arXiv subjects

Andy Nilipour

Publications and source records attributed to Andy Nilipour.

5 recordsLinked to original sources

arXiv2026

Optimal transport regularized dynamic radio interferometric reconstruction

We propose a new technique for dynamic video reconstruction of radio interferometric data using the optimal transport (OT) distance as a regularizer within the regularized maximum likelihood (RML) framework. Compared to other commonly used regularization terms in RML and related prior-based approaches, the OT distance more naturally captures information including physical motion and promotes coherent dynamics. This property makes the OT regularization particularly suitable for dynamic imaging of astrophysical phenomena on minute timescales. We perform a series of tests on simulated very long baseline interferometric (VLBI) observations of Sagittarius A$^\ast$ (SgrA*), the supermassive black hole at the Galactic Center, with the Event Horizon Telescope (EHT), using both geometric and general relativistic magnetohydrodynamic models. We demonstrate that adding an OT regularization term yields significant improvements in dynamic reconstructions compared to those without it, as quantified by better recovery of orbital motion and higher dynamic cross-correlation metrics. Continued developments in OT theory across various fields, proposed extensions to the EHT network, and broad applicability to other VLBI networks make it so that OT regularization for dynamic radio interferometric reconstructions will continue to be utilized and improved in the future.

astro-ph.IM↗

arXiv2026

Competing with AI Scientists: Agent-Driven Approach to Astrophysics Research

We present an agent-driven approach to the construction of parameter inference pipelines for scientific data analysis. Our method leverages a multi-agent system, Cmbagent (the analysis system of the AI scientist Denario), in which specialized agents collaborate to generate research ideas, write and execute code, evaluate results, and iteratively refine the overall pipeline. As a case study, we apply this approach to the FAIR Universe Weak Lensing Uncertainty Challenge, a competition under time constraints focused on robust cosmological parameter inference with realistic observational uncertainties. While the fully autonomous exploration initially did not reach expert-level performance, the integration of human intervention enabled our agent-driven workflow to achieve a first-place result in the challenge. This demonstrates that semi-autonomous agentic systems can compete with, and in some cases surpass, expert solutions. We describe our workflow in detail, including both the autonomous and semi-autonomous exploration by Cmbagent. Our final inference pipeline utilizes parameter-efficient convolutional neural networks, likelihood calibration over a known parameter grid, and multiple regularization techniques. Our results suggest that agent-driven research workflows can provide a scalable framework to rapidly explore and construct pipelines for inference problems.

cs.AI↗

arXiv2024

Turbulent Pressure Heats Gas and Suppresses Star Formation in Galactic Bar Molecular Clouds

The Central Molecular Zone (CMZ) of the Milky Way is fed by gas inflows from the Galactic disk along almost radial trajectories aligned with the major axis of the Galactic bar. However, despite being fundamental to all processes in the nucleus of the galaxy, these inflows have been studied significantly less than the CMZ itself. We present observations of various molecular lines between 215 and 230 GHz for 20 clouds with $|\ell| < 10^\circ$, which are candidates for clouds in the Galactic bar due to their warm temperatures and broad lines relative to typical Galactic disk clouds, using the Atacama Large Millimeter/submillimeter Array (ALMA) Atacama Compact Array (ACA). We measure gas temperatures, shocks, star formation rates, turbulent Mach numbers, and masses for these clouds. Although some clouds may be in the Galactic disk despite their atypical properties, nine clouds are likely associated with regions in the Galactic bar, and in these clouds, turbulent pressure is suppressing star formation. In clouds with no detected star formation, turbulence is the dominant heating mechanism, whereas photo-electric processes heat the star-forming clouds. We find that the ammonia (NH$_3$) and formaldehyde (H$_2$CO) temperatures probe different gas components, and in general each transition appears to trace different molecular gas phases within the clouds. We also measure the CO-to-H$_2$ X-factor in the bar to be an order of magnitude lower than the typical Galactic value. These observations provide evidence that molecular clouds achieve CMZ-like properties before reaching the CMZ

astro-ph.GA↗

arXiv2023

Signal Synchronization Strategies and Time Domain SETI with Gaia DR3

Spatiotemporal techniques for signal coordination with actively transmitting extraterrestrial civilizations, without the need for prior communication, can constrain technosignature searches to a significantly smaller coordinate space. With the variable star catalog from Gaia Data Release 3, we explore two related signaling strategies: the SETI Ellipsoid, and that proposed by Seto, which are both based on the synchronization of transmissions with a conspicuous astrophysical event. This dataset contains more than 10 million variable star candidates with light curves from the first three years of Gaia's operational phase, between 2014 and 2017. Using four different historical supernovae as source events, we find that less than 0.01% of stars in the sample have crossing times, the times at which we would expect to receive synchronized signals on Earth, within the date range of available Gaia observations. For these stars, we present a framework for technosignature analysis that searches for modulations in the variability parameters by splitting the stellar light curve at the crossing time.

astro-ph.IM↗

arXiv2023

Real-Time Technosignature Strategies with SN 2023ixf

Several technosignature techniques focus on historic events such as SN 1987A as the basis to search for coordinated signal broadcasts from extraterrestrial agents. The recently discovered SN 2023ixf in the spiral galaxy M101 is the nearest Type II supernova in over a decade, and will serve as an important benchmark event. Here we review the potential for SN 2023ixf to advance ongoing techonsignature searches, particularly signal-synchronization techniques such as the "SETI Ellipsoid". We find that more than 100 stars within 100 pc are already close to intersecting this SETI Ellipsoid, providing numerous targets for real-time monitoring within ~3$^\circ$ of SN 2023ixf. We are commencing a radio technosignature monitoring campaign of these targets with the Allen Telescope Array and the Green Bank Telescope.

astro-ph.IM↗