We present the discovery of an isolated compact group of galaxies that is extremely dense (median projected galaxy separation: 6.9 kpc), has a very low velocity dispersion (σ2D = 67 km s −1), and where all observed members show emission lines and are morphologically disturbed. These properties, together with the lack of spirals and the presence of a prominent tidal tail make this group one of t...

Based on recent X-ray observations of the Milky Way, Magellanic Clouds and nearby starburst galaxies we study population of high mass X-ray binaries, their connection with ultra-luminous X-ray sources and relation to the star formation. Although more subtle SFR dependent effects are likely to exist, the data in the lg(LX) ∼ 36 − 40.5 luminosity range are broadly consistent with existence of a "...

and – 2 – ABSTRACT Observations of ultraluminous infrared galaxies (ULIRGs) with an achieved resolution approaching the diffraction limit in the mid-infrared from 8-25 µm using the Keck Telescopes are reported. We find extremely compact structures, with spatial scales of < 0.3 ′′ (diameter) in six of the seven ULIRGs observed. These compact sources emit between 30% and 100% of the mid-infrared ...

Extragalactic sources from the IRAS Faint Source Catalog (FSC) which have the optically faintest magnitudes (E & 18) were selected by spatial coincidence with a source in the FIRST radio survey, and 28 of these sources have been observed with the Infrared Spectrograph on Spitzer (IRS). While an infrared source is always detected with the IRS at the FIRST position, only ∼ 50% of the infrared sou...

Mass segregation in a star cluster is studied in an analytical manner. We consider a two-component cluster, which consists of two types of stars with different masses. Plummer’s model is used for the initial condition. We trace the overall behaviors of the probability distribution functions of the two components and obtain the timescale of mass segregation as a simple function of the cluster pa...

We investigated the ability of the stellar models Starburst99 and MappingsIII to model starburst galaxies using infrared diagnostics and Spitzer data. The infrared diagnostics were useful for distinguishing between starforming galaxies and AGN. The theoretical starburst models indicate that the infrared emission-line ratios are largely degenerate and are extremely sensitive to the age of the st...

I will try to put the ultraluminous galaxy phenomenon into a broad cosmological context. Viewed from this perspective, the significance of ultraluminous galaxies and the ‘starburst vs. monster’ debate becomes clear. Ultraluminous galaxies are fascinating in their own right, allow detailed study of the processes by which massive spheroids were built and the IGM was heated and polluted, and resem...

The orbital decay and tidal disruption of a star cluster in a galaxy is studied in an analytical manner. Owing to dynamical friction, the star cluster spirals in toward the center of the galaxy. Simultaneously, the galactic tidal field strips stars from the outskirts of the star cluster. Under an assumption that the star cluster undergoes a self-similar evolution, we obtain the condition and ti...

We investigate techniques that can be used to determine ages of starburst regions containing populations beyond their early nebular phase. In particular, we study the strength of the Ca ii triplet (λλ 8498, 8542, 8662 Å) and the CO index (2.31–2.40 μm band) using synthetic models as the starburst evolves. For an instantaneous burst of star formation both of these absorption features remain stro...