Browsing by Author "Loubser, S. I."

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    Abundance ratios and IMF slopes in the dwarf elliptical galaxy NGC 1396 with MUSE
    (2016) Mentz, J. J.; La Barbera, F.; Peletier, R. F.; Falcon-Barroso, J.; Lisker, T.; van de Ven, G.; Loubser, S. I.; Hilker, M.; Sanchez-Janssen, R.; Napolitano, N.; Cantiello, M.; Capaccioli, M.; Norris, M.; Paolillo, M.; Smith, R.; Beasley, M. A.; Lyubenova, M.; Munoz, R.; Puzia, T.
    Deep observations of the dwarf elliptical (dE) galaxy NGC 1396 (M-V = -16.60, Mass similar to 4 x 10(8) M-circle dot), located in the Fornax cluster, have been performed with the Very Large Telescope/Multi Unit Spectroscopic Explorer spectrograph in the wavelength region from 4750 to 9350 angstrom. In this paper, we present a stellar population analysis studying chemical abundances, the star formation history (SFH) and the stellar initial mass function (IMF) as a function of galactocentric distance. Different, independent ways to analyse the stellar populations result in a luminosity-weighted age of similar to 6 Gyr and a metallicity [Fe/H]similar to -0.4, similar to other dEs of similar mass. We find unusually overabundant values of [Ca/Fe]similar to+0.1, and underabundant Sodium, with [Na/Fe] values around -0.1, while [Mg/Fe] is overabundant at all radii, increasing from similar to+0.1 in the centre to similar to+0.2 dex. We notice a significant metallicity and age gradient within this dwarf galaxy. To constrain the stellar IMF of NGC 1396, we find that the IMF of NGC 1396 is consistent with either a Kroupa-like or a top-heavy distribution, while a bottom-heavy IMF is firmly ruled out. An analysis of the abundance ratios, and a comparison with galaxies in the Local Group, shows that the chemical enrichment history of NGC 1396 is similar to the Galactic disc, with an extended SFH. This would be the case if the galaxy originated from a Large Magellanic Cloud-sized dwarf galaxy progenitor, which would lose its gas while falling into the Fornax cluster.
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    The Atacama Cosmology Telescope: A Catalog of >4000 Sunyaev-Zel'dovich Galaxy Clusters
    (2021) Hilton, M.; Sifon, C.; Naess, S.; Madhavacheril, M.; Oguri, M.; Rozo, E.; Rykoff, E.; Abbott, T. M. C.; Adhikari, S.; Aguena, M.; Aiola, S.; Allam, S.; Amodeo, S.; Amon, A.; Annis, J.; Ansarinejad, B.; Aros-Bunster, C.; Austermann, J. E.; Avila, S.; Bacon, D.; Battaglia, N.; Beall, J. A.; Becker, D. T.; Bernstein, G. M.; Bertin, E.; Bhandarkar, T.; Bhargava, S.; Bond, J. R.; Brooks, D.; Burke, D. L.; Calabrese, E.; Carrasco Kind, M.; Carretero, J.; Choi, S. K.; Choi, A.; Conselice, C.; Costa, L. N. da; Costanzi, M.; Crichton, D.; Crowley, K. T.; Dunner, R.; Denison, E. V.; Devlin, M. J.; Dicker, S. R.; Diehl, H. T.; Dietrich, J. P.; Doel, P.; Duff, S. M.; Duivenvoorden, A. J.; Dunkley, J.; Everett, S.; Ferraro, S.; Ferrero, I.; Ferte, A.; Flaugher, B.; Frieman, J.; Gallardo, P. A.; Garcia-Bellido, J.; Gaztanaga, E.; Gerdes, D. W.; Giles, P.; Golec, J. E.; Gralla, M. B.; Grandis, S.; Gruen, D.; Gruendl, R. A.; Gschwend, J.; Gutierrez, G.; Han, D.; Hartley, W. G.; Hasselfield, M.; Hill, J. C.; Hilton, G. C.; Hincks, A. D.; Hinton, S. R.; Ho, S-P. P.; Honscheid, K.; Hoyle, B.; Hubmayr, J.; Huffenberger, K. M.; Hughes, J. P.; Jaelani, A. T.; Jain, B.; James, D. J.; Jeltema, T.; Kent, S.; Knowles, K.; Koopman, B. J.; Kuehn, K.; Lahav, O.; Lima, M.; Lin, Y-T.; Lokken, M.; Loubser, S. I.; MacCrann, N.; Maia, M. A. G.; Marriage, T. A.; Martin, J.; McMahon, J.; Melchior, P.; Menanteau, F.; Miquel, R.; Miyatake, H.; Moodley, K.; Morgan, R.; Mroczkowski, T.; Nati, F.; Newburgh, L. B.; Niemack, M. D.; Nishizawa, A. J.; Ogando, R. L. C.; Orlowski-Scherer, J.; Page, L. A.; Palmese, A.; Partridge, B.; Paz-Chinchon, F.; Phakathi, P.; Plazas, A. A.; Robertson, N. C.; Romer, A. K.; Rosell, A. Carnero; Salatino, M.; Sanchez, E.; Schaan, E.; Schillaci, A.; Sehgal, N.; Serrano, S.; Shin, T.; Simon, S. M.; Smith, M.; Soares-Santos, M.; Spergel, D. N.; Staggs, S. T.; Storer, E. R.; Suchyta, E.; Swanson, M. E. C.; Tarle, G.; Thomas, D.; To, C.; Trac, H.; Ullom, J. N.; Vale, L. R.; Lanen, J. Van; Vavagiakis, E. M.; Vicente, J. De; Wilkinson, R. D.; Wollack, E. J.; Xu, Z.; Zhang, Y.
    We present a catalog of 4195 optically confirmed Sunyaev-Zel'dovich (SZ) selected galaxy clusters detected with signal-to-noise ratio >4 in 13,211 deg(2) of sky surveyed by the Atacama Cosmology Telescope (ACT). Cluster candidates were selected by applying a multifrequency matched filter to 98 and 150 GHz maps constructed from ACT observations obtained from 2008 to 2018 and confirmed using deep, wide-area optical surveys. The clusters span the redshift range 0.04 < z < 1.91 (median z = 0.52). The catalog contains 222 z > 1 clusters, and a total of 868 systems are new discoveries. Assuming an SZ signal versus mass-scaling relation calibrated from X-ray observations, the sample has a 90% completeness mass limit of M-500c > 3.8 x 10(14) M, evaluated at z = 0.5, for clusters detected at signal-to-noise ratio >5 in maps filtered at an angular scale of 24. The survey has a large overlap with deep optical weak-lensing surveys that are being used to calibrate the SZ signal mass-scaling relation, such as the Dark Energy Survey (4566 deg(2)), the Hyper Suprime-Cam Subaru Strategic Program (469 deg(2)), and the Kilo Degree Survey (825 deg(2)). We highlight some noteworthy objects in the sample, including potentially projected systems, clusters with strong lensing features, clusters with active central galaxies or star formation, and systems of multiple clusters that may be physically associated. The cluster catalog will be a useful resource for future cosmological analyses and studying the evolution of the intracluster medium and galaxies in massive clusters over the past 10 Gyr.