arXiv subjects

Evan Batteas

Publications and source records attributed to Evan Batteas.

3 recordsLinked to original sources

arXiv2025

Dark matter annihilation signals from the Large Magellanic Cloud and its impact on the Milky Way

We study the dark matter (DM) annihilation signals from the Large Magellanic Cloud (LMC) and the impact of the LMC on the DM annihilation signals from the Milky Way (MW) halo, using a MW-LMC analogue from the Auriga magneto-hydrodynamical simulations. We find that the gamma-ray signals from DM annihilation from the LMC rises above the MW foreground by a factor of greater than 100 for the s-wave velocity-independent annihilation model, as well as for the Sommerfeld, p-wave, and d-wave velocity-dependent models. We derive upper limits on the annihilation cross section of DM particles in the LMC using Fermi-LAT data for all velocity-dependent cross section models. Bounds for d-wave annihilation are more stringent by $\sim 4-6$ orders of magnitude relative to previous bounds from dwarf galaxies, and for p-wave emission our bounds are $\sim 2-3$ orders of magnitude more stringent. We also demonstrate that the impact of the LMC on the DM annihilation signals from the MW halo is greatest for the p-wave and d-wave models towards the outer MW halo, while the impact is minimal for Sommerfeld and s-wave models. The LMC boosts the DM density and velocity distribution in the outer MW halo, both by bringing in high-speed DM particles and by accelerating the DM particles of the MW, affecting the DM annihilation signals from the MW for the p-wave and d-wave models.

astro-ph.HE↗

arXiv2025

Enhancements in velocity-dependent dark matter annihilation in Galactic subhalos

We examine velocity-dependent dark matter annihilation in subhalos using a sample of six Milky Way-like galaxies from the Aurgia simulation suite. We quantify the enhancement in the annihilation rate in subhalos when including the contribution from particles in the smooth component of the halo that overlap with the subhalos. The enhancement in the annihilation rate scales with the smooth component of the host halo dark matter density, and is evident for subhalos over the resolvable mass range. Maximal enhancement factors are ~ 48 for p-wave models, and ~ 37,000 for d-wave models. For p and d-wave annihilation models, ~ 13 and ~ 6 subhalos, respectively, across all six host halos have emission from dark matter annihilation in their direction that is above the foreground emission from the smooth dark matter component, and would therefore be resolvable as sources. Such subhalos with the most significant enhancement factors tend to be on the lower end of the mass range and located closer to the center of the host galaxy. We provide a prescription to calculate the enhancement for subhalos as a function of distance from the Galactic center, and use this to examine the impact on dark matter limits from a couple of example dwarf spheroidals. We show that, including the enhancement factors, limits from individual dwarf spheroidals are at a cross section scale that may approach those derived from the Galactic center.

astro-ph.HE↗

arXiv2025

Ground-Based Reconnaissance Observations of 21 Exoplanet Atmospheres with the Exoplanet Transmission Spectroscopy Imager

One of the most prolific methods of studying exoplanet atmospheres is transmission spectroscopy, which measures the difference between the depth of an exoplanet's transit signal at various wavelengths and attempts to correlate the depth changes to potential features in the exoplanet's atmosphere. Here we present reconnaissance observations of 21 exoplanet atmospheres measured with the Exoplanet Transmission Spectroscopy Imager (ETSI), a recently deployed spectro-photometer on the McDonald Observatory Otto Struve 2.1 m telescope. ETSI measurements are mostly free of systematics through the use of a novel observing technique called common-path multi-band imaging (CMI), which has been shown to achieve photometric color precision on-par with space-based observations (300ppm or 0.03%). This work also describes the various statistical tests performed on the data to evaluate the efficacy of the CMI method and the ETSI instrument in combination. We find that none of the 8 comparisons of exoplanet atmospheres measured with ETSI and other observatories (including the Hubble Space Telescope) provide evidence that the spectra are statistically dissimilar. These results suggest that ETSI can provide initial transmission spectroscopy observations for a fraction of the observational and monetary overhead previously required to detect an exoplanet's atmosphere. Ultimately these reconnaissance observations increase the number of planets with transmission spectroscopy measurements by ~10% and provide an immediate prioritization of 21 exoplanets for future follow-up with more precious observatories, such as the James Webb Space Telescope. The reconnaissance spectra are available through the Filtergraph visualization portal at the URL: https://filtergraph.com/etsi/.

astro-ph.EP↗