A derivation of the free-free emission on the Galactic plane between l=20 and 44 degrees

Abstract

We present the derivation of the free-free emission on the Galactic plane between l=20 and 44 degrees and |b| < 4 degrees, using Radio Recombination Line (RRL) data from the HI Parkes All-Sky Survey (HIPASS). Following an upgrade on the RRL data reduction technique, which improves significantly the quality of the final RRL spectra, we have extended the analysis to three times the area covered in Alves et al. (2010). The final RRL map has an angular resolution of 14.8 arcmin and a velocity resolution of 20 km/s. A map of the electron temperature (Te) of the ionised gas is derived for the area under study using the line and continuum data from the present survey. The mean Te on the Galactic plane is 6000 K. The first direct measure of the free-free emission is obtained based on the derived Te map. Subtraction of this thermal component from the total continuum leaves the first direct measure of the synchrotron emission at 1.4 GHz. A narrow component of width 2 degrees is identified in the latitude distribution of the synchrotron emission. We present a list of HII regions and SNRs extracted from the present free-free and synchrotron maps, where we confirm the synchrotron nature of three objects: G41.12-0.21, G41.15+0.39 and G35.59-0.44. We also identify a bright (42 Jy) new double radio galaxy, J1841-0152, previously unrecognised owing to the high optical extinction in the region. The latitude distribution for the RRL-derived free-free emission shows that the WMAP Maximum Entropy Method (MEM) is too high by ~ 50 per cent, in agreement with other recent results. The extension of this study to the inner Galaxy region l=-50 to 50 degrees will allow a better overall comparison of the RRL result with WMAP.

17 pages, 15 figures. Submitted to MNRAS

References in corpus (4)

• The VLA Galactic Plane Survey
• The Green Bank Telescope HII Region Discovery Survey II. The Source Catalog
• Planck early results. XXI. Properties of the interstellar medium in the Galactic plane
• Connecting Synchrotron, Cosmic Rays, and Magnetic Fields in the Plane of the Galaxy

Cited by in corpus (42)

• Development of the Model of Galactic Interstellar Emission for Standard Point-Source Analysis of Fermi Large Area Telescope Data
• Science with the Murchison Widefield Array
• A Herschel [CII] Galactic plane survey III: [CII] as a tracer of star formation
• Planck 2015 results. XXV. Diffuse low-frequency Galactic foregrounds
• The HIPASS survey of the Galactic plane in Radio Recombination Lines
• A New 1.4GHz Radio Continuum Map of the Sky South of Declination +25 deg
• Planck intermediate results. XIV. Dust emission at millimetre wavelengths in the Galactic plane
• Cosmic rays, gas and dust in nearby anticentre clouds : I -- CO-to-H2 conversion factors and dust opacities
• QUIJOTE Scientific Results. II. Polarisation Measurements of the Microwave Emission in the Galactic molecular complexes W43 and W47 and supernova remnant W44
• Radio data and synchrotron emission in consistent cosmic ray models
• Impact of Simulated 1/f Noise for HI Intensity Mapping Experiments
• A multi-wavelength investigation of RCW175: an HII region harboring spinning dust emission
• A Green Bank Telescope Survey of Large Galactic HII Regions
• Planck intermediate results. XXV. The Andromeda Galaxy as seen by Planck
• Planck intermediate results. XXXIV. The magnetic field structure in the Rosette Nebula
• C-Band All-Sky Survey: A First Look at the Galaxy
• The Large-scale ISM of SS433/W50 Revisited
• HII Region Ionization of the Interstellar Medium: A Case Study of NGC 7538
• Planck intermediate results. XII: Diffuse Galactic components in the Gould Belt System
• Planck intermediate results. XXIII. Galactic plane emission components derived from Planck with ancillary data
• SIGGMA: A Survey of Ionized Gas in the Galaxy, Made with the Arecibo Telescope
• LOFAR 150-MHz observations of SS 433 and W 50
• Survey of Ionized Gas of the Galaxy, Made with the Arecibo telescope (SIGGMA): Inner Galaxy Data Release
• Ionization Profiles of Galactic HII Regions
• Untangling the Recombination Line Emission from HII Regions with Multiple Velocity Components
• COMAP Early Science: VI. A First Look at the COMAP Galactic Plane Survey
• The C-Band All-Sky Survey (C-BASS): Template Fitting of Diffuse Galactic Microwave Emission in the Northern Sky
• The C-Band All-Sky Survey (C-BASS): Constraining diffuse Galactic radio emission in the North Celestial Pole region
• Thermal and non-thermal emission in the Cygnus X region
• Galactic synchrotron emissivity measurements between 250° < l < 355° from the GLEAM survey with the MWA
• Detailed study of the microwave emission of the supernova remnant 3C 396
• Diffuse Ionized Gas in the Milky Way Disk
• Low frequency measurements of synchrotron absorbing HII regions and modeling of observed synchrotron emissivity
• A 4-6 GHz Radio Recombination Line Survey in the Milky Way
• Recent developments in astrophysical and cosmological exploitation of microwave surveys
• Thermal emission from the amorphous dust: An alternative possibility of the origin of the anomalous microwave emission
• The pros and cons of the inversion method approach to derive 3D dust emission properties of the ISM: the Hi-GAL field centred on (l,b)=(30${}^{\circ }$,0${}^{\circ }$)
• Observations of Anomalous Microwave Emission from HII regions
• QUIJOTE scientific results -- XVIII. New constraints on the polarization of the Anomalous Microwave Emission in bright Galactic regions: $\rho$\,Ophiuchi, Perseus and W43
• New supernova remnant candidates in the LOFAR Two Metre Sky Survey
• A Monte Carlo Implementation of Galactic Free-Free Emission for the EoR Foreground Models
• Removing systematics-induced 21-cm foreground residuals by cross-correlating filtered data