A search for stellar tidal streams around Milky Way analogues from the SAGA sample

Abstract

Context. Stellar tidal streams are the result of tidal interactions between a central galaxy and lower mass systems such as satellite galaxies or globular clusters. For the Local Group, many diffuse substructures have been identified and their link to the galaxy evolution has been traced. However, it cannot simply be assumed that the Milky Way or M 31 are representative of their galaxy class. Thus, a larger sample of analogue galaxies beyond the Local Group is required to bolster a broader generalisation of the underlying theory. Aims. We want to detect and photometrically characterise stellar streams around Milky Way (MW-) analogues in the local Universe in order to extend the observational evidence of interactions between this class of host galaxies and their satellites. This information will be applicable in a more general context around future studies on galaxy formation and evolution processes. Methods. In the present work, we identified and analysed stellar tidal streams around MW-analogue galaxies from the SAGA sample, using deep images of the DESI Legacy Imaging Surveys. For this sample, we obtained a range of r-band surface brightness limit between 27.8 and 29 mag arcsec^(−2) . We measured the surface brightness and colours of the detected streams using GNU Astronomy Utilities software. Results. We identified 16 new stellar tidal streams around MW-analogue galaxies at distances between 25 and 40 Mpc. In applying a statistical analysis to our findings for the SAGA II galaxy sample, we obtained a frequency of 12.2% ± 2.4% for these stellar streams. We measured the surface brightness and colours of the detected streams and carried out a comparison to the dwarf satellite galaxies population around galaxies belonging to the same SAGA sample. We show that the mean colour of the streams is 0.20 mag redder than that of the SAGA satellites; in addition, the streams are, on average, 0.057 ± 0.021 mag redder that their progenitor (for cases where a likely progenitor could be identified). Conclusions. The frequency of streams detected around MW-analogues in the Local Universe is in agreement with previous studies. The difference in colour between detected streams and satellites within the SAGA host galaxy sample could be explained by a combination of both selection biases in the SAGA study and physical processes.