Observations have evidenced that passively evolving massive galaxies at high redshift are much more compact than local galaxies with the same stellar mass. We argue that the observed strong evolution in size is directly related to the quasar feedback, which removes huge amounts of cold gas from the central regions in a Salpeter time, inducing an expansion of the stellar distribution. The new eq...

In this paper, we investigate the structures of galaxies which either have or have had three BHs using N -body simulations, and compare them with those of galaxies with binary BHs. We found that the cusp region of a galaxy which have (or had) triple BHs is significantly larger and less dense than that of a galaxy with binary BHs of the same mass. Moreover, the size of the cusp region depends st...

This paper introduces the concept of size functions in galaxy morphology classification, which are geometrical-topological shape descriptors which can be tailor-made to describe the shapes of objects of interest. For the three main classes of galaxies obtained from the Hubble classification scheme, namely, elliptical, spiral and lenticular, the size functions are obtained from two sets of measu...

We have conducted a systematic search for stellar disk truncations in disk–like galaxies at intermediate redshift (z<1.1) using the Hubble Ultra Deep Field (UDF) data. We use the position of the truncation as a direct estimator of the size of the stellar disk. After accounting for the surface brightness evolution of the galaxies, our results suggest that the radial position of the truncations h...

Using a sample of nine massive compact galaxies at z ∼ 2.3 with rest-frame optical spectroscopy and comprehensive U → 8μm photometry we investigate how assumptions in SED modeling change the stellar mass estimates of these galaxies, and how this affects our interpretation of their size evolution. The SEDs are fit to τ -models with a range of metallicities, dust laws, as well as different stella...

We present HST NICMOS+ACS and Spitzer IRAC+MIPS observations of 41 galaxies at 2 < z < 3.5 in the FIRES MS1054 field with red and blue rest-frame optical colors. About half of the galaxies are very compact (effective radii re < 1 kpc) at rest-frame optical wavelengths, the others are extended (1 < re < 10 kpc). For reference, 1 kpc corresponds to 0. 12 at z = 2.5 in the adopted cosmology. We se...

We examine the evolution of the sizes and number densities of disk galaxies using the high resolution images obtained by the Great Observatories Origins Deep Survey (GOODS) with the Advanced Camera for Surveys (ACS) on the Hubble Space Telescope (HST). The multiwavelength images are used to classify galaxies based on their rest–frame B-band morphologies out to redshift z ∼ 1.25. In order to min...