Dust populations and complex morphology of the young debris disk around HD 120326 based on panchromatic data

For decades, astronomers have attempted to classify galaxies based on their visual appearance. Beneath these neat categories of Spiral, Lenticular and Elliptical can lie very disparate galaxies, hosting very different assembly and evolutionary histories. I will present the results of a comprehensive census of the kinematic structure of local Universe galaxies, the results of which may be a little surprising. Zooming in to ~parsec scales, we can begin to examine individual structures in local galaxies with unprecedented detail. I will discuss my favourite structures, bars and bulges, and then turn the problem on its side by introducing and presenting first results from the GECKOS survey, an ESO/MUSE large program surveying 36 edge-on Milky Way-mass galaxies.The direct imaging technique is able to constrain planetary system architectures by probing regions at large (> 5 au) separations from the star. This approach can detect the near- and mid-infrared emission of young self-luminous giant planets and resolve circumstellar disks, such as debris disks, made up of leftover material from planet formation processes. Among more than a hundred debris disks spatially resolved, the young system HD 120326 stands out, displaying different disk substructures on both intermediate (30-150 au) and large (150-1000 au) scales.  In this seminar, I will present my multi-wavelength work on the debris disk around HD 120326, based on new VLT/SPHERE (1.0-1.8 µm) and ALMA (1.3 mm) data combined to archival HST/STIS (0.2-1.0 μm) and archival SPHERE data, recently published (Desgrange et al. 2025, A&A). In this study, I constrained the morphology and photometry of the debris disk, along with its dust properties. In particular, I developed the open-access code MoDiSc (Modeling Disks in Scattered light) to model the inner belt jointly using the SPHERE polarized and total intensity observations. Separately, my collaborators and I modeled the ALMA data and the spectral energy distribution (SED). I identified the inner belt as a planetesimal belt, with a semi-major axis of 43 au, a fractional luminosity of 1.8 x 10-3 , and a maximum degree of polarization of ~51 % at 1.6 μm. This could indicate that the dust particles have a low albedo or are small monomers in dust grain aggregates. The spectral slope of its reflectance spectrum is red between 1.0 and 1.3 μm and gray between 1.3 and 1.8 μm. The SPHERE data also show that there could be a halo of small particles or a second belt at distances <150 au. Using ALMA, my collaborators and I derived in the continuum (1.3 mm) an integrated flux of ~561μJy, without detection of any 12CO emission. At larger separations (>150 au), my reprocessing of the STIS data reveals a spiral-like feature spanning hundreds of astronomical units. This spiral-like feature could be triggered by a Jupiter-mass exoplanet based on our N-body simulations.