Study of Dust Structure nearby Asymptotic Giant Branch Star using IRAS Survey

This study performed an investigation of a dust environment, in the far-infrared bands (60 and 100 µm) of Infrared Astronomical Satellite (IRAS) survey, using the Sky View Virtual Observatory (https://skyview.gsfc.nasa.gov/current/). A far-infrared cavity structure (depression in the far-infrared background emission) of major diameter ∼ 61.8 pc and minor diameter ∼ 46.5 pc, in the sky coordinate, R.A. (J2000) = 21h 32m 44.47s and Dec. (J2000) = +55d 15m 16.8s, at a distance ∼ 3.58 kpc was found to lie around a carbon-rich Asymptotic Giant Branch star. We studied the temperature and mass of the dust, radiation intensity distribution, visual extinction, and far-infrared spectral distribution of the cavity structure using the softwares Aladin v2.5, SalsaJ, and ORIGIN 8.5. The range of temperature of dust was observed between 22.24 ± 0.81 K to 23.27 ± 0.21 K, and the entire mass of the cavity was determined to be 2.19 × 1031 kg. In addition, the fluctuating nature of the dust color temperature and Planck function was observed along major and minor diameters of the structure. Moreover, an opposite relationship of dust color temperature and visual extinction was found within the structure. Finally, from the far-infrared spectral distribution, abrupt reduction at 60 µm flux rather than a continual increase was observed, the connection between the AGB wind and the ambient interstellar medium could be the possible reason behind this. Our results obey the similar trends obtained for the other cavity structures in the previous studies; these findings validate the existing results for a new cavity structure around AGB star within the galactic coordinate -6o < b < +6o.

Fitting procedure for estimating interstellar extinction at high galactic latitudes

We determine the interstellar extinction in the selected high-latitude areas of the sky based on Gaia EDR3 astrometry and photometry and spectroscopic data from RAVE survey. We approximate the results with the cosecant law in each area thus deriving the parameters of the barometric formula for different lines of sight. The distribution of the parameters over the entire sky is described using spherical harmonics. As a result, we get a mathematical description of the interstellar visual extinction for different lines of sight and distances from the Sun which can be used for estimating interstellar extinction.

Study of Dust Properties of two Far Infrared Cavities near by Asymptotic Giant Branch stars under Infrared Astronomical Satellite Maps

The physical properties such as dust color temperature, dust mass, visual extinction, and Planck function with their distribution in the core region of two far-infrared cavities, namely FIC16-37 (size ~ 4.79 pc x 3.06 pc) located at R.A. (J2000): 16h 33m 57.25s & Dec. (J2000): -37d 47m 04.3s, and FIC12-58 (size ~ 22.54 pc x 14.84 pc) located at R.A. (J2000): 12h 52m 50.08s & Dec. (J2000): -58d 08m 55.02s, found within a galactic plane -10o to +10o nearby Asymptotic Giant Branch (AGB) stars namely AGB15-38 (R.A. (J2000): 15h 37m 40.74s & Dec. (J2000): -38d 20m 24.6s), and AGB12-57 (R.A (J2000): 12h 56m 38.50s & Dec. (J2000): -57d 54m 34.70s), respectively were studied using Infrared Astronomical Satellite (IRAS) survey. The dust color temperature was found to lie in the range of 23.95 ± 0.25 K to 23.44 ± 0.27 K with an offset about 0.5 K for FIC16-37, and 24.88 ± 0.27 K to 23.63 ± 0.98 K with an offset about 1 K for FIC12-58. The low offset in the dust color temperature indicated the symmetric distribution of density and temperature. The total mass of the cavities FIC16-37 and FIC12-58 were found to be 0.053 M☉ and 0.78 M☉, respectively. The contour plots of mass distribution of both of the cavities was found to follow the cosmological principle, suggesting the homogeneous and isotropic distribution of dust masses. The plot between temperature and visual extinction showed a negative correlation, suggesting that higher temperature has lower visual extinction and vice-versa. The distribution of Planck function along major and minor diameters of both of the cavities was found to be non-uniform, indicating oscillation of dust particles to get dynamical equilibrium. It further suggested the role of pressure-driven events nearby both cavities and suggested that dust particles are not in thermal equilibrium along the diameters.

Planck Function Distribution in the Far Infrared Cavity Nearby AGB Star at Galactic Latitude 0.6º

A far infrared cavity nearby AGB star namely AGB2308+6058 was found to be located centered at R. A. (J2000)= 23h 06m 54.6s and Dec. (J2000)= 61° 16' 09.8". Distribution of dust color temperature, dust mass and visual extinction of the far infrared cavity have studied. In addition, the distribution of Planck function along the compression and extension of the cavity also has studied. This cavity has found to be located nearby the AGB star around far infrared loop G110+00 at 730 pc. It is close to the Galactic plane at galactic latitude 0.6° therefore the radiation field is strong and the diameter of the cavity is found to be greater than 0.2°. The dust color temperatures was found to be in the range 22.76 ± 0.14 K to 23.55 ± 0.29 K with offset 0.79 K. The contour maps of dust color temperature and dust mass showed that the low temperature region have greater mass density. Planck function showed non-uniform distribution along its extension and compression, suggesting that the dust and grains are not in the local thermodynamic equilibrium, possibly due to nearby AGB star. A clearly noted result is from counter map of dust mass and visual extinction that they showed consistent nature in their distribution.

Where is the western part of the Galactic Center Lobe located really?

The Galactic Center Lobe (GCL) is a peculiar object widely protruding from the Galactic plane toward the positive Galactic latitude, which had been found toward the Galactic Center (GC) in the early days of the radio observation. The peculiar shape has suggested a relation with historical events, star burst, large explosion, and so on in the GC. However, the issue of whether the GCL is a single large structure located in the GC region is not yet settled conclusively. In the previous observations, the silhouette against the low-frequency emission was found in the western part of the GCL (WPGCL); this suggests that the part is located in front of the GC region. On the other hand, the Local Standard of Rest (LSR) velocity of the radio recombination line toward it was found to be as low as 0 km s−1. However, these observations cannot determine the exact position on the line-of-sight. There is still another possibility that it is in the near-side area of the GC region. In this analysis, we compare these results with the visual extinction map toward the GC. We found that the distribution of the visual extinction larger than 4 mag clearly corresponds to the silhouette of the WPGCL. The WPGCL must be located at most within a few kpc from us and not in the GC region. This would be a giant H ii region in the Galactic disk.

Study of a Far Infrared Cavity Around a Post-Asymptotic Giant Branch Star at Galactic Latitude -0.1º

We present dust color temperature, Planck function and visual extinction distributions of a far infrared cavity FIC19+30 found to be located around post-AGB star namely AGB20+29 at the galactic plane. Minimum and maximum dust color temperature of the core region of the cavity was found to be (22.17±0.23) K and (22.41±0.29) K respectively with offset value 0.24 K which suggests that the cavity is isolated and stable. The product of dust color temperature and visual extinction was found to be in the order of 10-4 K mag. The distribution of Planck function along the extension (major diameter) and compression (minor diameter) was found to be non-uniform distribution. Specifically dust particles are oscillating in order to get dynamical equilibrium which may be the cause of grain temperature. It further suggests that the dust particles in the cavities might not be in the thermal equilibrium possibly due to pressure driven events of nearby AGB stars. There is continuous increase in flux density with increase in wavelength as in case of nebula which suggests that number density of dust particles increase according to the increase in wavelength and vice-versa.

Study of a Far Infrared Cavity at 60 μm and 100 μm IRAS Map around the Carbon-Rich AGB Star at Galactic Latitude 8.6°

In this paper, we discussed about the dusty environment of the far infrared cavity around the AGB star located at R.A. (J2000) =01h41m 01s and Dec (J2000) = 71° 04’ 00 9, lying within far infrared loop G125+09 6 in the far infrared IRAS maps. A cavity like structure (major diameter ∼2.55pc & minor diameter ∼0.77pc) is found to lie at R.A. (J2000) = 01h46m57.2s and DEC (J2000) = 71°24’57.1”, located at a distance ∼ 220pc from the star. We studied the distribution of flux density, dust color temperature, dust mass, visual extinction in the cavity. We further studied the distribution Planck function along extension and compression, distribution of dust color temperature along square of the major and minor diameters. The dust color temperature is found to lie in the range (19.7±1.25) K to (21.1±0.55)K which shows the cavity is isolated and stable. A possible explanation of the results will be discussed.