Publication: A search for stellar tidal streams around Milky Way analogues from the SAGA sample
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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.
© The Authors 2023. We want to thank to Yao-Yuan Mao, Marla Geha and Risa Wechsler for providing the original SAGA sample for this paper and useful comments. We also thank Dustin Lang and John Moustakas for running the modified Legacypipe code to produce the images used here. DMD acknowledges financial support from the Talentia Senior Program (through the incentive ASE-136) from Secretaría General de Universidades, Investigación y Tecnología, de la Junta de Andalucía. DMD acknowledges funding from the State Agency for Research of the Spanish MCIU through the “Center of Excellence Severo Ochoa” award to the Instituto de Astrofísica de Andalucía (SEV-2017- 0709) and project (PDI2020-114581GB-C21/ AEI / 10.13039/501100011033). MAGF acknowledges financial support from the Spanish Ministry of Science and Innovation through the project PID2020-114581GB-C22. SRF acknowledges financial support from the Spanish Ministry of Economy and Competitiveness (MINECO) under grant number AYA2016-75808-R, AYA2017-90589- REDT and S2018/NMT-429, and from the CAM-UCM under grant number PR65/19-22462. SRF acknowledges support from a Spanish postdoctoral fellowship, under grant number 2017-T2/TIC-5592. APC is supported by the Taiwan Ministry of Education Yushan Fellowship and Taiwan National Science and Technology Council grant 109-2112-M-007-011-MY3. The photometry analysis in this work was partly done using GNU Astronomy Utilities (Gnuastro, ascl.net/1801.009) version 0.17. Work on Gnuastro has been funded by the Japanese MEXT scholarship and its Grant-in-Aid for Scientific Research (21244012, 24253003), the European Research Council (ERC) advanced grant 339659-MUSICOS, and from the Spanish Ministry of Economy and Competitiveness (MINECO) under grant number AYA2016-76219-P. The Leiden Observatory has provided facilities and computer infrastructure for carrying out part of this work. MA acknowledges the financial support from the Spanish Ministry of Science and Innovation and the European Union - NextGenerationEU through the Recovery and Resilience Facility project ICTS-MRR-2021-03-CEFCA.