Ghosts in the Attic: Mapping the Stellar Content of the S0 Galaxy NGC 5102,,

Abstract

The spatial distribution of stars in the nearby S0 galaxy NGC 5102 is investigated using images obtained with WIRCam and MegaCam on the Canada-France-Hawaii Telescope. With the exception of gaps between detector elements, the entire galaxy is surveyed in r ′ and i ′ , while the J and Ks data extend out to R GC ≈ 6 kpc, which corresponds to almost 7 disk scale lengths. A modest population of main sequence (MS) stars with M V < −3.5 and ages ≈ 70 Myr are detected throughout the disk, with the majority located in the southern half of the galaxy. The stellar disk in the northern half of the galaxy is warped, following structure that is also seen in HI. Objects with photometric properties that are consistent with those of bright AGB stars are seen throughout the disk, and the ratio of C stars to bright M giants is consistent with an overall increase in the star formation rate within the past 1 Gyr. Star-forming activity during the interval 0.1 − 2 Gyr was more centrally concentrated than during the past ≈ 100 Myr. The structure of the disk changes near R GC ≈ 5 kpc (5.5 disk scale lengths), in the sense that the radial surface density profile defined by red supergiants (RSGs) and bright AGB stars levels off at larger radii. RSGs and bright AGB stars are traced out to a radius of 14 kpc (15.6 scale lengths) along the 1 Based on observations obtained with the Megaprime/MegaCam, a joint project of the CFHT and CEA/DAPNIA, at the Canada-France-Hawaii Telescope, which is operated by the National southern portion of the major axis, while a tentative detection is also made of bright AGB stars at a projected distance of ≈ 16 kpc along the south east minor axis. A large clump of AGB stars that subtends ≈ 1 arcmin is identified to the west of the galaxy center. It is argued that this is the remnant of a companion galaxy that triggered past episodes of elevated star-forming activity.

Dominant dark matter and a counter-rotating disc: MUSE view of the low-luminosity S0 galaxy NGC 5102

“…On the one hand this interpretation is supported by the warped H i in the outer disc (van Woerden et al 1993). Davidge (2010) points out that this warp is also traced by the OAGB stars. On the other hand the author mentions that this interpretation is challenged by the current isolation of NGC 5102.…”

“…However during intermediate epochs the SFR was higher and 20% of the disc mass formed within the last 1 Gyr. Davidge (2010) finds hints for a merger in NGC 5102: at a projected distance of 18 kpc from the galaxy centre along the minor axis he finds a concentration of AGB stars and suggests this might be the remnant of a companion galaxy. On the one hand this interpretation is supported by the warped H i in the outer disc (van Woerden et al 1993).…”

THE STAR-FORMING HISTORIES OF THE NUCLEUS, BULGE, AND INNER DISK OF NGC 5102: CLUES TO THE EVOLUTION OF A NEARBY LENTICULAR GALAXY,,

“…As one of the nearest lenticular galaxies, it is an important laboratory for investigating the origins of this galaxy type in group environments. As is typical of lenticular galaxies, there is only modest star-forming activity in the disk (Davidge 2010;Karachentsev et al 2002), and the present-day star formation rate (SFR) is ∼ 0.02 M ⊙ year −1 (Davidge 2008).…”

“…Some structural properties of NGC 5102 hint at a past interaction with another system. The disk is warped, and there is a plume of stars that extends out to 16 disk scale lengths (Davidge 2010) that might be a tidal feature. While NGC 5102 does not have companions at the present day, a flyby encounter with a perturber that is now long gone could have left longlasting signatures in the disk (Kim et al 2014).…”

Time Variable Broad-Line Emission in NGC 4203: Evidence for Stellar Contrails

“…Thus, the average density of an object that will be tidally disrupted at a distance similar to the inner radius deduced for the ring (Section 3), corresponds to ∼ 10 −9 ρ , comparable to the average density expected for a late-type supergiant star, similar to Betelgeuse for example 10 . Consequently, it is quite plausible that the brightening of the double-peaked broad lines in NGC 4203 was caused by the ongoing tidal disruption of a red supergiant star which would have made ∼ 1.5 orbits in the time span of the STIS observations (see Davidge 2010, for evidence that red supergiant stars exist in S0 galaxies).…”