相关论文: Secondary Episode of Star Formation in Elliptical …
We use Hubble Space Telescope near-IR grism spectroscopy to examine the H-beta line strengths of 260 star-forming galaxies in the redshift range 1.90 < z < 2.35. We show that at these epochs, the H-beta star formation rate (SFR) is a factor…
The far-ultraviolet is the most rapidly evolving portion of the spectrum in both very young galaxies and very old galaxies. The ``UV upturn'' in the spectra of elliptical galaxies shortward of 2000 Angstroms offers a promising probe of the…
The effects of late gas accretion episodes and subsequent merger-induced starbursts on the photo-chemical evolution of elliptical galaxies are studied and compared to the picture of galaxy formation occurring at high redshift with an unique…
The results of UBV and H alpha imaging of a large sample of isolated dwarf irregular galaxies are interpreted in the context of composite stellar population models. The observed optical colors are best fit by composite stellar populations…
We consider the hypothesis that the formation of elliptical galaxies includes a phase in which star formation is mostly restricted to massive stars, with the bias towards high mass stars increasing with elliptical galaxy mass. The mass…
Compared to starburst galaxies, normal star forming galaxies have been shown to display a much larger dispersion of the dust attenuation at fixed reddening through studies of the IRX-beta diagram (the IR/UV ratio "IRX" versus the UV color…
From an analysis of almost 2000 GALEX images of galaxies with morphological types ranging from E to Sab, we have found a significant subset (28%) that show UV emission outside $R_{25}$. We have obtained H$\alpha$ imaging of ten such…
We present surface photometry of a sample of 52 galaxies from the GALEX and 2MASS data archives, these include 32 normal elliptical galaxies, 10 ellipticals with weak Liner or other nuclear activity, and 10 star forming ellipticals or…
We present the first results of a spectroscopic survey of Lyman break galaxies in the near-infrared aimed at detecting the emission lines of [O II], [O III], and Hbeta from the H II regions of star forming galaxies at z = 3. From…
The evolution of the comoving cosmic merger-rate density of neutron star binaries n_c(z) is calculated using a distribution of their merging times provided by population-synthesis computations of binary stars. We adopt an exponential law…
We present an analysis of the far-ultraviolet upturn phenomenon (UVX) observed in elliptical galaxies and spiral galaxy bulges. Our premise is that the UV radiation from these systems emanates primarily from extreme horizontal branch (EHB)…
We compare the H-beta line strengths of 1.90 < z < 2.35 star-forming galaxies observed with the near-IR grism of the Hubble Space Telescope with ground-based measurements of Ly-alpha from the HETDEX Pilot Survey and narrow-band imaging. By…
We present models of the late stages of stellar evolution intended to explain the UV upturn phenomenon in elliptical galaxies. Such models are sensitive to values of a number of poorly-constrained physical parameters, including metallicity,…
About 10 candidate Halpha emitting galaxies at z = 2.2 have been detected in a 2.1 um narrow band imaging survey covering an area of 100 sq. arcmin including the WFPC2 and STIS fields in the Hubble Deep Field South. Six of these have…
We use long-slit spectroscopy from Moran et al. to study the radial dependence of the recent star formation histories of nearby galaxies with stellar masses greater than 10^10M_sun. We fit stellar population models to the combination of…
We present preliminary results from spectral synthesis models of old stellar populations for the spectral range 912-4000 A with ~ 10A resolution, which can be used to investigate the UVX phenomenon and to assess ages and abundances. Model…
Using the Subaru very deep K'-band imaging and HST WFPC2/NICMOS archival data of the Hubble Deep Field North, we investigate the evolution of the stellar mass, color, morphology of galaxies to z ~ 3. We mainly examine the rest-frame U-V…
We analyse the detailed distribution of star-forming and post-starburst members in three distant (z = 0.31) galaxy clusters in terms of evolutionary sequences that incorporate secondary bursts of star formation on pre-existing stellar…
In the local Universe, 10% of massive elliptical galaxies are observed to exhibit a peculiar property: a substantial excess of ultraviolet emission (UVX) over what is expected from their old, red stellar populations. Several origins for the…
Much of the far-UV emission from elliptical galaxies is thought to arise from extreme horizontal branch stars and related objects. Only about 10% of the stellar population needs to evolve through this phase even in galaxies with the…