Recent Talks

One of the most fundamental questions in astronomy is how stars, the building blocks of the Universe, form. We generally understand that stars emerge from dense regions within molecular clouds, called prestellar cores, which collapse under gravity to form protostars, but many details of this process remain elusive. Despite significant advances in instrumentation and modelling, we still lack a complete understanding of how stars and planetary systems develop. A crucial piece of this puzzle lies in the protostellar phase, particularly the accretion process responsible for stellar mass growth at the early and more embedded stages of star formation. In this talk, I will review the current state of knowledge on accretion, presenting my work on last observational results of the early stages of star formation and discussing their implications for the broader star and planet formation scenario. 

Durham Adaptive Optics (DAO) is a powerful and flexible software solution for adaptive optics systems.  DAO enables real-time correction of wavefront distortions caused by atmospheric turbulence and optical aberrations, improving the image quality of ground-based telescopes. DAO takes a hardware-agnostic approach to processing pipelines, supporting distributed heterogeneous compute environments. Its high flexibility allows seamless integration with various hardware systems and configurations, accommodating different wavefront sensors (such as Shack-Hartmann and pyramid sensors), actuators (including deformable mirrors, tip-tilt mirrors, and spatial light modulators), and other components.

The presentation will cover the software's flexible architecture, which enables it to be integrated with a variety of hardware systems and configurations. We will showcase DAO’s user base and how DAO has been used to solve their adaptive optics real-time control needs. These examples will demonstrate DAO’s efficient data handling, parallel processing techniques, low latency, and minimal jitter, whilst emphasising its capacity to scale to AO systems of all size, from laboratory-based research projects to ELT-scale facility class systems.

In order to understand galaxy growth evolution, it is critical to constrain the evolution of its building block: gas. Mostly comprised by Hydrogen in its neutral (HI) and molecular (H2) phases, the latter is the one mostly directly associated to star-formation, while the neutral phase is considered the long-term gas reservoir. Both phases are difficult to detect directly either due to high excitation temperatures or low transition probability. As a result, while HI direct observations have been limited to the local Universe and extended to high redshifts when seen in absorption, H2 has been traced indirectly via tracers, either Carbon Monoxide (CO) rotational transitions, atomic Carbon fine structure transitions, or dust emission at (sub-)mm wavelengths. However, the latter best tracers the combined content of HI and H2 masses. In this work (Messias et al. 2024), we make use of an empirical relation between dust emission at millimeter wavelengths and total gas mass in the inter-stellar medium (M_HI plus M_H2) in order to retrieve the HI content in galaxies. We assemble an heterogeneous sample of 335 galaxies at 0.01<z<6.4 detected in both mm-continuum and carbon monoxide (CO) low-J transitions. More specifically, a blindly selected sub-sample had a special focus given its suitability to retrieve HI cosmological content when the Universe was ~2-6 Gyr old (1<z<3). Overall, we find no significant evolution with redshift of the M_HI/M_H2 ratio, which is about 1–3 (depending on the relation used to estimate M_HI). This also shows that M_H2-based gas depletion times are underestimated overall by a factor of 2–4. Compared to local Universe HI mass functions, we find that at least the number density of galaxies with M_HI>1E10.5 Msun significantly decreased since 8–12 Gyr ago. The specific sample used for this analysis is associated to 20-50% of the total cosmic HI content as estimated via Damped Lyman-alpha Absorbers. In IR luminous galaxies, HI mass content decreases between z~2.5 and z~1.5. Finally, the results obtained in this work allow us to report source detection predictions for SKA1 surveys and what is the most suitable strategy to detect HI at cosmic noon.

Wavefront sensing and adaptive optics, techniques developed from astronomy, have made their way to the ophthalmology practice. Correcting the aberrations of the eye has allowed unprecedented resolution to resolve fine structure in the human retina. On the other hand, wavefront sensing has become a ubiquitous technology to assess the optical quality of the eye and advanced refraction. Visual simulators, based on adaptive optics, allow patients to preview the world with prospective corrections and select the contact lenses, intraocular lenses or corneal refractive surgery pattern that best fits their visual function and perceptual preference

Dark sirens are sources of gravitational waves (typically mergers of black hole binaries) without an electromagnetic counterpart. The gravitational waveform measured by our detectors allows us to infer the distance (not the redshift) to those sources, and with the new generation of detectors such as the Einstein Telescope, the uncertainty in their angular position and distance will decrease dramatically. In this talk I will show that by correlating dark sirens and galaxies we can directly draw the Hubble redshift-distance relation, with minimal assumptions about the underlying cosmology. This allows for a direct measurement of the Hubble parameter, free of the systematics of standard sirens and without the model dependence of the Planck constraint, which can achieve an accuracy of 4% with run 5 of the LIGO-Virgo-Kagra network of gravitational wave detectors, and less than 1% with the future facility Einstein Telescope.

We present our results from observing the occultation of Betelgeuse by asteroid (319) Leona on December 12,2023, using a cutting-edge 64 x 64 pixel Single-Photon Avalanche Diode (SPAD) array mounted on a 10-inch telescope at the AstroCamp Observatory in Nerpio, Southeast of Spain, located just a few kilometers from the center of the occultation shadow path. This study marks a remarkable advancement in applying SPAD technology in astronomy. The SPAD array's asynchronous readout capacity and photon-counting timestamp mode enabled us to achieve a temporal resolution of I microsecond in our light curve observations of Betelgeuse. The data analysis addresses challenges inherent to SPAD arrays, such as optical cross-talk and afterpulses, which cause the photon statistics to deviate from a Poisson distribution. By adopting a generalized negative binomial distribution (NBD) for photon statistics, we accurately describe the observational data. This approach yields an optical cross-talk estimation of l.OlVo in our SPAD array and confirmed a negligible impact of spurious detected events from afterpulses. The meticulous statistical examination of photon data underscores our SPAD-array's exceptional performance in conducting precise astronomical observations. The observations reveal a major decrease in Betelgeuse's intensity by 77.78Vo at the occultation's peak, allowing the measurement of Betelgeuse's angular diameter to be 57.26 mas in the SDSS g-band. This measurement was obtained by employing a simplified occultation model and considering the known properties of Leona. This work not only demonstrates the potential of SPAD technology in astronomy but also sets a new standard for observations of transient celestial events, offering a precious public dataset for the astronomical community.

Supernovae represent the explosive death of a star. There is a small group of core-collapse supernovae whose peak luminosity in the light curve is so high that it cannot be explained by conventional models. Therefore, it is necessary to consider alternative boosting mechanisms to understand their origin.  In this talk, I will present the characterization of the largest sample of hydrogen-rich superluminous supernovae (SLSN II) available to date. I will discuss the possible mechanisms responsible for the observed features and the minimum requirements needed to conduct similar analyses using data from the Legacy Survey of Space and Time (LSST) of the Vera C. Rubin Observatory.

The atmosphere of a rocky or icy moon is the interface between its surface and its orbital environment, and encodes information about both its interior processes and its interactions with its host planet’s magnetosphere. Among the outer Solar System’s major moons, atmospheres range from the tenuous, sputtered O2 atmosphere of Europa to the dense, organics-laden atmosphere of Titan. Obtaining a complete picture of the atmospheric composition and dynamics requires a multi-wavelength approach, as different observing techniques are sensitive to different chemical components, altitudes, and excitation mechanisms. This talk will present recent observations of the atmospheres of satellites in the Jupiter and Saturn systems from observatories including HST, JWST, Keck, and ALMA, and will discuss how multi-wavelength approaches are giving us a more complete understanding of the atmospheres of these moons and enabling progress on key questions.

Strong gravitational evidence at galactic, extragalactic and cosmological scales exists to believe that most of the matter in our Universe, i.e. up to ∼85% of the total, is dark and non-baryonic. Yet, this dark matter (DM) has not been directly detected. Some of the most preferred scenarios suggest that DM consists of Weakly Interacting Massive Particles (WIMPs), which interact mostly gravitationally with baryonic matter.

A prediction of the standard LCDM cosmological model is that dark matter (DM) halos are teeming with numerous self-bound substructure, or subhalos. At small scales, subhalos may host no stars/gas at all and thus may not have visible astrophysical counterparts. The existence and precise properties of these ‘dark satellites’ represent important probes of the underlying cosmological model. Also, they may play a key role on the search for DM via its annihilation products. In this talk, I will present current numerical work to characterize the subhalo population with unprecedented detail, and will discuss on the importance that dark satellites may have for DM searches with present or future gamma-ray observatories. I will then summarize the recent efforts we made to search for them in gamma-ray data and to set constraints on the nature of the DM particle using these elusive targets.