arXiv subjects

Mary H. Minasyan

Publications and source records attributed to Mary H. Minasyan.

5 recordsLinked to original sources

arXiv2026

Spectral Map Making with SPHEREx

We present map-making methodologies and preliminary spectral data cubes for SPHEREx, a NASA Explorer mission that launched in March 2025 and has been performing an all-sky near-infrared spectral survey. The SPHEREx instrument observes from 0.75 to 5.0 microns with a spectral resolution ranging from 35 to 130 and a pixel size of 6.15". We define a nominal set of 102 wavelength channels, each of which maps the entire sky approximately twice per year. Among the main mission goals is an investigation of the cosmic history of galaxy formation through intensity mapping of the extragalactic background light (EBL), which is a primary motivation for the map maker described in this work. The SPHEREx dataset contains a wealth of additional mapping targets, e.g., resolved galaxies and nebulae and diffuse clouds of Galactic dust and gas, which display strong spectral features such as hydrogen recombination lines, molecular-hydrogen lines and emission from polycyclic aromatic hydrocarbons (PAHs). We describe how our map maker handles these various cases, how to mitigate foregrounds such as zodiacal light and upper-atmospheric emission and how to monitor and mitigate systematics and signal loss. Our maps are produced both in tangent-plane projection and in full-sky HEALPix format. Specialized maps will be released to accompany future publications from the SPHEREx Science Team, and a public mosaic tool will be made available by the NASA/IPAC Infrared Science Archive (IRSA).

astro-ph.IM↗

arXiv2026

SPHEREx mapping of diffuse PAH and H II emission in the Galactic plane

We present preliminary SPHEREx maps of diffuse Galactic emission tracing polycyclic aromatic hydrocarbons (PAHs) and ionized hydrogen gas, and we study their relationship across the Galactic plane. Since its launch in early 2025, the SPHEREx space telescope has been conducting an all-sky near-infrared spectral survey from 0.75 to 5.0 microns. We produce a large-scale map of the 3.3-micron PAH emission feature, which is bright and detectable throughout the Galactic plane, and find a strong correlation with the thermal dust radiance measured by Planck. We also trace ionized hydrogen gas by producing a map of Brackett-alpha emission at 4.05 microns. By combining the two maps, we identify extended shells of PAH emission associated with photodissociation regions surrounding ionized gas. We construct a PAH abundance map and find a significant anticorrelation between PAH abundance and ionized hydrogen, indicating systematic PAH depletion within ionized gas regions across the Galactic plane and demonstrating that ionizing radiation is a dominant driver of PAH abundance variations. These early SPHEREx results provide a large-scale view of PAHs and ionized hydrogen and preview the capability of the mission to map diffuse emission in the interstellar medium.

astro-ph.GA↗

arXiv2025

The SPHEREx Satellite Mission

SPHEREx, a NASA explorer satellite launched on 11 March 2025, is carrying out the first all-sky near-infrared spectral survey. The satellite observes in 102 spectral bands from 0.75 to 5.0 um with a resolving power ranging from 35 to 130 in 6.2 arcsecond pixels. The observatory obtains a 5-sigma depth of 19.5 - 19.9 AB mag for 0.75 to 3.8 um and 17.8 - 18.8 AB mag for 3.8 to 5.0 um after mapping the full sky four times over two years. Scientifically, SPHEREx will produce a large galaxy redshift survey over the full sky, intended to constrain the amplitude of inflationary non-Gaussianity. The observations will produce two deep spectral maps near the ecliptic poles that will use intensity mapping to probe the evolution of galaxies over cosmic history. By mapping the depth of infrared absorption features over the Galactic plane, SPHEREx will comprehensively survey the abundance and composition of water and other biogenic ice species in the interstellar medium. The initial data are rapidly released in the form of spectral images to the public. The project will release specialized data products over the life of the mission as the surveys proceed. The science team will also produce specialized spectral catalogs on planet-bearing and low-mass stars, solar system objects, and galaxy clusters 3 years after launch. We describe the design of the instrument and spacecraft, which flow from the core science requirements. Finally, we present an initial evaluation of the in-flight performance and key characteristics.

astro-ph.IM↗

arXiv2025

The effect of a short mean free path on HII regions and 21-cm tomography during reionization

Recent measurements of the mean free path (MFP) of ionizing photons at $z=6$ find that it is significantly shorter than extrapolations from lower $z$. This has a substantial impact on the topology of reionization and thus the prospects of tomography of the 21-cm signal from upcoming radio interferometers. In this work we develop the first analytic model of reionization which explicitly incorporates the MFP as a free parameter, allowing us to transparently explore its effect on the process. Our model is based on the excursion set formalism with an ionization condition which accounts for absorptions parameterized through the MFP. With the goal of observational comparison, we include additional modifications which make our model particularly suitable for predicting one-point statistics of the ionization field (and 21-cm signal), which are among the fundamental quantities for tomography. We find that the effect of the MFP is much more significant during the later stages of reionization, and that including a shorter MFP reduces the size of HII regions by around an order of magnitude towards the end of reionization compared with analytic models which do not account for the MFP. We find that the reported MFP value produces a contrast in the 21-cm signal of $\mathcal{O}$(1 mK) or less at resolutions $θ\sim $ 15--35 arcmin, an order of magnitude below naive estimates and up to a factor of several smaller than when using a larger MFP value extrapolated from low $z$, requiring significantly more sensitivity for imaging. We compare the contrast to noise estimates for arrays similar in size to HERA and SKA-Low and find that SKA has sufficient sensitivity for direct imaging (at the largest scales considered), while the predicted signal will be challenging for arrays similar in size to HERA. Our model indicates that more detailed sensitivity estimates are warranted in the context of a short MFP.

astro-ph.CO↗

arXiv2023

A Search for Technosignatures Around 11,680 Stars with the Green Bank Telescope at 1.15-1.73 GHz

We conducted a search for narrowband radio signals over four observing sessions in 2020-2023 with the L-band receiver (1.15-1.73 GHz) of the 100 m diameter Green Bank Telescope. We pointed the telescope in the directions of 62 TESS Objects of Interest, capturing radio emissions from a total of ~11,680 stars and planetary systems in the ~9 arcminute beam of the telescope. All detections were either automatically rejected or visually inspected and confirmed to be of anthropogenic nature. In this work, we also quantified the end-to-end efficiency of radio SETI pipelines with a signal injection and recovery analysis. The UCLA SETI pipeline recovers 94.0% of the injected signals over the usable frequency range of the receiver and 98.7% of the injections when regions of dense RFI are excluded. In another pipeline that uses incoherent sums of 51 consecutive spectra, the recovery rate is ~15 times smaller at ~6%. The pipeline efficiency affects calculations of transmitter prevalence and SETI search volume. Accordingly, we developed an improved Drake Figure of Merit and a formalism to place upper limits on transmitter prevalence that take the pipeline efficiency and transmitter duty cycle into account. Based on our observations, we can state at the 95% confidence level that fewer than 6.6% of stars within 100 pc host a transmitter that is detectable in our search (EIRP > 1e13 W). For stars within 20,000 ly, the fraction of stars with detectable transmitters (EIRP > 5e16 W) is at most 3e-4. Finally, we showed that the UCLA SETI pipeline natively detects the signals detected with AI techniques by Ma et al. (2023).

astro-ph.IM↗