Galaxian Contamination in Galactic Reddening Maps

Estimating the amount of foreground extinction due to the Milky Way dust along the line of sight is often a first step in determining the luminosity of an object. The amount of Galactic dust inferred by infrared emission maps can be contaminated by infrared light from nearby galaxies. By comparing extinction values at and around the location of nearby galaxies, we compile a list of 95 galaxies that likely contaminate the maps with an excess or improperly subtracted galaxian infrared emission, and tabulate our recommended values for the MW contribution. In addition to M82, which inspired this work, six more sources have an excess visual extinction A V of at least 0.05 mag greater than our annular values; including M83, NGC 1313, NGC 6822, NGC 918, UGC 11501, and UGC 11797. M33 is shown to be oversubtracted. NGC 88 and the outskirts of NGC 4258 are located in gaps in the Infrared Astronomical Satellite imaging. The recommended dust map values for the LMC, SMC, and M31 may also not be correctly returned by some software packages. Accurate reddening estimates are important for measuring stellar and supernova luminosities in these nearby galaxies.

Study of Dust Cavity around the White Dwarf WD 0352-049 in Infrared Astronomical Satellite Map

In this work, we have studied the far-infrared images of the dust cavity around the White Dwarf WD 0352-049 available in Infrared Astronomical Satellite Map from Sky View Observatory. The size of the cavity is 24.48 pc × 8.10 pc. We have studied the relative infrared flux density and calculated the dust color temperature and dust mass. The temperature of the whole cavity structure lies between a maximum value 24.09 ± 0.50 K to a minimum 21.87 ± 0.61K with fluctuation of 2.22 K and an average value of 23.09 ± 1.11 K. The small fluctuation of dust color temperature suggests that the dust in cavity structure is evolving independently and less disturbed from background radiation sources. The color map shows the identical distribution of flux at 60 μm and 100 μm and the inverse distribution of dust color temperature and dust mass. There is a Gaussian-like distribution of relative flux density, dust color temperature and dust mass. The Gaussian distribution of temperature suggests that the dusts in cavity are in local thermodynamic equilibrium. The study of relative flux density and dust color temperature along the major and minor axis shows there is a sinusoidal fluctuation of flux and temperature, which might be due to the wind generated by White Dwarf located nearby the center of the cavity structure. The total dust mass of the dust is found to be 0.07 Mʘ and that of gas is 13.66 Mʘ. The Jeans mass of the structure is less than the total mass of gas in the structure, suggesting the possibility of star formation activity by gravitational collapse in the future. Also, the study of inclination angle suggests that the three-dimensional shape of the structure is uniform and regularly shaped.

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.

Study of dust color temperature and visual extinction distribution of a far infrared cavity at 60 and 100 µm IRAS map around the AGB star at galactic latitude 8.6⁰

The dust-grain structure in the far infrared region under IRAS (Infrared Astronomical Satellite) Survey was studied using sky view virtual observatory. In order to find the possible far infrared cavity, we used SIMBAD database. In this paper, we discuss about the dusty environment of a far infrared cavity around the AGB star located at R.A. (J2000) =01h 41m 01s and Dec (J2000) = 71o 04’ 00” lying within far infrared loop G125+09 in the far infrared IRAS maps. A cavity like structure (major diameter ∼ 2.55 pc & minor diameter ∼ 0.77 pc) is found to lie at R.A. (J2000)= 01h 46m 57.2s and DEC (J2000)= 71o 24’ 57.1”, located at a distance ∼ 220 pc from the star. We studied the distribution of flux density, dust color temperature, dust mass, inclination angle, visual extinction and FIR spectral distribution of the cavity. We further studied the distribution of Planck function along extension and compression. The dust color temperature is found to lie in the range (19.7±0.65) K to 21.1±0.35) K which shows the cavity is isolated and stable. Product of visual extinction and dust color temperature is found to be less than one. A possible explanation of the results will be discussed. BIBECHANA 17 (2020) 42-49

X-ray - Infrared relation of AGNs and search for highly obscured accretion in the AKARI NEP Field

The infrared Astronomical Satellite AKARI conducted deep (∼0.4 deg2) and wide (∼ 5.4 deg2) surveys around the North Ecliptic Pole (NEP) with its InfraRed Camera (IRC) with nine filters continuously covering the 2–25 μm range. These photometric bands include three filters that fill the “ Spitzer gap” between the wavelength coverages of IRAC and MIPS. This unique feature has enabled us to make sensitive mid-infrared detection of AGN candidates at z∼1-2, based on the Spectral Energy Distribution (SED) fitting including hot dust emission in the AGN torus. This enables us to compare X-rays and the AGN torus component of the infrared emission to help us identify highly absorbed AGNs, including Compton-thick ones. We report our results of the Chandra observation of the AKARI NEP Deep Field and discuss the prospects for upcoming Spectrum-RG (eROSITA+ART-XC) on the AKARI Wide field.

Study of far infrared cavity around a post AGB star under IRAS survey at galactic latitude -3°

A systematic search of dust structure in the far infrared (100 μm and 60 μm) under Infrared Astronomical Satellite (IRAS) survey was performed using Sky View virtual Observatory. In order to find the possible candidate of cavity structure not yet studied, we used SIMBAD database to locate discrete sources in the region. A new relatively symmetric spherical cavity like structure (size: 1.354 pc x 0.971 pc) at R.A.(J2000) =08h 03m 01.65s, Dec.(J2000) = -360 35' 47.9" was found at the distance of about 2800 pc. In this article, we have calculated dust color temperature, dust mass and size. We also studied the flux density variation and then calculated temperature and mass profile of the dust of p-AGB star using data reduction software Aladin2.5 and Aladin8.0. We have studied a cavity like structure centered at R.A.(J2000) = 08h 04m 07.21s, Dec.(J2000) = -370 11' 48.0". The dust color temperature is found to lie in the range 21.6 ± 0.09 K to 22.5 ± 0.05 K with an offset of 0.9 K. Such low off set suggests that the post AGB is in local thermodynamic equilibrium. The total mass of the dust in the cavity structure is found about 5.93 x 1025 Kg (0.00003M⊙)BIBECHANA 1 6 (2019) 23-30

Mass Loss History of Evolved Stars (MLHES) Excavated by AKARI

We performed a far-IR imaging survey of the circumstellar dust shells of 144 evolved stars as a mission program of the AKARI infrared astronomical satellite. Our objectives were to characterize the far-IR surface brightness distributions of the cold dust component in the circumstellar dust shells. We found that (1) far-IR emission was detected from all but one object, (2) roughly 60–70 % of the target sources showed some extension, (3) 29 sources were newly resolved in the far-IR in the vicinity of the target sources, (4) the results of photometry measurements were reasonable with respect to the entries in the AKARI/FIS Bright Source Catalogue, and (5) an IR two-color diagram would place the target sources in a roughly linear distribution that may correlate with the age of the circumstellar dust shell.

Planetary Nebulae Detected in the AKARI Far-IR All-Sky Survey Maps

The AKARI Far-IR All-Sky Survey (AFASS) maps produced by the AKARI Infrared Astronomical Satellite enabled us to probe the far-IR sky for objects having surface brightnesses greater than a few to a couple of dozen MJy sr−1. Recently, we have verified that, if AFASS-measured fluxes are properly corrected for using the aperture correction method based on the empirical point-spread-function templates derived directly from the AFASS maps, point-source photometry measured from the AFASS maps reproduces fluxes in the AKARI bright source catalogue (BSC). We have surveyed the far-IR sky in the AFASS for Galactic planetary nebulae (PNe) based on the University of Hong Kong/Australian Astronomical Observatory/Strasbourg Observatory Hα Planetary Nebula database (HASHPNDB), preliminarily yielding far-IR fluxes for roughly 1000 Galactic PNe including a few hundreds of PNe not listed in the AKARI/BSC.

Dust Structure around AGB Star in 60μm and 100 μm IRAS Survey at Latitude 16.10°

A systematic search in the range of J2000 coordinate system provided by K.W. Shu & Y.J. Kwon (2011) of dust structure in the far infrared (100 μm and 60 μm) IRAS (Infrared Astronomical Satellite) survey was performed using Sky View virtual Observatory (1) so that some interesting isolated cavity structures surrounding the cavity structure were expected. The FITS images downloaded from sky view (1) was processed using software Aladin v 2.5. A cavity like structure (major diameter ∼ 3.57 pc & minor diameter ∼ 1.19 pc) lies in the coordinate of R.A. (J2000) 06h 31m 05s and DEC (J2000) 16d 06m 00s was found at the distance ∼ 310 pc (5). We studied the flux density variation and the temperature variation about major diameter, minor diameter and the distance between minimum temperature and minimum flux within the structure. We observed the variation of the temperature is 20.53 K to 21.42 K, with the offset of about 0.89 K, which shows the cavity is independently evolved. The mass profile of each pixel of the structure was also calculated using these temperature.The Himalayan Physics Vol. 6 & 7, April 2017 (48-53)

A STUDY OF A PULSAR WIND DRIVEN STRUCTURE IN FAR-INFRARED IRAS MAP AT LATTITUDE -10º

A systematic search of dust structure in the far infrared (100 μm and 60 μm) IRAS (Infrared Astronomical Satellite) survey was performed using Sky View Observatory. In order to find the possible candidate, we used SIMBAD database to locate discrete sources in the region. A deep cavity-like isolated far infrared dust structure (size ~ 4.46 pc × 2.23 pc) at galactic longitude: 284.360o, galactic latitude: -9.549o was found at the distance of about 375 pc. We have studied the flux density variation and then calculated temperature and mass profile of the dust and excess mass using data reduction software ALADIN 7.5 within this region. The dust color temperature was found to lie in the range 23.40 K to 29.28 K. An offset temperature of about 6.0 K was found. The total mass of the dust structure was found to be about 2.55×1027 kg and the excess mass per pixel was 2.52×1024 kg. We also studied the rate of mass loading around the structure. The energy of the pulsar required to create that in homogeneity in the structure was calculated to be 5.04×1036 J. Possible explanations of results will be presented.Journal of Institute of Science and Technology, 2017, 22 (1): 1-9