$J$-factors for self-interacting dark matter in 20 dwarf spheroidal galaxies

Dwarf spheroidal galaxies are among the most promising targets for indirect dark matter (DM) searches in $\gamma$-rays. The $\gamma$-ray flux from DM annihilation in a dwarf spheroidal galaxy is proportional to the $J$-factor of the source. The $J$-factor of a dwarf spheroidal galaxy is the line-of-sight integral of the DM mass density squared times $\langle \sigma_{\rm ann} v_{\rm rel} \rangle/(\sigma_{\rm ann} v_{\rm rel})0$,where$\sigma{\rm ann} v_{\rm rel}$istheDMannihilationcross-sectiontimesrelativevelocity$v_{\rm rel}=|{\bf v}{\rm rel}|$,anglebracketsdenoteaverageover${\bf v}{\rm rel}$,and$(\sigma_{\rm ann} v_{\rm rel})0$isthe$v{\rm rel}$-independent part of ${\sigma }_{\mathrm{a}\mathrm{n}\mathrm{n}}{v}_{\mathrm{r}\mathrm{e}\mathrm{l}}$. If ${\sigma }_{\mathrm{a}\mathrm{n}\mathrm{n}}{v}_{\mathrm{r}\mathrm{e}\mathrm{l}}$ is constant in $v_{\mathrm{r}\mathrm{e}\mathrm{l}}$, $J$-factors only depend on the DM space distribution in the source. However, if ${\sigma }_{\mathrm{a}\mathrm{n}\mathrm{n}}{v}_{\mathrm{r}\mathrm{e}\mathrm{l}}$ varies with $v_{\rm rel}$,asinthepresenceofDMself-interactions,$J$-factors also depend on the DM velocity distribution, and on the strength and range of the DM self-interaction. Models for self-interacting DM are increasingly important in the study of the small scale clustering of DM, and are compatible with current cosmological observations. Here we derive the $J$-factor of 20 dwarf spheroidal galaxies from stellar kinematic data under the assumption of Yukawa DM self-interactions. $J$-factors are derived through a profile Likelihood approach, assuming either NFW or cored DM profiles. We also compare our results with $J$-factors derived assuming the same velocity for all DM particles in the target galaxy. We find that this common approximation overestimates the $J$-factors by up to one order of magnitude. $J$-factors for a sample of DM particle masses, self-interaction coupling constants and density profiles are provided electronically, ready to be used in other projects.