A Predicted Correlation Between Age Gradient and Star Formation History in FIRE Dwarf Galaxies
Andrew S. Graus, James S. Bullock, Alex Fitts, Michael C. Cooper, Michael Boylan-Kolchin, Daniel R. Weisz, Andrew Wetzel, Robert Feldmann, Claude-André Faucher-… 展开作者
Andrew S. Graus, James S. Bullock, Alex Fitts, Michael C. Cooper, Michael Boylan-Kolchin, Daniel R. Weisz, Andrew Wetzel, Robert Feldmann, Claude-André Faucher-Giguère, Eliot Quataert, Philip F. Hopkins, Dusan Keres
备注：
13 pages, 8 figures. Submitted to MNRAS, comments welcome
We explore the radial variation of star formation histories in dwarf galaxies simulated with Feedback In Realistic Environments (FIRE) physics. The sample contains 9 low-mass field dwarfs with M_ star = 10^5 - 10^7 M_sun from previous FIRE results, and a new suite of 17 higher mass field dwarfs with M_star = 10^7 - 10^9 M_sun introduced here. We find that age gradients are common in our dwarfs, with older stars dominant at large radii. The strength of the gradient correlates with overall galaxy age such that earlier star formation produces a more pronounced gradient. The relation between formation time and strength of the gradient is driven by both mergers and star-formation feedback. Mergers can both steepen and flatten the age gradient depending on the timing of the merger and star formation history of the merging galaxy. In galaxies without significant mergers, early feedback pushes stars to the outskirts at early times. Interestingly, among galaxies without mergers, those with large dark matter cores have flatter age gradients because these galaxies have more late-time feedback. If real galaxies have age gradients as we predict, stellar population studies that rely on sampling a limited fraction of a galaxy can give a biased view of its global star formation history. We show that central fields can be biased young by a few Gyrs while outer fields are biased old. Fields positioned near the 2D half-light radius will provide the least biased measure of a dwarf galaxy's global star formation history.
Great Balls of Fire: Star Formation in Gas Clouds Accelerated by a Hot Wind
Center for Computational Astrophysics, Flatiron Institute（计算天体物理中心，Flatiron研究所）；Departamento de Física, Universidad Técnica Federico Santa María（费德里科·萨马亚技术大学物理系）；Millennium Nucleus for Galaxies (MINGAL)（星系千年核心（MINGAL））；INAF - Osservatorio Astronomico di Padova（意大利国家天体物理研究所帕多瓦天文台）；Dipartimento di Fisica e Astronomia ‘Galileo Galilei’, Universit ‘a di Padova（帕多瓦大学伽利略·伽利莱物理与天文学系）；Dipartimento di Fisica e Astronomia ”Augusto Righi”, Università di Bologna（博洛尼大学奥古斯托·里基物理与天文学系）
Portrait of a Galaxy on FIRE: Is the $α$-bimodality a natural consequence of inside-out disc growth in a hierarchical formation scenario?
Tartu Observatory, University of Tartu（塔尔图大学塔尔图天文台）；Instituto de Astrofísica de Canarias（加那利天体物理研究所）；Universidad de La Laguna（拉古纳大学）；Tallinn University of Technology（塔林理工大学）
The current generation of galaxy simulations can resolve individual giant molecular clouds, the progenitors of dense star clusters. But the evolutionary fate of these young massive clusters, and whether they can become the old globular clusters (GCs) observed in many galaxies, is determined by a complex interplay of internal dynamical processes and external galactic effects. We present the first star-by-star $N$-body models of massive ($N\sim10^5-10^7$) star clusters formed in a FIRE-2 MHD simulation of a Milky Way-mass galaxy, with the relevant initial conditions and tidal forces extracted fr…
Inside-out versus Upside-down: The Origin and Evolution of Metallicity Radial Gradients in FIRE Simulations of Milky Way-mass Galaxies and the Essential Role of Gas Mixing
The concurrent growth of supermassive black holes (SMBHs) and their host galaxies remains to be fully explored, especially at high redshift. While often understood as a consequence of self-regulation via AGN feedback, it can also be explained by alternative SMBH accretion models. Here, we expand on previous work by studying the growth of SMBHs with the help of a large suite of cosmological zoom-in simulations (MassiveFIRE) that are part of the Feedback in Realistic Environments (FIRE) project. The growth of SMBHs is modelled in post-processing with different black hole accretion models, placem…
In this paper, we study the age and spatial distributions of Cepheids in the Small Magellanic Cloud (SMC) as a function of their ages using the data from the OGLE III photometric catalogue. A period-age (PA) relation derived for the Classical Cepheids in the Large Magellanic Cloud (LMC) has been used to find the ages of Cepheids. The age distribution of the SMC Classical Cepheids is found to have a peak at log(Age) = 8.40+/-0.10 which suggests that a major star formation event might have occurred in the SMC at about 250+/-50 Myrs ago. It is believed that this star forming burst had been trigge…
I briefly review what has been recently learned from determinations of mean stellar ages and abundances from integrated light studies of early-type galaxies, and discuss some new questions posed by recent data. A short discussion of spectroscopic ages is presented, but the main focus of this review is on the abundances of Fe, Mg, Ca, N, and C, obtained from comparisons of measurements taken in integrated spectra of galaxies with predictions from stellar population synthesis models.
