Investigating the physics of star formation is of utmost importance in astrophysics. Understanding star formation also helps us understand the galaxy formation processes at larger scales as well as planet formation and evolution at smaller scales. We now know that stars form in fragmenting molecular clouds due to the interplay between various physical processes such as gravity, turbulence, and magnetic fields. After forming in the dense and dusty gas pockets, the stars co-evolve with the natal gas until the surrounding gas is dispersed. This co-evolution can be explored further to study the star formation laws that the forming stars obey. However, the details of such fragmentation processes and star formation laws are still lacking. I will provide a brief update on our current understanding of star formation, such as the physical processes responsible for fragmenting the gas clouds into “little” stars, along with the star formation laws and their significance in the broader astronomical community.

We use Gaia EDR3 to determine phase?space distribution and orbits of globular clusters NGC 7089, NGC 7099, NGC 1851, Pal 1, and Pal 2 of the Milky Way galaxy. Proper motions of given galactic globular clusters are taken from Gaia EDR3 whereas radial velocity and distances are taken from Vasiliev et al. (2019). We calculate the median value of the right ascension (RA), declination (DE), the proper motion in right ascension (pmRA), proper motion in declination (pmDE) and found that our results are in good agreement with the literature of Gaia DR2. Furthermore, we use Astropy to transform the equatorial coordinate frame into a Galactic frame. After that, with the help of coordinate transformation, we estimate the components of the velocity of clusters (U, V, W ), components of clusters position (X, Y, Z). We also calculate the mean angular momentum along the Z?axis (LZ), total energy (E), the apocentric distances (apo), the pericentric distances (peri), and eccentricity (ecc). We integrate orbit for 10 Gyr using Galpy with McMillan17 potential. For integrating orbit we adopt the peculiar velocity of the Sun, (u, v, w) = (11.1, 15.7, 7.25) km/s, circular velocity be vo = 233.1 km/s, distance between the Galactic centre and the Sun be ro = 8.1 kpc, and position of the Sun above the Galactic plane zo = 25 pc. The orbital evolution of the clusters helps to unravel the formation history of the Galaxy.

This project studies the regions of orbital stability for two hypothetical exomoons around a Jupiter-type exoplanet Laligurans in the HD 100777 (Sagarmatha) star system. The masses of the two exomoons are taken to be equal to Earth-mass and Lunar-mass respectively. For a satellite, there are two important limits to the region of orbital stability: Roche limit and Hill sphere. Roche limit is the minimum distance from the planet where the satellite can maintain stable orbits without facing tidal disruption. Hill sphere of the planet approximates the farthest gravitational influence a planet can have on its satellites. In addition, the presence of chaos in orbits has important implications for the orbital stability of the exomoon. For the purpose of our project, the Mean Exponential Growth of Nearby Orbits (MEGNO) criterion for chaos was therefore first used to predict regions of periodic, quasi-periodic, and chaotic orbits in the parameter space of each exomoon. We found stable orbits for both exomoons between distances 0.001 AU and 0.02 AU from Laligurans. Then direct orbital simulations were performed for selected values of initial semi-major axis to study the evolution of orbital parameters of both the exomoons. Ejections of both exomoons were observed for the orbits beyond the critical semi-major axis for the stable orbits at 0.02 AU. Lifetime and maximum eccentricity maps were used to further study regions of stable orbits for both the exomoons.

The solar-wind interaction with the magnetosphere-ionosphere (M-I) system constantly drives plasma convection within the polar regions of the ionosphere & this interaction causes the transfer of momentum and energy from the solar-wind to Geo-space. The interaction occurs mainly via two processes;

viz the viscous interaction and the magnetic reconnection. The viscous interaction is a purely mechanical phenomena. The velocity shear between the solar-wind flowing near the magnetopause and magnetospheric plasma along the flanks at higher latitudes produces waves that cause anti-sunward movement of magnetospheric plasma & this anti-sunward drag is followed by sunward flow at lower latitudes.Thus created viscous circulation produces current within the system because of magnetic shear due to viscous flow. The resulting electric field when integrated over a given direction gives us electric potential imposed on the ionosphere, which is termed as viscous potential. The main driver of this interaction system, the magnetic reconnection is the fundamental process within which

plasma from different magnetic domains interact physically & hence magnetic energy is converted into plasma energy. Both of these interactions results in the generation of an electrical field in the Earth�s ionosphere. The overall effect the viscous potential and reconnection potential is taken into account to measure the polar cap potential (PCP). The PCP has been considered as an indicator of the

quantity of energy flowing into and thru the magnetosphere�ionosphere system. In this research, we will analyze the results obtained from the Lyon-Fedder-Mobarry (LFM) simulation and will examine the interaction between Interplanetary Magnetic Field (IMF) with Geo-magnetic Field, the effect of increasing By on polar cap potential (PCP) during constant IMF Bz . We will also be able to show

that the viscous potential, which is so often assumed to be independent of IMF orientation, is reduced during times of northward IMF. We�ll also discuss the significance of these results for future uses like predicting space weather which is significant for this modern world which is becoming more space based day by day.

With the release of the Gaia EDR3 better estimation of parallax is available which was crossmatched with GALAH DR3 for full 6-dimensional phase space information. 3621 metal poor K-giant stars with metallicity [Fe/H]<-1 are taken with in 5 kpc<R<10 kpc and |Z|<4 kpc which are fitted to two component Gaussian to determine the rotational velocity. In which one component represents the stellar halo and shows the rotational velocity of VT =38+3−4km/s with dispersion of 97+2−2km/s that exhibits the prograde motion. Stellar halo shows a slight variation in the rotational velocity with metallicity. And, second component represents the disk with rotational velocity of 191+4−4km/s and dispersion 43+3−3km/s : high prograde motion. Inner halo hasa radially biased orbit with beta = 0.9−0.00005+0.00001.

Time of the Sunrise and Sunset at specific location plays a pivotal role for both the natural and anthropogenic activities such as agriculture, solar panel, remote sensing and more importantly in the aviation. Sunrise and Sunset times depend on the latitude, longitude, day of the year and height of the surrounding terrain. During this research, we have developed a numerical model to calculate Sunrise and Sunset times by factoring in different parameters like declination angle, equation of the time, latitude, longitude, and the refractive index of the medium. The Sunrise and Sunset times obtained from our model are compared with the National Oceanic and Atmospheric (NOAA)’s data for various cities located in both hemispheres. On comparing, the correlation coefficient between our data and NOAA’s data shows close agreement with minimal time difference, thus verifying the accuracy of our model. Furthermore, the data obtained from our model for Tribhuwan International Airport (TIA) is compared and analyzed with the current TIA model (TIA uses the Indian Ephemeris and interpolates). In this talk, I will present the details of our model, data acquisition methods and the impact of various parameters on Sunrise and Sunset times at different airports in Nepal.

Keywords: Sunrise, Sunset, Horizon, Geographical Co-ordinates, Equation of time

Solar radiation data are great significance for energy harvesting. The main objective of this paper is to study clearness index of atmosphere over Biratnagar (latitude: 26.45oN, longitude: 87.27oE, altitude:72 m above sea level),Eastern city of Nepal. Daily global solar radiation data are derived by using CMP6 Pyranometer for one year period(2015).The monthly ,annual and seasonal variations of global solar radiation, clearness index and visibility were analysed. The annual average of global solar radiation (GSR),clearness index (KT)and visibility are found to be 11.37 ± 3.76 MJ/m2/day , 0.37 ± 0.15 and 7.06 ± 5.56 km are respectively. In study period, no. of clear days(KT >0.65) and no. of cloudy days(KT <0.34) are found to be 26 and 172 respectively. Study of clearness index of atmosphere and its dependence on meteorological parameters (maximum temperature, minimum temperature, rainfall, relative humidity, total ozone column, ultraviolet index etc ) are used on agriculture, hydrology, climate change.

Metal abundance measurements throughout the cosmic ages track the history of galaxy formation and evolution from the initial pristine stars and galaxies to the present day metal-rich galaxies. Measuring abundances during the first ~1 billion years is especially important, as they are influenced by the nucleosynthetic signatures from the early stars. Evolution of metallicity of Damped/sub-Damped Lyman-alpha Absorbers (DLAs/sub-DLAs) detected in the spectra of quasars, which provide the neutral gas reservoirs for star formation at high redshift, is a powerful tracer of the cosmic star formation history. We have been expanding the measurements of elements such as S, O, Si, Fe, C etc in DLAs/sub-DLAs at z >4.5 using the high-resolution spectroscopic observations from the Very Large Telescope (VLT), the Magellan Telescope, and the Keck Telescope. We present the recent advances as well as the future prospects of the evolution of metals and dust, gas kinematics in gas-rich galaxies as well as the nucleosynthetic signatures from the early stars/galaxies in the universe.

The dust properties of C-rich AGB (Asymptotic giant branch) star with (Infrared Astronomical Satellite) IRAS 04427+4951 located at R.A. (J2000) = 04h 46m 33.636s and Decl. (J2000) = +49d 56m 23.77s was studied. We choose this AGB star candidate from a catalog of AGB stars in our Galaxy (Version 2017). The FITS (Flexible Image Transport System) image of this AGB star was obtained. The flux of ambient medium in the wavelength range of IRIS 60 micron and 100 micron and AKARI 90 micron and 140 micron was calculated along with the physical properties like dust color temperature, dust mass, Planck’s function, visual extinction, inclination angle and the variation of physical parameters with the diameter of the candidate at a distance of 3000.362 pc using different plots. We also calculated the mass whose average value was found to be 3.55 × 10^27 kg (1.79 × 10^−3 solar mass ) in IRIS and 5.34 × 10^27 kg (2.69 × 10^−3 solar mass ) in the AKARI survey and the dust color temperature of the corresponding C-rich star average value was found to be 23.485 K ± 0.009 K with offset temperature 1.272 K in IRIS and 14.893 K ± 0.004 K with offset temperature 0.721 K in AKARI survey. The lower offset temperature suggests it to be in thermal equilibrium. Due to the low value of standard error, we realized the star is in the early phase. The lower temperature variation means the symmetric distribution of density and temperature. The temperature in IRIS was higher than that of the AKARI survey as it has an inverse relation with flux and respectively with mass. The average value of the corresponding spectral density was found to be 8.75 × 10^−16Wm−2 sr−1Hz−1 in IRIS and 1.47 × 10^−16Wm−2 sr−1Hz−1 in AKARI. The size of the structure was 36.56 pc × 12.28 pc for IRIS with inclination angle 86.15◦ and size of structure 10.02 pc × 3.24 pc for AKARI Survey with inclination angle 86.08◦ . Inclination angle near about 90◦ (i → 90◦ ) means the dust cavity of our region of interest is corresponding to the view with the earth (edge-on orbit). The variation of dust color temperature along with visual extinction in both surveys was studied and concluded with an inverse relation between Av and Td.

Compact dwarf galaxies do not follow the mass-size scaling relation of normal galaxies. Although, galaxies formed in early universe are generally compact compare to present days galaxies, the formation and evolution of present compact galaxies is a puzzle. In this work, we study a compact dwarf galaxy, CG 0315, which is formed through the merging of even smaller galaxies. We performed its surface photometry on the publicly available optical r-band imaging data. The surface photometry shows that one-dimensional light profile is irregular and cannot be modelled with a parametric function like Sersic function. Using non-parametric method, we measured CG 0315 half-light radius of 221 parsec. This value is significantly smaller than that of a typical galaxy of same brightness, i.e. Mr = -15.2 magnitude. CG 0315 has star formation rate 0.01 M?/yr. Compare to the normal star-forming galaxies, the measured value of Star Formation Rate (SFR) of CG 0315 is normal. From these observational evidences, we concluded that CG 0315 will still be a compact dwarf galaxy, once its star-formation ceases and becomes well known compact elliptical galaxy. CG 0315 could, therefore, be a progenitor of elliptical galaxy. The phenomenon happens in the early universe where compact galaxies are common.

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?3.06 pc)located at R.A. (J2000): 16h33m57.25s& Dec. (J2000): -37?47?04.3??, and FIC12-58 (size?22.54 pc?14.84 pc) located at R.A. (J2000): 12h52m50.08s & Dec. (J2000): -58?08?55.02??, found within a galactic plane -10? to +10?nearby Asymptotic Giant Branch (AGB) stars namely AGB15-38 (R.A. (J2000): 15h37m40.74s & Dec. (J2000): -38?20?24.6??), and AGB12-57 (R.A (J2000): 12h56m38.50s& Dec. (J2000): -57?54?34.70??), 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 forFIC16-37, 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 plot 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 dust particles are not in thermal equilibrium along the diameters.

Researchers have studied the interplanetary magnetic field and solar-wind parameters that influence the development of geomagnetic storms for more than a decade. Interplanetary structures with intense, long-duration, and southward magnetic fields (Bz) that interact with the earth’s magnetic field and allow solar wind energy to be transported into the magnetosphere are the primary cause of magnetic storms. This study proposed a new technique for investigating the association between solar and interplanetary plasma parameters with geomagnetic storms. Cross wavelet analysis (XWT) is a bivariate wavelet analysis that examines the correlation between two signals in the time-frequency domain to see how phase angle describes the mechanism in casual and physical linkages between time series. The XWT exposes high common power regions as well as information regarding the phase relationships between the interplanetary magnetic field component (IMF-Bz), solar wind velocity (Vsw), and Symmetrical Ring Current Index (SYM?H). Another useful measure is how coherent the cross-wavelet transform is in time-frequency space. We used wavelet transform coherence (WTC) of two-time series to achieve this. Thus, the local correlation between two CWTs can be conceived of as WTC. The study’s findings will demonstrate that the suggested method is a simple, effective, and robust method for detecting locally phase-locked behavior between two-time series.

An accurate data of solar flux density is essential for promoting solar energy technology to fulfill the need for clean energy to solve the energy crisis problem and reduce the adverse effect of environmental pollution and climate change at that location. There is no more sufficient solar flux density data in developing countries like Nepal due to the lack of measuring instruments in different parts of Nepal. It is happened because of the scarcity of budget for the installation of instruments and proper maintenance and calibration. The main objective of this research is to select the best model to estimate the solar flux density, among the 14 models in the Mid-western region, Simikot (Lat. 29.967 oN, Long. 81.833 oE and Alt. 2990.0 m.a.s.l.) for a period of 2012-2016. The different models were used to estimate solar flux density by using meteorological parameters (temperature, relative humidity, and rainfall) using the regression technique. Finally, the observed and model estimated solar flux density of different models are compared using 10 different statistical validation indices: mean bias error(MBE), mean absolute error(MAE), root mean square error(RMSE), mean percentage error(MPE), relative root mean square error(RRMSE), root mean square relative error(RMSRE), t-statistic, uncertainty 95% (U95), maximum absolute relative error(MARE), and correlation coefficient(r) and to determine the most accurate model for the mid-hill region. In the end, it was found that the model TR6, which is temperature, relative humidity, and rainfall-based model is better than other models. It is concluded that the empirical constants of better model are a=14.84, b=5.48, c=15.08, d=-12.94, e=0.005, f=-0.01. The annual average solar flux density is found to be 4.54 kWhr/m^2/day. It is concluded that the finding empirical coefficients can be used for the prediction of the solar flux density at similar climatic regions of Nepal.

Keywords: Energy crisis, Meteorological parameters, Regression technique, Statistical indices, Solar flux density, Empirical constants.

We have analyzed a seismological catalog (Mc=4.0) of 989 earthquakes with a magnitude range of 2.9 ? mb ? 6.9 from January 1994 to November 2020. The study region is separated into two sub-regions (I) Region A – 27.3?N -30.3?N and 80?E -84.8?E and vicinity and (II) Region B – 26.4?N -28.6?N and 84.8?E -88.4?E and vicinity. We investigated the regional variations of Gutenberg�Richter parameters ‘a’ and ‘b’ and fractal dimension (D0) and relations among these parameters for aforesaid regions in central Himalaya. The b-value of frequency-magnitude distribution for seismicity within the study region is found homogeneous. It is within the range between 0.92 to 1.02 for region A and within 0.64 to 0.74 for region B. The seismic a-value for those regions ranges respectively between 5.385 to 6.007 and 4.565 to 5.218. The low b-values and low seismicity for region B may be associated with a low degree of heterogeneity and high rheological strength in the Crust. The high seismicity with high b-values obtained for region A may be associated with high heterogeneity as well as with low strength in the crust. The fractal dimension calculated ?1.74 for region A and ? 1.82 for region B indicate that the earthquakes were distributed over two-dimensional embedding space. We observed a negative correlation between D0 and b values for region A and a positive correlation for region B while the correlation between D0 and a/b value is just opposite for these two regions. The findings identify both regions A and B are high-stress regions. The results coming from the study agree with the results of the preceding works and reveal information about the regional variation of stress and difference in geological complexity in the study region.

The concentration of size segregated aerosol particles at the surface level over Pokhara was observed from January to September 2020 observed by particulate matter sensors. These concentrations of particles are compared with the column aerosol optical properties observed by Aerosol Robotic Network (AERONET) in the same city Pokhara. Mie Scattering Theory-based MIE Code is used to calculate the size segregated aerosol optical properties by using volume size distribution and refractive index of aerosol obtained from the AERONET. We observed that size segregated aerosol optical properties are significantly contributed by particles less than 1 micron in diameter than the aerosol particle of sizes in between 1 micron and 2.5 microns and the particle sizes between 2.5 microns and 10 microns diameters. These aerosol optical data are studied by analyzing and predicting the local effect of air pollution sources such as traffic and cooking activities. The variation of aerosol optical and concentration data is also compared with the meteorological parameters such as rainfall. AERONET optical data and the MODIS-based Aerosol Optical Depth are compared, and the aerosol sources are analyzed depending on NOAA’S HYSPLIT back trajectory cluster analysis. The trajectory analysis reveals transboundary pollution from Indo Gangetic Plain (IGP) region, local impact, and other neighboring countries significantly impacting the vertical column over the Pokhara. The directional contribution of air-mass trajectory shows the directional variation of air-mass contribution over Pokhara.

Ram pressure stripping (RPS)* is an important mechanism for galaxy evolution mainly in galaxy clusters. Recent observation suggests that some RPS galaxies have young stars formed in the stripped tails (sometimes called “jellyfish galaxies”). In this work, we present results from the HST observations of such RPS galaxy, ESO 137-002 in the closest rich cluster Abell 3627. The galaxy is known to host prominent X-ray and H? tailsl of at least 40 kpc in length. The data reveal significant features indicative of RPS in the galaxy, including asymmetric distribution of dust, dust filaments and dust clouds in ablation generally aligned with the direction of ram pressure, and young star clusters immediately upstream of the residual dust clouds. Some young star clusters are found in upstream of the galaxy and we argue star formation (SF) is triggered by ram pressure compression. Being a massive spiral, the SFR is moderate. On the other hand, we do not detect any active SF in the X-ray and H? tails of ESO 137-002 and place a limit on the SF efficiency in the tail. Hence, if selected by SF behind the galaxy in the optical or UV (e.g., surveys like GASP or using the Galex data), it will not be considered a “jellyfish” galaxy. Thus, galaxies like ESO 137-002 are important for our comprehensive understanding of RPS galaxies and the evolution of the stripped material. It also presents a great example of an edge-on galaxy experiencing a nearly edge-on RPS wind.

*ram pressure arises when ICM wind overcomes the gravitational potential of the galaxy, Gunn & Gott (1972)

This work investigates the performance of NeQuick 2, the ITU recommended TEC model, and observed GPS-vTEC over Nepal during the solar minimum. The NeQuick parameters are adjusted such that it can calculate the vTEC up to the height of the GPS orbit. NeQuick is devised to illustrate the median and quiet condition of the ionosphere. So, to check the actual reliability of the model, we have made a comparison between modeled and experimental vTEC by considering the monthly median GPS vTEC value of quiet days only. The outcome of our study shows that experimental vTEC overestimate NeQuick 2 prediction during March equinox and June solstice whereas NeQuick overestimates GPS observed vTEC in September equinox and December solstice. The high correlation (r> 0.85) between them reveals the good performance of the NeQuick 2 model with respect to GPS measured vTEC. However, the significant discrepancies between them are observed during the daytime.

The search of isolated dust structure is performed around the Supernova Remnants and Pulsar using Sky View Virtual Observatory in Improved Processing of IRAS Survey. An isolated dust structure at Galactic Longitude: 53.54^o & Galactic Latitude: +0.04^o (Right Ascension (J2000):?19?^h ?30?^m ?12.09?^s & Declination (J2000): +?18?^o ?16?^’ ?28.3?^”), having size: 41 pc ? 10.06 pc, is selected for further investigation. Using SIMBAD, it is found that many Supernova Remnants and Pulsars are embedded within and outside the dust structure. The infrared flux at 60 \mu m and 100 \mu m wavelength is taken from the FITS image using Aladin v2.5 software. The dust color temperature and dust mass are calculated from infrared flux. The distribution of infrared fluxes, dust color temperature and dust mass is studied via color map and Gaussian plot using Python 3.7. The dust color temperature lies between the maximum value 33.56 +- 3.32 K to minimum value 23.31 +-1.80 K, with an average value 26.92 +- 0.06 K and range 10.25 +_2.56 K. We use Gaia early third data release for the calculation of distance, which is 1667.89 pc. The total mass of dust and gas within the isolated dust structure is found to be 2.84 ? 10^31 kg (14.26 M_?) and 5.67 ? 10^33 kg (2851.33 M_?). The large fluctuation of temperature indicates that the isolated dust structure is not evolving independently, which might be due to the effect of Supernova Remnants, Pulsars and other radiation sources located within and outside the dust structure. The color map shows an identical distribution for infrared flux at 60 \mum and 100 \mum but no relation between the dust color temperature and dust mass. The distribution of infrared flux at both 60 \mum and 100 \mum are deviated from Gaussian nature, indicating high disturbance from background sources, such as Supernova Remnants and Pulsars. The distribution of dust color temperature and Planck�s also deviates from Gaussian nature, indicating the dust within the isolated structure are not in local thermodynamic equilibrium. The inverse relation between dust color temperature and spectral index is satisfied for dust structure. It can be concluded that the high radiation sources within and outside the dust structure are playing major roles within the dust structure for the asymmetrical distribution infrared flux and dust color temperature.

Key Words: Dust � Structure, Dust Color Temperature, Dust Mass, Supernova Remnants, Pulsar.