The Mexican Million Models Database: a virtual observatory for gaseous nebulae

The 3MdB (Mexican Million Models database) is a large database of photoionization models for H II regions. The number of free parameters for the models is close to 15, including the description of the ionizing Spectral Energy Distribution (effective temperature, luminosity, surface gravity, for different type of stellar atmosphere models) and the description of the ionized gas (distance to the ionizing source, density, abundances of the most common elements, dust). The outputs of the models are more than 70 emission line intensities, the ionic fractions and temperatures. All the parameters and outputs are included in the MySQL database, giving the possibility to the user to search into the database for example for all the models that reproduce a given set of observations.