Browsing by Author "Weijmans, A."

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    SDSS-IV MaNGA: spatially resolved star formation histories in galaxies as a function of galaxy mass and type
    (OXFORD UNIV PRESS, 2017) Goddard, D.; Thomas, D.; Maraston, C.; Westfall, K.; Etherington, J.; Riffel, R.; Mallmann, N. D.; Zheng, Z.; Argudo Fernandez, M.; Lian, J.; Bershady, M.; Bundy, K.; Drory, N.; Law, D.; Yan, R.; Wake, D.; Weijmans, A.; Bizyaev, D.; Brownstein, J.; Lane, R. R.; Maiolino, R.; Masters, K.; Merrifield, M.; Nitschelm, C.; Pan, K.; Roman Lopes, A.; Storchi Bergmann, T.; Schneider, D. P.
    We study the internal gradients of stellar population propertieswithin 1.5 R-e for a representative sample of 721 galaxies, with stellar masses ranging between 10(9)M circle dot and 10(11.5)M circle dot from the SDSS-IV MaNGA Integral-Field-Unit survey. Through the use of our full spectral fitting code FIREFLY, we derive light-and mass-weighted stellar population properties and their radial gradients, as well as full star formation and metal enrichment histories. We also quantify the impact that different stellar population models and full spectral fitting routines have on the derived stellar population properties and the radial gradient measurements. In our analysis, we find that age gradients tend to be shallow for both early-type and late-type galaxies. Mass-weighted age gradients of early-types arepositive (similar to 0.09 dex/Re) pointing to ` outsidein' progression of star formation, while late-type galaxies have negative light-weighted age gradients (similar to-0.11 dex/R-e), suggesting an ` inside-out' formation of discs. We detect negative metallicity gradients in both early-and late-type galaxies, but these are significantly steeper in late-types, suggesting that the radial dependence of chemical enrichment processes and the effect of gas inflow and metal transport are far more pronounced in discs. Metallicity gradients of both morphological classes correlate with galaxy mass, with negative metallicity gradients becoming steeper with increasing galaxy mass. The correlation with mass is stronger for late-type galaxies, with a slope of d(del[Z/H])/d(logM) similar to -0.2 +/- 0.05, compared to d(del[Z/H])/d(logM) similar to -0.05 +/- 0.05 for early-types. This result suggests that the merger history plays a relatively small role in shaping metallicity gradients of galaxies.
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    SDSS-IV MaNGA: The MaNGA Dwarf Galaxy Sample Presentation
    (2022) Cano-Diaz, M.; Hernandez-Toledo, H. M.; Rodriguez-Puebla, A.; Ibarra-Medel, H. J.; Avila-Reese, V; Valenzuela, O.; Medellin-Hurtado, A. E.; Vazquez-Mata, J. A.; Weijmans, A.; Gonzalez, J. J.; Aquino-Ortiz, E.; Martinez-Vazquez, L. A.; Lane, Richard R.
    We present the MaNGA Dwarf galaxy (MaNDala) Value Added Catalog (VAC), from the final release of the Sloan Digital Sky Survey-IV program. MaNDala consists of 136 randomly selected bright dwarf galaxies with M (*) < 10(9.1) M (circle dot) and M ( g ) > -18.5, making it the largest integral field spectroscopy homogeneous sample of dwarf galaxies. We release a photometric analysis of the g, r, and z broadband imaging based on the DESI Legacy Imaging Surveys, as well as a spectroscopic analysis based on the Pipe3D SDSS-IV VAC. Our release includes the surface brightness (SB), geometric parameters, and color profiles, Sersic fits as well as stellar population properties (such as stellar ages, metallicities, and star formation histories), and emission lines' fluxes within the FOV and the effective radii of the galaxies. We find that the majority of the MaNDala galaxies are star-forming late-type galaxies with n (Sersic,r) similar to 1.6 that are centrals (central/satellite dichotomy). MaNDala covers a large range of SB values (we find 11 candidate ultra-diffuse galaxies and three compact ones), filling the gap between classical dwarfs and low-mass galaxies in the Kormendy Diagram and in the size-mass/luminosity relation, which seems to flatten at 10(8) < M (*)/M (circle dot) < 10(9) with R ( e,r ) similar to 2.7 kpc. A large fraction of MaNDala galaxies formed from an early low-metallicity burst of SF, but also from late SF events from more metal-enriched gas: half of the MaNDala galaxies assembled 50% of their mass at z > 2, while the last 20% was at z < 0.3. Finally, a bending of the sSFR-M (*) relation at M (*) similar to 10(9) M (circle dot) for the main-sequence galaxies seems to be supported by MaNDala.