down to the surrounding 2-sigma contour. Then the mask is applied to the original, unsmoothed data cube.

The tar files below include FITS files generated using both approaches, with uncertainty maps having file tags like emom0.  Moments 0, 1, and 2 correspond to integrated intensity, mean velocity, and velocity dispersion respectively; also provided is the peak brightness within the mask.  We recommend using the smoothed mask for moment 0 because it will capture low-level flux better.  However, since higher moments are strongly influenced by the mask, the dilated mask is recommended to estimate moments 1 and 2 at the full resolution of the data.

The csh scripts to image the data and generate the moment maps can be found in this directory.