TITAN DR1: The Type Ia Supernova Trove from ATLAS in the Nearby Universe – Host Galaxies I: Associations, Redshifts and Derived Properties

We present the host-galaxy catalogue for TITAN DR1, a sample of 8378 spectroscopically confirmed Type Ia supernovae (SNe Ia) at z ≲ 0.15 – the largest homogeneous low-redshift SN Ia sample assembled to date. We describe the association of each SN with its host, the compilation of redshifts, measurements of uniform far-ultraviolet to mid-infrared (FUV–MIR) photometry, and the derivation of host properties through spectral energy distribution (SED) fitting. Combining four host-association methods with manual vetting, we securely identify hosts for 7856 SNe Ia (93.8%). We compile host-galaxy spectroscopic redshifts for 5522 objects and provide CMB-frame and peculiar-velocity-corrected redshifts. PSF-matched photometry is measured for 7568 host galaxies, including both global fluxes and local optical-only fluxes within a fixed 1.5 kpc aperture centred on the SN; Bagpipes returns successful global fits for all hosts and local fits for 7329. Stellar mass and rest-frame g − z colour are robustly measured from optical data alone, whereas reliable estimates of star-formation rate, dust attenuation, and mass-weighted age require broader wavelength coverage to break age–dust degeneracies, and are reported for 5827 hosts; in our redshift range, MIR data suffice and far-IR coverage is not required. The hosts span a representative low-redshift galaxy population, with a median stellar mass of log10(M*/M⊙) = 10.22 (60% high-mass; log10(M*/M⊙) > 10), 71% star-forming (log10(sSFR/yr−1) > −10.5), and an approximately exponential AV distribution. This catalogue provides the foundation for forthcoming analyses of the luminosity step and the broader role of galaxy environment in SN Ia standardization and cosmology.