We provide a simple theoretical model for the quasar luminosity function at high redshifts that naturally reproduces the statistical properties of the luminous SDSS quasar sample at redshifts z ∼ 4.3 and z & 5.7. Our model is based on the assumptions that quasar emission is triggered by galaxy mergers, and that the black hole mass is proportional to a power-law in the circular velocity of the h...

Within the current uncertainties in the treatment of the coupling between pulsation and convection, the limiting amplitude, nonlinear, convective models appear the only viable approach for providing theoretical predictions about the intrinsic properties of radial pulsators. In this paper we present the results of a comprehensive set of Cepheid models computed within such theoretical framework f...

Aims. We report the X-ray properties of young (∼3 Myr) bona fide brown dwarfs of the Taurus Molecular Cloud (TMC). Methods. The XMM-Newton Extended Survey of the TMC (XEST) is a large program designed to systematically investigate the X-ray properties of young stellar/substellar objects in the TMC. In particular, the area surveyed by 15 XMM-Newton pointings (of which three are archival observat...

We use a complete sample of about 140,000 galaxies from the Sloan Digital Sky Survey (SDSS) to study the size distribution of galaxies and its dependence on their luminosity, stellar mass, and morphological type. The large SDSS database provides statistics of unprecedented accuracy. For each type of galaxy, the size distribution at given luminosity (or stellar mass) is well described by a log-n...

I review the connection between dynamics and the baryonic mass distribution in rotationally-supported galaxies. The enclosed dynamical mass-to-light ratio increases with decreasing galaxy luminosity and surface brightness. The correlation with surface brightness appears to be the more fundamental, with the dependence on luminosity following simply from the weaker correlation between luminosity ...

We present a mid-infrared investigation of the scaling relations between supermassive black hole masses (MBH) and the structural parameters of the host spheroids in local galaxies. This work is based on 2D bulge-disc decompositions of Spitzer/IRAC 3.6 μm images of 57 galaxies with MBH estimates. We first verify the accuracy of our decomposition by examining the Fundamental Plane (FP) of spheroi...

Dwarf, irregular and infrared-luminous starburst galaxies are all known to have “steep” luminosity functions with faint-end behavior roughly φ(L) ∝ L−1.8. This form is exactly what is expected if the luminosities of these objects fade with time as L ∝ t−1.3, because the objects spend more time at low luminosities than high, even if they form with a wide range of initial masses. Models of young ...

I describe the disk mass–rotation velocity relation which underpins the familiar luminosity–linewidth relation. Continuity of this relation favors nearly maximal stellar mass-to-light ratios. This contradicts the low mass-to-light ratios implied by the lack of surface brightness dependence in the same relation. 1. Searching for the Physical Basis of the Tully-Fisher Relation The Tully-Fisher (T...

The time-delay between the emission-line variations and the continuum variations of a quasar or Seyfert galaxy can be used to estimate the distance between the broad line regions (BLRs) and the central source, and this technique is called the emission-line reverberation mapping (RM). Based on the RM observation, a relationship between the size of BLRs (RBLR) and the luminosity of AGNs can be es...

Using a phenomenological approach, we self-consistently model the redshift evolution of the ultraviolet (UV) and infrared (IR) luminosity functions across cosmic time, as well as a range of observed IR properties of UV-selected galaxy population. This model is an extension of the 2SFM (2 star-formation modes) formalism, which is based on the observed ”main-sequence” of star-forming galaxies, i....