J-PLUS: A wide-field multi-band study of the M 15 globular cluster

Abstract

Context. As a consequence of internal and external dynamical processes, Galactic globular clusters (GCs) have properties that vary radially. Wide-field observations covering the entire projected area of GCs out to their tidal radii (r tidal ) can therefore give crucial information on these important relics of the Milky Way formation era. Aims. The Javalambre Photometric Local Universe Survey (J-PLUS) provides wide field-of-view (2 deg 2 ) images in 12 narrow, intermediate and broad-band filters optimized for stellar photometry. Here we have applied J-PLUS data for the first time for the study of Galactic GCs using science verification data obtained for the very metal-poor ([Fe/H] ≈ −2.3) GC M 15 located at ∼ 10 kpc from the Sun. Previous studies based on spectroscopy found evidence of multiple stellar populations (MPs) through their different abundances of C, N, O, and Na. Our J-PLUS data provide low-resolution spectral energy distributions covering the near-UV to the near-IR, allowing us to instead search for MPs based on pseudo-spectral fitting diagnostics. Methods. We have built and discussed the stellar radial density profile (RDP) and surface brightness profiles (SBPs) reaching up to r tidal . Since J-PLUS FoV is larger than M 15's r tidal , the field contamination can be properly taken into account. We also demonstrated the power of J-PLUS unique filter system by showing colour-magnitude diagrams (CMDs) using different filter combinations and for different cluster regions. Results. J-PLUS photometric quality and depth are good enough to reach the upper end of M 15's main-sequence. CMDs based on the colours (u − z) and (J0378 − J0861) are found to be particularly useful to search for splits in the sequences formed by the upper red giant branch (RGB) and asymptotic giant branch (AGB) stars. We interpret these split sequences as evidence for the presence of MPs. Furthermore, we show that the (u − z) × (J0378 − g) colour-colour diagram allows us to distinguish clearly between field and M 15 stars, which is important to minimize the sample contamination. Conclusions. The J-PLUS filter combinations (u − z) and (J0378 − J0861), which are sensitive to metal abundances, are able to distinguish different sequences in the upper RGB and AGB regions of the CMD of M 15, showing the feasibility of identifying MPs without the need of spectroscopy. This demonstrates that the J-PLUS survey will have sufficient spatial coverage and spectral resolution to perform a large statistical study of GCs through multi-band photometry in the coming years.

Non-LTE chemical abundances in Galactic open and globular clusters

“…Similar to NGC 1904 and NGC 4833, M15 represents one of the oldest and metal-poor systems in the Galactic halo at a distance d = 10.4 kpc and 4.8 kpc below the Galactic plane (Harris 1996(Harris , 2010. Several studies report multiple stellar populations in the cluster (Larsen et al 2015;Nardiello et al 2018;Bonatto et al 2019).…”

The possible role of stellar mergers for the formation of multiple stellar populations in globular clusters

“…MSPs can be identified from the color spread in the color-magnitude diagram of a GC (CMDs; e.g. Gratton, Sneden, & Carretta 2004;Han, et al 2009;Milone et al 2017;Niederhofer, et al 2017a,b;Martocchia, et al 2018b;Bonatto, et al 2019) and the chromosome diagram (e.g. Milone et al 2015Milone et al , 2017Milone, et al 2018Lagioia, et al 2019).…”

J-PLUS: The Javalambre Photometric Local Universe Survey

“…To illustrate this science case, M 15 has been observed during J-PLUS science verification well beyond the tidal radius (R tidal = 21.5 arcmin, Harris 2010) with uniform photometry. The full analysis for this cluster using J-PLUS SVD is presented in Bonatto et al (2019). In this work, a study of the color-magnitude diagram (CMD) J0378 versus (J0378 − J0861) yields the detection of a clear split in the RGB into two distinct sequences, suggesting a link to light element abundances (since the J0378 and J0861 filters are sensitive to N and Ca).…”

“…-One pointing centered at the MW globular cluster M15 (Bonatto et al 2019). -Three pointings that continuously cover the galaxy clusters A2589 (z = 0.0414) and A2593 (z = 0.0440).…”

“…In this work, a study of the color-magnitude diagram (CMD) J0378 versus (J0378 − J0861) yields the detection of a clear split in the RGB into two distinct sequences, suggesting a link to light element abundances (since the J0378 and J0861 filters are sensitive to N and Ca). Further details are provided in Bonatto et al (2019).…”