arXiv subjects

Bradley Frank

Publications and source records attributed to Bradley Frank.

6 recordsLinked to original sources

arXiv2026

Exploring generative design AI tools for astronomical instrumentation: a CubeSat chassis case study

Generative design artificial intelligence (AI) tools are currently used in multiple scientific fields, yet their adoption in mechanical engineering computer-aided design (CAD) remains limited due to a lack of disseminated case studies, limited availability of accessible tools, insufficient training in CAD data, the absence of universal editable file formats and more. Mechanical design for astronomical instrumentation faces increasing complexity in thermal, vibrational, and mechanical requirements alongside tight project deadlines. This paper presents a practical evaluation of an AI and FEA based generative design tool applied to chassis design for the Active Deployable Optical Telescope (ADOT) CubeSat mission. Our analysis showcases the workflow steps including the setting of design, manufacturing and objective constraints. This study also shows the clear benefits of these types of tools, especially in the early brainstorming stages of multi-constrained mechanical structures, while also highlighting clear limitations like their black-box nature, the non-manufacturing-ready state of the results, and the time-consuming setup, limiting the tangible gain of these tools to high-value mechanical components.

astro-ph.IM↗

arXiv2026

ANDES, the high-resolution spectrograph for the ELT: design and performance analysis of the YJH spectrograph

The ArmazoNes high Dispersion Echelle Spectrograph (ANDES) is a powerful second-generation high-resolution spectroscopic instrument for the Extremely Large Telescope (ELT). The UBV, RIZ, and YJH modules comprise fibre-fed spectrographs of the ANDES baseline design and will offer continuous wavelength coverage of 0.35-1.8 $μ$m, with the addition of a K-band channel providing coverage up to 2.4 $μ$m. Coupled with a spectral resolution of $\sim$100,000, ANDES must deliver the required wavelength calibration stability of 1 m/s over 24 hours, with a goal of 0.02 m/s across 10 years. These requirements establish the framework for the infrared module of ANDES, the YJH Spectrograph, leading to what will likely be the largest cryogenic, ultra-stable, high-resolution spectrograph ever built, and will offer the unique ability to observe in both seeing- and diffraction-limited modes interchangeably. We present the current design and performance analysis of the ANDES YJH Spectrograph, outlining the engineering challenges encountered alongside the corresponding strategies adopted to navigate them. In particular, we detail the technology development of the primary dispersing element, an echelle grating mosaic that will span over a metre in length.

astro-ph.IM↗

arXiv2026

MIGHTEE HI observations of low surface brightness and ultra-diffuse galaxies in the XMM-LSS field

Untargeted neutral hydrogen (HI) surveys are well suited to identifying low surface brightness galaxies (LSBGs) that are gas rich, and they offer a complementary view to optically selected populations. We examined the LSBG population as identified via stellar and gaseous content using the MIGHTEE HI XMM-LSS early science data and the publicly available catalogs of optically identified LSBGs. There is currently little overlap between these datasets, with only three galaxies commonly detected. We performed surface brightness photometry of selected MIGHTEE HI detections to find 29 LSBGs, and 26 of these meet the size requirement (R_eff > 1.5 kpc) to be ultra-diffuse galaxies (UDGs). Furthermore, we extracted HI spectra at the location of all optically identified galaxies, placing upper limits on the HI-to-stellar mass ratio in these systems. While the HI-identified population overall tends toward bluer colors, the HI-identified and the optically selected samples mostly overlap in mean effective surface brightness, effective radii, and color. Although it is not straightforward to discern why the HI-identified LSBGs were missed in optical searches, this work highlights the utility of HI surveys in finding these faint systems. The HI-identified LSBGs are gas rich compared to the general HI-selected population. Furthermore, three out of four HI-selected UDGs with available kinematics show no systematic offset from the baryonic Tully-Fisher relation, although we are biased away from sources with low rotational velocities due to the low spectral resolution of the data. This work demonstrates the utility of HI observations for finding and characterizing the low surface brightness Universe.

astro-ph.GA↗

arXiv2023

HI Galaxy Signatures in the SARAO MeerKAT Galactic Plane Survey -- II. The Local Void and its substructure

The Local Void is one of the nearest large voids, located at a distance of 23 Mpc. It lies largely behind the Galactic Bulge and is therefore extremely difficult to observe. We use HI 21 cm emission observations from the SARAO MeerKAT Galactic Plane Survey (SMGPS) to study the Local Void and its surroundings over the Galactic longitude range 329$^{\circ}< \ell <$ 55$^{\circ}$, Galactic latitude $|b| <$ 1.5$^{\circ}$, and redshift $cz <$ 7500 km/s. We have detected 291 galaxies to median rms sensitivity of 0.44 mJy per beam per 44 km/s channel. We find 17 galaxies deep inside the Void, 96 at the border of the Void, while the remaining 178 galaxies are in average density environments. The extent of the Void is ~ 58 Mpc. It is severely under-dense for the longitude range 350$^{\circ}< \ell <$ 35$^{\circ}$ up to redshift $z <$ 4500 km/s. The galaxies in the Void tend to have \HI masses that are lower (by approximately 0.25 dex) than their average density counterparts. We find several potential candidates for small groups of galaxies, of which two groups (with 3 members and 5 members) in the Void show signs of filamentary substructure within the Void.

astro-ph.GA↗

arXiv2023

HI Galaxy Signatures in the SARAO MeerKAT Galactic Plane Survey $-$ I. Probing the richness of the Great Attractor Wall across the inner Zone of Avoidance

This paper presents the first HI results extracted from the SARAO MeerKAT Galactic Plane Survey (SMGPS) $-$ a narrow strip ($b \sim 3^\circ$) along the southern Milky Way. The primary goal consisted in tracing the Great Attractor (GA) Wall across the innermost Zone of Avoidance. We reduced a segment spanning the longitude range $302^\circ \leq \ell \leq 332^\circ$ for the redshift range $z \leq 0.08$. The superb SMGPS sensitivity (rms = 0.3-0.5 mJy beam$^{-1}$ per 44 kms$^{-1}$ channel) and angular resolution ($\sim$ 31" $\times$ 26") lead to a detection limit of log$(M_{\rm HI}/$M$_\odot) \geq$ 8.5 at the GA distance ($V_{\rm hel} \sim 3500 - 6500$ kms$^{-1}$). A total of 477 galaxy candidates were identified over the full redshift range. A comparison of the few HI detections with counterparts in the literature (mostly HIZOA) found the HI fluxes and other HI parameters to be highly consistent. The continuation of the GA Wall is confirmed through a prominent overdensity of $N = 214$ detections in the GA distance range. At higher latitudes, the wall moves to higher redshifts, supportive of a possible link with the Ophiuchus cluster located behind the Galactic Bulge. This deep interferometric HI survey demonstrates the power of the SMGPS in improving our insight of large-scale structures at these extremely low latitudes, despite the high obscuration and continuum background.

astro-ph.GA↗

arXiv2022

LADUMA: Discovery of a luminous OH megamaser at $z > 0.5$

In the local Universe, OH megamasers (OHMs) are detected almost exclusively in infrared-luminous galaxies, with a prevalence that increases with IR luminosity, suggesting that they trace gas-rich galaxy mergers. Given the proximity of the rest frequencies of OH and the hyperfine transition of neutral atomic hydrogen (HI), radio surveys to probe the cosmic evolution of HI in galaxies also offer exciting prospects for exploiting OHMs to probe the cosmic history of gas-rich mergers. Using observations for the Looking At the Distant Universe with the MeerKAT Array (LADUMA) deep HI survey, we report the first untargeted detection of an OHM at $z > 0.5$, LADUMA J033046.20$-$275518.1 (nicknamed "Nkalakatha"). The host system, WISEA J033046.26$-$275518.3, is an infrared-luminous radio galaxy whose optical redshift $z \approx 0.52$ confirms the MeerKAT emission line detection as OH at a redshift $z_{\rm OH} = 0.5225 \pm 0.0001$ rather than HI at lower redshift. The detected spectral line has 18.4$σ$ peak significance, a width of $459 \pm 59\,{\rm km\,s^{-1}}$, and an integrated luminosity of $(6.31 \pm 0.18\,{\rm [statistical]}\,\pm 0.31\,{\rm [systematic]}) \times 10^3\,L_\odot$, placing it among the most luminous OHMs known. The galaxy's far-infrared luminosity $L_{\rm FIR} = (1.576 \pm 0.013) \times 10^{12}\,L_\odot$ marks it as an ultra-luminous infrared galaxy; its ratio of OH and infrared luminosities is similar to those for lower-redshift OHMs. A comparison between optical and OH redshifts offers a slight indication of an OH outflow. This detection represents the first step towards a systematic exploitation of OHMs as a tracer of galaxy growth at high redshifts.

astro-ph.GA↗