A Tidally Stripped Stellar Component of the Magellanic Bridge

Abstract

Deep photometry of the Small Magellanic Cloud (SMC) stellar periphery (R = 4 • , 4.2 kpc) is used to study its line-of-sight depth with red clump (RC) stars. The RC luminosity function is affected little by young ( 1 Gyr) blue-loop stars in these regions because their main-sequence counterparts are not observed in the color-magnitude diagrams. The SMCs eastern side is found to have a large line-of-sight depth (∼23 kpc) while the western side has a much shallower depth (∼10 kpc), consistent with previous photographic plate photometry results. We use a model SMC RC luminosity function to deconvolve the observed RC magnitudes and construct the density function in distance for our fields. Three of the eastern fields show a distance bimodality with one component at the "systemic" ∼67 kpc SMC distance and a second component at ∼55 kpc. Our data are not reproduced well by the various extant Magellanic Cloud and Stream simulations. However, the models predict that the known H i Magellanic Bridge (stretching from the SMC eastward toward the Large Magellanic Cloud, LMC) has a decreasing distance with angle from the SMC and should be seen in both the gaseous and stellar components. From comparison with these models, we conclude that the most likely explanation for our newly identified ∼55 kpc stellar structure in the eastern SMC is a stellar counterpart of the H i Magellanic Bridge that was tidally stripped from the SMC ∼200 Myr ago during a close encounter with the LMC. This discovery has important implications for microlensing surveys of the SMC.

SMASH: Survey of the MAgellanic Stellar History

“…3. Common sources list: Early on in the development of PHOTRED, there were issues with constructing good PSFs for the deep (280 s), intermediate-band DDO51 observations for the MAPS survey (Nidever et al 2011(Nidever et al , 2013; which was the main motivation for writing PHOTRED). This was because there were a lot of point-like cosmic rays that overwhelmed the small number of real sources and made it difficult to create a good PSF source list just by culling via morphological parameters.…”

“…The MAPS survey used photometrically selected red giant stars to find that the older SMC stellar population followed the same exponential profile from the center of the SMC out to ∼7°.5, but that beyond that there was a break in the radial profile with stars extending out to ∼11°(later confirmed with DES data by Pieres et al 2017), potentially representing a classical stellar halo of the SMC. In addition, Nidever et al (2013) found evidence for a stellar component of the tidally stripped Magellanic Bridge; more recently, Belokurov & Koposov (2016) used Gaia DR1 data to find both young and old stellar bridges, although they are not spatially coincident, between the Clouds. Finally, Pieres et al (2017) used DES data to discover a stellar overdensity in the northern region of the SMC (at ∼8°) that might be a tidally stripped dwarf galaxy.…”

Astrophysical properties of star clusters in the Magellanic Clouds homogeneously estimated by ASteCA

“…regions (Subramanian & Subramaniam 2009;Nidever et al 2013;Scowcroft et al 2016). The 0.1 mag deviations allowed in this work give LOS depths of ∼5.7 kpc and ∼4.6 kpc for the S/LMC.…”

The VMC survey

“…The Small Magellanic Cloud (SMC), in particular, has an intriguing structure with a large extent along the line of sight (e.g. Subramanian & Subramaniam 2012;Nidever et al 2013;de Grijs & Bono 2015, and references therein) and a morphology that clearly depends on stellar population age (e.g. Cioni et al 2000a;Zaritsky et al 2000;Dobbie et al 2014;Subramanian & Subramaniam 2015;Deb et al 2015;Rubele et al 2015).…”