Current models of galaxy formation lack an efficient and physically constrained mechanism to regulate star formation (SF) in low and intermediate mass galaxies. We argue that the missing ingredient could be the effect of photoionization by local sources on the gas cooling. We show that the soft X-ray and EUV flux generated by SF is able to efficiently remove the main coolants (e.g., HeII, OV and FeIX) from the halo gas via direct photoionization. As a consequence, the cooling and accretion time of the gas surrounding star-forming galaxies may increase by one or two orders of magnitude. For a given halo mass and redshift, the effect is directly related to the value of the star formation rate (SFR). Our results suggest the existence of a critical SFR above which "cold" mode accretion is stopped, even for haloes with virial masses well below the critical shock-heating mass suggested by previous studies.The evolution of the critical SFR with redshift, for a given halo mass, resembles the respective steep evolution of the observed SFR for z<1. This suggests that photoionization by local sources would be able to regulate gas accretion and star formation, without the need for additional, strong feedback processes.
We study the morphological transformation from late types to early types and the quenching of galaxies with the seventh Data Release (DR7) of the Sloan Digital Sky Survey (SDSS). Both early type galaxies and late type galaxies are found to have bimodal distributions on the star formation rate versus stellar mass diagram ($\lg SFR - \lg M_*$). We therefore classify them into four types: the star-forming early types (sEs), the quenched early types (qEs), the star-forming late types (sLs) and the quenched late types (qLs). We checked many parameters on various environmental scales for their poten…
Observationally, it has been reported that the densest stellar system in the Universe does not exceed a maximum stellar surface density, $Σ^{\max}_{*}$ = $3\times10^5$M$_{\odot}$pc$^{-2}$, throughout a wide physical scale ranging from star cluster to galaxy. This suggests there exists a fundamental physics which regulates the star formation and stellar density. However, factors that determine this maximum limit are not clear. In this study, we show that $Σ^{\max}_{*}$ of galaxies is not a constant as previous work reported, but actually depends on the stellar mass. We select galaxy sample from…
Primordial Black Holes as Seeds for Extremely Overmassive AGN Observed by JWST
University of Texas at Austin（德克萨斯大学奥斯汀分校）；Weinberg Institute for Theoretical Physics, Texas Center for Cosmology and Astroparticle Physics, University of Texas at Austin（德克萨斯大学奥斯汀分校温伯格理论物理研究所、德州宇宙学与天体粒子物理中心）；Institute of Astronomy, University of Cambridge（剑桥大学天文研究所）；Universität Heidelberg, Zentrum fur Astronomie, Institut für Theoretische Astrophysik（海德堡大学天文学中心理论天体物理研究所）；Department of Astronomy, University of Texas at Austin（德克萨斯大学奥斯汀分校天文学系）；Max-Planck-Institut für Physik（马克斯·普朗克物理研究所）；Arnold Sommerfeld Center, Ludwig-Maximilians-Universität（慕尼黑大学阿诺德·索末菲理论物理中心）
Molecular gas properties of star-forming brightest group galaxies at $z \sim 0.3$
Alma Mater Studiorum Università di Bologna（博洛尼亚大学）；INAF - Osservatorio di Astrofisica e Scienza dello Spazio di Bologna（意大利国家天体物理研究所波伦亚天文台）；Zentrum für Astronomie, Universität Heidelberg（海德堡大学天文中心）；Observatoire de Paris, Collège de France, PSL University, Sorbonne University, CNRS, LUX（巴黎天文台，法兰西学院，PSL大学，索邦大学，法国国家科学研究中心，LUX）；Institut de Radioastronomie Millimétrique (IRAM)（毫米波射电天文研究所）；INFN - Sezione di Bologna（意大利国家核物理研究所博洛尼亚分部）；ITP, Universität Heidelberg（海德堡大学理论物理研究所）
