Stellar-mass black holes are among the most extreme endpoints of stellar evolution, yet they remain difficult to observe directly. In our Galaxy, most known systems are X-ray binaries, where accretion onto the compact object produces high-energy emission, or detached binaries in which the black hole is inferred from the motion of a visible companion. More recently, microlensing has provided the first evidence of an isolated galactic black hole. Despite expectations of a very large population in the Milky Way, only a few dozen systems currently have reliable dynamical mass estimates, while many more remain candidates. This mismatch between the expected and observed population limits our understanding of black-hole formation and evolution, but the known sample still allows meaningful statistical inferences, such as those done by Özel et al. (2010) and Farr et al. (2011).

In contrast, the extragalactic black-hole population has expanded rapidly through gravitational-wave detections. Catalogs from LIGO–Virgo–KAGRA (LVK) now contain hundreds of merger events, dominated by binary black holes, including objects with masses in the so-called lower mass gap between the heaviest neutron stars and the lightest black holes, \( \sim 2 - 5 M_{\odot}\). For galactic systems, this same region has long been debated: whether it reflects a true scarcity of compact objects or mainly observational bias. Updated analyses of the galactic sample suggest that this gap is more likely sparsely populated than completely empty (de Sá et al., 2022).

CatNoir is a living catalog of confirmed and candidate galactic stellar-mass black holes, continuously updated as new systems are reported and orbital parameters are revised. It complements broader community resources such as BlackCAT and WatchDog, which provides astrometric and photometric information. CatNoir focuses on dynamical mass determination. For each object, the catalogue compiles orbital and mass information from the literature, together with re-evaluated masses obtained within a consistent Bayesian framework. The sample spans low- and high-mass X-ray binaries, detached systems, and isolated black holes, and can be explored interactively on this page.

A central goal of the project is to characterize the galactic black-hole mass distribution and make it accessible to the community. Parametric models applied to the current sample indicate that the preferred shape depends on the population considered: the full combined sample is broadly consistent with a power-law-like distribution extending to higher masses, whereas low-mass X-ray binaries alone are better described by a more concentrated, Gaussian-like distribution. At the low-mass end, the inferred galactic distribution points to black holes with masses below those typically found in gravitational-wave merger events, supporting the picture of a partially filled lower mass gap in the Galaxy rather than a strict mass desert.

Because the catalog is updated regularly, the numbers shown here reflect the current state of the sample and analysis. If you find CatNoir useful, please cite the project. Suggestions and corrections are welcome via the contact page.