Journal
ASTRONOMY & ASTROPHYSICS
Volume 540, Issue -, Pages -Publisher
EDP SCIENCES S A
DOI: 10.1051/0004-6361/201117466
Keywords
galaxies: abundances; galaxies: evolution; galaxies: formation; Galaxy: disk
Categories
Funding
- STFC [ST/F007701/1]
- UK's Science & Technology Facilities Council [ST/F002432/1, ST/H00260X/1]
- Agence Nationale de la Recherche [ANR-08-BLAN-0274-01]
- NSERC
- CFI
- CRC
- NSRIT
- DEISA consortium
- EU [RI-031513, RI-222919]
- DEISA Extreme Computing Initiative
- UK's National Cosmology Supercomputer (COSMOS)
- University of Central Lancashire's High Performance Computing Facility
- CfCA/NAOJ
- JSS/JAXA
- Shared Hierarchical Academic Research Computing Network (SHARCNET)
- Agence Nationale de la Recherche (ANR) [ANR-08-BLAN-0274] Funding Source: Agence Nationale de la Recherche (ANR)
- Science and Technology Facilities Council [ST/F007701/1, ST/F007019/1, ST/H008586/1, ST/F002432/1, ST/G003025/1, ST/J001341/1, ST/H00260X/1, ST/J005673/1, ST/K00333X/1] Funding Source: researchfish
- STFC [ST/F002432/1, ST/H008586/1, ST/K00333X/1, ST/J001341/1, ST/F007019/1, ST/J005673/1, ST/F007701/1, ST/G003025/1, ST/H00260X/1] Funding Source: UKRI
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Aims. We examine radial and vertical metallicity gradients using a suite of disk galaxy hydrodynamical simulations, supplemented with two classic chemical evolution approaches. We determine the rate of change of gradient slope and reconcile the differences existing between extant models and observations within the canonical inside-out disk growth paradigm. Methods. A suite of 25 cosmological disks is used to examine the evolution of metallicity gradients; this consists of 19 galaxies selected from the RaDES (Ramses Disk Environment Study) sample, realised with the adaptive mesh refinement code RAMSES, including eight drawn from the field and six from loose group environments. Four disks are selected from the MUGS (McMaster Unbiased Galaxy Simulations) sample, generated with the smoothed particle hydrodynamics (SPH) code GASOLINE. Two chemical evolution models of inside-out disk growth were employed to contrast the temporal evolution of their radial gradients with those of the simulations. Results. We first show that generically flatter gradients are observed at redshift zero when comparing older stars with those forming today, consistent with expectations of kinematically hot simulations, but counter to that observed in the Milky Way. The vertical abundance gradients at similar to 1-3 disk scalelengths are comparable to those observed in the thick disk of the Milky Way, but significantly shallower than those seen in the thin disk. Most importantly, we find that systematic differences exist between the predicted evolution of radial abundance gradients in the RaDES and chemical evolution models, compared with the MUGS sample; specifically, the MUGS simulations are systematically steeper at high-redshift, and present much more rapid evolution in their gradients. Conclusions. We find that the majority of the models predict radial gradients today which are consistent with those observed in late-type disks, but they evolve to this self-similarity in different fashions, despite each adhering to classical inside-out growth. We find that radial dependence of the efficiency with which stars form as a function of time drives the differences seen in the gradients; systematic differences in the sub-grid physics between the various codes are responsible for setting these gradients. Recent, albeit limited, data at redshift z similar to 1.5 are consistent with the steeper gradients seen in our SPH sample, suggesting a modest revision of the classical chemical evolution models may be required.
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