J/A+A/678/A72 MeGaPluG survey. Lessons from the pilot study (Dokara+, 2023)
Metrewave Galactic Plane with the uGMRT (MeGaPluG) Survey:
Lessons from the pilot study.
Dokara R., Roy N., Menten K., Vig S., Dutta P., Beuther H., Pandian J.D.,
Rugel M., Rashid M., Brunthaler A.
<Astron. Astrophys. 678, A72 (2023)>
=2023A&A...678A..72D 2023A&A...678A..72D (SIMBAD/NED BibCode)
ADC_Keywords: Milky Way ; Radio continuum ; Interferometry
Keywords: surveys - radio continuum: ISM - ISM: supernova remnants -
ISM: H II regions - Galaxy: general - local interstellar matter
Abstract:
The advent of wide-band receiver systems on interferometer arrays enables
one to undertake high-sensitivity and high-resolution radio continuum
surveys of the Galactic plane in a reasonable amount of telescope time.
However, to date, there are only a few such studies of the first quadrant
of the Milky Way that have been carried out at frequencies below 1 GHz.
The Giant Metrewave Radio Telescope (GMRT) has recently upgraded its
receivers with wide-band capabilities (now called the uGMRT) and provides
a good opportunity to conduct high resolution surveys, while also being
sensitive to the extended structures.
We wish to assess the feasibility of conducting a large-scale snapshot
survey, the Metrewave Galactic Plane with the uGMRT Survey (MeGaPluG),
to simultaneously map extended sources and compact objects at an angular
resolution lower than 10'' and a point source sensitivity of
0.15mJy/beam.
We performed an unbiased survey of a small portion of the Galactic plane,
covering the W43/W44 regions (l=29°-35° and |b|<1°)
in two frequency bands: 300-500MHz and 550-750MHz. The 200MHz
wide-band receivers on the uGMRT are employed to observe the target field
in several pointings, spending nearly 14 minutes on each pointing in two
separate scans. We developed an automated pipeline for the calibration,
and a semi-automated self-calibration procedure is used to image each
pointing using multi-scale CLEAN and outlier fields.
We produced continuum mosaics of the surveyed region at a final common
resolution of 25'' in the two bands that have central frequencies of
400MHz and 650MHz, with a point source sensitivity better than 5mJy/beam.
A spectral index map is also obtained, which is helpful to distinguish
between thermal and nonthermal emission. Comparing with other surveys,
we validated the positions and flux densities obtained from our data.
We plan to cover a larger footprint of the Galactic plane in the near
future based on the lessons learnt from this study.
Description:
The two mosaics produced from this study, at their final common resolution
of 25 arcsecond, are provided here.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
list.dat 178 2 List of fits maps
fits/* . 2 Individual fits maps at 400MHz & 650MHz
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Byte-by-byte Description of file:list.dat
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Bytes Format Units Label Explanations
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1 A1 --- --- [G]
2- 10 F9.5 deg GLON Galactic longitude of center (J2000)
11- 19 F9.5 deg GLAT Galactic latitude of center (J2000)
21- 25 I5 --- Nx Number of pixels along X-axis
27- 30 I4 --- Ny Number of pixels along Y-axis
32- 50 A19 "datime" Obs.date Observation date
52- 57 F6.4 m lambda Observed wavelength
59- 64 I6 Kibyte size Size of FITS file
66- 86 A21 --- FileName Name of FITS file, in subdirectory fits
88-178 A91 --- Title Title of the FITS file
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Acknowledgements:
Rohit Dokara, rdokara(at)mpifr-bonn.mpg.de
(End) Patricia Vannier [CDS] 11-Aug-2023