We find two chemically distinct populations separated relatively cleanly in the [Fe/H]–[Mg/Fe] plane, but also distinguished in other chemical planes, among metal-poor stars (primarily with metallicities [{Fe}/{{H}}] -0.9) observed by the Apache Point Observatory Galactic Evolution Experiment (APOGEE) and analyzed for Data Release 13 (DR13) of the

Observations show that massive star formation quenches first at the centres of galaxies. To understand quenching mechanisms, we investigate the thermal and non-thermal energy balance in the central kpc of NGC 1097—a prototypical galaxy undergoing quenching—and present a systematic study of the nuclear star formation efficiency and its dependencies

We report deep spectroscopy of 10 planetary nebulae (PNe) in the Andromeda Galaxy (M31) using the 10.4 m Gran Telescopio Canarias (GTC). Our targets reside in different regions of M31, including halo streams and the dwarf satellite M32, and kinematically deviate from the extended disk. The temperature-sensitive [O III] λ4363 line is observed in all

The characterization of stellar streams in the Milky Way halo can provide important observational constraints on the ΛCDM cosmological model, which posits that galaxies form via the accretion of smaller satellites. One such stream, the 300 km/s stellar stream near the dwarf galaxy Segue 1 (300S), was detected in narrow-field spectroscopic surveys

To better understand how galaxy clusters form, we look at their progenitors which have not yet virialized: protoclusters. We use the Planck Collaboration (2016) published list of 2,151 protocluster candidate sources to explore further characterization as bonafide protoclusters or other extragalactic phenomena. We investigate the correlation of

Supermassive black holes, with masses more than a million times that of the Sun, seem to inhabit the centres of all massive galaxies. Cosmologically motivated theories of galaxy formation require feedback from these supermassive black holes to regulate star formation. In the absence of such feedback, state-of-the-art numerical simulations fail to