Indian Institute of Astrophysics

ABSTRACT Gravitational waves (GWs) offer a novel avenue for probing the Universe. An especially compelling application is an independent determination of the Hubble constant, $H_0$, using dark standard sirens, which associate GW signals with galaxy catalogues under the assumption that GW events are hosted by galaxies in the catalogue. However, due to the limited reach of telescopes, galaxy catalogues are largely incomplete at high redshifts. The commonly used Galaxy List for the Advanced Detector Era (GLADE+) catalogue, for example, is complete only up to redshift $z=0.1$. Handling this incompleteness necessitates the use of a model for the galaxy luminosity distribution, typically described by the Schechter function. In this paper, we examine the influence of the luminosity function model on dark sirens, focusing on its redshift evolution and its impact on $H_0$ and merger rate parameter measurements. We find that neglecting the evolution of the luminosity function can influence the prior in redshift on GWs, which has particularly high impact for distant GW events with limited galaxy catalogue support. Moreover, conducting a joint estimation of $H_0$ and the rate parameters, we find that allowing them to vary fixes the bias in $H_0$, but the rate evolution parameter $\gamma$ depends on the evolving luminosity function. Our results underscore the importance of incorporating the correct luminosity function evolution model to account for changes in galaxy populations over cosmic time, as this impacts rate parameters to which $H_0$ is sensitive.

Context . Studying young proto-planetary discs is essential for understanding planet formation, but traditional angular differential imaging introduces self-subtraction artefacts that make their small-scale structure difficult to interpret. We present high-resolution total- and polarised-intensity K s -band images of the LkCa 15 system that are free of such artefacts. Aims . LkCa 15 is a young proto-planetary system with a ~160 au disc and previous claims of two protoplanet candidates at 15 and 18 au. We aim to analyse the LkCa 15 proto-planetary disc using high-contrast imaging to search for super-Jupiter planets beyond 20 au and to characterise the dust distribution and grain composition. Methods . We used near-simultaneous reference-star differential imaging (RDI, ‘star-hopping’) to obtain self-subtraction-free K s -band images beyond 0.1″. We first modelled the K s -band total- and polarised-intensity images together with ALMA submillimetre continuum maps using RADMC-3D and a two grain-size (micron and millimetre) compact olivine model. Residual mismatches in the near-IR then motivated us to extract the scattering phase function, S ( θ ), and polarised fraction, P ( θ ), from the SPHERE data and compare them with aggregate-scattering models, which pointed to porous CAHP grains in the surface layer and led us to recompute the NIR scattered-light models with CAHP. Results . Our initial two grain-size (micron and millimetre) olivine model roughly reproduces the observed NIR and ALMA disc morphology, with a flared micron surface layer from ~25-85 au ( H / R ~ 0.08 at 50 au; surface gap ~35-40 au) and a millimetre mid-plane ring from ~55-130 au with a gap at ~75-100 au, for i ~ 50° and PA ~ 61°. The near-IR data, however, are less forward-scattering than the model. From the phase functions, we find that S ( θ ) rises by ~5× from θ ~ 90° to θ ~ 35°, while P ( θ ) shows a broad sub-Rayleigh peak with P max ~ 0.35 near θ ~ 90°. These analyses disfavour compact olivine Mie spheres and are better matched by porous aggregates (CAHP-128-100 nm), so we recomputed the NIR scattered-light models with CAHP-128-100 nm grains in the surface layer (retaining compact millimetre grains for the ALMA continuum), which improves the match to the K s -band morphology and polarisation. From the number ratio between the 12 μm and 2 mm grains, we inferred a size-distribution slope of ζ ~ −2.3. Although no new candidate planets were detected, we estimated upper mass limits: beyond 200 au, planets more massive than ~1.5 M J are unlikely, while in the inner disc planets up to ~3.6 M J could remain undetected. Conclusions . The star-hopping RDI data, together with phase-function diagnostics and RADMC-3D modelling with compact olivine and porous CAHP grains, allow us to reproduce the main observed features of the LkCa 15 system. The number ratio between the 12 μm and 2 mm olivine grains further shows that micron-sized grains are under-abundant relative to size distributions in the ISM or debris discs, providing new insights into grain growth and dust dynamics in gas-rich proto-planetary discs.

Context. Boxy/peanut and X-shaped (BP/X) bulges are prominent features in edge-on disk galaxies and they are believed to represent vertically thickened bars. Despite their relevance in bar evolution, a statistically robust census of these structures in large surveys remains lacking. Aims. We aim to provide the largest catalog of BP/X structures in edge-on galaxies to date, along with an investigation of their properties and role in shaping galaxy scaling relations. Methods. We selected a sample of 6684 edge-on galaxies from SDSS DR8 using Galaxy Zoo classifications, requiring a high edge-on probability (> 0.9) and a minimum of ten independent votes. We performed a two-dimensional (2D) image decomposition using GALFIT to obtain the structural parameters. The residual images were visually inspected to classify BP/X features into four categories: strong both-sided, both-sided, one-sided, and control (no BP/X). We also estimated the stellar mass, distance, and physical size for each galaxy. Results. Out of 6653 classified galaxies, we identified 1673 (∼25%) with both-sided BP/X features, 504 (∼8%) strong, and 1169 (∼17%) weak, as well as 1112 (∼17%) one-sided structures, making up a total of 2785 BP/X-hosting galaxies (∼42%). We find that one-sided structures, likely signatures of ongoing buckling, are more frequent than strong both-sided bulges across all stellar masses. The fraction of BP/X bulges increases with stellar surface mass density, indicating a connection with bar formation in dense discs. We also find that galaxies with strong BP/X bulges contribute to increased scatter in the stellar-mass-size and stellar-mass-surface-density relations, particularly at higher masses.

The redshifted 21 cm signal from the cosmic dawn and Epoch of Reionization (EoR) encodes important information about both astrophysical processes and primordial physics, such as inflation. In this work, we use morphological statistics to explore the sensitivity of the 21 cm signal to inflationary features and EoR dynamics simultaneously. Focusing on primordial features from particle production during inflation we generate semi-numerical simulations of the 21 cm signal across redshifts 5 < z < 35, incorporating these features. Using Minkowski Functionals (MFs), we analyze the morphology of 21 cm fields: density, neutral hydrogen fraction, spin temperature, and brightness temperature. We demonstrate that MFs are highly sensitive to both the amplitude and scale of primordial features, capturing rich morphological information. In particular, we show that MFs can robustly identify inflationary features and distinguish them from the standard model. We further explore various EoR scenarios, and demonstrate that combining MFs across redshifts can disentangle the signatures of primordial features from EoR effects. This approach opens new avenues for probing inflation with upcoming 21 cm surveys.

ABSTRACT We present photometric and spectroscopic studies of two core-collapse supernovae (SNe) 2008aq and 2019gaf in the optical wavelengths. Light curve and spectral sequence of both the SNe are similar to those of other Type IIb SNe. The pre-maximum spectrum of SN 2008aq showed prominent H $\alpha$ lines, the He lines started appearing in the near maximum spectrum. The near maximum spectrum of SN 2019gaf shows shallow H $\alpha$ absorption and He lines with almost similar strength. Both the SNe show transition from hydrogen-dominated spectra to helium-dominated spectra within a month after maximum brightness. The velocity evolution of SN 2008aq matches well with those of other well-studied Type IIb SNe, while SN 2019gaf shows higher velocities. Close to maximum light, the H $\alpha$ and He i line velocities of SN 2019gaf are $\sim$ 2000 and $\sim$ 4000 km s$^{-1}$ higher than other well-studied Type IIb SNe. Semi-analytical modelling indicates SN 2019gaf to be a more energetic explosion with a smaller ejecta mass than SN 2008aq. The zero-age main-sequence (ZAMS) mass of the progenitor estimated using the nebular spectra of SN 2008aq ranges between 13 and 20 M$_\odot$, while for SN 2019gaf, the inferred ZAMS mass is between 13 and 25 M$_\odot$. The [O i] to [Ca ii] lines flux ratio favours a less massive progenitor star in a binary system for both the SNe.

Abstract We present the results of low-resolution spectroscopic and densely sampled multiband photometric follow-up of supernova (SN) 2024aecx. The SN was discovered in the spiral galaxy NGC 3521 (distance ∼ 11 Mpc) within a day after the explosion. The early spectra of SN 2024aecx show a weak signature of hydrogen lines, which disappeared in ∼30 days after the explosion. Light curves in all bands show a distinct feature of two peaks, and the first peak is likely due to the emission from shock cooling. The early-phase evolution of the light curve of SN 2024aecx is similar to the typical Type IIb events, but the decay rate in different bands (e.g., Δ m 15 = 1.60 ± 0.05 mag, g band) is significantly faster in the postpeak phase. It attained the secondary maximum in ∼19 days ( g band) with a peak absolute magnitude of M g = –17.94 ± 0.10 mag. The colors of SN 2024aecx tend to be redder in early epochs (&lt;8 days), then it grows bluer for a period, then redder again &gt;20 days after explosion. The analytical model fitting to the light curves reveals an envelope mass and progenitor radius in the ranges ∼0.03–0.24 M ⊙ and ∼169–200 R ⊙ , respectively. Modeling of the pseudobolometric light curve suggests that synthesized 56 Ni in the explosion was ∼0.15 M ⊙ with ejecta mass and kinetic energy of ∼0.7 M ⊙ and ∼0.16 × 10 51 erg, respectively. The observational properties and modeling indicate that the progenitor of SN 2024aecx belongs to the category of extended progenitors.

The strategic integration of Intellectual Property (IP) macros between soft IPs and hard IPs is the base framework in the attainment of design timing closure and improved performance. Since the main limitations to signal timing, power distribution and silicon area efficiency are determined by these high-density blocks, their location is a critical factor in determining chip performance. Another major drawback of the traditional workflows is the physical integration that is not optimal, namely the definition of keepout margins. Small keepout margins around macros can easily lead to routing congestion where too much standard cell density around macro boundaries causes a lot of congestion. To reduce this, macro placement applies flyline analysis to chart logical connectivity, and avoids congestion by making sure the orientation is proper, keepout margins are mathematically sized to fit all the tracks, and has a huge impact on the QoR and the timeline to tape-out.

Abstract Stars primarily form in galactic spiral arms within dense, filamentary molecular clouds. The largest and most elongated of these molecular clouds are referred to as “bones,” which are massive, velocity-coherent filaments (lengths ∼20 to &gt;100 pc, widths ∼1–2 pc) that run approximately parallel and in close proximity to the Galactic plane. While these bones have been generally well characterized, the importance and structure of their magnetic fields (B-fields) remain largely unconstrained. Through the Stratospheric Observatory for Infrared Astronomy Legacy program FIlaments Extremely Long and Dark: a Magnetic Polarization Survey (FIELDMAPS), we mapped the B-fields of 10 bones in the Milky Way. We found that their B-fields are varied, with no single preferred alignment along the entire spine of the bones. At higher column densities, the spines of the bones are more likely to align perpendicularly to the B-fields, although this is not ubiquitous, and the alignment shows no strong correlation with the locations of identified young stellar objects. We estimated the B-field strengths across the bones and found them to be ∼30–150 μ G at parsec scales. Despite the generally low virial parameters, the B-fields are strong compared to the local gravity, suggesting that B-fields play a significant role in resisting global collapse. Moreover, the B-fields may slow and guide gas flow during dissipation. Recent star formation within the bones may be due to high-density pockets at smaller scales, which could have formed before or simultaneously with the bones.