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Stellar activity poses one of the main obstacles for the detection andcharacterisation of small exoplanets around cool stars, as it can induce radialvelocity (RV) signals that can hide or mimic the presence of planetarycompanions. Several indicators of stellar activity are routinely used toidentify activity-related signals in RVs, but not all indicators trace exactlythe same activity effects, nor are any of them always effective in all stars.We evaluate the performance of a set of spectroscopic activity indicators for Mdwarf stars with different masses and activity levels with the aim of finding arelation between the indicators and stellar properties. In a sample of 98 Mdwarfs observed with CARMENES, we analyse the temporal behaviour of RVs andnine spectroscopic activity indicators: cross-correlation function (CCF)full-width-at-half-maximum (FWHM), contrast, and bisector inverse slope (BIS),chromatic index (CRX), differential line width (dLW), and indices of thechromospheric lines H$\alpha$ and calcium infrared triplet. A total of 56 starsof the initial sample show periodic signals related to activity in at least oneof these ten parameters. RV is the parameter for which most of the targets showan activity-related signal. CRX and BIS are effective activity tracers for themost active stars in the sample, especially stars with a relatively high mass,while for less active stars, chromospheric lines perform best. FWHM and dLWshow a similar behaviour in all mass and activity regimes, with the highestnumber of activity detections in the low-mass, high-activity regime. Most ofthe targets for which we cannot identify any activity-related signals are starsat the low-mass end of the sample. These low-mass stars also show the lowest RVscatter, which indicates that ultracool M dwarfs could be better candidates forplanet searches than earlier types, which show larger RV jitter.

The CARMENES search for exoplanets around M dwarfs. Mapping stellar activity indicators across the M dwarf domain