相关论文: How old are the HII Galaxies?

The combination of huge databases of galaxy spectra and advances in evolutionary synthesis models in the past few years has renewed interest in an old question: How to estimate the star formation history of a galaxy out of its integrated…

If massive stars form by disk accretion, then bipolar outflows should be generated as in the case of low-mass star formation. High accretion rates lead to high outflow rates and make the wind density very large near the protostar. We…

The properties of galaxies follow scaling relations related to the physics that govern galaxy evolution. Based on these, we can identify galaxies undergoing specific evolutionary processes such as HI-excess galaxies, which have relatively…

The dynamical evolution of HII regions with and without stellar motion in dense, structured molecular clouds is studied. Clouds are modeled in hydrostatic equilibrium, with gaussian central cores and external halos that obey r**-2 and r**-3…

We examine the gas and stellar metallicities in a sample of HII galaxies from the Sloan Digital Sky Survey, which possibly contains the largest homogeneous sample of HII galaxy spectra to date. We eliminated all spectra with an insufficient…

Recent morphological studies (Telles \& Terlevich 1994) of HII galaxies, i.e. dwarf galaxies dominated by a very luminous starburst, have indicated that luminous HII galaxies tend to show distorted morphology suggestive of tidal…

We present the results on the study of the global and local M-Z relation based on the first data available from the CALIFA survey (150 galaxies). This survey provides integral field spectroscopy of the complete optical extent of each galaxy…

We explore the properties of galaxies on the outskirts of clusters and their dependence on recent dynamical history in order to understand the real impact that the cluster core has on the evolution of galaxies. We analyse the properties of…

We revisit the luminosity function (LF) of compact HII regions in the context of the inertial--inflow model (IIM), in which massive stars assemble over extended, mass-dependent timescales. The comparison of the compact-HII-region LF with…

The emission line ratios [OIII]5007/H-beta and [NII]6584/H-alpha have been adopted as an empirical way to distinguish between the fundamentally different mechanisms of ionization in emission-line galaxies. However, detailed interpretation…

The hypothesis that massive stars form by accretion can be investigated by simple analytical calculations that describe the effect that the formation of a massive star has on its own accretion flow. Within a simple accretion model that…

Explaining the formation and evolution of galaxies is one of the most challenging problems in observational cosmology. Many observations suggest that galaxies we see today could have evolved from the merging of smaller subsystems. Evolution…

Interstellar reddening corrections are necessary to reconstruct the intrinsic spectral energy distributions (SEDs) of accreting protostellar systems. The stellar SED determines the heating and chemical processes that can occur in…

We compare the gas distribution, kinematics and the current star formation in a sample of 10 very faint (-13.37 < M_B < -9.55) dwarf galaxies. For 5 of these galaxies we present fresh, high sensitivity, GMRT HI 21cm observations. For all…

Star cluster formation is a major mode of star formation in the extreme conditions of interacting galaxies and violent starbursts. Young clusters are observed to form in a variety of such galaxies, a substantial number resembling the…

We investigate the star formation and dust extinction properties of very luminous infrared galaxies whose spectra display a strong Hdelta line in absorption and a moderate [OII] emission (e[a] spectrum). This spectral combination has been…

In this paper we study the underlying stellar population of a sample of 65 nearby early-type galaxies predominantly located in low density environments. Ages, metallicities and [alpha/Fe] ratios have been derived through the comparison of…

Determination of the star formation rate can be done using mid-IR photometry or Balmer line luminosity after a proper correction for extinction effects. Both methods show convergent results while those based on UV or on [OII]3727…

We present numerical models of the nebular emission from H II regions around young stellar populations over a range of compositions and ages. The synthetic stellar pop- ulations include both single stars and interacting binary stars. We…

In integrated-light, some color-color diagrams that use optical and near-infrared photometry show surprisingly orthogonal grids as age and metallicity are varied, and they are coming into common usage for estimating the average age and…