Characterization of Low Surface Brightness structures in annotated deep images

Abstract

Context. The identification and characterization of Low Surface Brightness (LSB) stellar structures around galaxies such as tidal debris of on-going or past collisions is essential to constrain models of galactic evolution. So far most efforts have focused on the numerical census of samples of varying sizes, either through visual inspection or more recently with deep learning. Detailed analysis including photometry has been carried out for a small number of objects, essentially because of the lack of convenient tools able to precisely characterize tidal structures around large samples of galaxies. Aims. Our goal is to characterize in detail, and in particular obtain quantitative measurements, of LSB structures identified in deep images of samples consisting of hundreds of galaxies. Methods. We developed an online annotation tool that enables contributors to delineate with precision the shapes of diffuse extended stellar structures, as well as artefacts or foreground structures. All parameters are automatically stored in a database which may be queried to retrieve quantitative measurements. We annotated LSB structures around 352 nearby massive galaxies with deep images obtained with the Canada-France-Hawaii Telescope as part of two large programs: MATLAS and UNIONS/CFIS. Each LSB structure was delineated and labeled according to its likely nature: stellar shells, streams associated to a disrupted satellite, tails formed in major mergers, ghost reflections or cirrus. Results. From our database containing 8441 annotations, the area, size, median surface brightness and distance to the host of 228 structures were computed. The results confirm the fact that tidal structures defined as streams are thinner than tails, as expected by numerical simulations. In addition, tidal tails appear to exhibit a higher surface brightness than streams (by about 1 mag), which may be related to different survival times for the two types of collisional debris. We did not detect any tidal feature fainter than 27.5 mag arcsec −2 , while the nominal surface brightness limits of our surveys range between 28.3 and 29 mag arcsec −2 , a difference that needs to be taken into account when estimating the sensitivity of future surveys to identify LSB structures. Conclusions. We compiled an annotation database of observed LSB structures around nearby massive galaxies including tidal features that may be used for quantitative analysis and as a training set for machine learning algorithms.

Unveiling the Nature of Polar-ring Galaxies from Deep Imaging

“…As can be seen, the length of the tails of SPRC-73 and SPRC-238 is significantly longer and the width of the tail of SPRC-73 is ∼ 4 times larger than typically found around ETGs (see fig. 9 and 10 in Sola et al 2022), whereas their average surface brightness is of the same order as measured in the stellar tails and streams.…”

“…The material of the tidal stellar stream is expelled from the accreted companion and, thus, should have essentially the same colour as the satellite. Also, tidal streams look like long and thin filaments, usually fainter and thinner than tidal tails (Sola et al 2022). However, according to hydrodynamical cosmological simulations in Mancillas et al (2019), the lifetime of streams is, on average, longer (1.5-3 Gyr) than that of tidal tails, which become visible at a timescale of 0.7-1 Gyr after the start of the merger.…”

“…Recently, (Sola et al 2022) measured the properties (the area, size, and average surface brightness) for more than 8000 tidal structures around 352 nearby massive galaxies using deep images from the 3.6-meter Canada-France-Hawaii Telescope with approximately the same surface brightness limit as in the SDSS Stripe 82. One of the important conclusions of their study is that they do not detect any tidal features fainter than 27.5 mag arcsec −2 in the r band.…”

Remnants of recent mergers in nearby early-type galaxies and their classification

“…Thus, any correlations or characterization of merger structures found in these analyses can further provide crucial constraints on our understanding of the formation process of such peculiar embedded structures, along with finding their connection with galaxy evolution (e.g. Wang et al 2020;Sola et al 2022).…”

AGNs in post-mergers from the ultraviolet near infrared optical northern survey

“…The survey's 5-𝜎 point-source depth (24.85 mag in the 𝑟-band for the MegaCam wide-field optical imager) is sufficient to capture the low-surface brightness features necessary for merger identification in bright, low-redshift galaxies (e.g. Sola et al 2022). Estimates of the low-𝑧 merger rate suggest that the UNIONS footprint will include thousands of post-mergers (Lacey & Cole 1993;Lotz et al 2011;Bluck et al 2012;Casteels et al 2014;Rodriguez-Gomez et al 2015;Martin et al 2018).…”