Probing galactic cosmic ray distribution with TeV gamma-ray sky

The distribution of cosmic rays in the Galaxy is still uncertain and this affects the expectations for the diffuse gamma-ray emission produced by hadronic interactions of cosmic rays with the interstellar gas. We evaluate the diffuse gamma-ray flux at TeV energies by considering different assumptions for the cosmic ray distribution, including the recently emerged possibility of a decreasing cosmic ray spectral index in the inner Galaxy. The diffuse emission from the galactic central region (i.e. in the longitude range | l | ≤ 60) changes in the different scenarios by a relatively large factor and can be probed by TeV scale gamma-ray observations. By comparing the total flux produced by diffuse emission and point-like and extended sources resolved by HESS with the gamma-ray flux observed by Argo-YBJ, HESS, HAWC and Milagro, we show that experimental data can already discriminate among different hyphoteses for cosmic ray distribution. The constraints can be strengthened if the contribution of sources not resolved by HESS is taken into account.