Methanol masers at 6.7 GHz are the brightest of class II methanol masers and have been found exclusively towards massive star-forming regions. These masers can thus be used as a unique tool to probe the early phases of massive star formation. We present here a study of the spectral energy distributions of 320 6.7 GHz methanol masers chosen from the Methanol Multibeam catalogue, which fall in the Hi-GAL range (|l| ≤ 60°, |b| ≤ 1°). The spectral energy distributions are constructed from 870 to 70 µm using data from the ATLASGAL and Hi-GAL surveys. The emission from cold dust is modelled by a single grey body component fit. We estimate the clump properties such as mass, far-infrared luminosity, and column density using the best-fitting parameters of the SED fits. Considering the Kauffman criteria for massive star formation, we find that all but a few maser hosts have the potential to harbour at least one high-mass star. The physical properties of the methanol maser hosts are also discussed. The evolutionary stages of 6.7 GHz maser sources, explored using the mass luminosity diagram, suggest that they are predominantly associated with high-mass stars with the majority being in the accretion phase. However, we observe a small number of sources that could possibly be related to intermediate- or low-mass stars.

Abstract. Measurement of Cosmic Microwave Background (CMB) anisotropies has been playing a lead role in precision cosmology by providing some of the tightest constrains on cosmological models and parameters. However, precision can only be meaningful when all major systematic effects are taken into account. Non-circular beams in CMB experiments can cause large systematic deviation in the angular power spectrum, not only by modifying the measurement at a given multipole, but also introducing coupling between different multipoles through a deterministic bias matrix. Here we add a mechanism for emulating the effect of a full bias matrix to the Planck likelihood code through the parameter estimation code SCoPE. We show that if the angular power spectrum was measured with a non-circular beam, the assumption of circular Gaussian beam or considering only the diagonal part of the bias matrix can lead to huge error in parameter estimation. We demonstrate that, at least for elliptical Gaussian beams, use of scalar beam window functions obtained via Monte Carlo simulations starting from a fiducial spectrum, as implemented in Planck analyses for example, leads to only few percent of sigma deviation of the best-fit parameters. However, we notice more significant differences in the posterior distributions for some of the parameters, which would in turn lead to incorrect errorbars. These differences can be reduced, so that the errorbars match within few percent, by adding an iterative reanalysis step, where the beam window function would be recomputed using the best-fit spectrum estimated in the first step.

6.7 GHz methanol masers are the brightest of class II methanol masers that are regarded as excellent signposts in the formation of young massive stars. We present here a molecular line study of 68 6.7 GHz methanol maser hosts chosen from the Methanol Multibeam survey catalogue, which have MALT90 data available. We performed (1) pixel-by-pixel study of 9 methanol maser sources that have high signal-to-noise ratio and (2) statistical study taking into account the entire 68 sources. We estimated the molecular column densities and abundances of N2H+(1–0), HCO+(1–0), HCN(1–0), and HNC(1–0) lines. The derived abundances are found to be in congruence with the typical values found towards high-mass star-forming regions. We derived the column density and abundance ratios between these molecular species as an attempt to unveil the evolutionary stage of methanol maser sources. We found the column density and abundance ratio of HCN to HNC to increase and that of N2H+ to HCO+ to decline with source evolution, as suggested by the chemical models. The HCN/HNC, N2H+/HCO+, HNC/HCO+, and N2H+/HNC ratios of the methanol maser sources are consistent with them being at a later evolutionary state than quiescent phase and possibly protostellar phase, but at an earlier stage than $\mathrm{H}\, \small {{\rm II}}$ regions and photo-dominated regions.

Methanol masers at 6.7 GHz are the brightest of class II methanol masers and have been found exclusively towards massive star forming regions. These masers can thus be used as a unique tool to probe the early phases of massive star formation. We present here the SED studies of 284 methanol masers chosen from the MMB catalogue, which falls in the Hi-GAL range (|l| ≤ 60°, |b| ≤ 1°). The masers are studied using the ATLASGAL, MIPSGAL and Hi-GAL data at wavelengths ranging from 24−870 micrometers. A single grey body component fit was used to model the cold dust emission whereas the emission from the warm dust is modelled by a black body. The clump properties such as isothermal mass, FIR luminosity and MIR luminosity were obtained using the best fit parameters of the SED fits. We discuss the physical properties of the sources and explore the evolutionary stages of the sources having 6.7 GHz maser emission in the timeline of high mass star formation.