A Roadmap for Transient Hunters: Mapping Stellar Mass and Star Formation Rate Anisotropies in the Local Universe

Abstract

Over the past few decades, an increasing number of transients in nearby galaxies have been discovered through various survey projects. Unlike astrophysical phenomena at cosmological distances, transients in the local universe exhibit a pronounced anisotropy in their sky distribution. Consequently, adopting an appropriate survey strategy is essential to improve the efficiency of transient searches in the local universe. In this work, we utilized a large galaxy catalog to map the sky distributions of stellar mass and star formation rate (SFR) across different luminosity distance thresholds and angular resolutions of the grid on the celestial sphere. These maps can further serve to characterize the anisotropic spatial distribution of nearby extragalactic transients. For different angular resolutions of the celestial sphere, we find that the sky distributions of stellar mass of galaxies are similar to those of the SFR in the main anisotropic structures. As the luminosity distance threshold increases, the anisotropic structures of the sky distributions become more isotropic. We calculate the angular power spectra and fluctuations of the sky distribution of stellar mass and SFR at a given angular resolution and find that the angular power spectra and fluctuations decrease rapidly as the luminosity distance threshold increases. Finally, by qualitatively comparing the sky distribution of core-collapse supernovae with our SFR sky distribution, we find that the two exhibit consistent patterns in several prominent structures. The mapped sky distributions of stellar mass and SFR can serve as valuable references for future surveys in searching for extragalactic transients.