Radio and infrared study of southern H II regions G346.056−0.021 and G346.077−0.056

Abstract

Aims. We present a multiwavelength study of two southern Galactic H II regions G346.056−0.021 and G346.077−0.056 which are located at a distance of 10.9 kpc. The distribution of ionized gas, cold and warm dust and the stellar population associated with the two H II regions are studied in detail using measurements at near-infrared, mid-infrared, far-infrared, submillimeter and radio wavelengths. Methods. The radio continuum maps at 1280 and 610 MHz were obtained using the Giant Metrewave Radio Telescope to probe the ionized gas. The dust temperature, column density and dust emissivity maps were generated by using modified blackbody fits in the far-infrared wavelength range 160 -500 µm. Various near-and mid-infrared colour and magnitude criteria were adopted to identify candidate ionizing star(s) and the population of young stellar objects in the associated field. Results. The radio maps reveal the presence diffuse ionized emission displaying distinct cometary morphologies. The 1280 MHz flux densities translate to ZAMS spectral types in the range O7.5V -O7V and O8.5V -O8V for the ionizing stars of G346.056−0.021 and G346.077−0.056, respectively. A few promising candidate ionizing star(s) are identified using near-infrared photometric data. The column density map shows the presence of a large, dense dust clump enveloping G346.077−0.056. The dust temperature map shows peaks towards the two H II regions. The submillimetre image shows the presence of two additional clumps one being associated with G346.056−0.021. The masses of the clumps are estimated to range between ∼ 1400 to 15250 M . Based on simple analytic calculations and the correlation seen between the ionized gas distribution and the local density structure, the observed cometary morphology in the radio maps is better explained invoking the champagne-flow model. Conclusions.

Galatic HII region IRAS 17149$-$3916 -- A multiwavelength study

“…For the latter, the flux density is integrated within the respective 3σ contours. The quoted errors are estimated following the method discussed in Das et al (2018).…”

“…To understand the nature of cold dust emission, we generate the dust temperature and the molecular hydrogen column density maps following the procedure detailed in Das et al (2018) and Issac et al (2019) and briefly stated here. A pixelby-pixel modified blackbody modelling to the observed spectral energy distribution is carried out.…”

“…While observation of ionized gas kinematics is required to understand the origin of the observed morphology, in the discussion that follows, we discuss a few aspects based on the radio, column density, and FIR maps of the region associated with IRAS 17149−3916 along with the identification of E4 as the likely ionizing star (refer Section 4.2). Following the simple analytic expressions discussed in Das et al (2018), we derive a few shock parameters to probe the bow-shock model. Taking the spectral type of E4 to be O6.5V -O7V as estimated from the radio flux density, and assuming it to move at a typical speed of 10 km/s through the molecular cloud, we calculate the 'stand-off' distance to range between 2.6 arcsec(0.02 pc) − 3.1 arcsec(0.03 pc).…”

Multifrequency study of HH 137 and HH 138: discovering new knots and molecular outflows with Gemini and APEX

“…The discrepancy between the two values of mass is larger than the quoted uncertainties. Nonetheless, other authors have also found differences between the masses derived from the APEX 870 µm flux and the Herschel H 2 column density, in the sense that 870 µm masses are lower than H 2 column density masses (Dehar-veng et al 2010;Liu et al 2017;Dewangan et al 2017;Das et al 2018). In particular, Liu et al (2017) attributed this discrepancy to possible drawbacks in ground-based data reduction that underestimate the mass, due to the loss of large-scale emission when applying the sky noise subtraction.…”

GMRT survey of Cygnus OB2 region

“…GMRT is routinely used for probing the ionized emission associated with Galactic star forming regions. Das et al (2018) have for the first time presented low-frequency high-resolution maps of two southern HII regions, G346.056-0.021 and G346.077-0.056 which located at distance of 10.9 kpc. The ionized emission mapped at 610 and 1280 MHz are shown in Figure 7.…”