相关论文: Holmberg Ix: The Nearest Young Galaxy

I present the first results from a HST/NICMOS imaging study of the most metal-poor blue compact dwarf galaxy IZw18. The near infrared color-magnitude diagram (CMD) is dominated by two populations, one 10-20 Myr population of red super…

We present a spectroscopic and kinematic analysis of 79 nearby M dwarfs in 77 systems. All are low-proper-motion southern hemisphere objects and were identified in a nearby star survey with a demonstrated sensitivity to young stars. Using…

Context. NGC 205 is a peculiar dwarf elliptical galaxy hosting in its center a population of young blue stars. Their origin is still matter of debate, the central fresh star formation activity possibly being related to dynamical…

(Abridged) We present high-resolution HST imaging in the optical (WFPC2) and near-infrared (NICMOS) of a disk region 1 kpc NE of the starburst core in the nearby galaxy M82. This region, M82 ``B,'' has been suspected to be a fossil…

A revised metallicity calibration of the Stroemgren (b-y),m_1 diagram, based on a sample of globular cluster and field red giant stars, is presented. This new calibration has been used to determine Stroemgren metallicities ([Fe/H]_phot) for…

We present the star formation history of the extremely metal-poor dwarf galaxy DDO 68, based on our photometry with the Advanced Camera for Surveys. With a metallicity of only $12+\log(O/H)=7.15$ and a very isolated location, DDO 68 is one…

We present a study of the stellar populations of a sample of 39 local, field early-type galaxies whose HI properties are known from interferometric data. Our aim is to understand whether stellar age and chemical composition depend on the HI…

Recent James Webb Space Telescope (JWST) data analyses have shown that massive red galaxies existed at redshifts $z>6$, a discovery that is difficult to understand in the context of standard cosmology ($\Lambda $CDM). Here we analyze these…

We present a statistical observational study of the tidal dwarf (TD) population in the nearby Universe, by exploiting a large, homogeneous catalogue of galaxy mergers compiled from the SDSS. 95% of TD-producing mergers involve two spiral…

Using archival multi--epoch ACS/WFC images in the F606W and F814W filters of a resolved stellar field in Local Group dwarf elliptical galaxy M32 we have made an accurate Colour-Magnitude Diagram and a careful search for RR Lyr variable…

We use high-resolution ($\approx 10$ pc), zoom-in simulations of a typical (stellar mass $M_\star\simeq10^{10}M_\odot$) Lyman Break Galaxy (LBG) at $z\simeq 6$ to investigate the stellar populations of its six dwarf galaxy satellites, whose…

We present deep Hubble Space Telescope Advanced Camera for Surveys observations of the stellar populations in two fields lying at 20 and 23 kpc from the centre of M31 along the south-west semi-major axis. These data enable the construction…

Stellar photometry obtained using the Hubble Space Telescope is used to study the distributions of the number densities of stars of various ages in 12 irregular and dwarf spiral galaxies viewed edge-on. Two subsystems can be distinguished…

We have measured the orbital parameters of seven close binaries, including six new objects, in a radial velocity survey of 38 objects comprising a hot subdwarf star with orbital periods ranging from ~0.17 to 3 d. One new system, GALEX…

We present the results of medium-resolution spectroscopy of 28 globular clusters (GCs) in six nearby galaxies of different luminosities and morphological types, situated in: M33 (15 objects), M31 (3), IC10 (4), UGCA86 (4), HolmbergIX (1),…

The source X-9 was discovered with the {\it Einstein Observatory} in the field of M81, and is located in the dwarf galaxy Holmberg IX. X-9 has a 0.2-4.0 keV luminosity of $\sim 5.5\times 10^{39}$ ergs~s$^{-1}$, if it is at the same distance…

We analyse the stellar content of a large number of HII galaxies from the continua and absorption features of their spectra using population synthesis methods, in order to gain information about the star formation histories of these…

We present a new technique to determine age and metallicity of old stellar populations (globular clusters and elliptical galaxies) using an iterative principal component analysis on narrow band (Str\"omgren) colors. Our technique is capable…

We present the analysis of Lick absorption-line indices from three separate long-slit spectroscopic observations of the nearby isolated elliptical galaxy NGC 821. The three data sets present a consistent picture of the stellar population…

We present deep color-magnitude diagrams (CMDs) for a field along the outer disk of M31 based on archival Hubble Space Telescope Wide Field Planetary Camera 2 observations in the F555W (~V) and F814W (~I) filters. The CMDs, which contain a…