IIA MOUSUMI DASGalaxies, clusters, and intergalactic medium: A vision document for the Indian Astronomical Community
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.
IIA MAHESWAR, GAnalysis of forbidden neon emission lines in HAeBe stars using Spitzer IRS spectra
We analysed high-resolution mid-infrared spectra of 78 well-known Herbig Ae/Be (HAeBe) stars using Spitzer InfraRedSpectrograph data, focusing on the detection of [Ne II] and [Ne III] emission lines as indicators of ionized outflows or disc winds. Emission from [Ne II] at 12.81 μm or [Ne III] at 15.55 μm was identified in 25 sources, constituting the largest sample of HAeBe stars with these detected lines. Our analysis revealed a higher detection frequency of [Ne II] in sources with lower relative accretion luminosity (Lacc/L∗ < 0.1), suggesting a connection to the disc dispersal phase. We examined correlations between neon lines and various spectral features and investigated [Ne III]-to-[Ne II] line flux ratios to explore potential emission mechanisms. Neon emission is predominantly observed in Group I sources (75 per cent), where their flared disc geometry likely contributes to the observed emission, potentially originating from the irradiated disc atmosphere. Interestingly, we also find that Group II sources exhibit a higher median relative [Ne II] line luminosity (L[Ne II]/L∗), suggesting enhanced photoevaporation rates possibly associated with their more settled disc structures. However, larger samples and higher-resolution spectra are required to confirm this trend definitively. The high detection rate of the [Fe II] and [S III] lines, commonly associated with EUV-dominated regions, alongside a [Ne III]-to-[Ne II] emission ratio greater than 0.1 in sources where both lines detected, suggests that EUVradiation is the primary driver of neon emission in our sample.
IIA ARCHANA SOAMKinematic study of molecular gas in cometary globule – LBN 437
Bright-rimmed, cometary-shaped star-forming globules, associated with H II regions, are remnants of compressed molecular shells exposed to ultraviolet radiation from central OB-type stars. The interplay between dense molecular gas and ionizing radiation, analysed through gas kinematics, provides significant insights into the nature and dynamic evolution of these globules. This study presents the results of a kinematic analysis of the cometary globule, Lynds’ Bright Nebula (LBN) 437, focusing on the first rotational transition of 12CO and C18O molecular lines observed using the Taeduk Radio Astronomy Observatory. The averaged 12CO spectrum shows a slightly skewed profile, suggesting the possibility of a contracting cloud. The molecular gas kinematics reveals signatures of infalling gas in the cometary head of LBN 437, indicating the initial stages of star formation. The mean infall velocity and mass infall rate towards the cometary head of LBN 437 are 0.25 km s−1 and 5.08 × 10−4 M yr−1, respectively, which align well with the previous studies on intermediate or high-mass star formation.
IIA WAGEESH MISHRAProton heating estimates from near-Earth observations of coronal mass ejections in solar cycle 24 Open Access
As solar coronal mass ejections (CMEs) propagate through the heliosphere, they expend energy in heating protons to compensate for the cooling that occurs due to expansion. CME propagation models usually treat energy dissipation implicitly via a polytropic index (δ). Here we calculate the power dissipation implied by a given δ and compare it with the power available in the turbulent velocity fluctuations. We make this comparison using near-Earth in-situ observations of 27 of the most geoeffective CMEs (Dst < −75 nT) in solar cycle 24. For δ = 5/3, the power in the turbulent velocity fluctuations is ≈54% smaller than what would be required to maintain the proton temperature at the observed values. If the power in the turbulent cascade is assumed to be fully expended in local proton heating, the most probable value for δ is 1.35. Our results contribute to a better understanding of CME energetics, and thereby to improved CME propagation models and estimates of Earth arrival times.
IIA SIVARAM, CIs asteroid 33 Polyhymnia a dark matter (DM) degenerate object?
Polyhymnia (33 Polyhymnia) is a main belt asteroid in our solar system with a diameter around 54 km. The density of asteroid 33 Polyhymnia, located in the main asteroid belt, is calculated to be 75 g/cc. Researchers have speculated the possibility that Polyhymnia could be composed of high-density superheavy elements near atomic number 164. Here, we propose that Polyhymnia could be an asteroid composed of degenerate dark matter (DM) and there could be many such asteroids in our solar system. (This is following our earlier work suggesting that Planet Nine could be such an object.)
IIA ARCHANA SOAMThe JCMT BISTRO-3 survey: Variation of magnetic field orientations on parsec and subparsec scales in the massive star-forming region G28.34+0.06
Magnetic fields play a significant role in star-forming processes on core to clump scales. We investigate magnetic field orientations and strengths in the massive star-forming clump P2 within the filamentary infrared dark cloud G28.34+0.06 using dust polarization observations made using SCUBA-2/POL-2 on the James Clerk Maxwell Telescope (JCMT) as part of the B-field In STar-forming Region Observations (or BISTRO) survey. We compare the magnetic field orientations at the clump scale of ∼2 pc from these JCMT observations with those at the core scale of ∼0.2 pc from archival Atacama Large Millimeter/submillimeter Array data, finding that the magnetic field orientations on these two different scales are perpendicular to one another. We estimate the distribution of magnetic field strengths, which range from 50 to 430 μG over the clump. The region forming the core shows the highest magnetic field strength. We also obtain the distribution of mass-to-flux ratios across the clump. In the region surrounding the core, the mass-to-flux ratio is larger than 1, which indicates that the magnetic field strength is insufficient to support the region against gravitational collapse. Therefore, the change in the magnetic field orientation from clump to core scales may be the result of gravitational collapse, with the field being pulled inward along with the flow of material under gravity
IIA VINOD KRISHANCoupling of Alfven and magnetosonic waves in rotating hall magnetoplasmas
We study the linear theory of magnetohydrodynamic (MHD) waves, namely, the Alfvén and the fast and slow magnetosonic modes in a rotating Hall-MHD plasma with the effects of the obliqueness of the external magnetic field and the Coriolis force and show that these waves can be coupled either by the influence of the Coriolis force or the Hall effects. To this end, we derive a general form of the linear dispersion relation for these coupled modes by the combined influence of the Coriolis force and the Hall effects and analyze numerically their characteristics in three different plasma- β regimes: β∼1, β>1, and β<1, including some particular cases. We show that while the coupling between the Alfvén and the fast magnetosonic modes is strong in the low- β(β≲1) regime and the wave dispersion appears in the form of a thumb curve, in the high- β (β>1) regime, the strong coupling can occur between the Alfvén and the slow magnetosonic modes and the dispersion appears in the form of a teardrop curve. Switching of the coupling in the regime of β∼1 can occur, i.e., instead of a thumb curve, a teardrop curve appears when the obliqueness of propagation and rotational angle are close to 70° or more (but less than 90°). Implications of our results to solar and fusion plasmas are briefly discussed
IIA TANMOY SAMANTAFormation of chromospheric fan-shaped jets through magnetic reconnection
Recurrent chromospheric fan-shaped jets highlight the highly dynamic nature of the solar atmosphere. They have been named as “light walls” or “peacock jets” in high-resolution observations. In this study, we examined the underlying mechanisms responsible for the generation of recurrent chromospheric fan-shaped jets utilizing data from the Goode Solar Telescope at Big Bear Solar Observatory, along with data from the Atmospheric Imaging Assembly (AIA) and the Helioseismic and Magnetic Imager (HMI) on board the Solar Dynamics Observatory. These jets appear as dark elongated structures in Hα wing images, persist for over an hour, and are located in the intergranular lanes between a pair of same-polarity sunspots. Our analysis reveals that magnetic @ux cancellation at the jet base plays a crucial role in their formation. HMI line-of-sight magnetograms show a gradual decrease in opposite-polarity @uxes spanning the sequence of jets in Hα−0.8 Å images, suggesting that recurrent magnetic reconnection, likely driven by recurrent miniature @ux-rope eruptions that are built up and triggered by @ux cancellation, powers these jets. Additionally, magnetic Beld extrapolations reveal a 3D magnetic null-point topology at the jet formation site ∼1.25 Mm height. Furthermore, we observed strong brightening in the AIA 304 Å channel above the neutral line. Based on our observations and extrapolation results, we propose that these recurrent chromospheric fan-shaped jets align with the miniBlament eruption model previously proposed for coronal jets. Though our study focuses on fan-shaped jets in between same-polarity sunspots, a similar mechanism might be responsible for light-bridge-associated fan-shaped jets.
IIA PIYALI CHATTERJEEComputational astrophysics, data science and AI/ML in astronomy: A perspective from Indian community
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.
IIA SRIRAM, SOptical design studies for national large optical-IR telescope
A 10–12 m class national large optical-IR telescope (NLOT) is envisaged to meet the growing scientific requirements in astronomy and astrophysics. Telescopes of such dimensions can only be made by segmenting the primary mirror, as it eases a more prominent primary mirror’s fabrication, transportation, operation, and maintenance process. This paper presents the various optical designs analyzed for NLOT that can be fabricated using the India TMT Optics Fabrication Facility (ITOFF) at the Centre for Research and Education in Science and Technology (CREST) campus. We present the primary mirror segmentation details, its ideal optical performance, and study each design’s advantages and technical complexities. Based on the above analysis, we have narrowed it down to an optimal design, and its performance analysis is also discussed.