A feather on the hat: tracing the giant stellar stream around the Sombrero galaxy

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Martínez Delgado, David
Román, Javier
Erkal, Denis
Schirmer, Mischa
Laine, Seppo
Donatiello, Giuseppe
Jiménez, Manuel
Malin, David
Carballo Bello, Julio A.
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Oxford University Press.
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Recent evidence of extremely metal-rich stars found in the Sombrero galaxy (M104) halo suggests that this galaxy has undergone a recent major merger with a relatively massive galaxy. In this paper, we present wide-field deep images of the M104 outskirts obtained with a 18-cm amateur telescope with the purpose of detecting any coherent tidal features from this possible major merger. Our new data, together with a model of the M104 inner halo and scattered light from stars around the field, allow us to trace for the first time the full path of the stream on both sides of the disk of the galaxy. We fully characterize the ring-like tidal structure and we confirm that this is the only observable coherent substructure in the inner halo region. This result is in agreement with the hypothesis that M104 was created by a wet major merger more than 3.5 Gyr ago that heated up the stellar population, blurring all old substructure. We generated a set of numerical models that reproduce the formation of the observed tidal structure. Our best fit model suggests the formation of this stream in the last 3 Gyr is independent of the wet major merger that created the M104 system. Therefore, the formation of the tidal stream can put a constraint on the time when the major merger occurred.
© 2018 The Authors. DMD devotes this paper to Prof. Jose Luis Comellas, who guided him to find the Sombrero galaxy from his home rooftop in the 1980s. DMD acknowledges financial support from the Talentia Senior Program (through the incentive ASE-136) from Secretaría General de Universidades, Investigación y Tecnoloíıa, de la Junta de Andalucía. DMD and JR acknowledge 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). JR acknowledges support from the State Research Agency (AEI-MCINN) of the Spanish Ministry of Science and Innovation under the grant ”The structure and evolution of galaxies and their central regions”with reference PID2019-105602GB-I00/10.13039/501100011033 DMD also recognizes funds from the research project AYA 2007-65090. THELI made use of the following tools and data products: Source Extractor (Bertin & Arnouts 1996), Scamp (Bertin 2006), Swarp (Bertin et al. 2002), and the VizieR catalogue access tool, CDS, Strasbourg, France. Based on observations made with the William Herschel Telescope operated on the island of La Palma by the Isaac Newton Group of Telescopes in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de Canarias. This work has made use of data from the European Space Agency (ESA) mission Gaia (https://www.cosmos., processed by the Gaia Data Processing and Analysis Consortium (DPAC, https://www.cosmos.esa. int/web/gaia/dpac/consortium). Funding for the DPAC has been provided by national institutions, in particular the institutions participating in the Gaia Multilateral Agreement.
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