Downsizing does not extend to dwarf galaxies: identifying the stellar mass regimes shaped by supernova and AGN feedback
University of Hertfordshire（赫特福德大学）；University of Nottingham（诺丁汉大学）；University of Manchester（曼彻斯特大学）；University of Cambridge（剑桥大学）；Yonsei University（延世大学）
Ilin Lazar, Sugata Kaviraj, Garreth Martin, Christopher J. Conselice, Sophie Koudmani, Aaron E. Watkins, Sukyoung K. Yi, Darshan Kakkad, Thomas M. Sedgwick, Yoh… 展开作者
Ilin Lazar, Sugata Kaviraj, Garreth Martin, Christopher J. Conselice, Sophie Koudmani, Aaron E. Watkins, Sukyoung K. Yi, Darshan Kakkad, Thomas M. Sedgwick, Yohan Dubois, Julien E. G. Devriendt, Katarina Kraljic, Sebastien Peirani
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Accepted for publication in MNRAS, 14 pages, 7 figures
We explore how the fraction of red (quenched) galaxies varies in the dwarf galaxy regime (10^7 MSun < Mstar < 10^9.5 MSun), using a mass-complete sample of ~5900 dwarfs at z<0.15, constructed using deep multi-wavelength data in the COSMOS field. The red fraction decreases steadily until Mstar ~ 10^8.5 MSun and then increases again towards lower stellar masses. This 'U' shape demonstrates that the traditional notion of 'downsizing' (i.e. that progressively lower mass galaxies maintain star formation until later epochs) is incorrect -- downsizing does not continue uninterrupted into the dwarf regime. The U shape persists regardless of environment, indicating that it is driven by internal processes rather than external environment-driven mechanisms. Our results suggest that, at Mstar < 10^8 MSun, the quenching of star formation is dominated by supernova (SN) feedback and becomes more effective with decreasing stellar mass, as the potential well becomes shallower. At Mstar > 10^9 MSun, the quenching is driven by a mix of SN feedback and AGN feedback (which becomes more effective with increasing stellar mass, as central black holes become more massive). The processes that quench star formation are least effective in the range 10^8 MSun < Mstar < 10^9 MSun, likely because the potential well is deep enough to weaken the impact of SN feedback, while the effect of AGN feedback is still insignificant. The cosmological simulations tested here do not match the details of how the red fraction varies as a function of stellar mass -- we propose that the red fraction vs stellar mass relation (particularly in the dwarf regime) is a powerful calibrator for the processes that regulate star formation in galaxy formation models.
Previous studies of the stellar mean metallicity and [Mg/Fe] values of massive elliptical (E)~galaxies suggest that their stars were formed in a very short timescale which cannot be reconciled with estimates from stellar population synthesis (SPS) studies and with hierarchical-assembly. Applying the previously developed chemical evolution code, GalIMF, which allows an environment-dependent stellar initial mass function (IMF) to be applied in the integrated galaxy initial mass function (IGIMF) theory instead of an invariant canonical IMF, the star formation timescales (SFT) of E galaxies are re…
Massive ($\geq$8 $M_\odot$) stars perish via one of two fates: core-collapse supernovae (CCSNe), which release synthesized heavy elements, or failed supernovae, thereby forming black holes. In the conventional Galactic chemical evolution (GCE) scheme, a substantial portion of massive stars, e.g., all stars in the mass range of 8-100 $M_{\odot},$ are assumed to enrich the Galaxy with their nucleosynthetic products. However, this hypothesis conflicts with the observations, namely, few CCSNe whose progenitor stars are more massive than $\sim$18 $M_{\odot}.$ Here, we show that the chemical charact…
The origin of the $α$-enhancement of massive galaxies
我们研究的恒星$α$ -元素，铁丰度比，$[α/\mathrm{Fe}]_{\ast}$，现今的中央星系的起源，使用宇宙学，流体动力学模拟的演化和组装的银河系及其环境（EAGLE）项目。对于恒星质量为$M_{\ast} > 10^{10.5}$ M $_{\odot}$的星系，$[α/\mathrm{Fe}]_{\ast}$随着星系恒星质量和年龄的增加而增加。这些趋势与早期星系的观测结果非常一致，并且与“缩小”星系形成的假设相一致：质量较大的星系形成其大部分恒星的时间更早，速度更快，因此星际介质主要是由大质量恒星富集的$α$。然而，在没有活动星系核（AGN）反馈的情况下，$M_{\ast} > 10^{10.5}$ M $_{\odot}$星系中的$[α/\mathrm{Fe}]_{\ast}$随恒星质量变化大致不变，随平均恒星年龄变化而减小，这扩展了在有和没有活动星系核的模拟中发现的低质量星系的趋势。我们的结论是活动星系核反馈可以解释大质量星系的$α$增强，因为它抑制了它们的恒星形成，在早期淬灭了更大质量的星系，从而阻止了来自寿命更长的中等质量恒星（Ia型超新星）的铁被纳入年轻恒星。
Long ($>2$ s) gamma ray bursts (GRBs) are associated with explosions of massive stars, although in three instances, supernovae (SNe) have not been detected, despite deep observations. With new HI line and archival optical integral field spectroscopy data, we characterize the interstellar medium (ISM) of the host galaxy of one of these events, GRB 111005A, in order to shed light on the unclear nature of these peculiar objects. We found that the atomic gas, radio continuum, and rotational patterns are in general very smooth throughout the galaxy, which does not indicate a recent gas inflow or ou…
We present a model for the Galactic supernova remnant (SNR) VRO 42.05.01, suggesting that its intriguing morphology can be explained by a progenitor model of a supersonically moving, mass losing star. The mass outflows of the progenitor star were in the form of an asymmetric stellar wind focused on the equatorial plane of the star. The systemic motion of the parent star in combination with its asymmetric outflows excavated an extended wind bubble that revealed a similar structure to this of VRO 42.05.01. Currently the SNR is interacting with the wind bubble and it is dominantly shaped by it. E…
Supernova feedback in porous photoionized Giant Molecular Clouds
National Center for Theoretical Sciences, National Taiwan University（台湾大学理论科学中心）；University of St Andrews（圣安德鲁斯大学）；Center of Astronomy and Gravitation, Department of Earth Sciences, National Taiwan Normal University（台湾师范大学地球科学系天体物理与引力研究中心）；Institute of Astronomy and Astrophysics, Academia Sinica（中央研究院天文及天文物理研究所）；Heidelberger Institut für Theoretische Studien（海德堡理论研究所）
Dwarf spheroidal galaxies (dSphs) have been extensively investigated in the Local Group, but their low luminosity and surface brightness make similar work in more distant galaxy groups challenging. Modern instrumentation unlocks the possibility of scrutinizing these faint systems in other environments, expanding the parameter space of group properties. We use MUSE spectroscopy to study the properties of 14 known or suspected dSph satellites of Cen A. Twelve targets are confirmed to be group members based on their radial velocities. Two targets are background galaxies at 50 Mpc: KK 198 is a fac…
Core-collapse supernova remnants are the gaseous nebulae of galactic interstellar media (ISM) formed after the explosive death of massive stars. Their morphology and emission properties depend both on the surrounding circumstellar structure shaped by the stellar wind-ISM interaction of the progenitor star and on the local conditions of the ambient medium. In the warm phase of the Galactic plane (n = 1/cm3, T = 8000 K), an organised magnetic field of strength 7 microG has profound consequences on the morphology of the wind bubble of massive stars at rest. In this paper we show through 2.5D magn…
The alpha element to iron peak element ratio, for example [Mg/Fe], is a commonly applied indicator of the galaxy star formation timescale (SFT) since the two groups of elements are mainly produced by different types of supernovae that explode over different timescales. However, it is insufficient to consider only [Mg/Fe] when estimating the SFT. The [Mg/Fe] yield of a stellar population depends on its metallicity. Therefore, it is possible for galaxies with different SFTs and at the same time different total metallicity to have the same [Mg/Fe]. This effect has not been properly taken into con…
The Nearby Star Formation and Supernova Histories Reconstructed from Young Star Clusters
Center for Astrophysics — Harvard & Smithsonian（天体物理中心——哈佛与史密森尼学会）；Department of Astrophysics, University of Vienna（维也纳大学天体物理学系）；Department of Physics, University of Wisconsin–Whitewater（威斯康星大学惠特沃分校物理系）
The Origin and Evolution of the Mass-Metallicity Relation using GalICS
利用GalICS（Galerkin in Cosmological Simulations）分层星系形成的半解析模型，研究了星系的不同性质，包括恒星形成率（SFR）和流出量，对星系的质量金属度关系的形状的影响，并预测了红移z=2.27和z=3.54的星系的质量金属度关系.我们的GalICS版本非常详细地实现了化学进化，并且不太依赖于瞬时循环等近似方法。我们改变模型参数控制的效率和红移依赖的SFR以及效率的超新星反馈。我们发现，控制的SFR的因素影响的关系显着在所有的红移，需要一个强大的红移依赖性，1+z成比例，以重现所观察到的关系在低质量端。事实上，在任何红移，预测的关系在高质量的一端，导致一个较差的协议与观察在这一制度。我们还发现，与外流相关的参数的变化有一个最小的影响，在高红移的关系，但在最近的过去改变其形状。因此，我们的结论是，SFR和质量之间的关系，外流是唯一重要的在塑造的关系在晚些时候。当该关系是分层的SFR很明显，预测的星系与恒星质量增加有较高的SFR，支持星系缩小的关系是起源的观点。为了重现观测到的关系，我们改变了控制恒星形成效率及其红移依赖性的参数，并将预测的关系与Erb et al.（2006）在z=2.27时和Maiolino et al.（2008）在z=3.54时进行比较，以找到最佳拟合参数。（节录）
