Journal of Astrophysics and Astronomy最新文献

The evolution of the Universe together with galaxies, is one of the fundamental issues that we humans are most interested in. Both the observations of tidal streams from SDSS and the theory of (Lambda )CDM support the hierarchical merging theory. The study of high redshift celestial bodies contributes to a more in-depth study of cosmology. The LAMOST low-resolution search catalog DR11 v1.0 has released 11,939,296 spectra, including 11,581,542 stars, 275,302 galaxies and 82,452 quasars, and so on. The data of 28,780 stellar population synthesis of galaxies and some high redshift quasars are used to do a preliminary statistical research. We selected the data with small errors for analysis and obtained some basic statistical conclusions. Older galaxies have relatively larger stellar velocity dispersions. The larger the metallicity, the greater the stellar velocity dispersion. These statistical results are reasonable and consistent with previous work. Because the stellar velocity dispersion is driven by the total mass of a galaxy at the first order and more massive galaxies have older ages and greater metallicities. The spectra of high redshift quasars show clear Gunn–Peterson trough and Lyman-(alpha ) forest. The identified emission lines and high redshift celestial spectra released by LAMOST, can be used for cosmological research.

Our solar system, consisting of the Sun, planets, Moons, asteroids, and comets, along with gas, dust, ice, and radiation, is a very complex and dynamic system. Globally, planetary, astronomy, and small-body exploration programs have made great strides in understanding the formation and evolution of stellar systems while also providing detailed views of individual bodies. The forthcoming decades offer immense opportunities for planetary exploration from space and observations from ground telescopes that portend to very significantly expand not only the horizons of human exploration but also provide a more fundamental understanding of the evolutionary pathways that led to the myriad diversity in our Solar System. The past, present, and future of the solar system also serve as a Rosetta stone to decipher the physics, chemistry, and biology of the exo-planetary systems. Here, we recommend solar system exploration objectives for the decade and beyond in the context of current global developments in the field and research groups in India.

We study the effect of gravitational clustering at small scales on larger scales by studying mode coupling between virialized halos. We build on the calculation by Peebles (1974), where it was shown that a virialized halo does not contribute any mode coupling terms at small wave numbers k. Using a perturbative expansion in wave number, we show that this effect is small and arises from the deviation of halo shapes from spherical and also on tidal interactions between halos. We connect this with the impact of finite mass resolution of cosmological N-Body simulations on the evolution of perturbations at early times. This difference between the expected evolution and the evolution obtained in cosmological N-Body simulations can be quantified using such an estimate. We also explore the impact of a finite shortest scale up to which the desired power spectrum is realized in simulations. Several simulation studies have shown that this effect is small compared to the effect of perturbations at large scales on smaller scales. It is nevertheless important to study these effects and develop a general approach for estimating their magnitude. This is especially relevant in the present era of precision cosmology. We provide basic estimates of the magnitude of these effects and their power spectrum dependence. We find that the impact of small-scale cutoff in the initial power spectrum and discreteness increases with ((n+3)), with n being the index of the power spectrum. In general, we recommend that cosmological simulation data should be used only if the scale of non-linearity, defined as the scale where the linearly extrapolated rms amplitude of fluctuations is unity, is larger than the average inter-particle separation.

Galaxies, clusters, and the intergalactic medium (IGM) are the essential and interconnected components of the cosmic ecosystem. Galaxies, with their diverse morphologies and stellar populations, are the building blocks of cosmic structure, harboring stars, gas, dust, cosmic rays, magnetic fields, and dark matter. Galaxy clusters, immense gravitational unions of galaxies, offer profound insights into galaxy formation, cosmology, and the nature of dark matter. Bridging these cosmic islands is the IGM, a vast expanse of primordial gas enriched with traces of heavy elements. It harbors the majority of cosmic baryons distributed within an intricate network of filaments and voids. Together, galaxies, clusters, and the IGM offer a holistic view of the cosmic architecture, each playing a unique role in shaping the universe’s grand design. Indian scientists have made substantial contributions to research on galaxies, clusters, and the IGM, both theoretical and observational. To pursue and advance such contributions at par with the international level, the astronomical community emphasizes the urgent requirement for access to cutting-edge ground-based and space-based observatories and computing facilities. Access to state-of-the-art observational and computing facilities will sustain ongoing endeavors and enable Indian scientists to remain at the forefront of advancements in these fields, fostering continued relevance and innovation in astronomy research.

Radio detection of cosmic rays investigates the electromagnetic component of extensive air showers. It is possible to obtain the most critical properties of a cosmic ray, including the depth of shower maximum, energy, and type of primary particle, from radio measurements. Semnan University Radio Array is a new experiment that strives to detect radio emissions from extensive air showers induced by ultra-high energy cosmic rays. To fully harness the potential of the radio detection method in a self-trigger setup, it is essential to have artificial digital and analog filters to eliminate major unwanted emissions, analog-to-digital converters with appropriate specifications for accurate signal reconstruction, and data processing units capable of implementing software-based analysis alongside advanced digital signal processing techniques. This paper describes the design and implementation of a self-triggering approach in SURA-4 as the first phase of the SURA experiment to preserve cosmic ray candidates while removing unwanted emissions by utilizing the capabilities of analog and digital elements and incorporating a custom software framework for radio signal analyses. The ultimate validation of this approach for reliably distinguishing cosmic rays from anthropogenic radio frequency interferences will be pursued in future experiment phases, including cross-verification with three particle detectors.

The article ‘Confirmation of interstellar phosphine towards asymptotic giant branch star IRC(+)10216’ by A. Manna and S. Pal uses ALMA data of the C-star envelope IRC(+)10216 to claim a confirmation of the detection of (hbox {PH}_3) in this source. The article, however, incorrectly assigns an emission feature observed in the ALMA spectrum of IRC(+)10216 to (hbox {PH}_3), while we find that it arises from a highly vibrationally excited state of HCN. Concretely the feature can be confidently assigned to the (J=3)–2, (ell =0) transition of HCN in the (nu _1 + 4nu _2) vibrational state based on the observation of the (ell = +2) and (ell = -2) components of the same rotational transition, (J=3)–2, with the observed relative intensities in agreement with the relative line strengths. The detection of (hbox {PH}_3) in IRC(+)10216 remains confirmed based on the observation of the (J=1)–0 and (J=2)–1 lines with the single-dish telescopes IRAM 30m, ARO SMT 10m, and Herschel (Agúndez et al. 2008, 2014; Tenenbaum & Ziurys 2008).

The Be X-ray binary pulsar RX J0520.5(-)6932 in the Large Magellanic Cloud recently underwent an outburst after a gap of about 10 years. This paper presents the timing and spectral analysis of this transient system using the NuSTAR observation that was made near the peak of the outburst. Coherent pulsations were detected with a period of 8.029877(9) s (at MJD 60412.87) up to 50 keV. The pulse profile was single-peaked and asymmetric, with the presence of two local minima on the slowly rising edge up to about 18 keV. The hard X-ray pulse profiles were relatively smooth. The 3–50 keV FPMA–FPMB energy spectrum was well described by a thermally comptonized continuum with an electron temperature of (sim )5.3 keV and a photon index of (sim )1.36. A broad (sim )6.32 keV Fe emission line and a cyclotron resonant scattering feature (CRSF) with (sim )32.3 keV central energy, corresponding to a surface magnetic field strength of (sim ) (2.8times 10^{12}) G were also required to describe the energy spectrum. The pulse phase resolved spectroscopy indicated significant variation in energy and width of the CRSF and iron emission line. A (sim )14.6 keV absorption feature was also detected at specific pulse phases.

In contemporary astronomy and astrophysics (A&A), the integration of high-performance computing (HPC), big data analytics, and artificial intelligence/machine learning (AI/ML) has become essential for advancing research across a wide range of scientific domains. These tools are playing an increasingly pivotal role in accelerating discoveries, simulating complex astrophysical phenomena, and analyzing vast amounts of observational data. For India to maintain and enhance its competitive edge in the global landscape of computational astrophysics and data science, the Indian A&A community must embrace these transformative technologies fully. Despite limited resources, the expanding Indian community has made significant scientific contributions. However, to remain globally competitive in the coming years, it is vital to establish a robust national framework that provides researchers with reliable access to state-of-the-art computational resources. This system should involve the regular solicitation of computational proposals, which can be assessed by domain experts and HPC specialists, ensuring that high-impact research receives the necessary support. India can develop the talent, infrastructure, and collaborative environment necessary for world-class research in computational astrophysics and data science.

With the evolution of radio astronomy and related education and training, the demand for scalable, efficient, and remote systems in data acquisition, storage, and analysis has significantly increased. Addressing this need, we have developed a web interface for a log-periodic dipole antenna array integral to the SKA Test activities at the Gauribidanur Radio Observatory (77.428 E, 13.603 N). This interface, employing Python-based technologies such as Streamlit and PyVISA, along with Standard Commands for Programmable Instruments (SCPI) commands, offers a seamless and user-friendly experience. Our solution introduces a unique data acquisition approach, employing SCPI through Python to communicate with the setup’s data acquisition system. The web interface, accessible remotely via a secure WLAN network or VPN, facilitates user-initiated observations and comprehensive logging and offers advanced features like manual radio frequency interference masking, transit plotting, and fringe plot analysis. Additionally, it acts as a data hub, allowing for the remote downloading of observational data. These capabilities significantly enhance the user’s ability to conduct detailed post-observation data analysis. The effectiveness of this interface is further demonstrated through a successful solar transit observation, validating its utility and accuracy in real-world astronomical applications. The applications of this web tool are expandable. They can be tailored according to the Observatory’s goals and instrumentation, as well as the growing radio astronomy instrumentation and observing facilities at various educational institutions.

Chandrayaan-2 Large Area soft X-ray Spectrometer (CLASS) is a remote X-ray Fluorescence experiment to map the lunar surface elemental abundances. With its large effective area and low energy threshold, CLASS generates the highest spatial resolution maps of all major rock-forming elements on the Moon, such as Mg, Al, Si, Ca, Ti, and Fe. Five years of operation in lunar orbit has resulted in global coverage. With several lunar missions planned for this decade for in situ exploration and sample returns, the (15 times 15) km geochemical maps from CLASS will serve as an important dataset. This article highlights the scientific results of CLASS in the last five years and discusses its potential applications.